The Influence of Different Autologous Tendons on the Recovery of Knee Muscle Strength Following Anterior Cruciate Ligament Reconstruction: A Systematic Review and Network Meta-analysis

BACKGROUND: Outcomes of anterior cruciate ligament reconstruction (ACLR) vary significantly depending on autograft selection, particularly in restoring knee flexor and extensor strength, which are essential for athletic performance. The aim of this study was to investigate the impact of ACLR with different autografts on the recovery of knee flexor and extensor muscle strength. Subgroup analyses by follow-up duration were performed to characterize recovery across postoperative phases. METHODS: A frequentist network meta-analysis of randomized controlled trials (RCT) and observational studies was conducted. Databases (PubMed, Embase, Web of Science, Cochrane Library) were searched from inception to January 2025. Eligible studies reported isokinetic strength outcomes after ACLR. The primary outcome was the limb symmetry index (LSI) for peak torque, which represented the ratio of injured-limb strength to uninjured-limb strength, reflecting inter-limb symmetry. Secondary outcomes were peak torque, the hamstring-to-quadriceps (H/Q) ratio and side-to-side deficit. Risk of bias (RoB) was assessed using the Cochrane RoB and the Risk of Bias Assessment Tool for Non-randomized Studies (RoBANS). Certainty of evidence was graded using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework. Graft performance was ranked using surface under the cumulative ranking curve (SUCRA) probabilities, and mean differences (MDs) with 95% confidence intervals (CIs) were calculated. RESULTS: Thirty-one studies involving 2384 patients were included in the quantitative analysis. For knee extensor strength, assessed using LSI at 60°/s, 4-strand semitendinosus tendon (4S-ST) and 4-strand hamstring tendon (4S-HT) autografts outperformed bone-patella tendon-bone (BPTB) and quadriceps tendon (QT) autografts. At 180°/s, the 4S-HT autograft showed higher knee extensor strength LSI than the QT autograft, significantly outperformed the BPTB autograft at long-term follow-up (≥ 18 months), and consistently ranked highest according to SUCRA. The BPTB autograft also showed higher knee extensor strength LSI than the QT autograft. For knee flexor strength (LSI, at 60°/s and 180°/s), the QT autograft outperformed the 4S-HT autograft, with SUCRA consistently identifying the QT autograft as the top-ranked option and the 4S-HT autograft as the lowest-ranked option. No significant intergroup LSI differences were observed at short-term follow-up (≤ 6 months), whereas QT autograft's superiority in knee flexor strength became evident in the mid-term follow-up (6-12 months). The 4S-ST autograft may be superior to 4S-HT autograft in knee flexor strength LSI. Network inconsistency tests showed no significant inconsistency. However, GRADE assessments rated the certainty of evidence for comparisons of knee extensor and flexor strength between autografts as very low to low. CONCLUSIONS: The 4S-HT autograft was associated with greater knee extensor strength LSI, whereas the QT autograft had the most consistent advantage in knee flexor strength LSI. The 4S-ST autograft ranked between these grafts, but may provide greater knee flexor strength LSI than the 4S-HT autograft. The BPTB autograft was associated with greater knee extensor strength LSI than the QT autograft. Given the very low to low certainty of evidence, these findings should be interpreted with caution. PROSPERO REGISTRATION NUMBER: CRD42024530838.