Osteoarthritis (OA) is a major cause of disability in the adult population. As a progressive degenerative joint disorder, OA is characterized by cartilage damage, changes in the subchondral bone, osteophyte formation, muscle weakness, and inflammation of the synovium tissue and tendon. Although OA has long been viewed as a primary disorder of articular cartilage, subchondral bone is attracting increasing attention. It is commonly reported to play a vital role in the pathogenesis of OA. Subchondral bone sclerosis, together with progressive cartilage degradation, is widely considered as a hallmark of OA. Despite the increase in bone volume fraction, subchondral bone is hypomineralized, due to abnormal bone remodeling. Some histopathological changes in the subchondral bone have also been detected, including microdamage, bone marrow edema-like lesions and bone cysts. This review summarizes basic features of the osteochondral junction, which comprises subchondral bone and articular cartilage. Importantly, we discuss risk factors influencing subchondral bone integrity. We also focus on the microarchitectural and histopathological changes of subchondral bone in OA, and provide an overview of their potential contribution to the progression of OA. A hypothetical model for the pathogenesis of OA is proposed.

Driven by market demand, many biological and synthetic scaffolds have been developed during the last 15 years. Both positive and negative results have been reported in clinical applications for tendon and ligament repair. To obtain data for this review, multiple electronic databases were used (e.g., Pubmed and ScienceDirect), as well as the US FDA website and the reference lists from clinical trials, review articles and company reports, in order to identify studies relating to the use of these commercial scaffolds for tendon and ligament repair. The commercial names of each scaffold and the keywords 'tendon' and 'ligament' were used as the search terms. Initially, 378 articles were identified. Of these, 47 were clinical studies and the others were reviews, editorials, commentaries, animal studies or related to applications other than tendons and ligaments. The outcomes were reviewed in 47 reports (six on Restore, eight on Graftjacket, four on Zimmer, one on TissueMend, five on Gore-Tex, six on Lars, 18 on Leeds-Keio and one study used both Restore and Graftjacket). The advantages, disadvantages and future perspectives regarding the use of commercial scaffolds for tendon and ligament treatment are discussed. Both biological and synthetic scaffolds can cause adverse events such as noninfectious effusion and synovitis, which result in the failure of surgery. Future improvements should focus on both mechanical properties and biocompatibility. Nanoscaffold manufactured using electrospinning technology may provide great improvement in future practice.

Porcine small intestinal submucosa (SIS) has been recommended as a cell-free, biocompatible biomaterial for the repair of rotator cuff tendon tear. However, we have observed noninfectious edema and severe pain in patients who have undergone SIS implantation for tendon repair. The aim of this study was to conduct an independent assessment of the safety and efficacy of Restore SIS membrane. The Restore orthobiologic implant was examined by histology and the nested PCR technique using porcine immunoreceptor DAP12 gene to examine if SIS membrane contained porcine cells or DNA, respectively. The material was also implanted into mice and rabbits for the evaluation of biological reaction and inflammatory response. Restore SIS was found to contain multiple layers of porcine cells. Chloroacetate esterase staining showed that some of these cells were mast cells. Nested PCR of the DAP12 gene demonstrated that Restore SIS contained porcine DNA material. Subcutaneous implantation of Restore SIS membrane in mice, and in rabbits for rotator cuff tendon repair, showed that the membrane caused an inflammatory reaction characterized by massive lymphocyte infiltration. In conclusion, Restore SIS is not an acellular collagenous matrix, and contains porcine DNA. Our results contradict the current view that Restore SIS is a cell-free biomaterial, and that no inflammatory response is elicited by its implantation. We suggest that further studies should be conducted to evaluate the clinical safety and efficacy of SIS implant biomaterials.