title: Classification of High Intensity Zones of the Lumbar Spine and Their Association with Other Spinal MRI Phenotypes: The Wakayama Spine Study.
abstract: BACKGROUND
  High intensity zones (HIZ) of the lumbar spine are a phenotype of the intervertebral disc noted on MRI whose clinical relevance has been debated. Traditionally, T2-weighted (T2W) magnetic resonance imaging (MRI) has been utilized to identify HIZ of lumbar discs. However, controversy exists with regards to HIZ morphology, topography, and association with other MRI spinal phenotypes. Moreover, classification of HIZ has not been thoroughly defined in the past and the use of additional imaging parameters (e.g. T1W MRI) to assist in defining this phenotype has not been addressed.
  
  
  METHODS
  A cross-sectional study of 814 (69.8% females) subjects with mean age of 63.6 years from a homogenous Japanese population was performed. T2W and T1W sagittal 1.5T MRI was obtained on all subjects to assess HIZ from L1-S1. We created a morphological and topographical HIZ classification based on disc level, shape type (round, fissure, vertical, rim, and enlarged), location within the disc (posterior, anterior), and signal type on T1W MRI (low, high and iso intensity) in comparison to the typical high intensity on T2W MRI.
  
  
  RESULTS
  HIZ was noted in 38.0% of subjects. Of these, the prevalence of posterior, anterior, and both posterior/anterior HIZ in the overall lumbar spine were 47.3%, 42.4%, and 10.4%, respectively. Posterior HIZ was most common, occurring at L4/5 (32.5%) and L5/S1 (47.0%), whereas anterior HIZ was most common at L3/4 (41.8%). T1W iso-intensity type of HIZ was most prevalent (71.8%), followed by T1W high-intensity (21.4%) and T1W low-intensity (6.8%). Of all discs, round types were most prevalent (anterior: 3.6%, posterior: 3.7%) followed by vertical type (posterior: 1.6%). At all affected levels, there was a significant association between HIZ and disc degeneration, disc bulge/protrusion and Modic type II (p<0.01). Posterior HIZ and T1W high-intensity type of HIZ were significantly associated with disc bulge/protrusion and disc degeneration (p<0.01). In addition, posterior HIZ was significantly associated with Modic type II and III. T1W low-intensity type of HIZ was significantly associated with Modic type II.
  
  
  CONCLUSIONS
  This is the first large-scale study reporting a novel classification scheme of HIZ of the lumbar spine. This study is the first that has utilized T2W and T1W MRIs in differentiating HIZ sub-phenotypes. Specific HIZ sub-phenotypes were found to be more associated with specific MRI degenerative changes. With a more detailed description of the HIZ phenotype, this scheme can be standardized for future clinical and research initiatives.
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Teraguchi
authors.affiliation: Department of Orthopaedics and Traumatology, The University of Hong Kong, Professorial Block, 5th Floor 102 Pokfulam Road, Pokfulam, Hong Kong, SAR, China.
authors.forename: Dino
authors.initials: D
authors.lastname: Samartzis
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hashizume
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yamada
authors.affiliation: Department of Joint Disease Research, 22nd Century Medical & Research Center, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, 113-8655.
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Muraki
authors.affiliation: Department of Medical Research and Management for Musculoskeletal Pain, 22nd Century Medical & Research Center, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, 113-8655.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Oka
authors.affiliation: Department of Orthopaedics and Traumatology, The University of Hong Kong, Professorial Block, 5th Floor 102 Pokfulam Road, Pokfulam, Hong Kong, SAR, China.
authors.forename: Jason Pui Yin
authors.initials: JP
authors.lastname: Cheung
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Ryohei
authors.initials: R
authors.lastname: Kagotani
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Iwahashi
authors.affiliation: Department of Orthopaedic surgery, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyoku, Tokyo, 113-8655, Japan.
authors.forename: Sakae
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Japan Community Healthcare Organization Tokyo Shinjuku Medical Center, 5-1 Tsukudo-chome, Shinjuku-ku, Tokyo, Japan, 162-8543.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kawaguchi
authors.affiliation: Rehabilitation Services Bureau, National Rehabilitation Center for Persons with Disabilities, 1 Namiki 4-chome, Tokorozawa City, Saitama, Japan, 359-8555.
authors.forename: Kozo
authors.initials: K
authors.lastname: Nakamura
authors.affiliation: Rehabilitation Services Bureau, National Rehabilitation Center for Persons with Disabilities, 1 Namiki 4-chome, Tokorozawa City, Saitama, Japan, 359-8555.
authors.forename: Toru
authors.initials: T
authors.lastname: Akune
authors.affiliation: Department of Orthopaedics and Traumatology, The University of Hong Kong, Professorial Block, 5th Floor 102 Pokfulam Road, Pokfulam, Hong Kong, SAR, China.
authors.forename: Kenneth Man-Chee
authors.initials: KM
authors.lastname: Cheung
authors.affiliation: Department of Joint Disease Research, 22nd Century Medical & Research Center, Faculty of Medicine, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, Japan, 113-8655.
authors.forename: Noriko
authors.initials: N
authors.lastname: Yoshimura
authors.affiliation: Department of Orthopaedic Surgery, Wakayama Medical University, 811-1 Kimiidera, Wakayama, Japan, 641-8509.
authors.forename: Munehito
authors.initials: M
authors.lastname: Yoshida
mesh_terms: D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000000981:diagnostic imaging; D007564:Japan; D017116:Low Back Pain / Q000000981:diagnostic imaging; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged