Articular (surface) cartilage injuries of the knee can be devastating injuries. They can occur due to acute traumatic injuries (such as patella dislocations) or can arise in otherwise fit and well people due to vascular anomalies in the underlying supporting bone just below the joint surface (osteochondritis Dissecans). These conditions often occur in people in their late childhood, teenage and young adult years. Not only are immediate symptoms (pain, locking / catching, reduced weight bearing, swelling) problematic, but the knee can go on to develop further issues (osteoarthritis) in later years as a direct consequence.
Thankfully, there are multiple methods that can be employed to treat articular cartilage injuries of the knee. Dr Doneley is experienced in management of these conditions. Most cartilage injuries can be managed using arthroscopic (keyhole) surgery techniques alone. In some instances, open surgery (arthrotomy) is required.
Arthroscopy and Debridement
“Debridement” is the term employed to describe the removal of damaged tissue. In some instances, the most appropriate treatment for cartilage defects of the knee is to perform keyhole surgery to simply remove the loose / unstable cartilage fragments and then perform a “chondroplasty” (cartilage remodelling) procedure where the remaining surface cartilage of the knee is re-shaped (using mechanical shavers and electrical cautery devices) to create a smooth zone of transition between the undamaged regions of the knee and the region of cartilage injury. The greatest advantage of this approach is that the recovery period is usually very quick and does not require splinting, immobilisation or crutches.
This is performed as an arthroscopic procedure. If a very large cartilage fragment or loose body requires removal, one of the arthroscopy “portals” is made a little larger than normal to allow the fragment to be removed.
Microfracture of a cartilage defect is similar to Arthroscopy and Debridement (described above), however, in addition to the steps previously outlined, a reparative procedure is performed to the cartilage defect region to promote growth of fibrocartilage (similar to articular “hyaline cartilage”) within the defect, and in so doing, re-create a smooth joint surface.
The procedure involves cleaning the “crater” of the cartilage defect back to the underlying bone surface and removing unstable cartilage from the crater walls. The bony base of the cartilage defect is then drilled / punctured with fine-pointed instruments in a tight-knit pattern. This “microfracturing” technique allows blood and stem cells that are present within the bone marrow to enter and then fill the “crater” created by the missing cartilage.
The blood forms into a “superclot” in this location and over the course of several weeks, the clot transforms into a type of cartilage called fibrocartilage. Whilst not exactly the same as the normal “hyaline cartilage” of an uninjured knee, this fibrocartilage repair is often indistinguishable on imaging studies and repeat arthroscopy and can provide a very robust repair to the knee.
Due to the delicate nature of the blood clot and repair process, the knee needs to be treated quite differently in the first 6 weeks following surgery compared to simple arthroscopy and debridement. Crutches are usually mandatory and weight bearing is minimised. A splint if often fitted as well. Periods of time using a Continuous Passive Motion (CPM) Machine or an exercise bike set to zero resistance are prescribed every day for the first 6 weeks also. This low-force motion to the knee allows the surface of the clot to be moulded into its ideal shape and contour.
Microfracture is performed as an arthroscopic procedure.
Mosaicplasty is a procedure that is performed for more extensive cartilage defects or defects that have occurred in more vital regions of the knee joint. In this procedure, a cartilage transplant is performed, with cartilage (and its supporting bone) being moved from a less vital region of the knee to where it is more needed. The resultant appearance is that of a mosaic / tiled region at that site of the original cartilage defect (hence the name). The small gaps between the individual cartilage “tiles” fills in with fibrocartilage and the procedure is excellent for restoring the natural surface contour to a knee that has suffered a severe cartilage injury to a vital region. Following surgery, the knee needs to be protected with crutches and limited weightbearing whilst the cartilage tiles heal and bond into place (6 weeks).
Mosaicplasty is most commonly performed as a combined arthroscopic and mini-open procedure.
OCD debridement and fixation
In many cases of Osteochondritis Dissecans, a region cartilage and the bone that it adheres to, can become unstable or even break free from its natural location within the knee. If this is diagnosed at an early enough stage, the bone / cartilage fragment can often be re-fitted back into the location from which it came and then be fixed back into position using mechanical fixation methods. Pins or screws that are made from either absorbable plastic or metal are used. The fragment then heals back into position in much the same manner as healing of a broken bone. Splinting and crutches for at least 6 weeks is required after such surgery.
Fixation of bone / cartilage fragments is most commonly performed as a combined arthroscopic and mini-open procedure.