Axial-Loaded MRI Using a SpineMAC Device to Show
Narrowing of Dural Sac and Disc Height in Lumbar Spinal
Stenosis
Witaya Sungkarat, MD, PhD¹ , ⁴, Jiraporn Laothamatas, MD², Ladawan Worapruekjaru, MSc³, Boonthida Hooncharoen, MD⁴,
Jarruwat Charoensuk, PhD⁵, Khaisang Chousangsuntorn, DEng⁶
Affiliation : ¹ Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand ² Faculty of Health Sciences Technology, HRH Princess Chulabhorn College of Medical Science, Chulabhorn Royal Academy, Bangkok, Thailand ³ Division of Radiation Oncology, Department of Diagnostic and Therapeutic Radiology, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand ⁴ Advanced Diagnostic Imaging Center (AIMC), Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand ⁵ Department of Mechanical Engineering, Faculty of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand ⁶ Department of Radiological Technology, Faculty of Medical Technology, Mahidol University, Phutthamonthon, Nakhon Pathom, Thailand
Background: A lumbosacral spinal compression device has been developed by the authors (SpineMAC) to simulate normal weight-bearing by
axial-loading of the lumbar spine while the patient is in the supine position.
Objective: To investigate the effect of axial loading using a SpineMAC device, on lumbar spine, spinal canal, and spine curvature, in subjects with suspected spinal stenosis.
Materials and Methods: The present study was prospective cross-sectional study. Forty-five (21 males and 24 females) consecutive Thai adults underwent unloaded and axial-loaded supine magnetic resonance imaging (MRI) examinations of the lumbosacral spine. Radiographic parameters included cross-sectional area of disc (DA), cross-sectional area of dural sac (DCSA), disc height (DH), anterior to posterior distance of disc (DAP), L1-L3-L5 angle (LA), and lumbar lordosis (LL).
Results: During the axial-loaded MRIs, the pathologic features of the lumbar spinal stenosis such as the disc bulging, nerve root compression, narrowing of the spinal canal, and the spinal neural foramina, were frequently observed in L4-L5 and L5-S1. Radiographic parameters differences of more than 5% between unloaded and axial-loaded supine MRIs were observed in DCSA and DH. Narrowing of the dural sac due to axial compression was observed at the L4-L5 level (8.1%), while loss of DH was found at both the L5-S1 (-7.9%) and the L4-L5 (-6.8%) levels. Axial compression only slightly affected the DA and DAP of the intervertebral discs with a difference of 5% or less. Furthermore, it rarely changed the spine curvature (LL and LA) of the subjects, with a difference of 2% or less. LL decreased during axial loading and may not correlate with the findings during normal standing position. Although the authors found greater DA and DAP values in male (p<0.001) and obese (p<0.05) subjects, changes of radiographic parameters with axial loading were otherwise not correlated with sex, age, or body mass index.
Conclusion: An axial-loaded MRI, using a SpineMAC device, may be superior to conventional MRI when evaluating narrowing of the dural sac and disc height of patients.
Received 9 June 2020 | Revised 30 September 2020 | Accepted 7 October 2020
doi.org/10.35755/jmedassocthai.2020.12.11525
Keywords : Lumbar lordosis, Spinal stenosis, Axial loading, Weight bearing, Disc herniation, Low back pain
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