Fast and slow myosin as markers of muscle regeneration in mangled extremities: a pilot study

Mangled extremities were classically managed by amputation. But over the past few decades, with the advancement in surgical techniques, an increased number of limb salvages have been possible. As muscles usually get damaged in such grievous injuries, a thorough understanding of muscle regeneration may give a better insight into muscle healing in these injuries. Muscles are composed of slow and fast fibers which can be represented by slow and fast myosin, respectively. There are some animal studies which reported differential regeneration of slow and fast muscle fibers during muscle healing. We conducted this pilot study to find out whether the same holds true for muscle healing in mangled extremities also. This pilot study is designed in 15 patients with lower limb mangled extremities presenting to trauma center of PGIMER, Chandigarh, who were operated within 24 h of injury to see whether muscle healing in mangled extremities follows the same pattern. Biopsies were taken during initial surgery conducted within 24 h of injury and on the 7th day of injury when patient was posted again for secondary wound closure procedure or revision amputation. The biopsy samples were subjected to histopathological and immunohistochemistry examination using antibodies against fast and slow myosin. We found that the regenerating muscle fibers in the biopsy sample taken on the 7th day of injury showed only slow muscle fibers with the absence of fast muscle fibers when compared with the initial biopsy results showing differential regeneration of slow muscle fibers.