Long-term Outcome of a Muscle Union Procedure in Patients with Horizontal Paralytic Strabismus

Purpose: To report the long-term surgical outcomes of a muscle union procedure in patients with paralytic strabismus. Methods: We retrospectively reviewed the medical records of 20 patients who underwent muscle union procedure for paralytic strabismus from September 2010 to March 2018. We analyzed the clinical results before and at the final visit after surgery. We also compared the outcomes of the first year after surgery between patients with sixth cranial nerve palsy, with third cranial nerve palsy and with medial rectus muscle rupture after endoscopic sinus surgery. Results: The mean follow-up duration was 42 ± 20 months (12-79 months). The mean age at surgery was 40 ± 19 years (7-65 years). Eleven patients underwent surgery for sixth cranial nerve palsy, six patients underwent surgery for third cranial nerve palsy, and three patients underwent surgery for medial rectus rupture after endoscopic sinus surgery. The mean horizontal deviation at the primary eye position was 58 ± 19 prism diopters before surgery and decreased to 14 ± 17 prism diopters at the final visit. The success rate at the last visit was 60%. The mean horizontal deviation at postoperative 1 year was 4 ± 9 prism diopters in the sixth nerve palsy group and 26 ± 16 prism diopters in the third nerve palsy group (p = 0.002). The success rate was 91% in the sixth nerve palsy group and 33% in the third nerve palsy group at postoperative 1 year (p = 0.017). There were no complications during surgery or anterior segment ischemia for any of the patients. Conclusions: A muscle union procedure had good long-term surgical outcomes in patients with paralytic strabismus, especially in patients with sixth cranial nerve palsy. However, in the case of third cranial nerve palsy or rupture of the medial rectus muscle, the effects were limited.