INJURIES IN THE REGION OF THE WRIST AND HAND
Surgical Anatomy--FRACTURE OF LOWER END OF RADIUS: _Colles' fracture_;
_Chauffeur's fracture_; _Smith's fracture_; _Longitudinal
fracture_; _Separation of epiphysis_--FRACTURE OF LOWER END OF
ULNA: _Shaft_; _Styloid process_; _Separation of
epiphysis_--FRACTURE OF CARPAL BONES--DISLOCATION: _Inferior
radio-ulnar joint_; _Radio-carpal joint_; _Carpal bones_;
_Carpo-metacarpal joint_--SPRAINS--INJURIES OF FINGERS:
_Fractures_; _Dislocations_; _Mallet finger_.
INJURIES IN THE REGION OF THE WRIST
These include fractures of the lower ends of the bones of the forearm
and separation of their epiphyses; sprains and dislocations of the
inferior radio-ulnar, and of the radio-carpal articulations; and
fractures and dislocations of the carpus.
#Surgical Anatomy.#--The most important landmarks in the region of the
wrist are the styloid processes of the radius and ulna. The tip of the
radial styloid is palpable in the "anatomical snuff-box" between the
tendons of the long and short extensors of the thumb, and it lies
about half an inch lower than the ulnar styloid. The ulnar styloid is
best recognised on making deep pressure a little below and in front of
the head of the ulna, which forms the rounded subcutaneous prominence
seen on the back of the wrist when the hand is pronated.
The tubercle of the navicular (scaphoid) and the greater multangular
(trapezium) can be felt between the radial styloid and the ball of the
thumb, a little below the radial styloid; and the pisiform and hook of
the hamatum (unciform) are palpable, slightly below and in front of
the ulnar styloid.
In examining an injured wrist, the different bony points should be
located, and their relative positions to one another and to the
adjacent joints noted; and the shape, position, and relations of any
unnatural projection or depression observed, using the wrist on the
other side as the normal standard for comparison. The power and range
of movement--active and passive--at the various joints should also be
tested.
FRACTURE OF THE LOWER END OF THE RADIUS
#Colles' Fracture.#--This injury, which was described by Colles of
Dublin in 1814, is one of the commonest fractures in the body, and is
especially frequent in women beyond middle age. It is almost
invariably the result of a fall on the palm of the hand, in the
three-quarters pronated position, the force being received on the ball
of the thumb, and transmitted through the carpus to the lower end of
the radius which is broken off, the lower fragment being driven
backwards.
The fracture takes place through the cancellated extremity of the
bone, within a half to three-quarters of an inch of its articular
surface (Fig. 45). It is usually transverse, but may be slightly
oblique from above downwards and from the radial to the ulnar side. In
a considerable proportion of cases it is impacted, and not
infrequently the lower fragment is comminuted, the fracture extending
into the radio-carpal joint.
[Illustration: FIG. 43.--Colles' Fracture showing radial deviation of
hand.]
[Illustration: FIG. 44.--Colles' Fracture showing undue prominence of
ulnar styloid.]
When impaction takes place, it is usually reciprocal, the dorsal edge
of the proximal fragment piercing the distal fragment, and the palmar
edge of the distal fragment piercing the proximal. The periosteum is
usually torn and stripped from the palmar aspect of the fragments,
while it remains intact on the dorsum.
In the majority of cases the styloid process of the ulna is torn off
by traction exerted through the medial ulno-carpal (internal lateral)
ligament, and in a considerable proportion there is also a fracture of
one of the carpal bones.
The resulting _displacement_ is of a threefold character: (1) the
distal fragment is displaced backwards; (2) its carpal surface is
rotated backwards on a transverse diameter of the forearm; while (3)
the whole fragment is rotated so that the radial styloid comes to lie
at a higher level than normal.
[Illustration: FIG. 45.--Radiogram showing the line of fracture and
upward displacement of the radial styloid in Colles' Fracture.]
_Clinical Features._--In a typical case there is a prominence on the
dorsum of the wrist, caused by the displaced distal fragment, with a
depression just above it (Fig. 43); and the wrist is broadened from
side to side. The natural hollow on the palmar aspect of the radius is
filled up by the projection of the proximal fragment. The carpus is
carried to the radial side by the upward rotation of the distal
fragment, and the radial styloid is as high, or even higher, than that
of the ulna. The lower end of the ulna is rendered unduly prominent by
the flexion of the hand to the radial side. The fingers are partly
flexed and slightly deviated towards the ulnar side; and the patient
supports the injured wrist in the palm of the opposite hand, and
avoids movement of the part. Occasionally the median nerve is bruised
or torn, causing motor and sensory disturbances in its area of
distribution.
The general outline of the wrist and hand has been compared not
inaptly to that of "an inverted spoon." Pronation and stipulation are
lost, the joint is swollen, and there is tenderness on pressure,
especially over the line of fracture. Tenderness over the position of
the ulnar styloid may indicate fracture of that process, although it
is sometimes present without fracture. No attempt should be made to
elicit crepitus in a suspected case of Colles' fracture as the
manipulations are painful, and are liable to increase the
displacement.
_Treatment._--It cannot be too strongly insisted upon that success in
the treatment of Colles' fracture with displacement and impaction
depends chiefly upon complete and accurate reduction, and to enable
this to be effected a general anaesthetic is almost essential. The
surgeon grasps the patient's hand, as if shaking hands with him, and,
resting the palmar surface of the wrist on his bent knee, makes
traction through the hand, and counter-extension through the forearm,
with lateral movements, if necessary, to undo impaction. When the
fragments are freed from one another, the wrist is flexed, and the
hand carried to the ulnar side, while the lower fragment is moulded
into position by the thumb of the surgeon's disengaged hand. When
reduction is complete, the deformity disappears, and the two styloid
processes regain their normal positions relative to one another.
As there is no tendency to re-displacement and no risk of non-union,
no retentive apparatus is required, but, if it adds to the patient's
sense of security, a bandage or a poroplastic wristlet may be applied.
In severe cases, however, anterior and posterior splints, similar to
those used for fracture of both bones of the forearm, or a dorsal
splint padded so as to flex the wrist to an angle of 45 deg., but somewhat
narrower, may be employed. The hand and forearm are in any case
supported in a sling.
To avoid the stiffness that is liable to follow, massage and movement
of the wrist and fingers should be carried out from the first, the
range of movement being gradually increased until the function of the
joints is perfectly restored. If splints are used, they should be
discarded in a week, and the patient is then encouraged to use the
wrist freely.
The various special splints recommended for the treatment of Colles'
fracture, such as Carr's, Gordon's, the "pistol splint," and many
others, are all designed to correct the deformity as well as to
control the fragments. It has already been pointed out that if
reduction is complete there is no deformity to correct, and if it is
not complete the deformity cannot be corrected by any form of splint.
_Unreduced Colles' Fracture._--When union has been allowed to take
place without the displacement having been reduced, an unsightly
deformity results. In young subjects whose occupation is likely to be
interfered with, and in women for aesthetic reasons, the fracture is
reproduced and the displacement of the lower fragment corrected. This
is conveniently done by means of Jones' wrench, which grasps the
distal fragment and affords sufficient leverage to break the bone.
#Chauffeur's Fracture.#--A fracture of the lower end of the radius
frequently occurs from the recoil of the crank, "by back firing," in
starting the engine of a motor-car. The injury may be produced either
by direct violence, the handle as it recoils striking the forearm, or
by indirect violence, from forcible hyper-extension of the hand while
grasping the handle. The fracture may pass transversely through the
lower end of the radius, as in Colles' fracture, but is more often met
with two or three inches above the wrist (Fig. 46). It is treated on
the same lines as Colles' fracture.
[Illustration: FIG. 46.--Radiogram of Chauffeur's Fracture.]
A fracture of the lower end of the radius _with forward displacement
of the carpal fragment_, was first described by R. W. Smith of Dublin
(_Colles' fracture reversed_, or #Smith's fracture#) (Fig. 47). It is
nearly always due to forcible flexion, as from a fall on the back of
the hand. Like Colles' fracture, it may be transverse or slightly
oblique, impacted, or comminuted. The deformity is characterised by an
elevation on the dorsum running obliquely upwards from the ulnar to
the radial side of the wrist, and caused by the head of the ulna,
which remains in position, and the distal end of the proximal
fragment. Below this, over the position of the distal radial fragment,
is a gradual slope downwards on to the dorsum of the hand. Anteriorly
there is a prominence in the flexure of the wrist, and the distal
fragment may be felt under the flexor tendons. The hand deviates to
the radial side, and thereby still further increases the prominence
caused by the lower end of the ulna. The radial styloid is displaced
forward, upward, and to the radial side, and the ulnar styloid may be
torn off.
[Illustration: FIG. 47.--Radiogram of Smith's Fracture.
(Sir George T. Beatson's case.)]
When the deformity is not well marked, this injury may be mistaken for
forward dislocation of the wrist, for fracture of both bones low down,
or for sprain of the joint.
The _treatment_ is carried out on the same lines as in Colles'
fracture.
_Longitudinal fractures_ of the lower end of the radius opening into
the joint usually result from the hand being crushed by a heavy weight
or in machinery. They are often compound and comminuted.
#Separation of the lower epiphysis# of the radius, which is on the
same level as that of the ulna and lies above the level of the
synovial membrane of the wrist-joint, is comparatively common between
the ages of seven and eighteen, especially in boys, and is caused by
the same forms of violence as produce Colles' fracture.
Although clinically the appearances in these two injuries bear a
general resemblance to one another, separation of the epiphysis may
usually be identified by the directly transverse line of the dorsal
and palmar projections, the folding of the skin observed in the palmar
depression, the absence of abduction of the hand and the ease with
which muffled crepitus can be elicited (E. H. Bennett). The deformity
is readily reduced, and the fragments are easily retained in position.
This injury is often complicated with fracture of the shaft or styloid
process of the ulna, or with dislocation of the radio-ulnar joint, and
it is not infrequently compound, the lower end of the shaft being
driven through the skin on the palmar aspect immediately above the
wrist. Impairment of growth in the radius seldom occurs; when it does,
it results in a valgus condition of the hand (Fig. 48), calling for
resection of the lower end of the ulna.
[Illustration: FIG. 48.--Manus Valga following separation of lower
radial epiphysis in childhood.
(Mr. H. Wade's case.)]
The _treatment_ is the same as for Colles' fracture.
#Fracture of the Lower End of the Ulna.#--The lower end of the _shaft_
of the ulna is seldom fractured alone. The _styloid process_, as has
already been pointed out, is frequently broken in association with
Colles' and other fractures of the lower end of the radius.
Separation of the _lower epiphysis_ of the ulna sometimes occurs, and
in rare cases results in arrest of the growth of the bone, leading to
a varus condition of the hand and bending of the radius. Sometimes the
separated epiphysis fails to unite, and although this gives rise to no
disability, it is liable to lead to errors in the interpretation of
skiagrams.
The _treatment_ is similar to that for the corresponding injuries of
the radius.
Simultaneous separation of the _epiphysis of both radius and ulna_
sometimes occurs, and, as a result of severe violence, may be
compound, the lower ends of the diaphyses projecting through the skin
on the palmar aspect above the wrist.
#Fracture of Carpal Bones.#--The use of the Roentgen rays has shown
that fracture of individual carpal bones is commoner than was
previously supposed, and that many cases formerly looked upon as
severe sprains are examples of this injury.
The _navicular_ (scaphoid) and _lunate_ (semilunar) are those most
commonly fractured, usually by indirect violence, by forced
dorsiflexion from a fall on the extended hand. The clinical features
are: localised swelling on the radial side of the wrist, increase in
the antero-posterior diameter of the carpus, marked tenderness in the
anatomical snuff-box when the hand is moved laterally, especially in
the direction of adduction, and, rarely, crepitus. The median nerve is
sometimes over-stretched or partly torn. In many cases, however, the
symptoms are so obscure that an accurate diagnosis can only be made by
the use of the X-rays (Fig. 49). Codman recommends taking pictures of
the navicular by placing the two wrists of the patient in adduction,
and of the lunate, in abduction.
[Illustration: FIG. 49.--Radiogram showing Fracture of Navicular
(Scaphoid) Bone.]
The _treatment_ of simple fractures consists in massage and movement.
Codman and Chase recommend excision of the proximal half of the
fractured bone, through a dorsal incision to the lateral side of the
extensor digitorum communis. When the fracture is compound, the loose
fragments should be removed.
DISLOCATIONS IN THE REGION OF THE WRIST
Dislocation may occur at the inferior radio-ulnar, the radio-carpal,
mid-carpal, inter-carpal, or carpo-metacarpal joints, but the strong
ligaments of these articulations, the comparatively free movement at
the various joints, and the relative weakness of the lower end of the
radius whereby it is so frequently fractured, render dislocation a
rare form of injury.
Dislocation of the #inferior radio-ulnar# articulation may complicate
fracture of the lower end of the radius, or accompany sub-luxation of
the head of the radius. The head of the ulna usually passes backward.
In children, the commonest cause is lifting the child by the hand, and
the displacement is only partial. In adults, it may result from
forcible efforts at pronation or supination, as in wringing clothes,
or from direct violence, the separation being frequently complete, and
sometimes compound.
The head of the ulna is unduly prominent, and there is a depression on
the opposite aspect of the joint. The hand is generally pronated, the
rotatory movements at the wrist are restricted and painful, while
flexion and extension are comparatively free.
Reduction is effected by making pressure on the displaced bone and
manipulating the joint, especially in the direction of supination. If
the ligaments fail to unite, the head of the ulna tends to slip out of
place in pronation and supination--_recurrent dislocation_.
Dislocation at the #radio-carpal# articulation, usually spoken of as
_dislocation of the wrist_, is attended by tearing of the ligaments
and displacement of tendons, and is frequently compound. The carpus
may be displaced backward or forward, and the articular edge of the
radius towards which it passes may be chipped off.
_Backward_ dislocation is commonest, the injury resulting from a
severe form of violence, such as a fall from a height on the palm
while the hand is dorsiflexed and abducted. The clinical appearances
closely simulate those of Colles' fracture, or of separation of the
lower radial epiphysis, but the unnatural projections, both in front
and behind, are lower down, and end more abruptly (Fig. 50). The hand
is more flexed, and the palm is shortened. The styloid processes
retain their normal relations to one another, and the carpal bones lie
on a plane posterior to the styloids, the articular surfaces may be
recognised on palpation. The forearm is not shortened.
_Forward_ dislocation of the carpus may result from any form of forced
flexion, such as a fall on the back of the hand, or from direct
violence. The displaced carpus forms a marked projection on the palmar
aspect of the wrist, and there is a corresponding depression on the
dorsum. The attitude of the hand and fingers is usually one of
flexion.
In both varieties reduction is readily effected by making traction on
the hand and pushing the carpus into position. A moulded poroplastic
splint, which keeps the hand slightly dorsiflexed, adds to the comfort
of the patient, but this should be removed daily to admit of movement
and massage being employed.
[Illustration: FIG. 50.--Dorsal Dislocation of Wrist at Radio-carpal
Articulation, in a man, aet. 24, from a fall.]
#Dislocation of Carpal Bones.#--The two rows of carpal bones may be
separated from one another, or any one of the individual bones may be
displaced. These injuries are rare, and result from severe forms of
violence, usually from a fall on the extended hand. Pain, deformity,
and loss of function are the ordinary symptoms. The treatment consists
in making direct pressure over the displaced bone, while traction is
made on the hand, which is alternately flexed and extended.
Of these injuries that most frequently observed is displacement of the
_head of the capitate bone_ (_os magnum_) from the navicular
(scaphoid) and lunate (semilunar) bones. Frequently these bones are
fractured, and fragments accompany the displaced os magnum. In full
palmar flexion of the wrist the displaced head of the os magnum forms
a prominence on the dorsum opposite the base of the third metacarpal,
which temporarily disappears when the hand is dorsiflexed. There is an
increase in the antero-posterior diameter of the wrist, situated on a
lower level than that which accompanies fracture of the lower end of
the radius; flexion and extension of the wrist are limited; and in
some cases there are symptoms referable to pressure on the median
nerve. By keeping the hand in the dorsiflexed position for a week or
ten days, the bone may become fixed in its place and the function of
the wrist be restored, but it is often necessary to excise the bone.
The _lunate_ may be displaced forward by forcible dorsiflexion of the
hand, and forms a projection beneath the flexor tendons; there is
usually loss of sensibility in the distribution of the ulnar nerve in
the hand. The most satisfactory treatment is removal of the bone.
In a few cases the _navicular_ has been displaced (Fig. 51), and has
had to be subsequently replaced by operation. Separation of any of the
other bones is rare.
[Illustration: FIG. 51.--Radiogram showing Forward Dislocation of
Navicular (Scaphoid) Bone.]
#Carpo-metacarpal Dislocations.#--Any or all of the metacarpal bones
may be separated from the carpus by forced movements of flexion or
extension. The commonest displacement is backward. The thumb seems to
suffer oftener than the other digits. These injuries, however, are so
rare, and the deformity is so characteristic, that a detailed
description is unnecessary.
#Sprain of the wrist# is a common injury, and results from a fall on
the hand, a twist of the wrist, or from the back-firing of a
motor-crank dorsiflexing the hand. The marked swelling which rapidly
ensues may render it difficult to distinguish a sprain from the other
injuries that are liable to result from similar causes--Colles'
fracture, separation of the lower radial epiphysis, dislocation of the
wrist, and fractures and dislocations of the carpal bones.
In a sprain the normal relations of the styloid processes and other
bony points about the wrist are unaltered, and there is no radial
deviation of the hand, as in Colles' fracture. The most marked
swelling is over the line of the articulation on the anterior and
posterior aspects of the joint. There is usually some effusion into
the sheaths of the tendons passing over the joint, and in some cases
on moving the fingers a peculiar creaking, which may simulate
crepitus, can be elicited. There is marked tenderness on making
pressure over the line of the joint, as well as over one or other of
the collateral ligaments, depending upon which ligament has been
over-stretched or torn. Movements that tend to put the damaged
ligaments on the stretch also cause pain. It has to be borne in mind,
however, that in many cases of Colles' fracture there is extreme
tenderness on pressing over the ulnar styloid and medial ulno-carpal
ligament, as these structures are frequently injured as well as the
radius, but the point of maximum pain and tenderness is over the seat
of fracture of the radius. In all doubtful cases the X-rays should be
employed to establish the diagnosis.
The _treatment_ consists in the immediate employment of massage and
movement, supplemented by alternate hot and cold douches, on the same
lines as in sprains of other joints.
INJURIES OF THE FINGERS
#Fracture.#--_Fractures of the metacarpals of the fingers_ are
comparatively common. When they result from direct violence, such as
a crush between two heavy objects, they are often multiple and
compound. Indirect violence, acting in the long axis of the bone and
increasing its natural curve, such as a blow on the knuckle in
striking with the closed fist, usually produces an oblique fracture
about the middle of the shaft, the proximal end of the distal fragment
projecting towards the dorsum. Apart from this there is little
deformity, as the adjacent metacarpals act as natural splints and tend
to retain the fragments in position. A sudden sharp pain may be
elicited at the seat of fracture on making pressure in the long axis
of the finger; and unnatural mobility and crepitus may usually be
detected. These fractures are readily recognised by the X-rays. Firm
union usually results in three weeks.
The shaft of the _metacarpal of the thumb_ is frequently broken by a
blow with the closed fist. The fracture is usually transverse, and
situated near the proximal end of the shaft; frequently it is
comminuted, and in some instances there is a longitudinal split.
_Treatment._--When the fracture is transverse, and especially when it
implicates the middle or ring fingers, the most convenient method is
to make the patient grasp a firm pad, such as a roller bandage covered
with a layer of wool, and to fix the closed fist by a figure-of-eight
bandage. In this way the adjoining metacarpals are utilised as side
splints. Active and passive movements must be carried out from the
first, and the bandage may be dispensed with at the end of a week or
ten days.
In oblique fractures with a tendency to overriding of the fragments,
especially in the case of the index and little fingers, it is
sometimes necessary to apply extension to the distal segment of the
digit, by means of adhesive plaster, to which elastic tubing is
attached and fixed to the end of a bow splint, reaching well beyond
the finger-tips (Fig. 52). This should be worn for a week or ten days.
[Illustration: FIG. 52.--Extension apparatus for Oblique Fracture of
Metacarpals.]
#Bennett's Fracture of the Base of the First Metacarpal
Bone.#--Bennett of Dublin described an injury of the thumb which,
although comparatively common, is often mistaken for a sub-luxation
backward of the carpo-metacarpal joint, or a simple "stave of the
thumb." It consists in an "oblique fracture through the base of the
bone, detaching the greater part of the articular facet with that
piece of the bone supporting it which projects into the palm" (Fig.
53). We have frequently observed the fracture extend for a
considerable distance along the palmar aspect of the shaft.
[Illustration: FIG. 53.--Radiogram of Bennett's Fracture of Base of
Metacarpal of Right Thumb.]
It usually results from severe force applied directly to the point of
the thumb, driving the metacarpal against the greater multangular bone
(trapezium), and chipping off the palmar part of the articular
surface, but it may result from a blow with the closed fist. The rest
of the metacarpal slips backward, forming a prominence on the dorsal
aspect of the joint. The pain and swelling in the region of the
fracture often prevent crepitus being elicited, and as the deformity
is not at once evident, the nature of the injury is liable to be
overlooked. The fracture is recognised by the use of the X-rays.
Unless properly treated this injury may result in prolonged impairment
of function, full abduction and fine movements requiring close
apposition of the thumb being specially interfered with.
The _treatment_ consists in reducing the fracture by extension in the
attitude of full abduction and applying an accurately fitting pad over
the extremity of the displaced bone, maintained in position by a light
angular splint. This splint is first fixed to the extended and
abducted thumb, and while extension is made by pushing it downwards
the upper end is fixed to the wrist (Fig. 54 A). The apparatus is worn
for three weeks, being carefully readjusted from time to time to
maintain the extension and abduction. A moulded poroplastic splint
added on the same principle may be employed, and is more comfortable
(Fig. 54 B). Excellent results are obtained after reduction of the
displacement, by massage and movement from the first, and the support
merely of a figure-of-eight bandage (Pirie Watson).
[Illustration: FIG. 54.--A. Splint applied as used by Bennett. B.
Poroplastic Moulded Splint for Bennett's Fracture.]
#Fractures of phalanges# usually result from direct violence, and on
account of the superficial position of the bones, are often compound,
and attended with much bruising of soft parts. Force applied to the
distal end of the finger may also fracture a phalanx. The proximal
phalanges are broken oftener than the others. The deformity is usually
angular, with the apex towards the palm, and if union takes place in
this position, the power of grasping is interfered with. Unnatural
mobility and crepitus can usually be recognised, but, on account of
the swelling and tenderness, the fracture is apt to be overlooked.
Firm union takes place in two or three weeks. In oblique and
comminuted fractures, union may take place with overlapping, producing
a deformity which may prevent the wearing of a glove or of rings. In
compound fractures, non-union sometimes occurs, and causes persistent
disability. In doubtful cases radioscopy renders valuable aid, as the
parts are readily seen with the screen.
_Treatment._--Early movement and massage are all-important. The
contiguous fingers may be utilised as side splints, and a long palmar
splint projecting beyond the fingers is applied. In oblique and
comminuted fractures it may be necessary to anaesthetise the patient to
effect reduction. When it is particularly desirable to avoid
deformity, an open operation may be advisable.
#Dislocation.#--_Dislocation of the Metacarpo-phalangeal Joint of the
Thumb._--The commonest dislocation at this joint is a _backward_
displacement of the proximal phalanx, which may be complete or
incomplete. Its special clinical importance lies in the fact that much
difficulty is often experienced in effecting reduction.
This dislocation is usually produced by extreme dorsiflexion of the
thumb, whereby the volar accessory (palmar) and the collateral
ligaments are torn from their metacarpal attachments, the phalanx
carrying with it the volar accessory ligament and sesamoid bones. The
head of the metacarpal passes forward between the two heads of the
short flexor of the thumb, and the tendon of the long flexor slips to
the ulnar side. The phalanx passes on to the dorsum of the metacarpal,
where it is held erect by the tension of the abductor and adductor
muscles.
The attitude of the thumb is characteristic. The metacarpal is
adducted, its head forming a marked prominence on the front of the
thenar eminence, and the phalanges are displaced backwards, the
proximal being dorsiflexed and the distal flexed towards the palm.
Many explanations of the difficulty so often experienced in reducing
this variety of dislocation have been offered, but the consensus of
opinion seems to be that it is due to the interposition of the volar
accessory ligament and the sesamoid bones between the phalanx and the
metacarpal, and that this is most frequently the result of ill-advised
efforts at reduction. In some cases the tension of the long flexor
tendon may be a factor in preventing reduction, but the
"button-holing" by the short flexor is probably of no importance.
Reduction is to be effected by flexing and abducting the metacarpal
while the phalanx is hyper-extended and pushed down towards the joint
and levered over the head of the metacarpal.
When this manipulation fails, the volar accessory ligament should be
divided longitudinally through a puncture made with a tenotomy knife
on the dorsal aspect of the joint, so as to separate the sesamoid
bones and permit the passage of the head between them. An open
operation is seldom necessary.
Dislocation _forward_ is rare. It results from forced flexion of the
thumb with abduction, tearing the posterior and medial collateral
ligaments. The deformity is characteristic: the rounded head of the
metacarpal projecting behind the level of the joint, while the base of
the phalanx forms a prominence among the muscles of the thenar
eminence.
Reduction is easily effected by making traction on the phalanges and
carrying out movements of flexion and extension. The deformity,
however, is liable to be reproduced unless a retentive apparatus is
securely applied.
Dislocation of the thumb to one or other side is rare.
Dislocations of the _metacarpo-phalangeal joint of the fingers_ may be
backward or forward. They are less common than those of the thumb, but
present the same general characters. In the backward variety the same
difficulty in reduction occurs as is met with in the corresponding
dislocation of the thumb, and is to be dealt with on the same lines.
_Inter-phalangeal Dislocation._--The second and the ungual phalanges
may be displaced backwards, forwards, or to the side. The clinical
features are characteristic, and the diagnosis, as well as reduction,
is easy. These dislocations are frequently the result of machinery
accidents, and being compound and difficult to render aseptic, often
necessitate amputation.
_Persistent flexion of the terminal phalanx_ of the thumb or fingers
(_drop_ or _mallet finger_) may result from violence applied to the
end of the digit when in the extended position--as, for example, in
attempting to catch a cricket-ball. The terminal phalanx is flexed
towards the palm, and the patient is unable to extend it voluntarily.
A palmar splint is applied securing extension of the distal joint for
three or four weeks. If the deformity has been allowed to occur it can
only be corrected by an open operation, suturing or tightening the
extensor tendon at its insertion into the base of the terminal
phalanx.