title: Lumbar facet joint and intervertebral disc loading during simulated pelvic obliquity.
abstract: BACKGROUND
  Intervertebral disc and facet joints are the two primary load-bearing structures of the lumbar spine, and altered loading to these structures may be associated with frontal plane spinal deviations.
  
  
  OBJECTIVE
  To determine the load on the lumbar facet joint and intervertebral disc under simulated frontal plane pelvic obliquity combined loading, an in vitro biomechanical study was conducted.
  
  
  METHODS
  An in vitro biomechanical study using a repeated-measures design was used to compare L4-L5 facet joint and intervertebral disc loading across pure moment and combined loading conditions.
  
  
  METHODS
  Eight fresh-frozen lumbosacral specimens were tested under five loading conditions: flexion/extension, lateral bending, axial rotation using pure moment bending (±10 Nm), and two additional tests investigating frontal plane pelvic obliquity and axial rotation (sacrum tilted left 5° and at 10° followed by a ±10-Nm rotation moment). Three-dimensional kinematics, facet load, and intradiscal pressures were recorded from the L4-L5 functional spinal unit.
  
  
  RESULTS
  Sagittal and frontal plane loading resulted in significantly smaller facet joint forces compared with conditions implementing a rotation moment (p<.05). The facet joint had the highest peak load during the 10° combined loading condition (124.0±30.2 N) and the lowest peak load in flexion (26.8±16.1 N). Intradiscal pressure was high in lateral flexion (495.6±280.9 kPa) and flexion (429.0±212.9 kPa), whereas intradiscal pressures measured in rotation (253.2±135.0 kPa) and 5° and 10° combined loading conditions were low (255.5±132.7 and 267.1±127.1 kPa, respectively).
  
  
  CONCLUSIONS
  Facet loading increased during simulated pelvic obliquity in frontal and transverse planes, whereas intradiscal pressures were decreased compared with sagittal and frontal plane motions alone. Altered spinopelvic alignment may increase the loads experienced by spinal tissue, especially the facet joints.
authors.affiliation: Division of Biokinesiology and Physical Therapy, University of Southern California, 1540 E. Alcazar St, CHP-155, Los Angeles, CA 90089, USA; Spine Biomechanics and Tissue Engineering Laboratory, Cedars-Sinai Medical Center, 8700 Beverly Blvd., Davis Building, 6006, Los Angeles, CA 90048, USA. Electronic address: popovi16@msu.edu.
authors.forename: John M
authors.initials: JM
authors.lastname: Popovich
authors.forename: Judson B
authors.initials: JB
authors.lastname: Welcher
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Hedman
authors.forename: Wafa
authors.initials: W
authors.lastname: Tawackoli
authors.forename: Neel
authors.initials: N
authors.lastname: Anand
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Chen
authors.forename: Kornelia
authors.initials: K
authors.lastname: Kulig
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena / Q000502:physiology; D006801:Humans; D007403:Intervertebral Disc / Q000502:physiology*; D008159:Lumbar Vertebrae / Q000502:physiology*; D008875:Middle Aged; D011312:Pressure; D016059:Range of Motion, Articular; D016474:Weight-Bearing / Q000502:physiology*; D021801:Zygapophyseal Joint / Q000502:physiology*
keywords: Biomechanics; Disc pressure; Facet joint; Pelvic obliquity; Spinopelvic alignment