THUMB-IN-PALM DEFORMITY
The second most frequent and important deformity of the hand in cerebral palsy is the thumb-in-palm, adducted thumb, or clutched thumb deformity (Figure 73-11). This deformity blocks
entry of objects into the palm and, in addition,
prevents the thumb from assisting fingers in grasp or
pinch. Contributing to thumb-in-palm deformity are
spasticity of the flexor pollicis longus, flexor pollicis brevis, abductor
pollicis, and first dorsal interosseus, as well as weakness of the extensor
pollicis longus, extensor pollicis brevis, and adductor pollicis longus muscles.
Spasticity in the extensor pollicis longus muscle also may contribute to an
adduction deformity of the thumb during the release
phase (Figure 73-12). In 1981 House, Gwathney, and
Fidler classified thumb-in-palm deformities into four
major types based on the clinical appearance of the thumb. A type I deformity consists of a simple metacarpal
adduction contracture and is the most common pattern. A type II deformity
consists of a metacarpal adduction contracture combined with a
metacarpophalangeal flexion deformity. A type III deformity consists of a
metacarpal adduction contracture combined with a metacarpophalangeal
hyperextension deformity or instability; this is the second most common pattern.
A type IV deformity consists of a metacarpal adduction contracture combined with
metacarpophalangeal and interphalangeal flexion deformities; this is believed to
be the most severe deformity, being caused by spasticity in the flexor pollicis
longus, as well as in the intrinsic muscles in the thumb (Figure 73-13).
  |
and interphalangeal joints. |
 Click to enlarge |
exerted by powerful muscles. (Redrawn from Inglis AE, Cooper W, Bruton W: J Bone Joint Surg 52-A:253, 1970.) |
  Click to enlarge |
thumb is flexed at interphalangeal and metacarpophalangeal joints, and carpometacarpal joint is flexed and adducted. (From Smith RJ: J Hand Surg 7:327, 1982.) |
Although thumb-in-palm deformity may be caused
principally by spasticity of the flexor pollicis longus muscle, it is not caused
solely by this muscle. The flexor pollicis longus flexes the interphalangeal
joint, the metacarpophalangeal joint, and the carpometacarpal joint and also
acts as an adductor of the thumb. To be certain that
it is a principal deforming force, the patient should be able to decrease the
flexion of these joints by flexing the wrist. Conversely, extending the wrist
will cause an increase in deformity. The examiner should determine whether an
accompanying severe adduction deformity, caused by contracture of muscle or
other structures, is present. A weak adductor pollicis may be overpowered by a
tendon transfer; active adduction of the thumb by the
adductor pollicis should be checked with the wrist palmar flexed to determine
the strength of the muscle.
Treatment. Treatment of thumb-in-palm
deformity must be individualized after careful, repeated assessments of the
overall hand function, as well as function of the specific muscles contributing
to the deformity. Currently, a dynamic approach is used in the surgical
correction of this deformity, as described by House et al. This involves release
of contractures, augmentation of weak muscles, and skeletal stabilization,
especially of the metacarpophalangeal joint when necessary. A myotomy of the
adductor pollicis may be carried out through a palmar incision as described by
Matev (1963) or through a Z-plasty incision placed in the first web if a skin
contracture is present. Hoffer et al. (1983) found that preoperative
electromyography of the adductor pollicis was useful in determining whether a
partial or complete release of this muscle was necessary. If the adductor was
active during grasp, the patients were said to have selective control, and
release of the transverse head of the muscle only was considered because, in the
experience of Hoffer et al., pinch may be weak if complete myotomy is performed.
Release of the origin of the first dorsal interosseus muscle also may be
required. In long-standing type II deformities the origin of both the adductor
and the flexor pollicis brevis may require release, as described by Matev. In
type IV deformities the flexor pollicis longus may require lengthening proximal
to the wrist. Augmentation of a weak abductor pollicis longus may be necessary.
The most common muscles used for this augmentation are the palmaris longus, the
brachioradialis, and the flexor carpi radialis. Fusion of the thumb metacarpophalangeal joint is especially useful if a
hyperextension deformity of that joint is present. Arthrodesis may be performed
without damage to the physis if only articular cartilage is removed and a smooth
Kirschner wire is used for fixation.
Smith has proposed transfer of the flexor pollicis longus tendon to the
radial side of the thumb combined with tenodesis of
the distal joint. He recommends the operation for patients who have some use of
the affected hand, in addition to passive extension of the metacarpophalangeal
joint and abduction of the carpometacarpal joint with the wrist in flexion.
If the extensor pollicis longus contributes to the thumb deformity, it may be rerouted from Lister’s tubercle
as recommended by Manske (1985). Significant improvement in functional
activities was noted in 90% of his patients treated with this technique.
Myotomy
TECHNIQUE
Make an incision bordering the thenar crease in the palm, but avoid damaging the recurrent branch of the median
nerve or the innervation of the adductor pollicis. After retracting the long
flexors of the fingers, strip from the third metacarpal the origin of the
adductor pollicis. Cut from the deep transverse carpal ligament about two thirds
of the origin of the abductor pollicis brevis and all of the origins of the
flexor pollicis brevis and opponens pollicis (Figure
73-14). Also strip from the first metacarpal the origin of the first dorsal
interosseus. If necessary, carry out a capsulorrhaphy of the metacarpophalangeal
joint.
  Click to enlarge |
deformity (see text). (Modified from Swanson AB: Surg Clin North Am 48:1129, 1968.) |
Aftertreatment. A pressure dressing and a cast are applied holding the
first metacarpal (not the phalanges) in wide abduction and opposition. At 3
weeks the cast and sutures are removed and a splint is applied to hold the thumb in this same position. If tendon transfers have been
necessary, the cast is retained for 6 weeks. Splinting at night may be necessary
for a long time if the deformity tends to recur.
Release of contractures,
augmentation of weak muscles, and skeletal stabilization
TECHNIQUE (House et al.)
Step 1 (release of contractures). Through a Z-plasty incision
located along the first web space, release the origin of the first dorsal
interosseus muscle from the thumb metacarpal (Figure 73-15, A). Expose the intramuscular
portion of the tendon of the adductor pollicis and divide it obliquely to allow
a relative lengthening of the tendon while preserving bridging muscle fibers. If
a long-standing type II deformity exists with a flexion deformity of the
metacarpophalangeal joint, release the origin of both the adductor and the
flexor pollicis brevis if necessary. For a type IV deformity with spasticity of
the flexor pollicis longus muscle and interphalangeal flexion deformity,
lengthen the tendon of the flexor pollicis longus proximal to the wrist.
  Click to enlarge |
through Z-plasty first web incision. B, Transfer of palmaris longus to intact abductor pollicis longus, which has been released from first dorsal compartment. C, Transfer of distal portion of tendon of abductor pollicis longus to flexor carpi radialis, so-called dynamic tenodesis, and transfer of proximal segment of abductor pollicis longus into extensor pollicis brevis. D, Chondrodesis of thumb metacarpophalangeal joint for hyperextension deformity. (Redrawn from House JH, Gwathney FW, Fidler MO: J Bone Joint Surg 63-A:216, 1981). |
Step 2 (augmentation of weak muscles). If adduction of the thumb at the carpometacarpal joint is considerable, with
weakness of the abductor pollicis longus, then release the abductor pollicis
longus tendon from the first extensor compartment and allow the tendon to
subluxate volarly. Divide the palmaris longus tendon at the level of the wrist
and suture it into the abductor pollicis longus tendon in an end-to-side fashion
(Figure 73-15, B). The brachioradialis, as
well as the flexor carpi radialis, may be used instead of the palmaris longus if
desired. If there is no suitable donor for active transfer, then divide the
abductor pollicis longus tendon and reroute its distal portion volarly,
attaching it in an end-to-side fashion to the flexor carpi radialis tendon under
sufficient tension to maintain metacarpal abduction (Figure 73-15, C). This provides a dynamic
abductor tenodesis. If the flexion deformity at the metacarpophalangeal joint is
significant but stability of the joint is normal, then a similar tenodesis of
the extensor pollicis brevis tendon may be performed. Care must be taken not to
create a disabling hyperextension deformity at this joint.
Step 3 (skeletal stabilization). If there is a hyperextension
deformity of the metacarpophalangeal joint (type III deformity), then carefully
remove the articular cartilage of the metacarpophalangeal joint without damaging
the physis. Position the thumb and secure it with one
centrally placed 1-mm Kirschner wire (Figure
73-15, D).
Aftertreatment. The forearm and hand are immobilized for 4 weeks with
the thumb held in abduction and extension by a volar
plaster splint. Then active and assisted exercises of the wrist, thumb, and fingers are started. A long opponens splint
modified by the addition of a C bar or molded plastic orthosis is worn between
exercise periods for the next few weeks, after which splinting is continued at
night only until growth is completed or dynamic balance is attained and
stabilized.
Flexor pollicis longus
abductor-plasty
TECHNIQUE (Smith)
Make a radial midlateral incision from the middle of the distal phalanx of
the thumb to the neck of the first metacarpal (Figure 73-16, A). Elevate a volar skin flap
and transect the flexor pollicis longus tendon opposite the proximal phalanx (Figure 73-16, B). Tenodese the flexor pollicis
longus stump to the proximal phalanx or arthrodese the distal joint in 15
degrees of flexion (Figure 73-16, C to
E). Now make a longitudinal incision in the forearm just radial to the
tendon of the flexor carpi radialis, curving its distal portion ulnarward.
Identify the flexor pollicis longus tendon and draw it out through this
incision. Tunnel subcutaneously by blunt dissection on the radial side of the
thumb to the lateral side of the metacarpophalangeal
joint and pass the flexor pollicis longus tendon through this tunnel. With the
wrist in neutral position and the thumb at 50 degrees
of abduction, suture the tendon to the dorsoradial aspect of the
metacarpophalangeal joint with tension (Figure
73-16, F).
  Click to enlarge |
thumb exposes insertion of flexor pollicis longus, interphalangeal joint, and base of proximal phalanx. Second curved incision to radial side of wrist exposes flexor pollicis longus near its musculotendinous juncture and permits tendon to be withdrawn from carpal canal. B, Flexor pollicis longus is transected at its insertion and withdrawn from carpal canal through wrist incision. It is then passed subcutaneously to radial side of base of proximal phalanx. C to E, Interphalangeal joint of thumb is arthrodesed in about 15 degrees of flexion in adult. In child with open epiphysis, distal joint may be tenodesed in about 15 degrees of flexion. F, Transfer of flexor pollicis longus to radial side of proximal phalanx reduces adduction-flexion deformity and augments thumb abduction by transferred position of flexor pollicis longus. Interphalangeal arthrodesis improves metacarpophalangeal joint extension by increasing lever arm of extensor pollicis longus on metacarpophalangeal joint. (From Smith RJ: J Hand Surg 7:327, 1982). |
Aftertreatment. The hand is immobilized for 6 weeks with the thumb in abduction and the wrist in 30 degrees of flexion.
The thumb is splinted with a C-splint in the web for
an additional 6 weeks.
Redirection of extensor pollicis
longus
TECHNIQUE (Manske)
Through a palmar incision, release the adductor pollicis and the deep head
of the flexor pollicis brevis, as described by Matev and by Swanson. Release the
first dorsal interosseus muscle at its origin from the first metacarpal through
a longitudinal incision on the dorsum of the thumb.
Next extend the incision on the dorsum of the thumb
distally to the proximal phalanx, exposing the extensor aponeurotic hood (Figure 73-17, A). Identify the extensor
pollicis longus at the metacarpophalangeal joint and dissect it out from the
extensor aponeurosis for a distance of 10 mm distal to the joint. This leaves a
longitudinal defect 4 mm wide in the extensor hood. Take care to preserve the
margins of the aponeurosis sufficiently for subsequent closure. Identify the
extensor pollicis longus through a longitudinal incision at the distal radius
and withdraw it into the forearm (Figure 73-17,
B). Redirect the extensor pollicis longus tendon along the radial aspect
of the wrist, using the first extensor retinacular compartment as a pulley to
maintain its position by passing a curved hemostat or tendon passer from the
dorsal incision on the thumb along the course of the
extensor pollicis brevis tendon through the first extensor compartment. Grasp
the extensor pollicis longus tendon with the hemostat and retract it distally
through the first extensor compartment (Figure
73-17, C). If redirecting the tendon through this compartment is
difficult, the extensor pollicis longus can be routed around the extensor
pollicis brevis and adductor pollicis longus tendons just proximal to the
compartment and then into the dorsal incision on the thumb. Next pass the extensor pollicis longus tendon
through a transverse tunnel made in the capsule of the metacarpophalangeal joint
and suture it under sufficient tension to advance it 1 to 2 cm from its original
position (Figure 73-17, D). If the
metacarpophalangeal joint is hyperextensible, this tunnel should be placed
proximal to the articular surface to prevent further hyperextension. In this
situation a temporary Kirschner wire should be inserted across the slightly
flexed metacarpophalangeal joint. Suture the distal portion of the extensor
pollicis longus tendon into the extensor aponeurosis to close the longitudinal
defect and prevent flexion deformity at the interphalangeal joint (Figure 73-17, E). Close the incisions in
routine fashion.
  Click to enlarge |
extensor pollicis longus tendon to correct thumb-in-palm deformity (see text). (Redrawn from Manske PR: J Hand Surg 10-A:553, 1985). |
Aftertreatment. The thumb is immobilized in
abduction and extension in a short arm thumb spica
cast for 4 weeks. If a Kirschner wire has been inserted in the
metacarpophalangeal joint, it should be removed at 4 weeks. Then a removable
thumb spica splint is worn for 2 weeks; this splint
is removed three to four times daily for controlled active motion.
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