Dual-energy X-ray absorptiometry overestimates bone mineral density of the lumbar spine in persons with spinal cord injury

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.

Cross-Sectional Study of Knee Bone Mineral Density and Fragility Fractures in Patients with Neurological Injuries and Neuromuscular Disorders

BACKGROUND

Patients with neurological injury and neuromuscular disorders are at increased risk for osteoporosis and fragility fracture. This cross-sectional study investigated whether knee bone mineral density (BMD) correlates with fragility fracture in patients with neurological injury and neuromuscular injuries.

METHODOLOGY

In this retrospective chart review, 435 participants underwent dual-energy X-ray absorptiometry (DXA) for BMD analysis. Distal femur and proximal tibial BMD measurements were performed as per the Toronto protocol. Spine, hip, and forearm DXA was performed following the standards of the International Society of Clinical Densitometry, 2019. Blinded and independent clinical evaluations and laboratory exams were performed. Participants were divided into groups with and without fracture confirmed by clinical history and radiography.

RESULTS

Distal femur and proximal tibial BMD were measured in 288/435 (66.2%) participants. Osteoporosis was noted in 138/288 (47.9%) patients. Fractures occurred in 95/435 participants (21.8%), including one fracture in 64/435 participants (14.7%), two fractures in 24/435 participants (5.5%), and greater than two fractures in 7/435 patients (1.6%). Fractures were noted in 23/54 (42.6%) participants with post-polio syndrome, 21/66 with brain injury (31.8%), 3/10 (30%) with brain injury and spinal cord injury, 24/98 (24.5%) with neuromuscular disorders, 9/52 (17.3%) with nontraumatic spinal cord injury, and 15/155 (9.7%) with traumatic spinal cord injury. The median BMD of the knee and hip was lower in participants with fractures. Distal femur and proximal tibial BMD (odds ratio [OR] = 0.02, 95% confidence interval [CI]: 0.01-0.45) remained independently associated with fragility fracture in multivariable analysis.

CONCLUSION

Proximal tibial and distal femur BMD measurements offered additional information on neurological injury and neuromuscular disorders.

Biomechanical differences between able-bodied and spinal cord injured individuals walking in an overground robotic exoskeleton

Background

Robotic assisted gait training (RAGT) uses a powered exoskeleton to support an individual’s body and move their limbs, with the aim of activating latent, pre-existing movement patterns stored in the lower spinal cord called central pattern generators (CPGs) to facilitate stepping. The parameters that directly stimulate the stepping CPGs (hip extension and ipsilateral foot unloading) should be targeted to maximise the rehabilitation benefits of these devices.

Aim

To compare the biomechanical profiles of individuals with a spinal cord injury (SCI) and able-bodied individuals inside the ReWalk^TM powered exoskeleton and to contrast the users’ profiles with the exoskeleton.

Methods

Eight able-bodied and four SCI individuals donned a ReWalk^TM and walked along a 12-meter walkway, using elbow crutches. Whole-body kinematics of the users and the ReWalk^TM were captured, along with GRF and temporal-spatial characteristics. Discreet kinematic values were analysed using a Kruskall-Wallis H and Dunn’s post-hoc analysis. Upper-body differences, GRF and temporal-spatial characteristics were analysed using a Mann-Whitney U test (P<0.05).

Results

Walking speed ranged from 0.32–0.39m/s. Hip abduction, peak knee flexion and ankle dorsiflexion for both the SCI and able-bodied groups presented with significant differences to the ReWalk^TM. The able-bodied group presented significant differences to the ReWalk^TM for all kinematic variables except frontal plane hip ROM (P = 0.093,δ = -0.56). Sagittal plane pelvic and trunk ROM were significantly greater in the SCI vs. able-bodied (P = 0.004,δ = -1; P = 0.008,δ = -0.94, respectively). Posterior braking force was significantly greater in the SCI group (P = 0.004, δ = -1).

Discussion

The different trunk movements used by the SCI group and the capacity for the users’ joint angles to exceed those of the device suggest that biomechanical profiles varied according to the user group. However, upright stepping with the ReWalk^TM device delivered the appropriate afferent stimulus to activate CPGs as there were no differences in key biomechanical parameters between the two user groups.

A Primary Care Provider's Guide to Bone Health in Spinal Cord-Related Paralysis

Individuals with spinal cord injury/disorder (SCI/D) are at high risk for developing secondary osteoporosis. Bone loss after neurologic injury is multifactorial and is dependent on the time from and extent of neurologic injury. Most bone loss occurs in the first year after complete motor paralysis, and fractures occur most commonly in the distal femur and proximal tibia (paraplegic fracture). The 2019 International Society for Clinical Densitometry Position Statement in SCI establishes that dual-energy X-ray absorptiometry (DXA) can be used to both diagnose osteoporosis and predict lower extremity fracture risk in individuals with SCI/D. Pharmacologic treatments used in primary osteoporosis have mixed results when used for SCI/D-related osteoporosis. Ambulation, standing, and electrical stimulation may be helpful at increasing bone mineral density (BMD) in individuals with SCI/D but do not necessarily correlate with fracture risk reduction. Clinicians caring for individuals with spinal cord-related paralysis must maintain a high index of suspicion for fragility fractures and consider referral for surgical evaluation and management.

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

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

Regional bone mineral density differences measured by quantitative computed tomography: does the standard clinically used L1-L2 average correlate with the entire lumbosacral spine?

BACKGROUND CONTEXT

Quantitative computed tomography (QCT) of the lumbar spine is used as an alternative to dual-energy X-ray absorptiometry in assessing bone mineral density (BMD). The average BMD of L1-L2 is the standard reportable metric used for diagnostic purposes according to current recommendations. The density of L1 and L2 has also been proposed as a reference value for the remaining lumbosacral vertebrae and is commonly used as a surrogate marker for overall bone health. Since regional BMD differences within the spine have been proposed, it is unclear if the L1-L2 average correlates with the remainder of the lumbosacral spine.

PURPOSE

The aim of this study was to determine possible BMD variations throughout the lumbosacral spine in patients undergoing lumbar fusion and to assess the correlation between the clinically used L1-L2 average and the remaining lumbosacral vertebral levels.

STUDY DESIGN/SETTING

This is a retrospective case series.

PATIENT SAMPLE

Patients undergoing posterior lumbar spinal fusion from 2014 to 2017 at a single, academic institution with available preoperative CT imaging were included in this study.

OUTCOME MEASURES

The outcome measure was BMD measured by QCT.

METHODS

Standard QCT measurements at the L1 and L2 vertebra and additional experimental measurements of L3, L4, L5, and S1 were performed. Subjects with missing preoperative lumbar spine CT imaging were excluded. The correlations between the L1-L2 average and the other vertebral bodies of the lumbosacral spine (L3, L4, L5, S1) were evaluated.

RESULTS

In total, 296 consecutive patients (55.4% female, mean age of 63.1 years) with available preoperative CT were included. The vertebral BMD values showed a gradual decrease from L1 to L3 and increase from L4 to S1 (L1=118.8 mg/cm³, L2=116.6 mg/cm³, L3=112.5 mg/cm³, L4=122.4 mg/cm³, L5=135.3 mg/cm³, S1=157.4 mg/cm³). There was strong correlation between the L1-L2 average and the average of the other lumbosacral vertebrae (L3-S1) with a Pearson's correlation coefficient (r=0.85). We also analyzed the correlation between the L1-L2 average and each individual lumbosacral vertebra. Similar relationships were observed (r value, 0.67-0.87), with the strongest correlation between the L1-L2 average and L3 (r=0.87).

CONCLUSIONS

Our data demonstrate regional BMD differences throughout the lumbosacral spine. Nevertheless, there is high correlation between the clinically used L1-L2 average and the BMD values in the other lumbosacral vertebrae. We, therefore, conclude the standard clinically used L1-L2 BMD average is a useful bone quantity measure of the entire lumbosacral spine in patients undergoing lumbar spinal fusion.

The effects of robot assisted gait training on temporal-spatial characteristics of people with spinal cord injuries: A systematic review

CONTEXT

Robotic assisted gait training (RAGT) technology can be used as a rehabilitation tool or as an assistive device for spinal cord injured (SCI) individuals. Its impact on upright stepping characteristics of SCI individuals using treadmill or overground robotic exoskeleton systems has yet to be established.

OBJECTIVE

To systematically review the literature and identify if overground or treadmill based RAGT use in SCI individuals elicited differences in temporal-spatial characteristics and functional outcome measures.

METHODS

A systematic search of the literature investigating overground and treadmill RAGT in SCIs was undertaken excluding case-studies and case-series. Studies were included if the primary outcomes were temporal-spatial gait parameters. Study inclusion and methodological quality were assessed and determined independently by two reviewers. Methodological quality was assessed using a validated scoring system for randomized and non-randomized trials.

RESULTS

Twelve studies met all inclusion criteria. Participant numbers ranged from 5-130 with injury levels from C2 to T12, American Spinal Injuries Association A-D. Three studies used overground RAGT systems and the remaining nine focused on treadmill based RAGT systems. Primary outcome measures were walking speed and walking distance. The use of treadmill or overground based RAGT did not result in an increase in walking speed beyond that of conventional gait training and no studies reviewed enabled a large enough improvement to facilitate community ambulation.

CONCLUSION

The use of RAGT in SCI individuals has the potential to benefit upright locomotion of SCI individuals. Its use should not replace other therapies but be incorporated into a multi-modality rehabilitation approach.

Energy and Nutrient Issues in Athletes with Spinal Cord Injury: Are They at Risk for Low Energy Availability?

Low energy availability (LEA) and nutrient intake have been well studied in able-bodied athletes, but there is a lack of research examining these issues amongst athletes with spinal cord injury (SCI). To date, there have been no studies that have examined energy availability (EA) amongst this population. Furthermore, athletes with SCI may experience unique challenges around nutrition that may increase their risk of LEA. This review will evaluate the literature and assess whether this population is at risk for LEA. Due to the limited research on this topic, sedentary individuals with SCI and para athletes were also included in this review. Review of the current literature suggests that athletes with SCI may be at an increased risk for LEA. While research examining EA and risk of LEA in athletes with SCI is lacking, the number of athletes with SCI continues to increase; therefore, further research is warranted to assess nutrient and energy needs and their risk to this population.

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.

Risk factors for osteoporotic fractures in persons with spinal cord injuries and disorders

Clinical risk factors for fracture were explored among Veterans with a spinal cord injury. At the end of 11 years of follow-up, the absolute risk of fracture was approximately 20 %. Among the clinical and SCI-related factors explored, a prior history of fracture was strongly associated with incident fracture.

INTRODUCTION

Few studies to date have comprehensively addressed clinical risk factors for fracture in persons with spinal cord injury (SCI). The purpose of this study was to identify risk factors for incident osteoporotic fractures in persons with a SCI that can be easily determined at the point of care.

METHODS

The Veteran's Affairs Spinal Cord Dysfunction Registry, a national database of persons with a SCI, was used to examine clinical and SCI-related risk factors for fracture. Incident fractures were identified in a cohort of persons with chronic SCI, defined as SCI present for at least 2 years. Cox regression models were used to estimate the risk of incident fractures.

RESULTS

There were 22,516 persons with chronic SCI included in the cohort with 3365 incident fractures. The mean observational follow-up time for the overall sample was 6.2 years (median 6.0, IQR 2.9-11.0). The mean observational follow-up time for the fracture group was 3.9 years (median 3.3, IQR 1.4-6.1) and 6.7 years (median 6.7, IQR 3.1-11.0) for the nonfracture group. By the end of the study, which included predominantly older Veterans with a SCI observed for a relatively short period of time, the absolute (i.e., cumulative hazard) for incident fractures was 0.17 (95%CI 0.14-0.21). In multivariable analysis, factors associated with an increased risk of fracture included White race, traumatic etiology of SCI, paraplegia, complete extent of SCI, longer duration of SCI, use of anticonvulsants and opioids, prevalent fractures, and higher Charlson Comorbidity Indices. Women aged 50 and older were also at higher risk of sustaining an incident fracture at any time during the 11-year follow-up period.

CONCLUSIONS

There are multiple clinical and SCI-related risk factors which can be used to predict fracture in persons with a SCI. Clinicians should be particularly concerned about incident fracture risk in persons with a SCI who have had a previous fracture.

Perioperative complications associated with spine surgery in patients with established spinal cord injury

BACKGROUND CONTEXT

Only a small percentage of patients with spinal cord injury (SCI) require consideration for reconstructive surgery after their initial injury. For those who do, perioperative complications can be frequent and significant. There has been very little published literature examining treatment of these patients and essentially nothing to guide the surgeon in perioperative decision making and management.

PURPOSE

To identify some of the common challenges associated with surgery in this patient population and review the literature to highlight the perioperative concerns in patients with chronic SCI.

STUDY DESIGN

Review article.

METHODS

A primary PubMed literature search was performed and reviewed for patients with chronic SCI with emphasis on the complications and difficulties encountered during surgical treatment of patients with chronic SCI.

RESULTS

For those who do proceed with surgery in this patient population, preoperative nutrition, bone density, and skin should be evaluated and optimized. Preoperative inferior vena cava filters should be considered. The integrity of the reconstruction will be extensively challenged. In addition, augmented fixation and bracing should be contemplated.

CONCLUSIONS

Patients with chronic SCI who require spinal reconstruction provide many unique challenges. Indications for surgery must be strong as perioperative complications can be frequent and long-term outcomes unpredictable. Close monitoring for postoperative complications is essential.

Reduced Bone Density and Vertebral Fractures in Smokers. Men and COPD Patients at Increased Risk

RATIONALE

Former smoking history and chronic obstructive pulmonary disease (COPD) are potential risk factors for osteoporosis and fractures. Under existing guidelines for osteoporosis screening, women are included but men are not, and only current smoking is considered.

OBJECTIVES

To demonstrate the impact of COPD and smoking history on the risk of osteoporosis and vertebral fracture in men and women.

METHODS

Characteristics of participants with low volumetric bone mineral density (vBMD) were identified and related to COPD and other risk factors. We tested associations of sex and COPD with both vBMD and fractures adjusting for age, race, body mass index (BMI), smoking, and glucocorticoid use.

MEASUREMENTS AND MAIN RESULTS

vBMD by calibrated quantitative computed tomography (QCT), visually scored vertebral fractures, and severity of lung disease were determined from chest CT scans of 3,321 current and ex-smokers in the COPDGene study. Low vBMD as a surrogate for osteoporosis was calculated from young adult normal values. Male smokers had a small but significantly greater risk of low vBMD (2.5 SD below young adult mean by calibrated QCT) and more fractures than female smokers. Low vBMD was present in 58% of all subjects, was more frequent in those with worse COPD, and rose to 84% among subjects with very severe COPD. Vertebral fractures were present in 37% of all subjects and were associated with lower vBMD at each Global Initiative for Chronic Obstructive Lung Disease stage of severity. Vertebral fractures were most common in the midthoracic region. COPD and especially emphysema were associated with both low vBMD and vertebral fractures after adjustment for steroid use, age, pack-years of smoking, current smoking, and exacerbations. Airway disease was associated with higher bone density after adjustment for other variables. Calibrated QCT identified more subjects with abnormal values than the standard dual-energy X-ray absorptiometry in a subset of subjects and correlated well with prevalent fractures.

CONCLUSIONS

Male smokers, with or without COPD, have a significant risk of low vBMD and vertebral fractures. COPD was associated with low vBMD after adjusting for race, sex, BMI, smoking, steroid use, exacerbations, and age. Screening for low vBMD by using QCT in men and women who are smokers will increase opportunities to identify and treat osteoporosis in this at-risk population.

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.

Influences of nutrition and adiposity on bone mineral density in individuals with chronic spinal cord injury: A cross-sectional, observational study

BACKGROUND

Dietary inadequacy and adiposity, both prevalent in the chronic spinal cord injury (SCI) population, are known to influence bone turnover and may be potential modifiable risk factors for the development of sublesional osteoporosis following SCI. This pilot study in an SCI cohort aimed to assess measures of nutrition and obesity, to determine if these measures were associated with bone mineral density (BMD), and to compare these measures to a non-SCI control cohort.

METHODS

In a cross-sectional observational study, volunteers with chronic SCI (> 1 year post-injury, lesions from C1 to T12 and severity category A-D by the American Spinal Injury Association Impairment Scale) were assessed, and 8 non-SCI individuals were recruited as a comparison group. BMD at the femoral neck (FN) and lumbar spine (LS), and an estimate of visceral adipose tissue (VAT) from lumbar vertebrae 1 through 4 were measured using dual energy X-ray absorptiometry (DXA); nutrient intake of calcium, vitamins D & K, and protein were estimated using a food frequency questionnaire; plasma 25-hydroxyvitamin D (25(OH)D) was analyzed using ultra-high performance liquid chromatography/tandem mass spectroscopy; and serum leptin, adiponectin and insulin were analyzed using a multiplex assay.

RESULTS

A total of 34 individuals with SCI (n = 22 tetraplegic; n = 12 paraplegic; 94% male) who averaged 12.7 (9.0) years post-injury, age 40.0 (10.9) years and % body fat of 28.4 (7.3) were assessed. Multiple linear regression analyses in the SCI cohort showed significant associations between BMD at the FN and LS with leptin (FN: r = 0.529, p = 0.005; LS: r = 0.392, p = 0.05), insulin (FN: r = 0.544, p = 0.003; LS: r = 0.388, p = 0.05), and VAT percent (FN: r = 0.444, p = 0.02; LS: r = 0.381, p = 0.05). Adiponectin was only correlated with LS BMD (r = 0.429, p = 0.03). No significant relationships were found between BMD and serum 25(OH)D, or intakes of calcium, vitamins D & K, and protein. Intake of vitamin D was adequate in 69% of participants with SCI, where 91% of those persons consumed either vitamin D and/or multivitamin supplements. Vitamin D status was similar between SCI and non-SCI groups as was sub-optimal status (25(OH)D < 75 nmol/L) (60% of SCI compared to 50% of non-SCI). Participants with SCI had significantly lower FN BMD in comparison to non-SCI controls (p = 0.001).

CONCLUSIONS

Compromised BMD among individuals with SCI was not associated with a deficiency of vitamin D or other bone nutrients. The observed positive associations between BMD and leptin, insulin, adiponectin and VAT provide a framework to evaluate links between adiposity and bone health in a larger SCI cohort.

The effect of the cathepsin K inhibitor ONO-5334 on trabecular and cortical bone in postmenopausal osteoporosis: the OCEAN study

ONO-5334 (Ono Pharmaceutical Co., Ltd., Osaka, Japan) inhibits cathepsin K and has been shown to increase areal bone mineral density (BMD) at the hip and spine in postmenopausal osteoporosis. Quantitative computed tomography (QCT) allows the study of the cortical and trabecular bone separately and provides structural information such as cortical thickness. We investigated the impact of 2 years of cathepsin K inhibition on these different bone compartments with ONO-5334. The clinical study was a randomized, double-blind, placebo, and active controlled parallel group study conducted in 13 centers in six European countries. The original study period of 12 months was extended by another 12 months. A total of 147 subjects (age 55-75 years) of the QCT substudy who participated in the extension period were included. Subjects had been randomized into one of five treatment arms: placebo; ONO-5334 50 mg twice per day (BID); ONO-5334 100 mg once daily (QD); ONO-5334 300 mg QD; or alendronate 70 mg once weekly (QW). QCT was obtained to evaluate bone structure at the lumbar spine and proximal femur. After 24 months ONO-5334 showed statistically significant increases versus placebo for integral, trabecular, and cortical BMD at the spine and the hip (for ONO-5334 300 mg QD, BMD increases were 10.5%, 7.1%, and 13.4% for integral, cortical, and trabecular BMD at the spine, respectively, and 6.2%, 3.4%, and 14.6% for integral, cortical, and trabecular total femur BMD, respectively). Changes in cortical and trabecular BMD in the spine and hip were similar for alendronate as for ONO-5334. Integral volume did not demonstrate statistically significant changes under ONO-5334 treatment, thus there was no evidence of periosteal apposition, neither at the spine nor at the femur. Cortical thickness changes were not statistically significant for ONO-5334 in the spine and hip, with exception of a 2.1% increase after month 24 in the intertrochanter for ONO-5334 300 mg QD. Over 2 years ONO-5334 showed a statistically significant and persistent increase of trabecular and integral BMD at the spine and the hip. Cortical BMD also progressively increased but at a lower rate. Changes in bone size and of periosteal apposition were not observed.

Bone mineral density in spinal cord injury: an evaluation of the distal femur

Osteoporosis (OP) in spinal cord injury (SCI) patients is a secondary process in which numerous factors are involved. Diagnosing OP and the threshold for fractures in this population, based on bone mineral density (BMD) measured by double energy X-ray absorptiometry (DXA), is still a challenge. The aim of this study was to evaluate bone mineral loss by DXA, its relationship with body composition and fracture incidence, in complete paraplegics patients, compared with aged-matched controls; we include a nonstandard bone site, the distal femur, and describe the technical and practical aspects of this procedure. Twenty-five SCI patients were included in the study and 17 subjects as control group. No prior or recent fractures were observed in X-ray analysis. The BMD of all femoral sites was significantly lower in patients than in controls (femoral neck, total femur, and distal femur); no difference was observed between BMD of the lumbar spine of patients and controls. We found inverse relationship between time of SCI and bone mineral mass only for distal femur BMD. We conclude that the distal femur is a more sensitive bone site for assessing bone loss by DXA, in SCI patients, than the proximal femoral sites.

Changes in the structural and material properties of the tibia in patients with spinal cord injury

STUDY DESIGN

A cross-sectional study.

OBJECTIVES

To measure the change of structural and material properties at different sites of the tibia in spinal cord-injured patients using peripheral quantitative computerised tomography (pQCT).

SETTING

Orthopaedic research centre (UK).

METHODS

Thirty-one subjects were measured--eight with acute spinal cord injury (SCI), nine with chronic SCI and fourteen able-bodied controls. pQCT scans were performed at 2% (proximal), 34% (diaphyseal) and 96% (distal) along the tibia from the tibial plateau. Structural measures of bone were calculated, and volumetric bone mineral density (vBMD) was also measured at all three levels. Muscle cross-sectional area was measured at the diaphyseal level.

RESULTS

Structurally, there were changes in the cortical bone; in the diaphysis, the shape of the cross-section changed to offer less resistance to AP bending, and the cross-sectional area of the cortical shell decreased both proximally and distally. There were corresponding changes in vBMD in the anterior aspect of the cortical diaphysis, as well as proximal and distal trabecular bone. Changes in muscle occurred more rapidly than changes in bone.

CONCLUSION

There were clear changes of both structure and material at all three levels of the tibia in chronic SCI patients. These changes were consistent with specific adaptations to reduced local mechanical loading conditions. To assess fracture risk in SCI and also to monitor the effect of therapeutic interventions, the structure of the bone should be considered in addition to trabecular bone mineral density.

Intensive electrical stimulation attenuates femoral bone loss in acute spinal cord injury

OBJECTIVE

To determine whether intensive electrical stimulation (ES) can reduce femoral bone mineral density (BMD) loss in acute spinal cord injury (SCI).

DESIGN

Randomized controlled trial.

SETTING

Inpatient rehabilitation hospital.

PARTICIPANTS

Twenty-six subjects with C4 to T12 American Spinal Injury Association Impairment Scale A or B SCI less than 12 weeks postinjury.

METHODS

The control group received usual rehabilitative care and the intervention group received usual care plus 1 hour of ES over the quadriceps 5 days per week for 6 weeks.

MAIN OUTCOME MEASUREMENTS

Outcome measurements were collected at baseline, postintervention (interim), and 3 months postinjury (follow-up), and included dual energy x-ray absorptiometry, serum osteocalcin (OC), and urinary N-telopeptide (NTx).

RESULTS

In the control group, there was increasing BMD loss with distance from the spine (lumbar -1.88%, hip -12.25%, distal femur -15.15%, proximal tibia -17.40%). This trend was attenuated over the distal femur in the ES group (lumbar -1.29%, hip -14.45%, distal femur -7.40%, proximal tibia -12.31%). NTx increased over the 3 assessments in controls ([mean ± standard deviation] 115.00 ± 34.10, 154.86 ± 70.41, and 171.33 ± 75.8 nmol/mmol creatinine) compared with the ES group (160.56 ± 140.06, 216.71 ± 128.40, and 154.67 ± 69.12 nmol/mmol creatinine)-all of which were elevated compared with the reference range, and the differences between the 2 groups were not significant. Osteocalcin levels markedly decreased in the control group (12.90 ± 7.30, 24.00 ± 4.29, and 6.40 ± 7.28 μg/L) to subnormal levels, and remained stable and in the normal range in the ES group (13.80 ± 7.64, 11.86 ± 6.77, and 14.80 ± 12.91 μg/L), although differences between the groups were not significant.

CONCLUSIONS

Lower extremity BMD loss increases with distance from the spine. An intensive lower extremity ES program may attenuate BMD loss locally after acute motor complete SCI, although it is unknown whether these benefits are maintained in the long term.

Underestimation of bone loss of the spine with posterior-anterior dual-energy X-ray absorptiometry in patients with spinal cord injury

BACKGROUND

Bone mineral density (BMD) of the lumbar spine (L-spine) has been reported to be normal by routine posterior-anterior (PA) bone density imaging in patients with chronic spinal cord injury (SCI).

OBJECTIVE

To determine BMD of the L-spine by PA and lateral (LAT) dual-energy radiographic absorptiometry (DXA) in patients with chronic SCI.

DESIGN

Prospective study.

SETTING

Veterans Affairs Medical Center and a private rehabilitation facility.

METHODS

Measurements of the PA and LAT L-spine and hip were performed in 15 patients with SCI: 9 with tetraplegia and 6 with paraplegia. The DXA (GE Lunar Advance DXA) images were obtained using standard software. Results are reported as mean +/- SD.

RESULTS

The mean age was 35 +/- 15 years (range = 20-62 years), and the duration of injury was 57 +/- 74 months (range = 3-240 months). T- and Z-scores were lower for the LAT L-spine than those for PA L-spine (T-scores L2: -0.7 +/- 1.2 vs. 0.0 +/- 1.4, P < 0.01; L3: -0.9 +/- 1.6 vs. 0.3 +/- 1.3, P < 0.002; L2-L3: -0.8 +/- 1.3 vs. 0.2 1.3 vs. 0.2 +/- P < 0.001; Z-scores Z-0.3 +/- 1.1 vs. 0.2 +/- 1.2, P < 0.05; L3: -0.6 +/- 1.3 vs. 0.5 +/- 1.3, P < 0.01; L2-L3: -0.4 +/- 1.1 vs. 0.4 +/- 1.2, P < 0.005). The T- and Z-scores for the total hip (-1.1 +/- 1.0 and -1.0 +/- 1.0, respectively) and L2-L3 LAT L-spine demonstrated remarkable similarity, whereas the L2-L3 PA L-spine scores were not reduced. Bone mineral density of the LAT L-spine, but not the PA L-spine, was significantly reduced with increasing duration of injury.

CONCLUSIONS

Individuals with SCI may have bone loss of the L-spine that is evident on LAT DXA that may be misdiagnosed by PA DXA, underestimating the potential risk of fracture.