Effectively Measuring Exercise‐Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage

Abstract

Background: Determining the compositional response of articular cartilage to dynamic joint-loading using MRI may be a more sensitive assessment of cartilage status than conventional static imaging. However, distinguishing the effects of jointloading vs. inherent measurement variability remains difficult, as the repeatability of these quantitative methods is often not assessed or reported. Purpose: To assess exercise-induced changes in femoral, tibial, and patellar articular cartilage composition and compare these against measurement repeatability. Study Type: Prospective observational study. Population: Phantom and 19 healthy participants. Field Strength/Sequence: 3T; 3D fat-saturated spoiled gradient recalled-echo; T 1ρ-and T 2-prepared pseudosteady-state 3D fast spin echo. Assessment: The intrasessional repeatability of T 1ρ and T 2 relaxation mapping, with and without knee repositioning between two successive measurements, was determined in 10 knees. T 1ρ and T 2 relaxation mapping of nine knees was performed before and at multiple timepoints after a 5-minute repeated, joint-loading stepping activity. 3D surface models were created from patellar, femoral, and tibial articular cartilage. Statistical Tests: Repeatability was assessed using root-mean-squared-CV (RMS-CV). Using Bland-Altman analysis, thresholds defined as the smallest detectable difference (SDD) were determined from the repeatability data with knee repositioning. Results: Without knee repositioning, both surface-averaged T 1ρ and T 2 were very repeatable on all cartilage surfaces, with RMS-CV <1.1%. Repositioning of the knee had the greatest effect on T 1ρ of patellar cartilage with the surface-averaged RMS-CV = 4.8%. While T 1ρ showed the greatest response to exercise at the patellofemoral cartilage region, the largest changes in T 2 were determined in the lateral femorotibial region. Following thresholding, significant (>SDD) average exercise-induced in T 1ρ and T 2 of femoral (-8.0% and-5.3%), lateral tibial (-6.9% and-5.9%), medial tibial (+5.8% and +2.9%), and patellar (-7.9% and +2.8%) cartilage were observed. Data Conclusion: Joint-loading with a stepping activity resulted in T 1ρ and T 2 changes above background measurement error. Evidence Level: 2 Technical Efficacy Stage: 1

A pilot randomised prospective comparison of two approaches for tibial nailing using clinical and novel imaging outcome measures – study protocol

“…All joint regions are analysed including the patellofemoral joint. While the original validation paper did not include retropatellar cartilage due to the characteristics of the included clinical cohort, the technique has been successfully applied to the retropatellar cartilage 13 . Moreover, validation data for cartilage surface extraction are comparable to the femoral and tibial cartilage with mean distance error [95% limits of agreement] of 0.13 [-0.24, 0.50] mm (patella), 0.05 [-0.40, 0.50] mm (femur), 0.15 [-0.21, 0.52] mm (medial tibia) and 0.11 [-0.64, 0.85] mm (lateral tibia).…”

“…The novel nature of this study means that no previous data is available to enable us to perform a precise power calculation. However, we have used the data in a previous study 13 to provide a reasonable estimation of the sample size required. This study looked at the effect of exercise on knee cartilage, including the patella.…”

Comparing the Effect of Mechanical Loading on Deep and Superficial Cartilage Using Quantitative UTE MRI

“…The first MRI scan session of the left knee was performed after 15 minutes of rest to reduce the effect of any previous physical activity on the cartilage. 20 The participants were then instructed to perform loading exercises (50 weight-bearing deep knee bends) within about 2 minutes, which have been shown to sufficiently induce knee cartilage deformation according to previous study. 21 The second MRI scan session of the left knee was performed immediately after the completion of the knee bends.…”

Editorial for “Effectively Measuring Exercise‐Related Variations in T1ρ and T2 Relaxation Times of Healthy Articular Cartilage”

“…In this issue of JMRI, Kessler et al 10 measured compositional response of the femoral, tibial, and patellar articular cartilage to exercise‐induced loading and compared these compositional changes to intrasession‐based repeatability of T 1 ρ and T 2 mapping. This study utilized 10 healthy knee joints to measure the repeatability of T 1 ρ and T 2 relaxation times, with and without knee repositioning, between two successive MRI scans.…”

“…More specifically, implementation of QMRI to quantify the effects of these exercise‐based interventions on cartilage composition would be beneficial in understanding the long‐term clinical outcomes of these interventions on cartilage health in the OA population. This study by Kessler et al 10 provides an initial step towards the implementation and clinical interpretation of changes that occur in cartilage composition as an effect of exercise.…”