Minced Muscle Autografting Improves Bone Healing but not Muscle Function in a Porcine Composite Injury Model.

Composite tissue injuries (CTIs) in extremities include segmental bone defects (SBDs) and volumetric muscle loss. The objective of this study was to determine if skeletal muscle autografting with minced muscle grafts (MMGs) could improve healing in a SBD and improve muscle function in a porcine CTI model that includes a SBD and adjacent volumetric muscle loss injury. Adult Yucatan Minipigs were stratified into three groups including specimens with an isolated SBD, an SBD with volumetric muscle loss (CTI), and an SBD with volumetric muscle loss treated with MMG (CTI+MMG). Bone healing was quantified with serial xrays and post-mortem CT scanning. Muscle function was quantified with a custom in vivo force transducer. Muscle tissue content was determined by biochemical analyses and histology. Anterior cortex modified Radiographic Union Score for Tibia fractures (mRUST) decreased from 2.7 to 1.9 (p = 0.003) in CTI vs. SBD animals. MMG improved anterior mRUST scores to 2.5 in CTI+MMG specimens (p = 0.030 compared to CTI specimens) and overall mRUST scores increased from 9.4 in CTI specimens to 11.1 in CTI+MMG specimens (p = 0.049). Residual strength deficits at euthanasia were 42% in SBD (p<0.001), 44% in CTI (p<0.001) and 48% in CTI+MMG (p<0.001) compared to preoperative values. There were no differences in strength deficits between the three groups. Biochemical and histologic analyses demonstrated scattered differences between the three groups compared to contralateral muscle. MMG improved bone healing. However, the primary cause of muscle dysfunction and biochemical changes was the presence of a SBD. This article is protected by copyright. All rights reserved.