TREATING KNEE CARTILAGE INJURIES

Cartilage repair is at the forefront of orthopaedic surgery with new techniques being developed and their outcomes undergoing ongoing assessment.

When orthopaedic surgeons talk about "cartilage", we are talking about two different anatomical structures.

ARTICULAR CARTILAGE

Joints are coated with highly specialised "articular" cartilage.

This is a lubricated, low friction surface that allows joint movement. This can unfortunately become damaged with injury or as a result of arthritis. If the damaged area is of limited size, it is possible to treat it with a number of developing and established techniques


1) The simplest method is "edge stabilisation abrasion or radiofrequency chondroplasty" - a method of arthroscopically (keyhole) treating the damaged unstable tissue to reduce pain and facilitate the limited ability of articular cartilage to undergo intrinsic repair.

2) Microfracture or arthroscopic drilling - a method of stimulating the bone marrow to release cells that can "sit" in the cartilage defect and differentiate into cells that produce predominantly "scar" cartilage. This technique is generally reserved for smaller (less than 2cm squared) defects. It is a one stage procedure.

3) Combination arthroscopic drilling/microfracture and biomaterial "scaffold" - using a bioengineered substance in combination with the above mentioned technique to produce a more stable healing construct. This substance is generally either a "patch" or gel of collagen/protein. Some work is being done with carbon pads for larger lesions that looks promising.

4) Cell-ingrowth scaffolds - new products are being developed that act as scaffolding material for the surrounding healthy cartilage to grow into. (See Maio Regen)

5) Osteochondral autografts (OATS - osteochondral autologous transfer system)- cartilage and bone can be moved from one area of the joint to another. The main problem here is that almost all parts of a joint carry out a role in healthy joint movement. This procedure "sacrifices" the cartilage and bone from one "less essential" area and moves it (normally as a tube of cartilage and bone) to the damaged "more important" area. This is normally an area where more of the body weight is borne.

6) Osteochondral allografts - cartilage and bone can be moved (transplanted) from a different person's (or animal's) joint to the damaged area of the patient's joint. Graft survival rates are moderate with this technique

7) Autologous chondrocyte implantation - this is a 2 stage procedure where a small amount of cartilage is taken from the patient's joint at a first operation, and sent for processing in a lab. The cartilage cells (chondrocytes) are encouraged to multiply and specialise (or differentiate) to become good quality cartilage-generating cells in the lab environment. At a second procedure, the cells can then be put back into the damaged area of the joint, normally fixed onto a collagen membrane to facilitate the procedure.

 A re-arthroscopy of a cartilage injury thas has been repaired with "ACI"

  

8) Replacement of the damaged area with a micro, partial or total replacement

 

MENISCAL CARTILAGE

There are 2 "menisci" that sit on the inner and outer sides of the knee. Either meniscus is made of resilient fibrous cartilage and has more or less the shape of a "C". The 2 menisci carry out a very important role of:

a) shock absorption - acting as a cushion and defending the knee from articular cartilage injury

b) load transmission - distributing load to the knee to minimise "peak loading pressures"

c) joint lubrication and nourishment As a vital part of the joint,

its key function is to prevent the deterioration and degeneration of articular cartilage, and the onset and development of osteoarthritis. If damaged, it should often be treated since it provides an important cushion that protects the articular cartilage and helps to prevent knee arthrosis/arthritis. The medial meniscus is closely situated to the medial collateral ligament, which makes it less mobile and it is more prone to injuries for this reason.

A normal medial meniscus 

 

Research into meniscus repair has been the recipient of particular interest from the orthopedic community.

"Repair" attempts to stabilise the damaged meniscal cartilage by sewing it back together, to improve the chance that it will heal and continue protecting the knee's articular cartilage. If a damaged cartilage cannot be treated by repair it is often removed. Only the minimal damaged tissue should be removed to leave a stable residual rim as the relative risk of arthritis is up to 14x after total meniscal resection (at 20 years follow up).

Tears are more likely to heal in younger patients with smaller tears treated promptly after injury.

On the other side, tears in older patients that are more extensive and are delayed in receiving treatment, are less likely to heal.

Mr Arbuthnot is currently auditing the outcomes of the last 100 meniscal repairs he has carried out. 


Meniscal repair suture being advanced into position