Spring-mediated cranioplasty for scaphocephaly: techniques and outcomes

PURPOSE: Spring-mediated cranioplasty (SMC) is an established minimally invasive technique for the treatment of sagittal craniosynostosis. This study describes our surgical technique and evaluates long-term morphometric outcomes following SMC. METHODS: A retrospective review was performed of subjects who underwent SMC as primary treatment of sagittal craniosynostosis at our institution between 2011 and 2019. Demographic variables, perioperative data, spring characteristics, and cranial index (CI) were obtained. Subjects were stratified by their use of post-operative helmeting. Longitudinal CI changes were evaluated using linear mixed-effects models. Differences in CI change between subjects receiving 2 vs 3 springs were compared using Mann-Whitney U tests. Linear regression was used to evaluate total spring force as a predictor of percent change in CI. RESULTS: Seventy subjects were included. Seventy-four percent (n = 52) of the cohort received springs treatment only, whereas 26% (n = 18) additionally underwent post-operative helmeting. Mean pre-operative CI was 0.67. Mean age at spring placement was 3.5 months and mean time to spring removal was 108 days. The mean total spring force independent of spring number, measured to 20 mm initial opening, was 26.3 N. Mean post-operative CI at >10 years was 0.76 and 0.74 for non-helmeted and post-operative helmeted subjects, respectively. There was no significant difference in change in CI between subjects who received 2 or 3 springs, despite a significantly different mean total spring force (18.6 N versus 27.9, p < 0.001). Linear regression demonstrated that different minimum spring forces were required to reach adequate CI improvement based on total spring number. CONCLUSIONS: Spring-mediated cranioplasty is associated with durable correction of sagittal craniosynostosis with sustained long-term improvement as measured by cranial index. Further evidence is needed to elucidate predictors of CI change when using SMC, its effects on regional head shape changes in three dimensions, and to further explore the role of adjunct therapies such as helmeting.