Evaluating Mechanical Benefit of Wedge Osteotomies in Endoscopic Surgery for Sagittal Synostosis Using Patient-Specific 3D Printed Models

Abstract

Purpose: Endoscopically assisted sagittal strip craniotomy with subsequent cranial orthosis is a frequently used surgical approach for non-syndromic sagittal synostosis. Originally, this technique involved a wide sagittal strip craniectomy with bilateral wedge osteotomies. More recent studies suggest omitting wedge osteotomies, achieving similar outcomes. The controversy surrounding wedge osteotomies and our efforts to refine our technique led us to create models and evaluate the mechanical impact of wedge osteotomies. Methods: We conducted a 3D-print study involving preoperative CT scans of non-syndromic scaphocephaly patients undergoing Minimally Invasive Assisted Remodelation (MEAR) surgery. The sagittal strip collected during surgery underwent thickness measurement, along with a 3-point bending test. These results were used to determine printing parameters for accurately replicating the skull model. Model testing simulated gravitational forces during the postoperative course and assessed lateral expansion under various wedge osteotomy conditions. Results: The median sagittal strip thickness was 2.00 mm (range 1.35-3.46 mm) and significantly positively correlated (p = 0.037) with the median force (21.05N) of the 3-point bending test. Model testing involving 40 models demonstrated that biparietal wedge osteotomies significantly reduced the force required for lateral bone shift, with a trend up to 5 cm long cuts (p = 0.007). Additional cuts beyond this length or adding the occipital cut did not provide further significant advantage (p = 0.1643; p = 9.6381). Conclusion: Biparietal wedge osteotomies reduce the force needed for lateral expansion, provide circumstances for accelerated head shape correction, and potentially reduce the duration of cranial orthosis therapy.