Let’s talk about all the various treatments that we do for the articular cartilage when we are doing a biologic replacement.
When we look into a knee that has damage to the articular cartilage, we decide which of the cartilage procedures that we want to select in order to treat that damaged area -
If there is exposed bone, and it is a very small area such as 5 by 8mm or that type of range, then we will often just do a microfracture (photo on right) which will stimulate a healing response to a small area of articular cartilage loss.
Note that we violate all the principles of microfracture because in this case we want to fracture right through the ‘tide mark’ and create a true fresh fracture in the joint.
We then take articular cartilage and underlying cancellous bone from the intercondylar notch out of the knee, smash it into a paste and then impact that paste into the morselised defect. We do not try to fill the defect because these almost always hypertrophy and will fill on their own.
We have recently completed a study with Tony Radcliffe in San Diego that documents that within the paste graft there are progenitor cells which will go down the 'chondrocytic pathway' (form new articular cartilage cells) in the appropriate medium. So we know that we have stem cells or progenitor cells in that articular cartilage matrix. And we also did a study looking at whether or not there are progenitor cells in an old patient with arthritis – those patients that are coming in for total knee replacement – compared to a young patient who just has a focal defect. And in fact both patients had progenitor cells in the matrix in the paste that we take in order to fill the defect. And so for a large cartilage defect we will do a paste graft.
Now in the first 125 of those that we did, we required the patients to come back for ‘second-look’ arthroscopy and biopsy, and 70 of those patients did come back, and of those 7 biopsies about one third were graded as ‘hyaline-like’ one third were graded as ‘mixed’ and one third were graded as more ‘fibrocartilage’. ‘Hyaline-like’ would include articular cartilage matrix nearly indistinguishable from normal, where few cartilage cells are dispersed within glassy matrix (background substance). ‘Mixed’ would include hyaline-like plus fibrocartilagenous cells and collagen. ‘Fibrocartilage’ does not have the glassy appearance of normal articular cartilage, and contains pure fibrocartilage cells also not normally found in normal articular cartilage as well as collagen fibres.
We are currently doing a study to determine whether or not patients who had one type of tissue regeneration or another have a different outcome. Meaning, if you have fibrous tissue does that diminish the quality of your outcome over a period of 10-15 years? That study data will be out by the end of this year. Because those biopsies revealed articular cartilage regeneration that was every bit as good as any biopsies we had seen from any other cartilage procedure, such as ACI, we elected not to use ACI for any of the cartilage defects that we see, since ACI required two surgical interventions – one of them being ‘open’ – and required sewing of a periosteum (see this image) and also a very expensive cartilage growing procedure, we felt that a simple single-stage outpatient procedure where the cartilage was grafted in one step was more cost-effective and at least equally therapeutically-effective as any of the other procedures that we had seen. This is also true when we compared the data to mosaicplasty or OATS-type procedures, all of which we felt created too much of a defect in the bone, and when those procedures failed the patient was left with a very wide trough. And so we use a paste graft technique whenever there is exposed bone that is large enough as part of the biologic knee replacement procedure.
Why is paste grafting not yet a main stream procedure?
Well, in paste grafting there is no product that a company can get behind and sell, and because of that we never had a corporate support for a product of any kind. A surgeon can use any trephine, take the tissue out of the knee, use a simple graft smasher that most of the ENT (ear/nose/throat) sets have, and then return that graft directly back to the patient in the same procedure without incurring any additional charge. And so we were never able to entice a company to get behind paste-grafting even though we now have nice published studies of long term data and this July the Journal of Bone and Joint Surgery (British) will publish our 2-12 year data combining paste graft as well as chondroplasty and microfracture with meniscus transplantation for arthritic knees. So we think we have quite long term solid data that eventually other surgeons may decide to adopt to their armamentarium.