Abstract
Purpose: We assessed mid-term outcome of mobile cup shoulder prostheses for the treatment of degenerative shoulders with a destroyed cuff.
Material and methods: Forty-four biopolar prostheses were assessed with a mean follow-up of 32 months (range 13 – 50 months). The SOFCOT scoring chart was used. The morphological features of the different forms of shoulder degeneration with cuff destruction were analysed on standard x-rays to define anatomic conditions favourable for his type of implant.
Results: At last follow-up 86% of the shoulders exhibited little or no pain. Mean active anterior elevation was 59.6° – 82.84°, external rotation in position 1 was 8.86° to 301.68°, and internal rotation was 3.13 points to 5.68 points. The mean Constant score was 48.86 points (weighed score 69.13%). Seventy-seven percent of the patients were satisfied and had resumed their former activities. We had one anterior displacement of a shoulder with deltoid palsy and three complications requiring revision: one polyethylene insert which slipped out of the mobile cup, one conflict between the tendon of the long head of the biceps and the cup, and one anterioposterior conflict because of an oversized cup. One non-cemented prosthesis exhibited mobility at 33 months follow-up. One case of excessive lateralisation of the humerus, one mediocre joint congruency, and atrophy of the deltoid were also recorded.
The best outcomes were observed in joints with “centred” degeneration and cuff destruction. Preservation of a satisfactory centring of the cup avoided pain and enabled a mean anterior elevation of 1112.3° with a weighted Constant score of 90.5%.
For early excentred degeneration, preservation of the glenoid bone stock prevented perfect joint congruency leading to excessive lateralisation of the humerus: 20% of the shoulders remained painful and anterior elevation reached 68° with a weighted Constant score of 56%. Paradoxically, results were better in patients with severely excentered degeneration. “Acetabulation” of the shoulder preserved joint congruency and lengthened the lever arm of the deltoid by medialisation and lowering of the centre of rotation. Full pain relief was achieved in all such cases, with anterior elevation at 86° and a weighted Constant score at 78%.
Discussion: Biopolar arthroplasty is effective in shoulders with centred degeneration and cuff destruction. It is an interesting salvage solution for advanced-stage excentric degenerated shoulders beyond the limits of other implants. We propose a decisional tree based on an anatomic classification of the shoulder degeneration with cuff destruction.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
