THE EFFECT OF UNILATERALLY ADDED MASS TO THE LEGS ON ABLE-BODIED GAIT: IMPLICATIONS ON HEAVY PROSTHESIS DESIGN
ABSTRACT JUSTIN THOMAS GRACYALNY THE EFFECT OF UNILATERALLY ADDED MASS TO THE LEGS ON ABLE-BODIED GAIT: IMPLICATIONS ON HEAVY PROSTHESIS DESIGN (Under the direction of Dr. Ha Van Vo, Ph.D., MD, DPM) INTRODUCTION: General consensus is that lighter prostheses designs reduce gait deviations and improve energy efficiency; however, these studies have not been able to provide conclusive evidence on the overall effects of different mass distributions, particularly when heavier protheses are involved. METHODOLOGY: Several components of gait mechanics including sagittal and frontal plane joint kinematics, ground reaction forces (GRFs), and relative hamstring energy expenditure (RHEE) were evaluated in able-bodied subjects with unilaterally added mass to the legs simulating a best-case scenario for heavy transtibial and transfemoral prosthesis wearers. Five- and ten-pound masses were added unilaterally to the shank and/or thigh of 10 below-knee (i.e., calf-only) subjects (Baseline, 5lb, and 10lb groups) and 11 above-knee (i.e., calf and thigh) subjects (Baseline, 5lb/5lb and 5lb/10lb groups). RESULTS: Significant differences between weight conditions (p<0.05) were found in self-selected walking speed, cadence, swing time, and stance time. Significant decreases in knee flexion during mid-swing and hip flexion during terminal swing and increases in hip extension during pre-swing were observed with increasing weight. Trunk flexion was found to increase throughout the gait cycle while decreased contralateral trunk lean was found during swing phase of the weighted limb. Relative locations of maximum and minimum joint angles were less affected, and differences were generally not statistically significant. Weighted limb GRF curves generally showed decreased maximum heel strike and toe-off forces with a less defined mid-stance. RHEE was found to increase with heavier loads and was found to increase more with distal loading. DISCUSSION: Findings agree with previous studies regarding the recommendation to avoid distal loading unless other patient benefits are gained. Findings also support idea of kinematically invariant adaptions to gait for mass perturbations. Results suggest increased muscle activity in the lumbar spine with increasing weight with potential links to lower back. Further investigation into this linkage is suggested for future studies. Finally, findings suggest additional unilateral mass plays a significant role on gait and should be avoided when possible. CONCLUSION: This study shows that unilaterally added mass plays a significant role on able-bodied gait mechanics and can be used to support and provide insight for future prosthesis design.
Gracyalny, Justin Thomas