Radiograph-Based Evaluation of Uncemented Humeral Hemiarthroplasty.

Purpose: This study identifies whether a novel hemiarthroplasty implant that achieves fixation with an intramedullary screw accurately restores native anatomy based on radiographic parameters. Methods: 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. Results: 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. Conclusions: 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. Clinical relevance: These results suggest that uncemented hemiarthroplasty can reproduce anatomy based on radiographic parameters.