The posterior aspect of the elbow may be examined by keeping the joint flexed 90° with the palm resting on the table (Barr and Babcock 1991). This position allow easy demonstration of the main structures of the posterior elbow: the cubital tunnel and the ulnar nerve, the triceps muscle and tendon, the posterior fossa with the posterior fat pad and the olecranon bursa.

Cranial to the olecranon, US reveals the hypoechoic bellies of the triceps muscle and its tendon that is located eccentrically and slightly medial with respect to the midline (Fig. 21). The distal triceps tendon appears hyperechoic and typically exhibits striations as it fans out toward its insertion on the olecranon, a pattern somewhat similar to the quadriceps. These striations, with alternating hypo- and hyperechoic bands, are more likely due to interposition of fat between the tendon fibers and should not be misinterpreted as tendinosis or tear (Fig. 22). If examined in full elbow extension, the distal triceps tendon may also appear wavy, possibly mimicking a rupture. Tendon laxity is particularly evident in the elderly and represents a normal finding (Rosenberg et al. 1997). In addition, the preinsertional fibers of this tendon may appear hypoechoic owing to their oblique course (Fig. 22). Changes in orientation of the probe allow adequate correction of anisotropic effects in this area. The most distal portion of the triceps tendon should always be evaluated carefully to rule out enthesis calcifications.

Fig. 21a–c. Normal distal triceps tendon and olecranon fossa. a Extended-field-of-view mid-sagittal 12−5 MHz US image obtained with the elbow flexed over the olecranon process (O) and the posterior aspect of the distal humerus. The distal triceps tendon (arrowheads) appears as a beak-shaped hyperechoic structure in continuity with the hypoechoic bellies of the triceps muscle ™ that inserts approximately 1 cm distal to the apex (star) of the olecranon. Deep to the triceps, the olecranon fossa is delimited by the hyperechoic spoon-shaped contour of the humerus and the echogenic posterior fat pad (asterisks). Note the posterior rounded appearance of the trochlea (T) and the straight profile of the humeral shaft (HS) just above the posterior fossa. b,c Transverse 12−5 MHz US images obtained at the levels (vertical white bars) indicated in a. In b, the cross-sectional appearance of the distal myotendinous junction of the triceps is seen over the posterior trochlea (T). Observe that the tendon (curved arrow) arises slightly eccentrically relative to midline and the distal muscle (arrowheads). In c, the oval cross-sectional shape of the distal triceps tendon (arrows) is seen lying over the olecranon (O). The insert at the upper left side of the figure indicates probe positioning.

Fig. 22a,b. Distal triceps tendon: normal appearance mimicking disease. a Long-axis 12−5 MHz US image of the distal triceps tendon (arrowheads) with b diagram correlation reveals a striated intratendinous pattern composed of alternate hypo- and hyperechoic bands (arrows) which are related to fatty tissue strands intervening between the tendon fibers. Also, note the artifactual hypoechoic appearance (asterisk) of the tendon as it deflects to insert onto the olecranon process (O). This is due to anisotropy. T, trochlea. The insert at the upper left side of the figure indicates probe positioning.

The olecranon fossa appears as a wide and deep concavity of the posterior aspect of the humeral shaft filled with the hyperechoic posterior fat pad (Fig. 21a) (Miles and Lamont 1989). At both sides of this fossa, the posterior aspect of the medial and lateral epicondyles can be seen on transverse images. While examining the joint at 45° flexion, intra-articular fluid tends to move from the anterior synovial space to the olecranon recess, thus making the identification of small intra-articular effusions easier. Gentle rocking motion of the patient’s elbow during scanning may be helpful to shift elbow joint fluid into the olecranon recess. More distally, the olecranon process is imaged as a hyperechoic curvilinear structure that is separated from the overlying skin by a thin layer of loose connective tissue containing the synovial olecranon bursa. Because of its thin walls and absence of fluid content, the normal olecranon bursa is not visible at US. Care should be taken not to apply excessive pressure with the probe when evaluating this bursa because small bursal effusions may be squeezed away.

For evaluation of the posteromedial aspect of the joint, including the cubital tunnel and the ulnar nerve, the patient’s elbow should be placed in forceful external rotation to enable visualization and palpation of the medial epicondyle and olecranon. This can be obtained either with the patient seated and the elbow extended and hyperpronated with its dorsal aspect facing the examiner or, at least for the right side, with the patient supine and the arm abducted in maximal external rotation, hanging off the table (Martinoli et al. 2000; Jacobson et al. 2001).

To examine the cubital tunnel, the probe should be placed in the transverse plane with one end over the olecranon and the other over the medial epicondyle (Jacobson et al. 2001). Similar to the situation in other sites, bony landmarks work well in routine practice to select the correct probe positioning. Because the nerve passes through a narrow space delimited by prominent bones, small transducers are superior in evaluating this region. Long-axis scans are less useful than short-axis planes for following the ulnar nerve (Fig. 23). Systematic scanning in short-axis planes starts at the inner side of the upper arm, where the ulnar nerve courses in a superficial position relative to the triceps. At the humeral groove, the ulnar nerve is located close to the inside slope of the medial epicondyle. It typically appears as an ovoid structure close to the hyperechoic bony cortex of the epicondyle (Fig. 24a,b). In the distal portion of the tunnel, the ulnar nerve is visible between the humeral and ulnar heads of the flexor ulnaris carpi muscle (Fig. 24c,d). In normal states, the cross-sectional area of the ulnar nerve is slightly greater at the level of the epicondyle (6.8 mm2) than at the distal arm (5.7 mm2) and the proximal forearm (6.2 mm2) (Chiou et al. 1998). One should be careful not to confuse this normal increase in nerve size inside the cubital tunnel for a sign of ulnar neuropathy. Some discrepancies exists in literature on as what the size of the ulnar nerve should be considered normal. A cross-sectional area of 7.5mm2 was initially indicated as the threshold value for the cubital tunnel syndrome (Chiou et al. 1998). More recently, 7.9mm2 has been found as the mean value for the normal ulnar nerve at the cubital tunnel level (Jacob et al. 2004). These discrepancies seem, at least in part, related to differences among races and in study design. In the cubital tunnel, the ulnar recurrent artery and veins can readily be distinguished from the adjacent nerve on color Doppler imaging. In cases of engorgement, these veins become dilated and could mimic swollen individual nerve fascicles. Doppler imaging can help to avoid this pitfall. The cubital tunnel retinaculum and the arcuate ligament consist of thin fascia and, at least in normal states, they are not visualized with US, even using very high frequency US transducers. Dynamic imaging of the cubital tunnel is performed throughout full elbow flexion to assess the position of the ulnar nerve and the medial head of the triceps muscle relative to the medial epicondyle (Fig. 25). For this purpose, the probe is placed in the transverse plane over the epicondyle while the patient is asked to slowly flex the elbow (Jacobson et al. 2001). During this maneuver, it should be emphasized that the application of firm pressure on the skin with the transducer must be avoided because it may prevent the dislocation of the nerve from the tunnel.

Fig. 23. Normal ulnar nerve. Long-axis 12−5 MHz US image of the normal ulnar nerve obtained over the cubital tunnel with extended elbow. The relationships of the nerve (arrows) with the medial epicondyle (ME) and the flexor carpi ulnaris muscle (fcu) are shown. The ulnar nerve exhibits a hypoechoic appearance and a fairly uniform thickness throughout the tunnel. The insert at the upper left side of the figure indicates probe positioning.

Fig. 24a–d. Normal cubital tunnel. a Transverse 12−5 MHz US image at the proximal cubital tunnel level (condylar groove) with b T1w SE MR imaging correlation show the normal relationship of the ulnar nerve (arrow) with the medial epicondyle (ME). Observe the distal triceps tendon (asterisks) over the olecranon (O). c Transverse 12−5 MHz US image at the distal cubital tunnel level (proper cubital tunnel) with d T1w SE MR imaging correlation demonstrates the nerve (arrow) beneath the arcuate ligament (arrowheads) that joins the humeral (fcu1) and ulnar (fcu2) heads of the flexor carpi ulnaris muscle. The inserts at the upper left side of the figures indicate probe positioning.

Fig. 25a–d. a,b Photographs illustrating the scanning technique to assess the position of the right ulnar nerve relative to the medial epicondyle with elbow extension (a) and during progressive degrees of elbow flexion (b). Note that the probe remains stabilized on transverse plane between the medial epicondyle and the olecranon during full elbow motion. c,d Schematic drawings of the medial elbow examined in c extension and d fl exion illustrate the mechanism of ulnar nerve instability at the cubital tunnel. Note the absence of the Osborne retinaculum (see for comparison Fig. 8.7c). When the elbow is extended, the ulnar nerve (white arrow) is contained within the tunnel. Elbow flexion (black arrow) dislocates the ulnar nerve anteriorly to the medial epicondyle (ME). fcu, flexor carpi ulnaris muscle. Dashed line, appropriate probe positioning during scanning.

27. ANTERIOR ELBOW PATHOLOGY: DISTAL BICEPS TENDON TEAR

One of the most common causes of acute anterior elbow pain is rupture of the distal biceps tendon. These tears account for less than 5% of all biceps tendon lesions, proximal injuries being far more common (Agins et al. 1988). They typically occur after 40 years of age (mean 55 years) in manual laborers who attempt to lift a heavy object (or in weightlifters and body builders) or during vigorous eccentric contraction of the biceps against resistance. Distal biceps tendon tears may occur with either avulsion of the tendon by the radial tuberosity (more commonly) or midsubstance tear or injury at its myotendinous junction. Similar to other tendons, there is a relatively hypovascular zone within the distal biceps tendon, approximately 10 mm from its insertion on the radial tuberosity (Seiler et al. 1995). Repetitive impingement of this zone between the radius and the ulna during pronation movements seems to be a predisposing factor to start the degenerative process in the tendon substance (Seiler et al. 1995). In most cases, the rupture of the distal biceps tendon is associated with tearing of the lacertus fibrosus, but this latter structure may also remain intact. Clinically, a complete tendon tear presents with pain and a palpable defect with a proximal lump in the anterior aspect of the arm related to the retracted muscle (Fig. 26). Although weakened, elbow flexion is preserved due to the strong action of the brachialis muscle; on the contrary, supination of the forearm is more severely compromised because of the limited strength of the small supinator muscle. In most cases, the clinical diagnosis is straightforward and does not require an additional imaging study. Nevertheless, occult ruptures are more common than once thought and, in daily practice, they are becoming increasingly diagnosed with US even some time after the trauma. A delayed clinical diagnosis occurs mainly in the absence of significant muscle retraction because of an intact lacertus fibrosus, or when the retracted muscle is hidden from palpation with surrounding edema and hemorrhage.

Fig. 26a,b. Distal biceps tendon tear: physical findings. Photographs of two different patients who underwent a subacute and b chronic complete rupture of the distal biceps tendon. In a, the patient injured his left tendon while attempting to lift a heavy object. He presented with hemorrhagic skin over the medial elbow and proximal forearm and with a proximal lump (arrowheads) in the anterior aspect of the arm related to the retracted muscle. In b, the patient was a competitive body-builder who refused surgical repair of the ruptured tendon. Note the defect (arrowhead) in the anterior left arm due to the retracted muscle in comparison with the right side.

An early diagnosis of distal biceps tendon rupture is important because surgical outcome is improved in patients treated in the first weeks after trauma before the occurrence of tendon adhesions, degenerative changes and fatty muscle infiltration. The main US features of a complete tear of the distal biceps tendon include nonvisualization of the distal tendon, which appears proximally retracted (up to more than 10 cm from the radial tuberosity), and detection of hypoechoic fluid in the tendinous bed related to hematoma (Fig. 27) (Lozano and Alonso 1995; Miller and Adler 2000). The effusion is best recognized around the tendon stump (Fig. 28). With high-resolution transducers, US is not sensitive enough to can depict the normal lacertus fibrosus as a very thin fibrillar band over the pronator teres. The status of the lacertus fibrosus is, however, not a critical issue as it is not routinely involved in surgical repair of a torn distal biceps tendon. In addition, there is no evidence that the degree of tendon retraction is in itself predictive of the status of the lacertus fibrosus (Fig. 29) (Miller and Adler 2000). In case of its rupture, however, US can recognize perifascial fluid around the anterior and lateral aspects of the flexor-pronator group of muscles and a more striking tendon retraction (Fig. 29b).

Fig. 27a–d. Complete rupture of the distal biceps tendon. a Long-axis 12−5 MHz US image over the brachialis muscle (br) shows hypoechoic fluid (asterisks) filling the distal bed of the retracted distal biceps tendon (dbt) and surrounding its myotendinous junction. In this particular case, the tendon edge (arrowheads) lies distal to the joint line. b−d Short-axis 12−5 MHz US images obtained at the levels (vertical white bars) indicated in a demonstrate the torn and retracted tendon end (straight arrows) surrounded by hypoechoic hematoma (asterisks). The relationships of the torn tendon with the brachial artery (arrowhead), radial nerve (curved arrow), brachialis (br) and brachioradialis (brrad) muscles are shown.

Fig. 28a–c. Complete rupture of the distal biceps tendon. a Long-axis 12−5 MHz US image obtained proximal to the elbow joint with b,c correlative transverse T2w SE MR images acquired at the levels (vertical white bars) indicated in a show the retracted edge (arrows) of the distal biceps tendon (dbt) with hypoechoic fluid (asterisks) filling the gap.

Fig. 29a–c. Acute complete rupture of the distal biceps tendon associated with a torn bicipital aponeurosis. a Long-axis 12−5 MHz US image over the brachialis muscle (br) demonstrates a markedly retracted tendon edge (dbt), the hematoma at the rupture site (asterisks) and the absence of the tendon (arrows). b Short axis 12−5 MHz US image obtained at the level (vertical white bar) indicated in a reveals fluid (arrowheads and curved arrow) in the soft tissues surrounding the flexor-pronator group (fpg) of muscles, suggestive of a coincident injury of the lacertus fibrosus. In this case, the injury of the bicipital aponeurosis was surgically confirmed. a, brachial artery; v, cubital veins. c Gross operative view of the same case.

The less common tendinitis and partial tears of the distal biceps tendon present with localized pain and tenderness over the antecubital fossa. These conditions usually follow repetitive microtrauma or forceful biceps activation. Pain can be exacerbated during resisted elbow flexion or supination of the hand and is worsened by direct palpation of the tendon. At US, partial tears appear as hypoechoic thickening or thinning of the tendon and as contour irregularities or waviness without tendon discontinuity (Fig. 30) (Miller and Adler 2000). The assessment of these tears may be difficult with US due to anisotropy related to the oblique course of the tendon and to its deep position. The US appearance of biceps tendinitis is very similar to that of partial tears and the diagnostic accuracy of US for differentiating these conditions relies on availability of a high-quality transducer as well as on the overall experience of the examiner. In doubtful cases, MR imaging is an accurate means to confirm the diagnosis of partial tears (Falchook et al. 1994).

Fig. 30a–d. Partial rupture of the distal biceps tendon. a Long-axis and b short-axis 12−5 MHz US images obtained at level distal to the elbow joint with c, d correlative transverse T1w SE MR images demonstrate a thickened and heterogeneous tendon (arrows) inserting on the radial tuberosity (asterisk).

Surgical treatment in complete tendon tears includes repair and reattachment of the retracted tendon to the radial tuberosity or, alternatively, to the brachialis muscle or the ulnar tuberosity. The first technique gives better results in restoring supination but has a significantly higher risk of radial nerve injury. After surgery, the tendon appears thickened and hypoechoic with internal linear hyperechoic images related to sutures (Fig. 31).

Fig. 31a,b. Postoperative distal biceps tendon. After surgical repair, a long-axis and b short-axis 12−5 MHz US images reveal a thickened and wavy distal biceps tendon (arrows). Adhesions and irregularities in the peritendinous tissues are also seen. Observe the sutures, which appear as bright echoes (arrowheads) within the tendon substance.

 

28. BICIPITORADIAL (CUBITAL) BURSITIS

The distal biceps tendon is not invested by a synovial sheath but it is covered by a paratenon. Just proximal to the tendon insertion, it is in contact with the bicipitoradial (cubital) bursa. This bursa is located between the distal biceps tendon and the radial tuberosity to reduce friction during pronation of the forearm (Skaf et al. 1999). Bicipitoradial bursitis is a rare condition that may result from several causes (infection, inflammatory arthropathy, amyloidosis, etc.) but it is most commonly secondary to repetitive mechanical trauma as well as to tendinosis and tearing of the distal biceps. On clinical grounds, swelling of the bicipitoradial bursa can be appreciated as a nonspecific mass in the antecubital fossa often associated with antecubital pain, especially upon elbow motion and forearm rotation. Because the clinical picture of bursitis is similar to tendinitis and the deep location of the bursa makes it difficult to palpate, a definite diagnosis of cubital bursitis relies mainly on imaging findings.

When the bicipitoradial bursa is only mildly distended, US may have difficulty in distinguishing it from the adjacent distal biceps tendon that appears hypoechoic due to anisotropy (Miller and Adler 2000). Usually, transverse scans with the forearm supinated perform better in delineating the bursal shape. At US, bicipitoradial bursitis appears as a hypoechoic mass located in proximity to the distal biceps tendon (Liessi et al. 1996). It may have septa, thick walls and echogenic content. Rice bodies have been described in this bursa with US (Spence et al. 1998). When distended by a large amount of fluid, the bicipitoradial bursa can surround the distal portion of the distal biceps tendon completely, thus mimicking a tenosynovitis (Fig. 32). Bicipitoradial bursitis must be differentiated from synovial and ganglion cysts and other soft-tissue masses. Ganglia commonly arise from the anterior capsule and may expand at a variable distance from the joint, dissecting the soft tissues of the forearm (Steiner et al. 1996). Visualization of a pedicle that connects the cyst with the elbow joint cavity may help the diagnosis. Calcified bursitis may be encountered in patients with renal osteodystrophy (Fig. 33). For asymptomatic bursitis no treatment is necessary, whereas most symptomatic patients are successfully treated with rest, physiotherapy and anti-inflammatory drugs.

Fig. 32a,b. Bicipitoradial bursitis. a Longitudinal and b transverse 12−5 MHz US images over the antecubital fossa at level distal to the joint line show fluid distension of the bicipitoradial bursa (asterisks) which almost completely surrounds the adjacent normal distal biceps tendon (T), thus mimicking a tenosynovitis process.

Fig. 33a–d. Calcified bicipitoradial bursitis in a woman with chronic renal failure who presented with a palpable mass in the antecubital fossa and difficulties in pronation. a Photograph shows focal soft-tissue swelling (arrowheads) over the anterior proximal forearm. b Transverse and c longitudinal 12−5 MHz US images reveal extensive hyperechoic deposits (arrows) with faint posterior acoustic shadowing related to calcifications with the bicipitoradial bursa. The bursa exhibits thickened walls and the distal portion of the biceps tendon (T) is completely surrounded by calcifications. d Correlative lateral radiograph shows the bulk of calcifications (arrows) in the antecubital fossa.

 

29. MEDIAL ELBOW PATHOLOGY: MEDIAL EPICONDYLITIS (EPITROCHLEITIS)

Medial epicondylitis, commonly referred to as “golfer’s elbow”, “medial tennis elbow” or “pitcher’s elbow”, occurs far less commonly than lateral epicondylitis and usually presents with pain and tenderness over the anterior aspect of the medial epicondyle that is enhanced by grasping and by resisted pronation of the forearm. Some sporting activities requiring repetitive valgus stress to the elbow joint, such as golf, javelin throwing and squash, may predispose to this condition. Medial epicondylitis is produced by degeneration and tearing of the common flexor tendon relative to overuse of the flexor-pronator group of muscles. Enthesopathy is frequently observed instead of tendinopathy. In this condition, joint effusion is absent and the elbow retains a full range of movements. The US appearance of medial epicondylitis is similar to the appearance of the other degenerative tendinopathies that involve the attachment of tendons to bone and includes hypoechoic changes in the tendon substance secondary to tendinosis or to partial-thickness tears (Fig. 34) (Ferrara and Marcelis 1997). Complete tear of the common flexor tendon is rare. In this clinical setting, US can help to distinguish tendinopathy from a lesion of the underlying medial collateral ligament. Ulnar neuropathy may be associated with tendinosis of the common flexor tendon.

The medial collateral ligament is stronger than the lateral collateral ligament. Its degeneration and tearing with or without an injury of the adjacent common flexor tendon may be secondary to acute or chronically repeated overstretching in valgus stress during the acceleration phases of throwing or may result from a fall or from posterior dislocation of the elbow. Baseball pitching is the sporting activity most commonly associated with medial collateral ligament injuries and medial joint instability. When the anterior band is injured, high-resolution US reveals a thickened hypoechoic ligament with surrounding effusion slightly posterior and deep to the medial epicondyle (Vanderschueren et al. 1998; Jacobson and van Holsbeeck 1998; Ward et al. 2003). Calcifications can also be associated with ligamentous tears (Nazarian et al. 2003). In cases of complete rupture, US examination may show either a gap or focal hypoechoic areas in the proximal and distal portion of the ligament (Fig. 35) (de Smet et al. 2002). To improve the diagnostic confidence, high-frequency US examination can provide dynamic assessment of the degree of medial joint laxity in both neutral and valgus stressed positions (de Smet et al. 2002). In a series of asymptomatic baseball pitchers, the medial elbow joint space of the throwing arm was significantly wider during valgus stressing than the joint space in the elbow of the nonthrowing arm (Nazarian et al. 2003). In symptomatic patients, widening of the trochlea-ulna joint and soft tissue falling into the distracted joint space suggest a medial collateral ligament injury (de Smet et al. 2002). Dynamic US scanning may be particularly useful in the event of partial-thickness tears, in which the ligament is continuous but lax. Examination of the noninjured elbow should be obtained to compare the amount of joint widening that occurs during valgus stressing.

Fig. 35. Medial collateral ligament injury. Longitudinal 12−5 MHz US image obtained with valgus stress over the anterior band of the medial collateral ligament (arrowheads) shows a focal hypoechoic area in the proximal ligament and mild widening of the elbow joint (arrows) compatible with a ligamentous injury. ME, medial epicondyle; fm, flexor muscles.

31. EPITROCHLEAR LYMPHADENOPATHIES

Just proximal to the elbow and adjacent to the medial epicondyle and the medial neurovascular bundle, small lymph nodes may enlarge as a result of reactive or septic inflammation (Barr and Kirks 1993). One of the leading causes of medial epitrochlear regional lymphadenopathy is “cat-scratch” disease, an infection caused by a gram-negative bacterium, Bartonella henselae, usually transmitted by scratches of the hand by an animal (most patients have a history of exposure to a cat!). However, enlarged lymph nodes in the epitrochlear area may also be involved by other disorders, including benign and malignant forms. US reveals the appearance of reactive lymph nodes consisting of oval hypoechoic masses with an echogenic hilum, often hypervascular at color Doppler imaging (Fig. 36). This appearance is typical and works well to rule out other soft-tissue masses, such as neurogenic tumors or sarcomas. The US examination should be extended up to the axillary region in order to rule out the possible coexistence of axillary lymphadenopathies. In cat-scratch disease, lymphadenopathies may be multiple and contiguous. Clinically, they are accompanied by painful soft-tissue swelling and systemic symptoms, such as fever and malaise. The involved nodes have a hypervascular pattern at color and power Doppler imaging and tend to develop central necrosis and liquefaction (Carcía et al. 2000; Gielen et al. 2003). Hyperechoic infiltration of the perinodal fat due to cellulitis is a characteristic finding (Fig. 37a). Enlarged lymph nodes most often regress over weeks to months. Whatever the cause of epitrochlear lymphadenopathies, US may exclude a local soft-tissue mass, thus obviating the need for biopsy or resection of this pseudotumor (Gielen et al. 2003). With time from the acute process, and especially in the elderly, the reactive nodes may undergo diffuse, massive adipose infiltration leading to a broad and hyperechoic medulla and progressive atrophy of the outer cortex (Fig. 37b). In these cases, the examiner should be careful not to mistake these atrophic nodes for lipomas or other hyperechoic soft-tissue masses. Detection of a thin continuous hypoechoic rim related to the atrophic cortex of the node may help the diagnosis (Fig. 37b).

Fig. 36a–c. Epitrochlear lymphadenopathy. a Long-axis and b short-axis 12−5 MHz US images over the medial elbow in a patient with a painful palpable mass associated with the medial epicondyle. US identifies an oval hypoechoic mass with echogenic hilum consistent with a superficial lymph node (arrowheads). c Color Doppler imaging reveals a hypervascular pattern of the node with a vessel pedicle (arrow) that enters the hilum and branches through the hypoechoic cortex. This lymph node regressed 2 weeks after medical treatment.

Fig. 37a,b. Epitrochlear lymphadenopathies in two different individuals with a active cat-scratch disease and b without any signs of infectious or inflammatory abnormalities. In a, the inflamed node is completely hypoechoic (arrowheads) with loss of definition of the echogenic hilum and appears surrounded by abnormally hyperechoic fat (arrows) due to perinodal cellulitis. In b, massive adipose infiltration has occurred in an epitrochlear lymph node (arrowheads) leading to a broad hyperechoic medulla. The cortical portion is markedly reduced in thickness and appears as a thin peripheral hypoechoic rim (arrows).

 

32. LATERAL ELBOW PATHOLOGY

The most common disorder involving the lateral elbow is lateral epicondylitis, also known as “tennis elbow”, caused by repetitive traction on the osteotendinous attachment of the common extensor tendon (Regan et al. 1992). This condition can be the result of chronic microtrauma secondary to repetitive overuse related to professional or recreational activities leading to progressive degeneration and/or partial tears of the common extensor tendon (tendinopathy) or to damage to the bone insertion (enthesopathy). The extensor carpi radialis brevis is the more commonly affected component of the common extensor tendon. Although lateral epicondylitis typically occurs in tennis players who injure this tendon–especially during the backhand stroke, in which the extensors are subjected to a greater tensioning–this condition is seen far more commonly in nonathletes. In tendinopathy, patients report a localized pain over the common extensor tendon during or just after repetitive muscle activation, whereas in enthesopathy, pain is confined to the tendon’s insertional area. Physical examination reveals localized tenderness over the lateral aspect of the elbow radiating down to the proximal forearm or well localized over the lateral aspect of the epicondyle respectively. Intra-articular effusion is not an associated finding. In chronic longstanding disease, pain at rest and limitation in joint extension can be noted.

The diagnosis is usually based on clinical findings and does not require imaging studies. US may be useful to confirm the clinical diagnosis in doubtful or refractory cases, to reveal the extent and severity of the disease and to monitor the response to therapy. The main US features of lateral epicondylitis are preinsertional hypoechoic swelling of the tendon with focal or diffuse areas of decreased reflectivity in the tendon substance and loss of the fibrillary pattern related to tendinosis, fluid adjacent to the common tendon and ill-defined tendon margins (Figs. 38, 39) ( Maffulli et al. 1990; Connell et al. 2001; Miller et al. 2002d; Levin et al. 2005). In a recent series, the mean size of the focal hypoechoic areas was 8.7 mm (range 3–15 mm) (Connell et al. 2001). Although early tendon abnormalities may be confined to the superficial fibers (Fig. 38a,b), involvement of the deep fibers of the extensor carpi radialis brevis component is more common and may even extend down to the joint capsule (Fig. 38c,d). Similarly, the anterolateral and mid-portion of the common extensor tendon is more commonly involved, whereas the posterior portion usually remains unaffected (Fig. 38b) (Connell et al. 2001). In high-grade tendinosis, the angiofibroblastic infiltration based on migration of fibroblasts and vascular granulation tissue within the tendon substance causes a striking hypervascular pattern of the intratendinous hypoechoic areas at color and power Doppler imaging (Fig. 39b). Spurring at the common extensor tendon insertion and cortical irregularities at the anterolateral surface of the lateral epicondyle may also be recognized, although bony changes do not correlate with disease activity. Intratendinous calcifications may also be seen as part of crystal deposition diseases (Fig. 40). In partial tears, the common extensor tendon may appear thinned compared with the opposite side. In practice, discrimination of focal areas of tendinosis and partial tears can be difficult and US is reliable for recognizing a partial tear only when discrete anechoic cleavage planes with no fibers intact are visible in the tendon substance (Connell et al. 2001). These tears typically appear as longitudinal splits oriented from the bony insertion distally (Fig. 41). Thickening of peritendinous soft tissues and a thin layer of superficial fluid over the extensor tendon are also more often observed with partial tears. In complete tears, US identifies a fluid-filled gap separating the tendon from its bony attachment site (Fig. 42) (Jacobson and van Holsbeeck 1998; Connell et al. 2001). Overall, US has proved to be as specific but not as sensitive as MR imaging for evaluating epicondylitis (Miller et al. 2002). On the other hand, US of the common extensor tendon has high sensitivity but low specificity in the detection of symptomatic cases (Levin et al. 2005).

Fig. 38a–d. Lateral epicondylitis: spectrum of US appearances in a weightlifter with bilateral lateral elbow pain. a Long-axis and b short-axis 12−5 MHz US images over the right common extensor tendon origin reveal a hypoechoic focus (asterisks) of tendinosis in the superficial fibers of an otherwise normal-appearing tendon (arrowheads). c Long-axis and d short-axis 12−5 MHz US images over the left common extensor tendon origin demonstrate a large hypoechoic area (asterisks) affecting both superficial and deep fibers of the tendon (arrowheads), indicating severe tendinopathy. On cross-section, the abnormal hypoechoic areas with loss of fibrillary echotexture (asterisks) are seen involving the full thickness of the anterior half of the tendon (arrowheads). In both elbows, observe the integrity of the deepest fibers in relation to the lateral collateral ligament. LE, lateral epicondyle; RH, radial head.

Fig. 39a,b. Lateral epicondylitis in a professional tennis player with a history of chronic right lateral elbow pain. a Long-axis gray-scale 12−5 MHz US image reveals a hypoechoic focus (asterisks) in the most superficial fibers of the common extensor tendon origin (arrowheads), whereas the deep fibers are preserved. b Color Doppler imaging demonstrates a striking hypervascular pattern composed of series of tiny vessels throughout the intratendinous hypoechoic areas, characteristic of tendinosis. LE, lateral epicondyle; RH, radial head.

Fig. 40a,b. Calcifying lateral epicondylitis. a Long-axis 12−5 MHz US image with b radiographic correlation in a patient with calcium pyrophosphate crystals deposition disease and recent onset of lateral elbow pain demonstrates large calcified foci (arrows) within the common extensor tendon origin. LE, lateral epicondyle; RH, radial head.

Fig. 41. Partial-thickness tear of the common extensor tendon. Long-axis 12−5 MHz US image in a manual laborer who presented with acute onset of lateral elbow pain reveals a linear hypoechoic split (star) extending from the lateral epicondyle (LE) through the substance of the common extensor tendon origin. The torn deep fibers (arrowheads) are retracted just distal to the hypoechoic area. Note the integrity of the underlying lateral ulnar collateral ligament (asterisks). RH, radial head.

Fig. 42a–c. Complete rupture of the common extensor tendon. a Long-axis 12−5 MHz US image in a golfer player who complained of longstanding elbow pain with coronal b T1w SE and c fat-suppressed T2w SE MR imaging correlation shows a retracted common extensor tendon. Note the gap (arrowheads) related to the tear that separates the avulsed tendon edge (asterisk) from the lateral epicondyle (LE). RH, radial head.

Conservative treatment with rest, anti-inflammatory drugs, physiotherapy and local steroid injections gives satisfactory results in most cases of lateral epicondylitis. Surgical intervention with excision of the degenerated tissue, resection of the common extensor tendon and debridement of the extensor tendon origin with release of the annular ligament may be advocated in refractory cases. Confirmation of the disease and exclusion of other causes of lateral elbow pain which may mimic or accompany lateral epicondylitis, such as posterior interosseous nerve entrapment or lateral collateral ligament injuries, should, however, be ascertained with imaging modalities, and possibly with US, before submitting the patient to surgery.

 

33. LATERAL COLLATERAL LIGAMENT INJURY

In lateral epicondylitis, the lateral elbow ligamentous complex, and especially the lateral ulnar collateral ligament, should be routinely assessed because this ligament is commonly injured in association with tears of the common extensor tendon as a result of the same forces or overuse mechanisms on adjacent structures (Bredella et al. 1999). An unsuspected tear of this ligament may be the cause of conservative therapy failure in patient with lateral epicondylitis. In addition, when the torn lateral ulnar collateral ligament is not recognized preoperatively, the operative release of the common extensor tendon may be responsible for worsening of symptoms and onset of posterolateral rotatory instability of the elbow.

When the more superficial extensor carpi radialis brevis is torn, the deep lateral ulnar collateral ligament becomes more clearly distinguishable with US as a cord-like fibrillary structure located over the joint space. An isolated ligament tear appears as discontinuity of the deepest fibers of the extensor tendon origin, whereas tears involving both the ligament and the common extensor tendon cause a full-thickness interruption of fibers over the lateral aspect of the radiocapitellar joint and soft tissue hematoma around the proximal margin of the capitellum (Connell et al. 2001). Dynamic scanning during careful varus stressing can disclose lateral ulnar collateral ligament injury by depicting widening of the lateral elbow joint space compared with the opposite normal elbow (Fig. 43).

Fig. 43a–c. Complete tear of the common extensor tendon and the lateral ulnar collateral ligament. a, b Longitudinal 12−5 MHz US images obtained over the common extensor tendon origin a in neutral position and b with varus stressing. In a, US identifies a large horizontal hypoechoic cleft through the full thickness of the common extensor tendon origin (arrows) and the lateral ulnar collateral ligament (asterisks). In b, varus stress on the elbow shows widening of the radio-capitellar joint space (dashed lines). RH, radial head; LE, lateral epicondyle. c Correlative STIR MR image confirms the complete rupture of both structures (arrowheads).

In “pulled elbow”, a common injury among children due to slipping of the annular ligament over the radial head following forceful pronation, US is able to depict an increased distance between the radial head and the humeral capitellum probably due to the impingement of the annular ligament (Kosuwon et al. 1993).

 

34. SUPINATOR SYNDROME (POSTERIOR INTEROSSEOUS NEUROPATHY)

Supinator syndrome, also referred to as “posterior interosseous syndrome” or “radial tunnel syndrome”, is a rare compression neuropathy of the upper limb affecting the posterior interosseous nerve just near or behind the supinator muscle (Spinner 1968). This nerve is vulnerable to injury at the proximal edge of the superficial belly of the supinator muscle that forms a free, strong, fibrous arch, the “arcade of Frohse”. At this site, the posterior interosseous nerve may be tethered and entrapped by fibrous bands, fan-shaped recurrent radial vessels or by tightness of the passage within the superficial and deep layers of the supinator. In addition, it may be compressed by a variety of soft-tissue masses, such as paraosteal lipomas and deep ganglia. Radial head and neck fractures, including Monteggia fracture-dislocations, may also displace and encase the posterior interosseous nerve by callus as it passes through the supinator tunnel. Clinically, the posterior interosseous neuropathy produces a clinical picture distinct from a lesion of the radial nerve in the arm. In fact, the patient has a “finger drop” rather than the characteristic “wrist drop” of a radial neuropathy, because muscle weakness spares the extensor carpi radialis (Fig. 44). Extension of the fingers at the metacarpophalangeal joints is impaired and there is deficit of abduction and extension of the thumb. In addition, posterior interosseous neuropathy may cause burning pain and tenderness over the lateral elbow, possibly mimicking a “resistant lateral epicondylitis”.

Fig. 44a–d. Posterior interosseous nerve syndrome in a young woman who presented with a intense weakness in extending the right fingers, especially involving thumb movements, and b a longitudinal skin depression (arrow) over the dorsum of the forearm following a contusion to the lateral elbow. c Transverse 12−5 MHz US image at the middle dorsal forearm reveals loss in bulk and a hyperechoic appearance of the extensor pollicis longus (epl) and extensor pollicis brevis (epb) muscles relative to fatty atrophy. Surgery confirmed the traumatic injury of the posterior interosseous nerve. d Normal contralateral side. U, ulna; R, radius.

High-resolution US is able to identify the impingement of the posterior interosseous nerve in the supinator area. The compressed nerve typically appears swollen and hypoechoic proximal to or inside the supinator muscle (Bodner et al. 2002). In post-traumatic settings, the nerve may appear displaced by a malaligned radial head and may exhibit alternate thickened and thinned segments between the superficial and deep bellies of the supinator muscle as a possible result of stretching injury (Fig. 45). In addition, the nerve may be seen encased by hypoechoic scar tissue following a radial fracture (Fig. 46).

Fig. 45a–e. Posterior interosseous nerve syndrome in a patient with malaligned Monteggia fracture-dislocation (type IV). a Extended field-of-view 12−5 MHz US image reconstructed according to the longitudinal axis of the supinator tunnel demonstrates the posterior interosseous nerve (arrowheads) which alternates thickened and thinned portions as it traverses the supinator muscle (s). b–d Serial T2*GRE MR images reveal slight hyperintensity in the supinator muscle (s) due to denervation edema. The nerve (arrows) appears markedly hyperintense. R, radius. e Radiograph shows the malalignment of the radius, which appears subluxated anterolaterally.

Fig. 46a,b. Posterior interosseous nerve syndrome. a Transverse 12−5 MHz US image obtained over the supinator area in patient with a previous radial head fracture and radial nerve deficit demonstrates the posterior interosseous nerve (arrowheads) entrapped within a hypoechoic scar (arrows) in the area of the supinator muscle (s). b Gross operative view shows the main trunk of the radial nerve (asterisks) as it splits into the superficial cutaneous sensory branch (arrowheads) and the deep posterior interosseous nerve (narrow arrows). This latter nerve is irregularly swollen as it passes over the bone (large arrows) as a result of the scar encasement visible in a.

Decompressive surgery of the posterior interosseous nerve is indicated if there is continuous worsening or no recovery of function with a few months.

 

35. POSTERIOR ELBOW PATHOLOGY: DISTAL TRICEPS TENDON TEAR

Distal triceps tendon tear is an uncommon condition that mostly occurs at or close to the olecranon process of the ulna, often associated with a fleck of bone attached to the retracted tendon as a result of avulsion fracture (Fig. 47). The mechanism involves either forced flexion of the elbow against a contracting triceps, as occurs during a fall on an outstretched arm, or relates to a direct blow onto the olecranon process. Local steroid injection into the olecranon bursa, anabolic steroid abuse and pre-existing tendinosis may also have a role in the tendon rupture. As a rule, complete tears occur more frequently than partial tears, whereas disruption of either the muscle bellies or the myotendinous junction is rare. Complete rupture of the distal triceps tendon presents clinically with complete inability to extend the elbow, given the absence of other muscles that can assist in this movement. In the acute phase, however, the clinical diagnosis may be hampered by local soft-tissue swelling, inflammatory edema and pain that limit the physical examination. In such cases, US may be useful both to confirm the tendon injury and to differentiate between complete tears that require immediate surgery to avoid retraction of the tendon and partial tears that may be treated conservatively. In acute complete ruptures, US demonstrates the distal triceps tendon as wavy, retracted and surrounded by fluid (Fig. 48) (Kaempffe and Lerner 1996). US examination is also reliable to delineate the degree of tendon retraction and can help in the diagnosis of atypical ruptures, such as in cases of tears occurring at the myotendinous junction (Fig. 49). Due to the close anatomic relation of the distal triceps tendon with the medial epicondyle and the cubital tunnel, an acute ulnar nerve compression syndrome may occur secondary to a distal triceps tendon tear (Duchow et al. 2000). Degenerative tendinosis can be appreciated as a thickened hypoechoic tendon.

Olecranon bursitis, the most common superficial bursitis in the body, appears clinically as a lump overlying the olecranon process due to fluid distension or hypertrophy of the synovial membrane. The most common cause of olecranon bursitis is repetitive local contusion (student’s elbow, miner’s elbow) that leads to a painless local swelling covered by normal skin. Calcific enthesopathy of the distal triceps tendon is a predisposing factor. However, bursal distension can be appreciated in a variety of systemic disorders, such as rheumatoid arthritis, gout, hydroxyapatite and calcium pyrophosphate deposition diseases, as well as in septic conditions (e.g. Staphylococcus, tuberculosis); also patients under chronic hemodialysis treatment may occasionally have olecranon bursitis. When bursitis is secondary to infection or gout, bursal swelling is typically painful and associated with skin warmth and erythema due to local inflammatory changes. Because systemic findings are often absent in septic bursitis, the likelihood of an infected bursa must always be kept in mind. Similarly, when the patient has a history of tuberculous disease, a specific etiology of bursitis should first be suspected.

US demonstrates olecranon bursitis as a localized fluid collection and/or synovial wall hypertrophy within the subcutaneous tissue immediately posterior to the olecranon (Fig. 50). Soft-tissue hyperemia is often recognized with color and power Doppler imaging as an accompanying finding (Lin et al. 2000). The hypervascular pattern typically distributes in a rim-like peribursal pattern. In crystal deposition diseases, the US appearance of bursal fluid is more likely hyperechoic and associated with thickened and echogenic bursal walls (Fig. 51). In hemorrhagic and septic bursitis, the fluid may result in a complex appearance: edema of surrounding soft tissues and cellulitis are frequently associated (Fig. 52). However, these characteristics are too subtle to allow a definitive diagnosis based on US findings alone, and needle aspiration of fluid, possibly obtained under US guidance, is usually required for analysis and culture. In extreme cases, chronic synovial proliferation and fibrosis may make the bursa indistinguishable from a solid tumor. Calcified bursitis may occur in patients with chronic renal failure (Fig. 53). In rheumatoid arthritis, the bursal fluid may occasionally be seen dissecting the superficial soft tissues of the forearm following bursal rupture. In such patients, subcutaneous nodules can be seen in the olecranon region and along the proximal ulna. These nodules should be considered in the differential diagnosis as they can mimic olecranon bursitis or a solid neoplasm Distal to the olecranon bursa, an additional small subolecranon bursa can exist at the posterior aspect of the proximal ulnar shaft. In rare instances, this bursa can be involved by the same processes affecting the larger olecranon one (Fig. 54).

Fig. 50a–c. Chronic traumatic olecranon bursitis in a manual laborer who had recently injured several times his posterior right elbow. a Midsagittal and b transverse 12−5 MHz US images over the olecranon process (O) show a markedly distended olecranon bursa (arrowheads) containing thick septa (curved arrows) and anechoic effusion (asterisks). Straight arrows, distal triceps tendon. c Photograph showing the bursal lump (arrows) on the posterior elbow.

Fig. 51a–c. Hydroxyapatite olecranon bursitis. a Transverse and b,c longitudinal 12−5 MHz US images of a painful soft-tissue mass over the olecranon (O) show the olecranon bursa filled with homogeneous highly echogenic fluid (asterisks) that could be seen fluctuating during probe compression. The bursa exhibits thickened walls (arrowheads) and septa (arrows). In this case, needle aspiration of the bursal fluid revealed calcium milk solution.

Fig. 52a,b. Tuberculous olecranon bursitis. a Longitudinal gray-scale and b color Doppler 12−5 MHz US images in a patient with painful soft-tissue swelling over the posterior elbow. The olecranon bursa (arrowheads) shows irregular wall thickening and ill-defined margins due to coexisting peribursal cellulitis. Only a small amount of intrabursal fluid is seen (asterisks). dt, distal triceps tendon; O, olecranon.

Fig. 53a,b. Calcific olecranon bursitis in a patient with renal osteodystrophy. a Posterior midsagittal 12−5 MHz US image with b lateral radiographic correlation demonstrates a large calcification (asterisks) that lies superficial to the insertion of the distal triceps tendon (arrowheads) reflecting an extensively calcified bursa. Note the relation of the mass with the posterior olecranon fossa (star) and the humeral shaft (H).

Fig. 54a,b. Subolecranon bursitis nodule in a patient with severe rheumatoid arthritis. a Transverse 12−5 MHz US image reveals a painless heterogeneous soft-tissue mass (arrows) with mixed echotexture located in the subcutaneous tissue over the proximal posterior ulna, compatible with subolecranon bursitis. b Photograph of the same case shown in a.

37. CUBITAL TUNNEL SYNDROME

Ulnar nerve compression inside the cubital tunnel, the second most common entrapment syndrome of the upper limb after carpal tunnel syndrome, may occur either at the condylar groove or at the edge of the arcuate ligament (proper cubital tunnel). There are several causes of ulnar nerve damage, including direct extrinsic compression of the nerve against a shallow condylar groove, bone abnormalities (cubitus valgus, deformities from previous elbow fractures, osteoarthritis with medial osteophytes and loose bodies, heterotopic ossification) and a variety of space-occupying soft-tissue lesions, including thickening of the capsule and the medial collateral ligament, ganglia and accessory muscles (anconeus epitrochlearis muscle) (Stewart 1993). Clinically, the entrapment of the ulnar nerve at the elbow presents insidiously with medial elbow pain and a spectrum of complaints ranging from sensory symptoms in the ring and little fingers to weakness of the ulnar innervated hand muscles. Wasting of hand muscles is best appreciated at the first interosseous space and hypothenar eminence and causes a typical semiflexion deformity of the ring and little fingers that is commonly referred to as “claw hand” (Fig. 55). In addition, the little finger may stay slightly abducted (Wartenberg sign).

Fig. 55a–d. Claw-like deformity in the right hand of a young patient with severe ulnar neuropathy at the cubital tunnel level. a Photograph of the dorsal aspect of the hand reveals loss in bulk of the dorsal interosseous muscles (arrows) that lie in the intermetacarpal spaces. The atrophy of the ulnar-innervated hand muscles is more obvious at the first intermetacarpal space (asterisk). b Photograph of the palmar aspect of the hand shows the fourth and fifth fingers extended at the metacarpophalangeal joint and flexed at the interphalangeal joints. c Transverse 12−5 MHz US image at the dorsal aspect of the hand demonstrates a hyperechoic appearance of the dorsal interosseous muscles (asterisks) related to neurogenic fatty atrophy. d Contralateral healthy side. II–III–IV, metacarpals.

The diagnosis is essentially based on electrophysiologic studies. US typically demonstrates an abrupt narrowing and displacement of the nerve within the tunnel, possibly in association with a thickened retinaculum or a space-occupying lesion (Fig. 56) (Puig et al. 1999; Martinoli et al. 2000; Okamoto et al. 2000). Proximal to it, the compressed nerve appears swollen with loss of the fascicular pattern and, in some cases, hypervascularity at color Doppler imaging. As assessed by quantitative analysis with US, the nerve cross-sectional area at the epicondyle is significantly larger in patients with cubital tunnel syndrome than in healthy subjects or in the opposite normal elbow (Okamoto et al. 2000; Chiou et al. 1998). An ulnar nerve area ≥7.5 mm2 at the level of the epicondyle has been indicated as the threshold value for cubital tunnel syndrome (Chiou et al. 1998). These data are somewhat contradictory with a more recent paper which indicates 7.9mm2 as the mean cross-sectional area for the normal ulnar nerve at the elbow (Jacob et al. 2004). Besides assessing the ulnar nerve, a wide spectrum of extrinsic causes for nerve entrapment may be recognized with US as well, including congenital anomalies such as an accessory anconeus epitrochlearis muscle (Fig. 57), and acquired disease which in turn leads to an increased content–i.e., lipoma (Fig. 58)–or a decreased size–i.e. fracture residuals (Fig. 59)–of the tunnel.

Fig. 56a–e. Cubital tunnel syndrome. a Long-axis 12−5 MHz US image of the cubital tunnel in a patient with cubitus valgus demonstrates the ulnar nerve (arrowheads), which appears increasingly swollen and hypoechoic with absent fascicular pattern (asterisks) as it progresses towards the compression point (curved arrow). Observe the elevated floor of the tunnel relative to thickening of the medial capsule and medial ligamentous complex (arrows). b–d Transverse 12−5 MHz US images show b a normal-appearing ulnar nerve (arrowheads) at the distal arm, c a swollen and hypoechoic nerve (asterisks), just proximal to the tunnel, and d an abrupt narrowing in the cross-sectional area of the ulnar nerve (white arrow) beneath the Osborne retinaculum and superficial to the thickened floor (void arrows) of the tunnel. ME, medial epicondyle; O, olecranon. e Gross operative view of the same case.

Fig. 57a–d. Cubital tunnel syndrome in a patient with anconeus epitrochlearis muscle. a Short-axis and b long-axis 12−5 MHz US images of the cubital tunnel reveal the anconeus epitrochlearis muscle (straight arrows) that lies between the medial epicondyle (ME) and the olecranon (O) in close relation with a swollen ulnar nerve (curved arrow). Correlative transverse c T1w SE and d fat-suppressed T2w SE MR images demonstrate the aberrant muscle (straight arrows) within the cubital tunnel. In d, the ulnar nerve (curved arrow) appears markedly hyperintense as a result of compression neuropathy. ME, medial epicondyle; O, olecranon.

Fig. 58a–e. Cubital tunnel syndrome in a patient presenting with a superficial soft-tissue mass on the posteromedial elbow. a Reconstructed longitudinal and b transverse 12−5 MHz US images obtained just proximal to the cubital tunnel demonstrate the ulnar nerve (curved arrow) that shows a bowing course over an oval solid hyperechoic lesion (arrowheads) with well-defined margins, consistent with a lipoma. Note the close relationship of the mass with the nerve. c Transverse 12−5 MHz US image obtained at the cubital tunnel level shows the lipoma (arrowheads) that infolds within the tunnel leading to compression of the ulnar nerve (curved arrow). ME, medial epicondyle; O, olecranon. d,e Correlative transverse T1w SE MR images obtained d at the distal arm and e at the cubital tunnel levels confirm the lipomatous nature of the space-occupying lesion (L). Curved arrow, ulnar nerve; ME, medial epicondyle; O, olecranon.

Fig. 59a–g. Cubital tunnel syndrome in a patient with recent onset of symptoms related to right ulnar neuropathy who had undergone a fracture of the medial epicondyle when he was an adolescent. a,b Longitudinal 12−5 MHz US images of the cubital tunnel obtained a during flexion and b full extension of the elbow. a With elbow flexion, an anomalous bone (asterisk) can be appreciated as a hyperechoic image bulging within the tunnel and displacing a swollen and hypoechoic ulnar nerve (arrows). b With elbow extension, the nerve (arrows) forms an abnormal loop cranial to the anomalous bone (asterisk) and appears flattened and compressed against its superficial aspect. c,d Transverse 12−5 MHz US images with e,f T1w SE MR imaging correlation obtained c, e at the distal arm and d, f at the level of the medial epicondyle with extended elbow reveal a normal-appearing nerve (straight arrow) cranial to the compression point and a flattened hypoechoic nerve (curved arrows) over the anomalous bone (asterisk). g Plain radiograph shows an old fracture of the medial epicondyle (asterisk) with the fragment displaced toward the joint line.

Surgical decompression of the ulnar nerve at the elbow may include slitting the Osborne fascia and the aponeurosis of the flexor carpi ulnaris leaving the nerve inside the cubital tunnel. Alternatively, the nerve may be transposed out of the condylar groove and the cubital tunnel, anterior to the medial epicondyle and superficial to the flexor muscles (Fig. 60). This surgical option is preferred in cases of ulnar neuropathies caused by bone and joint disease. After surgical transposition, persistent symptoms are usually related to an excessive angling of the ulnar nerve as it passes deep to the arcuate ligament or to incomplete stabilization of the nerve in its new position. US is able to identify scar tissue along the course of the nerve in patients with recurrent symptoms or relapse of compressive causes (Fig. 61).

Fig. 60a–d. Postoperative ulnar nerve. a Transverse 12−5 MHz US image over the medial elbow with b T1w SE MR imaging correlation shows anterior transposition of the ulnar nerve (arrow) relative to the medial epicondyle (ME). The nerve is subcutaneous and lies over the flexor muscles (fm). Note the empty condylar groove (asterisk). c,d Gross operative views obtained c before and d after anterior transposition of the ulnar nerve (arrows) relative to the medial epicondyle (ME).

Fig. 61a–d. Postoperative patient with recurrence of symptoms after decompressive surgery of the ulnar nerve at the cubital tunnel for a ganglion cyst. a,b Transverse 12−5 MHz US images obtained a at the cubital tunnel level and b at the proximal forearm with c,d T1w SE MR imaging correlation show a relapsed cyst (asterisks) which constricts the transposed ulnar nerve (arrow). The patient underwent surgery again and the postoperative course was finally uneventful. ME, medial epicondyle.

 

38. ULNAR NERVE INSTABILITY

In the congenital partial or complete absence of the cubital tunnel retinaculum, the ulnar nerve may subluxate over the tip of the epicondyle or dislocate anterior to it with a transient snapping sensation during flexion of the elbow, to return inside the tunnel when the joint is extended. Ulnar nerve instability at the cubital tunnel can be considered a normal variant, being reported in between 16% and 47% of asymptomatic healthy people, subluxation being the most common form (Childress 1975; Okamoto et al. 2000). The condition is bilateral in almost three quarters of cases and asymptomatic at both clinical examination and nerve conduction studies. Patients may occasionally complain of only mild discomfort with tingling and paresthesias when the flexed elbow hits a firm surface such as the edge of a desk. In rare instances, however, chronic microtrauma of the nerve over the medial epicondyle due to repetitive dislocation can cause friction neuritis with symptoms and signs of ulnar nerve impairment. In such cases, nerve instability should be treated with surgical transposition of the nerve in order to avoid more serious damage.

the instability of the ulnar nerve during progressive elbow flexion, to recognize nerve abnormalities related to friction neuritis as well as to establish whether ulnar neuropathy is produced by compressive causes or instability because of the overlap in clinical findings (Jacobson and van Holsbeeck 1998; Jacobson et al. 2001). In subluxation, the nerve is seen moving over the apex of the medial epicondyle during full active elbow flexion but no further. In dislocation, the nerve may be seen snapping completely out of the cubital tunnel and migrating over the common flexor tendon origin (Fig. 62). During dynamic scanning, the snapping sensation may be felt by the examiner through the transducer. Careful scanning technique is needed to avoid excessive pressure with the probe over the epicondyle, which can prevent the nerve from dislocating. In cases of symptomatic friction neuritis, the ulnar nerve appears markedly swollen and hypoechoic with loss of fascicular echotexture, probably reflecting localized intraneural edema and fibrotic changes (Fig. 63). However, these abnormalities may occasionally be encountered in healthy subjects too, without any implication of disease.

Fig. 62a–f. Dynamic study of the cubital tunnel in ulnar nerve dislocation. a–c Schematic drawings and d–f respective series of transverse 12−5 MHz US images obtained a,d with extended elbow and during progressive degrees of elbow flexion (b,e and c,f). When the elbow is extended, the ulnar nerve (arrow) is contained within the tunnel. Elbow flexion gradually pushes the nerve over the medial epicondyle (ME) until it snaps completely out of the cubital tunnel to lie superficial to the common flexor tendon origin (ft). O, olecranon.

Fig. 63a–d. Dynamic study of the cubital tunnel in a patient with recurrent ulnar nerve dislocation and clinical symptoms of ulnar neuropathy. a–d Series of transverse 13−8 MHz US images acquired a with extended elbow and b–d throughout elbow flexion show a markedly swollen and hypoechoic nerve (arrow) that flattens and dislocates over the medial epicondyle (ME) during elbow flexion. In the symptomatic patient, this finding is suggestive of ulnar neuropathy based on a friction mechanism.

 

39. SNAPPING TRICEPS SYNDROME

With elbow flexion, anterior dislocation of the medial head of triceps muscle relative to the medial epicondyle can occur in combination with dislocation of the ulnar nerve. In this condition, referred to as “snapping triceps syndrome”, the dislocation of the muscle leads to concurrent dislocation of the adjacent ulnar nerve as these structures are contiguous (Fig. 64). Two palpable “snaps” are typically appreciated over the medial elbow, the first one reflecting dislocation of the ulnar nerve and the second, dislocation of the medial head of triceps muscle. The clinical presentation of this syndrome is variable and may include medial elbow pain, snapping sensation, ulnar neuropathy or a combination of these symptoms (Spinner and Goldner 1998). Somewhat similar to the isolated dislocation of the ulnar nerve, the snapping triceps may however remain asymptomatic and probably unrecognized in most cases. Although the cause of snapping triceps is still unknown, some possible congenital and acquired conditions have been advocated to explain this syndrome, such as a hypertrophied triceps muscle, an accessory triceps tendon and abnormal medial head of the triceps muscle, as well as post-traumatic osseous abnormalities. Differentiation between snapping triceps syndrome and isolated ulnar nerve dislocation as causes for medial elbow snapping is important in symptomatic subjects as the surgical treatments differ. For this purpose, dynamic US scanning is accurate in allowing direct visualization of transient dislocation of both structures during active flexion and extension of the elbow (Fig. 65) (Jacobson et al. 2001).

Fig. 64a,b. Snapping triceps syndrome. Schematic drawings of the posterior aspect of the elbow in a extension and b 90° flexion demonstrate the ulnar nerve (arrows) as it passes through the cubital tunnel and a prominent medial head (mh) of the triceps muscle ™. Note the absence of the Osborne retinaculum when compared with Fig. 7c. With elbow flexion, the medial edge of the triceps (arrowheads) and the ulnar nerve move anterior to the tip of the epicondyle. T, distal triceps tendon; fcu, flexor carpi ulnaris.

Fig. 65a–f. Dynamic study of the cubital tunnel in snapping triceps syndrome. a–c Series of transverse 12−5 MHz US images with d–f correlative schematic drawings obtained (a,d) with the elbow extended and (b,e and c,f) throughout elbow flexion. With extended elbow, the ulnar nerve (arrow) and the medial head of the triceps muscle (mht) are contained within the cubital tunnel. During progressive degrees of elbow flexion, the triceps pushes the ulnar nerve over the tip (asterisk) of the medial epicondyle (ME) until it snaps out of the tunnel. Then the triceps snaps out too. ft, common flexor tendon origin; O, olecranon.

Fig. 66a,b. Elbow joint effusion. a Schematic drawing of a midsagittal view through an extended elbow demonstrates fluid in the anterior (1) and posterior (2) portions of the joint. Deep to the brachialis (br) and triceps (tr) muscles, the anterior (asterisk) and posterior (star) fat pads are elevated by intra-articular fluid. b Lateral radiograph in a patient with abundant joint effusion reveals elevation of the anterior (asterisk) and posterior (star) fat pads from the surface of the humerus, leading to a “positive fat pad sign”, and increased density (arrows) at the level of the anterior and posterior recesses, reflecting synovitis.

Fig. 67a–d. Synovitis of the elbow joint: anterior joint recess. Longitudinal 12−5 MHz US images over the anterior coronoid recess a in normal state and b,c in two cases of joint synovitis presenting with b mild and c marked distention of the anterior synovial spaces by fluid and hypertrophied synovium. In normal conditions, a thin layer of fluid (arrow) may be encountered in the anterior coronoid recess, deep to the anterior fat pad (asterisks). This is a normal finding. When joint fluid expands into the anterior joint spaces, the anterior fat pad (asterisks) becomes elevated to assume a typical crescentic or “sail-like” appearance. In markedly distended joints, the anterior bulging of the joint cavity is more conspicuous and may extend down to the joint level. HC, humeral capitellum; RH, radial head. d Corresponding T2w SE MR image of the case illustrated in b.

Fig. 68a,b. Synovitis of the elbow joint: posterior joint recess. a Longitudinal 12−5 MHz US image over the posterior olecranon recess with b T2w SE MR imaging correlation in a patient with rheumatoid arthritis presenting with painful elbow and loss of extension. US shows a bulk of hypoechoic synovial pannus filling the recess (arrows). Deep to the triceps muscle ™, the posterior fat pad (asterisks) is elevated by the pannus. Note the prominence of the tip of the olecranon (O) and the humeral trochlea (TR) bulging within the recess.

Fig. 69a,b. Synovitis of the elbow joint: annular (periradial) recess. a Longitudinal 12−5 MHz US image over the anterior aspect of the radio-capitellar joint with b transverse T2w SE MR imaging correlation in a patient with rheumatoid arthritis reveals filling of the annular recess (white arrows) by hypoechoic synovial fluid (asterisks). The annular recess lies around the radial metaphysis and communicates with the joint cavity through a thin passageway (open arrow) deep to the annular ligament. Note the rounded profile of the humeral capitellum (HC) and the squared profile of the radial head (RH).

Fig. 70a,b. Rheumatoid arthritis. a,b Longitudinal 12−5 MHz US images over the anterior aspect of the radio-capitellar joint a in a normal subject and b in a patient with severe longstanding rheumatoid arthritis. In a, note the articular cartilage (rhombi) and the regular profile of the subchondral bone of the humeral capitellum (HC) and radial head (RH). In b, there is complete loss of the cartilage layer and the surface of bones appears diffusely irregular, reflecting erosions. Synovial pannus (asterisks) can be seen within the joint space and distending the annular recess.

Fig. 71a,b. Synovitis of the elbow joint: pitfall. a,b Transverse 12−5 MHz US images over the posterior olecranon recess a in a normal subject and b in a patient with rheumatoid arthritis and an olecranon recess (arrows) appears markedly distended by fluid. In a, the normal hypoechoic fat contained. In b the olecranon fossa, between the lateral (LE) and medial (ME) epicondyles, should not be confused with the synovitis process shown in b. In doubtful cases, careful dynamic examination with elbow flexion and extension movements may be helpful for the diagnosis. Note the erosion (arrowhead) on the posteromedial aspect of the lateral epicondyle. T, distal triceps tendon.

 

41. OSTEOARTHRITIS AND OSTEOCHONDRAL DAMAGE

Osteoarthritis of the elbow is basically post-traumatic in nature. It is typically seen in male patients with a history of manual labor (vibration tools), sport-related overuse or fracture malalignment. The dominant extremity is more frequently involved. Given the physiologic attitude of the elbow joint to valgus posture, the external radio-capitellar compartment is most commonly affected. Clinical findings are related to the degenerative process itself (stiffness and loss of motion, usually extension, related to spurring, swelling due to synovitis, local pain), compression of the ulnar nerve inside the cubital tunnel (local pain and tenderness, tingling of the ring and little fingers and, in chronic compression, wasting of the ulnar-innervated intrinsic hand muscles) as well as intra-articular loose bodies (intermittent joint locking and effusion).

Intra-articular loose bodies commonly migrate into the dependent portions of the joint and in the humeral depressions above the joint line, particularly the olecranon fossa, resulting in mechanical symptoms such as intermittent locking and loss of extension. In patients without a synovial effusion, the intra-articular location of a fragment can be established by demonstrating it between the articular cartilage and the anterior and posterior intracapsular fat pads. The small radial annular recess is rarely involved by loose bodies. Dynamic examination performed during flexion and extension of the elbow may be helpful in mobilizing the joint fluid and small loose bodies as well as for differentiating them from local heterotopic ossification and spurring (Fig. 72) (Bianchi and Martinoli 2000). In primary synovial chondromatosis, multiple chondral or osteochondral loose bodies typically display nearly equal size and can vary in number from a few to hundreds (Fig. 73). Advanced disease may result in disintegration of the articular surfaces. As already described in other anatomic sites, in the initial phase of disease the treatment includes removal of the loose bodies and synovectomy to prevent recurrence. Similar to a loose body, the os supratrochleare dorsale is an intra-articular ossicle located in the olecranon fossa that may be associated with pain and progressive loss of elbow extension with locking symptoms (Obermann and Loose 1983). This accessory ossicle is generally believed to be the result of a congenital anomaly rather than the consequence of previous trauma and may cause deepening and remodeling of the olecranon fossa as it increases in size. Differentiation between an os supratrochleare dorsale and a loose body is clinically not relevant because both fragments are treated by surgical removal.

Fig. 72a,b. Anterior spur mimicking a loose body. a Longitudinal 12−5 MHz US image with b lateral radiographic correlation demonstrates a prominent spur (arrow) over the coronoid fossa of the humerus. The spur is intracapsular in location and appears bordered by fluid (asterisk). During elbow movements, it remained still. Note the thin hypoechoic layer of articular cartilage (rhombi) that covers the humeral capitellum (HC). Br, brachialis muscle.

Fig. 73a−d. Primary synovial chondromatosis. a Longitudinal and b transverse 12−5 MHz US images over the anterior coronoid recess demonstrate multiple intra-articular loose bodies as hyperechoic fragments (arrowheads) of similar size with posterior acoustic shadowing lying inside the recess. Note the elevation of the anterior fat pad (asterisks) over the fragments and the thin hypoechoic layer of articular cartilage (rhombi) that overlies the humeral capitellum (HC). br, brachialis muscle. c Lateral radiograph and d transverse T1w GRE MR imaging of the same case showing the loose bodies (arrowheads).

In adolescents, US is also able to recognize deformities of the humeral capitellum in osteochondritis dissecans (Takahara et al. 1998, 2000a,b). This condition typically occurs in 13- to 16-year-olds, mainly as a result of chronic lateral impaction or repetitive valgus stress. The anterolateral articular surface of the capitellum is typically involved with localized subchondral bone flattening and subsequent fragmentation and loosening of bone fragments (Takahara et al. 2000a). US examination is best performed with an anterior approach while keeping the elbow extended (to view the proximal and middle parts of the anterior capitellum) and with a posterior approach while keeping the elbow flexed (to view the middle and distal parts of the anterior capitellum) (Takahara et al. 2000b). Detached bony fragments are depicted as echogenic foci in the osteochondral defect. US has also proved to be accurate in determining whether the lesion is stable or unstable (loosened fragments), with good (89%) agreement with surgical findings and MR imaging (Takahara et al. 2000b). In these patients, delay in the appropriate management can be avoided by an early US examination. Similar abnormalities may be encountered in Panner disease, a condition related to avascular necrosis of the ossification center of the capitellum that occurs in 5–11 years old children secondary to traumatic injures. Somewhat comparable to Legg-Calvé- Perthes disease in the hip, this latter condition has a benign outcome with no residual deformity of the capitellum and absence of loose body formation (Vanderschueren et al. 1998).

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42. OCCULT FRACTURES

Due to the anatomic complexity of the elbow joint, some undisplaced fractures, such as those involving the radial head and neck and the coronoid process, may remain occult radiographically, even when additional projections are performed. When cast immobilization is not employed as a prophylactic measure to avoid overtreatment, persistent pain and disability may lead the referring physician to acquire a US examination to rule out any possible soft-tissue abnormality about the elbow. With careful scanning technique, high-resolution US is able to identify acute elbow fractures based on detection of a step-off deformity or focal discontinuity of the hyperechoic cortical line (Fig. 74). In these cases, however, additional radiographic or MR imaging studies should always be obtained to confirm the US diagnosis. Dynamic scanning during careful passive-assisted pronation and supination of the forearm with the probe placed in the transverse plane over the radial head may be useful to exclude any fracture at this site. In doubtful cases, associated US signs, such as joint effusion, can be easily detected in intra-articular fractures and may suggest a more detailed analysis of the bone contour (Major and Crawford 2002). On the other hand, the absence of effusion in elbow injuries with negative plain radiographs may make further bone investigation with MR imaging unnecessary (Kessler et al. 2002). More than in adults, US seems to have a potential role for the evaluation of elbow fractures in children. In fact, there are difficulties in assessing bony abnormalities about the elbow in skeletally immature patients using plain radiographs because of the absence of the secondary centers of ossification (Fig. 75). When a radiographic sign of joint effusion is present but a fracture is not visualized, US may help in distinguishing the separation of the distal humeral epiphysis (Dias et al. 1988; Ziv et al. 1996) from elbow dislocation in neonates, as well as in detecting or excluding radial head (Lazar et al. 1998) and supracondylar fractures (Davidson et al. 1994; Brown and Eustace 1997).

Fig. 74a–d. Occult fracture of the right coronoid process in a woman following a ski accident. a The patient had a negative radiographic examination performed soon after the injury. b Two weeks later, she was submitted to US examination due to persistent elbow pain and loss of extension. US identified an interruption (curved arrow) of the hyperechoic cortical profile of the coronoid process (C), just cranial to the insertion of the brachialis (br). There was associated mild intra-articular effusion. HC, humeral capitellum. c Left healthy side for comparison. d Additional oblique view of the right elbow confirms the fracture.

Fig. 75a–c. Radial fracture in a 5-year-old child presenting with left lateral elbow pain and disability after a fall. a Longitudinal 12−5 MHz US image at the anterolateral elbow demonstrates increased distance between the humeral capitellum (HC) and the radial epiphysis related to an intervening hyperechoic joint effusion (asterisks). Note the hyperechoic dot (arrowheads) within the radial epiphysis representing the ossification center. At the radial metaphysis, US reveals a focal irregularity of the hyperechoic cortical line (arrow) suggesting a fracture. R, radius. b Contralateral healthy side for comparison. c Lateral radiograph of the left elbow confirms the diagnosis of radial fracture (arrow).

 

43. POSTERIOR DISLOCATION INJURY AND INSTABILITY

Elbow dislocation is most common in children less than 10 years old and accounts for 5−8% of all fractures and dislocations in adults, being second only to the shoulder. Usually, the ulna and radius dislocate posteriorly following a hyperextension mechanism, such as during a fall on the outstretched hand. The posterior translation can cause impaction fractures (i.e., coronoid process, humeral capitellum) and a variety of soft-tissue lesions, involving joint and ligaments, vessels and nerves. In such cases, US can occasionally be required to demonstrate soft-tissue complications, such as heterotopic ossification, contusion of the brachialis muscle and injuries to the brachial artery and the median and ulnar nerves (Figs. 76, 77). After a dislocation, instability of the elbow joint may result following progressive disruption of the lateral ulnar collateral ligament (posterolateral rotatory instability), tearing of the anterior and posterior joint capsule and then rupture of the medial collateral ligamentous complex (multidirectional instability).

Fig. 76a–d. Partial tear of the brachialis muscle as a consequence of posterior dislocation injury. a,b Longitudinal and c transverse 12−5 MHz US images of the anterior elbow obtained in the supracondylar area demonstrate a wide hypoechoic defect (large arrows) in the substance of the brachialis muscle (br) related to hematoma. The torn muscle tissue is surrounded by anechoic spaces. Note the relationship of the injured brachialis with the normal distal biceps muscle (arrowheads), brachial artery (a) and median nerve (curved arrow). d Contralateral healthy side. Corresponding transverse 12−5 MHz US image shown in c reveals an intact brachialis.

Fig. 77a–f. Traumatic injury of the median nerve and brachial artery following posterior dislocation of the elbow. The patient received primary surgical repair. a Long-axis 12−5 MHz US image over the trochlea (H) demonstrates fusiform swelling with an indistinct outer surface and hypoechoic changes (asterisks) of the median nerve (arrows) relative to a post-traumatic fusiform neuroma. b–d Short-axis 12−5 MHz US images obtained at the level (vertical white bar) indicated in a reveal nerve enlargement and loss of the internal fascicular pattern (asterisk) at the site of injury (b) compared with more proximal (a) and distal (c) levels. Note the close relation of the nerve with the adjacent brachial artery (a). e,f Long-axis gray-scale e and color Doppler f 12−5 MHz US images of the injured brachial artery show the site of vascular reconstruction (arrowheads).

 

44. ELBOW MASSES

Both solid and cystic masses can be encountered in the soft tissues of the elbow as incidental findings. Most are benign and have an indolent behavior, such as lipomas, ganglia and neural tumors, and can be easily diagnosed with US based on previously described criteria (Figs. 78, 79). Only occasionally, elbow masses may cause pain and specific symptoms related to their specific anatomic relationship with elbow structures, including joint impairment and nerve compression. In such cases, surgical excision is always indicated to ensure recovery of function. Also, US can be useful to distinguish normal findings that can simulate disease. At the elbow, this most often occurs in young women who seek advice because of a painless lump located anterior to the medial epicondyle that is best appreciated with full joint extension. This pseudomass is due to the anterior prominence of the medial portion of the epicondyle that becomes evident in females with hyperlax joints when extending the elbow >180°. In these cases, US can readily exclude any local space-occupying mass.

Fig. 78a,b. Ganglion cyst of the elbow in a patient who complained of mild paresthesias radiating over the dorsal thumb. a Longitudinal and b transverse 12−5 MHz US images over the radial head (RH) reveal a small lobulated anechoic fluid-filled mass (straight arrows) consistent with a ganglion, adjacent to the radial nerve (curved arrow). The ganglion had a thin pedicle in connection with the radio-capitellar joint, confirming its articular extension.

Fig. 79a,b. Lipoma in a patient with painless soft-tissue swelling over the anterior elbow. a Transverse 10−5 MHz US image over the distal humerus with b T1w GRE MR imaging correlation demonstrates an oval hypoechoic soft-tissue mass (L) located superficial to the brachialis muscle (br) that displaces the brachial artery (a) and the distal biceps tendon (arrows). In this particular case, the echotexture of lipoma is quite similar to the underlying brachialis and should not be interpreted as a normal muscle. Asterisk, medial edge of the humeral trochlea.