Posterior Cranial Vault Distraction Osteogenesis Utilizing a Posterior-Superior Distraction Vector in the Treatment of Mercedes Benz Pattern Craniosynostosis

Bilateral lambdoid and sagittal synostosis, or Mercedes Benz Syndrome, is a rare complex craniosynostosis resulting in frontal bossing, a tapered posterior fossa, and an anteriorly displaced cranial vertex. Its ideal surgical correction must result in posterior expansion, skull elongation, and caudal repositioning of the vertex. We present a craniometric analysis of skull changes with posterior-superior distraction and introduce a novel craniometric measure: vertex position. In this study, a retrospective review was performed to analyze outcomes of posterior cranial vault distraction osteogenesis (PVDO) using a posterior-superior distraction vector from 2016 to 2019. Cranial vertex position was measured as a fraction of the occipitofrontal diameter from rostral to caudal (0-1.0). Four patients underwent PVDO at mean age 10.61 +/- 3.16 months utilizing a posterior-superior distraction vector. Linear distraction distance averaged 30.30 +/- 0.90 mm with a mean consolidation period of 3.98 +/- 0.72 months. Mean corrected change in intra-cranial volume was 236.30 +/- 3.71 mL, at an average rate of 7.81 +/- 2.00 mL/mm of distraction. Increases in anterior cranial height (7.83 +/- 2.51 mm), middle cranial height (8.43 +/- 4.21 mm), posterior cranial height (13.15 +/- 7.45 mm), and posterior cranial fossa height (21.99 +/- 8.55 mm) were observed. Cranial vertex demonstrated a mean posterior movement of 0.18 +/- 0.13. PVDO utilizing a posterior-superior distraction vector for management of nonsyndromic bilateral lambdoid and sagittal synostosis effectively increases intracranial volume and height and provides an esthetic outcome with posterior movement of the cranial vertex.