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Thursday, March 11, 2004

CAS improves accuracy of cup placement in THA

By Nancy Fehr

Optimal acetabular component orientation in total hip arthroplasty (THA) is a complex three-dimensional problem with failure leading to increased wear and instability. Recent investigations have sought to define the radiographic analysis of cup position in the clinical setting, prosthetic issues such as range of motion and component impingement, and technical issues at the time of surgery such as body position and how to place the prosthesis in the desired location. Computer-assisted navigation represents a new technology that can be used to deal with all of these problems, according to researchers presenting Scientific Paper 31 on Wednesday.

Study authors reported substantial statistical improvement in accuracy of cup placement demonstrated using computer-aided surgery (CAS) compared to freehand methods. The final predicted CAS position nearly matched the computed tomography (CT) calculated position in every case.

The level III retrospective cohort study compared the efficacy of CAS to place acetabular component orientation in 45 abduction, 20 operative anteversion, as compared to freehanded techniques.

Sixty-nine patients who had undergone THA with freehand cup insertion were compared with 98 patients who had THA that used a CT-based computer navigation. A postoperative CT scan determined cup position with a validated computer algorithm.

Researchers included Rolf Georg Haaker, MD, and Andreas Ottersbach, MD, both of Brakel, Germany; James B. Stiehl, MD, of Milwaukee, Wisc.; Martin Stockheim, MD; K. Tiedjen, MD; and F. Rubenthaler, MD, all of Bochum, Germany.

  Comparison of abduction of the cup in 69 conventional and 92 navigated implanted cups

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