Its Yet Another Case for Gwilym

Two days later Paul sees the radiograph of 12-year-old Anthony, who has been complaining about pain and swelling of his lower arm for a few weeks (Fig. 8.13). The boy cannot remember a direct trauma. His mother,

I Bone Infarction

Bone Infarct Radiograph
Fig. 8.12 The calcifications within the cancellous bone of this humerus (arrows) are typical of a bone infarct.

however, recalls an incident four weeks ago when her son fell against the furniture while chasing his little sister through the apartment. Paul follows the same procedure he has used in Boris's case and classifies the lesion as a Lodwick grade III (see Table 8.2).

• What is Your Diagnosis? In this age group, Paul must contemplate the following diagnoses:

Osteosarcoma: The osteosarcoma develops in adolescents and young adults preferentially in the proximal humerus as well as the femur and tibia close to the knee joint. It causes osteolytic and osteoblastic destruction of the bone. As it is a fast-growing tumor, the cortical and can-cellous bone are eroded before the surrounding soft tissues are infiltrated. The periosteum does not succeed in capping the process: "sunburst"-like speculations emanate from the affected bone at a 90° angle to its long axis and "onion peel" or triangular ("Codman triangle," Fig. 8.14a) periosteal bone formation is the result. The os-teoblastic sarcoma type leads to sclerosis of the bone and bone formation in the surrounding soft tissues. Pulmonary metastases of this tumor type typically show ossifications (Fig. 8.14b).

I The Case of Anthony

Onion Peel Ray Finding
Fig. 8.13 The findings on this radiograph of 12-year-old Anthony are clear and impressive. Which diagnoses do you have to consider?

Ewing sarcoma: Ewing sarcoma is also a bone tumor of children and adolescents. It is a very aggressive lesion and therefore infiltrates and permeates the bone without giving it a chance to form any substantial sclerotic reaction. Ill-defined destruction of the affected bone results in a radiographic appearance that is often termed "moth-eaten." The periosteum behaves as in the case of osteosarcoma, with unsuccessful periosteal new bone formation (Fig. 8.15). Differentiation between the two entities is not possible radiographically with sufficient certainty.

Osteomyelitis: An acute hematogenous osteomyelitis, an infection of the bone, becomes visible in the radiograph through periosteal new bone formation and defects in the cortex and cancellous bone (Fig. 8.16). These signs, however, develop only weeks after the infection. Morphological differentiation from malignant bone lesions is difficult, especially in children. If the process is successfully walled off within the bone, a "Brodie abscess" is the consequence—a focus of osteolysis surrounded by a thick sclerotic margin. Chronic osteomyelitis is frequently maintained by a sequestered bone fragment that is devascular-ized and therefore inaccessible to antibiotics. These sequestered fragments tend to be very dense on the radiograph and are occasionally surrounded by a cavity, called "Totenlade" in German (meaning "ark of death"). Because they maintain the infection and are often accompanied by fistulas, they must be removed surgically.

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