The reversed Delta shoulder prosthesis in reconstruction of the proximal humerus after tumour resection.

The authors present two series of six and seven patients respectively, with a tumour of the proximal humerus, who were treated at two different institutions with a Delta type inverted shoulder prosthesis (DePuy International Ltd) after a Malawer type Ia or Ib resection. The rationale of using an inverted shoulder prosthesis is the aim to improve the functional outcome in rotator cuff deficient shoulders. This type of prosthesis medializes and lowers the centre of rotation, lengthens the lever arm of the deltoid muscle and improves its function. At one institution the resected part of the humerus was re-implanted after extracorporeal irradiation. It was fixed intramedullarly by cementation of the humeral prosthetic component to facilitate restoration of humeral height. This graft allowed reinsertion of muscles (deltoid, pectoralis, biceps) thus improving power generation postoperatively. The largest glenosphere, size 42, was routinely used to reconstruct the glenoid; this theoretically improves the functional outcome (increased external rotation) and stability. At the other institution no graft augmentation was used except in one patient. The height of the humeral prosthetic component was assessed after resection of the tumour by measurement of the resected part. The prosthetic stem was fitted in the remaining part of the humeral diaphysis, in three cases by cementation and in three cases by press-fit (hydroxyapatite coating). Muscle balance was appreciated intra-operatively. Stability of the prosthesis was directly related to the level of resection. Both techniques resulted in a minimum active abduction of 60 degrees, reaching 90 degrees or more in most patients. When compared to other results in the literature, this is a major functional improvement. The mean adjusted postoperative Constant score was 72.5% (range: 30-90%), and the mean MSTS score was 75.8% (range 36.7-96.7%).