Fracture healing: a consensus report from the International Osteoporosis Foundation Fracture Working Group

Murine Progeria Model Exhibits Delayed Fracture Healing with Dysregulated Local Immune Response

Background

Bone fracture is one of the most globally prevalent injuries, with an estimated 189 million bone fractures occurring annually. Delayed union or nonunion occurs in up to 15% of fractures and involves the interruption or complete failure of bone continuity following fracture. Preclinical testing is essential to support the translation of novel strategies to promote improved fracture repair treatment, but there is a paucity of small animal models that recapitulate clinical attributes associated with delayed fracture healing. This study explores whether the Zmpste24 -/- (Z24 -/- ) knockout mouse model of Hutchinson-Gilford progeria syndrome presents with delayed fracture healing. Leveraging the previously characterized Z24 -/- phenotype of genomic instability, epigenetic changes, and fragility, we hypothesize that these underlying alterations will lead to significantly delayed fracture healing relative to age-matched wild type (WT) controls.

Methods

WT and Z24 -/- mice received intramedullary fixed tibia fractures at ∼12 weeks of age. Mice were sacrificed throughout the time course of repair for the collection of organs that would provide information regarding the local (fracture callus, bone marrow, inguinal lymph nodes) versus peripheral (peripheral blood, contralateral tibia, abdominal organs) tissue microenvironments. Analyses of these specimens include histomorphometry, μCT, mechanical strength testing, protein quantification, gene expression analysis, flow cytometry for cellular senescence, and immunophenotyping.

Results

Z24 -/- mice demonstrated a significantly delayed rate of healing compared to WT mice with consistently smaller fracture calli containing higher proportion of cartilage and less bone after injury. Cellular senescence and pro-inflammatory cytokines were elevated in the Z24 -/- mice before and after fracture. These mice further presented with a dysregulated immune system, exhibiting generally decreased lymphopoiesis and increased myelopoiesis locally in the bone marrow, with more naïve and less memory T cell but greater myeloid activation systemically in the peripheral blood. Surprisingly, the ipsilateral lymph nodes had increased T cell activation and other pro-inflammatory NK and myeloid cells, suggesting that elevated myeloid abundance and activation contributes to an injury-specific hyperactivation of T cells.

Conclusion

Taken together, these data establish the Z24 -/- progeria mouse as a model of delayed fracture healing that exhibits decreased bone in the fracture callus, with weaker overall bone quality, immune dysregulation, and increased cellular senescence. Based on this mechanism for delayed healing, we propose this Z24 -/- progeria mouse model could be useful in testing novel therapeutics that could address delayed healing.

The Translational Potential of this Article

This study employs a novel animal model for delayed fracture healing that researchers can use to screen fracture healing therapeutics to address the globally prevalent issue of aberrant fracture healing.

Efficacy and Safety of Postmenopausal Osteoporosis Treatments: A Systematic Review and Network Meta-Analysis of Randomized Controlled Trials

Although a range of pharmacological interventions is available, it remains uncertain which treatment for osteoporosis is more effective. This network meta-analysis study aimed to compare different drug efficacy and safety in randomized controlled trials (RCTs) for the treatment of postmenopausal osteoporosis. PubMed, EMBASE, MEDLINE, Clinicaltrial.gov, Cochrane library, Google scholar were searched up to 31 October 2020. Randomized placebo-controlled trials that reported measures of bone mineral density (BMD) percentage change and/or numbers of adverse events of postmenopausal osteoporosis patients were included. Network meta-analysis was conducted using frequentist approach. Ninety-four RCTs comprising 15,776 postmenopausal osteoporosis females were included in the network meta-analysis. Compared with placebo, most interventions showed increase in BMD change. According to surfaces under the cumulative ranking curves (SUCRAs), strontium ranelate, fluoride, and hormone replacement therapy were most effective in increasing total hip, lumbar spine, and distal radius BMD, respectively. Parathyroid hormone (PTH) was most effective in preventing new hip fracture. When taking into account all anatomic sites, bisphosphonate (BP), monoclonal antibody (mAb), and fluoride have a balanced efficacy in increasing BMD at all sites. Considering both the effectiveness of increasing BMD and preventing hip fracture, mAb, BP, and PTH are more favorable among all interventions. The treatment effects of different medications on BMD percentage change are anatomic site-dependent. After weighing anti-osteoporosis treatment efficacy against risk of complications, BP and mAb are the more favorable interventions to increase BMD at all sites and reduce the risks of hip fracture and death.

Biological applications of copper-containing materials

Copper is an indispensable trace metal element in the human body, which is mainly absorbed in the stomach and small intestine and excreted into the bile. Copper is an important component and catalytic agent of many enzymes and proteins in the body, so it can influence human health through multiple mechanisms. Based on the biological functions and benefits of copper, an increasing number of researchers in the field of biomaterials have focused on developing novel copper-containing biomaterials, which exhibit unique properties in protecting the cardiovascular system, promoting bone fracture healing, and exerting antibacterial effects. Copper can also be used in promoting incisional wounds healing, killing cancer cells, Positron Emission Tomography (PET) imaging, radioimmunological tracing and radiotherapy of cancer. In the present review, the biological functions of copper in the human body are presented, along with an overview of recent progress in our understanding of the biological applications and development of copper-containing materials. Furthermore, this review also provides the prospective on the challenges of those novel biomaterials for future clinical applications.

The Effect of Alendronate on Osteoclastogenesis in Different Combinations of M-CSF and RANKL Growth Factors

Bisphosphonates (BPs) are compounds resembling the pyrophosphate structure. BPs bind the mineral component of bones. During the bone resorption by osteoclasts, nitrogen-containing BPs are released and internalized, causing an inhibition of the mevalonate pathway. As a consequence, osteoclasts are unable to execute their function. Alendronate (ALN) is a bisphosphonate used to treat osteoporosis. Its administration could be associated with adverse effects. The purpose of this study is to evaluate four different ALN concentrations, ranging from 10⁻⁶ to 10⁻¹⁰ M, in the presence of different combinations of M-CSF and RANKL, to find out the effect of low ALN concentrations on osteoclastogenesis using rat and human peripheral blood mononuclear cells. The cytotoxic effect of ALN was evaluated based on metabolic activity and DNA concentration measurement. The alteration in osteoclastogenesis was assessed by the activity of carbonic anhydrase II (CA II), tartrate-resistant acid phosphatase staining, and actin ring formation. The ALN concentration of 10⁻⁶ M was cytotoxic. Low ALN concentrations of 10⁻⁸ and 10⁻¹⁰ M promoted proliferation, osteoclast-like cell formation, and CA II activity. The results indicated the induction of osteoclastogenesis with low ALN concentrations. However, when high doses of ALN were administered, their cytotoxic effect was demonstrated.

Psoralen, a natural phytoestrogen, improves diaphyseal fracture healing in ovariectomized mice: A preliminary study

Psoralen is an effective active component extracted from Psoraleacorylifolia, which can promote bone formation in osteoporotic animals. However, to the best of our knowledge, its effect on fracture healing has not yet been examined. In the present study, open femur fractures were created in ovariectomy (OVX)-induced osteoporotic mice. OVX mice were treated with psoralen (psoralen+OVX group) or physiological saline (OVX group) by oral gavage. Radiographic and histological results demonstrated progressed callus consolidation in the psoralen+OVX group compared with the OVX group after 10 and 21 days of treatment. Qualitative histological analysis showed that the number of osteoclasts was significantly reduced in the psoralen+OVX group after treatment. Moreover, reverse transcription-quantitative PCR analysis of callus samples showed increased expression of bone morphogenetic protein-2 (BMP-2) and osteoprotegerin (OPG), and decreased expression of receptor activator of nuclear factor-κB ligand (RANKL) at 10 and 21 days post injury in the psoralen+OVX group compared with the OVX group. Furthermore, western blot analysis showed that psoralen significantly increased the expression of estrogen receptor (ER)-α, but had no effect on ER-β expression; these results were further confirmed by immunohistochemistry. To conclude, these results indicated that psoralen may promote callus formation and inhibit osteoclast genesis by increasing BMP-2 and ER-α levels, and OPG/RANKL ratio. Consequently, psoralen could be a possible treatment for osteoporotic fracture-related complications.

The Life of a Fracture: Biologic Progression, Healing Gone Awry, and Evaluation of Union

New knowledge about the molecular biology of fracture-healing provides opportunities for intervention and reduction of risk for specific phases that are affected by disease and medications. Modifiable and nonmodifiable risk factors can prolong healing, and the informed clinician should optimize each patient to provide the best chance for union. Techniques to monitor progression of fracture-healing have not changed substantially over time; new objective modalities are needed.

Does osteoporosis affect the healing of subcapital humerus and distal radius fractures?

Introduction

Animal models indicate that osteoporosis may negatively influence the fracture healing process, but clinical studies on this topic are scarce. In this study we investigated the effect of osteoporosis on fracture healing in patients with an upper extremity fracture.

Methods

This retrospective cohort study included all patients aged 50 years or older, with a fracture of the proximal humerus or the distal radius treated in the period June 2012 to July 2015 and a DEXA scan within a year after fracture. The incidence of delayed-union and non-union were compared between patients with or without osteoporosis (BMD T score ≤ -2.5SD). A secondary analysis was performed with a more pragmatically definition; BMD T score ≤ -2.5SD or a proximal humerus fracture with a T-score between -2.5SD and -1.0SD.

Results

Osteoporosis was diagnosed in 133/455 patients (29.2%). A total of 461 fractures (distal radius n = 311 and proximal humerus n = 150) were treated. Radiological delayed- or non-union was described in 11/461 cases (2.4%); all proximal humerus fractures of which 6 cases (1.3%) were clinically manifest. The incidence of delayed- or non-union in fracture treatment did not differ between patients with osteoporosis (5/137 fractures) and the patients without osteoporosis (6/324 fractures) (p = 0.27). In the second analysis a significantly higher incidence was found in patients with osteoporosis (10/214 fractures vs 1/247 fractures p = 0.003).

Conclusions

The results of this study suggest that osteoporosis does not significantly influence the progress of fracture healing in distal radius and proximal humerus fractures, although there seems to be a tendency towards a negative effect.

Novel Surgical Strategy for Treating Osteoporotic Vertebral Fractures with Cord Compression

Objectives

Treatment for osteoporotic vertebral fracture (OVF) with cord compression is challenging and it usually requires surgical interventions to decompress nerves and restore spinal sequences. To describe a novel surgical strategy for treating OVFs with cord compression.

Methods

This is a single‐center retrospective analysis. The inclusion criteria were Frankel grade C‐E, single level T₁₀‐L₂. Between January 2008 and December 2016, a total of 56 OVF patients (47 females and nine males, with an average age of 72 years (66–88 years), comprising of eight grade C, 23 grade D, and 25 grade E patients) were enrolled. The treatment algorithm included preoperative evaluation by MRI, extension CT, and radiography to classify the OVFs as type 1.1 (reducible, stable; n = 13), type1.2 (reducible, unstable; n = 16), type 2 (irreducible; n = 19) or type 2M (modifier; n = 8). Vertebroplasty (VP)/kyphoplasty (KP) was applied in type 1.1. VP/KP with posterior fixation and posterolateral fusion was applied in type 1.2. And additional laminectomy/osteotomy was used in type 2, except in a modifier group (2M) where same procedure as applied for type 1.2 was used. VAS, ODI, Cobb angle, Frankel functional grade, and complications were recorded.

Results

Thirteen cases were classified as type 1.1, 16 cases as type 1.2, 19 cases as type 2, and eight cases as type 2M. The follow‐up period was 38.9 months (range, 24–108 months). All patients were followed‐up in at least 24 months, in which time four patients died, two patients were lost at the last follow‐up, and 50 patients completed the full study. The total VAS and ODI improved from 8 (7, 9) and 75.5% (67.2%, 80.0%) preoperatively to 2 (1, 3) and 31% (24.0%, 37.0%) on conclusion, respectively (P < 0.01). The local kyphotic angle was corrected from 22.3° (17.1°, 33. 8°) preoperatively to 10.4° (6.4°, 15.3°) on conclusion (P < 0.01). Twenty‐three patients had achieved neurological recovery on conclusion (42E, 8D, P < 0.01). Asymptotic cement leakage was observed in 17/56 cases (30.4%), 6/56 in the affected vertebra (10.7%), and 24/330 in the screw trajectory (7.3%). At 2 years postoperatively, 11 new VFs had occurred in nine patients (16.1%), including VFs in nine adjacent segments that all occurred within 1 year after surgery. No cement migration or implant failure was noted.

Conclusion

The novel surgical strategy for treating OVFs with cord compression consists of the most tailored and least invasive treatment for each patient. The positive mid‐ and long‐term clinical and radiological outcomes observed could represent a step forward in devising the proposed algorithm.

Bone-seeking agents for the treatment of bone disorders

The targeting and delivery of therapeutic and diagnostic agents to bone tissue presents both a challenge and opportunity. Osteoporosis, Paget's disease, cancer, and bone metastases are all skeletal diseases whose treatment would benefit from new targeted therapeutic strategies. Osteoporosis, in particular, is a very prevalent disease, affecting over one in three women and one in five men in Canada alone with the cost to the healthcare system estimated at over $2.3 billion in 2010. Bone tissue is often considered a rigid structure when in reality there is a process of continuous remodeling that takes place via complex endocrine-regulated cell signaling pathways in addition to the signaling pathways unique to bone tissue. It is these specific boneremodeling processes that provide unique targeting opportunities but also present a number of challenges.

Proceedings of the 2017 Santa Fe Bone Symposium: Insights and Emerging Concepts in the Management of Osteoporosis

The 18th Annual Santa Fe Bone Symposium was held on August 4-5, 2017, in Santa Fe, New Mexico, USA. The symposium convenes health-care providers and clinical researchers to present and discuss clinical applications of recent advances in research of skeletal diseases. The program includes lectures, oral presentations by endocrinology fellows, case-based panel discussions, and breakout sessions on topics of interest, with emphasis on participation and interaction of all participants. Topics included the evaluation and treatment of adult survivors with pediatric bone diseases, risk assessment and management of atypical femur fractures, nonpharmacologic strategies in the care of osteoporosis, and skeletal effects of parathyroid hormone with opportunities for therapeutic intervention. Management of skeletal complications of rheumatic diseases was discussed. Insights into sequential and combined use of antiresorptive agents were presented. Individualization of patient treatment decisions when clinical practice guidelines may not be applicable was covered. Challenges and opportunities with osteoporosis drug development were discussed. There was an update on progress of Bone Health TeleECHO (Bone Health Extension for Community Healthcare Outcomes), a teleconferencing strategy for sharing knowledge and expanding capacity to deliver best-practice skeletal health care.

Efficacy and safety of bazedoxifene in postmenopausal women with osteoporosis: A systematic review and meta-analysis

INTRODUCTION

Bazedoxifene may be promising to treat osteoporosis of postmenopausal women. We conducted a systematic review and meta-analysis to explore the efficacy and safety of bazedoxifene in postmenopausal women with osteoporosis.

METHODS

PubMed, EMbase, Web of science, EBSCO, and Cochrane library databases were systematically searched. Randomized controlled trials (RCTs) assessing the effect of bazedoxifene on osteoporosis of postmenopausal women were included. Two investigators independently searched articles, extracted data, and assessed the quality of included studies. The primary outcomes were vertebral fracture and spine BMD at 3 and 7 years.

RESULTS

Four RCTs are included in the meta-analysis. Overall, compared with placebo intervention in postmenopausal women with osteoporosis, bazedoxifene intervention can significantly reduce the risk of vertebral fracture [risk risks (RRs) = 0.69; 95% confidence interval (95% CI) = 0.52-0.93; P = .01], and increase spine BMD at 3 years (Std. mean difference = 1.71; 95% CI = 1.55-1.87; P < .005) and 7 years (Std. mean difference = 8.31; 95% CI = 8.07-8.55; P < .005). Bazedoxifene intervention results in no increase in adverse events (RR = 1.00; 95% CI = 0.99-1.00; P = .34), serious adverse events (RR = 1.04; 95% CI = 0.97-1.12; P = .31), myocardial infarction (RR = 0.88; 95% CI = 0.51-1.52; P = .64), stroke (RR = 0.97; 95% CI = 0.64-1.46; P = .87), venous thromboembolic event (RR = 1.56; 95% CI = 0.92-2.64; P = .10), and breast carcinoma (RR = 1.03; 95% CI = 0.59-1.79; P = .92).

CONCLUSIONS

Compared with placebo intervention for the osteoporosis of postmenopausal women, bazedoxifene intervention is found to significantly reduce the incidence of vertebral fracture and increase spine BMD at 3 and 7 years, and results in no increase in adverse events, serious adverse events, myocardial infarction, stroke, venous thromboembolic event, and breast carcinoma.

Selective effect of hydroxyapatite nanoparticles on osteoporotic and healthy bone formation correlates with intracellular calcium homeostasis regulation

Adequate bone substitutes osseointegration has been difficult to achieve in osteoporosis. Hydroxyapatite of the osteoporotic bone, secreted by pathologic osteoblasts, had a smaller crystal size and lower crystallinity than that of the normal. To date, little is known regarding the interaction of synthetic hydroxyapatite nanoparticles (HANPs) with osteoblasts born in bone rarefaction. The present study investigated the biological effects of HANPs on osteoblastic cells derived from osteoporotic rat bone (OVX-OB), in comparison with the healthy ones (SHM-OB). A selective effect of different concentrations of HANPs on the two cell lines was observed that the osteoporotic osteoblasts had a higher tolerance. Reductions in cell proliferation, ALP activity, collagen secretion and osteoblastic gene expressions were found in the SHM-OB when administered with HANPs concentration higher than 25µg/ml. In contrast, those of the OVX-OB suffered no depression but benefited from 25 to 250µg/ml HANPs in a dose-dependent manner. We demonstrated that the different effects of HANPs on osteoblasts were associated with the intracellular calcium influx into the endoplasmic reticulum. The in vivo bone defect model further confirmed that, with a critical HANPs concentration administration, the osteoporotic rats had more and mechanically matured new bone formation than the non-treated ones, whilst the sham rats healed no better than the natural healing control. Collectively, the observed epigenetic regulation of osteoblastic cell function by HANPs has significant implication on defining design parameters for a potential therapeutic use of nanomaterials.

STATEMENT OF SIGNIFICANCE

In this study, we investigated the biological effects of hydroxyapatite nanoparticles (HANPs) on osteoporotic rat bone and the derived osteoblast. Our findings revealed a previously unrecognized phenomenon that the osteoporotic individuals could benefit from higher concentrations of HANPs, as compared with the healthy individuals. The in vivo bone defect model confirmed that, with a critical HANPs concentration administration, the osteoporotic rats had more mechanically matured new bone formation than the non-treated ones, whilst the sham rats healed no better than the natural healing control. The selective effect of HANPs might be associated with the intracellular calcium influx into the endoplasmic reticulum. Collectively, the observed epigenetic regulation by HANPs has significant implication on defining design parameters for a potential therapeutic use of nanomaterials in a pathological condition.

Bisphosphonates and atypical subtrochanteric fractures of the femur

OBJECTIVES

Bisphosphonates are widely used as first-line treatment for primary and secondary prevention of fragility fractures. Whilst they have proved effective in this role, there is growing concern over their long-term use, with much evidence linking bisphosphonate-related suppression of bone remodelling to an increased risk of atypical subtrochanteric fractures of the femur (AFFs). The objective of this article is to review this evidence, while presenting the current available strategies for the management of AFFs.

METHODS

We present an evaluation of current literature relating to the pathogenesis and treatment of AFFs in the context of bisphosphonate use.

RESULTS

Six broad themes relating to the pathogenesis and management of bisphosphonate-related AFFs are presented. The key themes in fracture pathogenesis are: bone microdamage accumulation; altered bone mineralisation and altered collagen formation. The key themes in fracture management are: medical therapy and surgical therapy. In addition, primary prevention strategies for AFFs are discussed.

CONCLUSIONS

This article presents current knowledge about the relationship between bisphosphonates and the development of AFFs, and highlights key areas for future research. In particular, studies aimed at identifying at-risk subpopulations and organising surveillance for those on long-term therapy will be crucial in both increasing our understanding of the condition, and improving population outcomes.Cite this article: N. Kharwadkar, B. Mayne, J. E. Lawrence, V. Khanduja. Bisphosphonates and atypical subtrochanteric fractures of the femur. Bone Joint Res 2017;6:144-153. DOI: 10.1302/2046-3758.63.BJR-2016-0125.R1.