Inducing Controlled Application of External Socket Reaction Moments to Quantify Unilateral Transtibial Prosthetic Alignment

Background: Important limitations of current prosthetic alignment approaches are the subjectivity by which it is determined and the lack of standardized quantifiable baseline values. The purpose of the current thesis is to describe a new method of alignment, which attempts to address these limitations. The new method steps away from the subjective dynamic alignment methods by finding a quantitative alignment method in a dynamic state. The study's research goal was to influence the moment at the base of the socket to a predetermined optimal ESRM of 0Nm/kg, defined as the final alignment moment.
Methods: Ten participants with a uni-lateral transtibial amputation were recruited. An instrumented prosthesis and a gait lab measured the external socket reaction moments during prosthetic stance phase. Two different conditions were applied; dynamic alignment, which is clinically applicable and computer-assisted, in which the prosthetist aligns the prosthesis to a predetermined kinetic optimum. Additionally, in both conditions the socket comfort score of the participants was inquired and a gait analysis was performed.
Results: For all participants the predetermined goal was achieved, with a significant (p<0.001) reduction of the external socket reaction moment in the final alignment condition. This resulted in a significant (p<0.001) decrease of the knee coronal moments as well. The socket comfort score did not significantly change, however two participants experienced a substantial decrease.
Conclusion: Optimisation of prosthetic alignment by a single kinetic parameter, the ESRM, may not be the ideal method. The ESRM alignment method does not address the position on which the moment is derived in relation to the knee joint centre. Therefore, future processes may involve assessment of kinetics of knee and hip joints in addition to the ESRM.