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Hyaline cartilage’s inability to self-repair can lead to osteoarthritis and joint replacement. Various treatments, including cell therapy, have been developed for cartilage damage. Autologous chondrocyte implantation (ACI) is considered the best option for focal chondral lesions. In this article, we aimed to create a narrative review that highlights the evolution and enhancement of our chondrocyte implantation technique: High-Density-ACI (HD-ACI) Membrane-assisted Autologous Chondrocyte Implantation (MACI) improved ACI using a collagen membrane as a carrier. However, low cell density in MACI resulted in softer regenerated tissue. HD-ACI was developed to improve MACI, implanting 5 million chondrocytes per cm2, providing higher cell density. In animal models, HD-ACI formed hyaline-like cartilage, while other treatments led to fibrocartilage. HD-ACI was further evaluated in patients with knee or ankle defects and expanded to treat hip lesions and bilateral defects. HD-ACI offers a potential solution for cartilage defects, improving outcomes in regenerative medicine and cell therapy. HD-ACI, with its higher cell density, shows promise for treating chondral defects and advancing cartilage repair in regenerative medicine and cell therapy.

Introduction: In this work we describe the use of high-density autologous chondrocyte implantation (HD-ACI) to treat 2 patients with chondral defects in the hip. Case Presentation: Two male, 35- and 37-year-old, with chondral lesions and femoroacetabular impingement (FAI) were included. Chondrocytes were isolated expanded in vitro and then implanted at a density of 5 million cells per cm2 onto a type I/III porcine collagen membrane. None of the patients had surgery-derived complications. Pain disappeared in both cases at 6 months after surgery and was maintained until follow-up end (36 months). International Hip Outcome Tool (iHOT) score increased at 6 and 12 months and then leveled off until month 36.Three-year arthro-MRI showed the cartilage defects had been filled with a material similar to the surrounding healthy cartilage. Conclusion: HD-ACI is a safe and effective technique for focal cartilage lesion treatment in patients affected by evolved FAI.

Purpose: To study clinical outcome of patients with bilateral ankle chondral defects treated with High-Density Autologous Chondrocyte Implantation (HD-ACI) in the same surgical act. Cases presentation: Two men (27 and 48 years-old) with chondral defects in both ankles evidenced by MRI. Chondral lesions were treated with HD-ACI in the same surgical act and anesthesia, consecutively. Patients were evaluated 2, 6 and 12 months after surgery to check for treatment safety and efficacy. Pain, evaluated by the Visual Analogic Scale (VAS), decreased from very high values (8.5 – 9) to normal or almost normal scores one year after surgery (0 – 1). Ankle functionality measured by the American Orthopedic Foot & Ankle Society score (AOFAS) and quality of life evaluated by the EuroQol five-dimensional five-level questionnaire (EQ-5D-5L) behaved similarly to pain. Thus, both parameters increased and/or slightly decreased at 2 months (AOFAS score: 53 and 51; EQ-5D-5L score: 0.42 and 0.33) and reached their maximum value at 12 months (AOFAS score: 90 and 89; EQ-5D-5L score: 0.89 and 0.91). MRI from both ankles revealed that chondral defects were filled with a material of similar aspect to the surrounding cartilage. Conclusion: Treatment of both ankles with HD-ACI in the same surgical act in patients with bilateral chondral lesions is a safe procedure, providing positive results from the clinical and patients’ quality of life points of view.