Using a custom variable-stiffness prosthesis, a research team compared prosthetic foot stiffness preferences of patients and prosthetists. On average, the researchers found that the prosthetist subjects preferred a 26 percent higher stiffness than the subjects with amputations and that the prosthetists were less consistent than the amputees in their preferences.
“The clinical process of matching and fitting lower-limb amputation patients with prosthetic componentry is as much art as it is science, and despite decades of research on the effects of prosthetic foot mechanics on gait, there is still a gap between researcher focus and clinical practice,” according to the study’s authors. With that in mind, the researchers focused on developing a better understanding of how people with below-knee amputations and certified prosthetists develop and communicate their preferences for prosthetic foot stiffness.
Seven certified prosthetists were recruited from the Shirley Ryan AbilityLab, and seven high-activity (K3-K4) subjects with transtibial amputations were recruited through the facility’s prosthetics and orthotics clinic. Prior to the study, the prosthetist subjects completed a questionnaire about the importance of prosthesis stiffness in clinical decision-making.
In the first part of the experiment, seven subjects with transtibial amputations walked on a variable-stiffness prosthetic foot set to a randomized stiffness, while several prosthetist subjects simultaneously observed their gait. After each trial, the amputees and prosthetists indicated the increase or decrease to stiffness that they would prefer. The method allowed the researchers to simultaneously measure amputee subject and prosthetist subject preferences and provided a reliability index indicating the consistency of their preferences.
In the second part of the experiment, the subjects with amputations were instructed to communicate verbally with one prosthetist subject to arrive at a mutually preferred stiffness.
The researchers concluded that mutual preference seemed to be dictated by the specific patient-prosthetist dynamic, and no clear trends emerged.
The open-access study, Comparing preference of ankle–foot stiffness in below-knee amputees and prosthetists, was published in Scientific Reports.