Study Design. 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.
Summary of Background Data. 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).
Conclusion. 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.
Level of Evidence: N/A
Features of disc health, including signal intensity and distinction between the annulus fibrosus and nucleus pulposus, were assessed using quantitative T2* magnetic resonance imaging. These imaging parameters were significantly correlated with functional mechanics of lumbar motion segments. This new methodology and analysis technique is a potential diagnostic tool for assessment of degeneration.
*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.
Address correspondence and reprint requests to Arin M. Ellingson, BS, University of Minnesota, Department of Biomedical Engineering, Nils Hasselmo Hall, Room 7-105, 312 Church St S.E., Minneapolis, MN 55455; E-mail: firstname.lastname@example.org
Acknowledgment date: December 21, 2012. First revision date: May 31, 2013. Second revision date: July 1, 2013. Acceptance date: July 16, 2013.
The manuscript submitted does not contain information about medical device(s)/drug(s).
NIH/NIAMS T32 AR050938 Musculoskeletal Training grant funds were received in support of this work.
Relevant financial activities outside the submitted work: patents.