title: Joint space predicts THA after hip arthroscopy in patients 50 years and older.
abstract: BACKGROUND
  All patients considering joint-preserving hip arthroscopy should be educated on the risk of THA after arthroscopy. The degree of radiographic osteoarthritis predicts subsequent THA. To provide patients with the best information, the best radiographic measure that predicts THA after hip arthroscopy should be identified.
  
  
  OBJECTIVE
  We therefore determined if Tönnis grade, Kellgren-Lawrence grade, or joint space narrowing was superior in predicting THA after hip arthroscopy.
  
  
  METHODS
  We retrospectively reviewed 203 patients 50 years of age or older treated with hip arthroscopy between March 2007 and October 2010. Of these, 96 patients met the study inclusion criteria. Sixty-five did not undergo THAs during the followup time (non-THA group) and 31 patients did (THA group). We determined Tönnis grade, Kellgren-Lawrence grade, and/or joint space narrowing before arthroscopy. The median followup for the non-THA group was 54 months (95% confidence interval, 49.9-58.9 months).
  
  
  RESULTS
  In 81% of the patients, joint space accurately predicted THA or non-THA, whereas Kellgren-Lawrence was accurate in 73% and Tönnis grade was accurate in 65%. On binary logistic regression, the only predictor (r(2) = 0.45) of THA was joint space of 2 mm or less.
  
  
  CONCLUSIONS
  Measuring joint space by determining if any measurement is 2 mm or less predicts patients progressing to THA after hip arthroscopy approximately 80% of the time. At this early time point, joint space measurements were the most accurate predictor of THA and should be used in patient education to define the risk of early failure from hip arthroscopy.
authors.affiliation: Center for Outcomes-Based Orthopaedic Research, The Steadman Philippon Research Institute, 181 W. Meadow Drive, Suite 100, Vail, CO 81657, USA. drphilippon@sprivail.org
authors.forename: Marc J
authors.initials: MJ
authors.lastname: Philippon
authors.forename: Karen K
authors.initials: KK
authors.lastname: Briggs
authors.forename: John C
authors.initials: JC
authors.lastname: Carlisle
authors.forename: Diana C
authors.initials: DC
authors.lastname: Patterson
mesh_terms: D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001182:Arthroscopy / Q000009:adverse effects; D003430:Cross-Sectional Studies; D005260:Female; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D015207:Osteoarthritis, Hip / Q000175:diagnosis / Q000601:surgery*; D011237:Predictive Value of Tests; D011859:Radiography; D012042:Registries; D012086:Reoperation; D012189:Retrospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D012720:Severity of Illness Index; D017211:Treatment Failure