Shoulder MRI is a tomographic technique that allows to study the structures forming the shoulder joint using the phenomenon of magnetic nuclear resonance. It visualizes the general configuration of the joint, the head of the humerus, the acromioclavicular joint, synovial bags, tendon-ligamentous apparatus and regional muscles. MRI can detect fractures, dislocations, autoimmune and inflammatory changes, tumor formations, ruptures and sprains of ligaments and muscles, tendon detachment, accumulation of synovial effusion and hemorrhagic fluid in the cavity of the joint capsule. If necessary, the study is supplemented with intravenous or intra-articular administration of contrast agents, which increases the cost of the procedure.
Shoulder MRI, as a rule, is used in notoriously difficult diagnostic situations and with insufficient information content of widely used imaging methods – ultrasound scanning, radiography and others. Among the diseases and pathological conditions, MRI may require:
- Shoulder injuries: fracture of the head of the humerus, dislocation of the shoulder, damage to ligaments, muscles and tendons. They are accompanied by pain, restriction of movements, defiguration of the joint and its increase in volume, the formation of subcutaneous hematomas. In fractures, there is bone crepitation and pain under axial load.
- Benign and malignant tumors. In the early stages, they do not cause clinical symptoms. When reaching significant sizes, they can be determined visually, constrain movements in the shoulder joint, make them painful.
- Deforming osteoarthritis, impingement syndrome. They are manifested by a gradual decrease in the volume of movements in the joint, a violation of its normal configuration, morning stiffness and crunching.
- Rheumatoid arthritis and other autoimmune lesions. Accompanied by pain, swelling of surrounding tissues, decreased mobility of the shoulder and general symptoms – subfebrility, decreased appetite, weakness. As a rule, other joints are also affected.
- Anomalies of development. They can be congenital or acquired. They are manifested by hyper- or hypoplasia of anatomical structures with preservation or violation of movements in the shoulder joint.
- Preparation for surgical treatment and monitoring of its results. Magnetic resonance imaging displays in detail the size of pathological formations and their interaction with healthy tissues. This allows you to make the correct order of the surgeon’s actions during the operation.
Shoulder MRI with intravenous contrast is used for a detailed study of blood vessels and differential diagnosis between benign neoplasms and cancerous tumors. Intra-articular administration of contrast agents visualizes in detail the articular cracks and the cavity of the shoulder joint.
The technique of tomography has limitations in application, which apply to studies of any anatomical area, including the shoulder joint. These include:
- Metallic foreign bodies. Metal structures for osteosynthesis (plates, pins), vascular clips, artificial heart valves and other similar elements implanted in the patient’s body are capable of shifting under the influence of magnetic nuclear radiation, harming the surrounding tissues.
- Electronic devices. Hearing aids, pacemakers and similar devices can fail under the influence of magnetic waves generated by the tomograph.
- Pregnancy in the first trimester. The effect has not been fully studied, so a potential teratogenic effect cannot be excluded.
- Claustrophobia, mental disorders, age up to 6 years, severe pain syndrome. The inability of patients to maintain a static position throughout the study significantly reduces the quality of the images obtained.
- The need for constant monitoring of vital signs. The MR scan procedure excludes the possibility of artificial lung ventilation, continuous heart rate monitoring or intravenous drip administration of drugs.
The use of contrast enhancement during shoulder MRI also has certain contraindications. This list includes:
- Allergy to a contrast agent. The administration of contrast agents to patients with individual intolerance can cause severe allergic reactions.
- Severe renal failure. Violation of the excretory function of the kidneys leads to a delay of contrast agents in the patient’s body.
- Hemolytic anemia, type 2 diabetes mellitus. Contrast agents can cause exacerbations of these diseases and seriously worsen the patient’s condition.
Sedatives are prescribed to patients who are unable to remain stationary during tomography, neuroleptanalgesia or anesthesia is performed. Planning a study with contrast enhancement requires additional preparatory measures:
- Setting up an allergy test with an injected contrast agent. Its implementation and obtaining a negative result excludes the development of anaphylactic reactions in the patient during the scan.
- Assessment of excretory kidney function. It is required for patients with nephrological pathologies in which the ability to excrete decreases. It includes an urinalysis, a biochemical blood test, a Rehberg test.
- Observance of hunger. 4-6 hours before the introduction of contrast, it is recommended to refrain from eating.
Methodology of conducting
- Patient is taken to a separate room-a locker room, where they offer to change into disposable underwear or a special bathrobe. It is also necessary to remove metal objects – jewelry, removable orthodontic structures, hearing aids, etc.
- The patient goes into the room with an MR tomograph, lies down on the scanner couch. If necessary, sedatives or contrast agents are administered to him.
- The position of the patient’s body inside the tomograph – lying on his back, with his head to the magnet, his hands lying along the trunk or slightly turned outward. The palm is placed on the rib with the thumb up. Rollers are placed in the armpit and under the elbow. If necessary, the examined arm can be fixed with straps. A flexible or surface RF coil is applied directly to the shoulder, as close as possible to the center of the magnet.
- Depending on the purpose and protocol of the procedure, shoulder MRI can last from 20 to 30 minutes.
- The native examination is painless, the patient hears only the hum and clicks that the tomograph emits while taking pictures. The introduction of contrast may be accompanied by mild nausea, dizziness or malaise. These side effects go away on their own after a few hours.
- Preparation of the results of the study takes from 2-3 hours to 1 day. They may include a digital media (CD-ROM, USB-drive) with the received tomograms, printed copies, a written opinion of a radiologist with a preliminary diagnosis and description of the images.
Interpretation of results
When visualizing the shoulder joint on MRI, all regional anatomical formations have certain characteristics. The head of the humerus is located in the articular cavity, homogeneous, clearly separated from the surrounding tissues. The cartilage coating is uniform in thickness and structure. The joint cavity and synovial bags contain a small amount of synovial fluid. The cartilaginous lip, ligaments and tendons are clearly differentiated, homogeneous, and do not contain areas of deformation. The acromioclavicular joint is displayed as a smooth-walled uniform slit. The muscle fibers on the tomogram have clear contours and a uniform signal.
- Violation of the structural integrity of bones, the formation of fragments, displacement of articular surfaces relative to each other, their exit beyond the joint capsule with the rupture of the latter, swelling of adjacent tissues, accumulation of blood in the joint are signs of bone fractures and dislocation of the shoulder joint.
- Deformation, violation of the uniformity and integrity of the cranio-acromial, cranio-clavicular, shoulder ligaments, supraspinatus, subacute and scapular muscles, the long head of the biceps and their tendons, cartilaginous lip indicate traumatic injuries and ruptures.
- Formations of different densities that are not related to the normal anatomical structures of the shoulder joint indicate the development of tumors. Benign neoplasms have a homogeneous signal, clear boundaries and a weak degree of vascularization, while cancer is characterized by germination into neighboring tissues, pronounced angiogenesis and signs of decay in the center.
- Degeneration of the cartilaginous layer, deformation of articular surfaces and violation of the general configuration of the shoulder joint, the formation of osteophytes is a manifestation of osteoarthritis and impingement syndrome.
- Pronounced increase or decrease in the size of the bones forming the shoulder joint, hypo- or atrophy of muscles, deformities of ligaments and tendons or their complete absence characterize congenital or acquired developmental abnormalities.
- Progressive narrowing of the articular gap or ankylosis, decreased signal from bone structures, increased amount of synovial fluid, thickening of the joint capsule are signs of rheumatoid arthritis or other autoimmune diseases of the shoulder joint.
- A large amount of effusion filling the cavities of the subacromial and subdelective synovial bags and increasing the joint capsule in volume, thickening of the synovial membrane indicates its inflammation – synovitis.