Purpose. The aim of this study was to assess the clinical and radiological result of the usage of chip bone graft in non-contained type bone defect in primary or revision total knee arthroplasty patients. Subjects and Methods. We investigated 32 patients who had underwent primary or revision total knee arthroplasty from March, 2014 to February, 2017 in our hospital, who had non-contained type of defect. The mean age was 73.1 years. 5 of them were males, while 27 of them were females. 7 of them were primary total knee arthroplasty patients, while 25 of them were revision patients. 8 of them had chip bone graft used both in the femur and tibia. 9 of them had chip bone graft used only in the tibia. The other 15 had chip bone graft used only in the femur. Wire-mesh was used in the 9 patients who had chip bone graft used only in the medial side of the tibia. We used KOOS (Knee injury and osteoarthritis outcome score), HSS (Hospital for Special Surgery knee service rating system) and WOMAC scores to assess the clinical result, before the surgery and at the last follow-up. In addition, we had follow-up x-rays and 3D CT done for the patients to check the mean bone union period. In addition, overall radiologic imaging studies were used for complications such as loosening, osteolysis and lesions with radiolucency. Result. The Mean follow-up period was 2.7 years (range; 2.1 to 5). The Mean preoperative KOOS was 102.8 (range; 47 to 132), while it became 31.8 postoperatively (range; 20 to 45). The mean HSS was 13.1 (range; 6 to 35), while it became 35.9 postoperatively (range; 24 to 64). The mean WOMAC was 82.9 (range; 62 to 92), while it became 22.5 postoperatively (range; 13 to 30). According to follow-up x-ray and CT, the mean bone union period was 10.6 months (range: 10 to 13). In follow-up 3D CT of all cases, we could check cortical healing and new bone formation, seen as medium to high-attenuating conglomerate. The graft-host junction showed trabecular ingrowth, while the medullary canal showed fibrous ingrowth. Radiologically, there was no complication such as loosening, osteolysis, migration and radiolucent lines around the stems or cement mantles. In addition, there was no complication such as infection. Conclusion. Chip bone graft is not a commonly used method for bone defect in total knee arthroplasty. According to the result of the usage of chip bone graft in primary or revision total knee arthroplasty with non-contained type of bone defect, it showed favorable result for the subject patients. Therefore, we can consider it as one of the effective methods to manage non-contained bone defect in knee arthroplasty. Keywords. Revision TKA, chip bone graft, wire-mesh, non-contained bone defect. For any figures or tables, please contact authors directly

A modular tibial insert exchange is a seemingly attractive benign and simple surgical alternative when compared to full knee revision. Unfortunately, the results have been less than satisfactory with modular insert exchange for polyethylene wear and knee instability. Babis et al reported the results of 56 isolated insert exchanges performed for wear or instability. The re-revision rate was 25% at a mean follow-up of 3-years and the cumulative survival rate was only 63.5% at 5.5 years. In another study, 27% (6/22) insert exchanges for wear required re-revision within 5 years. Bert et al reported scoring and damage in 89% of 55 retained components considered candidates for isolated insert exchange. Such damage could account for accelerated wear of a new insert.

These studies are misleading. The new insert must be polyethylene not prone to oxidation and accelerated wear. In a recent study of 177 revisions for wear and osteolysis, the survivorship of insert exchange using non-irradiated poly was 100%. Insert exchange does not correct the problem of a poor tibial locking mechanism. Whiteside and Katerberg reported 3 failures in 49 insert exchanges, fabrication of the tibial locking mechanism was used to address this problem. With revision for instability, insert exchange must provide full stability in both flexion and extension.

Tibial insert exchange must correct the underlying cause of failure that led to the revision surgery. Full knee revision is a complex procedure that brings with it increased risks of perioperative complications such as infection and should be reserved only for cases that will not do well with simple insert exchange.

From 1985 through 1997, 56 isolated tibial insert exchange revisions were performed at our institution. Fifty-five patients with wear or instability were included. Those with loosening of any of the components, history of infection, severe knee stiffness or problems with the extensor mechanism were excluded. There were 29 males (1 bilateral) and 26 female patients with a mean age of 66 years (range 35 to 83 years) at the time of revision surgery. Twenty-seven inserts were exchanged based on ligamentous instability, 24 because of insert wear or breakage including two cases of polyethylene dislodgment from the tibial base-plate and 5 for other reasons. Twelve knees had one to three prior revisions. Surveillance from index arthroplasty averaged 8.3 years (range 1.6 to 16.2 years) and since revision 4.6 years (range 2 to 14 years).

Knee Society and Function Scores improved from 56 and 50.9 prior to revision to 76 and 59 at final surveillance respectively. Fourteen (25%) of the 56 knees subsequently required re-revision after a mean of only three years (0.5–6.8) from tibial insert exchange. The cumulative survival at 5.5 years was 63.5% (95%CI=+/−14.4, n=19). Of the 27 patients with pre-operative instability, eight were revised and another four were considered as failures due to severe pain. Of the 24 failed inserts, five were re-revised, one was amputated as a result of chronic ankle osteomyelitis concomitant to a chronically painful arthroplasty, and another two inserts failed due to severe pain.

Isolated tibial insert exchange led to a surprisingly high early failure rate. Tibial insert exchange should therefore be undertaken with caution as an isolated method of total knee revision surgery even in those circumstances for which the modular insert was designed and felt to be of greatest value.

Aim. Local antibiotics released through a carrier is a commonly used technique to prevent infection in orthopaedic procedures. An interesting carrier in aseptic bone reconstructive surgery are bone chips impregnated with AB solution. Systemically administered Cefazolin (CFZ) is used for surgical site infection prophylaxis however in vitro study showed that fresh frozen and processed bone chips impregnated with CFZ solution completely release the CFZ within a few hours. On the other hand irradiated freeze-dried bone chips, treated with supercritical CO2 (scCO2) have been shown to be an efficient carrier for the antibiotics vancomycine or tobramycine. With this pilot study we wanted to investigate if CFZ solution impregnation of bone chips treated with scCO2 shows a more favorable release pattern of CFZ. Method. The bone chips were prepared using the standard scCO2 protocol and were impregnated with 100 mg/ml cefazolin at different timepoints during the process: before freeze drying (BC type A), after freeze drying (BC type B) and after gamma-irradiation. 0.5g of the impregnated bone grafts were incubated with 5ml of fetal calf serum (FCS) at 37°C. At 2, 4, 6, 8 and 24h of incubation 200µl of eluate was taken for analysis. After 24h the remaining FCS was removed, bone grafts were washed and new FCS (5ml) was added. Consecutive eluate samples were taken at 48, 72 and 96h of incubation. The concentration of CFZ in the eluates was measured with the validated UPLC-DAD method. Analysis was performed in triplicate. Results. The mean concentration of CFZ in the eluate obtained from BC type A incubated for 2h was higher compared to BC type B, respectively 581 mg/l and 297 mg/l. However, the elution profile is the same for both types: the CFZ concentration in the eluates drops within the first 24h from 581 mg/l to 365 mg/l (37%) for BC type A and from 297 mg/l to 132 mg/l (56%) for BC type B. After 24h no further significant CFZ release is seen. Impregnation of the bone chips before or after gamma irradiation did not affect this elution profile. Conclusions. Bone chips treated with scCO2 show a comparable elution pattern compared to non-scCO2 treated bone chips. AB release depends on the properties of the AB, making it impossible to copy the same impregnation protocol for different antibiotics. The stability of CFZ in solution at 37°C and its release are a major concern when establishing an impregnation protocol with CFZ

Aim. Allograft bone chips used in complex bone reconstruction procedures are associated with an increased infection risk. The perioperative use of systemic cefazolin is standard to prevent infection, but is less effective in the presence of avascular bone grafts. Bone chips have been described as a carrier for local delivery of antibiotics, but impregnation with cefazolin in a prophylactic setting has not been described. We aimed to obtain a prolonged cefazolin release from bone chips to maximize the prophylactic effect. Method. Three types of bone chips were evaluated: fresh frozen, decellularized frozen and decellularized lyophilized. Bone chips were incubated with 20 mg/ml cefazolin or treated with liquid hydrogel containing either 1 mg/ml fibrin or 1 mg/ml collagen and 20 mg/ml cefazolin. The cefazolin hydrogel was distributed in the porous structure by short vacuum treatment. Bone chips with cefazolin but without hydrogel were incubated for 20 min- 4h under atmospheric pressure or under vacuum. Cefazolin elution of bone chips was carried out in fetal bovine serum and analyzed by Ultra Performance Liquid Chromatography – Diode Array Detection. Results. Without hydrogel, cefazolin release was limited to 4 hours. When vacuum was applied during impregnation, elution of cefazolin exceeding the MIC (minimal inhibitory concentration) from decellularized lyophilized bone chips was obtained for 36 hours. Use of a collagen hydrogel and vacuum treatment resulted in a high concentration at 24 hours, but did not support prolonged release for any of the three types of tested bone chips. In contrast, combination of decellularized frozen bone chips with fibrin hydrogel resulted in an initial release of 533 μg/ml, declining to the MIC at 72 hours, while no longer measurable after 92 hours. Such elution profile is desirable, since high initial levels are important to maximize antibacterial action whereas the complete wash out prevents antibiotic resistance. By increasing the cefazolin concentration during impregnation, elution above the MIC could be obtained for 120 hours. Impregnated bone chips stored at −20° C for 3 months performed similarly to freshly impregnated bone chips. Conclusions. Bone chips processed with the described hydrogel-based impregnation protocol allows tunable delivery of cefazolin for a local prophylactic effect

Aim. To prevent infections after orthopaedic surgery, intravenous antibiotics are administered perioperatively. Cefazolin is widely used as the prophylactic antibiotic of choice. Systemic antibiotic therapy may however be less effective in longstanding surgery where bone allografts are used. Bone chips have been shown to be an effective carrier for certain types of antibiotics and may provide the necessary local antibiotic levels for prophylaxis. To be efficient a prolonged release is required. In contrast to vancomycin with proven efficient prolonged release from Osteomycin, this has not been described for cefazolin. We developed a protocol to bind cefazolin to bone chips by means of a hydrogel composed of proteins naturally present in the human body. Method. Three types of bone chips were evaluated: fresh frozen, decellularized frozen and decellularized lyophilized. Bone chips were incubated with 20 mg/ml cefazolin or treated with liquid hydrogel containing either 1 mg/ml fibrin or 1 mg/ml collagen and 20 mg/ml cefazolin. The cefazolin hydrogel was distributed in the porous structure by short vacuum treatment. Bone chips with cefazolin but without hydrogel were either incubated for 20 min- 4h or also treated with vacuum. Cefazolin elution of bone chips was carried out in fetal bovine serum and analysed by Ultra Performance Liquid Chromatography – Diode Array Detection. Results. Soaking of bone chips without hydrogel resulted in a quick release of cefazolin, which was limited to 4 hours. When vacuum was applied elution of >1 µg/ml cefazolin was measured for up to 36 hours. Combination with collagen hydrogel resulted in a higher cefazolin concentration released at 24 hours (3.9 vs 0.3 µg/ml), but not in a prolonged release. However, combination of decellularized frozen bone chips with fibrin hydrogel resulted in an initial release of 533 µg/ml followed by a gradual decline reaching the minimal inhibitory concentration for S. aureus at 72 hours (1.7 µg/ml), while not measurable anymore after 92 hours. Conclusions. Processed bone chips with hydrogel-cefazolin showed a markedly prolonged cefazolin release. When combined with a fibrin hydrogel, high initial peak levels of cefazolin were obtained, followed by a decreasing release over the following three days. This elution profile seems desirable, with high initial levels to maximize anti-bacterial action and low levels for a limited time to stimulate osteogenesis. Further preclinical studies are warranted to show effectiveness of hydrogel-cefazolin impregnated bone chips

Abstract. Background. The aim of the present experimental study was to analyse vancomycin elution kinetics of nine bone fillers used in orthopaedic and trauma surgery over 42 consecutive days. Methods. Two allograft bone chips (carriers 1 and 2), a calcium-sulfate matrix (carrier 3), a hydroxyapatite/calcium-sulphate composite (carrier 4), four bone cements (carriers 5-8) and a pure tricalcium phosphate matrix (carrier 9), either already contained vancomycin, or were mixed with it following manufacturer's recommendations. Over 42 days, half of elution medium was substituted by the same amount of PBS at 9 distinct time points. Vancomycin concentration in obtained samples were measured with a kinetic microparticle immunoassay, and masses consecutively calculated. To enhance comparability between carriers analysed, vancomycin mass released related to overall mass within each probe was determined. Notably, elution kinetics of carriers 1 to 4 have been published previously. Results. All carriers initially released high vancomycin masses, followed by constant reduction later into the experiment. Mean initial vancomycin masses released after 4 hours were highest for carriers 1 (337.7 ± 76.2 mg), 9 (68.4 ± 4.9 mg), and 2 (49.0 ± 54.6 mg). From prefinal (35 days) to last measurement (42 days) carriers 2 (8.6 ± 4.8 mg), 1 (2.4 ± 1.0 mg), and 5 (0.1 ± 0.1 mg) had released highest vancomycin masses. Notably, all five bone cements tested only released a small percental amount of their total mass up to the last measurement (42 days; 2.1% – 9.3%), whilst allografts and resorbable synthetic bone fillers discarded high percental values (22.5% – 79.2%). Conclusions. Elution kinetics differ between 9 antibiotic-loaded bone fillers, with high vancomycin masses released by allografts and resorbable bone fillers over time. Transferred to clinical practice, these may be favoured over bone cements in case prolonged and high antibiotic release is warranted rather than mechanical stability

Aim. Aim of this monocentric, prospective study was to evaluate the safety, efficacy, clinical and radiographical results at 24-month follow-up (N = 6 patients) undergoing hip revision surgery with severe acetabular bone defects (Paprosky 2C-3A-3B) using a combination of a novel phase-pure betatricalciumphosphate - collagen 3D matrix with allograft bone chips. Method. Prospective follow-up of 6 consecutive patients, who underwent revision surgery of the acetabular component in presence of massive bone defects between April 2018 and July 2019. Indications for revision included mechanical loosening in 4 cases and history of hip infection in 2 cases. Acetabular deficiencies were evaluated radiographically and CT and classified according to the Paprosky classification. Initial diagnosis of the patients included osteoarthritis (N = 4), a traumatic fracture and a congenital hip dislocation. 5 patients underwent first revision surgery, 1 patient underwent a second revision surgery. Results. All patients were followed-up radiographically with a mean of 25,8 months. No complications were observed direct postoperatively. HHS improved significantly from 23.9 preoperatively to 81.5 at the last follow-up. 5 patients achieved a defined good result, and one patient achieved a fair result. No periprosthetic joint infection, no dislocations, no deep vein thrombosis, no vessel damage, and no complaint about limbs length discrepancy could be observed. Postoperative dysmetria was found to be + 0.2cm (0cm/+1.0cm) compared to the preoperative dysmetria of − 2.4 cm (+0.3cm/−5.7cm). Conclusions. Although used in severe acetabular bone defects, the novel phase-pure betatricalciumphosphate - collagen 3D matrixshowed complete resorption and replacement by newly formed bone, leading to a full implant integration at 24 months follow-up and thus represents a promising method with excellent bone regeneration capacities for complex cases, where synthetic bone grafting material is used in addition to autografts

Femoral revision after cemented total hip arthroplasty (THA) might include technical difficulties, following essential cement removal, which might lead to further loss of bone and consequently inadequate fixation of the subsequent revision stem. Bone loss may occur because of implant loosening or polyethylene wear, and should be addressed at time of revision surgery. Stem revision can be performed with modular cementless reconstruction stems involving the diaphysis for fixation, or alternatively with restoration of the bone stock of the proximal femur with the use of allografts. Impaction bone grafting (IBG) has been widely used in revision surgery for the acetabulum, and subsequently for the femur in Paprosky defects Type 1 or 2. In combination with a regular length cemented stem, impaction grafting allows for restoration of femoral bone stock through incorporation and remodeling of the proximal femur. Cavitary bone defects affecting the metaphysis and partly the diaphysis leading to a wide femoral canal are ideal indications for this technique. In case of combined segmental-cavitary defects a metal mesh is used to contain the defect which is then filled and impacted with bone grafts. Cancellous allograft bone chips of 2 to 4 mm size are used, and tapered into the canal with rods of increasing diameters. To impact the bone chips into the femoral canal a dummy of the dimensions of the definitive cemented stem is inserted and tapped into the femur to ensure that the chips are firmly impacted. Finally, a standard stem is implanted into the newly created medullary canal using bone cement. To date several studies from Europe have shown favorable results with this technique, with some excellent long-term results reported. Advantages of IBG include the restoration of the bone stock in the proximal femur, the use of standard length cemented stems and preserving the diaphysis for re-revision. As disadvantages of the technique: longer surgical time, increased blood loss and the necessity of a bone bank can be mentioned

Previous studies have described an age-dependent distortion of bone microarchitecture for α-CGRP-deficient mice (3). In addition, we observed changes in cell survival and activity of osteoblasts and osteoclasts isolated from young wildtype (WT) mice when stimulated with α-CGRP whereas loss of α-CGRP showed only little effects on bone cell metabolism of cells isolated from young α-CGRP-deficient mice. We assume that aging processes differently affect bone cell metabolism in the absence and presence of α-CGRP. To further explore this hypothesis, we investigated and compared cell metabolism of osteoblasts and bone marrow derived macrophages (BMM)/osteoclast cultures isolated from young (8–12 weeks) and old (9 month) α-CGRP-deficient mice and age matched WT controls. Isolation/differentiation of bone marrow macrophages (BMM, for 5 days) to osteoclasts and osteoblast-like cells (for 7/14/21 days) from young (8–12 weeks) and old (9 month) female α-CGRP−/− and WT control (both C57Bl/6J) mice according to established protocols. We analyzed cell migration of osteoblast-like cells out of femoral bone chips (crystal violet staining), proliferation (BrdU incorporation) and caspase 3/7-activity (apoptosis rate). Alkaline phosphatase (ALP) activity reflects osteoblast bone formation activity and counting of multinucleated (≥ 3 nuclei), TRAP (tartrate resistant acid phosphatase) stained osteoclasts reflects osteoclast differentiation capacity. We counted reduced numbers of BMM from young α-CGRP−/− mice after initial seeding compared to young WT controls but we found no differences between old α-CGRP−/− mice and age-matched controls. Total BMM number was higher in old compared to young animals. Migration of osteoblast-like cells out of bone chips was comparable in both, young and old α-CGRP−/− and WT mice, but number of osteoblast-like cells was lower in old compared to young animals. Proliferation of old α-CGRP−/− BMM was higher when compared to age-matched WT whereas proliferation of old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation was lower. No differences in bone cell proliferation was detected between young α-CGRP−/− and age-machted WT mice. Caspase 3/7 activity of bone cells from young as well as old α-CGRP−/− mice was comparable to age-matched controls. Number of TRAP-positive multinucleated osteoclasts from young α-CGRP−/− mice was by trend higher compared to age-matched WT whereas no difference was observed in osteoclast cultures from old α-CGRP−/− mice and old WT. ALP activity, as a marker for bone formation activity, was comparable in young WT and α-CGRP−/− osteoblasts throughout all time points whereas ALP activity was strongly reduced in old α-CGRP−/− osteoblasts after 21 days of osteogenic differentiation compared to age-matched WT. Our data indicate that loss of α-CGRP results in a reduction of bone formation rate in older individuals caused by lower proliferation and reduced activity of osteogenic cells but has no profound effects on bone resorption rate. We suggest that the osteopenic bone phenotype described in aged α-CGRP-deficient mice could be due to an increase of dysfunctional matured osteoblasts during aging resulting in impaired bone formation

A cleaning process reduces the contamination risk in bone impaction grafting but also modifies the grain size distribution. The cleaned allograft shows a higher mechanical stability than the untreated group. In revision total hip replacement, bone loss can be managed by impacting porous bone chips. The bone chips have to be compacted to guarantee sufficient mechanical strength. To improve the safety of bone grafts and to reduce the risk of bacterial and viral contamination, cleaning processes are used to remove the organic portion of the tissue while maintaining its mechanical characteristics. A cleaning procedure described by Coraca-Huber et al. was compared to untreated allografts by performing a sieve analysis, followed by an uniaxial compression test. Differences in grain size distribution and weight loss during the cleaning procedure were compared to data from literature. Yield stress limits, flowability coefficients as well as initial density and density at the yield limit of the two groups were determined for each group over 30 measurements. The measurements were taken before and after compression with an impaction apparatus (dropped weight). The cleaning process reduced the initial weight by 56%, which is comparable to the results of McKenna et. al. Cleaned allograft showed a 25% lower weight of bone chips sized > 4 mm compared to data from a previous study. The cleaned bone chips showed a statistically significant (p > 0.01) higher yield limit to a compression force (0.165 ± 0.069 MPa) compared to untreated allograft after compaction (0.117 ± 0.062 MPa). The flowability coefficient was 0.024 for the cleaned allograft and 0.034 for the untreated allograft. Initial density as well as the density at the yield limit was higher for the untreated allografts, as the sample weight was twice as high as in the cleaned group, to compensate for the washout of the organic portion. The cleaned bone grafts showed a higher compaction rate, which was 31%, compared the the untreated group with a compaction rate of 22%. The cleaned allograft showed a higher compaction rate, which means that the gaps between the single grains are filled out with smaller particles, resulting in better interlocking. In the untreated allograft the interlocking mechanism is hindered by the organic elements. This observation is confirmed by a reduced flowabillity and a higher yield stress limit. The loss of weight as well as a higher compaction rate implies that more cleaned graft material is needed to fill bone defects in hip surgery. Sonication may damage the bone structure of the allograft and reduce the size of the particles

Femoral revision in cemented THA might include some technical difficulties, based on loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration due to incorporation and remodelling of the allograft bone by the host skeleton. Historically it has been first performed and described in Exeter in 1987, utilizing a cemented tapered polished stem in combination with morselised fresh frozen bone grafts. The technique was refined by the development of designated instruments, which have been implemented by the Nijmegen group from Holland. Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Cavitary bone defects affecting meta- and diaphysis leading to a wide or so called “drain pipe” femora, are optimal indications for this technique, especially in young patients. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient. Generally, the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Incorporation of these grafts has been described in 89%. Technical steps include: removal of failed stem and all cement, reconstruction of segmental bone defects with metal mesh (if necessary), preparation of fresh frozen femoral head allografts with bone mill, optimal bone chip diameter 2–5 mm, larger chips for the calcar area (6–8 mm), insertion of an intramedullary plug including central wire, 2 cm distal the stem tip, introduction of bone chips from proximal to distal, impaction started by distal impactors over central wire, then progressive larger impactors proximal, insertion of a stem “dummy” as proximal impactor and space filler, removal of central wire, retrograde insertion of low viscosity cement (0.5 Gentamycin) with small nozzle syringe, including pressurization, and insertion of standard cemented stem. The cement mantle is of importance, as it acts as the distributor of force between the stem and bone graft and seals the stem. A cement mantle of at least 2 mm has shown favorable results. Post-operative care includes usually touch down weightbearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches. Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to cold flow within the cement mantle, however, could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm. Survivorship with a defined endpoint as any femoral revision after 10-year follow up has been reported by the Exeter group being over 90%, while survivorship for revision as aseptic loosening being above 98%. Within the last years various other authors and institutions reported about similar excellent survivorships, above 90%. In addition, a long-term follow up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years. Impaction grafting might technically be more challenging and more time consuming than cement-free distal fixation techniques. It, however, enables a reliable restoration of bone stock which might especially become important in further revision scenarios in younger patients

Femoral revision in cemented THA might include some technical difficulties, based on loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration due to incorporation and remodeling of the allograft bone by the host skeleton. Historically, it has been first performed and described in Exeter in 1987, utilizing a cemented tapered polished stem in combination with morselised fresh frozen bone grafts. The technique was refined by the development of designated instruments, which have been implemented by the Nijmegen group from Holland. Indications might include all femoral revisions with bone stock loss, while the ENDO-Klinik experience is mainly based on revision of cemented stems. Cavitary bone defects affecting meta- and diaphysis leading to a wide or so called “drain pipe” femora, are optimal indications for this technique, especially in young patients. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient. Generally the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Incorporation of these grafts has been described in 89%. Technical steps include: removal of failed stem and all cement, reconstruction of segmental bone defects with metal mesh (if necessary), preparation of fresh frozen femoral head allografts with bone mill, optimal bone chip diameter 2 – 5 mm, larger chips for the calcar area (6 – 8 mm), insertion of an intramedullary plug including central wire, 2 cm distal to the stem tip, introduction of bone chips from proximal to distal, impaction started by distal impactors over central wire, then progressively larger impactors proximal, insertion of a stem “dummy” as proximal impactor and space filler, removal of central wire, retrograde insertion of low viscosity cement (0.5 Gentamycin) with small nozzle syringe, including pressurization, insertion of standard cemented stem. The cement mantle is of importance, as it acts as the distributor of force between the stem and bone graft and seals the stem. A cement mantle of at least 2 mm has shown favorable results. Originally the technique is described with a polished stem. We use standard brushed stems with comparable results. Postoperative care includes usually touch down weight bearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches. Survivorship with a defined endpoint as any femoral revision after 10 year follow up has been reported by the Exeter group being over 90%. While survivorship for revision related to aseptic loosening being above 98%. Within the last years various other authors and institutions reported similar excellent survivorships, above 90%. In addition a long term follow up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years. Impaction grafting might technically be more challenging and more time consuming than cement free distal fixation techniques. It, however, enables a reliable restoration of bone stock which might become important in further revision scenarios in younger patients

In Total Hip Arthroplasty (THA) bone loss is recovered by using compacted porous bone chips. The technique requires the morsellised allograft to be adequately compacted to provide initial stability for the prosthesis in order to prevent early massive subsidence and to induce bone remodeling. Therefore the bone grafts provide initial stability and an environment in which revascularization and incorporation of the graft into the host skeleton may occur. Acetabular reconstruction with impacted morsellised cancellous grafts and cement leads to satisfactory long-term results. In the acetabular impact-grafting procedure, a hammer and an impaction stick is used for manual compaction. Another technique uses a hammer driven by compressed air, which could lead to higher density and improved stability of bone chips in the acetabulum. The aim of this study was to compare two different compaction modes for bone impaction grafting for the acetabulum. The hypothesis was that a pneumatic impaction method would produce less variable results than the manual impaction mode and lead to better compaction results of the bone chips in less time. Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. For each compaction method and for each time interval (0, 3, 6, 9, 12, 15 and 30 [s] of compaction time) 30 measurements of force and distance variations were taken. From the measurements of force and distance variations bulk density, contact stiffness, impaction hardness and penetration resistance were calculated before and after the established time intervals of compaction. Since not all data was normally distributed the non-parametric U-Test was used for comparison of the two impaction methods. Particle size distribution was determined using sieve analysis according to Din 18123 standard after the compaction experiments. Results have shown that the pneumatic method leads to higher values in impaction hardness, contact stiffness and bulk density and is more suitable to increase the primary stability of the implant. The differences in bulk density, impaction hardness and contact stiffness where statistically significant (p<0.01). No significant differences were found between the two different methods concerning the penetration resistance. The coefficient of uniformity C. u. , calculated from the particle size distribution determined by the sieve analysis, has a value of 3.8. The particle size distribution is comparable to the results published in literature. Pneumatic impaction achieves higher density values in less time with less force applied and results in more reproducible outcomes when used. It reduces therefore the risk of bone fracture, as smaller peak forces are used for less time. However for optimal osteointegration it is not recommended to achieve maximum density. Further clinical studies should determine a reference value for optimal growth-in of osteocytes. Manual impaction shows more variable results and depends much on the experience of the surgeon. The pneumatic hammer is therefore a suitable tool to standardize the impaction process for acetabular bone defects

The technique involves impaction of cancellous bone into a cavitary femur. If segmental defects are present, the defects can be closed with stainless steel mesh. The technique requires retrograde fill of the femoral cavity with cancellous chips of appropriate size to create a new endomedullary canal. By using a set of trial impactors that are slightly larger than the real implants the cancellous bone is impacted into the tube. Subsequent proximal impaction of bone is performed with square tip or half moon impactors. A key part of the technique is to impact the bone tightly into the tube especially around the calcar to provide optimal stability. Finally a polished tapered stem is cemented using almost liquid cement in order to achieve interdigitation of the implant to the cancellous bone. The technique as described is rarely performed today in many centers around the world. In the US, the technique lost its interest because of the lengthy operative times, unacceptable rate of peri-operative and post-operative fractures and most importantly, owing to the success of tapered fluted modular stems. In centers such as Exeter where the technique was popularised, it is rarely performed today as well, as the primary cemented stems used there, rarely require revision. There is ample experience from around the globe, however, with the technique. Much has been learned about the best size and choice of cancellous graft, force of impaction, surface finish of the cemented stem, importance of stem length, and the limitations and complications of the technique. There are also good histology data that demonstrate successful vascularization and incorporation of the impacted cancellous bone chips and host bone. Our experience at the clinic was excellent with the technique as reported in CORR in 2003 by M Cabanela. The results at mid-term demonstrated minimal subsidence and good graft incorporation. Six of 54 hips, however, had a post-operative distal femoral fracture requiring ORIF. The use of longer cemented stems may decrease the risk of distal fracture and was subsequently reported by the author after reviewing a case series from Exeter. Today, I perform this technique once or twice per year. It is an option in the younger patient, where bone restoration is desired. Usually in a Paprosky Type IV femur, where a closed tube can be recreated and the proximal bone is reasonable. If the proximal bone is of poor quality, then I prefer to perform a transfemoral osteotomy, and perform an allograft prosthetic composite instead of impaction grafting, and wrap the proximal bone around the structural allograft. I prefer this technique as I can maintain the soft tissues over the bone and avoid the stripping that would be required to reinforce the bone with struts or mesh. Another indication for its use in the primary setting is in the patient with fibrous dysplasia

The vast majority of total hip replacements (THR) implanted today enable modularity by means of a tapered junction; based on the Morse taper design introduced for cutting tools in the 19. th. Century . 1. Morse-type tapers at the head-stem junction provide many benefits, key for a successful surgical outcome such as wider component selection and restoration of better biomechanics . 2. However, moving from mono-block to modular designs has not been without its issues. Fluid ingress and motion at the interface has led to a complex multifactorial degradation mechanism better known as fretting-corrosion . 3. Fretting-corrosion products created at the junction are commonly associated with adverse local tissue reactions . 4. . There is a wide variation in the taper junction of THR differing quite significantly from Morse's original design. Performance of the taper junction has been found to vary with different designs . 5,6. However, there is still a lack of common understanding of what design inputs makes a ‘good’ modular taper interface. The aim of this study was to better understand the links between implant design and fretting-corrosion initially focussing on the role of angular mismatch between male and female taper. A combination of experimental approaches with the aid of computational models to assist understanding has been adopted. A more descriptive understanding between taper design, engagement, motion and fretting-corrosion will be developed. Three different sample designs were created to represent the maximum range of possible angular mismatches seen in clinically available THR modular tapers (Matched: 0.020 ±0.002 °, Proximal: 0.127 ±0.016 °, Distal: −0.090 ±0.002 °). Head-stem components were assembled at 2 kN. Motion and fretting-corrosion at the interface was simulated under incremental uniaxial sinusoidal loading between 0.5–4 kN at 8 intervals of 600 cycles. The different types of motions at the interface was measured using a developed inductance circuit composed of four sensing coils, digital inductance converter chip (LDC1614, Texas Instruments, US) and microcontroller (myRIO, National Instruments, US). Fretting-corrosion was measured using potentiostatic electrochemical techniques with an over potential of +100 mV vs OCP (Ivium, NL). Complimentary finite element (FE) models were created in Ansys (Ansys 19.2, US). Under uniaxial loading, the ‘matched’ modular taper assemblies corroded most and allowed the greatest pistoning motion due to a seating action. ‘Distal’ and ‘proximal’ engaged modular tapers showed reduced corrosion and seating when compare to the ‘matched’ components. However the kinetics of corrosion and motion were interface dependent. It is hypothesized, and complimented by FEA analysis, that lower initial contact stress in the ‘matched’ modular tapers allows for greater subsidence and depassivation of the oxide layer and higher corrosion. ‘Matched’ modular tapers allowed less rotational and toggling motions compared to mismatched tapers, suggesting a reduced mismatch might perform better once the heads have seated over time. Future work involves tests conducted under a surgically relevant impaction force and physiological loading kinematics to develop this descriptive link between taper design, engagement and performance

Femoral revision in cemented THA might include some technical difficulties, based on the loss of bone stock and cement removal, which might lead to further loss of bone stock, inadequate fixation, cortical perforation or consequent fractures. Femoral impaction grafting, in combination with a primary cemented stem, allows for femoral bone restoration by incorporating and remodeling the allograft bone of the host skeleton. Historically, this was first performed and described in Exeter in 1987. Indications might include all femoral revisions with bone stock loss, while the Endo-Clinic experience is mainly based on revision of cemented stems. Nowadays our main indication is the Paprosky Type IIIb and Type IV. Contraindications are mainly: septical revisions, extensive circumferential cortical bone loss and noncompliance of the patient. Generally the technique creates a new endosteal surface to host the cemented stem by reconstruction of the cavitary defects with impacted morselised bone graft. This achieves primary stability and restoration of the bone stock. It has been shown, that fresh frozen allograft shows superior mechanical stability than freeze-dried allografts. Technical steps include: . –. removal of failed stem and all cement rests. –. reconstruction of segmental bone defects with metal mesh (containment). –. preparation of fresh frozen femoral head allografts with bone mill. –. optimal bone chip diameter 2 to 5 mm, larger chips for the calcar area (6–8 mm). –. insertion of an intramedullary plug including central wire, 2 cm distal the stem tip. –. introduction of bone chips from proximal to distal. –. impaction started by distal impactors over central wire, then progressive larger impactors proximal. –. insertion of a stem „dummy“ as proximal impactor and space filler. –. removal of central wire. –. retrograde insertion of bone cement (0.5 Gentamycin) with small nozzle syringe, including pressurisation. –. insertion of standard cemented stem. The cement mantle is of importance as it acts as the distributor of force between the stem and bone graft while sealing the stem. A cement mantle of at least 2 mm has shown favourable results. Post-operative care includes usually touch down weight bearing for 6–8 weeks, followed by 4–6 weeks of gradually increased weightbearing with a total of 12 weeks on crutches. Relevant complications include mainly femoral fractures due to the hardly impacted allograft bone. Subsidence of tapered polished implants might be related to coldflow within the cement mantle, however, it could also be related to micro cement mantle fractures, leading to early failure. Subsidence should be less than 5 mm. Survivorship with a defined endpoint as any femoral revision after 10-year follow-up has been reported by the Exeter group at over 90%. While survivorship for revision defined as aseptic loosening is even greater at above 98%. Within the last years various other authors and institutions reported similar excellent survivorships, above 90%. In addition a long-term follow-up by the Swedish arthroplasty registry in more than 1180 patients reported a cumulative survival rate of 94% after 15 years and 99% with the endpoint aseptic loosening. Impaction grafting is technically more challenging and more time consuming than cement free distal fixation techniques. However, it enables a reliable restoration of bone stock

Acetabular reconstruction of extensive bone defect is troublesome in revision total hip arthroplasty (rTHA). Kerboull or Kerboull type reinforcement acetabular device with allobone grafting has been applied since 1996. Clinical results of the procedure were evaluated. Patients. One hundred and ninety-two consecutive revision total hip arthroplasties were performed with allograft bone supported by the Kerboull or Kerboull type reinforcement acetabular device from 1996 to 2009. There were 23 men and 169 women. Kerboull plates were applied to 18 patients, and Kerboull type plates to 174. The mean follow up of the whole series was 8 years (4–18years). Surgical Technique. The superior bone defect was reconstructed principally by a large bulky allo block with plate system. Medial bone defect was reconstructed by adequate bone chips and/or sliced bone plates. After temporally fixation of bulky bone block with two 2.0mm K-wires, it was remodeled by reaming to fit the gap between host bone and plate, followed by fixation to the iliac bone by screws. Finally, residual space of the defect between host bone and the fixed plated was filled up with morselized cancellous bones, bone chips, and/or wedged bony fragments with impaction. This method was sufficiently applicable to AAOS Typeâ�, II, and III bone defects. In case of AAOS Typeâ�£, the procedure was also available after repairing discontinuation between distal and proximal bones by reconstrusion plate or allografting with tibial bone plates or sliced femoral head. Results. Nine patients (4.7%) required revision surgery (infection 5, breakage 3, and malalignment 1). The plate breakage was observed in 8 joints (4.2%). Three patients had no symptoms after the breakage. Three required revision, but the other cases were carefully observed without additional surgical intervention. Ten-year survival rate by Kaplan-Meier method was 96.6% when the endpoint was set revision by asceptic loosning. Conclusions. This study indicated that acetabular allograft reconstructions reinforced by Kerboull or Kerboull type acetabular device were able to recover bone stock with anatomic reconstruction of femoral head center, thus providing satisfactory clinical results in middle term period

The inflammatory cascade associated with prosthetic implant wear debris, in addition to diseases such as rheumatoid arthritis and periodontitis, it is shown to drastically influence bone turnover in the local environment. Ultimately, this leads to enhanced osteoclastic resorption and the suppression of bone formation by osteoblasts causing implant failure, joint failure, and tooth loosening in the respective conditions if untreated. Regulation of this pathogenic bone metabolism can enhance bone integrity and the treatment bone loss. The current study used novel compounds that target a group of enzymes involved with the epigenetic regulation of gene expression and protein function, histone deacetylases (HDAC), to reduce the catabolism and improve the anabolism of bone material in vitro. Human osteoclasts were differentiated from peripheral blood monocytes and cultured over a 17 day period. In separate experiments, human osteoblasts were differentiated from human mesenchymal stem cells isolated from bone chips collected during bone marrow donations, and cultured over 21 days. In these assays, cells were exposed to the key inflammatory cytokine involved with the cascade of the abovementioned conditions, tumour necrosis factor-α (TNFα), to represent an inflammatory environment in vitro. Cells were then treated with HDAC inhibitors (HDACi) that target the individual isoforms previously shown to be altered in pathological bone loss conditions, HDAC-1, −2, −5 and −7. Analysis of bone turnover through dentine resorptive measurements and bone mineral deposition analyses were used to quantify the activity of bone cells. Immunohistochemistry of tartrate resistant acid phosphatase (TRAP), WST-assay and automated cell counting was used to assess cell formation, viability and proliferation rates. Real-time quantitative PCR was conducted to identify alterations in the expression of anti- and pro-inflammatory chemokines and cytokines, osteoclastic and osteoblastic factors, in addition to multiplex assays for the quantification of cytokine/chemokine release in cell supernatant in response to HDACi treatments in the presence or absence of TNFα. TNFα stimulated robust production of pro-inflammatory cytokines and chemokines by PBMCs (IL-1β, TNFα, MCP1 and MIP-1α) both at the mRNA and protein level (p < 0 .05). HDACi that target the isoforms HDAC-1 and −2 in combination significantly suppressed the expression or production of these inflammatory factors with greater efficacy than targeting these HDAC isoforms individually. Suppression of HDAC-5 and −7 had no effect on the inflammatory cascade induced by TNFα in monocytes. During osteoclastic differentiation, TNFα stimulated the size and number of active cells, increasing the bone destruction observed on dentine slices (p < 0 .05). Targeting HDAC-1 and −2 significantly reduced bone resorption through modulation of the expression of RANKL signalling factors (NFATc1, TRAF6, CatK, TRAP, and CTR) and fusion factors (DC-STAMP and β3-integerin). Conversely, the anabolic activity of osteoblasts was preserved with HDACi targeting HDAC-5 and −7, significantly increasing their mineralising capacity in the presence of TNFαthrough enhanced RUNX2, OCN and Coll-1a expression. These results identify the therapeutic potential of HDACi through epigenetic regulation of cell activity, critical to the processes of inflammatory bone destruction

Total knee arthroplasty is an excellent operation and the results have been well documented for both cemented and cementless techniques. It is generally accepted that the results for cemented total knee outpace the results for cementless total knees. Despite this there remains great interest in developing systems and techniques that might allow predictable biologic fixation for knee arthroplasty. There is a long list of requirements that must be met to predictably allow bone ingrowth. These include viable bone, optimal pore size, optimal pore depth, optimal porosity, minimal gaps between bone and implant and minimal micromotion. Implant design is critical but it is proposed that operative techniques can help with some of these issues. We will discuss these operative issues during the surgical demo. These technique issues include: replication of normal posterior slope of the tibia, irrigation of all cuts to avoid thermal necrosis, and application of autologous bone chips to interface - “bone slurry”. These are obviously not all of the issues to consider but we feel they are some of the more important factors related to the cementless technique. The surgeon also has to be mindful of all of the other techniques that are essential to primary total knee arthroplasty. This demo will also utilise an ultracongruent bearing and with Vitamin E polyethylene