Orbital Dysmorphology in Unilateral Coronal Synostosis

Abstract

Unilateral coronal synostosis (UCS) produces overt craniofacial dysmorphology. UCS surgery in infancy aims to release the osseous restriction and normalize the fronto-orbital deformity. The quantitative effect of this surgery on the orbit and its contents is unknown. This study was conducted to quantify the preoperative orbital dysmorphology and its surgical outcome in patients with unilateral coronal synostosis. Twenty-eight UCS patients had preoperative three-dimensional computerized tomographic (CT) scans (at mean age 4.0 months), cranio-orbital reconstructive surgery (at 4.7 months), and postoperative scans (at 18.1 months). The CT data were analyzed using a computer workstation and AnalyzeTM biomedical imaging software. Four measurements were performed on both ipsilateral (same side as synostosis) and contralateral (opposite to synostosis) orbits of each scan: orbital index (OI, 100 x height/width of orbit), orbital cavity volume (OV), ocular globe volume (GV), and ventral globe Index (VGI, 100 x globe volume ventral to the anterior surface of orbital cavity/GV). The data were analyzed for statistical significance using Student's ttest. Preoperatively, the OI was significantly greater on the ipsilateral than on the contralateral side (113.7 vs. 87.3). There was a significant improvement on both sides of the orbit postoperatively, with ipsilateral 99.1 and contralateral 92.1. However, the difference between both sides remained significant. The OV was smaller in the ipsilateral orbits both pre- and postoperatively, with ipse/contralateral ratios of 95.8 and 95.2, respectively. Importantly, the GV was consistently smaller in the ipsilateral orbits preoperatively, with an ipse/contralateral ratio of 93.3. The ratio increased to 97.1 postoperatively, a statistically significant change. In the ipsilateral orbits, the preoperative VGI was significantly greater. The VGI improved postoperatively. These data indicate that UCS affects the development of the osseous orbit as well as its soft-tissue contents. After cranio-orbital surgery, there is diminution of asymmetry of both the bony orbit and its soft-tissue contents. Partial normalization of orbital dysmorphology occurred during the first postoperative year. UCS surgery in infancy does not prevent growth of orbital hard or soft tissues, and it seems to permit normalization of previously impaired growth.