Bone Mineral Density at the Distal Femur and Proximal Tibia and Related Factors During the First Year of Spinal Cord Injury

BACKGROUND: Spinal cord injury (SCI) can lead to disuse osteoporosis. The most vulnerable sites for fragility-induced fractures are the distal femur (DF) and proximal tibia (PT). The aim of this study was to evaluate changes in bone mineral density (BMD) at the DF and PT, as well as related factors, during the first year of SCI. PATIENTS AND METHODS: Thirty-six SCI patients within 12 months of their injury were selected, as were 36 healthy controls. The dual-energy X-ray absorptiometry was used to measure BMDs at the DF, PT, and hip of all subjects. According to the duration of SCI when receiving DXA scan, 36 SCI patients were divided into three subgroups. The BMDs of overall patients and subgroups were compared to those of controls. Biochemical markers of bone metabolism were detected in SCI patients. RESULTS: The BMDs at the DF, PT, and hips of overall SCI patients were significantly lower than those of controls. The percentage difference of BMD between SCI patients and controls at the DF and PT was higher than at the hip. The BMD at the PT of SCI within 6 weeks post-injury was lower than that of controls. The BMDs at the DF and PT of SCI during 6 weeks-3 months post-injury were lower than those of controls. Whereas there was no difference in the BMD at the hip during the first 3 months of SCI. Age and 25OHD were the influencing factors of DF BMD. Age and gender were found to influence PT BMD. CONCLUSION: The rapid loss of BMD at the PT and DF during the first year of SCI occurred significantly earlier than that of the hip. It is recommended to monitor the BMD of DF and PT in early-stage SCI patients, combined with detection of biochemical markers of bone metabolism.