Methods for designing patient-specific templates for optimized fitting of autologous bone augmentations in alveolar cleft osteoplasty

Following the current gold standard, autologous cancellous bone is used as part of alveolar cleft osteoplasty. To fill the bone defects, autologous bone material is harvested from the iliac crest using manual tools such as shepard chisels or trephine drills. The bone augmentations obtained in this way have a simple geometry, usually cylinders, and must then be manually adapted to the defect to be filled by the surgeon using surgical forceps and scissors. There are no established routines for the manufacturing of patient-specific, cost-effective surgical cutting guides. However, the accuracy of fit of the augmentations plays an important role in the healing process. This paper focuses on a concept for the creation of necessary sequenced incision geometries based on 3D X-ray data of alveolar cleft defects. As a result, a procedure is to be developed for the preoperative design of individualised surgical cutting guides based on image data. We described a workflow to segment the cleft defect using reverse engineering from Cone-beam computed tomography (CBCT) data. The data was further processed and a keyhole contour was created. A stamping guide and a cutting guide were then derived. The stamping guides were scaled 5, 10 and 15% larger than the defect. In addition, two half-shells were produced, which will be used to investigate the clamping forces and the biological consequences in a follow-up study. This article presents a developed routine for creating patient-specific templates and demonstrates its feasibility.