title: Outcome measures in clinical ACL studies: an analysis of highly cited level I trials.
abstract: OBJECTIVE
  Clinical research in the area of anterior cruciate ligament (ACL) injury has shown substantial growth during the last decade. This was accompanied by the establishment of a wide range of outcome measures used to address the demands of clinical studies. The aim of this study was to evaluate outcome measures reported by highly cited level I trials in ACL research and identify factors influencing citation metrics.
  
  
  METHODS
  The database of the Institute for Scientific Information (ISI) was utilized to screen journals under the subject categories "Orthopaedics", "Sports Sciences", "Radiology" and "General medicine" for the 50 most cited level I ACL trials based on predefined inclusion criteria. Metadata, citation metrics and outcome measures were extracted for each article. Frequencies of reported outcome measures were calculated, and a multiple linear regression model applied to identify factors influencing citation metrics.
  
  
  RESULTS
  Two independent outcome measures demonstrated an influence on acquisition of citations including: 1-report of the pivot-shift test and 2-inclusion of the Knee Injury and Osteoarthritis Outcome (KOOS) score. Furthermore, highly cited ACL trials frequently reported KT-1000 measures of anterior translation, range of motion (ROM), graft failure, Lysholm, Tegner and subjective International Knee Documentation (IKDC) scores.
  
  
  CONCLUSIONS
  This analysis reflects on the outcome measures utilized in highly cited level I trials impacting the field of ACL research. It also identifies factors likely to influence acquisition of citations. This is of both clinical and academic relevance when choosing appropriate measures for post-operative outcome evaluation after ACL surgery.
  
  
  METHODS
  I.
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland. sufian.ahmad@insel.ch.
authors.forename: Sufian S
authors.initials: SS
authors.lastname: Ahmad
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland.
authors.forename: Johannes C
authors.initials: JC
authors.lastname: Meyer
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland.
authors.forename: Anna M
authors.initials: AM
authors.lastname: Krismer
authors.affiliation: School of Medicine, University of Buckingham, Hunter Street, Buckingham, UK.
authors.forename: Suhaib S
authors.initials: SS
authors.lastname: Ahmad
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland.
authors.forename: Dimitrios S
authors.initials: DS
authors.lastname: Evangelopoulos
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland.
authors.forename: Sven
authors.initials: S
authors.lastname: Hoppe
authors.affiliation: Department of Orthopaedic Surgery and Traumatology, Inselspital, University Hospital of Bern, Freiburgstrasse, Bern, Switzerland.
authors.forename: Sandro
authors.initials: S
authors.lastname: Kohl
mesh_terms: D000070598:Anterior Cruciate Ligament Injuries / Q000453:epidemiology* / Q000601:surgery; D059549:Anterior Cruciate Ligament Reconstruction / Q000706:statistics & numerical data*; D015706:Bibliometrics; D017321:Clinical Trials, Phase I as Topic / Q000706:statistics & numerical data*; D006801:Humans; D017063:Outcome Assessment, Health Care; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*
keywords: ACL; Anterior cruciate ligament; Bibliometrics; Measures; Outcome; Randomized trial