ABSTRACT
AIM: To quantify, by histomorphometry, the effects of local insulin-like growth factor-1 (IGF-1) during mandibular distraction at various rates. METHODOLOGY: Mature rabbits underwent bilateral mandibular corticotomy and distraction lengthening. Recombinant IGF-1 was administered to two groups of rabbits via osmotic infusion pumps. Distraction regimes were as follows: Group A, 1 mm/day for 15 days; Group B, as for A plus IGF-1; Group C, 3 mm/day for 5 days; Group D, as for C plus IGF-1; and Group E, sham-operated controls. After a 28-day consolidation period, rabbits were sacrificed and bone deposition quantified using DEXA scanning, three-point bending, histological examination and sampled for histomorphometric analysis. RESULTS: DEXA scanning and three-point bending failed to detect any effect of distraction rate or of IGF-1 infusion. Histological and histomorphometric analysis suggested 1 mm/day to be the ideal distraction rate, as this was associated with greater osteoblastic activity and consistent bony union. However, IGF-1 infusion significantly enhanced osteoblastic activity at both distraction rates and resulted in bony union when distraction was performed at 3 mm/day. CONCLUSIONS: Distraction osteogenesis at a rate of 1 mm/day provides greater osteogenic stimulus than 3 mm/day. Exogenous IGF-1 has a positive influence on osteoblastic activity during distraction. Its effect is probably minimised by high levels of endogenous IGF-1.
Subject(s)
Insulin-Like Growth Factor I/pharmacology , Mandible/surgery , Osteogenesis, Distraction/methods , Animals , Biomechanical Phenomena , Bone Density , Male , Mandible/pathology , Mandible/physiopathology , Osteoblasts/physiology , Rabbits , Recombinant Proteins/pharmacology , Stress, MechanicalABSTRACT
The rabbit model has been used to study the effects of different rates of distraction upon mandibular bone. Bilateral distraction was performed at two different rates anterior to the molar teeth. Both experimental groups were significantly inferior to sham operated controls in terms of bone density (DEXA) and mechanical testing. No difference in new bone formation between the two distraction rates was detected by these modalities. However, histological examination revealed non-union to be more common in the rapidly distracted group. This suggests that attempts to shorten the duration of external fixation in clinical mandibular distraction osteogenesis should be by methods other than more rapid distraction.
