C-reactive protein of ≥ 20 mg/L and ultrasound finding of an effusion ≥ 7 mm has a high specificity and sensitivity in diagnosing paediatric hip septic arthritis.

PURPOSE: Differentiating septic arthritis (SA) from transient synovitis (TS) in children remains a diagnostic challenge. Several algorithms have been developed to diagnose SA including Kocher's criteria and its subsequent modifications, but reports show variable efficacy. This study aims to examine the diagnostic utility of a novel method only using C-reactive protein (CRP) and ultrasound (US) findings of effusion in differentiating SA from TS, determine the optimal values for these predictors and validate this method against existing clinical predictors. METHODS: A 5-year retrospective study was performed including all paediatric patients with acute, non-traumatic hip pain with a suspicion of SA. All patients were evaluated using Kocher's criteria, Caird's criteria, and the novel method. Multivariate logistic regression was performed to identify independent clinical predictors of SA. The degree of agreement between the various methods were assessed using Cohen's kappa (k). Receiver operating characteristics (ROC) curves were used to examine the diagnostic accuracy of this novel method as well as to determine optimal cut-offs for US effusion and CRP in diagnosing SA. RESULTS: Hundred and one patients were recruited. CRP and effusion on US were found to be independent predictors of SA. Both Kocher's and Caird's method showed good specificity (98.9%) but extremely poor sensitivity for SA (0%). When Kocher's four clinical predictors were present, probability of SA was only 59.16%. The k for both Kocher's and Caird's methods, was -0.017 indicating poor agreement. However the k in the novel method was 0.641, indicating good agreement. CONCLUSION: Our study showed that the novel method using CRP (≥ 20 mg/L) and US finding of effusion (≥ 7 mm) has a high specificity (97%) and sensitivity (71%) in diagnosing SA.

Is routine MRI necessary to exclude pathological fractures in patients with an oncological history?

INTRODUCTION: Magnetic resonance imaging (MRI) is the radiological modality of choice for diagnosing pathological fractures in situations of diagnostic uncertainty. With the increasing availability of MRI, we have observed a disturbing trend in utilising routine MRI scans to exclude pathological fractures in all patients with a history of cancer. The study objective was to determine if routine use of MRI scans in such patients is truly necessary and if other predictive factors can be utilised in lieu of the MRI scan. MATERIALS AND METHODS: A 3-year retrospective study was conducted reviewing all extremity MRI scans performed for suspected pathological fractures and compared to X-rays. All patients presented with an extremity fracture, a known diagnosis of solid organ cancer and had an MRI to determine if the fracture was pathological. Subjects were followed up with serial X-rays up to 1 year. RESULTS: 84 subjects were recruited. Comparing X-rays alone with MRI scans revealed 92% sensitivity and 98% specificity in detecting pathological fractures. Using X-rays in combination with an absent history of trauma increases the sensitivity to 100% but reduced the specificity to 91%. None of subjects in cancer remission had pathological fractures. CONCLUSIONS: MRI is an imperative tool for operative planning in pathological fractures; however, we recommend against the routine use of MRI to diagnose pathological fractures in oncological patients. Patients with solid organ cancer remission, a positive history of significant trauma prior to sustaining the fracture, and the absence of pathological features on plain radiographs are strongly predictive against pathological fractures.