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Does Removing Local Soft Callus Influence Early Fracture Healing?
Jonathan R. Danoff, MD; Ayhan Kilic, MD; Rebecca Rajfer, BS; Eugene Jang, MS; Yelena Akelina, DVM; Thomas Gardner, MCE; Melvin P. Rosenwasser, MD
Department of Orthopaedic Surgery, Columbia University Medical Center, New York, NY

Hypothesis: Removing soft callus at osteosynthesis in the first 1-2 weeks after injury may interfere with early fracture healing.  While it is necessary to remove the biological material from bone ends to adequately reduce the fracture, it is unclear what effect this has on fracture repair. We hypothesized that the removal of initial local fibrocartilage callus from a transverse femur fracture in a rat will be detrimental to early fracture healing.

Methods: An open, transverse femur fracture was created in 30 male Sprague-Dawley rats (320-360g) and stabilized with a 1.1 mm intramedullary Kirschner wire (K-wire). Twenty-one days later, the fracture site was surgically exposed, K-wire retracted, and a scalpel was passed through the fracture site. Group A (n=10) served as the control and the callus was not removed. In Group B (n=10), the callus was removed and discarded, and in group C (n=10), the callus was removed and within 5 minutes replaced at the fracture site. The wires were re-inserted and after an additional 21 days of healing, the rats were sacrificed and femurs harvested. Three-point bending was performed on the ex vivo femurs to determine failure force and energy to failure. Callus and bone volume were calculated using high resolution animal fluoroscopy and normalized to the contralateral uninjured femur.

Results: Twenty-nine of 30 rats survived the duration of the study. Formation of bridging callus was confirmed radiographically in all fractures at the 42-day time point. Structural properties declined in femurs with callus removed as there was a statistically significant decrease of 74% in energy to failure versus control (p<0.05), and a non-significant 51% decrease in failure load versus control (p=0.08). There was some recovery of failure force and energy to failure when the callus was replaced in comparison to callus removed by 39% and 59% respectively, but both values were still lower than control. These differences were not statistically significant. The normalized callus volume in the callus replaced group increased by 30% over control (p<0.05) with no statistically significant difference detected between the callus removal group and control.

Summary Points: We utilized a rat femur fracture model to recreate the typical fracture site preparation with callus removal.  Our data suggest that removal of local soft callus compromises early fracture healing. It is possible, although not proven by this study, that replacing the adjunct may mitigate these negative consequences. Total removal of early fibrocartilage callus may unnecessarily impair biological healing.

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