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Evaluation of focal bone lesions: basic principles and clinical scenarios

Royal National Orthopaedic Hospital, Brockley Hill, Stanmore, Middlesex HA7 4LP, UK

View larger version (300K): [in a new window]   Figure 1. (a) Simple bone cyst in the os calcis in an adult. Geographic bone destruction, well-defined, sclerotic margin and narrow zone of transition all imply slow growth. (b) Distal ulnar giant cell tumour (GCT). Geographic bone destruction, well-defined, non-sclerotic edge and narrow zone of transition imply more rapid growth rate than in (a). (c) Distal radial GCT. Geographic bone destruction, poorly-defined edge with no marginal sclerosis, and a narrow zone of transition imply a more aggressive, rapidly-growing lesion. Trabeculation and cortical expansion are non-aggressive features, and commonly seen in GCTs. These lesions are often seen in the distal radius. (d) Metastasis in the distal humerus. Geographic bone destruction with an ill-defined edge and moth-eaten appearance imply rapid bone lysis due to an aggressive lesion. (e) Primary bone lymphoma in the proximal femur. Moth-eaten bone destruction with a wide zone of transition and no identifiable edge—an aggressive, rapidly-growing lesion. (f) Ewing's sarcoma in the proximal humerus. Permeative bone destruction with small lucencies visible in the proximal diaphysis. There is widespread cortical abnormality and an extraosseous mass. A multilamellated periosteal reaction ("onion-skin" periosteal reaction) is noted.

View larger version (73K): [in a new window]   Figure 2. Enchondroma of the middle phalanx. A well-defined lesion showing geographic bone destruction, a narrow zone of transition, and a little marginal sclerosis proximally is suggestive of slow growth. Endosteal scalloping (arrows) and chondral-type matrix mineralization suggest a tumour of cartilage origin.

View larger version (133K): [in a new window]   Figure 3. Aneurysmal bone cyst (ABC) proximal tibial metaphysis. The marked expansion has thinned the posterior and medial cortex such that it is no longer radiographically visible. The interface with preserved tibia is well-defined with some sclerosis (a, arrow). A multilamellated periosteal response can be seen at the inferior margin of the lesion—a periosteal buttress (b, arrow)—often identified in this condition.

View larger version (121K): [in a new window]   Figure 4. Ewing's sarcoma in the femoral diaphysis. (a) Anteroposterior radiograph shows subtle lucency in the mid-femur, with periosteal reaction and soft tissue mass. A prominent mass of periosteal new bone on the medial side of the femur shows smooth indentation called saucerization, typically found in Ewing's sarcoma. (b) Coronal short tau inversion recovery MRI shows the cause of saucerization—the periosteal new bone has been pressure-eroded by extraosseous tumour.

View larger version (111K): [in a new window]   Figure 5. (a) Chondrosarcoma of the right ilium. Matrix mineralization of chondral type (punctate, in rings, arcs and commas), both in the ilium and also in the extraosseous mass (arrow). (b) Distal femoral osteosarcoma, matrix ossification. Aggressive, destructive lesion, with ill-defined medullary sclerosis and a large extraosseous mass surrounding the distal metadiaphysis. The mass contains streaks, and some cloud-like, fluffy densities, due to tumour bone formation. A small ossified nodule at the posteroinferior aspect of the mass is likely to represent metastasis to a local lymph node (arrow). A Codman's triangle can be seen at the anterosuperior aspect (curved arrow). (c) Ground glass density due to fibrous dysplasia. A well-defined lesion with a sclerotic rim is projected over the intertrochanteric region of the femur: it contains a uniform hazy increased density, due to fine bone spicules or thin calcified trabeculae.

View larger version (113K): [in a new window]   Figure 6. (a) Solid periosteal reaction which has absorbed onto the underlying cortex of the mid-tibia due to stress response. No fracture line is seen in the tibia but localized periosteal reaction at the superior aspect of the fibula indicates a fatigue fracture (arrow). (b) Langerhans cell histiocytosis distal humerus. There is a periosteal reaction indicated by a single lamella of bone, with a moth-eaten pattern of bone destruction. (c) Proximal tibial osteosarcoma. There is a spiculated periosteal reaction with a "hair-on-end" appearance at the posterior aspect of the diaphysis proximally, and diffuse medullary sclerosis with permeative destructive pattern indicates the underlying aggressive tumour.

View larger version (119K): [in a new window]   Figure 7. Parosteal lipoma anterior to left femur. (a) A fatty, lucent mass can be seen associated with mature ossification and cortical thickening at the anteromedial aspect of the bone (arrows). (b) Axial T1 weighted MR image shows fatty marrow within the ossified component (arrow), the homogeneously fatty mass and cortical thickening anteromedially. In this case, the periosteum has reacted to the parosteal location of the mass—there is no cortical breakthrough or involvement of the medulla.

View larger version (70K): [in a new window]   Figure 8. Double-density sign in mid-tibial osteoid osteoma. (a) Frontal and (b) lateral static images from radioisotope bone scan show central high activity due to the tumour nidus, and a surrounding zone of lesser activity due to reactive bone.

View larger version (79K): [in a new window]   Figure 9. (a) Axial CT image showing the nidus of osteoid osteoma, with surrounding reactive sclerosis, in the femoral head. (b) A radiofrequency electrode has been placed percutaneously into the centre of the lesion.

View larger version (218K): [in a new window]   Figure 1. (a) Eccentric solid periosteal reaction/cortical thickening, and medullary sclerosis in the proximal tibia. No nidus or fracture line is seen, and there is no focal bone destruction. (b) Coronal short tau inversion recovery MR image. There is medullary oedema and low signal (representing callus), with adjacent cortical irregularity. Oedema is seen adjacent to tibia in muscle and subcutaneous tissues. (c) Sagittal T1 MRI. Medullary oedema is seen as reduced signal within fatty marrow, and a cortical lesion is seen posteriorly. (d) Axial proton density and (e) T2 fat-saturated images showing medullary and soft tissue oedema. The cortex is thickened posteriorly, and contains a sagitally-orientated defect, which could be followed on adjacent axial images (arrow). (f) Axial high-resolution CT and (g) sagittal reconstruction. An ill-defined fracture line (arrow) with adjacent periosteal and endosteal callus is seen in the posterior tibia. A longitudinal/sagittal fracture line with surrounding callus is seen on the reconstructed image. Diagnosis: longitudinal tibial fatigue fracture.

View larger version (137K): [in a new window]   Figure 2. (a) Solid periosteal reaction/cortical thickening in the mid-tibia due to osteoid osteoma. (b) Axial high resolution CT with (c) sagittal reconstruction shows the small lucent tumour nidus within the surrounding reactive bone. MR images showed marked bone and extraosseous oedema.

View larger version (154K): [in a new window]   Figure 3. (a) Lateral and (b) anteroposterior radiographs of the mid-tibia in a child showing multilocular expansion affecting predominantly the cortex, but medullary sclerosis and lucency are also seen. The tibia is bowed anteriorly. No fibular involvement can be identified. Diagnosis: osteofibrous dysplasia.

View larger version (139K): [in a new window]   Figure 4. (a) Lateral and (b) anteroposterior radiographs of the mid-tibia and distal tibia and fibula in an adult. A multilocular lesion occupies the medulla with mild cortical expansion. The surrounding bone is sclerotic, and a further lesion is seen in the distal fibula. Diagnosis: adamantinoma. The imaging appearances can be identical to those of osteofibrous dysplasia.

View larger version (92K): [in a new window]   Figure 5. (a) Anteroposterior and (b) lateral radiographs of the femur. The features are those of a well-differentiated/low grade cartilaginous tumour, with chondral-type matrix mineralization and endosteal scalloping (arrows). Histology confirmed a chondrosarcoma, but enchondromas in long bones appear identical. (c) Coronal T1 weighted MR image showing the hypointense lobular chondral tumour. (d) Coronal short tau inversion recovery (STIR) MR image shows a high signal lobular tumour, with small foci of contained signal void due to matrix mineralization. Uncalcified hyaline cartilage typically shows marked hyperintensity on T2 and STIR images. Diagnosis: low grade chondrosarcoma.

View larger version (91K): [in a new window]   Figure 6. (a) Anteroposterior radiograph shows a radiodense lesion with predominantly peripheral mineralization, consistent with a large, mature proximal tibial infarct. (b) Axial CT image confirming peripheral distribution of mineralization typical of an infarct, with no matrix mineralization.

View larger version (133K): [in a new window]   Figure 7. (a) Aggressive bone lysis in the proximal humeral metadiaphysis. A permeative pattern of destruction is seen, with multiple tiny lucencies projected over the medulla, implying cortical involvement. There is an interrupted periosteal response (curved arrow) and an extraosseous mass is evident (arrows). (b) Sagittal short tau inversion recovery (STIR) and (c) T1 MR images show more extensive medullary involvement than suggested by the radiograph. Tumour crosses the growth plate into the epphysis, and extends through the cortex (arrows). The lesion is surrounded by oedema, which is hyperintense to the intermediate signal tumour on the STIR image. (d) Axial T2 weighted MR image showing circumferential extraosseous tumour and surrounding oedema. Diagnosis: Ewing's sarcoma.

View larger version (117K): [in a new window]   Figure 8. (a) Lateral and (b) anteroposterior radiographs of distal humerus in a child. There is moth-eaten aggressive bone destruction with focal cortical disruption (arrow), and periosteal response in a single lamina. (c) Coronal T1 and (d) axial T2 fat-saturated MR images of the distal humerus. There is extensive medullary infiltration, cortical destruction, extraosseous mass (arrow) and oedema. Diagnosis: Unifocal Langerhans cell histiocytosis (eosinophilic granuloma). The imaging findings can be very similar to those of Ewing's sarcoma.

View larger version (130K): [in a new window]   Figure 9. (a) Lateral radiograph of the knee. A densely ossified mass is seen at the posterior aspect of the distal femur, and there is sclerosis projected over the medulla. The cortex of the femur, which cannot be separated from the mass, appears intact. (b) Axial CT obtained prior to biopsy (note skin markers). The mass is diffusely dense, inseparable from posterior femur, and extends through the cortex. No unossified soft tissue component is seen. (c) Coronal T1 and (d) axial T2 MR images show the most densely ossified component of the lesion as low signal on both sequences (arrows). Diffuse ossification in the extraosseous mass is suggested by hypointensity on T2 images. Tumour abuts the popliteal vessels. Diagnosis: parosteal osteosarcoma.

View larger version (93K): [in a new window]   Figure 10. (a) Lateral radiograph of the femur showing an ossified mass abutting the bone. A thick, predominantly single lamina of periosteal new bone extends proximally and distally (arrows). (b) Axial CT through the lesion shows that the ossification is in a peripheral location (zoning phenomenon), and has matured to form an outer cortex and inner medulla. There is a lucent space separating the lesion from the femur. Diagnosis: post-traumatic myositis ossificans.

View larger version (105K): [in a new window]   Figure 11. (a) Lateral radiograph of the knee in an elderly patient. A densely mineralized mass is seen posteriorly, apparently separate from bone. (b) Axial CT confirms that the mass does not arise in bone, and is diffusely mineralized, not displaying the peripheral ossification of post-traumatic myositis ossificans. (c) Sagittal T1 weighted MR image shows a densely calcified mass and a large posterior unmineralized component (arrows). The mass arises in soft tissue. Diagnosis: synovial sarcoma.