Three dimensional finite element biomechanical analysis of unilateral coronal synostosis and reconstruction

Abstract

Objective To establish finite element models of skull, fronto-orbital advancement and fronto-orbital distraction osteogenesis of craniosynostosis, to analyze the mechanical characteristics of skull base and fronto-orbital operation area, so as to guide the later application of tractors. Methods One 6-year-old male patient with unilateral coronal synostosis was enrolled in October 2015. Three-dimensional (3D) computed tomography (CT) scan of skull was performed. DICOM data was imported into Mimics 17.0 for contour extraction and cranial 3D reconstruction. The skull model was processed by Mimics, Geomagic Studio 12.0, Hypermesh 12.0 and other software to establish a three-dimensional finite element model. The unilateral and bilateral fronto-orbital anterior osteotomy models were simulated respectively. The mechanical analysis was performed at point A in forehead area and point B in temporal area. Three different groups of traction forces were loaded: (1) 50 Newton for point A, 50 Newton for point B; (2) 80 Newton for point A and 50 Newton for point B; (3) 100 Newton for point A and 50 Newton for point B, to obtain the optimized traction force. Results Stress analysis was performed on established cranial finite element model, as well as unilateral and bilateral fronto-orbital advancement procedures. The stress distribution of the anterior and middle cranial fossae was found to be concentrated. After unilateral fronto-orbital advancement, the stress of anterior cranial fossa, especially the affected side, was decreased. The stress on both side in anterior cranial fossa was decreased after bilateral fronto-orbital advancement. After force was applied to point A and point B, the optimum deviation result at supraorbital notch point, midpoint of supraorbital margin, frontal temporal point and frontal zygomatic suture point in 3D (Deviation result of X value: -29.4%, -20.5%, -8.6%, -9.3%; Deviation result of Y value: 20.9%, 31.5%, 73.0%, 539.4%; Deviation result of Z value: 4.4%, 1.9%, 0.1%, 11.8%) demonstrated the application of traction force can inwardly, downwardly and forwardly move the bone flap. The optimized traction was 80 Newton at point A and 50 Newton at point B by preliminary assessment. Conclusions The finite element analysis of the fronto-orbital advancement can be used for more accurate preoperative simulation, to clarify the influence of fronto-orbital advancement on craniofacial morphology and development, as well as skull base. It also facilitates surgical decision and predicts the postoperative distraction vectors. Key words: Coronal suture; Craniosynostosis; Osteotomy; Osteogenesis, distraction; Finite element method; Biomechanical analysis