A new approach for assessment of wear in metal-backed acetabular cups using computed tomography : a phantom study with retrievals

• Background and purpose Polyethylene wear is an important cause of aseptic loosening in hip arthroplasty. Detection of significant wear usually happens late on, since available diagnostic techniques are either not sensitive enough or too complicated and expensive for routine use. This study evaluates a new approach for measurement of linear wear of metal-backed acetabular cups using CT as the intended clinically feasible method. Material and methods 8 retrieved uncemented metal-backed acetabular cups were scanned twice ex vivo using CT. The linear penetration depth of the femoral head into the cup was measured in the CT volumes using dedicated software. Landmark points were placed on the CT images of cup and head, and also on a reference plane in order to calculate the wear vector magnitude and angle to one of the axes. A coordinate-measuring machine was used to test the accuracy of the proposed CT method. For this purpose, the head diameters were also measured by both methods. Results Accuracy of the CT method for linear wear measurements was 0.6 nm and wear vector angle was 27 degrees. No systematic difference was found between CT scans. Interpretation This study on explanted acetabular cups shows that CT is capable of reliable measurement of linear wear in acetabular cups at a clinically relevant level of accuracy. It was also possible to use the method for assessment of direction of wear.

Ämnesord

TEKNIK OCH TEKNOLOGIER  -- Medicinteknik -- Medicinsk laboratorie- och mätteknik (hsv//swe)

ENGINEERING AND TECHNOLOGY  -- Medical Engineering -- Medical Laboratory and Measurements Technologies (hsv//eng)

Nyckelord

bone cement; polyethylene; acetabuloplasty; article; computer assisted tomography; computer program; diagnostic accuracy; diagnostic approach route; endoprosthesis loosening; ex vivo study; femur head; functional assessment; human; image analysis; metal backed acetabular cup; orthopedic equipment; phantom; reliability; acetabulum; computer simulation; hip arthroplasty; hip prosthesis; prosthesis; prosthesis failure; reproducibility; sensitivity and specificity; Acetabulum; Arthroplasty

Replacement

Hip; Computer Simulation; Hip Prosthesis; Humans; Polyethylene; Prosthesis Design; Prosthesis Failure; Reproducibility of Results; Sensitivity and Specificity; Tomography

X-Ray Computed

Medical engineering

Medicinsk teknik

Publikations- och innehållstyp

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