Interlimb Symmetry with Different Prosthetic Feet
In the same issue of JRRD, GNS Marianakis reported on preliminary data from a small group of new traumatic unilateral transtibial amputees who used both SACH and multiaxial flexible keel feet. Based on our cherished clinical assumption that a more symmetric gait is more desirable, Marianakis calculated various limb symmetry indexes after the patients had used their initial prostheses for approximately four months.
In addition to the small sample size of 9 subjects, this study did not randomize the order in which the feet were provided. All amputees were initially tested with the SACH foot they had worn on their preparatory prosthesis for several months. They then received a Greissinger Plus foot for one week and were then retested in the gait lab. This short period to acclimatize to the second component raises questions about whether these novice amputees had time to develop a mature gait pattern and benefit fully from the increased mobility of the multiaxial ankle-foot.
Overall, this study concludes that "all the measured spatial and termporal factors were significantly improved when the SACH foot was replaced by the Greissinger Plus foot". Interestingly, the symmetry indexes did not show significant differences for all parameters. In other words, clinically significant changes did not necessarily result in statistically significant improvements in the indexes studied. The author discusses some possible reasons why this was the result.
Equally interesting to me was the statement that "most patients still wanted to use the conventional SACH foot" even though they walked measurably better in the more sophisticated ankle-foot mechanism. The author speculated that one factor influencing this decision may be that their funding agencies refused to cover the costs for anything but the SACH component. This study raises a number of important clinical and scientific questions about patient acceptance of prosthetic components, and provides good food for thought regarding future studies. The entire article can be read or downloaded at www.vard.org/jour/04/41/4/marinaskis.html .