Marker-based method to measure movement between the residual limb and a transtibial prosthetic socket.

BACKGROUND: Limb movement between the residuum and socket continues to be an underlying factor in limb health, prosthetic comfort, and gait performance yet techniques to measure this have been underdeveloped.
OBJECTIVES: Develop a method to measure motion between the residual limb and a transtibial prosthetic socket. STUDY
DESIGN: Single subject, repeated measures with mathematical modeling.
METHODS: The gait of a participant with transtibial amputation was recorded using a motion capture system using a marker set that included arrays on the anterior distal tibia and the lateral epicondyle of the femur. The proximal or distal translation, anterior or posterior translation, and angular movements were quantified. A random Monte Carlo simulation based on the precision of the motion capture system and a model of the bone moving under the skin explored the technique's accuracy. Residual limb tissue stiffness was modeled as a linear spring based on data from Papaioannou et al.
RESULTS: Residuum movement relative to the socket went through ~30 mm, 18 mm, and 15° range of motion. Root mean squared errors were 5.47 mm, 1.86 mm, and 0.75° when considering the modeled bone-skin movement in the proximal or distal, anterior or posterior, and angular directions, respectively.
CONCLUSION: The measured movement was greater than the root mean squared error, indicating that this method can measure motion between the residuum and socket. CLINICAL RELEVANCE: The ability to quantify movement between the residual limb and the prosthetic socket will improve prosthetic treatment through the evaluation of different prosthetic suspensions, socket designs, and motor control of the prosthetic interface. © The International Society for Prosthetics and Orthotics 2015.