National Institutes of Health Pathways to Prevention Workshop: Research Gaps for Long-Term Drug Therapies for Osteoporotic Fracture Prevention

An electronic health record (EHR)-based risk calculator can predict fractures comparably to FRAX: a proof-of-concept study

Information in the electronic health record (EHR), such as diagnoses, vital signs, utilization, medications, and laboratory values, may predict fractures well without the need to verbally ascertain risk factors. In our study, as a proof of concept, we developed and internally validated a fracture risk calculator using only information in the EHR.

PURPOSE

Fracture risk calculators, such as the Fracture Risk Assessment Tool, or FRAX, typically lie outside the clinician workflow. Conversely, the electronic health record (EHR) is at the center of the clinical workflow, and many variables in the EHR could predict fractures without having to verbally ascertain FRAX risk factors. We sought to evaluate the utility of EHR variables to predict fractures and, as a proof of concept, to create an EHR-based fracture risk model.

METHODS

Routine clinical data from 24,189 subjects presenting to primary care from 2010 to 2018 was utilized. Major osteoporotic fractures (MOFs) were captured by physician diagnosis codes. Data was split into training (n = 18,141) and test sets (n = 6048). We fit Cox regression models for candidate risk factors in the training set, and then created a global model using a backward stepwise approach. We then applied the model to the test set and compared the discrimination and calibration to FRAX.

RESULTS

We found variables related to vital signs, utilization, diagnoses, medications, and laboratory values to be associated with incident MOF. Our final model included 19 variables, including age, BMI, Parkinson's disease, chronic kidney disease, and albumin levels. When applied to the test set, we found the discrimination (AUC 0.73 vs. 0.70, p = 0.08) and calibration were comparable to FRAX.

CONCLUSION

Routinely collected data in EHR systems can generate adequate fracture predictions without the need to verbally ascertain fracture risk factors. In the future, this could allow for automated fracture prediction at the point of care to improve osteoporosis screening and treatment rates.

Metabolic factors are not the direct mediators of the association between type 2 diabetes and osteoporosis

Objective

The causal relationship between type 2 diabetes mellitus (T2DM) and osteoporosis (OS) remains unclear. This study aims to investigate the causal relationship and explore the potential metabolic mechanism and its mediating role.

Methods

We conducted a comprehensive study, gathering data on 490,089 T2DM patients from the genome-wide association study (GWAS) database and selecting OS data from FinnGen and MRC-IEU sources, including 212,778 and 463,010 patients, respectively, for causal analysis. Simultaneously, we explored the potential roles of three obesity traits and 30 metabolic and inflammation-related mediating variables in the causal relationship.

Results

There is a strong causal relationship between T2DM and OS. The data from our two different database sources appeared in the same direction, but after correcting for body mass index (BMI), waist circumference (WC), and waist-to-hip ratio (WHR), the direction became the same. T2DM may increase the risk of OS [odds ratio (OR) > 1.5, p < 0.001]. Steiger's test results show that there is no reverse causality. No risk factors related to glycolipid metabolism, amino acid metabolism, and inflammation were found to mediate the causal relationship.

Conclusion

This study's findings indicate a robust causal relationship between T2DM and OS, influenced by relevant factors such as BMI. Our results shed light on the pathogenesis of OS and underscore the importance for clinicians to treat metabolic disorders to prevent osteoporosis.

Bridging, Mapping, and Addressing Research Gaps in Health Sciences: The Naqvi-Gabr Research Gap Framework

Innovations pertaining to the ever-evolving needs of the medical and healthcare sciences remain constant. This creates a gap between the rationalized needs of the study and the proposed research question. However, classifying, identifying, and addressing these research gaps require a systematic and precise structured map. Using the Medical Subject Heading (MeSH) terms "Research Gaps" AND "Healthcare" AND "Framework" in MEDLINE, Scopus, and CINAHL databases with the filters yielded no relevant literature. Therefore, this review aims to fill this practical and clinical knowledge gap by developing the Naqvi-Gabr Research Gap Framework through critical synthesis based on extensive research on medical and healthcare research gaps. Fourteen research gaps are distributed for allocation as per the healthcare delivery system approach: developing new treatments or prevention strategies, improving diagnostic tools and techniques, addressing health disparities, and improving access to healthcare services. This structured framework determines the strategic mapping of research gaps corresponding to the nature of the research. The identification and classification of the appropriate research gap led to precise and concise conclusions corresponding to the research process proposed in this study. Hence, the Naqvi-Gabr Research Gap Framework is a valuable tool for determining the potential application of gaps by researchers, policymakers, and other stakeholders with a productive address.

Electronic Health Records (EHRs) Can Identify Patients at High Risk of Fracture but Require Substantial Race Adjustments to Currently Available Fracture Risk Calculators

BACKGROUND

Osteoporotic fracture prediction calculators are poorly utilized in primary care, leading to underdiagnosis and undertreatment of those at risk for fracture. The use of these calculators could be improved if predictions were automated using the electronic health record (EHR). However, this approach is not well validated in multi-ethnic populations, and it is not clear if the adjustments for race or ethnicity made by calculators are appropriate.

OBJECTIVE

To investigate EHR-generated fracture predictions in a multi-ethnic population.

DESIGN

Retrospective cohort study using data from the EHR.

SETTING

An urban, academic medical center in Philadelphia, PA.

PARTICIPANTS

12,758 White, 7,844 Black, and 3,587 Hispanic patients seeking routine care from 2010 to 2018 with mean 3.8 years follow-up.

INTERVENTIONS

None.

MEASUREMENTS

FRAX and QFracture, two of the most used fracture prediction tools, were studied. Risk for major osteoporotic fracture (MOF) and hip fracture were calculated using data from the EHR at baseline and compared to the number of fractures that occurred during follow-up.

RESULTS

MOF rates varied from 3.2 per 1000 patient-years in Black men to 7.6 in White women. FRAX and QFracture had similar discrimination for MOF prediction (area under the curve, AUC, 0.69 vs. 0.70, p=0.08) and for hip fracture prediction (AUC 0.77 vs 0.79, p=0.21) and were similar by race or ethnicity. FRAX had superior calibration than QFracture (calibration-in-the-large for FRAX 0.97 versus QFracture 2.02). The adjustment factors used in MOF prediction were generally accurate in Black women, but underestimated risk in Black men, Hispanic women, and Hispanic men.

LIMITATIONS

Single center design.

CONCLUSIONS

Fracture predictions using only EHR inputs can discriminate between high and low risk patients, even in Black and Hispanic patients, and could help primary care physicians identify patients who need screening or treatment. However, further refinements to the calculators may better adjust for race-ethnicity.

Mechanism of bisphosphonate-related osteonecrosis of the jaw (BRONJ) revealed by targeted removal of legacy bisphosphonate from jawbone using competing inert hydroxymethylene diphosphonate

Bisphosphonate-related osteonecrosis of the jaw (BRONJ) presents as a morbid jawbone lesion in patients exposed to a nitrogen-containing bisphosphonate (N-BP). Although it is rare, BRONJ has caused apprehension among patients and healthcare providers and decreased acceptance of this antiresorptive drug class to treat osteoporosis and metastatic osteolysis. We report here a novel method to elucidate the pathological mechanism of BRONJ by the selective removal of legacy N-BP from the jawbone using an intra-oral application of hydroxymethylene diphosphonate (HMDP) formulated in liposome-based deformable nanoscale vesicles (DNV). After maxillary tooth extraction, zoledronate-treated mice developed delayed gingival wound closure, delayed tooth extraction socket healing and increased jawbone osteonecrosis consistent with human BRONJ lesions. Single cell RNA sequencing of mouse gingival cells revealed oral barrier immune dysregulation and unresolved proinflammatory reaction. HMDP-DNV topical applications to nascent mouse BRONJ lesions resulted in accelerated gingival wound closure and bone socket healing as well as attenuation of osteonecrosis development. The gingival single cell RNA sequencing demonstrated resolution of chronic inflammation by increased anti-inflammatory signature gene expression of lymphocytes and myeloid-derived suppressor cells. This study suggests that BRONJ pathology is related to N-BP levels in jawbones and demonstrates the potential of HMDP-DNV as an effective BRONJ therapy.

Crosstalk between the gut microbiota and postmenopausal osteoporosis: Mechanisms and applications

Postmenopausal osteoporosis (PMO) results from a reduction in bone mass and microarchitectural deterioration in bone tissue due to estrogen deficiency, which may increase the incidence of fragility fractures. The number of people suffering from PMO has increased over the years because of the rapidly aging population worldwide. However, several pharmacological agents for the treatment of PMO have many safety risks and impose a heavy financial burden to patients and society. In recent years, the "gut-bone" axis has been proposed as a new approach in the prevention and treatment of PMO. This paper reviews the relationship between the gut microbiota and PMO, which mainly includes the underlying mechanisms between hormones, immunity, nutrient metabolism, metabolites of the gut microbiota and intestinal permeability, and explores the possible role of the gut microbiota in these processes. Finally, we discuss the therapeutic effects of diet, prebiotics, probiotics, and fecal microbiota transplantation on the gut microbiota.

Knowledge and Needs of Resident Physicians Regarding Osteoporosis: A Nationwide Survey of Residents

Large‐scale studies have not addressed the knowledge level of US resident physicians regarding osteoporosis management. We gauged the knowledge level of family medicine, internal medicine, and obstetrics and gynecology resident physicians regarding osteoporosis management. In 2019, we sent an anonymous survey via e‐mail to all program directors of Accreditation Council for Graduate Medical Education–accredited residency programs in family medicine, internal medicine, and obstetrics and gynecology for distribution to resident physicians. Knowledge items assessed osteoporosis screening, diagnosis, and treatment. We received responses from 182 family medicine, 275 internal medicine, and 122 obstetrics and gynecology programs. Of 582 resident physician respondents, 31% were family medicine residents, 47% were internal medicine residents, and 21% were obstetrics and gynecology residents. Although 77% of respondents correctly selected the T‐score threshold for the diagnosis of osteoporosis among persons aged 50 years and older (−2.5), only 20% of respondents correctly identified minimal‐trauma hip fracture as being diagnostic of osteoporosis. One‐third of respondents correctly identified which medications were demonstrated in clinical trials to decrease hip fracture risk. Fifteen percent of respondents correctly identified that denosumab and alendronate are associated with osteonecrosis of the jaw; and 40% of respondents correctly identified that decline in bone density is more rapid after discontinuation of denosumab than after discontinuation of bisphosphonates. Less than half of resident physicians knew that bisphosphonate‐associated atypical femoral fractures are duration‐dependent. One‐quarter of respondents felt not at all prepared to manage osteoporosis. In this nationwide survey of resident physicians, knowledge regarding osteoporosis diagnosis and treatment was poor, with a striking lack of knowledge regarding the two most serious adverse effects of osteoporosis pharmacotherapy (osteonecrosis of the jaw and atypical femoral fractures). The undertreatment of osteoporosis is unlikely to improve without increased education of resident physicians. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Approaches to Fracture Risk Assessment and Prevention

PURPOSE OF REVIEW

To critically assess recent evidence concerning osteoporosis fracture risk.

RECENT FINDINGS

Robust instruments exist for predicting factures incorporating well-documented risk factors especially prior fracture whose magnitude varies with site, occurrence time, and age. Stratifying time-since-prior fracture has resulted in the concept of imminent fracture risk and increased focus on secondary fracture prevention. Secondary fracture prevention recommendations include fracture liaison service, pharmacologic and non-pharmacologic multidisciplinary intervention, and communicating that fractures in older adults are the predictable consequence of underlying osteoporosis rather than unfortunate accidents. Quality improvement in osteoporosis care includes diagnosing osteoporosis on the basis of clinical fractures rather than exclusively relying on bone density testing; applying diagnostic rather than screening approaches to patients with prior fractures; regularly updating fall and fracture histories; performing a physical exam focused on spinal curvature, posture, and musculoskeletal function; reviewing images to identify prevalent fractures that may have been missed; and general use of fracture risk algorithms at all stages of osteoporosis management. Communicating effectively with patients about osteoporosis and fractures, their consequences, and pharmacological and non-pharmacological management is the cornerstone of high-value care.

Cost-effectiveness of sequential daily teriparatide/weekly alendronate compared with alendronate monotherapy for older osteoporotic women with prior vertebral fracture in Japan

Using a Markov microsimulation model among hypothetical cohorts of community-dwelling older osteoporotic Japanese women with prior vertebral fracture over a lifetime horizon, we found that daily subcutaneous teriparatide for 2 years followed by weekly oral alendronate for 8 years was not cost-effective compared with alendronate monotherapy for 10 years.

PURPOSE

Teriparatide has proven efficacy in reducing osteoporotic fractures, but with substantial cost. We examined the cost-effectiveness of sequential teriparatide/alendronate (i.e., daily subcutaneous teriparatide for 2 years followed by weekly oral alendronate for 8 years) compared with alendronate monotherapy for 10 years among community-dwelling older osteoporotic women with prior clinical or morphometric vertebral fracture in Japan.

METHODS

Using a previously validated and updated Markov microsimulation model, we obtained incremental cost-effectiveness ratios (Japanese yen [¥] (or US dollars [$]) per quality-adjusted life year [QALY]) from the perspective of a single payer responsible for both public healthcare and long-term care. We assumed a lifetime horizon with a willingness-to-pay of ¥5million (or $47,500) per QALY in the base case. We modeled the cost of biosimilar teriparatide, which has been available since November 2019 in Japan, assuming the efficacy was the same as that of the brand version.

RESULTS

In the base case, sequential teriparatide/alendronate was not cost-effective compared with alendronate monotherapy. In deterministic sensitivity analyses, sequential teriparatide/alendronate would become cost-effective with 85%, 50%, and 15% price discounts to teriparatide at ages 70, 75, and 80, respectively, compared to the current biosimilar cost. Otherwise, results were especially sensitive to changes that affected efficacy of teriparatide or alendronate. In probabilistic sensitivity analyses, the probabilities of sequential teriparatide/alendronate being cost-effective were 0%, 1%, and 37% at ages 70, 75, and 80, respectively.

CONCLUSIONS

Among high-risk osteoporotic women in Japan, sequential teriparatide/alendronate was not cost-effective compared with alendronate monotherapy, even with the availability of biosimilar teriparatide.

Cost-effectiveness of zoledronic acid compared with sequential denosumab/alendronate for older osteoporotic women in Japan

Among hypothetical cohorts of older osteoporotic women without prior fragility fracture in Japan, we evaluated the cost-effectiveness of two treatment strategies using a simulation model. Annual intravenous zoledronic acid for 3 years was cost-saving compared with biannual subcutaneous denosumab for 3 years followed by weekly oral alendronate for 3 years.

PURPOSE

Osteoporosis constitutes a major medical and health economic burden to society worldwide. Injectable treatments for osteoporosis require less frequent administration than oral treatments and therefore have higher persistence and adherence with treatment, which could explain better efficacy for fracture prevention. Although annual intravenous zoledronic acid and biannual subcutaneous denosumab are available, it remains unclear which treatment strategy represents a better value from a health economic perspective. Accordingly, we examined the cost-effectiveness of zoledronic acid for 3 years compared with sequential denosumab/alendronate (i.e., denosumab for 3 years followed by oral weekly alendronate for 3 years, making the total treatment duration 6 years) among hypothetical cohorts of community-dwelling osteoporotic women without prior fragility fracture in Japan at ages 65, 70, 75, or 80 years.

METHODS

Using a previously validated and updated Markov microsimulation model, we obtained incremental cost-effectiveness ratios (Japanese yen [¥] (or US dollars [$]) per quality-adjusted life-year [QALY]) from the public healthcare and long-term care payer's perspective over a lifetime horizon with a willingness-to-pay of ¥5 million (or $47,500) per QALY.

RESULTS

In the base case, zoledronic acid was cost-saving (i.e., more effective and less expensive) compared with sequential denosumab/alendronate. In deterministic sensitivity analyses, results were sensitive to changes in the efficacy of zoledronic acid or the cumulative persistence rate with zoledronic acid or denosumab. In probabilistic sensitivity analyses, the probabilities of zoledronic acid being cost-effective were 98-100%.

CONCLUSIONS

Among older osteoporotic women without prior fragility fracture in Japan, zoledronic acid was cost-saving compared with sequential denosumab/alendronate.

Bisphosphonate drug holidays: Risk of fractures and mortality in a prospective cohort study

PURPOSE

This study examined osteoporotic fractures and mortality in patients pretreated with bisphosphonates (BPs) during BP holidays and ongoing BP use.

METHODS

Interview-based prospective observational study in a cohort of 1973 patients with BP treatment for at least 80% of the total time of the preceding 4 years. Patients were recruited from 146 primarily endocrinological, orthopedic and rheumatological practices and clinics across Germany between May 2013 and June 2015. Outcomes were analyzed by Cox proportional hazards regression in relation to treatment status at the time of the first interview (model 1) or using time-dependent treatment variables (model 2). Temporal changes in fracture risk during BP holidays were evaluated by comparisons among 3 incremental levels of simple moving averages of BP treatment during the preceding 12 months (BP-SMA levels 0%, >0% to <50%, and ≥50%).

RESULTS

For an observation period of up to 25 months, the adjusted hazard ratios (HRs) in model 1 for BP holidays compared to ongoing BP use were 0.87 (95% confidence interval [CI] 0.59-1.28) for major osteoporotic fractures (MOFs), 0.95 (95% CI 0.70-1.28) for any clinical osteoporotic fracture, 0.96 (95% CI 0.55-1.68) for clinical vertebral fractures, and 0.86 (95% CI 0.50-1.48) for mortality. The risk of MOFs was higher for the BP-SMA level 0%, corresponding to a time >12 months since the start of a BP holiday, than for the BP-SMA level >0% to <50%, corresponding mainly to a time >6 to ≤12 months since the start of a BP holiday (adjusted HR 2.28, 95% CI 1.07-4.86). We found an interaction between prevalent vertebral fractures (PVFs) and BP-SMA-related time to first MOF for BP-SMA as a continuous variable (p for interaction 0.046 in the adjusted model). The adjusted HR for MOFs for the BP-SMA level 0% compared to the BP-SMA level >0% to <50% was 3.53 (95% CI 1.19-10.51) with a PVF but was 1.44 (95% CI 0.49-4.22) without a PVF.

CONCLUSIONS

Fracture risk and mortality in patients with preceding BP treatment did not significantly differ between BP holidays and ongoing BP use for an observation period up to 25 months when outcomes were analyzed in relation to treatment at the time of the first interview. However, in the presence of a PVF, the risk of MOFs was higher for a BP-SMA level corresponding to a time >12 months since the start of a BP holiday than for a BP-SMA level corresponding mainly to a time >6 to ≤12 months since the start of a BP holiday. The presence of a PVF may increase the relative risk of MOFs associated with a longer BP holiday.

Osteoporosis treatment gap in a prospective cohort of volunteer women

Despite the availability of efficient drugs to prevent osteoporotic fractures, only a minority of women receives osteoporosis therapy after a fracture. The high treatment gap in our cohort consisted of unselected volunteer patients highlights the urgent need of additional education, especially for the medical profession, regarding the risk-benefit balance of treatment.

INTRODUCTION

Despite the availability of efficient drugs to prevent osteoporotic fractures, only a minority of women receives osteoporosis therapy after a fracture, with a treatment gap around 80%. This can have dramatic consequences for patients and the healthcare systems.

METHODS

In this study based on longitudinal data from the FRISBEE (Fracture RIsk Brussels Epidemiological Enquiry) cohort of 3560 volunteer women aged 60 to 85 years, we evaluated the 1-year treatment gap after a first major incident fragility fracture.

RESULTS

There were 386 first validated fragility fractures, 285 major osteoporotic fractures (MOF) and 101 "other major" fractures. The rate of untreated patients was 85.0% (82.8% for MOF versus 91.0 % for "other major" fracture sites) (p = 0.04), with a lower rate for spine (70.5%) and hip (72.5%) versus shoulder (91.6%) and wrist (94.1%) (p < 0.0001). More specifically, the treatment gap for patients with osteoporosis, defined by a T-score < - 2.5 SD was 74.6% versus 76.5% for patients with osteoporosis defined by the presence of hip, shoulder, or spine fractures, independently of DXA results. When considering age groups, the rate of untreated women was 87.9% for women 60-70 years old, 88.2% between 70 and 80 years and 77.8% above 80 years (p = 0.03), with a greater difference between women who were younger or older than 80 years at inclusion: 88.1% versus 77.8% (p = 0.009). A diagnosis of osteoporosis (p = 0.01) and age (p = 0.03) were the only clinical risk factors (CRFs) significantly associated with treatment initiation.

CONCLUSIONS

This study highlights the urgent need of additional education, especially for the medical profession, regarding the risk-benefit balance of treatment.

Practical management of fracture risk among peri- and postmenopausal women

Fractures and their consequences are the clinically important manifestation of osteoporosis; preventing fractures is the primary goal of management. Effective management is achievable given present knowledge and tools but is seldom prescribed. This review will cover the individual and social burden of fracture, essential information about fracture risk and its estimation, an approach to patient care emphasizing specific information to elicit and therapeutic strategies to pursue, and existing gaps in knowledge and important questions for future research.

Mitigating osteonecrosis of the jaw (ONJ) through preventive dental care and understanding of risk factors

It is well established that alterations in phosphate metabolism have a profound effect on hard and soft tissues of the oral cavity. The present-day clinical form of osteonecrosis of the jaw (ONJ) was preceded by phosphorus necrosis of the jaw, ca. 1860. The subsequent removal of yellow phosphorus from matches in the early 20th century saw a parallel decline in "phossy jaw" until the early 2000s, when similar reports of unusual jaw bone necrosis began to appear in the literature describing jaw necrosis in patients undergoing chemotherapy and concomitant steroid and bisphosphonate treatment. Today, the potential side effect of ONJ associated with medications that block osteoclast activity (antiresorptive) is well known, though the mechanism remains unclear and the management and outcomes are often unsatisfactory. Much of the existing literature has focused on the continuing concerns of appropriate use of bisphosphonates and other antiresorptive medications, the incomplete or underdeveloped research on ONJ, and the use of drugs with anabolic potential for treatment of osteoporosis. While recognizing that ONJ is a rare occurrence and ONJ-associated medications play an important role in fracture risk reduction in osteoporotic patients, evidence to date suggests that health care providers can lower the risk further by dental evaluations and care prior to initiating antiresorptive therapies and by monitoring dental health during and after treatment. This review describes the current clinical management guidelines for ONJ, the critical role of dental-medical management in mitigating risks, and the current understanding of the effects of predominantly osteoclast-modulating drugs on bone homeostasis.

Osteoporosis Epidemiology Among Adults With Cerebral Palsy: Findings From Private and Public Administrative Claims Data

Individuals with cerebral palsy (CP) have an increased risk for the early development of osteoporosis; however, little is known about the epidemiology of osteoporosis for adults with CP, which is vital to inform clinical practice for osteoporosis prevention, treatment, and management. The purpose of this cross-sectional study was to determine sex-stratified prevalence of osteoporosis among adults with CP, as compared with adults without CP. Data from 2016 were extracted from Optum Clinformatics Data Mart (private insurance administrative claims data) and a random 20% sample from the fee-for-service Medicare (public insurance administrative claims data). Diagnostic codes were used to identify CP and osteoporosis diagnoses. Sex-stratified prevalence of osteoporosis was compared between adults with and without CP for the following age groups: 18 to 30, 31 to 40, 41 to 50, 51 to 60, 61 to 70, and >70 years of age. The overall prevalence of osteoporosis was 4.8% for adults without CP (n = 8.7 million), 8.4% for privately insured adults with CP (n = 7,348), and 14.3% for publicly insured adults with CP (n = 21,907). Women and men with CP had a higher prevalence of osteoporosis compared with women and men without CP for all age groups. Finally, publicly insured women and men with CP had a higher prevalence of osteoporosis compared with privately insured women and men with CP for all age groups, except for the similar prevalence among the 18- to 30-year age group. These findings suggest that osteoporosis is more prevalent among adults with CP compared with adults without CP. Study findings highlight the need for earlier screening and preventive medical services for osteoporosis management among adults with CP. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

A Lot of Progress, With More to Be Done: A Response to NIH Pathways to Prevention Report "Research Gaps for Long-Term Drug Therapies for Osteoporotic Fracture Prevention"

The public health implications of osteoporosis are enormous but the disease remains underdiagnosed and undertreated. In October 2018, the National Institutes of Health (NIH) convened a Pathways to Prevention (P2P) Workshop entitled "Appropriate Use of Drug Therapies for Osteoporotic Fracture Prevention" designed to identify research gaps, suggest future research opportunities, and advance the field through an evidence-based assessment. By design, the P2P report focused on "gaps" in our knowledge base. Unfortunately, however, the report did not sufficiently acknowledge the current evidence that unequivocally demonstrates the therapeutic efficacy of existing pharmacologic therapies for osteoporosis, which has the potential to exacerbate the current crises in osteoporosis diagnosis and treatment. © 2019 American Society for Bone and Mineral Research.

How much do we know about the role of osteocytes in different phases of fracture healing? A systematic review

Background

Although emerging studies have provided evidence that osteocytes are actively involved in fracture healing, there is a general lack of a detailed understanding of the mechanistic pathway, cellular events and expression of markers at different phases of healing.

Methods

This systematic review describes the role of osteocytes in fracture healing from early to late phase. Literature search was performed in PubMed and Embase. Original animal and clinical studies with available English full-text were included. Information was retrieved from the selected studies.

Results

A total of 23 articles were selected in this systematic review. Most of the studies investigated changes of various genes and proteins expression patterns related to osteocytes. Several studies have described a constant expression of osteocyte-specific marker genes throughout the fracture healing cascade followed by decline phase with the progress of healing, denoting the important physiological role of the osteocyte and the osteocyte lacuno-canalicular network in fracture healing. The reports of various markers suggested that osteocytes could trigger coordinated bone healing responses from cell death and expression of proinflammatory markers cyclooxygenase-2 and interleukin 6 at early phase of fracture healing. This is followed by the expression of growth factors bone morphogenetic protein-2 and cysteine-rich angiogenic inducer 61 that matched with the neo-angiogenesis, chondrogenesis and callus formation during the intermediate phase. Tightly controlled regulation of osteocyte-specific markers E11/Podoplanin (E11), dentin matrix protein 1 and sclerostin modulate and promote osteogenesis, mineralisation and remodelling across different phases of fracture healing. Stabilised fixation was associated with the finding of higher number of osteocytes with little detectable bone morphogenetic proteins expressions in osteocytes. Sclerostin-antibody treatment was found to result in improvement in bone mass, bone strength and mineralisation.

Conclusion

To further illustrate the function of osteocytes, additional longitudinal studies with appropriate clinically relevant model to study osteoporotic fractures are crucial. Future investigations on the morphological changes of osteocyte lacuno-canalicular network during healing, osteocyte-mediated signalling molecules in the transforming growth factor-beta-Smad3 pathway, perilacunar remodelling, type of fixation and putative biomarkers to monitor fracture healing are highly desirable to bridge the current gaps of knowledge.The translational potential of this article: This systematic review provides an up-to-date chronological overview and highlights the osteocyte-regulated events at gene, protein, cellular and tissue levels throughout the fracture healing cascade, with the hope of informing and developing potential new therapeutic strategies that could improve the timing and quality of fracture healing in the future.