MR arthrography is a radiological examination that uses magnetic resonance imaging to diagnose damage in joints. To do this, contrast material is injected and the MRI machine is used to create images of the joint.
What is MR arthrography?
MR arthrography is a radiological examination that uses magnetic resonance imaging to diagnose damage in joints. MR arthrography involves creating an MRI image of the joint after an injection of X-ray contrast material. Magnetic resonance imaging, also known as MR or MRI for short, is an imaging technique used to create cross-sectional images of the body. The procedure is based on the principle of nuclear magnetic resonance. All tissues in the human body are made up of atoms, which in turn are made up of protons, electrons and neutrons. Protons have a spin, which means that they rotate around their own axis. This spin makes the protons magnetic. They align themselves in their own magnetic field parallel to other magnetic fields. A strong magnetic field is generated in the tube of the MRI, so the protons arrange themselves according to their nature. Briefly, a short electromagnetic pulse is then generated. This pulse disturbs the arrangement of the protons and they emit a weak but measurable signal. When the pulse disappears, the protons arrange themselves again in the usual field. During MRI, numerous such disruptive pulses are generated. The computer calculates the MRI images from the changes in the proton arrangement that then occur. MR arthrography is currently one of the most accurate methods for joint examination.
Function, effect, and goals
Under sterile conditions, local anesthesia and X-ray control, the first step is to puncture the joint to be examined. During this procedure, the attending physician inserts a needle through the skin and underlying tissue into the interior of the joint, where the contrast agent is then injected. To ensure that the contrast medium is distributed evenly throughout the joint, the patient should move the joint to all physiological degrees. This is followed by magnetic resonance imaging. No more than 20 minutes should elapse between the injection of the contrast medium and the MRI, otherwise parts of the contrast medium will already have been absorbed by the cells of the joint capsule. The examination is usually performed in the prone or supine position. Since it is somewhat noisy in the tube, those to be examined are given earplugs and/or headphones. The examination takes about 45 minutes. Body movements should be avoided during this time, otherwise the images cannot be taken correctly. Due to the high soft tissue contrast, MR arthrography can accurately diagnose joint diseases and joint disorders. Cartilage, ligament and tendon structures can be precisely differentiated thanks to excellent image quality. The most common indications for MR arthrography are complaints in the hip, shoulder, hand, elbow or ankle joints. Recognized indications for MR arthrography of the shoulder are dislocations following an accident or dislocations due to joint instability, as well as suspected injury to the superior labrum-biceps anchor complex. MR arthrography can also be used to make a diagnosis if tendon ruptures are suspected or if shoulder pain is unclear. MR arthrography of the elbow is usually performed when a simple MRI has not yet yielded a clear diagnosis. Primarily cartilage lesions or ligamentous lesions are examined here. Injuries of the ligaments and pathological changes of the articular cartilage, so-called chondropathies, are also the primary indications for MR arthrography in the wrist. Perforation of the triangular fibrocartilaginous complex (TFCC) can also be diagnosed quickly and reliably with this procedure. The TFCC is particularly impaired in the elderly or as a result of rheumatic diseases. For the examination, the contrast medium is injected into the so-called radioulnar joint, the joint between the radius and the ulna. If MR arthrography then shows a transfer of the contrast medium into the wrist, this indicates damage to the TFCC. Another condition for which MR arthrography is used is femoroacetabular impingement. This is a disorder in the transition from the femoral head to the femoral neck. In this case, the range of motion is disturbed in such a way that the neck of the femur abuts the edge of the acetabulum during normal movement.Sooner or later, this leads to osteoarthritis of the hip joint. MR arthrography can detect even the smallest lesions in the margins of the acetabulum. At the knee, MR arthrography is used primarily for injuries to the meniscus. Especially when conventional MRI has provided unclear results, arthrography can provide information about damage. For diagnosis of the ankle joint, simple MRI is usually preferred. Here, MR arthrography provides only additional information with regard to the presence of cartilage or bone lesions.
Risks, side effects, and hazards
MR arthrography is one of the minimally invasive procedures, but it is still a joint puncture. Joint punctures always carry a risk of infection. Bacteria can be brought into the joint through the puncture and cause an infection. These joint infections must be treated with antibiotics and, in more severe cases, surgery. In addition, bleeding into the joint may occur. Pain during the injection of contrast medium is also possible. After the examination, tension pain may occur in the joint, but this usually disappears after a few days. In rare cases, allergic reactions to the contrast medium can be observed. Apart from this, the contrast medium can also cause headaches or nausea. Circulatory disturbances are also among the undesirable side effects of MR arthrography. Before the examination, a detailed discussion should be held by the attending physician, including an explanation of all risks and side effects. If acute inflammations in the joint, allergies to contrast media or a suppression of the immune system are known, MR arthrography should not be performed. In general, however, the procedure is well tolerated.
