Altered mechanics and increased loading on intact limbs of individuals with a unilateral transtibial amputation in comparison with non-amputees during a start-stop task

Individuals with a unilateral transtibial amputation (ITTA) often experience greater loading on the intact limb during running and stepping tasks compared to individuals without amputation. This study aimed to investigate the mechanics of load absorption in the intact limb of ITTA and determine if increased ground reaction forces (GRF) persist during a start-stop task which (i) controlled touch-down velocity and (ii) removed the requirement for on-going locomotion. Data were collected using a twelve-camera motion capture system with two Kistler force platforms. Variables were extracted during the final loading phase of a 2-step start-stop task. The intact limb of ITTA and the dominant limb of able-bodied controls were compared using independent t-tests and effect size analysis. ITTA showed lower knee flexion angles at touchdown (p = 0.007, g = -1.43), and peak vertical GRF (p = 0.01, g = -1.33) compared to control subjects. ITTA also exhibited less hip (p = 0.14, g = 0.76) and ankle (p = 0.002, g = 1.82) absorptive power at touchdown and at peak vertical GRF (hip: p = 0.01, g = 1.23; ankle: p = 0.05, g = 0.97). ITTA exhibited greater peak vertical GRF (p = 0.01, g = 1.30) and braking GRF (p = 0.05, g = -0.96) on the intact limb compared to the controls. Our results indicate altered joint mechanics through the intact limb of ITTA are independent of the touchdown conditions or the need for ongoing locomotion. These altered joint mechanics increased loading experienced by the intact limb. Further work should be conducted examining a variety of other dynamic movements to fully understand the involved mechanics, so that intervention studies can be developed to reduce the load experienced by ITTA.