Elbow MRI

Clinical Chiropractic (2006) 9, 198—205

intl.elsevierhealth.com/journals/clch

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Elbow MRI Part 1. Normal imaging appearance of the elbow Michelle A. Wessely a,*, Kristin L. Hurtgen-Grace b, Julie-Marthe Grenier c a

Department of Radiology, Institut Franco-Europeen de Chiropratique (IFEC), 24 Boulevard Paul Vaillant Couturier, 94200 Ivry Sur Seine, France b New Zealand College of Chiropractic, P.O. Box 113-044, Epsom, Auckland, New Zealand c Department of Chiropractic, UQTR (University of Quebec, Trois-Rivieres), Quebec, Canada KEYWORDS Elbow; Humero-ulnar joint; MR imaging; Normal anatomy; Proximal radio-ulnar joint

Summary This article provides a brief overview of magnetic resonance imaging (MRI) of the elbow for the clinician. A basic review of MRI protocols for the region is followed by a discussion of the most common imaging sequences. The appearance of normal elbow anatomy is reviewed with emphasis on structures prone to injury. This is correlated to annotated images. Imaging of elbow pathology and trauma is discussed in part 2 of the article. # 2006 Published by Elsevier Ltd on behalf of The College of Chiropractors.

Introduction Magnetic resonance imaging of the elbow Magnetic resonance (MR) imaging of the elbow may not attract the same level of interest as MR imaging of the lumbar spine or the large extremity articulations; however, for those involved in treating functional impairment and pain of the elbow in clinical practice, it is a useful modality to consider, particularly in those cases where other forms of imaging have failed to provide a diagnosis and where an indepth visualization of the articulation is necessary. The elbow is structurally and functionally a complex articulation demanding an accurate and detailed knowledge of the normal anatomical rela* Corresponding author. Tel.: +33 1 4515 8918; fax: +33 1 4515 8911. E-mail address: [email protected] (M.A. Wessely).

tionships. Various injuries and pathologies may affect the elbow articulation involving the soft tissue and articular components. Therefore, fundamental knowledge of the joint’s normal MR imaging appearance is crucial in assisting the determination of the anatomical relationships and the presence or absence of pathology. The purpose of this article is to provide a foundation of the normal MR imaging appearance of the anatomical structures about the elbow for those involved with patients presenting with elbow disorders. Thereafter, part 2 will consider the most common disorders affecting the elbow and their MR imaging appearance.

Clinical indications MR imaging of the elbow is useful in the evaluation of an array of musculoskeletal disorders commonly involving an acute trauma or the chronic repetitive application of mechanical stress to the elbow

1479-2354/$32.00 # 2006 Published by Elsevier Ltd on behalf of The College of Chiropractors. doi:10.1016/j.clch.2006.09.003

Elbow MRI leading to pain and restriction of the patient’s normal activity. Although radiographs and ultrasound may be used initially to attempt to determine the source of pain and functional deficit, MR imaging may provide information that surpasses other imaging studies.1 Trauma often necessitates MR imaging of the elbow in both the acute setting as well as the chronic situation.2,3 Chronic trauma includes both chronic repetitive trauma, such as that experienced in sports activities involving a racquet such as tennis, or as a result of an initial acute trauma, whereafter the patient continues to be affected weeks or months after the original injury. In the acute trauma setting, patients sustaining dislocations of the elbow, most commonly posteriorly, may be at risk of associated conditions (for example, osteochondral injuries) that are important to be aware of since

199 the clinical outcome may be affected. In the chronic trauma setting, patients with persistent elbow symptoms related to sports may have the development of scar tissue; partial or complete tears of the tendons; and tendinous degeneration or articular changes, all of which may preclude a normal recovery. Those patients suffering with elbow symptoms following a previous trauma may develop complications such as a vascular necrosis or loose body formation resulting from an osteochondral injury, which benefit from MR imaging to determine the most appropriate clinical management of the patient. MR imaging of the elbow may also provide important information regarding the neural elements about the articulation as they continue their course in to the forearm and hand. The radial, median and ulnar nerves follow complicated pathways and may

Figure 1 MR imaging of the elbow usually consists of the three orthogonal planes: namely, sagittal, coronal and axial imaging sequences. The MR imaging provided demonstrates the scout views [a(i,ii), b(i,ii) and c(i,ii)], the initial imaging views that assist in the planning of each sequence. Note particularly in c(i,ii) the numbers, which correspond to the slice that has been performed. The top, middle and lower row of iii—v correspond to the resulting imaging. Figures a(iii—v) are images taken in the sagittal plane, T1-weighted sequence; figures b(iii—v) are in the coronal plane, short tau inversion recovery (STIR) sequence; figures c(iii—v) are in the axial plane, again with STIR.

200 be prone to being entrapped at a variety of locations by a wide variety of causes including injury, mass compression or developmental variants. Elbow surgery may also provoke the formation of scar tissue, which can adhere to the nerves leading to syndromes related to neural irritation, then entrapment and, eventually, chronic denervation. In such syndromes, the use of MR imaging may be helpful in determining the degree of involvement as well as indicating sites of potential reparation. However, in

M.A. Wessely et al. addition to MR imaging, clinical testing, including electromyography and nerve conduction tests, is an essential part of the work-up of the patient, thus correlating both the structure and function of the involved neural structures.

Protocol MR imaging of the elbow involves the patient lying in the supine position with the arm resting against the

Figure 2 MR imaging of the elbow in the axial plane, using STIR sequences (a—f), demonstrating the full spectrum of the intricate anatomical structures visible, the key to which is detailed in Table 1. A method for reviewing the anatomy is to select an individual anatomical structure and to trace it from its origin to insertion. Although perhaps time consuming, accuracy in identification of the structure and determination of a lesion affecting it may be appreciated.

Elbow MRI Table 1 Key to legend on figures H–—humerus R–—radius U–—ulna 1 Brachial artery 2 Cephalic vein 3 Radial nerve 4 Ulnar nerve 5 Median nerve 6 Basilic vein 7 Brachioradialis muscle 8 Brachialis muscle 9 Extensor carpi radialis longus muscle 10 Triceps muscle 11 Pronator teres muscle 12 Common flexor tendon 13 Biceps tendon 14 Anterior fat pad 15 Common extensor tendon 16 Anconeus muscle 17 Flexor carpi ulnaris muscle 18 Flexor digitorum (superficialis and profundus) muscles 19 Extensor digitorum muscle 20 Extensor carpi ulnaris muscle 21 Supinator muscle 22 Palmaris longus muscle 23 Flexor carpi radialis muscle 24 Lateral collateral ligament 25 Olecranon fossa 26 Biceps tendon 27 Posterior fat pad 28 Medial collateral ligament 29 Articular cartilage

body. A surface coil is used to improve the final image quality. The three planes of interest should be included: namely, axial, sagittal and coronal, in both the T1- and T2-weighted sequences if possible, to maximize the three-dimensional visualization of

201 the anatomic structures demonstrated (Figs. 1 and 2, Table 1). On occasion, intra-articular contrast may be added, especially if the clinical question involves the identification of a mass or in the determination of an active synovial-based disorder.4,5

Imaging anatomy Osseous anatomy The elbow is a compound, hinged synovial joint (ginglymus) composed of the distal humerus, and the proximal ulna and proximal radius, which, in turn, articulate by means of a synovial pivot (trochoid) joint. There are two prominent processes on the distal humerus, the medial and lateral epicondyles. The distal articular surface of the humerus is wide and flat. The lateral third, the capitellum, articulates with the radial head, which has a discshaped articular surface. The medial third, the trochlea, articulates with the ulna. The proximal ulna has been likened to a pipe wrench with the olecranon resembling the upper jaw, the coronoid process the lower jaw and the trochlear notch, the jaw itself. The lateral side of the coronoid process has a small, shallow notch or groove to articulate with the radial head. At the posterior surface of the distal humerus, between the medial and lateral epicondyles, lies the olecranon fossa and, on the anterior surface is the coronoid fossa with a thin layer of bone between the two.

Nerves The three nerves, median, radial and ulnar, are most easily recognizable on axial images of the elbow;

Figure 3 MR imaging of the elbow, coronal slices using the STIR sequence (a—d) to identify the anatomical structures visible in this plane (see Table 1 for key to legend). Despite the number of anatomical structures to identify, a suggestion is to choose those structures that present in practice commonly with pathology; for example, the common extensor tendon (structure 15) and appreciate the normal appearance in this set of images of a 24-year-old chiropractic student.

202 nonetheless, they may be difficult to identify owing to their size, anatomical relationship and signal intensity. The ulnar nerve is the nerve most commonly injured in the elbow, possibly due to the superficial position that the nerve takes in its course about the elbow. The nerves are distinguishable on MR imaging owing to the surrounding fat, particularly around the radial and median nerve (Fig. 3). The median nerve may also be identified if the patient’s arm is placed in pronation during the MR imaging, and, if there is a clinical question regarding the nerve, it is prudent to indicate this information to the radiographer or to the referring physician. Disorders of the nerves tend to manifest clinically as neuropathies. While the clinical examination may provide the general location of the neuropathy, imaging is useful to pinpoint the site as well as to identify the etiology of the neuro-

M.A. Wessely et al. pathy, which may be due to a variety of causes such as soft tissue masses relating to tumors or infection; trauma induced neuropathies; or scar tissue formation.6 MR imaging of neuropathies demonstrates that, compared to the normal intermediate signal intensity of the neural structures, the T2weighted sequence shows an increase in signal from the nerve and in the surrounding soft tissue, enlargement of the nerve and blurring of the individual fascicles.7 Such fascicles may not be distinguished on all MR imaging of the elbow; however, with the changes in the signal characteristics and structure of the nerve, the innervated muscular structures may also demonstrate change. An increase in the signal intensity on the T2-weighted sequence of the innervated muscles will be noted progressively and, eventually, atrophy of the involved muscle will be noted with fatty infiltration of the muscle compartment.8

Figure 4 MR imaging of the elbow in the sagittal plane, using the T1-weighted sequence (a—f), demonstrating the normal anatomical relationships of the articulation (see Table 1 for key to legend).

Elbow MRI

Bursae and synovial articulation Conditions typically associated with synovial articulations such as degeneration, proliferation and inflammation can affect the elbow and can be identified with MR imaging. In rheumatoid arthritis, thickening of the synovial membrane and associated pannus formation occurs with accumulation of intra-articular fluid. An increased signal intensity of the edematous synovium is seen, with hyperintense joint effusion. Erosions can be seen with decreased signal intensity and the nodules, present in 20% of sufferers, show as mixed signal intensity masses in the skin, synovium and tendons. Osteoarthritis is seen less commonly in the elbow compared to weight-bearing joints and findings are usually evident on plain films. MR imaging may be used to evaluate the integrity of the cartilage, identify focal defects and further evaluate those findings seen on X-ray.

203 Inflammatory conditions of the bursa can also be imaged with MR imaging and generally produce a high fluid signal intensity in the olecranon or bicipital radial bursae on T2-weighted images and low signal intensity on T1-weighted images. Inflammation of the olecranon bursa is typically seen after trauma and may also be present in inflammatory conditions such as rheumatoid arthritis, septic bursitis and crystal deposition disorders. The appearance of bicipitoradial bursitis is similar on MR imaging. This may start insidiously or be triggered by athletic activity. The olecranon and bicipitoradial bursae are not typically seen on MR imaging unless engorged with fluid. Acute osteomyelitis in children and chronic osteomyelitis in adults is often associated with infectious bursitis. MR imaging shows hyperintense marrow edema on T2-weighted images and cortical destruction. Brodie’s abscess, cellulitis, myositis and sinus tracts may also be evaluated with MR imaging.

Figure 5 MR imaging of the elbow, coronal slice using a T2-weighted sequence, showing an exquisite depiction of the lateral, or radial, collateral ligament (structure 24). This ligament should appear as a low signal intensity band coursing its way in an arc-like fashion laterally as demonstrated in this image.

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Figure 6 MR imaging of the elbow performed in the coronal plane, using a T1-weighted sequence (a) and a T2-weighted sequence (b). The images demonstrate the effect of a surgical device, which was inserted due to previous trauma about the elbow. This device is noted (see white ovals in both a and b)–—it is important to appreciate the technical artifact that is produced as a result of such apparatus, which may interfere with the interpretation of the final image.

Muscles Anterior The group of muscles that contribute to the soft tissue structures anteriorly include the biceps brachii and brachialis muscles (Fig. 3). The biceps brachii, which consists of two parts proximally, unites to form a common tendon above the elbow and inserts on the radial tuberosity. The bicipitoradial bursae separate the tendon from the anterior aspect of the radial tuberosity. The brachialis muscle lies deep to the biceps brachii and originates from the distal half of the anterior humerus, inserting on to the coronoid process.

Posterior The muscles that contribute to the posterior group of the elbow are the anconeus and triceps brachii. The anconeus is a small, triangular muscle of the posterior lateral elbow and, since it blends with the triceps, is often considered — functionally at least — as part of this muscle. It originates on the posterior lateral epicondyle of the humerus and inserts on to the posterior superior surface of the ulna. The triceps brachii attaches to the proximal surface of the olecranon and blends with the anconeus. The olecranon bursa lies between the triceps brachii tendon and the olecranon.

Medial The medial group of elbow muscles include the pronator teres, the palmaris longus and the hand flexor

group (flexor digitorum superficialis and profundus; flexor carpi radialis and ulnaris and flexor pollicus longus). The pronator teres muscle is the most superficial of the group and has two origins, one from the medial epicondyle (of the humeral head) and the second from the coronoid process (of the ulnar head) inserting on to the lateral surface of the mid-third of the radius. The medial or ulnar collateral ligament may also be identifiable along its course.9

Lateral The supinator and brachioradialis muscles with the extensor muscles of the hand and wrist form the lateral group (Figs. 4 and 5). The supinator muscle is the deepest muscle, originating on the lateral epicondyle of the humerus and inserting on to the proximal third of the radius. It contributes to the floor of the cubital fossa. The brachioradialis serves as the lateral boundary of the cubital fossa. Originating at the supracondylar ridge of the humerus the brachioradialis, it inserts on to the lateral surface of the distal radius (Figs. 4—6).

Conclusion MR imaging of the elbow is a detailed, effective choice of study to determine the pathoanatomy leading to a variety of presenting complaints. Precise knowledge regarding the soft tissue structures aids in a precise diagnosis and clinical management strategy. Articular based disorders equally can be determined especially with the accuracy in evaluating the cartilaginous component.

Elbow MRI

Clinical pearls  MR imaging of the elbow is useful in the clinical settings of acute trauma or chronic repetitive mechanical stress, both of which may result in pain and modification of the normal function of the elbow.  MR imaging planes should include axial, sagittal and coronal slices with both T1- and T2weighted sequences included in the study.  MR imaging interpretation should commence with the fluid sensitive sequences to determine regions of inflammation, fluid collection or bone edema. These may assist in the localization and, later, the characterization of the elbow disorder.  During the MR imaging interpretation, pick an anatomical structure and follow it from its origin to insertion on all three planes.  Make a checklist of the structures in which you are most interested given the correlation to the patient’s complaint and clinical presentations; however, be sure to evaluate the entire elbow region.

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205 2. Bohndorf K, Kilcoyne RF. Traumatic injuries: imaging of peripheral musculoskeletal injuries. Eur Radiol 2002;12(7):1605— 16. 3. Hoy G, Wood T, Phillips N, Connell D, Hughes DC. When physiology becomes pathology: the role of magnetic resonance imaging in evaluating bone marrow oedema in the humerus in elite tennis players with an upper limb pain syndrome. Br J Sports Med 2006;40(8):710—3. 4. Brunton LM, Anderson MW, Pannunzio ME, Khanna AJ, Chhabra AB. Magnetic resonance imaging of the elbow: update on current techniques and indications. J Hand Surg [Am] 2006;31(6):1001—11. 5. Fowler KA, Chung CB. Normal MR imaging anatomy of the elbow. Magn Reson Imaging Clin N Am 2004;12(2): 191—206. 6. Bencardino JT, Rosenberg ZS. Entrapment neuropathies of the shoulder and elbow in the athlete. Clin Sports Med 2006; 25(3):465—87. 7. Vucic S, Cordato DJ, Yiannikas C, Schwartz RS, Shnier RC. Utility of magnetic resonance imaging in diagnosing ulnar neuropathy at the elbow. Clin Neurophysiol 2006;117(3): 590—5. 8. Kijowski R, Tuite M, Sanford M. Magnetic resonance imaging of the elbow. Part II. Abnormalities of the ligaments, tendons, and nerves. Skeletal Radiol 2005;34(1):1—18. 9. Munshi M, Pretterklieber ML, Chung CB, Haghighi P, Cho JH, Trudell DJ, Resnick D. Bundle of ulnar collateral ligament: evaluation of anatomic relationships by using MR imaging, MR arthrography, and gross anatomic and histologic analysis. Radiology 2004;231(3):797—803.

Further reading 1. Pomeranz SJ. MRI total body atlas. Vol. 2, Orthopedics. MRI/ EFI, USA; 1999.