The safe zone for avoiding suprascapular nerve injury in bone block procedures for shoulder instability. A cadaveric study.

PURPOSE

The purpose of the study is to identify the safe zone in which the surgeon can place the screws for fixation of the coracoid graft during the Latarjet procedure to avoid injuries of the suprascapular nerve with the shoulder in internal and external rotation.

METHODS

The dissection on twelve fresh-frozen shoulders was performed according to a standard posterior approach to the gleno-humeral joint. The suprascapular nerve and its branches for the infraspinatus muscle were identified at the spinoglenoid notch region. Then, the distance between the glenoid and the suprascapular nerve at the spinoglenoid notch region was measured by using a ruler with the shoulder at 90° internal rotation and at 90° of external rotation.

RESULTS

The median distance between the glenoid and the suprascapular nerve was 12 mm (range 6-15 mm) with the shoulder at 90° of internal rotation and 19 mm (range 11-23 mm) with the shoulder at 90° of external rotation. The distance between the glenoid and the suprascapular nerve was statistically significantly greater with the shoulder at 90° of external rotation than 90° of internal rotation (P = 0.002).

CONCLUSIONS

The suprascapular nerve is furthest away from the glenoid with the shoulder at 90° of external rotation. Therefore, the placement of screws in external rotation of the humerus during glenoid bone block procedures likely reduces the risk of iatrogenic injuries of the suprascapular nerve.