MRI of joint components for osteoarthritis

The auxiliary apparatus of the joint, i. Ligaments, meniscuses, tendons, articular lips are important in maintaining static and dynamic stability, the distribution of mechanical stress and the functional integrity of the joints. The loss of these functions increases biomechanical wear and is the cause of damage to the joint, apparently because of a large reduction in the risk of osteoarthritis after meniscaectomy, with ruptures of the cruciate ligaments and the rotator cuff of the shoulder. These structures consist mainly of collagen, which provides a tension force, and also retains the protons of water. T2 collagen is usually so fast (<1 ms), which in most cases has the form of a low-intensity signal in all pulse sequences outlined by high-intensity structures, such as adipose tissue or synovial fluid.

Unbreakable ligaments look like dark bands. Interrupting them is a direct sign of rupture of ligaments. However, it should be borne in mind that an imitation of a ligament rupture can occur when an oblique plane is cut through an intact ligament. To display some bundles, you may need to select a plane. The anterior cruciate ligament of the knee joint is best seen on the oblique sagittal knee images in the neutral position or on the direct sagittal with a small abduction of the tibia, while the lower lig. The glenohumerale of the shoulder joint is basically statically stable when leaning the shoulder and is difficult to visualize if it were not for the position of the shoulder in the state of withdrawal and external rotation. The multiplanar 3-D reconstruction completely analyzes the integrity of the bundles, but is not the original image.

Menisci consist of fibrous cartilage and contain a large number of collagen fibers spatially arranged so as to resist the tension force when exposed to weight loads. The fibers are oriented predominantly circularly, especially in the peripheral part of the meniscus, which explains the tendency to tear, which runs longitudinally, therefore linear cracks between the collagen fibers are formed more often than across the fibers. When there is a local loss of collagen, for example, with myxoid or eosinophilic degeneration, which is usually accompanied by a local increase in water content, the T2 shortening effect decreases, and the signal from water is not masked and manifests as a round or linear portion with a mid-intensity signal inside the meniscus on short TE -images (T1-weighted by the proton density SE or GE), tends to gradually disappear with a long TE. These pathological signals are not ruptures, unlike the violation of the integrity of the meniscus. A meniscus rupture can be caused by a rough deformation of its surface. Sometimes a large amount of synovial fluid delineates the meniscus fracture and it is visualized on T2-VI, but in most cases undetected meniscus tears are not visible on long TE images. Short TE images are thus highly sensitive (> 90%), but somewhat nonspecific for meniscus ruptures, whereas long TE images are insensitive, although highly specific when they are visible.

MRI is sensitive to the full spectrum of tendon pathology and reveals tendinitis and ruptures in most cases with greater accuracy than clinical examination. Normal tendons have smooth edges and a homogeneous signal of low intensity with a long TE (T2-VI). The rupture of the tendon can be partial or complete and is depicted by varying degrees of interruption of the tendon by a high-intensity signal inside the tendon on T2-VI with MRI. With tenosynovitis fluid can be seen under the tendon sheath, but the tendon itself has a normal appearance. Tendonitis is usually the result of an expansion and uneven tendon, but a more reliable symptom is an increase in signal intensity within the tendon on T2-VI. Tendon rupture can be the result of mechanical wear due to friction against jagged osteophytes and sharp edges of erosion, or primary inflammation in the tendon itself. The detachment of the tendon from the attachment site can be acute. The tendons of the extensors of the wrist or hand, the rotator cuff of the shoulder and the tendon of the posterior tibialis muscle in the ankle joint are more often broken. Tendonitis and rupture of the rotator cuff of the shoulder and tendon of the long biceps head in most cases are manifested by pain and instability of the shoulder joint. A complete rupture of the rotator cuff of the shoulder is the result of anterior subluxation of the head of the humerus and is often leading in osteoarthritis.

Muscles contain less collagen and therefore have a medium intensity signal on T1 and T2-VI. Inflammation of the muscles sometimes accompanies arthritis and has a high intensity signal on T2-VI, because in both cases with the development of interstitial edema the water content rises and the lengthening of T2 is associated with the loss of collagen. Conversely, post-inflammatory fibrosis tends to reduce signal intensity on T2-VI, while marbled fatty muscle atrophy has a high-intensity fat signal on T1-VI. The localization of the process is typical for muscles.

It can be concluded that MRI is a highly effective diagnostic, non-invasive method that provides information on all the joint components at the same time and contributes to the study of structural and functional parameters in joint diseases. MRI can detect very early changes associated with degeneration of the cartilage, when the clinical symptoms are minimal or absent. Early detection of patients who have a risk of progression of the disease, found in an MRI study, makes it possible to prescribe appropriate treatment much earlier than using clinical, laboratory and radiological methods. The use of MP contrast agents significantly increases the informative value of the method for rheumatic joint diseases. Moreover, MRI provides objective and quantitative measurements of subtle, subtle morphological and structural changes in various joint tissues over time and is therefore a more reliable and easily reproducible method that helps monitor the course of osteoarthritis. MRI also facilitates the evaluation of the effectiveness of new drugs for the treatment of patients with osteoarthritis and allows rapid research. Further optimization of these measurements is necessary, since they can be used as powerful objective methods for studying the pathophysiology of osteoarthritis.

[1], [2], [3], [4], [5], [6]