Long-term changes in the tibia and radius bone mineral density following spinal cord injury

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.

Lumbar spine densitometry in people with spinal cord injury: Investigation of potential sources of errors

PURPOSE

People with spinal cord injury (SCI) experience a considerable loss of bone after the injury. Lumbar spine (LS) bone mineral density (BMD) has been reported to be within the normal range, or even higher when assessed with DXA, in people with SCI; hence, it has been hypothesized that sources of error may spuriously increase LS BMD. The aim of this study was to describe the frequency of potential sources of error that may alter LS BMD measurement in a cohort of individuals with chronic SCI at baseline and over a 2-year period.

METHODS

We analyzed baseline and 2-year follow up DXA scans (Hologic Discovery QDR 4500, Hologic Inc., MA, USA) previously performed from a cohort of males and females with chronic SCI. Two physicians independently reviewed each scan, commented on whether the scan was appropriate for BMD analysis, should be re-analyzed, or be removed from the dataset, and reported on the presence of potential sources of error in LS BMD measurement.

RESULTS

We reviewed 115 lumbar spine DXA scans from 58 participants, and 107 (93.0 %) scans from 52 participants presented at least one potential source of error. At baseline, the average number of potential sources of error per scan was 5.5 ± 1.7 and 5.7 ± 1.5 according to rater 1 and rater 2, respectively. Follow-up scans presented an average of 5.6 ± 1.6 and 5.7 ± 1.4 potential sources of error according to rater 1 and rater 2, respectively. Facet sclerosis, osteophytes and difficulty in detecting bone edges were the most prevalent sources of error.

CONCLUSION

The high frequency of potential sources of error is consistent with current recommendations against the use of LS BMD for fracture risk assessment in people with SCI.

Bone health education in individuals with spinal cord injury or disease-the Bare Bones Podcast Series: plan it, produce it, post it!

Introduction

The Consortium for Spinal Cord Medicine's inaugural Clinical Practice Guideline for Bone Health and Osteoporosis Management for Individuals with Spinal Cord Injury or Disease (CSCM-CPG) was published in 2022 for a clinician audience. The aim of this project was to develop a podcast series to ensure people with lived experience with Spinal Cord Injury or Disease (PLEX) understand the CSCM-CPG content and know how to act to reduce their fracture risk.

Methods

The "Bare Bones Podcast Series" consists of nine episodes; one related to each CSCM-CPG chapter. The podcast content and the questions asked in each podcast were co-developed by PLEX partners (PLEX-P) and the project team. Two PLEX-P acted as co-hosts for the series. The invited speaker(s) were CSCM-CPG expert panel members who participated in an informal dialogue with the hosts. Each podcast closes with a specific action a listener can do to advance their bone health. The related Educational Action Planning Tool (EAT) handouts contain text and infographic information specific to each podcast episode and include key concepts and a specific actionable take-home message. Local PLEX reviewers (PLEX-R) were invited to review podcast episodes and EATs and provide their feedback through focus group participation or one-on-one (1:1) interviews. The project team revised the podcast episodes and the EATs based on feedback from the PLEX-R prior to releasing them online.

Results

Nine podcast episodes and related EATs were designed and created collaboratively with 3 PLEX-P, 22 PLEX-R, 11 CSCM-CPG expert panel members, and the project team. The episodes were titled: "Introduction to the Bare Bones of Bone Health"; "Fracture 101"; "Blood Tests-a Window into You"; "I See Your Skeleton"; "Vitamin D for all, Calcium for Some"; "Get Moving and Loading"; "Pills or Poisons & Atomic Habits"; "Snap and Crack"; and "Directions for Research". The Bare Bones Podcast Series was shared through the project website.

Conclusions

The podcasts will aid PLEX and their family caregivers to advocate for ongoing bone health assessments and to promote an ongoing dialogue with care team members regarding how to prevent fractures and fracture-related morbidity and mortality.

A moderate spinal contusion injury in rats alters bone turnover both below and above the level of injury with sex-based differences apparent in long-term recovery

Spinal cord injury (SCI) leads to significant sublesional bone loss and high fracture rates. While loss of mechanical loading plays a significant role in SCI-induced bone loss, animal studies have demonstrated mechanical loading alone does not fully account for loss of bone following SCI. Indeed, we have shown that bone loss occurs below the level of an incomplete moderate contusion SCI, despite the resumption of weight-bearing and stepping. As systemic factors could also impact bone after SCI, bone alterations may also be present in bone sites above the level of injury. To examine this, we assessed bone microarchitecture and bone turnover in the supralesional humerus in male and female rats at two different ages following a moderate contusion injury in both sub-chronic (30 days) and chronic (180 days) time points after injury. At the 30-day timepoint, we found that both young and adult male SCI rats had decrements in trabecular bone volume at the supralesional proximal humerus (PH), while female SCI rats were not different from age-matched shams. At the 180-day timepoint, there were no statistical differences between SCI and sham groups, irrespective of age or sex, at the supralesional proximal humerus. At the 30-day timepoint, all SCI rats had lower BFR and higher osteoclast-covered trabecular surfaces in the proximal humerus compared to age-matched sham groups generally matching the pattern of SCI-induced changes in bone turnover seen in the sublesional proximal tibia. However, at the 180-day timepoint, only male SCI rats had lower BFR at the supralesional proximal humerus while female SCI rats had higher or no different BFR than their age-matched counterparts. Overall, this preclinical study demonstrates that a moderate contusion SCI leads to alterations in bone turnover above the level of injury within 30-days of injury; however male SCI rats maintained lower BFR in the supralesional humerus into long-term recovery. These data further highlight that bone loss after SCI is not driven solely by disuse. Additionally, these data allude to potential systemic factors exerting influence on bone following SCI and highlight the need to consider treatments for SCI-induced bone loss that impact both sublesional and systemic factors.

Using Risk Scores to Estimate Lower Extremity Fragility Fracture Risk among Individuals with Chronic Spinal Cord Injury: A Preliminary Model

Objectives

To develop SCI-FX, a risk score to estimate 5-year lower extremity fragility fracture risk among patients living with chronic spinal cord injury (cSCI).

Methods

Adults with traumatic cSCI (n = 90) participated in a 2-year prospective longitudinal cohort study describing bone mineral density (BMD) change and fracture incidence conducted at the Lyndhurst Centre (University Health Network), University of Waterloo, and Physical Disability Rehabilitation Institute of Québec City. Prior publication and clinical intuition were used to identify fragility fracture risk factors including prior fragility fracture, years post-injury, motor complete injury (AIS A/B), benzodiazepine use, opioid use, and parental osteoporosis. We conducted bivariate analyses to identify variables associated with fracture. Multiple logistic regressions were performed using fragility fracture incidence as the dependent variable and all variables from the univariate analyses with a highly liberal p value at 0.2. Using the odds ratios (ORs) from the multiple logistic regression model, a point system for fragility fracture risk score was developed, and the odds of fracture for each point was estimated.

Results

All initial variables, with the exception of benzodiazepine exposure, were included in the final model.

Conclusion

We identified a simple preliminary model for clinicians to estimate 5-year fracture risk among patients with cSCI based on their total score.

Comparison of DXA-based versus CT-based indices to predict prevalent fracture history in men with spinal cord injury

Fracture risk prediction remains challenging in adults with spinal cord injury. Here, we compare the ability of CT- and DXA-derived indices to discriminate between those with and without prevalent osteoporotic fracture. Novel CT-derived indices may offer improved assessment of fragility fracture risk as well as improved monitoring of response to therapies.

INTRODUCTION

Individuals with spinal cord injury are particularly susceptible to osteoporosis. As advanced imaging techniques become more readily available clinically, there is limited information on the relative strength of various outcomes for fracture risk prediction. The purpose of this study was to compare the ability of DXA-based versus CT-based indices to predict prevalent fracture history in adults with spinal cord injury.

METHODS

Thirty-six men with known SCI underwent dual energy X-ray absorptiometry and computed tomography assessments of the lower extremities. We used age-adjusted area under the curve models to compare the predictive value for each bone parameter to identify prevalent fracture history.

RESULTS

CT-based indices outperformed DXA-based indices at all sites. The site with the highest AUC was the trabecular BMD at the proximal tibial epiphysis.

CONCLUSIONS

CT imaging may have clinical utility to improve fracture risk prediction in adults with SCI. More work is needed to confirm these findings and to assess the value of CT-based indices to predict incident fracture, monitor longitudinal bone loss, and monitor response to various therapies, both pharmacological and rehabilitation.

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.

Relationships between T-scores at the hip and bone mineral density at the distal femur and proximal tibia in persons with spinal cord injury

Objective: To identify T-score values at the total hip (TH) and femoral neck (FN) that correspond to the cutoff value of <0.60 g/cm² for heightened risk of fracture at the distal femur (DF) and proximal tibia (PT).Design: Retrospective analysis of data in a research center's database. Setting: Community-based individuals with spinal cord injury (SCI). Participants: 105 unique individuals with SCI. Outcome Measurements: DXA derived areal BMD (aBMD) and T-score of the DF, PT, TH, and FN. Results: The aBMD at the DF and PT regions were predictors of T-scores at the TH (R² = 0.63, P < 0.001 and R² = 0.65, P < 0.001) and FN (R² = 0.55, P < 0.001 and R² = 0.58, P < 0.001). Using the DF and PT aBMD of 0.60 g/cm² as a value below which fractures were more likely to occur, the predicted T-score was -3.1 and -3.5 at the TH and -2.6 and -2.9 at the FN, respectively. However, when the predicted and observed T-score values disagree outside the 95% limit of agreement, the predicted T-score values are lower than the measured T-score values, overestimating the measured values between -2.0 and -4.0 SD. Conclusion: The DF and PT cutoff value for aBMD of 0.60 g/cm² was a moderate predictor of T-score values at the TH and FN, with considerable inaccuracies outside the clinically acceptable limits of agreement. As such, the direct measurement of knee aBMD in persons with SCI should be performed, whenever possible, prior to prescribing weight bearing upright activities, such as robotic exoskeletal-assisted walking.

Progressive Sublesional Bone Loss Extends into the Second Decade After Spinal Cord Injury

OBJECTIVE

The rate of areal bone mineral density (aBMD) loss at the knee (distal femur (DF) and proximal tibia ) and hip (femoral neck (FN) and total hip (TH)) was determined in persons with traumatic spinal cord injury (SCI) who were stratified into subgroups based on time since injury (TSI).

DESIGN

Cross-sectional retrospective review.

SETTING

Department of Veterans Affairs Medical Center and Private Rehabilitation Hospital.

PARTICIPANTS

Data on 105 individuals with SCI (TSI ≤12 months, n = 19; TSI 1-5 years, n = 35; 6-10 years, n = 19; TSI 11-20 years, n = 16; TSI >20 years, n = 15) and 17 able-bodied reference (AB_ref) controls.

INTERVENTIONS

NA Main Outcome Measures: The knee and hip aBMD values were obtained by dual energy X-ray absorptiometry (GE Lunar iDXA) using standard clinical software for the proximal femur employed in conjunction with proprietary research orthopedic knee software applications. Young-normal (T-score) and age-matched (Z-scores) standardized scores for the FN and TH were obtained using the combined GE Lunar/National Health and Nutrition Examination Survey (NHANES III) combined reference database.

RESULTS

When groups were stratified and compared as epochs of TSI, significantly lower mean aBMD and reference scores were observed as TSI increased, despite similar mean ages of participants among the majority of TSI epoch subgroups. Loss in aBMD occurred at the distal femur (DF), proximal tibia (PT), FN, and TH with 46%, 49%, 32%, and 43% of the variance in loss, respectively, described by the exponential decay curves with a time to steady state (t_ss) occurring at 14.6, 11.3, 14, and 6.2 years, respectively, after SCI.

CONCLUSIONS

Sublesional bone loss after SCI was marked and occurred as an inverse function of TSI. For aBMD at the hip and knee, t_ss extended into the second decade after SCI.

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).

Peripheral Quantitative Computed Tomography: Review of Evidence and Recommendations for Image Acquisition, Analysis, and Reporting, Among Individuals With Neurological Impairment

In 2015, the International Society for Clinical Densitometry (ISCD) position statement regarding peripheral quantitative computed tomography (pQCT) did not recommend routine use of pQCT, in clinical settings until consistency in image acquisition and analysis protocols are reached, normative studies conducted, and treatment thresholds identified. To date, the lack of consensus-derived recommendations regarding pQCT implementation remains a barrier to implementation of pQCT technology. Thus, based on description of available evidence and literature synthesis, this review recommends the most appropriate pQCT acquisition and analysis protocols for clinical care and research purposes, and recommends specific measures for diagnosis of osteoporosis, assigning fracture risk, and monitoring osteoporosis treatment effectiveness, among patients with neurological impairment. A systematic literature search of MEDLINE, EMBASE^©, CINAHL, and PubMed for available pQCT studies assessing bone health was carried out from inception to August 8th, 2017. The search was limited to individuals with neurological impairment (spinal cord injury, stroke, and multiple sclerosis) as these groups have rapid and severe regional declines in bone mass. Of 923 references, we identified 69 that met review inclusion criteria. The majority of studies (n = 60) used the Stratec XCT 2000/3000 pQCT scanners as reflected in our evaluation of acquisition and analysis protocols. Overall congruence with the ISCD Official Positions was poor. Only 11% (n = 6) studies met quality reporting criteria for image acquisition and 32% (n = 19) reported their data analysis in a format suitable for reproduction. Therefore, based on current literature synthesis, ISCD position statement standards and the authors' expertise, we propose acquisition and analysis protocols at the radius, tibia, and femur sites using Stratec XCT 2000/3000 pQCT scanners among patients with neurological impairment for clinical and research purposes in order to drive practice change, develop normative datasets and complete future meta-analysis to inform fracture risk and treatment efficacy evaluation.

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.

Bone loss at the distal femur and proximal tibia in persons with spinal cord injury: imaging approaches, risk of fracture, and potential treatment options

Persons with spinal cord injury (SCI) undergo immediate unloading of the skeleton and, as a result, have severe bone loss below the level of lesion associated with increased risk of long-bone fractures. The pattern of bone loss in individuals with SCI differs from other forms of secondary osteoporosis because the skeleton above the level of lesion remains unaffected, while marked bone loss occurs in the regions of neurological impairment. Striking demineralization of the trabecular epiphyses of the distal femur (supracondylar) and proximal tibia occurs, with the knee region being highly vulnerable to fracture because many accidents occur while sitting in a wheelchair, making the knee region the first point of contact to any applied force. To quantify bone mineral density (BMD) at the knee, dual energy x-ray absorptiometry (DXA) and/or computed tomography (CT) bone densitometry are routinely employed in the clinical and research settings. A detailed review of imaging methods to acquire and quantify BMD at the distal femur and proximal tibia has not been performed to date but, if available, would serve as a reference for clinicians and researchers. This article will discuss the risk of fracture at the knee in persons with SCI, imaging methods to acquire and quantify BMD at the distal femur and proximal tibia, and treatment options available for prophylaxis against or reversal of osteoporosis in individuals with SCI.

Effects of Treatment of Treadmill Combined with Electro-Acupuncture on Tibia Bone Mass and Substance PExpression of Rabbits with Sciatic Nerve Injury

The peripheral nervous system may play an important role in normal bone maintenance and remodeling. Substance P (SP) is a neuropeptide associated with bone loss and formation that may mediate the effects of the nervous system. The purpose of this study is to determine if treadmill running combined with electro-acupuncture at Jiaji acupoints (Jiaji-EA) affects tibial bone mass and SP expression in rabbits with sciatic nerve injury. Twenty-four juvenile male New Zealand white rabbits were randomly assigned to one of 4 groups: sham injury control (sham), sciatic never crush control (SNCr), treadmill running (treadmill), and Jiaji-EA combined with treadmill running (ET group). The SNCr, treadmill, and ET groups all had an induced sciatic never crush injury of approximately 2mm. Control groups received no intervention; the treadmill and ET groups were trained by treadmill; the ET group also received Jiaji-EA. After the 4 weeks of treatment, toe-spreading index (TSI), BMD, bone strength, and SP expression in the tibia were significantly lower in the nerve injury groups (SNCr, treadmill, and ET) compared to the sham groups (p<0.05). Treatment (treadmill and ET groups) increased all measures compared to the SNCr group (p<0.05). Further, TSI, BMD, bone strength, and SP expression in the ET group were higher than the treadmill group (p<0.05). Our results indicate that treadmill therapy combined with electro-acupuncture at Jiaji acupoints prevents bone loss in rabbit tibias after sciatic nerve injury. This may occur in two ways: indirectly in association with axon regeneration and directly via loading on the bone mediated through increased SP expression. This study provides important evidence for the clinical treatment of bone loss after peripheral nerve injury.

Measuring muscle and bone in individuals with neurologic impairment; lessons learned about participant selection and pQCT scan acquisition and analysis

Peripheral quantitative computed tomography (pQCT) can be used to examine bone strength outcomes and muscle size and fatty infiltration. Our research team and others have used it to examine bone loss after spinal cord injury (SCI). However, the high prevalence of restricted lower extremity range of motion, spasticity, edema, excessive muscle atrophy, or severe osteoporosis necessitates changes to standard protocols for screening, positioning during scan acquisition, and analysis methods. This manuscript outlines the challenges that we experienced using pQCT in individuals with SCI, and provides solutions, ones that may also be applicable when using pQCT in individuals with other chronic conditions or in older adults. Suggestions for participant screening, positioning individuals for scanning while in a wheelchair, scan site selection, need for attendant assistance, and considerations in the presence of secondary complications, such as contracture, spasticity, and paralysis, are presented. In the presence of very low bone mineral density or severe muscle atrophy, the default analysis modes provided by the manufacturer may not provide valid estimates of bone or muscle indices; we propose alternates. We have used watershed segmentation methods to determine muscle size and density based on lower precision error compared to threshold-based edge-detection segmentation, particularly for adults with SCI, where more fatty infiltration was present. By presenting our "lessons learned," we hope to reduce the learning curve for researchers using pQCT in the future.

Muscle Density and Bone Quality of the Distal Lower Extremity Among Individuals with Chronic Spinal Cord Injury

BACKGROUND

Understanding the related fates of muscle density and bone quality after chronic spinal cord injury (SCI) is an important initial step in determining endocrine-metabolic risk.

OBJECTIVE

To examine the associations between muscle density and indices of bone quality at the distal lower extremity of adults with chronic SCI.

METHODS

A secondary data analysis was conducted in 70 adults with chronic SCI (C2-T12; American Spinal Injury Association Impairment Scale [AIS] A-D; ≥2 years post injury). Muscle density and cross-sectional area (CSA) and bone quality indices (trabecular bone mineral density [TbBMD] at the distal tibia [4% site] and cortical thickness [CtTh], cortical area [CtAr], cortical BMD [CtBMD], and polar moment of inertia [PMI] at the tibial shaft [66% site]) were measured using peripheral quantitative computed tomography. Calf lower extremity motor score (cLEMS) was used as a clinical measure of muscle function. Multivariable linear regression analyses were performed to determine the strength of the muscle-bone associations after adjusting for confounding variables (sex, impairment severity [AIS A/B vs AIS C/D], duration of injury, and wheelchair use).

RESULTS

Muscle density was positively associated with TbBMD (b = 0.85 [0.04, 1.66]), CtTh (b = 0.02 [0.001, 0.034]), and CtBMD (b = 1.70 [0.71, 2.69]) (P < .05). Muscle CSA was most strongly associated with CtAr (b = 2.50 [0.12, 4.88]) and PMI (b = 731.8 [161.7, 1301.9]) (P < .05), whereas cLEMS was most strongly associated with TbBMD (b = 7.69 [4.63, 10.76]) (P < .001).

CONCLUSIONS

Muscle density and function were most strongly associated with TbBMD at the distal tibia in adults with chronic SCI, whereas muscle size was most strongly associated with bone size and geometry at the tibial shaft.

A comprehensive study of long-term skeletal changes after spinal cord injury in adult rats

Spinal cord injury (SCI)-induced bone loss represents the most severe osteoporosis with no effective treatment. Past animal studies have focused primarily on long bones at the acute stage using adolescent rodents. To mimic chronic SCI in human patients, we performed a comprehensive analysis of long-term structural and mechanical changes in axial and appendicular bones in adult rats after SCI. In this experiment, 4-month-old Fischer 344 male rats received a clinically relevant T13 contusion injury. Sixteen weeks later, sublesional femurs, tibiae, and L4 vertebrae, supralesional humeri, and blood were collected from these rats and additional non-surgery rats for micro-computed tomography (µCT), micro-finite element, histology, and serum biochemical analyses. At trabecular sites, extreme losses of bone structure and mechanical competence were detected in the metaphysis of sublesional long bones after SCI, while the subchondral part of the same bones showed much milder damage. Marked reductions in bone mass and strength were also observed in sublesional L4 vertebrae but not in supralesional humeri. At cortical sites, SCI induced structural and strength damage in both sub- and supralesional long bones. These changes were accompanied by diminished osteoblast number and activity and increased osteoclast number and activity. Taken together, our study revealed site-specific effects of SCI on bone and demonstrated sustained inhibition of bone formation and elevation of bone resorption at the chronic stage of SCI.

Individual selection of gait retraining strategies is essential to optimally reduce medial knee load during gait

BACKGROUND

The progression of medial knee osteoarthritis seems closely related to a high external knee adduction moment, which could be reduced through gait retraining. We aimed to determine the retraining strategy that reduces this knee moment most effective during gait, and to determine if the same strategy is the most effective for everyone.

METHODS

Thirty-seven healthy participants underwent 3D gait analysis. After normal walking was recorded, participants received verbal instructions on four gait strategies (Trunk Lean, Medial Thrust, Reduced Vertical Acceleration, Toe Out). Knee adduction moment and strategy-specific kinematics were calculated for all conditions.

FINDINGS

The overall knee adduction moment peak was reduced by Medial Thrust (-0.08Nm/Bw·Ht) and Trunk Lean (-0.07Nm/Bw·Ht), while impulse was reduced by 0.03Nms/Bw·Ht in both conditions. Toeing out reduced late stance peak and impulse significantly but overall peak was not affected. Reducing vertical acceleration at initial contact did not reduce the overall peak. Strategy-specific kinematics (trunk lean angle, knee adduction angle, first peak of the vertical ground reaction force, foot progression angle) showed that multiple parameters were affected by all conditions. Medial Thrust was the most effective strategy in 43% of the participants, while Trunk Lean reduced external knee adduction moment most in 49%. With similar kinematics, the reduction of the knee adduction moment peak and impulse was significantly different between these groups.

INTERPRETATION

Although Trunk Lean and Medial Thrust reduced the external knee adduction moment overall, individual selection of gait retraining strategy seems vital to optimally reduce dynamic knee load during gait.

Bone Mineral Density and Biochemical Markers of Bone Turnover during the First Year of Injury in Patients with Spinal Cord Injury

Background

Spinal cord injury (SCI) is associated with bone mass loss that can be complicated by fractures, which result in further disabilities for patients. After a SCI, the body starts losing large amounts of calcium and other minerals in the urine (demineralisation). This study aimed to assess the changes in bone mineral density (BMD) during the 1st year of acute SCI in patients with neurological deficit.

Methods

A total of 95 patients with acute SCI and neurological deficit were evaluated in this prospective study. Haematological investigations such as evaluation of serum calcium, serum phosphate, serum creatinine, and serum alkaline phosphatase (ALP) were carried out. Urinary investigations such as 24-hour urinary creatinine level and excretion of calcium and phosphate in the urine were measured. BMD was measured using dual-energy X-ray absorptiometry scan with Hologic QDR 2000 scanner (Explorer). All of the aforementioned parameters were measured again at 3, 6, and 12 months.

Results

Serum ALP at 1-year follow up was significantly raised (p < 0.05). The BMD at 1-year follow up had statistically significant lower values than the initial BMD at the hip (p < 0.05), proximal tibia (p < 0.00l), and distal tibial epiphysis (p < 0.001). The BMD in motor-complete SCI patients [American Spinal Injury Association (ASIA) grades A and B] had significant lower values than motor-incomplete SCI patients (ASIA C and D) at the hip (p < 0.05) and proximal tibial epiphysis (p < 0.05).

Conclusion

There was a marked decrease in BMD in metaphyseal sites than below the neurological deficit level with maximum decrease at the proximal tibia during the 1st year of SCI. Although the markers of osteoblastic activity did not show much change, the decrease in BMD was influenced by the neurological recovery after SCI.

Prediction of risk of fracture in the tibia due to altered bone mineral density distribution resulting from disuse: a finite element study

The disuse-related bone loss that results from immobilisation following injury shares characteristics with osteoporosis in post-menopausal women and the aged, with decreases in bone mineral density leading to weakening of the bone and increased risk of fracture. The aim of this study was to use the finite element method to: (i) calculate the mechanical response of the tibia under mechanical load and (ii) estimate of the risk of fracture; comparing between two groups, an able-bodied group and spinal cord injury patients group suffering from varying degrees of bone loss. The tibiae of eight male subjects with chronic spinal cord injury and those of four able-bodied age-matched controls were scanned using multi-slice peripheral quantitative computed tomography. Images were used to develop full three-dimensional models of the tibiae in Mimics (Materialise) and exported into Abaqus (Simulia) for calculation of stress distribution and fracture risk in response to specified loading conditions - compression, bending and torsion. The percentage of elements that exceeded a calculated value of the ultimate stress provided an estimate of the risk of fracture for each subject, which differed between spinal cord injury subjects and their controls. The differences in bone mineral density distribution along the tibia in different subjects resulted in different regions of the bone being at high risk of fracture under set loading conditions, illustrating the benefit of creating individual material distribution models. A predictive tool can be developed based on these models, to enable clinicians to estimate the amount of loading that can be safely allowed onto the skeletal frame of individual patients who suffer from extensive musculoskeletal degeneration (including spinal cord injury, multiple sclerosis and the ageing population). The ultimate aim is to reduce fracture occurrence in these vulnerable groups.

Measuring apparent trabecular density and bone structure using peripheral quantitative computed tomography at the tibia: precision in participants with and without spinal cord injury

The objective of the study was to investigate the precision of standard outcomes obtained using peripheral quantitative computed tomography as well as apparent trabecular structure measures in adults with and without spinal cord injury (SCI). Twelve individuals with SCI, mean (standard deviation [SD]) 20 (13)yrs postinjury and mean (SD) age 44 (9)yrs, and 21 individuals without SCI (mean [SD] age: 27 [5]yrs) participated. Repeat scans of tibia epiphysis (4%) and shaft (66%) were performed using a Stratec XCT-2000 (Stratec Medizintechnik, Pforzheim, Germany). Bone mineral density and geometry variables (e.g., cortical thickness, bone area, polar moment of inertia) were derived with manufacturer's software. The following apparent trabecular structure variables were determined using custom software: average trabecular thickness (TrTh) (mm), trabecular spacing (TrSp) (mm), and trabecular number (TrN) (1/mm); average hole size (HA) and maximum hole size (HM) (mm(2)); connectivity index (CI); cortical thickness (CTh) (mm); bone volume to total volume (BVTV) ratio. Root mean square standard deviation and root mean square coefficient of variation (RMSCV; root mean square coefficient of variation percent [RMSCV%]) were calculated. The RMSCV% for all standard bone mineral density and geometry variables was ≤2% except for total area (4% site), where precision was 3.8%. RMSCV% for bone structure variables were as follows: CTh 5.1, TrTh 1.7, TrN 1.9, TrSp 2.6, HA 9.5, HM 20.1, CI 5.1, and BVTV 1.4. Precision for bone density and geometry was excellent across a range of bone mineral densities. RMSCVs for some apparent trabecular structure variables were comparable to that of standard variables. The RMSCV for others may necessitate larger studies to detect between-group differences.

Spinal cord injury-induced osteoporosis: pathogenesis and emerging therapies

Spinal cord injury causes rapid, severe osteoporosis with increased fracture risk. Mechanical unloading after paralysis results in increased osteocyte expression of sclerostin, suppressed bone formation, and indirect stimulation of bone resorption. At this time, there are no clinical guidelines to prevent bone loss after SCI, and fractures are common. More research is required to define the pathophysiology and epidemiology of SCI-induced osteoporosis. This review summarizes emerging therapeutics including anti-sclerostin antibodies, mechanical loading of the lower extremity with electrical stimulation, and mechanical stimulation via vibration therapy.

Densidade mineral óssea de pessoas com lesão medular após seis meses de treino locomotor com suporte parcial de peso

INTRODUÇÃO: O treino locomotor com suporte parcial de peso (TLSP) pode ser aplicado na reabilitação de pessoas com lesão medular e proporcionar melhoras funcionais, da função cardiovascular e auxiliar na prevenção e tratamento da osteopenia e osteoporose, que são importantes complicações secundárias à LM. OBJETIVOS: Este estudo teve como objetivo determinar e comparar a densidade mineral óssea (DMO) antes e após seis meses de TLSP em sujeitos com LM incompleta. MÉTODO: A amostra foi composta por oito voluntários, com LM com classificações (ASIA) A, B e D. O grupo foi submetido a sessões de treinos, três vezes por semana, com duração de 15 minutos, a uma velocidade de 1,5 km/h. A descarga de peso sobre membros inferiores era aumentada em 5% do peso corporal a cada duas semanas, passando de 20% até 65% do peso corporal, desde o início até o fim do período. Foram realizados exames de densitometria óssea antes do início e logo após o encerramento do programa de treinamento. RESULTADOS: Houve aumento na DMO média do fêmur total que, apesar de pequeno (0,05 g/cm²), foi significativo (p = 0,034). Nas demais regiões (colo do fêmur e trocânter) não houve alteração significativa. CONCLUSÃO: O TLSP pode ter auxiliado na manutenção da DMO nas regiões do colo do fêmur e trocânter.

Predicting patient-specific rates of bone loss at fracture-prone sites after spinal cord injury

PURPOSE

People with spinal cord injury (SCI) experience bone loss and have an elevated rate of fracture in the paralysed limbs. The literature suggests an exponential time course of bone loss after SCI, but true rates may vary between patients. We propose systematic evaluation of bone status in the early stages of SCI to identify fast bone losers.

METHOD

A case series of six patients with complete SCI were scanned using peripheral quantitative computed tomography within 5 weeks and at 4, 8 and 12 months post-injury. Bone mineral density (BMD) and bone mineral content (BMC) were measured at fracture-prone sites in the tibia and femur. Patient-specific-predictions (PSP) of expected rates of bone loss were produced by individualising published model equations according to each patient's measured values at baseline. Wilcoxon Signed-Rank tests were used to identify changes between time-points; chi-squared tests for differences between measured and PSP values.

RESULTS

In the lower limbs, mean values decreased significantly between baseline and 8 months post-injury, by 19-31% for trabecular BMD, 21-32% for total BMD, and 9-29% for BMC. Most subjects showed no significant differences between PSP and measured values, but individuals with significantly faster rates of bone loss than predicted should be investigated further.

CONCLUSIONS

There was considerable intersubject variability in rates of bone loss after SCI. Patients showing the fastest bone loss could benefit from continued follow-up and possibly treatment.

Bone loss following spinal cord injury in a rat model

The current study was undertaken to follow the time course of bone loss in the proximal tibia of rats over several weeks following thoracic contusion spinal cord injury (SCI) of varying severity. It was hypothesized that bone loss would be more pronounced in the more severely injured animals, and that hindlimb weight bearing would help prevent bone loss. Twenty-six female Sprague-Dawley rats (200-225 g, 6-7 weeks old) received standard thoracic (T9) injuries at energies of 6.25, 12.5, 25, or 50 g-cm. The rats were scored weekly for hindlimb function during locomotion. At 0, 2 or 3, and 8 weeks, high-resolution micro-CT images of each right tibia were obtained. Mechanical indentation testing was done to measure the compressive strength of the cancellous bone structure. The 6.25 g-cm group showed near normal locomotion, the 12.5 and 25 g-cm groups showed the ability to frequently or occasionally generate weight-supported plantar steps, respectively, and the 50 g-cm group showed only movement without weight-supported plantar stepping. The 6.25, 12.5 and 25 g-cm groups remained at the same level of bone volume fraction (cancBV/TV=0.24±0.07), while the 50 g-cm group experienced severe bone loss (67%), resulting in significantly lower (p<0.05) bone volume fraction (cancBV/TV=0.11±0.05) at 8 weeks. Proximal tibia cancellous bone strength was reduced by approximately 50% in these severely injured rats. Instead of a linear proportionality between injury severity and bone loss, there appears to be a distinct functional threshold, marked by occasional weight-supported stepping, above which bone loss does not occur.

The changing landscape of spinal cord injury

In the past quarter century, spinal cord injury medicine has welcomed the proliferation of new medications and technologies that improve the survival and quality of life for people with spinal cord injury, but also endured the failure of strategies we hoped would salvage the cord in the acute phase. Surgical decompression and spinal stabilization should be pursued whenever indicated and feasible; however, there is no compelling evidence that early decompression facilitates neurological improvement. Methylprednisolone, the subject of over two decades of trials, has proven to be of marginal benefit in improving functional outcome. Recent advances in the management of the respiratory, cardiovascular, autonomic, endocrine, skeletal and integumentary systems have not only changed morbidity and survival of spinal cord injury patients but also improved quality of life. Progress has been made in the early diagnosis and effective treatment of cardiac arrhythmias, neurogenic shock, autonomic dysreflexia and orthostatic hypotension. Aggressive respiratory care for high cervical level of injury patients should include an option for phrenic nerve pacing as it is a viable rehabilitative strategy for appropriately selected patients. Pressure ulcers remain a significant psychological, financial, and functional burden for many people with SCI and for healthcare providers. This area will continue to require further work on early prevention and education. Despite extensive scientific and clinical data on neurogenic osteoporosis, there is no consensus regarding the best pharmacotherapeutic agents, dosing regimens, or rehabilitative strategies for prevention and treatment of bone loss. This chapter will focus on the advances.

An evidence-based review of aging of the body systems following spinal cord injury

STUDY DESIGN

Systematic review.

OBJECTIVE

To systematically review evidence on aging of the body systems after spinal cord injury (SCI).

SETTING

Toronto, Ontario and Vancouver, British Columbia, Canada.

METHODS

Electronic databases (MEDLINE/PubMed, CINAHL, EMBASE and PsycINFO), were searched for studies published between 1980 and 2009. The search was augmented by reviewing the reference lists of relevant papers. Non-intervention studies that were longitudinal or cross-sectional with able-bodied controls that were at minimum matched on chronological age were included for review. Levels of evidence were assigned to the study design using a modified Sackett scale.

RESULTS

Of the 74 studies selected for inclusion, 16 were longitudinal in design. The hypothesis that SCI represents a model for premature aging is supported by a large proportion of level 5 evidence for the cardiovascular and endocrine systems, level 2, 4 and 5 evidence for the musculoskeletal system, and limited level 5 evidence for the immune system. Only a few level 4 and 5 studies for the respiratory system were found. The evidence on the genitourinary system, gastrointestinal system, and for skin and subcutaneous tissues provide level 4 and 5 evidence that premature aging may not be occurring. The evidence on the nervous system does not provide evidence of premature aging as a result of SCI.

CONCLUSIONS

Premature aging appears to occur in some systems after SCI. Additional longitudinal studies are required to confirm these findings.

Response to functional electrical stimulation cycling in women with spinal cord injuries using dual-energy X-ray absorptiometry and peripheral quantitative computed tomography: a case series

BACKGROUND

Loss of bone mass is common after spinal cord injury (SCI). One rehabilitation modality that has shown some promise for maintaining bone health is the functional electrical stimulation (FES) cycle ergometer. Although there has been some research investigating bone health and FES cycle ergometry, few have provided a detailed description of the changes that can occur in bone mass and soft-tissue mass.

OBJECTIVE

To use 2 types of bone imaging, peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA), to provide a detailed description of bone and soft-tissue response to FES cycle ergometry training in women with SCI.

STUDY DESIGN

Case series; a 6-month program of FES cycle ergometry for women with chronic motor complete (n = 2) and incomplete (n = 1) SCI.

SETTING

Outpatient rehabilitation center in Canada.

METHODS

Three women participated in a thrice weekly 6-month exercise program of FES cycle ergometry. We used DXA (lower extremity) and pQCT at the midshaft (50%) and distal (5%) sites of the tibia to assess bone density and soft-tissue mass before and after the exercise program.

RESULTS

There was an increase or maintenance in bone mineral density by DXA and pQCT in the lower extremity for all 3 participants. Muscle mass by DXA increased in the lower extremity in 2 participants.

CONCLUSION

In this case series, we note a positive response in bone mass and soft-tissue mass in the lower extremity after a 6-month FES cycle ergometry program.

VA-based survey of osteoporosis management in spinal cord injury

OBJECTIVE

Although osteoporosis is common following spinal cord injury (SCI), no guidelines exist for its treatment, diagnosis, or prevention. The authors hypothesized that wide variations in diagnosis and treatment practices result from the absence of guidelines. This study sought to characterize the diagnosis and management practices within the VA health care system for osteoporosis following SCI.

DESIGN

Online survey regarding osteoporosis management in SCI composed of 27 questions designed to gather information on responder demographics, osteoporosis diagnostics, and treatment options.

SETTING

VA health care system.

PARTICIPANTS

VHA National SCI Staff Physicians and VHA National SCI Nurses (total n = 450) were sent an email with an invitation to participate.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

Practice patterns were assessed, including factors associated with ordering a clinical workup and prescribing osteoporosis treatment.

RESULTS

The response rate was 28%. Ninety-two prescribing practitioners (physicians, nurse practitioners, and physician assistants) were included in the analysis. Of these respondents, 50 (54%) prescribe medications for SCI-induced bone loss; 39 (42%) prescribe bisphosphonates and 46 (50%) prescribe vitamin D. There were 54 (59%) respondents who routinely order diagnostic tests, including dual energy x-ray absorptiometry scans in 50 (54%). Variations in practice were not explained by age, gender, or years practicing SCI medicine. Many respondents (23%) reported barriers to osteoporosis testing including lack of scanning protocols, cost, wheelchair inaccessibility of scanning facilities, and lack of effective treatment guidelines once osteoporosis is diagnosed.

CONCLUSIONS

Despite an absence of screening and treatment guidelines, more than half of all respondents are actively diagnosing and treating osteoporosis with bisphosphonates within the VA health care setting. These data suggest that evidence-based practice guidelines are necessary to reduce practice variations and improve clinical care for this population.

VA-based survey of osteoporosis management in spinal cord injury

OBJECTIVE

Although osteoporosis is common following spinal cord injury (SCI), no guidelines exist for its treatment, diagnosis, or prevention. The authors hypothesized that wide variations in diagnosis and treatment practices result from the absence of guidelines. This study sought to characterize the diagnosis and management practices within the VA health care system for osteoporosis following SCI.

DESIGN

Online survey regarding osteoporosis management in SCI composed of 27 questions designed to gather information on responder demographics, osteoporosis diagnostics, and treatment options.

SETTING

VA health care system.

PARTICIPANTS

VHA National SCI Staff Physicians and VHA National SCI Nurses (total n = 450) were sent an email with an invitation to participate.

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

Practice patterns were assessed, including factors associated with ordering a clinical workup and prescribing osteoporosis treatment.

RESULTS

The response rate was 28%. Ninety-two prescribing practitioners (physicians, nurse practitioners, and physician assistants) were included in the analysis. Of these respondents, 50 (54%) prescribe medications for SCI-induced bone loss; 39 (42%) prescribe bisphosphonates and 46 (50%) prescribe vitamin D. There were 54 (59%) respondents who routinely order diagnostic tests, including dual energy x-ray absorptiometry scans in 50 (54%). Variations in practice were not explained by age, gender, or years practicing SCI medicine. Many respondents (23%) reported barriers to osteoporosis testing including lack of scanning protocols, cost, wheelchair inaccessibility of scanning facilities, and lack of effective treatment guidelines once osteoporosis is diagnosed.

CONCLUSIONS

Despite an absence of screening and treatment guidelines, more than half of all respondents are actively diagnosing and treating osteoporosis with bisphosphonates within the VA health care setting. These data suggest that evidence-based practice guidelines are necessary to reduce practice variations and improve clinical care for this population.

Mammalian hibernation as a model of disuse osteoporosis: the effects of physical inactivity on bone metabolism, structure, and strength

Reduced skeletal loading typically leads to bone loss because bone formation and bone resorption become unbalanced. Hibernation is a natural model of musculoskeletal disuse because hibernating animals greatly reduce weight-bearing activity, and therefore, they would be expected to lose bone. Some evidence suggests that small mammals like ground squirrels, bats, and hamsters do lose bone during hibernation, but the mechanism of bone loss is unclear. In contrast, hibernating bears maintain balanced bone remodeling and preserve bone structure and strength. Differences in the skeletal responses of bears and smaller mammals to hibernation may be due to differences in their hibernation patterns; smaller mammals may excrete calcium liberated from bone during periodic arousals throughout hibernation, leading to progressive bone loss over time, whereas bears may have evolved more sophisticated physiological processes to recycle calcium, prevent hypercalcemia, and maintain bone integrity. Investigating the roles of neural and hormonal control of bear bone metabolism could give valuable insight into translating the mechanisms that prevent disuse-induced bone loss in bears into novel therapies for treating osteoporosis.

Bone steady-state is established at reduced bone strength after spinal cord injury: a longitudinal study using peripheral quantitative computed tomography (pQCT)

Spinal cord injury (SCI) is associated with a marked and rapid sublesional bone loss. So far, reports about the time course of adaptive changes in bone mass and structure in people with chronic and complete SCI are conflicting. Both, a continuous decline of bone parameters throughout the chronic phase of immobilisation as well as stabilisation of bone status on a low level have been documented. In our recently published cross-sectional study we suggested that subjects with a complete SCI reach a new bone steady-state in the paralysed limbs after extensive bone loss was complete. In addition, we described a time loss curve for each measured bone mineral density and geometry parameter and calculated its individual time to reach steady-state (tsteady-state). The aim of the present study was to test the findings of our cross-sectional study in a longitudinal design. Thirty-nine male subjects of the original cross-sectional study with complete SCI and paralysis duration between 0.9 and 34 years were included. Two follow-up pQCT measurements at 15 and 30 months after baseline measurement were performed at the distal epiphyses and mid shafts of the femur, tibia and radius. From the epiphyseal scans, bone mass, trabecular and total BMD were calculated. From the shaft scans, bone mass and cortical BMD, total and cortical cross-sectional areas and cortical thickness were determined. Repeated measures ANOVAs were performed with bone data at baseline, after 15 months and 30 months. Analyses were performed including only subjects with a lesion duration > or =t(steady-state) for each particular bone parameter. Bone parameters of tibial and femoral epi- and diaphyses were found to show no statistically significant differences between the three time points. Relative changes in bone parameters were small and ranged from -1.72% to +0.51% in the femur and from -1.67% to +0.42% in the tibia within 30 months of monitoring. Our data confirm the temporal limitation of the bone loss after complete SCI with stabilisation of BMD and geometric properties on a lower level-a finding of clinical importance considering the treatment strategies of bone loss after SCI with respect to lesion duration.

High-volume FES-cycling partially reverses bone loss in people with chronic spinal cord injury

Spinal cord injury (SCI) leads to severe bone loss in the paralysed limbs and to a resulting increased fracture risk thereof. Since long bone fractures can lead to comorbidities and a reduction in quality of life, it is important to improve bone strength in people with chronic SCI. In this prospective longitudinal cohort study, we investigated whether functional electrical stimulation (FES) induced high-volume cycle training can partially reverse the loss of bone substance in the legs after chronic complete SCI. Eleven participants with motor-sensory complete SCI (mean age 41.9+/-7.5 years; 11.0+/-7.1 years post injury) were recruited. After an initial phase of 14+/-7 weeks of FES muscle conditioning, participants performed on average 3.7+/-0.6 FES-cycling sessions per week, of 58+/-5 min each, over 12 months at each individual's highest power output. Bone and muscle parameters were investigated in the legs by means of peripheral quantitative computed tomography before the muscle conditioning (t1), and after six (t2) and 12 months (t3) of high-volume FES-cycle training. After 12 months of FES-cycling, trabecular and total bone mineral density (BMD) as well as total cross-sectional area in the distal femoral epiphysis increased significantly by 14.4+/-21.1%, 7.0+/-10.8% and 1.2+/-1.5%, respectively. Bone parameters in the femoral shaft showed small but significant decreases, with a reduction of 0.4+/-0.4% in cortical BMD, 1.8+/-3.0% in bone mineral content, and 1.5+/-2.1% in cortical thickness. These decreases mainly occurred between t1 and t2. No significant changes were found in any of the measured bone parameters in the tibia. Muscle CSA at the thigh increased significantly by 35.5+/-18.3%, while fat CSA at the shank decreased by 16.7+/-12.3%. Our results indicate that high-volume FES-cycle training leads to site-specific skeletal changes in the paralysed limbs, with an increase in bone parameters at the actively loaded distal femur but not the passively loaded tibia. Thus, we conclude that high-volume FES-induced cycle training has clinical relevance as it can partially reverse bone loss and thus may reduce fracture risk at this fracture prone site.

Five-year longitudinal bone evaluations in individuals with chronic complete spinal cord injury

BACKGROUND/OBJECTIVES

Knowledge of spinal cord injury (SCI) bone changes has been derived primarily through cross-sectional studies, many of which are controvertible. Longitudinal studies are sparse, and long-term longitudinal chronic studies are unavailable. The objective of this study was to provide a clearer perception of chronic longitudinal bone variations in people with complete SCI.

METHODS

Bone status of 31 individuals with chronic, complete SCI was assessed twice using dual-energy xray absorptiometry at an average interval of 5.06 +/- 0.9 years. Because the sample of women was small (4), the primary analyses of change and comparisons of those with paraplegia vs tetraplegia were confined to the male participants.

RESULTS

Spine Z-scores showed a significant increase (P < 0.0001). The average Z-scores, initial and followup, were within the normal range. Hip Z-scores also showed a significant increase (P < 0.0001), and hip bone mineral density (BMD) increased in 48% of the participants. Knee BMD and lower extremity total bone mineral showed significant decreases (P < 0.003 and P < 0.02, respectively), but increases were seen in 33% and 26% at the respective sites. Individuals with tetraplegia had significantly lower values across all regions (P < 0.0001), and changes were significantly different compared with paraplegia (P < 0.0001). Bone values and changes in men vs women, despite the small sample of women, showed highly significant differences (P < 0.003-0.002).

CONCLUSION

Chronic effects of complete SCI do not exclusively result in continued loss of BMD or a static state of lowered BMD; gain in BMD may occur. The nature and magnitude of the effects of complete SCI on BMD vary by site, with sex and level of injury, which has implications for treatment and its assessment.

Does standing protect bone density in patients with chronic spinal cord injury?

BACKGROUND/OBJECTIVE

To compare the t-scores of proximal femur and lumbar spine of patients with spinal cord injury (SCI) with different levels of weight bearing.

METHODS

Cross-sectional study comparing 3 groups of patients with SCI: patients with daily standing times of more than 1 hour, patients with daily standing times of less than 1 hour, and nonstanding patients. Seventy-one patients with chronic SCI were recruited. They were assigned to 1 of 3 groups according to their reported daily standing time. The bone density of lumbar and proximal femoral regions was measured with dual-energy x-ray absorptiometry.

RESULTS

The 3 groups were similar in terms of demographics and clinical variables. No significant difference was found among the mean t-scores of lumbar and proximal femoral regions of the groups. However, the patients in the group that stood more than 1 hour daily had a slight tendency to have higher t-scores than those in the control group.

CONCLUSIONS

There was no significant difference among the 3 groups. However, standing might be partially helpful in protecting the bone density in SCI by opposing the effects of immobilization.

Neuromotor and musculoskeletal responses to locomotor training for an individual with chronic motor complete AIS-B spinal cord injury

BACKGROUND/OBJECTIVE

To determine the effects of locomotor training (LT) using body weight support (BWS), treadmill, and manual assistance on muscle activation, bone mineral density (BMD), and body composition changes for an individual with motor complete spinal cord injury (AIS B), 1 year after injury.

METHODS

A man with chronic C6 AIS B (motor complete and sensory incomplete) spinal cord injury (SCI), 1 year after injury, completed 2 blocks of LT over a 9-month training period (35-session block followed by 8.6 weeks of no training and then a 62-session block).

RESULTS

Before training, muscle activation was minimal for any muscle examined, whereas after the 2 blocks of LT (97 sessions), hip and knee muscle activation patterns for the bilateral rectus femoris, biceps femoris, and gastrocnemius were in phase with the kinematics. Mean EMG amplitude increased for all bilateral muscles and burst duration increased for rectus femoris and gastrocnemius muscles, whereas burst duration decreased for the biceps femoris after 62 LT sessions. Before LT, left biceps femoris had a pattern that reflected muscle stretch, whereas after training, muscle stretch of the left biceps femoris could not totally account for mean EMG amplitude or burst duration. After the 62 training sessions, total BMD decreased (1.54%), and regional BMD decreased (legs: 6.72%). Total weight increased, lean mass decreased (6.6%), and fat mass increased (7.4%) in the arms, whereas fat mass decreased (3.5%) and lean mass increased (4%) in the legs.

CONCLUSIONS

LT can induce positive neural and body composition changes in a nonambulatory person with chronic SCI, indicating that neuromuscular plasticity can be induced by repetitive locomotor training after a motor complete SCI.

Prevention and Treatment of Bone Loss after a Spinal Cord Injury: A Systematic Review

Preserving and maintaining bone mass after a spinal cord injury (SCI) is crucial to decrease the risk of fragility or low trauma fractures- significant health events that occur as a result of minimal trauma such as falling during transfers or from a standing height or less. There is an increased risk for low trauma fractures after a SCI especially in the lower extremity. Therefore, purpose of this systematic review was to appraise the literature to provide clinical guidance for the optimization of bone health after SCI. The key research questions focused on prevention of acute bone loss and effective treatment of established low bone mass with long-standing SCI (≥ 1year). We report moderate evidence for the treatment of bone loss using pharmacology; however, non-pharmacological evidence for preventing and treating bone loss is limited.

Treatment with zoledronic acid ameliorates negative geometric changes in the proximal femur following acute spinal cord injury

Acute spinal cord injury is associated with rapid bone loss and an increased risk of fracture. In this double-blind, randomized, placebo-controlled trial, 17 patients were followed for 1 year after administration of either 4 or 5 mg of zoledronic acid or placebo. Bone mineral density (BMD) and structural analyses of the proximal femur were performed using the hip structural analysis program at entry, 6 months, and 12 months. The 17 subjects completed 12 months of observation, nine receiving placebo and eight zoledronic acid. The placebo group showed a decrease in BMD, cross-sectional area, and section modulus and an increase in buckling ratio at each proximal femur site at 6 and 12 months. Six months after zoledronic acid, BMD, cross-sectional area, and section modulus increased at the femoral neck and intertrochanteric regions and buckling ratio decreased consistent with improved bone stability. However, at 12 months, the femoral narrow-neck values declined to baseline. In contrast to placebo, the intertrochanteric region and femur shaft were maintained at or near baseline through 12 months in the zoledronic acid-treated group. Urine N-telopeptide excretion was increased at baseline and declined in both the placebo and treatment groups during the 12 months of observation. We conclude that a single administration of zoledronic acid will ameliorate bone loss and maintain parameters of bone strength at the three proximal femur sites for 6 months and at the femur intertrochanteric and shaft sites for 12 months.

Bone mineral density of the hip and knee in children with spinal cord injury

BACKGROUND/OBJECTIVE

To report on the bone mineral density (BMD) of the hip, distal femur, and proximal tibia in children with spinal cord injury (SCI) of at least 1-year duration and before skeletal maturity.

METHODS

BMD values were measured in 28 children (age, 9.6 +/- 2.5 years; range, 5-13 years) using dual-energy x-ray absorptiometry (DEXA) and were analyzed based on sex, injury, and time since injury. The hip values were compared with reported age- and sex-matched values in children without disability. No comparison was made at the knee because normative data were not available.

RESULTS

Average BMD values were 0.48 +/- 0.17 g/cm2 for the total hip, 0.48 +/- 0.17 g/cm2 at the femoral neck, 0.41 +/- 0.17 g/cm2 at the greater trochanter, 0.47 +/- 0.17 g/cm2 at Ward's triangle, 0.38 +/- 0.10 g/ cm2 at the distal femur, and 0.37 +/- 0.07 g/cm2 at the proximal tibia. Trends were observed with respect to sex, level of injury, and time since injury. Z-scores for the femoral neck, greater trochanter, and Ward's triangle were -1.65 +/- 1.02, -1.83 +/- 1.30, and -1.78 +/- 0.78, respectively, representing a 40% lower BMD in comparison with children without disability.

CONCLUSIONS

Children with a SCI seem to have a substantially lower BMD at the hip and knee in comparison with children without disability, placing them at the same risk for lower extremity fractures as adults with SCI, with potentially higher risks as they age given the lack of activity in a period of their life where exercise is essential for optimal bone health.

Body weight supported treadmill training in acute spinal cord injury: impact on muscle and bone

DESIGN

Longitudinal prospective case series.

OBJECTIVE

To evaluate the impact of early introduction post-spinal cord injury (SCI) of twice-weekly body-weight supported treadmill training (BWSTT) on muscle and bone.

SETTING

Centre for Health Promotion and Rehabilitation, McMaster University, Canada.

METHODS

Five individuals who had sustained traumatic SCI within 2-6 months participated in the study. Bone mineral densities (BMD) of proximal femur, distal femur, proximal tibia and lumbar spine were measured before and after training, as well as muscle cross-sectional area (CSA), BMD and bone geometry at mid-femur and proximal tibia. Serum osteocalcin and urinary deoxypyridinoline were measured at baseline, and after 24 and 48 sessions of training.

RESULTS

All participants experienced increased muscle CSAs, ranging from 3.8 to 56.9%. Reductions in BMD were evident in all participants at almost all lower limb sites after training, ranging in magnitude from -1.2 to -26.7%. Lumbar spine BMD changes ranged from 0.2 to -7.4%. No consistent changes were observed in bone geometry. BWSTT did not alter the expected pattern of change in bone biochemical markers over time. The individual with the greatest improvement in ambulatory ability demonstrated the smallest reduction in lower limb BMD. Conversely, the individual who completed the fewest BWSTT sessions demonstrated the greatest reductions in BMD.

CONCLUSIONS

Twice-weekly BWSTT appeared to partially reverse muscle atrophy after SCI, but did not prevent bone loss. Larger, controlled trials should evaluate whether relative preservation of bone loss occurs with regular BWSTT following acute SCI.

SPONSORSHIP

Ontario Neurotrauma Foundation.

Osteoporosis after spinal cord injury

Osteoporosis is a known consequence of spinal cord injury (SCI) and occurs in almost every SCI patient. It manifests itself as an increase in the incidence of lower extremity fractures. The pattern of bone loss seen in SCI patients is different from that usually encountered with endocrine disorders and disuse osteoporosis. In general, there is no demineralization in supralesional areas following SCI. Several factors appear to have a major influence on bone mass in SCI individuals, such as the degree of the injury, muscle spasticity, age, sex and duration after injury. At the lumbar spine, bone demineralization remains relatively low compared to that of the long bones in the sublesional area. A new steady state level between bone resorption and formation is reestablished about 2 years after SCI. SCI may not only cause bone loss, but also alter bone structure and microstructure. Trabecular bone is more affected than cortical bone in the SCI population. Numerous clinical series have reported a high incidence ranging from 1 to 34% of lower extremity fractures in SCI patients. The pathogenesis of osteoporosis after SCI remains complex and perplexing. Disuse may play an important role in the pathogenesis of osteoporosis, but neural factors also appear to be important. SCI also leads to impaired calcium and phosphate metabolism and the parathyroid hormone (PTH)-vitamin D axis. Pharmacologic intervention for osteoporosis after SCI includes calcium, phosphate, vitamin D, calcitonin and biphosphonates. However, the concomitant prescription of bone-active drugs for the prevention and treatment of osteoporosis remains low, despite the availability of effective therapies. Functional stimulated exercises may contribute to the prevention of bone loss to some extent. In addition, many unanswered questions remain about the pathogenesis of osteoporosis and its clinical management.

Bone loss and muscle atrophy in spinal cord injury: epidemiology, fracture prediction, and rehabilitation strategies

Individuals with spinal cord injury (SCI) often experience bone loss and muscle atrophy. Muscle atrophy can result in reduced metabolic rate and increase the risk of metabolic disorders. Sublesional osteoporosis predisposes individuals with SCI to an increased risk of low-trauma fracture. Fractures in people with SCI have been reported during transfers from bed to chair, and while being turned in bed. The bone loss and muscle atrophy that occur after SCI are substantial and may be influenced by factors such as completeness of injury or time postinjury. A number of interventions, including standing, electrically stimulated cycling or resistance training, and walking exercises have been explored with the aim of reducing bone loss and/or increasing bone mass and muscle mass in individuals with SCI. Exercise with electrical stimulation appears to increase muscle mass and/or prevent atrophy, but studies investigating its effect on bone are conflicting. Several methodological limitations in exercise studies with individuals with SCI to date limit our ability to confirm the utility of exercise for improving skeletal status. The impact of standing or walking exercises on muscle and bone has not been well established. Future research should carefully consider the study design, skeletal measurement sites, and the measurement techniques used in order to facilitate sound conclusions.