By: 25 October 2011

Sugano M, Nishii T, Miki H, Yoshikawa H, Sato Y, Tamura S.
J Bone Joint Surg (Br) 2007; 89-B: 455-50

Computer navigation is used increasingly in arthroplasty surgery and has been used to aid placement of the acetabular component more precisely. This study aimed to assess the mid-term clinical efficacy of navigation in the placement of a ceramic-on-ceramic bearing.

One hundred and eighty consecutive ceramic-on-ceramic uncemented total hip replacements were studied. Sixty were performed using navigation, one hundred and twenty without. Selection for navigation was not randomised. Navigation was aided by pre-operative CT scanning. The ideal orientation of the acetabular component was defined as 40° of inclination and 20°. Merle d’Aubigne and Postel hip scores were used for clinical assessment. Radiographic assessment was performed with anteroposterior and lateral radiographs at three and six months post-operatively and then annually. Acetabular component orientation was measured with an ellipse fitted to its rim. Follow-up was for a mean of six years.

There was no significant difference in age, diagnosis, gender, height or weight between the two groups. Mean operation time in the navigated group was longer (169 vs 111, p<0.0001). Post-operatively there were seven dislocations in the non-navigated group and none in the navigated group (p=0.049). There was no significant difference in mean inclination but variance was significantly greater in the non-navigated group. Anteversion was significantly greater in the non-navigated group. Thirty-one patients in the non-navigated group were outside Lewinnek’s safe zone compared to none in the navigated group. There was no significant difference in hip scores between the two groups. Impingement related problems were noted in seven of the non-navigated and none of the navigated group.

They conclude that CT-based navigation improves the precision of acetabular component orientation and reduced the rate of dislocations and impingement related mechanical problems.