Vastus lateralis/vastus medialis cross-sectional area ratio impacts presence and degree of knee joint abnormalities and cartilage T2 determined with 3T MRI - an analysis from the incidence cohort of the Osteoarthritis Initiative.
OBJECTIVE
To study the role of vastus lateralis/vastus medialis cross-sectional area CSA ratio (VL/VM CSA ratio) in preclinical knee osteoarthritis (OA) using magnetic resonance imaging (MRI)-based cartilage T2 mapping technique and morphological analysis at 3.0T in non-symptomatic, middle-aged subjects.


METHODS
174 non-symptomatic individuals aged 45-55 years with OA risk factors were selected from the Osteoarthritis Initiative (OAI) incidence cohort. OA-related knee abnormalities were analyzed using the whole-organ magnetic resonance imaging score (WORMS). Knee cartilage T2 maps were generated using sagittal 2D multi-echo spin-echo images of the right knee. CSA of thigh muscles was measured using axial T1W images of the right mid thigh. Spline-based segmentation of cartilage and muscles was performed on a SUN/SPARC workstation. Muscle measurements were normalized to body size using body surface area (BSA). Statistical significance was determined using Student's t-test, Pearson correlation test, and multiple regression models. To correct for multiple testing, Bonferroni adjustments were applied across all tests within each of the primary results tables (Tables III-VII).


RESULTS
Higher T2 values were associated with increased prevalence and severity of cartilage degeneration. In our study, male and female subjects with higher VL/VM CSA ratio demonstrated significantly lower mean cartilage T2 values (all compartments combined) (mean 44.10 vs 45.17, P=0.0017), and significantly lower WORMS scores (mean 14.12 vs 18.68, P=0.0316). Regression analyses of combined mean cartilage T2 using VL/VM CSA ratio as a continuous predictor showed a significant curvilinear relationship between these two variables (P=0.0082).


CONCLUSIONS
Our results suggested that higher VL/VM CSA ratio is associated with lower T2 values and decreased presence and severity of OA-related morphological changes. Additional studies will be needed to determine causality.
Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA 94143, USA. judong.pan@radiology.ucsf.edu
J
J
Pan
C
C
Stehling
C
C
Muller-Hocker
B J
BJ
Schwaiger
J
J
Lynch
C E
CE
McCulloch
M C
MC
Nevitt
T M
TM
Link
D002358:Cartilage, Articular / Q000473:pathology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007719:Knee Joint / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000453:epidemiology / Q000503:physiopathology*; D015995:Prevalence; D052097:Quadriceps Muscle / Q000033:anatomy & histology*; D015203:Reproducibility of Results; D012737:Sex Factors