Healing pattern after vertical ramus osteotomy by time intervals on micro-computed tomography

Abstract

Vertical ramus osteotomy (VRO) in mandible is a preferred method for mandibular prognathic patients. Few experimental studies of osseous healing and remodeling of VRO, unlike proper healing of fracture, have been conducted under similar clinical situations. Many clinicians using this procedure are thus greatly dependent on their own experiences. To better understand the healing pattern on adult beagle dogs after vertical ramus osteotomy, they were euthanized and observed at 1st week, 2nd week, 3rd week, 4th week, 6th week, and 8th week respectively. Each specimen was scanned in a micro-computed tomography – an imaging tool regarded as the gold standard for evaluation of bone morphology and microarchitecture and several parameters were calculated. We then reached the following conclusions: 1. The amount of newly formed bone increased up to 4th week, decreased slowly up to 6th week, and decreased sharply after 6th week.2. The new bone volume around the distal segment was larger than that around the proximal segment up to 6th week and vice versa at 8th week.3. The parameters in the new bone around the distal segment up to 6th week, such as BV (bone volume), BV/TV (bone volume fraction), BS/BV (specific bone surface), Tb.N (trabecular number), Tb.Sp (trabecular separation) as well as the parameters in the new bone around the proximal segment, such as Tb.Th (trabecular thickness) were statistically significant in demonstrating increased strength with the maturation of new bone. Together with the above results, the healing pattern after vertical ramus osteotomy showed active generation of new bone up to 4th week, followed by remodeling. New bone volume around the distal segment was larger than that around the proximal segment up to 6th week and vice versa at 8th week. Clinically, preservation of the distal segment vasculature which contribute to the early healing of VRO, importantly should be taken into consideration.