Role of an anterior flange on cortical strains through the distal humerus after total elbow arthroplasty with a latitude implant.

PURPOSE

Anterior flanges have been added to the humeral components of some total elbow arthroplasty systems to improve load transfer to the humerus and thereby reduce stress shielding in an effort to decrease the incidence of loosening. Either a wedge of bone or bone cement is placed between the anterior surface of the humerus and the flange. The purpose of this study was to quantify the cortical strains in the humerus as a function of these implantation options.

METHODS

Five cadaveric distal humeri were fitted with bending strain gauges at 2 levels on the diaphysis and axial strain gauges at 1 level. Each specimen was subjected to cantilevered bending and axial compressive loads. Subsequently, a humeral prosthesis was inserted, and testing was repeated with 3 materials behind the flange: no graft (simulating an implant with no flange), a wafer of cancellous bone, and a block of bone cement.

RESULTS

The presence of an anterior flange had no significant effect on load transfer through the distal humerus regardless of graft material. This was found to be consistent for both bending and axial loading modes at all gauge levels; however, the supporting collar effect of the implant may have influenced axial compression results.

CONCLUSIONS

These results suggest that for the Latitude humeral component studied, the placement of bone or bone cement behind the anterior flange may not influence the cortical strains in the distal humerus under bending loads. However, a flange may still influence cortical strains using another implant with different geometric and material properties than the currently studied design.