bone diseases 2 word

د- نجلاء حنون

Lec.2
RADIOLOGY
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, but the TC 99m radionuclide bone scan and MRI show changes much earlier in the course of the disease within a day or two .
Typically , , acute osteomyelitis affects the metaphysis of long bones , usually the femur and tibia , 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 . a 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 well before bone changes are evident on plain film, MRI is the imaging modality of choice & shows evidence of bone odema and pus accumulation in the bone & soft tissue .
In chronic osteomylitis the bone becomes thickened & sclerotic with loss of differentiation between the cortex & the medulla . within the bone there may be sequestra & areas of bone destruction ,this type of a lesion is known as bodies abscess .
Tuberculous osteomyelitis affects most frequently the spine & large joints , but any bone can be affected , produces large areas of bone destruction which , unlike pyogenic osteomyelitis , may be relatively asymptomatic in the early stages .
distinction of neoplasm from osteomyelitis :
It is not always possible using imaging tests to distinguish osteomyelitis from abone tumour and biopsy is then needed . with malignant bone tumor the radiographs are usually abnormal when the patient first presents , whereas with osteomyelitis the initial film are often normal .But if early films are not available , difficulties may arise in distinguishing acute osteomyelitis from a highly malignant tumour such as Ewing sarcoma or osteosarcoma , 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 .
Bones infarction :
Bones infarction occurs most often in the intra –articular portions of the bones , also infarct can occur in the shaft of a bone in several disease including caisson disease , sickle cell disease or following radiation therapy , in the acute phase no abnormality is visible , other than a very occasional periosteal reaction . 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 , outnumbering many times primary tumours. Metastases may be sclerotic , lytic or a mixture of lysis& sclerosis . The bones containing red marrow are the ones most frequently affects , namely the spine , skull , ribs, pelvis proximal humeri & femora .
Lytic metastases in adults most commonly arise from a carcinoma of the breast and bronchus , less commonly from carcinoma of the thyroid , kidney or colon And 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 in the long bones , metastases usually arise in the medulla and as they grow they enlarged and destroy the cortex . Metastases and myeloma are virtually the only causes of multiple obvious lytic lesions in bone . Metastases with bone expansion occurs in primary tumour of the kidney & thyroid . Perisotael reaction is uncommon with metastases , except in neuroblastoma .
Sclerotic metastases appear as ill-defined areas of increased density of varying size with ill-defined margins .In men they are most commonly due to metastases from carcinoma of the prostate & in women from carcinoma of breast .
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 , approximately 30% of metastases seen on a bone scan will not be visible on plain films .
MRI is better than radionuclide scanning for the detection of metastases, but it is more difficult to survey the whole skeleton , CT is less sensitive than MRI for detecting metastases .
Multiple myeloma
The myeloma deposits are most frequently seen in bones with active haemopoiesis .The bone lesions may resemble
- Lytic metastases in every waybut are often better defined and may cause expantion of the bone
- Diffuse marrow involvement may give rise to generalized loss of bone density , producing a picture similar to that of osteoporosis
Most myeloma deposit show increased activity on radionuclide bone scan ,in some of lesions even when large on plain X-ray may show no abnormality in bone scan ,MRI has good role in detecting multiple myloma lesions .


Multiple periosteal reactions
Multiple periosteal reactions are seen in conjunction with other sings in following :
-non-accidental injury
-widespread bone infection,e.g congenital syphilis
-venous stasis & ulceration of legs ( usually involving tibia & fibula )
- hypertrophic pulmonary osteoarthropathy , in this condition there is widespread periosteal reactions around bones of forearm & lower legs which , when severe extends to involve the hands & feet , finger clubbing is invariably present , the HPOA is seen in a number of conditions, the commonest of which is carcinoma of bronchus
- scurvy disease

Generalized decrease bone density ( osteopenia ):

The radiological diagnosis of decreased bone density is often difficult , especially as the appearance of the bones are markedly affected by radiographic exposure factors
The main causes of generalized decreased in bone density are :
-osteoporosis
-osteomalcia
-hyperparathyroidism
-multiple myeloma

Osteoporosis :

Is the consequence of a deficiency of protein matrix ( osteoid ) . The remaining bone is normally mineralized and appears normal histologically , but because the matrix is reduced in quantity there is necessarily a reduction in calcium content. Osteoporosis predisposes to fractures , particularly of the vertebral bodies & hips(femoral neck ) .
The most common causes of osteoporosis are :
1.Idiopathic :which subdivided according to age of onset e.g juvenile ,postmenopausal , senile . postmenopausal and senile osteoporosis are the commonest form :up to 50% of women over 60 years of age have osteoporosis
2. Cushing disease& steroid therapy
3.Disuse ( which can be caused by localized pain or immobilization of fracture ) .


Radiological diagnosis of osteoporosis is only made after other disease have been excluded
Changes of osteoporosis are best seen in the spine , in which there is an over all decrease in bone density with cortex stands out clearly as if penciled in , an important feature is collapse of the vertebral bodies , representing compression fractures , which result in Vertebral bodies appearing wedged or biconcave , with secondary widening of adjacent disc spaces .
Long bones have thin corices , many of trabeculae are resorbed but those that remain stand out clearly .

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 result in decresed production of endogenous vitamin D .
2. Malabsorption , result in impaired absorption of calcium & vitamin D
3.renal disease : when rickets developed despite normal amount of vitamin D in the diet , so name of vitamin D- resistance rickets ,& involve ( renal tubular defects, chronic renal failure ).
Regardless of the cause of the osteomalacia or rickets the bone changes are similar
In rickets the changes are maximal where bone growth is occurring , so they are best seen at the knee, wrist and ankle .seen as
1. Deficient the zone of provisional calcification .
2.Widening with irregularly mineralized metaphyses with cupping .
3.Increase distance between the visible epiphysis & the calcified portion of the metaphysis .
4.Generalized decrease in bone density .
5. Deformities of the bones occur because the under mineralized bone is soft , green stick fractures are common .
In osteomalacia the features are
1. Loss of bone density
2.Thinning of the trabeculae and the cortex
3.Looser zones (pseudofracturses ) , appear as lucent band running through the cortex at right angle which may have sclerotic margin making them more oblivious, they are commonest in the scapula , medial aspect of the femoral neck & in the pubic rami.
4.Bone deformity involving mainly the spine in which the vertebral bodies are bi concave , the femora may be bowed & in severe cases the side walls of the pelvis may bend inwards , giving to the so called triradiate pelvis .


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
Radiological sings of hyperparathyroidism :
1. Generalized loss of bone density with loss of the differentiation between the cortex & medulla , in advanced disease there may be marked deformity of the skeleton .
2.The hallmark is subperiosteal bone resorption which occurs particularly in the hands on the radial side of the middle phalanges and at the tips of the terminal phalanges , may associated with resorption of the outer end of the clavicle
3.Soft tissue calcification, vascular calcification & chondrocalcinosis sometimes occurs .
4.Brown tumour are occasionally present : are lytic lesions which may be single or multiple occur more commonly in the mandible & pelvis but any bone may be involve , its rare in the secondary hyperparathyroidism .

Generalized increase in bone density :

The conditions producing this appearance
1. sclerotic metastases are by far the commonest cause , from prostatic & breast
2. osteopetrosis ( marble bone disease ) :it is a congenital disorder in which the bones are densely sclerotic the bones are brittle and may fracture readily but also healed easily
3.myelosclerosis , replacement of the bone marrow by fibrous tissue & lay down of extratrabecular bone in patchy fashion , associated with spleenomegaly .

Alteration of the trabecular pattern & change in shape : occur in the following :
I- Paget disease :
It is usually a chance finding in an elderly patient . One or more bones may be affected, the usual site being the pelvis , spine , skull & long bones , bone softening causes bowing & deformity of the bones with pathological fracture may occur . 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
In the skull there are many circumscribed areas of sclerosis scattered in the skull vault giving mottled appearance , the most important DX are metastases due to prostatic or breast carcinoma which also occur in elderly but no bone expantion seen as with paget disease , pagets disease may mimic tumor on radionuclide bone scans as well as on plain film .

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 .
These sings including :
1. Thinning of the cortex and resorption of some of the trabeculae with thickening & stand out of that which are remain.
2. The skull showing widening of the diploe with perpendicular striation giving an appearance known as hair –on-end .
3. Ribs may be enlarge and the phalanges may become rectangular.
4. infarction at bone ends causes flattening & sclerosis of the humeral and femoral heads .
5. areas of bone destruction with periosteal new bone formation may be seen in the shaft of long bones due to infarction .


Changes in bone shape :
Occur in many form of congenital dysplasia , which all of them being rare , e.g of which is diaphyseal aclasia : in the diaphyseal aclasia ( multiple exostoses ) there are multiple bony projection known as osteochondromas or exostoses , they have cartilaginous cup which may contain calcification , when occur in the long bones they are near the metaphyses & directed away from the joint , occasionally chondrosarcoma may develop in the cartilage cup .