Osteonecrosis (ON) results from a reduction or total loss of blood supply to a region of bone,
followed by sclerosis,
collapse and secondary osteoarthritis.
The terms avascular or aseptic necrosis have been applied to subarticular or epiphyseal bone commitment.
Usually,
ON is a non-symptomatic condition and therefore its true prevalence is underestimated.
The clinical significance depends on the grade of articular collapse.
The core causes for bone ischemia are trauma,
corticosteroids and alcoholism,
although many have no evident explanation [1,2].
Osteonecrosis is a common situation among world community and the most typical affected sites are femoral head,
humeral head and scaphoid bone [3].
Legg-Calvé-Perthes (LCP) disease is an idiopathic avascular necrosis of the pediatric hip,
with a male predominance and seen most frequently between the age of 4 and 8 years,
when the femoral head is most at the vascular supply risk [4].
Children,
when symptomatic,
usually have limping gait or just refere knee pain on the affected side.
Older age at the time of diagnosis and an involvement of more than 50% of the femoral head are two indicators of a bad prognosis [4].
After the hip,
the humeral head is the second most common affected site by osteonecrosis [5,6].
It is one of the most important causes for shoulder joint pain,
but is an uncommon condition.
Although trauma is a common cause,
atraumatic necrosis can develop in patients with some risk factors as corticosteroid administration or heavy alcohol intake,
and some systemic disease as sickle cell disease,
rheumatoid arthritis and systemic lupus erythematous [7].
The diagnosis is made based in clinical and radiographic findings.
The treatment depends on the sevetity and chronicity of symptoms as the degree of radiographic progression.
The exact etiology of ON involving the lunate bone (Kienbock disease) is unknow but,
in some cases,
has been associated with history of trauma months before presentation[8].
A single blood supply on palmar or dorsal surface or a dual blood supply with no intraosseous anastomoses may explain some of the vulnerability of the lunate to avascular necrosis [9].
There is also a significant association between ulnar minus variance and Kienbock disease,
as a distal ulna is few milimeters shorter than the distal radius transmiting unequal forces to the lunate bone [3,4].
Conservative management with immobilisation and non-steroidal anti-inflammatory drugs is typically the initial management [9,10].
A radial shortening procedure to correct negative ulnar variance is the most tipical surgical therapy as it reduce the pressure transmitted to the lunate at the wrist [9].
The Freiberg’s disease is another cause of avascular necrosis affecting the metatarsal head with consequent subchondral collapse.
It occurs commonly on the second and third metatarsal heads [4,11] and is more frequently seen in younger females,
related to the trauma of bearing weight in high-heeled shoes [4,12].
It can be bilateral in up to 10% of the cases [13].
Despite the fact that the first ON radiographic sign takes several weeks to occur,
the characteristic imaging features can avoid additional radiologic evaluation.
The initial evaluation starts with a fast and easy method of imaging as radiography,
and the typical radiographic appearance of a compromised bone is patchy areas of lucency and sclerosis.
Occasionally,
radiography may also show early areas of articular collapse [3].
Magnetic Resonance (MR) imaging is generally refered as the most sensitive and specific image modality for diagnosis of ON [14-16].
Computerized Tomography (CT) scanning is not commonly used for the assessment of this condition,
but can be useful for describing the subchondral fractures [17].