• Purpose
• Who can have ACI?
• Procedure
• Preparation
• Recovery from ACI surgery
• Risks
• Success rate
• Summary

Autologous chondrocyte implantation (ACI) is a two-step surgical procedure to restore cartilage around a joint and treat cartilage defects.

Cartilage is the connective tissue found throughout the body that protects joints and bones. Cartilage consists of cells called chondrocytes.

“Autologous” means the transplant only involves cells or tissues from a person’s own body rather than a donor.

ACI is a procedure in which healthcare professionals take a small sample of cartilage from the affected area and extract the chondrocytes.

Professionals in a laboratory then expand and increase the number of chondrocytes. Finally, a surgeon returns the expanded chondrocytes into the affected area.

This article explains the purpose of ACI, who may have the procedure, and what to expect before, during, and after the procedure.

What is the purpose of ACI?

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The purpose of ACI is to treat articular cartilage defects or damage. Articular cartilage, or hyaline cartilage, is the cartilage covering the ends of bones where they form joints.

Injury or wear and tear can damage articular cartilage. Articular cartilage has a limited ability to heal itself, so medical treatments are necessary to stimulate new cartilage growth.

Without treatment, articular cartilage defects can cause severe pain, negatively affect joint function, and possibly lead to osteoarthritis.

ACI may permanently resolveTrusted Source cartilage defects. ACI usually treats issues relating to the distal femur, which is where the thigh bone joins the knee.

Surgeons may also use ACI to treat problems with the kneecap, but ACI is suitable for any joint with articular cartilage, such as the:

• ankle
• hip
• shoulder
• elbow
• big toe

Who is a good candidate for ACI?

ACI is a treatment option for certain people with articular cartilage defects. Doctors may consider it when other treatments have not worked. Experts generally recommend ACI for younger people, and it may be a good option for children or young adults.

ACI may also benefit athletes who are able to stop intensive training and competitions for 9 to 12 months. It may help improve an athlete’s quality of life after they retire from their sport. ACI may have the best outcomes among those who have not had any previous surgery on the bone.

Younger people with a single injury may be suitable candidates for procedures that restore articular cartilage. Older people or people with multiple problems within one joint may be less likely to benefit from cartilage restoration.

Read about nonsurgical treatments for knee arthritis.

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What does the ACI procedure involve?

ACI involves two stages: harvesting and implantation.

What does harvesting in ACI involve?

The first stage of ACI is to “harvest,” or remove, the cartilage cells from the affected joint. A surgeon will use arthroscopy to remove a small section of cartilage from a non-weight-bearing part of the joint.

Arthroscopy is a minimally invasive procedure in which a surgeon creates a small incision in the affected area. They then insert an arthroscope, which is a small instrument with a light and camera, into the joint.

The camera images appear on a screen, allowing a surgeon to see inside the joint and carry out the procedure. Once a surgeon has removed the cartilage sample, they close the incision.

A laboratory then receives the cartilage sample and separates the chondrocytes from the tissue. Next, the laboratory cultures or multiplies the chondrocytes for 3 to 5 weeks, increasing the cartilage cells to around 5 to 10 million cells in number.

What does implantation in ACI involve?

People have a second surgical procedure to implant the increased number of chondrocytes.

For implantation, a surgeon will use arthrotomy, a procedure that involves opening a joint. The surgeon will smooth over and prepare the area of damage and then cover it with a patch.

A surgeon then injects the new chondrocytes underneath the patch. The chondrocytes begin to grow within the joint, gradually replacing the area of damage with healthy cartilage.

Preparing for ACI surgery

People will need to follow a doctor’s instructions to prepare for ACI surgery. A doctor will discuss what to expect before, during, and after the procedure, and how to prepare. A person can follow these general preparation steps:

• Aim to get as healthy as possible in the weeks leading up to surgery, including staying physically active if possible, eating a healthy, balanced diet, and getting good quality sleep.
• If people smoke, stop smoking for as long as possible before surgery, as smoking can increase the risk of complications with surgery and healing.
• Follow any instructions around food, drink, and medication before surgery.
• Find some loose-fitting, comfortable clothes to wear after surgery.
• Arrange transportation to get home from the surgery, as people will not be able to drive following the procedure.

Recovery from ACI surgery

Recovery after ACI will include proper wound care and pain management. After ACI, people will follow a physical therapy rehabilitation program to help them recover. This includes therapies such as:

• motion training to help restore normal movement
• partial weight bearing on the affected joint, gradually increasing weight bearing over 3 months until the joint can fully bear weight
• using a continuous passive motion (CPM) machine, which moves the joint by itself to help restore movement

How long is the recovery period after ACI?

A rehabilitation program may last for around 10 to 12 weeks. Physical therapy aims to strengthen the joint and support muscles to restore normal mobility and range of motion.

People may need to wait several months before it is safe to return to strenuous activities or sports. Complete healing may take 12 to 15 months.

What are the risks or side effects of ACI?

As with all types of surgery, ACI has potential risks and complications. The most common complication of ACI is a thickening of the patch that the surgeon inserts into the joint in the implantation stage. Thickening can occur due to an increase in friction and poor surgical technique.

In current procedures, doctors use bioengineered patches rather than patches created from another area of the body. Bioengineered patches have led to complication rates falling below 10%.

In around 5% of cases, the graft may partially or completely loosen. The term for this is “delamination,” and it is a serious complication of ACI. People may require further surgery to treat delamination.

What is the success rate of ACI knee surgery?

A 2022 review found that, in 161 people who received ACI for knee osteoarthritis, the treatment resulted in sustained clinical improvements for up to 11 years, with a failure rate of around 10% in this time frame.

A 2019 studyTrusted Source, which lasted 18 years, examined the success rates of different ACI grafts in the knee. The graft’s 10-year survival rate was 86%.

Arthritis resources

To discover more evidence-based information and resources for arthritis, visit our dedicated hub.

Summary

ACI is a surgical treatment to regenerate cartilage. It can help treat cartilage defects, improve function, and reduce the risk of osteoarthritis.

ACI is a two-step procedure. A surgeon removes cartilage cells from the affected area, and a laboratory then increases the number of cartilage cells.

A surgeon implants the new cartilage cells in the affected area, which then grow and replace the damaged cartilage.

Full recovery may take several months and involves physical therapy to help restore normal mobility to the joint.

Last medically reviewed on December 4, 2024

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