Correlation between MRI and hip arthroscopy in children with Legg-Calve-Perthes disease

Most of the information available about Legg-Calve-Perthes disease (LCPD) at present is gained through imaging modalities including plain radiographs and magnetic resonance imaging (MRI). But the accuracy of MRI in this disease and its predictive value to reveal various intra-articular pathologies is not known. We correlated the findings of MRI with those seen on hip arthroscopy in children with active stage of LCPD.

We conducted a prospective observational study in which MRI findings were correlated with corresponding findings on hip arthroscopy in a cohort of 25 patients of active LCPD below 12 years of age. The parameters noted on MRI included status of ligamentum teres, status of the labrum, synovial effusion if any, condition of the femoral and acetabular articular cartilage including chondral flaps, chondral indentation and intra-articular loose bodies. The indication of performing hip arthroscopy was persistent severe hip pain (Wong-Baker FACES pain scale ≥ 3) after 6 months of conservative management. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated for MRI considering arthroscopy as a gold standard.

Synovial effusion was seen in a large number of patients on both MRI (17) and hip arthroscopy (24). The sensitivity (95% confidence interval) of MRI was found to be low, especially with respect to labral tears [25% (0.63-80.6)] and intra-articular loose bodies [20% (0.51-71.6)]. NPV for synovial effusion was also found to be low [12.5% (0.32-52.7)], although specificity and PPV of MRI were found to be good for all the parameters.

MRI cannot be completely relied upon for identifying all the intra-articular pathologies in children with LCPD, although it has a good complimentary role. In patients with severe persistent pain with suspicion for joint changes, hip arthroscopy can provide a safe and efficient procedure (better than MRI) for eliciting the associated joint pathology.