Bone disease Osteomylitis : Osteomyelitis is most often caused by staphylococcus aureus & usually affects infants & children. The initial radiographs are normal as bone changes are not visible until 10 -14 days after the onset of the infection. The TC 99m radionuclide bone scan and MRI show changes much earlier. the earliest sings on plain radiographs are soft tissue swelling , and bone destruction in the metaphysis with a periosteal reaction that eventually may become very extensive and surround the bone to form an involucrum

part of the original bone may die and form a separate dense fragment known as a sequestrum

a radionuclide bone scan will show increased activity both on the early ( blood pool ) images reflecting hyperaemia and on the delayed bone phase images.

U/S can demonstrate sub periosteal collections of pus . MRI is the imaging modality of choice & shows evidence of bone odema and pus accumulation in the bone & soft tissue .

distinction of neoplasm from osteomyelitis : With malignant bone tumor the radiographs are usually abnormal when the patient first presents , whereas with osteomyelitis the initial film are often normal . The presence of fever & some times of discharging sinuses usually help to diagnose of infective lesion. CT & MRI more informative. Bone scanning is positive in both osteomyelitis & malignant tumour and can not be used in differentiation .

bone infarction : Occurs most often in the intra –articular portions of the bones Can occur in the shaft of a bone in several disease including caisson disease , sickle cell disease or following radiation therapy. . once healed , they appear as irregular calcification in the medulla of along bone.

Multiple focal lesions Metastases : Metastases are by far the commonest malignant bone tumor. Metastases may be sclerotic , lytic or a mixture of lysis& sclerosis Lytic metastases. 1- in adults most commonly arise from a carcinoma of the breast and bronchus , less commonly from carcinoma of the thyroid , kidney or colon . 2- in children from neuroblastoma or leukaemia . Lytic metastases give rise to well defined or ill defined areas of bone destruction with out a sclerotic rim .the lesions vary from small holes to large areas of bone destruction.

Sclerotic metastases appear as ill-defined areas of increased density of varying size with ill-defined margins . 1-in men they are most commonly due to metastases from carcinoma of the prostate . 2-in women from carcinoma of breast , metastases with bone expansion occurs in primary tumour of the kidney & thyroid .

Mixed lytic & sclerotic metastases are not uncommon , they are often seen with carcinoma of beast .

A radionuclide bone scan is much more sensitive for detecting metastases than plain film . MRI is better than radionuclide scanning for the detection of metastases, but it is more difficult to survey the whole skeleton .

Multiple myeloma : frequently seen in bones with active haemopoiesislesions .may resemble lytic metastases in every way but are often better defined - diffuse marrow involvement may give rise to generalized loss of bone density MRI has good role in detecting multiple myloma lesions .

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Generalized decrease bone density ( osteopenia ): Osteoporosis : Is the consequence of a deficiency of protein matrix ( osteoid ) . the remaining bone is normally mineralized and appears normal histologically . The most common causes of osteoporosis are : idiopathic . cushing disease& steroid therapy . .disuse .

Changes of osteoporosis are best seen in the spine , decrease in bone density, compression fractures , vertebral bodies appearing wedged or biconcave , secondary widening of disc spaces . Long bones have thin cortices . Screening by measuring of bone mass using DEXA .

Rickets and osteomalacia : In these condition there are poor mineralization of osteoid .if this occur before epiphyseal closure the condition is known as rickets , in adult the condition is known as osteomalacia . The main causes of both above conditions :. 1- Dietary deficiency of vitamin D , or lack of exposure to sunlight. 2- malabsorption. 3-Renal disease.

In osteomalacia the features are . loss of bone density .Thinning of the trabeculae and the cortex .looser zones .bone deformity vertebral bodies are biconcave , the femora may be bowed & in severe cases the side walls of the pelvis may bend inwards , giving to the so called triradiate pelvis .

In rickets the changes are maximal where bone growth is occurring , so they are best seen at the knee, wrist and ankle .seen as . Deficient the zone of provisional calcification . .widening with irregularly mineralized metaphyses with cupping .increase distance between the visible epiphysis & the calcified portion of the metaphysis . .generalized decrease in bone density . . Deformities of the bones occur because the under mineralized bone is soft , green stick fractures are common .

Hyperparathyroidism: Excess parathyroid hormone secretion mobilizes calcium from the bones , resulting in a decrease in bone density , it may be primary from hyperplasia or tumour of the parathyroid glands or secondary to chronic renal failure . generalized loss of bone density. . subperiosteal bone resorption. . soft tissue calcification. .brown tumour.

Generalized increase in bone density : 1. sclerotic metastases. 2.osteopetrosis . 3 .myelosclerosis.

Alteration of the trabecular pattern & change in shape : occur in the following : I- Paget disease:radiologically the affected bone showing thickening of the trabeculae and of the cortex leading to loss of corticomudellary differentiation & increased bone density together with enlargement of the affected bones .

II.Haemolytic anemia : Radiological bony changes are seen in two main types ( thalassaemia & sickle cell disease ) & both show changes of marrow hyperplasia , but sickle cell disease can also showing signs of bone infarction & infection .

Changes in bone shape :