Joint loading and bone mineral density in persons with unilateral, trans-tibial amputation.

BACKGROUND Persons with unilateral, lower-extremity amputation sometimes develop osteoarthritis in the intact limb. The purpose of this study was to investigate gait mechanics and bone mineral density in unilateral, trans-tibial amputees to test the hypotheses that the intact limb knee and hip will have larger frontal plane net joint moments and bone mineral density than the prosthetic side and the limbs of control subjects. METHODS Proximal tibia and femoral neck bone mineral density and gait mechanics were measured from nine subjects with a unilateral, trans-tibial amputation and from age, gender, and mass matched control subjects. FINDINGS The amputee intact proximal tibia bone mineral density and peak knee internal abduction moment were 45% (P=0.001) and 56% (P=0.028) greater, respectively, than the prosthetic side. The intact limb femoral neck bone mineral density and peak hip internal abduction moment were 12% (P=0.095) and 33% (P=0.03) greater, respectively, than the prosthetic side. The intact knee frontal plane moment and bone mineral density were moderately larger than the control knee, while the intact and control hip were similar. INTERPRETATION Elevated frontal plane net joint moments and bone mineral density suggest the potential exists for premature knee joint degradation. Measuring frontal plane joint mechanics and bone mineral density may be important tools for assessing joint health in persons with unilateral, trans-tibial amputation.