Total shoulder arthroplasty with an anterior-offset humeral head in patients with a B2 glenoid

Abstract

Background: To address severe posterior subluxation associated with the Walch B2 glenoid deformity, the eccentricity of the prosthetic humeral head can be reversed, allowing the humerus to remain in a relatively posterior position while the prosthetic humeral head remains well-centered on the glenoid. This study describes the short-term outcomes after anatomic total shoulder arthroplasty (TSA) using this technique.

Methods: We retrospectively reviewed a consecutive series of patients with a B2 glenoid who underwent TSA with the prosthetic eccentric humeral head rotated anteriorly for excessive posterior subluxation noted intraoperatively. Medical records were reviewed for visual analog scale (VAS), American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), and Simple Shoulder Test (SST) scores. Final radiographs were analyzed for instability, lesser tuberosity osteotomy healing, and glenoid loosening.

Results: Twenty patients were included with outcome scores at a mean of 48 months. Mean VAS (P < .0001), ASES (P < .0001), and SST (P < .0001) scores improved significantly. Using the Lazarus classification for glenoid loosening, 5 patients had grade 1 lucency and 2 had grade 2 lucency at a mean of 24 months' follow-up. The remaining 13 patients had no glenoid lucencies. Radiographic decentering was reduced from a mean of 9.9% ± 5.7% preoperatively to 0.5% ± 3.0% postoperatively (P < .001). There were no cases of lesser tuberosity repair failures or revision surgery.

Conclusion: TSA in patients with a B2 glenoid with a reversed, anterior-offset humeral head to address residual posterior subluxation resulted in excellent functional outcomes at short-term follow-up with improvement in humeral head centering. Early radiographic follow-up suggests low risks of progressive glenoid lucencies and component loosening.

Keywords: B2 glenoid; Shoulder arthroplasty; glenohumeral osteoarthritis; shoulder subluxation.

Figure 1

Demonstration of reverse offset of the humeral head. (A) Sawbones model. (B) Schematic of anatomic dialing of an eccentric head. The prosthetic glenoid is indicated by the C shape to the left. (C) Schematic demonstrating reverse offset dialing of an eccentric head allowing the humeral shaft to remain posterior.

Figure 2

Preoperative radiographs demonstrating primary glenohumeral osteoarthritis with a biconcave (B2) glenoid. (A) True anteroposterior view. (B) Axillary view.

Figure 3

A line is drawn from the anterior rim of the glenoid to the posterior rim. A perpendicular line is drawn bisecting the glenoid line. A circle is drawn and fit to the humeral head. A line (AC) is drawn as a diameter through the circle and parallel to the glenoid line. Point B is the intersection of line AC and the perpendicular bisector of the glenoid line. The ratio lines BC/AC in a centered humeral head is 0.5. The percent decentering was calculated as (BC/AC − 0.5) × 100%. In this example, there is 12% posterior decentering preoperatively (A). Postoperatively (B), with placement of the eccentricity of the humeral head prosthesis anteriorly, there is <0.2% decentering.

Figure 4

Final postoperative radiographs showing concentric glenohumeral prosthetic alignment with a reverse offset humeral head and a healed lesser tuberosity osteotomy. (A) True anteroposterior view. (B) Axillary view.