Head posture and cervicovertebral anatomy as mandibular growth predictors.

In this study, the separate and the combined influence of head posture and cervicovertebral anatomy on mandibular growth direction was analysed. The subjects, 20 boys and 16 girls, were a subsample of 12-year-old Chinese children in Hong Kong, all with initial and 2-5-year follow-up lateral cephalometric radiographs recorded in natural head position (NHP). Postural variables were measured in terms of craniovertical, craniocervical, and cervicohorizontal angulations. Morphological variables of the craniocervical junction region were measured in terms of intervertebral space and atlantoaxial dimensions. Mandibular growth was estimated as the direction of displacement of prognathion in relation to the sella nasion line when superimposing on stable cranial base structures. The data were analysed with a multiple regression model, separately for boys and girls. In both sexes the height of the atlas dorsal arch showed a statistically significant correlation (P < 0.01) with mandibular growth direction (boys r = 0.54 and girls r = 0.62), while the craniovertical angulation correlated significantly only for the boys (NSL/VER r = 0.59, P < 0.01; C1/VER r = 0.49, P < 0.05). However, atlas dorsal arch height (DORS C1) combined with cervicohorizontal angulation (OPT/HOR) in girls and with craniovertical angulation (NSL/VER; C1/VER) in boys, displayed a significantly (P < 0.05) increased correlation (r = 0.76 and 0.71, respectively). Combination of atlas morphology and head posture predicts mandibular growth direction better than either variable alone.