A reliable method for measuring proximal tibia and distal femur bone mineral density using dual-energy X-ray absorptiometry

Preventing OsteoPorosis in Spinal Cord Injury (POPSCI) Study-Early Zoledronic Acid Infusion in Patients with Acute Spinal Cord Injury

Accelerated sub-lesional bone loss is common in the first 2-3 years after traumatic spinal cord injury (TSCI), particularly in the distal femur and proximal tibia. Few studies have explored efficacy of antiresorptives for acute bone loss prevention post-TSCI, with limited data for knee bone mineral density (BMD) or beyond two years follow-up. An open-label non-randomized study was performed at Royal North Shore Hospital and Royal Rehab Centre, Sydney between 2018 and 2023. An 'acute interventional cohort' (n = 11) with TSCI (duration ≤ 12-weeks) received a single infusion of 4 mg zoledronic acid (ZOL) at baseline. A 'chronic non-interventional cohort' (n = 9) with TSCI (duration 1-5-years) did not receive ZOL. All participants underwent baseline and 6-monthly blood tests (including CTx and P1NP) and 12-monthly DXA BMD scans (including distal femur and proximal tibia). Participants were predominantly Caucasian and male (mean age 38.4 years). At baseline, the 'acute' cohort had higher serum CTx, P1NP and sclerostin concentrations, while the 'chronic' cohort had lower left hip and knee BMD. Majority with acute TSCI experienced an acute phase reaction after ZOL (9/11; 82%). In the acute cohort, left hip BMD fell by mean ~ 15% by 48 months. Left distal femoral and proximal tibial BMD declined by mean ~ 6-13% at 12 months and ~ 20-23% at 48 months, with a tendency towards greater BMD loss in motor-complete TSCI. A single early ZOL infusion in acute TSCI could not attenuate rapidly declining hip and knee BMD. Prospective controlled studies are required to establish the optimal strategy for preventing early bone loss after acute TSCI.

Vitamin D status associates with skeletal muscle loss after anterior cruciate ligament reconstruction

BACKGROUNDAlthough 25-hydroxyvitamin D [25(OH)D] concentrations of 30 ng/mL or higher are known to reduce injury risk and boost strength, the influence on anterior cruciate ligament reconstruction (ACLR) outcomes remains unexamined. This study aimed to define the vitamin D signaling response to ACLR, assess the relationship between vitamin D status and muscle fiber cross-sectional area (CSA) and bone density outcomes, and discover vitamin D receptor (VDR) targets after ACLR.METHODSTwenty-one young, healthy, physically active participants with recent ACL tears were enrolled (17.8 ± 3.2 years, BMI 26.0 ± 3.5 kg/m2). Data were collected through blood samples, vastus lateralis biopsies, dual energy x-ray bone density measurements, and isokinetic dynamometer measures at baseline, 1 week, 4 months, and 6 months after ACLR. The biopsies facilitated CSA, Western blotting, RNA-seq, and VDR ChIP-seq analyses.RESULTSACLR surgery led to decreased circulating bioactive vitamin D and increased VDR and activating enzyme expression in skeletal muscle 1 week after ACLR. Participants with less than 30 ng/mL 25(OH)D levels (n = 13) displayed more significant quadriceps fiber CSA loss 1 week and 4 months after ACLR than those with 30 ng/mL or higher (n = 8; P < 0.01 for post hoc comparisons; P = 0.041 for time × vitamin D status interaction). RNA-seq and ChIP-seq data integration revealed genes associated with energy metabolism and skeletal muscle recovery, potentially mediating the impact of vitamin D status on ACLR recovery. No difference in bone mineral density losses between groups was observed.CONCLUSIONCorrecting vitamin D status prior to ACLR may aid in preserving skeletal muscle during recovery.FUNDINGNIH grants R01AR072061, R01AR071398-04S1, and K99AR081367.

GDF8 inhibition enhances musculoskeletal recovery and mitigates posttraumatic osteoarthritis following joint injury

Musculoskeletal disorders contribute substantially to worldwide disability. Anterior cruciate ligament (ACL) tears result in unresolved muscle weakness and posttraumatic osteoarthritis (PTOA). Growth differentiation factor 8 (GDF8) has been implicated in the pathogenesis of musculoskeletal degeneration following ACL injury. We investigated GDF8 levels in ACL-injured human skeletal muscle and serum and tested a humanized monoclonal GDF8 antibody against a placebo in a mouse model of PTOA (surgically induced ACL tear). In patients, muscle GDF8 was predictive of atrophy, weakness, and periarticular bone loss 6 months following surgical ACL reconstruction. In mice, GDF8 antibody administration substantially mitigated muscle atrophy, weakness, and fibrosis. GDF8 antibody treatment rescued the skeletal muscle and articular cartilage transcriptomic response to ACL injury and attenuated PTOA severity and deficits in periarticular bone microarchitecture. Furthermore, GDF8 genetic deletion neutralized musculoskeletal deficits in response to ACL injury. Our findings support an opportunity for rapid targeting of GDF8 to enhance functional musculoskeletal recovery and mitigate the severity of PTOA after injury.

Seated push-up tests: Reliable and valid measures for older individuals when used by primary healthcare providers

BACKGROUND

Body composition decline, lower limb impairments, and mobility deficits affect independence of older people. The exploration for a practical measure involving upper extremities may offer an alternative tool to be used by primary healthcare (PHC) providers for these individuals.

OBJECTIVE

To explore reliability and validity of seated push-up tests (SPUTs) among older participants when used by PHC providers.

METHODS

Older participants (n= 146) with an average age of > 70 years were cross-sectionally assessed using various demanding forms of SPUTs and standard measures to assess validity of the SPUTs. Reliability of the SPUTs were assessed in nine PHC raters, including an expert, health professionals, village health volunteers, and care givers.

RESULTS

The SPUTs demonstrated very good agreement, with excellent rater and test-retest reliability (kappa values > 0.87 and ICCs > 0.93, p< 0.001). Moreover, the SPUT outcomes significantly correlated with lean body mass, bone mineral contents, muscle strength and mobility of older participants (r, rp⁢b=-0.270 to 0.758, p< 0.05).

CONCLUSION

SPUTs are reliable and valid for older adults when used by PHC members. The incorporation of such practical measures is particularly important during this COVID-19 pandemic with limited people's hospital access.

Validity and feasibility of using a seated push-up test among community-dwelling older adults

BACKGROUND

Older individuals face a high risk of mobility and body composition decline, which can affect their independence. In light of a current uncertain healthcare situation created by the coronavirus (COVID-19) pandemic, healthcare paradigm has been shifted with increased demand for a practical measure to promote standard home healthcare services for all individuals, including older adults.

OBJECTIVE

This study explored the feasibility and validity of seated push-up tests (SPUTs) as clinical measures to reflect the body composition, muscle strength, and mobility among community-dwelling older individuals, aged ≥ 65 years (n = 82 ).

METHODS

Participants were cross-sectionally assessed using SPUTs with various demanding forms, including the 1-time SPUT (1SPUT) along with its upper limb loading SPUT (ULL-SPUT), 5-time SPUT (5SPUT), 10-time SPUT (10SPUT), and 1-min SPUT (1minSPUT) and standard measures.

RESULTS

Participants who passed and failed a 1SPUT showed significant differences in the outcomes of all standard measures (p < 0 . 05 ). The ULL-SPUT significantly correlated to all body composition, muscle strength, and mobility (r = 0 . 247 -0.785; p < 0 . 05 ). Outcomes of 1minSPUT significantly correlated with muscle strength and mobility outcomes (r = 0 . 306 -0.526; p < 0 . 05 ). Participants reported no adverse effects following the SPUTs.

CONCLUSION

The findings suggest the use of the 1SPUT, ULL-SPUT, and 1minSPUT as practical measures to reflect the body composition, muscle strength, and mobility of older individuals, according to their functional levels. The tests may especially clinically benefit those with lower limb limitations and those in settings with limited space and equipment.

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.

Assessment of body composition in spinal cord injury: A scoping review

The objective of this scoping review was to map the evidence on measurement properties of body composition tools to assess whole-body and regional fat and fat-free mass in adults with SCI, and to identify research gaps in order to set future research priorities. Electronic databases of PubMed, EMBASE and the Cochrane library were searched up to April 2020. Included studies employed assessments related to whole-body or regional fat and/or fat-free mass and provided data to quantify measurement properties that involved adults with SCI. All searches and data extractions were conducted by two independent reviewers. The scoping review was designed and conducted together with an expert panel (n = 8) that represented research, clinical, nutritional and lived SCI experience. The panel collaboratively determined the scope and design of the review and interpreted its findings. Additionally, the expert panel reached out to their professional networks to gain further stakeholder feedback via interactive practitioner surveys and workshops with people with SCI. The research gaps identified by the review, together with discussions among the expert panel including consideration of the survey and workshop feedback, informed the formulation of future research priorities. A total of 42 eligible articles were identified (1,011 males and 143 females). The only tool supported by studies showing both acceptable test-retest reliability and convergent validity was whole-body dual-energy x-ray absorptiometry (DXA). The survey/workshop participants considered the measurement burden of DXA acceptable as long as it was reliable, valid and would do no harm (e.g. radiation, skin damage). Practitioners considered cost and accessibility of DXA major barriers in applied settings. The survey/workshop participants expressed a preference towards simple tools if they could be confident in their reliability and validity. This review suggests that future research should prioritize reliability and validity studies on: (1) DXA as a surrogate 'gold standard' tool to assess whole-body composition, regional fat and fat-free mass; and (2) skinfold thickness and waist circumference as practical low-cost tools to assess regional fat mass in persons with SCI, and (3) females to explore potential sex differences of body composition assessment tools. Registration review protocol: CRD42018090187 (PROSPERO).

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.

Effects of Traction on Interpretation of Lumbar Bone Mineral Density in Patients with Duchenne Muscular Dystrophy: A New Measurement Method and Diagnostic Criteria Based on Comparison of Dual-Energy X-Ray Absorptiometry and Quantitative Computed Tomography

INTRODUCTION

This study aimed to compare the performance of dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT) in evaluating bone mineral density (BMD) of patients with Duchenne muscular dystrophy and scoliosis.

METHODOLOGY

Twenty-nine participants (mean age 19.72 ± 6.13 years) underwent whole spine radiography, DXA before and after traction, and QCT alone without traction. Scoliosis and vertebral rotation angles obtained before and after traction were compared, and BMD values from DXA were compared to those obtained via QCT. The scoliosis angle, presented as Cobb's angle of L1-L4, was measured.

RESULTS

Cobb's angle significantly decreased from 30.38° ± 24.83° before traction to 22.78° ± 20.41° after traction (p < 0.0001) and the Z-score decreased from -1.88 ± 1.59 to -2.86 ± 2.16 (p < 0.0001). Changes in rotation angle, BMD, and bone mineral content were not significant. Post-traction BMD values and Z-scores showed a higher correlation with QCT measurements than pretraction. Moreover, pre and post-traction Z-scores (≤-1.1 and -1.36, respectively) were more accurate in identifying patients with osteoporosis according to QCT scans compared with the preexisting Z-score of -2 or less.

CONCLUSION

Lumbar BMD measured via DXA and scoliosis allowed a more accurate diagnosis of osteoporosis when traction was applied.

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.

Training with FES-assisted cycling in a subject with spinal cord injury: Psychological, physical and physiological considerations

CONTEXT

People with spinal cord injury (SCI) experience the effects of a sedentary lifestyle very early on. Literature data suggest that programs using FES-assisted cycling would contribute to reduce the consequences of physical inactivity. The objective was to assess the feasibility of 12-month training on a FES-assisted bike of a subject with paraplegia for 21 years, T3, Asia Impairment Scale (AIS) A. An evaluation of morbidity, self-esteem, satisfaction, quality of life and duration of pedaling was performed. The impact on pain, cardiorespiratory function, body composition and bone metabolism were also assessed.

FINDINGS

The acceptability score of the training constraints increased from 51 to 59/65 and satisfaction was high around 8/10. The pedaling duration increased from 1' to 26' on the recumbent bike and from 1' to 15' on open terrain. No significant changes were found with BMD and cardiorespiratory measures during exercise tests. SF 36 showed significant improvement of more than 10% and the Rosenberg Self Esteem score rapidly improved from 36 to 39/40. At the end of the training, the patient reached the objective of the Cybathlon 2016 by covering 750 m in less than 8 minutes, at an average speed of 5.80 km/hr.

CONCLUSION/CLINICAL RELEVANCE

A person with high and complete level of SCI for more than 20 years can undertake this type of challenge if the prerequisites are met; this training is without danger if the safety precautions are respected; the challenge of participating in a competition had a powerful impact on JP's self-esteem and perceived quality of life.

Reliability of analysis of the bone mineral density of the second and fifth metatarsals using dual-energy x-ray absorptiometry (DXA)

Background

Metatarsal fractures, especially of the fifth metatarsal, are common injuries of the foot in a young athletic population, but the risk factors for this injury are not well understood. Dual-energy x-ray absorptiometry (DXA) provides reliable measures of regional bone mineral density to predict fracture risk in the hip and lumbar spine. Recently, sub-regional metatarsal reliability was established in fresh cadaveric specimens and associated with ultimate fracture force. The purpose of this study was to assess the reliability of DXA bone mineral density measurements of sub-regions of the second and fifth metatarsals in a young, active population.

Methods

Thirty two recreationally active individuals participated in the study, and the bone density of the second (2MT) and fifth (5MT) metatarsals of each subject was measured using a Hologic QDR x-ray bone densitometer. Scans were analyzed separately by two raters, and regional bone mineral density, bone mineral content, and area measurements were calculated for the proximal, shaft, and distal regions of the bone. Intra-rater, inter-rater, and scan-rescan reliability were then determined for each region.

Results

Proximal and shaft bone mineral density measurements of the second and fifth metatarsal were reliable. ICC's were variable across regions and metatarsals, with the distal region being the poorest.

Conclusions

Bone mineral density measurements of the metatarsals may be a better indicator of fracture risk of the metatarsals than whole body measurements. A reliable method for measuring the regional bone mineral densities of the metatarsals was found. However, inter-rater reliability and scan-rescan reliability for the distal regions were poor. Future research should examine the relationship between DXA bone mineral density measurements and fracture risk at the metatarsals.

Dual-energy X-ray absorptiometry and fracture prediction in patients with spinal cord injuries and disorders

Low T-scores at the hip predict incident fractures in persons with a SCI.

INTRODUCTION

Persons with a spinal cord injury (SCI) have substantial morbidity and mortality following osteoporotic fractures. The objective of this study was to determine whether dual-energy X-ray absorptiometry (DXA) measurements predict osteoporotic fractures in this population.

METHODS

A retrospective historical analysis that includes patients (n = 552) with a SCI of at least 2 years duration who had a DXA performed and were in the VA Spinal Cord Disorders Registry from fiscal year (FY) 2002-2012 was performed.

RESULTS

The majority of persons (n = 455, 82%) had a diagnosis of osteoporosis or osteopenia, with almost half having osteoporosis. BMD and T-scores at the lumbar spine were not significantly associated with osteoporotic fractures (p > 0.48) for both. In multivariable analyses, osteopenia (OR = 4.75 95% CI 1.23-17.64) or osteoporosis (OR = 4.31, 95% CI 1.15-16.23) compared with normal BMD was significantly associated with fractures and higher T-scores at the hip were inversely associated with fractures (OR 0.73 (95% CI 0.57-0.92)). There was no significant association of T-scores or World Health Organization (WHO) classification with incident fractures in those with complete SCI (p > 0.15 for both).

CONCLUSION

The majority (over 80%) of individuals with a SCI have osteopenia or osteoporosis. DXA-derived measurements at the hip, but not the lumbar spine, predict fracture risk in persons with a SCI. WHO-derived bone density categories may be useful in classifying fracture risk in persons with a 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.

Precision of dual-energy X-ray absorptiometry of the knee and heel: methodology and implications for research to reduce bone mineral loss after spinal cord injury

STUDY DESIGN

Methodological validation of dual-energy x-ray absorptiometry (DXA)-based measures of leg bone mineral density (BMD) based on the guidelines of the International Society for Clinical Densitometry.

OBJECTIVES

The primary objective of this study was to determine the precision of BMD estimates at the knee and heel using the manufacturer provided DXA acquisition algorithm. The secondary objective was to determine the smallest change in DXA-based measurement of BMD that should be surpassed (least significant change (LSC)) before suggesting that a biological change has occurred in the distal femur, proximal tibia and calcaneus.

SETTING

Academic Research Centre, Canada.

METHODS

Ten people with motor-complete SCI of at least 2 years duration and 10 people from the general population volunteered to have four DXA-based measurements taken of their femur, tibia and calcaneus. BMDs for seven regions of interest (RIs) were calculated, as were short-term precision (root-mean-square (RMS) standard deviation (g cm^-2), RMS-coefficient of variation (RMS-CV, %)) and LSC.

RESULTS

Overall, RMS-CV values were similar between SCI (3.63-10.20%, mean=5.3%) and able-bodied (1.85-5.73%, mean=4%) cohorts, despite lower absolute BMD values at each RIs in those with SCI (35%, heel to 54%, knee; P<0.0001). Precision was highest at the calcaneus and lowest at the femur. Except at the femur, RMS-CV values were under 6%.

CONCLUSIONS

For DXA-based estimates of BMD at the distal femur, proximal tibia and calcaneus, these precision values suggest that LSC values >10% are needed to detect differences between treated and untreated groups in studies aimed at reducing bone mineral loss after SCI.

Measurement of Bone: Diagnosis of SCI-Induced Osteoporosis and Fracture Risk Prediction

BACKGROUND

Spinal cord injury (SCI) is associated with a rapid loss of bone mass, resulting in severe osteoporosis and a 5- to 23-fold increase in fracture risk. Despite the seriousness of fractures in SCI, there are multiple barriers to osteoporosis diagnosis and wide variations in treatment practices for SCI-induced osteoporosis.

METHODS

We review the biological and structural changes that are known to occur in bone after SCI in the context of promoting future research to prevent or reduce risk of fracture in this population. We also review the most commonly used methods for assessing bone after SCI and discuss the strengths, limitations, and clinical applications of each method.

CONCLUSIONS

Although dual-energy x-ray absorptiometry assessments of bone mineral density may be used clinically to detect changes in bone after SCI, 3-dimensional methods such as quantitative CT analysis are recommended for research applications and are explained in detail.

Bone Imaging and Fracture Risk after Spinal Cord Injury

Spinal cord injury (SCI) is characterized by marked bone loss and an increased risk of fracture with high complication rate. Recent research based on advanced imaging analysis, including quantitative computed tomography (QCT) and patient-specific finite element (FE) modeling, has provided new and important insights into the magnitude and temporal pattern of bone loss, as well as the associated changes to bone structure and strength, following SCI. This work has illustrated the importance of early therapeutic treatment to prevent bone loss after SCI and may someday serve as the basis for a clinical fracture risk assessment tool for the SCI population. This review provides an update on the epidemiology of fracture after SCI and discusses new findings and significant developments related to bone loss and fracture risk assessment in the SCI population based on QCT analysis and patient-specific FE modeling.

Cardiorespiratory Fitness and Hip Bone Mineral Density in Women: A 6-Year Prospective Study

Cross-sectional studies and short term interventions focusing on fitness and bone mineral density (BMD) are common. However, few investigations have studied the effect of fitness on BMD over an extended period of time. The present study was conducted to determine the extent to which cardiorespiratory fitness influences risk of BMD loss at the hip over 6 yr. A prospective cohort design was used with 245 healthy, middle-aged women. Hip BMD was assessed using dual energy x-ray absorptiometry. Calcium and vitamin D were measured using the Block Food Frequency Questionnaire. Menopause status was measured by a questionnaire. Results showed that fit and unfit women experienced similar changes in hip BMD over time. Specifically, unfit women experienced a non-significant 7% increased risk of losing hip BMD compared to their counterparts (RR = 1.07, 95% CI = 0.66, 1.73). Adjusting statistically for differences in age, initial body weight, and hip BMD, weight change, menopause status, calcium and vitamin D intake, and time between assessments had little effect on the relationship. Fitness level did not influence risk of hip BMD loss over time.

Dual energy X-ray absorptiometry of the knee in spinal cord injury: methodology and correlation with quantitative computed tomography

STUDY DESIGN

Comparison of diagnostic tests; methodological validation.

OBJECTIVES

Primary: to investigate the precision and reliability of a knee bone mineral density (BMD) assessment protocol that uses an existing dual energy X-ray absorptiometry (DXA) forearm acquisition algorithm in individuals with spinal cord injury (SCI). Secondary: to correlate DXA-based knee areal BMD with volumetric BMD assessments derived from quantitative computed tomography (QCT).

SETTING

Academic medical center, Chicago, IL, USA.

METHODS

PARTICIPANTS

a convenience sample of 12 individuals with acute SCI recruited for an observational study of bone loss and 34 individuals with chronic SCI who were screened for a longitudinal study evaluating interventions to increase BMD.

MAIN OUTCOME MEASURES

Root-mean-square standard deviation (RMS-SD) and intra/inter-rater reliability of areal BMD acquired at three knee regions using an existing DXA forearm acquisition algorithm; correlation of DXA-based areal BMD with QCT-derived volumetric BMD.

RESULTS

The RMS-SD of areal BMD at the distal femoral epiphysis, distal femoral metaphysis and proximal tibial epiphysis averaged 0.021, 0.012 and 0.016 g cm(-2), respectively, in acute SCI and 0.018, 0.02 and 0.016 g cm(-2) in chronic SCI. All estimates of intra/inter-rater reliability exceeded 97% and DXA-based areal BMD was significantly correlated with QCT-derived volumetric BMD at all knee regions analyzed.

CONCLUSIONS

Existing DXA forearm acquisition algorithms are sufficiently precise and reliable for short-term assessments of knee BMD in individuals with SCI. Future work is necessary to quantify the reliability of this approach in longitudinal investigations and to determine its ability to predict fractures and recovery potential.

SPONSORSHIP

This work was funded by the Department of Defense, grant number DOD W81XWH-10-1-0951, with partial support from Merck & Co, Inc.