Early muscle-periosteal lesion inhibits fracture healing in rats

We assessed the effects of muscular detachment from the periosteum on fracture healing, focusing on a muscle-periosteal lesion in the initial healing process. In 30 male Wistar rats we produced a partial osteotomy in the mid-diaphysis of the left femur which was then manually broken. All fractures were reamed and stabilized with a 1.6 mm steel pin. The animals were randomly assigned to 3 groups. In group 1, an extraperiosteal detachment between muscle and periosteum was created in the middle third of the diaphysis. In group 2, an extraperiosteal detachment was created with application of an e-PTFE sheath (Gore-Tex® expanded polytetrafluoro-ethylene) around the shaft between muscle and periosteum during the first 2 weeks following fracture. In group 3, the dissection was identical, while the e-PTFE sheath was installed after 2 weeks. The rats were killed after 4 weeks, and their bones were evaluated radiographically and mechanically by the three-point bending test. The fractures healed by production of external callus, and radiographs revealed various degrees of periosteal callus with a ra-diolucent fracture line, most evident after early muscle-periosteal isolation. The callus area was significantly smaller after early muscle isolation, compared to extraperiosteal dissection alone and later tissue isolation. Bending moment and stiffness were also less in this group than in groups 1 and 3, while fracture energy was less than in group 1. No differences in mechanical properties were detected between extraperiosteal dissection alone and late-tissue isolation. This animal study underlines the importance of early muscle-periosteal apposition for fast periosteal healing of diaphyseal fractures.