Molecular origin of a loading-induced black layer in the deep region of articular cartilage at the magic angle.


Journal Article

PURPOSE: To investigate the molecular origin of an unusual low-intensity layer in the deep region of articular cartilage as seen in magnetic resonance imaging (MRI) when the tissue is imaged under compression and oriented at the magic angle. MATERIALS AND METHODS: Microscopic MRI (μMRI) T2 and T1 ρ experiments were carried out on 18 specimens, both native and degraded (treated with trypsin). The glycosaminoglycan (GAG) concentrations in the specimens were quantified by both sodium ICP-OES and μMRI Gd(DTPA)(2-) -contrast methods. The mechanical modulus of the specimens was also measured. RESULTS: Native tissue shows no load-induced layer, while the trypsin-degraded tissue shows clearly the low-intensity line at the deep part of tissue. The GAG reductions were confirmed by the sodium ICP-OES (from 81.7 ± 5.4 mg/mL to 9.2 ± 3.4 mg/mL), MRI GAG quantification (from 72.4 ± 6.7 mg/mL to 11.2 ± 2.9 mg/mL). The modulus reduction was confirmed by biomechanics (from 4.3 ± 0.7 MPa to 0.3 ± 0.1 MPa). CONCLUSION: Both T2 and T1 ρ profiles in native and degraded cartilage show strongly strain-, depth-, and angle-dependence using high-resolution MRI. The GAG reduction is responsible for the visualization of a low-intensity layer in deep cartilage when it is loaded and oriented at 55°.

Full Text

Duke Authors

Cited Authors

  • Wang, N; Kahn, D; Badar, F; Xia, Y

Published Date

  • May 2015

Published In

Volume / Issue

  • 41 / 5

Start / End Page

  • 1281 - 1290

PubMed ID

  • 24833266

Pubmed Central ID

  • 24833266

Electronic International Standard Serial Number (EISSN)

  • 1522-2586

Digital Object Identifier (DOI)

  • 10.1002/jmri.24658


  • eng

Conference Location

  • United States