Cartilage (hyaline cartilage or articular cartilage) is a 3-5 mm thin tissue that coats the boney surfaces inside our joints. It provides a very low friction articulation that ideally lasts a lifetime.
Cartilage can be damaged acutely through accidents, such as ACL tears or patellar (kneecap) dislocations, or degenerate slowly over time, eventually leading to osteoarthritis (wear and tear, rather than inflammatory arthritis).
Cartilage damage can start as a local "pothole" in the cartilage, that then enlarges with time until all cartilage is worn away and patients have bone-on-bone arthritis. These potholes can be treated with cartilage repair, while bone-on-bone arthritis is treated with osteotomies in younger and active patients. Older and more sedentary patients generally undergo joint replacement surgery.
Cartilage repair includes various surgical procedures such as microfracture, osteochondral autograft transfer (also known as OATS or Mosaicplasty), osteochondral allograft transplantation and autologous chondrocyte implantation (ACI/Carticel). These procedures are designed to heal cartilage damage by filling the cartilage defect with repair tissue.
The choice of procedure depends on the size and location of the defect. Generally speaking, larger defects are treated with ACI or osteochondral allograft transplantation, both of which require open incisions. Smaller defects in specific locations can be treated with microfracture or osteochondral autograft transfer, which can be performed with smaller incisions.
Once bone-on-bone arthritis has developed, cartilage repair is not an option anymore, and patients can be considered for joint replacement surgery or osteotomy (realigning a leg that is very bowlegged or knock-kneed).
Since cartilage repair has a long recovery time of up to one year before the patient can return to unrestricted activities, such as running or basketball, it is mainly performed in younger, active patients where joint replacement is not an option. Even though we have treated suitable patients as old as 60 with cartilage transplants, this is rare and our average patient is between 16 and 45 years of age.
Very generally speaking, patients will spend 1-3 days in the hospital, then use crutches for 8 weeks. They can return to stationary biking at 4-6 weeks, swimming and elliptical trainer at 8-12 weeks, and light jogging at 1 year. Unrestricted activities such as basketball, squash or longer-distance running is permitted after 18 months.
The transplant tissue grows and firms up over time, and early activity can harm or destroy the tissue.
While knee replacement is a very successful operation in older patients, as a mechanical implant it does not last forever (10-25 years). Once worn out, it has to be re-replaced (revision), a more difficult operation with lesser outcomes and patient satisfaction. Therefore, knee replacement surgery is ideally delayed until after age 50 or 60 if possible. Even though cartilage repair cannot guarantee that a knee replacement can be avoided forever, it has the potential to delay replacement until the patient is older and does not require one, or multiple, revision surgeries.
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