Autologous Chondrocyte Implantation (ACI) is an advanced surgical technique designed to repair damaged cartilage in joints, particularly the knee. Unlike traditional methods that merely relieve symptoms, ACI promotes the regeneration of healthy cartilage using the patient's own cells. This makes it a preferred choice for active individuals suffering from cartilage defects due to injury or wear-and-tear. The procedure has evolved over the years, with newer techniques like matrix-induced ACI (MACI) improving outcomes. ACI is especially beneficial for younger patients who want to avoid joint replacement and maintain long-term joint function.
Cartilage damage can lead to chronic pain, stiffness, and even arthritis if left untreated. ACI offers a biological solution by harnessing the body's natural healing ability. The process involves harvesting healthy cartilage cells, growing them in a lab, and re-implanting them into the damaged area. This two-stage procedure has helped many patients return to an active lifestyle with reduced pain and improved mobility.
ACI is a two-step process that leverages the patient's own chondrocytes (cartilage cells) to repair joint damage. In the first stage, a small sample of healthy cartilage is harvested arthroscopically from a non-weight-bearing area of the joint. These cells are then cultured in a lab for 4-6 weeks, multiplying into millions of new chondrocytes.
In the second stage, the grown cells are implanted into the damaged area. Surgeons use a periosteal patch or a collagen membrane to secure them in place. Over time, these cells integrate with the surrounding tissue, forming new, durable cartilage. Modern variations like MACI use a biodegradable scaffold to hold the cells, simplifying the procedure and improving results. The entire process takes advantage of the body’s natural biology, reducing rejection risks compared to synthetic grafts.
Did You Know? ACI was first introduced in Sweden in the 1980s and gained FDA approval in the 1990s. Since then, advancements like third-generation ACI have made the procedure minimally invasive with faster recovery.
ACI is ideal for patients with localized cartilage defects (typically 2-10 cm²) caused by trauma, osteochondritis dissecans, or early-stage arthritis. Ideal candidates include:
However, ACI is not recommended for patients with advanced osteoarthritis, infections, or severe bone loss. A thorough evaluation by an orthopedic surgeon, including MRI scans, determines eligibility. Weight management and commitment to post-op rehab are also crucial for success.
Stage 1: Arthroscopic Harvesting – A minimally invasive procedure collects a small cartilage sample (about 200-300 mg) from a non-critical joint area.
Lab Culturing – The chondrocytes are isolated and grown in a specialized lab for 4-6 weeks, expanding to 10-50 million cells.
Stage 2: Implantation – An open surgery or mini-arthrotomy is performed. The damaged cartilage is cleaned, and the new cells are implanted under a protective membrane or scaffold.
Closing & Recovery – The area is sealed, and the patient begins a structured rehab program. Full recovery takes 9-18 months, depending on the defect size and location.
Note: Newer techniques like MACI use pre-seeded scaffolds, reducing surgery time and improving cell distribution.
Recovery from ACI is gradual and requires patience. The first 6 weeks involve limited weight-bearing (crutches often required) to protect the healing cells. A continuous passive motion (CPM) machine may be used to stimulate cartilage growth.
Physical therapy starts early, focusing on:
Follow-up MRIs track progress. Patients must avoid high-impact activities (running, jumping) for at least a year to ensure proper cartilage maturation.
ACI offers several advantages compared to alternatives like microfracture or osteochondral grafting:
Unlike microfracture (which creates fibrocartilage), ACI produces stronger, more resilient tissue better suited for active patients.
While ACI is generally safe, potential risks include:
Choosing an experienced surgeon and adhering to post-op protocols minimizes these risks. Some patients may require a follow-up arthroscopy to address minor issues like tissue overgrowth.
Studies report 75-92% success rates for ACI, with outcomes improving as techniques advance (e.g., MACI). Key findings:
Factors affecting success include defect size, location, patient age, and adherence to rehab. While not perfect, ACI significantly outperforms microfracture in long-term durability.