Local administration of ibandronate and bone morphogenetic protein-2 after ischemic osteonecrosis of the immature femoral head: a combined therapy that stimulates bone formation and decreases femoral head deformity

Conservative Treatment in Avascular Necrosis of the Femoral Head: A Systematic Review

INTRODUCTION

Avascular necrosis (AVN) of the femoral head is a pressing orthopedic issue, leading to bone tissue death due to disrupted blood supply and affecting the quality of life of individuals significantly. This review focuses on conservative treatments, evaluating their efficacy as mainstay therapies. Enhanced understanding of AVN's pathophysiology and advancements in diagnostic tools have rekindled interest in non-surgical interventions, emphasizing personalized, multidisciplinary approaches for improved outcomes.

MATERIAL AND METHOD

A systematic search was conducted on PubMed, SCOPUS, and Google Scholar databases from January 2020 to August 2023, with the objective of focusing on conservative treatments for AVN of the femoral head. Eligible studies, including original research, case reports, and observational studies, were examined for relevant, well-documented patient outcomes post-conservative treatments, excluding non-English and surgically focused articles without comparative conservative data.

RESULTS

A systematic search yielded 376 records on AVN of the femoral head across multiple databases. After de-duplication and rigorous screening for relevance and quality, 11 full-text articles were ultimately included for a comprehensive qualitative synthesis, focusing on conservatively managing the condition.

CONCLUSIONS

This review evaluates the effectiveness of conservative treatments such as pharmacological interventions and physical modalities in managing AVN of the femoral head. Despite promising results in symptom alleviation and disease progression delay, variability in outcomes and methodological limitations in studies necessitate further rigorous, randomized controlled trials for a robust, patient-centric approach to optimize therapeutic outcomes in AVN management.

Effects of bone marrow-derived mesenchymal stem cell transplantation in piglet Legg-Calve-Perthes disease models: a pilot study

This preliminary study investigated the efficacy and safety of bone marrow-derived mesenchymal stem cell transplantation in a piglet Legg-Calve-Perthes disease (LCPD) model. The LCPD model was induced in two Landrace piglets (6- and 7-week-old, weighing 12 and 17 kg, respectively) by ligaturing the femoral neck. In the first piglet, the natural LCPD course was observed. In the second piglet, 4 weeks after ligaturing the femoral neck, simple medium and medium containing 2.44 × 10 7 bone marrow-derived mesenchymal stem cells were transplanted into the right and left femoral heads after core decompression, respectively. Plain radiographs were obtained every 4 weeks, and the epiphyseal quotient was calculated by dividing the maximum epiphysis height by the maximum epiphysis diameter. The piglets were sacrificed at 14 weeks postoperatively. The femoral heads were extracted and evaluated grossly, pathologically, and by using computed tomography. The transplanted cell characteristics were evaluated using flow cytometry. Flattening of the epiphysis was observed in both femoral heads of the first piglet and only in the right hip of the second piglet. The epiphyseal quotients immediately and at 14 weeks postoperatively in the right femoral head of the second piglet were 0.40 and 0.14, respectively, while those of the left femoral head were 0.30 and 0.42, respectively. Hematoxylin and eosin staining did not reveal physeal bar or tumor cell formation. The transplanted cells were 99.2%, 65.9%, 18.2%, and 0.16% positive for CD44, CD105, CD29, and CD31, respectively. Core decompression combined with bone marrow-derived mesenchymal stem cell transplantation prevented epiphyseal collapse.

Local BMP2 hydrogel therapy for robust bone regeneration in a porcine model of Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease is juvenile idiopathic osteonecrosis of the femoral head (ONFH) that has no effective clinical treatment. Previously, local injection of bone morphogenetic protein-2 (BMP2) for ONFH treatment showed a heterogeneous bone repair and a high incidence of heterotopic ossification (HO) due to the BMP2 leakage. Here, we developed a BMP2-hydrogel treatment via a transphyseal bone wash and subsequential injection of BMP2-loaded hydrogel. In vitro studies showed that a hydrogel of gelatin-heparin-tyramine retained the BMP2 for four weeks. The injection of the hydrogel can efficiently prevent leakage. With the bone wash, the injected hydrogel had a broad distribution in the head. In vivo studies on pigs revealed that the BMP2-hydrogel treatment produced a homogeneous bone regeneration without HO. It preserved the subchondral contour and restored the subchondral endochondral ossification, although it increased growth plate fusions. In summary, the study demonstrated a promising BMP2-hydrogel treatment for ONFH treatment, especially for teenagers.

Local Administration of Bone Morphogenetic Protein-2 Using a Hydrogel Carrier for Robust Bone Regeneration in a Large Animal Model of Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease is juvenile idiopathic osteonecrosis of the femoral head (ONFH) that has no effective clinical resolutions. Previously, local injection of bone morphogenetic protein-2 (BMP2) for ONFH treatment showed a heterogeneous bone repair and a high incidence of heterotopic ossification (HO) due to the BMP2 leakage. Here, we developed a BMP2-hydrogel treatment via a transphyseal bone wash and subsequential injection of BMP2-loaded hydrogel. In vivo studies showed that a hydrogel of gelatin-heparin-tyramine retained the BMP2 for four weeks. The injection of the hydrogel can efficiently prevent leakage. With the bone wash, the injected hydrogel had a broad distribution in the head. In vivo studies on pigs revealed that the BMP2-hydrogel treatment produced a homogeneous bone regeneration without HO. It preserved the subchondral contour and restored the subchondral endochondral ossification, although it increased growth plate fusions. In summary, the study demonstrated a promising BMP2-hydrogel treatment for ONFH treatment, especially for teenagers.

Emerging roles of growth factors in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a potentially disabling orthopedic condition that requires total hip arthroplasty in most late-stage cases. However, mechanisms underlying the development of ONFH remain unknown, and the therapeutic strategies remain limited. Growth factors play a crucial role in different physiological processes, including cell proliferation, invasion, metabolism, apoptosis, and stem cell differentiation. Recent studies have reported that polymorphisms of growth factor-related genes are involved in the pathogenesis of ONFH. Tissue and genetic engineering are attractive strategies for treating early-stage ONFH. In this review, we summarized dysregulated growth factor-related genes and their role in the occurrence and development of ONFH. In addition, we discussed their potential clinical applications in tissue and genetic engineering for the treatment of ONFH.

Biomaterial-Mediated Protein Expression Induced by Peptide-mRNA Nanoparticles Embedded in Lyophilized Collagen Scaffolds

In our aging society, the number of patients suffering from poorly healing bone defects increases. Bone morphogenetic proteins (BMPs) are used in the clinic to promote bone regeneration. However, poor control of BMP delivery and thus activity necessitates high doses, resulting in adverse effects and increased costs. It has been demonstrated that messenger RNA (mRNA) provides a superior alternative to protein delivery due to local uptake and prolonged expression restricted to the site of action. Here, we present the development of porous collagen scaffolds incorporating peptide-mRNA nanoparticles (NPs). Nanoparticles were generated by simply mixing aqueous solutions of the cationic cell-penetrating peptide PepFect14 (PF14) and mRNA. Peptide-mRNA complexes were uniformly distributed throughout the scaffolds, and matrices fully preserved cell attachment and viability. There was a clear dependence of protein expression on the incorporated amount of mRNA. Importantly, after lyophilization, the mRNA formulation in the collagen scaffolds retained activity also at 4 °C over two weeks. Overall, our results demonstrate that collagen scaffolds incorporating peptide-mRNA complexes hold promise as off-the-shelf functional biomaterials for applications in regenerative medicine and constitute a viable alternative to lipid-based mRNA formulations.

Tissue Engineering Strategies for Treating Avascular Necrosis of the Femoral Head

Avascular necrosis (AVN) of the femoral head commonly leads to symptomatic osteoarthritis of the hip. In older patients, hip replacement is a viable option that restores the hip biomechanics and improves pain but in pediatric, adolescent, and young adult patients hip replacements impose significant activity limitations and the need for multiple revision surgeries with increasing risk of complication. Early detection of AVN requires a high level of suspicion as diagnostic techniques such as X-rays are not sensitive in the early stages of the disease. There are multiple etiologies that can lead to this disease. In the pediatric and adolescent population, trauma is a commonly recognized cause of AVN. The understanding of the pathophysiology of the disease is limited, adding to the challenge of devising a clinically effective treatment strategy. Surgical techniques to prevent progression of the disease and avoid total hip replacement include core decompression, vascular grafts, and use of bone-marrow derived stem cells with or without adjuncts, such as bisphosphonates and bone morphogenetic protein (BMP), all of which are partially effective only in the very early stages of the disease. Further, these strategies often only improve pain and range of motion in the short-term in some patients and do not predictably prevent progression of the disease. Tissue engineering strategies with the combined use of biomaterials, stem cells and growth factors offer a potential strategy to avoid metallic implants and surgery. Structural, bioactive biomaterial platforms could help in stabilizing the femoral head while inducing osteogenic differentiation to regenerate bone and provide angiogenic cues to concomitantly recover vasculature in the femoral head. Moreover, injectable systems that can be delivered using a minimal invasive procedure and provide mechanical support the collapsing femoral head could potentially alleviate the need for surgical interventions in the future. The present review describes the limitations of existing surgical methods and the recent advances in tissue engineering that are leading in the direction of a clinically effective, translational solution for AVN in future.

Core Decompression with Local Administration of Zoledronate and Enriched Bone Marrow Mononuclear Cells for Treatment of Non-Traumatic Osteonecrosis of Femoral Head

Objective

To investigate the efficacy and safety of core decompression (CD) with local administration of zoledronate and enriched bone marrow mononuclear cells (BMMCS) for the treatment of non‐traumatic osteonecrosis of femoral head (ONFH).

Methods

A total of 17 patients (30 hips) diagnosed with stage II and III ONFH according to the 2019 revised Association for Research on Osseous Circulation (ARCO) staging criteria from 2012 to 2014 were retrospectively reviewed. The patients received the following therapy: the BMMCs and zoledronate were injected into the necrotic zone, respectively, along with CD. The mean age of the patients was 36.8 years; 14 were men and three were women. All patients included had non‐traumatic ONFH and a minimum follow‐up of 5 years, which ended when total hip arthroplasty (THA) was performed. Imaging modalities, including plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI) were taken pre‐ and postoperatively. Harris hip score (HHS) was used to evaluate the functional outcomes of femoral head necrosis. Kaplan–Meier analysis was adopted to determine the probability of survivorship with THA as the end point in this series of patients. The correlation between radiological progression or THA and related risk factors were further analyzed. All complications were recorded.

Results

With THA as the follow‐up endpoint, All patients were followed up for an average of 69.1 ± 20.5 months (range, 18–95 months). Preoperative imaging found six hips (20%) at ARCO stage II, 14 hips (46.7%) at stage IIIA, 10 hips (33.3%) at stage IIIB. Fourteen hips (46.7%) shown progression radiologically, while six hips (20%) underwent TKA among these patients with hip preservation. The cumulative survival was 80% (95% CI, 0.608–905) at 5 years with THA as the end point. HHS improved from 63.3 ± 8.7 preoperatively to 74.6 ± 20.6 postoperatively (P = 0.000). Radiological progression was found to be associated with ARCO stage, Japanese Investigation Committee (JIC) type, and corticosteroid exposure (P = 0.047; P = 0.012; P = 0.031). However, no correlation was found between conversion to THA and the known risk factors. No major complication was reported, with only four patients complaining about general weakness and muscle soreness, and all disappeared within 2–3 days.

Conclusions

The novel treatment modality could relieve pain, delay the progression of collapse, which might be an effective and safe method for hip preservation of early and mid‐term ONFH. However, the effect of this method may be related to ARCO stage, JIC type, and corticosteroid exposure.

Polymer Scaffolds-Enhanced Bone Regeneration in Osteonecrosis Therapy

Osteonecrosis without effective early treatment eventually leads to the collapse of the articular surface and causes arthritis. For the early stages of osteonecrosis, core decompression combined with bone grafting, is a procedure worthy of attention and clinical trial. And the study of bone graft substitutes has become a hot topic in the area of osteonecrosis research. In recent years, polymers have received more attention than other materials due to their excellent performance. However, because of the harsh microenvironment in osteonecrosis, pure polymers may not meet the stringent requirements of osteonecrosis research. The combined application of polymers and various other substances makes up for the shortcomings of polymers, and to meet a broad range of requirements for application in osteonecrosis therapy. This review focuses on various applying polymers in osteonecrosis therapy, then discusses the development of biofunctionalized composite polymers based on the polymers combined with different bioactive substances. At the end, we discuss their prospects for translation to clinical practice.

Phosphodiesterase-5 inhibition improves bone regeneration at the early stages of ischemic osteonecrosis of the femoral head in rats

Posttraumatic osteonecrosis of the femoral head (ONFH) affects patients at different ages and may lead to functional limitation and joint replacement, with total hip arthroplasty, which is a costly procedure. Proposed methods to optimize ischemic tissue regeneration have been reported. Phosphodiesterase-5 inhibitors act by inhibiting the degradation of guanosine 3',5'-cyclic monophosphate in the nitric oxide pathway, increasing its bioavailability and promoting vascular endothelial growth factor (VEGF)-mediated neovascular recruitment and the induction of tissue regeneration in the traumatized bone. Thirty male Sprague-Dawley rats (6 months old) were subjected to an experimental model of traumatic ONFH divided into two groups, according to the administration of 5 mg/kg sildenafil or water (control group). Rats were then killed at 7, 14, and 21 days. Histological (Goldner's trichrome), histochemical (periodic acid-Schiff [PAS]), and immunohistochemical (VEGF and osteopontin [OPN]) techniques were used to quantify bone and vascular responses. Higher levels of VEGF (p < 0.01) and OPN (p < 0.01) immunostaining in the epiphysis, the greater formation of osteoid tissue (p < 0.01 on Day 7; p < 0.05 on Day 14), and higher levels of PAS staining (p < 0.01 on Day 7) were observed in the sildenafil-treated group. The present study demonstrated that sildenafil optimized bone tissue regeneration by increasing VEGF signaling and OPN expression, with increased bone formation (osteoid and carbohydrate macromolecule deposition) in the early stages following traumatic ischemic insult. Thus, sildenafil treatment may improve the prognosis of patients with osteonecrosis.

Augmentation of implant surfaces with BMP-2 in a revision setting : effects of local and systemic bisphosphonate

AIMS

We wanted to evaluate the effects of a bone anabolic agent (bone morphogenetic protein 2 (BMP-2)) on an anti-catabolic background (systemic or local zoledronate) on fixation of allografted revision implants.

METHODS

An established allografted revision protocol was implemented bilaterally into the stifle joints of 24 canines. At revision surgery, each animal received one BMP-2 (5 µg) functionalized implant, and one raw implant. One group (12 animals) received bone graft impregnated with zoledronate (0.005 mg/ml) before impaction. The other group (12 animals) received untreated bone graft and systemic zoledronate (0.1 mg/kg) ten and 20 days after revision surgery. Animals were observed for an additional four weeks before euthanasia.

RESULTS

No difference was detected on mechanical implant fixation (load to failure, stiffness, energy) between local or systemic zoledronate. Addition of BMP-2 had no effect on implant fixation. In the histomorphometric evaluation, implants with local zoledronate had more area of new bone on the implant surface (53%, p = 0.025) and higher volume of allograft (65%, p = 0.007), whereas implants in animals with systemic zoledronate had the highest volume of new bone (34%, p = 0.003). Systemic zoledronate with BMP-2 decreased volume of allograft by 47% (p = 0.017).

CONCLUSION

Local and systemic zoledronate treatment protects bone at different stages of maturity; local zoledronate protects the allograft from resorption and systemic zoledronate protects newly formed bone from resorption. BMP-2 in the dose evaluated with experimental revision implants was not beneficial, since it significantly increased allograft resorption without a significant compensating anabolic effect. Cite this article: Bone Joint Res 2021;10(8):488-497.

Local administration of zoledronic acid prevents traumatic osteonecrosis of the femoral head in rat model

Background

Osteonecrosis of the femoral head (ONFH) is a refractory disease due to its unclear pathomechanism. Neither conservative treatment nor surgical treatment during the early stage of ONFH achieves satisfactory results. Therefore, this study aims to explore the available evidence on the effect of zoledronic acid on early-stage ONFH.

Methods

For groups were established:the Normal group, model group, Normal saline group(NS group) and zoledronic acid-treated group. The blood supply to the femoral head of animals in the model group and zoledronic acid-treated group was interrupted via a surgical procedure, and zoledronic acid was then locally administered to the femoral head. Four weeks after surgery, all the hips were harvested and evaluated by micro-CT and histopathology(H&E staining, TRAP staining, Toluidine blue staining and masson staining).

Results

The values of BMD, BS/BV and Tb.Th in the Normal group and zoledronic acid-treated group were significantly higher than those in the model group and NS group (p ​< ​0.05). The outcome of H&E staining, Toluidine blue staining and masson staining were consistent with that of micro-CT.

Conclusion

The local administration of zoledronic acid in the femoral head had positive effects on the bone structure of the femoral head in a modified rat model of traumatic ONFH and offered a promising therapeutic strategy during the early stage of ONFH.

The Translational potential of this article

This article could provide a choice for treating patients who have osteonecrosis of femora head and can be the basic research for advanced development over this disease

Fractures of the Proximal Femur in Childhood: A Review

BACKGROUND

Femoral neck fractures in children are rare injuries, occurring due to high-energy trauma. Due to the unique anatomy and blood supply of the proximal femur in growing children, these fractures are notorious for high rates of complications despite appropriate management. Classification of these fractures is according to the Delbet system, which not only guides management but also gives prognostic clues. Multiple fixation methods have been described and there is no consensus on what constitutes the best treatment. Osteonecrosis, non-union, coxa vara and premature physeal arrest are the most frequent complications.

PURPOSE

To review the current knowledge, discuss controversial aspects, and provide suggestions for future research.

METHODS

We have reviewed the literature on paediatric proximal femur fractures and have provided an evidence-based guide to the diagnosis and management of these injuries. Common complications have been elaborated and options for their prevention and/or management discussed.

CONCLUSION

There is universal agreement that anatomic reduction and stable internal fixation, supplemented by spica immobilization in younger children, are essential to obtain good outcomes. The role of capsular decompression, choice and configuration of implant, and appropriate timing of surgery are aspects that continue to be debated. Multicenter prospective studies are necessary to standardize treatment of these challenging injuries.

Efficacy of orthobiologic adjuvants to core decompression for hip preservation in avascular necrosis hip

Head preserving modalities in avascular necrosis (AVN) hip are variably effective in early stages, and further options that could prevent head distortion and osteoarthritis are needed. Core decompression (CD) is the most commonly used surgery in the early stages of osteonecrosis with variable rates of success. The present review aimed to determine the effectiveness of bone marrow aspirate concentrate (BMAC), platelet-rich plasma (PRP), bone morphogenetic proteins (BMP) or their combination with CD in early stages of AVN hip, prior to collapse of femoral head. Additionally, any newer unexplored modalities were also searched for and ascertained. PubMed and SCOPUS databases were searched for relevant articles in English language describing CD with aforementioned orthobiologics. We analysed a total of 20 studies published between 2011 and 2020. There were 6 retrospective and 14 prospective studies. PRP showed improved survival and functional outcomes; however, with only three studies, there is inconclusive evidence for its routine utilization. BMAC enhances the efficacy of CD which can further be increased by culture and expansion of cells or combining it with PRP to stimulate growth. In conclusion, CD with BMAC works more efficiently than CD alone prior to collapse of femoral head in AVN. However, PRP needs more evidence for extensive application. Addition of PRP to BMAC or culturing the latter could further enhance the potency of CD + BMAC combination. Very limited data is available for the efficacy of BMP-7 and the role of intraosseous bisphosphonates should be evaluated for a cheaper and potential alternative.

The role and underlying mechanisms of microRNA‑214 in Legg‑Calvé‑Perthes disease

Legg‑Calvé‑Perthes disease (LCPD) is a pediatric form of femoral head osteonecrosis with unknown etiology. MicroRNAs (miRs) have been revealed to serve an important role in LCPD. MiR‑214 serves an important role in chondrogenesis. The aim of the present study was to investigate the potential role of miR‑214 in LCPD and the underlying mechanisms. The expression levels of miR‑214 and B‑cell lymphoma 2 (Bcl‑2)‑associated X protein (Bax) in dexamethasone (DEX)‑treated TC28 cells, and the femoral head cartilage tissues, serum and primary chondrocytes of patients with LCPD, and healthy individuals were determined via reverse transcription quantitative polymerase chain reaction and western blot analysis. A luciferase reporter assay was conducted to investigate the association between miR‑214 and Bax, while cell viability was determined via an MTT assay, and flow cytometry was performed to investigate cell apoptosis. The results revealed that miR‑214 was downregulated and Bax was upregulated in DEX‑treated TC28 cells and tissues obtained from patients with LCPD. MiR‑214 was demonstrated to directly target Bax and negatively regulate its expression. DEX administration significantly suppressed cell proliferation, promoted apoptosis and decreased the Bcl‑2/Bax ratio in TC28 cells; overexpression of miR‑214 induced opposing effects, which were reversed by Bax overexpression. In conclusion, the results indicated that miR‑214 and Bax may be potential therapeutic targets for the future clinical treatment of LCPD.

The Pathogenesis and Treatment of Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes disease is a childhood hip condition in which the blood supply to the capital femoral epiphysis is interrupted, causing osteonecrosis and chondronecrosis that lead to progressive deformity of the femoral head and secondary degenerative osteoarthritis in later life. The etiology of Legg-Calvé-Perthes disease remains unclear, with both biological and mechanical factors playing important roles in the pathogenesis of the condition. The treatment of Legg-Calvé-Perthes disease remains controversial but is dependent on several salient factors, including the age at clinical onset, the extent of epiphyseal involvement, the stage of the disease, and the degree of femoral head deformity. The literature supports operative containment treatment in the early stage of disease. Such treatment has led to improved femoral head sphericity with better patient outcomes in multicenter prospective cohort studies. The number of hips that need to be treated operatively in order to achieve a modest treatment effect remains high. Multicenter prospective cohort studies have shown that 6 to 7 patients need to be managed to create 1 spherical femoral head that would not have otherwise occurred.

Drilling Combined with Adipose-derived Stem Cells and Bone Morphogenetic Protein-2 to Treat Femoral Head Epiphyseal Necrosis in Juvenile Rabbits

This study was designed to evaluate the effects of drilling through the growth plate and using adipose-derived stem cells (ADSCs) and bone morphogenetic protein-2 (BMP-2) to treat femoral head epiphyseal ischemic necrosis, which can be done in juvenile rabbits. Passagefour bromodeoxyuridine (BrdU)-labeled ADSCs were cultured, assayed with MTT to determine their viability and stained with alizarin red dye to determine their osteogenic ability. Two-month-old, healthy male rabbits (1.2 to 1.4 kg, n=45) underwent ischemic induction and were randomly divided into five groups (group A: animal model control; group B: drilling; group C: drilling & ADSCs; group D: drilling & BMP-2; and group E: drilling & ADSCs & BMP-2). Magnetic resonance imaging (MRI), X-ray imaging, hematoxylin and eosin staining and BrdU immunofluorescence detection were applied 4, 6 and 10 weeks after treatment. Approximately 90% of the ADSCs were labeled with BrdU and showed good viability and osteogenic ability. Similar results were observed in the rabbits in groups C and E at weeks 6 and 10. The animals of groups C and E demonstrated normal hip structure and improved femoral epiphyseal quotients and trabecular areas compared with those of the groups A and B (P<0.01). Group D demonstrated improved femoral epiphyseal quotients and trabecular areas compared with those of groups A and B (P<0.05). In summary, drilling through the growth plate combined with ADSC and BMP-2 treatments induced new bone formation and protected the femoral head epiphysis from collapsing in a juvenile rabbit model of femoral head epiphyseal ischemic necrosis.

Efficacy of bisphosphonates in the treatment of femoral head osteonecrosis: A PRISMA-compliant meta-analysis of animal studies and clinical trials

This study aimed to determine whether bisphosphonates exert an effect on preventing femoral head collapse after osteonecrosis of the femoral head (ONFH) in an animal model and in clinical trials. A systematic literature search was performed for studies published up to January 2017. Twenty-three articles (16 animal studies, seven clinical trials) were included in the meta-analysis. We found that the bisphosphonate group obtained significant improvement in epiphyseal quotients (MD = 15.32; 95% CI, 9.25-21.39) and provided better performance on bone volume (SMD = 1.57; 95% CI, 0.94-2.20), trabecular number (SMD = 1.30; 95% CI, 0.80-1.79), trabecular thickness (SMD = 0.77; 95% CI, 0.10-1.43) and trabecular separation (SMD = -1.44; 95% CI, -1.70 to -0.58) in the animal model. However, the bisphosphonate group did not achieve better results in pain score, Harris score, the occurrence rate of femoral head collapse, or total hip arthroplasty in the clinical trials. In conclusion, despite bisphosphonates significantly improving bone remodeling outcomes in animal models, no significant efficacy was observed in the treatment of ONFH in the clinical studies. Further studies are required to solve the discordant outcomes between the animal and clinical studies.

Effectiveness of Strontium Ranelate in the Treatment of Rat Model of Legg-Calve-Perthes Disease

BACKGROUND

Legg-Calve-Perthes disease (LCPD) causes osteonecrosis of the femoral head (ONFH) by temporarily interrupting the blood supply in children. Even with potential toward bone regeneration and revascularization in LCPD, the prognosis depends on the deformity of femoral heads, and successful rate with the current treatments varies. Antiresorptive therapy such as bisphosphonate, which maintains mechanical stability of the femoral head by inhibiting necrotic bone resorption, has proven effective in animal models. However, concerns on simultaneous decline in bone turnover rate still leave room for improvement. Strontium ranelate with dual effect on inhibiting bone resorption and accelerating bone formation is presumed to be an ideal therapy for reserving sphericity of femoral heads in LCPD.

MATERIALS AND METHODS

In this study of a rat model of ONFH, randomized groups of rats treated with strontium ranelate or normal saline are compared at different time points in analysis of radiological, histological, and bone morphometric changes. Gait analysis was also compared between the two groups.

RESULTS

The group treated with strontium ranelate recovered their normal gait earlier than the control group did. Bone density, trabecular thickness, sphericity of the femoral head, and bone regeneration potential were also preserved in the strontium ranelate group.

CONCLUSION

Strontium ranelate effectively prevented collapse of the ischemic femoral head and enhanced trabecular thickness in the rat model of LCPD. Hopefully, this preclinical experiment can improve the effectiveness of strontium ranelate treatment for pediatric ONFH.

Material properties of bone in the femoral head treated with ibandronate and BMP-2 following ischemic osteonecrosis

Bone morphogenetic protein (BMP)-2 and ibandronate (IB) decrease the femoral head deformity following ischemic osteonecrosis of the femoral head (ONFH). The purpose of this study was to determine the effects of BMP-2 and IB on the mineral content and nanoindentation properties of the bone following ONFH. ONFH was surgically induced in the femoral head of piglets. There were five groups: normal control, untreated, IB, BMP, and BMP + IB (n = 5/group). Backscattered electron imaging, Raman spectroscopy, and nanoindentation testing were performed. Both BMP and BMP + IB groups showed calcium content in the trabecular bone similar to the normal group, while the IB and no-treatment groups showed a significant increase in the calcium content compared to the normal group. The carbonate content relative to phosphate was significantly increased in the IB and BMP + IB groups (p < 0.01) compared to the normal group. No significant difference was found between the BMP and the normal group. The nanoindentation modulus of the bone in the IB group was significantly increased compared to the normal group (p < 0.05). No significant differences were observed between the BMP and BMP + IB groups compared to the normal group. The nanoindentation hardness measurements in the IB group were also significantly increased compared to the BMP and BMP + IB groups (p < 0.05). In summary, trabecular bone treated with BMP or BMP + IB had material properties comparable to normal bone whereas the bone in the IB group retained the increased mineral content and the nanoindentation hardness found in the necrotic bone. Hence, BMP or BMP + IB better restores the normal mineral content and nanomechanical properties after ONFH than IB treatment alone. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1453-1460, 2017.

Local Administration of Bisphosphonate-soaked Hydroxyapatite for the Treatment of Osteonecrosis of the Femoral Head in Rabbit

Background:

Systemic administration of bisphosphonates has shown promising results in the treatment of osteonecrosis of the femoral head (ONFH). However, few studies have evaluated the efficacy of local zoledronate (ZOL) administration in the treatment of ONFH. The purpose of this study was to investigate whether local administration of bisphosphonate-soaked hydroxyapatite (HA) could improve bone healing in an experimental rabbit model of ONFH.

Methods:

This experimental study was conducted between October 2014 and June 2015. Forty-five rabbits underwent simulated ONFH surgery. Immediately following surgery, they were divided into three groups: model (untreated, n = 15), HA (treated with HA alone, n = 15), and HA + ZOL (treated with HA soaked in a low-dose ZOL solution, n = 15). Histological, immunohistochemical, and quantitative analyses were performed to evaluate bone formation and resorption 2, 4, and 8 weeks after surgery.

Results:

Gross bone matrix and hematopoietic tissue formation were observed in the HA + ZOL group 4 weeks after surgery. The immunohistochemical staining intensities for 5-bromodeoxyuridine, runt-related transcription factor 2, osteocalcin, osteopontin, and osteoprotegerin were significantly higher in the HA + ZOL group than that in the model (P < 0.001, P < 0.001, P < 0.001, P < 0.001, and P = 0.018, respectively) and HA groups (P = 0.003, P = 0.049, P < 0.001, P = 0.020, and P = 0.019, respectively), whereas receptor activator of the nuclear factor-κB ligand staining intensity was significantly lower in the HA + ZOL group than that in the model and HA groups (P = 0.029 and P = 0.015, respectively) 4 weeks after surgery. No significant differences in bone formation or bone resorption marker expression were found between the three groups 2 or 8 weeks after surgery (P > 0.05).

Conclusions:

Local administration of HA soaked in a low-dose ZOL solution increased new bone formation while inhibiting bone resorption in an animal model of ONFH, which might provide new evidence for joint-preserving surgery in the treatment of ONFH.

Intraosseous Delivery of Bone Morphogenic Protein-2 Using a Self-Assembling Peptide Hydrogel

Osteonecrosis of the femoral head (ONFH) is a debilitating hip disorder, which often produces a permanent femoral head deformity and osteoarthritis. The local delivery of biological agents capable of stimulating bone healing offer potential new treatment options for patients with ONFH. Previous studies from our laboratory have shown that a local intraosseous infusion of bone morphogenic protein-2 (BMP-2) was effective in stimulating new bone formation in a piglet model of ischemic ONFH. However, infusion of BMP-2 solution was associated with unwanted dissemination of BMP-2 out of the femoral head and produced heterotopic ossification in the hip capsule. Injectable hydrogels offer a potential method to control the dissemination of biological molecules in vivo. In the present study, we evaluated the potential of a peptide-based, self-assembling hydrogel called RADA16 to transition from a solution to a gel following infusion into the femoral head, thereby preventing backflow, as well as its potential use as a delivery vehicle for BMP-2. Cadaver pig femoral heads were used to study the backflow and the distribution of RADA16 following an intraosseous infusion. Microcomputed tomography analysis following the infusion of RADA16 mixed with a radiocontrast agent revealed a significant decrease in the amount of back flow of radiocontrast agent down the needle track compared to the soluble infusion of radiocontrast without RADA16. Furthermore, RADA16 mixed with radiocontrast agent showed good distribution within the femoral head. In addition, in vitro experiments revealed that higher concentrations of RADA16 decreased the rate of BMP-2 dissemination out of the hydrogel. The BMP-2 that was released from RADA16 maintains its biological activity, inducing the phosphorylation of SMAD1/5/8 in pig primary bone marrow stromal cells. Lastly, pig primary bone marrow stromal cells showed significantly increased in vitro proliferation on RADA16 hydrogels over 1 week compared to tissue culture plastic, suggesting that it is a suitable matrix for supporting cellular proliferation. In conclusion, RADA16 showed potential for use as a drug delivery vehicle to control the delivery of BMP-2 within the femoral head. This novel therapy may be able to provide benefits to patients suffering from debilitating conditions such as osteonecrosis of the femoral head.

Synergistic local drug delivery in a piglet model of ischemic osteonecrosis: a preliminary study

A locally injectable system sequentially delivering an antiresorptive drug (clodronate) followed by an osteogenic agent (simvastatin) was hypothesized to improve femoral head microarchitecture, size, and shape compared with untreated or partial treatment groups in an established piglet osteonecrosis model. After 6 weeks, the clodronate+simvastatin treatment resulted in no collapse, microCT measurements and epiphyseal quotients within 10% of control, normal microstructure, and healthy histology. All other groups exhibited collapse, lower epiphyseal quotients and total femoral head volumes (P<0.05), and abnormal histology. This pilot study provides evidence of synergistic antiresorptive and osteogenic activities, which may prevent femoral head collapse in Perthes disease.

Osteonecrosis of the femoral head: treatment with ancillary growth factors

Osteonecrosis (ON) of the femoral head, also known as avascular necrosis (AVN) of the femoral head, is a progressive disease that predominantly affects younger patients. During early stage of ON, decompression of the femoral head has been commonly used to improve pain. The decompression has been augmented with nonvascularized or vascularized bone grafts, mesenchymal stems cells, and growth factors. The use of adjuvant growth factors to supplement the core decompression has mainly been limited to animal models in an attempt to regenerate the necrotic lesion of ON. Factors utilized include bone morphogenetic proteins, vascular endothelial growth factors, hepatocyte growth factors, fibroblast growth factors, granulocyte colony-stimulating factors, and stem cells factors. In animal models, the use of these factors has been shown to increase bone formation and angiogenesis. Although promising, the use of these growth factors and cell-based therapies clinically remains limited.

Predictive genetic markers of coagulation, inflammation and apoptosis in Perthes disease—Serbian experience

Perthes disease is one of the most common forms of pediatric femoral head osteonecrosis with an unknown etiology. Coagulation factors were the first genetic factors suspected to have a role in the pathogenesis of this disease, but studies showed inconsistent results. It is described that inflammation is present during early stages of Perthes disease, but its genetic aspect has not been studied extensively. Little is known regarding the status of apoptotic factors during the repair process that leads to the occurrence of hip deformity in patients. Therefore, the aim of this study was to analyze major mediators involved in coagulation, inflammation, and apoptotic processes as possible causative factors of Perthes disease. The study cohort consisted of 37 patients. Gene variants of TNF-α, FV, FII, and MTHFR genes were determined by PCR-RFLP, while IL-3 and PAI-1 were genotyped by direct sequencing. The expression level of Bax, Bcl-2, Bcl2L12, Fas and FasL was analyzed by quantitative reverse-transcriptase polymerase chain reaction (qRT-PCR) technique. Our results showed a significantly increased level of expression of pro-apoptotic factor Bax along with significantly higher Bax/Bcl-2 ratio in the patient group.

CONCLUSION

The results presented indicate that apoptosis could be one of the factors contributing to the lack of balanced bone remodeling process in Perthes patients.

COMP-angiopoietin1 potentiates the effects of bone morphogenic protein-2 on ischemic necrosis of the femoral head in rats

Angiogenesis is considered essential for proper bone regeneration. The purpose of this investigation was to determine if a combined therapy of bone morphogenetic protein-2 (BMP-2) and cartilage oligomeric matrix protein angiopoietin-1 (COMP-Ang1) can potentiate the therapeutic effect of BMP-2 in a rat model of ischemic necrosis of the femoral head (INFH). INFH was surgically induced in the femoral head of rats, and the animals were divided into the following groups: 1) a sham-operated group (sham group), 2) a bovine serum albumin-injected group (BSA group), 3) a BMP-2-injected group (BMP-2 group), and 4) a COMP-Ang1 and BMP-2-injected group (COMP-Ang1 + BMP-2 group) (n = 20/group). Radiologic, histologic, and histomorphometric assessments were performed to assess femoral head morphology, vascular density, and bone resorption activity. Western blots and immunohistochemical staining were performed to evaluate production of BMP-related signaling proteins in C3H10T1/2 cells and tissues. Real-time RT-PCR was performed to investigate expression of the target integrin gene, and the effect of integrin on C3H10T1/2 cells was determined using a cell adhesion assay. Radiographs obtained six weeks after injection revealed better preservation of the architecture of the femoral head in the COMP-Ang1 + BMP-2 group compared with the BSA and BMP-2 groups. Histological findings indicated increased trabecular bone and vascularity and decreased osteoclast bone resorption activity in the COMP-Ang1 + BMP-2 group compared with those in the BSA and BMP-2 groups. The combination of COMP-Ang1 and BMP-2 increased phosphorylation of Smad1/3/5, p38, and Akt. Increased integrin α3 and β1 mRNA expression in the COMP-Ang1 + BMP-2 group promoted cell adhesion. These results suggest that COMP-Ang1 preserved the necrotic femoral head through the potentiation of BMP-2 signaling pathways and angiogenesis. Combination treatment with COMP-Ang1 and BMP-2 may be a clinically useful therapeutic application in INFH.

Local administration of bone morphogenetic protein-2 and bisphosphonate during non-weight-bearing treatment of ischemic osteonecrosis of the femoral head: an experimental investigation in immature pigs

BACKGROUND

Non-weight-bearing decreases the femoral head deformity but increases bone resorption without increasing bone formation in an experimental animal model of Legg-Calvé-Perthes disease. We sought to determine if local administration of bone morphogenetic protein (BMP)-2 with or without bisphosphonate can increase the bone formation during the non-weight-bearing treatment in the large animal model of Legg-Calvé-Perthes disease.

METHODS

Eighteen piglets were surgically induced with femoral head ischemia. Immediately following the surgery, all animals received an above-the-knee amputation to enforce local non-weight-bearing (NWB). One to two weeks later, six animals received local BMP-2 to the necrotic head (BMP group), six received local BMP-2 and ibandronate (BMP+IB group), and the remaining six received no treatment (NWB group). All animals were killed at eight weeks after the induction of ischemia. Radiographic, microcomputed tomography (micro-CT), and histomorphometric assessments were performed.

RESULTS

Radiographic assessment showed that the femoral heads in the NWB, BMP, and BMP+IB groups had a decrease of 20%, 14%, and 10%, respectively, in their mean epiphyseal quotient in comparison with the normal control group. Micro-CT analyses showed significantly higher femoral head bone volume in the BMP+IB group than in the BMP group (p = 0.02) and the NWB group (p < 0.001). BMP+IB and BMP groups had a significantly higher trabecular number (p < 0.01) and lower trabecular separation (p < 0.02) than the NWB group. In addition, the osteoclast number per bone surface was significantly lower in the BMP+IB group compared with the NWB group. Calcein labeling showed significantly higher bone formation in the BMP and BMP+IB groups than in the NWB group (p < 0.05). Heterotopic ossification was found in the capsule of four hips in the BMP+IB group but not in the BMP group.

CONCLUSIONS

Administration of BMP-2 with bisphosphonate best decreased bone resorption and increased new bone formation during non-weight-bearing treatment of ischemic osteonecrosis in a pig model, but heterotopic ossification is a concern.

CLINICAL RELEVANCE

This preclinical study provides new evidence that BMP-2 with bisphosphonate can effectively prevent the extreme bone loss associated with the non-weight-bearing treatment and increase new bone formation in the femoral head in this animal model of ischemic osteonecrosis.

Evaluation of osteogenic cell differentiation in response to bone morphogenetic protein or demineralized bone matrix in a critical sized defect model using GFP reporter mice

We evaluated the osteoprogenitor response to rhBMP-2 and DBM in a transgenic mouse critical sized defect. The mice expressed Col3.6GFPtopaz (a pre-osteoblastic marker), Col2.3GFPemerald (an osteoblastic marker) and α-smooth muscle actin (α-SMA-Cherry, a pericyte/myofibroblast marker). We assessed defect healing at various time points using radiographs, frozen, and conventional histologic analyses. GFP signal in regions of interest corresponding to the areas of new bone formation was quantified using a novel computer assisted algorithm. All defects treated with rhBMP-2 healed. In contrast, the majority of the defects in the DBM (27/30) and control (28/30) groups did not heal. Quantitation of pre-osteoblasts demonstrated a maximal response (% GFP + cells/TV) in the Col3.6GFPtopaz mice at day 7 (7.2% ± 6.0, p < 0.05 compared to days 14, 21, 28, and 56). The maximal response of the Col2.3GFP cells was seen at days 14 (8.04% ± 5.0) and 21 (8.31% ± 4.32), p < 0.05. In contrast, DBM and control groups showed a limited osteogenic response at all time points. In conclusion, we demonstrated that the BMP and DBM induce vastly different osteogenic responses which should influence their clinical application as bone graft substitutes.

Recombinant human bone morphogenetic protein-2 in debridement and impacted bone graft for the treatment of femoral head osteonecrosis

The purpose of this study was to compare the clinical outcomes of impacted bone graft with or without recombinant human bone morphogenetic protein-2 (rhBMP-2) for osteonecrosis of the femoral head (ONFH). We examined the effect of bone-grafting through a window at the femoral head-neck junction, known as the “light bulb” approach, for the treatment of ONFH with a combination of artificial bone (Novobone) mixed with or without rhBMP-2. A total of 42 patients (72 hips) were followed-up from 5 to 7.67 years (average of 6.1 years). The patients with and without BMP were the first group (IBG+rhBMP-2) and the second group (IBG), respectively. The clinical effectiveness was evaluated by Harris hip score (HHS). The radiographic follow-up was evaluated by pre-and postoperative X-ray and CT scan. Excellent, good, and fair functions were obtained in 36, 12, and 7 hips, respectively. The survival rate was 81.8% and 71.8% in the first and second group, respectively. However, the survival rate was 90.3% in ARCO stage IIb, c, and only 34.6% in ARCO stage IIIa(P<0.05). It was concluded that good and excellent mid-term follow-up could be achieved in selected patients with ONFH treated with impacted bone graft operation. The rhBMP-2 might improve the clinical efficacy and quality of bone repair.

Open reduction and closed reduction internal fixation in treatment of femoral neck fractures: a meta-analysis

BACKGROUND

A meta-analysis was performed to assess the association between healing rate, avascular necrosis (AVN) of femoral head and two reductions-open reduction internal fixation (ORIF) and closed reduction internal fixation (CRIF) for femoral neck fracture.

METHODS

A literature-based search was conducted to identify all relevant studies published before September 10, 2013. The odd ratio (OR) and 95% confidence interval (CI) were used for estimating the effects of the two reduction methods. Data were independently extracted by two investigators who reached a consensus on all of the items. The heterogeneity between studies was examined by χ2-based Q statistic. Egger's regression analysis was used to evaluate publication bias. Statistical analysis was performed by Stata 10.0 software.

RESULTS

We examined 14 publications. The results of the present meta-analysis showed that AVN of femoral head were significant associated with the two reductions (CRIF vs. ORIF, OR=1.746, 95% CI 1.159-2.628, p=0.008), while the healing rate were not (CRIF vs. ORIF, OR=0.853, 95% CI 0.573-1.270, p=0.433).

CONCLUSION

The present meta-analysis indicated the risk of AVN of femoral head was significant higher after CRIF fixation compared with ORIF, but no association between the healing rate and the two reductions for femoral neck fracture.

Local delivery of recombinant human bone morphogenetic proteins and bisphosphonate via sucrose acetate isobutyrate can prevent femoral head collapse in Legg-Calve-Perthes disease: a pilot study in pigs

PURPOSE

Legg-Calve-Perthes disease is a paediatric condition encompassing idiopathic osteonecrosis of the femoral head (ONFH). Preventing collapse and the need for subsequent joint replacement remains the major goal of clinical management. This exploratory study utilises a porcine model of surgically induced ONFH.

METHODS

rhBMP-2 with and without zoledronic acid (ZA) was delivered by intra-osseous injection in the phase-transitioning sucrose acetate isobutyrate (SAIB) in an attempt to prevent femoral head collapse. Epiphyseal quotient (EQ) at eight weeks post-surgery was the primary outcome measure. Heterotopic ossification in the joint capsule and bisphosphonate retention in the femoral head were key secondary outcomes.

RESULTS

Femoral heads with ONFH and no treatment all collapsed (3/3, EQ < 0.4, P < 0.05 compared to no ONFH). Local delivery of rhBMP-2/SAIB into the femoral head prevented collapse by EQ measurement one of four samples; however, this specimen still showed evidence of significant collapse. In contrast, the combination of local rhBMP-2 and local ZA prevented collapse in two of four samples. Confocal fluorescence microscopy showed locally dosed bisphosphonate entered and was retained in the femoral head. This group also showed strong Calcein signal, indicating new bone formation. Treatment with rhBMP-2 was associated with a limited amount of heterotrophic ossification in the joint capsules in some specimens.

CONCLUSIONS

Operators reported SAIB to be an efficient way to deliver rhBMP-2 to the femoral head. These data suggest that rhBMP-2 is ineffective for preventing femoral head collapse without the addition of bisphosphonate. Further research will be required to validate the clinical efficacy of a combined local rhBMP-2/bisphosphonate approach.

Acute BMP2 upregulation following induction of ischemic osteonecrosis in immature femoral head

Juvenile ischemic osteonecrosis of the femoral head (IOFH) is one of the most serious hip conditions causing the femoral head deformity. Little is known about BMP signaling following ischemic osteonecrosis. In this study, we found acute BMP2 upregulation in the femoral head cartilage 24h after ischemic induction using our immature pig IOFH model. Similarly, in our ischemic osteonecrosis mouse model, BMP2 expression and BMP signaling were enhanced in the articular cartilage surrounding the necrotic bone. BMP2 was increased in cartilage explants and primary chondrocytes under hypoxia (1% O(2)) compared with normoxia (21% O(2)). Addition of the hypoxia inducible factor 1 (HIF1) activator DFO significantly increased BMP2 while HIF1 silencing (siHIF1) only partially reduced BMP2, suggesting other mechanisms of BMP2 upregulation being present. Hypoxia is known to induce the production of free oxygen radicals, which are converted to hydrogen peroxide (H(2)O(2)) by superoxide dismutase 2 (SOD2). As an alternative mechanism, we investigated the effect of H(2)O(2)/SOD2 production on BMP2 upregulation. Chondrocytes produced more H(2)O(2) under hypoxia than normoxia. H(2)O(2) addition to the chondrocyte culture also significantly increased BMP2 expression. SOD2 was also dramatically increased in the ischemic pig cartilage at 24h following surgery and in primary chondrocytes/cartilage explants culture under hypoxia. SOD2 protein addition to the chondrocyte culture significantly increased BMP2. Moreover, DFO significantly increased SOD2 while HIF1 silencing only partially reduced SOD2. These results suggest that the acute BMP2 response of chondrocytes to ischemic osteonecrosis is more dominantly through the H(2)O(2) production and only partly through the HIF1 pathway.

Evidence for using bisphosphonate to treat Legg-Calvé-Perthes disease

BACKGROUND

The rationale for using bisphosphonate (BP) therapy for Legg-Calvé-Perthes disease (LCPD) is the potential to prevent substantial femoral head deformity during the fragmentation phase by inhibiting osteoclastic bone resorption. However, it is unclear whether BP therapy decreases femoral head deformity.

QUESTIONS/PURPOSES

In this systematic review, we answered the following questions: (1) Does bisphosphonate (BP) therapy decrease femoral head deformity and improve pain and function in LCPD or other juvenile osteonecrotic conditions? And (2) does BP therapy decrease femoral head deformity in experimental studies of juvenile femoral head osteonecrosis?

METHODS

We searched the literature from 1966 to 2011 for clinical and experimental studies on BP therapy for juvenile femoral head osteonecrosis. Studies specifically addressing clinical and/or radiographic/histologic outcomes pertaining to pain and function and femoral head morphology were analyzed.

RESULTS

Three Level IV clinical studies met our inclusion criteria. Only one study initiated BP therapy during the precollapsed stage of osteonecrosis and reported prevention of femoral head deformity in nine of 17 patients. All studies noted subjective improvements of pain and gait in patients treated with intravenous BPs. Of the eight experimental studies reviewed, seven reported reduced femoral head deformity and six found better preservation of trabecular framework in animals treated with BPs.

CONCLUSIONS

Clinical evidence lacks consistent patient groups and drug protocols to draw definitive conclusions that BP therapy can decrease femoral head deformity in juvenile osteonecrotic conditions. Experimental studies suggest BP therapy protects the infarcted femoral head from deformity, but it lacks bone anabolic effect. Further basic and clinical research are required to determine the potential role of BPs as a medical treatment for LCPD.

The "bone morphogenic proteins" pathways in bone and joint diseases: translational perspectives from physiopathology to therapeutic targets

A large body of evidence supports an important role of bone morphogenic proteins (BMPs) pathways in skeletal development in the embryo. BMPs are also involved in skeletal homeostasis and diseases in the adult. They were first identified as major bone anabolic agents and recent advances indicate that they also regulate osteoclastogenesis and joint components via multiple cross-talks with other signaling pathways. This review attempts to integrate these data in the pathogenesis of bone and joints diseases, such as osteoporosis, fracture healing, osteoarthritis, inflammatory arthritis, or bone metastasis. The use of recombinant BMPs in bone tissue engineering and in the treatment of skeletal diseases, or future therapeutic strategies targeting BMPs signal and its regulators, will be discussed based on these considerations.

Osteonecrosis of the femoral head: An update in year 2012

Osteonecrosis is a phenomenon involving disruption to the vascular supply to the femoral head, resulting in articular surface collapse and eventual osteoarthritis. Although alcoholism, steroid use, and hip trauma remain the most common causes, several other etiologies for osteonecrosis have been identified. Basic science research utilizing animal models and stem cell applications continue to further elucidate the pathophysiology of osteonecrosis and promise novel treatment options in the future. Clinical studies evaluating modern joint-sparing procedures have demonstrated significant improvements in outcomes, but hip arthroplasty is still the most common procedure performed in these affected younger adults. Further advances in joint-preserving procedures are required and will be widely studied in the coming decade.

PDGF-Simvastatin Delivery Stimulates Osteogenesis in Heat-induced Osteonecrosis

Heat generated during implant osteotomy might lead to osteonecrosis and delayed bone repair, thus resulting in impaired early osseointegration and fixation of bone-anchoring devices. In this study, we proposed to overcome heat-induced injury to bone by fabricating core-shell polymeric biodegradable microspheres encapsulating a mitogenic factor, platelet-derived growth factor (PDGF), and a differentiation factor, simvastatin, in a simultaneous or sequential release profile. Microspheres encapsulating bovine serum albumin (BSA), PDGF, simvastatin, PDGF-in-core with simvastatin-in-shell, and simvastatin-in-core with PDGF-in-shell were delivered to fill standardized osteotomy sites on edentulous ridges of rat maxillae under irrigated or non-irrigated conditions. In the absence of irrigation, significant reduction of cell viability and increase in inflammation and sequestrum formation without evidence of osteogenesis were observed. Both PDGF and simvastatin deliveries facilitated cell viability and reduced osteonecrosis. Localized osteogenesis was seen under simvastatin treatment, while generalized but primitive osteogenesis was noted in PDGF-treated osteotomy sites. In addition, sequential PDGF-simvastatin delivery further augmented osteogenesis and promoted bone maturation. The results suggested that sequential PDGF-simvastatin delivery was an effective modality to prevent heat-induced complications and facilitate bone apposition after implant osteotomy, potentially favoring the early fixation of bone-anchoring devices and oral implant osseointegration.

Management of osteonecrosis in children and young adults with acute lymphoblastic leukaemia

Osteonecrosis is a disabling complication in children and young adults with acute lymphoblastic leukaemia. It can affect any or multiple joints but the hip and knee are most frequently involved and a cause of long-term disability. The problem is almost exclusively that of older children and young adults of whom over 70% have asymptomatic changes on screening magnetic resonance imaging and 15-20% have resulting symptoms. Dexamethasone is associated with a higher risk than prednisolone in US but not European or UK trials and alternate week scheduling of dexamethasone in the intensification course is associated with a lower risk than a continuous 3-week schedule in US trials. Genetic factors and obesity contribute to the risk, as do metabolic abnormalities caused by drugs, such as asparaginase, which increase tissue exposure to steroids. Management is primarily supportive but a minority of patients require surgical intervention including replacement of the affected joint. A variety of surgical techniques and, latterly, bisphophonates, have been tried to prevent progression but their efficacy remains uncertain. Whether patients should continue to receive steroids after diagnosis of osteonecrosis is uncertain but most trial investigators recommend stopping them after completion of the intensification phase of treatment.