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 life-style 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.

Relationship between the duration of paralysis and bone structure: a pQCT study of spinal cord injured individuals.

The aim of the present study was to describe bone loss of the separate compartments of trabecular and cortical bone, as well as changes in bone geometry of a large number of spinal cord injured (SCI) individuals. Eighty-nine motor complete spinal cord injured men (24 tetraplegics and 65 paraplegics) with a duration of paralysis of between 2 months and 50 years were included in the study. Distal epiphyses and midshafts of the femur, tibia, and radius were measured by peripheral quantitative computed tomography. The same measurements were performed in a reference group of 21 healthy able-bodied men of the same age range. In the femur and tibia, bone mass, total and trabecular bone mineral density (BMDtot and BMDtrab, respectively) of the epiphyses, as well as bone mass and cortical cross-sectional area of the diaphyses, showed an exponential decrease with time after injury in the spinal cord injured subjects. The decreasing bone parameters reached new steady states after 3-8 years, depending on the parameter. Bone mass loss in the epiphyses was approximately 50% in the femur and 60% in the tibia, while the shafts lost only approximately 35% in the femur and 25% in the tibia. In the epiphyses, bone mass was lost by reducing BMD, while in the shaft bone mass was lost by reducing cortical wall thickness, a process achieved by endosteal resorption advancing at a rate of about 0.25 mm/year within the first 5-7 years after injury. Except for a slight transient decrease in cortical BMD of the femoral and tibial shaft during the first 5 years after the spinal cord lesion, cortical BMD of the spinal cord injured subjects was found to be at reference values. Bone parameters of the radial epiphysis in paraplegic subjects showed no deficits compared to the reference group. Furthermore, a trend for an increased radial shaft diameter suggests periosteal apposition as a consequence of increased loading of the arms.