The use of magnetic resonance imaging (MRI) of the knee in current clinical practice: A retrospective evaluation of the MRI reports within a large NHS trust

Abstract

Background: Magnetic resonance imaging (MRI) is one of the most widely used investigations for knee pain as it provides detailed assessment of the bone and soft tissues. The aim of this study is to report the frequency of each diagnosis identified on MRI scans of the knee and explore the relationship between MRI results and onward treatment. Methods: Consecutive MRI reports from a large NHS trust performed in 2017 were included in this study. The hospital electronic system was consulted to identify whether a patient underwent x-ray prior to the MRI, attended an outpatient appointment or underwent surgery. Results: 4466 MRI knees were performed in 2017 with 71.2% requested in primary care and 28.1% requested in secondary care. The most common diagnosis was signs of arthritis (55.2%), followed by meniscal tears (42.8%) and ACL tears (8.3%). 49.4% of patients who had an MRI attended outpatients and 15.6% underwent surgery.The rate of knee surgery was significantly higher for patients who had their scans requested in secondary care (32.9% vs 8.9%, p < 0.001). Conclusion:The rate of surgical intervention following MRI is low and given these results it seems unlikely that the scan changes practice in most cases. The rate of surgery and outpatient follow up was significantly higher in scans requested by secondary care. We urge clinicians avoid wasteful use of MRI and recommend the use of plain radiography prior to MRI where arthritis may be present.

An automated, web-based triage tool may optimise referral pathways in elective orthopaedic surgery: A proof-of-concept study

“…They suggest that our findings might under-represent this, with a recent, large retrospective review finding that only 33% of patients with a PCP requested MRI went on to see an orthopaedic specialist. 8 , 10 , 22 This is supported by data demonstrating that MRIs requested by PCPs have been shown to have a significantly higher rate of ‘normal’ outcomes when compared to those requested by secondary care specialists, with one study concluding that ‘inappropriate investigations’ are three times more likely to have a ‘normal’ result. 8 , 10 , 22 …”

“… 8 , 10 , 22 This is supported by data demonstrating that MRIs requested by PCPs have been shown to have a significantly higher rate of ‘normal’ outcomes when compared to those requested by secondary care specialists, with one study concluding that ‘inappropriate investigations’ are three times more likely to have a ‘normal’ result. 8 , 10 , 22 …”

“…As the aim of our developed triage tool is to recommend appropriate investigations, this slightly mitigates the error, as both conditions require the same diagnostic imaging (MRI), so the clinical suggestion recommended by the e-triage tool's algorithm would not be affected. 8 Additionally, it would not be unsurprising if these patients were subsequently found to also have a MT, as is the case in up to 63% of ACL injuries. 33 Lastly, this pilot study only captured three patients with ACL tears, therefore additional data is required to make more accurate assumptions.…”

“… 7 Whilst MRI provides a detailed assessment of the soft tissue structures of the knee, it is an expensive and overburdened resource and there is little evidence to support the large volumes of PCP-requested MRIs each year. 8 , 9 Indeed, the use of MRI as a primary screening tool is deemed inappropriate and for KOA it has poor sensitivity, with plain radiographs preferred instead. 8 – 15 It is widely accepted that, for KOA, radiographs should be utilised before other imaging modalities, given their easy accessibility, relatively low cost and ability to detect bony pathology.…”

“… 8 , 9 Indeed, the use of MRI as a primary screening tool is deemed inappropriate and for KOA it has poor sensitivity, with plain radiographs preferred instead. 8 – 15 It is widely accepted that, for KOA, radiographs should be utilised before other imaging modalities, given their easy accessibility, relatively low cost and ability to detect bony pathology. 16 …”