A. Patel1, J. Wrigley2, G. Bullock3,4, M. Paterno5,6,7, T. Sell8, J. Losciale9
1Duke University, School of Medicine, Durham, United States, 2Duke University, Medical Research Library, Durham, United States, 3University of Oxford, Centre for Sport, Exercise and Osteoarthritis Research Versus, Oxford, United Kingdom, 4University of Oxford, Nuffield Department of Orthopaedics, Rheumatology, and Musculoskeletal Sciences, Oxford, United Kingdom, 5Cincinnati Children's Hospital Medical Center, Occupational Therapy and Physical Therapy, Cincinnati, United States, 6Cincinnati Children's Hospital Medical Center, Sports Medicine, Cincinnati, United States, 7University of Cincinnati College of Medicine, Pediatrics, Cincinnati, United States, 8Atrium Health, Musculoskeletal Institute, Charlotte, United States, 9University of British Columbia, Physical Therapy, Vancouver, Canada
Background: Current evidence suggests females are at greater risk for sustaining a primary anterior cruciate ligament (ACL) injury compared to males when playing similar sports. However, it is unknown if the same relationship exists for second ACL injury risk following primary ACL reconstruction (ACLR). Understanding the relationship between biologic sex and second ACL injury can help guide rehabilitation and second ACL injury prevention efforts.
Purpose: The purpose of this review was to determine differences in the incidence and risk of a second ACL injury following primary ACLR based on biologic sex, determine the between biologic sex-based difference in risk of an ipsilateral or contralateral injury, and determine if age, pre-injury activity level and return to sport (RTS)% were moderators of differences in second ACL injury risk between biologic sexes.
Methods: The Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. A literature search was conducted in 5 online databases using specific language related to “ACL injury”, “ACLR”, and “re-injury”. Risk of bias (RoB) was assessed using study design specific, domain-based tools. Data on second ACL injuries based on biologic sex, laterality of injury, RTS %, pre- and post-injury activity level were extracted. Incidence proportion and risk ratio (RR) meta-analyses were calculated for total-, ipsilateral-, and contralateral- second ACL injury for the total cohort and per biologic sex at 95% confidence interval (CI). Heterogeneity was assessed using I2. Meta-regressions were performed to determine the influence of age, pre-injury activity level and RTS% on second ACL injury risk between biologic sexes.
Results: Twenty-seven studies were included in this review, with 11 studies excluded from the meta-analysis due to high RoB. 16 studies (n=1548 females, n=1935 males) were meta-analyzed. Total second ACL injury incidence was 20.9% (females: 22.9%, males: 19.3%). Females (11.4%) and males (11.7%) sustained a similar incidence of ipsilateral ACL injuries. Females sustained a slightly higher incidence of contralateral ACL injuries compared to males (11.3% vs. 7.4%, respectively). A larger proportion of male injuries occurred to the ipsilateral knee (63.4%), while females had similar ipsilateral (49.3%) and contralateral (50.7%) ACL injury proportions. No differences between biologic sexes were observed for second ACL injury risk (RR= 0.94, 95%CI: 0.75-1.18; I2= 50%), ipsilateral ACL injury risk (RR= 0.74, 95%CI: 0.52-1.05; I2= 52%), or contralateral ACL injury risk (RR= 1.26, 95%CI: 0.99-1.60; I2= 0%). Age, pre-injury activity level and RTS% did not influence second ACL injury risk (R2 = 0.00).
Conclusion(s): A larger proportion of male second ACL injuries occurred to the ipsilateral knee, while females sustained a similar proportion of ipsilateral and contralateral knee injuries.
Implications: This work suggests second ACL injury prevention should target both knees for females and potentially bias the ipsilateral knee in males. This may be influenced by ACL injury baseline risk differences between biologic sexes. Future work is needed to identify the underlying mechanism for ipsilateral knee injuries in males.
Funding, acknowledgements: There was no funding source that supported this work.
Keywords: knee re-injury, gender differences, second ACL injury incidence
Topic: Sport & sports injuries
Did this work require ethics approval? No
Institution: Duke University
Committee: Institutional Review Board
Reason: Ethics approval is not required for systematic reviews of the literature.
All authors, affiliations and abstracts have been published as submitted.
