Osteoporosis after spinal cord injury

Integration of functional electrical stimulation during robotic-assisted intervention to increase bone mineral density in individuals with complete spinal cord injury: case report

INTRODUCTION

A spinal cord injury (SCI) leads to an alteration of the central nervous system which significantly impacts the health, function and quality of life of those affected. Since SCI leads to a loss lower limbs usage, sublesional osteoporosis is a common and established consequence with high risk of fracture in this population. The mechanical loading remains the most effective approach to stimulate physiologic bone remodeling. Furthermore, functional electrical stimulation, by producing active muscle contractions, would also increase bone mineral density. Combining functional electrical stimulation (FES) with mechanical stress during functional task such as walking or cycling would provide better results on BMD.

CASE PRESENTATION

This case report describes a 64-years old man with a chronic complete SCI (T2-T3; AIS A) who was gradually exposed to mechanical stress (walking robot, standing, bicycle) coupled with FES for 26 months. Bone mineral density of the femoral head (BMDf) was defined at 3 different time points (baseline, after 10 and 26 months). The Fracture Risk Assessment Tool (FRAX) was used to calculate T-scores based on BMDf. Before the intervention, BMDf indicated severe osteoporosis in this man. After 10 months of combined intervention, the BMDf decreased to reach the level of osteopenia after 26 months.

DISCUSSION

The implementation of an intervention combining weight-bearing during robotic-assisted walking and FES would improve bone mineral density and could reduce the risk of fracture in people with complete SCI.

Reducing endocrine metabolic disease risk in adults with chronic spinal cord injury: strategic activities conducted by the Ontario-Quebec RIISC team

PURPOSE

The Rehabilitation Interventions for Individuals with a Spinal Cord Injury in the Community (RIISC) team aimed to develop and evaluate innovative rehabilitation interventions to identify endocrine metabolic disease (EMD) risk, intending to reduce the frequency and severity of EMD related morbidity and mortality among adults living with chronic spinal cord injury or disease (SCI/D).

MATERIALS AND METHODS

An interprovincial team from Ontario and Quebec reviewed available EMD literature and evidence syntheses and completed an inventory of health services, policies and practices in SCI/D care. The review outcomes were combined with expert opinion to create an EMD risk model to inform health service transformation.

RESULTS

EMD risk and mortality are highly prevalent among adults with chronic SCI/D. In stark contrast, few rehabilitation interventions target EMD outcomes. The modelled solution proposes: 1) abandoning single-disease paradigms and examining a holistic perspective of the individual's EMD risk, and 2) developing and disseminating practice-based research approaches in outpatient community settings.

CONCLUSIONS

RIISC model adoption could accelerate EMD care optimization, and ultimately inform the design of large-scale longitudinal pragmatic trials likely to improve health outcomes. Linking the RIISC team activities to economic evaluations and policy deliverables will strengthen the relevance and impact among policymakers, health care providers and patients.

Long-term changes in bone mineral density and associated risk factors in individuals with spinal cord injury: A retrospective study

Individuals with spinal cord injury (SCI) experience a notable decrease in bone mass below the level of injury. While studies have primarily focused on the acute phase with a small cohort, this study aimed to provide comprehensive insights into bone loss patterns over time. A total of 427 individuals with SCI who underwent dual-energy X-ray absorptiometry (DXA) testing at the Korea National Rehabilitation Center (2010-2021) were included and analyzed by categorizing the DXA results into 1-year intervals based on postinjury duration. Demographic characteristics (age, sex, body mass index, and alcohol/smoking history) and SCI-related factors (etiology, severity, extent of injury, motor score, and Korean Spinal Cord Independence Measure 3rd edition) were collected and analyzed. Linear mixed models and Bonferroni post hoc tests were performed to assess temporal changes in bone mass and linear regression analysis to assess the associations between possible risk factors and bone loss. DXA results revealed that substantial annual bone loss occurred in the total hip site up to 3 years postinjury and in the femoral neck site up to 2 years postinjury. Old age, women, and low body mass index were significant risk factors for bone loss in the SCI population. Additionally, during the chronic phase, lower Korean Spinal Cord Independence Measure 3rd edition scores were associated with low bone mass. Significant annual bone loss in the hip region persists for up to 3 years postinjury in individuals with SCI. While prioritizing the risk factors for osteoporosis commonly used in the general population, applying the SCIM score in the chronic phase may provide additional information on bone loss risk.

Comparison of the prevalence of osteoporosis in people with spinal cord injury according to bone mineral density reference values for the diagnosis of osteoporosis: a retrospective, cross-sectional study

BACKGROUND

Spinal cord injury (SCI) is a complex cause of rapid low bone mass that easily predisposes the affected individuals to osteoporosis-induced fractures. Several studies have investigated osteoporosis pathophysiology in SCI; however, those associated with its diagnosis in SCI are limited. Additionally, errors in osteoporosis diagnosis and its prevalence vary based on the bone mineral density (BMD) reference values (BMDRV), and no studies have reported BMDRV application for osteoporosis diagnosis in individuals with SCI. Therefore, this study aimed to compare the prevalence of osteoporosis among Korean adults aged ≥ 50 years with SCI according to BMDRV for diagnosing osteoporosis.

METHODS

Overall, 855 patients with SCI who underwent BMD tests of the lumbar spine, femoral neck, and total hip at the National Rehabilitation Center (NRC) in Korea between 2010 and 2020 were included in this retrospective cross-sectional study. Osteoporosis was diagnosed in patients with SCI by comparing the differences in prevalence, diagnostic consistency, and risk factors according to the region-based BMDRV of the dual-energy x-ray absorptiometry (DXA) manufacturer and international BMDRV based on the Third National Health and Nutrition Examination Survey (NHANES III) data of females aged 20-29 years.

RESULTS

The prevalence of osteoporosis according to the T-score provided by a single reference population of the NHANES III (TNHA) (PONHA) (males: 26.69%; females: 69.35%) was significantly higher in females and males than that according to the T-scores provided by the DXA manufacturer (TDXA) (PODXA) (males: 15.32%; females: 43.15%). The lumbar spine and femoral neck were major osteoporosis diagnosis sites for the PODXA and PONHA, respectively. Risk factors for osteoporosis differed based on the probability of osteoporosis (also known as the OZ ratio) according to the BMD criteria; however, the risk factors were similar according to old age, female sex, low body mass index (BMI), and long SCI period. No significant relationship was noted between the different SCI-related clinical factors (p > 0.05).

CONCLUSIONS

The osteoporosis diagnostic site and prevalence in SCI differed according to the regional-based TDXA and international standards of the TNHA. Therefore, further studies on BMDRV are warranted to establish accurate diagnostic criteria for osteoporosis prevention in patients with SCI.

Genetic variation influences the skeletal response to hindlimb unloading in the eight founder strains of the diversity outbred mouse population

During disuse, mechanical unloading causes extensive bone loss, decreasing bone volume and strength. Variations in bone mass and risk of osteoporosis are influenced by genetics; however, it remains unclear how genetic variation affects the skeletal response to unloading. We previously found that genetic variation affects the musculoskeletal response to 3 weeks of immobilization in the 8 Jackson Laboratory J:DO founder strains: C57Bl/6J, A/J, 129S1/SvImJ, NOD/ShiLtJ, NZO/HlLtJ, CAST/EiJ, PWK/PhJ, and WSB/EiJ. Hindlimb unloading (HLU) is the best model for simulating local and systemic contributors of disuse and therefore may have a greater impact on bones than immobilization. We hypothesized that genetic variation would affect the response to HLU across the eight founder strains. Mice of each founder strain were placed in HLU for 3 weeks, and the femurs and tibias were analyzed. There were significant HLU and mouse strain interactions on body weight, femur trabecular BV/TV, and femur ultimate force. This indicates that unloading only caused significant catabolic effects in some mouse strains. C57BL/6 J mice were most affected by unloading while other strains were more protected. There were significant HLU and mouse strain interactions on gene expression of genes encoding bone metabolism genes in the tibia. This indicates that unloading only caused significant effects on bone metabolism genes in some mouse strains. Different mouse strains respond to HLU differently, and this can be explained by genetic differences. These results suggest the outbred J:DO mice will be a powerful model for examining the effects of genetics on the skeletal response to HLU.

Characteristics Associated with Bone Loss after Spinal Cord Injury: Implications for Hip Region Vulnerability

BACKGRUOUND

In individuals with spinal cord injury (SCI), bone loss progresses rapidly to the area below the level of injury, leading to an increased risk of fracture. However, there are limited data regarding SCI-relevant characteristics for bone loss and the degree of bone loss in individuals with SCI compared with that in non-SCI community-dwelling adults.

METHODS

Data from men with SCI who underwent dual-energy X-ray absorptiometry at the National Rehabilitation Center (2008 to 2020) between 12 and 36 months after injury were collected and analyzed. Community-dwelling men were matched 1:1 for age, height, and weight as the control group, using data from the Korea National Health and Nutrition Examination Survey (KNHANES, 2008 to 2011).

RESULTS

A comparison of the SCI and the matched control group revealed significantly lower hip region T-scores in the SCI group, whereas the lumbar spine T-score did not differ between groups. Among the 113 men with SCI, the paraplegia group exhibited significantly higher Z-scores of the hip region than the tetraplegia group. Participants with motor-incomplete SCI showed relatively preserved Z-scores of the hip region compared to those of the lumbar region. Moreover, in participants with SCI, the percentage of skeletal muscle displayed a moderate positive correlation with femoral neck Z-scores.

CONCLUSION

Men with SCI exhibited significantly lower bone mineral density of the hip region than community-dwelling men. Paraplegia rather than tetraplegia, and motor incompleteness rather than motor completeness were protective factors in the hip region. Caution for loss of skeletal muscle mass or increased adiposity is also required.

Challenges in Management of Proximal Humerus Diaphyseal Fracture in a Patient with Brachial Plexus Birth Injury: A Case Report

CASE

Two-and-a-half-month-old boy, a known case of brachial plexus birth injury, sustained proximal humeral diaphyseal fracture. Fracture healed in varus malunion and failed to remodel subsequently. Challenges were faced in the course of the management because of progression of the deformity. Finally, the fracture united after rigid internal fixation performed at 2.5 years.

CONCLUSION

Neuromuscular imbalance can lead to angular deformity at fracture site and cause unpredictable remodeling, as in our case. Conservative management may fail to achieve union with satisfactory alignment. Rigid internal fixation should be considered in such cases to achieve union.

The impact of rehabilitation in bone loss management of patients with spinal cord injury: A systematic review

BACKGROUND

Spinal cord injury (SCI) is a disabling condition characterized by multilevel skeletal muscle impairment and rapid cortical and trabecular bone loss. Rehabilitation is a cornerstone of the long-term management of patients with SCI; however, the optimal rehabilitation strategy for improving bone health has not been fully characterized.

OBJECTIVE

To characterize the current evidence supporting different rehabilitation interventions improving bone health in patients with SCI.

METHODS

On November 17th, 2022, five databases (PubMed, Scopus, Web of Science, Cochrane, and PEDro) were systematically searched for randomized controlled trials (RCTs) assessing SCI patients undergoing rehabilitation interventions. The primary outcomes were bone macroscopical effects. Secondary outcomes were changes in bone metabolisms and functional outcomes.

RESULTS

Out of 499 records, 11 RCTs met the eligibility criteria and were included. Electrical stimulation combined with physical exercise was assessed by 5 studies, standing intervention was assessed by 3 studies, vibration was assessed by 1 study, ultrasound therapy was assessed by 1 study, and electroacupuncture combined with a pulsed magnetic field was assessed by 1 study. The rehabilitation intervention was administered combined with pharmacological treatment (3 studies) or alone (8 studies). Positive effects in terms of BMD were reported by 3 studies. The quality assessment revealed some concerns in 9 out of 11 studies, in accordance with the Cochrane Risk of Bias assessment - version 2.

CONCLUSION

Our data suggest that multicomponent interventions including rehabilitation might be considered a suitable option to improve bone health management in SCI patients. Further studies are mandatory to characterize the optimal combination of non-pharmacological interventions reducing bone loss and improving the risk of fractures in patients with SCI.

Rehabilitation interventions to modify endocrine-metabolic disease risk in individuals with chronic spinal cord injury living in the community (RIISC): A systematic search and review of prospective cohort and case-control studies

CONTEXT

Endocrine-metabolic disease (EMD) is associated with functional disability, social isolation, hospitalization and even death in individuals living with a chronic spinal cord injury (SCI). There is currently very low-quality evidence that rehabilitation interventions can reduce EMD risk during chronic SCI. Non-randomized trials and alternative study designs are excluded from traditional knowledge synthesis.

OBJECTIVE

To characterize evidence from level 3-4 studies evaluating rehabilitation interventions for their effectiveness to improve EMD risk in community-dwelling adults with chronic SCI.

METHODS

Systematic searches of MEDLINE PubMed, EMBASE Ovid, CINAHL, Cochrane Database of Systematic Reviews, and PsychInfo were completed. All longitudinal trials, prospective cohort, case-control studies, and case series evaluating the effectiveness of rehabilitation/therapeutic interventions to modify/associate with EMD outcomes in adults with chronic SCI were eligible. Two authors independently selected studies and abstracted data. Mean changes from baseline were reported for EMD outcomes. The Downs and Black Checklist was used to rate evidence quality.

RESULTS

Of 489 articles identified, 44 articles (N = 842) were eligible for inclusion. Individual studies reported statistically significant effects of electrical stimulation-assisted training on lower-extremity bone outcomes, and the combined effects of exercise and dietary interventions to improve body composition and cardiometabolic biomarkers (lipid profiles, glucose regulation). In contrast, there were also reports of no clinically important changes in EMD outcomes, suggesting lower quality evidence (study bias, inconsistent findings).

CONCLUSION

Longitudinal multicentre pragmatic studies involving longer-term exercise and dietary intervention and follow-up periods are needed to fully understand the impact of these rehabilitation approaches to mitigate EMD risk. Our broad evaluation of prospective cohort and case-control studies provides new perspectives on alternative study designs, a multi-impairment paradigm approach of studying EMD outcomes, and knowledge gaps related to SCI rehabilitation.

Systemic inflammation after spinal cord injury: A review of biological evidence, related health risks, and potential therapies

Individuals with chronic traumatic spinal cord injury (SCI) develop progressive multi-system health problems that result in clinical illness and disability. Systemic inflammation is associated with many of the common medical complications and acquired diseases that accompany chronic SCI, suggesting that it contributes to a number of comorbid pathological conditions. However, many of the mechanisms that promote persistent systemic inflammation and its consequences remain ill-defined. This review describes the significant biological factors that contribute to systemic inflammation, major organ systems affected, health risks, and the potential treatment strategies. We aim to highlight the need for a better understanding of inflammatory processes, and to establish appropriate strategies to address inflammation in SCI.

Inflammaging and bone loss in a rat model of spinal cord injury

Spinal cord injury (SCI) results in significant loss of sublesional bone, adding to the comorbidity of SCI with an increased risk of fracture and post-fracture complications. Unfortunately, the effect of SCI on skeletal health is also likely to rise as the average age of SCI has increased and there are well-known negative effects of age on bone. To date, however, the impact of age and age-associated inflammation (inflammaging) on skeletal health after SCI remains largely unknown. To address this, we compared bone parameters in young (3 month) and middle-aged (9 month) male and female rats with a moderate thoracic contusion injury, to age and sex matched sham-operated controls. Skeletal parameters, locomotor function and serum cytokine levels were assessed at both subchronic (30 days) and chronic (180 days) time points post injury. We hypothesized that SCI would lead to a dramatic loss of bone immediately after injury in all SCI-groups, with inflammaging leading to greater loss in middle-aged SCI rats. We also predicted that while younger rats may re-establish bone properties in more chronic phases of SCI, middle-aged rats would not. Supporting these hypothesis, trabecular bone volume was significantly lower in male and young female SCI rats early after injury. Contrary to our hypothesis, however, there was greater loss of trabecular bone volume, relative to age-matched shams, in young compared to middle-aged SCI rats with no effects of SCI on trabecular bone volume in middle-aged female rats. Moreover, despite recovery of weight-supported locomotor activity, bone loss persisted into the chronic phase of injury for the young rats. Bone formation rates were lower in young male SCI rats, regardless of the time since injury, while both young and middle-aged female SCI rats had lower bone formation in the subchronic but not chronic phase of SCI. In middle-aged rats, SCI-induced higher osteoclast surfaces, which also persisted into the chronic phase of SCI in middle-aged females. Neither age nor SCI-induced increases in inflammation seemed to be associated with bone loss. In fact, SCI had more dramatic and persistent effects on bone in male rats, while aging and SCI elevated serum cytokines only in female rats. Overall, this study demonstrates SCI-induced loss of bone and altered bone turnover in male and female rats that persists into the chronic phase post-injury. The sex and age dependent variations in bone turnover and serum cytokines, however, underscore the need to further explore both mechanisms and potential therapeutics in multiple demographics.

Characterization of Gastrointestinal Hormone Dysfunction and Metabolic Pathophysiology in Experimental Spinal Cord Injury

Cardiometabolic disease is a leading complication of spinal cord injury (SCI) that contributes to premature all-cause cardiovascular morbidity and early death. Despite widespread reports that cardioendocrine disorders are more prevalent in individuals with SCI than those without disability, a well-defined pathophysiology has not been established. Autonomic dysfunction accompanying disruption of autonomic spinal tracts may contribute to dysregulation of energy metabolism via uncoupling of integrated hunger and satiation signals. In governing human feeding behaviors, these signals are controlled by a network of enteroendocrine cells that line the gastrointestinal (GI) tract. These cells regulate GI peptide release and autonomic systems that maintain direct neuroendocrine communication between the GI tract and appetite circuitry of the hypothalamus and brain stem. Here we investigate gene-expression and physiological changes in GI peptides and hormones, as well as changes in physiological response to feeding, glucose and insulin challenge and evaluate GI tissue cytoarchitecture following experimental SCI. Adult female mice (C57BL/6) were subjected to a severe SCI (65 kDyne) at T9, and a sham control group received laminectomy only. SCI results in chronic elevation of fasting plasma glucose levels, and an exaggerated glucose response after oral glucose and insulin tolerance test. Mice with SCI also exhibit significant alteration in gut hormone genes, plasma levels, physiological response to prandial challenge, and cell loss and gross tissue damage in the gut. These findings demonstrate that SCI has widespread effects on the GI system contributing to component Cardiometabolic disease risks factors and may inform future therapeutic and rehabilitation strategies in humans.

The genetic overlap between osteoporosis and craniosynostosis

Osteoporosis is the most prevalent bone condition in the ageing population. This systemic disease is characterized by microarchitectural deterioration of bone, leading to increased fracture risk. In the past 15 years, genome-wide association studies (GWAS), have pinpointed hundreds of loci associated with bone mineral density (BMD), helping elucidate the underlying molecular mechanisms and genetic architecture of fracture risk. However, the challenge remains in pinpointing causative genes driving GWAS signals as a pivotal step to drawing the translational therapeutic roadmap. Recently, a skull BMD-GWAS uncovered an intriguing intersection with craniosynostosis, a congenital anomaly due to premature suture fusion in the skull. Here, we recapitulate the genetic contribution to both osteoporosis and craniosynostosis, describing the biological underpinnings of this overlap and using zebrafish models to leverage the functional investigation of genes associated with skull development and systemic skeletal homeostasis.

Introducing the Concept of Exercise Holidays for Human Spaceflight - What Can We Learn From the Recovery of Bed Rest Passive Control Groups

In an attempt to counteract microgravity-induced deconditioning during spaceflight, exercise has been performed in various forms on the International Space Station (ISS). Despite significant consumption of time and resources by daily exercise, including around one third of astronauts' energy expenditure, deconditioning-to variable extents-are observed. However, in future Artemis/Lunar Gateway missions, greater constraints will mean that the current high volume and diversity of ISS in-flight exercise will be impractical. Thus, investigating both more effective and efficient multi-systems countermeasure approaches taking into account the novel mission profiles and the associated health and safety risks will be required, while also reducing resource requirements. One potential approach is to reduce mission exercise volume by the introduction of exercise-free periods, or "exercise holidays". Thus, we hypothesise that by evaluating the 'recovery' of the no-intervention control group of head-down-tilt bed rest (HDTBR) campaigns of differing durations, we may be able to define the relationship between unloading duration and the dynamics of functional recovery-of interest to future spaceflight operations within and beyond Low Earth Orbit (LEO)-including preliminary evaluation of the concept of exercise holidays. Hence, the aim of this literature study is to collect and investigate the post-HDTBR recovery dynamics of current operationally relevant anthropometric outcomes and physiological systems (skeletal, muscular, and cardiovascular) of the passive control groups of HDTBR campaigns, mimicking a period of 'exercise holidays', thereby providing a preliminary evaluation of the concept of 'exercise holidays' for spaceflight, within and beyond LEO. The main findings were that, although a high degree of paucity and inconsistency of reported recovery data is present within the 18 included studies, data suggests that recovery of current operationally relevant outcomes following HDTBR without exercise-and even without targeted rehabilitation during the recovery period-could be timely and does not lead to persistent decrements differing from those experienced following spaceflight. Thus, evaluation of potential exercise holidays concepts within future HDTBR campaigns is warranted, filling current knowledge gaps prior to its potential implementation in human spaceflight exploration missions.

Disuse Osteoporosis: Clinical and Mechanistic Insights

Disuse osteoporosis describes a state of bone loss due to local skeletal unloading or systemic immobilization. This review will discuss advances in the field that have shed light on clinical observations, mechanistic insights and options for the treatment of disuse osteoporosis. Clinical settings of disuse osteoporosis include spinal cord injury, other neurological and neuromuscular disorders, immobilization after fractures and bed rest (real or modeled). Furthermore, spaceflight-induced bone loss represents a well-known adaptive process to microgravity. Clinical studies have outlined that immobilization leads to immediate bone loss in both the trabecular and cortical compartments accompanied by relatively increased bone resorption and decreased bone formation. The fact that the low bone formation state has been linked to high levels of the osteocyte-secreted protein sclerostin is one of the many findings that has brought matrix-embedded, mechanosensitive osteocytes into focus in the search for mechanistic principles. Previous basic research has primarily involved rodent models based on tail suspension, spaceflight and other immobilization methods, which have underlined the importance of osteocytes in the pathogenesis of disuse osteoporosis. Furthermore, molecular-based in vitro and in vivo approaches have revealed that osteocytes sense mechanical loading through mechanosensors that translate extracellular mechanical signals to intracellular biochemical signals and regulate gene expression. Osteocytic mechanosensors include the osteocyte cytoskeleton and dendritic processes within the lacuno-canalicular system (LCS), ion channels (e.g., Piezo1), extracellular matrix, primary cilia, focal adhesions (integrin-based) and hemichannels and gap junctions (connexin-based). Overall, disuse represents one of the major factors contributing to immediate bone loss and osteoporosis, and alterations in osteocytic pathways appear crucial to the bone loss associated with unloading.

Prediction of Distal Femur and Proximal Tibia Bone Mineral Density From Total Body Dual Energy X-Ray Absorptiometry Scans in Persons with Spinal Cord Injury

Bone density decreases rapidly after spinal cord injury (SCI), increasing fracture risk. The most common fracture sites are at the knee (i.e., distal femur or proximal tibia). Despite this high fracture incidence, knee-specific scans for bone density using dual x-ray absorptiometry (DXA) were not available until 2014 and are still not routinely used in clinical practice today. This has made it difficult to determine the rehabilitation efficacy and hindered understanding of the long-term changes in knee areal bone density. The purpose of this investigation was to compare areal bone mineral density values for the knee from both total-body and knee-specific DXA scans in persons with SCI. A total of 20 participants (16 males) >1 yr-post spinal cord injury received two DXA scans; a total-body scan and a knee-specific scan. Standardized methods were used to create regions of interest to determine bone density of four regions - the epiphysis and metaphysis of the distal femur and proximal tibia - from the total-body scan. Linear regressions and Bland-Altman analyses were conducted to determine the correlation (r²) and agreement (mean bias ± 95% level of agreement) respectively between the two scan types for each region. Linear regression analyses showed strong significant (p < 0.001) relationships between the two scan types for the distal femur epiphysis (r² = 0.88) and metaphysis (r² = 0.98) and the proximal tibia epiphysis (r² = 0.88) and metaphysis (r² = 0.99). The mean bias ± 95% level of agreement were distal femur epiphysis (0.05 ± 0.1 g/cm²) and metaphysis (0.02 ± 0.04 g/cm²); proximal tibia epiphysis (-0.02 ± 0.1 g/cm²) and metaphysis (0.02 ± 0.03 g/cm²). Results suggest knee-specific bone density can be assessed using a total-body DXA scan. This may allow for more comprehensive use of DXA scans which would reduce the burden of multiple site-specific scans for persons with SCI and enable more widespread adoption of knee bone density assessment in this population.

Exercise and physical activity in individuals at risk of fracture

This is a review of evidence and practical tips on exercise for individuals with osteoporosis, including individuals with hip and vertebral fractures. Balance and functional training, with or without strength training, can prevent falls. Several types of exercise can improve outcomes that are important to patients, such as physical functioning or quality of life. Individuals with osteoporosis should prioritize balance, functional and resistance training ≥ twice weekly, where exercises, volume, intensity, and progression are aligned with the patient's goals and abilities. Patients who want to participate in other activities (e.g., walking, impact exercise, yoga, Pilates) can do them in addition to, but not instead of, balance and functional or strength training, if they can be done safely or modified. Avoid generic advice like "Don't bend or twist", which is difficult or impossible to operationalize, and may create fear and activity avoidance. Instead, be specific about the types of activities to avoid or modify, and provide tips on how to make daily activities safer, or signpost to resources from national osteoporosis societies. For example, not all bending or twisting is bad; it is activities that involve rapid, repetitive, sustained, weighted, or end range of motion twisting or flexion of the spine that may need to be modified, especially in individuals at high risk of fracture.

Osteopenia in a Mouse Model of Spinal Cord Injury: Effects of Age, Sex and Motor Function

Simple Summary

In the first two years following spinal cord injury, people lose up to 50% of bone below the injury. This injury-induced bone loss significantly affects rehabilitation and leaves people vulnerable to fractures and post-fracture complications, including lung and urinary tract infections, blood clots in the veins, and depression. Unfortunately, little is known about the factors driving this bone loss. In fact, even though we know that injury, age, and sex independently increase bone loss, there have been no studies looking at the cumulative effects of these variables. People with spinal injury are aging, and the age at which injuries occur is increasing. It is essential to know whether these factors together will further compromise bone. To examine this, we assessed bone loss in young and old, male and female mice after spinal injury. As expected, we found that aging alone decreased motor activity and bone volume. Spinal injury also reduced bone volume, but it did not worsen the effects of age. Instead, injury effects appeared related to reduced rearing activity. The data suggest that although partial weight-bearing does not reduce bone loss after spinal cord injury, therapies that put full weight on the legs may be clinically effective.

Abstract

After spinal cord injury (SCI), 80% of individuals are diagnosed with osteopenia or osteoporosis. The dramatic loss of bone after SCI increases the potential for fractures 100-fold, with post-fracture complications occurring in 54% of cases. With the age of new SCI injuries increasing, we hypothesized that a SCI-induced reduction in weight bearing could further exacerbate age-induced bone loss. To test this, young (2–3 months) and old (20–30 months) male and female mice were given a moderate spinal contusion injury (T9–T10), and recovery was assessed for 28 days (BMS, rearing counts, distance traveled). Tibial trabecular bone volume was measured after 28 days with ex vivo microCT. While BMS scores did not differ across groups, older subjects travelled less in the open field and there was a decrease in rearing with age and SCI. As expected, aging decreased trabecular bone volume and cortical thickness in both old male and female mice. SCI alone also reduced trabecular bone volume in young mice, but did not have an additional effect beyond the age-dependent decrease in trabecular and cortical bone volume seen in both sexes. Interestingly, both rearing and total activity correlated with decreased bone volume. These data underscore the importance of load and use on bone mass. While partial weight-bearing does not stabilize/reverse bone loss in humans, our data suggest that therapies that simulate complete loading may be effective after SCI.

Forearm bone mineral density in adult men after spinal cord injuries: impact of physical activity level, smoking status, body composition, and muscle strength

Background

In the present cross-sectional study, we analyzed the relationships of physical activity level, muscle strength, body composition, injury parameters, and smoking status with bone health in the non-paralyzed upper limb in adult men after spinal cord injuries (SCI).

Methods

The study covered 50 men after spinal cord injuries aged 35.6 ± 4.9 years (25 wheelchair rugby players and 25 non-athletes). Forearm bone mineral density (BMD), bone mineral content (BMC) in distal (dis) and proximal (prox) part was measured by densitometry. Body mass index (BMI) and body fat percentage (BF) were calculated. Fat mass (FM) and fat-free mass (FFM) were estimated from somatic data. An interview was conducted based on the Global Adult Tobacco Survey questionnaire. Muscle strength (maximal hand grip strength) was measured using a Jamar dynamometer.

Results

Active male smokers after SCI had significantly lower BMD dis, BMC dis and prox, T-score dis, and prox (large effect > 0.8) than male non-smokers after SCI. Physical activity was a significant predictor (positive direction) for BMC prox (adjusted R2 = 0.56; p < 0.001). The predictor of interactions of physical activity and fat mass was significant for BMC dis (positive direction, adjusted R2 = 0.58; p < 0.001). It was also found that the predictor of interactions of four variables: physical activity, fat mass, hand grip strength (positive direction), and years of active smoking (negative direction) was significant for BMD dis (adjusted R2 = 0.58; p < 0.001). The predictor of interactions of age at injury (additive direction) and the number of cigarettes smoked per day (negative direction) was significant for T-score prox (adjusted R2 = 0.43; p < 0.001). Non-smoking physically active men after SCI had the most advantageous values of mean forearm BMD.

Conclusion

Rugby can be considered a sport that has a beneficial effect on forearm BMD. The physically active men after SCI had significantly higher bone parameters. Physical activity itself and in interactions with fat mass, hand grip strength (positive direction), and years of active smoking (negative direction) had a significant effect on bone health in non-paralyzed upper limbs. Active smoking may reduce the protective role of physical activity for bone health.

MicroRNA-148a-3p is a candidate mediator of increased bone marrow adiposity and bone loss following spinal cord injury

Spinal cord injury is often followed by osteoporosis characterized by rapid and severe bone loss. This leads to an increased risk of osteoporotic fracture in people with spinal cord injury, resulting in increased healthcare costs, morbidity, and mortality. Though it is common, the mechanisms underlying this osteoporosis are not completely understood and treatment options are limited. No biomarkers have been identified for predicting fracture risk. In this study, we sought to investigate microRNA mediated mechanisms relating to osteoporosis following spinal cord injury. We studied subjects with acute SCI (n=12), chronic SCI (n=18), and controls with no SCI (n=23). Plasma samples from all subjects underwent transcriptomic analysis to quantify microRNA expression, after which miR-148a-3p was selected for further study. We performed CT scans of the knee on all subjects with SCI and analyzed these scans to quantify bone marrow adipose tissue volume. MiR-148a-3p was upregulated in subjects with acute SCI vs chronic SCI, as well as in acute SCI vs no SCI. Subjects with chronic SCI had greater levels of marrow adiposity in the distal femoral diaphysis compared to subjects with acute SCI. MiR-148a-3p levels were negatively associated with distal femoral diaphysis marrow adiposity. A multivariable model showed that miR-148a-3p and BMI explained 24% of variation in marrow adiposity. A literature search revealed that miR-148a-3p has multiple bone and fat metabolism related targets. Our findings suggest that miR-148a-3p is a mediator of osteoporosis following spinal cord injury and a potential future therapeutic target.

Unilateral cervical spinal cord injury induces bone loss and metabolic changes in non-human primates (Macaca fascicularis)

BACKGROUND/OBJECTIVE

The deleterious effects of chronic spinal cord injury (SCI) on the skeleton in rats, especially the lower extremities, has been proved previously. However, the long-term skeletal changes after SCI in non-human primates (NHP) have been scarcely studied. This study aimed to evaluate the bone loss in limbs and vertebrae and the bone metabolic changes in NHP after unilateral cervical spinal cord contusion injury.

METHODS

Twelve Macaca fascicularis were randomly divided into the SCI (n=8) and the Sham (n=4) groups. The SCI models were established using hemi-contusion cervical spinal cord injury on fifth cervical vertebra (C5), and were further evaluated by histological staining and neurophysiological monitoring. Changes of bone microstructures, bone biomechanics, and bone metabolism markers were assessed by micro-CT, micro-FEA and serological kit.

RESULTS

The NHP hemi-contusion cervical SCI model led to consistent unilateral limb dysfunction and potential plasticity in the face of loss of spinal cord. Furthermore, the cancellous bone mass of ipsilateral humerus and radius decreased significantly compared to the contralateral side. The bone volume fraction of humerus and radius were 17.2% and 20.1% on the ipsilateral while 29.0% and 30.1% on the contralateral respectively. Similarly, the thickness of the cortical bone in the ipsilateral forelimbs was significantly decreased, as well as the bone strength of the ipsilateral forelimbs. These changes were accompanied by diminished concentration of osteocalcin and total procollagen type 1 N-terminal propeptide (t-P1NP) as well as increased level of β-C-terminal cross-linking telopeptide of type 1collagen (β-CTX) in serological testing.

CONCLUSIONS

The present study demonstrated that hemi-SCI induced loss of bone mass and compromised biomechanical performance in ipsilateral forelimbs, which could be indicated by both muscle atrophy and serological changes of bone metabolism, and associated with a consistent loss of large-diameter cells of sensory neurons in the dorsal root ganglia.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

Our study, for the first time, demonstrated the bone loss in limbs and vertebrae as well as the bone metabolic changes in non-human primates after unilateral spinal cord injury (SCI). This may help to elucidate the role of muscle atrophy, serological changes and loss of sensory neurons in the mechanisms of SCI-induced osteoporosis, which would be definitely better compared with rodent models.

Delayed Systemic Treatment with Cannabinoid Receptor 2 Agonist Mitigates Spinal Cord Injury-Induced Osteoporosis More Than Acute Treatment Directly after Injury

Nearly all persons with spinal cord injury (SCI) will develop osteoporosis following injury, and further, up to 50% of all persons with SCI will sustain a fracture during their lives. The unique mechanisms driving osteoporosis following SCI remain unknown. The cannabinoid system modulation of bone metabolism through cannabinoid 1/2 (CB1/2) has been of increasing interest for the preservation of bone mass and density in models of osteoporosis. Using a thoracic vertebral level 8 (T8) complete transection in a mouse model, we performed daily treatment with a selective CB2 receptor agonist, HU308, compared with SCI-vehicle-treated and naïve control animals either immediately after injury for 40 days, or in a delayed paradigm, following 3 months after injury. The goal was to prevent or potentially reverse SCI-induced osteoporosis. In the acute phase, administration of the CB2 agonist was not able to preserve the rapid loss of cancellous bone. In the delayed-treatment paradigm, in cortical bone, HU308 increased cortical-area to total-area ratio and periosteal perimeter in the femur, and improved bone density in the distal femur and proximal tibia. Further, we report changes to the metaphyseal periosteum with increased presence of adipocyte and fat mass in the periosteum of SCI animals, which was not present in naïve animals. The layer of fat increased markedly in HU308-treated animals compared with SCI-vehicle-treated animals. Overall, these data show that CB2 agonism targets a number of cell types that can influence overall bone quality.

The efficacy and safety of bisphosphonate analogs for treatment of osteoporosis after spinal cord injury: a systematic review and meta-analysis of randomized controlled trials

Bisphosphonates can inhibit osteoclast-mediated bone resorption, prevent bone loss, and reduce the risk of osteoporotic fractures. Our meta-analysis of studies shows that early bisphosphonate administration after SCI was safe and beneficial to the BMD of the total hip and lumbar spine at 12 months.

INTRODUCTION

Rapid bone loss in the early stages of spinal cord injury (SCI) leads to an increased risk of osteoporotic fracture. A meta-analysis was conducted to assess the efficacy and safety of bisphosphonates for the treatment of osteoporosis after SCI.

METHODS

A literature search of the PubMed, EMBASE, Cochrane Library, and Web of Science databases identified nine randomized controlled trials with 206 individuals. This meta-analysis was performed using a random-effects model. The primary outcome was the percent change in bone mineral density (BMD) of the total hip, distal femur, and lumbar spine from baseline to 12 months. Bone turnover markers were secondary outcomes. The incidences of adverse events were assessed in order to evaluate safety.

RESULTS

There were significant differences in BMD of the total hip and lumbar spine or serum C-terminal telopeptide between the bisphosphonate and control groups but no difference in adverse events. The percent change in BMD of the distal femur and serum type 1 procollagen N-terminal peptide from baseline to 12 months was not superior in the treatment groups. Osteoclast-mediated bone resorption was inhibited by bisphosphonate administration. Subgroup analyses of participants treated with zoledronate at different sites revealed a beneficial effect on BMD of the total hip and lumbar spine but not the distal femur.

CONCLUSION

Early bisphosphonate administration after SCI was safe and beneficial to the BMD of the total hip and lumbar spine at 12 months.

Cardiometabolic risks and atherosclerotic disease in ApoE knockout mice: Effect of spinal cord injury and Salsalate anti-inflammatory pharmacotherapy

OBJECTIVE

To test in mice with a double mutation of the ApoE gene (ApoE-/-) whether spinal cord injury (SCI) hastens the native trajectory of, and established component risks for, atherosclerotic disease (AD), and whether Salsalate anti-inflammatory pharmacotherapy attenuates the impact of SCI.

METHODS

ApoE-/- mice were anesthetized and underwent a T9 laminectomy. Exposed spinal cords were given a contusion injury (70 k-dynes). Sham animals underwent all surgical procedures, excluding injury. Injured animals were randomized to 2 groups: SCI or SCI+Salsalate [120 mg/Kg/day i.p.]. Mice were serially sacrificed at 20-, 24-, and 28-weeks post-SCI, and body mass was recorded. At sacrifice, heart and aorta were harvested intact, fixed in 10% buffered formalin, cleaned and cut longitudinally for en face preparation. The aortic tree was stained with oil-red-O (ORO). AD lesion histomorphometry was calculated from the proportional area of ORO. Plasma total cholesterol, triglycerides and proatherogenic inflammatory cytokines (PAIC's) were analyzed.

RESULTS

AD lesion in the aortic arch progressively increased in ApoE-/-, significant at 24- and 28-weeks. AD in SCI is significantly greater at 24- and 28-weeks compared to time-controlled ApoE-/-. Salsalate treatment attenuates the SCI-induced increase at these time points. Body mass in all SCI groups are significantly reduced compared to time-controlled ApoE-/-. Cholesterol and triglycerides are significantly higher with SCI by 24- and 28-weeks, compared to ApoE-/-, and Salsalate reduces the SCI-induced effect on cholesterol. PAIC's interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor α (TNFα), monocyte chemoattractant protein-1 (MCP-1), and chemokine (C-C motif) ligand 5 (CCL-5) are significantly greater with SCI compared to ApoE-/- at varying timepoints. Salsalate confers a marginal reducing effect on PAIC's by 28-weeks compared to SCI. Regression models determine that each PAIC is a significant and positive predictor of lesion. (p's <0.05).

CONCLUSIONS

SCI accelerates aortic AD and associated risk factors, and anti-inflammatory treatment may attenuate the impact of SCI on AD outcomes. PAIC's IL-1β, IL-6, TNFα, MCP-1, and CCL-5 may be effective predictors of AD.

Three-Dimensional Quantification of Bone Mineral Density in the Distal Femur and Proximal Tibia Based on Computed Tomography: In Vitro Evaluation of an Extended Standardization Method

While alterations in bone mineral density (BMD) are of interest in a number of musculoskeletal conditions affecting the knee, their analysis is limited by a lack of tools able to take full advantage of modern imaging modalities. This study introduced a new method, combining computed tomography (CT) and computational anatomy algorithms, to produce standardized three-dimensional BMD quantification in the distal femur and proximal tibia. The method was evaluated on ten cadaveric knees CT-scanned twice and processed following three different experimental settings to assess the influence of different scans and operators. The median reliability (intraclass correlation coefficient (ICC)) ranged from 0.96 to 0.99 and the median reproducibility (precision error (RMSSD)) ranged from 3.97 to 10.75 mg/cc for the different experimental settings. In conclusion, this paper presented a method to standardize three-dimensional knee BMD with excellent reliability and adequate reproducibility to be used in research and clinical applications. The perspectives offered by this novel method are further reinforced by the fact it relies on conventional CT scan of the knee. The standardization method introduced in this work is not limited to BMD and could be adapted to quantify other bone parameters in three dimension based on CT images or images acquired using different modalities.

A Registration Method for Three-Dimensional Analysis of Bone Mineral Density in the Proximal Tibia

Although alterations in bone mineral density (BMD) at the proximal tibia have been suggested to play a role in various musculoskeletal conditions, their pathophysiological implications and their value as markers for diagnosis remain unclear. Improving our understanding of proximal tibial BMD requires novel tools for three-dimensional (3D) analysis of BMD distribution. Three-dimensional imaging is possible with computed tomography (CT), but computational anatomy algorithms are missing to standardize the quantification of 3D proximal tibial BMD, preventing distribution analyses. The objectives of this study were to develop and assess a registration method, suitable with routine knee CT scans, to allow the standardized quantification of 3D BMD distribution in the proximal tibia. Second, as an example of application, the study aimed to characterize the distribution of BMD below the tibial cartilages in healthy knees. A method was proposed to register both the surface (vertices) and the content (voxels) of proximal tibias. The method combines rigid transformations to account for differences in bone size and position in the scanner's field of view and to address inconsistencies in the portion of the tibial shaft included in routine CT scan, with a nonrigid transformation locally matching the proximal tibias. The method proved to be highly reproducible and provided a comprehensive description of the relationship between bone depth and BMD. Specifically it reported significantly higher BMD in the first 6 mm of bone than deeper in the proximal tibia. In conclusion, the proposed method offers promising possibilities to analyze BMD and other properties of the tibia in 3D.

Pathophysiology of Neurogenic Obesity After Spinal Cord Injury

Individuals with a spinal cord injury (SCI) have a unique physiology characterized by sarcopenia, neurogenic osteoporosis, neurogenic anabolic deficiency, sympathetic dysfunction, and blunted satiety associated with their SCI, all of which alter energy balance and subsequently body composition. The distinct properties of "neurogenic obesity" place this population at great risk for metabolic dysfunction, including systemic inflammation, hyperglycemia, dyslipidemia, and hypertension. The purpose of this article is to demonstrate the relationship between neurogenic obesity and the metabolic syndrome after SCI, highlighting the mechanisms associated with adipose tissue pathology and those respective comorbidities. Additionally, representative studies of persons with SCI will be provided to elucidate the severity of the problem and to prompt greater vigilance among SCI specialists as well as primary care providers in order to better manage the epidemic from a public health perspective.

Severe bone microarchitecture deterioration in a family with hereditary neuropathy: evidence of the key role of the mechanostat

In this report, we present three cases of individuals from the same family with a diagnosis of CMT with severe tibia bone microarchitecture deterioration assessed by HR-pQCT. Charcot-Marie-Tooth disease (CMT) or hereditary neuropathy involves both motor and sensory nerves. Falls are often the first manifestation in these patients and represent an important risk factor for fracture. The reduction of mechanical input on bone inhibits bone formation by osteoblasts and accelerates bone resorption by osteoclasts, leading to disuse osteoporosis. We report three cases of individuals from the same family with a diagnosis of CMT with severe tibia bone microarchitecture deterioration assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT). This affectation was exclusive to the tibia; the radius remained undamaged, showing the consequences of the lack of mobility and mechanical stimulation. Physical activity and rehabilitation, in addition to adequate calcium and vitamin D supplementation, may play an essential role in the management of this disease.

Dose-dependent skeletal deficits due to varied reductions in mechanical loading in rats

Reduced skeletal loading leads to marked bone loss. Animal models of hindlimb suspension are widely used to assess alterations in skeleton during the course of complete unloading. More recently, the effects of partial unloading on the musculoskeletal system have been interrogated in mice and rats, revealing dose-dependent effects of partial weight bearing (PWB) on the skeleton and skeletal muscle. Here, we extended these studies to determine the structural and functional skeletal alterations in 14-week-old male Wister rats exposed to 20%, 40%, 70%, or 100% of body weight for 1, 2, or 4 weeks (n = 11-12/group). Using in vivo pQCT, we found that trabecular bone density at the proximal tibia declined in proportion to the degree of unloading and continued progressively with time, without evidence of a plateau by 4 weeks. Ex vivo measurements of trabecular microarchitecture in the distal femur by microcomputed tomography revealed deficits in bone volume fraction, 2 and 4 weeks after unloading. Histologic analyses of trabecular bone in the distal femur revealed the decreased osteoblast number and mineralizing surface in unloaded rats. Three-point bending of the femoral diaphysis indicated modest or no reductions in femoral stiffness and estimated modulus due to PWB. Our results suggest that this rat model of PWB leads to trabecular bone deterioration that is progressive and generally proportional to the degree of PWB, with minimal effects on cortical bone.

Management of lower limb fractures in patients with spinal cord injuries

BACKGROUND

Low-energy fractures of the lower limb in patients post spinal cord injury (SCI) present significant management challenges. This is the first Australian study to review the experience from a tertiary referral SCI centre and aims to identify trends and suggest therapeutic options.

METHODS

Retrospective review over a 5-year period in patients with SCI treated for a lower limb fragility fracture. Patient demographics, spinal injury severity scores, fracture characteristics and treatment were assessed. Time to union, length of stay and treatment-related complications were also examined.

RESULTS

A total of 38 SCI patients with 42 lower extremity fractures met inclusion criteria. Mean age was 55.7 years and mean duration post-SCI at fracture was 22.5 ± 12.7 years. The femur (73.8%) was more commonly fractured than the lower leg (26.2%), with extra-articular distal femoral fractures most prevalent (35.7%). A total of 25 (60%) fractures were managed operatively, and 17 (40%) non-operatively. The majority of femoral fractures were managed with intramedullary nailing. Tibial fractures were more commonly managed non-operatively. Eight cases (19.1%) experienced complications, with a significant difference between frequency of complications in non-operative (35.3%) and operative (8.0%) groups; P = 0.045. All fractures united except one; time to union was shorter in patients treated surgically (13.6 ± 6.4 weeks) compared to those managed non-operatively (19.1 ± 8.1 weeks).

CONCLUSIONS

Lower limb fragility fractures in patients with SCI can be managed successfully via either operative or non-operative measures. In this series, fewer complications and shorter time to union were found in patients managed operatively.

Bone adaptation: Safety factors and load predictability in shaping skeletal form

Much is known about skeletal adaptation in relation to the mechanical functions that bones serve. This includes how bone adapts to mechanical loading during an individual's lifetime as well as over evolutionary time. Although controlled loading in animal models allows us to observe short-term bone adaptation (epigenetic mechanobiology), examining an assemblage of extant vertebrate bones or a group of fossils' bony structures can reveal the combined effects of long-term trends in loading history and the effects of natural selection. In this survey we examine adaptations that take place over both time scales and highlight a few of the extraordinary insights first published by John Currey. First, we provide a historical perspective on bone adaptation control mechanisms, followed by a discussion of safety factors in bone. We then summarize examples of structural- and material-level adaptations and mechanotransduction, and analyze the relationship between these structural- and material-level adaptations observed in situations where loading modes are either predictable or unpredictable. We argue that load predictability is a major consideration for bone adaptation broadly across an evolutionary timescale, but that its importance can also be seen during ontogenetic growth trajectories, which are subject to natural selection as well. Furthermore, we suggest that bones with highly predictable load patterns demonstrate more precise design with lower safety factors, while bones that experience less predictable loads or those that are less capable of repair and adaptation are designed with a higher safety factor. Finally, exposure to rare loading events with high potential costs of failure leads to design of structures with very high safety factor compared to everyday loading experience. Understanding bone adaptations at the structural and material levels, which take place over an individual's lifetime or over evolutionary time has numerous applications in translational and clinical research to understand and treat musculoskeletal diseases, as well as to permit the furthering of human extraterrestrial exploration in environments with altered gravity.

Bone Mineral Density Testing in Spinal Cord Injury: 2019 ISCD Official Position

Spinal cord injury (SCI) causes rapid osteoporosis that is most severe below the level of injury. More than half of those with motor complete SCI will experience an osteoporotic fracture at some point following their injury, with most fractures occurring at the distal femur and proximal tibia. These fractures have devastating consequences, including delayed union or nonunion, cellulitis, skin breakdown, lower extremity amputation, and premature death. Maintaining skeletal integrity and preventing fractures is imperative following SCI to fully benefit from future advances in paralysis cure research and robotic-exoskeletons, brain computer interfaces and other evolving technologies. Clinical care has been previously limited by the lack of consensus derived guidelines or standards regarding dual-energy X-ray absorptiometry-based diagnosis of osteoporosis, fracture risk prediction, or monitoring response to therapies. The International Society of Clinical Densitometry convened a task force to establish Official Positions for bone density assessment by dual-energy X-ray absorptiometry in individuals with SCI of traumatic or nontraumatic etiology. This task force conducted a series of systematic reviews to guide the development of evidence-based position statements that were reviewed by an expert panel at the 2019 Position Development Conference in Kuala Lumpur, Malaysia. The resulting the International Society of Clinical Densitometry Official Positions are intended to inform clinical care and guide the diagnosis of osteoporosis as well as fracture risk management of osteoporosis following SCI.

Carboxy terminal collagen crosslinks as a prognostic risk factor for fall-related fractures in individuals with established spinal cord injury

Study design

Prospective cohort study.

Objective

To study associations between specific bone turnover markers and fall-related fractures in individuals with spinal cord injury (SCI).

Setting

Rehabilitation Hospital.

Methods

Carboxy terminal collagen crosslinks (CTX), type-1 procollagen N-terminal (P1NP), albumin-corrected calcium (Ca²⁺), parathyroid hormone (PTH) and vitamin D were examined in a cohort of 106 participants with SCI at least 1 year post injury. The participants were followed for 1 year monitoring fall-related fractures.

Results

In total, 29 out of 106 reported having experienced a fall-related fracture post-injury at baseline, and 5 out of 100 had experienced a fall-related bone fracture during the 1 year follow-up. Our main findings were that high levels of serum CTX increased the odds of being in the fracture group, and that 25-hydroxy vitamin D (25 OHD) levels, Ca²⁺, PTH or P1NP were not associated with being in the fracture group.

Conclusions

We here present an association between high-CTX plasma levels at baseline and fall-related fractures reported during a 1-year follow-up among individuals with established SCI. We recommend studies with larger SCI populations before further clinical implications can be drawn.

Bone Health in Adaptive Sports Athletes

Adaptive sports athletes represent a growing population within the athletic community worldwide. Given potential cardiometabolic and psychosocial benefits of adaptive sports participation, the impact on bone health and injury risk in adaptive athletes is of increasing clinical interest. Impaired bone health as a result of low energy availability has been well described in able-bodied athletic women and, more recently, men as part of the female athlete triad and Relative Energy Deficiency in Sport (RED-S). However, the applicability of these models to adaptive athletes remains unclear given altered physiology and biomechanics compared with able-bodied counterparts. Thus, a literature review was completed to characterize the influence of adaptive sports participation and associated risk factors for impaired bone health in this unique population. To date, limited investigations demonstrate a consistent, positive effect of sports participation on bone health. Risk factors for impaired bone health include low energy availability and micronutrient deficiency.

Trabecular Bone Score at the Distal Femur and Proximal Tibia in Individuals With Spinal Cord Injury

Rapid declines in bone mineral density (BMD) at the knee after spinal cord injury (SCI) are associated with an increased risk of fracture. Evaluation of bone quality using the trabecular bone score (TBS) may provide a complimentary measure to BMD assessment to examine bone health and fracture risk after SCI. The purpose of this study was to assess bone mineral density (BMD) and trabecular bone score (TBS) at the knee in individuals with and without SCI. Nine individuals with complete SCI (mean time since SCI 2.9 ± 3.8 yr) and 9 non-SCI controls received dual-energy X-ray absorptiometry scans of the right knee using the lumbar spine protocol. BMD and TBS were quantified at epiphyseal, metaphyseal, diaphyseal, and total bone regions of the distal femur and proximal tibia. Individuals with SCI illustrated significantly lower total BMD at the distal femur (23%; p = 0.029) and proximal tibia (19%; p = 0.02) when compared with non-SCI controls. Despite these marked differences in BMD from both locations, significant differences in total TBS were observed at the distal femur only (6%; p = 0.023). The observed differences in total BMD and TBS could be attributed to reductions in epiphyseal rather than metaphyseal or diaphysis measurements. The relationship between TBS and duration of SCI was well explained by a logarithmic trend at the distal femoral epiphysis (r² = 0.54, p = 0.025). The logarithmic trend would predict that after 3 yr of SCI, TBS would be approximately 6% lower than the non-SCI controls. Further evaluation is needed to determine if TBS measures at the knee provide important information about bone quality that is not captured by traditional BMD.

Single limb immobilization model for bone loss from unloading

Hindlimb suspension is the most used model for inducing bone loss from unloading but requires a separate ground control group. This control group cannot be used for genetic studies involving outbred mice. In this study, we evaluated a single limb immobilization (SLI) model for inducing bone loss from unloading, with the contralateral limb from the same animal used as a control. Male 10-week old C57Bl/6J mice had one limb immobilized for one, two, or three weeks. Subsequently, an additional group of male 16-week old C57Bl/6J mice had one limb immobilized for three weeks. SLI resulted in decreased tibial trabecular BV/TV, Tb Th, and Tb N compared to contralateral limbs in young mice. Femoral trabecular BV/TV, Tb Th, Tb N, and femoral cortical area fraction were also decreased. Mechanical properties were not affected after three weeks. In adult mice, femoral trabecular BV/TV, Tb Th, and Tb N were decreased. Femoral stiffness, ultimate stress, and Young's modulus were decreased. Bone properties decreased by SLI were also decreased by hindlimb suspension previously. The results suggest SLI can be an effective model for inducing bone loss in growing and adult mice after three weeks of immobilization.

Bone fragility after spinal cord injury: reductions in stiffness and bone mineral at the distal femur and proximal tibia as a function of time

Computed tomography and finite element modeling were used to assess bone structure at the knee as a function of time after spinal cord injury. Analyzed regions experienced degradation in stiffness, mineral density, and content. Changes were well described as an exponential decay over time, reaching a steady state 3.5 years after injury.

INTRODUCTION

Spinal cord injury (SCI) is associated with bone fragility and an increased risk of fracture around the knee. The purpose of this study was to investigate bone stiffness and mineral content at the distal femur and proximal tibia, using finite element (FE) and computed tomography (CT) measures. A cross-sectional design was used to compare differences between non-ambulatory individuals with SCI as a function of time after injury (0-50 years).

METHODS

CT scans of the knee were obtained from 101 individuals who experienced an SCI 30 days to 50 years prior to participation. Subject-specific FE models were used to estimate stiffness under axial compression and torsional loading, and CT data was analyzed to assess volumetric bone mineral density (vBMD) and bone mineral content (BMC) for integral, cortical, and trabecular compartments of the epiphyseal, metaphyseal, and diaphyseal regions of the distal femur and proximal tibia.

RESULTS

Bone degradation was well described as an exponential decay over time (R2 = 0.33-0.83), reaching steady-state levels within 3.6 years of SCI. Individuals at a steady state had 40 to 85% lower FE-derived bone stiffness and robust decreases in CT mineral measures, compared to individuals who were recently injured (t ≤ 47 days). Temporal and spatial patterns of bone loss were similar between the distal femur and proximal tibia.

CONCLUSIONS

After SCI, individuals experienced rapid and profound reductions in bone stiffness and bone mineral at the knee. FE models predicted similar reductions to axial and torsional stiffness, suggesting that both failure modes may be clinically relevant. Importantly, CT-derived measures of bone mineral alone underpredicted the impacts of SCI, compared to FE-derived measures of stiffness.

TRIAL REGISTRATION

ClinicalTrials.gov (NCT01225055, NCT02325414).

Low Energy Availability, Menstrual Dysfunction, and Low Bone Mineral Density in Individuals with a Disability: Implications for the Para Athlete Population

Low energy availability, functional hypothalamic amenorrhea, and low bone mineral density are three interrelated conditions described in athletic women. Although described as the female athlete triad (Triad), males experience similar health concerns. The literature suggests that individuals with a disability may experience altered physiology related to these three conditions when compared with the able-bodied population. The goal of this review is to describe the unique implications of low energy availability, low bone mineral density, and, in females, menstrual dysfunction in individuals with a disability and their potential impact on the para athlete population. A literature review was performed linking search terms related to the three conditions with six disability categories that are most represented in para sport. Few articles were found that directly pertained to athletes, therefore, the review additionally characterizes literature found in a non-athlete population. Review of the available literature in athletes suggests that both male and female athletes with spinal cord injury demonstrate risk factors for low energy availability. Bone mineral density may also show improvements for wheelchair athletes or athletes with hemiplegic cerebral palsy when compared with a disabled non-athlete population. However, the prevalence of the three conditions and implications on the health of para athletes is largely unknown and represents a key gap in the sports medicine literature. As participation in para sport continues to increase, further research is needed to understand the impact of these three interrelated health concerns for athletes with a disability, accompanied by educational initiatives targeting athletes, coaches, and health professionals.

Lower extremity fractures in patients with spinal cord injury characteristics, outcome and risk factors for non-unions

CONTEXT

Sublesional osteoporosis is an important sequel after spinal cord injury (SCI) resulting in a high incidence of fractures and impaired osseous healing due to altered bone metabolism. The following study aims to identify demographic characteristics and outcome of patients with SCI with lower extremity fractures.

DESIGN

Retrospective observational study.

SETTING

Level-I cross-regional trauma center.

PARTICIPANTS

All patients with SCI suffering from osteoporotic/pathologic fractures during an 11-year-period (01/2003-12/2013) at the Center for Spinal Cord Injuries (Trauma Center Murnau) were analyzed via a chart review.

OUTCOME MEASURES

Demographics, surgical and radiologic outcome as well as complication rate were assessed with a special emphasis on union rates and independent risk factors for non-unions.

RESULTS

We identified 132 patients (105 males) who fulfilled the inclusion criteria. Most of them were paraplegic (n=101) and showed motor complete syndromes (n=119). Supracondylar femur fractures were the most prevalent in this study (n=47). We observed a non-union rate of 15.9% (n=21). The development of pseudarthrosis was associated with the time interval since the initial SCI (P < 0.010), delayed in-patient submission (P < 0.038), fracture classification (P < 0.002) and the localization of the fracture (P < 0.0001). The overall complication rate was 16.7%. All dislocated subtrochanteric femur fractures (Garden III and IV) (n=10) developed a non-union, regardless of their management (conservative or surgical). The following independent predictors for non-unions were identified: fracture localization (P < 0.0002), fracture classification (P < 0.056), and fracture management (P < 0.036).

CONCLUSIONS

Even though modern techniques allow surgical interventions in bones with reduced mineral density, non-unions remain a common complication in patients with SCI. Risk factors for non-unions of lower extremity fractures are identified.

Effects of ursolic acid on sub-lesional muscle pathology in a contusion model of spinal cord injury

Spinal Cord Injury (SCI) results in severe sub-lesional muscle atrophy and fiber type transformation from slow oxidative to fast glycolytic, both contributing to functional deficits and maladaptive metabolic profiles. Therapeutic countermeasures have had limited success and muscle-related pathology remains a clinical priority. mTOR signaling is known to play a critical role in skeletal muscle growth and metabolism, and signal integration of anabolic and catabolic pathways. Recent studies show that the natural compound ursolic acid (UA) enhances mTOR signaling intermediates, independently inhibiting atrophy and inducing hypertrophy. Here, we examine the effects of UA treatment on sub-lesional muscle mTOR signaling, catabolic genes, and functional deficits following severe SCI in mice. We observe that UA treatment significantly attenuates SCI induced decreases in activated forms of mTOR, and signaling intermediates PI3K, AKT, and S6K, and the upregulation of catabolic genes including FOXO1, MAFbx, MURF-1, and PSMD11. In addition, UA treatment improves SCI induced deficits in body and sub-lesional muscle mass, as well as functional outcomes related to muscle function, motor coordination, and strength. These findings provide evidence that UA treatment may be a potential therapeutic strategy to improve muscle-specific pathological consequences of SCI.

Nutritional Health Considerations for Persons with Spinal Cord Injury

Chronic spinal cord injury (SCI) often results in morbidity and mortality due to all-cause cardiovascular disease (CVD) and comorbid endocrine disorders. Several component risk factors for CVD, described as the cardiometabolic syndrome (CMS), are prevalent in SCI, with the individual risks of obesity and insulin resistance known to advance the disease prognosis to a greater extent than other established risks. Notably, adiposity and insulin resistance are attributed in large part to a commonly observed maladaptive dietary/nutritional profile. Although there are no evidence-based nutritional guidelines to address the CMS risk in SCI, contemporary treatment strategies advocate more comprehensive lifestyle management that includes sustained nutritional guidance as a necessary component for overall health management. This monograph describes factors in SCI that contribute to CMS risks, the current nutritional profile and its contribution to CMS risks, and effective treatment strategies including the adaptability of the Diabetes Prevention Program (DPP) to SCI. Establishing appropriate nutritional guidelines and recommendations will play an important role in addressing the CMS risks in SCI and preserving optimal long-term health.

Special considerations in the urological management of the older spinal cord injury patient

PURPOSE

This paper reports the key findings of Committee 8 of the Joint SIU-ICUD Consultation on Urologic Management of the Spinal Cord Injured Patient and address issues pertaining to the older person with a SCI and the time-related changes relevant to their urological, gastrointestinal and functional management.

METHODS

A literature review using the Pubmed and Ovid search engines was performed examining pertinent literature regarding SCI in the older patient.

RESULTS

There is a rising incidence of both traumatic and non-traumatic spinal cord injury (SCI) in older people and improvements in healthcare and nutrition mean patients with SCI are living longer. Outcomes after a SCI in the older person are a sum of the effects of injury and its management compounded by specific effects of ageing and the emergence of unrelated comorbidities. Changes in health, comorbidities, cognition and dexterity with ageing have an impact on function and are important considerations in the management of the older patient with SCI. Treatment decisions are thus increasingly complex due to the need to take into account these changes and accompanying polypharmacy. For the person living with a SCI, changes in circumstances (social and financial) have an impact on quality of life and influence management and support strategies.

CONCLUSIONS

Older patients with SCI face additional challenges both in the acute setting and with ageing. Clinicians should take into account comorbid conditions, mental health, physical function, cognition and social support in making management decisions. With the global ageing population, health services planning will need to allow for increase in resources required to care for older patients with SCI.

Assessment of Bone Mineral Density at the Distal Femur and the Proximal Tibia by Dual-Energy X-ray Absorptiometry in Individuals With Spinal Cord Injury: Precision of Protocol and Relation to Injury Duration

Spinal cord injury (SCI) is characterized by marked bone loss at the knee, and there is a need for established dual-energy X-ray absorptiometry (DXA) protocols to examine bone mineral density (BMD) at this location to track therapeutic progress and to monitor fracture risk. The purpose of this study was to quantify the precision and reliability of a DXA protocol for BMD assessment at the distal femur and the proximal tibia in individuals with SCI. The protocol was subsequently used to investigate the relationship between BMD and duration of SCI. Nine individuals with complete SCI and 9 able-bodied controls underwent 3 repeat DXA scans in accordance with the short-term precision methodology recommended by the International Society of Clinical Densitometry. The DXA protocol demonstrated a high degree of precision with the root-mean-square standard deviation ranging from 0.004 to 0.052 g/cm² and the root-mean-square coefficient of variation ranging from 0.6% to 4.4%, depending on the bone, the region of interest, and the rater. All measurements of intra- and inter-rater reliability were excellent with an intraclass correlation of ≥0.950. The relationship between the BMD and the duration of SCI was well described by a logarithmic trend (r² = 0.68-0.92). Depending on the region of interest, the logarithmic trends would predict that, after 3 yr of SCI, BMD at the knee would be 43%-19% lower than that in the able-bodied reference group. We believe the DXA protocol has the level of precision and reliability required for short-term assessments of BMD at the distal femur and the proximal tibia in people with SCI. However, further work is required to determine the degree to which this protocol may be used to assess longitudinal changes in BMD after SCI to examine clinical interventions and to monitor fracture risk.

Analysis of the evolution of cortical and trabecular bone compartments in the proximal femur after spinal cord injury by 3D-DXA

Marked trabecular and cortical bone loss was observed at the proximal femur short-term after spinal cord injury (SCI). 3D-DXA provided measurement of vBMD evolution at both femoral compartments and cortical thinning, thereby suggesting that this technique could be useful for bone analysis in these patients.

INTRODUCTION

SCI is associated with a marked increase in bone loss and risk of osteoporosis development short-term after injury. 3D-DXA is a new imaging analysis technique providing 3D analysis of the cortical and trabecular bone from DXA scans. The aim of this study was to assess the evolution of trabecular macrostructure and cortical bone using 3D-DXA in patients with recent SCI followed over 12 months.

METHODS

Sixteen males with recent SCI (< 3 months since injury) and without antiosteoporotic treatment were included. Clinical assessment, bone mineral density (BMD) measurements by DXA, and 3D-DXA evaluation at proximal femur (analyzing the integral, trabecular and cortical volumetric BMD [vBMD] and cortical thickness) were performed at baseline and at 6 and 12 months of follow-up.

RESULTS

vBMD significantly decreased at integral, trabecular, and cortical compartments at 6 months (- 8.8, - 11.6, and - 2.4%), with a further decrease at 12 months, resulting in an overall decrease of - 16.6, - 21.9, and - 5.0%, respectively. Cortical thickness also decreased at 6 and 12 months (- 8.0 and - 11.4%), with the maximal decrease being observed during the first 6 months. The mean BMD losses by DXA at femoral neck and total femur were - 17.7 and - 21.1%, at 12 months, respectively.

CONCLUSIONS

Marked trabecular and cortical bone loss was observed at the proximal femur short-term after SCI. 3D-DXA measured vBMD evolution at both femoral compartments and cortical thinning, providing better knowledge of their differential contributory role to bone strength and probably of the effect of therapy in these patients.

Rehabilitation Interventions to modify endocrine-metabolic disease risk in Individuals with chronic Spinal cord injury living in the Community (RIISC): A systematic review and scoping perspective

CONTEXT

Endocrine-metabolic disease (EMD) risk following spinal cord injury (SCI) is associated with significant multi-morbidity (i.e. fracture, diabetes, heart disease), mortality, and economic burden. It is unclear to what extent rehabilitation interventions can modify EMD risk and improve health status in community-dwelling adults with chronic SCI.

OBJECTIVES

To characterize rehabilitation interventions and summarize evidence on their efficacy/effectiveness to modify precursors to EMD risk in community-dwelling adults with chronic SCI.

METHODS

Systematic searches of MEDLINE PubMed, EMBASE Ovid, CINAHL, CDSR, and PsychInfo were completed. All randomized, quasi-experimental, and prospective controlled trials comparing rehabilitation/therapeutic interventions with control/placebo interventions in adults with chronic SCI were eligible. Two authors independently selected studies and abstracted data. Mean differences of change from baseline were reported for EMD risk outcomes. The GRADE approach was used to rate the quality of evidence.

RESULTS

Of 489 articles identified, 16 articles (11 studies; n=396) were eligible for inclusion. No studies assessed the effects of rehabilitation interventions on incident fragility fractures, heart disease, and/or diabetes. Individual studies reported that exercise and/or nutrition interventions could improve anthropometric indices, body composition/adiposity, and biomarkers. However, there were also reports of non-statistically significant between-group differences.

CONCLUSIONS

There was very low-quality evidence that rehabilitation interventions can improve precursors to EMD risk in community-dwelling adults with chronic SCI. The small number of studies, imprecise estimates, and inconsistency across studies limited our ability to make conclusions. A high-quality longitudinal intervention trial is needed to inform community-based rehabilitation strategies for EMD risk after chronic SCI.

Management of Lower Extremity Long-bone Fractures in Spinal Cord Injury Patients

The AO classification system, used as a guide for modern fracture care and fixation, follows a basic philosophy of care that emphasizes early mobility and return to function. Lower extremity long-bone fractures in patients with spinal cord injury often are pathologic injuries that present unique challenges, to which the AO principles may not be entirely applicable. Optimal treatment achieves healing without affecting the functional level of the patient. These injuries often result from low-energy mechanisms in nonambulatory patients with osteopenic bone and a thin, insensate soft-tissue envelope. The complication rate can be high, and the outcomes can be catastrophic without proper care. Satisfactory results can be obtained through various methods of immobilization. Less frequently, internal fixation is applied. In certain cases, after discussion with the patient, amputation may be suitable. Prevention strategies aim to minimize bone loss and muscle atrophy.