Fascia Healing after Induced Tibialis Anterior Muscle Strain: an Experimental Study in Wistar Rats

Background. Recurrence following muscle strain is a serious problem encountered in sports. Muscle and fascia are mechanically integrated in transmitting muscular force. Fascial injury has been associated with muscle strain which may explain its potential contribution to impaired muscle recovery. This study aimed at describing structural changes of fascia and muscle as well as limb function recovery during the various healing stages following strain injury in rodents. Methods. Thirty-two adult male Wistar rats were randomly and equally divided into four groups: normal control and three muscle strain injury groups. Tibialis Anterior muscle was strained in the three injured groups then all rats were allowed free cage mobility until euthanasia after 2 days (acute group), 9 days (subacute group), or 21 days (chronic and normal groups). The sciatic function index was used to assess functional recovery while histopathology scoring and histomorphometry quantified tissue healing. Results. Cellularity significantly increased in muscle and fascia tissues only in the acute stage (p < 0.05). Collagen degeneration was significant in the acute and subacute stages in muscle (p < 0.05), whereas fascia showed significant degeneration only at the subacute stage (p < 0.05). Fascia thickness significantly increased in all examined stages (p < 0.05), while muscle fibers width and interstitial dilatation increased only in the acute and subacute stages (p < 0.05). Muscle fibrosis was significant in the subacute and chronic stages (p < 0.05). Function was not significantly different between all groups at all examined stages (p > 0.05). Conclusions. Strain injury involves all fascia and muscle structures. Healing of all structures occurs spontaneously by the chronic stage, except for fascia thickness and muscle fibrosis. Future studies are recommended to investigate whether incorporating fascia as a therapeutic goal would decrease muscle injury recurrence.