Bipolar shoulder arthroplasty for irreparable rotator cuff tear: A preliminary report and a video-fluoroscopy study

Purpose of the study Management of patients with massive irreparable rotator cuff tears associat ed with severe glenohumeral joint degeneration presents a difficult clinica l challenge. The present study reports on 24 patients with disabling should er pain due to relator cuff arthropathy treated using a bipolar arthroplast y. Material and methods Between 1995 and 1997, a bipolar shoulder arthroplasty (Biomet, Warsaw, In) was used in 24 patients (25 shoulders) with rotator cuff arthropathy. Pati ents were monitored for an average of 14.5 months (range 12 to 24 months). The coracoacromial ligament was maintened in all patients to provide antero superior stability. The rotator cuff was irreparable and no attempt was mad e to cover the superior defect. Postoperative results were reviewed with th e Constant score and the Swanson score. In order to verify the head-shell m otion and to analyze the dynamic comportement of bipolar arthroplasties, we recorded anterior active elevation and active rotations with video-fluoros copy. Results At final the follow-up, 21 shoulders had no or slight pain. Average active flexion improved to 84.8 degrees after operation from 62.4 degrees beforeha nd. 13 patients achieved more than 90 degrees of active flexion after opera tion. Active external rotation improved from a mean 3 to 28.8 degrees. Befo re surgery the average Constant score was 17.62. Postoperatively, the avera ge Constant score was 46.97 and the average Swanson score was 23.13. Compli cations requiring reoperation occurred in 2 cases: 1 component dislocation (Head-shell), 1 subluxation of the long head of the biceps. Radiographic ev aluation at follow up demonstrated no humeral stem loosening or component m igration and no bony erosion of the coracoacromial arch. Rupture of the inf raspinatus tendon (absolute Constant score: p=0.04, adjusted Constant score : p=0.02, Swanson score: p=0.03, Functional score: p=0.04), preoperative an terior subluxation of the humeral head (absolute Constant score: p=0.03, ad justed Constant score: p=0.05, anterior elevation: p=0.01, functional score : p=0.04), preoperative narrowing of the acromio-humeral interval (adjusted Constant score: p=0.02, overall mobility: p=0.02, anterior elevation: p=0. 03) may jeopardize the subsequent success of bipolar shoulder arthroplasty. The results of this study suggest that the radius curvature of the shell m ust match that of the bony surface of the glenoid and the coracoacromial ar ch (absolute Constant score: p=0.003, adjusted Constant score: p=0.005, ove rall mobility: p=0.002, anterior elevation: p=0.0008, functional score: p=0 .002). Recording of anterior active elevation with video-fluoroscopy allowe d to identify 3 different types of movements after bipolar shoulder arthrop lasty. Recording of internal and external rotation allowed to distinguish 2 differents types of movements. Motion appeared to occur between the bipola r shell and the head. The amount of motion was variable and depended on the biomechanics. Discussion and conclusion Bipolar shoulder arthroplasty is an effective surgical option for patients with massive irreparable tears of the rotator cuff with concomitant glenohu meral arthritis. Satisfactory pain relief and modest gains in motion result in significant functional improvement in this "low functional demand" popu lation. Predictive factors have been identified and should be discussed bef ore surgery.