Zoledronic acid improves femoral head sphericity in a rat model of perthes disease

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.

Biochanin A inhibits endothelial dysfunction induced by IL‑6‑stimulated endothelial microparticles in Perthes disease via the NFκB pathway

Endothelial dysfunction caused by the stimulation of endothelial microparticles (EMPs) by the inflammatory factor IL-6 is one of the pathogenic pathways associated with Perthes disease. The natural active product biochanin A (BCA) has an anti-inflammatory effect; however, whether it can alleviate endothelial dysfunction in Perthes disease is not known. The present in vitro experiments on human umbilical vein endothelial cells showed that 0-100 pg/ml IL-6-EMPs could induce endothelial dysfunction in a concentration-dependent manner, and the results of the Cell Counting Kit 8 assay revealed that, at concentrations of <20 µM, BCA had no cytotoxic effect. Reverse transcription-quantitative PCR demonstrated that BCA reduced the expression levels of the endothelial dysfunction indexes E-selectin and intercellular cell adhesion molecule-1 (ICAM-1) in a concentration-dependent manner. Immunofluorescence and western blotting illustrated that BCA increased the expression levels of zonula occludens-1 and decreased those of ICAM-1. Mechanistic studies showed that BCA inhibited activation of the NFκB pathway. In vivo experiments demonstrated that IL-6 was significantly increased in the rat model of ischemic necrosis of the femoral head, whereas BCA inhibited IL-6 production. Therefore, in Perthes disease, BCA may inhibit the NFκB pathway to suppress IL-6-EMP-induced endothelial dysfunction, and could thus be regarded as a potential treatment for Perthes disease.

Molecular Biomarkers in Perthes Disease: A Review

BACKGROUND

Perthes disease is a juvenile form of osteonecrosis of the femoral head that affects children under the age of 15. One hundred years after its discovery, some light has been shed on its etiology and the biological factors relevant to its etiology and disease severity.

METHODS

The aim of this study was to summarize the literature findings on the biological factors relevant to the pathogenesis of Perthes disease, their diagnostic and clinical significance, and their therapeutic potential. A special focus on candidate genes as susceptibility factors and factors relevant to clinical severity was made, where studies reporting clinical or preclinical results were considered as the inclusion criteria. PubMed databases were searched by two independent researchers. Sixty-eight articles were included in this review. Results on the factors relevant to vascular involvement and inflammatory molecules indicated as factors that contribute to impaired bone remodeling have been summarized. Moreover, several candidate genes relevant to an active phase of the disease have been suggested as possible biological therapeutic targets.

CONCLUSIONS

Delineation of molecular biomarkers that underlie the pathophysiological process of Perthes disease can allow for the provision of earlier and more accurate diagnoses of the disease and more precise follow-ups and treatment in the early phases of the disease.

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.

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

Skeletal Morbidity in Children and Adolescents during and following Cancer Therapy

Skeletal abnormalities are common in children and adolescents diagnosed and treated for a malignancy. The spectrum ranges from mild pain to debilitating osteonecrosis and fractures. In this review, we summarize the impact of cancer therapy on the developing skeleton, provide an update on therapeutic strategies for prevention and treatment, and discuss the most recent advances in musculoskeletal research. Early recognition of skeletal abnormalities and strategies to optimize bone health are essential to prevent long-term skeletal sequelae and diminished quality of life in childhood cancer survivors.

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.

Protocol for a randomised control trial of bisphosphonate (zoledronic acid) treatment in childhood femoral head avascular necrosis due to Perthes disease

INTRODUCTION

Perthes disease (PD) is an idiopathic disorder presenting with avascular necrosis to the femoral head, which frequently results in flattening. Long-term function is directly related to the subsequent femoral head sphericity. Current treatment includes mechanical modalities and surgical procedures, which are therapeutic but are not uniformly able to prevent collapse. The use of the nitrogen-containing bisphosphonate zoledronic acid (ZA) to inhibit osteoclastic bone resorption is aimed at preserving femoral head strength, reducing collapse and thus maintaining shape. The proposed multicentre, prospective, randomised controlled trial intends to evaluate the efficacy of ZA treatment in PD.

METHODS AND ANALYSIS

An open-label randomised control trial recruiting 100 children (50 each treatment arm) 5 to 16 years old with unilateral PD. Subjects are randomly assigned to either (a) ZA and standard care or (b) Standard care. The primary outcome measure is deformity index (DI), a radiographic parameter of femoral head roundness assessed at 24 months, following 12 months of ZA treatment (3-monthly doses of ZA 0.025 mg/kg at baseline, 3, 6, 9 and 12 months) plus 12 months observation (group A) or 24 months of observation (group B). Secondary outcome measures are femoral head subluxation, Faces Pain scale, Harris hip score and quality of life. Assessments are made at baseline, 3 monthly during the first year of follow-up and then 6 monthly, until the 24th month.

ETHICS AND DISSEMINATION

The study commenced following the written approval from the Human Research Ethics Committee. Safety considerations regarding the effects of ZA are monitored which include the subject's symptomatology, mineral status, bone mass and turnover activity, and metaphyseal modelling. Data handling plan requires that all documents, clinical information, biological samples and investigation results will be held in strict confidence by study investigators to preserve its safety and confidentiality.

TRIAL REGISTRATION NUMBER

Australian and New Zealand Clinical Trials ACTRN12610000407099, pre-results.

Incidence and outcome of osteonecrosis in children and adolescents after intensive therapy for acute lymphoblastic leukemia (ALL)

Osteonecrosis (ON), a significant complication following treatment of acute lymphoblastic leukemia (ALL), has a profound impact on quality of life of ALL survivors. We studied incidence and outcome of ON in patients treated on or according to Australian and New Zealand Children's Haematology/ Oncology Group (ANZCHOG) study 8 at The Children's Hospital at Westmead. The study involved retrospective chart review of the patients. ON was defined by development of symptoms and confirmed by magnetic resonance imaging. From 2002-2011, 251 patients (143M, 108F, 59 Standard Risk (SR), 159 Medium Risk (MR) 5 High Risk (HR), and 28 Very high risk (VHR)) were treated according to study 8. Eighteen (7M, 11F, 2 SR, 12 MR, 4 VHR) patients developed ON (7.2%). Median age at diagnosis was 13.05 years(4.3-16.7). Incidence of ON in patients > 10 years at diagnosis was 29%. Six out of 18 patients developed ON after allogeneic stem cell transplantation. Median time from diagnosis to the development of ON following chemotherapy for ALL was 1.15 years (range 0.25-2.12). Most patients were treated with intravenous Zoledronic acid. At last follow-up, three patients had undergone arthroplasty, two patients were symptom free, and the remaining 13 patients reported persistent pain with activity. A majority of patients with ON of the hips had radiological progression. Overall, 7% of patients with ALL developed ON. Age >10 years was the most important risk factor. At last follow-up, 70% of patients had persistent symptoms. Although Zoledronic acid improved pain, most patients with ON of the hips had radiological progression.

Vascular evaluation after cervical hip fractures in children: a case series of eight children examined by scintigraphy after surgery for cervical hip fracture and evaluated for development of secondary radiological changes

Femoral neck fractures in children and young adults are rare, but have a high risk of avascular necrosis (AVN) and subsequent gradual collapse of the femoral head. In 2006, we initiated the use of scintigraphy for the diagnosis of vascular impairment after a cervical fracture in children. In the present retrospective case study, we evaluated the effect of the remaining postoperative circulation in the femoral head after fracture in terms of the development of AVN and secondary degenerative changes of the hip joint. Eight children, four girls and four boys [mean age 11.5 years (7-16)], had been operated for a cervical or a basocervical hip fracture between 2006 and 2012. The femoral head circulation was evaluated postoperatively with scintigraphy and all children had been followed radiographically for a minimum of 1 year. The Ficat classification was used to stage the AVN and the Stulberg classification was used to stage the sphericity of the femoral head at follow-up. In two patients, the femoral head had normal circulation postoperatively and they also had normal radiographs at follow-up. In two patients, the entire femoral head was avascular postoperatively and at follow-up, one patient had normal radiographs and one had both subchondral sclerosis and flattening. These two patients had been treated with bisphosphonates and prolonged non-weight-bearing. Four patients had postoperatively retained circulation in parts of the femoral head. Three of these four patients had normal radiographs at follow-up. Evaluation of the remaining circulation after surgery may help to predict the outcome and guide the postoperative regime in children with a femoral neck fracture.

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.

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.

Bone morbidity in childhood leukemia: epidemiology, mechanisms, diagnosis, and treatment

Skeletal abnormalities are commonly seen in children and adolescents with leukemia. The spectrum ranges from mild pain to debilitating osteonecrosis (ON) and fractures. In this review, we summarize the skeletal manifestations, provide an update on therapeutic strategies for prevention and treatment, and discuss the most recent advances in musculoskeletal research. Early recognition of skeletal abnormalities and strategies to optimize bone health are essential to prevent long-term skeletal sequelae and diminished quality of life observed in children and adolescents with leukemia.

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.

Use of zoledronic acid for treatment of chemotherapy related osteonecrosis in children and adolescents: a retrospective analysis

BACKGROUND

Osteonecrosis (ON) is a disabling complication of chemotherapy, especially steroids in children and adolescents. There are few reports in the literature of non-surgical management of ON. Patients with chemotherapy related ON, treated with zoledronic acid (ZA) were analyzed for clinical and radiological outcome.

METHODS

Retrospective chart review. Serial joint radiographs were performed to assess response and graded according to Association Research Circulation Osseous (ARCO) system. All patients were evaluated for bone turnover and bone mineral density (BMD) at set intervals.

RESULTS

Twenty children with ON were treated with ZA for median duration of 13 months (range 5-25) with median number of doses being 6 (2, 8). Five (25%) patients were pain free at the end of treatment and had minimal joint destruction on X-ray (ARCO score II); 5 (25%) underwent arthroplasty due to severe joint destruction and pain limiting activity (ARCO score III/IV); 10 (50%) reported ongoing pain with activity, none on regular analgesia. BMD analysis showed increase in lumbosacral BMD after 1 year of treatment. Compared to patients with ON of the knees, majority of patients with ON of the hips had radiological progression.

CONCLUSION

ZA was well tolerated and improved joint pain in the majority of patients. Despite treatment with ZA, most patients with ON of hips had progressive joint destruction requiring arthroplasty. Patients with ON of the knees appeared to have radiological stabilization. Novel treatment strategies should be considered to prevent this debilitating complication in survivors of childhood cancer.

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.

Altered cellular kinetics in the growth plate of the femoral head of spontaneously hypertensive rats

PURPOSE

Pathologic changes in the growth plate remain unknown in Legg-Calvé-Perthes (LCP) disease. Spontaneously hypertensive rats have proven to be a good model for studying LCP disease. This study investigated the histopathologic changes and the expression of vascular endothelial growth factor in the growth plate of spontaneously hypertensive rats (SHR).

MATERIALS AND METHODS

Sixty SHR rats were divided into two groups: those showing osteonecrosis (SHR+n group: 32), and those showing normal ossification (SHR-n group: 28). Thirty Wister Kyoto rats served as a control. For histomorphological measurement, the length of each zone of the growth plate was measured. Cell kinetics was measured by 5-bromo-2'-deoxyuridin (BrdU) immunohistochemistry and transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) assays. Vascular endothelial growth factor (VEGF) immunohistochemistry was used to identify of expression of VEGF.

RESULTS

The lengths of growth plates of the SHR+n group were significantly shorter in the initial growth period than those of the other groups. The lowest proliferative rate and the highest apoptosis rate were observed in the SHR+n group at the initial growth period. The expression of VEGF in the growth plate of the SHR group was lower than the control group, and it was lower in the SHR+n group than in the SHR-n group.

CONCLUSION

The growth plate of the SHR+n group was found to be affected by disease process of ischemic necrosis of the femoral head, and this might explain the relative overgrowth of the greater trochanter in the later stages of LCP disease.

Pathophysiology and new strategies for the treatment of Legg-Calvé-Perthes disease

Legg-Calvé-Perthes disease is a juvenile form of idiopathic osteonecrosis of the femoral head that can lead to permanent femoral head deformity and premature osteoarthritis. According to two recent multicenter, prospective cohort studies, current nonoperative and operative treatments have modest success rates of producing a good outcome with a spherical femoral head in older children with Legg-Calvé-Perthes disease. Experimental studies have revealed that the immature femoral head is mechanically weakened following ischemic necrosis. Increased bone resorption and delayed new bone formation, in combination with continued mechanical loading of the hip, contribute to the pathogenesis of the femoral head deformity. Biological treatment strategies to improve the healing process by decreasing bone resorption and stimulating bone formation appear promising in nonhuman preclinical studies.

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.

Pathophysiology, classifications, and natural history of Perthes disease

Since the original reports of Legg-Calvé-Perthes disease (LCPD), much research effort has been undertaken to improve understanding of this idiopathic hip disorder. This article focuses on the current knowledge of the pathophysiology, classifications, and natural history of LCPD. Although the cause of LCPD remains largely unknown, some insight has been gained on its pathophysiology through experimental studies using animal models of ischemic necrosis. The few available clinical studies on the natural history of LCPD suggest that femoral head deformity is well tolerated in short and intermediate terms, but 50% of patients develop disabling arthritis in the sixth decade of life.

Bisphosphonates in orthopedic applications

Bisphosphonates (BPs) exert potent effects on the skeleton. As such, there are important questions relating to how treatment with BPs for metabolic disorders might affect outcomes of orthopedic problems. A further question is what role, if any, might BPs play as adjunctive therapeutics for orthopedic problems. This article outlines the research thus far in the application of BPs to the management of osteonecrosis, bone repair, and joint arthroplasty. Many animal studies show a benefit to decreasing bone resorption in models of osteonecrosis. These include studies in both small and large animals, backed up by limited human data. Further clinical trials are underway for this indication. In bone repair, again, multiple studies exist. There are concerns that BPs could interfere with the normal processes of healing. Some of the controversy about benefits or adverse effects of BPs in this context can be distilled down to effects of dosing and administration. With some exceptions, longer intervals between dosing seem to be more beneficial while not producing adverse healing effects in animal studies. In joint arthroplasty, animal studies suggest a role for topical or systemic BPs for enhancing bone on-growth to implant surfaces and strength of mechanical fixation, although these are yet to be confirmed in clinical studies. Clinical studies show that BPs inhibit periprosthetic bone loss due to strain-adaptive remodeling and after impaction bone grafting, although an efficacy in inhibiting inflammatory bone loss due to wear particle-induced osteolysis has not been confirmed. Lastly, as anabolic drugs have become available, there is increasing interest in their combined use with BPs. From experimental data, manipulation of both the anabolic and catabolic responses is a powerful approach in models of bone repair.

Bisphosphonates: the first 40 years

The first full publications on the biological effects of the diphosphonates, later renamed bisphosphonates, appeared in 1969, so it is timely after 40years to review the history of their development and their impact on clinical medicine. This special issue of BONE contains a series of review articles covering the basic science and clinical aspects of these drugs, written by some of many scientists who have participated in the advances made in this field. The discovery and development of the bisphosphonates (BPs) as a major class of drugs for the treatment of bone diseases has been a fascinating story, and is a paradigm of a successful journey from 'bench to bedside'. Bisphosphonates are chemically stable analogues of inorganic pyrophosphate (PPi), and it was studies on the role of PPi as the body's natural 'water softener' in the control of soft tissue and skeletal mineralisation that led to the need to find inhibitors of calcification that would resist hydrolysis by alkaline phosphatase. The observation that PPi and BPs could not only retard the growth but also the dissolution of hydroxyapatite crystals prompted studies on their ability to inhibit bone resorption. Although PPi was unable to do this, BPs turned out to be remarkably effective inhibitors of bone resorption, both in vitro and in vivo experimental systems, and eventually in humans. As ever more potent BPs were synthesised and studied, it became apparent that physico-chemical effects were insufficient to explain their biological effects, and that cellular actions must be involved. Despite many attempts, it was not until the 1990s that their biochemical actions were elucidated. It is now clear that bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of the bone-resorbing osteoclasts. Bisphosphonates are internalised by osteoclasts and interfere with specific biochemical processes. Bisphosphonates can be classified into at least two groups with different molecular modes of action. The simpler non-nitrogen containing bisphosphonates (such as etidronate and clodronate) can be metabolically incorporated into non-hydrolysable analogues of ATP, which interfere with ATP-dependent intracellular pathways. The more potent, nitrogen-containing bisphosphonates (including pamidronate, alendronate, risedronate, ibandronate and zoledronate) are not metabolised in this way but inhibit key enzymes of the mevalonate/cholesterol biosynthetic pathway. The major enzyme target for bisphosphonates is farnesyl pyrophosphate synthase (FPPS), and the crystal structure elucidated for this enzyme reveals how BPs bind to and inhibit at the active site via their critical N atoms. Inhibition of FPPS prevents the biosynthesis of isoprenoid compounds (notably farnesol and geranylgeraniol) that are required for the post-translational prenylation of small GTP-binding proteins (which are also GTPases) such as rab, rho and rac, which are essential for intracellular signalling events within osteoclasts. The accumulation of the upstream metabolite, isopentenyl pyrophosphate (IPP), as a result of inhibition of FPPS may be responsible for immunomodulatory effects on gamma delta (γδ) T cells, and can also lead to production of another ATP metabolite called ApppI, which has intracellular actions. Effects on other cellular targets, such as osteocytes, may also be important. Over the years many hundreds of BPs have been made, and more than a dozen have been studied in man. As reviewed elsewhere in this issue, bisphosphonates are established as the treatments of choice for various diseases of excessive bone resorption, including Paget's disease of bone, the skeletal complications of malignancy, and osteoporosis. Several of the leading BPs have achieved 'block-buster' status with annual sales in excess of a billion dollars. As a class, BPs share properties in common. However, as with other classes of drugs, there are obvious chemical, biochemical, and pharmacological differences among the various BPs. Each BP has a unique profile in terms of mineral binding and cellular effects that may help to explain potential clinical differences among the BPs. Even though many of the well-established BPs have come or are coming to the end of their patent life, their use as cheaper generic drugs is likely to continue for many years to come. Furthermore in many areas, e.g. in cancer therapy, the way they are used is not yet optimised. New 'designer' BPs continue to be made, and there are several interesting potential applications in other areas of medicine, with unmet medical needs still to be fulfilled. The adventure that began in Davos more than 40 years ago is not yet over.

Future biologic treatments for Perthes disease

Standard surgical approaches for Perthes disease consist of nonoperative physical treatments or surgical treatment. Several investigators have been working on a better understanding of the pathophysiology and pathobiology of Perthes disease. Most of the focus has been on antiresorptive treatments. Other treatment avenues, however, include controlling the inflammatory phase of Perthes disease, increasing revascularization of necrotic bone, and anabolic strategies to increase bone formation. This article presents a current pathophysiological model of Perthes disease, reviews experimental strategies in pharmaceutical treatments, and suggests future areas for research.

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

BACKGROUND

Bisphosphonate therapy has been shown to preserve the osteonecrotic femoral head in experimental and short-term clinical studies. However, a lack of new bone formation within the preserved femoral head due to the inhibition of bone remodeling is a concern. The purpose of this investigation was to determine if combined therapy consisting of ibandronate and bone morphogenetic protein-2 (BMP-2) can preserve the shape of the femoral head and stimulate new bone formation in an immature animal model of ischemic osteonecrosis.

METHODS

Ischemic osteonecrosis was surgically induced in immature pigs. Four groups were studied: normal, treated with saline solution, treated with ibandronate, and treated with both ibandronate and BMP-2 (the ibandronate + BMP-2 group). The animals were killed eight weeks after surgery. Radiographic, histological, and histomorphometric assessments were performed.

RESULTS

Radiographic assessment showed better preservation of the femoral head shape-i.e., a 54% (CI [95% confidence interval]: 22%, 86%) higher mean epiphyseal quotient-in the ibandronate + BMP-2 group than in the saline group. Histological assessment showed increased trabecular bone in the ibandronate + BMP-2 group as compared with that in the saline group. The mean values for trabecular bone volume, thickness, and number and for osteoblast surface were an average of 400% (CI: 242%, 558%), 212% (CI: 166%, 259%), 71% (CI: 6%, 137%), and 2402% (CI: 2113%, 2693%) higher, respectively, in the ibandronate + BMP-2 group than in the saline group. The osteoclast number was significantly reduced in the ibandronate + BMP-2 group compared with that in the saline group (-59% [CI: -75%, -42%]). The mean osteoblast surface value in the ibandronate + BMP-2 group was significantly higher (2567% [CI: 2258%, 2877%]) than that in the ibandronate group. Heterotopic ossifications were present in the capsule of the hip joint in the ibandronate + BMP-2 group.

CONCLUSIONS

A combination of ibandronate and BMP-2 decreased femoral head deformity while stimulating bone formation in an immature animal model of ischemic osteonecrosis.

Transplantable delivery systems for in situ controlled release of bisphosphonate in orthopedic therapy

IMPORTANCE OF THE FIELD

Bisphosphonates (BPs), structurally similar to pyrophosphates and functionally superior in restraining osteoclast-induced bone resorption, have been widely used as clinical drugs in the treatment of osteoporosis, bone voids and associated inflammation. However, owing to their high aqueous solubility and the consequently high rate of loss during oral administration, the loading and targeting of BPs pose major challenges in practice. Alternative delivery routes such as nasal, subcutaneous/intramuscular injection have contributed little to improving the bioavailiability and efficacy of BPs. To improve and optimize the delivery efficiency and efficacy of BPs, numerous strategies have been developed and adopted. Studies on controlled release of BPs provide important information on the fabrication of BP delivery systems for in situ treatment. As BPs play an important therapeutic role in osteoporosis and similar diseases, it has become essential and vital to survey various reported fabrication methodologies of these systems and the consequential orthopedic treatments so as to keep abreast with advances in their clinical use.

AREAS COVERED IN THIS REVIEW

Transplantable delivery systems for controlled release of BP are reviewed from literature published since 2000. The fabrication pathways and the release of BPs from various material systems are discussed in case studies. Recent progress in CaP models based on the strong and specific chelation between BPs and calcium phosphate crystals is highlighted.

WHAT THE READER WILL GAIN

This review offers an outline of the advances in BP controlled release and delivery systems for orthopedic therapy.

TAKE HOME MESSAGE

Understanding the cutting-edge BP controlled release and delivery systems for in situ treatment is key to the successful design of a more promising and perfect delivery system for orthopedic therapy. Moreover, developing such delivery systems incorporating the numerous advantages of BPs and controlled release environment requires substantially more flexible models to control better the fate of BP drugs.

Bisphosphonate use in conditions other than osteoporosis

Bisphosphonates are the gold standard of treatment of postmenopausal osteoporosis, male osteoporosis, and steroid-induced osteoporosis. They have potential use in multiple musculoskeletal conditions other than osteoporosis and have also been shown to treat Paget's disease of the bone and osteogenesis imperfecta. Bisphophonates may have potential use in periprosthetic bone loss, osteonecrosis of the hip, fibrous dysplasia, and calcinosis in juvenile dermatomyositis.

Bisphosphonate-associated osteomyelitis of the jaw: guidelines for practicing clinicians

OBJECTIVE

To evaluate the literature and discuss the risk factors, mechanisms, pathophysiologic aspects, and recommended management of bisphosphonate-associated osteomyelitis of the jaw (BAOMJ).

METHODS

More than 350 published articles, case reports mentioning BAOMJ, and independent histology slides from BAOMJ lesions were reviewed critically. The most pertinent publications are cited and discussed.

RESULTS

The incidence of BAOMJ increases after extraction of teeth, dentoalveolar surgical procedures, or recent oral trauma leading to exposed maxillary or mandibular bone. Contributory factors include poor oral hygiene, oral infections, periodontal disease; recent or ongoing corticosteroid administration or chemotherapy; compromised immune status; diabetes or vascular insufficiency; old age; chronic diseases; and malignancies. On average, 1 of every 100,000 patients treated with bisphosphonates orally for osteoporosis or Paget disease of bone may develop BAOMJ-like lesions. Patients with cancer often receive bisphosphonate doses 10 times or higher, and also more frequently, than those used in patients with osteoporosis or Paget disease of bone. Therefore, greater frequency of administration of bisphosphonates, higher dosages, and prolonged use (that is, for more than 2 years) are likely to be factors triggering BAOMJ.

CONCLUSION

The association of bisphosphonate therapy with BAOMJ is rare in noncancer patients and is likely to be a class effect that may occur with use of any bisphosphonate. Whether patients with cancer require such a high frequency of intravenously administered bisphosphonates needs to be investigated. Following established guidelines can decrease the risks of BAOMJ in vulnerable patients. Rather than necrotic bone, current evidence supports an infectious and perhaps immunologic underlying cause for BAOMJ. The estimated incidence of BAOMJ among noncancer patients receiving bisphosphonates is about 0.001%, whereas among patients with cancer receiving intravenous bisphosphonate therapy the incidence is between 0.5% and 4%, depending on the dose, frequency, and duration of therapy (on average, approximately 2%). Nevertheless, the benefits of bisphosphonates far outweigh the risks.

Pharmacovigilance and reporting oversight in US FDA fast-track process: bisphosphonates and osteonecrosis of the jaw

More than half of all serious adverse reactions are identified 7 or more years after a drug receives approval from the US Food and Drug Administration (FDA). In 2002, 9 months after the intravenous bisphosphonate zoledronic acid received regulatory approval for marketing, the FDA received reports of nine patients with cancer, who were treated with zoledronic acid, who unexpectedly developed osteonecrosis of the jaw. During the next 2 years, three oral surgeons described 104 patients with cancer with osteonecrosis of the jaw in the medical literature and identified intravenous bisphosphonate therapy as being common to the care of these patients. In subspecialty medical, radiology, and dental journals, case reports and case series described clinical features of osteonecrosis of the jaw in patients with cancer who were treated with bisphosphonates. Manufacturer-sponsored epidemiological studies reported the first estimates of the incidence of this toxic effect, ranging from 0.1% to 1.8%. By contrast, independent epidemiological efforts from clinicians and the International Myeloma Foundation reported incidence estimates between 5% and 10%. Between 2003 and 2005, warnings about the risks of bisphosphonate-associated osteonecrosis were disseminated by national regulatory agencies, the manufacturers of bisphosphonates, and the International Myeloma Foundation. From 2006, independent clinical recommendations for diagnosis, prevention, and treatment of this toxic effect have been disseminated by manufacturers, national regulatory authorities, the International Myeloma Foundation, and medical specialty organisations. Furthermore, independent efforts by pharmaceutical manufacturers, dental and medical professionals, a non-profit organisation (the International Myeloma Foundation), patients, and regulatory authorities has led to the rapid identification and dissemination of safety information for this serious adverse reaction. Better coordination of safety-related pharmacovigilance initiatives is now needed.

Mechanisms of action of bisphosphonates: similarities and differences and their potential influence on clinical efficacy

Bisphosphonates (BPs) are well established as the leading drugs for the treatment of osteoporosis. There is new knowledge about how they work. The differences that exist among individual BPs in terms of mineral binding and biochemical actions may explain differences in their clinical behavior and effectiveness.

INTRODUCTION

The classical pharmacological effects of bisphosphonates (BPs) appear to be the result of two key properties: their affinity for bone mineral and their inhibitory effects on osteoclasts.

DISCUSSION

There is new information about both properties. Mineral binding affinities differ among the clinically used BPs and may influence their differential distribution within bone, their biological potency, and their duration of action. The antiresorptive effects of the nitrogen-containing BPs (including alendronate, risedronate, ibandronate, and zoledronate) appear to result from their inhibition of the enzyme farnesyl pyrophosphate synthase (FPPS) in osteoclasts. FPPS is a key enzyme in the mevalonate pathway, which generates isoprenoid lipids utilized for the post-translational modification of small GTP-binding proteins that are essential for osteoclast function. Effects on other cellular targets, such as osteocytes, may also be important. BPs share several common properties as a drug class. However, as with other families of drugs, there are obvious chemical, biochemical, and pharmacological differences among the individual BPs. Each BP has a unique profile that may help to explain potential clinical differences among them, in terms of their speed and duration of action, and effects on fracture reduction.

Bone degeneration and recovery after early and late bisphosphonate treatment of ovariectomized wistar rats assessed by in vivo micro-computed tomography

Bisphosphonates are antiresorptive drugs commonly used to treat osteoporosis. It is not clear, however, what the influence of the time point of treatment is. Recently developed in vivo micro-computed tomographic (CT) scanners offer the possibility to study such effects on bone microstructure in rats. The aim of this study was to determine the influence of early and late zoledronic acid treatment on bone in ovariectomized rats, using in vivo micro-CT. Twenty-nine female Wistar rats were divided into the following groups: ovariectomy (OVX, n = 5), OVX and zoledronic acid (ZOL) at week 0 (n = 8), OVX and ZOL at week 8 (n = 7), and sham (n = 9). CT scans were made of the proximal tibia at weeks 0, 2, 4, 8, 12, and 16; and bone structural parameters were determined in the metaphysis. Two fluorescent labels were administered to calculate dynamic histomorphometric parameters. At week 16, all groups were significantly different from each other in bone volume fraction (BV/TV), connectivity density, and trabecular number (Tb.N), except for the early ZOL and control groups which were not significantly different for any structural parameter. After ZOL treatment at week 8, BV/TV, structure model index, Tb.N, and trabecular thickness significantly improved in the late ZOL group. The OVX and ZOL groups showed, respectively, higher and lower bone formation rates than the control group. Early ZOL treatment inhibited all bone microstructural changes seen after OVX. Late ZOL treatment significantly improved bone microstructure, although the structure did not recover to original levels. Early ZOL treatment resulted in a significantly better microstructure than late treatment. However, late treatment was still significantly better than no treatment.

The deformity index as a predictor of final radiological outcome in Perthes’ disease

The deformity index is a new radiological measurement of the degree of deformity of the femoral head in unilateral Perthes’ disease. Its values represent a continuous outcome measure of deformity incorporating changes in femoral epiphyseal height and width compared with the unaffected side. The sphericity of the femoral head in 30 radiographs (ten normal and 20 from patients with Perthes’ disease) were rated blindly as normal, mild, moderate or severe by three observers. Further blinded measurements of the deformity index were made on two further occasions with intervals of one month.

There was good agreement between the deformity index score and the subjective grading of deformity. Intra- and interobserver agreement for the deformity index was high. The intraobserver intraclass correlation coefficient for each observer was 0.98, 0.99 and 0.97, respectively, while the interobserver intraclass correlation coefficient was 0.98 for the first and 0.97 for the second set of calculations.

We also reviewed retrospectively 96 radiographs of children with Perthes’ disease, who were part of a multicentre trial which followed them to skeletal maturity. We found that the deformity index at two years correlated well with the Stulberg grading at skeletal maturity. A deformity index value above 0.3 was associated with the development of an aspherical femoral head. Using a deformity index value of 0.3 to divide groups for risk gives a sensitivity of 80% and specificity of 81% for predicting a Stulberg grade of III or IV.

We conclude that the deformity index at two years is a valid and reliable radiological outcome measure in unilateral Perthes’ disease.

Bisphosphonates: mode of action and pharmacology

The profound effects of the bisphosphonates on calcium metabolism were discovered over 30 years ago, and they are now well established as the major drugs used for the treatment of bone diseases associated with excessive resorption. Their principal uses are for Paget disease of bone, myeloma, bone metastases, and osteoporosis in adults, but there has been increasing and successful application in pediatric bone diseases, notably osteogenesis imperfecta. Bisphosphonates are structural analogues of inorganic pyrophosphate but are resistant to enzymatic and chemical breakdown. Bisphosphonates inhibit bone resorption by selective adsorption to mineral surfaces and subsequent internalization by bone-resorbing osteoclasts where they interfere with various biochemical processes. The simpler, non-nitrogen-containing bisphosphonates (eg, clodronate and etidronate) can be metabolically incorporated into nonhydrolysable analogues of adenosine triphosphate (ATP) that may inhibit ATP-dependent intracellular enzymes. In contrast, the more potent, nitrogen-containing bisphosphonates (eg, pamidronate, alendronate, risedronate, ibandronate, and zoledronate) inhibit a key enzyme, farnesyl pyrophosphate synthase, in the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small guanosine triphosphate (GTP)-binding proteins (which are also GTPases) such as Rab, Rho, and Rac. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explains the loss of osteoclast activity. The recently elucidated crystal structure of farnesyl diphosphate reveals how bisphosphonates bind to and inhibit at the active site via their critical nitrogen atoms. Although bisphosphonates are now established as an important class of drugs for the treatment of many bone diseases, there is new knowledge about how they work and the subtle but potentially important differences that exist between individual bisphosphonates. Understanding these may help to explain differences in potency, onset and duration of action, and clinical effectiveness.

Retention, distribution, and effects of intraosseously administered ibandronate in the infarcted femoral head

The local distribution, retention, and effects of intraosseous administration of ibandronate in the infarcted femoral heads were studied. Intraosseous administration effectively delivered and distributed ibandronate in the infarcted femoral heads and decreased the femoral head deformity in a large animal model of Legg-Calve-Perthes disease.

INTRODUCTION

Bisphosphonate therapy has gained significant attention for the treatment of ischemic osteonecrosis of the femoral head (IOFH) because of its ability to inhibit osteoclastic bone resorption, which has been shown to contribute to the pathogenesis of femoral head deformity. Because IOFH is a localized condition, there is a need to explore the therapeutic potential of local, intraosseous administration of bisphosphonate to prevent the femoral head deformity. The purpose of this study was to investigate the distribution, retention, and effects of intraosseous administration of ibandronate in the infarcted head.

MATERIALS AND METHODS

IOFH was surgically induced in the right femoral head of 27 piglets. One week later, a second operation was performed to inject (14)C-labeled or unlabeled ibandronate directly into the infarcted head. (14)C-ibandronate injected heads were assessed after 48 h, 3 weeks, or 7 weeks later to determine the distribution and retention of the drug using autoradiography and liquid scintillation analysis. Femoral heads injected with unlabeled ibandronate were assessed at 7 weeks to determine the degree of deformity using radiography and histomorphometry.

RESULTS

Autoradiography showed that (14)C-Ibandronate was widely distributed in three of the four heads examined at 48 h after the injection. Liquid scintillation analysis showed that most of the drug was retained in the injected head, and almost negligible amount of radioactivity was present in the bone and organs elsewhere at 48 h. At 3 and 7 weeks, 50% and 30% of the (14)C-drug were found to be retained in the infarcted heads, respectively. Radiographic and histomorphometric assessments showed significantly better preservation of the infarcted heads treated with intraosseous administration of ibandronate compared with saline (p < 0.001).

CONCLUSIONS

This study provides for the first time the evidence that local intraosseous administration is an effective route to deliver and distribute ibandronate in the infarcted femoral head to preserve the femoral head structure after ischemic osteonecrosis. In a localized ischemic condition such as IOFH, local administration of bisphosphonate may be preferable to oral or systemic administration because it minimizes the distribution of the drug to the rest of the skeleton and bypasses the need for having a restored blood flow to the infarcted head for the delivery of the drug.

Osteonecrosis in children and adolescents with cancer - an adverse effect of systemic therapy

Osteonecrosis (ON) is recognised increasingly as a complication of the treatment of cancer in children and adolescents. It is especially prevalent among survivors of acute lymphoblastic leukaemia and non-Hodgkin lymphoma, in whom as many as 1/3 may be affected, likely reflecting the cumulative exposure to glucocorticosteroid therapy. The pathogenesis is complex and includes suppression of bone formation, expansion of the intra-medullary lipocyte compartment and a direct effect on nutrient arteries. Children > or =10 years of age are at particular risk and the disorder is substantially more common in Whites than in Blacks. Genetic predispositions have been identified. ON is often multi-articular and bilateral, affecting weight-bearing joints predominantly. Surgical management options are of concern in young growing subjects, although injection of autologous marrow into affected sites offers promising results. Other novel approaches include the use of anti-resorptive drugs and strategies for prevention, such as with lipid-lowering agents, are being explored.

RANKL inhibition: a novel strategy to decrease femoral head deformity after ischemic osteonecrosis

A novel therapeutic strategy to decrease the development of femoral head deformity after ischemic osteonecrosis was studied in a large animal model of total head infarction. RANKL inhibition through exogenous osteoprotegerin administration significantly decreased pathologic bone resorption and deformity during repair of the infarcted head.

INTRODUCTION

Legg-Calvé-Perthes disease (LCPD) is a juvenile form of osteonecrosis of the femoral head that can produce permanent femoral head deformity (FHD) and premature osteoarthritis. The development of FHD in LCPD is closely associated with the repair process, characterized by a predominance of bone resorption in its early stage that produces a fragmented appearance and collapse of the femoral head. We present here a novel strategy to preserve the femoral head structure after ischemic osteonecrosis based on inhibition of interaction between RANK and RANKL using exogenous administration of osteoprotegerin (OPG-Fc) in a large animal model of ischemic osteonecrosis.

MATERIALS AND METHODS

Ischemic osteonecrosis was surgically induced in 18 male piglets by placing a ligature tightly around the right femoral neck to disrupt the blood flow to the right femoral head. Two weeks after the induction of total head infarction, OPG-Fc or saline was administered subcutaneously to nine animals per group for 6 weeks. The contralateral, normal (left) femoral heads from the animals treated with saline served as normal, nondisease controls. All animals were killed at 8 weeks when severe FHD has been previously shown to occur because of the repair process dominated by osteoclastic bone resorption. Radiographic, histomorphometric, and immunohistochemical assessments were performed.

RESULTS

Radiographic assessment showed significantly better preservation of the femoral head structure in the OPG-Fc group compared with the saline group. Epiphyseal quotient (the ratio of epiphyseal height to diameter) was significantly higher in the OPG-Fc group (0.41 +/- 0.09) compared with the saline group (0.24 +/- 0.08, p < 0.001). Histomorphometric assessment revealed a significant reduction in the number of osteoclasts present in the OPG-Fc group (5.9 +/- 5.3mm(-2)) compared with the saline group (39.6 +/- 13.8 mm(-2), p < 0.001). Trabecular bone volume, number, and separation were significantly better preserved in the OPG-Fc group compared with the saline group (p < 0.001). No significant difference in femoral length was observed between the OPG-Fc and saline groups. Immunostaining revealed the presence of OPG-Fc only within the blood vessels, with no apparent staining of bone matrix or trabecular bone surfaces.

CONCLUSIONS

To our knowledge, this is the first study to show that RANKL inhibition decreases bone resorption and FHD after ischemic osteonecrosis. Because RANKL inhibitors do not bind to bone, their effects on resorption are reversible as the drug is cleared from circulation. The reversible nature of RANKL inhibitors is very appealing for treating pediatric bone diseases such as LCPD, where the resorptive stage of the disease lasts for 1-2 years.

Local bioavailability and distribution of systemically (parenterally) administered ibandronate in the infarcted femoral head

Recent studies show that bisphosphonates can decrease the development of femoral head deformity following ischemic osteonecrosis by inhibiting osteoclast-mediated bone resorption. Given the potential new indication, improved understanding of pharmacokinetics of bisphosphonates as it applies to the infarcted head would be beneficial. The purpose of this study was to investigate the local bioavailability and the distribution of ibandronate in the infarcted head at the avascular and vascular phases of the disease process. Ischemic osteonecrosis of the femoral head was surgically induced in 15 piglets. One, 3, and 6 weeks following the induction of ischemia, which represent various stages of revascularization and repair, 14C-labeled ibandronate was administered intravenously. Twenty-four hours following 14C-drug administration, the level of radioactivity and its distribution in the infarcted heads were determined using liquid scintillation analysis and autoradiography. A significant correlation was found between the extent of revascularization and the level of radioactivity measured in the infarcted heads (r=0.80, P<0.05). The radioactivity level in the infarcted heads measured by liquid scintillation was similar to the negative controls at 1 week when revascularization was absent, but it increased significantly at 6 weeks when extensive revascularization was present (P<or=0.00004). Autoradiographic assessment showed similar silver grain counts in the infarcted heads compared to the background at 1 week. At 3 weeks, a significant increase in the silver grain count was observed in the necrotic regions of the infarcted heads compared to the background (P=0.001) even though only a small area of the heads (2%) was found to be revascularized, suggesting diffusion of 14C-drug from the revascularized to the non-revascularized areas of the head. At 6 weeks, extensive 14C-drug binding was observed in the areas of revascularization with preferential binding of 14C-drug to the newly formed bone compared to the remaining necrotic bone (P=0.000001). These results indicate that revascularization and repair produce significant alteration of local bioavailability and distribution of ibandronate in the infarcted head. To our knowledge, this is the first study to examine the local bioavailability and distribution of bisphosphonate in the infarcted head. Current findings have important implications with regard to the timing and dosing of bisphosphonate after the onset of ischemic osteonecrosis.

Bisphosphonates: From Bench to Bedside

The discovery and development of the bisphosphonates (BPs) as a major class of drugs for the treatment of bone diseases has been a fascinating journey that is still not over. In clinical medicine, several BPs are established as the treatments of choice for various diseases of excessive bone resorption, including Paget's disease of bone, myeloma and bone metastases, and osteoporosis. Bisphosphonates are chemically stable analogues of inorganic pyrophosphate, and are resistant to breakdown by enzymatic hydrolysis. Bisphosphonates inhibit bone resorption by being selectively taken up and adsorbed to mineral surfaces in bone, where they interfere with the action of the bone-resorbing osteoclasts. Bisphosphonates are internalized by osteoclasts and interfere with specific biochemical processes. Bisphosphonates can be classified into at least two groups with different molecular modes of action. The simpler non-nitrogen-containing bisphosphonates (such as clodronate and etidronate) can be metabolically incorporated into nonhydrolyzable analogues of adenosine triphosphate (ATP) that may inhibit ATP-dependent intracellular enzymes. The more potent, nitrogen-containing bisphosphonates (such as pamidronate, alendronate, risedronate, ibandronate, and zoledronate) are not metabolized in this way but can inhibit enzymes of the mevalonate pathway, thereby preventing the biosynthesis of isoprenoid compounds that are essential for the posttranslational modification of small GTP-binding proteins (which are also GTPases) such as rab, rho, and rac. The inhibition of protein prenylation and the disruption of the function of these key regulatory proteins explain the loss of osteoclast activity and induction of apoptosis. The key target for bisphosphonates is farnesyl pyrophosphate synthase (FPPS) within osteoclasts, and the recently elucidated crystal structure of this enzyme reveals how BPs bind to and inhibit at the active site via their critical N atoms. In conclusion, bisphosphonates are now established as an important class of drugs for the treatment of many bone diseases, and their mode of action is being unraveled. As a result their full therapeutic potential is gradually being realized.

Pamidronate treatment of steroid associated osteonecrosis in young patients treated for acute lymphoblastic leukaemia--two-year outcomes

AIMS

To assess outcomes of young patients with osteonecrosis (ON) treated with pamidronate in terms of relief of pain, prevention of progress and bony collapse of involved area.

PATIENTS AND METHODS

A non-randomised interventional study in six patients with a history of acute lymphoblastic leukaemia (ALL) for which treatment protocols included long-term, high dose use of glucocorticoids. Subsequent development of ON was treated with a bisphosphonate (pamidronate) for 2 years. Mobility and pain control were assessed regularly with MRI and X-ray of affected areas at 0, 12 and 24 months.

RESULTS

Reduction in pain was reported in four of six patients in the first year with increased mobility. Two patients who had radiological evidence of joint destruction prior to treatment and when continued on corticosteroids reported no improvement in pain or mobility. In the second year, patients who started treatment in the first few months after diagnosis were stable while patients who had treatment initiated later deteriorated but had less pain than prior to treatment with pamidronate. MRIs of affected areas were completely unchanged over 2 years. X-rays revealed no new bony collapse in four of six patients after 12 months of treatment. However, three of six patients continued to undergo extensive collapse of femoral heads (one at 12 months, two at 24 months) and all these required urgent hip replacement.

CONCLUSION

Pamidronate treatment has a palliative effect in control of pain and may delay the natural history of bony collapse in the acute phase of ON, especially in early treated patients, but does not prevent late bone collapse and joint destruction in corticosteroid treated patients with ALL. Larger studies are needed to provide evidence as to whether bisphosphonate is indicated for treatment of ON for patients using corticosteroids.

Transient disturbance in physeal morphology is associated with long-term effects of nitrogen-containing bisphosphonates in growing rabbits

Bisphosphonates have clinical benefit in children with severe osteogenesis imperfecta or osteoporosis and potential benefit in children with Perthes disease or undergoing distraction osteogenesis. However, there is concern about the effects of bisphosphonates on the physis and bone length. In 44 growing rabbits, zoledronic acid caused a transient disruption of physeal morphology, retention of cartilaginous matrix in trabeculae and cortical bone of the metaphysis, and a minor decrement in tibial bone length at maturity.

INTRODUCTION

Data from growing animal models suggest that bisphosphonates cause retention of longitudinal cartilaginous septa at the chondro-osseous junction, extension of trabeculae to the metaphyseal-diaphyseal junction, and varying dose-dependent effects on longitudinal growth. However, there is a lack of data regarding effects of intermittent use of nitrogen-containing bisphosphonates on the physis and on tibial length in models reaching maturity.

MATERIALS AND METHODS

Contralateral tibias of juvenile rabbits were examined after right tibial distraction osteogenesis from two previous studies. Animals were randomized to receive 0.1 mg/kg zoledronic acid (ZA) IV at 8 weeks of age (ZA*1) or 8 and 10 weeks of age (ZA*2) or saline. Body mass was analyzed from 5 to 44 weeks of age; tibial length and proximal physeal-metaphyseal histology and histomorphometry were analyzed at 8-52 weeks of age.

RESULTS

Tibial length was 3% less at 14 weeks of age in the ZA*2-treated versus saline group (p<0.05) in both studies, and this difference persisted at maturity in the long-term study group (26 weeks of age, p<0.05). Total body mass gain from 5 to 26 weeks of age was 14% less in ZA*2-treated than saline animals (p<0.05). Rate of weight gain from 8 to 10 weeks of age was 76% less in ZA*2 compared with saline animals (p<0.05). Radiographs showed radiodense lines in the metaphyses of ZA-treated bones, corresponding to the number of doses. Histologically, lines resulting from the first dose of ZA contained longitudinal cartilaginous matrix cores surrounded by bone, whereas those from the second dose contained spherical cores of matrix caused by transient disruption of physeal morphology after the first dose of ZA. Resorption of these lines at later times was radiographically and histologically evident, but remnants of cartilaginous matrix remained in the cortical bone of ZA-treated animals.

CONCLUSIONS

ZA treatment within the final 13.5% of the rabbit tibial growth period caused a transient disruption in physeal morphology and resorption associated with retention of cartilaginous matrix and coinciding with a persistent 3% decrement in tibial length. Disruption of physeal morphology and potential loss of bone length should be considered when administering nitrogen-containing bisphosphonates to children before closure of the major physes.