Skeletal Stability of Orthognathic Surgery: A Comparison of Patients Over and Under 40 Years of Age

Orthognathic surgery is the treatment of choice for correction of dentofacial deformities secondary to jaw size discrepancies and asymmetries. Although patients have been typically in the second or third decade of life, there has been a noted increase in patients ≥40 years of age undergoing orthognathic surgery.^{1, 2} In general, these older patients seek treatment to manage severe malocclusion or obstructive sleep apnea.¹Skeletal stability and other surgical outcomes are not well documented in this group. The purpose of this study is to compare skeletal stability following maxillary and mandibular advancement procedures in patients over and under 40 years of age.

This was a retrospective cohort study of all patients who underwent maxillary or mandibular advancement procedures at Massachusetts General Hospital from 2004-2012. Subjects were included if preoperative, postoperative and 1 year (+/- 2 months) postoperative lateral cephalograms were available. Subjects were excluded if they underwent a setback or non-conventional orthognathic surgery procedures (e.g. osteotomies for distraction osteogenesis, condylar reconstruction) or had a diagnosis of hemifacial microsomia, craniofacial microsomia, or other craniofacial syndromes or incomplete records. Demographic variables including age and gender, and type(s) of procedures performed were documented. The predictor variable was age over or under 40 years. The outcome variable was skeletal stability measured via standard linear and angular cephalometric measurements taken preoperatively (T0), immediately postoperatively (T1), and at 1 year follow-up (T2). Skeletal and dental movements were also quantified in the vertical and horizontal planes by assessing changes in position of A point, B point, U1 tip, and L1 tip. Statistical comparisons were performed using Student’s t-test.

During the study period a total of 139 subjects (25 subjects ≥ 40) had adequate radiographic records and were included. Procedures included: One piece Le-Fort 1 osteotomy (53 subjects, 7 subjects ≥40), bilateral sagittal split osteotomies (28 subjects, 4 subjects ≥40), or both (58 subjects, 14 subjects ≥40). For subjects undergoing Le-Fort 1 osteotomy alone, those over 40 had significantly less maxillary vertical relapse with 1.34 mm less upward shift in A point compared to subjects under 40 at T2 (p = 0.0463). Subjects over 40 had greater overall operative change (T0 – T1) across all mandibular procedures compared to subjects under 40, though the difference was not statistically significant. For subjects undergoing bimaxillary surgery, those over 40 years of age had significantly less horizontal mandibular relapse with 1.28 degrees less decrease in SNB (p = 0.0336) and 1.58 mm less horizontal relapse at B point (p = 0.0161). Subjects over 40 undergoing bimaxillary surgery also had less change in overjet, though not statistically significant. Other postsurgical changes in SNA, SNB, ANB, overbite, overjet, as well as relapse in the vertical and horizontal planes were similar between the age groups for all procedures.

The results of this study indicate that patients over 40 may have improved skeletal stability 1 year postoperatively compared to patients under 40 despite undergoing larger operative movements. This may be due to physiologic differences in muscle tone or the soft tissue envelope in the aging patient that may contribute to skeletal stability. As a greater number of older patients elect for orthognathic surgery in the current era, understanding differences in outcome related to age will allow for better patient education and improve the overall patient experience.

References

1.  Peacock ZS, Lee CC, Klein KP, Kaban LB: Orthognathic surgery in patients over 40 years of age: indications and special considerations. J Oral Maxillofac Surg 72:1995, 2014

2. Venugoplan SR, Nanda V, Turkistani K, Desai S, Allareddy V: Discharge patterns of orthognathic surgeries in the United States. J Oral Maxillofac Surg 70:e77, 2012