د- نجلاء حنون Lec. 3 Radiology joints disease imaging techniques

1.Plain film examination remains important for imaging joint disease

2.MRI is being used with increasing frequency , MRI is indicated in the following:

.Meniscal & ligamentous tears in the knee .

.Rotator cuff tears of the shoulder

.Avascular necrosis of the hip

.Septic arthritis

3.Artherography :involves injecting contrast medium into the joint space directly& then performing an MR scan . MRI arthrography has a role in the shoulder and wrist.

I.Signs indicating the presence of an arthritis .

1.joint space narrowing : it is due to destruction of articular cartilage ,it occur in all forms of joint disease , except avascular necrosis

2.Soft tissue swelling :swelling of the soft tissue around a joint may be seen in any arthritis accompanied by a joint effusion , it is a feature of inflammatory ,and particularly infective , arthritis . discreet soft tissue swelling around the joints can be seen in the gout due to gouty tophi .

3.Osteoporosis : seen in the bones adjacent to the joints in many painful conditions , the under use of the bones seems to be an important mechanism , it more severe in rheumatoid and tuberculous arthritis .

II.Sings that point to the cause of an arthritis

1.Articular erosions : an erosions is an area of destruction of the articular cortex and the adjacent trabecular bone usually accompanied by destruction of the articular cartilage ,causes of the erosions :

*Inflammatory overgrowth of the synovium ( pannus ) which occurs in

.Rheumatoid arthritis ,which is by far the commonest cause of an erosive arthropathy.

.Juvenile RA ( stills disease ) .

.Psoriasis.

.Reiter disease .

.Ankylosing spondylitis.

.Tuberculosis .

*Response to the deposition of urate crystals in gout .

*Destruction caused by infection ( pyogenic & tuberculos arthritis ).

*Synovial over growth produced by repeated hemorrhage in hemophilia & relating bleeding disorders .

*Newplastic overgrowth of synovium e.g synovial sarcoma.

2.Osteophytes ,subchondral sclerosis & cyst : are all features of osteoarthritis , a characteristic increase in the density of subchondral bone is seen in avascular necrosis .

3.Alteration in the shape of the joint : e.g slipped epiphysis , developmental dysplasia of the hip , osteochondritis dissecans & avascular necrosis in later stage.

RA is a polyarthritis caused by inflammatory overgrowth of synovium known as pannus ,it is virtually always involves the hands & feet , principally the metacarpo-& metatarso-phalangeal joints & the wrist joints .

The changes seen in plain radiograph :

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  .Periarticular soft tissue swelling and osteoporosis.
  
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  .Joint space narrowing due to destruction of the articular cartilage by pannus.
  
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  .Bony erosions which occur initially at the joint margins which seen first around the metatarso -or metacarpophalangeal joints ,proximal interphalangeal joints & on the styloid process of the ulna , later , extensive erosions may disrupt the joint surface
  
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  .Ulnar deviation is usually present at this stage .with very severe destruction , the condition is referred to as arthritis mutilans , similar changes are seen in large joints.
  
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  . With severe disease , there may be subluxation at the atlantoaxial joint due to laxity of the transverse ligaments which holds the odontoid peg against the anterior arch of the atlas , atlantoaxial instability can be well demonstrated with MRI .
  

Juvenile rheumatoid arthritis (still sdisease ; juvenile chronic poly arthritis ):

Shows many features similar to RA but erosions are less prominent . The knee , ankle and wrist are the joints most commonly affected . hyperemia from joint inflammation causes epiphyseal enlargement & premature fusion .

psoriasis :

There is an erosive arthreopathy with predominant involvement of the terminal interphalangeal joints .

In gout ,the deposition of the urate crystals in the joint & in the adjacent bone gives arise to an arthritis which most commonly affects the metatarsophalangeal joint of the big toe ,the radiological changes involving :

1.soft tissue swelling 2 . erosions occur later in coarse of disease and may be at distance from the articular cortex with well defined & often sclerotic edges , produced by deposition of urate crystals . 3 . usually no osteoporosis seen. 4 . localized soft tissue lumps caused by collection of sodium urate , aknown as tophi , which may be large & sometimes showing calcification .

Pyogenic arthritis :

Usually caused by staphylococcus aureus , there is rapid destruction of the articular cartilage followed by destruction of the sub chondral bone and soft tissue swelling seen around joint . Joint effusion is first sing which can be detected by U/S , MRI is often performed if diagnosis is still in doubt

Tuberculous arthritis:

Hip & knee joint are most commonly affected joints radiological features :

1.Joint space narrowing 2.Erosions which may cause extensive destruction of the articular cortex 3. Severe osteoporosis 4. In later stages there may be gross disorganization of the joint with calcify debris near the joint.

Hemophilia & bleeding disrorder :

Repeated haemorrahge in to the joints result in soft tissue swelling , erosions and cyst in subchondral bone , the epiphysis may enlarge & fuse prematurely .

OA is the commonest form of arthritis , resulting from wear & teat of the articular cartilage . the hip & knee are frequently involved , the wrist joints of the hand and metatarsophalngeal joints of the big toe are also frequently involved

Features seen in OA :

1.joint space narrowing : with loss of joint space is maximal in the weight bearing portion of the joint e.g in the hip it is often maximum in the superior part of the joint whereas in the knee it is the medial compartment that usually narrows

2. Osteophytes are bone bony spurs , often quite large which occur at the articular margin

3. Subchondral sclerosis , usually occur in both side of the joint

4. Subchondral cysts may be seen beneath the articular cortex often in association with sub chondral sclerosis , RA & OA are the two types of arthritis most commonly encountered , they show many distinguishable features which listed in the following table :

0A RA

1.joint space narrowing uniform. 2. Erosions a characteristic feature. 3. not a feature but erosion enface may mimic cysts. 4. sclerosis is not a feature unless there is secondary OA. 5. osteoporosis often present .

1.joint space narrowing maximal at weight- bearing site. 2. erosions don’t occur but crumbling of the joint surface may mimic erosions. 3.subchindral cyst & sclerosis may be seen. 4.sclerosis is a prominent feature. 5. no osteoporosis.

Neuropathic joint :

Changes are seen in the feet of diabetics with peripheral neuropathy .The predominant features is resorption of the bones ends and calcification of the arteries in the feet is often present. There may also be bone destruction due to infection . Diagnosing osteomylitis in the bones of the feet in diabetic patient can be difficult because bone destruction can be due to neuropathy ,or to a combination of the two.

Avascular necrosis , also known as osteonecrosis , is where there is death of bone due to interruption of the blood supply . It occur most commonly in the intra articular portions of the bones , is associated with following conditions :

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  Steroid therapy .
  
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  Collagen vascular disease.
  
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  Radiotherapy .
  
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  Sickle cell disease .
  
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  Exposure to high pressure environment e.g tunnel workers & deep-sea divers ( caisson disease ) .
  
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  Fracture.
  

1. Increase density of the subchondral bone with irregularity of the articular contour or even fragmentation of the bone with epiphyseal collapse .

2. Characteristic crescentic lucent line may be seen just beneath the articular cortex.

3.Articular cartilage space is preserved until degenerative changes super even.

4.In sub capital fracture of the femoral neck & fracture through the waist of the scaphoid bone , the femoral head & proximal pole of the scaphoid become fragmented & dense due to the ischemia .

MRI is imaging modality of choice for demonstrating a vascular necrosis and may show changes at time so early when radiograph may be normal .

Osteochondritis

A group of conditions , in which no associated cause for a vascular necrosis can be found . but the osteochondritis are now regarded as being due to impaired blood supply associated with repeated trauma .

A vascular necrosis of the femoral head in children , is the most important example of the osteochondritis . the plain radiograph changes :

1.The earliest change is increase in density and flattening of the femoral epiphyses which later on progress to collapse & fragmentation .

2. metaphysis widened & consequently the femoral neck enlarge and may contain small cyst .

3.Joint space is widened but the accetabulum not affected .

4.With healing, the femoral head reforms but remain permanently flattened & therefore responsible for early OA in later life .

It is localized form of the a vascular necrosis , small fragment of bone becomes separated from the articular surface of a joint leaving a defect , and the bony fragment can often be detected lying free within the joint , this condition occur most frequently in the knee & ankle joints , DX can be established by plain film , but MRI & CT are excellent imaging methods.

Occurs between the age of 9 and 17 years , and may present with pain in the hip or pain referred to the knee . the epiphysis slips posteriorly from normal position it is best appreciated on a lateral film of the hip , with a greater degree of slip , the condition can be recognized on the frontal view as down ward displacement of the epiphysis .

Referring to the dislocation or subluxation of the hip in infant . Best imaging modality is U/S as the head still cartilaginous in this age group not seen in plain film , but later in life condition is easier to DX by plain film and the features are lateral and upper displacement of the head of the femur, increased slope to the acetabular roof is sometimes seen .