Prosthetic design of reverse shoulder arthroplasty contributes to scapular notching and instability

Figure 1 Scapular notching according to the 4-grade Sirveaux classification. Reproduced with permission and copyright of the British Editorial Society of Bone and Joint Surgery (Reprinted with permission from Sirveaux F et al[15], Figure 3).

Figure 2 Distance between the inferior glenoid osseous rim (upper arm of the arrow) and the lowest point of the glenoid sphere (lower arm of the arrow) on the external rotation anteroposterior view. Reprinted with permission from Levigne C et al[23], Figure 8.

Figure 3 The prosthesis-scapular neck angle (PSNA) is the angle subtended by the intersection of line AB and line BC. Point C is located 1 cm medial to the junction of the glenosphere and the most inferior and lateral bone of the inferior glenoid rim or scapular neck. The peg-glenoid rim distance (PGRD) is the distance between points B and D. PGRD: Peg-glenoid rim distance; PSNA: Prosthesis-scapular neck angle. Reprinted with permission from Simovitch et al[16], Figure 4A.

Figure 4 Glenoid inclination is the angle formed between a horizontal line and a line parallel to the back surface of the glenoid sphere. If it is > 90° it is classified as superiorly tilted, and if it is ≤ 90° it is classified as inferiorly tilted. Reprinted with permission from Levigne et al[23], Figure 11.

Figure 5 Illustration of measurement of the prosthesis-scapular neck angle and the prosthesis-scapular bone angle. A: The prosthesis-scapular neck angle is the angle between a line from superior to inferior along the glenoid baseplate and a line from the most inferior point of the baseplate’s prosthesis-bone interface to a point 1 cm medially along the inferior scapular neck; B: The prosthesis-scapular bone angle uses a point 6 cm medial along the scapular border to draw the second line. PSNA: Prosthesis-scapular neck angle; PSBA: Prosthesis-scapular bone angle. Reprinted with permission from Kempton et al[24], Figure 3.

Figure 6 The receiver operating characteristic curve reveals the sensitivity and specificity for predicting the inferior glenoid tilt.