MUSCULOSKELETAL OR BONES IMAGING

MUSCULOSKELETAL OR BONES IMAGING

what are the aim of imaging of musculoskeletal system they are
To be able to list the advantages and risks of plain radiography, computerized tomography, magnetic resonance imaging, ultrasound and isotope scanning when imaging the musculoskeletal system

• To understand how to write a good imaging request card

• To know the law in relation to radiation

INTRODUCTION

Imaging is an intricate part of musculoskeletal diagnosis, and image-guided, minimally invasive techniques also play a major role in treatment. In broad terms, radiographs are the best method of looking for bony lesions or injuries. magnetic reso­nance imaging (MRI) shows bone marrow disease, muscle
tendon and soft-tissue disorders. and ultrasound has better resolution than MRI for small structures. with the added advantage of show­ing dynamic changes. Computerised tomography (CT enables visualization of the fine detail of bony structures, clarifying abnor­malities seen on plain radiographic films

There are occasions when a combination of techniques will be important. and due consideration should be given to reducing the

ionizing radiation burden to the patient. using ultrasound and

MRI as primary investigations whenever appropriate

Comparison with previous radiographs and other images can

be invaluable in making a new diagnosis.Great efforts should be made to obtain such images as this not only reduces the amount of radiation a patient receives but very often improves patient care Type of Imaging

• Radiographs plain X rays are best for bone lesion and injuries

• MRI scanning is goad for bone marrow disease and tendon and soft tissue

disorders

• CT scanning enables visualization of the fine detail of bony structures

• Ultrasound has better resolution in soft tissues and can be used dynamically

HOW TO REQUEST IMAGING

Best practice invariably depends on close collaboration between the radiologist and the referrer and must take into account local expertise and access to facilities.The start of this important communication is most often the request card

The details that are important are

The patient's name• the patient's date of birth the patient's address and post code the post code is often the key to patient administration system (PAS) databases
the telephone number of the patient (enables quick contact with the patient)the patient's weight (obese patients may not be safe in a CT or MRI scanner)in The case of female patients. the date of the last menses (important for all radiation procedures and MRI to exclude the possibility of pregnancy) if she has not been sterilized; other relevant past medical history. i.e. diabetes. epilepsy, renal failure, allergies and anticoagulation, as all of these can affect what contrast can be given safely the name of the clinician who is in charge of care and of the requesting clinician, with a legible contact telephone and/or bleep number

There are absolute contraindications to MRI. These are the presence of pacemaker or cranial aneurysm clips and the first trimester of pregnancy. Around 20% of patients are claustropho­bic and so cannot tolerate being inside the magnet of the MRI scanner
It is important to consider why the request is being made, and what investigation is most appropriate, when filling in a request card. In complex cases, the most appropriate investigation will be best decided after discussion with the radiologist. Radiographers can carry out requests only within defined guidelines. Clear

Summary of Contraindication to MRI

• Pacemakers

• Intracranial dips

• Size and weight above limits far machine

• First trimester of pregnancy

• Caustrophobia

INTERPRETING IMAGING

Highly complex imaging should be left to professional radiologists to interpret, but the clinician should be able to examine a bone radiograph to exclude major abnormalities
Patients who are claustrophobic may often be examined after intravenous sedation with a benzodiazepine. However, the monitoring of sedated patients inside an MRI unit is difficult and potentially hazardous. Each case must be reviewed with regard to risk versus potential benefit. It helps to be warned of potential claustrophobia as simple measures such as showing the patient the magnet some days before the examination may be sufficient to calm anxiety. In addition, a patient who cannot enter the magnet takes a potential examination slot and the time is often wasted

You should develop, learn and practise your own method for ensuring that you study all of these in each case. This will take a long time when you start, but speed comes with practice

Some abnormalities on the radiograph may prompt you to look at other areas of the film or may require an additional view to be taken. This knowledge can be attained only by reading and experience Do not forget that radiologists are always delighted to help you with interpreting a film; they are not so happy when they have to report that an incorrect conclusion has been drawn

TRAUMA

Musculoskeletal trauma is best imaged by an initial plain radiograph. All skeletal radiographs, for whatever reason they are being performed, should be taken from TWO different angles. Usually these are at right angles to each other. This is very important in trauma because a fracture or dislocation may not be visible on a single view If this fails to make a clear diagnosis, or if there is suspicion of soft-tissue injuries, then cross-sectional studies are indicated In the spine, CT is a normal second-line investigation, but this should always be performed with reference to good-quality plain radiographs, including oblique views if necessary There is a risk that CT may fail to diagnose fractures in the axial plane. Sections should be thin, but care must be taken not to cover too wide an area, as the radiation burden may be excessive. This is perhaps even more so with the advent of multislice CT If there is concern about spinal cord compression, MRI will be the technique of choice, and MRI is mandatory in patients in whom there is facetal dislocation if surgical reduction is being considered. MRI is now the preferred technique for assessing root compression

ULTRASOUND

Ligament, tendon and muscle injuries are probably best imaged in the first instance by ultrasound. This has the advantages of having a high resolution for small structures. The ultra structure of tendons may be clearly identified. The ability to stress liga­ments and to allow tendons to move during the investigation allows ultrasound to take on an extra dimension, which greatly improves its diagnostic value. Myofascial hernias will be detected only by dynamic ultrasound; they are rarely visible on other imaging techniques. The use of 'panoramic' or 'extended field of view' ultrasound provides images that are more easily interpreted by an observer not performing the ultrasound examination. and are of particular assistance to surgeons planning a procedure. Ultrasound will demonstrate most foreign bodies in soft tissues. including those that are not radiopaque Summary of ultrasound

• Good for soft tissues

• No radiation

• Excellent for cyst and foreign bodies

• Dynamic studies can be performed

• The interpretation is observer dependent

• Interaction with the patient helps the radiologist reach the most likely diagnosis

MAGNETIC RESONANCE

MRI has the great advantage of being easy to interpret away from the patient and in retrospect. Provided that the areas are ade­quately covered by images,it usually gives a more complete exam­ination of the region of the body than other techniques. The magnetic resonance signal from bone is zero and therefore the cortex of the bone and callus will appear black. Fractures may be difficult to identify if they are old, but an acute injury would be easily shown up by the surrounding oedema. The sequences will be chosen by the radiologist and depend on the problem being investigated, as well as on the characteristics of the machine being used

of providing a metabolic study of bone

Summary of MRI

• Films can be viewed in the out-patient deportment and in operating theatre

• Soft-tissue oedema can highlight bone problems
No signal from bone cortex Sequence need to be skillfully chosen

Areas of increased turnover will show increased activity. It also has the strength of being able to examine the whole of the skeleton, and provides a screening tool. There is still a signifi­cant role for nuclear medicine in the detection of metastases and stress lesions However, MRI is rapidly overtak­ing nuclear medicine in these areas and arguably is the pre­ferred technique. In general, MRI makes a more specific diagnosis
NUCLEARMEDICINE isotope bone scanning

Nuclear medicine, and in particular isotope bone scintigraphy, has the advantage
Summary of Nuclear medicine
• A useful screening lest• Defines the extent of disease

• Uses radiation and takes all day

Non-specific, on abnormal result will require more imaging

WHAT ARE THE ROLE OF IMAGING IN DEGENERATIVE DISEASE LIKE
Synovitis

Plain radiographs are the mainstay of assessment for Joints. Typical changes of a degenerative or an erosive arthropathy are well-known and understood . However, early arthropathy may not be visible on plain radiographs. Gadolinium­ enhanced MRI IS probably the most sensitive method for detect­ing synovial thickening, but there is currently debate as to whether ultrasound may be more sensitive. Ultrasound shows effusions and synovial thickening clearly, and shows the increased blood flow around the affected joints.

Articular cartilage damage

Articular surface disease is difficult to detect using non-invasive techniques. MRI is probably the best method, although it is not sensitive to early chondral changes. Magnetic resonance arthrography is currently the imaging gold standard. Saline mixed with a dilute quantity of gadolinium-labelled DTPA (diethylene triamine penta-acetic acid) is introduced into the joint by needle puncture. This is then followed by MRI. Using this technique, more subtle changes in the articular surface can be seen, includ­ing thinning, fissuring and ulceration. However,early softening of articular cartilage will not be visible.Magnetic resonance arthrography is also useful for detecting labral tears in the shoulder or hip, and in the assessment of patients who have undergone a previous meniscectomy.The triangular fibrocartilage of the wrist is also difficult to assess fully without arthrography )

In the shoulder rotator cuff trauma and degenerative changes can be studied using ultrasound or MRI. In experienced hands, ultrasound has a higher accuracy rate, because image resolution is better and because the mechanical integrity of the cuff can be tested by dynamically stressing it. MRI has the advantage of being able to show pathology in the subcortical bone

In the majority of arthropathies and degenerative disorders, serial imaging is useful. Changes in films taken weeks or months apart are far easier to see and interpret than a single snapshot

Choices of imaging

• Plain radiographs are good for assessing joint disease

• Synovitis can be detected using ultrasound or enhanced MRI

• Early damage to articular cartilage damage is difficult to image

• Rotator cuff lesions are best studied using ultrasound or MRI

• Destructive lesions are best studied first on plain rodiograph

• MRI is best for staging tumours

• Biopsy con be guided by fluoroscopy, a or ultrasound

MASS LESIONS AND MALIGNANT DISEASE

The plain radiograph is the best method of assessing destructive lesions in bones. There is considerable experience in the interpretation of these films especially with regard to whether the lesion is benign or malignant .Plain radiographs are also vital in the assessment of soft-tissue calcification in tumours of muscle, tendon and subcutaneous fat. When a lesion is detected, there needs to be an early decision as to whether this is benign or malignant. If there is a suspicion of malignancy on the plain radiograph, or any uncertainty, then local staging is indicated. This is best performed by MRI for both bone and soft-tissue lesions.At this stage, it is likely that a biopsy will be indicated, and imaging guidance is a useful method. Soft­ tissue and bone biopsy needles may be guided by CT ,ultrasound or interventional MRI systems The route of punc­ture, should be avoid vital structures and be agreed with the surgeon who will perform local excision if the lesion proves to be malig­nant. Care should be taken to avoid contaminating other compartments. In all circumstances. samples are best sent to both histopathology and microbiology departments for examination. It may be difficult to tell on imaging whether or not a lesion is infected, and histology often provides a clear diagnosis in inflammatory conditions

Mass lesion in muscle and soft tissue are very effectively examined by ultrasound. In the majority of patients, the ultra­ sound can be diagnostic. there by avoiding the need for further imaging.This is most often the case when a lesion is purely cystic and, a, most soft tissue masses are cysts, ultrasound is a very effec­tive screening test. There are occasions when no mass lesion is found at the site of concern and then reassurance can be offered. If the ultrasound examination is normal. this effectively exclude, soft-tissue neoplasia. A reasonable protocol is to perform ultra­ sound on all palpable 'lesions' co exclude cysts and patient. with­out any identifiable mass and to proceed to MRI only when there is a solid or partly solid element to an unidentifiable lesion, Tumour vascularity is best assessed by Doppler ultrasound. It can be studied by intravenous gadolinium-DTPA­ enhanced MRI; however. this is a more expensive and invasive technique, providing no more
information than Doppler ultra­sound

Summary of Imaging of malignant lesions in bone

•Plain radiographs are good for making the diagnosis

• MRI is best for local staging

• CT detects lung metastases

• Fluoroscopy,CT. MRI or ultrasound can be used to guide the biopsy
Summary of Imaging of soft-tissue lesions

• Ultrasound is the best for screening, it often is the only imaging required

• MRI is best for local staging and follow up

• Doppler ultrasound can assess vascularity cheaply and well

• Ultrasound is useful for biopsy

Imaging of potentially Infected bone and joint

• Plain radiographs may be needed to exclude bone erosion

• Ultrasound is sensitive for on effusion and can be used for guided
aspiration

• MRI is useful to define activity of osteomyelitis

INFECTION

In the early stages of joint infection. the plain films may be nor­mal. but they should still be performed to exclude bony erosions, in case a painful joint is the first sign of an arthroparthy, Ultrasound examination is the easiest and most accurate method of assessing joint effusions, although, when an effusion is identi­fied, it is not possible to discriminate between blood and pus. Aspiration guided by ultrasound is the best method of making this distinction. Magnetic resonance examination may be required to assess early articular cartilage and bone involvement. Plain radiographs should be used to examine patients with sus­pected osteomyelitis. They will demonstrate or exclude bony destruction, calcification and sequestrum formation. Computerised tomography may be needed to give a cross-sec­tional view, in order to assess the extent of bony sequestrum. MRI is the preferred technique to use to define activity and extent of infection as it shows not only the bony involvement but also the extent of oedema and soft-tissue involvement Abscesses may be detected or excluded and subperiosteal oedema is readily visible. MRI can be used as a staging procedure to follow the response to intravenous antibiotics and to plan sur­gical intervention. Serial magnetic resonance examinations are very useful in the management of complex osteomyelitis.
However, patients with chronic osteomyelitis would be best assessed by a combination of imaging techniques. MRI is the most effective for assessing the extent of the disease and its activity

METABOLIC BONE DISEASE

Plain radiographs should be the first images of patients with metabolic bone disease. They may detect the subperiosteal ero­sions in hyperparathyroidism or, more commonly, the osteopenia in osteoporosis, but they cannot be used quantify osteoporosis. The apparent density of the bone on the film is linked to the pen­etration of the rays, among other variables, as well as to the bone density. If a quantitative method is needed however. bone mineral density using dual X-ray absorptiometry (DEXA) is the most accurate and practical Quantitative CT is an alternative technique. although this is less readily available. Ultrasound transmission measurement in the extremities has its advocates as it arguably measures factors that better represent the strength of bone rather than its density. its limitations are that it cannot be used to study the vertebrae or hip, and these are the sites where osteoporotic fractures occur most frequently Summary of Imaging for metabolic bone disease

• Plain rodiographs will show the textural changes in bone

• Dual X·ray absorptiometry quantifies osteoporosis

we can summarized the above as follow


After physical examination, plain radiographs are the single-most important diagnostic tool for evaluating a patient with a complaint
related to the musculoskeletal system. Before obtaining a computerized tomography (CT scan) or a magnetic resonance image (MRI). a plain radiograpy should always be taken. A minimum of two views at right angles to one another should be obtained. Obliques are of­ten useful to visualize certain aspects of the skeletal anatomy. The quality of the radiograph is important; the bone should be clearly seen and the soft tissues. although visible, should not interfere with visualization of the bone.

There are a few anatomic areas that are known to be troublesome on plain radiographs. Seeing cervical 7 ( C7 ) on the lateral can be difficult and it is important when evaluating a patient with neck pain to be sure it is visible. This can be done by having the patient's arms pulled down while the lateral view is taken or by taking a "swimmer's" view. Pa­tients with a dislocated shoulder will not want their shoulder moved and obtaining a lateral view can be difficult. For an anterior dislo­cation this usually will not a problem because the dislocation can be easily appreciated on the anteroposterior (AP) view. Unfortunately, for a posterior dislocation, the AP view can fail to show the disloca­tion, and it may be missed if the lateral view is not also obtained. A lateral or equivalent view of the shoulder should always be obtained. A "scapular lateral" view can be taken without the patient having to move the arm. Because non displaced fractures of the distal humerus in children can be particularly difficult to appreciate, radiographs of the opposite elbow are usually-taken when a child has an elbow injury without an obvious fracture. Fractures of the carpal navicular often are not displaced and cannot be seen on the initial radiographs.

For a patient with a wrist injury and pain, but no obvious fracture, it is recommended to treat the patient as if the patient has a fractured carpal navicular and repeat a radiograph in 10 to 14 days because the fracture is usually visible then. Patients with low back pain, especially young patients, may have an injury or abnormality of the pars. The pars is seen best with an oblique view of the lumbar spine. These are suggested for any patient with persistent lower back pain whose AP and lateral views are normal. Non displaced fractures of the femoral neck are often not visible on plain radiographs. Because these fractures should be internally stabilized as soon as possible, immediate diagnosis is necessary. An MRI of the femoral neck is the best method to use in the elderly patient who has fallen and has hip pain hut whose plain radiograph does not show an apparent fracture. Whenever evaluating a patient with ankle pain, three views of the ankle should be obtained. The usual AP and lateral views should be taken in addition to a "mortise" view . Combined, these three views allow for better assessment of the relationship between the distal fibula and tibia.

All aspects of the image need to be examined and it is recommended that a routine method be used to review the film. Often it is best to initially ignore the most obvious abnormality while carefully searching other aspects of the radiograph in an effort to discover more subtle ones. Specifically, examination of the soft tis­sues often shows abnormal densities, calcification, or ossification. The bone's medullary canal and cortex should be examined and subtle periosteal reactions should be looked for. Specific conditions relating to the joint should also be suspected such as thinning of the radiolucency of the joint that indicates loss of articular cartilage, thickening of the subchondral bone that indicates degenerative joint disease, the presence of osteophytes or an incorrect alignment.

When examining a bone with a fracture, it is important to look at
all parts of the bone (i.e., a fracture at the periphery of the film can be easily missed). Remember that adjacent joints may be damaged and should be examined with both a physical examination and radio­ graphs. The specifics of the fracture should be noticed and recorded in the patient's record and can include whether the fracture is simple or comminuted; whether it is a spiral, oblique, or transverse; its location in the bone; and whether it is diaphyseal, metaphyseal, or intra-articular . In children, it should be noted whether the fracture crosses the growth plate. The answers to these ques­tions are critical in deciding what treatment is needed. For most musculoskeletal abnormalities further radiographic evaluations are not needed.

Ultrasound can be used for musculoskeletal conditions but is not commonly obtained. Advances in ultrasound technology have allowed examination of tendons and ligaments in real time, but are dependent on the technical expertise of the person performing the examination.

Nuclear studies are often used to evaluate the skeletal system. Teclmetium-99 Tc) bone scans are the most commonly used. study. The 99Tc is tagged to phosphorus, which attaches itself to the bone. The amount of 99Tc attached to the bone is directly related to bone formation. Therefore, any reactivity of the bone is seen as a "hot" spot. The patient is injected with the 99Tc and approximately 2 hours later images are taken. The scan is sensitive but not spe­cific. Indium (In) scans are used primarily to determine if there is an infection. White blood cells from the patient are tagged with In and injected into the patient. Because the tagged white blood cells concentrate at the site of an infection, the scan has a "hot" spot.
Thallium scans are also occasionally used to identify soft-tissue inflammatory lesions.

Computed axial tomography (CAT) is the best method to use for visualizing the details of bone and calcification. It is often used
to evaluate fractures, especially comminuted ones and those involv­ing an articular surface . Three-dimensional reconstructions can be done to better evaluate the injury. CT is useful in the evaluation of patients with suspected herniated nucleus pulposus, although MRI is probably better.

MRI is most valuable for the examination of soft tissues. It is particularly valuable in examining the soft tissue around joints. Torn ligaments and meniscus can usually be seen on an MRI . It is also an excellent means of examining the soft tissues of the extremities and the spine. The spinal canal is visible and damage to the spinal cord can be seen easily.


TAGS:IMAGING,MUSCULOSKELETAL,BONES