Addition of anterolateral ligament reconstruction to primary hamstring autograft ACLR improves objective rotatory stability and reduces re-tear rates: a systematic review and meta-analysis

BACKGROUND: Anterior cruciate ligament reconstruction (ACLR) aims to restore knee stability following anterior cruciate ligament (ACL) rupture. Although hamstring tendon (HT) autografts are the most used, no meta-analysis has specifically evaluated failure rates following primary ACLR with HT in comparisons between standalone ACLR and ACLR combined with anterolateral ligament reconstruction (ALLR). PURPOSE: To assess whether adding ALLR to HT autograft ACLR reduces rotatory instability and re-tear rates, and to compare associated complications. METHODS: A systematic electronic search was conducted between January and February 2025 using the Nested Knowledge platform (AutoLit, Nested Knowledge), including data from Cochrane, PubMed, Europe PubMed Central, ClinicalTrials.gov, and the Directory of Open Access Journals, along with supplementary manual searches. Search terms included combinations of "Anterior Cruciate Ligament," "ACL," "Anterolateral Ligament," "Antero-Lateral Ligament," and "ALL." Two independent researchers performed screening, and eligible articles underwent full-text review. Inclusion criteria were comparative studies of patients receiving primary single-bundle HT autograft ACLR versus those receiving combined HT ACLR and ALLR. Collected and analyzed data included baseline characteristics; outcomes of pivot shift (PS), laxity measurements, Lachman, and Anterior Drawer tests; complications; re-tear; patient-reported outcome measures (PROMs); and return to athletic activity. The meta-analysis included both prospective and retrospective studies comparing primary HT autograft ACLR with and without ALLR. RESULTS: A total of 4373 studies were screened, and 12 studies comprising 1274 participants were included. The follow-up duration was 31.87 ± 13.36 months in the ACLR group and 31.01 ± 13.25 months in the ACLR-ALLR group. The mean age was 27.08 ± 3.37 years in the ACLR group and 25.00 ± 3.19 years in the ACLR-ALLR group. The injury-to-surgery interval was 6.86 ± 5.41 months and 6.20 ± 5.49 months in the ACLR and ACLR-ALLR groups, respectively. A postoperative PS odds ratio of 0.20 was observed in the ACLR-ALLR group compared with the ACLR group (p < 0.0001), reflecting a relative risk reduction of 81.86% and a number needed to treat of 11.74 to prevent a single event of high-grade pivot shift. Re-tear rates were significantly lower in the ACLR-ALLR group (2.58%) compared with the ACLR group (11.37%) (p < 0.00001). Athletic activity, body mass index, sex distribution, complications, and PROMs were comparable between the two groups (p > 0.05). CONCLUSIONS: This meta-analysis demonstrates that the addition of ALLR to single-bundle ACLR using HT significantly improves both translational and rotatory stability, reduces the incidence of high-grade pivot shift by 81.86%, and lowers re-tear rates from 11.37% to 2.58%. Notably, these biomechanical benefits are achieved without a corresponding increase in surgical complications, while patient-reported outcomes remain comparable. Although ALLR has traditionally been reserved for selected high-risk patients and elite athletes, the present findings suggest that its potential benefits may extend beyond these populations. Future high-quality randomized trials with standardized outcome reporting are warranted to further refine patient selection and define optimal indications.