The effect of anterior cruciate ligament reconstruction on the risk of knee reinjury.

BACKGROUND Although there is evidence that very active, young patients are better served with anterior cruciate ligament reconstruction, there is a lack of objective data demonstrating that future knee injury is prevented by these procedures. HYPOTHESIS Anterior cruciate ligament reconstruction protects against reinjury of the knee that would require reoperation. STUDY DESIGN Retrospective cohort study. METHODS A cohort of 6576 active-duty army personnel who had been hospitalized for anterior cruciate ligament injury from 1990 to 1996 were identified. Using the Total Army Injury and Health Outcomes Database, the authors followed these individuals for up to 9 years and collected clinical, demographic, and occupational data. These data were evaluated with bivariate and multivariable analyses to determine the effect of anterior cruciate ligament reconstruction on the rate of knee reinjury that required operation. RESULTS Of the 6576 study subjects, 3795 subjects (58%) underwent anterior cruciate ligament reconstruction and 2781 (42%) did not. The rate of reoperation was significantly lower among the anterior cruciate ligament reconstruction group (4.90/100 person-years) compared with those treated conservatively (13.86/100 person-years; P < .0001). Proportional hazard regression analyses adjusted for age, race, sex, marital status, education, and physical activity level confirmed that anterior cruciate ligament reconstruction was protective against meniscal and cartilage reinjury (P < .0001). Secondary medial meniscal injury was more common than secondary lateral meniscal injury (P < .003). Younger age was the strongest predictor of failure of conservative management leading to late anterior cruciate ligament reconstruction (P < .0001). CONCLUSIONS Anterior cruciate ligament reconstruction protected against reoperation in this young, active population; younger subjects were more likely to require late anterior cruciate ligament reconstruction. CLINICAL RELEVANCE Strong consideration should be given to anterior cruciate ligament reconstruction after anterior cruciate ligament injury in young, active individuals.