Muscle and bone adaptations after treadmill training in incomplete Spinal Cord Injury: a case study using peripheral Quantitative Computed Tomography.

We describe the use of peripheral Quantitative Computed Tomography (pQCT) to identify musculoskeletal responses to partial body-weight supported treadmill training (BWSTT) in incomplete spinal cord injury (SCI). Long-term health consequences of SCI include extensive muscle atrophy, severe bone loss and an increased fracture risk in the affected limbs, mostly at both tibial epiphyses and the distal femoral epiphysis. Regular treadmill training may slow or reverse bone loss by recruiting available lower-limb musculature and loading the leg bones dynamically. The potential for detailed analysis of musculoskeletal changes using pQCT is illustrated with a single case study (14.5 years post-SCI), who completed seven months of partial BWSTT. Pre- and post-training lower-limb pQCT scans were taken to quantify changes in trabecular bone, cortical bone, and soft-tissue. Trabecular bone mineral density increased by 5% (right) and 20% (left) in the distal tibia. Changes in proximal tibia and distal femur were negligible. Increases in muscle cross-sectional area were 6% (right) and 12% (left) in the lower leg, 7% (right) and 5% (left) in the thigh. We suggest that treadmill training may lead to positive musculoskeletal adaptations at clinically-relevant sites. Such changes can be measured in detail using pQCT.

Arm-cranking exercise assisted by Functional Electrical Stimulation in C6 tetraplegia: a pilot study.

Tetraplegic volunteers undertook progressive exercise training, using novel systems for arm-cranking exercise assisted by Functional Electrical Stimulation (FES). The main aim was to determine potential training effects of FES-assisted arm-crank ergometry (FES-ACE) on upper limb strength and cardiopulmonary (fitness) in tetraplegia. Surface FES was applied to the biceps and triceps during exercise on an instrumented ergometer. Two tetraplegic volunteers with C6 Spinal Cord Injury (SCI) went through muscle strengthening, baseline exercise testing and three months of progressive FES-ACE training. Repeat exercise tests were carried out every four weeks during training, and post-training, to monitor upper-limb strength and cardiopulmonary fitness. At each test point, an incremental test was carried out to determine peak work rate, peak oxygen uptake, gas exchange threshold and oxygen uptake-work rate relationship during FES-ACE. Peak oxygen uptake for Subject A increased from 0.7 l/min to 1.1 l/min, and peak power output increased from 7 W to 38 W after FES-ACE training. For Subject B, peak oxygen uptake was unchanged, but peak power output increased from 3 W to 8 W. These case studies illustrate potential benefits of FES-ACE in tetraplegia, but also the differences in exercise responses between individuals.

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.