Overview of Cartilage Graft
Joint pain is a common issue that can be caused by a variety of reasons such as injuries, diseases, or conditions. From 2013 to 2015, it was estimated that almost 23% of adults in the United States were diagnosed with some form of arthritis or similar conditions. This shows how widespread the problem of joint pain is.
For a long time, medical professionals have been trying to understand the reason behind joint pain so they can come up with ways to provide relief. Joint pain, particularly arthritis, is one of the most common and costly health issues. In 2013, around $140 billion was spent in the US for treating arthritis. And with more people growing old, the cost is expected to double or even triple in the next few years. So, finding effective treatments is both crucial and economically necessary.
The knee is one of the joints that are most often affected by cartilage loss. People over 45 years old are particularly susceptible, with reported cases of knee osteoarthritis ranging from 19.2% to 27.8%. Moreover, in a national health survey, nearly 37% of participants aged 60 and above showed signs of knee osteoarthritis in their X-ray results.
Therefore, a lot of focus is put into finding ways to repair the knee’s damaged cartilage. One known surgical operation is osteochondral allograft transplantation. This involves transferring a piece of cartilage (the substance that lets your joints move smoothly) and a small amount of bone from a donor’s knee to the damaged area. Imagine fixing a pot or hole on a street by filling it with new asphalt and underground layers, that’s how this surgery works. It’s effective in treating large cartilage defects or arthritis caused by a previous injury.
Anatomy and Physiology of Cartilage Graft
The articular cartilage, also known as hyaline cartilage, is a part of the body that we need to understand well if we are preparing for a procedure known as osteochondral allograft transplantation. This cartilage helps bones to move smoothly against one another in the joints.
About 65% to 80% of the cartilage is made up of an extracellular matrix, which is a mesh-like material within the cartilage. This matrix consists of water, a protein called type II collagen, and another substance called proteoglycan.
There are cells within the cartilage called chondrocytes that make the collagen, proteoglycans, and enzymes. These cells are formed from something called chondroblasts, and they react to physical pressure and changes in fluid pressure.
Regular articular cartilage is made up of four main layers:
1. The superficial zone, also known as the tangential zone, is the top layer and has the highest amount of collagen and the smallest amount of proteoglycans. Collagen fibers in this zone run parallel to the joint. This is the only place where you’ll find cells called articular progenitor cells.
2. The intermediate zone is beneath the superficial zone and is the thickest layer. It has quite a bit of both collagen, which is randomly oriented, and proteoglycans, which makes it different from the other zones.
3. The deep zone, or basal layer, is located under the intermediate zone. This zone has the highest volume of proteoglycans and the lowest volume of collagen, and the collagen fibers here go perpendicular relative to the joint.
4. The tidemark is the deepest layer and separates the cartilage from the bone beneath it, known as the subchondral bone.
Why do People Need Cartilage Graft
Osteochondral allograft transplantation is a treatment recommended for sizeable, painful cartilage damage within joints. It specifically treats damage areas larger than 2 cm x 2 cm. For smaller injuries, alternative treatments like using a graft from the patient’s own tissues or a technique known as microfracture can be used effectively.
Many studies have discovered that severe cartilage damage suitable for this kind of transplantation makes up 5 to 20% of all patients getting a joint examination done via a scope. About 4 to 5% of these patients are younger than 40 years old. It’s also worth noting, about half of these patients experienced this cartilage damage due to trauma.
Many younger patients, whose symptoms failed to improve without surgery, may find relief from cartilage transplant procedures. This treatment could potentially enhance their quality of life and help avoid more invasive surgeries, like joint replacement, in the future.
When a Person Should Avoid Cartilage Graft
There are certain cases where people would be advised not to go through with a type of surgical transplant called ‘osteochondral allograft transplantation’, which is a procedure used to treat damaged or diseased bone or cartilage. People at a continued high risk for a condition called osteonecrosis, where there’s not enough blood reaching your bone, causing it to break down, are often advised to avoid this type of surgery.
Folks who are regular users of a type of anti-inflammatory medicine known as corticosteroids are also often cautioned against this operation.
Smoking cigarettes and having a history of inflammatory arthritis, where your immune system mistakenly attacks the cells in your joint capsule, are circumstances that could prevent you from being suitable for this surgery.
On a related note, the surgery is usually not recommended in instances where there’s a lack of meniscus (a cartilage that acts as a cushion in the knee). This condition is often flagged through techniques like MRI scans, which use magnetic fields and radio waves to make a detailed image of the inside of your body, or diagnostic arthroscopy, which is a minimally invasive procedure used to identify problems in a joint.
Various studies have shown that a surgery called ‘meniscal allograft transplantation’, which involves transplanting a donor’s meniscus into a patient, can improve the chances of the bone or cartilage graft surviving after surgery.
Preparing for Cartilage Graft
Osteochondral allografts, or pieces of bone and cartilage, that are used for transplants come from tissue banks supervised by the Food and Drug Administration. These tissues are usually sourced from donors who passed away within 24 hours and are ideally between the ages of 15 and 40. The cells in the cartilage, known as chondrocytes, need to stay alive for the transplant to work.
Success in these transplants depends on several factors. These include an intact outside layer of the tissue, living chondrocytes, and the patient’s own bone accepting the new graft. These allografts can be stored in a fresh state, frozen or cryopreserved, and each method affects the tissue’s properties in different ways.
It’s found that keeping the grafts fresh has the highest chance of keeping the chondrocytes alive, especially if stored at room temperature. For safety reasons, the tissue donors are tested for diseases like HIV, hepatitis B and C, and HTLV (human T-lymphotropic virus) before the tissue is harvested.
How is Cartilage Graft performed
Whether you need a medical procedure involving a donated bone graft to fix a defect in the cartilage of your joint depends on the size and location of the gap in the cartilage. Smaller gaps can be filled with a single graft, which perfectly fits into the gap, giving full coverage of the cartilage shortfall and blending in well with the surrounding tissues.
It’s worth knowing that, because cartilage is quite soft, it’s not possible to transplant only the cartilage. It must be transplanted with some of the underlying bone because this supports the cartilage and keeps it in place.
For larger gaps in the cartilage, a larger cut may be needed in the joint so as to fully see the defect and ensure that the entire gap is appropriately filled. It’s very important that a healthy rim of cartilage can interface with the edges of the graft so that the new tissue can integrate properly.
There are a few different methods to replace larger areas of missing cartilage. For example, the “Snowman” or mosaicplasty technique uses two grafts. The first graft is placed and held in place, then the second graft is added, slightly overlapping the first. This covers a larger joint surface and the two grafts “flow” into each other. It’s a bit like how small, round tiles fit together to cover a larger floor surface.
The “Shell” technique is great for irregularly shaped cartilage gaps and gaps that are hard to get to with a standard cut into the joint, like defects on the back side of the thigh bone close to the knee. With this technique, the entire affected recipient site can be completely removed. A matched donor bone is shaped and positioned to cover the recipient lesion, acting as a protective “shell”.
Alternatively, the “small fragment allograft” technique might be used for defects of the tibial plateau (the top part of your shin bone) where the entire unit is replaced by a donor unit and held in place with a screw.
While we are talking about bone grafting methods, it’s worth mentioning that there are new technologies that use scaffolding or membranes made out of cartilage that can be stitched or glued to the cartilage defects found in the knee. This is a promising new approach that, in some cases, will mean a bone graft isn’t needed.
Possible Complications of Cartilage Graft
Like any surgery, there’s always a small chance of experiencing pain, bleeding, or damage to nearby body parts during an arthroscopy when conducted by a well-trained surgeon. There’s also a low risk of getting an infection. The most significant worry is that the graft (the tissue used to repair the damage) might not survive.
In cases where people undergo this procedure to treat injuries, the success rate is quite high with grafts lasting well in the long-term. However, the graft may not survive as long in people with cartilage damage due to post-traumatic arthritis, diseased bone tissue, or bone disease.
To achieve the best results, it’s vital to identify and treat the underlying cause of the cartilage damage. If a person’s cartilage issue stems from a physical abnormality or a health disorder, and this isn’t addressed, the surgery could fail. This could potentially worsen the joint’s function.
What Else Should I Know About Cartilage Graft?
Defects in the articular cartilage (the smooth, white tissue that covers the ends of bones where they come together to form joints) often cause pain and discomfort, significantly impacting a person’s quality of life. If non-surgical treatments don’t work, a method known as osteochondral autograft or allograft transplantation is a good option. This procedure involves transplanting healthy cartilage from the patient or a donor to the damaged areas.
This treatment can significantly reduce or even eliminate joint pain, allowing patients to resume their regular activities without resorting to more intrusive or risky procedures like total knee replacement surgery. Maintaining an active lifestyle is essential for good physical and mental health.
