title: Age-Related Risk Factors for Revision Anterior Cruciate Ligament Reconstruction: A Cohort Study of 21,304 Patients From the Kaiser Permanente Anterior Cruciate Ligament Registry.
abstract: BACKGROUND
  It is not clear whether risk factors for revision anterior cruciate ligament reconstruction (ACLR) are the same throughout patients' lives.
  
  
  OBJECTIVE
  To assess (1) the risk of revision ACLR by age and (2) age-specific risk factors for revision ACLR.
  
  
  METHODS
  Cohort study; Level of evidence, 2.
  
  
  METHODS
  A cohort study using patients having undergone primary ACLR who were registered in the Kaiser Permanente ACLR Registry (February 2005 to June 2013) was conducted. Aseptic revision was the main endpoint. Age was evaluated as a risk factor for revision. The cohort was stratified into 4 age groups: <21, 21-30, 31-40, and >40 years. Graft type, sex, body mass index (BMI), and race were assessed as revision risk factors within each group. Survival analyses were conducted.
  
  
  RESULTS
  Of the 21,304 patients evaluated, 7026 (33%) patients were aged <21 years, 5762 (27%) were 21-30 years, 4656 (22%) were 31-40 years, and 3860 (18%) were >40 years. Allografts were used in 8671 (41%) patients, hamstring autografts in 6823 (32%), and bone-patellar tendon-bone (BPTB) autografts in 5260 (25%). The 5-year revision probability was highest in patients <21 years old (9.0%; 95% CI, 8.0%-10.1%) and lowest in those >40 years old (1.9%; 95% CI, 1.3%-2.7%). Compared with patients aged >40 years, the adjusted revision risk for patients aged <21 years was 7.76 (95% CI, 5.52-10.90). In patients aged <21 years, a lower revision risk was seen in female patients (hazard ratio [HR], 0.76; 95% CI, 0.61-0.93) compared with male patients, patients with a BMI of 30-35 kg/m(2) (HR, 0.75; 95% CI, 0.59-0.95) and BMI >35 kg/m(2) (HR, 0.49; 95% CI, 0.34-0.70) compared with those with a BMI <30 kg/m(2), and black patients (HR, 0.55, 95% CI, 0.36-0.85) compared with white patients. Sex, BMI, and race were not associated with the risk of revision in older patients. In patients ≤40 years old, those with allografts had a higher risk of revision than those with BPTB autografts (HR, 2.69, 2.35, and 3.04 for patients aged <21, 21-30, and 31-40 years, respectively). Patients <21 years old with hamstring autografts had a 1.61 times (95% CI, 1.20-2.17) higher risk of revision than did patients with BPTB autografts; these differences were not identified in older patients.
  
  
  CONCLUSIONS
  Age at the time of ACLR surgery is a strong risk factor for revision ACLR. Other risk factors for revision ACLR, such as graft type, sex, race, and BMI, may vary in strength and significance over a patient's life. Understanding the age-related risk factors associated with revision ACLR may help with appropriate patient counseling and optimal graft choice when performing ACLR.
authors.affiliation: Kaiser Permanente Baldwin Park, Baldwin Park, California, USA gregory.b.maletis@kp.org.
authors.forename: Gregory B
authors.initials: GB
authors.lastname: Maletis
authors.affiliation: Surgical Outcomes and Analysis Department, Kaiser Permanente, San Diego, California, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Chen
authors.affiliation: Surgical Outcomes and Analysis Department, Kaiser Permanente, San Diego, California, USA.
authors.forename: Maria C S
authors.initials: MC
authors.lastname: Inacio
authors.affiliation: Kaiser Permanente Sand Canyon, Irvine, California, USA.
authors.forename: Tadashi T
authors.initials: TT
authors.lastname: Funahashi
mesh_terms: D000328:Adult; D000367:Age Factors; D016118:Anterior Cruciate Ligament / Q000503:physiopathology / Q000601:surgery; D000070598:Anterior Cruciate Ligament Injuries; D059549:Anterior Cruciate Ligament Reconstruction / Q000379:methods*; D015992:Body Mass Index; D064594:Bone-Patellar Tendon-Bone Grafts; D037001:Directive Counseling; D005260:Female; D006801:Humans; D008297:Male; D017847:Patellar Ligament / Q000601:surgery; D016016:Proportional Hazards Models; D012042:Registries; D012086:Reoperation / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate; D014481:United States / Q000453:epidemiology
keywords: ACL; age; anterior cruciate ligament reconstruction; graft; knee ligaments; revision; risk factor