Wear of the ultra-high molecular weight polyethylene articular surface has been recognized as a major factor threatening the long-term success of total hip arthroplasty. Manual techniques that have been used to measure femoral head penetration into the polyethylene have been plagued with poor reproducibility and limited accuracy. Using a previously described phantom model simulating an unworn total hip arthroplasty, we previously demonstrated significant limitations in the accuracy of several widely used computerized wear measurement programs. A major component of these inaccuracies is projectional distortion of the femoral head and acetabular shell on the radiograph. These inaccuracies can be "corrected for" mathematically.Methods:
In the present follow-up study, we evaluated a widely used hip wear measurement software program (Hip Analysis Suite version 184.108.40.206) that corrects for these projectional errors with use of our previously described "zero wear" phantom model. A cementless metal-backed acetabular component was evaluated radiographically at three different cephalocaudad locations with respect to a radiopaque centering target. At all three positions, the cup was aligned in three different angles of planar abduction (35°, 45°, 55°) and four angles of planar anteversion (10°, 20°, 30°, 40°). The accuracy and reproducibility of Hip Analysis Suite version 220.127.116.11 were determined and compared with the results obtained with the earlier version, Hip Analysis Suite version 4.0.Results:
Hip Analysis Suite version 18.104.22.168 was significantly more accurate than Hip Analysis Suite version 4.0 for determining linear wear and volumetric wear. Hip Analysis Suite version 22.214.171.124 was significantly more accurate for determining femoral head penetration at the different cephalocaudad acetabular positions and over the range of acetabular component anteversion and abduction angles in comparison with Hip Analysis Suite version 4.0.Conclusions:
With use of the same methodology that was used to evaluate earlier versions of Hip Analysis Suite, the present study showed improvement in the accuracy of wear measurement with Hip Analysis Suite version 126.96.36.199 as compared with Hip Analysis Suite version 4.0.Clinical Relevance:
On the basis of the results of the present study, Hip Analysis Suite version 188.8.131.52 appears to fulfill the needs for a user-friendly, efficient, and accurate method of assessment of polyethylene wear following total hip arthroplasty.