This review article discusses the similarities in pathogenesis between post-traumatic osteoarthritis and hemarthrosis, and the potential implications on meniscus health and repair. Bleeding into the intra-articular joint space, hemarthrosis, is likely to play a role in the pathogenesis of post-traumatic osteoarthritis following injury to the knee joint. This review article highlights findings published in various studies that illustrate similarities in the physiological progression of hemarthrosis and that of osteoarthritis. Additionally, in consideration of the damaging effects that blood products may incite on joint health and meniscus integrity, this review article takes into account the therapeutic uses of blood products to support meniscal repair.
One study showed that in 132 cases of acute hemarthrosis of the knee, 77% were caused by an ACL tear. In other studies cited, hemarthrosis within 4 hours of acute injury correlated with significant injury to meniscus fibrocartilage, leading to a 50% increased risk of developing osteoarthritis within 15 years of injury. This is due to a condition known as hemophilic synovitis that progresses into hemarthrosis characterized by the degradation of articular cartilage and subchondral bone, further causing significant joint impairment.
Similarities among the pathogenesis of blood-induced joint damage and post-traumatic osteoarthritis are identified with respect to pro-inflammatory cytokines and the exacerbation of reactive oxygen species released in the joint space. Following a significant hemolytic event within the joint, there is deposition of iron-containing products into the synovium. These iron-saturated products increase tissue damage. Additionally, a review of studies show a 2-fold increase in cell proliferation within the synovium of human subjects when exposed to byproducts of iron; thus, even acute blood exposure can result in hyperplasia and angiogenesis in the joint. Synovial hyperplasia caused by blood in the joint creates a hypoxic environment and, subsequently, leads to increased vascularity to provide more oxygen recruitment. Increased vascularity thereby increases infiltration of macrophages, which have also been implicated as an immune response in osteoarthritis. These recruited macrophages lead to elevated concentrations of reactive oxygen species in the synovial fluid. In the presence of iron, the catalytic activation of these free radicals may cause cell death to the articulating cartilage of the joint.
Interestingly, improved success of meniscus repair when performed concurrently with ACL reconstruction may be due to factors attributed to intra-articular bleeding and exposure to growth factors released from bone drilling and intercondylar microfracture during the repair procedure. Bone marrow-derived mesenchymal stem cells (MSCs) have the ability to differentiate into various cell types and secrete bioactive factors that promote tissue repair. Bone marrow aspirate, however, is harvested from the iliac crest. Once centrifuged, bone marrow aspirate separates into three layers: plasma layer, buffy coat layer, and the RBC layer. Bone Marrow Aspirate Concentrate (BMAC) is primarily composed of the buffy coat layer but also contains a portion of both the plasma and RBC layers. Platelet-rich Plasma (PRP) is, yet, another autologous source of concentrated growth factors processed from peripheral blood. During PRP processing, the concentration of inflammatory products that inhibit healing versus the concentration of growth factors that promote healing is dependent upon the subject from which the blood is drawn. One study showed a significant decrease in gene expression of cartilaginous proteins in PRP processed from a patient with osteoarthritis compared to that of healthy donors. A review of published studies highlights that different disease states influence the bioactivity of PRP, which may ultimately demonstrate negative therapeutic outcomes.
BMAC is generated by centrifugation and filtering of bone marrow aspirate cells to yield a concentrate that contains 3- to 41-fold concentrated MSCs. BMAC preparation concentrates growth factors and platelets that may aid in tissue healing. However, it also contains 10- to 100-fold increased concentrations of pro-inflammatory cytokines. How much is too much? Does the good out-weigh the bad? More research is needed to understand the effects of blood and marrow components and the potential benefits these components have on meniscus tissue integrity and repair. Moreover, research is needed to carefully interrogate the effects of bone marrow-derived growth factors released during ACL reconstruction on meniscus repair with bone drilling and microfracture, by which findings from these studies could be applied to orthobiologic techniques to improve meniscus healing. Nonetheless, there may be factors present in BMAC and PRP that are detrimental to the regeneration and repair of the meniscus due to the concentration of harmful blood and marrow components. Additional research is needed to help discern the long-term effects of these blood- and marrow- derived products on meniscus repair and progression of post-traumatic osteoarthritis. Access the review article here.