Thanapong Waitayawinyu and Scott N. Oishi
DEFINITION
The thumb-in-palm deformity is a fixed adduction–flexion posture in the affected hand of the patient with spastic cerebral palsy. This influences both hand function and hygiene.
ANATOMY
Imbalance of the spastic thumb flexor–adductor and the paretic thumb extensor results in thumb-in-palm deformity (FIG 1A).
The adductor pollicis (AP) is the most commonly involved muscle; the abductor pollicis brevis (APB) is usually not involved.13
The spastic AP, the first dorsal interosseous muscle, or both adduct the thumb and index metacarpals and cause first web space contracture.
If the flexor pollicis brevis (FPB) is spastic, the thumb metacarpophalangeal (MCP) joint will develop a flexion deformity.
Involvement of both the AP and FPB results in a thumb flexion and adduction posture with the thumb lying across the palm.
Involvement of the flexor pollicis longus (FPL) results in added thumb interphalangeal (IP) joint flexion (FIG 1B).
Weak thumb extensor and abductor pollicis longus (APL) may also contribute to the deformity.
FIG 1 • Thumb-in-palm deformity (A) demonstrating metacarpophalangeal laxity and hyperextension (B).
Active function of the extensor pollicis longus (EPL) and extensor pollicis brevis (EPB) may result in hyperextension of the thumb MCP joint.
PATHOGENESIS
Upper motor neuron lesions due to antenatal cerebral infarcts, kernicterus, intraventricular bleeding, head trauma, anoxia, and other causes result in spasticity, which in turn causes shortening of the myotendinous unit and secondary contractures.
Paresis of muscles may contribute to greater deformity when spastic muscles are unopposed.
NATURAL HISTORY
A supple thumb-in-palm posture is a normal finding in infants during the first year. Persistence of a tightly closed thumb in palm longer than 1 year is abnormal and should be evaluated.
The deformity is usually correctable at first and then progresses to a fixed deformity as myostatic contracture develops.
A progressive and variable-size discrepancy of the involved limb may develop, resulting in a smaller thumb.1
The lack of thumb extension and abduction can impair hand grip, function, appearance, and hygiene.
PATIENT HISTORY AND PHYSICAL FINDINGS
A complete history and physical examination of a child with cerebral palsy should be done carefully and thoroughly.
Input from other professionals such as neurologists and occupational therapists is often helpful.
Repeated observation or videotaping of the child during various activities can also be useful for accurate evaluation.
The diagnosis and pattern of cerebral palsy should be confirmed before planning treatment.
Associated deformities of the spastic upper extremity such as finger and wrist flexion, forearm pronation, elbow flexion, and shoulder adduction and internal rotation should also be evaluated. Surgical treatment of thumb-in-palm deformity may be only one part of surgical care of the involved extremity.
Thumb muscle involvement, motion, and stability should be evaluated in the physical examination before organizing the treatment plan.
Individual muscle involvement is detected by observing thumb position and palpating spastic or contracted muscles (Table 1).
Motion and stability are assessed by passive and active range of thumb abduction–adduction, flexion–extension, and palmar abduction and opposition.
The pattern of voluntary grasp and release of large objects and manipulation of small objects should be determined by observing the child during functional activities.
Sensory deficits impair function. Assessment of sensation should include stereognosis.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Electrophysiologic testing and selective nerve blocks may help in localizing involved muscles and identifying muscles available for tendon transfers.
Select nerve blocks may help differentiate between spastic, spared, and fibrotic muscles.
Dynamic electromyography (EMG) with motion analysis may offer important information for planning tendon transfer surgery.4
Radiographs may reveal thumb joint instability or growth disturbance.
DIFFERENTIAL DIAGNOSIS
Clasped thumb
Distal arthrogryposis
Absence of thumb extensor (faux extensor agenesis)
NONOPERATIVE MANAGEMENT
Use of tone-reducing medication such as botulinum toxin to the adductor pollicis can soften the deformities and improve joint range of motion for nonoperative management.3
In mild deformity, nonoperative treatment with orthoses may help in maintaining thumb abduction, but too-rigid splinting may result in limited thumb motion.
SURGICAL MANAGEMENT
The principles of surgery for thumb-in-palm deformity are the following2 :
Release of spastic muscles or contractures
Augmentation of paretic muscles
Stabilization of unstable thumb joints
Release of contracture with or without augmentation of weak muscles aims to rebalance the thumb muscles, depending on the pattern of motor dysfunction of the thumb and the patient's degree of voluntary control.
Release of spastic muscle or myostatic contractures can be performed by intrinsic muscle release of the AP, FPB, APB, and first dorsal interosseous.
Extrinsic muscle release of the FPL may be considered if it is affected.
Secondary skin and fascial contracture of the first web space need to be addressed by four-flap or double-opposing Z-plasty.
Augmentation of paretic thumb abduction and extension can be accomplished by a combination of tenodesis and tendon rerouting or transfers and depends on the specific deficit, the muscles available, and the extent of voluntary control of selected muscles.
Thumb MCP joint arthrodesis or sesamoid capsulodesis should be considered for stabilizing the thumb MCP joints when the joint remains unstable.2
These joint stabilization procedures can also enhance tendon transfer procedures for extension–abduction.
Thumb MCP joint arthrodesis is considered when tendon transfer fails to correct the deformities or when sesamoid capsulodesis cannot control the hyperextension of the MCP joint.1
Thumb carpometacarpal (CMC) joint stabilization is indicated when metacarpal adduction cannot be controlled. CMC fusion, which preserves scaphotrapezial motion, is preferable to the rigid intermetacarpal fusion.2
Thumb IP joint fusion is usually not necessary, but this procedure may be indicated when the IP joint flexion contracture is severe or in the rare event of an FPL rupture after lengthening.2
Table 2 lists surgical options for treating thumb-in-palm deformity.
Preoperative Planning
General planning for surgery includes comprehensive evaluation with a multispecialty approach.
Surgery should be done when the central nervous system has matured and the child is old enough to cooperate with postoperative therapy—usually at least 5 to 6 years old.5
Associated abnormalities (eg, seizures, mental status problems) should be assessed and the management optimized before surgery is contemplated.
Patient understanding and emotional readiness as well as family and social support should be addressed before surgery.
Physical examination under anesthesia is crucial. This can differentiate spastic from myostatic conditions and can accurately evaluate the stability of thumb joints.
Positioning
The patient is placed in the supine position, and surgery is performed under general anesthesia and tourniquet control.
Approach
Surgical approaches for thumb-in-palm deformity depend on the objectives.
Release of static or longstanding intrinsic contracture is usually performed through a curved incision located over the line of the thenar crease to release the origin of the adductor pollicis with or without the origin of the FPB.7
Release of a simple intrinsic contracture may be performed through the first web space approach to release the adductor pollicis and the first dorsal interosseous muscle, combined with four-flap or double-opposing Z-plasty to release the secondary web space contracture.2
A surgical approach by a small incision over the volar aspect of the distal forearm is used for extrinsic release of the FPL tendon, if necessary.
A dorsal approach to the thumb and a dorsoradial approach over the wrist is used for augmentation of thumb extensors, with a volar-radial approach being used for augmentation of the thumb abductor.
TECHNIQUES
RELEASE OF CONTRACTURES
Release of Static Intrinsic Contracture
A curved skin incision is performed next to the line of the thenar crease, extending distally from the carpal tunnel area (TECH FIG 1A).
The superficial palmar arch and median nerve, including its motor branch to the thenar muscle, distal to the transverse carpal ligament are identified and protected. Careful dissection must be performed because occasionally the motor branch comes through the transverse carpal ligament instead of being distal to this structure (TECH FIG 1B).
The flexor digitorum sublimis and profundi are identified and retracted ulnarly with the neurovascular bundle.
The transverse head of adductor pollicis is identified and divided from its origin on the third metacarpal (TECH FIG 1C,D).
The motor branch of the ulnar nerve and the deep palmar arch are identified and protected.
Release of the oblique head of the adductor pollicis from its origin at the bases of the second and third metacarpal, capitate, and trapezoid is performed.
The FPB origin at the transverse carpal ligament and trapezium may also be released if this muscle limits abduction and extension of the thumb ray.
The first dorsal interosseous may be released at the distal portion of the muscle from the ulnar aspect of the first metacarpal if needed to obtain adequate passive abduction and extension of the thumb.
Release of Simple Intrinsic Contracture
A four-flap Z-plasty over the contracted first web space is designed (TECH FIG 2A,B).
After the skin incision, the dorsal fascia is incised while protecting the neurovascular bundles.
The first dorsal interosseous is released at its origin from the thumb metacarpal.
The adductor pollicis is lengthened by release in an oblique cut at its intramuscular tendon; the surgeon should aim to preserve some adductor function (TECH FIG 2C).
Four skin flaps are rearranged to increase the first web space (TECH FIG 2D).
Release of Extrinsic Contracture
A small longitudinal incision over the distal-volar aspect of the forearm is performed.
The FPL tendon is exposed and incised over the musculotendinous portion.
The thumb interphalangeal joint is hyperextended until 1 cm of distal sliding of the FPL tendon is identified.
The FPL may be lengthened by Z-lengthening of the FPL tendon, with 0.5 mm of lengthening for each degree of correction.1
TECH FIG 1 • Intrinsic release. A. A curved incision is made over the thenar crease. B. Thenar release showing motor branch. C,D. Thumb intrinsics are released.
TECH FIG 2 • Four-flap Z-plasty over first web space. A,B. Skin markings. C. Elevation of flaps and adductor exposure. D. After rotation of skin flaps.
AUGMENTATION OF WEAK MUSCLES
Abductor Pollicis Longus Augmentation
Two small transverse incisions over the volar wrist crease and the first extensor compartment are made, aiming to expose the palmaris longus (PL) or flexor carpi radialis (FCR) and APL, respectively.
The superficial branch of the radial nerve is identified and protected.
The first extensor compartment is then opened, and the APL is identified. Each slip of the APL tendon should be pulled into tension to show the best slip for carpometacarpal joint abduction.
At the volar incision, the palmar branch of the median nerve is identified and protected. The PL tendon is then divided.
The selected APL tendon slip is translocated volarly until acceptable thumb metacarpal abduction is achieved.
The PL tendon is passed through a subcutaneous tunnel to the volar-radial incision.
End-to-side tendon weave of the PL to the translocated APL is then performed under sufficient tension to obtain appropriate thumb abduction (TECH FIG 3A).
Alternatively, the APL tendon may be cut and the distal segment rerouted volarly and woven with end-to-end PL or end-to-side FCR. The proximal segment of the APL may be used to augment thumb MCP joint extension by end-to-side anastomosis with the EPB (TECH FIG 3B).
TECH FIG 3 • A. Transfer of palmaris longus to translocated abductor pollicis longus (APL) by end-to-side anastomosis. B. APL augmentation by rerouting of the distal segment and anastomosis with end-to-end pollicis longus or end-to-side flexor carpi radialis. Thumb metacarpophalangeal joint extension is augmented by anastomosis of the proximal segment of APL with end-to-side extensor pollicis brevis.
Extensor Pollicis Longus Rerouting
A dorsal skin incision over the thumb MCP and IP joint and another small longitudinal incision just ulnar to the Lister tubercle are used for this procedure.6
The EPL tendon is identified and divided 10 mm distal to the MCP joint. The tendon is then retracted out to the second incision (TECH FIG 4A).
The EPL tendon is rerouted to the radial aspect of the Lister tubercle and passed subcutaneously around the APL and EPB tendon (TECH FIG 4B).
The tendon is then passed through the MCP joint capsule (TECH FIG 4C).
The thumb is set in appropriate abduction and IP extension. The rerouted EPL is sutured back to the extensor mechanism 10 mm distal to the defect.
The rerouted EPL may be reinforced by the transfer of the PL, FCR, or brachioradialis.
The EPL may be divided proximal to the Lister tubercle, leaving the tendon attached to its insertion. Rerouting is then performed from distal to proximal (TECH FIG 4D).8
The EPL may be rerouted to the new pulley created from the extensor retinaculum (TECH FIG 4E,F).1
TECH FIG 4 • Extensor pollicis longus (EPL) rerouting. A. EPL tendon is divided distally and mobilized. B. The tendon is rerouted to the radial aspect of the Lister tubercle and passed subcutaneously around the abductor pollicis longus and extensor pollicis brevis tendon. C. The rerouted EPL is sutured back to the extensor mechanism. D. Modified EPL rerouting technique. The EPL tendon is divided proximal to the Lister tubercle, rerouted to the first extensor compartment, and sutured back to the proximal stump. E,F. EPL routing to the retinaculum. E.The EPL tendon is released from the third extensor compartment and rerouted radially. F. The new pulley for the rerouted EPL is created from the extensor retinaculum.
STABILIZATION OF THUMB METACARPOPHALANGEAL JOINT
Thumb Metacarpophalangeal Joint Arthrodesis
A dorsoulnar incision is made over the thumb MCP joint.
The extensor mechanism is split longitudinally, and the ulnar collateral ligament is then detached from the metacarpal head to expose the joint (TECH FIG 5A).
The articular cartilage of the metacarpal head is removed with a scalpel and the proximal phalanx epiphysis is shaved until the secondary center of ossification is exposed (TECH FIG 5B). This allows fusion of the epiphyses and preserves the physis.
The joint is set in 10 degrees of flexion, 10 degrees of abduction, and slight pronation,9 and a small (1 mm in diameter), smooth Kirschner wire is passed through the joint centrally to minimize epiphyseal damage (TECH FIG 5C).
TECH FIG 5 • Thumb metacarpophalangeal (MCP) arthrodesis. A. After the extensor mechanism over the MCP joint is split longitudinally, the ulnar collateral ligament is detached from the metacarpal head. B. The articular cartilage of the metacarpal head is removed. The epiphyseal plate of the proximal phalanx is preserved. C. After the joint is set, smooth Kirschner wires are used to maintain the joint position.
Sesamoid Capsulodesis
A curved dorsoradial incision is made over the thumb MCP joint.11
The accessory collateral ligament is divided at its insertion into the volar plate.
The volar plate is then mobilized to expose the radial sesamoid.
The articular cartilage of the sesamoid is denuded. A cortical defect is created at the head–neck junction of the metacarpal.
The suture is passed through the sesamoid–volar plate and metacarpal defect with straight needles by using a Kirschner wire driver (TECH FIG 6A).
The MCP joint is set to 30 degrees of flexion. The intraosseous suture is then tied over the dorsal surface of the metacarpal under the extensor tendons to secure the sesamoid to the metacarpal neck.
A Kirschner wire is passed through the joint to maintain the joint position for 6 weeks (TECH FIG 6B).
TECH FIG 6 • Sesamoid capsulodesis. The volar plate is mobilized to expose the radial sesamoid. The articular cartilage of the sesamoid is denuded corresponding with the cortical defect created at the head–neck junction of the metacarpal. A. The suture is passed through the sesamoid–volar plate and metacarpal defect. B. The intraosseous suture is tied over the dorsal surface of the metacarpal under the extensor tendons. A Kirschner wire is used to maintain the joint position.
POSTOPERATIVE CARE
Postoperative care for contracture releases includes immobilization in a short-arm thumb spica cast maintaining full thumb radial abduction and 20 degrees of palmar abduction for 4 weeks.
Removable splinting is then continued for another 4 to 6 weeks.
If tendon transfer has been done, immobilization should be extended to 6 weeks, followed by additional splinting for 6 weeks. Dynamic splinting may be considered.
Immobilization of the MCP arthrodesis with a thumb spica cast should be continued until radiographic healing is detected.
OUTCOMES
The functional outcome of thumb-in-palm deformity should be assessed before and after surgery by the physician, therapist, parent, and patient.
House et al2 demonstrated improved functional grade in all 56 patients postoperatively. Half of patients improved three or more grades.
Tonkin et al12 found good results in 32 patients after surgical correction of thumb-in-palm deformity. The average follow-up was 32 months (range, 10 to 88 months).
The thumb was maintained out of palm in 29 of 32 patients (30 of 33 thumbs).
Patients could perform lateral pinch in 26 of 33 thumbs.
Many patients improved function, but no patient improved from dependent to independent functioning.
COMPLICATIONS
Inadequate release of contracted or fibrotic muscle may result in insufficient release of the thumb out of the palm.
Adhesions along the transferred tendon may cause loss of excursion postoperatively.
Improper techniques such as overlengthening and an incorrect vector of transfer may result in limited active abduction and extension of the thumb.
Untreated or inadequate treatment of an unstable MCP joint may result in failed tendon transfer.
Avoiding neurovascular injury is crucial. Care should be taken to properly identify and protect neurovascular bundles throughout surgery.
An improper rehabilitation program and social support may result in failed treatment.
REFERENCES
· Goldner JL, Koman LA, Gelberman R, et al. Arthrodesis of the metacarpophalangeal joint of the thumb in children and adults: adjunctive treatment of thumb-in-palm deformity in cerebral palsy. Clin Orthop Relat Res 1990;253:75–89.
· House JH, Gwathmey FW, Fidler MO. A dynamic approach to the thumb-in-palm deformity in cerebral palsy. J Bone Joint Surg Am 1981;63A:216–225.
· Koman LA, Mooney JF III, Smith B, et al. Management of cerebral palsy with botulinum A toxin: preliminary investigation. J Pediatr Orthop 1993;13:489–495.
· Kozin SH, Keenan MA. Using dynamic electromyography to guide surgical treatment of the spastic upper extremity in the brain-injured patient. Clin Orthop Relat Res 1993;288:109–117.
· Lawson RD, Tonkin MA. Surgical management of the thumb in cerebral palsy. Hand Clin 2003;19:667–677.
· Manske PR. Redirection of extensor pollicis longus in the treatment of spastic thumb-in-palm deformity. J Hand Surg Am 1985;10A:553–560.
· Matev IB. Surgical treatment of flexion–adduction contracture of the thumb in cerebral palsy. Acta Orthop Scand 1970;41:439–445.
· Rayan GM, Saccone PG. Treatment of spastic thumb-in-palm deformity: a modified extensor pollicis longus tendon rerouting. J Hand Surg Am 1996;21A:834–839.
· Swanson AB. Surgery of the hand in cerebral palsy. In: Flynn JE, ed. Hand Surgery. Baltimore: Williams & Wilkins, 1982:476–488.
· Tonkin MA. Thumb deformity in the spastic hand: classification and surgical techniques. Tech Hand Up Extrem Surg 2003;7:18–25.
· Tonkin MA, Beard AJ, Kemp SJ, et al. Sesamoid arthrodesis for hyperextension of the thumb metacarpophalangeal joint. J Hand Surg Am 1995;20A:334–338.
· Tonkin MA, Hatrick NC, Eckersley JRT, et al. Surgery for cerebral palsy, part 3—classification and operative procedures for thumb deformities. J Hand Surg Br 2001;26B:465–470.
· Zancolli EA, Zancolli E Jr. Surgical rehabilitation of the spastic upper limb in cerebral palsy. In: Lamb DW, ed. The Paralyzed Hand. Edinburgh: Churchill Livingstone, 1987:153–168.