title: Risk factors associated with revision and contralateral anterior cruciate ligament reconstructions in the Kaiser Permanente ACLR registry.
abstract: BACKGROUND
  Patients generally choose to undergo anterior cruciate ligament reconstruction (ACLR) to return to their active lifestyles. However, returning to their previous activity level may result in a retear of their reconstructed knee or an injury to their contralateral anterior cruciate ligament (CACL).
  
  
  OBJECTIVE
  To determine the risk factors associated with revision ACLR and contralateral ACLR (CACLR), compare the survival of the reconstructed ACL with the CACL, and determine how the risk factors associated with revision ACLR compare with those for CACLR.
  
  
  METHODS
  Cohort study; Level of evidence, 3.
  
  
  METHODS
  A retrospective cohort study of prospectively collected data from the Kaiser Permanente ACLR registry between February 1, 2005, and September 30, 2012, was conducted. Primary ACLR cases without history of contralateral knee ACL injury were included. The study endpoints included revision ACLR and CACLR. Graft type (bone-patellar tendon-bone [BPTB] autograft, hamstring autograft, and allograft) was the main exposure of interest, and patient characteristics were evaluated as risk factors for revision ACLR and CACLR. Survival analyses were conducted.
  
  
  RESULTS
  A total of 17,436 ACLRs were evaluated. The median age was 27.2 years (interquartile range, 18.7-37.7 years), and 64% were males. The 5-year survival for index ACLR was 95.1% (95% CI, 94.5%-95.6%), and for CACL it was 95.8% (95% CI, 95.2%-96.3%). Overall, the cohort had a mean of 2.4 ± 1.7 years of follow-up; 18.2% were lost to follow-up. There were fewer CACLRs per 100 years of observation (0.83) than there were revision ACLRs (1.05) during the study period (P < .001). There was a statistically significant difference in the density of revision ACLR and CACL in BPTB autografts (0.74 vs 1.06, respectively; P = .010), hamstring autografts (1.07 vs 0.81; P = .042), and allografts (1.26 vs 0.67; P < .001). The risk factors for revision ACLR and contralateral surgery were different (P < .05). After adjusting for covariates, factors associated with higher risk of revision ACLR were as follows: allografts, hamstring autografts, male sex, younger age, lower body mass index (BMI), and being white as opposed to black. Factors associated with higher risk of CACLR were as follows: younger age, female sex, and lower BMI.
  
  
  CONCLUSIONS
  The 5-year revision-free and CACLR-free survival rate in this study was 95.1% and 95.8%, respectively. Allografts and hamstring autografts had a higher risk of revision ACLR surgery, and BPTB autografts had a higher risk of CACLR. Males were found to have a higher risk of revision ACLR, and females had a higher risk of CACLR. Increasing age and increasing BMI decreased the risk of both revision and CACLR.
authors.affiliation: Kaiser Permanente, Baldwin Park, California, USA gregory.b.maletis@kp.org.
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Maletis
authors.affiliation: Kaiser Permanente Surgical Outcomes and Analysis Department, San Diego, California, USA.
authors.forename: Maria C S
authors.initials: MC
authors.lastname: Inacio
authors.affiliation: Kaiser Permanente, Irvine, California, USA.
authors.forename: Tadashi T
authors.initials: TT
authors.lastname: Funahashi
mesh_terms: D000293:Adolescent; D000328:Adult; D001741:Black or African American; D000367:Age Factors; D064591:Allografts; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D064592:Autografts; D015992:Body Mass Index; D064594:Bone-Patellar Tendon-Bone Grafts; D005260:Female; D006279:Health Maintenance Organizations / Q000706:statistics & numerical data; D006801:Humans; D007718:Knee Injuries / Q000208:ethnology / Q000601:surgery*; D008297:Male; D012042:Registries; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D015996:Survival Rate; D044465:White People; D055815:Young Adult
keywords: ACL; allografts; contralateral ACL; contralateral knee; knee, ligaments; revision ACL