Magnification of digital hip radiographs differs between clinical workplaces

<div><p>Preoperative planning for total hip arthroplasty includes templating on anteroposterior radiographs. It is necessary to consider radiographic magnification in order to scale templates accurately. Studies dealing with hip templating report different values of radiographic magnification. It is not clear if the observed difference in magnification between the studies is caused by variability in studied groups, methodology or instrumentation. We hypothesize that there is a difference in magnification between clinical workplaces. Within this study, radiographic magnification was estimated on 337 radiographs of patients after total hip surgery from five orthopaedic departments in the Czech Republic. Magnification was determined for each patient as a ratio between diameter of implanted femoral head measured on radiogram and its true size. One-way ANOVA revealed significant differences in magnification between workplaces (F(4,332) = 132, p≤0.001). These results suggest that radiographic magnification depends on the workplace where it is taken or more precisely on radiographic device. It indicates potential limits in generalizability of results of studies dealing with preoperative planning accuracy to other institutions.</p></div

Radiographic magnification determined in clinical studies.

<p>Femoral head after THA is used as a magnification reference.</p

Boxplot of radiographic magnification.

<p>Hip radiographic magnification measured from radiographs of patients after total hip replacement at five hospitals.</p

Radiographic magnification obtained at five workplaces.

<p>Radiographic magnification obtained at five workplaces.</p

Clinics, X-ray devices and patients included in the study.

<p>Clinics, X-ray devices and patients included in the study.</p

Schematic diagram showing radiological magnification.

<p>(A and B) various positions of hip joint over the table, (A vs. B) various radiological setups.</p