Numerous investigators have described osteogenic differentiation of bone marrow stromal cells obtained from both murine and human sources over the past decade. The ease of access and large available quantity of adipose tissue, however, makes Adipose-Derived Stem Cells (ADSC) a far more practical alternative for clinical applications, such as operative treatment of non-unions and regeneration of critical bone defects. Therefore, the primary goal of this research endeavor is to achieve osteogenic differentiation of ADSC. Previous work has already demonstrated that bone morphogenetic protein receptor 1A (BMP receptor 1A) signaling is required for healing critical bone defects. Based on this evidence, we used a lentiviral vector to increase expression of BMP receptor 1A by our stem cell population in order to direct their differentiation into the osteoblastic lineage. We harvested subcutaneous adipose tissue intraoperatively from consenting patients undergoing elective lipoplasty and panniculectomy procedures. The stromal vascular fraction was isolated from this tissue and further refined by passaging in selective media to yield a stable population of ADSC in primary culture. Both the identity and homogeneity of this stem cell population was confirmed using adipogenic induction media and differentiation cocktails. In addition, we subcloned an expression plasmid containing the BMP receptor 1A locus in tandem with green fluorescent protein (GFP) under the transcriptional control of a single promoter. This plasmid was packaged into a lentiviral vector to provide a reliable method of achieving both genomic integration and long-term expression of the BMP receptor 1A gene. Hence, transduction of ADSC using this vector resulted in overexpression of BMP receptor 1A by these multipotent cells. The GFP was then utilized as a reporter gene to screen and enrich the ADSC population for only those stem cells with a robust expression of BMP receptor 1A. The ADSC that overexpressed BMP receptor 1A were found to achieve osteogenic differentiation after 18 to 20 days of in vitro culture, as revealed by immunohistochemistry assays for osteocalcin. Osteogenic differentiation was further confirmed by alizarin red staining and quantitative PCR for alkaline phosphatase gene expression as a biomarker for the osteoblastic lineage. Our results demonstrate that stem cells derived from the adipose tissue of a patient represent a viable means of culturing autologous osteoblasts in vitro for future implantation at the site of critical bone defects. This method of attaining osseous regeneration is intuitively appealing, given the minimal donor site morbidity associated with removing subcutaneous fat. By transducing the ADSC with a lentiviral vector, we have also collected further evidence implicating the critical importance of signaling mediated by the BMP receptor 1A during osteogenesis. Further tissue engineering studies are now in progress to evaluate the osteogenic differentiation potential of these stem cells under hydrostatic and fluid flow shearing mechanical loads

Introduction. We describe a minimally invasive technique that permits intra-focal bone graft of non-union sites with minimal disturbance of soft tissues and vascularity, and present the results of this technique. Materials and Methods. 10 patients with established tibia fracture non-union were judged suitable for the technique, and were treated in our limb reconstruction unit between January 1995 to June 2007. Eight patients were male, 2 were females with a mean age of 37.4 years (27–64). Five fractures were in the distal tibia and five were diaphyseal fractures. Five fractures were as a result of high velocity and 6 fractures were open. Average number of previous operations were 3 (range 1–7). Time lapse between injury to trephine grafting procedure was mean of 34 (6–168 months). 5 patients had a sedentary job, 2 were labourers and 2 were not working. There were 5 smokers and 2 obese patients. Six cases were of infected non-unions. Operative technique. Under general anaesthesia, the graft(s) was first obtained from the iliac crest using a guide wire centred trephine. A stab incision was made at the non-union site under image control. A core was taken across the non-union, taking care to breach both bone fragments. A trephine core was rolled in Bone Morphogenetic Protein (BMP-7). This was then introduced through the trephine in to the non-union site and pushed with the plunger into the defect created by the cylindrical plug taken from the site. After this, the trocar with the stylet in place was gradually withdrawn with small oscillating motions to fill in the path of the trocar. This was repeated about 3–4 times at the non-union site. The stab wound were closed with interrupted Nylon. Results. 10 patients underwent treatment for complex non-union after initial operation (average number 3) at the referring centre. Treatment in a circular fixator ranged from 10–33 months (20.7 months) with reapplication in 2 patients. Average number of procedures were 4 (range 1–7). Trephine grafting was performed in all cases; BMP was used in 4 cases along with iliac crest bone graft. All patients attained clinical and radiological union with CT confirmation required in 2 patients. 4 patients with sedentary job returned to work, manual workers returned to low demand occupation. Conclusion. The technique described is a safe and effective treatment method for this complex problem with limited donor site morbidity and avoids prolonged hospital stay

The purpose of this study was to quantify the effect of BMP 7 and recombinant Human (rh) BMP 2 at stimulating bone formation and bone union in trauma and elective orthopaedic surgery. Methods. We retrospectively reviewed the use of BMP 7 and rhBMP 2 at the Queen Alexandra Hospital between 2005 and 2012. The minimum follow up was three months. Inclusion criteria consisted of all patients who had failed to achieve previous surgical bone union and then received either BMP 7 or rhBMP 2 in an attempt to achieve bone union (as part of revision surgery). Patients who have not completed a minimum of three months follow up were excluded. Bone union was defined clinically and radiographically. Results. 17 patients were included (9 elective and 8 trauma patients). 9 patients received BMP2 (8 trauma and 1 elective) and 8 received rhBMP 2 (all elective). The average number of attempted fusions with autogenous bone graft prior to the use of BMP agent in the trauma and elective group was 2 and 3 respectively. The overall union rate following the use of BMP was 94.1%. 1 patient from the BMP 7 group (trauma patient) failed to unite. The union rate with BMP 7 and rhBMP 2 was 88.9% and 100% respectively. Following the use of BMP the average time to union was 117 days (BMP 7 124 days and rhBMP 2 112 days). Conclusion. Our results suggest both BMP 7 and rhBMP 2 to be an effective means of stimulating bone formation and bone union in patients with established non-union, in both trauma and elective orthopaedic surgery

Cahill et. al. published a large review of the use of BMP in spinal fusions. They reviewed the nationwide inpatient database, which represents approximately 25% of use U.S. Community Hospitals from the years 2002 to 2006. This included over 300,000 fusion type procedures. They noted increased complications with the use of anterior cervical procedures specifically increased complications with increased dysphasia and wound complications. Due to these concerns, the Food and Drug Administration released last year a public health notification about the potential life threatening complications related to the use of BMP in anterior cervical spine fusions. Joseph & Rampersaud noticed a 20% incidence of heterotopic ossification in patients undergoing this procedure versus only 8% for patients who had undergone fusions without BMP. Wong et. al. published a report on five cases of neurologic injury that relate to the use of BMP and the formation of heterotopic bone. Again, the suggestion of a barrier or closure defect was brought up and this may help minimise the risks; however, further work is noted. Multiple authors have noted a phenomenon of osteolysis occurring around graft fusion sites for the use of BMP. McCullen et. al. evaluated that 32 levels in 26 patients who had undergone a TLIF procedure. It is unclear the carcinogenic and tetraogenic effects of the use of BMP in the spine and also, the effects of repeat exposures on BMP has yet to be addressed. Finally, the long term cost and benefits of the use of BMP on the health care system has yet to be fully addressed. So in conclusion, BMP2 is effective in producing fusions especially in challenging environments, deformity, smoking and infection. However, the complications continue to be a concern especially with regards to interbody fusions as well as in the cervical spine

Periosteum is important for bone homoeostasis through the release of bone morphogenetic proteins (BMPs) and their effect on osteoprogenitor cells. Smoking has an adverse effect on fracture healing and bone regeneration. The aim of this study was to evaluate the effect of smoking on the expression of the BMPs of human periosteum. Real-time polymerase chain reaction was performed for BMP-2,-4,-6,-7 gene expression in periosteal samples obtained from 45 fractured bones (19 smokers, 26 non-smokers) and 60 non-fractured bones (21 smokers, 39 non-smokers). A hierarchical model of BMP gene expression (BMP-2 > BMP-6 > BMP-4 > BMP-7) was demonstrated in all samples. When smokers and non-smokers were compared, a remarkable reduction in the gene expression of BMP-2, -4 and -6 was noticed in smokers. The comparison of fracture and non-fracture groups demonstrated a higher gene expression of BMP-2, -4 and -7 in the non-fracture samples. Within the subgroups (fracture and non-fracture), BMP gene expression in smokers was either lower but without statistical significance in the majority of BMPs, or similar to that in non-smokers with regard to BMP-4 in fracture and BMP-7 in non-fracture samples. In smokers, BMP gene expression of human periosteum was reduced, demonstrating the effect of smoking at the molecular level by reduction of mRNA transcription of periosteal BMPs. Among the BMPs studied, BMP-2 gene expression was significantly higher, highlighting its role in bone homoeostasis

Introduction. Total joint arthroplasty is associated with substantial blood loss as well as changes in basic metabolic labs. Routinely patients receive multiple post-operative blood draws for measuring hematocrit, hemoglobin (H&H), and basic metabolic panels (BMP). Based on a multimodal approach to blood conservation and pre-operative optimization, we questioned the need to check daily labs on our inpatient primary total hip and knee patients. The purpose of this study was to identify risk factors for transfusion and metabolic abnormalities requiring treatment in an attempt to reduce the number of post-operative blood draws and labs. Methods. We retrospectively reviewed all 1134 patients who underwent primary total hip (THA) or total knee arthroplasty (TKA) from July 2016 to March 2017 in our inpatient hospital setting. There were 733 TKA and 401 THA. Pre- and post-operative lab values were reviewed and correlated with transfusion and medical treatments. Results. Twelve patients received a post-operative transfusion (1.1%). In TKA patients 2 of 733 (0.2%) were transfused while in THA patients 10 of 401 (2.4%) were transfused. Of the 12 patients receiving transfusions 11 were females, and in all 12 the pre-operative hemoglobin was less than 13. For the overall series of 1134 patients, 176 (15.5%) required potassium chloride supplementation based on BMP. Only patients with pre-existing renal disease or diuretic treatment received potassium chloride supplementation. Conclusions. Based on our findings, only patients with pre-operative hemoglobin less than 13 require post-operative H&H. Additionally, only patients with low pre-operative potassium, history of renal disease, or active treatment with a diuretic require post-operative BMP

Bone morphogenetic proteins (BMPs) are able to induce osteogenic differentiation in many cells, including muscle cells. However, the actual contribution of muscle cells to bone formation and repair is unclear. Our objective was to examine the capacity of myogenic cells to contribute to BMP-induced ectopic bone formation and fracture repair. Osteogenic gene expression was measured by quantitative PCR in osteoprogenitors, myoblasts, and fibroblasts following BMP-2 treatment. The MyoD-Cre x ROSA26R and MyoD-Cre x Z/AP mouse strains were used to track the fate of MyoD+ cells in vivo. In these double-transgenic mice, MyoD+ progenitors undergo a permanent recombination event to induce reporter gene expression. Ectopic bone was produced by the intramuscular implantation of BMP-7. Closed tibial fractures and open tibial fractures with periosteal stripping were also performed. Cellular contribution was tracked at one, two and three week time points by histological staining. Osteoprogenitors and myoblasts exhibited comparable expression of early and late bone markers; in contrast bone marker expression was considerably less in fibroblasts. The sensitivity of cells to BMP-2 correlated with the expression of BMP receptor-1a (Bmpr1a). Pilot experiments using the MyoD-Cre x Rosa26R mice identified a contribution by MyoD expressing cells in BMP-induced ectopic bone formation. However, false positive LacZ staining in osteoclasts led us to seek alternative systems such as the MyoD-cre x Z/AP mice that have negligible background staining. Initially, a minor contribution from MyoD expressing cells was noted in the ectopic bones in the MyoD-cre x Z/AP mice, but without false positive osteoclast staining. Soft tissue trauma usually precedes the formation of ectopic bone. Hence, to mimic the clinical condition more precisely, physical injury to the muscle was performed. Traumatising the muscle two days prior to BMP-7 implantation: (1) induced MyoD expression in quiescent satellite cells; (2) increased ectopic bone formation; and (3) greatly enhanced the number of MyoD positive cells in the ectopic bone. In open tibial fractures the majority of the initial callus was MyoD+ indicating a significant contribution by myogenic cells. In contrast, closed fractures with the periosteum intact had a negligible myogenic contribution. Myoblasts but not fibroblasts were highly responsive to BMP stimulation and this was associated with BMP receptor expression. Our transgenic mouse models demonstrate for the first time that muscle progenitors can significantly contribute to ectopic bone formation and fracture repair. This may have translational applications for clinical orthopaedic therapies

The management of upper limb nonunions can be challenging and often with unpredictable outcomes. In the study we present the results of treatment of upper limb nonunions treated in our institution with BMP-7 biological enhancement. Between 2004 and 2011 all consecutive patients who met the inclusion criteria were followed up prospectively. Union was assessed with regular radiological assessment. At the final follow up clinical assessment included the disabilities of the Arm, Shoulder and Hand (DASH) score, range of movement and patient satisfaction. The mean follow up was 12 months (12–36). In total 42 patients met the inclusion criteria with a mean age of 47. Anatomical distribution of the nonunion sites included 19 cases of mid/proximal radius/ulna, 14 humerus, 6 distal radius and 3 clavicles. 5 patients had septic nonunion, 35 had atrophic nonunion, 11 had previous open fractures, and 10 had bone loss (range 1–3 cm). The mean number of operations performed and the mean time from injury to BMP application was 1.5 and 26 months, respectively. 40 patients had both clinical and radiological union whereas 2 had partial radiological union but a pain free range of motion. BMP was applied in isolation in 1 case and 41 cases the application was combined with autologous bone grafting. The range of movement of the affected limb, DASH score and patient satisfaction were optimum at the final follow up. This study supports the use of BMP-7 as a bone stimulating adjunct for the treatment of complex and challenging upper limb nonunions

Background. Despite aggressive debridement, thorough irrigation, administration of systemic antibiotics and staged treatment, many open fractures still become infected. A graft that can promote bone regeneration and prevent infection could decrease complications. Polyurethane (PUR) scaffolds have been previously shown in separate studies to be non-toxic, osteoconductive, can promote bone growth through BMP delivery and prevent infection by having sustained release of an antibiotic. This scaffold can deliver both BMP and vancomycin simultaneously; the purpose of this study is to determine if the co-delivery of the antibiotic inhibits bone formation. Methods. Using an established critical size defect rat femur model, the amount of bone formation created by PUR scaffolds containing low and high doses of rhBMP-2 (2.4 μg and 22.4 μg respectively) and 0.8 mg vancomycin (8% of graft by weight) were compared to scaffolds that contained rhBMP-2 without antibiotics. After 4 weeks, the femurs were harvested and bone growth was assessed using microCT. Results. There were no significant differences in bone growth between the groups that had the high dose of rhBMP-2. Surprisingly, the scaffolds that had the low dose of rhBMP-2 and vancomycin promoted more bone formation than scaffolds that had rhBMP-2 and no antibiotics. Conclusions. The addition and co-delivery of vancomycin to the scaffolds did not inhibit bone growth. The addition of vancomycin to the PUR scaffolds may have altered the release kinetics of the rhBMP-2; this may explain the increase of bone formation in this group. This study demonstrates that incorporation of a therapeutic and a clinically-relevant level of vancomycin does not inhibit bone formation. These results suggest that a dual delivery bone graft has potential to reducing complications associated with open fractures

Statement of purpose. To determine the outcome of the use of Bone Morphogenetic Protein 7 (BMP7) as a replacement for bone graft in a limb reconstruction unit. Methods. Retrospective case note and imaging review was performed on a cohort of 71 consecutive patients from October 2009 to October 2012 in whom BMP7 was used to achieve union. The patients were identified from a pharmacy database. Factors analysed included the perceived indication, location in the skeleton, age, comorbidities, type of procedure (non-union, fusion, docking site etc), complications and need for revision surgery. Results. BMP7 was used in 71 patients with a median age of 63 (mean 58, range 17–86). The majority of patients were in the seventh decade. 62 were non-unions, eight were for fusion of docking site and one for fusion of an osteotomy. Circular external fixation was used in 20, IM nails in four, and plate fixation in 47. Indications for using BMP7 as opposed to bone graft included advanced age, immunosuppressive comorbidities or medication and obesity. In 65 cases bony union was achieved after the index procedure and one patient needed further surgery. There were five failures: two patients died before union and three failed to heal with the index intervention, leading to 74 procedures in 71 patients. BMP7 was used in several anatomic sites: femur (n=29), humerus (n=15), tibia (n=18) and in fusion of a joint (n=9). Overall success rate for achieving union was 93%. Local inflammation lasting a mean of three weeks was seen in six cases, and five patients developed heterotopic ossification, of which one was symptomatic. Conclusion. BMP 7 can be used as a replacement for autologous bone graft with predictable success in situations where bone graft harvest may be deemed unsuitable either because of local or systemic factors

Aim. To analyse the results of the use of Recombinant Bone Morphogenic Protein (BMP-7) for treatment of fracture nonunions at our institution. Material and methods. From 2001 to 2006, 23 patients with fracture nonunion were treated with BMP-7 for bone healing. There were 14 male and 9 females. The mean age of patients was 45 years (Range 21-76 yrs). There were 11 femoral, 9 tibial and 3 humerus fractures. There were 4 open injuries. The average number of operations before BMP-7 insertion was 2.66 (Range 0-6). The mean time between the injury and BMP insertion was 54 months (Range 5-312). 9 patients had previous autologous bone graft inserted without union. Results. All the fracture went on to unite within an average of 7 months (Range 4-16). 4 patients had BMP-7 insertion on its own. In another 3 patients it was mixed with allograft. In the rest of 16 patients BMP-7 was mixed with autologous bone graft. 2 patients needed BMP-7 insertion on 2 separate occasions. In all except 1 patient the original fixation of the fracture had to be revised. There were no complications from the use of BMP-7. Conclusion. Use of recombinant BMP-7 lead to fracture union in all our patients. We believe that the use of BMP-7 improved the chances of fracture healing in persistent nonunions and it is safe and easy to use

We report on the clinical, radiographic and functional outcomes after salvage arthrodesis for complex ankle and hind-foot problems - the Portsmouth experience with the Ilizarov ring fixator. 11 patients underwent ankle and hind-foot (tibio-calcaneal) arthrodeses using an Ilizarov ring fixator between 2006 and 2010. The indications included failed fusion after primary arthrodesis, sepsis complicating internal fixation of fractures, talar avascular necrosis and failed total ankle arthroplasty (TAR). All patients had undergone multiple previous surgeries, which had failed. There were 8 males and 3 females in this group. Average age of the patients was 58 (43 years – 77 years) Mean follow up was 36 months (7 – 60 months). Mean frame time was 24 weeks (15 – 36 weeks). BMP 2 (Inductos) was used in three cases. The procedure was combined with a proximal corticotomy and lengthening in 2 patients who had undergone a talectomy and tibio-calcaneal fusion. There were no major complications apart from minor pin site infections requiring oral antibiotics. There were no deep infections, thromo-embolic issues, CRPS, or functional problems on account of limb shortening. Patients were assessed clinically, radiologically and using functional outcome scores - EQ50 and AOFAS. Solid arthrodesis was achieved in all but one patient who was subsequently revised with a hind-foot nail. All patients were satisfied with their overall improvement in pain and function. We conclude that this is an effective salvage technique for complex ankle and hind-foot problems in patients with impaired healing potential, insufficient bone stock and progressive deformity

The key factors in Tissue Engineering are multipotent stem cells, growth factors (necessary to manipulate cell destiny) and scaffolds (3D constructs which support the growing tissue). Mesenchymal stem cells are the most important part of this equation, and it is procurement and manipulation of these that lies at the heart of tissue engineering. Luckily, mensenchymal stem cells can be obtained from many tissues, including synovium, bone marrow and periosteum. The use of bioreactors to optimise culture conditions and improve cell viability provides an opportunity to control stem cell destiny. Various Tissue Engineering strategies exist: manipulating cells in situ with osteogenic growth factors, such as BMP; implanting whole tissue grafts; and the use of Gene therapy. The tissues that concern orthopaedic surgeons are very diverse and no single tissue engineered construct will be able to fulfil all our clinical needs. Tissue engineering of articular cartilage is very difficult technically, but once accomplished will revolutionalise practice. The challenge lies in being able to produce cartilage as similar to native hyaline cartilage as possible. Although promising, ACI, using culture expanded cells, is able at best to produce hyaline-like cartilage but not the real thing. Multipotent mesenchymal stem cells are being used in this field. Even simply injecting these intraarticularly has been shown to retard the progression of OA in animal models. When attempting to regenerate meniscal cartilage, the mechanical properties of the scaffold become crucial, as the biomechanics of the knee are highly hostile. Ligaments and tendons, though the least complex tissues architecturally, have very high tensile properties which will be hard to replicate. The challenging aspects of Orthopaedic Tissue Engineering are manifold, yet the field itself is growing in leaps and bounds. Despite some initial setbacks, the new developments in this discipline are very encouraging

A Ruys, School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, Sydney. The effects of bone anabolics can be maximised by systemic co-treatment with an anti-catabolic. Local treatment may reduce the total drug required and produce superior outcomes, although high dose local bisphosphonate has been reported to impair bone formation. We have explored local co-delivery of anabolic/anti- catabolic bone drugs at different doses. We manufactured biodegradable poly-D,L-lactic acid (PDLLA) polymer pellets containing 25g BMP-7 as an anabolic with or without 0.002mg-2mg Pamidronate (PAM) as an anti-catabolic. Polymer pellets were surgically implanted into the hind limb muscle of female C57BL6 mice. Animals were sacrificed at three weeks post- implantation and bone formation was assessed by radiography, microcomputed tomography (microCT) and histology. Histological staining on five Âm paraffin sections included haematoxylin/eosin, alcian blue/picrosirius red, and tartrate- resistant acid phosphatase (TRAP). Radiographic and microCT data confirmed that 0.02mg and 0.2mg local PAM doses significantly augmented BMP-7 induced bone formation. In contrast, 2mg local PAM dramatically reduced the amount of bone present. This dose was comparable to that used by Choi et al who also reported impaired bone formation in a skull defect model.2 three-dimensional microCT and histological analyses of the ectopic bone and surrounding muscle showed a cortical shell covering the polymer pellet, which had not completely resorbed. Histological analysis at the pellet/bone interface showed tissue granulation and no inflammation, suggesting a high biocompatibility of the PDLLA polymer. The presence of bisphosphonate also decreased the amount of fatty marrow tissue seen within between the cortical shell and the unresorbed polymer. For the first time we can demonstrate synergy with local BMP/bisphosphonate. This study confirms that high local PAM doses can have negative effects, indicating a need to avoid overdosing. The lack of implant degradation suggests a need to optimise polymer degradation for bone tissue engineering application

Sclerostin is a negative regulator of osteoblast differentiation and bone formation. Expressed by osteocytes, it acts through antagonising the Wnt/â-catenin pathway and/or BMP activity. Distraction osteogenesis, used for limb lengthening and reconstruction, can be complicated by disuse osteopenia and poor healing response, both of which would benefit from pro anabolic therapy. We examined the effects of Sclerostin Antibody (Scl-AbIII, Amgen Inc.,) in a rat model of distraction osteogenesis. A femoral osteotomy was stabilized with an external fixator in male Sprague Dawley rats. After a week of latency, the gap was distracted twice daily for 14 days to a total of 7 mm. Saline or Scl-Ab was administered twice weekly throughout the distraction period and up to 4, 6 or 8 weeks post commencement of distraction. Three groups were examined: Saline, Continuous Scl-Ab throughout the study (C Scl-Ab), and Delayed Scl-Ab with commencement of Scl-Ab after distraction (D Scl-Ab). Regenerate bone mineral content (BMC), determined by DEXA, was increased 36% at 4 weeks and 86% at 6 weeks with C Scl-Ab, resulting in a 65% increase in bone mineral density (BMD) at 6 weeks, compared with Saline (p<0.01). D Scl-Ab treatment showed a 41% increase in BMC and a 31% increase in BMD compared with Saline at 6 weeks (p<0.05). At 8 weeks, C Scl-Ab remained significantly increased over Saline (72% in BMC; 60% in BMD). Micro-CT scans of the regenerate revealed increases in bone volume of 88% with C Scl Ab and 65% with D Scl-Ab compared with Saline at 6 weeks (p<0.05). By 8 weeks, these increases were 36% for C Scl-Ab (p<0.05) and 37% for D Scl-Ab compared with Saline (p<0.01). Importantly, mean moment of inertia was increased over two-fold in both Scl-Ab groups at 6 weeks compared with Saline (p<0.05). Histology at 6 weeks confirmed micro-CT data with 85–88% increases in bone volume/tissue volume (BV/TV) in the regenerate with both C Scl-Ab and D Scl-Ab compared with Saline (p<0.05). Analysis of bone formation at 6 weeks revealed increases in mineral apposition rate of 56% in C Scl-Ab and 52% in D Scl-Ab compared with Saline (p<0.05). Scl-Ab treatment increased bone formation in this model of distraction osteogenesis, resulting in a larger regenerate callus (increased BMC and BV/TV). We expect further studies to reveal increases in mechanical strength. Scl-Ab may hold promise as a therapeutic to accelerate regenerate formation and consolidation in distraction osteogenesis for limb reconstruction

Construction of a functional skeleton is accomplished through co-ordination of the developmental processes of chondrogenesis, osteogenesis, and synovial joint formation. Infants whose movement in utero is reduced or restricted and who subsequently suffer from joint dysplasia (including joint contractures) and thin hypo-mineralised bones, demonstrate that embryonic movement is crucial for appropriate skeletogenesis. This has been confirmed in mouse, chick, and zebrafish animal models, where reduced or eliminated movement consistently yields similar malformations and which provide the possibility of experimentation to uncover the precise disturbances and the mechanisms by which movement impacts molecular regulation. Molecular genetic studies have shown the important roles played by cell communication signalling pathways, namely Wnt, Hedgehog, and transforming growth factor-beta/bone morphogenetic protein. These pathways regulate cell behaviours such as proliferation and differentiation to control maturation of the skeletal elements, and are affected when movement is altered. Cell contacts to the extra-cellular matrix as well as the cytoskeleton offer a means of mechanotransduction which could integrate mechanical cues with genetic regulation. Indeed, expression of cytoskeletal genes has been shown to be affected by immobilisation. In addition to furthering our understanding of a fundamental aspect of cell control and differentiation during development, research in this area is applicable to the engineering of stable skeletal tissues from stem cells, which relies on an understanding of developmental mechanisms including genetic and physical criteria. A deeper understanding of how movement affects skeletogenesis therefore has broader implications for regenerative therapeutics for injury or disease, as well as for optimisation of physical therapy regimes for individuals affected by skeletal abnormalities.

Cite this article: Bone Joint Res 2015;4:105–116

Currently, there is no animal model in which to evaluate the underlying physiological processes leading to the heterotopic ossification (HO) which forms in most combat-related and blast wounds. We sought to reproduce the ossification that forms under these circumstances in a rat by emulating patterns of injury seen in patients with severe injuries resulting from blasts. We investigated whether exposure to blast overpressure increased the prevalence of HO after transfemoral amputation performed within the zone of injury. We exposed rats to a blast overpressure alone (BOP-CTL), crush injury and femoral fracture followed by amputation through the zone of injury (AMP-CTL) or a combination of these (BOP-AMP). The presence of HO was evaluated using radiographs, micro-CT and histology. HO developed in none of nine BOP-CTL, six of nine AMP-CTL, and in all 20 BOP-AMP rats. Exposure to blast overpressure increased the prevalence of HO.

This model may thus be used to elucidate cellular and molecular pathways of HO, the effect of varying intensities of blast overpressure, and to evaluate new means of prophylaxis and treatment of heterotopic ossification.

Cite this article: Bone Joint J 2015;97-B:572–6