Magnetic resonance imaging of osteonecrosis and osteoarthrosis in exercising quadriplegics and paraplegics.

Degenerative bone and joint diseases that commonly accompany spinal cord injury (SCI) may be exacerbated by physical activity of the lower extremities. To determine if orthopaedic stress imposed by electrically stimulated cycling exercise is associated with osteonecrosis or osteoarthrosis in persons with chronic SCI, ten quadriplegics and paraplegics who had each undergone electrical stimulation cycle ergometry exercise two or three times weekly for longer than 1.5 years underwent magnetic resonance examinations of the femoral heads and the dominant knee. Three of the ten subjects had no evidence of meniscal or bone marrow pathologies, osteochondritis dessicans, avascular necrosis, joint effusion or accumulation or soft tissue tears. The magnetic resonance scans of six subjects were noted to have very mild effusion, slight meniscal degeneration and minimal chondromalacia patellae. Consistent patterns of bone or joint pathology were not discernible among these scans, and the positive findings did not represent threatening clinical states. The scans of one subject showed heterogenous regions of bone infarct characteristic of osteochondritis and avascular necrosis, observations that were atypical of all other subjects. No injuries consistent with the biomechanics of cycling exercise were observed in any subject. Despite the high sensitivity of magnetic resonance imaging in detecting bone and joint deterioration, significant bone and joint findings represented only 14 of 150 observations, less than previously reported in sedentary subjects with SCI. This study suggests that electrical stimulation cycle ergometry does not foster bone or joint deterioration in individuals with chronic SCI.