The subscapularis-sparing windowed anterior technique for total shoulder arthroplasty

Abstract

Background: Traditionally, total shoulder arthroplasty (TSA) involves detaching the subscapularis tendon through either tenotomy or lesser tuberosity osteotomy. A subscapularis-sparing approach avoids detachment but may make re-creation of the anatomy more difficult because of limited exposure. The primary aim of this study was to evaluate the ability to re-create the proximal humeral geometry and assess for osteophyte removal with this technique. The secondary aim was to assess for complications or an inability to complete the procedure with this technique.

Methods: We performed a retrospective review of a consecutive series of 47 patients (100% with osteoarthritis; 59% Walch type A and 41% Walch type B; 50% male and 50% female patients; and average body mass index, 28.21 ± 4.6) who underwent the subscapularis-sparing windowed anterior technique for TSA. The ability to reconstruct the proximal humeral geometry and remove the inferior osteophytes was assessed by 2 independent observers using the center-of-rotation difference (ΔCOR) between the native and prosthetic humeral heads. The ability to complete the procedure was recorded, and a chart review was performed to assess for complications.

Results: The procedure was successfully completed in 44 of the 47 patients. Radiographic review demonstrated an average ΔCOR of 2.28 mm (range, 0.2-6.05 mm; intraclass correlation coefficient, 0.971), below the previously reported acceptable ΔCOR of 3 mm. The ΔCOR was >3 mm in 31.8% of patients (14 of 44; 8 Walch type A and 6 Walch type B; 9 male and 5 female patients). There was no difference in ΔCOR based on Walch type (P = .824). Male patients on average showed a higher ΔCOR (2.62 mm) than female patients (1.94 mm) (P = .099) and more commonly had a ΔCOR > 3 mm (P = .195). Body mass index was not significantly correlated with ΔCOR (r = 0.077, P = .619). For all cases in which the ΔCOR was >3 mm, the prosthetic humeral head was undersized. Osteophytes were successfully removed in 75% of cases (33 of 44) and had no effect on average ΔCOR (P = .468). No revisions or mechanical failures in the early postoperative period were identified in the treatment group of 44 patients (range, 3-15 months). In the group with unsuccessful treatment, there was 1 case of infection treated with 1-stage revision reverse TSA.

Discussion: The subscapularis-sparing windowed anterior technique is an effective approach to TSA that allows for early unrestricted motion. Over 90% of cases can be completed using this technique. Radiographic analysis demonstrated that this approach can be used successfully without compromising anatomic reconstruction of the proximal humerus. Further study is necessary to identify patient factors that would favor a traditional deltopectoral approach and to assess the functional outcomes of this technique.

Keywords: Shoulder; anatomic; arthroplasty; minimally invasive; radiographic analysis; reconstruction; subscapularis; total shoulder arthroplasty.