BACKGROUND: The direction of loading to disc tissue in response to postural changes has been investigated. However, the reported original method may not adequately represent the disc hydration profile.
OBJECTIVE: To investigate the reliability of a modified method to measure the direction of shift of disc hydration in response to side-bending.
METHODS: Each lumbar disc of 10 healthy subjects was scanned with T2-weighted magnetic resonance imaging in supine (neutral) position and left side-bending position in lying. A mid-point over the pixel intensity profile line was obtained. The differences in mid-point values between the neutral and side-bending positions were plotted in each direction on a X–Y coordinates plane and the angle (θ) of each plotted point from the X-axis was calculated.
RESULTS: The Intraclass Correlation Coefficients (ICC) of the mid-point values during left side-bending along the sagittal and coronal directions of the disc ranged between 0.72–0.98 and 0.80–0.96, respectively. It was estimated that calculating θ values twice yielded an ICC of 0.8 at each disc level.
CONCLUSIONS: The modified method was reliable in capturing gross disc hydration profiles. The direction of shift in disc hydration in response to side-bending can be identified using averaged values of θ that was calculated twice.
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