Transfer of Flexor Carpi Ulnaris for Wrist Flexion Deformity
Ann E. Van Heest
DEFINITION
Cerebral palsy is a primary central nervous system dysfunction that leads to significant functional impairment due to its secondary peripheral manifestations in the upper extremity.
The upper motor neuron lesion in the brain leads to loss of normal inhibition of tone (ie, spasticity), loss of motor control in the limb (ie, weakness), or impaired coordination of muscle activity (ie, athetosis).
The most common manifestation is spasticity.
Spastic hemiplegia is the main type of cerebral palsy for which upper extremity surgery is indicated.
In spastic hemiplegia due to cerebral palsy, the most common peripheral manifestations in the upper limb are shoulder internal rotation, elbow flexion, forearm pronation, wrist flexion and ulnar deviation, finger clenching or swan necking, and thumb-in-palm deformity.
Increased muscle spasticity causes muscle imbalance across joints, which leads to impaired function and over time can lead to joint contractures with skeletal deformation.
The wrist is the most commonly affected joint and will be the focus of this chapter.
ANATOMY
Five primary wrist motors control wrist joint position.
The three wrist extensor muscles are the extensor carpi radialis brevis (ECRB), the extensor carpi radialis longus (ECRL), and the extensor carpi ulnaris muscles (ECU).
The two wrist flexor muscles are the flexor carpi radialis (FCR) and the flexor carpi ulnaris (FCU).
The finger and thumb flexor muscles (flexor digitorum profundus [FDP], flexor digitorum superficialis [FDS], and flexor pollicis longus [FPL]) cross the wrist joint and exert a wrist flexion force. The finger and thumb extensor muscles (extensor pollicis longus [EPL], extensor indicis proprius [EIP], extensor digitorum communis [EDC], and extensor digiti quinti [EDQ]) also cross the wrist joint and exert a wrist extension force.
Each of the muscles that crosses the wrist joint exerts a vector force for wrist extension and flexion as well as radial and ulnar deviation.3 These vector force graphs can be used to help determine which muscles are the major deforming force for wrist flexion posturing.
In cerebral palsy, the most common deformity is wrist flexion associated with ulnar deviation.
The muscle with the greatest flexion and ulnar deviation vector is the FCU.
The FCU is most commonly the deforming force, particularly because it may be coupled with a weak wrist extensor-radial deviator (ECRL and ECRB).
PATHOGENESIS
In the early stages of spastic hemiplegia, the joints and muscles will be supple, with full passive range of motion.
With skeletal growth, the muscle imbalance across joints over time leads to muscle-tendon unit shortening and joint contractures, eventually leading to skeletal deformity.
Increased FCU tone overpowers the decreased strength of the ECRL and ECRB, leading to a wrist flexion posture.
NATURAL HISTORY
In spastic hemiplegia due to cerebral palsy, the FCU is the most common deforming force, pulling the wrist into flexion and ulnar deviation.
Over time, the overpull of the FCU leads to contracture of the muscle, which may lead to fixed contracture of the wrist joint.
Ultimately, a fixed skeletal deformity can occur by the time of skeletal maturity.
Initial management involves exercises to keep the FCU stretched and to prevent contracture of the muscle.
If muscle contractures develop, splinting may be necessary to prevent worsening of wrist joint contractures.
Tendon transfer surgery is best performed before fixed contractures develop.
If fixed joint contractures and muscle contractures exist, a salvage procedure with muscle lengthenings, wrist fusion, or both may be necessary.
PATIENT HISTORY AND PHYSICAL FINDINGS
Patient evaluation begins with interviewing the parents regarding use of the affected limb.
Most commonly, children with spastic hemiplegia will show premature hand dominance, favoring the unaffected side even as young as 6 months of age.
This may be the presenting complaint leading to the diagnosis of cerebral palsy.
Delay of normal pinch and grasp function patterning at 1 year of age is evident.
Generalized patterns of upper extremity use for activities of daily living, commensurate with the child’s age, are discussed with the parents and child. The clinician also observes for bimanual skills such as doing zippers and buttons, cutting food, and tying shoes.
The child’s functional use of the hand can be quantified using House classification of upper extremity functional use:
In this nine-level classification, functional use is assessed as follows: does not use, passive assist (poor, fair, good), active assist (poor, fair, good), and spontaneous use (partial, complete).
This provides a baseline that the physician can use to help communicate the functional goals of treatment with the parents.
Agreement with the parents on the child’s present overall level of limb function serves as a baseline for comparing the outcome of treatment.
Examinations and tests to perform include the following:
Passive range of motion of each joint. If a joint is passively stiff, a joint contracture exists. Tendon transfer surgery is best performed in patients with full passive mobility of all joints.
Volkmann angle test. This test indicates muscle contracture, as the finger flexors are biarticular, crossing both the wrist joint and the finger joints.
Active range of motion of the wrist. This indicates whether this patient has control to be able to actively extend the wrist. If this is absent, a tendon transfer surgery may be indicated to provide better active wrist extension.
Active range of motion of the fingers with the wrist held in a neutral position. This test indicates whether a wrist extensor tendon transfer surgery would be helpful. If the patient has better digital control with the wrist in an extended position, then a wrist extensor tendon transfer surgery would be helpful. If the patient has no digital extension, then an FCU tendon transfer should be considered to the EDC. If the patient develops a clenched fist with wrist neutral position, then a wrist extensor tendon transfer would be contraindicated.
If a patient has full passive mobility of the joints and no muscle contractures of the finger flexors but positions the wrist in significant flexion, leading to impairment with grasp and release or fine motor tasks, then a wrist extensor tendon transfer surgery to improve wrist position would be indicated.
Stereognosis testing. Impaired stereognosis does not preclude surgical intervention, but it is important to identify it preoperatively as a part of the disability present.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Motion laboratory analysis has been used to assist in determining the position of the joints of the upper extremity during tasks.
A fine needle electrode can be used to determine whether phasic control of the muscle occurs during grasp and release.
A muscle that is well controlled with phasic activity, without significant or continuous spasticity, is the best candidate for muscle-tendon transfer surgery.6
DIFFERENTIAL DIAGNOSIS
Wrist flexion posturing due to ineffective wrist extensors
Flexor contracture or spasticity
Wrist or carpal abnormalities
NONOPERATIVE MANAGEMENT
Occupational therapy includes the use of splints, stretching and strengthening programs, and active functional use activities.
Two types of splints can be used: nighttime serial static splinting for treatment of muscle or joint contractures and daytime splints for prepositioning the hand to improve active function.
The indication for nighttime splinting is contractures.
If no contractures of the muscles or joints exist, nighttime splinting is not necessary and is a waste of time and money for the child and family.Related posts:
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