Bone has a number of different functions in the skeleton including the physical roles of support, protection and sound wave conduction. The mechanical properties, required for these different functions varies and can be achieved by compositional adaption of the bone material, in addition to changes in shape and architecture. A number of previous studies have demonstrated the relationship between mechanical function and mineral to collagen ratio in bones from different species. The aim of this study is to test the hypothesis that the mineral to collagen ratio is higher in bone with a mechanically harder matrix within a species. The red deer (Cervus elaphus) (n=6) was chosen as a model for studying bone with extreme properties. The mechanical properties of the antler, metacarpal bone and tympanic bulla were defined by indentation using a bench-top indentation platform (Biodent). The mineral to collagen ratio was quantified using Raman spectroscopy. The deposition of mineral was studied at macro-level using pQCT. The results showed that the hardness (Indentation Distance Increase) was lowest in the metacarpal (8.5µm), followed by the bulla bone (9.4µm) and highest in the antler (14.5µm). Raman spectroscopy showed a mineral:collagen ratio of 1:0.10 (bulla), 1:0.13 (metacarpal) and 1:0.15 (antler) for the different bones. This does not follow the more linear trend previously shown between young's modulus and the mineral:collagen ratio. The location of the mineral appeared to differ between bone types with pQCT revealing locations of concentrated density and banding patterns in antler. Interestingly, Raman spectra showed differences in the amide peaks revealing differences in protein structure. The results reject the hypothesis but also suggest that the organisation of mineral and collagen has an impact on the hardness modulus. We demonstrate that the red deer provides a good model for studying bone specialisation. This work will provide the basis for further investigation into collagen as a controlling factor in mineral deposition

Background. Following an anterior cruciate ligament (ACL) injury, the affected knee is known to experience bone loss and is at significant risk of becoming osteoporotic. Surgical reconstruction is performed to attempt to restore the function of the knee and theoretically restore this bone density loss. Cross-sectional analysis of the proximal tibia using peripheral quantitative computed tomography (pQCT) enables localised analysis of bone mineral density (BMD) changes. The aim of this study was to establish the pattern of bone density changes in the tibia pre- and post- ACL reconstruction using pQCT image analysis. Methods. Eight patients who underwent ACL reconstruction were included. A cross sectional analysis of the proximal tibia was performed using a pQCT scanner pre-operatively and one to two years post-operatively on both the injured and contralateral (control) knee. The proximal two and three percent slices [S2 and S3] along the tibia were acquired. These were exported to Matlab(tm) and automated segmentation was performed to remove the tibia from its surrounding structures. Cross correlation was applied to co-register pairs of images and patterns of change in BMD were mapped using a t-test (p<0.05). Connected components of pixels with significant change in BMD were created and used to assess the impact of ACL injury & reconstruction on the proximal tibial BMD. Results. Prior to surgical ACL reconstruction, the BMD in the injured leg was significantly reduced relative to the control leg [S2: p=0.002, S3: p=0.002]. Post surgery, the proximal tibial BMD did not change in either leg [Control S2: p=0.102, S3: p=0.181; Injured S2: p=0.093, S3: p=0.439]. The post surgical images demonstrated patterns of increasing BMD surrounding the tunnel in the form of compact bone. Discussion. A significant reduction in proximal tibial BMD was observed in the ACL injured legs relative to control legs. The pattern of pre-operative bone loss was generally observed to be global across the entire slice. No change in BMD was observed following ACL reconstruction, in either injured or control leg. These results indicate that proximal tibial BMD is reduced and does not change after ACL reconstruction

Summary. Our results prove that Demineralised Cortical Bone (DCB) can be used as biological tendon graft substitute, combined with correct surgical technique and the use of suture bone anchor early mobilisation can be achieved. Introduction. Surgical repair of tendon injuries aims to restore length, mechanical strength and function. In severe injuries with loss of tendon substance a tendon graft or a substitute is usually used to restore functional length. This is usually associated with donor site morbidity, host tissue reactions and lack of remodelling of the synthetic substitutes which may result in suboptimal outcome. In this study we hypothesise that DCB present in biological tendon environment with early mobilisation and appropriate tension will result in remodelling of the DCB into ligament tissue rather that ossification of the DCB at traditional expected. Our preparatory cadaveric study (abstract submitted to CORS 2013) showed that the repair model used in this animal study has sufficient mechanical strength needed for this animal study. Methods. 6 mature female sheep undergone surgical resection of the distal 1 cm of the right patellar tendon and osteotomy of patellar tendon attachment at the tibial tuberosity under general anaesthesia. Repair was done using DCB with 2 suture bone anchor. Animals were allowed immediate mobilisation after surgery and were sacrificed at 12 weeks. The force passing through the operated and non-operated legs was assessed preoperatively and at week 3, week 6, week 9 and week 12 bay walking the animals over a force plate. Radiographs were taken immediately after euthanasia, the Patella-Tendon-tibia constructs were retrieved and pQCT scan was done. Histological analysis included tenocytes and chondrocytes cell counts, semi-quantitative scoring of the neo-enthesis and polarised microscopy. Result. In this study, none of the retrieved specimens showed any evidence of ossification of the DCB as proved by the pQCT analysis. One animal failed to show satisfactory progress after week 3, X-rays showed patella alta, on specimen retrieval no damage to the DCB was found, sutures and stitches were intact and no evidence of anchor pullout was found. Force plate analysis of the other 5 animals showed satisfactory progression over time with 44% functional weight bearing at week 3 progressing to 79% at week 12. There was full range of movement of the stifle joint after 12 weeks. Histological analysis proved formation of neo-enthesis with evidence of cellulisation, vascularisation and remodelling of the collagen leading to ligamentisation of the DCB. Discussion. Surgical reconstruction of damaged tendons is technically challenging, patellar tendon injuries presents even more challenging situation as it involves weight bearing joint. It is generally accepted that a period of immobilisation with passive range of movement exercises and protected weight bearing for up to 6 weeks post operatively is usually advised. Some surgeons use offloading metal wire to protect the repair for 6 weeks involving second surgical procedure to remove the wire. Demineralised bone is usually used in orthopaedics to utilise its osteogenic properties as bone graft substitute and to enhance osteogenesis in load bearing situations. In our study we explored a potential new use of the demineralised bone as tendon graft substitute, it acts as collagen scaffold allowing host cells to remodel its fibres into ligament like structure

Osteoarthritis (OA) affects bone cartilage and underlying bone. Mechanically, the underlying bone provides support to the healthy growth of the overlying cartilage. However, with the progress of OA, bone losses and cysts occur in the bone and these would alter the biomechanical behaviour of the joint, and further leading to bone remodelling adversely affect the overlying cartilage. Human femoral head and femoral condyle were collected during hip or knee replacement operation due to the end stage of osteoarthritis (age 50–70), and the cartilage patches were graded and marked. A volunteer patient, with minor cartilage injury in his left knee while the right knee is intact, was used as control. Peripheral quantitative computed tomography (pQCT) was used to scan the bone and to determine the volumetric bone mineral density (vBMD) distribution. The examination of retrieved tissue explants from osteoarthritic patients revealed that patches of cartilage were worn away from the articular surface, and patches of intact cartilage were left. The cysts, ranging from 1 to 10mm were existed in all osteoarthritic bones, and were located close to cartilage defects in the weight-bearing regions, and closely associated with the grade of cartilage defect as measured by pQCT. The bone mineral density (vBMD) distribution demonstrated that the bones around cysts had much higher vBMD than the trabecular bone away from the cysts. Compared to the subchondral bone under thicker cartilage, subchondral bone within cartilage defect has higher vBMD. This may result from the mechanical stimulation as a result of bone-bone direct contact with less protection of cartilage in cartilage defect regions. This study showed an association between cartilage defect and subchondral bone mineral density distribution. Cysts were observed in all osteoarthritic samples and they are located close to cartilage defects in the weight-bearing regions. Cartilage defect altered the loading pattern of the joints, this leading to the bone remodelling and resultant bone structural changes as compared to the normal bone tissues. This work was financially supported by The ARUK Proof of Concept Award (grant no: 21160)

Osteoarthritis (OA) is a common, debilitating joint disease involving degeneration of cartilage and bone. It has been suggested that subtle changes in the molecular structure of subchondral bone may precede cartilaginous changes in the osteoarthritic joint. To explore these changes Raman spectroscopy was employed as a diagnostic tool. Raman spectroscopy measures inelastic scattered laser light produced when photons interact with chemical materials. Resultant changes in wavelength form spectra relative to the chemical composition of the given sample: with bone this includes the mineral and matrix components, unlike conventional X-rays. The aim of our study is to explore the hypothesis: Changes in matrix composition of osteoarthritic subchondral bone can be detected with Raman spectroscopy. pQCT and Raman spectroscopy were employed to determine the bone mineral density (BMD) and bone quality, respectively. Ten medial compartment OA and five control (non-OA) tibial plateaus were interrogated and analysis performed to compare OA to control, and medial to lateral compartments. The subchondral bone of the medial OA compartments had higher BMD (p=0.05) and thickness compared to lateral and control samples. Spectral analysis revealed there is no difference between the medial and lateral compartments within either cohort. However, there is a statistically significant (p=0.02) spectral difference between the OA and control specimens. The detection of bone matrix changes in osteoarthritis using Raman spectroscopy contributes to the understanding of the biochemical signature of subchondral bone across diseased and control tibial plateaus. This technique has potential to shed light on the role of bone in osteoarthritis

Repair of tendon injuries aims to restore length, mechanical strength and function. We hypothesise that Demineralised Cortical Bone (DCB) present in biological tendon environment will result in remodelling of the DCB into ligament tissue. A cadaveric study was carried out to optimize the technique. The distal 1cm of the patellar tendon was excised and DCB was used to bridge the defect. 4 models were examined, Model-1: one anchor, Model-2: 2 anchors, Model-3: 2 anchors with double looped off-loading thread, Model-4: 2 anchors with 3 threads off-loading loop. 6 mature sheep undergone surgical resection of the distal 1cm of the right patellar tendon. Repair was done using DCB with 2 anchors. Immediate mobilisation was allowed, animals were sacrificed at 12 weeks. Force plate assessments were done at weeks 3, 6, 9 and 12. Radiographs were taken and pQCT scan was done prior to histological analysis. In the cadaveric study, the median failure force for the 4 models; 250N, 290N, 767N and 934N respectively. In the animal study, none of the specimens showed evidence of ossification of the DCB. One animal failed to show satisfactory progress, X-rays showed patella alta, on specimen retrieval there was no damage to the DCB and sutures and no evidence of anchor pullout. Functional weight bearing was 79% at week12. Histological analysis proved remodelling of the collagen leading to ligamentisation of the DCB. Results prove that DCB can be used as biological tendon substitute, combined with the use of suture bone anchor early mobilisation can be achieved

Introduction. The interstitial fluid of bone fluid flow is supplied by flowing blood. Blood flow is determined by three kinds of muscles: cardiac, smooth, and skeletal. Cardiac muscle establishes baseline blood pressure. Smooth muscle controls vessel diameter and skeletal muscle creates intermittent intravascular pressure pulses. For the tibia the relevant skeletal muscle is the gastrocnemius which functions as a muscle pump. This study tested the hypotheses: 1) skeletal muscle-caused pressure pulses increase cortical blood flow, 2) extravasation of vascular fluid and, consequently, interstitial bone fluid flow are enhanced by resultant increased microvascular pressure and 3) bone healing is enhanced by increased bone fluid flow. Methods. Eighteen skeletally mature female New Zealand white rabbits were implanted with bone chamber windows (BCIs) as described previously. The windows were exposed at three weeks and observed weekly until Week 10 using intravital microscopy. During observation, the subject was suspended in prone position in a mesh fabric torso sling jacket so as to eliminate gravity-based reaction forces. Electrodes of a transcutaneous electrical nerve stimulator (TENS) were gel-glued at each rabbits gastroc-soleus position; but activated only in the 11 experimentals. A 4Hz 2.8 ± 1.3V impulse was delivered for 60 minutes. Still and video images were obtained at 0, 2, and 60 minutes following injection of 1μm fluorescent microspheres. Each such injection was followed by injection of 70 kD FITC- or RITC-dextran to define vascularity and capillary filtration. Additional still images were obtained at 5, 30, and 55 minutes. Muscle contraction forces during TENS were obtained acutely following the Week 10 observation with a Futek force transducer cell through an attached nylon suture. Bone mineral density was obtained at Week 3 and Week 10 with a Stratec pQCT and associated software. Data were analyzed statistically using a Wilcoxon signed rank test. Results. All three hypotheses were supported statistically by the data. The average force produced by TENS stimulated gastrocnemius contraction was 18.98 ± 9.42 N/kg muscle. This produced a microstrain of 192μe in bone around the BCI. Bloodflow results are shown in the figure. On average, flow decreased in controls by 12.6% and increased in experimentals by about 2%. Capillary filtration in experimentals was about 34.6% higher than controls after 60 minutes of TENS. Bone formation rate was 62.5% higher with TENS. Conclusion. In order to understand the role of fluid flows in bone physiology, we need to know the how and where of movement. These results suggest the part played by skeletal muscle in bone fluid movement cannot be ignored. As with many evolutionary adaptations, the muscle pump's hydrodynamic contribution to bone may be redundant and merely serve as a backup to percolation from poroelastic deformation. On the other hand, it may be crucial in disuse osteoporosis instigating conditions such as microgravity. The measured increases in capillary filtration and blood flow suggest that intravascular pressure which drives the former and resultant percolation has been increased by the muscle pump. It follows that fluid shear on cortical bone cells also increased. The challenge now is to obtain local flow measurements that would tell us how much

Objectives

The treatment of osteoporotic fractures is a major challenge, and the enhancement of healing is critical as a major goal in modern fracture management. Most osteoporotic fractures occur at the metaphyseal bone region but few models exist and the healing is still poorly understood. A systematic review was conducted to identify and analyse the appropriateness of current osteoporotic metaphyseal fracture animal models.

This study was designed to test the hypothesis that the sensory innervation of bone might play an important role in sensing and responding to low-intensity pulsed ultrasound and explain its effect in promoting fracture healing. In 112 rats a standardised mid-shaft tibial fracture was created, supported with an intramedullary needle and divided into four groups of 28. These either had a sciatic neurectomy or a patellar tendon resection as control, and received the ultrasound or not as a sham treatment. Fracture union, callus mineralisation and remodelling were assessed using plain radiography, peripheral quantitative computed tomography and histomorphology.

Daily ultrasound treatment significantly increased the rate of union and the volumetric bone mineral density in the fracture callus in the neurally intact rats (p = 0.025), but this stimulating effect was absent in the rats with sciatic neurectomy. Histomorphology demonstrated faster maturation of the callus in the group treated with ultrasound when compared with the control group. The results supported the hypothesis that intact innervation plays an important role in allowing low-intensity pulsed ultrasound to promote fracture healing.

Operative fixation is the treatment of choice for a rupture of the distal tendon of biceps. A variety of techniques have been described including transosseous sutures and suture anchors. The poor quality of the bone of the radial tuberosity might affect the load to failure of the tendon repair in early rehabilitation.

The aim of this study was to determine the loads to failure of different techniques of fixation and to investigate their association with the bone mineral density of the radial tuberosity.

Peripheral quantitative computed tomography was carried out to measure the trabecular and cortical bone mineral density of the radial tuberosity in 40 cadaver specimens. The loads to failure in four different techniques of fixation were determined.

The Endobutton-based method showed the highest failure load at 270 N (sd 22) (p < 0.05). The mean failure load of the transosseous suture technique was 210 N (sd 66) and that of the TwinFix-QuickT 5.0 mm was 57 N (sd 22), significantly lower than those of all other repairs (p < 0.05). No significant correlation was seen between bone mineral density and loads to failure.

The transosseous technique is an easy and cost-saving procedure for fixation of the distal biceps tendon. TwinFix-QuickT 5.0 mm had significantly lower failure loads, which might affect early rehabilitation, particularly in older patients.

The reduced stability of hydroxyapatite (HA)-coated implants in osteopenic conditions is considered to be a major problem. We therefore developed a model of a boosted cementless implantation in osteopenic rats.

Twelve-week-old rats were either ovariectomised (OVX) or sham-operated (SO), and after 24 weeks plain or HA-coated implants were inserted. They were treated with either a prostaglandin EP4 receptor agonist (ONO-4819) or saline for one month.

The EP4 agonist considerably improved the osteoporosis in the OVX group. Ultrastructural analysis and mechanical testing showed an improvement in the implant-bone attachment in the HA-coated implants, which was further enhanced by the EP4 agonist. Although the stability of the HA-coated implants in the saline-treated OVX rats was less than in the SO normal rats, the administration of the EP4 agonist significantly compensated for this shortage. Our results showed that the osteogenic effect of the EP4 agonist augmented the osteoconductivity of HA and significantly improved the stability of the implant-bone attachment in the osteoporotic rat model.