Cylindric (10 mm diameter X 15 mm deep) osteochondral defects were created in the medial femoral condyles of 5 horses to mimic clinical cases of subchondral bone cysts after debridement. The defects were created with either a standard square ended drill bit or a compaction drill bit. The compaction drill bit compresses bone laterally and distally creating a dense wall and floor. Twelve-mm sternal cancellous cylinders were compressed to 9.25 mm and inserted into the femoral defects where they were presumed to expand and tighten the fit. The end result was sternal cancellous bone that exactly fit the femoral defects. Fluorochrome bone labels were used to confirm the origin of bone present in the defects at necropsy, which was performed after 6 months. Successful graft incorporation occurred in 3 of the compacted and 2 of the noncompacted defects. The surfaces of the successful cancellous bone grafts contained predominately fibrocartilage. The unsuccessful noncompacted defects expanded laterally and deeply into the parent bone epiphysis while the unsuccessful compacted defects remained confined to the originally created size. / Master of Science

Osteoarthritis (OA) is a debilitating disease that affects millions of people. It is characterized by the degeneration of articular cartilage, narrowing of the joint cavity, damage to the subchondral bone, loss of synovial fluid, and osteophyte formation. These symptoms can cause muscle weakness, decrease in range of motion at the joint, and pain. Pain is the symptom that is most frequently treated. However, pinpointing the exact origin and location that is causative to the pain can be difficult. Patients of OA commonly have areas of subchondral edema identified on an MRI as marrow bone lesions (BML). On a CT image, these BML are found to be areas of bone resorption within the subchondral bone of the affected joint called subchondral bone cysts (SBC). These cysts are hypothesized to be a source of pain in OA as well as progression of the disease. The synovial intrusion theory for cyst formation states that there is a physical connection made between the joint cavity and the SBC through which synovial fluid travels. The bony contusion theory describes micro cracks developing below the articular cartilage within the subchondral bone causing bone necrosis and SBC formation. This study was undertaken to investigate the histological presentation of the contents of the SBC and the surrounding area.Seven human femoral head samples, ranging from age 49-72 years old, from patients who received total hip arthroplasty due to OA were examined. Three areas were sectioned from each femoral head including an area containing a cyst, an area of primary compressive bone, and an area at the medial side of the femoral head. These sections were then stained for bone, cartilage, and nerves and examined histologically. Sclerotic bone was shown to surround each cyst cavity, while cysts were composed of a mixed connective tissue infiltrated with multiple blood vessels and potential nerve fibers. With further investigation of these structures, the location of the nerve fibers within the SBC could be a possible source of pain in OA and a target for future treatments and therapies. Within the femoral head, cysts were found to be both shallow and deep to the articular cartilage. Shallow cysts may support the synovial intrusion theory for cyst formation while deep cysts could support the bony contusion theory. In relation to articular cartilage, cysts were not only found below a degraded articular cartilage surface as expected but also below intact, less degraded cartilage. This in depth look at the cells and tissues present within and surrounding the cyst provides information to better understand the pathology of OA and possibly an alternative method for treating the disease.

Osteoarthritis is a chronic degenerative joint disease that affects the whole joint, including the articulating surfaces and capsular tissues in and around the joint (Hügle and Geurts 2016). Osteoarthritis currently impacts 27 million Americans (Racine 2015). Two prominent features in osteoarthritis that are correlated with greater pain and reduced function are MRI-identified bone marrow lesions and CT-identified subchondral bone cysts (Kumar et al. 2013). At this time, the relationship between bone marrow lesions and subchondral bone cysts has not been confirmed. Nor has the nature of the tissues associated with these clinical signs been fully characterized, pointing to the need for further research to identify the composition of subchondral bone cysts as these cysts could be a potential target for therapeutic intervention. This study focused on characterizing the tissue content of subchondral bone cysts in osteoarthritic femoral heads. Osteoarthritic femoral heads were collected from male and female patients, ranging in age from 43-72 years old, who underwent total hip replacement. After surgery, the femoral heads were fixed in 4% paraformaldehyde and scanned via micro-computed tomography (MicroCT). The MicroCT images were used to identify regions in each head containing large subchondral bone cysts, the primary compressive bone, and anterior cartilage. These regions were mapped to the actual femoral head and guided the dissection of the femoral head. Samples from each of the regions were decalcified, embedded in paraffin, and cut into 5-micron-thick histological sections which were then mounted onto slides. Each section was stained in Safranin-O/Fast green and hematoxylin and eosin to visualize the tissues present. Immunohistochemistry with anti-CD31 was carried out on selected slides to identify blood vessels. The samples within all three regions of the femoral head were graded histologically for the presence of subchondral bone cysts, whether cartilage was within the cyst region, if the histological section matched its corresponding MicroCT image, if the articular cartilage was fibrillated, the presence of sclerotic bone, the presence of osteophytes, and the presence of blood vessels. It was clear that many of these samples were in later stages of osteoarthritis considering most samples exhibited all of the above characteristics, contained fibrous tissue, and had little normal fatty marrow. Typically, subchondral bone cysts presented beneath fibrillated and degenerated articular cartilage, contained fibrous tissue that was much more intensely vascularized and innervated as compared to normal fatty marrow, and was surrounded by sclerotic trabecular bone. In some cases, osteophytes also formed at the articular surface beneath areas of degenerated cartilage. Some subchondral bone cysts contained cartilage and even smooth muscle cells in addition to fibrous connective tissue. The varied location of the subchondral bone cysts shows the need for further research as to how their etiologies develop. The content of the subchondral bone cysts suggests that areas with disrupted trabeculae become intensely vascularized to allow the influx of inflammatory materials and mesenchymal stem cells to lay down fibrous tissue and thicken the surrounding trabeculae to stabilize the weakened microstructure of the femoral head. By gaining a comprehensive understanding of the pathology of osteoarthritis and of subchondral bone cysts in particular, the progression of the disease can be more firmly established and potential new treatments can be developed.

京都大学 / 0048 / 新制・課程博士 / 博士(人間健康科学) / 甲第21460号 / 人健博第67号 / 新制||人健||5(附属図書館) / 京都大学大学院医学研究科人間健康科学系専攻 / (主査)教授 杉本 直三, 教授 藤井 康友, 教授 松田 秀一 / 学位規則第4条第1項該当 / Doctor of Human Health Sciences / Kyoto University / DFAM

Background: Osteoarthritis (OA) is a debilitating joint disease marked by cartilage and bone changes. Morphological and mechanical changes to bone, which are thought to increase overall bone stiffness, result in distorted joint mechanics and accelerated cartilage degeneration. Using a parametric finite element (FE) model of the proximal tibia, the primary objective of this study was to determine the relative and combined effects of OA-related osteophyte formation, and morphological and mechanical alterations to subchondral and epiphyseal bone on overall bone stiffness. The secondary objective was to assess how simulated bone changes affect load transmission in the OA joint. Methods: The overall geometry of the model was based on a segmented CT image of a cadaveric proximal tibia used to develop a 2D, symmetric, plane-strain, FE model. Simulated bone changes included osteophyte formation and varied thickness and stiffness (elastic modulus) in subchondral and epiphyseal bone layers. Normal and OA related values for these bone properties were based on the literature. “Effective Stiffness (K)” was defined as the overall stiffness of the proximal tibia, calculated using nodal displacement of the loaded area on the subchondral cortical bone surface and the load magnitude. Findings: Osteophyte formation and thickness or stiffness of the subchondral bone had little effect on overall bone stiffness. Epiphyseal bone stiffness had the most marked effect on overall bone stiffness. Load transmission did not differ between OA and normal bone. Interpretation: Results suggest that epiphyseal (trabecular) bone is a key site of interest in future analyses of OA and normal bone. Results also suggest that observed OA-related alterations in epiphyseal bone may result in OA bone being more flexible than normal bone.

The mandibular condyles represent important growth sites within the facial skeleton. Condylar growth is not a pacemaker of mandibular development, but it provides regional adaptive growth that is of considerable clinical significance, as the condyle’s upward and backward growth movement regulates the anteriorly and inferiorly directed displacement of the mandible as a whole. Orthopedic problems of the temporomandibular joint (TMJ), such as displacement of the TMJ disk, are common in the adolescent population. Clinical studies of mandibular asymmetry and mandibular retrognathia in adults as well as in children and adolescents, have reported an association with coexisting non-reducing displacement of the TMJ disk without identifying the cause and effect. Through experimental studies causality has been established, and unilateral affliction during growth has been shown to retard ipsilateral mandibular development with facial asymmetry as the sequel. It was hypothesized that bilateral non-reducing TMJ disk displacement during growth would impair mandibular development bilaterally, resulting in mandibular retrognathia. TMJ disk displacement has repeatedly been demonstrated to induce histological reactions of the condylar cartilage. An additional assumption was therefore that a non-deranged TMJ disk function is crucial for the maintenance of the growing condyle’s biophysical environment, and that a connection ought to exist between the amount of condylar cartilage changes caused by TMJ disk displacement and the amount of subsequent adverse mandibular growth. It was also hypothesized that non-reducing displacement of the TMJ disk in growing individuals would result in qualitative and quantitative changes of the condylar subchondral bone. An improved experimental cephalometric method was developed in order to optimize the reliability of longitudinal radiographic evaluation of fast growing small animals. Bilateral non-reducing TMJ disk displacement was surgically created in ten growing New Zealand White rabbits, with ten additional rabbits serving as a sham operated control group. The amount and direction of craniofacial growth was followed over time in serial cephalograms, aided by tantalum implants in the jaws. The study period was chosen to correspond to childhood and adolescence in man. The assessed growth of each side of the mandible was correlated to the histological feature of ipsilateral condylar cartilage at the end of the growth period. The amount and composition of subchondral bone from three regions of interest in the condyle, and the expression of local growth factors in the adjacent condylar cartilage was evaluated. The results verified that bilateral non-reducing TMJ disk displacement retarded mandibular growth bilaterally; the extent corresponding to mandibular retrognathia in man. Displacement of the TMJ disk during the growth period induced condylar cartilage adaptive reactions that were associated with both an adverse amount and direction of mandibular growth, manifesting in a retrognathic mandibular growth pattern. Growth impairment fluctuated over time, with the most striking retardation occurring during periods of increased general growth, implying a local growth reduction explicitly counteracting general hormonal growth acceleration. A significant decrease of the total amount of subchondral bone, in spite of a general increase of new bone formation in the experimental condyles, pointed to a reparative compensation for an extensive resorption of subchondral bone due to displacement of the TMJ disk, but not to the extent that normal growth would be maintained. These results constitute an explanation for the adverse mandibular development following non-reducing TMJ disk displacement in growing individuals. This project has shown that non-reducing displacement of the TMJ disk during growth has significant consequences on facial development. The findings strongly advocate early and accurate diagnosis and treatment of TMJ disk displacement in the adolescent population, thereby presumably reducing the need for future orthodontic and surgical craniofacial corrective therapy. The results furthermore enhance the need for full appraisal of TMJ disk function in the adolescent population during orthodontic functional therapy, as the condylar cartilage and subchondral bone reactions to a concomitantly displaced non-reducing TMJ disk must be expected to interfere with the intended growth stimulating treatment. The findings of intact articular layers in spite of gross histological and morphological soft and hard tissue changes as a sequel to TMJ disk displacement in growing individuals, implicate a clinical risk of false positive radiographic diagnosis of degenerative changes of the TMJ in children and adolescents.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21019号 / 医博第4365号 / 新制||医||1028(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 別所 和久, 教授 安達 泰治, 教授 妻木 範行 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Osteoarthritis (OA) is a chronic disease that affects the joints, most commonly hands, hips, knees, feet, and spine (Litwic et al. 2013). The disease becomes more common with advanced age and is one of the most prevalent causes of disability in older populations. Currently there is no cure besides total joint replacement surgery, and there will be approximately 4 million Americans living with a hip replacement by the end of the next decade (Maradit Kremers et al. 2015). Osteoarthritis was classically characterized as a disease of progressive articular cartilage degradation, but the degeneration involves all tissues of the synovial joint including the periarticular muscles, joint capsule, synovium, ligaments, and subchondral and metaphyseal bone. The cause of pain in OA is not well understood, but it is known that bone marrow lesions (BMLs) identified in subchondral bone by MRI are an important determinant of pain (Felson et al. 2001; Kumar et al. 2013). Abnormal blood vessel growth may be responsible MRI signature of BMLs, and the commonality between pathways for angiogenesis and neurogenesis suggests this pathologic process may be the source of pain in OA. The objective of this study was to characterize the histologic nature of subchondral cysts identified by micro computed tomography (μCT) which had been registered with MRI images in which marrow lesions were identified. Femoral heads were collected from 10 patients (6 females and 4 females; age 29-80) who underwent total hip arthroplasty. All patients had MRIs performed within 6 months prior to surgery. The heads were fixed and scanned with μCT to identify cysts in the subchondral bone. A block of the femoral head containing the cyst of interest was resected and processed for histologic analysis. The sections were stained with either Safranin-O and Fast Green or hematoxylin and eosin to view the nature and composition of the tissue. A two-dimensional image from the μCT that corresponded to the histologic slice was matched with a coronal view from the MRI. The primary compressive group was reliably identified on μCT images and served as good indicator for orienting the CT to match with the MRI. The subchondral cysts that were matched to MRI all consisted of predominantly fibrous bone marrow and frequently had a large number of blood vessels within the tissue. Three of the eight cysts had cartilage intrusions that were located mostly within peripheral trabecular bone, though one cyst contained a nodule of cartilage surrounded by organized fibers with the texture of granulation tissue. The process of image registration was mostly performed manually, but the development of this process will contribute to a more refined, semi-automated process in the future. The ability to correlate the histopathology of CT-identified lesions with a signature patter on MRI will be an important tool for better characterizing the nature of BMLs and understanding the pathogenesis of OA.

L'importance de l'os sous-chondral dans la pathogenèse et la prise en charge de l'arthrose intéresse les cliniciens et la communauté scientifique. En effet, il existe des liens forts entre l'os sous-chondral et le cartilage, maintenant l'intégrité de ce dernier reposant sur l'os sous-chondral pour fournir un support mécanique et un soutien nutritionnel. Ici, nous avons étudié la relation entre les structures osseuses et cartilagineuses et l'approvisionnement vasculaire dans l'arthrose de la humaine.Nous avons recueilli 37 plateaux tibiaux arthrosiques prélevés après arthroplastie totale du genou. Dans ces mêmes plateaux, plusieurs carottes ont été prélevées et scannés par microtomographie. Les projections résultantes ont été reconstruites, puis segmentées manuellement pour séparer l'os sous-chondral de l'os trabéculaire et une analyse microarchitecturale a été développée sous les deux structures osseuses. Les échantillons ont été décalcifiés, coupés en sections de 16 heures, colorés dans de l'HES et classés en 6 groupes selon l'échelle OARSI. La surface de l'os sous-chondral et l'épaisseur et la surface du cartilage articulaire ont été cultivées. Le nombre de vaisseaux dans le sous-chondral a été compté par deux opérateurs différents et une coloration immunofluorescente avec du VEGF a été effectuée. Enfin, le cartilage, l'os sous-chondral et trabéculaire ont été utilisés pour mesurer les marqueurs ribonucléiques et protéiques liés à la vascularisation, l'innervation et l'inflammation.La microstructure de l'os a évolué au fur et à mesure que l'arthrose s'aggrave. L'os sous-chondral s'est épaissi et est devenu plus poreux. La fraction volumique osseuse, l'épaisseur trabéculaire, l'espacement et le nombre de trabécules ont été corrélés positivement avec le score OARSI. Une diminution significative du nombre de vaisseaux sanguins a été observée au dernier stade de l'arthrose. Enfin, les marqueurs ribonucléiques et protéiques liés à la vascularisation, à l'innervation et à l'inflammation ont été modulés au cours du développement de la pathologie. Pris ensemble, nos données montrent une interaction et des structures de soutien dynamiques entre l'os sous-chondral et le cartilage. La compréhension des voies de signalisation, l'unité biochimique du cartilage dans les articulations et la communication intercellulaire entre le cartilage et l'os sous-chondral peuvent mener à l'élaboration de stratégies plus efficaces pour traiter les patients souffrant d'arthrose. / The importance of subchondral bone in the pathogenesis and management of osteoarthritis retain the interest of clinicians and the scientific community. Indeed, there are strong links between the subchondral bone and the cartilage, maintaining the integrity of the latter resting on the subchondral bone to provide mechanical and nutritional support. Here, we investigated the relationship between bone and cartilage structures and vascular supply in human osteoarthritis.We collected 37 osteoarthritic tibial plates taken after total knee arthroplasty. In these same plates, several carrots were removed and scanned by microtomography. The resulting projections were reconstructed, then manually segmented to separate the subchondral bone from the trabecular bone and a microarchitectural analysis was done on both bone structures. The samples were decalcified, cut into 4 μm sections, stained in HES and classified into 6 groups according to the OARSI scale. The surface of the subchondral bone and the thickness and surface of the articular cartilage were measured. The number of vessels in the subchondral region was counted by two different operators and a VEGF immunofluorescent staining was performed. Finally, cartilage, subchondral and trabecular bone were used to measure ribonucleic and protein markers related to vascularization, innervation and inflammation.The microconstructure of the bone has evolved as osteoarthritis worsens. The subchondral bone has thickened and become more porous. Bone volume fraction, trabecular thickness, spacing and number of trabeculae were positively correlated with the OARSI score. A significant decrease in the number of blood vessels was observed in the last stage of osteoarthritis. Finally, ribonucleic and protein markers related to vascularization, innervation and inflammation were modulated during the development of the pathology. Taken together, our data show dynamic interaction and support structures between subchondral bone and cartilage. Understanding of signaling pathways, the biochemical unity of cartilage in the joints and intercellular communication between cartilage and subchondral bone can lead to the development of more effective strategies for treating patients with osteoarthritis.

No description available.