title: Standardized radiologic protocol for the study of common coccygodynia and characteristics of the lesions observed in the sitting position. Clinical elements differentiating luxation, hypermobility, and normal mobility.
abstract: METHODS
  Ninety-one patients with common coccygodynia and 47 control subjects prospectively underwent dynamic radiographic imagery.
  
  
  OBJECTIVE
  To standardize the radiologic protocol to better define normal and abnormal mobility of the coccyx, and to study clinical parameters useful in classifying and differentiating the lesions.
  
  
  BACKGROUND
  In a previous study, comparison of films taken in the sitting and standing positions allowed to individualize two distinct coccygeal lesions: luxation and hypermobility. Measurement technique was precise and reproducible, but the control group was not pain-free. No specific clinical features were described.
  
  
  METHODS
  Standing films were made first. Control subjects were healthy volunteers. The following items were recorded: presence of an initial traumatic event, elapsed time before investigation, body mass index, presence of an acute pain when passing from sitting to standing, effect of intradiscal steroid injection, and angle of the coccyx with respect to the seat.
  
  
  RESULTS
  Hypermobility was defined as a flexion of more than 25 degrees, luxation by displacement of more than 25% of the coccyx. The base angle is a good predictor of the direction in which the coccyx moves when sitting. In the "luxation" group, a history of initial trauma, a shorter clinical course, pain when standing up, increased body mass index, and satisfactory results with intradiscal injection were found more frequently than in the "normal" group. The "hypermobility" group had characteristics between these two groups.
  
  
  CONCLUSIONS
  Common coccygodynia is associated in 48.4% of patients with a luxation or hypermobility of the coccyx. A distinct clinical presentation was found in individuals with luxation of the coccyx.
authors.affiliation: Department of Orthopaedic Medicine and Rehabilitation, Hotel-Dieu Universitary Hospital, Paris, France.
authors.forename: J Y
authors.initials: JY
authors.lastname: Maigne
authors.forename: B
authors.initials: B
authors.lastname: Tamalet
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D003050:Coccyx; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000000981:diagnostic imaging* / Q000503:physiopathology; D011187:Posture; D011859:Radiography; D013122:Spinal Diseases / Q000000981:diagnostic imaging* / Q000503:physiopathology