Measurement of polyethylene thickness in total hip arthroplasty. A technique analysis.

Accurate radiographic measurement techniques are necessary to evaluate wear characteristics of different metals, ceramics, and plastics. This study evaluated a standard technique for radiographic measurement of acetabular component thickness. Twenty-one acetabular components retrieved after revision surgery were studied. Radiographic measurement of polyethylene thickness was performed at two points on radiographs taken within 2 months of the revision surgery. Measurements were made at the area of greatest polyethylene wear and at the center of the component, and these measurements were compared to direct measurement of the retrieved component. The 42 data points obtained revealed an average difference between the radiographic and direct measurements of 0.18 mm. A regression model demonstrated no significant difference (P = .85) between these measurements. Additionally, when comparing the central-point measurement to the thinnest wear-point measurement, no difference was noted, indicating that wear in the sagittal plane did not affect radiographic measurement accuracy. Radiographic measurement of acetabular component thickness is accurate to within 0.18 mm. This degree of accuracy allows for radiographic wear analysis, as long as the standard measurement technique is utilized.