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Published 9/1/2016

Risk Factors for ACL Re-tears in Athletes

Study examines impact of sex, age, and graft size
Female athletes, athletes younger than age 25, and athletes with a graft size less than 8 mm are at increased risk for an anterior cruciate ligament (ACL) re-tear after reconstruction, according to study data presented at the 2016 annual meeting of the American Orthopaedic Society for Sports Medicine.

"The minimum size required for a successful quadruple hamstring autograft ACL reconstruction remains controversial," the authors write. In addition, "the risks of ACL re-tear in younger patients who tend to participate in a higher level of sports activity, and female athletes who have numerous predisposing factors, are poorly defined."

The purpose of the study was to identify risk factors for graft re-tears within 2 years of ACL reconstruction (ACLR). The researchers hypothesized that female sex, a smaller size graft, and younger patients would increase the odds of sustaining a subsequent ACL tear.

Cohort study
The study involved 503 athletes (235 females; 268 males; mean age = 27 years) who had undergone primary autograft hamstring ACLR between September 2009 and December 2012. All patients had a minimum of 2 years of follow-up. All surgeries were performed by a single surgeon using the same surgical technique and rehabilitation protocol. Exclusion criteria were the following:

  • infection
  • revision
  • double-bundle technique
  • multiligament injuries
  • rehabilitation noncompliance
  • use of bone-to-bone autograft/allograft/hybrid graft

Patients who were pain-free, had equal quadriceps/hamstring strength, and had successfully completed the rehabilitation program were allowed to return to sport 6 to 12 months after surgery.

The rate of re-tears among the 503 athletes was 5.6 percent (28 patients; 17 females). The mean graft size was 7.9 mm. Statistical analysis using univariate and multivariate logistic regression analysis revealed a significant association between ACL re-tear and graft size less than 8 mm (P = 0.008) and age younger than 25 years (P = 0.001). Female sex was also predictive of re-tear (P = 0.13).

"Our research found that female patients younger than age 25 with a graft size of less than 8 mm have an increased chance of re-tearing their ACL following reconstruction. Predisposing factors—including estrogen levels, anatomic differences, poor neuromuscular control, and decreased knee strength—may also contribute to the increased re-tear rate. ACL re-tear is multifactorial and physicians should also consider other potential causes such as the specific sport played, the athlete's level of competition and position on the team, the extent of contact in the sports activity, and the patient's tendency for risk-taking behavior, which are harder to quantify and control in a study. More research is needed to further determine the exact causes," said the study's lead author Duong Nguyen, MD, FRCSC, MSc(c), DipSportsMed (ABOS/CASEM) of Toronto, Canada, who is affiliated with McMaster University.

"Given the results of our study, we believe orthopaedic surgeons should counsel their younger, female ALCR patients accordingly. They should consider modifying their surgical techniques to utilize larger size grafts and/or rehabilitation strategies to lessen the chance of a re-tear," concluded Dr. Nguyen.
Dr. Nguyen's disclosure information can be accessed at

Bottom Line

  • The risk of an ACL re-tear following reconstruction in young athletes, particularly females, is poorly defined.
  • This study sought to identify risk factors for re-tears in athletes who had undergone autograft hamstring ACLR.
  • The study revealed that female sex, age younger than 25 years, and graft size less than 8 mm were predictive of ACL re-tear.