Hi, I'm Paul Caldwell at Tucker Orthopedics and Orthopedic Research Virginia in Richmond, Virginia. It's an honor to be part of the Comprehensive Advanced Knee Arthrospy Lab course. My task today is to talk a little about smaller cartilage lesions. We're going to debate a little bit between microfracture and osteochondral autograft transplantation known as OATs. I do have disclosures. They're available within the meeting agenda as well as the AOSS website. I'm going to set the stage a little bit for treatment of small chondral lesions just to kind of get us ready for this debate. We know they occur within two-thirds of patients undergoing knee arthroscopy. They're present in about 50% of athletes undergoing ACL reconstruction. If these chondral lesions are left untreated, they can certainly progress and limit an active lifestyle. In the review of the literature, we know that focal cartilage lesions are more likely to experience a progression to cartilage damage if left untreated. I thought this was an interesting study looking at 10- to 15-year data on 51 patients with an ACL and a single focal chondral lesion compared with a matched cohort of 51 patients undergoing ACL reconstruction alone. They discovered chondral lesions, grade 3-4, measuring approximately 2 centimeters squared in half these patients. They followed them for up to 15 years, and there was no statistical difference with scoring. So it's often difficult to tell which patients need treatment. Our best modality for measuring cartilage lesions is, of course, the MRI. The difficulty with MRI is the fact that it traditionally underestimates cartilage lesions. If you look at many studies, the MRI can underestimate cartilage lesions up to 65% of the actual lesion. The difficulty with measuring cartilage lesions, and most of them are not square, if you remember your math, the area of a circle is pi times radius squared. We consider this with a dime being a small area. Certainly if you look at the area of a dime, it's about 2.5 centimeters squared. Even though we consider this small, this is a pretty large cartilage lesions when you consider the average size of a medial form of condyle is about 32 millimeters in width. So this algorithm, even though it's an older algorithm, still has clinical relevance. We're going to be talking about lesions in the lower left of both these algorithms. These are smaller cartilage lesions. We're going to talk a little bit about microfracture as well as OATs. These are the two modalities that we're considering when treating cartilage lesions. Traditionally microfracture has been performed by perforating the subchondral bone every three to four millimeters to release bone marrow elements to induce cartilage repair. This was popularized by Stedman in the 1980s using an awl, and we've subsequently migrated to a K-wire drill to perform less damage to the subchondral bone. This is a pretty technically simple procedure. It can be done arthroscopically. It's a very low cost. The goal of this procedure, as we said, is to breach the subchondral bone, and this promotes stem cells, growth factors, platelets to really form a big fiber and clot, and this will eventually remodel into fiber cartilage to fill the defect. The primary limitation of this is it's really healing with mature fiber cartilage that contains type one collagen. There's potential for interlesional osteophytes with only a small amount of type two collagen present. This reparative technique results in deficiency of durability compared with true articular cartilage. Looking at osteochondral autograft transplantation, this is a procedure that traditionally transplants healthy osteochondral cartilage from a low weight bearing cartilage surface to the defect site. It establishes a new hyaline cartilage surface. We're really limited to the amount of cartilage that's available for this because in essence we're robbing Peter to pay Paul. Again, this is a single healthy osteochondral plug, or you can use multiple plugs. This is called mosaicplasty. The advantages of this technique is really you're resurfacing the defect with normal hyaline cartilage. It's a single stage procedure. It can be formed open as well as arthroscopically, and again, it's a relatively low cost. The disadvantages is that you're creating an osteochondral defect somewhere else in the knee. It's most commonly performed open, and it's more technically demanding than microfracture. Let's look at surgical trends. If you consider surgical trends in the knees from 2004 to 2011, articular cartilage procedures had an annual incidence growth of approximately 5%. Certainly from 2005 on, chondroplasty and microfracture treatment were trending downward. If you look at restorative treatment options, they were trending upward. If you look at this graph from 2010 to 2016, it's very clear that microfracture is trending downward, whereas open autograft transplantation as well as arthroscopic transplantation are trending upward. Let's review the literature a little bit. This is a great study. It's a prospective randomized clinical study. You won't find anything better than that comparing osteochondral autograft transplantation and microfracture. They took 60 athletes, and they were really randomized to receive one of these procedures. Certainly, they followed these at regular intervals, and they even had 50% of these athletes undergo an arthroscopy with a biopsy at one year. This is a very thorough study. They found that functional and objective assessment showed that 96% had excellent and good results with osteochondral transplantation, whereas only 52% with microfracture. The OATS technique in the athletic population allowed for a higher rate of return and a maintenance of sports participation to the pre-injury level compared with microfracture. This is a retrospective comparison of osteochondral transplantation to microfracture for symptomatic chondral defects of the thermocondyle and trochlea. They looked at 96 patients and certainly concluded that osteochondral transplantation mosaicplasty maintained a superior level of athletic activity compared to those treated with microfracture. If you look at this meta-analysis comparing microfracture and OATS, six prospective studies were evaluated with 249 patients, and they concluded that OATS may achieve a higher level of activity with a lower risk of failure than microfracture. This is a systematic review looking at level one and two studies of microfracture. They found nine short-term studies and six long-term studies. The majority of these studies showed poor clinical outcomes. Smaller lesions in younger patients showed short-term improvement with gradual decline after five years. If you look at return to sports, this is scientific evidence gathered. Osteochondral transplantation had the highest return to sports in athletes, 91 percent, and their return to sports was approximately seven months after osteochondral transplantation, whereas microfracture took approximately eight months to return to sports. If you look at this systematic review, they looked at 11 studies, including 658 patients. Patients who underwent osteochondral transplantation had a 93 percent return to sport at a mean of 6.5 months, whereas microfracture only returned 59 percent of patients at an average of 17 months. This is a great study out of University of Virginia. This showed that the mean time to return to sports for 20 athletes was 83 days after osteochondral transplantation. Many of these lesions were small, but it certainly demonstrates how quickly athletes can recover after this procedure and return to play. This is a summary of treatment of small chondral lesions. Remember, we're dealing with lesions that are approximately 1.5 to 2 centimeters squared. These are often treated with meniscal and ligament symptoms. Many of these will not be symptomatic if they are left alone, so remember, don't over-treat these lesions. Please consider a two-stage approach to these lesions. Surgical trends, as well as review of the literature, support oats over microfracture, and I personally don't perform microfracture alone anymore in my practice. Thanks for your attention.

cartilage lesions

microfracture

osteochondral autograft transplantation

MRI scans

surgical trends