MRI findings of juvenile acute pure cartilage fracture of the knee joint

Objective: To study the MRI manifestation of juvenile acute pule cartilage fracture of the knee joint. Methods: The MRI changes of cartilage, subcartilage low signal line and subcartilage bone were analysed retrospectively in 26 juvenile patients with acute pure cartilage fracture confirmed by arthroscopy. Sagittal and coronal MRI scanning were performed in 26 patients. Using fast low angle shot fat saturation T1-weighted image (FLASH-FS-T1WI) sequences, spin echo T1-weighted image (SE-TWI) and fast imaging with steady-state precession three dimensional fat saturation T2-weighted image(FISP-3D -FS- T2WI) sequences in sagittal plane, SE-T1WI and multi echo data image combination T2-weighted imaging (MEDIC or ME-T2WI) in coronal plane. Using ME-T2WI sequence, axial plane MRI scanning in 5 patients. Results: Twenty-seven sites of 26 patients include 8 patella, 7 femoral medial condyle, 11 femoral lateral condyle and l tibial plateau. Three types pure cartilage fracture were observed, totally defect of the cartilage in 7 sites (include 3 patella, 2 femoral medial condyle, 1 femoral lateral condyle and 1 tibial plateau), fissuring fracture in 3 sites (include 2 femoral medial and 1 femoral lateral condyles), superficial defect of the cartilage in 17 sites (include 5 patella, 3 femoral medial and 9 femoral lateral condyle). Corpus liberum was found in 21 patients' knee joints by arthroscopy, but only 3 cases by MRI. Bone bruise was detected, and subcartilage low signal lines were normal. Conclusion: Using FLASH-FS- T1WI, SE-T1WI, FISP-3D-FS-T2WI and ME-T2WI sequences, sagittal and coronal MRI scanning in femoral and tibial plateau pure cartilage fractures, and using ME-T2WI sequence axial scanning in patellar cartilage fractures may show the position, extension and types of the acute pure cartilage fracture of the knee joint. MRI is the best non-invasive method for studying cartilage fracture. (authors)