Influence of knee positions on T2, T*2, and dGEMRIC mapping in porcine knee cartilage.
We examined the influence of flexed knee positions on cartilage MR assessments. Sagittal T(2), T*(2), and delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) maps of the femoral cartilage were obtained in eight 6-month-old porcine femorotibial joints in the extended knee position (position A: flexion 0 degrees and femoral shaft in parallel with the amplitude of static field), flexed knee position (position B: flexion 40 degrees and femoral shaft oriented at 40 degrees to the amplitude of static field), and oblique-placed knee-extended position (position C: flexion 0 degrees and femoral shaft oriented at 40 degrees to the amplitude of static field). Comparison of the MR parameters between positions A and C showed isolated influence of the magic-angle effect, and comparison between positions A and B showed effects of knee flexion. Proteoglycan and hydroxyproline content in cartilage specimen at each region of interest had no significant correlation with T(2), T*(2), and dGEMRIC values. At the central zone, located on a weight-bearing area and parallel to the amplitude of static field, T(2)/T*(2)/dGEMRIC values increased by 6.8/11/0.8% at position C and by 24/44/31% at position B compared with position A. There was a significant increase in T(2) and T*(2) values at position B compared with those at position A. The substantial changes in T(2), T*(2), and dGEMRIC were shown in response to knee flexion, presumably due to the compounding influence of the magic-angle effect and change in the intra-articular biomechanical condition.
Shiomi
Toshiyuki
T
Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan.
Nishii
Takashi
T
Myoui
Akira
A
Yoshikawa
Hideki
H
Sugano
Nobuhiko
N
D000818:Animals; D002358:Cartilage, Articular / Q000033:anatomy & histology* / Q000502:physiology*; D007596:Joints / Q000033:anatomy & histology* / Q000502:physiology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011187:Posture / Q000502:physiology*; D016059:Range of Motion, Articular / Q000502:physiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013552:Swine