Abstract
In image-free navigation system, three bony landmarks (typically both anterior superior iliac spines (ASIS) and pubic symphysis) are registered intraoperatively by manual palpation. If the registration of bony landmarks is inaccurate, the final orientation of the cup determined by the navigation system will also be inaccurate. We therefore examined intra-and intersurgeon variability in registration and the distance between registration points in each bony landmark with two surgical positions.
Thirty-seven THAs were performed in the lateral position and 15 THAs were performed in the supine position. The cup was fixed using the image-free Ortho-Pilot hip navigation system (B. Braun Aesculap, Tuttlingen, Germany). The registration was repeated two more times by operator and assistant, and the intra-and intersurgeon variability of cup abduction angle and anteversion was analyzed by ICC (intraclass correlation coefficients). In 25 hips, the distance between intrasurgeon registration points and that between intersurgeon registration points in each landmark were calculated.
The ICC in the lateral position ranged between 0.59 and 0.81, and between 0.85 and 0.95 in the supine position. The ICCs of cup abduction angle for the intra-and intersurgeon variability were 0.92 and 0.95 for the supine position and 0.65 and 0.59 for the lateral position. Those of anteversion were 0.93, 0.85, and 0.81, 0.72, respectively.
The variability of registration of collateral and contralateral ASIS in the lateral position was greater than that in the supine position.
In image-free navigation system, the variability of registration points depended on bony landmarks and patient position. The registrations of pubic symphysis in the supine position and all bony landmarks in the lateral decubitus position are standing further improvement.
Correspondence should be addressed to Diane Przepiorski at ISTA, PO Box 6564, Auburn, CA 95604, USA. Phone: +1 916-454-9884; Fax: +1 916-454-9882; E-mail: ista@pacbell.net
