Refinement and initial characterization of a murine mandibular distraction osteogenesis model.

OBJECTIVE: To establish and initially characterize a reproducible mouse mandibular distraction osteogenesis (DO) model using a modular precision device. METHODS: An external distractor was designed based on micro-CT data of C57BL/6 mouse mandibles. Fifty-four mice were randomized into sham, fracture, acute distraction, and gradual distraction groups. The gradual group underwent osteotomy, 5-day latency, 10-day distraction (0.15 mm/12 h, total 3 mm), and 4-week consolidation period. The acute group underwent 5-day latency and single 3 mm distraction on postoperative day 6 (POD 6). Fracture group underwent osteotomy only, while the sham underwent surgical exposure only. Samples were collected from the gradual group at POD 6, 10, 15, 22, 29, 43; other groups at POD 43. Bone regeneration was evaluated by micro-CT and histology. RESULTS: The distraction gap reached 3.02 ± 0.13 mm, consistent with the 3.0 mm target. Body weight recovered favorably. Micro-CT revealed that the gradual group exhibited characteristic DO temporal patterns: limited bone formation during distraction with low BV/TV (0.94 ± 0.44% at POD 6), followed by marked mineralization during consolidation, reaching 38.07 ± 2.86% at POD 43 (P < 0.0001 vs. POD 6). Histology showed ordered collagen deposition along the distraction vector during distraction, with subsequent trabecular maturation during consolidation. At POD 43, the gradual group had significantly higher BV/TV, Tb.Th, and Tb.N than both the fracture and acute groups (all P < 0.05). CONCLUSION: A reproducible mouse mandibular DO model was established, providing a reliable platform for investigating mechanically induced craniofacial bone regeneration.