Relevance of the project

Wearers of lower leg prostheses often complain of discomfort: they have pain or tissue damage at the leg stump because of pressure and friction, assymetric or abnormal walking pattern, fatigue during walking, pain in the joints, muscle pains, etc. A lot of these complaints could be minimalized by the optimal configuration and alignment of the prostheses [Schmalz (2002), Blumentritt (2001), Huang (2000), Summers (1987)]. This is the job of the orthopedic technologist, and more particularly the prosthetist.

A lower leg prosthesis consists of 3 essential parts (view image 1): the prosthesis socket, the foot and the construction that connects these two (tube, anchors and adapters). The lower leg prosthesis is normally covered with an esthetic finish. The entire design of a lower leg prosthesis consists of the choice of all parts and the adjustment of the adapters.

Image 1: basic parts of a lower leg prosthesis

Despite the fact that almost every part of the lower leg prosthesis has undergone a huge evolution through the development of new technologies, knowledge and materials, it is striking that the techniques and devices to align prostheses have remained virtually the same ever since the 60’s of last century.

The tools that are used for alignment have evolved from a plumb line to several alignment and balancing devices. These tools are, however, not sufficient enough to adjust a prosthesis efficiently and individually, because they are only based on a static alignment. None of these systems take the gait pattern or comfort of the prosthesis user into account.
After this static alignment, the prosthetist will therefore align the prosthesis “dynamically” during a gait test. For this, he observes the prosthesis user visually during his walk. Manual adjustments are then made “by trial and error” until the prosthetist and user don’t see any significant improvements anymore. This leads to a time consuming and exhausting activity for both the orthopedic technologist as well as the patient, without any guarantee on a satisfactory result.

At this moment, prosthetists can only rely on their own experience and expertise for this empirical “dynamic” alignment: there are no tools to determine the optimal configuration and alignment for the patient’s comfort. Simulations with a gait simulator (OVERAS II project, IWT-090181) provide the opportunity to map the influence of the prosthesis design and alignment on the comfort of the prosthesis user during walking (image 2).

Image 2: robotic gait simulator

A great advantage of these simulations is the opportunity to study many combinations in design and exceptional cases with parameters that are difficult (or not advisable) to measure in vivo. Because of the uniqueness of every prosthesis wearer, it’s impossible to collect the same amount of information through professional experience, even in a labour-intensive way.