W4 Sonosim: Wrist

Which of the following statements correctly characterizes Lister's tubercle?

B. It separates the second and third dorsal fibro-osseous compartment Correct. Lister's tubercle is an important anatomic landmark located along the distal dorsal aspect of the radius. The second fibro-osseous compartment is radial to Lister's tubercle, and the third compartment is ulnar. Lister's tubercle is a critical anatomic landmark that can be located with palpation. It is also an important sonographic landmark.

Carpal Tunnel Carpal tunnel borders: --Carpal bones --Flexor retinaculum Carpal tunnel contents: --Nine flexor tendons --Median nerve

Right Wrist (Axial Cross Section)

Guyon's Canal Guyon's canal borders: --Flexor retinaculum --Volar carpal ligament --Pisiform bone --Hook of hamate Guyon's canal contents: --Ulnar nerve --Ulnar artery --Ulnar vein

Right Wrist (Axial Cross Section)

Bones of the distal row: Trapezium Trapezoid Capitate Hamate

Right Wrist (Dorsal Aspect)

Carpal Bones Bones of the proximal row: Scaphoid Lunate Triquetrum Pisiform

Right Wrist (Volar Aspect)

This image has been taken in a transverse orientation, just distal to Lister's tubercle. Which of the following structures is identified by the indicator line?

Scapholunate ligament Correct. Distal to Lister's tubercle, the scapholunate ligament is encountered, which is seen best in a transverse orientation. This area is best visualized when the wrist is positioned in ulnar deviation. Similar to tendons, ligaments have a bright hyperechoic linear sonographic appearance. The scapholunate ligament can be seen in the accompanying image traversing between the scaphoid bone and lunate. The carpal tunnel is imaged from the volar wrist, while Lister's tubercle is imaged from the dorsal wrist.

The carpal tunnel is a space on the volar wrist bordered on its dorsal, radial, and ulnar sides by carpal bones, and bordered on its volar surface by the dense, fibrous flexor retinaculum, which is also called the transverse carpal ligament. Nine flexor tendons, the deep and superficial flexor tendons of the 2nd through 5th digits and flexor pollicis longus tendon, are accompanied by the median nerve within the carpal tunnel. The median nerve travels superficially within the carpal tunnel, just beneath the flexor retinaculum.

The carpal tunnel is a fixed, nondistensible space, which becomes smaller when carpal bones shift during wrist flexion and extension. The flexor retinaculum is a connective tissue ligamentous structure, attached to the pisiform and scaphoid proximally and to the hamate and trapezium distally. It forms the roof of the carpal tunnel. The ulnar nerve, artery, and veins pass through the wrist outside of the carpal tunnel, via Guyon's canal. The superficial and thin flexor carpi radialis and palmaris longus tendons are also located outside of the carpal tunnel.

Dorsal First Compartment Abductor pollicis Longus- volarly Extensor pollicis Brevis-dorsally

The dorsal wrist is often described as having six compartments, which can be visualized with ultrasound. Along the lateral aspect of the radial styloid we find the first compartment, which contains two tendons. These two tendons are the abductor pollicis longus, positioned volarly, and extensor pollicis brevis, positioned dorsally. The retinaculum, located superficial to both tendons, may occasionally have a septum which dives deep and splits the compartment in two. The tendinous slips of the abductor pollicis longus can be traced distally over the scaphoid.

Patient Positioning -Patient in a seated position, facing the examiner, with both wrists resting on lap, towel roll, or table -Wrist in neutral position -Focused exam targets a specific area -Complete examination starts dorsal and proceeds to volar side

Wrist sonography can be very focused, with the exam targeting a discrete symptomatic structure. Alternatively, in fields such as rheumatology, a more systematic sonographic screening examination is commonly performed. Ideally, the patient is in a seated position, facing the examiner, with both wrists resting on their lap, towel roll, or a table. A recumbent position is acceptable and may be better for some patients. The wrist is initially positioned in a neutral stance. The wrist is then mildly deviated in the ulnar or radial direction as needed to facilitate certain image windows.

Which of the following statements accurately describes muscles associated with the hand?

A Muscles are classified into groups, as either intrinsic or extrinsic. C. Volar tendons are frequently enclosed in a tendon sheath.

Which of the following statements correctly characterizes the carpal bones?

A They are arranged in two rows. B They consist of eight bones. C They include at least one sesamoid bone. D All of the above

Guyon's canal contains which of the following structures?

A. Ulnar nerve Correct. The triangular space located to the radial side of the pisiform bone is known as Guyon's canal, also known as the ulnar canal, where the ulnar nerve, artery, and veins travel. Guyon's canal is a depression between the pisiform bone and the hook of the hamate, which is converted into a several centimeter long fibro-osseous canal by the overlying volar carpal ligament. The pisiform serves as its ulnar border and the hook of the hamate as its radial border. The flexor retinaculum and volar carpal ligament form the floor and the roof of the canal, respectively. The ulnar nerve sits in an ulnar position with respect to the artery. Like the median nerve in the carpal tunnel, the ulnar nerve can become compressed within Guyon's canal. Close

Which of the following statements regarding the dorsal fourth compartment of the wrist is correct?

A.The dorsal fourth wrist compartment lies along the radial side of the radioulnar groove. Correct. Looking in a dorsal transverse plane over the mid-wrist, one sees the fourth compartment. It is located over the most ulnar aspect of the dorsal radius. It contains the extensor digitorum communis and extensor indicis proprius tendons. The fifth compartment, containing the extensor digiti minimi, is immediately adjacent to the fourth compartment, along its ulnar side. When one analyzes the dorsal radioulnar groove, the fourth compartment overlies the radial side, while the fifth overlies the ulnar side.

Which of the following statements correctly characterizes the carpal tunnel?

C.The carpal tunnel becomes smaller with wrist flexion and extension. Correct. The carpal tunnel is a space on the volar wrist bordered on its dorsal, radial, and ulnar sides by carpal bones, and bordered on its volar surface by the dense, fibrous flexor retinaculum, also called the transverse carpal ligament. Nine flexor tendons, the deep and superficial flexor tendons of the 2nd through 5th digits and flexor pollicis longus tendon, are accompanied by the median nerve within the carpal tunnel. The median nerve travels superficially within the carpal tunnel, just beneath the flexor retinaculum. The carpal tunnel is a fixed, nondistensible space, which becomes smaller when carpal bones shift during wrist flexion and extension. The flexor retinaculum is a fixed connective tissue ligamentous structure, securely attached to the pisiform and scaphoid proximally and to the hamate and trapezium distally. It forms the roof of the carpal tunnel.

Which of the following statements regarding Guyon's canal is correct?

C.The pisiform and hook of the hamate form the ulnar and radial borders of the canal, respectively. Correct. Guyon's canal is located along the ulnar aspect of the wrist and is best seen in a transverse plane. The pisiform bone serves as a helpful landmark. Guyon's canal is located just to the radial side of the pisiform. Recall that the pisiform serves as its ulnar border and the hook of the hamate as its radial border. The flexor retinaculum and volar carpal ligament form the floor and the roof of the canal, respectively. Within Guyon's canal, the ulnar artery is seen on the radial side, and the ulnar nerve on the ulnar side.

Scapholunate Ligament (Right Wrist, Transverse Plane)

Distal to Lister's tubercle, the scapholunate ligament is encountered, which is seen best in a transverse orientation. This area is best visualized when the wrist is positioned in ulnar deviation. Similar to tendons, ligaments have a bright hyperechoic linear sonographic appearance. The internal architecture of ligaments is more compact and densely organized than tendons. However, there is more variability in the elements contained within the ligament, for example, collagen and elastin, which results in ligaments having a more variable echogenicity. The Scapholunate Ligament can be seen in the accompanying image traversing between the scaphoid bone and lunate.

Transducer Selection Linear-Array Transducer High-frequency linear transducers (15 to 10 MHz) Match transducer footprint to site of interest Optimize gain and focal point settings Optimize depth

High-frequency transducers, in the 15 to 10 MHz range, are ideally utilized for wrist imaging. Linear transducers are preferred in most cases. The hockey-stick transducer, a variant of the linear transducer, is also very popular for wrist sonography. Select a transducer with a physical footprint that approximates the site of interest. This will ensure maximum contact between the transducer and underlying skin. Musculoskeletal presets should be selected, when available, to optimize gain and focal zone settings. The depth selection should be appropriate for the anatomy being scanned.

Multiple types of anatomic structures can be seen with wrist sonography. Each has unique elements that helps differentiate and identify respective structures. Tendons can be identified as bright echogenic bands. In short axis, they appear as bright hyperechoic punctate dots surrounded by a well-defined ovoid or circular hyperechoic sheath. In short axis, nerves have a heteroechoic honeycomb-shaped appearance.

In long axis, nerves appear as bright hyperechoic lines separated by hypoechoic layers. They resemble tendons but are less echogenic. The synovial sheaths encircling tendons have a thin echogenic linear appearance, and normally contain a trace amount of synovial fluid. Tendons, nerves, and ligaments often display anisotropy. Anisotropy was discussed in greater detail in the Fundamentals and Soft-Tissue Modules.

Which of the following statements correctly characterizes the triangular fibrocartilage complex?

It resides between the distal radiocarpal joint and the distal radioulnar joint Correct. The ulna is not considered to be part of the radiocarpal joint as it is separated from the radiocarpal joint by the triangular fibrocartilage complex, or TFCC. The triangular fibrocartilage resides between the distal radiocarpal joint and the distal radioulnar joint between the radius and ulna. Hence, the radiocarpal joint is located between the radius and the triangular fibrocartilage complex, on one side, and the proximal row of carpal bones on the other, while the triangular fibrocartilage complex separates the radiocarpal and distal radioulnar joint

Lister's Tubercle (Transverse View)

Lister's tubercle, located over the dorsal radius, is a useful landmark that separates the more radially located second compartment from the more ulnar-positioned third compartment. The extensor pollicis longus tendon is located just ulnar to Lister's tubercle. Distally, the extensor pollicis longus crosses the extensor carpi radialis brevis and extensor carpi radialis longus tendons.

Distal Second Compartment (Transverse View)

Moving towards midline in a transverse plane along the dorsum of the wrist, we arrive at the second compartment. It contains the extensor carpi radialis longus and extensor carpi radialis brevis tendons. The extensor carpi radialis longus tendon is located radial to the extensor carpi radialis brevis tendon, which is located immediately adjacent to Lister's tubercle. Progressing proximally over the tendons leads to the abductor pollicis longus and extensor pollicis brevis muscles, which are located superficially in the distal forearm.

Wrist Tendons Muscles: --Intrinsic muscles are located in the hand --Extrinsic muscles are located in the forearm Extrinsic tendons: --Dorsal tendons are finger extensors --Volar (relating to the palm of the hand) tendons are finger flexors Tendon sheaths at retinaculum mitigate tendon friction and secure tendons

Musculature of the Right Forearm and Hand

Which of the following statements describing the sonographic characteristics of wrist anatomy is correct?

None of the above Correct. Tendons can be identified as bright echogenic bands. In short axis, they appear as bright hyperechoic punctate dots surrounded by a well-defined ovoid or circular hyperechoic sheath. In short axis, nerves have a heteroechoic honeycomb-shaped appearance. In long axis, nerves appear as bright hyperechoic lines separated by hypoechoic layers. They resemble tendons but are less echogenic. The synovial sheaths encircling tendons have a thin echogenic linear appearance, and normally contain a trace amount of synovial fluid.

The wrist contains eight carpal bones, which are arranged in two rows. The proximal row, from a radial-to-ulnar direction, is made up of the scaphoid, lunate, triquetrum, and pisiform bones. The pisiform is unique because it is a sesamoid bone located within the flexor carpi ulnaris tendon. Its only articulation is with the triquetrum bone. Sesamoids are bones that are contiguous with a tendon and serve to mitigate friction as the tendon passes over a joint. They are located in the upper and lower extremities. Without sesamoid bones, the tendon would rub against adjacent bones, leading to tendon degeneration.

The four carpals of the distal row, again from radial to ulnar, are the trapezium, trapezoid, capitate, and hamate bones

Carpal Joints (Longitudinal Plane)

The hyperechoic cortices of carpal bones act as a landmark for the synovial recess of the radiocarpal and midcarpal joints. These are best defined in a long-axis plane. The relative thickness and echogenicity of the synovium should be noted. In addition to extensor tendon compartments and joint recesses, sonography of the dorsal wrist can evaluate the triangular fibrocartilage complex. Cartilage has an anechoic internal appearance with hyperechoic margins.

Radial Artery, Veins, and Nerve

The radial artery, nerve, and paired veins, along with the cephalic vein, are shown in this image, volar and dorsal to the radial styloid respectively. As one progresses distally, the radial nerve and its branches assume a more superficial position above the tendons, while the radial artery assumes a deeper position below the tendons

Radioulnar Joint (Transverse Plane)`

The triangular fibrocartilage complex spans the triangular gap between the ulnar styloid process, the proximal carpals, on the ulnar side, and the radius. The triangular fibrocartilage complex serves to strengthen the radioulnar joint and to distribute compressive loads to the distal radius and ulna, while preserving carpal joint flexibility. The dorsal radioulnar joint is seen best in transverse, proximal to the radioulnar joint line.

Wrist (Volar Aspect)

The wrist complex includes carpal bones along with radiocarpal and mid-carpal joints. The radiocarpal joint consists of the distal end of the radius, an articular disc, and carpal bones. The ulna is not considered to be part of the radiocarpal joint as it is separated from the radiocarpal joint by the triangular fibrocartilage complex, or TFCC. The triangular fibrocartilage resides between the distal radiocarpal joint and the distal radioulnar joint between the radius and ulna. Hence, the radiocarpal joint is located between the radius and the triangular fibrocartilage complex, on one side, and the proximal row of carpal bones, on the other, while the triangular fibrocartilage complex separates the radiocarpal and distal radioulnar joints. The radioulnar articular disc is located between the ulna and the proximal row of carpals.

Right Wrist (Dorsal Aspect)

The wrist is a highly complex structure and consists of radiocarpal, radioulnar, mid-carpal, intercarpal joints, ligaments, tendons, and connective tissue. A series of wrist articulations support hand flexion, extension, supination, pronation, and ulnar and radial deviation. Wrist bones are linked through an array of ligaments that are divided into intrinsic and extrinsic groups. Intrinsic ligaments originate and insert on carpal bones, while extrinsic ligaments connect carpal bones to the metacarpals or radius.

Right Wrist (Axial Cross Section)

The wrist is commonly analyzed from volar and dorsal perspectives as well as fibro-osseous passageways, such as the carpal tunnel and Guyon's canal (Lee). Discrete fibrocartilaginous complexes have been defined within the wrist, such as the triangular fibrocartilage complex formed by the triangular fibrocartilage disc, radioulnar ligaments, and ulnocarpal ligaments. Lister's tubercle is an important anatomic landmark that resides along the dorsal aspect of the radius. It is a bony prominence that is located just proximal to the radiocarpal joint, approximately midway between the radial styloid process and the radioulnar joint.