Background

Recent literature has focused on identifying potential risk factors for contralateral anterior cruciate ligament (ACL) injury and reconstruction. However, there is a lack of studies comparing the results of contralateral ACL reconstruction (ACLR) with those of primary ACLR. Patients undergoing contralateral ACLR need thorough counselling regarding their expectations after surgery. Studying a cohort of patients who consecutively underwent ACLR in both knees would accurately determine the results of contralateral ACLR in comparison with those of primary ACLR. These findings would be helpful for clinicians to inform and set expectations for patients undergoing contralateral ACLR.

Purpose

To evaluate and compare knee laxity and functional knee outcome between primary and contralateral ACLR.

Methods

Patients who underwent primary and subsequent contralateral ACLR at our institution, from 2001 to 2017, were identified in our local database. The inclusion criteria were: the same patients who underwent primary and contralateral hamstring tendons or bone-patellar tendon-bone autograft ACLR and no associated ligament injuries. The KT-1000 arthrometer, with an anterior tibial load of 134-N, was used to evaluate knee laxity preoperatively and 6 months postoperatively. The Knee injury and Osteoarthritis Outcome Score (KOOS) was collected preoperatively and at the 1-year follow-up.

Results

A total of 326 patients with isolated primary and contralateral ACLR met the inclusion criteria (47.9% males; mean age at primary ACLR 23.9 ± 9.4 years and contralateral ACLR 27.9 ±10.1 years). An ANOVA for repeated measurements was used for comparisons of laxity and KOOS subscales scores between primary and contralateral ACLR. The arthrometric laxity measurements were available for primary and contralateral ACLR for 226 patients. The mean preoperative and postoperative anterior tibial translation (ATT), as well as the mean ATT reduction from preoperatively to postoperatively, did not differ significantly between primary and contralateral ACLR. The KOOS was available for primary and contralateral ACLR for 256 patients. No significant differences were found preoperatively and at the 1-year follow-up between primary and contralateral ACLR for any of the five KOOS subscales.

Conclusions

The findings in this study showed that anterior knee laxity and functional knee outcome after contralateral ACLR are comparable to those after primary ACLR. It is important for clinicians to counsel patients about their expectations after contralateral ACLR. This study shows that the results after contralateral ACLR in terms of knee laxity and functional knee outcome are predictable and likely to be comparable to those after primary ACLR.