Abstract
Introduction Malposition of the acetabular component in total hip arthroplasty is associated with a number of significant complications. In this study we acertain the accuracy of an imageless computer based surgical navigation system for positioning the acetabular component, using a mechanical hip device.
Methods A mechanical hip device was constructed that allowed accurate measurement of inclination and version, leg length and lateral offset of the acetabular and femoral components. In 31 cases these parameters were varied while a blinded operator would place the cup in the predetermined position in the mechanical hip jig. The values given by the navigation system on the screen were recorded and compared to the measurements obtained directly from the mechanical hip device.
Results The mean difference between value set by an independent person and value read by the navigation system was; inclination of the cup 0.97 ± 0 and the ante-version of the cup 1.58 ± 0.83. The leg length change contributed by the cup showed a mean difference between beforehand set value and read value on the screen of 1.48 ± 1.36 mm and for lateral offset change by the cup of 1.58 ± 0 mm.
Conclusions The accuracy of the hip navigation unit demonstrated in this study is well within the limits that would be required for clinical usage as a surgical aid in total hip arthroplasty and could provide the surgeon with a tool that enables significant improvement in accuracy for acetabular positioning.
The abstracts were prepared by Mr Jerzy Sikorski. Correspondence should be addressed to him at the Australian Orthopaedic Association, Ground Floor, William Bland Centre, 229 Macquarie Street, Sydney NSW 2000, Australia.
None of the authors have received any payment or consideration from any source for the conduct of this study.
