Computational modelling of patient specific spring assisted lambdoid craniosynostosis correction

Abstract

Lambdoid craniosynostosis (LC) is a rare non-syndromic craniosynostosis characterised by fusion of the lambdoid sutures at the back of the head. Surgical correction including the spring assisted cranioplasty is the only option to correct the asymmetry at the skull in LC. However, the aesthetic outcome from spring assisted cranioplasty may remain suboptimal. The aim of this study is to develop a parametric finite element (FE) model of the LC skulls that could be used in the future to optimise spring surgery. The skull geometries from three different LC patients who underwent spring correction were reconstructed from the pre-operative computed tomography (CT) in Simpleware ScanIP. Initially, the skull growth between the pre-operative CT imaging and surgical intervention was simulated using MSC Marc. The osteotomies and spring implantation were performed to simulate the skull expansion due to the spring forces and skull growth between surgery and post-operative CT imaging in MSC Marc. Surface deviation between the FE models and post-operative skull models reconstructed from CT images changed between ± 5 mm over the skull geometries. Replicating spring assisted cranioplasty in LC patients allow to tune the parameters for surgical planning, which may help to improve outcomes in LC surgeries in the future.

Validation of an in-silico modelling platform for outcome prediction in spring assisted posterior vault expansion

“…Surgical cuts were replicated using the patient-specific osteotomy dimensions and locations retrieved from post-operative CT scans and operation notes. Each skull geometry was discretized in Simpleware ScanIP (Borghi et al, 2019;Bozkurt et al, 2020) and imported in ANSYS mechanical 19 R1 (Canonsburg, Pennsylvania, US).…”

“…The foramen magnum of each skull was fully constrained (Nagasao et al, 2011) to prevent rigid translations/rotations. The stainless-steel springs were modeled using node-to-node linear spring conditions implemented in ANSYS (Borghi et al, 2019) applied on opposite notches (replicating the groves produced during surgery to slot in the spring distractor ends) as reported in in Borghi et al, 2017, Bozkurt et al, 2020.Spring expansion was simulated for a length of time equivalent to 3*τ PVE, since the exponential rise reaches a value equivalent to 98% of its maximum after a time equal to 3τ. We performed a careful mesh sensitivity analysis on element size and order on 5 selected patients, to achieve optimal balance between accuracy (i.e., convergence of simulated total deformations with a deviation threshold of 5%) and CPU time (Viceconti et al, 2005).…”

“…Simulated models and post-operative CT reconstructed skulls were compared visually on a mid-line sagittal cross section and with a colour map to represent surface deviations. The effect of the skin layer and the contact between the scalp and the skull were considered negligible based on previous studies (Borghi et al, 2018;Bozkurt et al, 2020;Moazen et al, 2019).…”

Management of Lambdoid Craniosynostosis: A Comprehensive and Systematic Review

“…However, younger age confers a larger anesthetic risk with the potential for lasting effects, and the treatment benefits may not be as durable for endoscopic procedures, even requiring helmet orthoses for significant periods postoperatively to maintain positioning. Waiting for the patient to mature further (6-12 months) allows for a more definitive correction of the deformity and more directly achieved cosmesis via contouring [112]. However, the bone has become further mineralized and is more difficult to manipulate while also causing more bleeding and a greater rate of side effects.…”

“…MRI also localizes important vascular structures such as the torcula and the transverse venous sinuses and their relation to the suture. The 3 main surgical approaches are open cranial vault reconstruction, endoscopic suturectomy, and spring-assisted distraction osteogenesis [112][113][114][115]. A comparison of these techniques, along with their technical attributes, benefits, and considerations, is summarized in Table 4.…”