Ocular advancement in monobloc distraction.

Background: Monobloc distraction has been demonstrated to be an efficacious, safe, and stable method of providing functional and aesthetic improvement in children with syndromic craniosynostosis. Although the movement of bony structures following monobloc distraction has been quantitatively assessed before, objective analysis of the movement of soft tissues, such as the globe, has not been published previously. The authors present a method that assesses globe movement following monobloc distraction, using computed tomographic scan data.

Methods: The preoperative and postoperative computed tomographic scans of 10 patients with Pfeiffer's and Crouzon's syndromes, undergoing monobloc distraction, were assessed. Scan data were loaded into voxel image-rendering software that produced a three-dimensional reconstruction. Direct measurements between preoperative and postoperative images were taken.

Results: An average upper face osseous distraction distance of 12.94 mm, with an average lower face distraction of 14.19 mm, was achieved in all 10 children. The authors measured average globe movements on three planes and calculated an average left eye forward movement of 5.28 mm and average right eye forward movement of 6.33 mm. In all, globe advancement was approximately two fifths of the distance advanced by the surrounding bone.

Conclusions: Forward movement of the globe following monobloc distraction has not previously been described. Although there is no current evidence for optic nerve stretch and compromise in monobloc surgery, the functional implications of these findings should be formally assessed.