Factors affecting knee laxity following anterior cruciate ligament reconstruction using a hamstring tendon.

Background: The aim of the present study was to investigate the correlation between the pre-operative and intraoperative factors that predict postoperative knee laxity following anterior cruciate ligament (ACL) reconstruction using a hamstring tendon.

Methods: The subjects included 108 patients (male, n=49; female, n=59) with ACL-deficient knees who had undergone double-bundle reconstruction. The median time between injury and surgery (TBIS) was 27.5weeks (range one to 504). The patients were divided into two groups according to the side-to-side difference (SSD) in anterior translation on a stress radiograph one year after undergoing the operation (Group A: SSD of <3mm and Group B: SSD of ≥3mm) and were compared regarding such factors as age at surgery, sex, body mass index, pivot shift test, TBIS, pre-operative laxity, concomitant ligament, meniscus, and articular cartilage injury. A logistic regression analysis was performed to identify the factors associated with knee laxity.

Results: The postoperative SSD values after one year were correlated with the TBIS (r=0.28; P<0.01). Eighty-one and 27 knees were classified into Groups A and B, respectively, based on the SSD at one year after surgery. The TBIS in Group B (60.2weeks) was significantly longer than that in Group A (16.6weeks; P<0.01). A logistic regression analysis showed that there was a significant association between the TBIS and postoperative knee laxity (P<0.01; odds ratio 1.013; 95% CI 1.002-1.023).

Conclusion: Increased knee laxity was associated with the time between injury and surgery.