1Medical College of Wisconsin, Milwaukee, WI, USA, 2Children's Hospital of Wisconsin, Milwaukee, WI, USA.
PURPOSE: To examine the post-operative skull growth of patients operated for sagittal synostosis by serial analysis of 3D reconstructions of the skull.
METHODS: 22 patients operated between 1999 and 2003 underwent pre-operative 3D CT scans of the craniofacial region, and serial post-operative scans at 4 weeks, one year, and yearly afterwards. The DICOM data from the CT scans were uploaded on a special-purpose software for mathematical analysis. Technical steps of the uploading, aligning and analysis will be presented. Minimum follow-up was one year.
RESULTS: All patients were operated using a standardized technique. The cranial index improved from 66.4 pre-operatively to 74.5 at one year. The 3D analysis showed continued abnormal growth patterns up to 5 years post-operatively. Transverse growth continued to be the dominant vector of growth up to one year (until ossification-bridging of the vertex craniectomy). Beyond one year, the main area of transverse growth was overlying the temporal suture, producing a distinctive temporal bossing in patients. The parietal areas showed minimal growth afterwards. Growth was mainly occipital between 1-3 years of age, and frontal afterwards, up to 5 years of age. A low frontal bossing also occurred in some of our patients and resolved spontaneously. The frontal bossing was observed to migrate cephalad, away from the orbital rim.
CONCLUSION: These observations suggest a continued post-operative abnormal growth pattern of the skull, longer than previously suggested. The described 3D analysis technique could offer a useful tool for the clinician in evaluating his post-operative results.
Surface-Distance analysis of the 6-18 months post-operative period (12-24 months of age) in a patient that showed early bridging-ossification of the vertex ostectomy. Note increased growth at the level of the coronal sutures and at the level of the temporo-parietal suture. This may be the etiology of the appearance and aggravation of temporal bossing at this age, since the temporo-parietal suture becomes a major site of transverse expansion. A: Anterolateral view of the skull, face has been removed. B: posterolateral view. C: base of skull. Note predominance of frontal growth D: vectors representing magnitude and direction of changes can be viewed to identify regional axes of growth