Review Question - QID 217839

Scapular notching occurs more commonly in Grammont style reverse protheses with higher humeral neck-shaft angles (155º vs. 135º).

Reverse total shoulder arthroplasty (rTSA) can be used to manage cases of rotator cuff arthropathy, pseudoparalysis, abnormal glenoid morphology and proximal humerus fracture. The rTSA functions by moving the shoulder's center of rotation medial and inferior so that the deltoid lever arm can function to allow active range of motion. Surgeons must understand how implant modifications can affect risk for other complications intraoperatively. Traditionally, one of the most common complications after rTSA has been scapular notching. This occurs when the medial aspect of the humeral component impinges on the inferior aspect of the glenoid. This was more common with the original 155º Grammont prosthesis because the more valgus neck-shaft angle led to medialization of the humeral component and therefore, a higher risk of impingement. It is thought that using a more varus humeral component, increasing the size and lateral offset of the glenosphere and positioning the glenoid baseplate as inferiorly as possible are all ways to mitigate the risk of scapular notching.

Gutierrez et al. evaluated the effects on abduction range of motion and inferior scapular impingement with different glenosphere diameters, offsets, glenoid baseplate positions, and humeral component neck-shaft angles. They noted that a more lateral center of rotation (still medial to normal shoulder) increased the impingement free range of motion the most. They also found that decreasing the humeral neck-shaft angle and positioning the glenoid component more inferior had the greatest effect on minimizing scapular notching.

Levigne et al. examined scapular notching in a multicenter study with 326 patients who underwent rTSA. They noted that >60% of patients had radiographic evidence of scapular notching at average 4 year follow-up. They correlated an increased risk of notching with treatment for cuff-tear arthropathy, atrophy of the infraspinatus, narrowed acromiohumeral distance, and superior placement of the glenoid component.

Cheung et al. published a review of complications in rTSA. They start by discussing general indications for rTSA and provide an overview of potential complications. As for scapular notching, they note that the incidence seems particularly dependent on glenosphere offset, glenosphere position, bone loss and the time the prosthesis is in place for.

Figure A shows an AP radiograph of a rTSA where concomitant scapular notching is noted at the inferior glenoid. Illustration A demonstrates the Sirveaux classification of scapular notching.

Incorrect Answers:
Answer 1: Placing the glenoid baseplate inferiorly along the glenoid rim decreases the risk for scapular notching.
Answer 2: Increasing the diameter of the glenosphere increase the surrounding glenoid coverage and therefore decreases the risk of scapular notching along the inferior scapular neck.
Answer 3: Increasing glenosphere offset effectively lateralizes the construct, which moves the humeral tray further from the scapular neck, lowering the risk of notching.
Answer 4: Increasing the degree of humeral retroversion may increase the degree of postoperative external rotation, but would not increase the risk for scapular notching.