Racial differences in biochemical knee cartilage composition between African-American and Caucasian-American women with 3 T MR-based T2 relaxation time measurements--data from the Osteoarthritis Initiative.
OBJECTIVE
To determine whether knee cartilage composition differs between African-American and Caucasian-American women at risk for Osteoarthritis (OA) using in vivo 3 T MRI T2 relaxation time measurements.


METHODS
Right knee MRI studies of 200 subjects (100 African-American women, and 100 closely matched Caucasian-American women) were selected from the Osteoarthritis Initiative (OAI). Knee cartilage was segmented in the patellar (PAT), medial and lateral femoral (MF/LF), and medial and lateral tibial compartments (MT/LT)). Mean T2 relaxation time values per compartment and per whole joint cartilage were generated and analyzed spatially via laminar and grey-level co-occurrence matrix (GLCM) texture methods. Presence and severity of cartilage lesions per compartment were graded using a modified WORMS grading. Statistical analysis employed paired t- and McNemar testing.


RESULTS
While African-American women and Caucasian-Americans had similar WORMS cartilage lesion scores (P = 0.970), African-Americans showed significantly lower mean T2 values (∼1 ms difference; ∼0.5SD) than Caucasian-Americans in the whole knee cartilage (P < 0.001), and in the subcompartments (LF: P = 0.001, MF: P < 0.001, LT: P = 0.019, MT: P = 0.001) and particularly in the superficial cartilage layer (whole cartilage: P < 0.001, LF: P < 0.001, MF: P < 0.001, LT: P = 0.003, MT: P < 0.001). T2 texture parameters were also significantly lower in the whole joint cartilage of African-Americans than in Caucasian-Americans (variance: P = 0.001; contrast: P = 0.018). In analyses limited to matched pairs with no cartilage lesions in a given compartment, T2 values remained significantly lower in African-Americans.


CONCLUSIONS
Using T2 relaxation time as a biomarker for the cartilage collagen network, our findings suggest racial differences in the biochemical knee cartilage composition between African-American and Caucasian-American women.
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; Department of Radiology, Beijing Jishuitan Hospital, 4th Medical College of Peking University, Beijing, China. Electronic address: Aihong.Yu@ucsf.edu.
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Yu
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA. Electronic address: Ursula.Heilmeier@ucsf.edu.
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Heilmeier
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA. Electronic address: Martin.Kretzschmar@ucsf.edu.
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Kretzschmar
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA. Electronic address: gabby.joseph@ucsf.edu.
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Joseph
Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA. Electronic address: fliu@psg.ucsf.edu.
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Liu
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA; Institut für diagnostische und interventionelle Radiologie, Technische Universitaet Muenchen, Munich, Germany. Electronic address: Hans.Liebl@ucsf.edu.
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Liebl
Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA. Electronic address: cmcculloch@epi.ucsf.edu.
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McCulloch
Department of Epidemiology and Biostatistics, University of California San Francisco, San Francisco, CA, USA. Electronic address: mnevitt@psg.ucsf.edu.
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Nevitt
Center for Healthy Aging, University of California Davis, Davis, CA, USA. Electronic address: nancy.lane@ucdmc.ucdavis.edu.
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Lane
Musculoskeletal and Quantitative Imaging Research Group, Department of Radiology & Biomedical Imaging, University of California San Francisco, San Francisco, CA, USA. Electronic address: thomas.link@ucsf.edu.
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Link
D001741:Black or African American; D000368:Aged; D002358:Cartilage, Articular / Q000737:chemistry* / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging / Q000379:methods; D008875:Middle Aged; D011859:Radiography; D014481:United States; D044465:White People
Cartilage; Knee; MRI; Race; T2 relaxation time