Bilateral rapidly destructive arthrosis of the hip joint resulting from subchondral fracture with superimposed secondary osteonecrosis.

A 57-year-old woman suffered rapid destruction of both hip joints over a 10 months period. At the first visit, her radiographs demonstrated slight joint space narrowing and acetabular cyst formation in both hips. Five months later, joint space narrowing had further progressed, and intra-articular injection of steroid was given in both hips. However, the hip pain gradually became worse. Five months later, both joint spaces had totally disappeared and both femoral heads had undergone massive collapse. At gross examination, both resected femoral heads showed extensive opaque yellow areas consistent with osteonecrosis. Microscopic examination of these areas revealed evidence of both extensive fracture and callus formation, as well as necrosis throughout, indicating that the osteonecrosis observed in this case was a secondary phenomenon superimposed on pre-existing osteoarthritis and subchondral fracture. There were many pseudogranulomatous lesions in the marrow space and necrotic area, where tiny fragments of bone and articular cartilage, surrounded by histiocytes and giant cells, were embedded, such as are typically seen in rapidly destructive arthrosis. No radiologic or morphologic evidence of primary osteonecrosis was noted. This case indicates that at least some cases of rapidly destructive arthritis are the result of subchondral fracture with superimposed secondary osteonecrosis.

ECM-Aware Cell-Graph Mining for Bone Tissue Modeling and Classification.

Pathological examination of a biopsy is the most reliable and widely used technique to diagnose bone cancer. However, it suffers from both inter- and intra- observer subjectivity. Techniques for automated tissue modeling and classification can reduce this subjectivity and increases the accuracy of bone cancer diagnosis. This paper presents a graph theoretical method, called extracellular matrix (ECM)-aware cell-graph mining, that combines the ECM formation with the distribution of cells in hematoxylin and eosin (H&E) stained histopathological images of bone tissues samples. This method can identify different types of cells that coexist in the same tissue as a result of its functional state. Thus, it models the structure-function relationships more precisely and classifies bone tissue samples accurately for cancer diagnosis. The tissue images are segmented, using the eigenvalues of the Hessian matrix, to compute spatial coordinates of cell nuclei as the nodes of corresponding cell-graph. Upon segmentation a color code is assigned to each node based on the composition of its surrounding ECM. An edge is hypothesized (and established) between a pair of nodes if the corresponding cell membranes are in physical contact and if they share the same color. Hence, multiple colored-cell-graphs coexist in a tissue each modeling a different cell-type organization. Both topological and spectral features of ECM-aware cell-graphs are computed to quantify the structural properties of tissue samples and classify their different functional states as healthy, fractured, or cancerous using support vector machines. Classification accuracy comparison to related work shows that ECM-aware cell-graph approach yields 90.0% whereas Delaunay triangulation and simple cell-graph approach achieves 75.0% and 81.1% accuracy, respectively.

Subchondral fracture following arthroscopic knee surgery. A series of eight cases.

BACKGROUND: Osteonecrosis has been reported as a rare complication of arthroscopic knee surgery, with the diagnosis based on radiographic findings associated with recurrent or worsening clinical symptoms. The term osteonecrosis has been applied to this clinical entity despite a lack of pathologic evidence to support the diagnosis. The purpose of this study was to document the pathologic changes involved in this rare process. METHODS: Patients who had undergone an arthroscopic procedure followed by a total knee replacement within two years were eligible for the study. Inclusion criteria included pre-arthroscopy magnetic resonance imaging findings consistent with a meniscal tear with otherwise normal bone morphology followed by a provisional diagnosis of post-arthroscopy osteonecrosis based on subsequent imaging studies. Patients were excluded if a laser-assisted device had been utilized during the arthroscopy. Seven patients (eight knees) with an average age of sixty-four years met the criteria and were included in the study group. RESULTS: All patients had undergone an arthroscopic medial meniscectomy, and two also had had a chondroplasty, with use of a mechanical shaver. Seven of the post-arthroscopy lesions involved the medial femoral condyle, and one lesion involved the medial tibial plateau. Pathologic analysis revealed a subchondral fracture with callus formation, indicated by the presence of woven bone, in all cases. Four patients had essentially intact articular cartilage overlying the lesion, which was characterized by disruption of the trabecular architecture indicative of subchondral bone fracture. The other four patients had an isolated osteochondral defect with reparative tissue within the base of the defect. Only two knees had localized evidence of osteonecrosis, which appeared to be secondary to the fracture. CONCLUSIONS: This study provides pathologic evidence supporting the concept that subchondral fracture, and not osteonecrosis, is the major event in this rare complication following arthroscopy. Further investigation into the etiology of this condition is warranted.

Rapid acetabular osteolysis secondary to subchondral insufficiency fracture.

A 93-year-old man presented with a one-month history of persistent left hip pain of sudden onset. At first visit, radiographs revealed a fracture line at the medial portion of the acetabulum with no displacement. Magnetic resonance imaging revealed bone marrow edema in the corresponding medial portion of the acetabulum. Radiographs obtained 2 months later showed rapid acetabular osteolysis with associated prominent migration of the femoral head into the acetabulum. Histology obtained from the hip joint was consistent with a subchondral insufficiency fracture with no evidence of massive chondrolysis. Our case was considered as a subchondral insufficiency fracture of the left acetabulum resulting in rapid acetabular osteolysis (protrusio acetabuli).

Rapid destruction of the femoral head after a single intraarticular injection of corticosteroid into the hip joint.

We describe a 50-year-old woman who had a 10-year history of left groin pain. She experienced rapid collapse of the femoral head during a 3-month period after a single injection of corticosteroid into the hip joint, in which osteonecrosis was histologically observed.

The role of joint architecture in the etiology of arthritis.

Focal degenerative changes occur in some joints very early in life. These changes in the articular cartilage appear to occur in the unloaded, rather than the loaded, areas of the joint. One possible cause for this pattern of degeneration is lack of use or stress in these particular areas of the joint; just as unused bone and unused muscle atrophy, so may unused cartilage. If these unloaded areas were never subjected to mechanical stress, degeneration at these sites perhaps would not be important. However, bones, including their articular ends, are in a constant state of change through the process of remodeling, which continues throughout life. Joint surfaces are not, in general, spherical, and therefore must be incongruent during most of their arc of movement. In the young person, this incongruity maintains physiologic loading and joint nutrition. Studies have shown age-related changes in the remodeling process that lead to increasing joint congruity in old age. These age-related increases in congruity may result in a redistribution of load in the joint such that there is an increased stress on formerly unloaded atrophic cartilage. Arthritis always results in a change in joint shape. It is suggested that a change in shape caused by a disturbance in the remodeling process may itself be an important contributing cause of osteoarthritis.