Periosteal incarceration versus interposition adipose tissue grafting in physeal fractures: pilot study in immature rabbits

PURPOSE: The purpose of this study is to evaluate bar formation following physeal fracture with incarcerated periosteum or adipose tissue graft using radiographic and histological methods in an immature rabbit model. METHODS: Ten-week-old rabbits underwent induced proximal tibia physeal fractures with a contralateral sham. Fractures had periosteum (n = 5) or adipose tissue (n = 5) interposed. Radiographs were compared over time by tibial medial-lateral side difference (TMLSD)(mm), femoral-tibial angle and tibia plateau angle, and physeal bars evidence. MicroCT was performed, growth plates reconstructed, and physeal area calculated and normalized to same animal contralateral physes. Physeal disruption and chondrocyte organization were evaluated histologically. RESULTS: Radiographic: After 6 weeks, physeal bars formed in both periosteum (4 of 4) and fat groups (3 of 5). The periosteum group showed a significant increase in the TMLSD between immediate post-op and 10 days later (p = 0.028); but, after 6 weeks, TMLSD change was not significantly different between the three groups (p = 0.161). MicroCT: The normalized physeal area of every physis in the fat group was more than 0.9 (0.99 ± 0.06). Only half of the periosteum group was over 0.9 (0.81 ± 0.24). Histology: Physeal disruption was seen by microscopic evaluation in none of the sham group, all 4 in the periosteum group and 4 of 5 in the fat group. CONCLUSIONS: Fat interposition may prevent, or at least delay, the onset of bars across a fractured physis compared to periosteum, but it is not completely protective.