COMPUTER AIDED NAVIGATION – A USEFUL TOOL IN RESURFACING HIP ARTHROPLASTY

Abstract

Aim: To test the accuracy of implant positioning in using computer navigation in Resurfacing hip arthroplasty

Materials and methods: Brain Lab was used to register 13 cadavers. The component position was fine tuned to a desirable valgus angle. Wire was passed using navigation. The femoral heads were sectioned after insertion of the prosthesis. The measurements from the screen-shots and the transverse sections were analysed using AutoCad®

Results: The Brain lab Registered the femoral heads to 124.91° ± 14.25° (Range 97° −148° ) CCD. The actual neck shaft angles were 126.11° ± 5.33°. The implants were placed in an angulation’s of 131.46° ± 5.27 ° (Range 116° −137° ) and a version of −0.85° ± 2.1° this gave a valgus of 5.91° ± 13.66°. The position of the wire in the isthmus of the neck was −0.52 mm ± 0.69 mm inferior to the centre and 1.7mm ± 1.9 mm posterior to the centre on the transverse sections (n=6). The components were in 8.69° ± 4.95° (n= 6) valgus to the native neck shaft angle. In only 1 hip the femoral head implanted was of the same size as suggested by navigation, in all the rest of the hips the femoral component was of a larger size. This was because it was felt that implanting a smaller size would cause notching of the superolateral neck.

Conclusion: There is a learning curve involved for registering the femoral heads using computer navigation systems, however the navigation gives the surgeon a distinct advantage of being able to choose the point of entry, implant the prosthesis in as valgus position as possible in relation to the femoral head, translate the implant anteriorly and place the peg in the centre of the femoral neck in both the planes. The computer-aided navigation can optimise the component positioning and thereby provide excellent results.