Immunohistochemical analysis of bone metabolism in osteonecrosis of the femoral head.

Osteonecrosis of the femoral head occurs because of the suppression of blood circulation. At the level of the area affected by the ischemic phenomenon, there are two types of events, in the first stage there is necrosis of the cellular elements, followed by a reparatory phase of the spongy bone tissue. The objective of the study was the histological and immunohistochemical (IHC) analysis of bone metabolism in the repair phase. We observed the action of the main cells involved in the remodeling, the osteoblasts and the osteoclasts, following the reaction of the markers of their activity: osteoprotegerin, osteonectin, osteopontin. We included 23 patients diagnosed with femoral head osteonecrosis, stage II, Ficat and Arlet classification, biological material required for histological and IHC analysis being obtained during hip arthroplasty. Regardless of the age or presence of risk factors, the reaction to osteoprotegerin was mildly positive, being only highlighted at the level of the reactive dividing line, being absent in the other areas, indicating a reduced activity of inhibiting differentiation and activation of osteoclasts, also highlighted with classical histology methods, the affected area being well-defined and we could observe the necrotic tissue resorption by osteoclasts. The intense positive reaction of osteopontin and osteonectin, especially at the line of demarcation, is due to the increase in the number of osteoblasts required for the synthesis of neoformation bone tissue. We believe that the aspects revealed by our study can be a track in finding new-targeted therapies useful in stopping the development of the disease.