Metastatic diaphyseal fractures of the shaft of the humerus. The structural strength evaluation of a new method of treatment with a segmental defect prosthesis.

The surgical treatment of extensive metastatic diaphyseal lesions of the humerus with pathologic fractures is difficult. Patients with failed internal fixation often have large segments of bone loss. Rigid fixation often is not possible in these cases. Four patients were treated with a titanium segmental defect (SD) prosthesis with good clinical results. A comparative in vitro analysis of fixation with the SD prosthesis, a Rush rod, and a dynamic compression plate (DCP) augmented with methylmethacrylate was performed. The SD prosthesis performed better than the Rush rod and DCP in both the nondestructive four-point bending test and the destructive torsional test. The reconstructed humeri using the SD prosthesis had a torsional strength approaching that of an intact specimen. Hence, the SD prosthesis is a useful adjunct device in treating patients with extensive destructive lesions of the humerus secondary to metastatic disease and hematologic malignancies and in patients with malignant diseases who have had failed attempts at internal fixation.