EXTENDED REPORT

Accuracy of quantitative magnetic resonance imaging in the detection of ex vivo focal cartilage defects

H Graichen¹, D Al-Shamari¹, S Hinterwimmer¹, R von Eisenhart-Rothe¹, T Vogl², F Eckstein³

¹ Research Group for Kinematics and Biomechanics, Orthopaedic Department, University of Frankfurt, Frankfurt, Germany
² Institute for Clinical and Interventional Radiology, University of Frankfurt, Frankfurt, Germany
³ Institute of Anatomy, Paracelsus Private Medical University, Salzburg, Austria

Correspondence to:
Dr H Graichen
Research Group for Kinematics and Biomechanics, Orthopedic Department, University of Frankfurt, Marienburgstr, 2, 60528 Frankfurt, Germany; h.graichen{at}em.uni-frankfurt.de

Background: No established, non-invasive diagnostic procedure for quantifying focal cartilage defects is currently available.

Objective: To test the accuracy of quantitative magnetic resonance imaging (qMRI) for reliable determination of cartilage defect size in various compartments of the human knee.

Methods: 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 T₁ weighted water excitation gradient echo sequence at a resolution of 1.5 mmx0.31 mmx0.31 mm. The defect size was computed from the image data after interactive segmentation and compared with the known dimensions of the cylinders.

Results: 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.

Conclusions: 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.

Abbreviations: OA, osteoarthritis; qMRI, quantitative magnetic resonance imaging

Keywords: focal cartilage defects; osteochondrosis dissecans; magnetic resonance imaging; validation; knee joints

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