Investigating the effect of age on skeletal stability after sagittal split ramus osteotomy for mandibular setback

Abstract

(J Korean Assoc Oral Maxillofac Surg 2012;38:354-9) Objectives: The purpose of this study was to investigate whether the age factor would be related with stability of mandibular setback surgery for patients with mandibular prognathism. Materials and Methods: We compared the relapse patterns of 47 patients divided into three age groups (termed younger, adult, and older). The younger group consisted of patients between 15 and 17 years old; the adult group was made up of patients between 21 and 23 years old, and the older group was made up of patients more than 40 years old. The positional change of B point was evaluated at preoperative, postoperative, and follow-up states. Results: The horizontal relapse ratio was 21.7% in the younger group, 15.3% in the adult group, and 15.7% in the older group. Although relatively higher degrees of relapse were found in the younger group, this increase was not statistically significant. Spearman's correlation analysis was performed to explore other factors contributing to relapse. We subsequently found that the amount of relapse was related to horizontal setback. Conclusion: Although the degree of relapse in younger patients is not significant;y higher compared to other groups. The major contributing factor to relapse after sagittal split ramus osteotomy is amount of setback rather than age when the surgery was performed to patients over than 15 years of age.Key words: Mandibular osteotomy, Age, Relapse, Sagittal split ramus [paper submitted 2012. 7. 9 / revised 2012. 9. 3 / accepted 2012. 10. 8] authors already investigated the degrees of relapse after the SSRO surgery, there had been no consensus as to the contribution of the age factor to relapse. Several old studies investigated the age factor and degree of relapse after the SSRO surgery, but it was a retrospective study with advance SSRO surgery on adolescents with retrognathic mandible [13][14][15] ; hence the need to investigate the potential influence of age on relapse after setback SSRO surgery.As already announced by Lewis and Roche 16 in 1988, mandible growth is completed at 18 years. However, the late growth of the mandible continues into the third decade, and that would influence the outcome of setback SSRO surgery 16 . Further more, bone healing capacity is known to decrease among elder patients; hence the higher tendency of relapse in adult patients because of muscular activity 17 . Therefore, we investigated a retrospective study with the following hypotheses after setback SSRO surgery: 1) Younger patients (below 17 years) will experience higher degree of relapse as they grow up, and; 2) Older patients (40 years and up) will also show higher degree of relapse since their bone union will be slower than that of younger patients.

Condylar Changes Following Mandibular Setback Using Manual Guidance

“…The duration of time required for recovery to the preoperative condylar position after orthognathic surgery has varied in previous studies, ranging from 6 months [15,17] to 3 years [34]. Lee et al [30] reported a trend of condyles returning to their preoperative position over time, which was consistent with the findings of this study (Table 2), demonstrating a common pattern of condylar displacement after surgery. The present study revealed significant positional changes between T0 and T2 only in the y-axis (p < 0.05: Table 2).…”

“…Lee et al [30] reported a significant increase in intercondylar distance due to lateral condylar movement in patients with asymmetry and mandibular prognathism. Similarly, our study found that patients with mandibular asymmetry (more than a 3 mm difference between the right and left setback amount) showed significant anterior movement between T0 and T1 (p = 0.003: Table 3).…”

“…Condylar displacement following orthognathic surgery is influenced by several factors, including the type of surgery (single-or two-jaw), the extent of mandibular setback, the degree of mandibular asymmetry, and the fixation method [13][14][15]17,20,[27][28][29][30][31][32][33]. However, the direction of condylar displacement is not consistent across these factors.…”