Decreases in bone mineral density at cortical and trabecular sites in the tibia and femur during the first year of spinal cord injury.

BACKGROUND: Disuse osteoporosis occurs in response to long-term immobilization. Spinal cord injury (SCI) leads to a form of disuse osteoporosis that only affects the paralyzed limbs. High rates of bone resorption after injury are evident from decreases in bone mineral content (BMC), which in the past have been attributed in the main to loss of trabecular bone in the epiphyses and cortical thinning in the shaft through endocortical resorption. METHODS: Patients with motor-complete SCI recruited from the Queen Elizabeth National Spinal Injuries Unit (Glasgow, UK) were scanned within 5weeks of injury (baseline) using peripheral Quantitative Computed Tomography (pQCT). Unilateral scans of the tibia, femur and radius provided separate estimates of trabecular and cortical bone parameters in the epiphyses and diaphyses, respectively. Using repeat pQCT scans at 4, 8 and 12months post-injury, changes in BMC, bone mineral density (BMD) and cross-sectional area (CSA) of the bone were quantified. RESULTS: Twenty-six subjects (5 female, 21 male) with SCI (12 paraplegic, 14 tetraplegic), ranging from 16 to 76years old, were enrolled onto the study. Repeated-measures analyses showed a significant effect of time since injury on key bone parameters at the epiphyses of the tibia and femur (BMC, total BMD, trabecular BMD) and their diaphyses (BMC, cortical BMD, cortical CSA). There was no significant effect of gender or age on key outcome measures, but there was a tendency for the female subjects to experience greater decreases in cortical BMD. The decreases in cortical BMD in the tibia and femur were found to be statistically significant in both men and women. CONCLUSIONS: By carrying out repeat pQCT scans at four-monthly intervals, this study provides a uniquely detailed description of the cortical bone changes that occur alongside trabecular bone changes in the first year of complete SCI. Significant decreases in BMD were recorded in both the cortical and trabecular bone compartments of the tibia and femur throughout the first year of injury. This study provides evidence for the need for targeted early intervention to preserve bone mass within this patient group.

Improving respiration in patients with tetraplegia by functional electrical stimulation: an anatomical perspective.

Patients with tetraplegia often have respiratory complications because of paralysis of the abdominal and intercostal muscles. Functional electrical stimulation (FES) has been used to improve breathing in these patients by applying surface stimulation to the abdominal muscles. We aimed to find the best nerves to stimulate directly to increase tidal volume and make cough more effective. Surface electrodes were placed on a patient's abdominal wall to find the optimum points for surface stimulation. These positions were plotted on a transparent sheet. The abdomino-intercostal nerves were dissected in five male dissecting room cadavers matched for size with the patient. The plastic sheet was then superimposed over each of the dissections to clarify the relationship between optimum surface stimulation points and the underlying nerves. Results show that the optimum surface stimulation points overlie the course of abdomino-intercostal nerves T9, 10, and 11. The success with selecting stimulation points associated with T9, 10, and 11 is probably because of the large mass of abdominal muscle supplied by these nerves. The constant position of the nerves below the ribs makes the intercostal space a possible site for direct stimulation of the abdomino-intercostal nerves.

Spinal injuries in Scottish mountaineers.

OBJECTIVE: To identify the frequency and pattern of spinal injury sustained in mountaineering accidents. METHODS: All patients with spinal injuries sustained while mountaineering who were treated at the Queen Elizabeth National Spinal Injuries Unit from 1992 to 2001 were studied. Information was obtained from hospital notes, and each patient completed a questionnaire. RESULTS: Twenty-one patients with spinal injuries sustained in mountaineering accidents were identified. Fourteen patients (67.7%) were experienced mountaineers. Four (19.0%) were rock climbing, 6 (28.6%) were winter climbing, 6 (28.6%) were hill walking, and 5 (23.8%) were winter walking. Ten patients (47.6%) sustained cervical injuries, 5 (23.8%) sustained thoracic injuries, 5 (23.8%) sustained lumbar injuries, and 1 (4.8%) sustained cervical and lumbar injuries. Nineteen patients (90.5%) sustained fractures, 1 (4.8%) sustained a dislocation, and 1 (4.8%) sustained a fracture dislocation. Seventeen patients (81.0%) were neurologically intact, 2 (9.5%) sustained complete cord injury, and 2 (9.5%) sustained incomplete cauda equina lesions. Ten patients (47.6%) required internal fixation of their fractures. Fourteen patients (57.1%) sustained other significant injuries. CONCLUSIONS: This is the first study specifically aimed to describe patterns of spinal injuries and their outcomes in mountaineers. The group we studied had sustained fractures at differing spinal levels with no specific injury pattern. The incidence of cord injury was lower than in other spinal injury patient groups. The majority had also sustained other significant and potentially distracting injuries. Prehospital care providers should maintain a high suspicion of spinal injury in this group.

Control strategies for integration of electric motor assist and functional electrical stimulation in paraplegic cycling: utility for exercise testing and mobile cycling.

AIM: The aim of this study was to investigate feedback control strategies for integration of electric motor assist and functional electrical stimulation (FES) for paraplegic cycling, with particular focus on development of a testbed for exercise testing in FES cycling, in which both cycling cadence and workrate are simultaneously well controlled and contemporary physiological measures of exercise performance derived. A second aim was to investigate the possible benefits of the approach for mobile, recreational cycling. METHODS: A recumbent tricycle with an auxiliary electric motor is used, which is adapted for paraplegic users, and instrumented for stimulation control. We propose a novel integrated control strategy which simultaneously provides feedback control of leg power output (via automatic adjustment of stimulation intensity) and cycling cadence (via electric motor control). Both loops are designed using system identification and analytical (model-based) feedback design methods. Ventilatory and pulmonary gas exchange response profiles are derived using a portable system for real-time breath-by-breath acquisition. RESULTS: We provide indicative results from one paraplegic subject in which a series of feedback-control tests illustrate accurate control of cycling cadence, leg power control, and external disturbance rejection. We also provide physiological response profiles from a submaximal exercise step test and a maximal incremental exercise test, as facilitated by the control strategy. CONCLUSION: The integrated control strategy is effective in facilitating exercise testing under conditions of well-controlled cadence and power output. Our control approach significantly extends the achievable workrate range and enhances exercise-test sensitivity for FES cycling, thus allowing a more stringent characterization of physiological response profiles and estimation of key parameters of aerobic function. We further conclude that the control approach can significantly improve the overall performance of mobile recreational cycling.

Prophylaxis of thromboembolism in spinal injuries--survey of practice in spinal units in the British Isles.

AIM: Survey and discussion of the current thromboembolic prophylaxis practice in spinal injury units within the British Isles. BACKGROUND: Deep vein thrombosis and pulmonary embolism are major causes of morbidity and mortality in patients with spinal injuries. A wide range of thromboprophylactic measures have been proposed. The optimum treatment and duration for thromboprophylaxis in spinal injuries is unknown. Different spinal units within the British Isles use different measures despite similar training backgrounds. The present study was performed to review practice and make suggestions on best practice using literature review. METHODS: All the 13 regional and national spinal injury referral centres within the British Isles were contacted to find out their protocols for thromboembolic prophylaxis in patients with acute spinal injuries. RESULTS: All units replied. A wide variation in methods used was found in different spinal units ranging from no chemical prophylaxis to oral anticoagulation with warfarin and contrasting views on the use of antithromboembolic stockings. CONCLUSION: All units recognised the risk of thromboembolism after spinal injuries. A wide variety of thromboprophylactic measures are used.