Does osteotomizing the lower border of the mandible affect the lingual split pattern in a sagittal split ramus osteotomy?

Aim: The purpose of this study was to evaluate the effect of adding a fourth osteotomy at the lower border of the mandible on the lingual cortical fracture pattern in bilateral sagittal split ramus osteotomies.

Patients and methods: The sample of the study consisted of 20 patients (12 male and 8 female, with a mean age of 26.79 ± 7.12 years) with mandibular deformities who needed bilateral sagittal split ramus osteotomy. One side underwent a traditional sagittal split ramus osteotomy, and the procedure was modified on the other side by adding a 1 cm horizontal osteotomy at the lower border of the mandible, just distal to the caudal end of the vertical buccal osteotomy cut. A 3D CBCT was used to identify the split pattern.

Results: In the total sample, 40% of the lingual splits ran vertically toward the lower border of the mandible (LSS1), 20% of the splits passed horizontally to the posterior border of the mandible (LSS2), 32.5% of the splits took place along the inferior alveolar canal (LSS3), and 7.5% of the splits were unfavourable fractures (LSS4). On the inferior border osteotomy sides, the distribution of LSS1, LSS2, LSS3, and LSS4 was 10 (25%), 6 (15%), 4 (10%), and 0 (00), respectively. Their distribution on the sides without inferior border osteotomy was 6 (15%), 8 (20%), 13 (32.5%), and 3 (7.5%), respectively. Statistical analysis revealed a significant difference between the two groups (p < 0.05).

Conclusion: Inferior border osteotomy tends to direct the lingual split fracture line toward the lower and posterior borders of the mandible and minimizes bad splits; however, further studies are needed to confirm our findings.