After transfemoral amputation, patients with longer residual limbs experienced a faster self-selected walking velocity compared with patients with shorter residual limbs, according to study results published in Clinical Orthopaedics and Related Research.
“Although the relationship between energy expenditure and the level of amputation has been explored previously, comparisons with regard to residual limb length or orientation within a single level are lacking,” the researchers wrote. “When compared with more distal amputations allowing for retention of vital musculature and joints such as in knee disarticulation or transtibial amputation, transfemoral amputation typically resulted in higher energy cost. The purpose of this study was to compare residual limb length and orientation in patients with transfemoral amputation with energy efficiency.”
Long vs. short residual limbs
Researchers separated 26 adults with acute, trauma-related unilateral transfemoral amputations into groups based on residual limb length and residual femoral angle for analysis. Patients underwent gait and metabolic analysis testing at a minimum of 24 postoperative months. The original microprocessor-controlled C-Leg (Ottobock, Duderstadt, Germany) or the second generation of the C-Leg were worn by 20 of the patients, while the remaining patients wore either a microprocessor knee similar to the C-Leg (fluid, hydraulic, Endolite Mercury; Endolite Miamisburg, Ohio; Ottobock Power Knee) or a hydraulic unit (fluid, mechanical, Ottobock 3R80 or the Össur Total Knee; Össur, Foothill Ranch, Calif.).
Among the residual limb ratio groups, researchers found that patients with longer residual limbs walked faster than patients with short residual limbs, a result which confirmed previous studies. However, researchers found no other differences in the other metabolic cost parameters between the short and long residual limb length cohorts or the femoral abduction angle cohorts. Researchers also found a fair correlation between speed and the excursion of the body center of mass in the mediolateral direction, but found no differences with the numbers available when comparing types of prosthetic knee component.
“The length of the residual limb in those with traumatic transfemoral amputations had no effect on energy expended during gait other than the speed,” Johanna Bell, MSE, biomedical gait lab research engineer at Walter Reed National Military Medical Center, told O&P Business News. “We had thought that a longer limb would be more important in gaining higher function. However, it may be that treatment of the remaining musculature and tissue to create a sound residual limb and rehabilitation are key.”
According to the researchers, this study presents several limitations and confounding factors. The relationship between residual limb length and some metabolic variables should be explored in additional research, and the cutoff selected for separating the study groups could be altered. The researchers did not factor the weight, knee center or weight distribution of the prosthesis into the energy cost of individuals, which may or may not impact the metabolic efficiency at a self-selected pace. The mass of the patients also included the mass of the prosthesis, which may not have accurately represented the work being performed. However, according to the researchers, “the components worn by patients were not substantially different from one another in either weight or functional capabilities.”
“A larger group of subjects would be beneficial in determining whether there is a significant effect of limb length,” Bell said. “Additionally, looking into the treatment of the limb during the amputation (ie, musculature attachment) including those with knee disarticulations and known issues with muscle attachment (no myodesis/myoplasty) would also be beneficial.” — by Casey Tingle
Disclosure: Bell has no relevant financial disclosures.