Abstract
Aim: to compare the reliability of pre-operative templating for total hip and knee arthroplasty using printed digital radiographs versus conventional radiographs.
Materials and Methods: a prospective continuous study commenced January 2005. The PACS digital imaging system was introduced in May 2005 and the radiology department adopted a policy of printing orthopaedic radiographs to ‘true size’. All consultants and their registrars undertaking primary total hip and knee arthroplasty were asked to participate in the study and agreed. The operating surgeon completed a proforma for each Total Hip Replacement (THR) performed noting the templated cup and stem size and offset. Following the surgery the actual sizes and offset of the components implanted were also recorded on the proforma. A similar procedure was followed for the femoral and tibial components of Total Knee Replacements (TKR).
Results: there were 254 completed proformae. 186 pro-formae for conventional radiographs and 68 proformae for printed digital radiographs. Templating was possible from all the conventional radiographs; however templating was only possible from 58 of 68 (85%) digital radiographs as the images were obviously not true size. The templated sizes of both hip and knee components from conventional radiographs were more predictive of the actual size implanted in all cases. Furthermore there were a greater number of predicted outlying sizes using printed digital radiographs.
Conclusion: digital radiographs, even those said to be true size are unreliable for the purposes of pre-operative planning.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
