Bone Mineral Density Loss After Combat-Related Lower Extremity Amputation

Objectives: Determine the incidence, severity, and associated risk factors for the development of low bone mineral density (BMD) after combat-related lower extremity amputation. Design: Retrospective case-control comparison. Setting: Tertiary care military treatment facility. Patients/Participants: One hundred fifty-six lower extremity amputees, representing 182 amputations (121 unilateral, 35 bilateral). Intervention: All patients underwent dual energy x-ray absorptiometry scanning during the treatment period. Main Outcome Measurements: The Z score was the main outcome measure. We identified all patients with low BMD (Z < -1.0) and conducted multivariate analysis to identify significant risk factors for low BMD development. Results: The observed rate of low BMD was 42%. The average Z score was -0.6 +/- 1.1 among unilateral amputations and -1.2 +/- 1.0 among bilateral amputations (P = 0.005). Risk factors for the development of low BMD were prolonged time to first ambulation [odds ratio (OR) = 1.39; 95% confidence interval (CI): 1.003-1.93; P = 0.048], prolonged time to dual energy x-ray absorptiometry (OR = 1.10; 95% CI: 1.02-1.18; P = 0.009), and more proximal amputation level (OR = 7.27; 95% CI: 3.21-16.49; P < 0.001). Among unilateral amputees, we detected a significant difference in the BMD of the intact and amputated limbs (-1.0; 95% CI: -1.1 to -0.8; P < 0.001). Conclusions: Proximal amputation level and delayed ambulation demonstrated a significant relationship with low BMD after traumatic and trauma-related amputation. We conclude that transfemoral amputees are at greater risk of BMD loss and that disuse atrophy is a primary factor in the development of low BMD. Prevention should focus on early and aggressive weight bearing rehabilitation and assessing levels and appropriately supplementing calcium and vitamin D. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.