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Avascular Necrosis and Related Disorders

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.


AP and tangential views of the elbow demonstrating cystic lucency of the capitulum consistent with osteochondritis dissecans or AVN


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.

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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