Histopathological and immunohistochemical aspects of bone tissue in aseptic necrosis of the femoral head

Abstract

Femoral head osteonecrosis, also known as avascular necrosis, is a disease with a multifactorial etiology, characterized by a profound change of bone architecture, which leads to the diminishing of bone resistance and femoral head collapse. The main causes that lead to femoral head necrosis are represented by the decrease of local blood perfusion and increase of intraosseous pressure, because of an excessive development of adipose tissue in the areolas of the trabecular bone tissue in the femoral head. The histopathological and immunohistochemical (IHC) study performed by us showed that most of bone trabeculae were damaged by necrotic-involutive processes, their sizes being reduced, both regarding their length and their diameter; generally, the spans were thin, fragmented, distanced among them, which led to the occurrence of some large areolar cavities, full of conjunctive tissue, rich in adipocytes. Some of the residual bone spans even presented microfractures. In the structure of the trabecular bone tissue, numerous cavities showed lack of content, which indicates the death of osteocytes inside, while the endosteum appeared very thin, with few osteoprogenitor, flattened, difficult to highlight cells. The IHC study showed a low reaction of the bone reparatory processes and a reduced multiplication capacity of bone cells involved in the remodeling and remake of the diseased bone tissue. Nevertheless, there were identified numerous young conjunctive cells (fibroblasts, myofibroblasts), positive to proliferating cell nuclear antigen (PCNA), cells that have a high capacity of multiplication, participating in the formation of a fibrous conjunctive tissue (sclerous) instead of the damaged bone trabeculae. The formation of fibrous conjunctive tissue causes the reduction of mechanical resistance of the femoral head and its collapse. The IHC study of the microvascularization in the femoral head damaged by aseptic osteonecrosis showed the presence of a very low vascular system, both in the residual bone trabeculae and in the sclerous conjunctive tissue. Of the inflammatory cells present in the spongy bone tissue of the femoral head affected by osteonecrosis, the most numerous ones were the macrophages. Both macrophages and T-and B-lymphocytes had a heterogenous distribution.

Therapie chondraler und osteochondraler Läsionen der Hüfte

“…Over time, this can result in the loss of articular cartilage, exposing the underlying bone and leading to the formation of osteochondral lesions. It is important to note that AVN and its association with chondral and osteochondral lesions can vary depending on the specific location and extent of the AVN, as well as individual patient factors [ 28 – 30 ].…”

Emerging factors affecting peri‐implant bone metabolism

“…Interestingly, some studies have reported a local decrease in B‐cell counts in osteonecrosis, while high numbers of activated B cells are presented in the blood 228,232,239,240 …”

The role of immune cells in modulating chronic inflammation and osteonecrosis

“…Compared to healthy people, ONFH patients show significantly higher numbers of CD5+CD19+ B1 cells, CD86+CD19+ and CD95+CD19+ activated B cells, and CD27+CD95+CD19+ memory B cells in the blood ( 79 , 85 ). Conversely, osteonecrotic tissue shows local decreases in the number of memory B cells and the total number of B cells ( 86 ). These observations emphasize the importance of B cells in maintaining the normal bone microenvironment and the ability of different B cell subtypes to influence the progression of osteonecrosis.…”