Risk of suprascapular nerve injury in open Trillat procedure: an anatomical study

Purpose The open Trillat Procedure described to treat recurrent shoulder instability, has a renewed interest with the advent of arthroscopy. The suprascapular nerve (SSN) is theoretically at risk during the drilling of the scapula near the spinoglenoid notch. The purpose of this study was to assess the relationship between the screw securing the coracoid transfer and the SSN during open Trillat Procedure and define a safe zone for the SSN. Methods In this anatomical study, an open Trillat Procedure was performed on ten shoulders specimens. The coracoid was fixed by a screw after partial osteotomy and antero-posterior drilling of the scapular neck. The SSN was dissected with identification of the screw. We measured the distances SSN-screw (distance 1) and SSN-glenoid rim (distance 2). In axial plane, we measured the angles between the glenoid plane and the screw (α angle) and between the glenoid plane and the SSN (β angle). Results The mean distance SSN-screw was 8.8 mm +/- 5.4 (0–15). Mean α angle was 11°+/- 2.4 (8–15). Mean β angle was 22°+/- 6.7 (12–30). No macroscopic lesion of the SSN was recorded but in 20% (2 cases), the screw was in contact with the nerve. In both cases, the β angle was measured at 12°. Conclusion During the open Trillat Procedure, the SSN can be injured due to its anatomical location. Placement of the screw should be within 10° of the glenoid plane to minimize the risk of SSN injury and could require the use of a specific guide or arthroscopic-assisted surgery.