Trabecular organization in mandibular osteodistraction in growing and maturing rats.

Purpose: Our goal was to investigate the trabecular organization of the distraction regenerate during various consolidation phases and as a result of various distraction rates.

Materials And Methods: One hundred ninety-two growing and maturing rats (96 each) received unilateral mandibular osteotomies and distraction device placement. They were randomly allocated into 4 distraction rate groups (0, 0.2, 0.4, and 0.6 mm/day for 5 days) after a 3-day latency. Eight rats from each rate group were sacrificed at early (10 days), mid (24 days) and late (38 days) consolidation time points. Harvested hemimandibles were embedded in micro-bed resin, sectioned sagittally at 10 mum thickness and stained using the Von Kossa method. The histologic images were captured and processed using Adobe Photoshop (Version 7.0; Adobe Systems Inc, San Jose, CA). Custom-made software (MacAzimuth; written by Prof. J.M. Rensberger, University of Washington) was further used to analyze the orientation (anisotropy and angle distribution) and mass (density and thickness) of trabecular structures in the regenerates.

Results: Trabecular orientation significantly differed at the mid-consolidation time point with less anisotropy ( P < or = .000 to .023) and narrower angular distribution ( P < or = .007 to .021). Trabecular mass increased significantly from early to mid-consolidation ( P < or = .000 to .002). Growing rats showed greater trabecular organization than maturing rats did at the same time points ( P < or = .000 to .009). The trabecular organization parameters were associated significantly with bone mineral density and microdensity ( P < or = .000 to .044).

Conclusion: The peak change in orientation occurred around the mid-consolidation with a greater increase in trabecular mass. Growing rats showed a greater capacity for trabecular organization at earlier time points. However, distraction rate did not have an effect on trabecular organization. These results suggest that trabecular organization can be used as an important indicator to evaluate bone maturation and quality in the distraction regenerate.