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The final follow-up plain radiograph is sufficient for clinical evaluation of polyethylene wear in total hip arthroplasty

Authors: Stilling, Maiken1; Larsen, Kristian2; Andersen, Niels T3; Søballe, Kjeld1; Kold, Søren1; Rahbek, Ole1

Source: Acta Orthopaedica, Volume 81, Number 5, October 2010 , pp. 570-578(9)

Publisher: Informa Healthcare

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Background and purpose Radiostereometric analysis (RSA) is a highly accurate tool for assessment of polyethylene (PE) wear in total hip arthroplasty (THA); however, PE wear measurements in clinical studies are often limited to plain radiographs. We evaluated the agreement between PE wear measured with PolyWare software, which uses plain radiographs, and by model-based RSA, which uses stereo radiographs.

Methods Measurements of PE wear postoperatively and at final follow-up (after mean 6 years) on plain radiographs of 12 patients after cementless THA were evaluated with PolyWare software and the results were compared with those from RSA as the gold standard (Model-based RSA using elementary geometrical shape models; EGS-RSA). With PolyWare, we either used the final radiographic follow-up (PW1) only or both the postoperative follow-up and the final follow-up (PW2).

Results The 2D mean wear measured (in mm) was 0.80, 1.07, and 0.60 for the PW2, PW1, and RSA method. 2D intra-method repeatability was similar for PW1 and RSA with limits of agreement (LOAs, in mm) of ± 0.22, and ± 0.23, respectively. 2D inter-method concurrent validity was best between PW1 and EGS-RSA with LOAs of ± 0.55. For 2D linear wear measurements, the PW1 method had a clinical repeatability similar to that of RSA.

Interpretation PW1 is sufficient for retrospective determination of 2D wear from medium-term wear measurements above 0.5 mm, It alleviates the need for baseline plain radiographs, has a clinical precision similar to that of RSA, and is easy and inexpensive to use.

Document Type: Research Article


Affiliations: 1: 1Department of Orthopedics, Aarhus University Hospital 2: 3Orthopedic Research Unit, Department of Orthopedics, Hospital Unit West, Holstebro, Denmark 3: 2Department of Biostatistics, School of Public Health, Aarhus University, Aarhus

Publication date: October 1, 2010

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