Cartilage is not only worth saving, but also worth rebuilding. That's why talented surgeons and scientists around the world have been working hard for decades to find methods to reconstruct cartilage to injured area. Microfracture is one of the most common method in limited size lesions, and perhaps to most widely known method at the moment. For larger lesions, there are many techniques available. Cartilage surgery results in specialised units can even give over 80-90% success in joint reconstruction.
Cartilage reconstruction can be done as arthroscopic or open surgery depending on damaged cartilage area location and reconstruction technique used. The majority of cartilage reconstruction procedures are performed in the knee joint, though many operative techniques can be performed also in other joints, for example in ankle and shoulder. It is absolutely important that results of cartilage surgery are documented, that is why ICRS (www.cartilage.org) has initiated a world-wide registry for follow up of treatment results. Registry is available for cartilage surgery units.
Cartilage reconstruction can be done as arthroscopic or open surgery depending on damaged cartilage area location and reconstruction technique used. The majority of cartilage reconstruction procedures are performed in the knee joint, though many operative techniques can be performed also in other joints, for example in ankle and shoulder. It is absolutely important that results of cartilage surgery are documented, that is why ICRS (www.cartilage.org) has initiated a world-wide registry for follow up of treatment results. Registry is available for cartilage surgery units.
saloplasty
Professor Salo has worked with bone and cartilage biology for a long time. His initial idea on using DBX Putty® in joint reconstruction goes back to early 2000's. At those years he was responsible for for use of different kind of bone void fillers in Helsinki University Hospital Trauma Center. That was the time when commercial osteoconductive and osteoinductive products came widely on the market. Since then he systematically went through literature and gathered results on bone healing with different DBMs. It seemed quite evident that based on earlier data, DBM should be able to stimulate both bone and cartilage reconstruction, and could perhaps be used in joint facet reconstruction. It was in 2005 when the first operation with DBX Putty® was performed to fill up a large defect in elbow after fracture. At the same time a severe lateral condyle defect in tibia was reconstructed with the same method, requiring more than 20 cc putty graft. After following up two different kind of defects it was evident that at least the functional outcome was much better than could have been expected. Since those years Salo has developed these techniques so that even large tissue defects in knee and ankle area can mostly be treated by arthroscopic surgery. Large cavity used in abrasion arthroplasty has been modified to 4,5 mm drillings in bone to give larger contact area to bone and pericyte-MSC cells per each square-cm of cartilage defect, and to save mechanical support of subchondral bone plate.
Very shortly, use of this kind of filler makes it possible to reconstruct large defects arthroscopically, prevents excess bleeding in joint, and serves as a stimulant for pericyte-MSC line cells to produce bone and cartilage. A strong guiding factor for tissue growth in these surroundings is blood circulation. Joint space side is typically with poor blood circulation leading to lower oxygen levels and pH values. These prevent bone formation but favor cartilage formation. Early mobilisation leads to mechanical stimuli on joint surface further enhancing cartilage formation. In subchondral bone pH is more neutral and oxygen levels higher, making bone formation possible in mechanically stable surroundings. See more...
Very shortly, use of this kind of filler makes it possible to reconstruct large defects arthroscopically, prevents excess bleeding in joint, and serves as a stimulant for pericyte-MSC line cells to produce bone and cartilage. A strong guiding factor for tissue growth in these surroundings is blood circulation. Joint space side is typically with poor blood circulation leading to lower oxygen levels and pH values. These prevent bone formation but favor cartilage formation. Early mobilisation leads to mechanical stimuli on joint surface further enhancing cartilage formation. In subchondral bone pH is more neutral and oxygen levels higher, making bone formation possible in mechanically stable surroundings. See more...
What is DBM or DBX®?
Demineralised bone matrix (DBM) is a group name for all bone grafts which have been manufactured after removing most of the mineral naturally occuring in hard bone. There are several commercial products, but all of them are made out of human cortical bank bone, by chipping it into small pieces and using acid to demineralise these. The final product is created by packing this graft to a specific form. DBX® is one commercial brand (DePuy Johnson) and DBX Putty® one specific product in that product line. It is injectable, comes packed in syringes and is therefore ready to use out of the shelf. Two reasons why we use just this product in Saloplasty, are that it is injectable and easy to pressurise in drill holes. Another point is that when we started these operations in 2005, this was to our knowledge the only DBM product on the market with hyaluronate as a binding agent. Hyaluronate is a natural structural part of cartilage, it serves as an anti-inflammatory agent in joint, and is widely used to treat mild or moderate osteoarthrosis as intra-aricular injections.
Thinking about cartilage regeneration, there are early works showing that DBM made out of the cortical bone is a stronger stimulant than DBM of trabecular bone origin. Commercial products rely on cortical bone origin. There are also papers showing that growth factor concentration in DBM products varies between different lot series. This is natural, since they all are of biological origin. In the same way, surroundings where DBM is used, varies in many biological aspects in different patients.
Thinking about cartilage regeneration, there are early works showing that DBM made out of the cortical bone is a stronger stimulant than DBM of trabecular bone origin. Commercial products rely on cortical bone origin. There are also papers showing that growth factor concentration in DBM products varies between different lot series. This is natural, since they all are of biological origin. In the same way, surroundings where DBM is used, varies in many biological aspects in different patients.
What does DBM do inside osteochondral lesions?
Old abrasion arthroplasty is a technique where chondral defect area originally was made deeper by cyretting the damaged joint facet deep into subchondral bone. Results were generally not so satisfied, but in some cases it gave reasonable results and this technique was used. Certain principles still come from those days to current techniques. Basically, it was already in 1930's when Campbell published his paper "Physiology of arthroplasty". Campbell reported several cases, where the joint facet damage was so deep that underlying bone was included. In these cases a spontaneous arthroplasty was reported, with proper functional outcome despite of the altered joint structure in X-rays. It encouraged thinking that deep bone layers can have potential to stimulate or guide growth of a new joint facet with good functional outcome. Current cartilage reconstruction methods offer many possibilities and different strategies, but all of them have to meet the biological surroundings, and mechanical requirements inside joint under cyclic load.
Use of DBM as a putty was initially just a filling material of old abrasion arthroplasty cavity. That was a salvage procedure in some cases with no other option left in surgical tool box. But why is it favorable to fill up deep bone defect?
Requirements of successful cartilage repair and reconstruction include achieving a solid base resisting and standing weigth bearing. DBX putty® is not a solid material, and it will not harden inside joint. But when injected to a bowl like defect it has a high compression strength. Typically, when injecting and further compressing this kind of material, hyaluronate diffuses around the injection area, and remaining small pieces of demineralised bone actually fill the defect.
Filling has another important function. If abrasion groove or large drilling holes are left as such, they will allow a huge bleeding inside the joint, leading to massive hemarthrosis and unfavorable scar tissue formation. In the old days filling was made with bone graft, either autograft or allograft, which was packed on area and compressed to stop bleeding. In modern sandwitch techniques the principle is the same, trying to get mechanical properties, prevent excessive bleeding and produce a smooth gliding surface. No matter what is the filler, it will not be the final one in successful cases. Grafting material is eated up by macrophages, osteoclasts and other cells which clean up the area. This is immediately followed by orchestrated production of new tissues.
Tissue formation and especially growing new tissues in a predictable manner has been of huge interest for hundred years. Some animals, like salamander, can even grow new limb after amputation. It is not yet possible in humans even after heavy work done on this sector. There is an almost countless number of possibilities and basic science knowledge on what kind of growth factors and other agents are needed to make the bone heal, or how to culture MSCs to cartilage cells in lab. When comparing these factors in differentiation of cartilage and bone cells, known differences are not so many. Much more clear are the requirements on physical and chemical surroundings to support or inhibit either cartilage or bone formation. Bone is never formed in surroundings which is not mechanically stable. Neither is it formed in areas with impaired blood circulation leading to low pH value and low oxygen levels (pO2). In theory, this should prefer bone growth in the deepest layers, and prevent coincidental bone formation in the joint space. In all techniques and filling materials, first question is how they can produce proper surface and tight and secure contact to bone.
But there is another direction, too. And this is important, lateral integration. With any technique used to repair cartilage defect, a good ingrowth or contact to surrounding cartilage layer is needed. This is required also with mini metal implants, so virtually any technique requires good cartilage shoulders around filling or implant. Based on clinical knowledge and imaging findings cartilage defect is always surrounded by cartilage with impaired quality. It is therefore important to clean up and debride these areas largely enough to get a good contact to surroundings. It makes sense to limit shearing forces during initial recovery period after surgery until lateral integration is ready.
Use of DBM as a putty was initially just a filling material of old abrasion arthroplasty cavity. That was a salvage procedure in some cases with no other option left in surgical tool box. But why is it favorable to fill up deep bone defect?
Requirements of successful cartilage repair and reconstruction include achieving a solid base resisting and standing weigth bearing. DBX putty® is not a solid material, and it will not harden inside joint. But when injected to a bowl like defect it has a high compression strength. Typically, when injecting and further compressing this kind of material, hyaluronate diffuses around the injection area, and remaining small pieces of demineralised bone actually fill the defect.
Filling has another important function. If abrasion groove or large drilling holes are left as such, they will allow a huge bleeding inside the joint, leading to massive hemarthrosis and unfavorable scar tissue formation. In the old days filling was made with bone graft, either autograft or allograft, which was packed on area and compressed to stop bleeding. In modern sandwitch techniques the principle is the same, trying to get mechanical properties, prevent excessive bleeding and produce a smooth gliding surface. No matter what is the filler, it will not be the final one in successful cases. Grafting material is eated up by macrophages, osteoclasts and other cells which clean up the area. This is immediately followed by orchestrated production of new tissues.
Tissue formation and especially growing new tissues in a predictable manner has been of huge interest for hundred years. Some animals, like salamander, can even grow new limb after amputation. It is not yet possible in humans even after heavy work done on this sector. There is an almost countless number of possibilities and basic science knowledge on what kind of growth factors and other agents are needed to make the bone heal, or how to culture MSCs to cartilage cells in lab. When comparing these factors in differentiation of cartilage and bone cells, known differences are not so many. Much more clear are the requirements on physical and chemical surroundings to support or inhibit either cartilage or bone formation. Bone is never formed in surroundings which is not mechanically stable. Neither is it formed in areas with impaired blood circulation leading to low pH value and low oxygen levels (pO2). In theory, this should prefer bone growth in the deepest layers, and prevent coincidental bone formation in the joint space. In all techniques and filling materials, first question is how they can produce proper surface and tight and secure contact to bone.
But there is another direction, too. And this is important, lateral integration. With any technique used to repair cartilage defect, a good ingrowth or contact to surrounding cartilage layer is needed. This is required also with mini metal implants, so virtually any technique requires good cartilage shoulders around filling or implant. Based on clinical knowledge and imaging findings cartilage defect is always surrounded by cartilage with impaired quality. It is therefore important to clean up and debride these areas largely enough to get a good contact to surroundings. It makes sense to limit shearing forces during initial recovery period after surgery until lateral integration is ready.
Exercise and rehabilitation
Cartilage problem is not just a focal defect in your joint facet, but it can impair joint and limb function for a long time before even noticed. Pain, discomfort or exercise related swelling all lead to changed activity level, and in many cases patient learns a new way to use his or hers joint to avoid or to decrease symptoms. We talk about muscle memory and coordination of the joint, whole limb and core. That is why physiotherapy is so integral part of cartilage surgery. In most of the cases patient can do mobilisation and even muscle strength exercises quite fast, but a change in motion control and possible imbalance in muscle forces is challenging. It is not safe to return to sports before the reconstruction is solid enough, and patient has force enough to handle landing from jumps without high risk for new accident. Taken together, if demineralised bone is used for reconstruction, then depending on the area, safe RTP (return to play) e.g. in soccer is 10 to 14 months in large reconstructions.
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