title: Instantaneous helical axis methodology to identify aberrant neck motion.
abstract: BACKGROUND
  Neck pain afflicts 30-50% of the U.S. population annually; however we currently have poor diagnostic differentiation techniques to inform individualized treatment. Planar neck kinematics has been shown to be correlated with neck pain, but neck motion is much more complex than pure planar activities. Our objective was to define a methodology for determining aberrant neck kinematics and assess it.
  
  
  METHODS
  We examined a complex neck kinematic activity of neck circumduction and computed the pathway of motion using the instantaneous helical axis approach in 81 patients with non-specific neck pain and in 20 non-matched symptom free subjects. Neck circumduction, or rolling of the head, represents a complex neck kinematic activity, investigating the innate coupled motion of the cervical spine at the end ranges of motion in all directions. Instance of discontinuities in the helical axis patterns, or folds, were identified and labeled as occurrences of aberrant motion.
  
  
  RESULTS
  The instances of aberrant motion, or folds, which are nearly non-existent in the healthy sample group, are present in both the pre- and post-treatment neck pain patients. Following a treatment intervention of the symptomatic patients, pain and neck disability index decreased significantly (P<0.001) concomitant with a decrease in the number of folds (P=0.021).
  
  
  CONCLUSIONS
  The present study highlights a new technique using an instantaneous helical axis approach to detect subtle abnormalities in the pathway of motion of the head about the trunk, during a neck circumduction exercise.
authors.affiliation: Department of Biomedical Engineering, University of Minnesota, Minneapolis, MN, USA. Electronic address: ellin224@umn.edu.
authors.forename: Arin M
authors.initials: AM
authors.lastname: Ellingson
authors.forename: Vishal
authors.initials: V
authors.lastname: Yelisetti
authors.forename: Craig A
authors.initials: CA
authors.lastname: Schulz
authors.forename: Gert
authors.initials: G
authors.lastname: Bronfort
authors.forename: Joseph
authors.initials: J
authors.lastname: Downing
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Keefe
authors.forename: David J
authors.initials: DJ
authors.lastname: Nuckley
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D009038:Motion; D009068:Movement; D009333:Neck / Q000503:physiopathology*; D019547:Neck Pain / Q000145:classification* / Q000503:physiopathology* / Q000534:rehabilitation; D010147:Pain Measurement / Q000379:methods*; D016059:Range of Motion, Articular
keywords: Aberrant motion; Cervical spine; Helical axis; Kinematics; Neck pain
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