Objectives
- to know the common soft tissue masses of the wrist and fingers and their US appearance
- identify signs of and causes for nerve dysfunction at the level of the wrist
- appreciate the normal and abnormal appearance of the scapholunate ligament

Soft tissue masses
Sonography can readily diagnose the majority of soft tissue masses around the wrist, of which approximately 25% respectively are
- ganglia
- non tumour tendon pathology
- soft tissue neoplasms (usually benign)
- other
Ganglia usually appear on US as uni or multilocular anechoic masses, often with tortuous necks extending from their site of origin.
Hypertrophic accessory muscles can present as soft tissue masses and the extensor digitorum brevis manus muscle may mimick a dorsal SL ganglion.

Most soft tissue masses in the digits can be confidently diagnosed with sonography. Ganglia are commonest. The commonest solid mass in the digit is the entity of Giant Cell Tumor of Tendon Sheath. It has a lobulated or multi-lobulated contour, contains relatively uniform low level echoes and may demonstrate flow on colour Doppler. Glomus tumors typically occur in the region of the nail bed. They are hypoechoic. They usually (but not always) are hyperemic on colour Doppler.

Nerve Disorders
Carpal tunnel syndrome (CTS) is a clinical syndrome supported by EMG findings. Diagnostic US may be helpful in cases of carpal tunnel syndrome with unusual or atypical manifestations, particularly for the exclusion of a soft tissue mass or flexor tenosynovitis. A number of US findings have been found to be present in idiopathic carpal tunnel syndrome, both subjective (eg loss of deformability) and objective (cross sectional area > 0.09cm2).
The main role of US is to exclude a secondary cause of CTS, although some authors suggest it is comparable to EMG and may be considered the initial investigation - this is controversial.
Anatomic variations at the wrist are common and are often implicated as the causative factor in the development of carpal and ulnar tunnel syndromes. A high bifurcation of the median nerve, persistent median artery and anomalous muscles have all been associated with carpal tunnel syndrome.

Guyons canal is a fibroosseus tunnel formed by the flexor retinaculum and pisiform through which the ulnar nerve passes. Causes of ulnar nerve pathology at this level include - Repetitive trauma eg cyclists
Mass eg ganglion
Fractured hook of hamate
Ulnar artery thrombosis

The superficial sensory branch of the radial nerve is prone to trauma, both iatrogenic and accidental, and it is important to be able to identify this structure.

Intrinsic Wrist Ligaments
The dorsal band of the scapholunate ligament can be well visualized with US. The normal ligament appears as a hyperechoic fibrillar structure, taught through radial and ulnar deviation. An abnormal ligament appears as a fluid filled defect or abnormally hypoechoic thick tissue in the expected location of the ligament.