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Effects of latency and rate on bone formation in a porcine mandibular distraction model
M J Troulis1, J Glowacki, D H Perrott
1Department of Oral and Maxillofacial Surgery, Massachusetts General Hospital, Harvard School of Dental Medicine, Boston, USA.
Purpose:
Long treatment protocols currently limit the application of distraction osteogenesis (DO). The purpose of this study was to develop a porcine model for DO and to define the effects of latency and distraction rate on bone formation.
Materials And Methods:
Distractors were placed through submandibular incisions. For analysis of latency, mandibular osteotomies were distracted after 0 (n = 3) or 4 (n = 2) days at a rate of 1 mm/d (7 days) with 14 days fixation. For analysis of rate, osteotomies were distracted at 1 mm (n = 4), 2 mm (n = 4), or 4 mm (n = 4) per day to produce a 12-mm gap with 24 days fixation. DO wounds were assessed in vivo with bimanual palpation to detect mobility across the gap. Harvested specimens were evaluated by gross appearance and bimanual palpation. Standardized radiographic techniques were used to estimate bone density.
Results:
During DO, animals showed normal activity. There were no infections, and no distractors were removed prematurely. Clinical and radiographic evaluation of the groups that underwent distraction after 0- or 4-day latency showed equivalent healing. In the comparison of distraction rates, stability was greatest in the group distracted at 1 mm/d.
Conclusions:
A porcine model for mandibular DO has been developed in which mandibular lengthening was successfully performed without latency and at a rate of 1 mm/d. The relationships among latency, gap size, rate, and duration of fixation are poorly understood and can be defined with relevant animal models.