title: Optimization of Cranio-Orbital Remodeling: Application of a Mathematical Model.
abstract: Cranio-orbital remodeling aims to correct the dysmorphic skull associated with craniosynostosis. Traditionally, the skull is reconstructed into a shape that is subjectively normal according to the surgeon's perception. We present a novel technique using a mathematical algorithm to define the optimal location for bony osteotomies and to objectively reshape the fronto-orbital bar into an ideal normal skull contour. Using pre-operative computed tomography images, the abnormal skull contour at the frontal-orbital region was obtained for infants planned to undergo cranio-orbital remodeling. The ideal skull shape was derived from an age- and sex-matched normative skull library. For each patient, the mathematical technique of dynamic programming (DP) was applied to compare the abnormal and ideal skull shapes. The DP algorithm identifies the optimal location of osteotomy sites and calculates the objective difference in surface area remaining between the normative and dysmorphic skull shape for each solution applied. By selecting the optimal solution with minimal objective difference, the surgeon is guided to reproducibly recreate the normal skull contour with defined osteotomies. The DP algorithm was applied in 13 cases of cranio-orbital remodeling. Five female and 8 male infants with a mean age of 11 months were treated for craniosynostosis classified as metopic (n = 7), unicoronal (n = 4), or bicoronal (n = 2). The mean OR time was 190.2  min (SD 33.6), mean estimated blood loss 244  cc (SD 147.6), and 10 infants required blood transfusions. Compared with a historical crania-orbital remodeling group treated without application of the algorithm, there was no significant difference in OR time, estimated blood loss, or transfusion rate. This novel technique enables the craniofacial surgeon to objectively reshape the fronto-orbital bar and reproducibly reconstruct a skull shape resembling that of normal infants.
authors.affiliation: *Division of Plastic and Reconstructive Surgery, University of Toronto, Toronto †Department of Combinatorics & Optimization, Faculty of Mathematics, University of Waterloo, Waterloo ‡Centre for Image Guided Innovation and Therapeutic Intervention §Division of Neurosurgery ||Division of Plastic and Reconstructive Surgery, Centre for Craniofacial Care and Research, The Hospital for Sick Children, Toronto, Canada.
authors.forename: Kathryn V
authors.initials: KV
authors.lastname: Isaac
authors.forename: Jochen
authors.initials: J
authors.lastname: Koenemann
authors.forename: Ricardo
authors.initials: R
authors.lastname: Fukasawa
authors.forename: David
authors.initials: D
authors.lastname: Qian
authors.forename: Andre
authors.initials: A
authors.lastname: Linhares
authors.forename: Nikoo R
authors.initials: NR
authors.lastname: Saber
authors.forename: James
authors.initials: J
authors.lastname: Drake
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Forrest
authors.forename: John H
authors.initials: JH
authors.lastname: Phillips
authors.forename: Phuong D
authors.initials: PD
authors.lastname: Nguyen
mesh_terms: D000465:Algorithms; D016063:Blood Loss, Surgical; D001803:Blood Transfusion; D016022:Case-Control Studies; D017076:Computer-Aided Design; D003398:Craniosynostoses / Q000601:surgery*; D003399:Craniotomy / Q000379:methods; D005260:Female; D005624:Frontal Bone / Q000002:abnormalities / Q000601:surgery; D006801:Humans; D007223:Infant; D008297:Male; D008954:Models, Biological; D061646:Operative Time; D009915:Orbit / Q000002:abnormalities / Q000601:surgery; D010027:Osteotomy / Q000379:methods; D010294:Parietal Bone / Q000002:abnormalities / Q000601:surgery; D010347:Patient Care Planning; D019651:Plastic Surgery Procedures / Q000379:methods*; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods