DEVELOPMENT, VALIDATION AND INITIAL RESULTS OF A FEMORAL ALIGNMENT DEVICE FOR RESURFACING ARTHROPLASTY OF THE HIP

Abstract

Aim: The purpose of the study was to develop an instrument for positioning a resurfacing femoral component.

Materials and Methods: A new alignment device was developed, which references the natural anatomy of the patient and positions the implant in valgus, slight ante-version and centrally in the femoral neck.

Results: The device was used to position a resurfacing femoral component in 20 cadaveric femora (Group A) and in 15 patients (Group B). In the cadaver group, the valgus and version angles as well as the position of the component relative to the femoral neck centerline were assessed, using pre- and post-operative radiographs and transverse slices of the femoral necks along the component center line. In group A, the achieved valgus and ante-version angles were 9.95 ± 2.35 degrees and 1.87 ± 3.85 degrees, respectively. In the vertical plane, the implant was 0.50 ± 1.52 mm superior and in the horizontal plane, 0.57 ± 1.84 mm posterior to the centreline of the femoral neck. In the patient group, the valgus angle was 9.79 ± 5.38 degrees and the implant was 0.67 ± 1.27 mm inferior in the vertical plane. There was no notching in any of the cases. There was a very strong correlation between the pre op Neck Shaft angle and the postoperative valgus achieved (r =0.902)

Conclusion: The alignment device was quick and easy to use and positioned the femoral resurfacing component accurately and reproducibly referencing the native anatomy. The small size of the instrument makes it useful in minimally invasive techniques. The self-centering three-point design proved to be stable and superior to other currently available instruments.