Abstract
Malignant bone tumours or metastasis of the upper humerus may cause significant loss of function especially in those patients with resectional arthroplasty of the shoulder. One method for achieving functional reconstruction of the humerus concerned is replacement with a modular endoprosthesis. Little is known about clinical and radiological results in these rare circumstances. Between 1993 and 1997 we treated 21 patients (22 shoulders) with enlarged osteolytic destructions of the proximal humerus caused by metastatic spread or primary malignant tumours. Patients with additional involvement of the glenoid were excluded from this study. The average follow-up was 3.9 years. Every 3 months all patients were followed-up clinically and radiographically. Prior to surgery, diagnosis was established by incisional biopsy and the outcome determined the therapeutic algorithm (radiotherapy, chemotherapy, surgery). In most cases of metastatic lesions, surgery was the first treatment. According to the regional spread of the tumour, various amount of bone and soft tissues had to be removed. The distal stem of the prosthesis was inserted in a cementless way and secured to bone with two interlocking screws. The length of the diaphyseal part depended on the site of osteotomy. Soft-tissue coverage of the large implant was achieved in all patients. Early complications were lymphogenic oedema and superficial wound dehiscence. One patient developed a deep infection, which had to be managed surgically. According to the functional rating system of the Musculoskeletal Tumour Society for the upper extremity the overall results were inversely proportional to the extent of resection. None of our patients achieved unrestricted motion of the shoulder concerned. The most important finding was a proximal migration of the prosthesis causing a painful subacromial impingement, mainly a consequence of the resection of the deltoid muscle and the rotator cuff. In summary, a modular endoprosthesis cannot be recommended generally as the method of choice. If the muscular balance of the shoulder is too weak to act as a joint centralizer the endoprosthesis has no advantage over a simple diaphyseal spacer.