Autologous Minced Muscle Grafts Improve Muscle Strength in a Porcine Model of Volumetric Muscle Loss Injury

The traumatic loss of muscle tissue, defined as volumetric muscle loss (VML) injury, has no definitive therapy. The purposes of this study were: (1) to develop a porcine model of VML and (2) to investigate autologous minced muscle grafts (1-mm3 pieces of muscle) as a potential therapeutic. Minced grafts were evaluated because they have promoted fiber regeneration and functional recovery in rat VML models and do not require US Food and Drug Administration approval for clinical use. In 5 female Yorkshire-cross pigs, ≈5 g (≈20%) of tissue was excised from the peroneous tertius muscle (≈3 × 3 × 1.5-cm defect) of each leg. The defect in one leg was treated with autologous minced grafts derived from the contralateral leg. Maximal isometric tetanic strength assessments of the dorsiflexor muscles (ie, the peroneous tertius muscle) were performed before and biweekly up to 12 weeks postinjury. VML injury resulted in a −43.5% ± 7.2% strength deficit 12 weeks postinjury in nonrepaired legs. Autologous minced muscle graft repair significantly improved strength over 12 weeks (32% strength increase 12 weeks postinjury vs. nonrepaired muscles with a remaining −27.8% ± 7.0% strength deficit; P < 0.001). Nonrepaired muscles developed extensive fibrosis and presented no evidence of muscle fiber regeneration within the defect area. Minced graft-treated muscles presented areas of putative de novo muscle fiber regeneration within the defect area, although extensive fibrotic tissue deposition was also present. Autologous minced muscle grafts partially restored neuromuscular strength in a novel porcine model of VML.