title: Incidence rate of anterior cruciate ligament reconstructions.
abstract: BACKGROUND
  Anterior cruciate ligament (ACL) reconstructions are among the most common sports medicine procedures performed in the US each year. Differences have been reported in the incidence rates (IRs) of ACL tears among male and female national elite athletes. However, there is little information in the published literature that assesses IRs for ACL reconstructions done in the Health Maintenance Organization (HMO) setting specifically. Different populations may show variation in ACL reconstruction IRs.
  
  
  OBJECTIVE
  This study reports on the IR of ACL reconstructions in a predefined population and compares the differences in age and sex over time.
  
  
  METHODS
  A retrospective analysis of 4485 ACL reconstructions performed within Kaiser Permanente Southern California between 2001 and 2005 was completed by a query of an administrative database. Trends in IRs per 100,000 members were calculated and compared across age, sex, and the five-year study period.
  
  
  METHODS
  Linear regression was used to test trends in IR. Sex distribution was compared using the χ(2) test. Analysis of variance was used to compare the mean age from year to year in males and females. The independent sample t-test was used to compare mean age between males and females for each independent year.
  
  
  RESULTS
  The IR of ACL reconstructions in females rose significantly (p = 0.010) from 14.4 in 2001 (95% confidence interval [CI], 12.6-16.3) to 19.3 in 2005 (95% CI, 17.2-21.5). Within specific age groups, IR increased significantly for females age 14 to 17 (p = 0.013), 18 to 21 (p = 0.017), and 45 to 49 years (p = 0.014). The most dramatic change was seen in the female age category of 14 to 17 years, which increased at a rate of 8.14 cases/100,000 members per year.
  
  
  CONCLUSIONS
  Identifying the sex and age groups with most rapidly increasing rates of ACL reconstructions is important in implementing ACL injury-prevention programs.
authors.forename: Rick P
authors.initials: RP
authors.lastname: Csintalan
authors.forename: Maria C S
authors.initials: MC
authors.lastname: Inacio
authors.forename: Tadashi T
authors.initials: TT
authors.lastname: Funahashi