A specific pathological postural adaptation is suspected in patients exhibiting maxillo-mandibular deformity (MMD); however, none study reported a correlation between facial dimensions and posture.

In this study, we hypothesized that pathological postural adaptations are related to long-face deformity and subsequent oral breathing in patients with MMD

Thirty patients with MMD and 20 healthy subjects. Breathing mode, postural alignment and cephalometry were analyzed through a biplanar X-ray (EOS imaging®) of the skeleton in an upright position, followed by three-dimensional reconstruction.

Patients with MMD exhibited hyperkyphosis of the lower region of the cervical spine (C3-C7 angle: 10.6° [3.9; 17.5] vs. 3.2° [-6.4; 7.6], p < 0.01), forward head posture (OD-C7 angle: 10.5° [8.5; 15.1] vs. 6.2° [3.0; 8.4], p < 0.01), and backward sagittal balance compared with controls (sagittal vertical axis:15.7 mm [-25.9; -5.2] vs. -1.4 mm [-17.8; 7.0], p = 0.014). Cervical hyperkyphosis, the forward head posture, and the backward sagittal balance were related to higher values of the Frankfort-mandibular plane angle (a cephalometric variable used to assess face length). In patient with MMD, oral breathing was correlated to the FMA angle.

MMD is associated with a specific pathological postural adaptation which is correlated with Long-face deformity and oral breathing. Our results suggest that the altered posture originates from the upper airways.