2015 ISAKOS Biennial Congress ePoster #1207

Quantitative MRI-T2 Mapping of Articular Cartilage Following Anatomic Anterior Cruciate Ligament Reconstruction: Relationship to Patient Reported Measures of Symptoms, Activity, and Participation

Rajan Manmohan, BS, Pittsburgh, PA UNITED STATES
Nikhil Kurapati, BS, Pittsburgh, PA UNITED STATES
Eric Thorhauer, BS, Seattle, WA UNITED STATES
Freddie H. Fu, MD, Pittsburgh, PA UNITED STATES
Scott Tashman, PhD, Pittsburgh, PA UNITED STATES
James J. Irrgang, PT, PhD, FAPTA, Pittsburgh, PA UNITED STATES

University of Pittsburgh, Department of Orthopaedic Surgery, Pittsburgh, PA, USA

FDA Status Not Applicable

Summary: Six months following ACL reconstruction (ACLR) there is a loss of normal collagen structure in the femoral cartilage as indicated by elevated T2 relaxation times (T2RTs) in ACLR versus contralateral knee; elevated T2RTs in the femoral cartilage of the ACLR knee in comparison to the contralateral knee was associated with increased pain and decreased levels of activity and participation.

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Abstract:

Introduction

Loss of normal cartilage structure and function is likely related to the development of knee osteoarthritis that commonly occurs after anterior cruciate ligament reconstruction (ACLR). T2 MRI mapping can be used to assess cartilage structure and composition. Elevated T2 relaxation times (T2RTs) correspond to altered water content and collagen structure of the cartilage matrix. The aim of this study was to determine if there are differences in T2RTs between ACLR and contralateral knees and to determine if those differences are related to patient-reported measures of symptoms, activity and participation.

Methods

Thirty-six subjects with complete ACL tears participated in a prospective randomized clinical trial to assess anatomic ACL reconstruction. Subjects underwent MRI T2 mapping and completed the International Knee Documentation Committee Subjective Knee Form (IKDC-SKF) and Knee Injury and Osteoarthritis Outcome Score including the Pain (KOOS-Pain) and Activities of Daily Living (KOOS-ADL) subscales six months after ACLR. T2 images of the non-meniscal weight-bearing zone of the medial femoral condyle and tibial plateau in the ACLR and contralateral knees were selected based on meniscus landmarks and clear delineation between femoral and tibial cartilage. MATLAB MRImapper software was used to analyze T2 spin echo times of 21.2, 31.8, 42.4, 53.0, 63.6 and 74.2 ms in matrices of 289x289 or 337x337. Full thickness, deep, and superficial regions of interest (ROI) in femoral and tibial cartilage were selected manually and T2RT maps were generated. Intra-tester reliability was analyzed for three separately generated T2RT maps per ROI. The differences in T2RT maps between each ROI in the ACLR and contralateral knee were tested using a two-tailed paired t-test (p=0.05). Pearson correlation coefficients were estimated to determine the relationships between the differences in T2RTs between the ACLR and contralateral knees (delta-T2RTs) and patient-reported measures of symptoms, activity and participation.

Results

Intra-class correlations ranged from 0.86-0.99 with a mean of .93 across all ROIs, demonstrating strong intra-tester reliability. T2RTs in all regions were elevated in the ACLR knee versus the contralateral knee but differences were only significant for the full-thickness and superficial femoral ROIs. For the full thickness and superficial femoral ROIs, there were significant moderate negative correlations between delta-T2RTs and patient-reported outcomes, indicating that increases in T2RTs following ACLR are associated with increased pain and decreased activity and participation [full thickness femoral delta-T2RTs with KOOS-ADL (R=-0.37 p=0.03), and KOOS-Pain (R=-0.34 p=0.04); superficial femoral delta-T2RTs with KOOS-ADL (R=-0.36 p=0.03), KOOS-Pain (R=-0.35 p=0.03), and IKDC-SKF (R=-0.36 p=0.03)].

Discussion

Six months following ACLR there is a loss of normal collagen structure in the femoral cartilage as indicated by elevated T2RTs in ACLR versus contralateral knees. Elevated T2RTs in the femoral cartilage of the ACLR knee relative to the contralateral knee are associated with increased pain and decreased levels of activity and participation. Further study needs to include longitudinal research to determine if these early alterations in cartilage structure, as evidenced by elevated T2RTs, are the precursor to future symptomatic and/or radiographic knee osteoarthritis.

Acknowledgements: National Institution of Arthritis and Musculoskeletal and Skin Diseases, Grant no. 1R01AR056630-01A2