A transfemoral prosthesis wearer demonstrates lateral trunk bending from heel strike to midstance. Which of the following is the LEAST likely cause?

• A. High medial wall
• B. Weak hip abductors
• C. Prosthesis that is too short
• D. Prosthesis that is too long

Answer: (C)

Lateral trunk bending during early stance is a compensatory strategy to keep the body's center of mass over the prosthetic limb when coronal-plane stability is challenged. In a transfemoral prosthesis, this pattern is most often seen when the socket fit is poor or the hip abductors on the prosthetic side are weak. A high medial wall pushes on the medial thigh and tends to provoke a trunk shift toward the prosthesis to relieve pressure. Weak hip abductors reduce the ability to hold the pelvis level during stance, so the trunk leans toward the prosthetic side to maintain balance. If the prosthesis is too long, the alignment changes can also induce compensations that involve trunk positioning to maintain stability. A prosthesis that is too short, however, does not typically produce this lateral trunk bending pattern; it more often leads to other alignment and stability issues.