Muscular Asymmetries in Anatomical Donors with Lower-Limb Amputations

Purpose: Muscle atrophy from amputation has been associated with increased gait asymmetry, fall risk, and overuse injuries. This study investigated between-limb muscular differences in donors with lower-limb amputations to determine if findings reflect living individuals. We hypothesized each donor's most compromised limb would show less muscle mass, lower pennation angle and PCSA, and fewer and smaller type 1 fibers compared to their most intact limb. Methods: Two male unembalmed donors 61-67 years of age with diabetic lower-limb amputations were obtained through the UNTHSC Willed Body Program. Four muscles were dissected from each limb: gluteus maximus, sartorius, rectus femoris, and biceps femoris long head. PCSA was calculated using the following formula: [(muscle mass x cos(pennation angle)] / [fiber length x muscle density (1.067 g/cm-3)]. Histological (H&E) staining of muscle tissue determined fiber density and cross-sectional area. Immunohistochemical (IHC) staining identified the percentage of fibers containing the fast isoform of myosin heavy chain (MHC), or type 2 "fast-twitch" fibers. Results: Biceps femoris PCSA was 18.1-68.6% larger on each donor's most compromised limb compared to their most intact limb. Histological staining also showed smaller cross-sectional biceps femoris muscle fibers on the most compromised side compared to the most intact side. IHC analyses of fiber phenotype in these muscles are ongoing. Conclusion: Knowledge of muscle adaptations following amputation in donors can confirm accurate biomechanical modeling and inform rehabilitation techniques to reduce muscle atrophy.