Early Osteoarthritis (OA) and its prevention has become an important topic in many meetings on cartilage repair and induced probably one of the most important shifts of paradigm in the treatment algorithm of cartilage defects. Early OA includes on one hand a still circumscribed lesions of the joint surface, but it also covers early signs of the ongoing process of degeneration and inflammation leading to OA. This combination seems to be the most prominent pathophysiology in patients leading to medical treatment. Isolated Cartilage defects which are only circumscribed lesions are rare and not representative for the clinical problems orthopedic surgeons are seeing in their daily practice. Therefor clinical studies do not reflect the actual patients population, where surface defects are often associated with synovitis, general changes in the biological environment in the synovial fluid and also morphological changes of the menisci and ligaments as well as background factors like joint alignment and bodyweight. So, the cartilage repair technologies have arrived in the real world. Cartilage registries clearly see early OA as the dominant indication for cartilage surgery.
Early OA is characterized by the progredient loss of cartilage integrity and cellularity which eventually leads to the functional impairment of the joint. A hallmark of the osteoarthritic degenerative process is the exuberant production of proinflammatory cytokines (e.g., IL-1β, TNF-α), matrix metalloproteinases (e.g., MMP-1, -3, -13), and reactive oxygen and nitrogen species (ROS, RNS) by chondrocytes and synoviocytes. Thereby these cells become integral players in the vicious circle driving disease progression. So overall, OA is a complex process of biomechanically induced degeneration, reactive inflammation, and a general aging process with changing cellular activity.
Conservative therapies of OA include nutrients, drugs and injectables like corticosteroids, hyaluronic acid, and platelet-rich plasma as well as mesenchymal stem cells. However, the progress of the disease and persistence of symptoms might indicate early surgery and not to await the development of a full OA.
Working groups of ICRS have taken on the problem and developed a systematic approach to early OA and recently published a book with that focus. The definition or early OA is related to joint symptoms like tenderness on the joint space or crepitation, radiological Kellgren Lawrence grades between around one and two. MRI changes generally reflecting ICRS grades 1-2 with one area more than that. Furthermore, unnormal joint alignment, partial meniscus defects and functional or structural instability of the joint might be associated with the condition described above. The later mentioned conditions are obviously the hallmark of indicating surgery in early OA, since the biomechanical situation of the joint with regards to alignment, meniscus deficiency and instability is probably the most important factor in progressing OA conditions. The indication is even more critical if a cartilage defect or zonal degeneration is associated with the biomechanical malcondition. In the knee a femoro-tibial malalignment of more than 5 degrees is considered substantial and should be addressed at the same time as the cartilage defect on the overloaded joint-compartment. Same applies for instable situations after ACL ruptures, because a cartilage repair procedure will just be successful in a stable joint. Acute meniscus ruptures should be addressed immediately anyway, even more so if a suture is possible. Degenerative lesions are depending on symptoms of locking or painful movement, whereas asymptomatic degeneration of the meniscus should be observed to what degree the lesion might contribute the clinical situation. There is still discussion in the priority of the surgical procedures which can be concomitant or sequential, however the plan has to be discussed with the patient and his needs and compliance.
The most critical decision for surgery is the defect of the local osteoarthritic process or defect on the joint surface itself. A symptomatic defect bigger than 2 square centimeters is obviously an indication for surgery, although the question is how much degenerative changes in the knee beside the defect do we accept? Age is obviously a fact, but individual age (genetic background) has to be considered. Most of treatment-studies with regenerative surgery like microfracture with biomaterial (AMIC) or chondrocyte transplantation show better results below the age of 40. Defects with ICRS grades 1 or 2 might not be an indication for direct surgery since the prognosis is uncertain and there is no evidence for such lesions. In cases of persistent pain, the presence of bone edema has to be assessed by MRI, because other options like subchondroplasty, drilling or osteoporotic drugs might be more be more favorable, sometimes unloading of the joint can overcome the symptoms. Other surgical options like allografts have widened the indication of local OA since they immediately provide a stable situation of the replaced joint surface and provide a sustainable solution. Due to the lack of fresh allografts in Europe partial joint replacement and synthetic resorbable implants have become popular, however they are often just an in-between solution on the way to total joint replacement.
As a conclusion surgery is clearly indicated regarding the background-factors like alignment and instability and acute meniscus lesions in early OA because the benefit of osteotomies, ACL reconstruction and meniscus surgery including allograft is evident with regards to OA progression prevention.
The preventive effect of cartilage surgery on the defect itself is more critical to be discussed depending on age, expectation, compliance and goals of the patient. So it is more important to treat the patient, than just to concentrate too much on the surgery in this complex process of early OA.
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