Foster-type modification of the Knapp procedure for anomalous superior rectus muscles in syndromic craniosynostoses.

Purpose: To describe the surgical management of anomalous superior rectus muscles in patients with syndromic craniosynostoses.

Methods: Retrospectively reviewed were case notes of 3 patients with vertical deviations that were thought to have anomalous superior rectus muscles.

Results: All 3 patients had hypotropia preoperatively, and 2 had coexisting exotropia. Two patients exhibited massive subconjunctival fibrosis intraoperatively, but none had undergone previous strabismus surgery, although they had undergone craniofacial procedures. Orbital imaging (either computed tomographic or magnetic resonance imaging scans) confirmed an absent or thinned superior rectus muscle in all 3 patients. All 3 underwent a Knapp procedure with appropriate recession and resection of the transposed horizontal rectus muscles if indicated. A nonabsorbable suture was placed in the sclera at the upper border of each horizontal rectus muscle to draw this border closer to the vertical midline, approximately 16 to 18 mm from the limbus (Foster-type modification). In each case, the hypotropia and upgaze were improved but not completely normalized.

Conclusions: A Foster-type modification of the Knapp procedure satisfactorily corrected the hypotropia in these patients. Orbital imaging can confirm the presence of an anomalous superior rectus muscle. The massive subconjunctival fibrosis may be explained by the type of previous craniofacial surgery the patients had undergone.