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Orthopaedic Clinic

Diagnostic Imaging

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PLAIN FILM RADIOGRAPH  – Radiographic images are produced by attenuation of        x-rays as they pass through intervening tissues before striking an appropriately sensitized plate or film. The more dense an impenetrable the tissue, the lesser the amount of x-rays that will pass and therefore more black or white will be the image in film. Metallic implant will therefore appear intensly white; bones to a lesser degree and soft tissue will have different shades depending on their density. Usually for a scientific interpretation at least two projections preferably perpendicular to each other’s plane is required. A convenient sequence for examination of an x-rays is Mnemonic ABCDE i.e  Alignment - Bone – joint Cartilage - other Diagnostic association/Disc spaces - Everything else (soft tissue shadows).

 

a) The soft tissue

• Muscle planes - wasting or swelling, look for bulging outime.

• Fat pads signs.

• Calcifations in the soft tissue.

 

b) Bones

• Look for overl all alignment.

• The periosteal surface( periosteal new bone formation is seen in infec-tions,

   fracture and margnancy)

• The corlex (evidence of fracture or any destruction)

• The endosteum (is it shaep and clear or excavated)

• Density

• Increased (scerosis) or decreased (osteopenia)

•Trabecular structure – regularly arranged or absent.

 

c ) Joint Cartilage - Radiographically the joint cinsists of the articulating bones iwth a

radiolucent space in between them. This radiolucency is formed by the aiticular caitilage and the synovial fluid and may vary in thickness from 1mm or less in the ceupal joint, to upto 6mm in the knees.

• Note the joint kline orientation and congruity

• Asymmetryb of joint space & mairowing

• Radiolucentcysts

• Periarticular erosiions

• osteophytes

• calcification of cartilage of menisci (Chandrocalcinosis)

 

Describing a fracture - acute or maluniting or noncosion

i )   # line situation in the bone

ii ) Configuratiion of the # line viz transverse, spiral, oblique, comminuted, butterfly etc.

iii) Displacement of distal fragment -shift, angulation (till) rotation ctwist

iv)  # ends

v) Sign of union eq callus

vi) Joint above and belos the # site

vii)  Any evidence of complication -Myositis, AVN, osteopenia, RSD etc.

 

Describibng a tumor-

 

i)   Site of lesion

ii ) Shape of lesion

iii) Radiolucent isclertic

iv) Charcter of the matrix – calcification etc.

v) Sclerotic rimming

vi) Zone of transition - narrow indicates benign, wide malignant.

vii) Bony expansion

viii)Nature of peristeal reation other investingation

 

Arthrography

 

• loose bodies seen as filling defects

• Torn meniscus, ligamentustear can be visualised

• In children unossified caitilage head can be outlines.

• In spine discography c injection into disc can indicate disc degeneration

 

Myelography

 

• largely been replaced by non-invasive methods like MRI

• Main idication remains spinal tumor which are intramedullary & failed back syndrome.

 

Computed Tomography.

 

• Useful in assesment of tumor size & stored

• diagnosis of spinal disorder

• Joint abnormalities

• Pelvic lesion

• Assesment of complex fractures.

With suitable equitrment & software, the transaxial images can be reconstructed to give sagittal and coronal images & even three dimensional reconstruction images.

 

Magnetic Resonance Imaging:

           

The intensity of an MR signal of a tissue depends partly on the density of hydrogen nuclei in the tis-sue scanned and partly on the spin characterstics and relaxation rates follow-ing proton excitation. This phenomenon of relaxation is defined by two independent timeconstants, T1 and T2 thus giving rise to two simultaneous signal. Tissues containing abundant hydrogen (fat, cancellous bone and narrow) emit high intensity ssignals that produce the bright-est images, those containing little hydrogen (cortical bone,ligament, tendon adn air) appear black. Intermediate in the grey scale are caitilage, spinal canal and muscle. In producing, these image the T1 or T2 characterstics of a given tissue can be weighted for aditional information. The T1 - weighted images show greater definition and provide almost anatomical pictures; the T2 - weighted images tell more about the physiological characterstics of the tissue. An STIR (short tau inversion recovery) is a pulse sequence in whic the signal from fat are supresses and ther is encresed controst for water containing tissue.

 

Diagnostic Ultrasonography:

 

Depending on their structure, different tissues are reffered to as highly echogenic, mildly echogenic; and sernixolid organs manifest varying de-gree of echogencity the cystic lesion & deteeting intraarticular fluid. It is also use-ful as a means of screening newborns for congenital disolocation of hip, Rotator culf

fears.

 

Radionucleid Imaging:

 

Photon emission by radionucleirdes taken up in spicific tissue can be recorded by either a simple rectilin-ear scasnner or a gamma camera. to produce an image which reflects current activity in that tissue or rogan . The ideal isotope for this purpose is TC 99 which has short halflife of 6 hours and is rapidly excreted. 99mtc HDP is given I.V and its actuity is recorded in two stages

 

i ) Perfusion or blood poolphase.

ii ) The bone phase - 8 hours late whe the isotope has been taken by the bone.

 

The abnormalityu seen can be

 

i ) Increased activity in the perfusion phase - due to increased soft tissue blood

fau - one of the caudinal features of inflamatiion and infection.

 

ii ) Increased activity in the bone phase: due to increased accumulation in newly forming bone, seen usually in fracture, in-fection, local tumor or any bone healing.

 

iii) Decreased activity in perfusion phase suggest local vascular flow dimention

 

iv) Decreased activity in bone phase is result of absent or dimnishel blood supply to particular part of bone or replacement of bone tissue by fibrous tissue eg – femoral head after termoral neck fractures.

 

Main indication for bane scans are:-

i ) Diagnosis of avascular necrosis of femorathead

ii ) Detection of skeltal secondries

iii) Diagnosis of perthes disease

iv) Diagnosis of stress practure

v) Diagnosis bone abscess

vi) Diagnosis osteoid osteoma

vii) Investingating septic or aseptic loos-ening of hip prosthesis.

 

Other radionuclides used are

i ) 99Tc -Sc

ii ) 67Go - used to identify infection

iii) Indium - III labelled leucocyte are alsoouseful for defectly infection.

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