Individuals with transfemoral amputations often have difficulty descending sloped surfaces due to increased lower-limb range of motion and torque requirements. Toward this end, a team of researchers conducted a study to evaluate how experienced prosthesis users descended a sloped surface using the Ottobock X2® compared to a conventional knee, either mechanical (MECH) or microprocessor (MP); the study is an article in press in the journal Clinical Biomechanics. The researchers are affiliated with Walter Reed National Military Medical Center, Bethesda, Maryland; the U.S. Department of Defense/U.S. Department of Veterans Affairs Extremity Trauma and Amputation Center of Excellence; and the Center for the Intrepid, San Antonio.
Descent technique and biomechanics were assessed in 21 service members with unilateral transfemoral amputations as they descended an instrumented 10 degree slope at a self-selected walking velocity. Study findings show that use of the X2 in the MECH group resulted in greater hill assessment scores (8.5 to 11), due primarily to decreased reliance on handrail use. Use of the X2 in the MP group increased the cohort’s prosthetic knee flexion to a median of 6.4 degrees at initial contact and 73.7 degrees in swing, contributing to longer prosthetic limb steps and increased self-selected velocity. Additionally, use of the X2 in the MP group increased prosthetic limb impact peaks, improving impact peak symmetry to -1.3 percent.
The researchers stated that decreased reliance on handrail use when the MECH users descended in the X2 indicates improved function and perhaps greater confidence in the device. Additional biomechanical improvements for existing MP users suggest potential longer-term benefits with regard to intact limb health and overuse injuries.