Analysis of the cephalometric changes in the first 3 months after spring-assisted cranioplasty for scaphocephaly.

BACKGROUND: Spring-assisted cranioplasty (SAC) has become an accepted treatment for patients with sagittal craniosynostosis; however, the early effects of springs on skull dimensions have never been assessed with objective measurements in the literature. The present study evaluated the changes in skull dimensions and intracranial volume (ICV) during the first 3 months after SAC for sagittal synostosis.

METHODS: Sixteen patients with sagittal synostosis underwent SAC. The cephalic index (CI) and the distance between the spring foot plates were chronologically measured until spring removal at 3 months. Pre- and post-treatment CT scans available for 6 patients were used to assess changes in head shape. Thirteen patients underwent objective aesthetic assessment using pre- and post-operative photographs. Statistical analysis was performed using the linear mixed model for chronological data, t-test statistics for normative data comparisons and Wilcoxon's signed rank test for non-parametric data.

RESULTS: For scaphocephalic patients, pre-operative and post-operative CIs were 0.70 and 0.74 (p = 0.001), respectively. Cranial widening towards normative values was observed (p = 0.0005). A continuous expansion in the distance between the spring foot plates was observed over the treatment period. Frontal and occipital angles were not affected by SAC despite apparent clinical improvements in frontal bossing and occipital prominence. CT analysis demonstrated relative reduction in the anterior cranial volume (p = 0.01) and relative expansion of the superior occipital volume (p = 0.03).

CONCLUSIONS: Spring expansion was most marked in the hours following spring insertion. The expansion rate reduced to the minimum by day 1 post-operatively. Clinical benefits of SAC resulted from an increase in the bi-temporal width that camouflaged the frontal bossing. Improvement in occipital prominence was due to superior occipital volume expansion, allowing the occiput to remodel to a more rounded shape.