Graves' Orbitopaty: Inferior Rectus Tendon Elongation for Large Vertical Squint Angles that cannot be Corrected by Simple Muscle Recession

Background: In motility disorders related to Graves' orbitopathy, recession of fibrotic eye muscles is the treatment of choice. Correction of very large squint angles can be difficult, since the distance of recession is limited by the necessity to maintain a sufficient arc of contact. A new technique of tendon elongation has been developed in order to maintain sufficient arcs of contact even in patients with large horizontal squint angles, especially after orbital decompression surgery. The established dose-effect relationship cannot simply be conveyed to inferior rectus muscle surgery, due to a different impact of simple recession on inferior and medial rectus muscles. Methods: Recession of the inferior rectus muscle was performed in 10 patients with simultaneous suturing of bovine pericardium (Tutopatch (R)). This procedure was performed as primary surgery in 7 patients (2 after orbital decompression) and as secondary procedure in 3 patients. Squint angle (far distance), bulbus excursion movements and field of binocular single vision were evaluated pre- and postoperatively. Results: Alignment (far distance) was achieved in 8 of 10 cases at the final follow-up examination. Two patients required corrective prisms. Visual fields were virtually free of diplopia in all patients. The dose-response effect for tendon elongation of the inferior rectus muscle was identical to that for the simple recession of this muscle. There were no complications. Conclusions: The new technique of tendon elongation using a bovine pericardium graft is applicable in large vertical squint angles (with or without prior bony orbital decompression) as well as for corrections after insufficient simple recessions (by realignment of the muscle and secondary suturing of the graft). Functional improvement can thus be achieved through surgery of a single muscle, keeping the other muscles in reserve for further interventions (lowering the risk of postoperative anterior segment ischaemia). There is a dose effect analogous to large horizontal squint angles in Graves' orbitopathy (dosing formula: 1 mm inferior rectus recession [including graft] leads to 2.0 degrees vertical angle reduction). This corresponds to simple recessions of the inferior rectus muscle but differs from tendon elongations of the medial rectus muscles.