Disc degeneration assessed by quantitative T2* (T2 star) correlated with functional lumbar mechanics.
METHODS
Experimental correlation study design to quantify features of disc health, including signal intensity and distinction between the annulus fibrosus and nucleus pulposus, with T2* magnetic resonance imaging (MRI) and correlate with the functional mechanics in corresponding motion segments.


OBJECTIVE
Establish the relationship between disc health assessed by quantitative T2* MRI and functional lumbar mechanics.


BACKGROUND
Degeneration leads to altered biochemistry in the disc, affecting the mechanical competence. Clinical routine MRI sequences are not adequate in detecting early changes in degeneration and fails to correlate with pain or improve patient stratification. Quantitative T2* relaxation time mapping probes biochemical features and may offer more sensitivity in assessing disc degeneration.


METHODS
Cadaveric lumbar spines were imaged using quantitative T2* mapping, as well as conventional T2-weighted MRI sequences. Discs were graded by the Pfirrmann scale, and features of disc health, including signal intensity (T2* intensity area) and distinction between the annulus fibrosus and nucleus pulposus (transition zone slope), were quantified by T2*. Each motion segment was subjected to pure moment bending to determine range of motion (ROM), neutral zone (NZ), and bending stiffness.


RESULTS
T2* intensity area and transition zone slope were significantly correlated with flexion ROM (P = 0.015; P = 0.002), ratio of NZ/ROM (P = 0.010; P = 0.028), and stiffness (P = 0.044; P = 0.026), as well as lateral bending NZ/ROM (P = 0.005; P = 0.010) and stiffness (P = 0.022; P = 0.029). T2* intensity area was also correlated with lateral bending ROM (P = 0.023). Pfirrmann grade was only correlated with lateral bending NZ/ROM (P = 0.001) and stiffness (P = 0.007).


CONCLUSIONS
T2* mapping is a sensitive quantitative method capable of detecting changes associated with disc degeneration. Features of disc health quantified with T2* predicted altered functional mechanics of the lumbar spine better than traditional Pfirrmann grading. This new methodology and analysis technique may enhance the assessment of degeneration and enable greater patient stratification for therapeutic strategies.


METHODS
N/A.
*Department of Biomedical Engineering †Department of Orthopaedic Surgery ‡Department of Radiology, Center for Magnetic Resonance Research §Department of Physical Medicine and Rehabilitation, Musculoskeletal Biomechanics Research Laboratory, University of Minnesota, Minneapolis, MN.
Arin M
AM
Ellingson
Hitesh
H
Mehta
David W
DW
Polly
Jutta
J
Ellermann
David J
DJ
Nuckley
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging / Q000503:physiopathology*; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D055815:Young Adult