ACL-injured subjects are at an increased risk of developing osteoarthritis. There is a need to detect early osteoarthritic changes for the development of treatments that can slow or stop osteoarthritis progression. T2 and ADC are considered reflective of the structure and composition of cartilage, and may be valuable for detecting early osteoarthritis. This study used two qDESS acquisitions to obtain T2 and ADC maps in 10 ACL-reconstructed subjects and 10 controls 3-weeks, 3-months and 9-months post-surgery. Our results show that T2 cluster analysis was able to detect changes to the ACL-reconstructed knee as early as 3-months post-surgery.
Twenty subjects (30 knees) were included in this study: 10 ACL-injured subjects undergoing ACL-reconstruction surgery (5 women, 5 men, mean age: 39±12 years, BMI: 23 ± 1.5) and 10 age, BMI and sex matched controls (5 women, 5 men, mean age: 37±13 years, BMI: 23 ± 1.5). The affected and contralateral knees of the ACL-reconstructed subjects and the right knee of the control subjects were scanned in a 3T MRI scanner using 2 quantitative double-echo in steady-state (qDESS with low and high diffusion sensitivity) sequences (10-minute scan-time per knee) at 3 time-points: 3-weeks post-ACL reconstruction (baseline), 3-months post-ACL reconstruction and 9-months post-ACL-reconstruction.
T2 and ADC values were calculated from the qDESS sequences as previously described6,7. The femoral cartilage was manually segmented in the sagittal plane (Fig.1a). Femoral cartilage T2 and ADC projections were created by fitting a cylinder to the segmentations and radially projecting the data into angular bins4 (Fig.1b). T2 maps were separated into superficial and deep layers (Fig.1c) based on the midpoint of thickness. Femoral cartilage T2 projections were registered to the baseline time point for each knee (Elastix)8, and difference maps were created by subtracting the baseline projection from each of the 3-month and 9-month projections (for both superficial and deep T2 maps) (Fig.1d). Clusters in difference maps were quantified as a contiguous set of pixels with an area greater than 12.4mm2 consisting of values greater than twice the standard deviation of control subjects’ difference maps (Fig.1e)4. ADC values were averaged over the femoral cartilage at each time-point (Fig.2). Our outcomes were reported as the change in T2 percent cluster area (ΔT2%CA) and average ADC. We used a general linear model with Bonferroni’s correction to test for differences in ΔT2%CA and ADC values between ACL-reconstructed, contralateral, and control knees (α<0.05).
[1] D. Simon, R. Mascarenhas, B.M. Saltzman, M. Rollins, B. R. Bach Jr., and P.MacDonald, “The Relationship between Anterior Cruciate Ligament Injury and Osteoarthritis of the Knee,” Advances in Orthopedics, vol. 2015, Article ID 928301, 11 pages, 2015.
[2] D.E. Meuffels, M.M. Favejee, M.M. Vissers, et al, “Ten year follow-up study comparing conservative versus operative treatment of anterior cruciate ligament ruptures. A matched-pair analysis of high level athletes,” British Journal of Sports Medicine 2009;43:347-351.
[3] X. Li, D. Kuo, A. Theologis, J. Carballido-Gamio, C. Stehling, T. M. Link, B. Ma, and S. Majumdar. “Cartilage in Anterior Cruciate Ligament–Reconstructed Knees: MR Imaging T1ρ and T2—Initial Experience with 1-year Follow-up,” Radiology 2011 258:2, 505-514
[4] U.D. Monu, C.D. Jordan, B.L. Samuelson, B.A. Hargreaves, G.E. Gold, E.J. McWalter, “Cluster analysis of quantitative MRI T2 and T1ρ relaxation times of cartilage identifies differences between healthy and ACL-injured individuals at 3T”, Osteoarthritis and Cartilage, Volume 25, Issue 4, 2017, Pages 513-520, ISSN 1063-4584.
[5] J.G. Raya, G. Melkus, S. Adam-Neumair, et al. Change of Diffusion Tensor Imaging Parameters in Articular Cartilage With Progressive Proteoglycan Extraction. Investigative Radiology 2011;46:401.
[6] B. Sveinsson, A.S. Chaudhari, G.E. Gold, B.A. Hargreaves, “A simple analytic method for estimating T2 in the knee from DESS”, Magnetic Resonance Imaging, Volume 38, 2017, Pages 63-70, ISSN 0730-725X.
[7] B. Sveinsson, A.S. Chaudhari, G.E. Gold, B.A. Hargreaves, “A simple analytic method for estimating T2 in the knee from DESS”, Magnetic Resonance Imaging, Volume 38, 2017, Pages 63-70, ISSN 0730-725X.
[8] S. Klein, M. Staring, K. Murphy, M.A. Viergever and J.P.W. Pluim, "elastix: a toolbox for intensity based medical image registration," IEEE Transactions on Medical Imaging, vol. 29, no. 1, pp. 196 - 205, January 2010.