GLOMUS TUMOR
The normal subungual space is very small,
with a thickness of only 1–2 mm.
Various types of tumors can affect the subungual space and includes benign solid tumors (glomus tumor,
subungual exostosis,
soft-tissue chondroma,
keratoacanthoma,
hemangioma,
lobular capillary hemangioma),
benign cystic lesions (epidermal and mucoid cysts),
and malignant tumors (squamous cell carcinoma,
malignant melanoma) [1].
Glomus tumors represent 1- 5% of the soft-tissue tumors in the hand.
At pathologic examination,
glomus tumors are hamartomas developed from the neuromyoarterial glomus bodies which are highly specialized arteriovenous anastomosis responsible for thermoregulation [1,2].
Glomus bodies are present in the stratum reticularis of the dermis throughout the body,
but they are highly concentrated in the digits,
palms,
and soles of the feet.
Up to 75% of the glomus tumors occur in the hand,
and approximately 65% of these are in the fingertips,
particularly in the subungual space [1].
Clinical manifestations include intense,
often pulsating pain,
spontaneous or provoked by mild trauma,
and temperature sensitivity [1,3].
Usually,
these tumors present like a small,
reddish blue nodule measuring 3 to 10 millimeters in diameter,
and the most common location is the subungual region of the distal phalanges (Figure 1) [4].
At ultrasonography (US),
a glomus tumor usually manifests as a nonspecific,
solid,
hypoechoic mass beneath the nail (Figure 2),
hypervascular at color Doppler imaging (specific for the diagnosis),
and can be associated with erosion of the underlying phalangeal bone [1].
Magnetic resonance (MR) imaging features include intermediate or low signal intensity on T1-weighted images,
marked hyperintensity on T2-weighted images,
and strong enhancement after the injection of gadolinium-based contrast material (Figure 3) [1].
TENOSYNOVIAL GIANT CELL TUMOR
Tenosynovial giant cell tumor (localized and a diffuse form) is a mostly benign proliferative process.
In the past,
is was also known as pigmented villonodular tenosynovitis (PVNTS) of the tendon sheath,
localized or focal nodular synovitis,
or giant cell tumor of the tendon sheath [5].
It represents a benign,
hypertrophic synovial process characterized by villous,
nodular,
and villonodular proliferation and hemosiderin pigmentation.
These components vary in predominence from lesion to lesion [6].
Although uncommon,
hands and wrists are the sites most affected by the giant cell tumor (65%–89% of cases) [5,7].
Clinical symptoms include a soft-tissue mass and pain,
whereas joint dysfunction or swelling are unusual [5].
Patologically,
it manifests as a circumscribed,
lobulated,
cauliflower-like,
nodular soft-tissue mass that is attached to the tendon sheath [6].
At US,
it usually appears as a homogeneous hypoechoic mass adjacent to a tendon.
The adjacent tendon is usually normal.
There is often internal vascularity visible at Doppler imaging (Figure 4) [5].
At MR imaging,
tenosynovial giant cell tumor appears as a focal mass,
often adjacent to or surrounding a tendon.
It has intermediate or low T1 and T2 signal intensity and shows enhancement with contrast medium administration (Figure 4).
Heterogeneous high T1 and T2 signal intensity can also be seen in these lesions.
If there is hemosiderin deposition within the mass,
it can show susceptibility artifact (blooming) on gradient-echo [5].
EXTENSOR TENDON INJURIES
Injuries to the extensor mechanism of the finger are common because it consists of thin,
superficially located structures.
These anatomic structures predispose tendons to lacerations and also to closed tendon injuries,
including avulsion [8,9].
The extensor tendons reach the hand by passing through fibro-osseous tunnels or dorsal compartments in the wrist.
Near the midportion of the metacarpals,
the extensor tendons are interconnected by the juncturae tendinum,
which prevent independent extension of the digits.
At the metacarpalphalangeal (MCP) joint,
these extrinsic tendons are stabilized over the dorsum of the metacarpal head by the extensor hood [8].
The extensor mechanism of the fingers is divided into topographic zones,
which extend from the forearm to the distal phalanx.
It provides a background for understanding and predicting the results of injuries at any level [9].
Injury patterns are differentiated into open or closed,
sharp or blunt,
traumatic or degenerative lesions.
Closed tendon injuries are quite common including the “mallet finger”,
the “boutonnière deformity”,
avulsions and injuries to the connexus intertendineus (Figures 5 and 6) [10].
The modalities of choice for evaluation of finger soft tissues include MR imaging and US [11].
In general,
normal ligaments and tendons have low signal intensity on MR images,
and appears as long bright echogenic fibrillated structures at US.
Disruption manifests as increased signal intensity at MR images [8],
and hipoecogenicity at US.
SAGITTAL BAND LESION (Boxer's Knuckle)
The extensor hood is an aponeurotic sheet overlying the MP joint.
It comprises the central extensor tendon and two distinct transverse peripheral fibers termed sagittal bands.
The ulnar sagittal band and the radial sagittal band arise from the palmar plate and the intermetacarpal ligament at the neck of the metacarpal bone.
The sagittal bands have a superficial thin layer that crosses the dorsal surface of the tendon and unites with fibers on the other side,
and a thicker deep layer on both sides of the tendon that forms a groove to hold
tendon in place [12].
Sagittal band injuries occur as a result of a direct blow or forced flexion of the finger,
often with ulnar deviation.
At physical examination,
the patient will often have swelling at the dorsal aspect of the MCP joint and an inability to fully extend the finger [11].
Tendon dislocation can occur also in individuals who have inflammatory joint disorders (eg,
rheumatoid arthritis) that attenuate or disrupt the sagittal bands,
and in individuals with congenitally deficient or absent sagittal bands.
[12]
Boxer’s knuckle refers to sagittal band disruption,
enabling extensor tendon instability,
which can be associated with MCP capsular tears and even articular cartilage damage.
The term “boxer’s knuckle” came about due to a high incidence of the injury among boxers,
often incurred when landing a punch [13].
Dynamic US performed with the patient alternately extending and flexing the MCP joint depicts the position change of the common extensor tendon as it occurs (Figure 6) [11,
12].
Magnetic resonance images shows deformity of the sagittal band with increased T2 signal intensity of the soft tissues at the site of injury and disruption of the thin low-signal-intensity sagittal band with intervening fluid signal intensity in complete tears [11].
FLEXOR TENDON INJURIES
The flexor tendons are less commonly injured than the extensor tendons,
because they are more protected by their deeper location within the hand.
Laceration of the tendons within their midsubstance is more common than avulsion at osseous insertions [12].
The digital flexor tendons pass through the carpal tunnel before spreading out in the palm toward their respective fingers.
Each finger has two flexor tendons: the flexor digitorum superficialis (FDS),
which inserts on the midportion of the middle phalanx,
and the flexor digitorum profundus (FDP),
which lies volar to the FDS and inserts on the volar base of the distal phalanx [8].
As with extensor tendon injuries,
we can divide the lesions into two groups: open injuries and closed injuries [8].
Ultrasonography and magnetic resonance imaging can help to differentiate between complete and partial lacerations,
with an appearance similar to that of extensor tendon injuries (Figures 8,
9 and 10) [12].
VOLAR PLATE INJURIES
The proximal interphalangeal (PIP) joint is a hinged joint with a bicondylar anatomy that allows a wide range of flexion and extension movements.
The main stabilizers of the joint are the surrounding soft tissues,
especially the collateral ligaments and the volar plate [8].
The volar plate is a thick fibrocartilaginous structure that constitutes the palmar aspect of the PIP joint capsule.
Distally,
it is firmly attached to the volar lip of the base of the middle phalanx,
and it prevents hyperextension of the PIP joint [8,11].
Volar plate avulsion injuries are caused by joint hyperextension or dislocation,
most commonly at the PIP joint [11].
They can be isolated or associated with other injuries such as collateral ligaments tears [13],
and are categorized into three types: type I,
avulsion of the distal aspect of the plate; type II,
greater involvement of the surrounding soft tissues,
which can cause subluxation of the joint; and type III,
injury with associated fracture and dislocation [11].
Patients typically have tenderness along the volar surface of the joint and may have great difficulty holding the finger in a hyperextended position [13].
At MR images,
the volar plate appears as a lowsignal intensity structure best seen in a sagittal plane [8].
MR imaging findings of injury to the volar plate include nonhomogeneous signal intensity on T1- and T2-weighted images,
together with thickening and contour irregularities.
Disrupted attachment with a gap is observed when avulsion of the volar plate takes place,
also seen at US (Figures 11,
12,
13 and 14B) [8].
COLLATERAL LIGAMENT INJURIES
The ligaments that surround each MCP,
PIP,
and distal interphalangeal (DIP) joint are all similar in configuration.
For each joint,
there is both a radial collateral ligament (RCL) and an ulnar collateral ligament (UCL),
each of which is further subdivided into a proper collateral ligament and an accessory collateral ligament.
The proper collateral ligament is taut in flexion,
whereas the accessory collateral ligament is taut in extension These components of the collateral ligaments are difficult to distinguish on conventional images [8,11].
Collateral ligaments injuries are related to axial loading and dorsiflexion.
The radial collateral ligament is frequently injured,
usually at its proximal insertion.
Most injuries are incomplete tears associated with minimal instability.
MR and US images may show diffuse ligament swelling and thickening with intrasubstance tears.
In complete tears,
both imaging modalities can demonstrate ligament detachment or frank discontinuity with extracapsular fluid leakage (Figures 14,
15 ans 16) [13].
FINGER PULLEY INJURIES
The pulley system is made up of five annular and three cruciate pulleys through which the
flexor tendons glide [13].
The main function of the annular pulleys is to fix the tendon sheaths to the bony skeleton,
thus stabilizing the tendon during finger flexion and avoiding palmar “bowstringing”.
The cruciform pulleys are designed to permit deformation of the tendon sheath during flexion without impingement of the tendon itself [8].
Lesions of the pulley system are recognized with increasing frequency due to the growing popularity of activities,
such as rock climbing,
that impose extensive stress on the supporting structures of the hand and fingers [8].
The A2 annular pulley is the most commonly injured pulley (“climber’s finger”),
followed by A3,
A4,
and A1 [11,13].
In annular pulley tears,
the flexor tendons instead of coursing along the concavity of the phalanges,
lie at a variable distance from the bone. As a consequence,
the ruptured pulley can be ascertained by identifying the site of maximal volar bowstringing: In A2 pulley tears maximal volar displacement is seen over the proximal phalanx,
whereas in A4 pulley tears bowstringing occurs over the middle phalanx [13].
US and MR imaging allow the assessment of pulley system lesions.
It can be directly demonstrated by increased intrasubstance signal intensity and edema within the pulley itself or disruption of its fibers ( Figures 17 and 18) [11].
RHEUMATOID TENOSYNOVITIS
The tendons about the wrist are surrounded by a synovial sheath,
and are at risk for synovium-based inflammatory processes,
including reumathoid arthritis (RA),
an autoimmune process usually centered on the synovium of the wrist and hands [5,14].
Dorsal extensor compartments of the wrist are more commonly involved than the volar compartment in early rheumatoid arthritis.
The extensor carpi ulnaris tendon seems to be the
most frequently involved [14].
At US,
tenosynovitis appears as thickened echogenic areas often surrounded by tenosynovial fluid (Figure 19).
Power Doppler US is a useful tool to show hyperemia associated with the inflammation [5].
At MR imaging,
RA involvement of the tendons manifests with synovial hypertrophy,
soft-tissue thickening and inflammatory changes as well as presence of tendon sheath fluid.
This may eventually result in formation of a discrete tenosynovial pannus.
The inflamed synovium can demonstrate intense enhancement after administration of contrast medium.
Attenuation of the tendon is a worrisome sign for possible impending rupture [5].
FOREIGN BODY
Accidental penetration of foreign bodies in the hand is common particularly in labor class and
most of the times they are removed without any sequelae.
However,
if missed
initially,
these foreign bodies may get retained in the tissues to remain asymptomatic
or result in wide range of complications including pain,
abscess,
chronic discharging wound,
necrotizing fasciitis,
bone and joint destructive lesions,
granulomas with impairment of tendon mobility or triggering of digits,
migration,
delayed tendon ruptures,
neurodeficits,
pyogenic granulomas,
and vascular events.
Missing the foreign bodies is not uncommon and this entity is deemed as one of the major causes of medical litigation [14,
15].
In general,
current literature states that neurovascular (or potential) injury,
tendon laceration,
cosmetic deformity,
functional impairment,
and chronic pain are indications for wound exploration and foreign body removal.
Contraindications to removal include deep embedding or inaccessibility,
unacceptable iatrogenic risks to neurovascular structures during the retrieval process,
minute size,
inert material,
and asymptomatic presentation [16].
Ultrasound imaging is useful particularly in the detection of non-radiopaque foreign bodies (not seen in conventional radiography),
and can provide guidance for removal of foreign objects if they are not readily found at surgery (Figure 20).
Computed tomography (CT) and magnetic resonance imaging may be used in rare instances if other studies have failed to detect a suspected foreign object,
particularly a small wood or wood-like fragment.
CT and MR are the best studies to evaluate complications of retained foreign bodies [17].