Revision anterior cruciate ligament reconstruction restores knee laxity but shows inferior functional knee outcome compared with primary reconstruction

PURPOSE: To evaluate and compare knee laxity and functional knee outcome between primary and revision anterior cruciate ligament (ACL) reconstruction in the same cohort of patients. METHODS: Patients who underwent primary and revision ACL reconstruction (ACLR) at Capio Artro Clinic, Stockholm, Sweden, from 2000 to 2015, were identified in our local database. Inclusion criteria were: same patients who underwent primary hamstring tendons (HT) and revision bone–patellar tendon–bone (BPTB) autograft ACLR, no associated ligament injuries and no contralateral ACL injuries/reconstructions. The cause of revision ACLR was graft rupture for all patients. The KT-1000 arthrometer, with an anterior tibial load of 134-N, was used to evaluate knee laxity preoperatively and 6-month postoperatively. The Knee Injury and Osteoarthritis Outcome Score (KOOS) was collected preoperatively and at the 1-year follow-up. RESULTS: A total of 118 patients with primary and revision ACLR arthrometric laxity measurements were available (51.0% males; mean age at primary ACLR 21.7 ± 7.1 years and revision ACLR 24.3 ± 7.5 years). The mean preoperative and postoperative anterior side-to-side (STS) difference values were not significantly different between primary and revision ACLR. However, primary ACLR showed a significantly higher frequency of postoperative anterior STS difference > 5 mm compared with revision ACLR (8.4 vs 5.0%; P = 0.02). The KOOS was available for primary and revision ACLR for 73 patients (55.4% males; mean age at primary ACLR 21.6 ± 7 years and revision ACLR 24.7 ± 7.3 years). Preoperatively, revision ACLR showed significantly higher scores in all KOOS subscales, except for the activity of daily living (ADL) subscale. For the primary ACLR, the improvement from preoperatively to the 1-year follow-up was significantly greater in all KOOS subscales and, the postoperative scores were superior for Pain, ADL and Sports subscales compared with revision ACLR. CONCLUSIONS: The findings of this study showed that anterior knee laxity is restored with revision BPTB autograft ACLR after failed primary HT autograft ACLR, in the same cohort of patients. However, revision ACLR showed a significantly inferior functional knee outcome compared with primary ACLR. It is important for clinicians to inform and set realistic expectations for patients undergoing revision ACLR. Patients must be aware of the fact that having revision ACLR their knee function will not improve as much as with primary ACLR and the final postoperative functional outcome is inferior. LEVEL OF EVIDENCE: Retrospective cohort study, Level III.