The influence of the tibial plateau slopes on injury of the anterior cruciate ligament: a meta-analysis.

PURPOSE: The purpose of this meta-analysis was (1) to examine the effect of the tibial plateau slopes (medial and lateral) on anterior cruciate ligament (ACL) injury and (2) to investigate gender differences between ACL-injured subjects and gender-matched controls.

METHODS: The PubMed database was searched through to 1 November 2011 to identify studies that met pre-stated inclusion criteria. Reference lists of retrieved articles were also reviewed. Two authors independently extracted information on the designs of the studies, the characteristics of the study participants, exposure and outcome assessments, and control for potential confounding factors. A meta-analysis was conducted, and either a fixed- or a random-effects model was used to calculate the overall weighted mean difference (WMD).

RESULTS: Twelve studies (n = 1,871: 923 patients in the ACL-injured group and 938 patients in the control group) were included. The medial tibial plateau slope in the ACL group ranged from 1.8° ± 3.7° to 12.1° ± 3.3° while it ranged from 2.9° ± 2.8° to 9.5° ± 3° among the controls. The lateral tibial plateau slope in the ACL ranged from 1.8° ± 3.2° to 11.5° ± 3.5° and 0.3° ± 3.6° to 9° ± 4° in the control group. Statistically significant increased angles were observed in ACL-injured group compared to control group for medial tibial plateau slope (WMD, 1.1°; 95 % confidence interval, 0.5°-1.7°) and lateral tibial plateau slope (WMD, 1.8°; 95 % confidence interval, 1.3°-2.3°). Sensitivity analysis and subgroup analysis proved this to be a reliable result.

CONCLUSIONS: The current meta-analysis suggests that both, increased medial and lateral tibial plateau slopes, are associated with increased susceptibility to ACL injury regardless of gender. In addition, this study indicates a stronger evidence for lateral tibial plateau slope to be associated with ACL injury compared with medial tibial plateau slope due to the larger increased angle value and on the basis of consistency among the included studies.