Lecture no. 2 Prepared by Dr.Salah Mohammad Fatih MBChB,DMRD,FIBMS(radiology) Solitary bone lesions

Radiological approach for diagnosis of solitary bone lesions

 1 st try to decide whether the lesion is benign (i.e. stable or very slow growing) or whether the lesion is aggressive (malignant tumor or infection).

1. Age of the patient. This can be an extremely important determinant in some lesions in which the age range of occurrence may be quite narrow. For example, Malignant osseous lesions in patients; under one year ; metastatic neuroblastoma. age range of 1 to 30 years ; osteosarcoma or Ewing's sarcoma. In the 30- to 60-years range ; chondrosarcoma, primary lymphoma, or malignant fibrous histiocytoma, age range over 50 ; metastatic disease or multiple myeloma.

2-Location of the lesion Three different types of locations should be noted: 1- the particular bone that is involved. ( long bone,flat bone, small bones) 3- the location in a transverse axis. (central, eccentric, or a cortically- based). 3- the location in a longitudinal axis of a long bone. (epiphysis, metaphysis or diaphysis). Certain lesion occur at the certain sites; E.g. Osteomyelitis characteristically occur in the metaphyseal areas specially of the knee & lower tibia whereas giant cell tumor occur in subarticular areas

3- zone of transition i.e. Zone of transition of the lesion from abnormal to normal bone; A wide zone of transition denotes an aggressive lesion. A narrow zone is a much less aggressive lesion. well defined sclerotic edge is almost certainly benign.

4- adjacent cortex Any destruction of the adjacent cortex indicates an aggressive lesion such as a malignant tumor or osteomyelitis

5- Expansion Bone expansion with an intact well formed cortex usually indicate a slow growing lesion such as an encondroma or fibrous dysplasia.

6-periosteal reaction Presence of an active periosteal reaction in the absence of the trauma usually indicates an aggressive lesion

7-Soft tissue involvement. Cortical breakthrough of a bone lesion to create a soft tissue mass generally suggest an aggressive lesion (infection or tumor). ill define soft tissue swelling adjacent to focal bone destructive lesion suggest infection. well define soft tissue swelling adjacent to the bone lesion suggest neoplasm& such soft tissue masses will often distort but not obliterate nearby muscle planes.

8-Pattern of bone destruction Common terminology includes ; "geographic" (well-defined or map-like lesion, the least aggressive pattern), "moth-eaten" (holes, with less well-defined margins, appearing more aggressive) "permeative" (a poorly demarcated pattern which is often very difficult to visualize and represents a highly aggressive lesion)

9. calcific densities within the lesion (tumor matrix) allow categorization of a lesion as bone producing versus cartilage producing. Diffuse ill defined calcification within the lesion suggest osteoid lesion. presence of a patchy calcification of popcorn or stippled type with density more than normal bone usually indicate cartilaginous tumor

10-Size of the lesion Generally, a larger lesion (greater than 5 cm) is more likely to be malignant or aggressive, but there are many exceptions to this statement, and other determinants are generally more important than this one.

11. Polyostotic versus Monostotic This is the last most important point, since polyostotic lesions automatically restrict the number of disease processes that might be considered. For example, nonaggressive polyostotic lesions should be confined to; fibrous dysplasia Paget's disease Histiocytosis multiple exostosis multiple enchondromatosis Aggressive polyostotic lesions would be confined to osseous metastases multiple myeloma primary bone tumor with osseous metastases, multifocal osteomyelitis, aggressive histiocytosis, and multifocal vascular bone tumors.

Bone tumors

Investigations; 1- plain film radiography in general is the best imaging technique for making the Dx. 2- MRI&CT often shows the full extend of the tumor & show the effects on the surrounding structures& the relation ship to the neurovascular bundles 3- Isotope scan is used to Dx metastatic bone disease

Primary bone tumors 1- malignant 2- benign

1- primary malignant bone tumors

1- plain radiograph; usually have; Wide zone of transition Poorly defined margin. Lesion may destroy the cortex. Periosteal reaction is often present. Soft tissue mass may be seen.

Poorly defined margin & wide zone of transition. Soft tissue mass destroy the cortex Periosteal reaction

2- Isotope scan Malignant bone tumor show increased activity in the lesion.

3-MRI MRI is the most accurate technique in showing the local extend of the tumor with the advantage that images may be produced in coronal & sagittal planes & MRI provides this information better than CT

Osteosarcoma(osteogenic sarcoma) Age ; mainly 5-20 years but also seen in elderly following malignant transformation of paget’s disease. Location;Is often arise in the metaphysis, most commonly around the knee joint. X-ray finding; 1. often there is bone destruction & new bone formation with typical florid speculated periosteal reaction(sunray appearance). 2. The tumor may elevate periosteum to form Codman’s triangle

Chondrosarcoma Age; years Site; most common sites are pelvic bones, scapulae, humerie & femorae Radiographic finding; 1. It produce lytic expansible lesion contains flecks of calcification. 2. It can be difficult to be distinguished from its benign counterpart (enchndroma), but condrosarcoma usually less well defined in at least one portion of its outline & may show a periosteal reaction & soft tissue component. chondrosarcoma may arise from malignant degeneration of the benign cartilaginous tumors.

Ewing sarcoma Is a highly malignant tumor. Age; most commonly occur in the children,usually between 5-15 years. site; it arise mostly in the long bone, usually in diaphyseal region. X-ray finding; It produce an ill define bone destruction with periosteal reaction that is typically onion skin in appearance.

Giant cell tumor Has features of both malignant & benign tumor, it is locally invasive but rarely metastasizes. Age; usually years. site; it is most commonly occur around the knee & wrist after the epiphysis have fused. X-ray finding; Expanding destructive lesion which is subarticular in position. the margin is fairly well defined but the cortex is thin & may be in places completely destroyed.

2-Benign bone tumors

Common x-ray finding; Narrow zone of transition with sclerotic rim. Cause expansion but rarely produce cortical breakdown. periosteal reaction is unusual unless there is has been a fracture through the lesion. There is no soft tissue mass.

Isotope scan; shows little or no increase in the activity unless fracture has been occurred through the lesion. MRI & CT scan: are rarely needed in their evaluation

Encondroma Are seen as lytic expanding lesion. Most commonly seen in the hand. They often contain flecks of calcium & frequently present as a pathological fracture.

Fibrus dysplasia May affect one or more bone It occur most commonly in the long bones& ribs. Radiologically it appear as lucent area with a well defined edge and may expand the bone, there may be sclerotic rim around the lesion

Simple bone cyst Occurs in children & young adult. Most common sites are humerous & femur X-ray; Lucency across the width of the shaft of the bone with well defined edge. The cortex may be thin & the bone expanded. Often the 1 st clinical finding is pathological fracture

Aneurysmal bone cyst are neoplasm. Mostly seen in children & young adult. Common site; spine, long bone & pelvis. Radiological finding; 1. X-ray; purely lytic & cause massive bone expansion of the cortex. 2. CT & MRI may show the blood pool within the cyst. 3. Major differential Dx is Giant cell tumor

Oseoid osteoma Is a painful condition found most commonly in the femur & tibia in young adults. Radiological appearance; it has a characteristic appearance; Small lucency sometime with central specks of calcification (nidus) surrounded by dense sclerotic rim & periosteal reaction may be seen.

oseomyelitis Usually occur in infant& children. Initial radiographic appearance is normal & bone changes are not visible until days of the infection. Most sensitive imaging modalities are isotope scan & MRI which may shows the disease within 1-2 days.

Acute oseomyelitis Typically affect metaphysis of the long bone. X-ray finding; The earliest sign on the plan radiograph is soft tissue swelling with characteristic obliteration of fat plains & may be apparent within 1st 2 days of the clinical manifestations. local osteoporosis may be seen within days of the onset of the symptoms. bone destruction in the metaphysis with periosteal reaction that eventually may become very extensive & surround the bone to form involucrum which is usually visualized after 3 weeks. Part from the original bone may die & separate to form dense fragment called sequestrum.

sequestrum

Isotope scan; increased activity in both early & delay phase. MRI; is the investigation of choice & may shows evidence of bone edema & pass accumulation in the bone & soft tissue

Chronic oseomyelitis The bone become thickened & loss differentiation between the cortex & the medulla

TB oseomyelitis Spine is the most common site followed by large joints, but any bone may be affected. The disease produce large areas of bone destruction & unlike pyogenic infection, the disease is relatively asymptomatic in the early stage.