Single versus triple daily activation of the distractor: No significant effects of frequency of distraction on bone regenerate quantity and architecture

Objectives: To study the effect of two different frequencies of distraction on the quantity and architecture of bone regenerate using micro-computed tomography, and to determine whether radiographic and ultrasonographic bone-fill scores provide reliable predictive value for the amount of new bone in the distraction area. Material and methods: Twenty-six skeletally mature rabbits underwent three full days of latency, after which midface distraction was started. Low-frequency group (n = 12): a distraction rate of 0.9 mm/d achieved by one daily activation for 11 days to create a 10 mm distraction gap. High-frequency group (n = 12): idem, but three daily activations were used instead of one. Control group (n = 2) underwent no distraction. After 21 days of consolidation, bone-fill in the distraction area was assessed by means of ultrasonography and radiography. Micro-computed tomography was used to quantify new bone formation and bone architecture. Results: Relative bone volume (BV/TV) showed a tendency towards a difference (P = 0.09) between the low and high-frequency groups. No significant differences were found for bone architecture. No significant correlation between BV/TV values and bone-fill scores was found. Conclusions: An increase in rhythm from one to three activations daily does not create significantly more bone. Bone-fill score values provided no reliable predictive value for the amount of new bone formation. (c) 2007 European Association for Cranio-Maxillofacial Surgery