High tibial osteotomy (HTO) using locking plate is a well-established surgery to realignment lower limb, decrease mechanical stress on the affected compartment of the knee and achieve good long-term clinical outcomes [Citation1].
Osteoarthritis (OA) has long been interpreted as a degenerative disease resulting from long-term mechanical loading and aging. Recently, many studies report that pathology of OA is a multifactorial disease that involves pathological processes in the knee joint structure (cartilage, subchondral bone, meniscus, ligament, muscle, and synovium) [Citation2]. Furthermore, most patients with OA have systemic inflammation. Therefore, the pathology of OA also involves the aspect of inflammatory disease, not just the aspect of degenerative disease due to mechanical loading.
Kumagai previously described [Citation3] regarding biomarkers of OA, including inflammatory cytokines, degradative enzymes, and cartilage breakdown products such as interleukin (IL)-1β, 6, 8, 10, tumor necrosis factor-α (TNF-α), matrix metalloproteinase (MMP)-2, 3, 9, 13, vascular endothelial growth factor (VEGF), and cartilage oligomeric matrix protein (COMP). These OA biomarkers can be detected in blood, urine, and synovial fluid. Moreover, Bosch previously describedCitation2 that inflammation in the synovium and fat pad of infrapatellar results in the production of pro-inflammatory cytokines which penetrate the cartilage via the synovial fluid to promote the expression of catabolic mediators. The most remarkable involvement in the initiation and progression of OA has been described for IL-1, 6, 15, 17, 18, and TNF-α, of which IL-β and TNF-α have been the most extensively studied [Citation4]. MMPs are considered a pivotal role in degradation of cartilage, and previous studies suggested that MMPs are higher in OA patients than in healthy individuals [Citation5]. VEGF is an angiogenic factor which contributes to the etiology of OA [Citation6], and VEGF levels are higher in OA patients than in non OA subjects [Citation7].
HTO can preserve own knee joint and the induce the biological remodeling, including cartilage regeneration regardless cartilage regeneration techniques such as microfracture, abrasion arthroplasty, mosaicplasty, and stem cell therapy [Citation3]. However, the biological mechanics regarding the OA condition after HTO are not still clear.
Several studies have reported the effectiveness of an additional arthroscopic procedure combined with HTO in improving the clinical result. Although one comparison of HTO alone versus HTO with an arthroscopic procedure reported no advantage in terms of clinical score, another study confirmed that HTO with an arthroscopic procedure is an effective procedure for osteoarthritis and intra-articular lesions in terms of the clinical result [Citation8,Citation9]. Moreover, several studies have evaluated OA biological markers. One such study reported the effectiveness of an arthroscopic procedure combined with HTO [Citation10]. The authors found that if the cartilage injury had an Outerbridge classification of Grade III, the joint cavity needed to be cleaned; if the cartilage injury was Grade IV, microfracture treatment was needed on the exposed subchondral sclerosis area, which needed to be formed or partially resected when there was a concomitant meniscal injury; if there was a loose body, it needed to be removed by arthroscopy and the hyperplastic synovial tissue was removed. They evaluated the serum levels of inflammatory factors (IL-1β, 6, 17) and clinical outcome and concluded that HTO with an arthroscopic procedure shortens the hospital stay of patients with medial knee osteoarthritis, improves knee joint function, relieves pain, and reduces serum levels of inflammatory factors at 1, 3, and 6 months after surgery without complications [Citation10]. Another study evaluated the levels of OA biomarkers in the synovial fluid before versus after HTO without an arthroscopic procedure and found that the IL-6, 8, MMP-2, 3, 13, VEGF, and COMP levels were reduced after HTO [Citation3]. Furthermore, there was a regeneration of cartilage after HTO in 38% of patients. However, this regeneration in cartilage did not relate with the synovial fluid levels of biomarkers [Citation3]. This result suggests that HTO alone (without an arthroscopic procedure) can change the intra-articular environment.
HTO can alter the intra-articular biomechanical and biological environment. Moreover, an additional arthroscopic procedure may be more effective for improving the OA biomarker levels. Further study is needed to clarify not only the pathology of OA but also the most effective procedure with which to treat OA.
Acknowledgments
We thank Kelly Zammit, BVSc, from Edanz (https://jp.edanz.com/) for editing a draft of this manuscript.
Disclosure statement
No potential conflict of interest was reported by the author(s).
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