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Autologous Chondrocyte Implantation

Autologous Chondrocyte Implantation

The Autologous chondrocyte implantation (ACI) has been a part of treatment approaches for patients with knee cartilage damage since 1987. With the new advancements in the medicinal field, it has evolved greatly and is now one of the most preferred treatment options.

To date, it has been able to treat 85% of the patients allowing them to live a pain-free life. Studies have proved that the overall success rate of ACI is higher in younger patients who have had less than two surgeries previously on their knees and present with a higher preoperative symptom score. While studying its long-term impacts on adolescents who got ACI between 1996 and 2013, 96% reported better knee function.

What Is This Treatment Procedure?

Autologous Chondrocyte Implantation is primarily a surgical procedure used to treat articular cartilage defects that extend to their full thickness in the knee joint. FDA approves the procedure for correcting cartilage defects at the lower end of the femur. However, it is also performed on the kneecap and other body joints for effective treatment.

The process of ACI can be categorized into three generations including;

  • 1st Generation: chondrocytes cells are injected under a periosteal flap
  • 2nd Generation: chondrocytes are implanted under a collagen membrane
  • 3rd Generation: cells either seeded or in scaffold

ACI involves the placement of chondrocytes within the matrix to increase cell delivery through a minimally invasive procedure. This allows the replication of the normal architect of the cartilage through the newly implanted cartilage-producing cells, i.e., chondrocytes. These new cells increase the mesenchymal stem cells and growth factors to boost the growth of new cartilage. In addition, it replaces the area of joint cartilage that has been destroyed to provide exceptional results during the patient’s rehabilitation.

Autologous Chondrocyte Implantation Contraindications

Like every other procedure, there are certain contraindications of ACI in which it is preferred not to go for the surgery as the risk overweighs the benefits. These include the following.

  • Any inflammatory disease of the joints
  • Metabolic disorder
  • The patient is a smoker
  • Chronic use of narcotics
  • More than 55 years old
  • The joint space has narrowed due to loss of more than 50% thickness of cartilage
  • Untreated septic arthritis
  • History of treatment of septic arthritis in last 12 months
  • Crystal deposition
  • BMI of more than 35 kg/m2 (overweight)
  • Collagen allergy
  • Refusal to coordinate during rehabilitation


There are certain factors where ACI is indicated as it is more likely to produce favorable results. These include:

  • Femur, trochlea, and patella showing the defect of more than 2 cm2
  • Patient aged between 13 and 55 years
  • Failure of other treatment options
  • Patients’ approval of coordination for postoperative rehabilitation
  • Defects of osteochondral and focal chondral

Procedure of Autologous Chondrocyte Implantation

The procedure of ACI is divided into a series of stages, out of which the first one takes less than 30 minutes. In comparison, the major surgery of implantation is performed after eight weeks and takes a little longer depending on the joint condition.

Before getting the patient prepped for the surgery, a preoperative assessment is done where the history is taken to identify the nature of the patient’s disability and pain. Moreover, a general physical examination is performed to rule out contraindications. Lastly, scans are obtained, out of which MRI is the most diagnostic in terms of revealing the defects.

In the first stage, the surgeon applies anesthesia and examines the knee area using an arthroscopic probe. Once satisfied, they take out a minimum of 200 – 300g of the cartilage from a non-weight bearing area, mostly superior to the lateral intercondylar notch.

This articular cartilage is then sent for biopsy to isolate and identify the chondrocyte cells responsible for producing the normal cartilage.

Once these cells are obtained, they are cultivated in the lab and increased in number for over 6 – 8 weeks before finally being implanted.

During the second stage, an incision is made to expose the lesion or area of defect for the arthrotomy. Then the defective cartilage is cleaned out until it reaches the healthy one so that a sterile patch can be placed over it and stitched securely. Underneath the patch, the healthy harvested chondrocytes are implanted to fill the space where they later form hyaline-like cartilage, similar to the original one in its characteristics. The incision is then sewed back and left for recovery.

As the patient is recovering, they are clearly instructed not to put any weight on the knee for a minimum of 8 weeks. Physiotherapy plays a key role during the recovery time as it helps regain the mobility and strength of the joint. Most of the time, a continuous passive motion (CPM) machine is suggested to improve the chances of the surgery’s success. After 6 months, the patient can participate in light activities, whereas in 9 – 12 months, they can go back to doing heavy sports.

Autologous Chondrocyte Implantation Complications

Research has identified that despite ACI being a commonly performed procedure, it still has some associated complications. These are as follows.

  • The inability of the implanted cartilage to regenerate and fill the gap of cartilage defect
  • Excessive replication and growth of the chondrocytes resulting in hypertrophy of the cartilage
  • Fusion of the healthy and newly formed cartilage in a disorientated or disturbed manner
  • Delamination, i.e., fracture of new cartilage into multiple layers
  • The buildup of scar tissue resulting in arthrofibrosis

Further studies indicated that the risk of failure or complications after ACI is more likely in the first Generation, where a periosteal patch is used than the collagen one.


Autologous Chondrocyte Implantation is undoubtedly an expensive procedure but one of the best treatment options for joint diseases involving defective cartilage. It costs around $40,000, but this may vary depending on the country it is performed in.

What is the alternative


Cartilage in the knee has a poor blood supply, which is why it struggles to repair and regenerate. It is the oxygen and nutrients in our blood supply that helps to heal and regenerate structures in the body.

Prolotherapy is a non-invasive treatment that involves the injection of regenerative solution into these structures to provide a direct supply of what is required to heal and repair.

As the treatment is helping to treat the root cause of the problem, it is deemed to be a permanent fix.


  1. Minas, T., Ogura, T., & Bryant, T. (2016). Autologous Chondrocyte Implantation. JBJS essential surgical techniques, 6(2), e24. https://doi.org/10.2106/JBJS.ST.16.00018
  2. Mistry, H., Connock, M., Pink, J., Shyangdan, D., Clar, C., Royle, P., Court, R., Biant, L. C., Metcalfe, A., & Waugh, N. (2017). Autologous chondrocyte implantation in the knee: systematic review and economic evaluation. Health technology assessment (Winchester, England), 21(6), 1–294. https://doi.org/10.3310/hta21060
  3. Beck, J. J., Sugimoto, D., & Micheli, L. (2018). Sustained Results in Long-Term Follow-Up of Autologous Chondrocyte Implantation (ACI) for Distal Femur Juvenile Osteochondritis Dissecans (JOCD). Advances in orthopedics, 2018, 7912975. https://doi.org/10.1155/2018/7912975

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