MANDIBULAR DYSMORPHOLOGY IN UNICORONAL SYNOSTOSIS AND PLAGIOCEPHALY WITHOUT SYNOSTOSIS

Patients with unicoronal synostosis (UCS) or plagiocephaly without syn ostosis (PWS) have distinctive skull dysmorphologies. Associated mandi bular dymorphologies have been suspected but not quantified. This stud y was performed to test the hypothesis that discrete mandibular dysmor phology exists in both UCS and PWS. All patients at a tertiary referra l center at a medical school-affiliated children's hospital with confi rmed diagnosis of UCS or PWS with adequate pretreatment CT data were i ncluded in the study population, which population was comprised of 20 UCS, 23 PWS, and 8 normal infants. Each patient had a head CT scan usi ng 2-mm slices. 3-D images were created using Analyze(TM) a biomedical imaging program. The mandibles were isolated, and the coordinates of 8 landmarks were sampled from each mandible by a single investigator: a single volume value was measured, and 9 linear distances and 4 angle s were calculated. Corresponding measurements from each hemimandible w ere expressed as ratios of ipsilateral/contralateral side. In UCS, the affected side was defined as the side ipsilateral to the synostosis; in PWS, the affected side was defined as the side ipsilateral to the o ccipital flattening. The results from both groups were t tested for st atistical significance. For UCS, statistically significant (p < .001) findings included: ipsilateral hemimandibular volume 5% smaller than c ontralateral; affected hemimandibular body length 1.9% shorter; affect ed genial angle 2.6% more acute; affected coronoid process tilted ante riorly 2.5%; and distances from condylion and tip of the coronoid proc ess to the chin landmarks 4% shorter on the affected side. For PWS, si gnificant findings included: affected hemimandibular volume 3.8% large r; ramal height 3.5% shorter; mandibular body length 3% longer; and co ronoid process tilted anteriorly by 2.3% on the affected side. In the UCS/PWS comparison, findings included: affected hemimandibular volume in UCS 8.7% less; affected genial angle in UCS 3% more acute; affected mandibular corpus length in UCS 5% shorter; distances from the condyl ion and the tip of the coronoid process to the chin landmarks 4% short er on the affected side in UCS. The hypothesized presence of diagnosis specific mandibular dysmorphology in UCS and PWS is confirmed. This a nalysis forms the baseline for study of the effects of unperturbed gro wth or therapeutic interventions upon the dentoskeletal dysmorphology of these anomalies.