Landmark-Independent Method to Determine Midsagittal Plane and Its Clinical Application in Craniomaxillofacial Trauma

The purpose of this study was to explore new landmark-independent methods suitable for determining the midsagittal plane (MSP) in patients with craniomaxillofacial trauma and its clinical application.

Preoperative spiral computed tomography data of 25 patients with craniomaxillofacial trauma were imported into Mimics software (Materialise, Leuven, Belgium) to reconstruct 3-dimensional skull models. In the experimental group, the MSP was determined by different landmarks that were clear, were scattered, and did not have displacement according to the types of fractures. In the control group, the MSP was determined by a traditional landmark-dependent method based on the nasion, posterior nasal spine, and anterior nasal spine. After virtual fracture reduction, facial symmetry was determined to verify the reliability of both the landmark-dependent and landmark-independent methods.

By use of the landmark-independent method proposed in this study, the minimal, maximal, and average registered distance between the skull model after reduction and the mirror skull model was 0.5531, 1.2065, and 0.8287 mm, respectively. By use of the traditional landmark-dependent method, the minimal, maximal, and average registered distance between the skull model after reduction and the mirror skull model was 0.7914, 1.9415, and 1.2250 mm, respectively. When an average distance of less than 1.5 mm between the 2 registered models was set as the criterion for qualified fracture reduction, all 25 cases in the experimental group had qualified reduction whereas 9 cases in the control group had unqualified reduction (P < .05).

Compared with the traditional landmark-dependent system, the landmark-independent method is more reliable in determining the MSP in patients with craniomaxillofacial trauma. Selection of different landmarks in different types of fractures makes it more precise to reconstruct the MSP and can guide virtual reduction of fractures more effectively, which lays the foundation for subsequent surgical navigation and guide-plate printing. The method is easy to perform and appropriate for digital evaluation of surgery.