fibrocartilage; 6, distal ulna; 7, base of second metacarpal; 8, trapezoid; 9, capitate; 10, scaphoid; 11, scapholunate ligament; 12, distal radius. (Courtesy
of Drs Allen S Prober and Robert J Ward, Tufts University, Boston, MA, USA.)
Synovial membrane The synovial membrane lines the fibrous Synovial cavities of carpometacarpal joints are prolonged slightly
capsule. between the metacarpal bases. The synovial joint between the pisiform
and triquetrum is usually isolated.
Muscles producing movement Movements accompany those of
the intercarpal and midcarpal joints, and are described on page 874. Wrist ligaments
The distal radio-ulnar joint and triangular fibrocartilage complex are
CARPAL JOINTS described on pages 845–848.
Intracapsular ligaments lie between the fibrous and synovial layers
The intercarpal joints connect the carpal bones. Their articular surfaces of the wrist joint; their margins may not be distinct. Extracapsular liga-
are saddle-shaped, ellipsoid or spheroidal. The carpal bones are ments are superficial to the fibrous layer. Most wrist ligaments lie within
connected by an extensive array of ligaments, not all of which are spe- the joint capsule; the only exceptions are the flexor and extensor reti-
cifically named. The flexor retinaculum is an accessory intercarpal nacula and the pisotriquetral ligament. The wrist ligaments are further
ligament. classified into extrinsic and intrinsic named ligaments. Some of the
extrinsic ligaments have superficial and deep parts; the latter are iden-
Joints of the proximal carpal row tifiable at wrist arthroscopy but the former are not. Wrist ligaments are
conventionally named from proximal to distal and from radial to ulnar,
Joints of the proximal carpal row are between the scaphoid, lunate e.g. the radioscaphocapitate ligament passes between the radius,
and triquetrum. In addition, the pisiform articulates with the palmar scaphoid and capitate.
surface of the triquetrum at a small, oval, almost flat, synovial pisotri-
Extrinsic ligaments


quetral joint. A thin capsule surrounds the joint. The synovial cavity is
usually separate but may communicate with that of the radiocarpal The extrinsic ligaments connect the carpus with the forearm bones. They
joint. tend to be longer than the intrinsic ligaments and are approximately
one-third as strong.
Joints of the distal carpal row
Extrinsic palmar carpal ligaments
When the synovial lining of the carpal tunnel is dissected away, two
Joints of the distal carpal row are between the trapezium, trapezoid,
V-shaped ligamentous bands are visible with their apices lying distally
capitate and hamate. There is little movement at these joints.
(see Fig. 50.17A). The limbs of the ‘V’ take origin from the radius and
ulna, respectively; the apex of one ‘V’ attaches to the distal row and that
Midcarpal joint
of the second ‘V’ to the proximal row.
The midcarpal joint, between the scaphoid, lunate and triquetrum Radioscaphocapitate ligament The radioscaphocapitate liga-
(proximally), and trapezium, trapezoid, capitate and hamate (distally), ment originates from the radial styloid and the palmar lip of the radius,
is a compound articulation that may be divided descriptively into and has three parts. The radial part inserts on to the lateral aspect of
medial and lateral parts. Throughout most of the medial compartment, the waist of the scaphoid (radial collateral ligament). The middle part
the convexity formed by the head of the capitate and hamate articulates continues as part of the distal ‘V’ and inserts on to the distal pole of
with a reciprocal concavity formed by the scaphoid, lunate and much the scaphoid. The ulnar part passes over the proximal pole of the
of the triquetrum. However, most medially, the curvatures are reversed, scaphoid towards the mid-carpus and blends with the fibres that origi-
forming a compound sellar joint. In the lateral compartment, the tra- nate from the ulnar side of the triangular fibrocartilage complex to form


pezium and trapezoid articulate with the scaphoid, forming a second the arcuate ligament over the palmar aspect of the capitate. A few of the
planosellar compound articulation. fibres of the radioscaphocapitate ligament attach to the body of the
capitate. There is a discrete interval between the inferior margin of this
Carpal synovial membrane The extensive carpal synovial mem- ligament and the palmar horn of the lunate (the space of Poirier).
brane lines an irregular articular cavity. Its proximal part is between the
distal surfaces of the scaphoid, lunate and triquetrum, and the proximal Long radiolunate ligament The long radiolunate ligament arises
surfaces of the second carpal row. It has proximal prolongations adjacent to the radioscaphocapitate ligament on the palmar lip of the
between the scaphoid and lunate, and lunate and triquetrum, and three radius, passes over and supports the proximal pole of the scaphoid, and
distal prolongations between the four bones of the second row. The inserts into the palmar horn of the lunate. It is discrete from the radio-
prolongation between the trapezium and trapezoid and/or between the scaphocapitate ligament, from which it is separated by the interliga-
trapezoid and capitate is often continuous with corresponding car- mentous sulcus, continuous with the space of Poirier.
pometacarpal joints, either from the second to the fifth, or from the
second and third only. In the latter case, the joint between the hamate Radioscapholunate (ligament of Testut) The radioscapho lu-
and fourth and fifth metacarpal bones has a separate synovial mem- nate ligament is covered by a thick synovial lining and is a visible
brane and the carpometacarpal interosseous ligament is interposed. landmark during wrist arthroscopy.


WRiST And HAnd
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Short radiolunate ligament The short radiolunate ligament is part Arthroscopy of the wrist and hand
of the proximal ‘V’. It arises from the palmar lip of the lunate fossa of
the radius and passes directly to the palmar horn of the lunate. On the Arthroscopy of the wrist joint may be carried out through up to 11
ulnar side, its fibres blend with those of the palmar triangular fibrocar- described portals, although only a few of these are favoured; most are
tilage complex as they pass to their insertion on the lunate. dorsally situated. Some are, as de Smet (2002) has described, ‘frighten-
ingly’ close to key anatomical structures. Consequently, only the skin
Ulnolunate ligament The ulnolunate ligament originates from the
should be incised when establishing a portal, and the remaining dis-
palmar aspect of the ulna adjacent to the short radiolunate ligament
section should be carried out with blunt artery forceps and using blunt
and inserts on to the palmar horn of the lunate. Part of this fibre
probes presaged by the introduction of a 22 gauge needle.
complex arches radially and blends with part of the radioscaphocapitate
complex to form the arcuate ligament.
MOVEMENTS AND LOADING OF THE WRIST JOINT
Ulnotriquetral (ulnar collateral) ligament The ulnotriquetral
ligament arises from the palmar aspect of the ulna, inserts into the Movements of the wrist (carpal kinematics)
medial aspect of the triquetrum, and continues distally to a further
attachment to the medial aspect of the hamate. The ulnolunate and
The movements at the radiocarpal and intercarpal joints are consid-
ulnotriquetral ligaments are also attached to the marginal ligament of
ered together. The approximate ranges of active movement are flexion
the triangular fibrocartilage complex.
(85°), extension (85°), adduction (ulnar deviation) (45°), abduction
Extrinsic dorsal carpal ligaments (radial deviation) (15°) and circumduction (all measurements are
approximate).
The dorsal wrist ligaments are comparatively thin and are reinforced by


The range of flexion is greater at the radiocarpal joint, while in exten-
the floor and septa of the fibrous tunnels for the six dorsal compart-
sion there is more movement at the midcarpal joint (Fig. 50.19). Hence,
ments. The extrinsic dorsal carpal ligaments and the intrinsic dorsal
the proximal surfaces extend further posteriorly on the lunate and
intercarpal ligaments have a ‘Z’-shaped configuration (see Fig. 50.17C).
scaphoid bones. These movements are limited chiefly by antagonistic
muscles; therefore, the range of flexion is perceptibly diminished when
Dorsal radiolunotriquetral ligament The dorsal radiolunotri-
the fingers are flexed, due to increased tension in the extensors. Only
quetral ligament has superficial and deep components. The superficial
when the joints are forced to the limits of flexion or extension are the
part connects the radius and triquetrum, and the deep part connects
dorsal or palmar ligaments fully stretched.
the radius, lunate and triquetrum. The wide superficial component
During extension of the wrist, the distal carpal bones rotate into
arises from the dorsal margin of the distal radius and courses ulnar-
extension with slight radial deviation, while during the ‘dart-throwing’
wards to insert on the dorsal edge of the triquetrum. The deep compo-
movement (from radial deviation and extension into ulnar deviation
nent takes a narrower origin from the ulnar aspect of the distal dorsal
and flexion), movement occurs almost entirely at the distal row of the
radius and passes in an ulnar direction to attach to part of the lunotri-
carpus.
quetral articulation and the intrinsic lunotriquetral ligament.
Most adduction occurs at the radiocarpal joint. The lunate articu-
Intrinsic ligaments lates with both the radius and articular disc when the hand is in the
midposition but, in adduction, it articulates solely with the radius, and
The intrinsic ligaments of the wrist are attached to carpal bones (see
the triquetrum now comes into contact with the articular disc (Fig.
Fig. 50.17B). They are stronger and shorter than extrinsic ligaments and


50.20A). Much of the proximal articular surface of the scaphoid
are connected with the extrinsic ligament complexes by interdigitating
becomes subcapsular beneath the radial collateral ligament and forms
fibres. The intrinsic ligaments are subdivided into ligaments that
a smooth, convex, palpable prominence in the floor of the ‘anatomical
connect the carpal bones of the proximal and distal rows, respectively,
snuff-box’.
and ligaments that connect the rows by crossing over the midcarpal
Abduction from the neutral position occurs at the midcarpal joint.
joint.
Radiographs of abducted hands show that the capitate rotates round an
anteroposterior axis so that its head passes medially and the hamate
Proximal row interosseous ligaments The scapholunate and
conforms to this; the distance between the lunate and the apex of the
lunotriquetral ligaments are clinically and biomechanically important
hamate is increased (Fig. 50.20B). The scaphoid rotates around a trans-
structures. In the sagittal plane, they have an approximately horseshoe-
verse axis, and its proximal articular surface moves away from the
shape configuration with palmar, midcarpal and dorsal components.
capsule to articulate solely with the radius. Movements are limited
The scapholunate ligament contains short transverse fibres connecting
by antagonistic muscles and, at extremes, by the carpal collateral
the dorsal aspect of the respective bones and more obliquely orientated
ligaments.
fibres connecting the palmar aspect. The tighter dorsal component of
The proximal row (scaphoid, lunate and triquetrum) is an inter-
the ligament acts as a hinge facilitating flexion and extension of the
calated segment; no tendons insert on to the bones of the row. It is
scaphoid. The ligament continues in its midcarpal section as an inter-
inherently unstable and controlled by specific retaining and gliding
osseous membrane. The lunotriquetral ligament has similar dorsal,
ligaments. Its relative position is determined by the spatial configura-
midcarpal interosseous and palmar components, but the fibres of the
tions of the radius, triangular fibrocartilage complex and ulna on one
dorsal and palmar components are similarly orientated, which pre-


side, and the rigid distal carpal row on the other. The proximal carpal
cludes the same pattern of preferential movement as occurs between
row is subject to two opposing moments: the scaphoid straddles the
the lunate and scaphoid. The interosseous membranes of the scapholu-
proximal and distal rows and tends to rotate the proximal row into
nate and lunotriquetral ligaments separate the midcarpal from the
flexion under axial load and radial deviation. At the same time, there
radiocarpal joint spaces. Dye injected into one of these joint spaces that
is a force tending to extend the proximal row, which is initiated by the
leaks to the other denotes a tear of one of these ligaments.
distal row and transmitted via the midcarpal ligaments to the tri-
quetrum (Fig. 50.21). Stability of the midcarpal joint is thus ensured
Distal row interosseous ligaments The strong distal row inter-
during both movement and loading.
osseous ligaments connect and stabilize the capitate, hamate, trapezium
The distal carpal row (trapezium, trapezoid, capitate and hamate)
and trapezoid. They have superficial and deep components, and, unlike
can be regarded as one rigid structure. The scaphoid bridges the proxi-
the ligaments of the proximal row, are seldom torn.
mal and distal carpal rows and provides a functional couple between
the two.
Palmar midcarpal ligaments The fan-shaped palmar
scaphocapitate–trapezoid ligament arises from the scaphoid. It has two Muscles producing movements
parts, the scaphotrapeziotrapezoidal ligament and the more ulnar Flexion Flexors carpi radialis and ulnaris and palmaris longus produce
scaphocapitate ligament. The triquetrohamate and triquetrocapitate flexion, assisted by flexors digitorum superficialis and profundus, and
ligaments lie towards the ulnar side of the carpus. flexor pollicis longus.
Dorsal midcarpal ligaments The dorsal intercarpal ligament Extension Extensors carpi radialis longus, brevis and ulnaris, assisted


assists in stabilization of the proximal carpal row. It arises from the by extensors digitorum, digiti minimi, indicis and pollicis longus,
trapezoid and distal pole of scaphoid, and passes across the dorsal horn produce extension.
of the lunate to be attached to the triquetrum. The ligament forms the
floor of the fourth and fifth extensor compartments. The lateral scapho- Adduction (ulnar deviation) Flexor and extensor carpi ulnaris produce
trapeziotrapezoidal ligament is on the radial side. adduction.


Wrist and hand
874.e1
05
RETPAHC
A B C
Third metacarpal Fifth metacarpal
First metacarpal
Second metacarpal
Trapezium
Capitate
Hamate
Trapezoid
Scaphoid
Lunate Pisiform Triquetrum
Radius Radius
Ulna
Palmar Dorsal
Load Tension developing in Direction of rotation
constraining ligaments
Fig. 50.21 The effect of axial loading on the rotatory movements of the bones of the wrist. A, The scaphoid flexes but is constrained on its palmar
aspect by the scaphotrapeziotrapezoidal ligaments and dorsally by the scapholunate ligament. B, The lunate follows the scaphoid into flexion and is
restrained by the dorsal radiolunate ligament. C, The triquetrum flexes with the scaphoid and lunate; it is constrained on its palmar aspect by the
triquetrohamate and triquetrocapitate ligaments, and dorsally by the radiotriquetral ligament.
There are five possible dorsal portals (1–2, 3–4, 4–5, 6–R, 6–U) for The carpus was originally thought to move simply as proximal and
viewing the radiocarpal joint and two (MCR, MCU) for the midcarpal distal rows (row or rigid body theory) (Johnston 1907). According to
joint. These are named by their relation to the six extensor compart- this view, during the composite movement of wrist flexion and exten-
ments. The 1–2 portal is usually avoided because the radial artery lies sion, approximately two-thirds of movement occurs at the radiocarpal
a mean 3 mm (range 1–5 mm) radially, as do branches of the super- joint and one-third at the midcarpal joint. The carpus was later judged
ficial radial nerve (range 1–6 mm) (Abrams et al 1994). The 3–4 portal to move in lateral central and medial columns more than it did in rows,
is normally used as the main viewing portal and the 4–5 portal for and the radius–lunate–capitate was described as a three-bar linkage


instrumentation. The dorsal cutaneous branch of the ulnar nerve lies system (column theory) (Navarro 1921). This theory was modified
within 2.5 mm of the 6-R portal. Inflow is via the arthroscope (in the (Taleisnik 1976) to incorporate the specific stabilizing role of the
3–4 portal) and outflow through a separate 6–U portal. The articular scaphoid as it bridges the proximal and distal rows. A further theory
surfaces of the scaphoid and lunate are seen distally, linked by the proposed that the bones were linked by their ligaments in a ring con-
scapholunate ligament. Proximally, the triangular fibrocartilage complex figuration, so that any breakage of the key links leads to instability (ring
may be viewed. Tears of its central portion are commonly seen in older theory). Most recently, the ‘four-unit’ theory suggests that the distal
patients; congenital perforations are occasionally found. Bucket handle carpal row moves as a single unit, and the scaphoid, lunate and tri-
tears of the triangular fibrocartilage complex may be excised, or repaired quetrum move in complex but characteristic relationships that are
if they occur in the peripheral vascularized portion. The radial midcar- dependent on the given movement. Clinical observation provides some
pal portal is used to view the scaphocapitate joint. The ulnar midcarpal support for each of these theories.
portal is used for instrumentation and for viewing the ulnar portion of
the midcarpal joint.
Volar portals (radial, VR, midcarpal, VMC and ulnar, VU) are less
favoured but retain certain advantages, including the ability to view the
dorsal capsule, the dorsal radiocarpal ligament and the palmar sub-
regions of the scapholunate and lunotriquetral interosseous ligaments.
Use of the volar radial portal carries with it the potential for damage to
flexor carpi radialis, the palmar cutaneous branch of the median nerve
and the lateral cutaneous nerve of the forearm, all of which can run
close to, but not within 3 mm of, the portal. The volar ulnar portal lies
more than 5 mm away from the ulnar neurovascular bundle, provided


the entry point in the capsule is deep to the ulnar edge of the profundus
tendons (Slutsky 2002).


Joints
875
05
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1 2
A
A
3 4
1 2
B
3 4
1 2
B
Fig. 50.20 A, A radiograph of the hand in full adduction (ulnar deviation):
dorsopalmar projection. The arrows point to the scaphoid on the radial
side and to the pisiform on the ulnar side. Compare with B and observe
that the movements occur at both the radiocarpal and intercarpal joints.
B, A radiograph of the same hand in full abduction (radial deviation). The
arrows point to the hamate and pisiform. Compare with A and note that:
the scaphoid and lunate have passed medially (ulnarly) so that the latter
articulates to a large extent with the articular disc of the distal radio-ulnar
joint; the pisiform is now widely separated from the styloid process of the
ulna; the scaphoid, having rotated round a transverse axis, is much
foreshortened; the apex of the hamate has been thrust away from the
lunate by the rotation of the capitate around an anteroposterior axis; a
gap has opened up between the distal portions of the hamate and
triquetrum; and the long axes of the capitate and lunate are now almost
C in the same straight line.
3 4
carpi ulnaris. During radial and ulnar deviation, extensor carpi radialis
Fig. 50.19 A, A radiograph of the hand and wrist in full flexion: lateral
longus and extensor carpi ulnaris have a greater excursion, whereas that
aspect. Compare with B, and note the relative positions of the capitate
of flexor carpi radialis is relatively small. The axes of rotation for flexion/
and lunate, and the lunate and radius. B, A radiograph of the hand and
wrist: lateral aspect. The long axes of the third metacarpal, capitate and extension and radial/ulnar deviation intersect at a point in the proximal
lunate are, approximately, in line with the long axis of the radius. Note the part of the capitate bone. Flexor carpi radialis and flexor carpi ulnaris


relative positions of the capitate and lunate, and the lunate and radius. are most efficient in flexion, extensor carpi radialis brevis in extension,
C, A radiograph of the hand and wrist in full extension: lateral aspect. extensor carpi radialis longus in radial deviation and extensor carpi
Compare with B and note the alterations in the relative positions of the ulnaris in ulnar deviation (Horii et al 1993).
capitate and lunate, and the lunate and the radius. Key: 1, capitate; 2,
lunate; 3, tubercle of the trapezium; 4, tubercle of the scaphoid. Loading of the wrist (carpal kinetics)
Abduction (radial deviation) Flexor carpi radialis, extensors carpi radi- Axial loading, i.e. load or force applied along a line parallel to the long
alis longus and brevis, with abductor pollicis longus and extensor pol- bones of the arm, occurs in clenching the fist. In most activities, loading
licis brevis, produce abduction. is multiplanar with a combination of vectors of force. Grasping an
Flexor carpi ulnaris is stronger than extensor carpi ulnaris, which, in object whilst lifting it against gravity with the elbow in flexion causes
turn, is stronger than extensors carpi radialis longus and brevis, and transverse and axial loading.
flexor carpi radialis. The other muscles are all weaker. It is for this reason
Force transmission
that these muscles tend to be selected for the major tendon transfers
around the wrist (Brand 1985). During flexion and extension, flexor Radiocarpal joint
carpi radialis, flexor carpi ulnaris and extensor carpi radialis brevis have The radiocarpal and ulnocarpal articulations can be described in terms
a greater excursion than extensor carpi radialis longus and extensor of specific fossae, namely: the scaphoid and lunate fossae of the radius,


WRiST And HAnd
876
6
nOiTCES
and the facet formed by the distal aspect of the triangular fibrocartilage Carpometacarpal joint of the thumb
complex. The scaphoid fossa contributes 43%, the lunate fossa 46%,
and the triangular fibrocartilage complex 11% of the total area of this Articulating surfaces The carpometacarpal joint of the thumb is a
articulating surface. Under physiological conditions, the contact area
sellar (saddle) joint between the first metacarpal base and trapezium.
between this surface and the proximal carpal row is about 20%. Greater
Its extensive articular surfaces and their topology ensure that the joint
contact is seen in forearm supination, radial deviation and dorsiflexion
enjoys a wide mobility.
of the wrist. Lesser contact occurs in forearm pronation, ulnar deviation
and palmar flexion of the wrist. Axial loading increases the contact area Ligaments The first metacarpal and trapezium are connected by
to a maximum of about 40%. Force across the joint also varies with the
lateral, anterior and posterior ligaments and a fibrous capsule. The
position of the forearm and the degree of wrist flexion. For a given load
broad lateral ligament runs from the lateral surface of the trapezium
in wrist-neutral position, 50% of force passes across the scaphoid fossa,
to the radial side of the metacarpal base. The palmar and dorsal liga-
35% through the lunate fossa and 15% across the triangular fibrocarti-
ments are oblique bands that converge to the ulnar side of the meta-
lage complex. With a power grip, there is slight ulnar deviation and the
carpal base from the palmar and dorsal surfaces of the trapezium,
proportion of force passing across the scaphoid and lunate fossae
respectively.
reverses.
Synovial membrane The synovial membrane lines the joint capsule
Midcarpal joint and is separate from it.
With the wrist in neutral position, 50–60% of a given load is transmit-
ted from the distal row through the capitate to the scaphoid and lunate. Joint movements Except at initiation, flexion is accompanied by


Up to 30% of the load is transmitted via the scaphotrapeziotrapezoid medial rotation, and medial rotation involves flexion. Linkage of move-
joint and up to 20% via the hamate–triquetral joint. ments is due largely to the shape of the articular surfaces and to the
obliquity of the dorsal ligament (which, when taut, anchors the ulnar
distal radio-ulnar joint (dRUJ) side of the metacarpal base while its radial side continues to move).
Contraction of flexor pollicis brevis, assisted by opponens pollicis, pro-
See page 845.
duces medial rotation with flexion; combined with abduction, this
opposes the thumb pulp to the pulps of the slightly flexed fingers. Full
Specific actions extension of the thumb metacarpal entails slight lateral rotation, attrib-
utable to the saddle shape of the joint and to the action of the palmar
ligament (which is similar to that of the dorsal ligament in flexion).
See Video 50.1.
(For further reading, see Edmunds (2011), Ladd et al (2013).)
Power grip Muscles producing movements The muscles producing move-
In power grip, the wrist is positioned in mid-dorsiflexion and the object ments at the carpometacarpal joint of the thumb are as follows.
is tightly gripped. Force is transmitted from the hand and wrist via the
radiocarpal joint and triangular fibrocartilage complex to both bones Flexion Flexion is produced by flexor pollicis brevis and opponens
of the forearm, through the elbow joint to the humerus, and from there, pollicis, aided by flexor pollicis longus when the other joints of the
via the glenohumeral joint, to the pectoral girdle. Dynamic muscle thumb are flexed.
action accounts for transmission of a large part of the force; a smaller
proportion is transmitted through the osseoligamentous structures. The Extension Extension is produced by abductor pollicis longus and exten-
distribution of force between the radius and ulna varies dynamically sors pollicis brevis and longus.
and depends on the absolute value of load, degree of forearm rotation


and position of the carpus relative to the forearm. Abduction Abduction is produced by abductors pollicis brevis and
longus.
Hammer action
Adduction Adduction is produced by adductor pollicis.
The action exemplified by hammering, where the wrist alternates
between the dorsoradial and the palmar–ulnar position, is an impor-
Opposition Opponens pollicis and flexor brevis pollicis simultaneously
tant movement for a wide variety of activities. It is believed that load
flex and medially rotate the abducted thumb. Interpulpal pressure, or
distributes dynamically as the position of the carpus moves relative to
that generated by digital grasping, is increased by adductor pollicis and
the forearm and there are consequent changes in the relative position
flexor pollicis longus.
of the carpal bones.
Circumduction Circumduction is produced by extensors, abductors,
Carpal instability flexors and adductors acting consecutively in this, or reverse, order.
Second to fifth carpometacarpal joints
The upper limb has evolved to facilitate the placing of the hand in space
for prehension. However, mobility of the hand on the forearm has
evolved at the expense of stability. A wrist is said to be kinetically un- The second to fifth carpometacarpal joints are synovial ellipsoid joints
stable when it cannot bear physiological loads without giving way or between the carpus and second to fifth metacarpals. Although widely
causing injury. A wrist is kinematically unstable when it exhibits sudden classed as plane, they have curved articular surfaces that are often of
changes in carpal alignment, i.e. during a specific movement, there is a complex saddle shape. The bones are united by articular capsules and
‘clunk’ as one or more of the carpal bones moves abnormally with by dorsal, palmar and interosseous ligaments.
respect to the others. Stability of the various joints, so that the bones
maintain normal anatomical relations with respect to each other Ligaments The dorsal ligaments are the strongest, and connect the
throughout the normal range of motion, is essential for physiological dorsal surfaces of the carpal and metacarpal bones. The second meta-
load-bearing. carpal has two ligaments, from the trapezium and trapezoid; the third


has two, from the trapezoid and capitate; the fourth has two, from the
capitate and hamate; and the fifth has a single band from the hamate,
CARPOMETACARPAL JOINTS which is continuous with a similar palmar ligament, forming an incom-
plete capsule.
The first carpometacarpal joint (CMCJ), or basal joint of the thumb, is The palmar ligaments are similar, except that the third metacarpal
a saddle joint that permits opposition of the thumb. The second to fifth has three: a lateral from the trapezium, superficial to the tendon sheath
carpometacarpal joints exhibit an increasing range of movement, pro- of flexor carpi radialis, an intermediate from the capitate, and a medial
gressing from the radial to the ulnar side. Thus, there is little mobility from the hamate.
at the base of the index ray but considerable mobility at the base of the The interosseous ligaments consist of two short, thick, fibrous bands.
small finger ray, which facilitates ‘cupping’ of the palm of the hand. They are limited to one part of the carpometacarpal articulation and
Compressive forces between the metacarpals and the distal carpal row connect contiguous distal margins of the capitate and hamate with
are estimated to be upwards of ten times the forces at the tips of the adjacent surfaces of the third and fourth metacarpal bones; they may
fingers during ‘pinch’ or ‘chuck’ grip. be united proximally.


Wrist and hand
876.e1
05
RETPAHC
Some degree of carpal instability may occur as part of inherent
hypermobility in affected individuals. Usually, it occurs only after
rupture or attenuation of intrinsic and extrinsic carpal ligaments and
may be detected either clinically or radiologically as malalignment of
the carpal bones (Fig. 50.22). In theory, any pattern of traumatic carpal
instability is possible. In practice, certain patterns predominate.
When axially loaded, the distal row of the carpus compresses the
proximal row, causing the scaphoid to rotate into flexion and prona-
tion. Provided the scapholunate and lunotriquetral ligaments remain
intact, the load is transmitted to the lunate and triquetrum. If the mid-
carpal stabilizers are disrupted, the proximal row of the carpus will be
loaded into flexion, producing the characteristic pattern of volar inter-
calated segment instability (VISI). In the proximal row, the scaphoid
exhibits the greatest range of movement, the lunate less and the tri-
quetrum the least. Consequently, the scapholunate and lunotriquetral
ligaments tighten as the scaphoid is progressively flexed, thereby
increasing the intrinsic stability of the proximal row. If, however, the
scapholunate ligaments have been disrupted (scapholunate dissocia-
tion), the scaphoid can flex excessively and loading of the lunate and
triquetrum by the distal row of the carpus will force them into abnor-
mal extension (dorsal intercalated segment instability, or DISI).
A
B
Fig. 50.22 Scapholunate dissociation. A, Anteroposterior view. B, Lateral
view. Dissociation between the scaphoid and lunate, as shown here,
leads to collapse of the scaphoid into flexion and the lunate into
extension (dorsal intercalated segment instability, or DISI), thus removing
the inbuilt tension across the proximal row. This causes the gap between
the scaphoid and lunate in A.


Joints
877
05
RETPAHC
Synovial membranes The synovial membranes are often continu- Distal interphalangeal joint
ous with those of the intercarpal joints. Occasionally, the joint
between the hamate and fourth and fifth metacarpal bones has a Proximal interphalangeal joint
separate synovial cavity, bounded laterally by the medial interosseous
ligament and its extensions to the palmar and dorsal parts of
the capsule.
Proximal phalanx Middle phalanx Distal phalanx
Muscles producing movements Slight gliding movements are
effected by the long flexor and extensor muscles of the digits.
Collateral ligament
(cord-like part)
INTERMETACARPAL JOINTS
Collateral ligament
(fan-like part)
Articulating surfaces The second to fifth metacarpal bases articu-
late reciprocally by small cartilage-covered facets connected by dorsal,
Volar plate
palmar and interosseous ligaments.
Fibrous capsule The intermetacarpal joints have fibrous capsules. Metacarpal
Ligaments The dorsal and palmar ligaments pass transversely from
bone to bone. The interosseous ligaments connect contiguous surfaces
just distal to their articular facets.
Synovial membranes The synovial membranes are continuous
with those of the carpometacarpal articulations.
Movements at the carpometacarpal and intermetacarpal
joints Movements at the carpometacarpal and intermetacarpal articu- Fig. 50.23 The metacarpophalangeal and digital joints of the left third
finger: medial aspect.
lations are limited to slight gliding, sufficient to permit some flexion–
extension and adjunct rotation; ranges vary in different joints. They are
partly accessory movements occurring when the palm is ‘cupped’, as in
grasping an object. The fifth metacarpal is most movable and the second
and third are the least mobile. These variations are easily demonstrated Collateral ligaments The collateral ligaments are strong, round cords
by opposing each digit to the thumb over the palmar centre. About that flank the joints. Each is attached to the posterior tubercle and
two-thirds of the movements are those of the thumb, as described adjacent pit on the side of its metacarpal head, and each passes disto-


above, but during opposition, the carpometacarpal and metacarpal anteriorly to the side of the anterior aspect of its phalangeal base
joints of the little finger become flexed, abducted and laterally rotated, (Fig. 50.23).
accounting for the remaining third of the movement. The close-packed
position probably coincides with carpal extension. A further accessory Synovial membrane The metacarpophalangeal joints are lined by
movement is spiral twisting of the whole metacarpus on the carpus. a synovial membrane.
Muscles producing movements The flexors and extensors of the Joint movements These include flexion, extension, adduction,
second to fifth digits move the carpometacarpal and intermetacarpal abduction, circumduction and limited rotation. Rotation accompanies
joints. flexion–extension, e.g. when the finger flexes and rotates to place its tip
near the centre of the palm. The range of rotation is frequently increased
as a result of the resistance of a grasped object. Active flexion is 90° or
METACARPOPHALANGEAL JOINTS more, whereas extension ranges from 10° (index) to 30° (little); both
movements are limited mostly by antagonistic muscles. The metacarpo-
The metacarpal heads are adapted to shallow concavities on the phalangeal joint of the thumb has a flexion–extension range of approxi-
phalangeal bases; they are not regularly convex but are partially mately 60°, which is almost entirely flexion. Slight lateral rotation
divided on their palmar aspects and, thus, almost bicondylar. accompanies digital flexion of digits 3–5. Flexion of the index finger
may be accompanied by minimal lateral rotation or no rotation; a small
Fibrous capsule The metacarpophalangeal joints all have fibrous degree of medial rotation is frequently observed. Other movements are
capsules. adduction–abduction (maximal range 25°), which invariably accom-
panies the corresponding carpometacarpal movements and increases
Ligaments Each metacarpophalangeal joint has a palmar and two their combined range; and slight rotation, which accompanies flexion–
collateral ligaments. extension. Of the second to fifth metacarpophalangeal joints, the


second is most mobile in adduction–abduction (approximately 30°),
Palmar ligaments The palmar ligaments (volar plates) are unusual. followed by the fifth, fourth and third.
They are thick, dense and fibrocartilaginous, and are sited between, and
connected to, the collateral ligaments. They are attached loosely to the Accessory movements Accessory movements are further rotation
metacarpals but firmly to the phalangeal bases. Their palmar aspects (most marked in the thumb), anteroposterior and lateral translation of
are blended with the deep transverse palmar ligaments and are grooved a phalanx or metacarpal, and distraction.
for the flexor tendons, whose fibrous sheaths connect with the sides of
the grooves. Their deep surfaces increase articular areas for the metacar- Muscles producing movements The muscles producing move-
pal heads. ments at the metacarpophalangeal joints are as follows.
Deep transverse metacarpal ligaments The deep transverse metacar- Flexion Flexion is produced by flexors digitorum superficialis and pro-
pal ligaments are three short, wide, flat bands that connect the palmar fundus, assisted by the lumbricals, interossei and flexor digiti minimi
ligaments of the second to fifth metacarpophalangeal joints. They are brevis (in the little finger). In the thumb, flexors pollicis longus and
related anteriorly to the lumbricals and digital vessels and nerves, and brevis, and the first palmar interosseous, are involved.
posteriorly to the interossei. Bands from the digital slips of the central
palmar aponeurosis join their palmar surfaces. On both sides of the Extension Extension is produced by extensor digitorum, assisted in the
third and fourth metacarpophalangeal joints, but only the ulnar side of second and fifth digits by extensor indicis and extensor digiti minimi,
the second and radial side of the fifth joints, transverse bands of the respectively. In the thumb, extensors pollicis longus and brevis are
dorsal digital expansions join the deep transverse metacarpal ligaments. involved.
The lumbricals and the phalangeal attachments of the dorsal interossei


lie anterior to this band; the remaining attachments of the dorsal and Adduction In extended fingers, adduction is produced by the palmar
palmar interossei are posterior to it (see Fig. 50.29). interossei; the long flexors are predominant during flexion. In the


WRiST And HAnd
878
6
nOiTCES
thumb, limited metacarpophalangeal adduction is possible and may be arteries pass underneath these check ligaments to reach the vinculae
attributable to adductor pollicis and the first palmar interosseous. (see Fig. 50.24).
Abduction In extended fingers, abduction is produced by the dorsal Collateral ligaments The collateral ligaments pass from the lateral
interossei, assisted by the long extensors (except in the middle finger), aspect of the head of one phalanx to the volar aspect of the base of the
and abductor digiti minimi in the minimus. In the thumb, abductor adjacent phalanx. An accessory component to the collateral ligament
pollicis brevis (which also contributes to opposition) is involved. When arises in continuity with the main ligament and passes in a volar direc-
the fingers are flexed at the interphalangeal joints, active abduction is tion to attach to the volar plate.
restricted (it is virtually zero when metacarpophalangeal and inter-
phalangeal joints are flexed); if the long digital flexors are inactive, Synovial membrane Each interphalangeal joint has a synovial
passive abduction is free. Inability to abduct actively in this position lining.
may be due to shortening of the dorsal interossei and abductor digiti
minimi by flexion, but the altered line of pull of the interossei relative Factors maintaining stability Stability is conferred by the articular
to the axis of movement is probably the determining factor. contours of the joint surfaces and the collateral ligaments. The flexor
and extensor tendons and retinacular ligaments provide secondary sta-
Gamekeeper’s thumb bilization. Stability against hyperextension of the proximal interphalan-
geal joint is enhanced by the three-dimensional box arrangement that
Available with the Gray’s Anatomy e-book is produced by the collateral ligament–volar plate complex.
Joint movements Active movements at the interphalangeal joints
INTERPHALANGEAL JOINTS are flexion and extension, and are greater in range at the proximal
joints. Flexion is considerable, whereas extension is limited by tension


The interphalangeal joints are uniaxial hinge joints (see Fig. 50.23). of the digital flexors and terminated by tension in the palmar ligaments
and non-articular compression. Full extension is the close-packed posi-
Fibrous capsule Each interphalangeal joint has a fibrous capsule. tion. Flexion and extension are accompanied by slight rotation; during
flexion, this turns the digital pulps slightly laterally, i.e. to face the
Ligaments Each interphalangeal joint has a palmar ligament (the opposed thumb, and an opposite rotation occurs during extension.
volar plate) and two collateral ligaments (Fig. 50.24). The long extensor
tendons take the place of the dorsal capsular ligaments. Extensions from Accessory movements Accessory movements are limited rotation,
the extensor expansion, each collateral ligament and the palmar liga- abduction, adduction and anteroposterior translation. They permit the
ment all pass into the joint cavity and provide a significant increase to fingers to adapt to the shapes of gripped objects and help to protect
the articular surface area of the phalangeal base; their deformable against stresses and strains.
nature improves joint congruence.
Muscles producing movements The muscles producing move-
Palmar ligament (volar plate) The volar plate constitutes the floor of ments at the interphalangeal joints are as follows.
the interphalangeal joint. In the proximal interphalangeal joint, the
distal end of the volar plate is thickened laterally where it is firmly Flexion Flexion is produced at the proximal interphalangeal joints by
attached to the base of the middle phalanx at the position of the true the flexors digitorum superficialis and profundus; at distal interphalan-
collateral ligament attachment. Centrally, it is more delicate and blends geal joints, by flexor digitorum profundus; and at the thumb inter-
with the volar periosteum of the middle phalanx. Proximally, the volar phalangeal joint, by flexor pollicis longus.
plate is also very delicate in its central portion, but it is thickened lat-
erally to form the ‘check rein ligaments’, which attach to the periosteum Extension Extension is produced by extensors digitorum, digiti minimi


of the proximal phalanx just within the walls of the A2 pulley compo- and pollicis longus, in association with abductor pollicis longus and
nent of the fibrous flexor sheath. Nutrient branches of the digital extensor pollicis brevis. Extension occurs simultaneously in both joints
in digits 2–5.
Simultaneous flexion at the metacarpophalangeal joints and exten-
sion at the interphalangeal joints of a digit are essential for the fine
movements of writing, drawing, threading a needle, etc. The lumbricals
and interossei are primary agents in flexing the metacarpophalangeal
A4 pulley
joints and also in extending the interphalangeal joints via their attach-
ments to the dorsal digital expansions.
A3 pulley
Mallet finger
Accessory collateral Available with the Gray’s Anatomy e-book
Blood vessel supplying ligament
tendon via vincula brevum
Swan neck deformity
Collateral ligament
C1 pulley of proximal inter-
phalangeal joint Available with the Gray’s Anatomy e-book
Volar plate
Boutonnière deformity
Available with the Gray’s Anatomy e-book
A2 pulley
VASCULAR SUPPLY OF THE JOINTS OF THE WRIST
AND HAND
The radiocarpal joint is supplied by branches of the anterior inter-
osseous artery, anterior and posterior carpal branches of the radial and
Metacarpophalangeal joint
ulnar arteries, palmar and dorsal metacarpal arteries, and recurrent rami
of the deep palmar arch. The carpal joints are supplied by the posterior
carpal branches of the radial and ulnar arteries, and by the anterior
interosseous artery. The carpometacarpal joint of the thumb receives its
Fig. 50.24 Anatomy of the volar plate at a proximal interphalangeal joint. blood supply from the radial artery and its first dorsal metacarpal
The blood vessel supplying the flexor tendons via the vincula brevum is branch. The second to fifth carpometacarpal joints are supplied by the
shown; the mesentery forming the vinculum has been omitted. posterior carpal branches of the radial and ulnar arteries, by twigs from


Wrist and hand
878.e1
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RETPAHC
The ulnar collateral ligament of the metacarpophalangeal joint of the Mallet finger is a traumatic rupture, avulsion fracture or laceration of
thumb may be avulsed from its distal attachment to the base of the the terminal slip of the extensor tendon to the terminal phalanx of the
proximal phalanx by a combination of forced extension and radial finger that can result from forced flexion of the distal phalanx of the
deviation of the joint. The injury was reported to occur in gamekeepers fully extended finger; it is a well-known injury in cricketers. The patient
while breaking the necks of game, but can occur following simple falls is unable to extend the terminal phalanx actively, although the distal
on to the outstretched hand, especially in skiers who have the straps of interphalangeal joint can be extended passively.
ski poles wrapped around their thumbs.
The ulnar collateral ligament is normally covered by the aponeurotic Swan neck deformity involves hyperextension of the proximal inter-
insertion of the tendon of adductor pollicis. Following avulsion, the phalangeal joint, together with distal interphalangeal joint flexion,
proximal end can become superficially displaced around the proximal caused by relative overactivity of the extensors acting at the proximal
free edge of the aponeurotic insertion of the adductor. This soft tissue interphalangeal joint compared with the flexors. It arises as a result of
interposition prevents the ends of the avulsed ligament from healing. intrinsic muscle spasm, long-standing mallet finger or dysfunction of
If left untreated, a firm, palpable, inflammatory swelling occurs. Surgical flexor digitorum superficialis; it can only occur if there is also some
repair requires division of the aponeurotic insertion of adductor pol- laxity of the volar plate.
licis, followed by bony reattachment of the avulsed ligament and repair
of the aponeurosis. Boutonnière deformity is a flexion deformity of the proximal inter-
The comparable injury to the radial collateral ligament is less phalangeal joint following either division or laxity in the central slip of
common and constitutes only 10–42% of collateral ligament injuries the extensor tendon (which normally inserts into the base of the middle


(Edelstein et al 2008). It is caused by sudden, forced adduction of the phalanx). An essential feature is hyperextension at the distal inter-
metacarpophalangeal joint as the result of a fall or during ball games. phalangeal joint. The deformity usually occurs as a result of either
The ligament may be ruptured in its mid-substance or avulsed from trauma or rheumatoid arthritis, causing the lateral bands of the extensor
either bony attachment. Early identification is essential because the tendon to migrate in a volar direction and the head of the proximal
proximal phalanx of the thumb will subluxate ulnarwards and may phalanx to migrate dorsally. Initially, the deformity is passively correct-
rotate, leading to degeneration of the articular surface. Interposition of able, but, with time, the soft tissues around the joint contract and a
the torn or avulsed portion is uncommon because the adductor apo- fixed deformity results.
neurosis lies over the radial collateral ligament.


Muscles
879
05
RETPAHC
the anterior interosseous artery, and from the palmar digital arteries. just proximal and distal, respectively, to A3. At the distal interphalan-
The metacarpophalangeal joints receive their blood supply from the geal joint, there is one pronounced cruciate system, C3, which lies
dorsal and palmar metacarpal arteries, the arteria princeps pollicis, and between A4 and A5. Variations occur frequently. During flexion, the
the arteria radialis indicis. The interphalangeal joints are supplied by cruciate fibres become orientated more transversely in the digits, and
branches from the palmar digital arteries. the edges of adjacent anular pulleys approximate so that they form, in
full flexion, a continuous tunnel of transversely orientated fibres. Surgi-
cally, the most important pulleys that prevent bowstringing of the flexor
INNERVATION OF THE JOINTS OF THE WRIST tendons are the A2 and A4 pulleys.
AND HAND In the thumb, there are three constant pulleys: two anular and one
oblique (Fig. 50.26). The A1 pulley is located at the metacarpo-
phalangeal joint. The oblique pulley is located over the mid-portion of
The radiocarpal joint is innervated by the anterior and posterior inter-
the proximal phalanx and its fibres pass from the ulnar aspect proxi-
osseous nerves, with contributions from the median, ulnar and radial
mally to the radial aspect dorsally. The A2 pulley is thinner than the A1
nerves. The anterior interosseous nerve and posterior interosseous nerve
pulley and is situated just proximal to the interphalangeal joint. The
innervate the central two-thirds of the anterior and posterior wrist joint
oblique pulley is the most important pulley in the thumb for maintain-
capsule, including the radiocarpal joint. These appear to be pure affer-
ing the action of flexor pollicis longus.
ent nerve fibres with mechanoreceptor endings, of which there are an
average of 10 in each dorsal radiocarpal ligament (Tomita et al 2007). Synovial sheaths of the carpal flexor tendons


In the palmar radiocarpal ligaments, however, Golgi organs, Pacinian
Two synovial sheaths envelop the flexor tendons as they traverse the
corpuscles, Ruffini endings and free nerve endings are found (Petrie
carpal tunnel: one for flexors digitorum superficialis and profundus, the
et al 1997). An uneven distribution of these throughout the ligaments
other for flexor pollicis longus. These sheaths typically extend into the
would suggest specific functional adaptation but the precise nature of
forearm for 2.5 cm proximal to the flexor retinaculum and, occasion-
this is unclear. The carpometacarpal joint of the thumb is innervated
ally, communicate with each other deep to it. The sheath of the flexors
by articular twigs from the posterior interosseous nerve and the super-
digitorum tendons reaches about halfway along the metacarpal bones,
ficial branch of the radial nerve. The second to fifth carpometacarpal
where it ends in blind diverticula around the tendons to the index,
joints are innervated by branches of the ulnar nerve, the anterior inter-
middle and ring fingers (see Fig. 50.25). The sheath is prolonged
osseous, and the superficial radial and dorsal ulnar nerves. The meta-
around the tendons to the little finger and is usually continuous with
carpophalangeal joints are innervated by twigs from the palmar digital
their digital synovial sheath. A transverse section through the carpus
branches of the median and ulnar nerve, the deep terminal branch of
shows that the tendons are invaginated into the sheath from the lateral
the ulnar nerve, and the posterior interosseous nerve. The interphalan-
side (Fig. 50.27). The parietal layer lines the flexor retinaculum and the
geal joints are innervated by the palmar digital branches of the median
floor of the carpal tunnel, and is reflected laterally as the visceral layer
nerve (to the thumb, index, middle and ring fingers), and the ulnar
over the tendons of flexor digitorum superficialis ventrally and flexor
nerve (to the ring and little fingers).


digitorum profundus dorsally. Medially, a recess formed by the visceral
layer of the sheath insinuates between the two groups of tendons and
passes laterally for a variable distance. The sheath of flexor pollicis
MUSCLES longus, which is usually separate, is continued along the thumb as far
as the insertion of the tendon.
EXTRINSIC LONG FLEXORS AND EXTENSORS
Vincula
The extrinsic long flexors and extensors are described on pages 848– The phenomenon of tendon gliding within a fibrous sheath requires a
855. The flexor and extensor retinacula are described on pages 863, 864. very specialized arrangement of the vascular supply. Folds of synovial
membrane containing a loose plexus of fascial fibres carry blood vessels
to the tendons at certain defined points. These folds, vincula tendi-
Long flexor tendon apparatus
num (Fig. 50.28), are of two kinds. Vincula brevia, of which there are Flexor tendon sheaths
two in each finger, are attached to the deep surfaces of the tendons near
The fibrous sheaths of the flexor tendons are specialized parts of the to their insertions. There is, thus, one vinculum brevium attaching
palmar fascia. Each finger has an osseo-aponeurotic tunnel that extends flexor digitorum profundus to the region of the distal interphalangeal
from midpalm to the distal phalanx. The thumb has a tunnel for flexor joint, and a more proximal vinculum deep to flexor digitorum super-
pollicis longus that extends from the metacarpal to the distal phalanx. ficialis at the proximal interphalangeal joint. Vincula longa are filiform;
The proximal border is, to some extent, a matter of definition because usually two are attached to each superficial tendon, one to each deep
the transverse fibres of the palmar aponeurosis may be considered to tendon.
be a part of the pulley system. The sheath consists of arcuate fibres that
arch anteriorly over bone, tendons (where the sheath is required to be Trigger finger
stiff) and the centres of joints (where a bucket-handle of arcuate fibres
is a mechanically favourable arrangement). In contrast, where the
Available with the Gray’s Anatomy e-book


sheath is required to fold to permit joint flexion, it consists of cruciate
fibres. These fibrous sheaths are lined by a thin synovial membrane that
Synovial sheaths of the carpal extensor tendons
provides a sealed lubrication system containing synovial fluid. The
synovial membrane extends from the distal phalanx to midpalm in the Six tunnels deep to the extensor retinaculum transmit the extensor
case of the index, middle and ring fingers, and further proximally in tendons, each containing a synovial sheath. The tendons of abductor
the case of the little finger (Fig. 50.25). The sheaths around the thumb pollicis longus and extensor pollicis brevis lie in a tunnel on the lateral
and little finger are continuous with the flexor sheaths in front of the side of the styloid process of the radius; there may be a separate synovial
wrist. The parietal synovial membrane is reflected on to the surface of sheath for each, or the tendon of the abductor may be double. The
the flexor tendon, forming a visceral synovium. tendons of extensors carpi radiales longus and brevis lie behind the
A standard nomenclature for the anular (A) and cruciform (C) styloid process; the tendon of extensor pollicis longus lies on the medial
pulleys is used (Doyle and Blythe 1975). The usual pattern is as follows side of the dorsal tubercle of the radius; the tendons of extensors digi-
(see Fig. 50.25). The A1 pulley is situated anterior to the palmar carti- torum and indicis lie in a tunnel on the medial side of the tubercle; the
laginous plate of the metacarpophalangeal joint and may extend over tendon of extensor digiti minimi lies opposite the interval between the
the proximal part of the proximal phalanx. The A2 overlies the middle radius and ulna; and the tendon of extensor carpi ulnaris lies between
third of the proximal phalanx. It is the strongest pulley and arises from the head and the styloid process of the ulna. The tendon sheaths of


well-defined longitudinal ridges on the palmar aspect of the phalanx. abductor pollicis longus, extensors pollicis brevis and longus, extensors
Its distal edge is well developed. A pouch or recess of synovium extends carpi radiales and extensor carpi ulnaris stop immediately proximal to
superficial to the free edge of the pulley fibres so that the free edge forms the bases of the metacarpal bones, while those of extensors digitorum,
a lip protruding into the synovial space. A3 is a narrow pulley lying indicis and digiti minimi are sometimes prolonged a little more distally
palmar to the proximal interphalangeal joint. A4 overlies the middle along the metacarpus.
third of the middle phalanx, and A5 overlies the distal interphalangeal
joint. The cruciate fibres are numbered in a slightly different manner. De Quervain’s tenovaginitis
C0 is palmar to the metacarpophalangeal joint. There are two cruciate
zones, C1 and C2, at the proximal interphalangeal joint, and they lie Available with the Gray’s Anatomy e-book


Wrist and hand
879.e1
05
RETPAHC
Trigger finger is a stenosing tenovaginitis that affects the fibrous flexor
sheaths of the fingers or thumb within the palm. The affected sheath
thickens and entraps the contained tendons, which become constricted
at the site of entrapment and bulge distal to it. This produces a distinct
nodule in the palm of the hand and the finger now snaps as the tendon
nodule passes through the constriction on flexing the finger. The cor-
responding extensor muscle is insufficiently powerful to extend the
affected finger, so the patient does this passively, accompanied by a
painful snap. Treatment frequently requires surgical division of the A1
pulley of the flexor sheath to relieve the stricture.
De Quervain’s tenovaginitis is a stenosing tenovaginitis of unknown
aetiology that occurs in the first dorsal compartment at the level of the
radial styloid. It involves the common extensor sheath containing
the tendons of abductor pollicis longus and extensor pollicis brevis.
There is palpable thickening of the tendon sheath with painful limita-
tion of extension of the thumb. Treatment frequently requires division
of the thickened sheath, care being taken to avoid the adjacent super-
ficial radial nerve; division of the sheath produces no functional
impairment.


WRiST And HAnd
880
6
nOiTCES
A B
Zone II Zone I
A1 A2 A3 A4 A5
C1 C2 C3
A5
C3
A4
C2
A3
C1
Synovial sheath
A2
Fibrous flexor sheath A1
Palmar digital artery
Palmar digital nerve
Arteria radialis indicis
First dorsal interosseous
Adductor pollicis Common synovial sheath
Variable palmar connection
between ulnar and
median nerves
Lateral palmar digital artery to thumb
Superficial palmar arch
Flexor pollicis brevis
Abductor digiti minimi
Recurrent branch of median nerve
Abductor pollicis brevis Deep branch of ulnar nerve
Guyon's canal
Flexor retinaculum
Palmar cutaneous branch
Palmar cutaneous branch of of ulnar nerve
median nerve Flexor carpi ulnaris
Ulnar nerve
Abductor pollicis longus and
Ulnar artery
extensor pollicis brevis
Flexor pollicis longus Palmaris longus
Flexor carpi radialis Median nerve
Radial artery
C
Fig. 50.25 Synovial sheaths of the tendons and fibrous flexor tendon
sheaths on the flexor aspect of the left wrist and hand. The synovial
sheaths are shown in blue. A, The lateral aspect, showing the anular and
cruciate pulleys of the flexor tendon sheath. B, The palmar aspect, showing
the synovial sheaths. Details of the anular and cruciate pulleys are shown
on the middle finger; the extension of the digital arteries and nerves to the
end of this finger have been omitted for clarity. C, Variation in the
5% 89% arrangement of the synovial sheaths to the digits.
Extensor tendon apparatus
in shape, with its base proximal. It receives the conjoined tendons of
The extensor digitorum tendons emerge through the fourth dorsal the interosseous and lumbrical muscles and is almost translucent
compartment on to the dorsum of the hand, where they are joined between its margins and the tendon of extensor digitorum. Transverse


together distally by a varying pattern of oblique interconnections, the fibres (the sagittal bands) pass to the volar plate and transverse meta-
juncturae tendinae. These typically pass in a distal direction from carpal ligaments, separating the phalangeal attachment of the dorsal
middle finger to index finger, and from ring finger to middle and little interosseous from the rest of the muscle, and the palmar interosseous
fingers. Proximal lacerations to the middle finger extensor tendon may from the lumbrical muscle. Injuries to the sagittal bands can lead to
result in only partial loss of extension because of these tendinous subluxation of the extensor tendon.
interconnections. The margins of the extensor expansions are thickened on the radial
At the level of the metacarpophalangeal joint, each extensor tendon side by the tendons of the lumbrical and interosseous muscles, and on
is held in a central position over the dorsum of the joint by a flat, the ulnar side either by the tendon of an interosseous alone or, in the
fibrous extensor expansion (Fig. 50.29). The expansion extends on to case of the fifth digit, by abductor digiti minimi.
the dorsum of the proximal phalanx of each digit, forming a movable The tendons of the interossei join the extensor expansion at the level
hood that moves distally when the metacarpophalangeal joint is flexed, of the proximal portion of the proximal phalanx, while the tendons of
and proximally when it is extended. Each extensor tendon blends with the lumbricals join the extensor mechanism further distally at the mid-
the extensor expansion along its central axis and is separated from the portion of the proximal phalanx. Their line of pull is anterior to the
metacarpophalangeal joint by a small bursa. The expansion is triangular axis of rotation at the metacarpophalangeal joint, but dorsal to the axis


Muscles
881
05
RETPAHC
Fig. 50.26 The flexor sheath of
the left thumb, showing the
anular and oblique pulleys. (From
Doyle JR, Blythe WF 1977
Anatomy of the flexor tendon
sheath and pulleys of the thumb.
J Hand Surg 2:149–51. With
permission from the American
A2
Society for Surgery of the Hand.)
Oblique pulley
Transverse head of
adductor pollicis
Deep head A1
flexor pollicis
brevis
Synovial sheath
of flexor pollicis
longus
Ulnar nerve and artery Palmaris longus Fig. 50.27 A transverse
section through the left wrist
Muscles of hypothenar eminence Muscles of thenar eminence at the level of the distal row
Median nerve of the carpus, showing the
muscle tendons (in grey)
Flexor pollicis longus and their synovial sheaths
Flexors digitorum Flexor carpi radialis (in green).
superficialis and profundus
Trapezium
Triquetrum
Hamate Abductor pollicis longus
Extensor pollicis brevis
Extensor carpi ulnaris
Trapezoid
Extensor digiti minimi
Cephalic vein
Dorsal branch of ulnar nerve Superficial radial nerve
Basilic vein Radial artery
Capitate
Extensors carpi radialis longus and brevis
Extensor pollicis longus
Extensor digitorum
Extensor indicis
Fig. 50.28 The tendons and vincula tendinum of
Transverse part of the index finger and the muscles in the first
adductor pollicis intermetacarpal space of the left hand: lateral
aspect.
Oblique part of
Flexor digitorum superficialis adductor pollicis
Vincula longa Extensor pollicis longus
Flexor digitorum profundus
Extensor pollicis brevis
Abductor pollicis brevis
Vincula brevia
Digital fibrous sheath
Dorsal extensor expansion
First lumbrical
First dorsal interosseous
Radial artery


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Extensor tendon
A B
Sagittal band
Metacarpophalangeal joint
Distal interphalangeal joint Transverse retinacular ligament
Distal interphalangeal joint
Triangular ligament
Oblique retinacular ligament
Oblique retinacular ligament
Proximal interphalangeal joint
Deep transverse
Proximal interphalangeal joint
intermetacarpal ligament
Central slip of extensor tendon Dorsal and palmar interossei
C Lumbrical
Lateral band
Dorsal and palmar interossei
Collateral ligament
Deep transverse
Metacarpophalangeal joint metacarpal ligament
Sagittal band
Lumbrical
Lumbrical
Transverse retinacular ligament
Oblique retinacular ligament
Palmar interosseous
Dorsal interosseous
Extensor tendon
Fig. 50.29 The extensor mechanism of the finger. A, Dorsal view. B, Lateral view. C, Lateral view in flexion.
of rotation at the proximal interphalangeal joint. The extensor mecha- unites with the superficial head on the sesamoid bone and base of the
nism trifurcates into a central slip and two lateral bands just proximal first phalanx.
to the proximal interphalangeal joint. The central slip receives a contri- The superficial head is frequently blended with opponens pollicis.
bution from the tendons of the lumbricals and interossei via the lateral The deep head varies considerably in size and may even be absent.
bands. Similarly, some fibres from the central region pass to each lateral
band, producing a criss-cross arrangement of fibres. The central slip Relations Flexor pollicis brevis lies superficial in the thenar eminence
attaches to the base of the middle phalanx, while the lateral bands and is distal to abductor pollicis brevis. It is crossed by the motor
continue distally; they eventually fuse together and insert into the distal branch of the median nerve.
phalanx. The tension in the central slip and the lateral bands varies as
the finger moves between flexion and extension and plays a crucial role Actions Flexor pollicis brevis flexes the metacarpophalangeal joint.


in coordinating synchronous activity between the proximal and distal
interphalangeal joints. Testing Flexor pollicis brevis is palpated whilst flexing the metacarpo-
The transverse and oblique retinacular ligaments of Landsmeer phalangeal joint, with the interphalangeal joint fully extended.
connect the fibrous flexor sheath to the extensor apparatus. The trans-
Abductor pollicis brevis
verse retinacular ligament passes from the A3 pulley of the fibrous flexor
sheath at the level of the proximal interphalangeal joint to the lateral Attachments Abductor pollicis brevis is a thin, subcutaneous muscle
border of the lateral extensor band. The oblique retinacular ligament in the proximolateral part of the thenar eminence (see Figs 50.25B,
lies deep to the transverse retinacular ligament. It originates from the 50.30). It arises mainly from the flexor retinaculum, but a few fibres
lateral aspect of the proximal phalanx and flexor sheath (A2 pulley) and spring from the tubercles of the scaphoid bone and trapezium and from
passes volar to the axis of rotation of the proximal interphalangeal joint, the tendon of abductor pollicis longus. Its medial fibres are attached by
but in a dorsal and distal direction, to insert into the terminal extensor a thin, flat tendon to the radial side of the base of the proximal phalanx
tendon. of the thumb, and its lateral fibres join the dorsal digital expansion of
the thumb. The muscle may receive accessory slips from the long and
short extensors of the thumb, opponens pollicis, or the styloid process
INTRINSIC MUSCLES OF THE HAND of the radius.
The intrinsic muscles of the hand are organized into three groups plus Relations Abductor pollicis brevis lies proximomedial to flexor pol-
a superficial muscle. The thenar muscles include flexor pollicis brevis, licis brevis in the superficial part of the thenar eminence.
abductor pollicis brevis, opponens pollicis and adductor pollicis. The
hypothenar muscles include abductor digiti minimi, flexor digiti Actions Abductor pollicis brevis draws the thumb ventrally in a plane


minimi brevis and opponens digiti minimi. The interossei and lumbri- at right angles to the palm of the hand (abduction).
cals act on the fingers. Palmaris brevis is a superficial muscle that lies
beneath the ulnar palmar skin. Testing The patient abducts the thumb at right angles to the palm
against resistance; the muscle can be seen and felt.
Flexor pollicis brevis
Attachments Flexor pollicis brevis lies medial to abductor pollicis Opponens pollicis
brevis (Fig. 50.30). It has superficial and deep parts. The superficial Attachments Opponens pollicis lies deep to abductor pollicis brevis
head arises from the distal border of the flexor retinaculum and the (see Fig. 50.30). It arises from the tubercle of the trapezium and the
distal part of the tubercle of the trapezium, and passes along the radial flexor retinaculum, and is attached to the whole length of the lateral
side of the tendon of flexor pollicis longus. It is attached by a tendon border, and the adjoining lateral half of the palmar surface of the meta-
that contains a sesamoid bone to the radial side of the base of the carpal bone of the thumb.
proximal phalanx of the thumb. The deep part arises from the trapezoid
and capitate bones and from the palmar ligaments of the distal row of Relations Opponens pollicis lies deep between the other two muscles
carpal bone, and passes deep to the tendon of flexor pollicis longus. It of the thenar eminence and is revealed only when they are retracted.


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Tendons of flexor digitorum superficialis
Palmar interossei
Tendons of flexor digitorum superficialis (cut)
Tendinous sheath of
flexor pollicis longus
Dorsal interossei
Adductor pollicis, transverse head
Flexor pollicis brevis, superficial head
Flexor pollicis brevis, deep head
Capsule of fifth metacarpophalangeal joint
Abductor pollicis brevis
Abductor digiti minimi (cut)
Opponens pollicis Lumbricals
Flexor pollicis brevis, superficial head
Opponens digiti minimi
Abductor pollicis brevis
Flexor digiti minimi brevis
Abductor digiti minimi
Flexor retinaculum
Tendinous sheaths of abductor longus and extensor pollicis brevis
Pisiform
Tendons of flexor digitorum profundus
Tendinous sheath of flexor carpi radialis
Tendon of flexor carpi ulnaris
Palmar radiocarpal ligament
Ulnar, styloid process
Tendon of flexor pollicis longus
Ulna
Tendon of brachioradialis
Pronator quadratus
Radius
Interosseous membrane of forearm
Fig. 50.30 The muscles of the left hand. The deep layer is shown after cutting the flexor retinaculum and partial removal of several superficial muscles:
palmar aspect. (With permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright
2013.)
Actions Opponens pollicis flexes the metacarpal bone of the Relations The deep palmar arch and the deep branch of the ulnar
thumb. nerve pass between the two heads of the muscle. Anteriorly, adductor
pollicis is crossed by the flexor tendons of the index finger and their
Testing The patient touches the base of the little finger against sheath, and the first lumbrical, and is overlapped by flexor pollicis
resistance. brevis. Posteriorly, it abuts against the first dorsal interosseous muscle;


together, these muscles form the mass of the first web space of the hand.
Adductor pollicis
Attachments Adductor pollicis arises by oblique and transverse Actions Adductor pollicis is the largest and most powerful of the
heads (see Figs 50.26, 50.28, 50.30). The oblique head is attached to intrinsic muscles and acts to approximate the thumb to the palm of the
the capitate bone, the bases of the second and third metacarpal bones, hand. It acts optimally when the abducted, rotated and flexed thumb
the palmar ligaments of the carpus, and the sheath of the tendon of is opposed to the fingers in gripping.
flexor carpi radialis. Most of the fibres converge into a tendon (contain-
ing a sesamoid bone) that unites with the tendon of the transverse head Testing The patient adducts the thumb at right angles to the palm
and is attached to the ulnar side of the base of the proximal phalanx against resistance.
of the thumb. The deepest fibres may pass into the medial side of the
Abductor digiti minimi
dorsal digital expansion of the thumb. On the lateral side of the oblique
head, a considerable fasciculus, described as the ‘deep head’ of flexor Attachments Abductor digiti minimi arises from the pisiform bone,
pollicis brevis, passes deep to the tendon of flexor pollicis longus to the tendon of flexor carpi ulnaris and the pisohamate ligament (see Figs
join flexor pollicis brevis. The transverse head is the deepest of the 50.25B, 50.30). It ends in a flat tendon that divides into two slips: one
muscles of the thumb; it is triangular and arises from the distal two- is attached to the ulnar side of the base of the proximal phalanx of the
thirds of the palmar surface of the third metacarpal. The fibres converge little finger, and the other to the ulnar border of the dorsal digital expan-
to be attached, with the oblique head and the first palmar interosseous, sion of extensor digiti minimi. The muscle may have two or three slips


to the base of the proximal phalanx of the thumb. The two parts of the and may be fused with flexor digiti minimi brevis. An additional slip
adductor vary in relative size and degree of connection. may arise from the flexor retinaculum, antebrachial fascia, or tendons


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of palmaris longus or flexor carpi ulnaris, and may be partly attached
to the fifth metacarpal by a slip from the pisiform.
Relations Abductor digiti minimi lies along the ulnar border of flexor
digiti minimi brevis and overlies opponens digiti minimi.
Actions Abductor digiti minimi abducts the little finger away from the
fourth, e.g. in the habitual spreading of the digits when they are
extended. Abduction is also possible when digits 2–4 are tightly
adducted in flexion or extension.
Second palmar interosseous
Testing The little finger is abducted against resistance. Third palmar interosseous
Flexor digiti minimi brevis Fourth palmar interosseous
Attachments Flexor digiti minimi brevis arises from the convex
surface of the hook of the hamate and the palmar surface of the flexor
retinaculum, and inserts into the ulnar side of the base of the proximal
phalanx of the little finger with abductor digiti minimi (see Fig. 50.30).
It may be absent, or fused with the abductor, and it may attach to the
distal end of the fifth metacarpal by a muscular slip.
Relations Flexor digiti minimi brevis lies lateral to the abductor. Its
origin is separated from that of the abductor by the deep branches of
the ulnar artery and nerve.
Actions Flexor digiti minimi brevis produces flexion of the little finger
at its metacarpophalangeal joint, together with some lateral rotation.
Fig. 50.31 The palmar interossei of the left hand: palmar aspect. Note
Testing The subject flexes the metacarpophalangeal joint of the little that there is no first palmar interosseous in this specimen. (With
finger against resistance with the interphalangeal joints in extension. permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.)
Opponens digiti minimi
Attachments Opponens digiti minimi is a triangular muscle lying


under cover of the flexor and abductor (see Fig. 50.30). It arises from
the convexity of the hook of the hamate and the contiguous portion of them (see Fig. 50.30; Fig. 50.31). The middle finger has no palmar
the flexor retinaculum, and inserts along the whole length of the ulnar interosseous. The remaining digits have palmar interossei on their
margin of the fifth metacarpal bone and the adjacent palmar surface. aspects that face the middle finger. The first arises from the ulnar side
The muscle is often divided into two lamellae by the deep branches of of the palmar surface of the base of the first metacarpal bone and is
the ulnar artery and nerve. It blends to a variable degree with its inserted into a sesamoid bone on the ulnar side of the proximal
neighbours. phalanx; from here, it passes to the phalanx and, usually, also into the
dorsal digital expansion. It is often rudimentary. The second arises from
Relations Opponens digiti minimi lies on the ulnar margin and the ulnar side of the second metacarpal bone and is inserted into the
adjacent palmar surface of the fifth metacarpal, overlapped by, and same side of the digital expansion of the index finger. The third arises
often partly fused with, the other two muscles of the hypothenar from the radial side of the fourth metacarpal bone and is inserted
eminence. together with the third lumbrical. The fourth arises from the radial side
of the fifth metacarpal bone and is attached with the fourth lumbrical
Actions Opponens digiti minimi flexes the fifth metacarpal bone, and to the base of the proximal phalanx. The attachment of these
drawing it forwards and rotating it laterally at the carpometacarpal muscles to the dorsal digital expansions (see Fig. 50.29) stabilizes the
joint; this deepens the hollow of the palm. These actions, together with extensor tendons on the convex heads of the metacarpal bones during
flexion and some lateral rotation at the metacarpophalangeal and inter- flexion and extension at the metacarpophalangeal joints. The interossei


phalangeal joints, bring the digit into opposition with the thumb. show little variation in their arrangement, although they may, occasion-
ally, be duplicated.
Testing The patient opposes the tip of the little finger to the tip of the
thumb with the interphalangeal joints of the little finger in extension. Relations The first palmar interosseous lies anterior to the lateral
head of the first dorsal interosseous and is overlapped anteriorly by the
Palmaris brevis
oblique head of adductor pollicis, which also crosses anterior to the
Attachments Palmaris brevis is a thin, quadrilateral muscle lying second palmar interosseous. The third and fourth are overlapped by the
beneath the skin of the ulnar side of the palm (see Fig. 50.7A). It arises long flexor tendons of the ring and little finger, respectively, within their
from the flexor retinaculum and the medial border of the central part flexor sheaths.
of the palmar aponeurosis and is attached to the dermis on the ulnar
border of the hand. Actions Palmar interossei adduct the fingers towards the longitudinal
axis of the middle finger. Interossei have a considerable cross-sectional
Relations Palmaris brevis is superficial to the ulnar artery and the area and, therefore, contribute strongly to metacarpophalangeal joint
superficial terminal branch of the ulnar nerve. flexion and interphalangeal extension. When the interossei are para-
lysed, the grip strength of the hand is reduced and the arc of finger
Actions Palmaris brevis wrinkles the skin on the ulnar side of the motion is abnormal, with a tendency for the fingers to claw. Each inter-
palm of the hand and deepens the hollow of the palm by accentuating osseous has a considerable ability to rotate the digit at the metacarpo-
the hypothenar eminence. phalangeal joint. Generally, this is not obvious because interossei act
in pairs, but it may occur where one interosseous is deficient as a result
Testing The patient opposes the thumb to the little finger; the skin of injury or congenital deformity.
on the ulnar side of the palm is seen to pucker.
Testing The patient adducts the index ring and little fingers against
Interossei
resistance.


The interossei occupy the intervals between the metacarpal bones and
are divided into a palmar and a dorsal set. dorsal interossei
Attachments Dorsal interossei consist of four bipennate muscles,
Palmar interossei each arising from the adjacent sides of two metacarpal bones, but more
Attachments Palmar interossei are smaller than dorsal interossei and extensively from the metacarpal bone of the finger into which the
lie on the palmar surfaces of the metacarpal bones rather than between muscle passes (see Figs 50.29–50.30; Fig. 50.32). They insert on the


Muscles
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RETPAHC
Tendons of flexor digitorum profundus
Tendons of
flexor digitorum superficialis
Tendons of
flexor
digitorum
superficialis
Tendons of
Tendons of lumbricals First lumbrical
palmar interossei
Third lumbrical
Second lumbrical
Tendons of
extensor
Fourth lumbrical
digitorum
Fourth dorsal
interosseous Second dorsal
Third dorsal interosseous Tendons of
interosseous First dorsal flexor digitorum
interosseous profundus
Fig. 50.33 Lumbricals of the left hand: palmar aspect. (With permission
from Waschke J, Paulsen F (eds), Sobotta Atlas of Human Anatomy, 15th
ed, Elsevier, Urban & Fischer. Copyright 2013.)
responding finger and is attached to the lateral margin of the dorsal
digital expansion of extensor digitorum covering the dorsal surface of
the finger. Variations in the attachments of the lumbricals are common.
Fig. 50.32 The dorsal interossei of the left hand: dorsal aspect. (With Any of them may be unipennate or bipennate. When they are bipen-
permission from Waschke J, Paulsen F (eds), Sobotta Atlas of Human nate, the two heads arise from adjoining tendons of flexor digitorum
Anatomy, 15th ed, Elsevier, Urban & Fischer. Copyright 2013.) profundus, and, in the case of the first lumbrical, from the tendon of
flexor pollicis longus. Accessory lumbrical slips may be attached to an
adjacent tendon of flexor digitorum superficialis.
bases of the proximal phalanges and separately into the dorsal digital Actions Lumbricals arise from flexor tendons and insert into the
expansions. There is a narrow triangular interval between the double extensor apparatus. Since both attachments are mobile, they have the
origin of each of these muscles; the radial artery passes through the first potential for producing movement at either. The action on the exten-
of these intervals, and a perforating branch from the deep palmar arch sor apparatus extends both interphalangeal joints in a coordinated


passes through each of the others. The first and largest muscle is some- manner. The mode of action at the metacarpophalangeal joints is dis-
times called abductor indicis. It is attached to the radial side of the puted, but if there is a flexor action, it is very weak. The effect on the
proximal phalanx of the index finger and to the capsule of the adjoin- flexor digitorum profundus attachment is to pull the tendon distally.
ing metacarpophalangeal joint. The second and third are attached to The combined action on both origin and insertion is, therefore, to
the radial and ulnar sides of the middle finger, respectively. Whereas alter the posture of the finger to allow more interphalangeal extension.
the second generally reaches the digital expansion and the proximal Pinching the index finger against the thumb without a lumbrical
phalanx, the third usually extends only to the digital expansion. The would result in a nail-to-nail contact; the addition of the lumbrical
fourth may be wholly attached to the digital expansion, but it often increases the interphalangeal joint extension and results in pulp-to-
sends an additional slip to the proximal phalanx. pulp pinch. Lumbricals contain many muscle spindles and have a long
fibre length; it is, therefore, reasonable to assume that they play a role
Relations The first dorsal interosseous abuts anteriorly with adductor in proprioception.
pollicis. The other dorsal interossei occupy the spaces between the
second and the fifth metacarpal bones. Testing Lumbricals cannot be tested in isolation but only as the
lumbrical–interosseous muscle complex. The examiner holds the meta-
Actions Dorsal interossei abduct the fingers away from the longitudi- carpophalangeal joint of the index finger in hyperextension and the
nal axis of the middle finger. See also the description of the actions of subject is instructed to extend the proximal interphalangeal joint
the palmar interossei above. against resistance. This test is repeated on the other fingers.
Vascular supply to the intrinsic muscles
Testing The patient abducts the index, middle and ring fingers against
resistance. The first dorsal interosseous is tested with the subject’s of the hand


fingers and palm flat on the table. The subject tries to abduct the index Flexor pollicis brevis is supplied by the superficial palmar branch of the
finger against the examiner’s resistance. The muscle belly can be felt radial artery, and branches from the princeps pollicis artery and radialis
and seen. indicis artery. Abductor pollicis brevis is supplied by the superficial
palmar branch of the radial artery and, often, by an independent
Lumbricals branch directly from the radial artery lying on the radial aspect of the
Attachments The four small lumbrical muscles arise from the thumb. Opponens pollicis is supplied by the superficial palmar branch
tendons of flexor digitorum profundus (see Figs 50.29–50.30; Fig. of the radial artery and by branches from the first palmar metacarpal
50.33). The first and second arise from the radial sides and palmar artery (when present), arteria princeps pollicis, arteria radialis indicis
surfaces of the tendons of the index and middle fingers, respectively. and the deep palmar arch. Adductor pollicis is supplied by the arteria
The third arises from the adjacent sides of the tendons of the middle princeps pollicis and arteria radialis indicis (sometimes combined as
and ring fingers, and the fourth from the adjoining sides of the tendons the first palmar metacarpal artery) and by branches from the deep
of the ring and little fingers. Each passes to the radial side of the cor- palmar arch. Abductor digiti minimi and flexor digiti minimi brevis are


WRiST And HAnd
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supplied by the deep palmar branch of the ulnar artery and branches pollicis brevis. In this way, different postures of the thumb can be pro-
from the ulnar end of the superficial palmar arch; the medial border of duced by the interplay of flexor and extensor forces. These simple
the little finger is supplied by the palmar digital artery. Opponens digiti guiding principles should provide an understanding of muscle action
minimi is supplied by the deep palmar branch of the ulnar artery and in the hand that is sufficient for most purposes.
branches from the medial end of the deep palmar arch. Palmaris brevis In considering the role of a particular muscle, there is a tendency to
is supplied by branches from the ulnar end of the superficial palmar concentrate on motion. Indeed, many muscles are named on the basis
arch. The palmar interossei are supplied by branches from the deep of the movements that they generate, although others, often those
palmar arch, arteria princeps pollicis, arteria radialis indicis, palmar whose actions are the most difficult to interpret, are described according
metacarpal arteries, proximal and distal perforating arteries, and to their morphology or situation. A more important function may be
common and proper digital (palmar) arteries. The dorsal interossei are the nature of the force generated. For example, although flexor pollicis
supplied by the dorsal metacarpal arteries (first to fourth), palmar longus flexes the thumb (see above), a large range of flexion is actually
metacarpal arteries (second to fourth), radial artery (first), arteria prin- required in only a few activities, such as certain ripping tasks. In most
ceps pollicis, arteria radialis indicis, three perforating branches from pinch and manipulative tasks, the role of the thumb is to apply isomet-
the deep palmar arch (proximal perforating arteries) and three distal ric force, which it does with such precision that it is possible to pick up
perforating branches. Their tendons are supplied by branches from the an egg and neither crush nor drop it. Thus, for much of the time, flexor


common and proper palmar digital arteries and the dorsal digital pollicis longus behaves as an extremely sophisticated mechanism for
arteries. the application of force, in which contraction and proprioception are
The first and second lumbricals are supplied by the first and second equally important.
dorsal metacarpal and dorsal digital arteries. The third and fourth lum- The anatomical position of the hand (palm flat and pointing an-
bricals are supplied by the second and third common palmar digital teriorly, forearm supinated) is a convenient standard for studying struc-
arteries, and the third and fourth dorsal digital arteries and their anas- tural relationships. The hand in the relaxed (anaesthetized) position
tomoses with the palmar digital arteries. adopts a posture of partial flexion and mid-supination/pronation (the
reader can verify this by relaxing completely and observing forearm and
Innervation of the intrinsic muscles hand position).
of the hand
The superficial head of flexor pollicis brevis is usually innervated by SPECIAL FUNCTIONS OF THE HAND
the recurrent motor branch of the median nerve, and the deep head is
usually innervated by the deep branch of the ulnar nerve; variation is
Closing the hand
common. Abductor pollicis brevis is innervated by the recurrent
motor branch of the median nerve and is the only thenar muscle that
is constantly supplied by the median nerve. Opponens pollicis is Available with the Gray’s Anatomy e-book
innervated by the lateral terminal branch of the median nerve and,
commonly, by a branch of the deep terminal branch of the ulnar Role of the long digital flexors
nerve. Adductor pollicis, abductor digiti minimi, flexor digiti minimi
brevis, opponens digiti minimi and all the interossei are innervated by
Available with the Gray’s Anatomy e-book
the deep branch of the ulnar nerve; the first dorsal interosseous and
adductor pollicis are supplied by its most distal portion. Palmaris
Role of the wrist
brevis is innervated by the superficial branch of the ulnar nerve. The
first and second lumbricals are innervated by the median nerve, and
the third and fourth lumbricals by the deep terminal branch of the Available with the Gray’s Anatomy e-book


ulnar nerve. The third lumbrical frequently receives a supply from the
median nerve. The first and second lumbricals are, occasionally, inner- Making a tight fist
vated by the deep terminal branch of the ulnar nerve.
Available with the Gray’s Anatomy e-book
MOVEMENTS OF THE HAND
Opening the hand
The apparently simple human functions of closing the hand to grasp
an object, or opening the palm to release it, are, in reality, tasks of Available with the Gray’s Anatomy e-book
considerable mechanical complexity, requiring the simultaneous con-
traction of many individual muscles. The isolated action of a single
Movements of the thumb
muscle may be inferred from the positions of its origin and insertion,
and the estimated line of action (usually, the centre line of the muscle)
in relation to the axes of all the joints traversed by the muscle and its The thumb does not easily assume the classical anatomical position.
tendon. The limb can be regarded as a chain of joints crossed by Therefore, the normal descriptive anatomical terms, i.e. anterior, pos-
muscles. If it is known which muscles are active, then the reason why terior, medial and lateral, do not readily apply. The terms ‘palmar’,
one joint moves and others do not is a matter of simple mechanical ‘dorsal’, ‘ulnar’ and ‘radial’ have been adopted in clinical practice.
relationships. For example, flexor pollicis longus is considered to have An opposable thumb requires a different system of control from
a major role as a flexor of the interphalangeal joint of the thumb. the other digits. Since the metacarpal is much more mobile than in
However, the position of its tendon relative to more proximal joints in the digits, muscles are needed to control the extra freedom of move-
the limb gives it the potential for producing flexion at the metacarpo- ment. The basic active movements are flexion–extension, abduction–
phalangeal joint and also at the trapeziometacarpal and wrist joints. In adduction, rotation and circumduction. In the resting position of the
the living subject, the actual motion that takes place depends on which first metacarpal, flexion and extension are parallel with the palmar
other muscle groups are acting, and so the potential for movement must plane, and abduction and adduction occur at right angles to this.


be considered for each joint in the chain in turn. Motion at the wrist is Flexion and extension should be confined to motion at the inter-
generally balanced by wrist extensors. Motion at the trapeziometacarpal phalangeal or metacarpophalangeal joints (see Video 50.1). Palmar
joint is balanced by abductor pollicis longus. Flexor pollicis longus will abduction (see Video 50.1), in which the first metacarpal moves away
then have an action as a flexor of the metacarpophalangeal and inter- from the second at right angles to the plane of the palm, and radial
phalangeal joints only. abduction (see Video 50.1), in which the first metacarpal moves away
The factor that determines whether one or both of two joints will from the second with the thumb in the plane of the palm, occur at the
move is the turning moment at each. The greater the perpendicular carpometacarpal joint. The opposite of radial abduction is ulnar adduc-
distance from the line of muscle or tendon pull to the axis of the joint, tion, or transpalmar adduction, in which the thumb crosses the palm
the stronger is the turning effect of the muscle at the joint, but the towards its ulnar border. In clinical practice, the term adduction is
smaller the range of joint motion that can be produced. In the case of generally used without qualification. Circumduction describes the
flexor pollicis longus, the tendon is situated further from the axis of the angular motion of the first metacarpal, solely at the carpometacarpal
metacarpophalangeal joint than from the axis of the interphalangeal joint, from a position of maximal radial abduction in the plane of the
joint; it will, therefore, tend to produce flexion preferentially at the palm towards the ulnar border of the hand, maintaining the widest
metacarpophalangeal joint, unless that joint is restrained by extensor possible angle between the first and second metacarpals (see Video


Wrist and hand
886.e1
05
RETPAHC
It is clear that the fingers and palm of the hand flex in gripping, grasping The reader can observe the relationship between digits and wrist by
or making a fist, but there are subtle differences in hand posture in these performing the following manœuvre. The wrist is held in a relaxed,
various activities. The basic mechanisms of hand closure will be mid-supinated position, with the elbow flexed at 90°. If the forearm is
described before special grips are considered. now rotated into pronation, the wrist will fall into flexion and the
As the digits flex, the wrist usually extends (dorsiflexes) at the same fingers will automatically extend. If the forearm is rotated into supina-
time. The involvement of the long digital flexors in this movement will tion, the wrist will extend and the fingers flex. The finger movements
be considered first, followed by an analysis of the role of the wrist. compensate for the wrist movements and are entirely automatic; they
are made without the need for any excursion of forearm flexor or exten-
Flexor digitorum superficialis acts principally to flex the proximal inter- sor tendons. This test, the wrist tenodesis test, is a useful way of examin-
phalangeal joints, through its insertions into the middle phalanges. ing the limb for tendon injury. The pointing finger (which does not
However, in each digit, it also has an action on the metacarpophalan- move with wrist motion) ‘points to’ a tendon injury.
geal joint because the tendon passes anterior to that joint. The muscle Wrist motion is controlled principally by two wrist flexors (flexor
has the potential to produce flexion at the wrist for the same reason. carpi radialis and flexor carpi ulnaris) and three extensors (extensors
The fact that each tendon arises from an individual muscle slip allows carpi radialis longus and brevis, and extensor carpi ulnaris). Although
the clinician to test one finger at a time. The reader can verify this by the radiocarpal joint has some functional similarity to a ball and socket
attempting to flex each digit individually while using the other hand to joint, it is possible to think of the wrist as a variable hinge joint, the


keep the distal interphalangeal joints of the remaining fingers in exten- axis of which may be set in a number of inclinations. For example, in
sion. This test is frequently used in clinical practice and is useful for the using a hammer, it is useful to rotate the wrist backwards and forwards
middle and ring fingers, where flexion of one finger alone must be about an axis that permits not only wrist flexion but also ulnar devia-
attributed to flexor digitorum superficialis. The index finger, however, tion. It would be very restricting to have a pure hinge joint with col-
has its own profundus musculotendinous unit and may, therefore, lateral ligaments of fixed length. In this context, the wrist flexors and
move independently under the action of this tendon. Many individuals extensors may be regarded as variable collateral ligaments that allow
cannot flex the proximal interphalangeal joint of the little finger alone, the joint to be set about a number of different axes.
usually because of linkage between the tendons of the ring and little
finger flexor digitorum superficialis, but occasionally because super- It is possible to observe and to palpate the muscle groups that are active
ficialis is deficient. Most individuals can flex the metacarpophalangeal in making a tight fist. Flexor digitorum profundus and flexor digitorum
joint of the little finger using flexor digiti minimi. superficialis are active, and flexor carpi ulnaris contracts strongly, as do
Flexor digitorum profundus is the only flexor of the distal inter- the wrist extensors. Palpation of the long digital extensors on the
phalangeal joint. It also contributes, together with superficialis, to dorsum of the wrist, the first dorsal interosseous in the thumb web, and
flexion at the proximal interphalangeal and metacarpophalangeal of the other interossei and the thenar and hypothenar muscles, will
joints. These two long flexors (sometimes called extrinsic flexors because confirm that all these muscles are contracting. As a firm fist is swung
the muscle bellies are outside the hand) can be considered to act forwards in anger, brachioradialis stands out; at the moment of impact,