title: Motion characteristics of the lumbar spine in the normal population.
abstract: METHODS
  The present study investigated the dynamic motion characteristics of the lumbar spine in the normal population using a potentiometric analysis system.
  
  
  OBJECTIVE
  To assess the ability of a triaxial potentiometric analysis system to measure dynamic motion in the lumbar spine, and to use this system to form a database of dynamic motion characteristics from which normal parameters of motion and the factors affecting this motion could be defined.
  
  
  BACKGROUND
  Spinal motion has been studied using a variety of different methods, the majority of which have been limited either in terms of reliability, accuracy, or invasiveness and many have been only of a static nature. There has been no previous study into the normal dynamic motion characteristics of the lumbar spine.
  
  
  METHODS
  The accuracy of the system was determined by a series of tests against a calibrated engineering mill, and the reliability of the system was assessed on 10 subjects with repeated measurements over a 3-day period. Values of range of motion and angular velocity were obtained from 203 normal subjects during flexion and extension, lateral flexion, and rotation.
  
  
  RESULTS
  The results of the calibration testing revealed excellent accuracy, and it was shown that the system was repeatable. Initial analysis of the results indicated that sex differences did exist with men having 58.4 degrees of flexion and women having 53.4 degrees. Age appeared to have an influence on motion, and a gradual reduction was seen with each decade (P < 0.001), with the 20-29-year age range having 59.5 degrees mean flexion, the 30-39-year group having 58.1 degrees, the 40-49-year group having 53.7 degrees, the 50-60-year group having 57.5 degrees, and the 60-70-year group having 45.9 degrees. Multiple regression techniques revealed that only a few factors are important with respect to motion and that these varied according to the characteristic being defined.
  
  
  CONCLUSIONS
  Range of motion tended to be affected by age and sex, whereas velocity was only affected by distance moved, with occupation and body mass index having little or no influence on the motion. The factors identified could only account for a small proportion of the variation seen, suggesting that it is difficult to predict the motion characteristics with any degree of sensitivity.
authors.affiliation: Orthopaedic Surgery Royal Postgraduate Medical School, Hammersmith Hospital, London, United Kingdom.
authors.forename: A H
authors.initials: AH
authors.lastname: McGregor
authors.forename: I D
authors.initials: ID
authors.lastname: McCarthy
authors.forename: S P
authors.initials: SP
authors.lastname: Hughes
mesh_terms: D000328:Adult; D000368:Aged; D002138:Calibration; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009983:Orthopedic Equipment / Q000592:standards; D016059:Range of Motion, Articular; D012016:Reference Values; D012044:Regression Analysis; D015203:Reproducibility of Results