Key words
ultrasound - anatomy - nervous-peripheral - hand
Introduction
Peripheral nerve pathologies of the forearm, wrist and hand can stem from a myriad
of causes, such as compression, direct and indirect trauma, tumors and scar tissue
[1]. While thorough history taking and clinical examination can help to narrow down
the location of neural damage, further examinations are necessary to exactly locate
the site of damage and define the cause: in this context electrophysiological studies
[2] can only determine the approximate location of neural damage and gather information
as to whether sensory or motor neuron, demyelinating or axonal damage predominates.
The causative mechanisms cannot be identified in the early course of the disease in
numerous cases. Thus, an appropriate therapeutic concept may not be deduced in a timely
fashion.
High-resolution ultrasound (HRUS), on the other hand, which is increasingly used in
the diagnosis of peripheral neuropathies due to its high resolution and low technical
requirements, allows for rapid identification of the location and causative mechanisms
of neural damage [1]
[3]. Technical advances enable depiction and assessment of tiny nerves and nerve branches
[4]
[5]. Nonetheless, successful identification of the location and assessment of small
nerve branches mostly rely on thorough knowledge of human topography of the peripheral
nerves. Following the course of peripheral nerves and nerve branches distally from
a main stem is time consuming and can be hindered by nerve segments not being sufficiently
accessible to HRUS due to surrounding anatomic structures, by variations in branching
patterns or by masking tissue alterations, such as scar tissue or hematoma. Anatomical
landmarks can be employed to quickly identify distal nerve branches and possible lesions.
The aims of this study were to define standard sonoanatomic landmarks for the peripheral
nerves of the forearm, wrist and hand in two embalmed cadavers as a prerequisite and
to evaluate these landmarks in a prospective study in 20 healthy volunteers.
Materials and methods
Anatomical studies
HRUS of two cadaver forearms was performed on a Philips iU22 with a 17-5 MHz broadband
linear transducer (Philips, Washington, USA) before preparation or cryosection to
define eight section planes with relevant branching of the median, ulnar and radial
nerve ([Fig. 1]). Intracutaneous sutures were then applied to define exact planes for preparation
or cryosection.
Fig. 1 Predefined section planes by ultrasound (see also [Table 1]) with pink lines at the predefined nerve segments: (1) proximal superficial branch
of the radial nerve, (2) dorsal branch of the ulnar nerve, (3) distal superficial
branch of the radial nerve, (4) palmar branch of the median nerve, (5) branching of
the ulnar nerve in Gyon’s canal, (6) thenar branch of the median nerve, (7) common
digital palmar nerves and (8) branching into proper digital nerves.
Abb. 1 Vordefinierte Schallkopfpositionen (siehe auch [Tab. 1]) mit pinken Linien an den vordefinierten Nervensegmenten: (1) proximaler Ramus superficialis
des N. radialis, (2) Ramus dorsalis des N. ulnaris, (3) distaler Ramus superficialis
des N. radialis, (4) Ramus palmaris des N. medianus, (5) Aufzweigung des N. ulnaris
in der Guyon’schen Loge, (6) Thenar Ast des N. medianus, (7) Nn. digitales palmares
communes, (8) Aufzweigung in die Nn. Digitales palmares proprii.
All cadavers at the institutional Department for Anatomy & Embryology were from participants
who voluntarily donated their bodies for teaching and research [6]. Cadavers were preserved in a carbol-formalin solution for at least 1 year [7]
[8]. Two cadaver arms from one donor were selected for preparations. Preparations of
the left arm involved removal of the cutis, subcutaneous tissue and muscle fasciae
and mobilization of the muscles. Utmost care was taken to preserve the neurovascular
structures and muscle tendons. Relevant anatomical structures surrounding the neural
branches that could act as potential landmarks were then defined including muscle
bellies, tendons, bones and vessels. Frozen sections (–20 °C) of the right arm were
then performed at eight predefined segments. To avoid tissue distortion due to thawing,
photo documentation was performed immediately after cryosection with a Nikon D300S
(Nikon; Tokyo, Japan).
Validation of landmarks in healthy volunteers
To assess the validity of the landmarks defined in the two cadaver arms, both arms
in 20 healthy volunteers (10 female, 10 male; average age: 33 ± 9.9 years, range:
25–54 years) were examined using a Philips iU22 with a 17-5 MHz linear transducer
(Philips, Washington, USA) and a 1 cm gel stand-off pad (Geistlich Pharma; Wollhusen,
Switzerland). The exclusion criteria were prior surgery, recent trauma of the upper
extremity, known acute or chronic neuropathies such as CTS or other compression neuropathies
and neurogenic pain syndrome. All volunteers provided written consent and the examinations
were performed in accordance with the declaration of Helsinki [9]. All data was collected anonymously. The examiners S.P. and V.S. had over 10 and
5 years of experience in musculoskeletal sonography, respectively.
The examiners worked in consensus following this schedule: First, the predefined landmarks
from the cadaver study were identified and then the detectability of the relevant
nerve segment was assessed as sufficient or insufficient.
Landmark-based anatomy
Radial nerve
The superficial branch (R. superficialis n. radialis) runs medially along the brachioradial
muscle and reaches the back of the hand, giving off the dorsal digital nerves (Nn.
digitales dorsales). An infrequent anastomosis to the ulnar nerve is known as Ramus
communicans cum ulnare [10]
[11].
Structures along the proximal superficial branch are anteriorly the tendon of the
brachioradial muscle, laterally the radial vessels and dorsally the tendons of the
extensor carpi radialis brevis and longus muscles. At the distal forearm, the nerve
can be found subcutaneously at the dorsal side of the forearm giving off branches
to the thumb, index, middle and ring finger.
The proximal superficial branch can be identified when positioning the transducer
at the transition from the proximal to middle third of the forearm. The nerve can
be found running along the tendons of the brachioradialis and extensor carpi radialis
longus and brevis muscles ([Fig. 2]).
Fig. 2 Proximal segment of the superficial branch of the radial nerve: anatomical preparation
overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The proximal segment of the superficial branch of the radial nerve (yellow, white
arrowhead) can be seen crossing under the tendon of the brachioradial muscle (purple).
Radial artery (red, *).
Abb. 2 Proximales Segment des Ramus superficialis N. radialis: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Das proximale Segment des R. superficialis N. radialis (gelb, weißer Pfeilkopf)
unterkreuzt die Sehne des M. brachioradialis (violett). A. radialis (rot, *).
The distal part can be located around 5 cm proximal to the radial foveola at the radial
edge of the radius. The nerve is located anterior to the tendons of the extensor carpis
radialis longus muscle, dorsal to the brachioradialis tendons and the radial vessels
and atop the tendon of the abductor pollicis longus muscle, which it crosses over
at the height of the styloid process of the radius ([Fig. 3]). After crossing the radial foveola the dorsal digital nerves originate.
Fig. 3 Distal segment of the superficial branch of the radial nerve: anatomical preparation
overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. Distal segment of the superficial branch of the radial nerve (yellow) with its branches
to the dorsal first digit (empty white arrowhead), second digit (white arrowhead)
and third digit (black arrowhead). Radial artery (red, *).
Abb. 3 Distales Segment des Ramus superficialis N. radialis: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Distales Segment des R. superficialis N. radialis (gelb) mit Ästen zum dorsalen
Daumen (leerer weißer Pfeilkopf), zweiten Finger (weißer Pfeilkopf) und dritten Finger
(schwarzer Pfeilkopf). A. radialis (rot, *).
The deep branch of the radial nerve (R. profundus n. radialis) runs underneath the
supinator muscle giving off small muscle branches and reaching the wrist as the posterior
interosseous nerve. The nerve can be found most easily at the proximal border of the
supinator muscle.
Median nerve
The palmar branch leaves the median nerve at the distal forearm, runs alongside its
main stem under the radial edge of the palmaris longus tendon and penetrates the palmar
aponeurosis. In its proximal course, it is radially surrounded by the flexor carpi
radialis tendon, radial artery and the palmaris longus muscle as well as the tendons
of the superficial finger flexor on the ulnar side and can be found by placing the
transducer 3–5 cm proximal of the linea carpi ([Fig. 4]).
Fig. 4 Palmar branch of the median nerve: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The palmar branch of the median nerve (yellow, white arrowhead) can be found between
the tendon of the long palmar muscle (purple, ulnar) and radial carpal flexor (purple,
radial).
Abb. 4 Ramus palmaris N. medianus: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Der Ramus palmaris N. medianus (gelb, weißer Pfeilkopf) kann zwischen den Sehnen
des M. palmaris longus (violett, ulnar) und des M. flexor carpi radialis aufgefunden
werden.
After passing the carpal tunnel, the median nerve divides into the 1st to 3rd common palmar finger nerves ([Fig. 5]). There are anastomoses between the deep branch of the ulnar nerve and motor branches
of the median nerve, also called Riche-Cannieu-anastomosis [12].
Fig. 5 Thenar branch of the median nerve: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The thenar branch (yellow, white arrowhead) shows a variable course through or around
the transverse ligament (purple). The common finger nerves can also be identified
(c, yellow).
Abb. 5 Thenarer Ast des N. medianus: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Der thenare Ast hat einen variablen Verlauf durch und um das Ligamentum transversum
(violett). Die Nn. digitales palmares communes sind mit abgebildet (c, gelb).
Either originating from the median nerve or from the first common finger nerve, the
thenar branch usually can be located by placing the transducer over and parallel to
the thenar crease, even though the thenar branch’s origin and course are highly variable.
In the carpal tunnel, the small thenar branch (approx. 1 mm2) is anteriorly surrounded by the transverse ligament, radially by the tendon of the
flexor carpi radialis muscle and deeper by the tendon of the long flexor pollicis
muscle. On the ulnar side, the common finger nerves, originating from the median nerve,
accompany it ([Fig. 5]). Before entering the thenar musculature, the thenar branch may loop back over the
transverse ligament in a superficial segment.
Ulnar nerve
The ulnar nerve enters Gyon’s canal at the height of the distal carpi palmaris crease
between the pisiform bone and the hamulus of the hamate bone [13] and reaches the palm of the hand after splitting into the deep motor branch and
the superficial sensory branch before or within Gyon’s canal [10]. The palmar aponeurosis and the palmaris brevis muscle form the medial, the flexor
retinaculum the dorsal and the pisiform bone the ulnar-sided walls of Gyon’s canal
([Fig. 6]). Within Gyon’s canal, the branches or the main stem are accompanied by the superficial
branch of the ulnar artery. The contents of Gyon’s canal can easily be visualized
by placing the transducer on the pisiform bone at the linea carpis palmaris distalis.
Fig. 6 Gyon’s canal: anatomical preparation overview including proximal (green) and distal
(orange) cutting plane a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound images d–f. Within Gyon’s canal, the ulnar nerve (yellow, white arrowhead) is accompanied by
the ulnar artery (red, *). It then divides into the superficial (e, small white arrowhead) and deep branch (f, small black arrowhead).
Abb. 6 Gyon’sche Loge: anatomische Präparation mit proximaler (grün) und distaler (orange)
Schnittebene a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierende hochauflösende Ultraschallbilder d–f. Innerhalb der Guyon’schen Loge wird der N. ulnaris (gelb, weißer Pfeilkopf) von
der A. ulnaris begleitet (rot, *). Dann zweigt er sich in einen oberflächlichen (e, kleiner weißer Pfeilkopf) und einen tiefen Ast (f, kleiner schwarzer Pfeilkopf) auf.
Distal to the Gyon’s canal, the superficial structures lie on the pisohamate ligament,
while the deep branch runs under the pisohamate ligament and between the abductor
digiti minimi and short flexor digiti minimi muscles. Here rare compression syndromes
can occur due to crossing vascular branches of the accompanying deep palmar arch [14] ([Fig. 6]). Both branches can be found at the outlet of Gyon’s canal distal to the pisiform
bone. The deep branch is usually accompanied by the deep palmar arch originating from
the ulnar artery. The superficial branch can most easily be identified at its entry
into the thenar musculature at the palmaris brevis muscle.
The sensory dorsal branch of the ulnar nerve ([Fig. 7]) originates at the middle of the forearm and runs superficially on the back of the
forearm covered by superficial veins, where it innervates the dorsal skin of the lateral
half of the 4th and the 5th finger [10]. It can be found by placing the transducer at the ulnar edge of the forearm 3–5 cm
proximal to the ulnar head.
Fig. 7 Dorsal branch of the ulnar nerve: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The dorsal branch of the ulnar nerve (yellow, white arrowhead) can be found covered
by superficial veins and on top of the tendons of the ulnar carpal extensor and extensor
digiti minimi (purple) at the height of the pisiform and triquetrum (turquoise).
Abb. 7 Ramus dorsalis N. ulnaris: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Der Ramus dorsalis N. ulnaris (gelb, weißer Pfeilkopf) wird von oberflächlichen
Venen bedeckt und kann über den Sehnen des M. extensor carpi ulnaris und M. extensor
digiti minimi (violett) auf Höhe des Os pisiforme und triquetrum (türkis) aufgefunden
werden.
The palmar branch of the ulnar nerve arises approximately 5 cm to the Gyon’s canal
and runs alongside the ulnar nerve ([Fig. 8]). It provides sensory innervation to the hypothenar skin.
Fig. 8 Palmar branch of the ulnar nerve: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The hypothenar branch (yellow, white arrowhead) can be found alongside the ulnar
nerve (yellow, black arrowhead) in the carpal tunnel at the height of the pisiform
(turquoise), accompanied by the ulnar artery (red, *).
Abb. 8 Ramus palmaris N. ulnaris: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Der Ramus palmaris N. ulnaris (gelb, weißer Pfeilkopf) kann in der Guyon’schen Loge
auf Höhe des Os pisiforme (türkis) neben dem N. ulnaris aufgefunden werden und wird
von der A. ulnaris begleitet (rot, *).
Common and proper finger nerves
The median nerve branches into three and the ulnar nerve into two common finger nerves.
The flexor retinaculum and the palmar aponeurosis form the superficial border for
all common finger nerves, while the finger flexor tendons run under the first three
nerves. The remaining two common finger nerves can be found anterior to the pisohamate
ligament ([Fig. 9]).
Fig. 9 Common finger nerves: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The median nerve (yellow, large white arrowhead) gives off common finger nerves
(yellow, small arrowheads), which run alongside the flexor tendons (purple) and are
accompanied by respective common finger arteries. The retinaculum flexorum (purple)
has been dissected.
Abb. 9 Nn. digitales palmares communes: anatomische Präparation a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Der N. medianus (gelb, großer weißer Pfeilkopf) gibt Nn. digitales palmares communes
ab, die neben den Flexorensehnen (violett) verlaufen von den jeweiligen Fingerarterien
begleitet werden. Das Retinaculum flexorum wurde gespalten (violett).
At the height of the distal transverse ligament, the common finger nerves split into
the proper finger nerves. Three proper finger nerves arise from the first common finger
nerve, innervating the skin of the thumb and the radial side of the index finger.
The other common finger nerves each divide into two proper finger nerves, innervating
the radial and ulnar-sided skin of two adjacent fingers.
To visualize the proper finger nerves, the transducer should be placed on the proximal
phalanges, where the nerves can be found alongside the finger vessels ([Fig. 10]).
Fig. 10 Proper finger nerves: anatomical preparation overview a, color-highlighted magnification b, anatomical cross-section c, and corresponding high-resolution ultrasound image d. The proper finger nerves (yellow, small white arrowheads) arise from the common
finger nerves (see also [Fig. 9]) and run on the ulnar and radial side of the flexor tendons (purple) and are accompanied
by a small proper finger artery (red, *).
Abb. 10 Nn. digitales palmares proprii: Nn. digitales palmares communes: anatomische Präparation
a, eingefärbte Vergrößerungsaufnahme b, anatomischer Schnitt c, korrespondierendes hochauflösendes Ultraschallbild d. Die Nn. digitales palmares proprii (gelb, kleiner weißer Pfeilkopf) werden von den
Nn. digitales palmares communes (siehe [Abb. 9]) gebildet und verlaufen auf der ulnaren und radialen Seite der Flexorensehnen (violett).
Sie werden von kleinen Fingerarterien begleitet (rot, *).
Transducer positions and anatomical landmarks for the nerves of the forearm, wrist
and hand are summarized in [Table 1].
Table 1
List of nerves of the upper extremity including information on transducer positioning
and relevant landmarks.
Tab. 1 Liste der Nerven an der oberen Extremität mit Informationen zur Schallkopfpositionierung
und relevanten Landmarken.
|
nerve
|
nerve branch
|
sonographic guidelines
|
anatomical landmarks
|
|
radial nerve
|
superficial branch (proximal)
|
place transducer at the transition from proximal to middle third of radial forearm.
|
palmar: tendon of brachioradialis muscle
medial: radial vessels
dorsal: tendons of long and short extensor carpi radialis muscles
|
|
superficial branch (distal)
|
place transducer 5 cm proximal to the radial foveola at the radial edge of the forearm.
|
radial: tendon of brachioradialis muscle
dorsal: extensor carpi radialis longus distal: abductor pollicis longus
|
|
deep branch (proximal)
|
locate the proximal border of the supinator muscle, the nerve can be found running
underneath.
|
distal: proximal border of the supinator muscle.
Palmar: supinator muscle BELLY, arch of Frohse
|
|
ulnar nerve
|
dorsal branch
|
place transducer at the ulnar edge of forearm 3–5 cm proximal to the ulnar head.
|
palmar: tendon of the flexor carpi ulnaris muscle
dorsal: tendon of the extensor carpi ulnaris muscle and distal ulna
|
|
main stem (Gyon’s canal)
|
place transducer at the linea carpis palmaris distalis over the pisiform bone.
|
palmar: palmar aponeurosis and palmaris brevis muscle
dorsal: retinaculum flexorum
ulnar: pisiform bone
|
|
palmar branch
|
place transducer 3 cm proximal to the pisiform bone.
|
accompanied by main ulnar nerve stem.
|
|
superficial branch
|
place transducer distal to the pisiform bone in transverse orientation.
|
proximal: outlet of Gyon’s canal
dorsal: pisohamate ligament
palmar: palmaris brevis muscle
|
|
deep branch
|
place transducer distal to the pisiform bone in transverse orientation.
|
proximal: outlet of Gyon’s canal
palmar: pisohamate ligament
ulnar: abductor digiti minimi
radial: short flexor digiti minimi
accompanied by the deep palmar arch
|
|
common palmar finger nerves
|
place transducer over the radial wrist at the height of the pisiform bone parallel
to the distal linea carpi palmaris.
|
distal: pisiform bone
palmar: pisohamate ligament
dorsal: tendons of the superficial flexor digitorum muscles, lumbrical muscles
|
|
proper palmar finger nerves
|
place transducer on the proximal phalanges.
|
dorsal: finger artery
radial/ulnar: phalanges
|
|
median nerve
|
palmar branch
|
place transducer 3–5 cm proximal of the linea carpi palmaris distalis at the anterior
forearm.
|
radial: tendon of the flexor carpi radialis and radial artery
ulnar: tendon of the palmaris longus muscle (if present) and flexor digitorum superficialis
(deeply located)
|
|
thenar branch
|
place transducer over and parallel to the thenar crease (linea vitalis).
|
palmar: flexor retinaculum and palmar aponeurosis (palmar)
radial: tendon of the flexor carpi radialis and flexor pollicis longus muscle (deeply
located)
ulnar: common digital nerves, stemming from the median nerve
|
|
common palmar finger nerves
|
place transducer on a connecting line between the scaphoid and pisiform bones.
|
radial: thenar muscles
palmar: flexor retinaculum
dorsal: tendons of the superficial flexor digitorum muscles, lumbrical muscles
|
|
proper palmar finger nerves
|
place transducer on the proximal phalanges.
|
dorsal: finger artery
radial/ulnar: phalanges
|
Evaluation of landmarks in healthy volunteers
Evaluation of landmarks in healthy volunteers
Following the proposed landmark-based approach, a detection rate of 100 % could be
achieved for all nerves and nerve branches except for the thenar branch of the median
nerve. Here, only 45 % could be detected in right arms and 35 % in left arms ([Table 2]). No influence of age or sex on the detection rate could be demonstrated.
Table 2
Detection rates of the various nerves and nerve segments in healthy volunteers following
the proposed visualization guidelines.
Tab. 2 Detektionsraten der unterschiedlichen Nerven und Nervenäste an gesunden Probanden
unter Verwendung der vorgeschlagenen Leitlinien.
|
|
detection rate
|
|
nerve segment
|
right arm (%)
|
left arm (%)
|
|
radial nerve
|
superficial branch (proximal)
|
100
|
100
|
|
superficial branch (distal)
|
100
|
100
|
|
ulnar nerve
|
dorsal branch
|
100
|
100
|
|
Gyon’s canal
|
100
|
100
|
|
median nerve
|
thenar branch
|
45
|
35
|
|
palmar branch
|
100
|
100
|
|
median & ulnar nerve
|
common finger nerves
|
100
|
100
|
|
proper finger nerves
|
100
|
100
|
Discussion
Nerve damage of the forearm, wrist and hand can occur for various reasons like trauma,
compression syndromes and tumors [5]
[15]. Exact location identification and evaluation of small nerve lesions is complicated
by complex topography, small structure scale and oftentimes subtle neural alterations.
Thus, the learning curve for radiologists in the area of nerve sonography is considered
steeper than, for example, via MRI [16]. While correct and timely diagnosis is essential for a patient’s outcome [17]
[18], especially correct location identification can be time-consuming if following the
nerves from a proximal segment, particularly if proximal segments of a given nerve
cannot be visualized due to masking or lack of ultrasound penetration. Therefore,
the relation of nerves and landmarks can be used for quicker identification of small
nerve branches [19].
In this sonoanatomic study, we could demonstrate that the use of predefined landmarks
is a valid and reproducible tool for the identification and evaluation of small nerve
branches. Almost all nerve branches we examined had a high detection rate. Only the
thenar branch of the median nerve could be detected in less than half of wrists. A
standardized approach relying on landmarks further requires less experience in finding
nerve branches and should speed up learning in residents.
The most common causes of peripheral nerve lesions are compression neuropathies and
trauma [16]
[18]. Neoplasms and inflammatory states occur less frequently [16]. HRUS allows for dynamic examinations and targeted provocation of symptoms. Thus,
a correlation between clinical presentation and sonomorphologic alterations is possible
[20]. HRUS enables differentiation between neurapraxia/axonotmesis on the one hand and
neurotmesis, i. e. complete discontinuity of the nerve on the other [17]
[18]
[20]. Rapid diagnosis and treatment are essential especially in posttraumatic or iatrogenic
nerve lesions [16]. Outcome rapidly worsens if delays occur in this early stage of nerve trauma [17]
[18]. Furthermore, HRUS can yield (preliminary) information on the nerve route, normal
variants, the extent of the discontinuity and whether a graft will be needed [18].
Beyond purely diagnostic applications, HRUS enables sonographers to perform imaging-guided
neural interventions. Diagnostic and therapeutic targeting and perineural injection
of local anesthetics in patients with chronic pain [21] or phenol for the treatment of e. g. stump neuroma [22] are already routinely performed.
One limitation of this study is the low detection rate of the thenar branch – which
can be damaged during carpal tunnel release surgery [23]
[24] – in healthy volunteers. The definition of a singular landmark is complicated by
its small cross-sectional area, highly variable origin and course [24]. Due to its exploratory nature and overall study design, no intra- or inter-observer
correlation was performed. Only two cadaver arms were examined, thus anatomical variations
were not included in this study. Furthermore, the healthy volunteers we examined were
rather young. Nerve detection rates in the elderly, overweight or chronically ill
may be lower.
Conclusion
This sonoanatomic correlation study demonstrates the validity and reproducibility
of standardized guidelines based on predefined anatomical landmarks in the detection
of peripheral nerve branches of the hand and wrist. The findings should simplify and
accelerate the location identification and diagnosis of peripheral nerve lesions of
the forearm, wrist and hand with HRUS.
-
Peripheral nerve pathologies can be assessed with high-resolution ultrasound.
-
Following the nerves from proximal to distal can be time-consuming and difficult,
especially in immobile patients.
-
A landmark-based approach facilitates even the depiction of tiny nerves/nerve branches.
-
Beyond purely diagnostic applications, high-resolution ultrasound enables sonographers
to perform imaging-guided interventions in real time.
