A Craniometric Analysis of the Posterior Cranial Base After Posterior Vault Distraction

Background: Posterior vault distraction osteogenesis (PVDO) has been demonstrated to effectively increase intracranial volume, treat increased intracranial pressure, and improve head shape in syndromic patients. The purpose of this study is to compare changes along the posterior cranial base before and after distraction. Methods: A retrospective review was completed of subjects who underwent PVDOwith computed tomography scans at 2 time-points: within 3 months preoperatively and 1 to 6 months postoperatively. Using Mimics software, craniometric landmarks were identified and surface area of the foramen magnumwas calculated. Acomparison of pre- to postoperative measurements was completed using Wilcoxon matched-paired signed rank tests and linear regression. Results: A total of 65 PVDO subjects were identified, 12 subjects met inclusion criteria. Mean operative age was 3.0 +/- 4.0 years. The cranial vault was distracted on average 25.0 +/- 6.0 mm, with those < 12 months of age distracted 29.5 +/- 4.9 mm and >12 months of age distracted 22.0 +/- 4.9 mm (P = 0.0543). There was a significant increase in pre- to postoperative foramen magnum surface area (52.1 +/- 63.2 mm(2), P = 0.002), length (0.9 +/- 1.4 mm, P = 0.050), and width (0.6 +/- 1.0 mm, P = 0.050). Similarly, linear distances between nasion and posterior cranial base landmarks such as foramen magnum (3.4 +/- 4.2 mm, P = 0.010), and occipital protuberance (9.1 +/- 9.6 mm, P = 0.003) were increased. Subjects under 12 months had a greater percentage increases in posterior vault length than those over 12 months. Conclusion: Posterior vault distraction osteogenesis is associated with an increase in size of the foramen magnum, and lengthening of the posterior cranial base, both of which may be beneficial in patients with turribrachycephaly.