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1 Introduction

The role of ultrasound (US) in the assessment of musculoskeletal disorders is persistently increasing (Van Holsbeeck and Introcaso 2001; Mc Nally 2004; Brasseur and Tardieu 2006; Bianchi and Martinoli 2007). Recent developments in hardware and software of US equipments and in particular use of small-size, high-frequency transducers have allowed accurate assessment of a wide variety of hand and wrist disorders. The main advantages of US are its low cost, readiness, non invasivity and possibility to perform a dynamic examination. The main disadvantage is the impossibility to detect and assess deep structures, located behind bones. In addition, US is a highly operator-dependent technique and has a long learning curve. US has been used in the assessment of wrist and hand traumatic, degenerative and infective disorders, as well as in evaluating local masses (Read et al. 1996; Ferrara and Marcelis 1997; Bianchi et al. 1999, 2001, 2003; Teefey et al. 2000; Milbradt et al. 1990; Chiou et al. 2001; Moschilla and Breidahl 2002). Additional studies have stressed its role in the evaluation of inflammatory arthritis (Koski 1992; Grassi et al. 1993). Quantification of inflammation and of structural damage is mandatory in the assessment, management and monitoring of rheumatoid arthritis (RA). Without appropriate treatment (e.g. DMARD’s, biologics), RA inflammation can progress and result in joint dysfunction and deformity. An early diagnosis can lead to early instauration of a successful treatment. Standard radiographs have an important role to identify changes such as osteopenia, joint space reduction or erosions in patients with advanced arthritis. US is a useful tool in the assessment and follow-up of early to established RA (Wakefield et al. 2000, Szkudlarek et al. Szkudlarek et al. 2004a, b) and can efficiently guide local procedures such as aspiration of effusions or therapeutic injection (Karim et al. 2001). In RA US can detect different pathologic changes including synovitis, cartilage and bone changes, tenosynovitis and tendon tears, bursitis, rheumatoid nodules or secondary nerve entrapment (e.g. carpal tunnel syndrome). Clinical studies have shown that US is as effective or even more effective in detecting inflammatory changes as clinical examination. Sensitivity and specificity of US in assessment of joints changes in RA is comparable to MR imaging (Backhaus et al. 1999; Backhaus et al. 2002; Szkudlarek et al. 2004a, b; Scheel et al. 2006). Power Doppler and Colour Doppler US detects active synovial inflammation associated with hypervascularisation and neoangiogenesis. In the presence of an active synovitis, there is an increase in signal activity, which is correlated to the degree of inflammatory activity. Therefore, the use of color and power Doppler US facilitates a differentiation between active and inactive synovitis. Furthermore, numerous studies have shown a good correlation between activity of synovitis at power Doppler and inflammatory changes evident at MRI and at histopathology studies (Walther et al. 2001; Terslev et al. 2003). Echo-contrast-enhanced US has shown an improvement in the measurement of synovial thickness and activity of synovial processes in patients with rheumatoid arthritis and allows better differentiation between effusion and synovial proliferation (Goldberg et al. 1994; Blomley et al. 2001). Besides assessment of the synovium, US can evaluate pathological changes of cartilages and bones if performed using high-resolution ultrasound probes. Bone erosions are a pathophysiological hallmark of RA. US can provide a more accurate and comprehensive assessment of bone erosions than plain radiography. The size of erosions can be monitored to evaluate disease progression.

Accurate knowledge of the normal anatomy, technique of US examination and of the US appearance of the hand and wrist are definite pre-requisites for a successful US examination. The target of this chapter is to present the technique of the US examination and the normal US anatomy of the hand and wrist.

2 Technique of Examination and Normal US Appearance

Before starting the US examination, any previous imaging studies and blood tests, if available, are reviewed. Every effort must be made to obtain a recent radiographic examination, in at least two perpendicular views, since this allows a good analysis of joints and bones and is complementary to US that permit an excellent assessment of most soft tissues. A brief clinical evaluation is always obtained since it helps in pointing the attention of the examiner to a specific area, thus shortening the time of examination and allowing a more detailed local assessment. The patient is asked for duration of symptoms, type and rhythm of pain (mechanic or inflammatory), presence of tingling, numbness or morning stiffness. If pain is the main symptom, its location and modification during muscle contraction or joint movements can often orient toward the correct diagnosis. In De Quervain tenosynovitis, for example, a sharp, acute pain located over the radial styloid and worsened by ulnar deviation of the wrist with the thumb flexed is highly suggestive of the diagnosis. The distribution of peripheral tingling can indicate the injured nerve (radial, ulnar or median). A brief regional physical examination including assessment of any local or diffuse swelling, warm or reddens follows. The joint range of motion and local tenderness are also briefly assessed.

Schematically, there are two main kinds of performing a US examination of the wrist and hand. A focused examination generally performed in patients suffering from disorders affecting the periarticular tissues and a systemic examination mostly directed to the joints. The first is a shorter examination concentrated on a specific region, selected by the sonologist according to the data available from the physician’s US request, type of symptoms and results of the brief clinical examination described earlier. We perform this type of examination in the vast majority of our patients. To give an example in a patient presenting with a painless lump at the dorsum of the wrist suspected to be a ganglion by the referring physician, the US examination can be limited to the dorsal aspect of the wrist. A time-consuming, detailed examination of all metacarpophalangeal and interphalangeal joints is not necessary and useless in such a patient. The second type of US examination is a more time-consuming, systematic examination usually obtained only in patients with a clinical suspicion or diagnosis of systemic arthritis. In both cases, a scrupulous technique of realization of the US examination, including images obtained in several planes and dynamic test, must be deployed (Creteur and Peetrons 2000; Middleton et al. 2001; Lee and Healy 2005; Tagliafico et al. 2007).

For didactic purposes, we first describe the basic anatomy of the main structures amenable to US assessment followed by description of the US technique of examination and of the normal US anatomy. We will follow an anatomic pattern, starting with the dorsal aspect of the wrist and the hand followed by the palmar aspect.

For optimal US examination of the wrist and hand, the patient sat facing the examiner with the forearm resting on the examination bed. We routinely start the examination by scanning the dorsal aspect of the wrist followed by the hand through transverse and sagittal sonograms. Then, the patient is asked to supinate the hand that now lies on its dorsal aspect, to allow examination of its palmar aspect. Again transverse sonograms are followed by longitudinal images. Color Doppler is routinely obtained. Dynamic scanning allows identification of each extensor and flexor tendon of the fingers and, most importantly, allows optimal judgement of tendons’ gliding and eventual impingement inside osteofibrous tunnels. This is very useful in judging presence of tendons adhesions. Application of variable pressure with the transducer permits obtaining additional data. A firm pressure helps in eliciting local pain and thus in focalizing the examination. It also assists in judging consistency of masses facilitating for example the diagnosis of soft tissue lipoma. On the contrary, large amount of gel must be used in assessing fluid collections in order to lessen local pressure trough the probe and avoid inadvertent displacement of the fluid that can result in a negative examination. In assessing presence of vessels with color Doppler, excessive pressure can result in squeezing of vessels resulting in impossibility to accurately detect local hypervascular changes. In testing the permeability of subcutaneous veins, color Doppler is obtained during squeezing of the soft tissues distal to the site of examination performed with the contralateral hand of the examiner. This allows a temporary increase in venous blood velocity and its easier detection at color Doppler. On the contrary, blocking the venous drainage at the forearm causes dilatation of the distal vein and results in stagnation of blood inside venous masses. As previously discussed, palpation under US guidance can be realized through the transducer when a large mass is evaluated. When the mass is small, US-guided palpation is better performed by using an opened paper clip. Once placed between the transducer and the skin, this can be followed under real-time scanning thanks to its typical posterior comet tail artifact. This technique works well in cutaneous marking of soft tissue foreign bodies as well as in accurate localization of small neuromas.

3 Dorsal Aspect

US allows an accurate evaluation of the dorsal aspect of wrist and hand (Figs. 1, 2, 3, 4, 5, 6, 7, 8). Accessory muscles can be found at the dorsal face of the wrist (Muncibì et al. 2008) as anatomic variants mimicking local tumors. They show at US the typical internal muscle structure made by alternating hypoechoic (muscle fibers) and hyperechoic (fibroadipose septa) bands. Dynamic examination during resisted contraction shows contraction of the accessory muscle thus confirming the diagnosis. Located under the skin and subcutaneous tissues, a thin fascia covers the extensor tendons (ET). These tendons origin from the miotendineous junctions, located in the forearm at different level for each muscle, run distally between the joint plane and the subcutaneous tissue, to finally insert into the bone of the wrist and hand. Since all ET change their course before joining their insertion, they are prone to instability during changes of position of the wrist and hand joints. To avoid instability, the ET run inside fibrosseous tunnels. These are made by the surface of bones covered by periosteum (the floor) and by superficial fibrous bands named retinacula (the ceiling). To further increase tendons stability, the bone surface is not flat but made by grooves, sulci or protuberances. A synovial sheath composed by a visceral and parietal layer, gliding one over the other, surrounds the tendons and reduces local frictions during gliding. The visceral layer is adherent to the tendon and moves with it, while the parietal layer is lax and blends with the retinacula and other peritendineous structures. The layers are separated by a thin amount of synovial fluid. At the level of the distal radius and wrist, the twelve ET run inside six tunnels. The tunnels are numbered from the most radial to the most ulnar. The first tunnel is located over the radial styloid while the sixth is found at the level of the cubital head. Table 1 resumes the arrangement of the tendons inside the six tunnels.

Fig. 1
figure 1

Dorsal aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a. US shows the crossing of the tendon of the first extensor compartment (black arrowhead) over those of the second compartment (white arrowhead). Asterisk distal part of the muscle of the first extensor compartment. d Sonogram obtained as shown in c. US shows the miotendineous junctions of the extensor pollicis longus (small star) and extensor indicis proprius (large star). The extensor digitorum communis tendons (white arrow) are located more superficially. Note the interosseous membrane (black arrow) appearing as a hyrechogenic structure connecting the ulna and the radius

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Fig. 2
figure 2

Dorsal aspect. a, c, e Probe positioning for transverse examination. b, d, f corresponding sonograms. b White arrowhead extensor digitorum communis tendons, black arrowhead extensor pollicis longus tendon. d White arrowhead extensor digitorum communis tendons, arrow extensor carpi ulnaris tendon. f Black arrowhead extensor pollicis longus tendon, stars extensor carpi radialis tendons

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Fig. 3
figure 3

Dorsal aspect. a Probe positioning for transverse examination b corresponding sonogram. White arrowheads extensor digitorum communis tendons, void arrowhead retinaculum of the 4th compartment of the extensor tendons. White arrow extrinsic dorsal carpal ligaments and radiocarpal synovial space, black arrow dorsal band of the scapho-lunate ligament

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Fig. 4
figure 4

Dorsal aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a. Met metacarpals, DIM dorsal interosseous muscles, black arrowheads extensor tendons. d Sonogram obtained as shown in c. White arrowheads extensor indicis proprius and extensor digitorum communis tendon of the index

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Fig. 5
figure 5

Dorsal aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a. Met metacarpal, white arrowhead extensor digitorum tendon, asterisks subcutaneous veins. d Sonogram obtained as shown in c. White arrowheads extensor digitorum communis tendons, black arrowheads sagittal bands

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Fig. 6
figure 6

Dorsal aspect. a, c, e Probe positioning for longitudinal examination. b, d, f corresponding sonograms. b Asterisk triangular fibrocartilage complex, white arrowhead extensor carpi ulnaris tendon, star base of the fifth metacarpal. d Black arrowhead extensor digitorum communis tendons, 1 radiocarpal joint, 2 mediocarpal joint. f Arrow extensor tendons of the first compartments, RA radial artery

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Fig. 7
figure 7

Dorsal aspect. a Probe positioning for longitudinal examination. b Sonogram obtained as shown in a. b Arrows extensor digitorum communis tendon, P1 proximal phalanx. c Sonogram obtained with 90° of flexion of the metacarpophalangeal joint. White arrowheads articular cartilage, black arrowhead subchondral bone plate

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Fig. 8
figure 8

Dorsal aspect. a, c Probe positioning for longitudinal and transverse examination. b Sonogram obtained as shown in a. 1 Met first metacarpal, white arrowheads aponeurosys of the adductor pollicis brevis muscle, asterisk ulnar collateral ligament. d Sonogram obtained as shown in c. 1 Met first metacarpal, white arrowheads aponeurosys of the adductor pollicis brevis muscle, asterisk ulnar collateral ligament, arrow extensor pollicis longus tendon

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Table 1 Extensor tendons
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US shows the ET as hyperechoic, homogeneous structures showing a typical fibrillar structure in the longitudinal sonograms. The borders of normal tendons are regular and well defined. The normal synovial sheath and the tiny amount of fluid contained inside it can’t be detected even if high-resolution transducers are used. Retinacula are imaged at US as hyper or hypoechoic structures depending on the incidence of the US bean. They present different thickness depending of the fibroosseous tunnel examined. The retinaculum of the fourth compartment is the thicker and, since it appears mostly hypoechoic, can simulate an effusion to unexperienced examiners (Robertson et al. 2007). The mean value or retinaculas’ thickness in other tunnels is around 0.3-0.5 mm. In case of suspicion of mild thickening of retinacula, the contralateral side can be scanned to improve diagnostic confidence. In normal conditions, color Doppler does not allow detecting the normal vascularisation of tendons, sheath or retinacula. Any Doppler signals inside these structures must be retained as pathologic. Axial images allow a good analysis of details of different ET. To give an example, the APL is almost always made by multiple thin tendons rather then by a single tendon (De Maeseneer et al. 2009). This normal variation seems to facilitate impingement inside the first osteofibrous tunnel.

Deep to the ET of the third compartment, located close to the lateral aspect of the Lister’s tubercle, the distal sensitive branch of the posterior interosseous nerve can be seen running from the forearm to the dorsal aspect of the wrist. At its distal portion, the normal nerve can present a bulbous swelling (Acrel’s ganglion) that must not be interpreted as a pathologic neuroma or as evidence of chronic compression. The origin of this fusiform swelling is unknown. Histologically, it is made by normal peripheral nerve structures without any neuronal cell bodies (Tubbs et al. 2007). The term pseudoganglion seems then more appropriate then that of ganglion. In younger subjects, a small artery (distal anterior interosseous artery) can be detected running close to the nerve. The distal radio-ulnar, radiocarpal, mediocarpal and carpo-metacarpal joints can be well imaged and changes related to degenerative or erosive arthropathy detected. US can efficiently guide intraarticular injections (Lohman et al. 2007) under real time control. This helps in avoiding injury to adjacent structures such as nerves and vessels and in confirming the correct site of injection. US allows detection and assessment of several extrinsic articular ligaments as well as of the scapho-lunate ligament (Griffith et al. 2001; Jacobson et al. 2002; Finlay et al. 2004; Boutry et al. 2005; Taljanovic et al. 2008; Bihan et al. 2009; Renoux et al. 2009).

At the level of the dorsum of the hand and of the fingers, the ET can be followed till their distal insertion by US. The EPB is one of the thinnest tendons and inserts into the base of the proximal phalanx of the thumb. The two extensor carpi tendons (ECRB and ECRL) can be followed till their insertion into the base of the second and third metacarpals. The EPL has a more complex course. At the distal radius, it reflects on the medial aspect of the Lister’s tubercle, a bony ridge separating the third and the second compartment of the ET. Then, it points to the base of the thumb and overlies the ECRB and ECRL tendons. Finally, it joins the EPB at the level of the head of the first metacarpal to then insert into the base of the distal phalanx of the thumb. The EPL is then subject to local friction at two levels: at the Lister tubercle and when it crosses with the two extensor carpi tendons (De Maeseneer et al. 2005). The index has two extensor tendons, the communis and the indicis proprius, which runs medial to the communis. They have similar size and course. The EIP can be harvested and used as a tendon graft in several surgical procedures. The extensor digitorum communis tendons present a high variable organization at the dorsum of the hand related to presence of the so-called tendinous junctions. These are thin tendons directed obliquely and joining adjacent ET. The dorsal interossei muscles can be seen appreciated lying among the hyperechoic metatarsals.

At the level of the metacarpophalangeal joints, the ET are retained over the dorsal aspect of the joint by the sagittal bands, thin ligaments that prevent palmar displacement of the tendons during flexion of the fingers. These bands appear as thin hyperechoic laminae covering the tendons and inserting into the periphery of the capsule. At the level of the proximal phalanx, the ET of the 2–5 fingers split into a central band and two lateral bands. The central band inserts into the base of the middle phalanx while the lateral bands join into the midline to insert into the distal phalanx. The ET are well assessed by US at the level of the MCP joint. Their distal splitting is sometimes difficult to be appreciated at transverse images. Longitudinal images allow visualization of the insertion of the central band as well as of the distal insertion into the distal phalanx. Details of the insertion of the intrinsic muscles are not detected at US. The metacarpophalangeal and interphalangeal joints can be imaged in the sagittal and axial plane. US allows an accurate assessment of erosive articular changes (McNally 2008). The cartilage of the metacarpal and phalanx head can be judged by using a dorsal and palmar approach in the extended and flexed joint while the cartilage of the bases of the phalanges are not detectable at US. US examination performed during gentle stress of the fingers’ joints can help in judging the capsuloligamteous complex. This is most often performed at the level of the MCP of the thumb in the evaluation of tears of the ulnar collateral ligament.

4 Palmar Aspect

The palmar aspect of the wrist houses several tendons, nerves, and vessels (Figs. 9, 10, 11, 12, 13, 14, 15). Abbreviations for these structures are listed in Table 2. The most superficial and thinnest tendon is the PG that runs in the midline of the wrist within the subcutaneous tissue. The PG presents a high anatomic variability. It can be absent or be replaced by a muscle (palmaris inversus). In a deeper position, the flexor tendons of the fingers (FDS, FDP, FPL) run inside the carpal tunnel (CT), a fibroosseous tunnel made by the carpal bones (the floor) and a palmar thick ligament, the transverse carpal ligament (TCL) (the ceiling). Inside the CT, the tendons are surrounded by a common synovial sheath enveloping the FDS and FDP of the 2–5 fingers. This common sheath generally communicates with the digital sheath of the fifth finger. The 2–4 fingers have separate digital sheaths. The FPL has a separate long sheath extending from the CT till to the proximal phalanx of the thumb. The FCR, a strong tendon surrounded by its own synovial sheath, is also located inside the CT but runs in a separate lateral channel. In its distal portion, the FCR overlies the tubercle of the scaphoid and reflects over the palmar aspect of scapho-trapezio-trapezoid joint to deepen and reach its distal insertion into the base of the 2 and 3 metacarpals. The FCU is a straight tendon located at the medial aspect of the anterior face of the wrist that inserts into the proximal pole of the pisiform. Since it has a straight course this tendon is not surrounded by a synovial sheath but by its peritenon, a thin connective tissue lamina that facilitates its gliding. Besides several tendons, the CT houses also the MN, a flat nerve located just under the TCL at the radial aspect of the tunnel. The nerve has a close relation with the FDP and FDS of the index. It innervates the muscles of the thenar eminence as well as the 1st and 2nd lumbrical muscles. The MN is responsible for sensitivity of the first three fingers and radial aspect of the fourth finger. Details of its anatomy and anatomic variations will be discussed in more details in Nerve Entrapment Syndromes. The Guyon’s tunnel is a small fibrooseeous tunnel located superficially and medially to the CT. It is delimited by the TCL and the lateral aspect of the pisiform (the roof) and the palmar carpal ligament (the ceiling). The tunnel houses, embedded by fat, the UN and the UAr surrounded by several UVe. The nerve is located between the artery and the pisiform. At variable level inside the tunnel or immediately distal to it, the UN splits in one motor branch and one or two sensitive branches. A more detailed description of the Guyon’s anatomy will be presented in Nerve Entrapment Syndromes. The UN is responsible for sensitivity of the fifth finger and medial aspect of the fourth finger. At the radial aspect of the wrist, the RAr is found running deep to the superficial fascia surrounded by satellite veins. The artery has close relation with the distal part of the sensitive branch of the RN. At the palm of the hand, the FDS and the FDP of the 2–5 fingers run together to join the base of the fingers. Their synovial sheaths are not detectable even when high-frequency transducers are used. The FDP, located just inferior to the FDS, give insertion to the lumbricals muscles. The vessels and the branches of the MN and UN run together located among the lumbricals muscles and the FDS surrounded by fat. More deeply are located the palmar interossei muscles. Utilization of high-frequency probes allows an optimal assessment of the anatomy of the flexor tendons at the fingers. Transverse images show splitting of the FDS at the level of the proximal phalanx. The two tendineous laminae are located from proximal to distal: first superior, then lateral and medial and finally, inferior to the FDP tendon. They insert into the base of the middle phalanx. The FDP presents typically a triangular aspect with the base inferior in proximal scans and superior in more distal images. A frequent anatomic variation is bifidity of the FDP at the level of the distal part of the middle phalanx. This must not be interpreted as a posttraumatic longitudinal split. Longitudinal images are best suited to evaluate the tendons dynamically. When performed at the level of the MCP joint during flexion of the DIP joint, they show selective movements of the FDP tendon. Simultaneous flexion of the IPP joint allows concomitant movements of the FDS tendon. The insertion of the two FDS hemitendons can be imaged at the level of the intermediate phalanx by displacing the transducer medially and laterally. The insertion of the FDP into the base of the P3 is ready evident on sagittal images obtained over the distal phalanx. A variety of pulleys (annular and cruciform) retain the flexor tendons against the palmar aspect of the phalanges thus preventing palmar instability during flexion (Bodner et al. 1999; Martinoli et al. 2000). Annular pulleys are quite rigid and are the main structures that prevent tendons bowstringing during flexion. They are numbered from 1 to 5 from proximal to, distal. The A2 and A4 pulleys located, respectively, at the base of P1 and P2 are functionally the most important. The annular pulleys are visualized as thin hyperechoic structures in longitudinal images. They show a normal thickening of their insertion in transverse images. The cruciform pulleys are more lax and located among the annular pulleys. They can be visualized at US only when a significant amount of fluid is present inside the tendon sheath.

Fig. 9
figure 9

Palmar aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a. Sc scaphoid, P pisiform, FTs flexor tendons, white arrowhead median nerve, black arrowheads transverse carpal ligament. d Sonogram obtained as shown in c. Tr trapezium, H hook of the hamate, FTs flexor tendons, white arrowhead median nerve, black arrowheads transverse carpal ligament

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Fig. 10
figure 10

Palmar aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a. FCUt and FCUm tendon and muscle of the flexor carpi ulnaris, white arrowhead ulnar nerve, black arrowhead ulnar artery. d Sonogram obtained as shown in c (Guyon’s tunnel). Pis pisiform, CT carpal tunnel, white arrowhead ulnar nerve, black arrowhead ulnar artery

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Fig. 11
figure 11

Palmar aspect. a, c Probe positioning for transverse examination. b Sonogram obtained as shown in a (Guyon’s tunnel). Pis pisiform, CT carpal tunnel, large white arrowhead superficial branch of the ulnar nerve, small white arrowhead deep branch of the ulnar nerve, black arrowhead ulnar artery. d Sonogram obtained as shown in c (Guyon’s tunnel), Hook hook of the hamate bone, large white arrowhead superficial branch of the ulnar nerve, small white arrowhead deep branch of the ulnar nerve, black arrowhead ulnar artery

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Fig. 12
figure 12

Palmar aspect. a, c, e Probe positioning for longitudinal examination. b, d, f corresponding sonograms. b Pis pisiform, white arrowheads flexor carpi ulnaris tendon. d Black arrowhead median nerve, white arrowheads flexor digitorum tendons. f Large white arrowhead flexor carpi radialis tendon, small white arrowhead flexor pollicis longus tendon, Tr Trapezium

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Fig. 13
figure 13

Palmar aspect. a, c, e Probe positioning. b, d, f Corresponding sonograms. b 1 Met first metacarpal, white arrowhead flexor pollicis longus tendon. d P1 proximal phalanx of the thumb, S sesamoid bone, white arrowhead flexor pollicis longus tendon. F Fts flexor tendons, L lumbrical muscle, PIM palmar interosseous muscles, Met metacarpal, white arrowhead common palmar digital artery, black arrowhead palmar digital nerve

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Fig. 14
figure 14

Palmar aspect. a, c, e Probe positioning for longitudinal examination. b, d, f corresponding sonograms. b Met metacarpal, P1 proximal phalanx, PP palmar plate, white arrowheads flexor digitorum superficialis and profundus tendons, large black arrowhead cartilage of the metacarpal head. d P2 middle phalanx, white arrowheads flexor digitorum superficialis and profundus tendons, small black arrowhead A4 annular pulley. F P3 distal phalanx, white arrowhead flexor digitorum profundus tendon

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Fig. 15
figure 15

Palmar aspect. a Probe positioning for transverse examination. b–g corresponding sonograms obtained from proximal to distal. b–g White arrowheads Annular pulleys, S flexor digitorum superficialis tendon, P flexor digitorum profundus tendon, PP palmar plate of the metacarpophalangeal joint, black arrowhead cartilage of the metacarpal head, Met metacarpal, P1 proximal phalanx, P2 middle phalanx, P3 distal phalanx

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Table 2 Anatomic structures of the palmar aspect of the wrist
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The different joints of the fingers can be examined by sagittal and axial sonograms. The palmar plates are well depicted as hyperechoic structures, with homogeneous internal appearance, inserting into the base of the phalanges. Examination performed during gentle hyperextension of the examined joint can help in analysis of local tears or avulsions. The palmar articular synovial recess is ready evident and must be analyzed for local effusion or synovial hypertrophy. Axial sonograms of the digital soft tissues allow assessment of the digital vessels and nerves till the level of the distal interphalangeal joint if high-frequency transducers are used.