title: Spondylolysis and spondylolisthesis: prevalence of different forms of instability and clinical implications.
abstract: METHODS
  Imaging study with an evaluation of incidences and clinical correlation.
  
  
  OBJECTIVE
  To evaluate the incidence of 3 different types of instabilities in patients with spondylolysis or isthmic spondylolisthesis. Clinical findings are correlated with imaging findings, and the imaging findings are analyzed with regard to their clinical implications.
  
  
  BACKGROUND
  Spondylolysis and isthmic spondylolisthesis are common disorders. An unstable slip is the most well-known form of instability, but other forms also exist. However, the incidence of these instabilities and their clinical implications are yet unclear.
  
  
  METHODS
  A total of 140 patients with 141 levels of spondylolysis identified by MRI (magnetic resonance imaging) were included in this study. Using positional MRI, the instability of the slip, an increased angular movement, and movement in the spondylolytic cleft were assessed. On the basis of clinical findings, the patients were classified as presenting with either radicular or nonradicular symptoms. The incidence of the instabilities was recorded and correlated with the incidence of radicular symptoms.
  
  
  RESULTS
  Fifteen patients had an unstable slip (anterior instability); 35, an increased angular movement (angular instability); and 34 patients, a movement in the spondylolytic cleft (posterior instability). All forms of instability could be found together. No instability at all was found in 76 patients. Radicular symptoms were found significantly more often in patients with one or more of the described instabilities compared with patients without instability.
  
  
  CONCLUSIONS
  All 3 described forms of instability are common in spondylolysis or isthmic spondylolisthesis and associated with radicular pain. This finding stresses the value of positional MRI in the evaluation of patients with spondylolysis and isthmic spondylolisthesis, especially if radicular symptoms are present.
authors.affiliation: Privatpraxis für Upright MRT, Köln, Germany. p.niggemann@mrt-koeln.de
authors.forename: Pascal
authors.initials: P
authors.lastname: Niggemann
authors.forename: Johannes
authors.initials: J
authors.lastname: Kuchta
authors.forename: Hans-Konrad
authors.initials: HK
authors.lastname: Beyer
authors.forename: D
authors.initials: D
authors.lastname: Grosskurth
authors.forename: Thorsten
authors.initials: T
authors.lastname: Schulze
authors.forename: Karl-Stefan
authors.initials: KS
authors.lastname: Delank
mesh_terms: D001696:Biomechanical Phenomena; D016009:Chi-Square Distribution; D005858:Germany; D006801:Humans; D007593:Joint Instability / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D015995:Prevalence; D011379:Prognosis; D016059:Range of Motion, Articular; D013168:Spondylolisthesis / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D013169:Spondylolysis / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology