Pigmented villonodular synovitis: MR imaging in pediatric patients

Objectives: To describe the usefulness of gradient-echo imaging and contrast-enhanced MR imaging in diagnosing and assessing the extent of pigmented villonodular synovitis (PVNS) in pediatric patients. Patients and methods : Retrospective analysis of five pediatric patients (median age 14 years) with PVNS of the knee examined with a 1.5-T unit. Signal characteristics were obtained comparing T1- and proton-density (PD)-weighted imaging with gradient-echo imaging and enhanced imaging. The extent of the disease was assessed using the arthroscopic approach. Signal intensity ratios were statistically analyzed. Results: Compared to PD- and T1-weighted imaging sequences, gradient-echo imaging provides superior depiction of the extent of the disease due to signal decay (T2*-effect) of hemosiderin-laden thickened synovium and masses. Inflamed synovium with low hemosiderin deposition was identified on enhanced imaging. Beside the suprapatellar bursa and Hoffa's fat pad, the area posterior to the cruciate ligaments is commonly involved. No bony abnormalities were present. Conclusion: Gradient-echo imaging together with enhanced imaging is useful in diagnosing and assessing the extent of PVNS in pediatric patients. A low signal mass behind the cruciate ligaments may represent an important diagnostic feature. Bony abnormalities were always absent.