Tendon Elongation with Bovine Pericardium in Patients with Severe Esotropia after Decompression in Graves' Orbitopathy-efficacy and Long-term Stability.

Background/aims: We performed a retrospective analysis to examine clinical results, establish a dose-effect coefficient and analyze the long-term efficacy of tendon elongation with bovine pericardium (Tutopatch®) for surgical correction of severe esotropia, occurring after three-wall orbital decompression for dysthyroid optic neuropathy in patients with Graves' orbitopathy (GO).

Methods: Tendon elongation of the medial rectus muscle (MR) was performed in our institution using an interponate of bovine pericardium in 60 patients (27 underwent unilateral and 33 bilateral surgery). Success-rate (total horizontal deviation of 10 prism-diopters (PD) or less and evidence of binocular single vision with or without prism glasses) and horizontal motility were examined 3 months, 1 and >4 years after surgery. A dose-effect coefficient for deviation reduction (PD) per recession distance (mm) was established.

Results: Horizontal deviations between 28-80 were corrected. Diplopia in primary-gaze disappeared in 65% of the patients after 3 months and in 83% after one year (including 12 patients who underwent subsequent surgery after 3-month follow-up). Patients with deviations ≤40 after unilateral and ≤50 after bilateral tendon elongation showed higher primary success-rates after 3 months (78% and 72%). Vertical deviations (≤10) were corrected by the procedure in 28% without need of recession of the inferior rectus (IR). Only 3 patients showed overcorrection after one year. One of these underwent revision surgery, in which the interponate was no longer discernible from surrounding fibrotic scar tissue. At >4-year follow-up (4.3-15years) effects were stable and 95% of patients showed fusion in primary gaze. Median dose-effect coefficient was lower after tendon elongation (1.8/mm) compared to conventional medial rectus recession in patients with GO. Horizontal motility was slightly decreased, but much more symmetric around primary gaze.

Conclusion: Tendon elongation with a bovine pericardium implant is a safe surgical method, suitable to correct severe esotropia after decompression surgery. A lower dose-effect has to be taken into account. Patients with esotropia ≥42 should not be treated with unilateral, but bilateral tendon elongation, to avoid undercorrections. In patients with deviations ≥52 it has to be further investigated if the application of even higher elongation distances is viable or if another approach-the recession of more than one rectus muscle has to be performed simultaneously to handle the severe restriction. Generally, a step-by-step approach is advisable, since small vertical deviations could also be corrected in a third of patients with the procedure and the dose-effect was more variable as in medial recessions without tendon elongation.