Abstract
Background: The measurement facility on PACS is used to aid decision making. This facility is inaccurate and does not reflect clinical parameters, rendering its use ineffectual. Previous works utilised only a single prostheses type, were under-powered and not statistically robust.
Aim: To establish and statistically analyse the reliability of PACS software for the measurement of orthopaedic parameters at a university teaching hospital.
Methods: Retrospective analysis of radiographs of 100 patients (50 hip hemi-arthroplasty, 50 intra-medullary nailing) was performed to provide a wide base and allow a comparison of the spherical implant and a nail.
Implant sizing from theatre records was compared with the post-operative films. The size of the implant on radiograph, the magnification of the exposure and the effect of further magnification was noted. Analysis of the results was by paired student’s t testing incorporating inter-observer error into the test statistic.
Results: The hip prostheses were found to be oversized (range: 7–16mm; mean: 10.9mm). This is highly significant (p=< 0.01). The nails were similarly oversized (range: 0–6mm; mean: 1.87mm). This result was significant (p=< 0.05) although the error was less than for the spherical prosthesis. This is presumed due to the nature of the implant size and the distance of the implant from the cassette during exposure.
Discussion: This study demonstrates with statistical significance the unreliability of PACS measurement software. The manufacturer was contacted and has confirmed that accurate imaging can only be obtained on a named case, calibrated image. This has implications for all orthopaedic surgeons.
The abstracts were prepared by Major SA Adams. Correspondence should be addressed to Major M Butler, CSOS, Institute of Naval Medicine, Crescent Road, Alverstoke, Hants PO12 2DL
