Assessment of anthropometric, systemic, and lifestyle factors influencing bone status in the legs of spinal cord injured individuals

The aim of the present study was to assess the influence of muscle spasms, systemic or lifestyle factors on bone mass and geometry of the femur and the tibia in people with long-standing spinal cord injury (SCI). Fifty-four motor complete SCI people with paralysis duration of between 5 and 50 years were included in the study. Spasticity was measured by means of the Ashworth scale. Distal epiphyses and mid shafts of the femur, tibia, and radius were measured by peripheral quantitative computed tomography. From the epiphyseal scans, trabecular and total bone mineral density (BMDtrab and BMDtot) were calculated, and from the shaft scans, cortical BMD (BMDcort), total and cortical cross-sectional area (CSAtot and CSAcort), and muscle cross-sectional areas (CSAmus) were determined. Personal characteristics, anthropometric, as well as life-style factors, were assessed by means of a questionnaire. A Spearman correlation matrix was produced with measured data. Correlation coefficients exceeding 0.3 were tested for significance by performing linear regression for parametric data and ANOVA for non-parametric data. Subjects with higher spasticity scores had significantly larger CSAmus in the upper and lower leg. Both spasticity and CSAmus were found to be significantly related to BMDtrab and BMDtot of the distal epiphysis of the femur and to CSAcort of the femoral shaft. In the lower leg, bone parameters of the tibia were found to be strongly related to corresponding bone parameters of the radius, which suggests a systemic origin. No significant relationships were found between bone parameters and any of the lifestyle factors. The extent of bone loss caused by disuse of the lower extremities in people with long-standing SCI is influenced by systemic factors. Additionally, spasticity has a positive effect on bone parameters of the femur.