Autograft anterior cruciate ligament reconstruction results in improved graft synovial coverage and stability, while remnant-preserving techniques further enhance synovialization: A systematic review and meta-analysis.

Purpose: To compare graft synovialization and tear rates between autograft and allograft anterior cruciate ligament (ACL) reconstruction based upon second-look arthroscopy (SLA), along with joint stability, subjective and objective clinical outcomes.

Methods: A systematic search of PubMed, Embase and the Cochrane Library was conducted on 7 March 2025, to identify studies reporting graft synovial coverage and tear rates on SLA following primary ACL reconstruction. Meta-analyses were conducted using a random-effects model with logit transformation. Study weights were calculated via the inverse variance method. Heterogeneity was assessed using Cochran's Q and the I² statistic. Forest plots were created to display individual and pooled estimates with 95% confidence intervals.

Results: A total of 26 clinical studies comprising 2891 patients were included in this systematic review. Of these, 2164 patients underwent ACL reconstruction with autografts and 727 with allografts. SLA was performed in 2009 patients, including 1570 in the autograft group (78.1%) and 481 in the allograft group (23.9%). Good synovial coverage (>50% of the graft) was observed in 1303 autograft cases (83%) and 341 allograft cases (70.9%) (p < 0.001). Poor synovial coverage (<50%) was seen in 146 autografts (9.3%) and 93 allografts (19.3%) (p < 0.001). Torn grafts were found in 125 autografts (8%) and 25 allografts (10%) (n.s.). No significant differences in synovial coverage or graft tear rates were observed when comparing single bundle versus double bundle ACL reconstructions. Mean anterior tibial translation was significantly lower in the autograft group compared to the allograft group (1.23 ± 0.68 vs. 2.00 ± 0.38 mm; p < 0.001). No significant differences were noted in postoperative Lachman (n.s.) and pivot shift tests (n.s.), or in subjective outcomes based on Lysholm (p = 0.05) and Tegner scores (n.s.). However, significantly more patients in the autograft group achieved normal (A) or nearly normal (B) International Knee Documentation Committee (IKDC) objective scores (p = 0.02), whereas higher rates of abnormal or severely abnormal (grades C and D) IKDC scores were observed in the allograft group (p < 0.001). Remnant-preserving ACL reconstruction resulted in significantly better synovial coverage, fewer graft tears and improved knee stability compared to conventional ACL reconstruction (all p < 0.001), with no difference in cyclops lesion incidence (n.s.).

Conclusions: Autograft ACL reconstruction showed superior synovial coverage, lower retear and failure rates, reduced anterior tibial translation and better IKDC objective scores compared to allografts. Remnant-preserving techniques further enhanced synovial coverage, lowered graft tear rates and improved joint stability. No significant differences in synovial coverage, graft tears or failure rates were observed between single bundle and double bundle ACL reconstruction.

Level of evidence: Level IV, systematic review and meta-analysis.