Overview of Shoulder Arthrogram
Arthrography, a way of taking detailed images of joints, has been a crucial tool in musculoskeletal radiology for nearly a century. It was first described in 1933 when a researcher named Oberholzer used it to study shoulder dislocations. He injected air into the shoulder joint to help see the internal structures on a radiograph, a type of imaging photo. A year later, another researcher suggested that injecting a contrast material, a special dye, into the shoulder could help identify tears in the rotator cuff, the group of muscles and tendons that stabilize the shoulder.
Today we have more advanced imaging technology like CT (computed tomography) scans and MRI (magnetic resonance imaging). MRI is now the top choice for studying joints since it can clearly differentiate between various types of soft tissues. However, a CT scan can be used as an alternative for patients who can’t have an MRI due to claustrophobia or certain other health conditions.
Glenohumeral arthrography, specifically related to the shoulder joint, is still widely used. During this procedure, a contrast dye is injected into the joint, typically under the guidance of an imaging technology like fluoroscopy or ultrasound (though a CT scan can also be used). This method allows doctors to get a very detailed look at the components within the shoulder joint.
Importantly, there are two types of arthrography: direct and indirect. Direct arthrography involves injecting the contrast dye directly into the joint for the imaging procedure. Indirect arthrography creates similar images without requiring a direct injection into the joint.
Traditionally, arthrography used plain x-ray images and a technique known as fluoroscopy, but today, most patients have a CT scan or an MRI after the contrast dye is injected. This contrast dye helps differentiate between the structures within the joint, such as cartilage and muscles, making them easier to see and diagnose potential injuries or abnormalities.
The glenohumeral joint in the shoulder is complex, containing both static structures (those that provide stability) and dynamic structures (those which facilitate movement). The static structures include the glenoid (the socket of the shoulder blade), glenoid labrum (a ring of cartilage), the humeral head (the ball at the top of the arm bone), and the capsule (a group of ligaments that surround the joint). The dynamic structures include the rotator cuff and other muscles around the joint.
Imaging techniques are chosen based on the specific clinical scenario, but usually start with a plain film x-ray. Following this, specialists might perform an MRI or CT scan for more detailed evaluation. The MRI can provide important insight into soft tissues like the rotator cuff, tendons, and muscles. In some cases, a special type of scan called a radionuclide bone scan can be used to check for infection or possible metastases, which are areas where a cancer has spread.
Arthrography continues to be an important tool for examining joints. It involves injecting contrast into the joint either through direct puncture (for traditional arthrography and CT arthrography) or using a special agent (for MR arthrography). This allows doctors to obtain images for an in-depth assessment of joint conditions.
Anatomy and Physiology of Shoulder Arthrogram
The glenohumeral joint is a kind of joint, known as a “ball and socket joint,” that connects your upper arm to your body. It allows you to move your arm in many ways, like stretching it out, bending it, lifting it sideways, or rotating it. It’s one of the most flexible joints in our body but is not very stable because of this flexibility.
This joint is formed where your upper arm bone, the humerus, meets a part of your shoulder blade, the scapula. Both these parts are covered with a kind of smooth tissue called cartilage. The place on your arm bone where it connects, the head of the humerus, is bigger than where it connects on the scapula, the glenoid fossa. While this allows a wide range of motion, it also makes the joint unstable. To stabilize it, the glenoid fossa is deepened by a fibrocartilage rim known as the glenoid labrum. Surrounding the joint is a soft tissue sheath called a joint capsule. This capsule is quite flexible, allowing for more motion in the joint. There’s also a membrane inside this capsule that produces a fluid, which decreases the friction between the parts of the joint.
Special fluid-filled sacs called bursae are also present in this joint. They act as cushions and reduce friction during movement. Notable ones are the subacromial and subscapular bursae. The subacromial bursa reduces friction below your shoulder muscle, making it easier for you to move your arm. The subscapular bursa reduces wear on the tendons that connect your muscles to your bones during movement.
The group of muscles that help rotate your arm, the rotator cuff, starts from your scapula and attaches to your humerus. The rotator cuff has four muscles, which almost wrap around the head of your humerus. The four muscles’ tendons merge and fuse with most of the joint capsule. The long tendon of your biceps muscle, which moves your forearm, goes through this joint from a covering within a groove in the humerus and attaches to the top margin of the glenoid.
Furthermore, there are certain parts of your shoulder joint that offer stability. The clavicle or collarbone is an S-shaped bone that connects with the sternoclavicular joint medially and the acromioclavicular joint laterally. The scapula or shoulder bone is a triangular bone with three parts: the body, spine, and neck. This bone has three structures that connect with the clavicle and the humeral head. The glenoid fossa in the scapula is the place where the joint forms. It has a certain structure resembling a pear, which helps maintain shoulder stability.
Moving on, there are certain processes occurring within this joint that are crucial. For example, the coracoid process is a part of the scapula that occurs from the anterolateral aspect. The morphology of the coracoid varies, but the orientation can impact the movement and lead to subsequent impingement with the tendon of the subscapularis muscle.
The acromion or the outward end of the spine of the scapula connects with the collarbone. The acromion has different shapes that have been classified into three types. A type one acromion is flat, a type two is curved, and type three is hooked. A type three acromion is thought to be acquired and not present by birth.
Lastly, the head of the humerus is usually tilted backwards by approximately 30 degrees. The head is covered by cartilage that is thicker in the center but thinner on the periphery. There is a bare area on the back of the humeral head, which is between the attachment of the synovial membrane and joint capsule with nearby cartilage. This bare area increases in certain situations, such as tears in the supraspinatus muscle or lesions in the cartilage.
Why do People Need Shoulder Arthrogram
Doctors may order an MRI arthrogram (a special kind of MRI scan) of the shoulder to take a closer look at parts of it that can’t be seen well without using a special contrast dye. These areas might include things like the biceps-labral complex (the area around the upper arm muscle and shoulder joint), the ligaments (tissues that connect bones), the labrum (the ring of cartilage around the shoulder socket), the rotator interval (part of the shoulder), and the joint capsule (thicker tissue around the shoulder joint).
An injury to any one or more of these areas could cause shoulder instability, which means the shoulder becomes loose or dislocated easily. If you have shoulder instability, you might have pain, feel like your shoulder joint is too loose, or have repeated dislocations. In cases like this, an MRI arthrogram can help doctors see the details of the shoulder joint, such as any tears in the ligaments or rotator cuff (the group of muscles that stabilizes your shoulder), any injuries to the labrum or other bones around your shoulder socket. This is particularly helpful in cases where a previous rotator cuff repair might be causing issues.
Before doing this detailed test, doctors usually first take simple X-ray images of the shoulder area. An MRI arthrogram can also be helpful if a doctor suspects that you have adhesive capsulitis (a condition that causes shoulder stiffness and pain, also known as “frozen shoulder”) or if you’re still having symptoms after you’ve had shoulder surgery.
When a Person Should Avoid Shoulder Arthrogram
There are certain conditions that may prevent a doctor from being able to perform a process called glenohumeral arthrography, which is a diagnostic procedure used to view the shoulder joint. Such conditions include an ongoing infection in the shoulder, the tissues around it, or the skin where the needle is supposed to be inserted. If there’s a skin infection, known as cellulitis, on top of the shoulder joint, the procedure shouldn’t be done to avoid spreading the infection inside the shoulder when the needle is inserted.
A disorder called Reflex Sympathetic Dystrophy (RSD) can also prevent this procedure from happening. RSD is also known as a type of Complex Regional Pain Syndrome. It’s a long-term condition that causes intense burning pain, usually in your arms or legs. RSD can also cause changes to your skin and bones, swelling, excessive sweating, and increased sensitivity to touch (termed allodynia). RSD usually starts after an injury to your tissue without any related nerve damage and is thought to be caused by issues with part of your nervous system called the sympathetic nervous system. The procedure can reactivate RSD if you have it.
Some patients may have a history of allergic reactions to the contrast agents used in the procedure. In such cases, the doctor can follow a special plan to prevent an allergic reaction or use a solution called normal saline to distend, or swell, the shoulder for a specific type of arthrography called MR arthrography. If an allergic reaction happens, it’s often linked to the anesthetic or the iodine solution used, instead of the gadolinium solution. If you’re undergoing blood-thinning treatment, the doctor can usually still perform the arthrography as long as your INR value, which likens the thickness of your blood, is less than 1.5 to 2.0. Be aware that there’s a balance of risks and benefits to stop taking your blood-thinning medication for this procedure. In patients taking blood-thinner, the doctor might also consider using a thinner needle.
If you’re unable to undergo an MRI for whatever reasons- such as being claustrophobic, having surgical implants, or being unable to stay still during the scan- CT arthrography can be used as an alternative. This method can also be used if an earlier MRI scan didn’t give clear results. The CT scan provides very fine details, it is more widely available and takes less time. It is also better at identifying certain bone changes and pathologic calcifications, such as calcium build-ups in your tendons or certain types of lesions. CT scans are less likely to be affected by movement ‘artifacts,’ which refers to distortions in the imaging.
Use of gadolinium-based contrast agents is something to be considered if a patient is pregnant. These agents can cross over into the unborn baby’s circulation and pass out into the amniotic fluid, which surrounds the baby in the womb. While there’s no strong evidence to suggest these agents harm the unborn child, their effects aren’t fully understood. If the patient is pregnant, these agents should be avoided unless there’s no other option and the benefits of the scan outweigh the potential risks to the unborn baby. When used in nursing mothers, a tiny amount of the agent can be passed into the breast milk, but only an extremely small amount from the milk can be absorbed by the baby and is unlikely to be harmful. However, if any concerns arise from the referring doctor, the radiologist, or the patient, the mother can be asked to discard breast milk for 24 hours after receiving the contrast agent. It’s also worth noting that using these agents is generally safe and routine in newborns and infants. As stopping breastfeeding can be stressful for both mother and child, it’s not essential to stop nursing for 24 hours after receiving the contrast agent.
Equipment used for Shoulder Arthrogram
An arthrogram is a medical procedure in which a special dye, known as contrast, is injected into a joint, in this case the glenohumeral joint or shoulder joint, so that it can be seen clearly on X-rays or other imaging. To keep everything clean and free from bacteria during this procedure, things like skin cleansers, sterile drapes, and sterile swabs are used.
The contrast is prepared in a certain way and is put into syringes. A 20 mL syringe is used for preparation, a 10 mL syringe is used for the actual injection, and a 1 mL syringe is used for a type of contrast called gadolinium.
The injection is done with a 25 gauge needle, which is a thin needle, for the local anesthetic, and then a slightly larger 20 to 22 gauge needle for the arthrogram itself. The doctor will use tools like fluoroscopy, ultrasound, or computer tomography to help guide them during the procedure. A local anesthetic, like 1% lidocaine, is used to numb the skin and the pathway that the needle will take.
For a CT arthrogram, a non-ionic iodinated contrast is required. The injected solution is diluted to a one-to-one ratio with normal saline or lidocaine. For an MR arthrogram, gadolinium contrast is used.
There are different ways to prepare the contrast. One common way is to use a 20 mL syringe that includes 5 mL of iodinated contrast mixed with 15 mL of normal saline and gadolinium contrast at approximately two millimoles per liter. If there might be a delay before the MR arthrogram, a small amount of epinephrine can be considered.
Sometimes a long-lasting anesthetic or a corticosteroid is used to help figure out if the patient’s pain is coming from inside the joint. Some studies have found that ropivacaine can be less toxic than bupivacaine or lidocaine.
It’s important to note that some reports have found that these long-lasting anesthetics can be toxic to cartilage. The corticosteroid should be injected only after the contrast, so it doesn’t interfere with the diagnostic exam. It should not be injected at all if there’s a possibility of an infection.
After the arthrogram, the patient will have a CT scan or MRI to get more images after the injection.
Who is needed to perform Shoulder Arthrogram?
Your main doctor usually decides when you need a certain type of medical test, and it’s the same for an arthrogram. An arthrogram is a procedure that helps doctors see the inside of your joints, like your knee or shoulder, in more detail. Your doctor will let you know why you need this procedure and will talk through the potential benefits and risks with you. It’s very important that your doctor understands whether it’s safe for you to have this type of procedure.
Then there’s the radiologist, who’s a kind of doctor that specializes in these types of procedures and interpreting the images they produce. They’re in charge of pretty much everything to do with your arthrogram: they decide what kind of special imaging (MRA or CTA) is needed, what setting to use on the machine, and how to interpret the images. They also review and report on the findings and are responsible for making sure that the images are clear and accurate.
The radiologist needs to know a lot about the medicines they use in these procedures, which can highlight different parts of your body on the images. They choose the right one for you and make sure that it’s used safely and effectively.
Finally, there are some other medical professionals who will be involved too. This might include a physician assistant, nurse practitioner, or a special kind of radiologist assistant who’s been trained to help with these types of procedures. These professionals can do certain examinations and help take care of you under the supervision of the radiologist. Then there’s the radiology technologist, who helps to make sure you’re comfortable and safe during the procedure. This person helps to get you ready for the procedure and positions you inside the MRI machine. They’re also in charge of getting the data from the MRI, which the radiologist will then interpret.
Preparing for Shoulder Arthrogram
Before any medical procedure, the doctor will explain to the patient what the process will involve, the benefits, risks, and other options available. They will also ask the patient to for their approval to carry out the procedure. This is known as obtaining informed consent. The doctor will confirm details about the specific part of the body that needs treatment and if there are any allergies the patient may have. In case the patient needs to have an MRI scan after the procedure, the doctor will have to confirm that patient can safely have an MRI. This includes asking about things like whether the patient has a pacemaker or spinal stimulator.
The doctor who referred a patient for an elective arthrogram (an x-ray of a joint after injection of a contrast substance) will usually manage the patient’s blood-thinning medication. This commonly includes asking the patient not to take this medication for a few days and making sure the blood is not too thin before the procedure. This is especially important for patients on warfarin, a common blood-thinning medicine. The possibility of a blood clot or lump that may need to be removed should also be discussed with the patients who are on blood-thinning medicine.
In an arthrogram, an injection goes into the joint and it is usually done under fluoroscopy (like an X-ray but in real time), CT scan or ultrasound guidance. The type of injection used will depend on whether the patient is having a CT scan or an MRI scan.
For a CT scan, an iodine-based contrast is used to inject into the joint so it can be seen clearly on the scan.
For an MRI, the injection is a diluted solution of gadolinium-based contrast (a type of substance that makes certain tissues, abnormalities, or disease processes more clearly visible). There can also be a mixture of local anesthetic with normal saline (saltwater solution) to reduce any pain from the procedure. A small injection of this solution is enough to expand the joint for clear visibility on scans.
When the injection is done under fluoroscopy or CT guidance, a small amount of diluted iodine contrast is first injected to confirm it’s getting into the correct spot in the joint. The MRI scan should be done within 90 minutes after the injection to ensure the best imaging quality.
How is Shoulder Arthrogram performed
A shoulder arthrogram is a test done to check the muscles in your shoulder (also known as the rotator cuff) and find any tears in the labrum, a part of your shoulder joint. If this test is done along with a Magnetic Resonance Imaging (MRI), it can also give detailed information about the cartilage and structures within the shoulder joint. It’s important that the test is done correctly to avoid inaccurate results or harm to the patient. If the contrast media – a substance used to enhance the images – is placed wrongly, it could create misleading images. Further, an improperly placed needle could cause injury.
A series of techniques have been used to do a shoulder arthrogram since it was first done in 1933. For example, it was initially recommended to position the patient at an angle while the needle is advanced into the space. Later, it was suggested to place the patient in a lying-down position to avoid injuring the glenoid labrum, a part of your shoulder joint. An important indicator that the needle is in the correct place is if the fluid level of the local anaesthetic drops. An added technique suggests rotating the shoulder internally once the needle tip is at the humeral head (a part of your upper arm bone) to ease the placement of the needle within the joint.
Before the procedure begins, it’s important to take the right X-ray images — these aid in doing the arthrogram correctly. These X-rays can help identify any calcium deposits in the rotator cuff complex. If these are not seen before injecting the contrast medium, they could be wrongly interpreted as the contrast agent seeping into the rotator cuff, showing up as a tendon tear.
Positioning the patient in the right way is key to a successful arthrogram and to minimise complications. Usually, patients lie on their back with their shoulders slightly rotated externally. An alternate approach, called the Schneider technique, is also available but it carries the risk of perforating important anterior structures or even causing these structures to absorb the contrast agent which could distort the images, leading to misinterpretation.
A posterior approach, wherein the patient lies face-down with the shoulder raised, has also been discussed. This approach is suggested when it’s best to avoid the anterior approach because of some condition that could cause injury or interpretive errors with the MRI. In this approach, the needle goes through the infraspinatus tendon, another part of the shoulder.
It’s also important to keep the patient in the right supine position, i.e., lying down with their face up. This helps to avoid contact with the glenoid labrum while advancing the needle in the anterior-posterior direction towards the humeral head. A comfortable level of external rotation of the shoulder joint also has to be maintained as excessive external rotation could be uncomfortable for the patient and make the placement of the needle more difficult.
Once the patient is properly positioned, a radiopaque instrument and fluoroscopy – a type of medical imaging – are used to locate the joint insertion site for needle insertion. The target is the medial upper quadrant of the humeral head. The focus is to ensure the needle does not go too far on either side.
Possible Complications of Shoulder Arthrogram
Getting a procedure on your joint space comes with certain risks. These include the chance of getting an infection in the joint, having an allergic reaction, bleeding, reacting to the contrast dye, and damaging nearby structures. While it’s uncommon to get an infection, the risk can be higher for older people and those with certain conditions like diabetes, skin infection, or rheumatoid arthritis. Although using antibiotics to prevent an infection isn’t typically necessary, we let patients know that there’s a chance of infection and tell them what to watch for after the procedure.
One common problem after treatment is pain in the joint. This pain, which can affect up to 66% of patients, is likely due to inflammation of the joint lining, a condition called synovitis. This usually happens a few hours after the procedure, but it tends to go away after a few days. A common cause of this inflammation is the contrast dye used in the procedure. This irritation, also known as chemical synovitis, usually gets better on its own and can be treated with over-the-counter anti-inflammatory medication like ibuprofen or naproxen.
There are no known cases of a condition called nephrogenic systemic fibrosis related to this type of procedure as of now. If the joint space isn’t reached properly during the procedure, the contrast dye can end up outside the joint. Other possible issues include skin rash (urticaria) and a sudden drop in heart rate, blood pressure, or fainting (vasovagal reaction).
What Else Should I Know About Shoulder Arthrogram?
An arthrogram is an imaging test that allows doctors to look at your joints, such as your shoulder, in detail. It can help identify any damage or issues within the joint. For instance, it can reveal any abnormal connections between your joint and other body parts, tears in tissues like tendons or ligaments, inflammation, abnormalities in your cartilage, and loose bodies (small loose fragments of bone or cartilage that float in your joint fluid).
The imaging helps get a clear view of various structures inside your shoulder like various ligaments, the capsule (the lining of your joint), the glenoid labrum (a ring of cartilage around the shoulder socket), and the biceps-labral complex (where the biceps muscle connects to the shoulder).
If the arthrogram is normal, there will be no evidence of any damage to the structures in your shoulder, including the muscles, tendons, cartilage or bones. You will be able to see a thin, shadowy line at the top of the upper arm bone covered by the cartilage. The soft tissues around your shoulder should be clear and free of any imaging dye. There will also be a clear hollow within the shoulder joint, this is where the long tendon of the bicep muscles sits.
On the other hand, a problem in the arthrogram can show up as any clear passage between the space below the acromion (a bony prominence on top of your shoulder) and the shoulder joint, indicating a complete tear in the muscles of the rotator cuff (a group of muscles and their tendons that work to hold your shoulder joint together).
The test can also reveal other abnormalities, like partial tears in the rotator cuff, any spaces filled with imaging dye close to the neck of the arm bone, or any abnormalities related to conditions such as adhesive capsulitis (where your shoulder joint has limited movement due to inflammation).
These observations can help doctors understand what’s happening inside your shoulder joint and guide them towards the best course of treatment. Remember, it’s important for the correct amount of imaging dye to be present in the correct places in your shoulder for the best assessment.
