Prosthetic Limbs After Leg Amputation: Alternative Method of Socket Design

Comparison of Rectified and Unrectified Amputee Sockets

People who have had a leg amputated often choose to use a prosthetic (artificial) leg. This study will evaluate a new method of making prosthetic legs for people who have had an amputation below the knee.

The traditional assumption when fabricating a transtibial amputee (TTA) socket is that the residual limb is not homogeneous in its ability to tolerate load. As a result, prosthetic sockets are currently fabricated by modifying a positive mold to account for this non-homogeneity; these are called rectified sockets. Unrectified sockets retain the shape of the residual limb, except for a distal end pad. Unrectified sockets use an alginate gel method of fabricating that is simpler and less time consuming than the method used to fabricate rectified sockets. This study will compare patient satisfaction and function with rectified and unrectified sockets.

Participants in this study will be randomized to either a recitified socket group or an unrectified socket group. Participants will wear the socket for a minimum of 4 weeks. Participants will then fill out a Prosthesis Evaluation Questionnaire (PEQ). The PEQ quantifies patient satisfaction by evaluating nine validated scales. Functional measures of energy expenditure, kinematics, and ground reaction forces during gait will also be collected. After 4 weeks, participants in the rectified socket group will switch to an unrectified socket and participants in the unrectified socket group will switch to a rectified socket. At the end of 4 weeks with the new socket, participants will once again fill out the PEQ and undergo functional assessment. At the end of study participation, each participant will freely choose the socket they wish to have in their final prosthesis.

Thus far, 10 study participants with unilateral transtibial amputations have been evaluated after randomly wearing both rectified and unrectified sockets for 4 weeks. Results indicated no differences between sockets for gait speed and timing, gait kinematics and kinetics, gait energy expenditure, and Rate of Perceived Exertion (RPE). There were also no differences in the Prosthetic Evaluation Questionnaire. Four participants selected the rectified socket and 6 selected the unrectified socket as their exit socket.

Inclusion Criteria

• Unilateral transtibial amputation
• Mature residual limbs (i.e., no major change in stump volume due to atrophy or other destabilizing factors)
• Continuously worn a prosthesis for at least 1 year prior to study entry
• Scheduled for a new prosthesis
• Independent ambulation
• No acute health problems

Exclusion Criteria

• Constant recurring prosthetic problems (i.e., adherent scar tissue, neuromas, bony protuberances at distal end)
• Requires gel inserts, additional ply socks, or other atypical fitting components or methods
• Health status that prohibits patient from performing graded exercise test