Healing physiology following delayed surgery for femoral midshaft fracture caused by high-energy injury: an in vivo study in dogs

OBJECTIVE: An experimental model of severe soft tissue damage was designed to simulate high-energy fracture and observe the fracture healing process following early surgery and surgery delayed by 1 week. METHODS: Forty dogs were randomized to Group A (immediate surgery) and B (delayed surgery). The femur was broken, and the two ends were forcefully stabbed to damage the surrounding soft tissues. The fracture was repaired using a custom six-hole steel plate. Four dogs were killed on day 3 and weeks 1, 2, 4, and 8 following bone fracture. Soft tissue and bone were examined by light and electron microscopy. RESULTS: In Group A, no callus was present at 1, 2, 4, and 8 weeks following fracture, resulting in atrophic nonunion. In Group B, visible weak external callus was present 1 week following fracture, and good external callus growth was present at 2, 4, and 8 weeks, leading to callus healing. CONCLUSION: These findings suggest that the first week is critical for fracture healing. Absence of callus in the early stage is indicative of absence of callus growth throughout the entire healing process, while the presence of callus in the early stage is indicative of vigorous callus growth thereafter.