Osteonecrosis and Osteochondrosis

Abstract

Osteonecrosis (ON) means bone death. The term describes the condition in which bone, due to whatever reason, is deprived of blood and thus oxygen, which leads to ischemia, leading to relatively fast cell death (2–3 h) (McCarthy 2006). This cell death is followed by a complex process of bone resorption and bone formation. Ultimately, it leads, often, to bone degradation and structural collapse (Assouline-Dayan et al. 2002). Interestingly, it is not the necrosis itself that will lead to the collapse, but this is predominantly due to the repair process, particularly the resorptive component of this repair, that leads to the subchondral fractures that are often seen (Glimcher and Kenzora 1979a, b, c). There are many synonyms of osteonecrosis in which the etiology of this disease is often reflected within the name like avascular necrosis, ischemic necrosis, and bone infarction. Aseptic necrosis is also used to emphasize the fact that the condition almost never results from infectious disease (Pearce et al. 2005). Bone infarction is usually reserved to describe osteonecrosis in the metaphysis or diaphysis of a long bone, while osteonecrosis is usually used to describe ischemic death in the epiphysis or subarticular zone. Although osteonecrosis is quite commonly seen in various parts of the skeleton (e.g., hip and shoulder), its incidence and prevalence in the foot and ankle are less common. The percentage in which osteonecrosis involves the foot or ankle is roughly estimated to be around 3–4% (Cooper et al. 2010; Delanois et al. 1998; Issa et al. 2014). However, there is no definitive data that can be extracted from the literature, but if all the different types of osteonecrosis (including the osteochondrosis, see below) are considered, the percentage is most likely higher than the estimated figures.