Comparison of a Patient-Specific Proximal Segment Positioning Appliance and the Conventional Method in Sagittal Split Ramus Osteotomy

Sagittal split ramus osteotomy (SSRO) is a widely used orthognathic surgery technique to correct mandibular deformities. During SSRO, accurate positioning of the proximal segment is critical for ensuring temporomandibular joint (TMJ) health, symmetry, and long-term surgical stability. However, conventional positioning relies heavily on the surgeon's visual judgment and experience, which may lead to postoperative complications such as condylar displacement, facial asymmetry, and TMJ dysfunction.

This prospective, randomized clinical study introduces a patient-specific proximal segment positioning appliance developed through STL-based 3D design using Blender and printed with biocompatible surgical guide resin via a Formlabs SLA 3D printer. Each patient will undergo SSRO (with or without Le Fort I osteotomy), and the custom appliance will be used to guide the proximal segment on one mandibular side. The opposite side will be positioned conventionally, allowing intra-patient comparison.

Postoperative CBCT images will be obtained at 1 month and converted to STL format. These models will be aligned with preoperative plans using MeshLab software to evaluate linear and rotational deviations. Surgical time, ease of application, and TMJ symptoms will be documented. Statistical analysis will include paired t-tests or Wilcoxon signed-rank tests depending on data distribution.

This study will generate clinically meaningful data regarding the effectiveness and safety of patient-specific guides in mandibular segment positioning. The proposed method also holds commercialization potential and may reduce intraoperative variability and dependence on surgeon experience.