Acute anterolateral knee instability in adults: combined proximal ACL and ALL injury repair is not inferior to standard ACL reconstruction with LET in 2 years.

OBJECTIVES: The objective was to compare the clinical results of ACL and ALL repair with those of standard ACL reconstruction + LET. The hypothesis was that combined repair is non-inferior to standard reconstruction + LET in adults with acute anterolateral knee instability. METHODS: Patients with severe acute anterolateral instability (ACL + ALL injuries) who underwent early ACL surgery (injury-to-surgery interval < 14 days), a total of 58 patients, were prospectively enrolled in the study. ACL injuries were classified according to the Sherman classification. Patients with a proximal injury (types 1 and 2) were assigned to receive ACL repair (ACLrep) (n = 37), patients with types 3 and 4 and moderate tissue quality (n = 21) were assigned to receive ACL reconstruction (ACLrec) + lateral extra-articular tenodesis (LET). Repair consisted of transosseous suture of the stump to the anatomic origin of the ACL and direct repair of the ALL. Reconstruction consisted of standard ACL reconstruction by semitendinosus-gracilis (STG) autograft + LET. PROMs included IKDC, Lysholm, KOOS, and assessment of anteroposterior (AP) knee laxity in 2 years. RESULTS: A sample size calculation showed that 21 patients in each group were needed for a 95% power (with a 95% CI) to show non-inferiority of the repair group considering an arthrometric side-to-side difference of at least +1.5. Patients in the ACLrep group showed better results on all scales: mean IKDC was 95.51 ± 52.4 versus 86.92 ± 13.92 (p = 0.02); mean KOOS was 97.49 ± 2.71 versus 93.50 ± 7.05 (p = 0.009); and mean Lysholm was 96.98 ± 5.14 versus 91.69 ± 10.08 (p = 0.02). There was no difference in the KT1000 measurement (ACLrep: 1.70 ± 1.02; ACLrec: 2.21 ± 0.80; p = 0.11). The one-sided 95% CI was 1.7 (to 2.02) (< at the 3.01 limit for non-inferiority) for ACLrep and 2.21 (to 2.46) for ACLrec, p = 0.147. Therefore, non-inferiority was proven CONCLUSION: In acute knee instability resulting from a combined ACL and ALL injury, direct repair is non-inferior in terms of PROM and knee laxity compared to standard ACL + LET reconstruction in 2 years.