Cranial Shape Changes in Nonsyndromic Unilateral Lambdoid Synostosis after Open Posterior Vault Remodeling

Background:The purpose of this study was to quantify change in cranial morphology in patients with nonsyndromic unilateral lambdoid craniosynostosis (ULC) from presentation (t0), after open posterior switch-cranioplasty (t1), and at 2-year follow-up (t2). Methods:Volumetric, linear, and angular analysis were performed on computed tomographic scans at the three time points and against normal control subjects. Significance was set at P < 0.05. Results:Twenty-two patients were included. ULC cranial vault asymmetry index was higher than in control subjects before surgery (6.22 & PLUSMN; 3.55) but decreased after surgery (3.00 & PLUSMN; 2.53) to become comparable with the normal asymmetry range present in the controls. After surgery, both diagonals increased, but more on the fused side. In the 2 years after surgery, both diagonals in patients with ULC grew proportionately, but the fused diagonal remained slightly shorter than the patent side. Total cranial volume was higher in patients with ULC than in control subjects after surgery but became comparable at t2. Cranial base angulation improved by t2 but did not approach normal, and ear position remained unchanged. The facial twist was higher than in controls at t0 and t1 but was comparable at t2. Coronal asymmetry improved with surgery but remained undercorrected at t2, with the greatest residual asymmetry at opisthion. Conclusions:Open-switch cranioplasty normalizes cranial vault asymmetry index by increasing the fused cranial diagonal more than the patent side and is stable at 2 years. Skull base twist does not normalize, but facial twist approaches normal. Technique improvement should focus on residual coronal asymmetry present at opisthion.