title: Scoring the Current Risk Stratification Guidelines in Follow-up Evaluation of Patients After Metal-on-Metal Hip Arthroplasty: A Proposal for a Metal-on-Metal Risk Score Supporting Clinical Decision-Making.
abstract: BACKGROUND
  In the follow-up evaluation of patients with metal-on-metal (MoM) hip replacements, current evidence suggests that orthopaedic surgeons should avoid reliance on any single investigative tool. Current risk stratification guidelines can be difficult to interpret because they do not provide guidance when there are several risk factors in different groups (high and low risk). To improve the clinical utility of risk stratification guidelines, we designed a scoring system to assess the risk of revision.
  
  
  METHODS
  The study population consisted of 1,709 patients (1,912 hips) enrolled in a multicenter follow-up study of a recalled MoM hip replacement. Eleven scoring criteria were determined on the basis of existing follow-up algorithm recommendations and consisted of patient-related factors, symptoms, clinical status, implant type, metal ion levels, and radiographic imaging results. Forward stepwise logistic regression was conducted to determine the minimum set of predictive variables for the risk of revision and to assign variable weights. The MoM risk score for each hip was then created by averaging the weighted values of each predictive variable.
  
  
  RESULTS
  Receiver operating characteristic curve analysis yielded good discrimination between all revised and unrevised hips, with an area under the curve of 0.82 (p < 0.001). The odds of revision for the group with a high MoM risk score were increased by 5.8-fold (95% confidence interval [CI], 3.1 to 11.0) relative to the moderate risk group and by 21.8-fold (95% CI, 9.9 to 48.0) compared with the low risk group.
  
  
  CONCLUSIONS
  Although the use of MoM hip arthroplasty has been limited since 2010, we continue to be faced with the follow-up and risk assessment of thousands of patients who have not had a revision. As more knowledge about risk stratification is gained, the complexity of the algorithms is expected to increase. We propose the use of the MoM risk score as a tool to aid in the clinical decision-making process.
  
  
  METHODS
  Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Hussey
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Rami
authors.initials: R
authors.lastname: Madanat
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Gabrielle S
authors.initials: GS
authors.lastname: Donahue
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.|Department of Orthopaedics, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Rolfson
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Bragdon
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Orhun K
authors.initials: OK
authors.lastname: Muratoglu
authors.affiliation: Harris Orthopaedic Laboratory, Massachusetts General Hospital, Boston, Massachusetts hmalchau@mgh.harvard.edu.|Department of Orthopaedic Surgery, Harvard Medical School, Boston, Massachusetts.
authors.forename: Henrik
authors.initials: H
authors.lastname: Malchau
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D000066491:Clinical Decision-Making; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008875:Middle Aged; D011475:Prosthesis Failure; D012086:Reoperation; D018570:Risk Assessment; D012307:Risk Factors; D055815:Young Adult