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.

Summary

Treatment of equine naturally occurring over-strain tendinopathy with mesenchymal stem cells suspended in bone marrow supernatant resulted in significant improvements compared to saline treated tendons in the normalisation of biomechanical, morphological, and compositional parameters with no adverse effects.

Clinical evidence that patients with type 2 diabetes mellitus (T2DM) have increased risk of fractures is reported. Furthermore, thiazolidinediones, used to treat T2DM increases the risk of secondary osteoporosis & subsequent fractures. The osteogenic potency of metformin is reported in vitro, few studies have investigated the effects of metformin on bone mass and fracture healing in vivo. We aimed to investigate the effects of metformin on fracture healing in vivo.

Osteoarthritis is associated with changes to the matrix composition of subchondral bone. Raman spectroscopy has the potential to detect in vivo the molecular changes in osteoarthritic subchondral bone. The objectives were to determine the levels of mineralisation, carbonate accumulation and bone remodelling in osteoarthritic subchondral bone, which we defined as within 3mm of articular cartilage. This was compared to the proximal-compartment (10mm distal to articular cartilage) and the head-neck junction. Five osteoarthritic (average age: 76 years) and five normal cadaveric femoral heads (average age: 72 years) were scanned using peripheral quantitative computed tomography and then sectioned coronally. Raman spectroscopy was then used to scan the femoral heads. All scans were done in the plane of the longitudinal axis of the diaphysis. Cores were subsequently extracted and sodium dodecyl sulphate polyacrylamide gel electrophoresis performed to determine the levels of homotrimeric collagen. The phosphate-to-amide I ratio, from the Raman spectra, in osteoarthritic subchondral bone was significantly greater than controls (p=0.023). Within osteoarthritic specimens, the phosphate-to-amide I ratio increased proximally. The density in osteoarthritic subchondral bone was 89mg/cm3 higher than controls (p=0.022), and 494mg/cm3 higher than the osteoarthritic proximal-compartment (p<0.001). Moreover, carbonate substitution into the apatite crystals decreased in osteoarthritic specimens. The carbonate-to-amide I ratio was highest in osteoarthritic subchondral bone. Furthermore, the median α1-to-α2-chain ratio in osteoarthritic specimens was 2:1. The changes found in subchondral bone are important in the pathogenesis of osteoarthritis. This study shows that Raman spectroscopy can detect differences between osteoarthritic specimens and controls, further supporting its potential use in diagnosing bone disorders.

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.

We investigated the effect of adjuvant and neoadjuvant chemotherapy regimens on the tibial regenerate after removal of the external fixator in a rabbit model of distraction osteogenesis using New Zealand white rabbits.

Forty rabbits were randomly distributed into two groups. In the neoadjuvant group, half of the rabbits received 1mg/kg cisplatinum & 2mg/kg adriamycin at eight weeks of age followed by 1mg/kg cisplatinum & 4mg/kg adriamycin at ten weeks of age. The remaining ten received an identical volume of normal saline using the same regimen. The adjuvant group differed only in the timing of the chemotherapy infusion. Half received the initial infusion ten days prior to the osteotomy, with the second infusion four days following the osteotomy. Again, the remaining ten rabbits received an identical volume of normal saline using the same regimen. This produced an identical interval between infusions and identical age at osteotomy in both groups. All rabbits underwent a tibial osteotomy at 12 weeks of age. Distraction started 24hours after osteotomy at a rate of 0.75mm a day for 10 days, followed by 18 days without correction to allow for consolidation of the regenerate.

At week 16 there was no difference in Bone Mineral Density (BMD), Bone Mineral Content (BMC) or volumetric Bone Mineral Density (vBMD) in the adjuvant group. Neoadjuvant chemotherapy appears to have a significant detrimental effect on BMD, vBMD and BMC. Despite this there were no significant alterations in the mechanical properties of the regenerate. Histologically there was a trend for increased cortical thickness in the control groups compared to intervention however this did not prove statistically significant.

In conclusion, adjuvant chemotherapy may be more beneficial for cases where distraction osteogenesis is being considered to replace segmental bone loss after tumour excision.

Synthetic bone grafts are used in several major dental and orthopaedic procedures. Strontium, in the form of strontium ranelate, has been shown to reduce fracture risk when used to treat osteoporosis. The aim of the study was to compare bone repair in femoral condyle defects filled with either a 10% strontium substituted bioactive glass (StronBoneTM) or a TCP-CaSO4 graft. We hypothesise that strontium substituted bioactive glass increases the rate of bone ingrowth into a bone defect when compared to a TCP-CaSO4 ceramic graft.

A critical size defect was created in the medial femoral condyle of 24 sheep; half were treated with a Sr-bioactive glass (StronBoneTM), and in the other animals defects were filled TCP-CaSO4. Two time points of 90 and 180 days were selected. The samples were examined with regard to: bone mineral density (BMD) from peripheral quantitative CT (pQCT), mechanical properties through indentation testing, and bony ingrowth and graft resorption through histomorphometry.

The radiological density of Sr-bioactive glass in the defect is significantly higher than that of the TCP-CaSO4-filled defect at 90 and 180 days, (p=0.035 and p=0.000). At 90 days, the stiffness of the defect containing Sr-bioactive glass and is higher than that of the TCP-CaSO4 filled defect, (p=0.023). At 6 months there is no significant difference between the two materials. Histomorphometry showed no significant difference in bone ingrowth at any time point, however significantly more of the graft is retained for the StronBoneTM treatment group than the TCP-CaSO4 group at both 0 days (p=0.004) and 180 days (p=0.000). The amount of soft tissue within the defect was significantly less in the StronBoneTM group than for the TCP-CaSO4 group at 90 days (p=0.006) and 180 days (p=0.000)

The data shows the mechanical stability of the defect site is regained at a faster rate with the strontium substituted bioglass than the TCP-CaSO4 alternative. Histomorphmetry shows this is not due to increased bone ingrowth but may be due to the incorporation of stiff graft particles into the trabeculae. Sr-bioactive glass produces a stronger repair of a femoral condyle defect at 3 months compared with TCP-CaSO4.

Unique progenitor cells have been identified recently and successfully cultured in vitro from human articular cartilage. These cells are able to maintain chondrogenic potential upon extensive expansion. In this study, we have developed a sheep, ex-vivo model of cartilage damage and repair, using these progenitor cells. This study addresses the question can such a model be used to determine factors required for progenitor cell proliferation, differentiation and integration of matrix onto bone. The hypothesis was that sheep allogenic cartilage derived progenitor cells could regenerate artificially damaged sheep articular cartilage in an osteochondral culture model. Progenitor cells were derived from ovine articular cartilage using a differential adhesion assay to fibronectin and expanded clonally. These clonal cells were marked with lentiviral vectors derived from the Human Immunodeficiency Virus-1. When a self-inactivating lentiviral vector encoding a ubiquitous phosphoglycerate kinase promoter, driving a Green Fluorescent Protein (GFP) reporter gene, was used to transduce these cells, up to 80% of these progenitor cells expressed GFP. Normal sheep medial femoral condyles containing about 2mm thick sub-condral bone were obtained and 4mm circular defects created on the cartilage surface using a biopsy punch. Condyles were cultured for two weeks in vitro with GFP labelled progenitor cells within a fibrin glue scaffold (Tisseel Lyo) and matrix production (collagen) as determined by spatially offset Raman spectroscopy and immunohistochemistry was demonstrated. Progenitor cells were able to proliferate and differentiate into collagen producing cells. Such an ex-vivo model system is an effective tool for the analysis of cartilage repair from various sources of stem cells. These ex-vivo experiments and variations on defect type, size, titration of scaffold and progenitor cell numbers requirements can further be used as a basis for screening prior to in vivo experiments.

Introduction

Open fractures occur with an annual incidence of 11.5 per 100,000 (6900 pa in UK). Infection rates, even with intravenous broad-spectrum antibiotics, remain as high as 22%. For this reason necessary bone grafting is usually delayed until soft-tissue cover of the bone injury is achieved. A biodegradable bone graft that released sustained high concentrations of antibiotics and encouraged osteogenesis, that could be implanted safely on the day of injury would reduce infection rates and avoid reoperation and secondary grafting. The non –union rate (approx 350 pa in UK) should also be reduced. Such a graft, consisting of a PLA/PGA co –polymer and containing antibiotics, is under development and here we report assessment of spectrum and duration of antimicrobial activity and effect of addition of antibiotics on mechanical properties.

It is thought that metal ions from metal on metal bearing hip replacements cause DNA damage and immune dysfunction in the form of T cell mediated hypersensitivity. To explore the hypothesis that there is a relationship between metal ion levels and DNA damage and immune dysfunction in matched patient groups of hip resurfacings and standard hip replacements reflected in the levels of lymphocyte subtypes (CD3+ T cells, CD4+ T helper cells, CD8 +T cytotoxic/suppressor cells, CD16 +Natural Killer and CD19+ B cells) in peripheral blood samples, we analysed peripheral blood samples from 68 patients: 34 in the hip resurfacing group and 34 in the standard hip arthroplasty group. Samples were analysed for counts of each sub-group of lymphocyte and cytokine production. Whole blood cobalt and chromium ion levels were measured using inductively-coupled mass spectrometry. All hip components were well fixed.

Cobalt and chromium levels were significantly elevated in the resurfacing group compared to the hybrid group (p<0.001). There was a statistically significant decrease in the resurfacing group's level of CD8+ cells (T cytotoxic/suppressor) (p=0.010). No other subgroup of lymphocytes was significantly affected. Gamma interferon levels post antigen challenge were severely depressed in the hip resurfacing group.

A threshold level of blood cobalt and chromium ions for depression of CD8+ T cells was observed. Hip resurfacing patients have levels above this threshold whilst standard hip replacements fall below it. The patients all had normal levels of CD16 +Natural Killer and CD19+ B cells suggesting that this is not a bone marrow toxic effect. Cytokine analysis confirmed that some aspects of T cell function in hip resurfacing patients are severely depressed.

Introduction: Conflicting opinions exist as to whether bone healing is affected by the administration of bisphosphonates for osteoporosis. In an animal model, we assessed the effect of bisphosphonates on osteoporotic fracture healing and whether the timing of administration made a difference.

Methods: 36 female Wistar rats underwent a mid-diaphyseal femoral osteotomy six weeks after ovariectomy. They were then divided into 3 groups:

no treatment (control);

Results: Of the 36 rats, 8 were unable to complete the study. Group 3 differed from control in three respects: higher bone mineral content (BMC) and density (BMD); larger callus; lower torsional stiffness. Group 2 did not differ significantly from control. There was a significant positive correlation between stiffness and change in BMC in group 1 (r=0.85, p< 0.001) but not so for group 2 (r=0.2, p> 0.05) and group 3 (r=0.04, p> 0.05). A similar trend existed for all radiographic parameters in the three groups.

Conclusion: The results suggest that, with early bisphosphonate treatment, although there is an increase in the size of the callus, that callus is biomechanically inferior. Furthermore, administration of bisphosphonates at either stage destroys the relationship between radiographic and mechanical parameters used to assess fracture healing.

Background: The cause of intervertebral disc degeneration (IVDD) is multifactorial. One proposed mechanism is that IVDD originates in the nucleus pulposus (NP) and progresses radially to the annulus fibrosis (AF). Failure of current treatment modalities in preventing and treating IVDD and thereby low back pain have led to a growing interest in tissue-engineered solutions where a biological repair is induced. By preventing the abnormality at the NP it may be possible to halt further progression of IVDD. Injection of NP cells into an early degenerative IVD, where the AF is still intact, may retard the degenerative process and is presently under investigation. Using a 3-dimensional scaffold that could be successfully introduced into the NP cavity through minimally invasive techniques would prevent the loss of chondrocytic phenotype of the cells and be an improvement over the existing technique by which cells are directly injected into the NP cavity.

Methods:

CaSO4 and CaCO3 3% alginate hydrogels were injected into the NP cavity of a bovine tail. After 90 minutes the tail was dissected to reveal the gel.

Results:

Injectable alginate suspensions formed solid viscoelastic gels, filling the exact shape of the NP cavity.

Discussion: This study demonstrates that slowly polymerising CaCO3 and CaSO4 alginate gels are injectable and capable of sustaining NP cells in-vitro. Cells remain viable, maintain their phenotype, proliferate and produce ECM during the culture period. CaCO3 alginate gel provides a 3-dimensional matrix more favourable to NP cellular activity than the CaSO4 alginate gel. Synvisc® has a chondro-stimulatory effect on NP cells in-vitro. These effects are similar to those observed previously with hyaluronic acid, in that it binds to cell surface CD44 receptors, thereby affecting essential cellular functions and cytoskeleton structure. Synvisc® however has an advantage in that it is highly viscous and can reside longer within an alginate construct thereby having a sustained long-term stimulatory effect. This study demonstrates a successful tissue-engineered approach for replacing the NP and, subject to further studies, may be used for retarding mild-to-moderate IVDD, alleviating lower back pain and restoring a functional NP through a minimally invasive technique.

We previously demonstrated that cartilaginous tissue was induced on a reamed acetabular articulation in an ovine hemiarthroplasty model with three different femoral head sizes. At maximum loading during stance phase, the acetabular peak stresses immediately after reaming could reach approximately 80 MPa under direct implant-bone contact with in-vitro measurements.

We aimed to establish finite element (FE) models of the ovine hip hemiarthroplasty which examine stress distribution on the reamed acetabula by three head sizes. We hypothesized that the stress distribution did not differ between different sizes when the joint is congruent and that the peak stresses in the acetabulum immediately after reaming occurred in the dorsal acetabulum.

Three two-dimensional FE models of ovine hip hemi-arthroplasty were built; each comprised a head component, 25, 28, and 32 mm in diameter, and an acetabular component. The acetabular geometry was acquired from an ovine acetabular histological section. The head was moved to partly intersect with the acetabulum representing the reaming procedure and a congruent contact was confirmed. Cortical bone and cancellous bone were modelled as linear elastic, with moduli of 20 and 1.2 GPa, respectively. Variable moduli were also assessed. The finest mesh for each model consisted of over 100,000 four-node quadrilateral elements. Loading conditions were chosen to represent peak hip joint force developed during the stance phase. Stress distribution in the acetabular area in contact with the head was plotted against the articulating arc length.

The results confirmed that the stress distribution between different prosthetic head sizes in a reamed hemiarthroplasty model did not change when the joint was congruent. The peak compressive stresses occurred in the dorsal acetabulum with the 32 mm model being the highest at approximately 69 MPa, the 28 mm model at 63 MPa, and the 25 mm model at 54 MPa. An increase in the cancellous modulus and a decrease in the cortical modulus increased the peak stresses in the dorsal acetabulum.

This presents an indicative study into the effect of prosthetic femoral head sizes on the stress distribution in the acetabulum. The idealized 2-D models showed reasonable agreement when compared quantitatively with the in vitro study.

Objective: To challenge the validity of using biomarker concentrations in synovial fluid for the assessment of joint pathology.

Hypothesis: Synovial fluid biomarker concentrations are influenced by both cartilage and synovial fluid volumes.

Methods: Synovial fluid volumes were determined from the equine metacarpophalangeal (MCP), proximal inter-phalangeal (PIP) and distal interphalangeal (DIP) joints, which have different disease prevalences.

Chondrocyte density was calculated from a defined site in each joint.

Cartilage volume was measured by novel application of Peripheral Quantitative Computed Tomography (pQCT).

Cartilage oligomeric matrix protein (COMP), glycos-aminoglycans (GAG) and total protein (TP) concentrations were measured and then adjusted for cartilage and synovial fluid volume and compared between joints.

Results: Mean synovial fluid volume was significantly greater in the MCP than the distal joints (p< 0.0001) (3.2 ±0.5ml, 0.5 ±0.1ml and 0.6 ±0.1ml respectively). In contrast, the DIP had the greatest cartilage volume compared to the proximal joints (5360 ±667mm3 2640mm3, 1940 ±331mm3 respectively). There was no significant difference in the cartilage cellularity between all joints.

The DIP had higher TP, COMP and GAG concentrations, however, when values were expressed per unit cartilage volume the opposite was found, with the MCP then exhibiting significantly higher concentrations.

Conclusions: These data show the joint with the highest prevalence to osteoarthritis has the lowest biomarker synovial fluid concentrations but the highest biomarker levels per unit cartilage, suggesting a higher release. These results indicate that meaningful interpretation of biomarkers in synovial fluid require consideration of both fluid and cartilage volume.

Background: As the understanding of bone repair mechanics has advanced the integrity of the bone pin interface has emerged as a key factor in determining the success of external fracture fixation. The benefits of using pins coated with Hydroxyapatite (HA) are well documented however the thickness of the conventional plasma spray coating precludes its use for modification of the surface of fine features in implants. Consequently new electro-chemical techniques for pre-coating implants with a ‘biomimetic’ HA layer using simulated body fluids (SBF) have been pioneered. In this study we test the hypothesis that varying the technique for deposition of HA by electrolysis of SBF alters the morphology of the HA surface which will modify the level of osseointegration. Method: Three alternative methods of HA coating the Barerre, Redepenning and Kumar techniques were compared. Tantalum coated stainless steel pins were coated then used to stabilise a mid-diaphyseal osteotomy in three sheep using an orthofix fixator for a period of ten weeks. Insertion and extraction torques were measured to calculate the pin performance index (PPI). Sections of the bones were then examined using scanning electron microscopy to determine the percentage of bone in contact with the pin surface and the percentage of new bone formation. Results: The different coating protocols resulted in different HA crystal morphologies. The extraction torque exceeded the insertion torque for both the Barerre and Redepenning methods and their PPI exceeds that of plasma spray coatings. The Redepenning technique was shown to perform sig-nificantly better than both the Barerre (p=0,001) and Kumar (p=0,001) techniques with 49.4% of the pin surface in contact with bone. These results were mirrored on analysis of new bone formation with the Redepen-ning technique showing 70.2% of new bone formation compared to the Barerre (55.4%) and Kumar (53.8%) methods. Conclusion: These results indicate that the Redepenning technique is the most effective for creating a bio mimetic HA coating in terms of bonding to bone and promoting new bone formation. This technique holds significant advantages over the conventional plasma spray technique for example the coating thickness can be easily controlled and additional proteins such as bone morphogenic proteins and antibiotics can be incorporated. It may therefore represent a new era in the use of HA coating.

The skeletal system exhibits functional adaptation. For bone the mechanotransduction mechanisms have been well elucidated; in contrast, the response of tendon to its mechanical environment is much more poorly understood despite tendon disorders being commonly encountered in clinical practice. This study presents a novel approach to developing an isolated tendon system in vivo. This model is used to test the hypothesis that stress-shielding, and subsequent restressing, causes significant biomechanical changes. We propose a control mechanism that governs this process.

A custom-built external fixator was used to functionally isolate the ovine patellar tendon(PT). In group 1 animals(n=5) the right PT was stress-shielded for 6 weeks. This was achieved by drawing the patella towards the tibial tubercle, thus slackening the PT. In group 2 (n=5) the PT was stress-shielded for 6 weeks. The external fixator was then removed and the PT physiologically loaded for a further 6 weeks. In each case, the PT subsequently underwent tensile testing and measurement of length(L) and cross-sectional area(CSA). The untreated left PTs acted as controls (n=10).

6 weeks of stress-shielding significantly decreased material and structural properties of tendon compared to controls (elastic modulus(E) 76.2%, ultimate tensile strength(UTS) 69.3%, stiffness(S) 79.2%, ultimate load(UL) 68.5%, strain energy(SE) 60.7%; p< 0.05). Ultimate strain(US), L and CSA were not significantly changed. 6 weeks of subsequent functional loading (Group 2) caused some improvement in material properties, but greater recovery in structural properties (E 79.8%, UTS 91.8%, S 96.7%, UL 92.7%, SE 96.5%). CSA was significantly greater than Group 1 tendons at 114% of control value.

Previous models of tendon remodelling have relied on either joint immobilization or direct surgical procedures. This model allows close control of the tendon’s mechanical environment whilst allowing normal joint movement and avoiding surgical insult to the tendon itself. The hypothesis that stress-shielding, and subsequent restressing, causes significant biomechanical changes has been upheld. We propose that the biomechanical changes observed are governed by a strain homeostasis feedback mechanism.

Introduction: There have been 70,000 hip resurfacings implanted, predictions are for it to become 12% of the US hip replacement market by 2010 (Goldmann Sachs report Oct 2005). There is concern that the cobalt and chromium ions released from metal on polyethylene hip replacements cause immune dysfunction in the form of T cell mediated hypersensitivity (indicated by increased numbers and stimulation of T cells). If metal ions cause significant effects on white blood cells we might reasonably expect to detect this by simply measuring numbers of white blood cells.

Aim : To examine the possibility that raised metal ions may cause an abnormal number of white blood cells, termed a blood dyscrasia.

Method : Peripheral blood samples were analysed from 68 patients: 34 in the hip resurfacing group and 34 in the standard hip arthroplasty group. Samples were analysed for counts of each sub-group of lymphocyte. Functional assessment was also performed using a activation panel of white cell CD markers. Whole blood cobalt and chromium ion levels were measured using inductively-coupled mass spectrometry. All hip components were well fixed.

Results : Cobalt and chromium levels were significantly elevated in the resurfacing group compared to the hybrid group (p< 0.001). There was a statistically significant decrease in the resurfacing groups’ level of CD8⁺ cells (T cytotoxic/suppressor) (p=0.010). There was a characteristic pattern of immune modulation seen on the activation panel.

Conclusions : We found an immune modulation in patients with metal on metal hip resurfacing. This was not a hypersensitivity reaction. This change in T cell function may be detrimental or beneficial to patients.

Current bone grafts include allograft and autografts, both of which have limitations. Tissue engineering biotechnology has shown considerable promise in improving grafts. A competent graft material should ideally have osteoconductive and osteoinductive properties and comprise of bone forming cells and osteoinductive growth factors. In this study, we have evaluated the in vitro formation of bone and have used human demineralised bone matrix [DBM] and human insoluble collagenous matric [ICM] as scaffolds for mesenchymal stem cells [MSCs] and osteogenic protein [OP-1]. The objective was to determine whether combined addition of OP-1 and MSCs resulted in a superior bone graft substitute by improving the inherent osteoinductive property.

DBM and ICM were prepared and combined with rhOP [1.4 mg/0.25 mg of bone] and MSCs [1 x 105/ ml]. Statistically significant differences in MSC proliferation were seen between materials with and without OP-1 [P< 0.05}, n=8] in DBM on day 1, and both DBM and ICM on day 7 and 14. Enhanced osteogenic differentiation was observed in the presence of OP-1 when compared to DBM alone and on DBM and ICM with OP-1. In conclusion MSCs and OP-1 can be seeded together on DBM and ICM and Von Kossa staining and X-ray analysis confirmed in vitro de novo bone formation, with DBM + MSCs + OP-1 being more successful in this regard.

Conclusion: To date, no other study, to the author’s knowledge, has used MSCs and OP-1 together on a graft material; this funding, therefore, has very important clinical implications.

Limitations of allografts and autografts for bone repair have increased the demand for a synthetic bone graft substitute for load-bearing and non-load bearing osseous defects. Tissue engineering of bone has thus been implicated to circumvent and eliminate the limitations of existing therapies, with living cell-scaffold constructs ultimately “integrating” with the patients own tissue. Bone engineering requires cells, growth inducing factors and a scaffold for delivery of cells to the anatomic site, creation of 3-D space for tissue formation and mechanical support. In this study, we investigated whether addition of osteogenic Protein-1 (OP-1) enhanced the osseoinductive properties of hydroxyapatite (HA) loaded with mesenchymal stem cells (MSCs). The study was conducted over a fourteen day period and the two groups HA/MSC and HA/MSC loaded with OP-1 were analysed qualitatively by SEM and quantitatively by assessment of proliferation (Alamar blue assay and total cellular DNA) and differentiation marker alkaline phosphatase activity (ALP). HA/MS/OP-1 showed a statistically significant (p< 0.05) increase in cell proliferation (286.52 ± 58.2) compared to the unloaded samples (175.62 ± 23.51). ALP activity (release) was also significantly enhanced (p < 0.05) in the loaded samples at day 14 (12.63 ± 1.58) compared to the control (2.73 ± 1.07).

Conclusion: the osseoinductive potential of HA was markedly improved by the incorporation of MSC’s and OP-1. This type of graft could provide improved mechanical stability at an earlier time point, and may influence future clinical application of HA for load bearing sites.

Restoration of bone stock is the single greatest challenge facing the revision hip surgeon today. This has been dealt with by means of impaction grafting with morsellised allograft from donor femoral heads.

Alternatives to allograft have been sought. This study investigates the use of a porous biphasic ceramic in impaction grafting of the femur.

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 2 and group four 10% allograft and 90% BoneSave as the graft material.

Function was assessed by measuring peak vertical reaction forces. Changes in bone mineral density were measured by DEXA scanning. Loosening and subsidence were assessed radiographically and by examination of explanted specimens.

All outcome measures showed no statistically significant difference between the four groups after eighteen months of full function.

Conclusion: When used as allograft expanders, Bone-Save and similar porous biphasic ceramics perform as well as pure allograft in impaction grafting of the femur.