Autologous Chondrocyte Implantation for Knee Cartilage Defects: Five-Year Follow-Up

Abstract

Background: Autologous chondrocyte implantation (ACI) has evolved through three technical generations for treating
symptomatic articular cartilage defects of the knee, yet its comparative durability against microfracture and osteochondral
grafting remains debated. Objective: To synthesise evidence on ACI's generational evolution and five-year and longer functional outcomes, durability, andreturn to sport relative to alternative cartilage repair techniques.Methods: Narrative review of randomised trials, long-term cohort studies, and meta-analyses.Findings: Randomised trials show ACI and matrix-induced ACI (MACI) achieve functional outcomes equal to or better thanmicrofracture at two to five years, with superior durability beyond five years, particularly for larger defects; MACI reoperationrates at 10-17 years (9.0%) are markedly lower than pooled first/second-generation ACI failure rates at 11.4 years (18%).Conclusions: ACI/MACI provides durable, generation-dependent improvement in knee function, favouring larger defects and younger patients, though comparative superiority over osteochondral grafting remains procedure- and lesion-specific.