A reverse shoulder arthroplasty with increased offset for the treatment of cuff-deficient shoulders with glenohumeral arthritis

Abstract

Inherent disadvantages of reverse shoulder arthroplasty designs based on the Grammont concept have raised a renewed interest in less-medialised designs and techniques. The aim of this study was to evaluate the outcome of reverse shoulder arthroplasty (RSA) with the fully-constrained, less-medialised, Bayley-Walker prosthesis performed for the treatment of rotator-cuff-deficient shoulders with glenohumeral arthritis. A total of 97 arthroplasties in 92 patients (53 women and 44 men, mean age 67 years (standard deviation (sd) 10, (49 to 85)) were retrospectively reviewed at a mean follow-up of 50 months ((sd 25) (24 to 96)). The mean Oxford shoulder score and subjective shoulder value improved from 47 (sd 9) and 24 points (sd 18) respectively before surgery to 28 (sd 11) and 61 (sd 24) points after surgery (p < 0.001). The mean pain at rest decreased from 5.3 (sd 2.8) to 1.5 (sd 2.3) (p < 0.001). The mean active forward elevation and external rotation increased from 42(°)(sd 30) and 9(°) (sd 15) respectively pre-operatively to 78(°) (sd 39) and 24(°) (sd 17) post-operatively (p < 0.001). A total of 20 patients required further surgery for complications; 13 required revision of components. No patient developed scapular notching. The Bayley-Walker prosthesis provides reliable pain relief and reasonable functional improvement for patients with symptomatic cuff-deficient shoulders. Compared with other designs of RSA, it offers a modest improvement in forward elevation, but restores external rotation to some extent and prevents scapular notching. A longer follow-up is required to assess the survival of the prosthesis and the clinical performance over time.

Role of the Remaining Rotator Cuff Following Reverse Total Shoulder Arthroplasty

“…The initial Delta-I prosthesis medialized the center of rotation of the glenohumeral joint and lowered (distalizing) the humerus in relation to the scapula, increasing the deltoid lever arm. 10,11,46 Although effectively restoring shoulder elevation, 40,41 rotational deficits, primarily in ER, were not addressed with the medialized design. 11,39 Subsequent biomechanical and clinical studies discovered that by decreasing the offset of the prosthesis from the scapula, the medialized design failed to appropriately tension the posterior rotator cuff muscles necessary for restoring ER.…”

“…5,30,41,47 To improve the biomechanical disadvantages inherent within the medialized design, investigators experimented with designs to improve soft tissue tensioning by decreasing medialization. 46,48 Subsequent modifications sought to increase prosthetic offset while lateralizing the prosthetic glenoid component. Prosthetic lateralization was achieved by either increasing the offset of the glenosphere and/or baseplate (metallic lateralization) or inserting autologous bone graft harvested from the humerus, placed between the native glenoid and the baseplate (bony-increased offset RSA).…”

“…48,49 Cuff et al 50 found significant improvement in average ER from 15 to 51 degrees (P < 0.001) in a cohort of 74 patients followed for a minimum of 5 years using an increased offset prosthesis (reverse shoulder prosthesis; Encore Medical, Austin, TX). Middleton et al, 46 utilizing the increased offset Baylay-Walker prosthesis (Stanmore Implants, Elstree, UK), following 92 patients for a minimum of 50 months reported a mean increase in ER from 9 to 24 degrees (P < 0.001). Furthermore, Boileau and colleagues reported a 10 degrees increase in ER and 1.3 degrees increase in IR using their novel bony-increased offset RSA design.…”

Radiologic Comparison of Humeral Position according to the Implant Designs Following Reverse Shoulder Arthroplasty: Analysis between Medial Glenoid/Medial Humerus, Lateral Glenoid/Medial Humerus, and Medial Glenoid/Lateral Humerus Designs

“…[16][17][18] However, due to the more lateralized COR, the deltoid abductor moment arm of the LGMH design is less than the MGMH designs. 12,19,20) Furthermore, there is an increased risk of baseplate failure and glenoid loosening due to stress concentration and shear forces on the bone-implant surface of the glenoid component. 12,[19][20][21][22] The MGLH design allows the lateral position of the humerus to compensate for the relative medialization of the COR due to the medial glenoid position.…”

“…12,19,20) Furthermore, there is an increased risk of baseplate failure and glenoid loosening due to stress concentration and shear forces on the bone-implant surface of the glenoid component. 12,[19][20][21][22] The MGLH design allows the lateral position of the humerus to compensate for the relative medialization of the COR due to the medial glenoid position. 15) The lateral position of the humerus allows better tensioning of the residual rotator cuff, greater deltoid wrapping, and increased deltoid abductor moment arms as compared with the original Grammont design.…”