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Cone-beam CT image analysis of condylar changes following orthognathic surgery

2005; Elsevier BV; Volume: 99; Issue: 3 Linguagem: Inglês

10.1016/j.tripleo.2004.11.038

1528-395X

An de MOl, William R. Proffit, Lucía Cevidanes, L’Tanya J. Bailey,

Facial Trauma and Fracture Management

Systematic prospective observational studies have led to significant progress in the application of orthognathic surgery to treat dentofacial deformity. Remodeling of the mandibular condyles, a potential factor in postsurgical stability, has not been adequately evaluated previously. The development of cone-beam CT (CBCT) scanners has made it feasible to follow changes of the condyles and relate them to treatment outcomes. In order to assess condylar changes in 3 dimensions using CBCT, new measurement procedures have been developed based on previous work by Harris et al.1Harris M.D. Van Sickels J.E. Alder M. Factors influencing condylar position after the bilateral sagittal split osteotomy fixed with bicortical screws.J Oral Maxillofac Surg. 1999; 57: 650-654Google Scholar To develop quantitative measurement techniques assessing 3D condylar position, orientation, and morphology using CBCT. Subjects were scanned presurgically and 3 times postsurgically with the NewTom QR-DVT 9000 (QR-NIM, Verona, Italy). Initial data of the first 15 subjects of an expected total sample of 100 subjects were collected. Preliminary measurements were limited to (1) condylar angulation and (2) mediolateral distance between the condyle and the midsagittal plane (MSP). Presurgical and 4-6 weeks postsurgical scans were evaluated. Six patients had maxillary surgery only and served as controls. Nine patients had 2-jaw surgeries. For each condyle, a set of axial slices encompassing the medial and lateral poles were transferred to ImageJ (NIH, Bethesda, Md). From the image stack a maximum-intensity image was created. After outlining the outer contour of the condyle, the angle of the major axis of a best-fit ellipse was calculated. The average of 3 consecutive measurements with a maximum separation of 1 degree was recorded. MSP was defined as the line dividing the clivus and the base of the vomer in equal halves. The condylar angles were calculated with respect to MSP. The median of the change in condylar angulation in the control group was 0.9 degrees (IQR = 1.2) and in the 2-jaw surgery group 3.3 degrees (IQR = 2.2) (Mann-Whitney P < .05). The change in distance between the condyle and MSP was 0.3 mm (IQR = 0.2) and 0.6 mm (IQR = 0.8), respectively (Mann-Whitney P > .05). These limited preliminary data suggest that CBCT measurements of condylar angulation and mediolateral position are sufficiently robust, allowing meaningful comparisons of groups. Subject recruitment, data collection, and registration of 3D models are ongoing.