OSTEOCHONDROSIS: A group of disorders including osteonecrosis,
normal variation, or stress/trauma related changes that appear
OSTEONECROSIS: A.K.A. Avascular necrosis, AVN, Aseptic
necrosis, Ischemic necrosis. Death to osseous and marrow components
due to a lack of sufficient blood supply. There are two types
of osteonecrosis: 1) Epiphyseal infarction and 2)
These two types of osteonecroses look nothing alike, radiographically.
The metaphyseal infarction (or medullary infarct) most commonly
takes place at the metadiaphyseal region of long bones, typically
the proximal humerus and tibia, and the distal femur. The
radiographic features are described as calcification in a
"serpentine" fashion. This type of osteonecrosis
is rarely of clinical significance.
Medullary bone infarct of distal
Bone infarct of the proximal humerus
The epiphyseal infarction takes place, obviously at the epiphysis,
but more specifically at the subarticular cortex. This type
of osteonecrosis is the focus of this web site.
The terms osteochondrosis and osteonecrosis often times can
cause confusion for students, professors, and practicing doctors.
Most likely this confusion stemmed from discoveries of various
conditions, originally termed "osteochondrosis",
that resulted in an irregular and fragmented radiographic
appearance. It was at that time believed that all of these
conditions were caused by a deficient blood flow due to one
of many causes, which in turn led to necrotic bone, finally
resulting in remodeled, irregular and fragmented bone. Now
we know that not only can a lack of blood supply lead to this
appearance, but also trauma or stress to apophyseal regions
(e.g. tibial tubercle or vertebral endplate) and even completely
normal ossification may, at times, lead to a irregular or
fragmented appearance. Therefore, to group all of these conditions
under one heading of osteochondrosis based on exclusively
radiographic appearance, not taking into account pathogenesis,
etiology, or clinical significance is unrewarding to say the
A heterogeneous group of conditions that look similar on
the plain film, but may or may not involve avascular necrosis,
may or may not be clinically significant, and may at times
be completely normal!
While this is a ridiculous statement, further research has
led to a refinement of the various diseases that fall under
the big umbrella of osteochondrosis.
These different conditions may be grouped into one of three
categories that you may note on the left hand portion of this
page. They are:
- Disorders of true osteonecrosis, either primary or secondary;
- Disorders related to abnormal stress or trauma without
evidence of true osteonecrosis;
- Variations of normal ossification.
Osteonecrosis refers to the death of bone due to a lack of
blood supply. This deficiency may be initiated at the arteries,
veins, or capillaries as a result of many different possible
causes that will eventually compromise the arterial flow.
A fragmented appearance may also be due to abnormal stresses
at a tendon insertion, e.g., Osgood Schlatter's and Sinding-Larsen-Johansson
diseases, or from stresses on the bone itself, e.g., Scheuermann's
disease, without any evidence of loss of blood supply, and
therefore can not be accurately termed osteonecrosis.
The last category of "disorders" is actually
normal or a variation of normal ossification of certain
bones, again without any pathologic evidence of true osteonecrosis.
Those bones include the calcaneus, tarsal navicular, and the