[Effect of segmental Le Fort I osteotomy and bilateral sagittal split ramus osteotomy on the condyle position in skeletal class III malocclusion patients].

OBJECTIVE: To investigate the effect of segmental Le Fort I osteotomy and bilateral sagittal split ramus osteotomy (BSSRO) on the condyle position in skeletal class III malocclusion patients.

METHODS: In this retrospective study, 19 patients with skeletal class III malocclusion who met the inclusion criteria were enrolled. All the patients underwent the segmental Le Fort I osteotomy and BSSRO. Cone beam computed tomography (CBCT) scans were performed in the following phases: T1: within one week before the surgeries; T2: within one week post-surgery;T3:three months post-surgery; T4: 6 to 14 months post-surgery. The posterior spaces, anterior spaces and the superior spaces of the bilateral temporomandibular joints were measured according to the Kamelchuk method respectively. The fossa ratios of the condyle and the distribution of the condyle positions related to the glenoid fossa (anterior, concentric and posterior position)were calculated. The results were analyzed statistically.

RESULTS: The posterior space, the anterior space and the superior space of bilateral temporomandibular joints in T2 phase[right: (2.78±1.23) mm, (2.47±0.89) mm, (3.07±0.85) mm; left: (2.93±0.83) mm, (2.69±1.14) mm, (3.44±1.16) mm] showed significantly larger spaces than those in T1 phase [right: (1.81±0.95) mm, (1.65±0.55) mm, (2.13±0.52) mm; left: (2.12± 1.05) mm, (1.79±0.59) mm, (2.15±0.93) mm],in T3 phase [right: (2.08±1.25) mm, (1.79±0.68) mm, (1.80±0.76) mm; left: (2.05±0.75) mm, (1.99±0.94) mm, (2.14±0.71) mm] and in T4 phase [right: (1.94±0.77) mm, (1.81±0.69) mm, (2.05±0.69) mm; left: (1.89±0.69) mm, (1.80±0.61) mm, (2.19±0.75) mm], P<0.05. No significant differences were observed among T1,T3 and T4 phases in the terms of the joint spaces of both sides(P>0.05).The fossa ratio and the condyle position related to the glenoid fossa had no significant difference in all the four phases (P>0.05).The results suggested that the condyle moved downward in T2 phase and changed to the original pre-surgery position in T3 phase, then keot stable in T4 phase.

CONCLUSION: Segmental Le Fort I osteotomy and BSSRO caused significant and transient changes of the condyle position in skeletal class III malocclusion patients. However, the condyle tended to move back to the original pre-surgery position and might keep stable.