Non-pharmacological treatment and prevention of bone loss after spinal cord injury: a systematic review

An evaluation of the muscle-bone unit theory among individuals with chronic spinal cord injury

STUDY DESIGN

Cross-sectional observation.

OBJECTIVES

To explore the association between muscle size and function, and indices of bone strength among a sample of adults with chronic spinal cord injury (SCI).

SETTING

Ontario, Canada.

METHODS

Sixty-five participants (n=47 men) with chronic SCI (C1-T12 American Spinal Injury Association Impairment Scale (AIS) A-D) were recruited, mean±s.d. age 49.4±12.8 years and years post-injury 14.3±10.7. Muscle cross-sectional area (CSA) and indices of bone strength at the distal tibia and tibia shaft were measured by peripheral quantitative computed tomography. Muscle CSA was multiplied by tibia length to obtain muscle-bending moment (MBM), a surrogate of torque. Plantar flexor components of the lower-extremity motor scores (pf-LEMS) were used as clinical measures of muscle function. Pearson's correlations (r) were used to determine the strength of relationships.

RESULTS

Correlations were found between MBM and indices of bone strength at the distal tibia and tibia shaft (r=0.44-0.56), as well as between pf-LEMS and indices of bone strength at the distal tibia and tibia shaft (r=0.37-0.71). pf-LEMS had a stronger association with bone variables at the distal tibia compared with MBM (r=0.6 vs r=0.4). All relationships between muscle and bone remained significant when controlling for the duration of injury.

CONCLUSION

It appears that lower limb muscle size and function are more strongly correlated with bone strength indices at the distal tibia than at the tibia shaft among individuals with SCI. The relationships between muscle and bone are clinically important, as muscle CSA and strength (motor scores) are potentially amenable to rehabilitation intervention(s).

Minimal trauma fractures: lifting the specter of misconduct by identifying risk factors and planning for prevention

Minimal trauma fractures are an unfortunate, yet not uncommon, event for frail elderly individuals in long term care facilities. These fractures result in significant morbidity including pain and loss of function along with significantly increased mortality. Further concern exists for the medico-legal issues raised after a minimal trauma fracture is discovered. The controversy at hand is whether such fractures are primarily the result of inadequate, careless, or abusive care practices. We build a case to the contrary. Although the data regarding this condition are limited, there exists a reasonable evidence base to identify an at-risk patient population. We present a representative case and subsequent literature review of minimal trauma fractures to illustrate the condition, including risk factors, mode of presentation, and patient outcomes. No direct research has been conducted on the pathophysiology of these fractures. Extrapolating from other similar conditions and likely associated comorbid illnesses, we explore possible physiologic explanations for their occurrence. Again, no direct investigation into prevention or treatment of minimal trauma fractures has been published. Instead, we consider a variety of pharmacologic and nonpharmacologic interventions that may modify the risk for minimal trauma fractures considering the previously identified risk factors and probable pathophysiologic changes leading to fracture development. We propose that reducing minimal trauma fractures in the frail elderly nursing home population will require careful staff education, close attention to identify at-risk patients, and implementation of select interventions aimed at preventing such fractures.

Improvement of femoral bone quality after low-magnitude, high-frequency mechanical stimulation in the ovariectomized rat as an osteopenia model

The treatment and prevention of osteoporosis involve great challenges. Nonpharmacological and supportive therapy procedures, sport, and physical exercises seem to prevent bone loss and improve bone mass. In the present study, we examined the effect of whole-body vertical vibration (WBVV) on femoral intertrochanteric bone quality in the rat osteoporosis model. Sixty female Sprague-Dawley rats, 3-month old, were ovariectomized (OVX) or sham-operated. After 3 months, each group was divided into two subgroups. In one of the subgroups, rats were treated with WBVV at 90 Hz (3.9 g) for 35 days; the second subgroup remained untreated. After killing the animals, biomechanical strength and trabecular bone architecture of the proximal region of femurs were analyzed. New cortical bone appositions and mineral density of femurs were additionally measured. Treatment with WBVV resulted in improved biomechanical properties. Maximal load and stiffness of the intertrochanteric region of femurs after WBVV were significantly enhanced. Maximal load and stiffness in treated OVX animals reached the levels observed in untreated sham rats. WBVV significantly improved all measured histomorphometric parameters in the trabecular area. Treated rats showed significantly improved mineral content in ashed femurs compared to untreated animals. A comparison of widths of fluorescence bands in cortical bone of subtrochanteric cross sections did not show any significant differences between the groups after WBVV. Low-magnitude, high-frequency mechanical stimulation improves bone strength in the proximal femur and may be a possible nonpharmacologic treatment option for postmenopausal osteoporosis.

Video game-based neuromuscular electrical stimulation system for calf muscle training: a case study

A video game-based training system was designed to integrate neuromuscular electrical stimulation (NMES) and visual feedback as a means to improve strength and endurance of the lower leg muscles, and to increase the range of motion (ROM) of the ankle joints. The system allowed the participants to perform isotonic concentric and isometric contractions in both the plantarflexors and dorsiflexors using NMES. In the proposed system, the contractions were performed against exterior resistance, and the angle of the ankle joints was used as the control input to the video game. To test the practicality of the proposed system, an individual with chronic complete spinal cord injury (SCI) participated in the study. The system provided a progressive overload for the trained muscles, which is a prerequisite for successful muscle training. The participant indicated that he enjoyed the video game-based training and that he would like to continue the treatment. The results show that the training resulted in a significant improvement of the strength and endurance of the paralyzed lower leg muscles, and in an increased ROM of the ankle joints. Video game-based training programs might be effective in motivating participants to train more frequently and adhere to otherwise tedious training protocols. It is expected that such training will not only improve the properties of their muscles but also decrease the severity and frequency of secondary complications that result from SCI.

Diagnosis and treatment of osteoporosis in spinal cord injury patients: A literature review

OBJECTIVE

To present an up-to-date literature review of osteoporosis in spinal cord injury (SCI) patients, in view of the seriousness of this complication (with a high risk of fractures) and the complexity of its diagnosis, evaluation and treatment.

METHODS

A Medline search with the following keywords: immobilization osteoporosis, spinal cord injury, bone loss, dual energy X-ray absorptiometry (DEXA), bisphosphonate.

RESULTS

Our analysis of the literature noted a bone metabolism imbalance in SCI patients, with accelerated early bone resorption (particularly during the first 6 months post-injury). Although dual energy X-ray absorptiometry constitutes the "gold standard" diagnostic method, the decrease in bone mineral density only becomes significant 12 months after the injury. Bisphosphonate therapy has proven efficacy. Despite the frequent use of various physical therapies, these methods have not been found to be effective.

CONCLUSION

Although our literature review did not identify any guidelines on the strategy for diagnosing and treating osteoporosis in SCI patients, several findings provide guidance on procedures for early diagnosis and preventive treatment.

Mechanical factors and bone health: effects of weightlessness and neurologic injury

Bone is a dynamic tissue with homeostasis governed by many factors. Among them, mechanical stimuli appear to be particularly critical for bone structure and strength. With removal of mechanical stimuli, a profound bone loss occurs, as best observed in the extreme examples following exposure to space flight or neurologic impairment. This review provides an overview of the changes in bone density and structure that occur during and after space flight as well as following neurologic injury from stroke and spinal cord injury. It also discusses the potential mechanisms through which mechanical stimuli are postulated to act on bone tissue.