LAUSR

BACKGROUND The purpose was to quantify change in cranial morphology in non-syndromic unilateral lambdoid craniosynostosis (ULC) patients from presentation (t0), after open posterior switch-cranioplasty (t1), and at two-year follow-up (t2). METHODS Volumetric, linear and angular analysis were performed on computed tomographic scans at the three timepoints and against normal controls. Significance was set at p<0.05. RESULTS Twenty-two patients were included. ULC cranial vault asymmetry index (CVAI) was higher than controls before surgery (6.22 ± 3.55) but decreased after surgery (3.00 ± 2.53) to become comparable to the normal asymmetry range present in the controls. After surgery both diagonals increased, but more on the fused side. In the two years after surgery, both diagonals in ULC grew proportionately, but the fused diagonal remained slightly shorter than the patient side. Total cranial volume was higher in ULC than controls 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 controls at t0 and t1 but was comparable at t2. Coronal asymmetry improved with surgery but remained under-corrected at t2, with the greatest residual asymmetry at opisthion. CONCLUSIONS Open switch cranioplasty normalizes CVAI by increasing the fused cranial diagonal more than the patent and is stable at two years. Skull base twist does not normalize but facial twist approaches normal. Technique improvement should focus on residual coronal asymmetry present at opisthion. LEVEL OF EVIDENCE III.