This study shows that, in the absence of a departmental policy for routinely performing WB knee radiographs, the vast majority of non-traumatic knee radiographs requested by GPs in patients over the age of 40 are performed non-WB (98%). In the financial year of 2011 – 2012 the national cost of all diagnostic radiology to the NHS budget was £815 million (Department of Health 2012). To put the extrapolated unnecessary direct costs (£200,052) calculated from our study into context this would account for 0.025% of diagnostic radiology costs. In the current politico-economic climate, this saving, while modest compared to the whole NHS budget, represents a significant and unnecessary cost, which can be readily and easily addressed.
Our department sees approximately 1000 new knee patients annually. Of these patients, approximately 300 patients (in 2012) would fit our inclusion criteria (age over 40, no previous arthroplasty or fixation, no trauma). Therefore, as a representation of patients seen by our department for suspected knee osteoarthritis, 19% (56 out of 300) require an unnecessary repeat of the knee imaging at the time of their outpatient visit. This would therefore support the view that a significant amount of time is wasted in the outpatient setting repeating these radiographs. The overall numbers of patients actually requiring such repeat radiographs remain, however relatively small (n = 56). However, this may be due to the reluctance of specialist clinicians in subjecting patients to further radiation in repeating radiographs as WB.
There is good evidence that tibio-femoral joint space narrowing is good evidence for cartilage loss (Buckland-Wright et al. 1995). In addition, our study confirms that WB compared to non-WB films significantly increase the amount of joint space narrowing on plain radiographs (p = 0.035), and hence the severity of osteoarthritis when reported by a radiologist. This represents an area of possible delayed or missed diagnosis, with its potential costs in terms of complaints and/or litigation.
From the results of our study, the numbers of patients who may be suffering from such a delay could potentially be quite large, with a pool of up to 1867 patients (those who had non-WB radiographs and did not have repeat WB radiographs) being under-diagnosed with regard to the extent of their knee osteoarthritis. This may then result in delayed/inappropriate treatment or referral of such patients to specialist care.
Jayatilaka et al. (2012) in a study of 41 patients over a two-week period found none of the patients referred by GPs to orthopaedic outpatients had WB radiographs requested prior to consultation. A higher proportion of patients in our study had WB knee radiographs requested prior to being seen in our orthopaedic clinic (2.3%), however a significantly lower amount of radiographs initially performed non-WB were repeated in our study (2.9% vs. 25%). In our literature search this was the only study found looking at the requesting trends of GPs with regards to WB and non-WB knee radiographs. Given the time period and sample size of our study, we believe our findings to be a comprehensive representation of plain radiograph requests by GPs investigating knee osteoarthritis.
Our study raises the question whether a national policy to routinely perform elective knee radiographs with the patient WB should be implemented, or at the very least discussed between primary care institutions, radiology and orthopaedic departments. In the absence of such a national policy existing, our study suggests that it would be prudent for doctors in all specialities to request all AP and lateral knee radiographs as weight bearing (or “erect”) views, unless there is a history of trauma or the patient is not able to bear weight on the knee.
Limitations of the study and areas for future research
A limitation of our study is that patients who had an initial radiograph at our institution but subsequently referred by their GP to another institution for their knee pathology would not be included in our results. Likewise, patients who have had their initial radiograph elsewhere and then subsequently referred to the orthopaedic department at our institution would not have their imaging available to view on our system. However, we believe these numbers to be relatively small.
In addition, the reporting radiologist was not blinded as to whether the radiographs were WB or non-WB, thus potentially biasing reporting. However we regard joint space loss as a significantly objective measure of degeneration for bias to have a minimal influence. Further studies on WB vs. non-WB views should however involve reporting by a radiologist who is blinded to the manner in which the films were taken. The WB and non-WB images were each viewed once by a single radiologist in this study when reporting therefore intra-observer and inter-observer variation was not calculated. Further studies should involve more than one blinded radiologist to report images more than once in order for this to be determined.
Our study has investigated the direct costs of repeating radiographs in patients, but there also remain additional un-quantified indirect costs, which include, wasted clinical time - a service cost - to the clinicians and radiographers who might otherwise be able to use that time treating other patients. Other indirect costs include the potential of delayed or missed diagnosis of osteoarthritis, further unnecessary investigations ordered such as MRI, unnecessary radiation exposure to the patient and also causing, in general, a poorer patient experience, a subject of increasing relevance in these times.