Practical ultrasonographic technique to precisely identify and differentiate tendons and ligaments of the elbow at the level of the humeral epicondyles: anatomical study

Abstract

Objectives: To develop a practical step-by-step technique to precisely identify and differentiate tendons and ligaments attaching to the humeral epicondyles, to confirm through gross anatomical study the accurate structure identification provided by this technique and to determine the frequency at which each structure can be identified in healthy volunteers.

Materials and methods: First, ten fresh frozen cadavers (6 men, age at death = 58-92 years) were examined by two musculoskeletal radiologists and a step-by-step technique for the identification of tendons and ligaments at the level of humeral epicondyles was developed. Second, the accurate identification of structures was confirmed through gross anatomical study including anatomical sections on five specimens and layer-by-layer dissection technique on five others. Finally, 12 healthy volunteers (6 men, average age = 36, range = 28-52) were scanned by two radiologists following the same technique.

Results: An ultrasonographic technique based on the recognition of bony landmarks and the use of ultrasonographic signs to differentiate overlapping structures was developed and validated through gross anatomical study. In healthy volunteers, most tendons and ligaments were identified and well-defined in ≥ 80% of cases, except for the extensor carpi radialis brevis and extensor digiti minimi tendons on the lateral epicondyle (having common attachments with the extensor digitorum communis) and the palmaris longus tendon on the medial epicondyle (absent, or common attachment with the flexor carpi radialis).

Conclusion: A step-by-step approach to the ultrasonographic assessment of tendons and ligaments at the humeral epicondyles allowed accurate identification of and differentiation among these structures, in particular those relevant to pathological conditions.

Keywords: Anatomy; Elbow; Epicondylitis; Ligament; Tendon; Ultrasound.

Fig. 1

Anatomy of the medial (a) and lateral (b) epicondyles and the respective tendon and ligament attachment sites (c and d) shown on a CT of the elbow with surface rendering. a and b show the bony landmarks that are consistently visible at ultrasonography: the medial and lateral epicondyles (dotted circles), the supracondylar ridge (blue arrows), the epicondylar ridge (white arrows), the anterolateral flat area (red) and the semilunar area (yellow). The distribution of tendon and ligament attachments on the medial and lateral epicondyles is indicated on c and b. The ECRB and the EDC/EDm tendons have a conjoint tendon (dashed line in d). PT: pronator teres, FCR: flexor carpi radialis, FDS: flexor digitorum superficialis, PL: palmaris longus, FCU: flexor carpi ulnaris, MCL: medial collateral ligamentous complex, ECRL: extensor carpi radialis longus, ECRB: extensor carpi radialis brevis, EDC: extensor digitorum communis, EDm: extensor digiti minimi, Supin: supinator tendon, ECU: extensor carpi ulnaris, LCL: lateral collateral ligamentous complex

Fig. 2

Ultrasonographic assessment technique for the lateral epicondyle with position of the different ultrasonographic views on the lateral epicondyle shown on a CT with surface rendering (a), on photographs of a volunteer (b–e), with corresponding ultrasonographic images (f–i): View 1: supracondylar ridge (easily identified in the short-axis plane of the distal humerus): the muscular attachment of the ECRL onto the supracondylar ridge is identified. View 2: anterosuperior aspect of epicondyle (slightly moving the probe distally to the epicondyle from View 1, at its anterior aspect): the conjoint ECRB/EDC/EDm tendon is visible. View 3: intermediate view (between views 2 and 4): from superficial to deep, the EDC/EDm tendons, supinator tendon and LCL are visible. View 4: posterior aspect of epicondylar ridge: From surface to deep, the ECU tendon can be easily identified. ECRL: Extensor carpi radialis longus, ECRB: extensor carpi radialis brevis, EDC: extensor digitorum communis, EDm: extensor digiti minimi, Supin: supinator tendon, ECU: extensor carpi ulnaris, LCL: lateral collateral ligamentous complex, ScR : supracondylar ridge, Ec : epicondyle, EcR : epicondylar ridge

Fig. 3

Ultrasonographic assessment technique for the medial epicondyle with position of the different ultrasonographic views on the lateral epicondyle shown on a CT with surface rendering (a), on photographs of a volunteer (b–e), with corresponding ultrasonographic images (f–i): View 1: supracondylar ridge (easily identified in the short-axis plane of the distal humerus): the muscular attachment of the pronator teres onto the supracondylar ridge is identified. View 2: anterosuperior aspect of epicondyle (slightly moving the probe distally to the epicondyle from View 1, at its anterior aspect): from superficial to deep, three structures can be differentiated by the presence of echogenic lines/difference of echogenicity: the FCR tendon, the FDS tendon and the MCL. View 3: intermediate view (between views 2 and 4): from superficial to deep, three structures can be differentiated by the presence of echogenic lines/difference of echogenicity: the palmaris longus tendon (inconsistent; not visible here), the FDS tendon and the MCL. View 4: epicondylar ridge: from surface to deep, the FCU tendon and the MCL can be easily identified. FCR: flexor carpi radialis, FDS: flexor digitorum superficialis, PL: palmaris longus, MCL: medial collateral ligamentous complex, FCU: flexor carpi ulnaris, ScR : supracondylar ridge, Ec : epicondyle, EcR : epicondylar ridge

Fig. 4

Identification of a hyperechogenic line between the lateral collateral ligamentous complex (LCL) and the overlying extensor digitorum communis (EDC) tendon at ultrasonography (a) corresponding to a radiolucent line on radiograph (b), likely corresponding to a fat layer (arrowheads). The interface is also seen on the backlit gross anatomical slice (c)

Fig. 5

Progressive layer by layer dissection technique. A progressive layer by layer dissection technique is presented for the lateral (a) and medial (b) epicondyles. Each structure is identified at ultrasonography. The identified structure is then resected at dissection. The ultrasonography is repeated, with the confirmation of the correct identification of anatomical structures. In a, arrowheads point at the interface between the EDC and LCL. In b, arrows point at the interface between the FDS and the MCL. EDC: extensor digitorum communis, LCL: lateral collateral ligamentous complex, FDS: flexor digitorum superficialis, MCL: medial collateral ligamentous complex