[Mid-term results of shoulder arthroplasty for primary osteoarthritis]. / Résultats à moyen terme de la prothèse d'épaule dans l'omarthrose primitive.

INTRODUCTION: Primary osteoarthritis of the glenohumeral joint is less common than that of the hip and knee, but it is not so rare. The use of prosthetic arthroplasty for the management of end-stage osteoarthritis remains the treatment of choice. We reviewed our experience of shoulder arthroplasties in 48 patients (51 shoulders) with 60 months average follow-up (24-124). MATERIALS AND METHODS: Forty-eight patients (51 shoulders) underwent shoulder replacement for primary osteoarthritis. There were 15 men and 36 women. Average age was 65 years. A total shoulder arthroplasty was performed in 43, and a hemiarthroplasty in 8. A Neer II monobloc implant was used in 27, and a modular implant in 24. The humeral implant was cemented in all cases but 3. An all-polyethylene cemented glenoid implant was used in all total shoulder arthroplasties. A rotator cuff tear was found in 8 cases. RESULTS: According to Neer rating scale, an excellent result was found in 19 cases (37%), a satisfactory result in 27 (53%), and a non-satisfactory result in 5 (10%). According to Constant's criteriae, pain improved from 1.5 to 12 points, activity from 7 to 16.5 points, and mobility from 14 to 31 points. Active anterior elevation improved from 73 to 140 degrees, with a gain of 67 degrees; active external rotation improved from 9 to 40 degrees, with a gain of 31 degrees. Internal rotation improved also from the ability of the thumb to reach the sacrum to T12. The ponderated Constant score calculated for 22 patients was 91 p.cent. Radiographic analysis showed lucent lines around the humeral component in 10 cases (19%), and around the glenoid in 29 cases (67%). A complete lucent line not greater than 1mm size, was present in only 15 glenoid implants (35%). There was no case of component loosening in our series at the longest follow-up, as well as no revision procedure. Only the preoperative rotator cuff status influenced statistically the final result. Best results were obtained with total shoulder arthroplasties compared to hemiarthroplasty, and with modular implants compared to monobloc. DISCUSSION: Shoulder arthroplasty has become the standard for the treatment of primary osteoarthritis. Proximal humeral head prosthetic replacement can be a very successful procedure in patients with glenohumeral arthritis; however the degree and consistency of pain relief is not as great nor as predictable as in total shoulder arthroplasties. Also, clinical results seem to deteriorate with time. Revision rate is approximatively of 20%, usually for persistant pain. The clinical results of total shoulder arthroplasty continue to be excellent with longer follow-up period. The frequency of complications and the need for revision is low. However, when revision surgery is needed, the most common reason is for glenoid loosening. Good results can be expected especially in primary osteoarthritis with pain relief in almost all cases, good motion (three-fourths or four-fifths normal), improvement of functional activities, and patient satisfaction in at least 90% of the cases.