1. Septic arthritis The joint infection occurs at any age group
but more common in children , usually affects
one joint , If more than one joint is infected, an
immune defect should be suspected .
A joint may be contaminated by:
I. direct intervention-following surgery, aspiration or perforating injury.
2. spread from adjacent bone.
3. haematogenous spread-direct infection of synovium by septic emboli.

2. Radiological finding(Plain film)
1- distention of the joint : due to synovial thickening and effusion. 2- osteoporosis : local decrease of bone density around the joint due to hyperemia & immobilization. 3- joint narrowing : due to destruction of cartilage which affect all compartment of the joint . 4- cortical destruction : initially appears as local blurred area and then eroded the cortex at all subarticular surface , finally subarticular bone destruction occurs. sever cases are characterized by massive destruction , subluxation and dislocation. During recovery , bone calcify and in severe cases fibrous and bony ankylosis may result.

4. Avascular necrosis
Osteochondritis of the femoral capital epiphysis ( Perth’s disease )
This condition is commoner in boys than girls (M : F = 4 : I) and most cases present between 4 and 9 years of age , following ischaemia the ossific nucleus of epiphysis necroses, causing growth arrest. The overlying cartilage,which is supplied by synovial fluid, survives and thickens especially in the non weight-bearing regions, medially and laterally. Dense, necrotic bone resorbs and is slowly replaced by vital bone.

5. Radiological finding(Plain film)
1- lateral dislocation of the femoral head : due to joint effusion or thickening in the ligamentum teres .
2- subcortical fissures in the femoral ossific nucleus , transient and early signs .
3- reduction in the size of ossification epiphysis , due to growth retardation , which lead to wide medial part of the joint.
4- increase density of the femoral ossification nucleus due to trabecular compression .

7. The role of MRI in joint disease)
Knee joint : is very useful in diagnosis of menisci
tears, the fluid or mixoid change within the
menisci seen as bright signal intensity on T2 WI ,
if signal extend to the surface of menisci a tear is
present .
The cruciate ligament are especially shown , the
posterior Ligament is thick and easy seen , but it
is not often injured , while the anterior one is
thinner and more easily damage , often it is
associated with medial menisci injury .

9. Shoulder joint : MRI show the change in tendons , the tendonitis and tear seen as bright signal in T2 weighted image at the rotated cuff insertion.

10. RADIOLOGY OF SKELETAL SYSTEM Lecture 4 Spines

11. Plain spine X-rays
In most units worldwide, plain X-rays are still widely used.
AP & LAT. Views of region of interest is initially used, supplementary oblique views are occasionally helpful to show the IV foramina in the cervical region and the pars interarticularis in the lumbar region.
Stability of the cervical or lumbar spine still is best studied by lateral views in flexion and extension.
plain X-ray remain the first-line investigation for spinal trauma.

12. Vertebral body located anteriorly with rectangular shape , the vertebral end plates (the upper and lower margins of each vertebra ) is well defined ,sclerotic and regular out line . Vertebral bodies separated from each other by disk which appears as radiolucent space which radiologically called disk space . Posterior neural arch consist of vertebral pedicles , lamina, transverses process and spinous process .

15. On conventional radiographs: bone density is assessed, the next observation should be the alignment of the spine. A normal spine should show cervical and lumbar lordosis,thoracic kyphosis. Abnormalities in alignment may result from incorrect positioning of the patient but often reflect an underlying problem.

16. Such abnormalities may be minor such as straightening or reversal of normal cervical lordosis in the case of muscle spasm. More significant misalignment such as scoliosis, may be either idiopathic or secondary to an underlying lesion. Major alterations in alignment such as subluxation may result from trauma.

17. Computed Tomography: CT is widely used to image the spine in the evaluation of almost all types of pathologic conditions Most common indications include degenerative disc disease , spinal tumors and trauma.

18. Also give detailed information on bony structures.
CT examination can demonstrate the ligamentum flavum, nerve roots , epidural fat and other structures that cannot be identified discretely on plain films .
Also give detailed information on bony structures.

20. MR Imaging:
MR imaging allows visualization of intraspinal anatomy with much higher resolution than does any other modality.
The ability to image directly in the sagittal plane contributes a great
deal to the evaluation of the diseased spine

21. Because dense cortical bone has few mobile protons ,MR imaging is sometimes limited in its ability to demonstrate either osteophytes that may be a source of clinical symptoms or calcific components of other lesions.
In such cases, CT with its superb depiction of bony detail may be useful as an adjunct examination.
On the other hand, MR imaging is very sensitive in its ability to detect abnormalities in bone marrow.

22. The vertebral bodies normally contain a large amount of bone marrow.
On a T1-weighted image, normal adult (yellow/fatty) bone marrow has a "high signal" (i.e., it is hyperintense, or whitish in color), and CSF has a "low signal" (i.e., it is hypointense, or black in color).
Neural tissue, such as the spinal cord or nerve roots, is intermediate in signal intensity.
Cortical bone, lacking mobile protons to produce a signal, is hypointense on all pulse sequences.

23. On T2-WI , marrow becomes lower in signal intensity, CSF becomes hyperintense, and neural tissue maintains an intermediate signal intensity.
However, the spinal cord appears relatively lower in signal intensity, as it is surrounded by CSF with its very high signal intensity.
The intervertebral discs in normal individuals are typically of intermediate signal on T1-WI and because of their water content, appear hyperintense on T2-weighted images.

25. Myelography: is employed most commonly to evaluate the disks herniations and to rule out spinal cord compression caused by tumor or trauma.
CT and MR imaging have replaced myelography.
However, in many locations still commonly performed.
It is often followed by a post myelogram CT examination.

26. Radiological Sings of abnormality:
1- disk space narrowing : decrease the height of disk in compared with neighbor disk spaces which must be near equal height , narrowed disk space seen in the infected disk ( diskitis ) or in the degenerative disk disease.
2- vertebral body collapse : decrease height of the vertebra which can involves all vertebra
( vertebra plana ) , or part of it e.g. anterior part (wedge collapse) this condition seen in the trauma or tumor ( either primary or secondary ), can be detected by plain film , CT scan and MRI.

27. 3-alteration of vertebral body density : either decrease which can be localized ( local lytic lesion ) or generalized ( osteoporosis or osteomalacia) , or increase which also either local or generalized , best and early detected by CT scan and then by plain film , less by MRI.
4- pedicles destruction : the pedicles are best seen on frontal view ,destruction of pedicles causes them to disappear ,this sign mostly seen in secondary metastases.  
5- para-vertebral mass: it appear as soft tissue swelling adjacent to the spine, it occurs with infection but may also seen with malignant neoplasm and following trauma.

28. Degenerative disk disease( spondylosis )
is a useful general term for this process caused by wear and tear. The process involves the intervertebral discs, vertebral bodies and facet joints usually all together but to varying extent. 
The degenerated disks may herniated into the surrounding tissues and may presses on the spinal cord or spinal nerves.
The degenerated discs often stimulate the formation of osteophytes which may also presses on spinal cord.

29. Degenerative disk disease( spondylosis )
The degenerated disks most commonly occurs in the lower cervical and lower lumber regions.
Even when there is disc herniation producing neurological signs plain film of the spine may be normal .

30. Radiological features of spondylosis in plain film
1- disk space narrowing .
2- irregular , sclerotic vertebral end plat.
3- osteophytes , (anterior and posterior) , the posterior osteophytes more serous because it will cause compression on the exit foramen of nerve root .

32. MRI features of spondylosis :
The disk is seen clear in the MRI , the first sign of degenerative disk disease is decrease signal intensity in T2 weighted image ( dehydrated disk ) , then narrowing disk space , with irregular vertebral end plat .
The herniated disk is easy seen by MRI in sagittal view T2 weighted image , the disc protrusion vary in size from small bulge ( which can be central or paracentral and some time it is extreme lateral ) to complete herniated disc material

33. MRI features of spondylosis :
some time the herniated part may separated from parent disc and migrated for distance (called migratory or sequstred disc) all above types of the herniated disk lead to compression upon the nerve roots and spinal cord , a long compression may lead to ischemic change , this change can be detected by MRI as local increase signal intensity on T2 weighted images.

35. Infection: Osteomyelitis /Diskitis
In adults the disk itself has a relatively poor blood supply, so primary infection is rare.
In children, however, arteries penetrate the growing disk, providing a direct route for hematogenous primary infection .
The most common spinal site of hematogenous infection is the vertebral body, particularly the portions near the endplates, which have the richest blood supply.

36. Infection: Osteomyelitis /Diskitis
Vertebral osteomyelitis then develops ,with loss of marrow signal on T1 weighted images and endplate definition.
As pyogenic infection breaks through the endplate into the disk, diskitis ensues.

37. Plain film :
The early sign is blurred or vanishing the cortex of vertebral endplates , then destruction and narrowing of disk space .
The adjacent vertebral bodies ( above and below ) showing area of destruction as a lytic lesion which vary in size from small size to large involve all vertebral body.

39. MRI :
The early sign is increase signal intensity
( bright in T2 weighted image ) , then reduction in height of the disk with destruction and alteration signal intensity of the adjacent vertebra body , as well as the para- vertebral abscess or collection can be detected easy and detect it extension.

40. STIR sequence
sagittal T1

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