Abstract
Sagittal craniosynostosis consists of premature fusion (ossification) of the sagittal suture during infancy, resulting in head deformity and brain growth restriction. Spring-assisted cranioplasty (SAC) entails skull incisions to free the fused suture and insertion of two springs (metallic distractors) to promote cranial reshaping. Although safe and effective, SAC outcomes remain uncertain. We aimed hereby to obtain and validate a skull material model for SAC outcome prediction. Computed tomography data relative to 18 patients were processed to simulate surgical cuts and spring location. A rescaling model for age matching was created using retrospective data and validated. Design of experiments was used to assess the effect of different material property parameters on the model output. Subsequent material optimization—using retrospective clinical spring measurements—was performed for nine patients. A population-derived material model was obtained and applied to the whole population. Results showed that bone Young’s modulus and relaxation modulus had the largest effect on the model predictions: the use of the population-derived material model had a negligible effect on improving the prediction of on-table opening while significantly improved the prediction of spring kinematics at follow-up. The model was validated using on-table 3D scans for nine patients: the predicted head shape approximated within 2 mm the 3D scan model in 80% of the surface points, in 8 out of 9 patients. The accuracy and reliability of the developed computational model of SAC were increased using population data: this tool is now ready for prospective clinical application.
Highlights
The infant cranial vault consists of flat bones joined by cranial sutures (Opperman 2000), membranous soft tissue important both at birth and for brain growth
We presented a spring-assisted cranioplasty (SAC) case study using patient-specific finite element (FE) modelling, which proved that the overall head shape change can be realistically modelled, provided the correct location of springs as well as spring models is recorded during surgery: the material properties needed patient-specific tuning to accurately capture spring/skull behaviour over time (Borghi et al 2018)
The pre-op surface scans available for the nine patients were compared with the initial model reconstructed from computed tomography (CT) and with the rescaled model using the growth curve and derived equation: the rescaled model showed statistically significant improvement in root mean square error (RMSE)
Summary
The infant cranial vault consists of flat bones joined by cranial sutures (Opperman 2000), membranous soft tissue important both at birth and for brain growth. Sutures close naturally over time; premature suture closure— called craniosynostosis—is a pathology with a prevalence of up to one in 1700 live births (Fearon 2014). This pathology mainly causes aesthetic problems, recent findings show that up to 24% of patients affected by non-syndromic craniosynostosis develop intracranial hypertension (Wall et al 2014) with cognitive, speech and behavioural sequelae. A number of procedures have been described to treat sagittal synostosis with no clear consensus on timing and technique. The range of methods goes from total calvarial remodelling, when the surgeon harvests and repositions several bone flaps in the whole vault, to minimally invasive procedures (i.e. spring-assisted cranioplasty, endoscopically assisted suturectomy). The attractiveness of minimally invasive techniques comes mainly from the reduced surgical access needed, the lower rate of blood transfusion and the shorter operating and hospitalization time. In our Centre, the preferred minimally invasive technique is spring-assisted cranioplasty (SAC),
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
