J Desrochers1, A Yung2, D Stockton3, D Wilson4. 1. Center for Hip Health and Mobility & Department of Orthopaedics, University of British Columbia, 2635 Laurel Street, Vancouver, BC, V5Z 1M9, Canada. Electronic address: jane.desrochers@hiphealth.ca. 2. MRI Research Center, University of British Columbia, Vancouver, BC, Canada. Electronic address: ayung@mail.ubc.ca. 3. Department of Orthopaedics, Clinical Investigator Program and Center for Hip Health and Mobility University of British Columbia, Vancouver, BC, Canada. Electronic address: djstockton@telus.net. 4. Department of Orthopaedics & Centre for Hip Health and Mobility University of British Columbia and Vancouver Coastal Health Research Institute. Electronic address: david.wilson@ubc.ca.
Abstract
OBJECTIVE: To assess the potential of using ΔT2 as an indirect index of cartilage strain by quantifying the relationship between local in situ compressive strain and ΔT2 through the full depth of human tibial and femoral articular cartilage. DESIGN: Osteochondral samples (n = 4) of human tibial and femoral cartilage were harvested from cadavers and imaged in a Bruker 7T research MRI scanner under increasing displacement-controlled compressive strains. T2 was calculated for 3D double echo steady state (DESS) image volumes at each strain level. A decaying exponential model estimated local, depth-dependent strains. Strained image volumes were non-linearly warped back to their unloaded configurations and ΔT2 was calculated by image subtraction. Linear modeling assessed local relationships between strain and ΔT2. RESULTS: Bulk average tibial T2 was 13.2 ms for unstrained cartilage and ranged from 13.0 to 13.1 ms under strain; femoral T2 was 14.0 ms for unstrained cartilage and ranged from 13.5 to 14.8 ms under strain. Local ΔT2 in strained cartilage varied with depth. Linear modeling revealed significant correlations between in situ strain and ΔT2 for both tibial and femoral cartilage; correlation coefficients were higher for tibial cartilage. CONCLUSIONS: Changes in bulk average T2 are unsuitable as a quantitative surrogate measure of cartilage strain because bulk averaging masks important local variations. High-resolution measures of local ΔT2 have potential value as a surrogate for strain; however, their value is limited until we fully understand the influence of factors like age, joint surface and degeneration on the strain vs T2 relationship.
OBJECTIVE: To assess the potential of using ΔT2 as an indirect index of cartilage strain by quantifying the relationship between local in situ compressive strain and ΔT2 through the full depth of human tibial and femoral articular cartilage. DESIGN: Osteochondral samples (n = 4) of human tibial and femoral cartilage were harvested from cadavers and imaged in a Bruker 7T research MRI scanner under increasing displacement-controlled compressive strains. T2 was calculated for 3D double echo steady state (DESS) image volumes at each strain level. A decaying exponential model estimated local, depth-dependent strains. Strained image volumes were non-linearly warped back to their unloaded configurations and ΔT2 was calculated by image subtraction. Linear modeling assessed local relationships between strain and ΔT2. RESULTS: Bulk average tibial T2 was 13.2 ms for unstrained cartilage and ranged from 13.0 to 13.1 ms under strain; femoral T2 was 14.0 ms for unstrained cartilage and ranged from 13.5 to 14.8 ms under strain. Local ΔT2 in strained cartilage varied with depth. Linear modeling revealed significant correlations between in situ strain and ΔT2 for both tibial and femoral cartilage; correlation coefficients were higher for tibial cartilage. CONCLUSIONS: Changes in bulk average T2 are unsuitable as a quantitative surrogate measure of cartilage strain because bulk averaging masks important local variations. High-resolution measures of local ΔT2 have potential value as a surrogate for strain; however, their value is limited until we fully understand the influence of factors like age, joint surface and degeneration on the strain vs T2 relationship.
Authors: Hollis A Crowder; Valentina Mazzoli; Marianne S Black; Lauren E Watkins; Feliks Kogan; Brian A Hargreaves; Marc E Levenston; Garry E Gold Journal: J Orthop Res Date: 2021-02-03 Impact factor: 3.494
Authors: Andrew M Schmidt; David J Stockton; Michael A Hunt; Andrew Yung; Bassam A Masri; David R Wilson Journal: BMC Musculoskelet Disord Date: 2020-11-30 Impact factor: 2.362