Post-traumatic knee MRI findings and associations with patient, trauma, and clinical characteristics: a subgroup analysis in primary care in the Netherlands.

Abstract

BACKGROUND: The added value of magnetic resonance imaging (MRI) in primary care is still being debated. A high diagnostic yield can be expected in young and active patients with post-traumatic knee complaints. AIM: To determine the frequency of MRI abnormalities in young and active patients (aged 18-45 years) and the associations with patient, trauma, and clinical characteristics. DESIGN AND SETTING: A subgroup analysis of 174 patients, aged 18-45 years with knee trauma of <6 months, allocated to MRI in a randomised controlled trial on the yield of MRI in primary care. Patients were recruited by 150 GPs in the Netherlands from October 2012 to November 2015. METHOD: Associations were expressed using mean differences, odds ratio (OR) and predictive values. RESULTS: Sixty-seven out of 174 patients (39%) had a positive MRI finding, predominantly anterior cruciate ligament (ACL) ruptures (22%) and/or traumatic meniscal tears (15%). Patients with a pre-existing musculoskeletal comorbidity had a two-fold lower prevalence of positive MRI findings (21%), OR 3.0 (95% confidence interval [CI] = 1.3 to 7.0). A 'sports related trauma' showed the highest OR of 4.6 (95% CI = 2.2 to 9.3) for a positive MRI finding. Clinical scores were statistically, significantly worse in patients with positive MRI findings, with mean differences ranging from 10 to 20%. Furthermore, increasing duration of complaints was correlated with decreasing prevalence rates of positive MRI findings. Overall, a popping sound and direct swelling showed the highest positive predictive value of 65% for the presence of positive MRI findings. CONCLUSION: The results from this study enable a preselection of patients to increase the diagnostic yield of MRI in primary care.