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.
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)
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.
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 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.
Carpal tunnel (median nerve compression)
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.
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.
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