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Cartilage Reconstruction

Chondral (cartilage) reconstruction is a series of techniques and evolving technologies for treating localized loss / damage to articular cartilage. Cartilage reconstruction is not and will not be a treatment for arthritis in the foreseeable future. Cartilage reconstruction may however prevent arthritis developing in an otherwise normal knee. Articular cartilage is highly specialized tissue that is difficult to reproduce. None of the current techniques available to deal with chondral defects produces perfect articular cartilage and all have quite long and initially restrictive rehabilitation protocols. The ideal candidate for cartilage reconstruction has a single lesion, supported by a normal meniscus and an undamaged opposing cartilage surface in a stable, well aligned knee and who is willing and able to comply with the rehab protocol. Age is a less important consideration although 15 years olds are always going to heal better than 50 year olds. Any coexisting pathology needs be dealt with at the same time so cartilage reconstruction is frequently combined with ligament reconstruction and bone realigning procedures (osteotomies). Multiple cartilage lesions can be treated at the same time provided they are not kissing lesions (2 lesions on opposing surfaces in contact with each other). The most common scenarios in which isolated chondral lesions are found are in association with ACL rupture, patellofemoral dislocation and Osteochondritis Dissecans.

Numerous techniques can be used to reconstruct cartilage. They include:

  1. Microfracture: The cartilage lesion is cleared to its bone base and to a healthy surrounding cartilage margin. A series of tiny holes (microfractures) are made in the bony base of the lesion. A blood clot which contains bone marrow stem cells fills the defect and matures over a period of many months into fibrocartilage. This technique is cheap and produces reasonable but unpredictable results. The stem cells in the bone marrow can make bone as well as cartilage and the cartilage that is formed is fibrocartilage (repair cartilage) not proper articular cartilage. Frequently therefore the result of a microfracture an overgrowth of bone covered by a very thin layer of cartilage. Looks OK but may not function normally or durably.

  2. ACI / MACI: This is a two stage technique that begins with an arthroscopic (keyhole) harvest of articular cartilage from the knee. The harvested cartilage is sent to a laboratory, the cartilage cells are removed from the cartilage matrix, stimulated to reproduce and sent back to the surgeon for reimplantation around 6 weeks later. With ACI the cells are in a liquid solution and in MACI they are attached to a collagen membrane. MACI evolved out of ACI and was widely used in Australia until the Federal Government recently withdrew Medicare funding for the technique. MACI is very expensive and although it produces better cartilage than a microfracture the results may not be sufficiently superior to microfracture to warrant the frightful expense. MACI may be made available again as a research technique but probably will not be generally available again.

  3. Autologous Osteochondral Transfer (OAT): OAT has been around for over 20 years and is a very useful technique. OAT involves moving cylindrical grafts of cartilage and bone from an area where no load is taken into the cartilage defect. OAT has its limitations and is technically unforgiving but does leave proper articular cartilage in the grafted area. Because the graft comes from the knee itself the size of the lesion that can be grafted is limited by the amount of donor tissue than can be harvested without causing problems at the donor site. OAT is the procedure of choice for treating an Osteochondritis Dissecans lesion in-situ.
    Fig 1. Cartilage lesion on
    medial femoral condyle.
    Fig 2. Same lesion after
    OAT reconstruction.

  4. Biomimetic Nanomatrix Implantation: Nanomatrix technology is set to revolutionize musculoskeletal surgery. First generation nanomatrices are just now becoming available and will evolve rapidly in coming decades. A nanomatrix provides an environment in which bone marrow stem cells can live while they reconstruct the cartilage defect. The trick is getting the stem cells to make bone where bone belongs and articular cartilage where it belongs. Nanomatrices do this by using bone like crystals embedded in the nanofibres to stimulate bone formation in the deeper layers only. Nanomatrices are implanted into a slot in the host bone rather than laid on the surface of the bone as occurs with a MACI. Nanomatrix technology is new and no long term results exist. Work in animals has produced some very exciting results and as this technology evolves over the coming decades many new frontiers are set to opened up.
Fig 3. Implanted nanomatrix (animal). Fig 4. Mature graft
Fig 5. Defect preparation. Fig 6. Nanomatrix implanted


All of the above techniques are done through keyholes or reasonably small incisions. They are frequently combined with other procedures such as osteotomy and ligament reconstruction. They are done as day procedures or with a night in hospital depending on the technique used and what other surgery is combined with it.

Elevation and ice therapy are important to minimize pain and swelling in the first two weeks. No cartilage reconstruction will tolerate weight bearing, unrestricted motion or powerful muscular contraction across the knee in the first six weeks. Crutches and usually knee splints are required for six weeks regardless of the technique. Full weight bearing and full unrestricted movement is allowable around 10 weeks and gentle resistance work begins around three months. Impact loading (running) comes much lateral depending on the technique but generally is around six months with OAT and around 10 months with the other techniques.

Risks and Complications

As with any surgery, there are potential risks involved. The decision to proceed with the surgery is made because the advantages of surgery outweigh the potential disadvantages.

It is important that you are informed of these risks before the surgery takes place.

  • Infection. Infection can occur with any operation. In the knee this can be superficial or deep. Superficial infections are treated with antibiotics. Deep infections always require surgical treatment as well as antibiotics. Deep infection is an uncommon but very serious complication and many measures are employed during the course of having a cartilage reconstruction to prevent it. A new cartilage graft is completely unable to resist infection and a deep wound infection invariably destroys the graft
  • Blood Clots (Deep Venous Thrombosis).These can form in the calf muscles and can travel to the lung (Pulmonary embolism). These can occasionally be serious and even life threatening. If you get calf pain or shortness of breath at any stage, you should notify your doctor. As with infection, many measures are employed to prevent this complication. These include compression stockings, calf compressors, IV fluids, blood thinning medications but by far the most important is early mobility.
  • Stiffness in the Knee (Arthrofibrosis). This very uncommon can occur in around. Controlling swelling is the key to early movement and movement prevents stiffness. Ice therapy and elevation is critical in the first two weeks.
  • Neurovascular injury (Damage to nerves and blood vessels). Cartilage grafting is done through safe surgical corridors and major nerves and arteries are not at risk.
  • Graft Failure. In ideal circumstances the above techniques have success rates of around 90%. This figure rapidly diminishes outside of ideal circumstances. For this reason many cartilage reasons are not worth reconstructing as the results don’t warrant the time, expense and risk involved. If you have an ideal lesion strict adherence to the rehab protocol is very important if damage to an immature graft is to be avoided.
  • Numbness. The skin on the outside edge of the incision will be numb after the surgery. Most people are very aware of this in the first 6 months after surgery. The sensation of numbness fades with time but probably never returns absolutely to normal.
Dr. Peter McEwen - Surgery of Knee
Dr. Peter McEwen - Surgery of Knee
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Arthroscopic Surgery - Dr. Peter McEwen - Surgery of Knee
Cartilage Repair - Dr. Peter McEwen - Surgery of Knee
Partial Knee Replacement - Dr. Peter McEwen - Surgery of Knee
Realignment Surgery - Dr. Peter McEwen - Surgery of Knee
Total Knee Replacement - Dr. Peter McEwen - Surgery of Knee
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Australian Orthopaedic Association Royal Australasian College of Surgeons
International Cartilage Repair Society International Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine
Crocodiles Orthopaedic Research Institute of Queensland

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