No established, non-invasive diagnostic procedure for quantifying focal cartilage defects is currently available.
To test the accuracy of quantitative magnetic resonance imaging (qMRI) for reliable determination of cartilage defect size in various compartments of the human knee.
24 tibial and patellar cartilage plates were harvested during knee arthroplasty. 74 cylindrical defects with diameters of 3, 5, and 8 mm were created with a punch. In 15 specimens (51 defects), the cartilage cylinders (inside the punch) were removed (approach 1), while in 9 specimens (23 defects) the surrounding tissue was removed mechanically and the cartilage cylinder was left in place (approach 2). All plates were imaged with a T(1) weighted water excitation gradient echo sequence at a resolution of 1.5 mm x 0.31 mm x 0.31 mm. The defect size was computed from the image data after interactive segmentation and compared with the known dimensions of the cylinders.
Although there was a significant overestimation of the defect size by qMRI in 3 mm defects (mean (SD) +1.3 (0.58) mm = +/-42%; p<0.001), the overestimation was only +1.0 (0.57) mm (+/-21%; p<0.05) in 5 mm defects and +0.1 (0.39) mm (+/-4%; p = 0.31) in 8 mm defects (approach 1). Values were similar for approaches 1 and 2 and for patellar and tibial cartilage plates.
These findings show that qMRI allows accurate quantification of focal cartilage defects. It may therefore represent a valuable tool in the diagnosis of traumatic cartilage lesions, osteochondrosis dissecans, and osteochondral fractures, and in monitoring their responsiveness to surgical or other treatments.