The Case of Boris Packer

There Any Madicine For Cortex
Fig. 8.1 You see a magnified view of the knee radiograph of Boris Packer. Is there anything abnormal?

• What is Your Diagnosis? These are frequent benign bone tumors in childhood and adolescence:

Enostosis: The enostosis, also called "bone island," is an island of cortical bone within the cancellous bone. Radi-ologically it appears as a focal, mostly round or oval sclerosis of the cancellous bone without any response in the surrounding bone (Fig. 8.2). The enostosis often does not show activity on bone scans and can thus be differentiated from osteoblastic metastases in ambivalent cases.

Enostosis

Enostosis

Differentiating Bone Island

Fig. 8.2 This dense bone island (arrows) is located in the distal metaphysis of the tibia close to the cortex.

Osteoma: An osteoma consists of very dense bone and occurs most often in the paranasal sinuses (Fig. 8.3). It can be associated with intestinal polyposis (Gardner syndrome).

Osteoid osteoma: This tumor is most often located in the bony cortex of the femur and tibia but also in the axial skeleton. It consists of a severe periosteal reaction with new bone formation around an often rod-shaped nidus that contains a neurovascular bundle (Fig. 8.4). Nocturnal pain that is relieved by low-dose acetylsalicylic acid is a typical symptom. The interventional radiologist can treat this lesion by inserting a radiofrequency needle into the nidus and ablating the neurovascular bundle by electrical coagulation or by alcohol instillation.

Enchondroma: An enchondroma is a cartilaginous, lo-bulated tumor within the marrow space of cancellous bone, frequently in the hand bones (Fig. 8.5). It tends to

Osteoma

Osteoma

Frontal Sinus Osteoma Symptoms

Fig. 8.3 This pea-sized dense sclerotic lesion (arrows) sits in the left frontal sinus. It is an osteoma in a typical location.

Fig. 8.2 This dense bone island (arrows) is located in the distal metaphysis of the tibia close to the cortex.

Fig. 8.3 This pea-sized dense sclerotic lesion (arrows) sits in the left frontal sinus. It is an osteoma in a typical location.

I Osteoid

Osteoma

I Osteoid

Osteoma

Frontal Sinus

Fig. 8.4a The dorsal cortex of the tibia is significantly thickened—a nidus can only be suspected. b CT gives more information. The reactive new bone formation around the nidus is well appreciated. This nidus must be resected/drilled out by the surgeons or ablated with alcohol or coagulated electrically by the interventional radiologist.

I Enchondroma

I Enchondroma

Fig. 8.5 A number of typical enchondromas are depicted in the proximal and middle phalanx of this finger. They can cause fractures.

Fig. 8.5 A number of typical enchondromas are depicted in the proximal and middle phalanx of this finger. They can cause fractures.

(syn.: Oilier disease) may be present that may lead to fractures in affected bones during childhood and malignant transformation in adulthood (up to 30%). If soft tissue hemangiomas are also seen, Mafucci syndrome is present.

I Osteochondroma

I Osteochondroma

Osteochondroma Finger

Fig. 8.4a The dorsal cortex of the tibia is significantly thickened—a nidus can only be suspected. b CT gives more information. The reactive new bone formation around the nidus is well appreciated. This nidus must be resected/drilled out by the surgeons or ablated with alcohol or coagulated electrically by the interventional radiologist.

have a sharp margin, can erode the cortex, and occasionally contains "popcorn" shaped calcifications. If symptoms arise, especially in older patients, a malignant transformation into a chondrosarcoma must be excluded. If endchon-dromas arise at multiple locations, an enchondromatosis

Fig. 8.6a This typical cartilaginous exostosis extends medially and takes the bone cortex with it. If these lesions reside in the direct vicinity of a neurovascular bundle, mechanical impairment may develop. They may fracture, as this one has at its base. b This is a broad-based osteochondroma of the proximal metaphysis of the humerus in a young patient (the epiphyseal cartilage is still visible). It shows a thick cartilaginous cap. With increasing age, this chondral cap will lose its thickness. This MR sequence is a dedicated T2-weighted chondral sequence on which the cartilage demonstrates a very high signal. c Chon-dromatous tumors may turn into malignant chondrosarcomas such as this one. The popcorn-like structure of the cartilaginous calcifications is quite typical for this entity. These are tumors of the older patient.

I Nonossifying Fibroma

I Nonossifying Fibroma

Nonossifying Fibroma
Fig. 8.7 Have a look at the bubbly bone lesion (arrows) in the dorsal proximal tibia hugging the bone cortex. It has a sclerotic margin. This is a typical nonossifying fibroma that should best be left untouched. It heals on its own come adulthood.

is a frequent incidental finding in children and adolescents.

Giant cell tumor: The giant cell tumor occurs in early adulthood (never during childhood) and usually lodges close to the knee joint (approx. 50%). It is often associated with an eccentric osteolysis that can erode or expand the cortex (Fig. 8.8a). Infiltration of the soft tissues is possible and emphasizes the semimalignant character of the tumor. In sectional imaging modalities, fluid-fluid interfaces are occasionally visible inside the tumor (Fig. 8.8b).

Paul must, however, also exclude some other diagnoses:

Fibrous dysplasia: In this bone malformation, which can occur as a single lesion or multiple lesions (associated with cafe-au-lait skin lesions and precocious puberty as part of the McCune-Albright syndrome), the tubular bone is expanded and often bent, and the bony cortex is often eroded but not completely perforated. The inner structure of the bone has a "ground glass" appearance (Fig. 8.9a) on CT. In the skull the irregular sclerosis and the expansion of the bone dominate the picture (Fig. 8.9b, c), which can lead to an injury of cranial nerves.

Osteochondroma: An osteochondroma or a osteocartila-ginous exostosis (Fig. 8.6a) is a frequently stalked protrusion of the metaphyseal bone with a cartilaginous cap (Fig. 8.6b) that can calcify and normally decreases in thickness as the skeletal growth comes to an end. The exostoses can cause restrictions of movement as well as injuries to the vessels and nerves. If the thickness of the cap increases again, or if new symptoms arise, a malignant transformation to a chondrosarcoma (up to 25 %) must be excluded, especially if multiple osteochondromas are present (Fig. 8.6c).

Nonossifying fibroma: This tumor has a bubbly, grapelike appearance with a sclerotic margin and is found immediately adjacent to the inner surface of the metaphyseal cortex of mostly long tubular bones. With increasing skeletal age it moves toward the epiphysis (Fig. 8.7). It

Bone cyst:

Simple bone cyst: The simple bone cyst becomes symptomatic when the weakened cortical bone fractures at its site. It is a bubbly lesion located in the metaphysis ofcan-cellous bone close to the epiphysis, often with a sclerotic margin. The lesion is fluid-filled and expands the cortex slightly. If it fractures, hemorrhage into the cyst may occur and a cortical fragment often falls inside the lesion. This is as typical a sign for a bone cyst as there is in radiology and is called the "fallen-fragment sign" (Fig. 8.10a). Aneurysmal bone cyst: This lesion is an osteolytic process and consists of a blood-filled cavity. The aneurysmal bone cyst is located eccentrically in the metaphysis of tubular bones. The cortex may be expanded and perforated. For that reason differentiation from malignant lesions is not always possible. On MRI or CT fluid-fluid interfaces may be seen within the cystic fluid (Fig. 8.10b).

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