title: Preoperative Outcome Scores Are Predictive of Achieving the Minimal Clinically Important Difference After Arthroscopic Treatment of Femoroacetabular Impingement.
abstract: BACKGROUND
  There is increasing interest in defining meaningful improvement in patient-reported outcomes. Knowledge of the thresholds and determinants for successful femoroacetabular impingement (FAI) outcomes is evolving.
  
  
  OBJECTIVE
  To define preoperative outcome score thresholds and determine clinical/demographic patient factors predictive for achieving the minimal clinically important difference (MCID) after arthroscopic FAI surgery.
  
  
  METHODS
  Cohort study (diagnosis); Level of evidence, 2.
  
  
  METHODS
  A prospective institutional hip preservation registry was reviewed to identify patients undergoing arthroscopic FAI surgery. The modified Harris Hip Score (mHHS), the Hip Outcome Score (HOS), and the international Hip Outcome Tool (iHOT-33) were administered at baseline and 1 year postoperatively. The MCID was calculated using a distribution-based method. Receiver operating characteristic (ROC) analysis was used to calculate cohort-based threshold values predictive of achieving the MCID. The area under the curve (AUC) was used to define predictive ability, with AUC >0.7 considered acceptably predictive. Multivariable analysis identified patient factors associated with achieving the MCID. Sensitivity analysis was performed to derive the MCID by an alternative anchor-based method.
  
  
  RESULTS
  There were 364 patients (mean [±SD] age, 32.5 ± 10.3 years), and 57.1% were female. The MCID for the mHHS, HOS-Activities of Daily Living (HOS-ADL), HOS-Sports, and iHOT-33 was 8.2, 8.3, 14.5, and 12.1, respectively. ROC analysis findings (threshold, percentage achieving the MCID, and strength of association) for these tools were as follows: mHHS (60.5, 77.2%, and 0.68, respectively), HOS-ADL (83.3, 68.1%, and 0.85, respectively), HOS-Sports (58.3, 65.9%, and 0.76, respectively), and iHOT-33 (53.9, 81.9%, and 0.65, respectively). The likelihood for achieving the MCID significantly declined above these thresholds. In multivariable analysis, a higher sagittal center-edge angle (CEA) (odds ratio [OR], 1.04; 95% CI, 1.01-1.08) was a positive predictor of achieving the MCID on the iHOT-33, while a higher Outerbridge grade for the acetabulum was a negative predictor (OR, 0.56; 95% CI, 0.32-0.99) on the mHHS. Sensitivity analysis confirmed these variables and identified relative femoral retroversion as another negative predictor (OR, 0.40; 95% CI, 0.17-0.94).
  
  
  CONCLUSIONS
  The HOS had excellent predictive ability for identifying patient thresholds of achieving the MCID; patients with preoperative scores below identified thresholds were most likely to achieve the MCID. Additionally, anterior acetabular undercoverage, chondral injuries, and relative femoral retroversion were clinically significant negative modifiers of outcomes. These findings have implications for managing preoperative expectations of FAI surgery.
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Benedict U
authors.initials: BU
authors.lastname: Nwachukwu
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Kara
authors.initials: K
authors.lastname: Fields
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Brenda
authors.initials: B
authors.lastname: Chang
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Danyal H
authors.initials: DH
authors.lastname: Nawabi
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Kelly
authors.affiliation: Hospital for Special Surgery, New York, New York, USA.
authors.forename: Anil S
authors.initials: AS
authors.lastname: Ranawat
mesh_terms: D000328:Adult; D001182:Arthroscopy; D005260:Female; D057925:Femoracetabular Impingement / Q000601:surgery*; D006801:Humans; D008297:Male; D000071081:Minimal Clinically Important Difference; D011184:Postoperative Period; D011446:Prospective Studies; D055815:Young Adult
keywords: epidemiology; femoroacetabular impingement; hip arthroscopic surgery; minimal clinically important difference; outcome; quality of life