Radiograph-Based Evaluation of Uncemented Humeral Hemiarthroplasty

This study identifies whether a novel hemiarthroplasty implant that achieves fixation with an intramedullary screw accurately restores native anatomy based on radiographic parameters.

Six cadaveric specimens were stripped of soft tissue. A novel hemiarthroplasty with modular components was implanted into each cadaver. Radiographic measurements were taken to compare pre- and postimplantation anatomy.

The average age of the cadavers was 62.7 years. The trochlear width of the implant averaged 3.39 mm (range, 2.37-4.7 mm) smaller than the native trochlear width. The implant capitellum center averaged 5.28 mm (range, 3.92-7.29 mm) away from the native capitellum center on the anteroposterior (AP) view and 3.74 mm (range, 1.13-6.57 mm) on the lateral view. The distance between the humeral centerline and the center of the implanted trochlea averaged 0.5 mm (0.15-0.95 mm) from the native distance. The offset between the centerline of rotation in the native humerus and in the implant averaged 0.35 mm (range, 0.08-0.87 mm) on the AP view. The angle between the intramedullary (IM) canal of the native elbow and the IM screw was, on average, 0.67° (range, 0.14-2.30°) on the AP view and 1.45° (range, 0.52-2.57°) on the lateral view. The angle between the IM screw and the component body was, on average, 1.95° (range, 0.94-3.0°) on the AP view and 2.21° (range, 0.97-5.55°) on the lateral view.

Native anatomy can be matched when implanting a distal humerus hemiarthroplasty that employs modular, intramedullary fixation. Angular laxity between the body component and IM screw accommodates variable patient anatomy of the distal humerus.

These results suggest that uncemented hemiarthroplasty can reproduce anatomy based on radiographic parameters.