Transverse view ultrasound of the extensor carpi radialis longus and brevis tendons.
Compartment 3:Extensor Pollicis Longus (EPL)
Compartment 3 scan plane:
Extensor Pollicis Longus tendon.
Ultrasound- The EPL tendon is tucked against Lister’s Tubercle. The Extensor digitorum longus common tendon is adjacent, in compartment 4.
Compartment 4: Extensor Digitorum Communis tendons (ED)
Compartment 4 scan plane:
Extensor Digitorum tendons.
Ultrasound of the Extensor Digitorum Communis tendon at the level of the extensor retinaculum.
Compartment 4 scan plane:
Extensor Digitorum tendons.
Ultrasound of the common extensor digitorum tendons which have divided into 4 proximal to the wrist crease.
Compartment 5:Extensor Digiti Minimi (EPM)
Ultrasound scan plane of the extensor digiti minimi.
This is a small tendon. It lies ulnar to compartment 4 but varies in it’s proximity to the extensor digitorum communis tendon and the more ulnar, extensor carpi ulnaris tendon.
Ultrasound of Extensor Digiti Minimi tendon, immediately ulnar to the extensor digitorums.
Compartment 6:Extensor Carpi Ulnaris (ECU)
Compartment 6 scan plane:
Extensor Carpi Ulnaris tendon.
Ultrasound of the Extensor Carpi Ulnaris tendon.
Scapho-lunate ligament:
Scapho-lunate ligament scan plane.
Ultrasound – Scapho-lunate ligament is seen as a fibrillar tight band.
Visualising the SCL does not exclude carpal instability.
Another normal proximal intersection demonstrating variation in musculature. This example shows a commonly seen larger extensor Pollicis Brevis musculotendinous junction.
Normal distal intersection of the wrist
Ultrasound of the distal intersection in the wrist as EPL crosses the ECR tendons.
Proximal intersection normal ultrasound appearance.
Ultrasound of the Palmaris longus tendon in a transverse plane at the wrist crease.
Triangular Fibro Cartilage Complex (TFCC)
Unlike the radius, the Ulna does not articulate directly with the carpal bones.
The TFCC is a heterogeneous area of tissue between the Ulna and the Triquetrum
Scan plane for ultrasound of the Triangular Fibro-cartilage Complex (TFCC)
The complex anatomical planes of the TFCC make it difficult to investigate well with ultrasound.
SCAN PROTOCOL
Role of Ultrasound
Ultrasound 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.
Patient Preparation
None required.
Equipment setup
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 mis-diagnosis).
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.
Common Pathology
Joint effusions
Teno-synovitis
Athroses
Tendon tears
Foreign bodies
Abscess/collections
Carpal tunnel (median nerve compression)
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
Schematic of the dorsal wrist tendons.
Abductor pollicis longus(APL) and Extensor Pollicis Brevis (EPB)The posterior wrist is conveniently divided into 6 compartments:
Extensor Carpi Radialis (ECR) longus and Brevis
Extensor Pollicis Longus (EPL)
Extensor Digitorum (ED)
Extensor Digiti Minimi (EDM)
Extensor Carpi Ulnaris (ECU)
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.
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 Scapho-lunate instability. The scaphoid will rotate abnormally during wrist movement, which if left untreated can lead to significant chronic wrist degeneration.
NOTE:
Visualising the SCL does not exclude carpal instability. (REF: AJR article )
ANTERIOR WRIST
A basic schematic of the anterior wrist tendons and Carpal Tunnel. Click image to enlarge
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.
On Ultrasound: As with carpal tunnel look for ganglia, accessory muscles and asymmetry with the contra lateral side