Bilaminar pattern of tibial condyle cartilage layer on the fat-suppressed 3D gradient echo images: artifact or structural and biochemical difference in composition of cartilage?

The purpose of this study was to examine if an unusual bilaminar pattern of lateral tibial condyle cartilage layer on the far-suppressed three-dimensi onal (3D) spoiled gradient echo sequence is artifactual or correlates with structural and/or biochemical composition of cartilage. The laminar appeara nce of the lateral tibial condyle cartilage layer was studied on fat-suppre ssed 3D spoiled gradient echo MR images of the knee joint in 67 patients (m ean age: 28y) performed at 1.0 Tesla. After i.v. administration of gadopent etate dimeglumine, diffusion of the contrast media into cartilage layer was qualitatively analysed over time on inversion recovery spin echo images of knee joints of five asymptomatic volunteers (mean age. 25y). In a patient with osteosarcoma and total knee replacement, MR examination of cartilage l ayer of lateral tibial plateau was compared with histologic specimens stain ed with Safranin-O. demonstrating proteoglycan distribution in cartilage. T he retrospective analysis of 67 knee joints revealed a bilaminar appearance of lateral tibial condyle cartilage layer in the gradient echo images in t he majority of cares (81%) with a statistically significant tendency to a t rilaminar pattern in patient older than 20 years. With i.v. contrast admini stration, the contrast enhancement was only observed in the superficial zon e of tibial cartilage layer. Histologic specimens in one patient demonstrat ed a good correlation between thickness of proteoglycan-free and proteoglyc an-rich laminae of lateral tibial condyle on Safranin-O staining with hyper intense and hypointense zones, respectively, on corresponding fat-suppresse d 3D spoiled gradient echo images (correlation coefficient of 0.87). Bilami nar pattern of tibial condyle cartilage layer on fat-suppressed 3D spoiled gradient echo images in younger subjects is not an artifact or an intrachon dral lesion, but it may represent a regional difference in composition of e xtracellular cartilage matrix possibly produced by a highly-oriented collag en fiber structure associated with a high concentration of proteoglycans in the middle and deep portion of the cartilage layer. (C) 2001 Elsevier Scie nce Inc. All rights reserved.