Purpose: The aim of this study was to determine the rates of contralateral anterior cruciate ligament (ACL) rupture and of ACL graft rupture after ACL reconstruction using either patellar tendon or hamstring tendon autograft, and to identify any patient characteristics that may increase this risk.
Type of study: Case series.
Methods: Over a 2-year period, 760 endoscopic ACL reconstructions were performed in 743 patients. Bone-patellar tendon-bone autograft was used in 316 patients and 4-strand hamstring tendon in 427 patients. Those patients with a previous contralateral ACL rupture or those who underwent a simultaneous bilateral ACL reconstruction were excluded, leaving 675 knees (675 patients) for review. Persons not involved in the index operation or the care of the patient conducted follow-up assessment by telephone interview conducted 5 years after surgery. Patients were questioned about the incidence of ACL graft rupture, contralateral ACL rupture, symptoms of instability or significant injury, family history of ACL injury, and activity level according to the International Knee Documentation Committee scale. From our prospective database we obtained further information on graft source, meniscal or articular surface injury, and gender. Binary logistic regression was used to measure the relative association between the measured variables and the risk of graft rupture and contralateral ACL rupture.
Results: Five years after primary ACL reconstruction, 612 of the 675 patients (90.7%) were assessed. ACL graft rupture occurred in 39 patients (6%) and contralateral ACL rupture occurred in 35 patients (6%). Three patients suffered both a graft rupture and a contralateral ACL injury. The odds of ACL graft rupture were increased 3-fold by a contact mechanism of initial injury. Return to level 1 or 2 sports increased the risk of contralateral ACL injury by a factor of 10. The risk of sustaining an ACL graft rupture was greatest in the first 12 months after reconstruction. No other studied variable increased the risk of repeat ACL injury.
Conclusions: After reconstruction, repeat ACL injury occurred in 12% of patients over 5 years. Twelve months after reconstruction, the ACL graft is at no greater risk than the contralateral ACL, suggesting that adequate graft and muscular function for most activities is achieved by this time. Risk factors for repeat ACL injury identified included a return to competitive side-stepping, pivoting, or jumping sports, and the contact mechanism of the index injury. Female patients were at no greater risk of repeat ACL injury than male patients and graft choice did not affect the rate of repeat ACL injury.
Level of evidence: Level IV, case series.