Preoperative Soft Tissue Thickness Influences the Alteration of Soft Tissue Movement in Orthognathic Surgery

Background: Reports on soft tissue movement after orthognathic surgery exhibit significant variability, with a lack of consensus on standardized measurements. This creates challenges in making accurate predictions about post-surgery tissue movement and determining the potential impact of preoperative soft tissue thickness on the extent of movement.

Aim: To investigate the relationship between preoperative soft tissue thickness and the degree of soft tissue movement in comparison to hard tissue movement following orthognathic surgery.

Materials and Methods: This study involves a retrospective analysis of lateral cephalometric X-rays obtained from patients who underwent orthognathic surgery at a single medical center between September 1, 2013, and September 1, 2018. Demographic and operative data were gathered. Preoperative cephalometric X-rays were used to measure soft tissue thickness, and postoperative X-rays (taken >6 months after surgery) were superimposed by aligning fixed bony points. Linear regression was employed to investigate the correlation between different variables and the extent of jaw movement.

Results: For upper jaw surgeries involving advancements up to 5 mm, there was an observed reduction in the relative movement of soft tissue, correlating with an increase in the initial thickness (r = -0.288). In mandibular advancements, there was a distinct decrease in the ratio of soft tissue movement with an increase in initial soft tissue thickness (r = -0.418). Conversely, there was no correlation in mandibular setback cases (r = 0.062). A similar correlation, demonstrating a decrease in relative soft tissue movement with an increase in initial soft tissue thickness, was identified in advancement genioplasty (r = -0.411).
Conclusion: The findings of this research reveal a consistent pattern of decreased relative movement of soft tissue in orthognathic surgery, which is associated with an increase in its initial thickness.