Introduction: Cases of obstructive sleep apnea syndrome have been described after setback osteotomy. Although such cases are rare, they emphasize the importance of taking into account the structure of the upper airways when performing this type of procedure. We studied the modifications provoked in the upper airways by mandibular setback osteotomy performed for dysmorphism.
Material and method: We conducted a retrospective cephalometric study in a series of 25 patients. Preoperative and late postoperative films were digitalized to obtain a precise measurement of the bone displacements and changes in the caliber of the retrovelar and retrolingual spaces. The statistical analysis examined the parameters modified by surgery, particularly airway parameters, and those factors which influenced these modifications.
Results: We observed a reduction in the retrolingual space [mean 1.7 mm (p < 0.05)] and displacement of the hyoid bone [mean 2 mm lowering compared with the bi-spinal plane (p < 0.05) and 4.1 mm setback in the Francfort projection (p < 0.01)]. These modifications were not correlated with the mandibular setback (measured as the gonial mental angle) but were strongly dependent on variations in the gonial angle. In 20% of the cases, mandibular setback produced a paradoxical effect: enlargement of the airways.
Discussion: Little work has been done on the modifications in the upper airways provoked by osteotomies. Mandibular setback osteotomy can, though only a few cases have been reported, create an anatomic situation favoring obstructive sleep apnea. This series demonstrated the very wide variability of the effects on the upper airways.
Conclusion: The risk of apnea should be included as an important parameter in assessing indications for setback osteotomy.