The reversible adjustable coupling: A lightweight and low-cost alignment component for the lower limb prosthesis

BACKGROUND: The alignment of the lower limb prosthesis is an integral part of the prosthetic fitting. A properly aligned prosthesis contributes to optimal gait and overall function of the patient. The current offering of alignment componentry is expensive for low-income countries. The purpose of this study was to develop a lightweight and low-cost alignment coupler for the lower limb prosthesis. METHODS: An alignment coupler called the reversible adjustable coupling was designed and manufactured. Measurements of total anterior/posterior and medial/lateral and rotation in prostheses were recorded and mechanical testing performed. Swiftness and difficulty of use was also recorded. RESULTS: The reversible adjustable coupling permitted acceptable ranges of anterior/posterior and medial/lateral translation and 30° of internal and external rotation of prosthetic componentry. Repetitive loading of the coupling at a speed of 1 Hz under 1.28 kN load for 2000 cycles was successful, as were static and strength tests. DISCUSSION: The coupler provided acceptable ranges of anterior/posterior and medial/lateral and rotation adjustment and is acceptable for potential use in the alignment of both exoskeletal and endoskeletal prosthesis. The final weight of the component was 166 g and cost of $55.00 USD is affordable for low-income countries for use in clinical and educational settings.