We have developed and tested the accuracy of a completely automated method for polyethylene (PE) wear measurement of digitised antero-posterior and lateral radiographs.

New computer algorithms have been developed to measure PE wear on digitised hip radiographs. The only user input required is the file name of the x-ray. Validation was performed by simulation of PE wear in an acrylic phantom. Radiographs were analysed with the new software and results were compared to know penetration of the femoral head.

Accuracy using 10 antero posterior and lateral phantom radiographs was within ±0.08mm (95% CI) of the real femoral head penetration. There was no inter or intra-observer error (identical results with all measurements). Perhaps most importantly, this system gave accurate results in 94% of 600 clinical radiographs of variable quality. Only 74% of this same group of radiographs were considered of sufficient quality to allow reliable manual measurement.

This new method of PE wear measurements eliminated inter and intra-observer error, allowing comparison of wear results between different institutions. Accuracy is improved, but still limited by resolution of the scanned image.