Ultrasound of the Wrist

ltrasound is a valuable diagnostic tool in assessing the following indications in the wrist:

• Muscular, tendinous and ligamentous damage (chronic and acute)
• Bursitis
• Joint effusion
• Vascular pathology
• Haematomas
• Soft tissue masses such as ganglia, lipomas
• Classification of a mass eg solid, cystic, mixed
• Post surgical complications eg abscess, oedema
• Guidance of injection, aspiration or biopsy
• Relationship of normal anatomy and pathology to each other
• Some bony pathology.

LIMITATIONS

Recent surgery or injections may degrade image quality through the presence of air in the tissue.

• Use of a high resolution probe (10-15MHZ) is essential when assessing the superficial structures of the wrist.
• Careful scanning technique to avoid anisotropy (and possible misdiagnosis).
• Beam steering or compounding can help to overcome anisotropy in linear structures such as tendons.
• Good colour / power / Doppler capabilities when assessing vessels or vascularity of a structure.
• Be prepared to change frequency output of probe (or probes) to adequately assess both superficial and deeper structures.

 SCANNING TECHNIQUE

• Begin your scan at the wrist crease.
• Initially, survey each tendon in transverse from the musculo-tendinous junction to the distal insertion.
• Then assess in longitudinal also.
• The tendon sheaths approximately extend for a couple of cm either side of the wrist crease.
• If necessary, you can compare with the contralateral side.

POSTERIOR WRIST

The posterior wrist is conveniently divided into 6 compartments: 

1. Abductor pollicis longus(APL) and Extensor Pollicis Brevis (EPB)

2- Extensor Carpi Radialis (ECR) longus and Brevis ( ECRL, ECRB )

3- Extensor Pollicis Longus (EPL).

You must also scan the scapholunate ligament, and the radial -scaphoid joint area for Ganglion cysts, effusion, tears, thickness, lipoma, mass, vascular pathology,loose bodies, hematoma and abscess formation.

4 .Extensor Digitorum (ED)

                          5. Extensor Digiti Minimi – QUINTI .(EDM).

                              6. Extensor Carpi Ulnaris (ECU)

                     THE PALMAR ASPECT; THE FLEXOR TENDONS.

Calcifications.

Ganglion cyst rising from Scapho-lunate.

compartment 1 and 2.

Cysts can rise from the joints, or tendon sheath.you have to know the wrist bone anatomy so you can find out the origin of the cyst.

CHECK LIST;

FOR TRIGGER FINGERS , always check the palmar flexor tendons, and the dorsal extensor tendons . THe flexor tendons will show you the information of the tendon sheath, thickness, tenosynovitis with hyperemia, ganglion cysts etc.Use color flow .

tendon sheath cyst.

always check the radial-scaphoid joint for effusion, cysts, etc.

check for lipoma and other masses,

LIPOMA PRESSING THE MEDIAN NERVE.PALMAR SIDE OF THE WRIST.

These are all tethered by the extensor retinaculum which overlies ,and in some areas reflects around, the tendons.

Begin by scanning over the lateral wrist crease at the anatomical “snuff-box”. You should see the APL & EPB in compartment 1. To check, both tendons should be able to be followed up the thumb. If they go to the carpus you have slipped medially onto compartment 2. Work your way sequentially across the wrist assessing each tendon individually.

De Quervain’s tenosynovitis – Compartment 1 .

• Inflammation of the Abductor Pollicis Longus and Extensor pollicis Brevis tendons.
• Overuse injury.
• Patients present with focal, point tenderness laterally over the radial styloid.

Proximal intersection syndrome

Extensor Pollicis Brevis crossing over extensor Carpi Radialis longus & Brevis.

Distal intersection syndrome

Ext Pollicis Longus crossing over extensor Carpi Radialis longus & Brevis.

Scapho-lunate ligament

The wrist is essentially divided into 3 joint planes:

1. and 2. The radiocarpal and midcarpal Joints allow wrist flexion, extension and lateral deviation.

3. The distal radio-ulnar joint allows the forearm and hand to rotate. (Pronation / Supination).

These joints are supported by a series of extrinsic and intrinsic ligaments. The scapholunate ligament is the most important dorsal intrinsic stabiliser.

• Injury occurs with a hyperextension of the wrist. Similar mechanism to a scaphoid fracture but results in a ligament tear instead.
• If only a partial tear it is usually stable.
• If complete, it results in Scapholunate instability. The scaphoid will rotate abnormally during wrist movement, which if left untreated can lead to significant chronic wrist degeneration.

ANTERIOR WRIST

Carpal Tunnel Syndrome 

This is the most common peripheral nerve entrapment. It occurs when the median nerve is compressed by the overlying flexor retinaculum.

• Ultrasound cannot exclude Carpal tunnel syndrome. The accepted standard for diagnosis is a nerve conduction study.
• Our role is to identify possible causes for the patient’s symptoms.

Look for: Tendon abnormalities, Ganglia ,Fluid, Accessory muscles, Any asymmetry with the contralateral side.

There have been several proposed methods of quantitative assessment for carpal tunnel. In our experience, these have not been reliable. They include:

• Nerve cross sectional area of >10 square mm proximal to the retinaculum.
• Nerve flattening ratio of 3:1 (Yesildag et al – Clinical Radiology).

Guyon’s Canal Syndrome

Canal bordered by the pisiform & hamate and roofed by a reflection of the flexor retinaculum. The ulna nerve and artery pass through and may become entrapped or injured. Repetitive injury such as cycling or using heel of hand as hammer.

Triangular FibroCartilage Complex (TFCC)

• A section of cartilage and ligaments at the distal ulna.
• Provides a continuous gliding surface along the forearm-carpal joint.

Affected by:Natural degeneration with age, Or injuries:

• FOOSH
• Forced rotation (stuck drill)
• Racquet sports
• Direct blow to medial wrist

A wrist series should include images specific to the area clinically indicated from a thorough history and physical examination.

• Document the normal anatomy. Any pathology found in 2 planes, including measurements and any vascularity.

FOR The power point on the wrist trauma and pathology please see these slides on this site.

http://www.smirg.org/lectures/ultrasound_wrist_and_hand/w_and_h.html

For the You tube , How to ultrasound the wrist please see Dr Scot video on this site;  https://www.youtube.com/watch?v=txMGtvWb2XI

Thank you for reading.

Steve Ramsey, PhD – Public Health.

MSc – Medical Ultrasound.

Calgary, Alberta- Canada.