We used a biodegradable mesh to convert an acetabular defect into a contained defect in six patients at total hip replacement. Their mean age was 61 years (46 to 69). The mean follow-up was 32 months (19 to 50). Before clinical use, the strength retention and hydrolytic in vitro degradation properties of the implants were studied in the laboratory over a two-year period. A successful clinical outcome was determined by the radiological findings and the Harris hip score. All the patients had a satisfactory outcome and no mechanical failures or other complications were observed. No protrusion of any of the impacted grafts was observed beyond the mesh. According to our preliminary laboratory and clinical results the biodegradable mesh is suitable for augmenting uncontained acetabular defects in which the primary stability of the implanted acetabular component is provided by the host bone. In the case of defects of the acetabular floor this new application provides a safe method of preventing graft material from protruding excessively into the pelvis and the mesh seems to tolerate bone-impaction grafting in selected patients with primary and revision total hip replacement

Impacted morsellised allografts have been used successfully to address the problem of poor bone stock in revision surgery. However, there are concerns about the transmission of pathogens, the high cost and the shortage of supply of donor bone. Bone-graft extenders, such as tricalcium phosphate (TCP) and hydroxyapatite (HA), have been developed to minimise the use of donor bone. In a human cadaver model we have evaluated the surgical and mechanical feasibility of a TCP/HA bone-graft extender during impaction grafting revision surgery. A TCP/HA allograft mix increased the risk of producing a fissure in the femur during the impaction procedure, but provided a higher initial mechanical stability when compared with bone graft alone. The implications of the use of this type of graft extender in impaction grafting revision surgery are discussed

This study investigates the use of porous biphasic ceramics as graft extenders in impaction grafting of the femur during revision hip surgery. Impaction grafting of the femur was performed in four groups of sheep. Group one received pure allograft, group two 50% allograft and 50% BoneSave, group three 50% allograft and 50% BoneSave type 2 and group four 10% allograft and 90% BoneSave as the graft material. Function was assessed using an index of pre- and post-operative peak vertical ground reaction force ratios. Changes in bone mineral density were measured by dual energy X ray absorptiometry (DEXA) scanning. Loosening and subsidence were assessed radiographically and by histological examination of the explanted specimens. There was no statistically significant difference between the four groups after 18 months of unrestricted functional loading for all outcome measures

We examined osteochondral autografts, obtained at a mean of 19.5 months (3 to 48) following extracorporeal irradiation and re-implantation to replace bone defects after removal of tumours. The specimens were obtained from six patients (mean age 13.3 years (10 to 18)) and consisted of articular cartilage (five), subchondral bone (five), external callus (one) and tendon (one). The tumour cells in the grafts were eradicated by a single radiation dose of 60 Gy. In three cartilage specimens, viable chondrocytes were detected. The survival of chondrocytes was confirmed with S-100 protein staining. Three specimens from the subchondral region and a tendon displayed features of regeneration. Callus was seen at the junction between host and irradiated bone

Our aim was to analyse the effect of avascularity on the morphology and mechanical properties (tensile strength, viscoelasticity) of human bone-patellar-tendon-bone (BPTB) grafts in vitro. These were harvested at postmortem and stored submerged in denaturated human plasma at a constant pH, pO. 2. , pCO. 2. , temperature and humidity under sterile conditions. Mechanical testing was performed two and four weeks after removal of the graft. The mean ultimate strength was 1085.7 ± 255.8 N (control), 1009.0 ± 314.9 N (two weeks cultured) and 1076.8 ± 414.8 N (four weeks cultured). There was no significant difference in linear stiffness or deformation to failure between the groups. There was a difference in viscoelasticity between the control group and the avascular grafts and the latter had significant lower peak load-to-load ratios after 15 minutes compared with the control group. After two and four weeks the graft contained viable fibroblasts. There was regular cellularity in the superficial layers and decreased cellularity in the midportion. The structure of the collagen including the crimp pattern appeared to be normal in polarised light. We conclude that avascularity does not significantly affect ultimate failure loads or stiffness of BPTB grafts. Slight changes in viscoelasticity were induced, but the significance of the increased stress relaxation is not fully understood

In order to investigate the osteoinductive properties of allograft used in impaction grafting and the effect of strain during impaction on these properties, we designed an in vitro experiment to measure strain-related release of bone morphogenetic protein-7 (BMP-7) from fresh-frozen femoral head allograft. A total of 40 10 mm cubes of cancellous bone were cut from ten samples of fresh-frozen femoral head. The marrow was removed from the cubes and the baseline concentrations of BMP-7 were measured. Specimens from each femoral head were allocated to four groups and subjected to different compressive strains with a material testing machine, after which BMP-7 activity was reassessed. It was present in all groups. There was a linear increase of 102.1 pg/g (95% confidence interval 68.6 to 135.6) BMP-7 for each 10% increase in strain. At 80% strain the mean concentration of BMP-7 released (830.3 pg/g bone) was approximately four times that released at 20% strain. Activity of BMP-7 in fresh-frozen allograft has not previously been demonstrated. This study shows that the freezing and storage of femoral heads allows some maintenance of biological activity, and that impaction grafting provides a source of osteoinductive bone for remodelling. We have shown that BMP-7 is released from fresh-frozen femoral head cancellous bone in proportion to the strain applied to the bone. This suggests that the impaction process itself may contribute to the biological process of remodelling and bony incorporation

Impacted bone allograft is often used in revision joint replacement. Hydroxyapatite granules have been suggested as a substitute or to enhance morcellised bone allograft. We hypothesised that adding osteogenic protein-1 to a composite of bone allograft and non-resorbable hydroxyapatite granules (ProOsteon) would improve the incorporation of bone and implant fixation. We also compared the response to using ProOsteon alone against bone allograft used in isolation. We implanted two non-weight-bearing hydroxyapatite-coated implants into each proximal humerus of six dogs, with each implant surrounded by a concentric 3 mm gap. These gaps were randomly allocated to four different procedures in each dog: 1) bone allograft used on its own; 2) ProOsteon used on its own; 3) allograft and ProOsteon used together; or 4) allograft and ProOsteon with the addition of osteogenic protein-1. After three weeks osteogenic protein-1 increased bone formation and the energy absorption of implants grafted with allograft and ProOsteon. A composite of allograft, ProOsteon and osteogenic protein-1 was comparable, but not superior to, allograft used on its own. ProOsteon alone cannot be recommended as a substitute for allograft around non-cemented implants, but should be used to extend the volume of the graft, preferably with the addition of a growth factor

We have tested the axial and torsional stability of femoral components after revision arthroplasty in a cadaver model, using impacted morsellised cancellous graft and cement. Each one of six matched pairs of fresh frozen human femora had either a primary or a revision prosthesis cemented in place. For the ‘revision’ experiments, all cancellous bone was removed from the proximal femur which was then over-reamed to create a smooth-walled cortical shell. An MTS servohydraulic test frame was used to apply axial and torsional loads to each specimen through the prosthetic femoral heads with the femur submerged in isotonic saline solution at 37°C. The mean subsidence was 0.27 ± 0.17 mm for the primary and 0.52 ± 0.30 mm for the revision groups. The difference was statistically significant (p < 0.025), but the mean subsidence was < 1 mm in both groups. The mean maximum torque before failure was 42.9 ± 26.9 N-m for the primary and 34.8± 20.7 N-m for the revision groups. This difference was not statistically significant (p > 0.015). Based on our results we suggest that revision of the femoral component using morsellised cancellous graft followed by cementing with a collarless prosthesis with a polished tapered stem restores the integrity of the proximal femur and provides immediate stability of the implant

Limited success in regenerating large bone defects has been achieved by bridging them with osteoconductive materials. These substitutes lack the osteogenic and osteoinductive properties of bone autograft. A direct approach would be to stimulate osteogenesis in these biomaterials by the addition of fresh bone-marrow cells (BMC). We therefore created osteoperiosteal gaps 2 cm wide in the ulna of adult rabbits and either bridged them with coral alone (CC), coral supplemented with BMC, or left them empty. Coral was chosen as a scaffold because of its good biocompatibility and resorbability. In osteoperiosteal gaps bridged with coral only, the coral was invaded chiefly by fibrous tissue. It was insufficient to produce union after two months. In defects filled with coral and BMC an increase in osteogenesis was observed and the bone surface area was significantly higher compared with defects filled with coral alone. Bony union occurred in six out of six defects filled with coral and BMC after two months. An increase in the resorption of coral was also observed, suggesting that resorbing cells or their progenitors were present in bone marrow and survived the grafting procedure. Our findings have shown that supplementation of coral with BMC increased both the resorption of material and osteogenesis in defects of a clinical significance

We reconstructed defects in the infraspinatus tendon using polytetrafluoroethylene (PTFE) felt grafts in 31 beagle dogs and examined the mechanical responses and histocompatibility. Except for one infected specimen, all the reconstructed infraspinatus tendons healed. We examined eight specimens each immediately after surgery and at six and 12 weeks. The ultimate tensile strength of the reconstructed tendons was 60.84 N, 172.88 N, and 306.51 N immediately after surgery and at six and 12 weeks, respectively. The stiffness of the specimens at the PTFE felt-bone interface was 9.61 kN/m, 64.67 kN/m, and 135.09 kN/m immediately after surgery and at six and 12 weeks, respectively. Six tendons were examined histologically at three, six, 12 and 24 weeks. Histological analysis showed that there was ingrowth of fibrous tissue between the PTFE fibres. Foreign-body reactions were found at the margin of the PTFE-bone interface between 12 and 24 weeks. The mechanical recovery and tissue affinity of PTFE felt to bone and to tendon support its use for reconstruction of the rotator cuff. The possible development of a foreign-body reaction should be borne in mind

We studied the effects of irradiation on the reintegration of autologous osteoarticular grafts over a period of 24 weeks in a canine model. In 16 foxhounds the medial femoral condyle was resected, irradiated and immediately replanted. In the control group resection and replantation were performed without irradiation. Reintegration was assessed by macroscopic analysis, histology, radiography and gait analysis. Reintegration was equal at 12 weeks, but significantly inferior in the irradiated group after 24 weeks with delayed bone remodelling. The articular cartilage showed modest degeneration. Conventional radiography and histology showed corresponding changes. Limb function was adequate but the gait was inferior in the treated group

An experimental sheep model was used for impaction allografting of 12 hemiarthroplasty femoral components placed into two equal-sized groups. In group 1, a 50:50 mixture of ApaPore hydroxyapatite bone-graft substitute and allograft was used. In group 2, ApaPore and allograft were mixed in a 90:10 ratio. Both groups were killed at six months. Ground reaction force results demonstrated no significant differences (p > 0.05) between the two groups at 8, 16 and 24 weeks post-operatively, and all animals remained active. The mean bone turnover rates were significantly greater in group 1, at 0.00206 mm/day, compared to group 2 at 0.0013 mm/day (p < 0.05). The results for the area of new bone formation demonstrated no significant differences (p > 0.05) between the two groups. No significant differences were found between the two groups in thickness of the cement mantle (p > 0.05) and percentage ApaPore-bone contact (p > 0.05).

The results of this animal study demonstrated that a mixture of ApaPore allograft in a 90:10 ratio was comparable to using a 50:50 mixture.

Objectives. The aim of this experimental study on New Zealand’s white rabbits was to investigate the transplantation of autogenous growth plate cells in order to treat the injured growth plate. They were assessed in terms of measurements of radiological tibial varus and histological characteristics. . Methods. An experimental model of plate growth medial partial resection of the tibia in 14 New Zealand white rabbits was created. During this surgical procedure the plate growth cells were collected and cultured. While the second surgery was being performed, the autologous cultured growth plate cells were grafted at the right tibia, whereas the left tibia was used as a control group. . Results. Histological examinations showed that the grafted right tibia presented the regular shape of the plate growth with hypertrophic maturation, chondrocyte columniation and endochondral calcification. Radiological study shows that the mean tibial deformity at the left angle was 20.29° (6.25 to 33) and 7.21° (5 to 10) in the right angle. . Conclusion. This study has demonstrated that grafting of autogenous cultured growth plate cells into a defect of the medial aspect of the proximal tibial physis can prevent bone bridge formation, growth arrest and the development of varus deformity. Cite this article: Bone Joint Res 2014;3:310–16

We used an in vivo model to assess the use of an autogenous cancellous bone block and marrow graft for augmenting tendon reattachment to metallic implants. We hypothesised that augmentation of the tendon-implant interface with a bone block would enable retention of the graft on the implant surface, enhance biological integration, and result in more consistent functional outcomes compared with previously reported morcellised graft augmentation techniques. A significant improvement in functional weight-bearing was observed between six and 12 weeks. The significant increase in ground reaction force through the operated limb between six and 12 weeks was greater than that reported previously with morcellised graft augmented reconstructions. Histological appearance and collagen fibre orientation with bone block augmentation more closely resembled that of an intact enthesis compared with the morcellised grafting technique. Bone block augmentation of tendon-implant interfaces results in more reliable functional and histological outcomes, with a return to pre-operative levels of weight-bearing by 24 weeks

The complications of impaction bone grafting in revision hip replacement includes fracture of the femur and subsidence of the prosthesis. In this in vitro study we aimed to investigate whether the use of vibration, combined with a perforated tamp during the compaction of morsellised allograft would reduce peak loads and hoop strains in the femur as a surrogate marker of the risk of fracture and whether it would also improve graft compaction and prosthetic stability. We found that the peak loads and hoop strains transmitted to the femoral cortex during graft compaction and subsidence of the stem in subsequent mechanical testing were reduced. This innovative technique has the potential to reduce the risk of intra-operative fracture and to improve graft compaction and therefore prosthetic stability

Surgical reconstruction of articular surfaces by transplantation of osteochondral autografts has shown considerable promise in the treatment of focal articular lesions. During mosaicplasty, each cylindrical osteochondral graft is centred over the recipient hole and delivered by impacting the articular surface. Impact loading of articular cartilage has been associated with structural damage, loss of the viability of chondrocytes and subsequent degeneration of the articular cartilage. We have examined the relationship between single-impact loading and chondrocyte death for the specific confined-compression boundary conditions of mosaicplasty and the effect of repetitive impact loading which occurs during implantation of the graft on the resulting viability of the chondrocytes. Fresh bovine and porcine femoral condyles were used in this experiment. The percentage of chondrocyte death was found to vary logarithmically with single-impact energy and was predicted more strongly by the mean force of the impact rather than by the number of impacts required during placement of the graft. The significance of these results in regard to the surgical technique and design features of instruments for osteochondral transplantation is discussed

Allograft bone is widely used in orthopaedic surgery, but peri-operative infection of the graft remains a common and disastrous complication. The efficacy of systemic prophylactic antibiotics is unproven, and since the graft is avascular it is likely that levels of antibiotic in the graft are low. Using an electrical potential to accelerate diffusion of antibiotics into allograft bone, high levels were achieved in specimens of both sheep and human allograft. In human bone these ranged from 187.1 mg/kg in endosteal (. sd. 15.7) to 124.6 (. sd. 46.2) in periosteal bone for gentamicin and 31.9 (. sd. 8.9) in endosteal and 2.9 (. sd. 1.1) in periosteal bone for flucloxacillin. The antibiotics remained active against bacteria in vitro after iontophoresis and continued to elute from the allograft for up to two weeks. Structural allograft can be supplemented directly with antibiotics using iontophoresis. The technique is simple and inexpensive and offers a potential means of reducing the rate of peri-operative infection in allograft surgery. Iontophoresis into allograft bone may also be applicable to other therapeutic compounds

We developed an in vivo model of the attachment of a patellar tendon to a metal implant to simulate the reconstruction of an extensor mechanism after replacement of the proximal tibia. In 24 ewes, the patellar tendon was attached to a hydroxyapatite (HA)-coated titanium prosthesis. In 12, the interface was augmented with autograft containing cancellous bone and marrow. In the remaining ewes, the interface was not grafted. Kinematic gait analysis showed nearly normal function of the joint by 12 weeks. Force-plate assessment showed a significant increase in functional weight-bearing in the grafted animals (p = 0.043). The tendon-implant interface showed that without graft, encapsulation of fibrous tissue occurred. With autograft, a developing tendon-bone-HA-implant interface was observed at six weeks and by 12 weeks a layered tendon-fibrocartilage-bone interface was seen which was similar to a direct-type enthesis. With stable mechanical fixation, an appropriate bioactive surface and biological augmentation the development of a functional tendon-implant interface can be achieved

Soaking bone grafts in a bisphosphonate solution before implantation can prevent their resorption and increase the local bone density in rats and humans. However, recent studies suggest that pre-treatment of allografts with bisphosphonate can prevent bone ingrowth into impaction grafts. We tested the hypothesis that excessive amounts of bisphosphonate would also cause a negative response in less dense grafts. We used a model where non-impacted metaphyseal bone grafts were randomised into three groups with either no bisphosphonate, alendronate followed by rinsing, and alendronate without subsequent rinsing, and inserted into bone chambers in rats. The specimens were evaluated histologically at one week, and by histomorphometry and radiology at four weeks. At four weeks, both bisphosphonate groups showed an increase in the total bone content, increased newly formed bone, and higher radiodensity than the controls. In spite of being implanted in a chamber with a limited opportunity to diffuse, even an excessive amount of bisphosphonate improved the outcome. We suggest that the negative results seen by others could be due to the combination of densely compacted bone and a bisphosphonate. We suggest that bisphosphonates are likely to have a negative influence where resorption is a prerequisite to create space for new bone ingrowth

Objectives. The purpose of this study was to evaluate chronological changes in the collagen-type composition at tendon–bone interface during tendon–bone healing and to clarify the continuity between Sharpey-like fibres and inner fibres of the tendon. Methods. Male white rabbits were used to create an extra-articular bone–tendon graft model by grafting the extensor digitorum longus into a bone tunnel. Three rabbits were killed at two, four, eight, 12 and 26 weeks post-operatively. Elastica van Gieson staining was used to colour 5 µm coronal sections, which were examined under optical and polarised light microscopy. Immunostaining for type I, II and III collagen was also performed. Results. Sharpey-like fibres comprised of type III collagen in the early phase were gradually replaced by type I collagen from 12 weeks onwards, until continuity between the Sharpey-like fibres and inner fibres of the tendon was achieved by 26 weeks. Conclusions. Even in rabbits, which heal faster than humans, an observation period of at least 12 to 26 weeks is required, because the collagen-type composition of the Sharpey-like fibre bone–tendon connection may have insufficient pullout strength during this period. These results suggest that caution is necessary when permitting post-operative activity in humans who have undergone intra-bone tunnel grafts

The properties of impacted morsellised bone graft (MBG) in revision total knee arthroplasty (TKA) were studied in 12 horses. The left hind metatarsophalangeal joint was replaced by a human TKA. The horses were then randomly divided into graft and control groups. In the graft group, a unicondylar, lateral uncontained defect was created in the third metatarsal bone and reconstructed using autologous MBG before cementing the TKA. In the control group, a cemented TKA was implanted without the bone resection and grafting procedure. After four to eight months, the animals were killed and a biomechanical loading test was performed with a cyclic load equivalent to the horse’s body-weight to study mechanical stability. After removal of the prosthesis, the distal third metatarsal bone was studied radiologically, histologically and by quantitative and micro CT. Biomechanical testing showed that the differences in deformation between the graft and the control condyles were not significant for either elastic or time-dependent deformations. The differences in bone mineral density (BMD) between the graft and the control condyles were not significant. The BMD of the MBG was significantly lower than that in the other regions in the same limb. Micro CT showed a significant difference in the degree of anisotropy between the graft and host bone, even although the structure of the area of the MBG had trabecular orientation in the direction of the axial load. Histological analysis revealed that all the grafts were revascularised and completely incorporated into a new trabecular structure with few or no remnants of graft. Our study provides a basis for the clinical application of this technique with MBG in revision TKA

Objectives. Osteophytes are products of active endochondral and intramembranous ossification, and therefore could theoretically provide significant efficacy as bone grafts. In this study, we compared the bone mineralisation effectiveness of osteophytes and cancellous bone, including their effects on secretion of growth factors and anabolic effects on osteoblasts. Methods. Osteophytes and cancellous bone obtained from human patients were transplanted onto the calvaria of severe combined immunodeficient mice, with Calcein administered intra-peritoneally for fluorescent labelling of bone mineralisation. Conditioned media were prepared using osteophytes and cancellous bone, and growth factor concentration and effects of each graft on proliferation, differentiation and migration of osteoblastic cells were assessed using enzyme-linked immunosorbent assays, MTS ((3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium)) assays, quantitative real-time polymerase chain reaction, and migration assays. Results. After six weeks, the area of mineralisation was significantly higher for the transplanted osteophytes than for the cancellous bone (43803 μm. 2. , . sd. 14660 versus 9421 μm. 2. , . sd. 5032, p = 0.0184, one-way analysis of variance). Compared with cancellous bone, the conditioned medium prepared using osteophytes contained a significantly higher amounts of transforming growth factor (TGF)-β1 (471 pg/ml versus 333 pg/ml, p = 0.0001, Wilcoxon rank sum test), bone morphogenetic protein (BMP)-2 (47.75 pg/ml versus 32 pg/ml, p = 0.0214, Wilcoxon rank sum test) and insulin-like growth factor (IGF)-1 (314.5 pg/ml versus 191 pg/ml, p = 0.0418, Wilcoxon rank sum test). The stronger effects of osteophytes towards osteoblasts in terms of a higher proliferation rate, upregulation of gene expression of differentiation markers such as alpha-1 type-1 collagen and alkaline phosphate, and higher migration, compared with cancellous bone, was confirmed. Conclusion. We provide evidence of favourable features of osteophytes for bone mineralisation through a direct effect on osteoblasts. The acceleration in metabolic activity of the osteophyte provides justification for future studies evaluating the clinical use of osteophytes as autologous bone grafts. Cite this article: K. Ishihara, K. Okazaki, T. Akiyama, Y. Akasaki, Y. Nakashima. Characterisation of osteophytes as an autologous bone graft source: An experimental study in vivo and in vitro. Bone Joint Res 2017;6:73–81. DOI: 10.1302/2046-3758.62.BJR-2016-0199.R1

The role of bone-graft extenders in impaction revision surgery is becoming increasingly important. Tricalcium phosphate and hydroxyapatite have been shown to be both biocompatible and osteoconductive, yet many surgeons remain reluctant to use them. The difficulty in handling bone-graft extenders can be partly alleviated by using porous particles and adding clotted blood. In an in vitro model we measured the cohesive properties of various impaction graft mixes. Several factors were evaluated including the use of pure bone graft compared with mixes with extender, washing the bone and the addition of clotted blood. Our findings showed that pure allograft bone particles had significantly higher cohesion than when mixed with extender (p < 0.001). Washing had no effect on cohesion. The addition of clotted blood significantly increased the cohesion of both pure bone (p < 0.019) and mixes with pure bone and with porous graft extender (p < 0.044)

The use of impaction bone grafting during revision arthroplasty of the hip in the presence of cortical defects has a high risk of post-operative fracture. Our laboratory study addressed the effect of extramedullary augmentation and length of femoral stem on the initial stability of the prosthesis and the risk of fracture. Cortical defects in plastic femora were repaired using either surgical mesh without extramedullary augmentation, mesh with a strut graft or mesh with a plate. After bone impaction, standard or long-stem Exeter prostheses were inserted, which were tested by cyclical loading while measuring defect strain and migration of the stem. Compared with standard stems without extramedullary augmentation, defect strains were 31% lower with longer stems, 43% lower with a plate and 50% lower with a strut graft. Combining extramedullary augmentation with a long stem showed little additional benefit (p = 0.67). The type of repair did not affect the initial stability. Our results support the use of impaction bone grafting and extramedullary augmentation of diaphyseal defects after mesh containment

The use of impacted, morsellised bone grafts has become popular in revision total hip arthroplasty (THA). The initial stability of the reconstruction and the effectiveness of any subsequent process of revitalisation and incorporation will depend on the mechanical integrity of the graft. Our aim in this study was to document the time-dependent mechanical properties of the morsellised graft. This information is useful in clinical application of the graft, in studies of migration of the implant and in the design of the joint. We used 16 specimens of impacted, morsellised cancellous bone from the sternum of goats to assess the mechanical properties by confined compression creep tests. Consideration of the graft material as a porous, permeable solid, filled with fluid, allowed determination of the compressive modulus of the matrix, and its permeability to fluid flow. In all specimens the compression tests showed large, irreversible deformations, caused by flow-independent creep behaviour as a result of rolling and sliding of the bone chips. The mean permeability was 8.82 *10. −12. m. 4. /Ns (SD 43%), and the compressive modulus was 38.7 MPa (SD 34%). No correlation was found between the apparent density and the permeability or between the apparent density and the compressive modulus. The irreversible deformations in the graft could be captured by a creep law, for which the parameters were quantified. We conclude that in clinical use the graft is bound to be subject to permanent deformation after operation. The permeability of the material is relatively high compared with, for example, human cartilage. The confined compression modulus is relatively low compared with cancellous bone of the same apparent density. Designs of prostheses used in revision surgery must accommodate the viscoelastic and permanent deformations in the graft without causing loosening at the interface

We examined solvent-dried, gamma-irradiated (SD-R) allografts and fresh-frozen (FF) allografts mechanically and morphologically. Before transplantation, FF grafts were more than six times stronger than SD-R grafts. After four weeks, the tensile strength was about the same in both groups. At 24 weeks only collagen fibrils of small diameter were observed in the SD-R grafts while in FF grafts fibrils of small and intermediate diameter were seen. Clinically, we suggest that SD-R grafts could be used as a favourable alternative to FF grafts if care was taken regarding their initial mechanical weakness

In order to clarify the role of cytokines in the remodelling of the grafted tendon for ligament reconstruction we compared the responses to interleukin (IL)-1β, platelet-derived growth factor (PDGF)-BB and transforming growth factor (TGF)-β1 of extrinsic fibroblasts infiltrating the frozen-thawed patellar tendon in rats with that of the normal tendon fibroblasts, in regard to the gene expression of matrix metalloproteinase (MMP)-13, using Northern blot analysis. We also examined, immunohistologically, the local expression of IL-1β, PDGF-BB, and TGF-β1 in fibroblasts infiltrating the frozen-thawed patellar tendon. Northern blot analysis showed that fibroblasts derived from the patellar tendon six weeks after the freeze-thaw procedure in situ showed less response to IL-1β than normal tendon fibroblasts with respect to MMP-13 mRNA gene expression. The immunohistological findings revealed that IL-1β was over-expressed in extrinsic fibroblasts which infiltrated the patellar tendon two and six weeks after the freeze-thaw procedure in situ, but neither PDGF-BB nor TGF-β1 was over-expressed in these extrinsic fibroblasts. Our findings indicated that IL-1β had a close relationship to matrix remodelling of the grafted tendon for ligament reconstruction, in addition to the commencement of inflammation during the tissue-healing process

Objectives. We sought to determine if a durable bilayer implant composed of trabecular metal with autologous periosteum on top would be suitable to reconstitute large osteochondral defects. This design would allow for secure implant fixation, subsequent integration and remodeling. Materials and Methods. Adult sheep were randomly assigned to one of three groups (n = 8/group): 1. trabecular metal/periosteal graft (TMPG), 2. trabecular metal (TM), 3. empty defect (ED). Cartilage and bone healing were assessed macroscopically, biochemically (type II collagen, sulfated glycosaminoglycan (sGAG) and double-stranded DNA (dsDNA) content) and histologically. Results. At 16 weeks post-operatively, histological scores amongst treatment groups were not statistically different (TMPG: overall 12.7, cartilage 8.6, bone 4.1; TM: overall 14.2, cartilage 9.5, bone 4.9; ED: overall 13.6, cartilage 9.1, bone 4.5). Metal scaffolds were incorporated into the surrounding bone, both in TM and TMPG. The sGAG yield was lower in the neo-cartilage regions compared with the articular cartilage (AC) controls (TMPG 20.8/AC 39.5, TM 25.6/AC 33.3, ED 32.2/AC 40.2 µg sGAG/1 mg respectively), with statistical significance being achieved for the TMPG group (p < 0.05). Hypercellularity of the neo-cartilage was found in TM and ED, as the dsDNA content was significantly higher (p < 0.05) compared with contralateral AC controls (TM 126.7/AC 71.1, ED 99.3/AC 62.8 ng dsDNA/1 mg). The highest type II collagen content was found in neo-cartilage after TM compared with TMPG and ED (TM 60%/TMPG 40%/ED 39%). Inter-treatment differences were not significant. Conclusions. TM is a highly suitable material for the reconstitution of osseous defects. TM enables excellent bony ingrowth and fast integration. However, combined with autologous periosteum, such a biocomposite failed to promote satisfactory neo-cartilage formation. Cite this article: E. H. Mrosek, H-W. Chung, J. S. Fitzsimmons, S. W. O’Driscoll, G. G. Reinholz, J. C. Schagemann. Porous tantalum biocomposites for osteochondral defect repair: A follow-up study in a sheep model. Bone Joint J 2016;5:403–411. DOI: 10.1302/2046-3758.59.BJR-2016-0070.R1

Two acetabula which contained large bone allografts introduced at revision arthroplasty were obtained at post-mortem. The allografts had been placed in superior defects to support cementless acetabular components, and both hips were functioning well at the time of death. Clinical radiographs demonstrated apparent healing of graft to host bone, no graft collapse and stability of the acetabular components. Microscopic examination of sections through these specimens showed that the bulk allografts were encapsulated in fibrous tissue. Vascularity was increased at the host-graft interface, but there was limited evidence of bone union between the graft and the host. In the few areas where union had occurred, revascularisation extended no more than 2 mm beyond the graft-host interface. Within the body of the graft, the acellular matrix of trabecular bone maintained structural integrity up to 48 months after surgery. In areas where the allograft was adjacent to an implant, there was fibrous tissue orientated parallel to the implant surface. The acetabulum which contained a porous-coated component showed evidence of bone growth into the porous surface where it was in contact with viable host bone. No ingrowth occurred in areas where the porous coating was in contact with the graft. Although the grafts were functioning well, allograft revascularisation and remodelling were minimal, and the radiological appearance of healing did not correlate with histological findings

We compared the ability of three different posterior cruciate ligament (PCL) reconstructions to restore normal anteroposterior laxity to the knee from 0 to 130° of knee flexion. Cadaver knees were tested intact, after PCL rupture or after bone-patellar tendon-bone grafting. Grafts were performed isometrically or with a single bundle representing the anatomical anterior PCL fibre bulk (aPC) or with a double bundle that added the posterior PCL fibre bulk (pPC). The grafts were tensioned to restore normal knee laxity at 60° of flexion, except for the pPC which was tensioned at 130°. The isometric graft led to overconstraint as the knee extended resulting in high graft tension in extension and excess laxity in flexion. The aPC graft matched normal laxity from 0 to 60° of flexion but was lax from 90 to 130° of flexion. Only the double-bundled graft could restore normal knee laxity across the full range of flexion

Free patellar tendon grafts used for the intra-articular replacement of ruptured anterior cruciate ligaments (ACL) lack perfusion at the time of implantation. The central core of the graft undergoes a process of ischaemic necrosis which may result in failure. Early reperfusion of the graft may diminish the extent of this process. We assessed the role of peritendinous connective tissue in the revascularisation of the patellar tendon graft from the day of implantation up to 24 days in a murine model using intravital microscopy. The peritendinous connective-tissue envelope of the graft was either completely removed, partially removed or not stripped before implantation into dorsal skinfold chambers of recipient mice. Initial revascularisation of the grafts with preserved peritendinous connective tissues began after two days. The process was delayed by five to six times in completely stripped patellar tendons (p < 0.05). Only grafts with preserved connective tissues showed high viability whereas those which were completely stripped appeared to be subvital. The presence of peritendinous connective tissues accelerates the revascularisation of free patellar tendon grafts

We studied various aspects of graft impaction and penetration of cement in an experimental model. Cancellous bone was removed proximally and local diaphyseal lytic defects were simulated in six human cadaver femora. After impaction grafting the specimens were sectioned and prepared for histomorphometric analysis. The porosity of the graft was lowest in Gruen zone 4 (52%) and highest in Gruen zone 1 (76%). At the levels of Gruen zones 6 and 2 the entire cross-section was almost filled with cement. Cement sometimes reached the endosteal surface in other Gruen zones. The mean peak impaction forces exerted with the impactors were negatively correlated with the porosity of the graft

We studied peridural fibrosis in 16 dogs after laminectomies at the L2, L4 and L6 levels. They received either a free fat graft, a biodegradable mechanical barrier (polyethylene oxide (PEO)/polybutylene terephthalate (PBT) copolymer), or no treatment. The animals were killed after 4, 12, 26 and 52 weeks. Histomorphometry showed extensive and consistent peridural fibrosis in control and PEO/PBT groups. Fat grafts produced significantly less fibrous tissue, but the presence of the fat graft in the bony defect prevented closure. Degradation of the PEO/PBT barrier resulted in the formation of more fibrous tissue. We conclude that up to one year a free fat graft is effective in reducing the amount of peridural scarring

We used fresh small-fragment osteochondral allografts to reconstruct post-traumatic osteochondral defects in 126 knees of 123 patients with a mean age of 35 years. At a mean follow-up of 7.5 years (2 to 20), 108 knees were rated as successful (85%) and 18 had failed (15%). The factors related to failure included age over 50 years (p = 0.008), bipolar defects (p < 0.05), malaligned knees with overstressing of the grafts, and workers’ compensation cases (p < 0.04). Collapse of the graft by more than 3 mm and of the joint space of more than 50% were seen more frequently in radiographs of failed grafts. Our encouraging clinical results for fresh small-fragment osteochondral allografts show that they are indicated for unipolar post-traumatic osteochondral defects of the knee in young active patients

Objectives. Lengthening osteotomies of the calcaneus in children are in general grafted with bone from the iliac crest. Artificial bone grafts have been introduced, however, their structural and clinical durability has not been documented. Radiostereometric analysis (RSA) is a very accurate and precise method for measurements of rigid body movements including the evaluation of joint implant and fracture stability, however, RSA has not previously been used in clinical studies of calcaneal osteotomies. We assessed the precision of RSA as a measurement tool in a lateral calcaneal lengthening osteotomy (LCLO). Methods. LCLO was performed in six fixed adult cadaver feet. Tantalum markers were inserted on each side of the osteotomy and in the cuboideum. Lengthening was done with a plexiglas wedge. A total of 24 radiological double examinations were obtained. Two feet were excluded due to loose and poorly dispersed markers. Precision was assessed as systematic bias and 95% repeatability limits. Results. Systematic bias was generally below 0.10 mm for translations. Precision of migration measurements was below 0.2 mm for translations in the osteotomy. Conclusion. RSA is a precise tool for the evaluation of stability in LCLO. Cite this article: Bone Joint Res 2015;4:78–83

We revised 24 consecutive hips with loosening of the femoral stem using impaction allograft and a cemented stem with an unpolished proximal surface. Repeated radiostereometric examinations for up to two years showed a slow rate of subsidence with a mean of 0.32 mm (−2.0 to +0.31). Fifteen cases followed for a further year showed the same mean subsidence after three years, indicating stabilisation. A tendency to retroversion of the stems was noted between the operation and the last follow-up. Retroversion was also recorded when displacement of the stem was studied in ten of the patients after two years. Repeated determination of bone mineral density showed an initial loss after six months, followed by recovery to the postoperative level at two years. Defects in the cement mantle and malalignment of the stem were often noted on postoperative radiographs, but did not correlate with the degrees of migration or displacement. After one year, increasing frequency of trabecular remodelling or resorption of the graft was observed in the greater trochanter and distal to the tip of the stem. Cortical repair was noted distally and medially (Gruen regions 3, 5 and 6). Migration of the stems was the lowest reported to date, which we attribute to the improved grafting technique and to the hardness of the graft

Impaction allograft is an established method of securing initial stability of an implant in arthroplasty. Subsequent bone integration can be prolonged, and the volume of allograft may not be maintained. Intermittent administration of parathyroid hormone has an anabolic effect on bone and may therefore improve integration of an implant. Using a canine implant model we tested the hypothesis that administration of parathyroid hormone may improve osseointegration of implants surrounded by bone graft. In 20 dogs a cylindrical porous-coated titanium alloy implant was inserted into normal cancellous bone in the proximal humerus and surrounded by a circumferential gap of 2.5 mm. Morsellised allograft was impacted around the implant. Half of the animals were given daily injections of human parathyroid hormone (1–34) 5 μg/kg for four weeks and half received control injections. The two groups were compared by mechanical testing and histomorphometry. We observed a significant increase in new bone formation within the bone graft in the parathyroid hormone group. There were no significant differences in the volume of allograft, bone-implant contact or in the mechanical parameters. These findings suggest that parathyroid hormone improves new bone formation in impacted morsellised allograft around an implant and retains the graft volume without significant resorption. Fixation of the implant was neither improved nor compromised at the final follow-up of four weeks

Aternatives to autogenous bone graft for spinal fusion have been investigated for many years. It has been shown that osteoconductive materials alone do not give a rate of fusion which is comparable to that of autogenous bone graft. We analysed the effectiveness of porous ceramic loaded with cultured mesenchymal stem cells as a new graft material for spinal fusion in an animal model. Posterolateral fusion was carried out at the L4/L5 level in 40 White New Zealand rabbits using one of the following graft materials: porous ceramic granules plus cultured mesenchymal stem cells (group I); ceramic granules plus fresh autogenous bone marrow (group II); ceramic granules alone (group III); and autogenous bone graft (group IV). The animals were killed eight weeks after surgery and the spines were evaluated radiographically, by a manual palpation test and by histological analysis. The rate of fusion was significantly higher in group I compared with group III and higher, but not significantly, in group I compared with groups II and IV. In group I histological analysis showed newly formed bone in contact with the implanted granules and highly cellular bone marrow between the newly formed trabecular bone. In group II, thin trabeculae of newly formed bone were present in the peripheral portion of the fusion mass. In group III, there was a reduced mount of newly formed bone and abundant fibrous tissue. In group IV, there were thin trabeculae of newly formed bone close to the decorticated transverse processes and dead trabecular bone in the central portion of the fusion mass. In vitro cultured mesenchymal stem cells may be loaded into porous ceramic to make a graft material for spinal fusion which appears to be more effective than porous ceramic alone. Further studies are needed to investigate the medium- to long-term results of this procedure, its feasibility in the clinical setting and the most appropriate carrier for mesenchymal stem cells

This study explored the relationship between the initial stability of the femoral component and penetration of cement into the graft bed following impaction allografting. Impaction allografting was carried out in human cadaveric femurs. In one group the cement was pressurised conventionally but in the other it was not pressurised. Migration and micromotion of the implant were measured under simulated walking loads. The specimens were then cross-sectioned and penetration of the cement measured. Around the distal half of the implant we found approximately 70% and 40% of contact of the cement with the endosteum in the pressure and no-pressure groups, respectively. The distal migration/micromotion, and valgus/varus migration were significantly higher in the no-pressure group than in that subjected to pressure. These motion components correlated negatively with the mean area of cement and its contact with the endosteum. The presence of cement at the endosteum appears to play an important role in the initial stability of the implant following impaction allografting

We examined the mechanical properties of Vicryl (polyglactin 910) mesh in vitro and assessed its use in vivo as a novel biomaterial to attach tendon to a hydroxyapatite-coated metal implant, the interface of which was augmented with autogenous bone and marrow graft. This was compared with tendon re-attachment using a compressive clamp device in an identical animal model. Two- and four-ply sleeves of Vicryl mesh tested to failure under tension reached 5.13% and 28.35% of the normal ovine patellar tendon, respectively. Four-ply sleeves supported gait in an ovine model with 67.05% weight-bearing through the operated limb at 12 weeks, without evidence of mechanical failure. Mesh fibres were visible at six weeks but had been completely resorbed by 12 weeks, with no evidence of chronic inflammation. The tendon-implant neoenthesis was predominantly an indirect type, with tendon attached to the bone-hydroxyapatite surface by perforating collagen fibres

The treatment of bony defects of the tibia at the time of revision total knee replacement is controversial. The place of compacted morsellised bone graft is becoming established, particularly in contained defects. It has previously been shown that the initial stability of impaction-grafted trays in the contained defects is equivalent to that of an uncemented primary knee replacement. However, there is little biomechanical evidence on which to base a decision in the treatment of uncontained defects. We undertook a laboratory-based biomechanical study comparing three methods of graft containment in segmental medial tibial defects and compared them with the use of a modular metal augment to bypass the defect. Using resin models of the proximal tibia with medial defects representing either 46% or 65% of the medial cortical rim, repair of the defect was accomplished using mesh, cement or a novel bag technique, after which impaction bone grafting was used to fill the contained defects and a tibial component was cemented in place. As a control, a cemented tibial component with modular metal augments was used in identical defects. All specimens were submitted to cyclical mechanical loading, during which cyclical and permanent tray displacement were determined. The results showed satisfactory stability with all the techniques except the bone bag method. Using metal augments gave the highest initial stability, but obviously lacked any potential for bone restoration

We studied bone-tendon healing using immunohistochemical methods in a rabbit model. Reconstruction of the anterior cruciate ligament was undertaken using semitendinosus tendon in 20 rabbits. Immunohistochemical evaluations were performed at one, two, four and eight weeks after the operation. The expression of CD31, RAM-11, VEGF, b-FGF, S-100 protein and collagen I, II and III in the bone-tendon interface was very similar to that in the endochondral ossification. Some of the type-III collagen in the outer layer of the graft, which was deposited at a very early phase after the operation, was believed to have matured into Sharpey-like fibres. However, remodelling of the tendon grafted into the bone tunnel was significantly delayed when compared with this ossification process. To promote healing, we believe that it is necessary to accelerate remodelling of the tendon, simultaneously with the augmentation of the ossification

Conventional non-steroidal anti-inflammatory drugs (NSAIDs) and newer specific cyclo-oxygenase-2 (cox-2) inhibitors are commonly used in musculoskeletal trauma and orthopaedic surgery to reduce the inflammatory response and pain. These drugs have been reported to impair bone metabolism. In reconstruction of the anterior cruciate ligament the hamstring tendons are mainly used as the graft of choice, and a prerequisite for good results is healing of the tendons in the bone tunnel. Many of these patients are routinely given NSAIDs or cox-2 inhibitors, although no studies have elucidated the effects of these drugs on tendon healing in the bone tunnel. In our study 60 female Wistar rats were randomly allocated into three groups of 20. One received parecoxib, one indometacin and one acted as a control. In all the rats the tendo-Achillis was released proximally from the calf muscles. It was then pulled through a drill hole in the distal tibia and sutured anteriorly. The rats were given parecoxib, indometacin or saline intraperitoneally twice daily for seven days. After 14 days the tendon/bone-tunnel interface was subjected to mechanical testing. Significantly lower maximum pull-out strength (p < 0.001), energy absorption (p < 0.001) and stiffness (p = 0.035) were found in rats given parecoxib and indometacin compared with the control group, most pronounced with parecoxib

We compared the biological characteristics of extrinsic fibroblasts infiltrating the patellar tendon with those of normal, intrinsic fibroblasts in the normal tendon in vitro. Infiltrative fibroblasts were isolated from the patellar tendons of rabbits six weeks after an in situ freeze-thaw treatment which killed the intrinsic fibroblasts. These intrinsic cells were also isolated from the patellar tendons of rabbits which had not been so treated. Proliferation and invasive migration into the patellar tendon was significantly slower for infiltrative fibroblasts than for normal tendon fibroblasts. Flow-cytometric analysis indicated that expression of α5β1 integrin at the cell surface was significantly lower in infiltrative fibroblasts than in normal tendon fibroblasts. The findings suggest that cellular proliferation and invasive migration of fibroblasts into the patellar tendon after necrosis are inferior to those of the normal fibroblasts. The inferior intrinsic properties of infiltrative fibroblasts may contribute to a slow remodelling process in the grafted tendon after ligament reconstruction

Cryopreserved patellar tendon allografts are often recommended for reconstruction of anterior cruciate ligaments (ACLs) because living donor fibroblasts are thought to promote repair. Animal studies, however, indicate that ligaments regenerate from recipient rather than donor cells. If applicable to man, these observations suggest that allograft cell viability is unimportant. We therefore used short tandem repeat analysis with polymerase chain reaction (PCR) amplification to determine the source of cells in nine human ACLs reconstructed with cryopreserved patellar tendon allografts. PCR amplification of donor and recipient DNA obtained before operation and DNA from the graft obtained two to ten months after transplantation revealed the genotype of cells and showed only recipient cells in the graft area. Rather than preserve the viability of donor cells, a technique is required which will facilitate the introduction of recipient cells into patellar tendon allografts

This study investigated the quality and quantity of healing of a bone defect following intramedullary reaming undertaken by two fundamentally different systems; conventional, using non-irrigated, multiple passes; or suction/irrigation, using one pass. The result of a measured re-implantation of the product of reaming was examined in one additional group. We used 24 Swiss mountain sheep with a mean tibial medullary canal diameter between 8 mm and 9 mm. An 8 mm ‘napkin ring’ defect was created at the mid-diaphysis. The wound was either surgically closed or occluded. The medullary cavity was then reamed to 11 mm. The Reamer/Irrigator/Aspirator (RIA) System was used for the reaming procedure in groups A (RIA and autofilling) and B (RIA, collected reamings filled up), whereas reaming in group C (Synream and autofilling) was performed with the Synream System. The defect was allowed to auto-fill with reamings in groups A and C, but in group B, the defect was surgically filled with collected reamings. The tibia was then stabilised with a solid locking Unreamed Humerus Nail (UHN), 9.5 mm in diameter. The animals were killed after six weeks. After the implants were removed, measurements were taken to assess the stiffness, strength and callus formation at the site of the defect. There was no significant difference between healing after conventional reaming or suction/irrigation reaming. A significant improvement in the quality of the callus was demonstrated by surgically placing captured reamings into the defect using a graft harvesting system attached to the aspirator device. This was confirmed by biomechanical testing of stiffness and strength. This study suggests it could be beneficial to fill cortical defects with reaming particles in clinical practice, if feasible

In impaction grafting of contained bone defects after revision joint arthroplasty the graft behaves as a friable aggregate and its resistance to complex forces depends on grading, normal load and compaction. Bone mills in current use produce a distribution of particle sizes more uniform than is desirable for maximising resistance to shear stresses. We have performed experiments in vitro using morsellised allograft bone from the femoral head which have shown that its mechanical properties improve with increasing normal load and with increasing shear strains (strain hardening). The mechanical strength also increases with increasing compaction energy, and with the addition of bioglass particles to make good the deficiency in small and very small fragments. Donor femoral heads may be milled while frozen without affecting the profile of the particle size. Osteoporotic femoral heads provide a similar grading of sizes, although fewer particles are obtained from each specimen. Our findings have implications for current practice and for the future development of materials and techniques

The healing of a hamstring graft to bone is the weak link in the reconstruction of a cruciate ligament using this donor material. We therefore investigated the augmentation of healing at the tendon-bone interface using calcium-phosphate cement (CPC). We performed semitendinosus autograft reconstructions of the anterior cruciate ligament on both knees of 22 New Zealand white rabbits. The interface between the grafted tendon and the bone tunnel for one knee was filled with CPC. Six rabbits were killed at the end of the first and second post-operative weeks in order to evaluate the biomechanical changes. Two rabbits were then killed sequentially at the end of weeks 1, 3, 6, 12 and 24 after operation and tissue removed for serial histological observation. Histological examination showed that the use of CPC produced early, diffuse and massive bone ingrowth. By contrast, in the non-CPC group of rabbits only a thin layer of new bone was seen. Mechanical pull-out testing at one week showed that the mean maximal tensile strength was 6.505 ± 1.333 N for the CPC group and 2.048 ± 0.950 N for the non-CPC group. At two weeks the values were 11.491 ± 2.865 N and 5.452 ± 3.955 N, respectively. Our findings indicate that CPC is a potentially promising material in clinical practice as regards its ability to reinforce the fixation of the tendon attachment to bone and to augment the overall effectiveness of tendon healing to bone

We analysed the bacterial contamination of 1999 bone allografts retrieved from 200 cadaver donors under sterile operating conditions. The effect of various factors on the relative risk of contamination was estimated using a multiple logistic regression model. Organisms of low pathogenicity were cultured from 50% of the grafts and of high pathogenicity from 3%. The risk of contamination with low pathogenic organisms (mainly skin commensals) increased by a factor of 1.6 for each member added to the procurement team. The risk of contamination with high pathogenic organisms (mainly contaminants from the gastrointestinal tract) was 3.4 times higher in donors with a traumatic cause of death and 5.2 times higher in those with a positive blood culture. Preceding organ procurement did not significantly influence the risk of contamination. Rinsing the graft with an antibiotic solution was not an effective decontamination method. The major source of contamination is exogenous and is strongly influenced by the procurement team. Contamination from endogenous sources can be controlled by donor selection. We discuss methods that can be used to decrease contamination and the rate of discarding of bone allografts

Composites of chondrocytes and polymerised fibrin were supplemented with insulin-like growth factor-I (IGF-I) during the arthroscopic repair of full-thickness cartilage defects in a model of extensive loss of cartilage in horses. Repairs facilitated with IGF-I and chondrocyte-fibrin composites, or control defects treated with chondrocyte-fibrin composites alone, were compared before death by the clinical appearance and repeated analysis of synovial fluid, and at termination eight months after surgery by tissue morphology, collagen typing, and biochemical assays. The structure of cartilage was evaluated histologically by Toluidine Blue reaction and collagen type-I and type-II in situ hybridisation and immunohistochemistry. Repair tissue was biochemically evaluated by DNA assay, proteoglycan quantitation and characterisation, assessment of collagen by reverse-phase high-performance liquid chromatography, and collagen typing using cyanogen bromide digestion and peptide separation by polyacrylamide gel electrophoresis. The results at eight months showed that the addition of IGF-I to chondrocyte grafts enhanced chondrogenesis in cartilage defects, including incorporation into surrounding cartilage. Gross filling of defects was improved, and the tissue contained a higher proportion of cells producing type-II collagen. Measurements of collagen type II showed improved levels in IGF-I-treated defects, supporting in situ hybridisation and immunohistochemical assessments of the defects. IGF-I improves the repair capabilities of chondrocyte-fibrin grafts in large full-thickness repair models

We performed biopsies during reoperation for minor complications in two active young patients 9 and 19 months after massive bone allograft implantation for bone tumour. The grafts were dead and resorption-apposition activity, when present, was predominantly in subperiosteal areas. Inflammatory infiltration was very seldom found. Features considered as ‘microfractures’ or ‘microcracks’ were noted in the cortical ring together with the formation of woven bone, in areas with remodelling. Such cracks are likely to be of mechanical origin and do not inevitably lead to complications

We have evaluated in vivo a novel, polymer-based, matrix for tissue engineering of bone. A segmental defect of 15 mm was created in the ulna of New Zealand white rabbits to determine the regenerative properties of a porous polylactide-co-glycolide matrix alone and in combination with autogenous marrow and/or the osteoinductive protein, BMP-7. In this study four implant groups were used: 1) matrix alone; 2) matrix with autogenous marrow; 3) matrix with 20 μg of BMP-7; and 4) matrix with 20 μg of BMP-7 and autogenous marrow. The results showed that the degree of bone formation was dependent on the properties of the graft material. The osteoconductive sintered matrix structure showed significant formation of bone at the implant-bone interface. The addition of autogenous marrow increased the penetration of new bone further into the central area of the matrix and also increased the degree of revascularisation. The osteoinductive growth factor BMP-7 induced penetration of new bone throughout the entire structure of the implant. The most effective treatment was with the combination of marrow cells and osteoinductive BMP-7

We analysed the cellular immune response in ten transplantations of different massive bone allografts, of which five had a poor clinical outcome. Cytotoxic T lymphocytes (CTL) and T helper lymphocytes (TH) against mismatched donor antigens were found in all patients. More importantly, CTL with a high affinity for donor antigens were found in five cases. High-affinity CTL need no CD8 molecule to stabilise the antigen binding and are strongly associated with rejection of heart and corneal transplants. Even after removal of most of the bone-marrow cells, we found high-affinity CTL and high TH frequencies. This T-cell response could be detected over a period of years. We conclude that frozen bone allografts can induce high-affinity donor-specific CTL. The present assay allows qualification and quantification of the levels of CTL and TH in the blood. This approach may be helpful in studying the effect of the immune response on the outcome of the graft

From November 1994 to March 1997, we harvested 137 grafts of the femoral head from 125 patients for donation during total hip arthroplasty according to the guidelines of the American Associations of Tissue Banks (AATB) and the European Association of Musculo-Skeletal transplantation (EAMST). In addition to the standards recommended by these authorities, we performed histopathological examination of a core biopsy of the retrieved bone allograft and of the synovium. Of the 137 allografts, 48 (35.0%) fulfilled all criteria and were free for donation; 31 (22.6%) were not regarded as suitable for transplantation because the serological retests at six months were not yet complete and 58 (42.3%) were discarded because of incomplete data. Of those discarded, five showed abnormal histopathological findings; three were highly suspicious of low-grade B-cell lymphoma, one of monoclonal plasmacytosis and the other of non-specific inflammation of bone marrow. However, according to the standards of the AATB or EAMST they all met the criteria and were eligible for transplantation. Our findings indicate that the incidence of abnormal histopathology in these retrieved allografts was 3.6%. Since it is essential to confirm the quality of donor bones in bone banking, we advise that histopathological screening of donor bone should be performed to exclude abnormal allografts

Our aim was to examine the potential of autologous perichondral tissue to form a meniscal replacement. In 18 mature sheep we performed a complete medial meniscectomy. The animals were then divided into two groups: 12 had a meniscal replacement using strips of autologous perichondral tissue explanted from the lower rib (group G) and six (group C) served as a control group without a meniscal replacement. In all animals restriction from weight-bearing was achieved by means of transection and partial resection of tendo Achillis. Six animals (four from group G and two from group C) were each killed at 3, 6 and 12 months. The grafts and the underlying articular cartilage were removed and studied by gross macroscopic examination, light microscopy, SEM, polarised light examination, and by biomechanical tests. In all the transplanted animals a new perichondral meniscus developed. After three months the transplants resembled normal menisci in size and thickness, while in the control animals only small rims of spontaneously grown tissue were seen. Microscopically, the perichondral menisci showed a normal orientation of collagen fibres and normal cellular characteristics, but in the central region, areas of calcification disturbed the regular tissue differentiation. Healing tissue in control animals lacked the normal fibre orientation and cellularity. SEM of perichondral menisci showed surface characteristics similar to those of normal sheep menisci without fissures and lacerations; the control specimens had these defects. The femoral and tibial cartilage in contact with the new menisci had normal surface characteristics apart from one animal with slight surface irregularities. Control animals showed superficial lesions after three months which increased at six to 12 months postoperatively. Microangiography of the newly grown tissue demonstrated a less intense vascularisation after three months when compared with normal menisci. The failure stress and tensile modulus of perichondral menisci were significantly lower than those of normal contralateral menisci, and spontaneously regenerated tissue in meniscectomised animals had even lower values. There were no significant differences in values between newly grown perichondral menisci and spontaneously grown tissue

Objectives

The objective of this study was to investigate the therapeutic effect of peripheral blood mononuclear cells (PBMNCs) treated with quality and quantity control culture (QQ-culture) to expand and fortify angiogenic cells on the acceleration of fracture healing.

Objectives

Mesenchymal stem cells have the ability to differentiate into various cell types, and thus have emerged as promising alternatives to chondrocytes in cell-based cartilage repair methods. The aim of this experimental study was to investigate the effect of bone marrow derived mesenchymal stem cells combined with platelet rich fibrin on osteochondral defect repair and articular cartilage regeneration in a canine model.

Objectives

To explore the therapeutic potential of combining bone marrow-derived mesenchymal stem cells (BM-MSCs) and hydroxyapatite (HA) granules to treat nonunion of the long bone.

Objectives

Regenerative medicine is an emerging field aimed at the repair and regeneration of various tissues. To this end, cytokines (CKs), growth factors (GFs), and stem/progenitor cells have been applied in this field. However, obtaining and preparing these candidates requires invasive, costly, and time-consuming procedures. We hypothesised that skeletal muscle could be a favorable candidate tissue for the concept of a point-of-care approach. The purpose of this study was to characterize and confirm the biological potential of skeletal muscle supernatant for use in regenerative medicine.

Objectives

After an injury, the biological reattachment of tendon to bone is a challenge because healing takes place between a soft (tendon) and a hard (bone) tissue. Even after healing, the transition zone in the enthesis is not completely regenerated, making it susceptible to re-injury. In this study, we aimed to regenerate Achilles tendon entheses (ATEs) in wounded rats using a combination of kartogenin (KGN) and platelet-rich plasma (PRP).

Objectives

We have observed clinical cases where bone is formed in the overlaying muscle covering surgically created bone defects treated with a hydroxyapatite/calcium sulphate biomaterial. Our objective was to investigate the osteoinductive potential of the biomaterial and to determine if growth factors secreted from local bone cells induce osteoblastic differentiation of muscle cells.

Objectives

The major problem with repair of an articular cartilage injury is the extensive difference in the structure and function of regenerated, compared with normal cartilage. Our work investigates the feasibility of repairing articular osteochondral defects in the canine knee joint using a composite lamellar scaffold of nano-ß-tricalcium phosphate (ß-TCP)/collagen (col) I and II with bone marrow stromal stem cells (BMSCs) and assesses its biological compatibility.

Objectives

The period of post-operative treatment before surgical wounds are completely closed remains a key window, during which one can apply new technologies that can minimise complications. One such technology is the use of negative pressure wound therapy to manage and accelerate healing of the closed incisional wound (incisional NPWT).

We evaluated two reconstruction techniques for a simulated posterolateral corner injury on ten pairs of cadaver knees. Specimens were mounted at 30° and 90° of knee flexion to record external rotation and varus movement. Instability was created by transversely sectioning the lateral collateral ligament at its midpoint and the popliteus tendon was released at the lateral femoral condyle. The left knee was randomly assigned for reconstruction using either a combined or fibula-based treatment with the right knee receiving the other. After sectioning, laxity increased in all the specimens. Each technique restored external rotatory and varus stability at both flexion angles to levels similar to the intact condition. For the fibula-based reconstruction method, varus laxity at 30° of knee flexion did not differ from the intact state, but was significantly less than after the combined method.

Both the fibula-based and combined posterolateral reconstruction techniques are equally effective in restoring stability following the simulated injury.

The treatment of osteochondral lesions and osteoarthritis remains an ongoing clinical challenge in orthopaedics. This review examines the current research in the fields of cartilage regeneration, osteochondral defect treatment, and biological joint resurfacing, and reports on the results of clinical and pre-clinical studies. We also report on novel treatment strategies and discuss their potential promise or pitfalls. Current focus involves the use of a scaffold providing mechanical support with the addition of chondrocytes or mesenchymal stem cells (MSCs), or the use of cell homing to differentiate the organism’s own endogenous cell sources into cartilage. This method is usually performed with scaffolds that have been coated with a chemotactic agent or with structures that support the sustained release of growth factors or other chondroinductive agents. We also discuss unique methods and designs for cell homing and scaffold production, and improvements in biological joint resurfacing. There have been a number of exciting new studies and techniques developed that aim to repair or restore osteochondral lesions and to treat larger defects or the entire articular surface. The concept of a biological total joint replacement appears to have much potential.

Cite this article: Bone Joint Res 2013;2:193–9.

We used demineralised bone matrix (DBM) to augment re-attachment of tendon to a metal prosthesis in an in vivo ovine model of reconstruction of the extensor mechanism at the knee. We hypothesised that augmentation of the tendon-implant interface with DBM would enhance the functional and histological outcomes as compared with previously reported control reconstructions without DBM. Function was assessed at six and 12 weeks postoperatively, and histological examination was undertaken at 12 weeks.

A significant increase of 23.5% was observed in functional weight-bearing at six weeks in the DBM-augmented group compared with non-augmented controls (p = 0.004). By 12 weeks augmentation with DBM resulted in regeneration of a more direct-type enthesis, with regions of fibrocartilage, mineralised fibrocartilage and bone. In the controls the interface was predominantly indirect, with the tendon attached to the bone graft-hydroxyapatite base plate by perforating collagen fibres.

For the treatment of ununited fractures, we developed a system of delivering magnetic labelled mesenchymal stromal cells (MSCs) using an extracorporeal magnetic device. In this study, we transplanted ferucarbotran-labelled and luciferase-positive bone marrow-derived MSCs into a non-healing femoral fracture rat model in the presence of a magnetic field. The biological fate of the transplanted MSCs was observed using luciferase-based bioluminescence imaging and we found that the number of MSC derived photons increased from day one to day three and thereafter decreased over time. The magnetic cell delivery system induced the accumulation of photons at the fracture site, while also retaining higher photon intensity from day three to week four. Furthermore, radiological and histological findings suggested improved callus formation and endochondral ossification. We therefore believe that this delivery system may be a promising option for bone regeneration.

We used interconnected porous calcium hydroxyapatite ceramic to bridge a rabbit ulnar defect. Two weeks after inducing the defect we percutaneously injected rabbit bone marrow-derived mesenchymal stromal cells labelled with ferumoxide. The contribution of an external magnetic targeting system to attract these cells into the ceramic and their effect on subsequent bone formation were evaluated.

This technique significantly facilitated the infiltration of ferumoxide-labelled cells into ceramic and significantly contributed to the enhancement of bone formation even in the chronic phase. As such, it is potentially of clinical use to treat fractures, bone defects, delayed union and nonunion.

We welcome letters to the Editor concerning articles that have recently been published. Such letters will be subject to the usual stages of selection and editing; where appropriate the authors of the original article will be offered the opportunity to reply.

The purpose of this anatomical study was to explore the morphological variations of the semitendinosus and gracilis tendons in length and cross-section and the statistical relationship between length, cross-section, and body height.

We studied the legs of 93 humans in 136 cadavers. In 43 specimens (46.2%) it was possible to harvest the tendons from both legs.

We found considerable differences in the length and cross-section of the semitendinosus and the gracilis tendons with a significant correlation between the two. A correlation between the length of the femur, reflecting height, and the length of the tendons was only observed in specimens harvested from women. The reason for this gender difference was unclear. Additionally, there was a correlation between the cross-sectional area of the tendons and the length of the femur. Surgeons should be aware of the possibility of encountering insufficient length of tendon when undertaking reconstructive surgery as a result of anatomical variations between patients.

We attempted to repair full-thickness defects in the articular cartilage of the trochlear groove of the femur in 30 rabbit knee joints using allogenic cultured chondrocytes embedded in a collagen gel. The repaired tissues were examined at 2, 4, 8, 12 and 24 weeks after operation using histological and histochemical methods. The articular defect filling index measurement was derived from safranin-O stained sections. Apoptotic cellular fractions were derived from analysis of apoptosis in situ using TUNEL staining, and was confirmed using caspase-3 staining along with quantification of the total cellularity. The mean articular defect filling index decreased with time. After 24 weeks it was 0.7 (sd 0.10), which was significantly lower than the measurements obtained earlier (p < 0.01). The highest mean percentage of apoptotic cells were observed at 12 weeks, although the total cellularity decreased with time. Because apoptotic cell death may play a role in delamination after chondrocyte transplantation, anti-apoptotic gene therapy may protect transplanted chondrocytes from apoptosis.

We investigated the antibiotic concentration in fresh-frozen femoral head allografts harvested from two groups of living donors. Ten samples were collected from patients with osteoarthritis of the hip and ten from those with a fracture of the neck of the femur scheduled for primary arthroplasty. Cefazolin (1 g) was administered as a pre-operative prophylactic antibiotic. After storage at −80°C for two weeks the pattern of release of cefazolin from morsellised femoral heads was evaluated by an in vitro broth elution assay using high-performance liquid chromatography. The bioactivity of the bone was further determined with an agar disc diffusion and standardised tube dilution bioassay. The results indicated that the fresh-frozen femoral heads contained cefazolin. The morsellised bone released cefazolin for up to four days. The concentration of cefazolin was significantly higher in the heads from patients with osteoarthritis of the hip than in those with a fracture. Also, in bioassays the bone showed inhibitory effects against bacteria.

We concluded that allografts of morsellised bone from the femoral head harvested from patients undergoing arthroplasty of the hip contained cefazolin, which had been administered pre-operatively and they exhibited inhibitory effects against bacteria in vitro.

Ovine articular chondrocytes were isolated from cartilage biopsy and culture expanded in vitro. Approximately 30 million cells per ml of cultured chondrocytes were incorporated with autologous plasma-derived fibrin to form a three-dimensional construct. Full-thickness punch hole defects were created in the lateral and medial femoral condyles. The defects were implanted with either an autologous ‘chondrocyte-fibrin’ construct (ACFC), autologous chondrocytes (ACI) or fibrin blanks (AF) as controls. Animals were killed after 12 weeks. The gross appearance of the treated defects was inspected and photographed. The repaired tissues were studied histologically and by scanning electron microscopy analysis.

All defects were assessed using the International Cartilage Repair Society (ICRS) classification. Those treated with ACFC, ACI and AF exhibited median scores which correspond to a nearly-normal appearance. On the basis of the modified O’Driscoll histological scoring scale, ACFC implantation significantly enhanced cartilage repair compared to ACI and AF. Using scanning electron microscopy, ACFC and ACI showed characteristic organisation of chondrocytes and matrices, which were relatively similar to the surrounding adjacent cartilage.

Implantation of ACFC resulted in superior hyaline-like cartilage regeneration when compared with ACI. If this result is applicable to humans, a better outcome would be obtained than by using conventional ACI.

The aim of this study was to evaluate the cultivation potential of cartilage taken from the debrided edge of a chronic lesion of the articular surface. A total of 14 patients underwent arthroscopy of the knee for a chronic lesion on the femoral condyles or trochlea. In addition to the routine cartilage biopsy, a second biopsy of cartilage was taken from the edge of the lesion. The cells isolated from both sources underwent parallel cultivation as monolayer and three-dimensional (3D) alginate culture. The cell yield, viability, capacity for proliferation, morphology and the expressions of typical cartilage genes (collagen I, COL1; collagen II, COL2; aggrecan, AGR; and versican, VER) were assessed. The cartilage differentiation indices (COL2/COL1, AGR/VER) were calculated. The control biopsies revealed a higher mean cell yield (1346 cells/mg vs 341 cells/mg), but similar cell proliferation, viability and morphology compared with the cells from the edge of the lesion. The cartilage differentiation indices were superior in control cells: COL2/COL1 (threefold in biopsies (non-significant)); sixfold in monolayer cultures (p = 0.012), and 7.5-fold in hydrogels (non-significant), AGR/VER (sevenfold in biopsies (p = 0.04), threefold (p = 0.003) in primary cultures and 3.5-fold in hydrogels (non-significant)).

Our results suggest that the cultivation of chondrocytes solely from the edges of the lesion cannot be recommended for use in autologous chondrocyte implantation.

Gene therapy with insulin-like growth factor-1 (IGF-1) increases matrix production and enhances chondrocyte proliferation and survival in vitro. The purpose of this study was to determine whether arthroscopically-grafted chondrocytes genetically modified by an adenovirus vector encoding equine IGF-1 (AdIGF-1) would have a beneficial effect on cartilage healing in an equine femoropatellar joint model.

A total of 16 horses underwent arthroscopic repair of a single 15 mm cartilage defect in each femoropatellar joint. One joint received 2 × 10⁷ AdIGF-1 modified chondrocytes and the contralateral joint received 2 × 10⁷ naive (unmodified) chondrocytes. Repairs were analysed at four weeks, nine weeks and eight months after surgery. Morphological and histological appearance, IGF-1 and collagen type II gene expression (polymerase chain reaction, in situ hybridisation and immunohistochemistry), collagen type II content (cyanogen bromide and sodium dodecyl sulphate-polyacrylamide gel electrophoresis), proteoglycan content (dimethylmethylene blue assay), and gene expression for collagen type I, matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, aggrecanase-1, tissue inhibitor of matrix metalloproteinase-1 (TIMP-1) and TIMP-3 were evaluated.

Genetic modification of chondrocytes significantly increased IGF-1 mRNA and ligand production in repair tissue for up to nine weeks following transplantation. The gross and histological appearance of IGF-1 modified repair tissue was improved over control defects. Gross filling of defects was significantly improved at four weeks, and a more hyaline-like tissue covered the lesions at eight months. Histological outcome at four and nine weeks post-transplantation revealed greater tissue filling of defects transplanted with genetically modified chondrocytes, whereas repair tissue in control defects was thin and irregular and more fibrous. Collagen type II expression in IGF-1 gene-transduced defects was increased 100-fold at four weeks and correlated with increased collagen type II immunoreaction up to eight months.

Genetic modification of chondrocytes with AdIGF-1 prior to transplantation improved early (four to nine weeks), and to a lesser degree long-term, cartilage healing in the equine model.

The equine model of cartilage healing closely resembles human clinical cartilage repair. The results of this study suggest that cartilage healing can be enhanced through genetic modification of chondrocytes prior to transplantation.

In this study a combination of autologous chondrocyte implantation (ACI) and the osteochondral autograft transfer system (OATS) was used and evaluated as a treatment option for the repair of large areas of degenerative articular cartilage. We present the results at three years post-operatively. Osteochondral cores were used to restore the contour of articular cartilage in 13 patients with large lesions of the lateral femoral condyle (n = 5), medial femoral condyle (n = 7) and patella (n = 1). Autologous cultured chondrocytes were injected underneath a periosteal patch covering the cores. After one year, the patients had a significant improvement in their symptoms and after three years this level of improvement was maintained in ten of the 13 patients. Arthroscopic examination revealed that the osteochondral cores became well integrated with the surrounding cartilage. We conclude that the hybrid ACI/OATS technique provides a promising surgical approach for the treatment of patients with large degenerative osteochondral defects.

Objectives

To review the systemic impact of smoking on bone healing as evidenced within the orthopaedic literature.

Objectives

Recent studies have shown that modulating inflammation-related lipid signalling after a bone fracture can accelerate healing in animal models. Specifically, decreasing 5-lipoxygenase (5-LO) activity during fracture healing increases cyclooxygenase-2 (COX-2) expression in the fracture callus, accelerates chondrogenesis and decreases healing time. In this study, we test the hypothesis that 5-LO inhibition will increase direct osteogenesis.

We compared the quality of debridement of chondral lesions performed by four arthroscopic (SH, shaver; CU, curette; SHCU, shaver and curette; BP, bipolar electrodes) and one open technique (OPEN, scalpel and curette) which are used prior to autologous chondrocyte implantation (ACI). The ex vivo simulation of all five techniques was carried out on six juvenile equine stifle joints. The OPEN, SH and SHCU techniques were tested on knees harvested from six adult human cadavers.

The most vertical walls with the least adjacent damage to cartilage were obtained with the OPEN technique. The CU and SHCU methods gave inferior, but still acceptable results whereas the SH technique alone resulted in a crater-like defect and the BP method undermined the cartilage wall. The subchondral bone was severely violated in all the equine samples which might have been peculiar to this model. The predominant depth of the debridement in the adult human samples was at the level of the calcified cartilage. Some minor penetrations of the subchondral end-plate were induced regardless of the instrumentation used.

Our study suggests that not all routine arthroscopic instruments are suitable for the preparation of a defect for ACI. We have shown that the preferred debridement technique is either open or arthroscopically-assisted manual curettage. The use of juvenile equine stifles was not appropriate for the study of the cartilage-subchondral bone interface.

We evaluated the histological changes before and after fixation in ten knees of ten patients with osteochondritis dissecans who had undergone fixation of the unstable lesions. There were seven males and three females with a mean age of 15 years (11 to 22). The procedure was performed either using bio-absorbable pins only or in combination with an autologous osteochondral plug. A needle biopsy was done at the time of fixation and at the time of a second-look arthroscopy at a mean of 7.8 months (6 to 9) after surgery.

The biopsy specimens at the second-look arthroscopy showed significant improvement in the histological grading score compared with the pre-fixation scores (p < 0.01). In the specimens at the second-look arthroscopy, the extracellular matrix was stained more densely than at the time of fixation, especially in the middle to deep layers of the articular cartilage.

Our findings show that articular cartilage regenerates after fixation of an unstable lesion in osteochondritis dissecans.

This review is aimed at clinicians appraising preclinical trauma studies and researchers investigating compromised bone healing or novel treatments for fractures. It categorises the clinical scenarios of poor healing of fractures and attempts to match them with the appropriate animal models in the literature.

We performed an extensive literature search of animal models of long bone fracture repair/nonunion and grouped the resulting studies according to the clinical scenario they were attempting to reflect; we then scrutinised them for their reliability and accuracy in reproducing that clinical scenario.

Models for normal fracture repair (primary and secondary), delayed union, nonunion (atrophic and hypertrophic), segmental defects and fractures at risk of impaired healing were identified. Their accuracy in reflecting the clinical scenario ranged greatly and the reliability of reproducing the scenario ranged from 100% to 40%.

It is vital to know the limitations and success of each model when considering its application.

We developed a new porous scaffold made from a synthetic polymer, poly(DL-lactide-co-glycolide) (PLG), and evaluated its use in the repair of cartilage. Osteochondral defects made on the femoral trochlear of rabbits were treated by transplantation of the PLG scaffold, examined histologically and compared with an untreated control group.

Fibrous tissue was initially organised in an arcade array with poor cellularity at the articular surface of the scaffold. The tissue regenerated to cartilage at the articular surface. In the subchondral area, new bone formed and the scaffold was absorbed. The histological scores were significantly higher in the defects treated by the scaffold than in the control group (p < 0.05).

Our findings suggest that in an animal model the new porous PLG scaffold is effective for repairing full-thickness osteochondral defects without cultured cells and growth factors.

Critical size defects in ovine tibiae, stabilised with intramedullary interlocking nails, were used to assess whether the addition of carboxymethylcellulose to the standard osteogenic protein-1 (OP-1/BMP-7) implant would affect the implant’s efficacy for bone regeneration. The biomaterial carriers were a ‘putty’ carrier of carboxymethylcellulose and bovine-derived type-I collagen (OPP) or the standard with collagen alone (OPC). These two treatments were also compared to “ungrafted” negative controls. Efficacy of regeneration was determined using radiological, biomechanical and histological evaluations after four months of healing. The defects, filled with OPP and OPC, demonstrated radiodense material spanning the defect after one month of healing, with radiographic evidence of recorticalisation and remodelling by two months. The OPP and OPC treatment groups had equivalent structural and material properties that were significantly greater than those in the ungrafted controls. The structural properties of the OPP- and OPC-treated limbs were equivalent to those of the contralateral untreated limb (p > 0.05), yet material properties were inferior (p < 0.05). Histopathology revealed no residual inflammatory response to the biomaterial carriers or OP-1. The OPP- and OPC-treated animals had 60% to 85% lamellar bone within the defect, and less than 25% of the regenerate was composed of fibrous tissue. The defects in the untreated control animals contained less than 40% lamellar bone and more than 60% was fibrous tissue, creating full cortical thickness defects. In our studies carboxymethylcellulose did not adversely affect the capacity of the standard OP-1 implant for regenerating bone.

We hypothesised that meniscal tears treated with mesenchymal stem cells (MSCs) together with a conventional suturing technique would show improved healing compared with those treated by a conventional suturing technique alone. In a controlled laboratory study 28 adult pigs (56 knees) underwent meniscal procedures after the creation of a radial incision to represent a tear. Group 1 (n = 9) had a radial meniscal tear which was left untreated. In group 2 (n = 19) the incision was repaired with sutures and fibrin glue and in group 3, the experimental group (n = 28), treatment was by MSCs, suturing and fibrin glue.

At eight weeks, macroscopic examination of group 1 showed no healing in any specimens. In group 2 no healing was found in 12 specimens and incomplete healing in seven. The experimental group 3 had 21 specimens with complete healing, five with incomplete healing and two with no healing. Between the experimental group and each of the control groups this difference was significant (p < 0.001).

The histological and macroscopic findings showed that the repair of meniscal tears in the avascular zone was significantly improved with MSCs, but that the mechanical properties of the healed menisci remained reduced.

In a rabbit model we investigated the efficacy of a silk fibroin/hydroxyapatite (SF/HA) composite on the repair of a segmental bone defect. Four types of porous SF/HA composites (SF/HA-1, SF/HA-2, SF/HA-3, SF/HA-4) with different material ratios, pore sizes, porosity and additives were implanted subcutaneously into Sprague-Dawley rats to observe biodegradation. SF/HA-3, which had characteristics more suitable for a bone substitite based on strength and resorption was selected as a scaffold and co-cultured with rabbit bone-marrow stromal cells (BMSCs). A segmental bone defect was created in the rabbit radius. The animals were randomised into group 1 (SF/HA-3 combined with BMSCs implanted into the bone defect), group 2 (SF/HA implanted alone) and group 3 (nothing implanted). They were killed at four, eight and 12 weeks for visual, radiological and histological study.

The bone defects had complete union for group 1 and partial union in group 2, 12 weeks after operation. There was no formation of new bone in group 3. We conclude that SF/HA-3 combined with BMSCs supports bone healing and offers potential as a bone-graft substitute.

Human articular cartilage samples were retrieved from the resected material of patients undergoing total knee replacement. Samples underwent automated controlled freezing at various stages of preparation: as intact articular cartilage discs, as minced articular cartilage, and as chondrocytes immediately after enzymatic isolation from fresh articular cartilage. Cell viability was examined using a LIVE/DEAD assay which provided fluorescent staining. Isolated chondrocytes were then cultured and Alamar blue assay was used for estimation of cell proliferation at days zero, four, seven, 14, 21 and 28 after seeding. The mean percentage viabilities of chondrocytes isolated from group A (fresh, intact articular cartilage disc samples), group B (following cryopreservation and then thawing, after initial isolation from articular cartilage), group C (from minced cryopreserved articular cartilage samples), and group D (from cryopreserved intact articular cartilage disc samples) were 74.7% (95% confidence interval (CI) 73.1 to 76.3), 47.0% (95% CI 43 to 51), 32.0% (95% CI 30.3 to 33.7) and 23.3% (95% CI 22.1 to 24.5), respectively. Isolated chondrocytes from all groups were expanded by the following mean proportions after 28 days of culturing: group A ten times, group B 18 times, group C 106 times, and group D 154 times.

This experiment demonstrated that it is possible to isolate viable chondrocytes from cryopreserved intact human articular cartilage which can then be successfully cultured.

An understanding of the remodelling of tendon is crucial for the development of scientific methods of treatment and rehabilitation. This study tested the hypothesis that tendon adapts structurally in response to changes in functional loading. A novel model allowed manipulation of the mechanical environment of the patellar tendon in the presence of normal joint movement via the application of an adjustable external fixator mechanism between the patella and the tibia in sheep, while avoiding exposure of the patellar tendon itself. Stress shielding caused a significant reduction in the structural and material properties of stiffness (79%), ultimate load (69%), energy absorbed (61%), elastic modulus (76%) and ultimate stress (72%) of the tendon compared with controls. Compared with the material properties the structural properties exhibited better recovery after re-stressing with stiffness 97%, ultimate load 92%, energy absorbed 96%, elastic modulus 79% and ultimate stress 80%. The cross-sectional area of the re-stressed tendons was significantly greater than that of stress-shielded tendons.

The remodelling phenomena exhibited in this study are consistent with a putative feedback mechanism under strain control. This study provides a basis from which to explore the interactions of tendon remodelling and mechanical environment.

The aim of this biomechanical study was to investigate the role of the dorsal vertebral cortex in transpedicular screw fixation. Moss transpedicular screws were introduced into both pedicles of each vertebra in 25 human cadaver vertebrae. The dorsal vertebral cortex and subcortical bone corresponding to the entrance site of the screw were removed on one side and preserved on the other. Biomechanical testing showed that the mean peak pull-out strength for the inserted screws, following removal of the dorsal cortex, was 956.16 N. If the dorsal cortex was preserved, the mean peak pullout strength was 1295.64 N. The mean increase was 339.48 N (26.13%; p = 0.033). The bone mineral density correlated positively with peak pull-out strength.

Preservation of the dorsal vertebral cortex at the site of insertion of the screw offers a significant increase in peak pull-out strength. This may result from engagement by the final screw threads in the denser bone of the dorsal cortex and the underlying subcortical area. Every effort should be made to preserve the dorsal vertebral cortex during insertion of transpedicular screws.

We have investigated whether cells derived from haemarthrosis caused by injury to the anterior cruciate ligament could differentiate into the osteoblast lineage in vitro. Haemarthroses associated with anterior cruciate ligament injuries were aspirated and cultured. After treatment with β-glycerophosphate, ascorbic acid and dexamethasone or 1,25 (OH)₂D₃, a significant increase in the activity of alkaline phosphatase was observed. Matrix mineralisation was demonstrated after 28 days and mRNA levels in osteoblast-related genes were enhanced.

Our results suggest that the haemarthrosis induced by injury to the anterior cruciate ligament contains osteoprogenitor cells and is a potential alternative source for cell-based treatment in such injury.

Repeated trauma to the radial head may be one of the causative factors in the genesis of osteochondritis dissecans of the capitellum. We measured the force, contact area and pressure across the radiocapitellar articulation of the elbow before and after radial shortening osteotomy in five fresh-frozen cadaver upper limbs with loads of 45, 90 and 135 N, respectively. Measurements were made on pressure-sensitive film placed in the radiocapitellar articulation with the forearm in the supinated, neutral and pronated positions before and after radial shortening. Radial shortening significantly reduced the mean force and contact area across the radiocapitellar articulation in all positions of the forearm.

The re-establishment of vascularity is an early event in fracture healing; upregulation of angiogenesis may therefore promote the formation of bone. We have investigated the capacity of vascular endothelial growth factor (VEGF) to stimulate the formation of bone in an experimental atrophic nonunion model.

Three groups of eight rabbits underwent a standard nonunion operation. This was followed by interfragmentary deposition of 100 μg VEGF, carrier alone or autograft.

After seven weeks, torsional failure tests and callus size confirmed that VEGF-treated osteotomies had united whereas the carrier-treated osteotomies failed to unite. The biomechanical properties of the groups treated with VEGF and autograft were identical. There was no difference in bone blood flow.

We considered that VEGF stimulated the formation of competent bone in an environment deprived of its normal vascularisation and osteoprogenitor cell supply. It could be used to enhance the healing of fractures predisposed to nonunion.

We used a canine intercalary bone defect model to determine the effects of recombinant human osteogenic protein 1 (rhOP-1) on allograft incorporation. The allograft was treated with an implant made up of rhOP-1 and type I collagen or with type I collagen alone.

Radiographic analysis showed an increased volume of periosteal callus in both test groups compared with the control group at weeks 4, 6, 8 and 10. Mechanical testing after 12 weeks revealed increased maximal torque and stiffness in the rhOP-1 treated groups compared with the control group.

These results indicate a benefit from the use of an rhOP-1 implant in the healing of bone allografts. The effect was independent of the position of the implant. There may be a beneficial clinical application for this treatment.