Fundamental Musculoskeletal MRI - Coursework Example

1. Anatomy of the Elbow With the three bones of the arm contributing to its structure, the elbow is a hinge-type synovial joint of the upper extremity that provides both structure and function. In detail, the wide and flattened distal end of the humerus, specifically the middle trochlea, articulates with the proximal end of ulna, while its lateral capitellum articulates with the radial head at the proximal end of the radius. In addition, posterior to the trochlea is the olecranon fossa, and above this space is the posterior capsular attachment of the humerus. The anterior elbow, on the other hand, has two fossae: medial coronoid fossa and lateral radial fossa. However, similar to the posterior elbow, only one capsular attachment covers these two fossae. The proximal end of the ulna has two processes, the olecranon and coronoid, with the former being the site of attachment of the triceps tendon. Aside from the head, the radius also has a tuberosity, located beneath the medial aspect of the neck (Bhutani, 2011). The structure of the elbow is maintained by a weak fibrous tissue that envelopes the whole joint. The synovial membrane lines the inner surface of the capsule, and in between the synovial membrane and capsule are several fat pads. The collateral ligament complexes on the elbow are found to overlie the capsule. The radial or lateral collateral ligamentous complex consisting of the the radial ligament, annular ligament, lateral ulnar collateral ligament, and accessory ligament attaches superiorly to the lateral epicondyle and inferiorly to the radial notch of the ulna and to the annular ligament. On the other hand, the ulnar or medial collateral ligament spans from the medial epicondyle to the coronoid and olecranon processes. At the elbow is another joint, called the radioulnar joint, which is between the radial head and the radial notch of the ulna (Bhutani, 2011). Figure 1. Diagram of the Elbow. From The Ohio State University Wexner Medical Center. Tennis Elbow [online] Available at: 2. and 3. Elbow MRI 2. In conducting elbow MRI, patient can be positioned prone or supine, with the arm overhead. Taking the latter is more comfortable for the patient (Vahlensieck, Genant, Reiser, 2000). Imaging is from 10 cm above the elbow joint to the bicipital tuberosity (Bhutani, 2011). The elbow MRI imaging options are axial, sagittal, coronal, oblique and reformatted thin-section gradient-echo images. The axial image is necessary to assess neurovascular, tendon, and muscle anatomy. The sagittal view is also taken for biceps and triceps tears or to define the extent of a lesion seen on axial MRIA. On the other hand, coronal plane can be used to assess articular surfaces, common tendons and collateral ligaments (Bancroft, Berquist, Peterson, and Kransdorf, 2007). Figure 2 (left) and 3. Prone positioning with the arm flexed and shoulder abducted, and the output MRI image on the right. From Elbow MRI Protocol and Anatomy. [online] Available at: 3. MRI imaging of the elbow of postoperative patients are susceptible to metallic-susceptibility artifact, which results from any metallic biomedical implants such as endoprostheses and internal orthopedic devices (Bennett, Wang and Donahue). This can be minimized by increasing the bandwidth, aligning the metal along the long axis of the magnet bore, using fast-spin echo sequences, preventing fat suppression, orienting the frequency- encoding direction along the main longitudinal axis of the implanted hardware, and increasing the frequency-encoding gradient strength (Bancroft, Berquist, Peterson, and Kransdorf, 2007). Frequent motion artifacts can also occur in elbow MRI, especially among children. This can be prevented by placing the patient in supine position (Vahlensieck, Genant, Reiser, 2000). Figure 4. Metallic susceptibility artifact (red arrows). From Awh, M. (2011) Hip Arthroplasty [online] Available at: http://www.radsource.us/clinic/1102 Figure 5. Motion Artifact. From CT Dictionary [online] Available at: 4. Calcifying Tendonitis a.) Calcifying tendonitis is a usually asymptomatic condition in which macroscopic, poorly crystallized hydroxyapatite deposits are found on any of the tendons in the rotator cuff. Symptomatic patients, on the other hand, may complain of 1) chronic, relatively mild pain of the shoulder pain and tenderness radiating to the deltoid insertion or neck, with intermittent flares caused by arm elevation or lying on the shoulder, 2) difficulty in elevating the shoulder, loss of the shoulder’s range of motion or 3) severe and acute shoulder pain and tenderness. However, one cannot predict the size of the deposit based on the severity of symptoms, although symptoms usually present when deposits are larger than 1.5 cm. Catching or crepitus may be noted as well (Woodward, 2011). b) Although the pathophysiology of calcifying tendinitis is still being debated upon, the disease has been suggested to progress to four different stages based on their pathologic and clinical features. The first stage, the formative phase, is characterized by the initiation and enlargement of calcium deposits on a portion of a tendon that has undergone fibrocartilaginous transformation. In the resting phase, the deposit neither increase nor decrease in size. Consequently, symptoms may or may not be present depending on the size of the deposit after the formative phase. Once the deposit illicit an inflammatory reaction, the disease enters the resorptive phase. Vascularization occurs around the deposit, and inflammatory cells are delivered to the site to soften the calcium deposits. At times, however, the softened deposit leaks into the subacromial fossa, causing severe pain. Finally, in postcalcific phase, the deposits are fully and resorbed, and the collagen pattern of the tendon is repaired (Woodward, 2011). Treatment of calcifying tendonitis depends on the phase at which the condition is diagnosed. In detail, the resorptive phase, despite having the worse symptoms, is still self-limited. In fact, the condition may resolve spontaneously, no matter what phase, and is rarely associated with rotator cuff tears. Relieving management such as needling, aspiration and lavage may be done to resolve temporarily the accompanying symptoms. However, a patient may opt for surgery, especially when the symptoms are progressing, when conservative care cannot be given, and when it interferes with daily activities. But, presence of local infection is a contraindication to surgery. In contrast, calcifying tendonitis in formative or resting phases may need extracorporeal shock wave therapy (ECSW), as lavage may not be as effective in these phases. If, for some reason these procedures cannot be conducted, analgesics such as nonsteroidal anti-inflammatory drugs (NSAIDs) may be prescribed to provide pain relief (Woodward, 2011). c.) Plain x-rays of true anterolateral, lateral, anteroposterior (AP), axillary, and supraspinatus outlet views with the shoulder in internally and externally rotated should be able to detect calcification in any rotator cuff tendon. The sensitivity of plain X-ray in detecting calcific deposits is 0.90 relative to ultrasound. The appearance of the deposit can vary depending on which phase the tendinitis is on. Formative and resting phases are characterized by localized, homogenous and well-delineated deposits, while diffuse, heterogenous, amorphous, fluffy, and poorly demarcated deposits are found in resorptive phase. Upon detection, deposits must be characterized by its location, especially the nearby tendons, and its size. Arthrogram with radiopaque dye is not usually necessary, although it can be done when there is indication of rotator cuff tear. On the other hand, MRI is not necessary in diagnosing calcifying tendonitis, although it is more than 95% accurate in detecting calcifications. T1-weighted MRI of a calcific deposit reveals decreased signal intensity. In cases of edema, increased signal intensity around the deposits may be present in a T2-weighted MRI image. This can be mistaken as a rotator cuff tear (Woodward, 2011). Figure 6. Focal calcification on T2-weighted MRI image (red arrow). A similar hypodensity may be observed in rotator cuff. From Quinn, S. F. (2009). Hydroxyapatite Deposition Disease [online] Available at: 5. a) Ganglion Figure 7. Ganglion Cyst. From (2011). Ganglion Cyst [online] Available at: Ganglions are idiopathic, asymptomatic masses usually found on the hands and wrists, adjacent to joints or tendons. Most cases are women. It is a capsule covered by a thin connective tissue and containing mucinous material (Teh and Whiteley, 2007). Although usually causing cosmetic disturbance, it can exert mass effects on arteries, veins, tendons and nerves, thus resulting to pain, triggering of tendons, progressive growth in size, spontaneous draining, and tissue ischemia depending on its location. Because it is benign, observation, reassurance, or aspiration and/or injection are sufficient in the management of ganglions. However, surgical intervention may be necessary in cases of discomfort, dysfunction, skin breakdown, nail deformity or multiple episodes of drainage (Schena, 2010). Imaging of a ganglion cyst using MRI produces a unilocular or multilocular rounded or lobular fluid signal mass adjacent to a joint or tendon sheath. Although many small ganglia may be mistaken for effusion, the scarcity of fluid in the remainder of the joint and the focal nature of the fluid is an indication of ganglion (Teh and Whiteley, 2007). T1-weighted MRI of the transverse plane shows low signal intensity similar to that of the surrounding musculature (Vahlensieck, Genant, Reiser, 2000). However, increased protein concentrations and hemorrhage may increase the intensity of a ganglion in a T1-weighted image (Teh and Whiteley, 2007). T2-weighted MRI imaging, on the other hand, demarcates the high signal intensity of the mass with the surrounding tissue (Vahlensieck, Genant, Reiser, 2000). Figure 8. Ganglion cyst in MRI. From Alsalam, H. (2011) Ganglion Cyst [online] Available at:< http://radiopaedia.org/images/634932> b) Carpal Tunnel Syndrome Carpal tunnel syndrome (CTS), presenting initially as sensory defect including numbness, paresthesia, and pain in the median nerve distribution, which aggravate to include motor weakness, is caused by impingement of the median nerve that runs within the carpal tunnel. Along with the median nerve are the flexor digitorum profundus, flexor digitorum superficialis and flexor pollicis longus (Vahlensieck, Genant, Reiser, 2000). The constricted position of the nerve in cases of high pressures within the carpal tunnel causes venous outflow, back pressure, edema formation, and nerve ischemia, starting out as demyelination and subsequently leading to axonal degeneration. If left untreated, it may cause irreversible median nerve damage and loss of hand function. Females are more affected than males, and incidence of CTS mostly among people aged 45-60 years (Ashworth, 2011). MRI is the most sensitive and most specific diagnostic tool for Carpal Tunnel Syndrome. Axial plane shows bowing of the flexor retinaculum. Inflammation of the synovium presents as a low-signal intensity on a T1-weighted image in contrast to the high-signal intensity in a T2-weighted MRI image and short tau inversion recovery (STIR) sequences. Preservation of nerve architecture and fluid within the carpal tunnel are also signs of inflammation. Meanwhile, flow-sensitive sequences or dynamic contrast-enhanced MRI can identify a circulatory etiology for carpal tunnel syndrome (Browning, 2011). Figure 9. MRI of carpal tunnel syndrome shows T2-weighed signal intensity of the median nerve (white arrow). From Carpal Tunnel Syndrome: Slideshow [online] Available at: References Ashworth, N.L. (2011). Carpal Tunnel Syndrome. [online] Available at: < http://emedicine.medscape.com/article/327330-overview> [04 April 2012] Bancroft, L.W., Berquist, T.H., Peterson, J.J., and Kransdorf, M.J. 2007. Imaging of Elbow Pathology. Applied Radiology, 36(7), pp. 26-35. Bennett, L.H., Wang, P.S. and Donahue, M.J. Artifacts in Magnetic Resonance Imaging from Metals. [online] Available at: [04 April 2012] Bhutani, C. (2011). Elbow MRI. [online] Available at: [04 April 2012] Browning, P.D. (2011). Carpal Tunnel Syndrome Imaging [online] Available at: < http://emedicine.medscape.com/article/388525-overview#a21> [04 April 2012] Schena, A. (2010). Ganglions [online] Available at: < http://emedicine.medscape.com/article/1243525-overview> [04 April 2012] Tej, J. and Whiteley, G. 2007. MRI of Soft Tissue Masses of the Hand and Wrist. The British Journal of Radiology. 80, pp. 47-63. The Ohio State University Wexner Medical Center. Tennis Elbow [online] Available at: Woodward, A.H. (2011). Calcifying Tendonitis [online] Available at: < http://emedicine.medscape.com/article/1267908-overview > [04 April 2012] Read More