The Effect of Sequencing of Maxillary and Mandibular Advancement Surgery on Achieving Planned Movements in Obstructive Sleep Apnea Patients

The surgical standard of care for the treatment of severe obstructive sleep apnea (OSA) includes maxillomandibular advancement surgery (MMA) to improve the pharyngeal airway. There is no clear consensus in the literature regarding whether the maxilla or mandible should be stabilized first during the operation. Recommendations from various authors are based on personal anecdote or case reports.(1, 2) The method used by most surgeons is to first place the maxilla in the desired position and then bring the mandible to it. A common intra-operative observation when fixating the maxilla first is that the advancement of the mandible is less than predicted. When treatment planning for OSA patients, it is especially important to achieve the desired skeletal movements during MMA to maximize the improvement in the pharyngeal airway. The purpose of this study is to determine if the sequencing of surgery to simultaneously advance the maxilla and mandible have an effect on achieving the planned movements in obstructive sleep apnea patients.

50 patients who underwent MMA surgery between 2003 and 2012 performed at the QE II Health Science Center, Halifax, Nova Scotia to treat OSA were included in this study. 25 patients who underwent MMA with Maxilla First were assigned to group Mx, and 25 patients who underwent MMA with Mandible First were assigned to group Md. All patients completed both pre-op and post-op polysomnography studies with a measured Apnea-Hypopnea Index (AHI). The degree of advancement was measured by comparing pre-op and post –op lateral cephalograms using Delaire cephalometric analysis landmarks. Horizontal measurements were measured along the Y-axis in relation to a line perpendicular to C3: (reference plane approximating the horizontal plane) through Clp (apex of posterior clinoid process). Maxillary reference points included the PNS: (posterior nasal spine), M: (distal cusp of first maxillary molar) and UI: (upper incisor tip). Mandibular reference points included LI: (lower incisor tip) and B point: (innermost curvature from chin to alveolar junction). 

STATA statistical software was used for data analysis. A t-test was used to compare means while a Mann-Whitney U test was used to compare medians. The landmarks of the two groups were compared to the planned movements. There was no statistical significance observed in the following variables PNS: 0.16mm Md > Mx (CI -1.5 to 1.2, p < 0.8), M: 1mm Md > Mx (p < 0.1), LI 0mm Md = Mx (p < 0.7), B 0mm Md = Mx (p < 1). Variable UI showed statistical significance with a difference in the upper incisor tip UI: 2mm Md > Mx (CI -3.4 to -0.6, p < 0.006).

In this sample, variable UI showed a statistically significant difference in outcomes of the two procedures. Patients who underwent MMA with fixation of the mandible first were found to have a 2mm greater advancement of the maxilla than patients who underwent fixation of the maxilla first. This result suggests that performing an MMA with fixation of the mandible first would lead to achieving a more predictable movement as planned.

1.         Turvey T. Sequencing of two-jaw surgery: the case for operating on the maxilla first. J Oral Maxillofac Surg. 2011 Aug;69(8):2225.

2.         Perez D, Ellis E, 3rd. Sequencing bimaxillary surgery: mandible first. J Oral Maxillofac Surg. 2011 Aug;69(8):2217-24.