Objectives:The minimum size required for a successful quadrupled hamstring autograft ACL reconstruction
remains controversial. 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. Purpose: To identify risk factors for graft re-tears
within 2 years of ACL surgery. The hypotheses are that female sex, a smaller size
graft, and younger patients will increase the odds of failure. Study Design Cohort
Study. Level of evidence, 3.Methods:A cohort of 503 athletes undergoing primary, autograft hamstring ACL reconstruction,
performed by a single surgeon using the same surgical technique and rehabilitation
protocol, between September-December 2012, was followed for a total duration of 2
years. Return to play was allowed between 6 and 12 months post-surgery upon completion
of functional testing. Exclusion criteria included infections, revisions, double bundle
techniques, multi-ligament injuries, non-compliance, BTB/allografts/hybrid grafts.
Primary outcome consisted of binary data (ACL graft re-tear or no tear) as measured
on physical exam (Lachman and pivot shift) and MRI. Multivariate logistic regression
statistical analysis with model fitting was used to investigate the predictive value
of sex, age, and graft size on ACL re-tear. Secondary sensitivity analyses were performed
on the adolescent subgroup, age and graft size as categorical variables, and testing
for interactions among variables. Sample size was calculated based on the rule of
10 events per independent variable for logistic regression.Results:The mean age of the 503 athletes was 27.5 (SD 10.6; range = 12-61). There were 235
females (47%) and 268 males (53%) with a 6% rate of re-tears (28 patients; 17 females).
Mean graft size was 7.9 (SD 0.6; range = 6-10). Univariate analyses of graft size,
sex, and age only in the model showed that younger age (odds ratio [OR] = 0.86; 95%
confidence interval [CI] = 0.80-0.93; P = .001] and smaller graft size (OR = 0.36;
95% CI = 0.18-0.70; P = .003) were significantly predictive of re-tear. Female sex
was correlated with re-tear but was not significant (OR = 1.8; 95% CI = 0.84-3.97;
P = .13). Multivariate analysis with all 3 variables in the model showed similar significant
results. Graft size < 8 mm (OR = 2.95; 95% CI = 1.33-6.53; P = .008) and age < 25
(OR = 7.01; 95% CI = 2.40-20.53; P = .001) were significantly predictive of re-tear.
Entire model was statistically significant (Omnibus test P = .001; Hosmer-Lemeshow
statistic P = .68; Receiver Operating Curve [ROC] = 0.8).Conclusion:Surgeons should counsel their patients who are female, younger than 25 and with a
graft size less than 8 mm accordingly and consider modifying their surgical or rehabilitation
techniques to mitigate these re-tear risks.