title: In vivo evidence for tibial plateau slope as a risk factor for anterior cruciate ligament injury: a systematic review and meta-analysis.
abstract: BACKGROUND
  In vivo studies reporting tibial plateau slope as a risk factor for anterior cruciate ligament (ACL) injury have been published with greatly increasing frequency.
  
  
  OBJECTIVE
  To examine and summarize the in vivo evidence comparing tibial slope in ACL-injured and uninjured populations.
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  We reviewed publications in Scopus, SPORTDiscus, CINAHL, and PubMed to identify all studies reporting a measure of tibial plateau slope between ACL-injured groups and controls. A meta-analysis was performed including calculation of effect size and 95% confidence interval as well as 95% confidence intervals for the mean values of the measurement in each study.
  
  
  RESULTS
  Fourteen studies met our inclusion/exclusion criteria. Five of 6 radiographic studies reporting medial tibial plateau slope (MTPS) demonstrated significant differences between controls and ACL-injured groups, while only 1 of 7 magnetic resonance imaging (MRI) studies reported significant differences between groups. Mean MTPS measurements and standard deviations reported for controls ranged from 2.9° ± 2.8° anterior to 9.5° ± 3° posterior. For ACL-injured patients, MTPS ranged from 1.8° ± 3.5° anterior to 12.1° ± 3.3° posterior. Lateral tibial plateau slope (LTPS) was reported to be significantly greater in ACL-injured groups in all 5 MRI-based studies reporting group comparisons. Mean values for LTPS in controls ranged from 0.3° ± 3.6° anterior slope to 9° ± 4° posterior slope. In ACL-injured groups, mean reported LTPS values ranged from 1.8° ± 3.2° to 11.5° ± 3.54° posterior slope.
  
  
  CONCLUSIONS
  Despite high measures of reliability for the various methods reported in current studies, there is vast disagreement regarding the actual values of the slope that would be considered "at risk." Reported tibial slope values for control groups vary greatly between studies. In many cases, the study-to-study differences in "normal" tibial slope exceed the difference between controls and ACL-injured patients. The clinical utility of imaging-based measurement methods for the determination of ACL injury risk requires more reliable techniques that demonstrate consistency between studies.
authors.affiliation: Sports Health and Performance Institute, The Ohio State University, Columbus, OH 43221, USA.
authors.forename: Samuel C
authors.initials: SC
authors.lastname: Wordeman
authors.forename: Carmen E
authors.initials: CE
authors.lastname: Quatman
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Kaeding
authors.forename: Timothy E
authors.initials: TE
authors.lastname: Hewett
mesh_terms: D016118:Anterior Cruciate Ligament / Q000473:pathology*; D000070598:Anterior Cruciate Ligament Injuries; D006801:Humans; D007718:Knee Injuries / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D012307:Risk Factors; D013977:Tibia / Q000473:pathology*