Abstract
Aim: The purpose of the study was to compare the placement of the guide wire for the femoral components in hip resurfacing, implanted using computer navigation and a new alignment device(jig).
Materials and Methods: The study was conducted on 13 cadaveric femora. Registration of the femoral head was carried out using Computer Aided Navigation system, Brainlab (BL) by the senior author. Guide wires were inserted using BL by the senior author and subsequently with the alignment device (jig) by the junior author. The junior author was blinded to the templated position and implanted the wire using the jig. In 6 femurs the implantation of the prosthesis was carried out in the position suggested by the BL and in 7 by the jig. All the femora were sectioned transversely after implantation and measurements were taken using callipers and subsequently using Autocad.
Results: There was no notching of the superior femoral neck in either of the groups. The mean and standard deviation of the anatomic neck-shaft angles was 124.91° ± 14.25°. The wire-shaft angle in the BL group was 131.46° ± 5.27° and in the jig group 134.08° ± 3.80°. In the BL group the wire was in 0.85° ± 2.15° of retroversion as compared to 1.38° ± 4.19° of anteversion in Jig group. The position of the wires at the narrowest cross section of the femoral neck is shown in figure.
Conclusion: The alignment device consistently positioned the wire more valgus and anteverted than Computer aided navigation, which was desired. In all cases, the wire position was well within acceptable limits. Computer aided navigation does not seem to offer distinct advantages in resurfacing hip replacements.
Correspondence should be addressed to Mr John Hodgkinson, BHS, c/o BOA, The Royal College of Surgeons, 35–43 Lincoln’s Inn Fields, London WC2A 3PE.
