Tendons are consisted of parallel fibrils,
and on high-resolution ultrasound appear as hyperechoic,
uniformly thick structures with fibrillar texture.
They have thin hyperechoic synovial sheath,
spreading distally to the fingers in flexor tendons,
but only present at carpal level in extensor tendons.
Normally there is small amount of anechoic fluid within the synovial sheath (Fig.1,
2).
Fig. 1: Normal flexor tendon
Fig. 2: Normal flexor tendon and nerve, longitudinal view
Ligaments,
same as tendons are consisted of collagen type 1 tissue.
They also have hyperechoic fibrillar structure (Fig.3).
Both tendons and ligaments can appear hypo/anechoic,
due to anisotropy artefact,
if the ultrasound beam doesn’t fall perpendicularly on their surface.
Fig. 3: Normal scapholunate ligament
Normal periphery nerve is composed of hypoechoic fascicles,
surrounded by hyperechoic perineurium and epineurium.
They appear round or oval in transverse plain,
and linear in longitudinal plane (Fig.2,4).
Fig. 4: Normal median nerve-transverse view at proximal carpal tunnel level
Muscles are composed of hypoechoic fascicles and hyperechoic perimysium and epimysium (Fig.5).
Fig. 5: Transverse (superficial part) and longitudinal (deep part) view of normal muscles on ultrasound
We can only visualise the hyperechoic sharp cortical bone surface (Fig.3).
Dorsal side of the wrist is separated into 6 extensor compartments with the extensor retinaculum (Fig.6).
Fig. 6: Dorsal wrist, compartments: 1 Abductor policis longus, extensor policis brevis
2 Extensor carpi radialis longus et brevis
3 Extensor policis longus
4 Extensor digitorum, extensor indicis
5 Extensor Digiti minimi
6 Extensor carpi ulnaris
R, U-Radius, Ulna
Transverse view of normal dorsal wrist is explained in Fig.7.
The best anatomic landmark on ultrasound is the Lister tubercle,
on the dorsal side of the radius,
dividing the second and third extensor compartment.
Fig. 7: Normal dorsal wrist-transverse view
2 Extensor carpi radialis longus et brevis
3 Extensor policis longus
4 Extensor digitorum, extensor indicis
R, U-Radius, Ulna
Carpal bones and the flexor retinaculum form the carpal tunnel on the palmar side of the wrist (Fig.8).
Fig. 8: Palmar wrist: FCR- Flexor carpi radialis
FPL-Flexor policis longus
PL- Palmaris longus
FDS-Flexor digitorum superficialis
FDP-Flexor digitorum profundus
FCU-Flexor carpi ulnaris
NM-Nervus medianus
NU-Nervus ulnaris
AR, AU-Arteria radialis et ulnaris
S, L, T, P-Os scaphoideum, lunatum, triquetrum, pisiforme
Transverse view of the normal flexor tendons and n.
medianus inside the tunnel and the other structures on the palmar side of the wrist is explained in Fig.9.
Fig. 9: Normal palmar wrist-transverse view: FCR- Flexor carpi radialis
FPL-Flexor policis longus
PL- Palmaris longus
FDS-Flexor digitorum superficialis
FDP-Flexor digitorum profundus
FCU-Flexor carpi ulnaris
NM-Nervus medianus
S, L Os scaphoideum, lunatum
Tenosynovitis is inflammation of the tendon sheath.
Etiology can be different.
Metabolic diseases,
such as Rheumatoid arthritis,
gout,
collagenoses and also bacterial infection can bring to tenosynovitis.
Work related tenosynovitis- result of chronic repetitive microtrauma is among the most common causes.
Fig. 10: Severe tenosynovitis of flexor tendon
There are different ultrasound signs for tenosynovitis.
Increased amount of fluid inside the sheath,
which is usually anechoic or hypoechoic in septic and haemorrhagic tenosynovitis is commonly visible.
Thickening of the tendon sheath,
which could be uniform or eccentric and nodular,
and thickening of the tendon with loosing of normal texture is also present (Fig.10,
11,
12).
Sometimes small peritendinous cysts appear.
Fig. 11: Tenosynovitis
Work related-overuse tenosynovitis can be a result of repetitive wrist movements,
vibration forces,
direct pressure or trauma,
unnatural position of wrist for long periods of time (Fig.12).
Fig. 12: Overuse tenosynovitis due to friction with osteosynthetic material (OSM)
Commonest types of overuse tenosynovitis are trigger finger,
de Quervain tenosynovitis,
intersection syndrome,
tendinitis of m.
extensor carpi ulnaris (Fig.13),
tendinitis of m.
flexor carpi radialis.
Fig. 13: Extensor carpi ulnaris tendinitis
Trigger finger-tenosynovitis stenosans is an inflammation of flexor tendons.
Tendon of m.
flexor pollicis longus is most commonly affected.
Clinically there is painful and difficult flexion,
locking of the finger and snapping.
On ultrasound hypertrophy/ thickening of the annular ligament A1 pulley,
together with other signs of tendon inflammation is visible (Fig.14).
Fig. 14: A. Normal annular ligament-A1 pulley
B. Ligament hypertrophy in trigger finger
De Quervain tenosynovitis is an inflammation of the first extensor compartment,
tendons of m.
abductor pollicis longus and m.
extensor pollicis brevis at the level of the wrist (Fig.15).
Fig. 15: A. Normal tendons in first extensor compartment
B. de Quervain tenosynovitis
Tendon ruptures can total or partial,
spontaneous in inflammatory conditions or traumatic.
Traumatic rupture is a result of direct section with sharp object,
or forced hyperextension in flexor tendon rupture.
There is a distraction of the fibrillar pattern,
separation and fluid-blood between the tendon fragments in total rupture,
or hypoechoic defect inside the tendon in partial ruptures (Fig.16).
Transverse scanning of the tendon is suggested to best visualize the location of fragments and extent of retraction in full thickness tear.
Fig. 16: Partial thickness tear in chronic tenosynovitis
Majority of hand and wrist focal lesions are benign,
and pseudotumors are more common than true neoplastic lesions.
Focal lesions include ganglion cysts,
giant cell tumors,
fibromatosis,
tendon sheath fibromas,
haemangiomas,
lipomas,
glomus tumors,
epidermal cysts.
Malignant sarcomas are very rare in hand and wrist.
Fig. 17: Dorsal wrist ganglion cyst
Ganglion cysts are the commonest hand and wrist focal lesions,
accounting for 50-70% of hand and wrist masses.
Their origin is joint or tendon synovial sheath.
Majority of ganglion cysts are on the dorsal wrist,
60%,
about 20% are on the palmar side of the wrist,
about 10% originate from the flexor tendons,
and another 10% appear on the dorsal side of distal interphalangeal joint.
Ultrasound is a precise diagnostic tool for evaluating ganglion cysts.
They are anechoic,
clearly demarcated lesions with posterior acoustic enhancement.
Sometimes thin neck leading to the joint space can be visualized (Fig.17).
They can be unilocular or multiseptated (Fig.18).
Fig. 18: Multiseptated dorsal ganglion cyst
After ganglion cysts,
giant cell tumors are the commonest soft tissue masses of hand and wrist.
Although histologically they are very similar to pigmented villonodular synovitis,
their potential for growth and malignant transformation suggest they should be considered tumors.
They are hypoechoic,
homogenous,
sometimes lobulated,
usually clearly demarcated masses growing adjacent to the tendons (Fig.19).
Fig. 19: Giant cell tumor of flexor tendon sheath
Benign peripheral nerve sheath tumors-schwanommas and neurofibromas are usually hypoechoic,
heterogeneous,
oval,
fusiform lesions,
central or eccentric in relation to nerve (Fig.20).
Fig. 20: Schwanomma
Carpal tunnel syndrome is the commonest entrapment neuropathy.
The median nerve is compressed in the carpal tunnel between the flexor retinaculum and carpal bones (Fig.21,
22,
23,
24).
Ultrasound is used for carpal tunnel syndrome,
some studies show that specificity and sensitivity is similar to the electromyography exam.
Fig. 21: Carpal tunnel syndrome, axial view
Most used ultrasound sign for carpal tunnel syndrome is cross-section area of median nerve of 10 mm2 or more measured on carpal tunnel inlet (Fig.22).
Fig. 22: Severe carpal tunnel syndrome. Cross-section area of median nerve of 24 mm2
Physiological variations of median nerve at carpal tunnel exist,
and the commonest is the bifid median nerve (Fig.23).
Fig. 23: Carpal tunnel syndrome in bifid median nerve
Cross-section area of both segments should be examined for adequate assessment of carpal tunnel syndrome.
Another sign is bulging of flexor retinaculum of 2.5 mm or more,
measured at distal carpal tunnel (Fig.24).
Fig. 24: Carpal tunnel syndrome
Traumatic injury of a nerve at wrist level could be a result of sharp object injury.
There is a nerve discontinuity on ultrasound.
A rare complication of nerve trauma is neuroma.
It’s a benign proliferation of axons and Schwann cells appearing on ultrasound as oval,
hypoechoic distension of a nerve segment (Fig.25).
Fig. 25: Neuroma of median nerve