title: Facet orientation and tropism: Associations with asymmetric lumbar paraspinal and psoas muscle parameters in patients with chronic low back pain.
abstract: BACKGROUND
  Many studies have explored the relationship between facet tropism and facet joint osteoarthritis, disc degeneration and degenerative spondylolisthesis. However, the associations between facet orientation and tropism, and paraspinal muscles have not been studied.
  
  
  OBJECTIVE
  To analyze the associations between facet orientation and tropism, and parameters of paraspinal muscles in patients with chronic low back pain.
  
  
  METHODS
  Ninety-five patients with chronic low back pain were consecutively enrolled. Their facet joint angles were measured on computed tomography (CT) while gross cross-sectional area (GCSA), functional cross-sectional area (FCSA) and T2 signal intensity of lumbar paraspinal and psoas muscle were evaluated on magnetic resonance imaging (MRI).
  
  
  RESULTS
  The GCSA and FCSA were significantly smaller for multifidus muscle (P< 0.001), but significantly larger for erector spinae and psoas muscles (P< 0.001), in coronally-orientated group than those in sagittally-orientated group. The differences of bilateral GCSA and FCSA of multifidus muscle were significantly larger in facet tropism group than those in no facet tropism group (P= 0.009 and P= 0.019).
  
  
  CONCLUSIONS
  Muscular asymmetries may develop in the lumbar region of the spine, which are associated with facet asymmetry in patients with chronic low back pain. Longitudinal studies are needed to understand the causal relationship between facet orientation and tropism and muscular asymmetry in future.
authors.affiliation: Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: W B
authors.initials: WB
authors.lastname: Xu
authors.affiliation: Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: S
authors.initials: S
authors.lastname: Chen
authors.affiliation: Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: S W
authors.initials: SW
authors.lastname: Fan
authors.affiliation: Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: F D
authors.initials: FD
authors.lastname: Zhao
authors.affiliation: Key Laboratory of Biotherapy of Zhejiang Province, Hangzhou, Zhejiang, China.
authors.forename: X J
authors.initials: XJ
authors.lastname: Yu
authors.affiliation: Department of Orthopedics, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China.
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Hu
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D055959:Intervertebral Disc Degeneration / Q000150:complications; D017116:Low Back Pain / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D008161:Lumbosacral Region / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D000072458:Orientation, Spatial; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D016658:Psoas Muscles / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000503:physiopathology; D014057:Tomography, X-Ray Computed; D021801:Zygapophyseal Joint / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology
keywords: Facet orientation; T2 signal intensity; computed tomography; cross-sectional area; erector spinae; facet tropism; magnetic resonance imaging; multifidus; paraspinal muscle; psoas major