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HUMERUS
Capitulum
Panner's disease is an osteochondrosis of the capitulum
of the humerus, probably representing true osteonecrosis.
This is a rare disease first described in 1927 by Panner.
Further descriptions over time indicate that this disease
typically occurs between the ages of 5 and 10 years and affects
boys almost exclusively, most of the time being linked
to a history of trauma.
Clinical findings in Panner's disease typically are mild
and complete recovery is frequent. Pain and stiffness and
restricted extension motion of the elbow are seen as well
as local tenderness over the capitulum. Effusion, and sometimes
even a flexion contracture can be detected on physical examination.
Radiographically, increased density of the capitulum, fissuring,
increase in the radio-humeral space, and eventually fragmentation
and resorption can occur. Often times comparison radiographs
to the uninvolved side can be helpful in cases of subtle Panner's
disease. Over time, reconstitution of the capitulum is observed,
and in most cases no residual deformity is seen.
Detecting of the subchondral radiolucent band in the capitulum
in early stages of this disorder is very similar to Legg-Calve-Perthes
disease. This abnormality is a similar phenomenon as the crescent
sign, representing subchondral collapse indicating that osteonecrosis
has occurred probably secondary to a traumatic insult with
disruption of the blood supply to the bone. Panner's disease
occurs at an age when the capitulum is supplied by only one
or two discrete vessels. Lateral compression injuries resulting
from repetitive valgus stresses damages the blood supply.
The major differential diagnosis for Panner's disease is osteochondritis
dissecans and the radiographic findings are essentially identical.
Principally, the differential diagnosis is based on the age
of the patient with osteochondritis dissecans typically occurring
in adolescence or adults at a time when ossification of the
capitulum is completed. Both etiologies, then, are the result
of trauma.
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AP and tangential views of the elbow
demonstrating cystic lucency of the capitulum consistent
with osteochondritis dissecans or AVN
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AP and oblique lateral views reveal
similar findings as in the previous figure. The definitive
diagnosis of avascular necrosis versus osteochondritis
dissecans based on these x-rays is unreasonable.
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HASS' DISEASE
AVN of the SHOULDER
Avascular necrosis of the humeral head is described by the
eponym Hass' disease. The typical radiographic findings of
avascular necrosis such as mixed sclerosis and lucency, fragmentation,
and sub articular collapse are present in the proximal humeral
epiphysis in a similar fashion as classic avascular necrosis
of the hip. The subarticular crescent-shaped lucency is also
characteristic. The classic radiographic finding which is
the hallmark for avascular necrosis in the proximal humerus
is the "snowcap sign", an intense sub- articular
reactive sclerosis which is quite specific for avascular necrosis
of the humeral head (Hass' disease).
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