Background
Stenotic femoral intercondylar notch is considered as a risk factor for anterior cruciate ligament (ACL) injury and three-dimensional notch volume is used as a marker for the injury. The primary purpose of this study was to assess the difference in notch volume between the ACL-injured and uninjured in men and women combined or stratified by sex. The secondary purpose was to assess the difference in notch volume between the ACL-intact men and women.
Methods
A search of PubMed/Medline, Scopus, Google Scholar, and Cochrane databases from inception to December 9, 2020, was conducted without restrictions using the following terms: ACL, notch, volume, notch volume, femoral notch volume, and intercondylar notch volume. Studies that compared the ACL-injured with uninjured controls were included. Independent extraction of articles by two authors using predefined data fields including study quality indicators was done. All pooled analyses were based on the inverse-variance weighted random effects model and mean difference was chosen as the effect measure.
Results
Nine studies (1,169 knees) qualified for overall analysis (both sexes combined) and significant heterogeneity was observed, which disappeared after pooling studies with age-sex matched controls and those without. Notch volume in the ACL-injured was 0.75 cm
3
(95% confidence interval [CI], 0.53–0.96 cm
3
), which was smaller than that in the age- and sex-matched controls. Six studies qualified for analysis in men. Notch volume in the ACL-injured men was smaller, especially when non-contact ACL injury was considered (1.40 cm
3
; 95% CI, 1.08–1.73 cm
3
). Five studies qualified for analysis in women and ACL-injured women had smaller notch volume irrespective of the mechanism of injury (0.38 cm
3
; 95% CI, 0.18–0.59 cm
3
). Notch volume of the uninjured men was larger than that of the uninjured women (1.86 cm
3
; 95% CI, 1.54–2.18 cm
3
).
Conclusions
ACL-injured adults have smaller notch volume than the age- and sex-matched controls. Non-contact ACL-injured males have smaller notch volume compared to ACL-intact males. ACL-injured females have smaller notch volume irrespective of the nature of injury. Men have higher notch volume than women. The quality of evidence is very low to low.