Metastatic lesions of the humerus treated with the isoelastic diaphysis prosthesis.

Between January 1, 1987, and December 31, 1997, an isoelastic polyacetal resin prosthesis was used in 50 patients with metastatic bone disease to reconstruct pathologic or impending fractures of the humeral diaphysis. Fifty-seven operations were performed, including seven revision surgeries. The patients were assessed before and after surgery for limb function and quality of life using a modified Karnofsky scale. The mean survival time was 440 days. Ninety-one percent of the operations resulted in restoration or improvement of quality of life. Limb function was good or excellent in more than 80% of the patients after surgery. Breaking of the implant (n = 3), loosening of the implant (n = 2), periprosthetic fracture (n = 1), hematoma (n = 2), infection (n = 1), and one radial nerve paralysis were the main complications. In the cases of implant failure, the prosthesis broke at the site of a locking screw that was inserted across the prosthetic shaft in the cementless implantation technique. This kind of complication could be avoided by using bone cement for implantation or additional plate osteosynthesis between the prosthesis and humeral shaft. The isoelastic diaphyseal prosthesis offers a promising method of treating patients with metastatic lesions of the humeral shaft.