AAOS Comprehensive Orthopaedic Review

Section 3 - Pediatrics

Chapter 30. Pediatric Neuromuscular Disorders

I. Cerebral Palsy

A. Epidemiology

 

1. Cerebral palsy (CP) has an incidence of 1 to 3 per 1,000 live births.

 

2. Prematurity and low birth weight (<1,500 g) increase the incidence to 90 per 1,000.

 

B. Pathoanatomy

 

1. CP is a static encephalopathy, ie, a nonprogressive, permanent injury to the brain that is caused by injury, damage, defect, or illness.

 

2. CP can affect the child's motor development as well as speech, cognition, and sensation.

 

3. Although the brain injury is static, the peripheral manifestations (eg, contractures and bony deformities) in patients with CP often are not static.

 

C. Risk factors for CP are listed in

Table 1.

 

D. Evaluation

 

1. Positive predictive factors for walking

 

a. Sitting by age 2 years

 

b. Pulling to stand by age 2 years

 

2. Poor prognostic indicators for walking

 

a. Persistence of 2 or more primitive reflexes (eg, Moro) at age 1 year

 

b. Not sitting by age 5 years

 

c. Not walking by age 8 years

 

3. Computerized 3-dimensional gait analysis can aid in distinguishing abnormalities in gait pattern.

 

E. Classification—Several classification systems are useful in treating CP.

 

1. Physiologic—The location of the brain injury will cause different types of motor dysfunction.

 

a. Patients with spastic-type (pyramidal) CP exhibit increased tone or rigidity with rapid stretch. This can lead to gait disturbances and contracture. These patients most often benefit from orthopaedic interventions.

 

b. Patients with dyskinetic (extrapyramidal) or choreoathetoid CP exhibit involuntary movements, athetosis, and dystonia. This type is less frequently seen since Rh-immune globulin has been administered to prevent Rh incompatibility between mother and infant.

 

c. Patients with ataxia (cerebellar) exhibit disturbed balance and coordination.

 

d. Patients with mixed types show spasticity and dyskinesia.

 

2. Anatomic—The affected areas of the body are described in

Table 2.

 

3. Functional—The patient is assigned a grade of functioning according to ambulation and activities (

Figure 1).

 

F. Treatment

 

1. Physical therapy (PT) addresses development of gait and functional mobility with gait trainers, walkers or crutches, and prevention of contracture through stretching, bracing, and standing programs.

 

2. Occupational therapy (OT) addresses fine motor function, activities of daily living (ADLs), self-feeding, self-dressing, and communication through speech or adaptive equipment.

 

[Table 1. Risk Factors for Cerebral Palsy]

[Table 2. Anatomic Classification of Cerebral Palsy]

3. Speech therapy is often requisite, particularly in children with significant bulbar involvement.

 

4. Splinting or serial casting may prevent or improve spasticity and contracture.

 

5. Bracing is often used to improve joint or limb position in stance or ambulation or to prevent deformity.

 

a. Supramalleolar orthoses (SMOs) may be used to control coronal plane deformities of the foot and ankle (pronation or supination) but do not address the sagittal plane (equinus or calcaneus).

 

b. Ankle-foot orthoses (AFOs) may be used to stabilize the ankle joint.

 

i. Solid-ankle AFOs may be used to prevent equinus or a crouched stance due to uncontrolled dorsiflexion at the ankle. Prevention of equinus and calcaneus has been shown to improve walking speed and stride length for most children.

 

ii. Hinged AFOs may be used to allow dorsiflexion while preventing equinus during gait.

 

iii. Floor-reaction AFOs cause knee extension to improve crouched gait secondary to ankle plantar flexion weakness.

 

c. Knee-ankle-foot orthoses (KAFOs) stabilize the knee and are useful for maintaining knee position in children who walk very limited distances or only stand.

 

6. Antispasticity medicines

 

a. Baclofen

 

i. Oral administration is common, but dosage needs to be adjusted if relaxation is accompanied by an unacceptable amount of sedation.

 

ii. Intrathecal baclofen (ITB) is administered by an intrathecal pump and is associated with less sedation. ITB is considered only if oral medications (including baclofen) have failed. Potential recipients are nonambulatory patients with moderate to severe spasticity and patients with a component of dystonia.

 

b. Valium is administered orally, but it also can result in significant sedation before sufficient muscle relaxation is obtained.

 

7. Surgical spasticity management—Selective dorsal rhizotomy (SDR) reduces spasticity by selectively cutting dorsal nerve rootlets between L1 and S1.

 

a. SDR may be indicated in ambulatory patients with diplegia, age 3 to 8 years with good selective motor control and intelligence in the "normal" range.

 

b. Fewer than 50% of rootlets should be cut at any given level.

 

c. Cautions—SDR can increase the risk of spine and hip deformities and may increase weakness as the child reaches adolescence.

 

8. Botulinum toxin affects the neuromuscular junction by irreversibly binding synaptic proteins to block the presynaptic release of acetylcholine.

 

a. Botulinum toxin A is the form commonly used in the United States for children with CP.

 

b. In CP, intramuscular botulinum toxin injection results in 3 to 6 months of relaxation in spastic muscles; it is commonly used in conjunction with PT, stretching, casting, or bracing.

 

c. Botulinum toxin is useful for dynamic spasticity only, not for fixed contractures.

 

d. Botulinum toxin may be considered a temporizing measure to delay surgery.

9. Surgical intervention is generally undertaken when a patient has plateaued or worsened in regard to function and/or deformity despite nonsurgical interventions.

 

10.

Table 3 lists recommended surgical interventions for common gait disturbances associated with CP.

 

G. Spine problems specific to CP

 

1. Scoliosis

 

a.

The incidence and severity are related to the severity of CP.

i. Scoliosis occurs in >50% of patients with quadriplegia and in ~1% with hemiplegia.

 

ii. Scoliosis progression is common after skeletal maturity in patients with quadriplegia.

b.

Treatment

i. Bracing may not be an effective treatment of neuromuscular scoliosis in children with CP, but it may be effective in the treatment of idiopathic curves in children with mild involvement.

 

[Figure 1. Gross motor function classification system (GMFCS) for ages 6-12 years.]

   

 

[Table 3. Surgical Treatment of Common Gait Disturbances in Cerebral Palsy]

 

ii.

Surgery, typically fusion that is performed from the upper thoracic spine to the pelvis in nonambulatory patients, may be indicated for large curves that cause pain and/or interfere with sitting.

 

2. Lumbar hyperlordosis

 

a. Lumbar hyperlordosis can occur.

 

b. It is almost always secondary to hip flexion contractures.

 

H. Hip problems specific to CP

 

1. Subluxation

 

a. Epidemiology/overview

 

i. Subluxation is uncommon in the ambulatory patient, but it is very common in the nonambulatory patient.

 

ii. Subluxation (usually posterosuperior) is due to adductor and iliopsoas spasticity, and non-weight-bearing status.

 

iii. Hip subluxation will develop in 50% of quadriplegic CP patients.

 

iv. 50% to 75% of dislocated hips will become painful.

 

b. Treatment

 

i. Goals are to prevent hip subluxation and dislocation, maintain comfortable seating, and facilitate care and hygiene.

 

ii. Treatment is based on radiologic assessment with the Reimer migration percentage (

Figure 2).

 

iii. Nonsurgical treatment consists first of PT and range of motion (ROM), hip abduction orthosis, with consideration of botulinum toxin injections to adductors.

 

iv. Surgical management is appropriate with progressive subluxation to ≥50% subluxation (Reimer index). Patients younger than 8 years and with <60% subluxation can be treated with adductor and iliopsoas release. Patients younger than 8 years and with >60% subluxation or older than 8 years and with >40% subluxation should be treated with proximal femoral osteotomy (varus derotational osteotomy—VDRO) and possible pelvic osteotomy (Dega or Albee-type). Older children with closed triradiate cartilage or those with recurrent subluxation may benefit from a Schanz or Chiari pelvis osteotomy. Children with failed hip reconstruction or older children with arthritis, even without previous surgery, may require resection arthroplasty (Castle procedure) for pain relief.

 

c. Pitfalls—The Castle procedure requires careful interposition of the hip capsule and muscle in the joint space, and the recovery time is often prolonged (6 months or more).

 

2. Scissoring

 

a. Scissoring (due to adductor tightness) at the hip joint can interfere with gait and hygiene and is treated with proximal adductor release.

 

b. Obturator neurectomy should not be performed.

 

3. Hip flexion contracture is treated with intramuscular iliopsoas lengthening.

 

I. Lever arm dysfunction associated with CP

 

1. Lever arm dysfunction results in posterior displacement of the ground reaction force relative to the knee and often results in crouch and power abnormalities in gait.

 

2. Intoeing from femoral anteversion can be treated with femoral rotational osteotomies.

 

3. Intoeing from internal tibial torsion can be treated with supramalleolar tibial osteotomies (concurrent fibular osteotomy is not needed).

 

4. Intoeing is rarely due to medial hamstring spasticity because of the small lever arm of the hamstrings.

 

5. Pes planus (pes valgus)

 

a. Pes planus is common in patients with diplegia and quadriplegia.

 

[Figure 2. Schematic representation showing how the Reimer migration percentage is measured from an AP radiograph. The Hilgenreiner (h) and Perkin (P) lines are drawn. Distance A (the distance from P to the lateral border of the femoral epiphysis) is divided by distance B (the width of the femoral epiphysis) and multiplied by 100 to calculate the Reimer migration percentage (A/B × 100).]

b. The foot is externally rotated due to spastic gastrocnemius, soleus, and peroneal muscles, with weak tibialis posterior function.

 

c. Patients bear weight on the medial border of the foot, on the talar head.

 

d. The foot is unstable in push-off.

 

e. Treatment

 

i. Mild planovalgus feet can be treated with SMOs or AFOs.

 

ii. Moderate to severe deformities can be treated with a calcaneal osteotomy. Calcaneal lengthening osteotomy (best undertaken after age 6 years) is able to restore normal anatomy and is combined with peroneus brevis lengthening and tightening of the medial talonavicular joint capsule and/or posterior tibial tendon. The peroneus longus should not routinely be lengthened, because this will exacerbate first ray dorsiflexion. A medial calcaneal sliding osteotomy enhances alignment but creates a secondary (compensatory) deformity.

 

iii. Severe deformities can be treated with subtalar fusion, although this is usually only needed in very large children and/or those with extreme laxity. (Triple arthrodesis is almost never required.)

 

iv. Compensatory midfoot supination can be treated with first ray plantar flexion osteotomy,

 

[

Table 4. Causes of Anterior Knee Pain in Cerebral Palsy]

   often with a peroneus brevis lengthening.

 

J. Knee problems specific to CP

 

1. Crouched gait

 

a. Causes—The most common cause is tight hamstrings, although crouch may be secondary to excessive ankle dorsiflexion or ankle equinus.

 

b. Treatment

 

i. Nonsurgical treatment includes PT, bracing (such as knee immobilizers at night), and botulinum toxin injection.

 

ii. Surgical treatment is medial (and possibly lateral) hamstring lengthening. Lengthening medial and lateral hamstrings in an ambulatory patient carries an increased risk of recurvatum.

 

2. Stiff-knee gait

 

a. Stiff-knee gait causes difficulties with foot clearance in swing phase and tripping.

 

b. The cause is often overactivity of the rectus femoris (RF) in swing phase.

 

c. Treatment is with distal RF transfer. Indications for surgery are decreased magnitude and/or delayed timing of peak knee flexion in swing phase in conjunction with overactivity of the RF in swing phase.

 

3. Anterior knee pain—Causes of anterior knee pain in CP are listed in Table 4.

 

4. Knee contracture—In a nonambulatory patient, hamstring release may be useful to maintain leg position in a standing program.

 

K. Foot and ankle—Abnormal position or ROM at the foot and ankle cause gait abnormalities and decrease push-off power. Goals of treatment include a painless, plantigrade (stable) foot.

 

1. Equinus deformity results from gastrocnemiussoleus muscle complex spasticity. It can create toe-walking or a back-knee (genu recurvatum) gait.

 

a. Nonsurgical treatment includes stretching, PT for ROM, AFO use, and botulinum toxin injection.

 

b. Surgical treatment should be considered only in patients with fixed contractures.

 

i. Testing under anesthesia helps determine whether a gastrocnemius recession or Achilles tendon lengthening is appropriate. If the ankle is in equinus with the knee flexed and extended, then the soleus is also tight, and an Achilles tendon lengthening should be performed. If the ankle comes above neutral with the knee flexed (gastrocnemius relaxed), then a gastrocnemius recession should be performed.

 

ii. Overlengthening the heel cord may cause crouched gait, calcaneus foot position, and poor push-off power. This is less of a problem with a gastrocnemius recession than with an Achilles tendon lengthening.

 

2. Equinovarus foot deformity can cause painful weight bearing over the lateral border of the foot and instability in stance phase.

 

a. The anterior tibialis and/or the posterior tibialis (the invertors) overpowers the peroneals (the evertors), whereas a tight gastrocnemiussoleus muscle causes equinus.

 

b. Dynamic EMG is useful in distinguishing whether the anterior tibialis and/or the posterior tibialis is causing the varus.

 

c. Clinically, the tibialis anterior can be checked using the confusion test.

 

i. The patient sits on the edge of the examining table and flexes the hip actively.

 

ii. The tibialis anterior will fire.

 

iii. If the forefoot supinates as it dorsiflexes, the varus is at least partially due to the tibialis anterior.

 

iv. If the forefoot just dorsiflexes, the varus is likely not due to the tibialis anterior.

 

d. Clinically, the posterior tibialis is assessed by tightness as the hindfoot is positioned in valgus.

 

e. Generally, isolated forefoot supination comes from the tibialis anterior, while hindfoot varus comes from the posterior tibialis.

 

f. Anterior tibialis and/or posterior tibialis split tendon transfers are recommended rather than full tendon transfers because whole tendon transfers may lead to overcorrection.

 

g. Tibialis posterior lengthenings are helpful in less severe deformities that are caused by the posterior tibialis.

 

h. Pitfalls

 

i. Rigidity of the varus must be assessed preoperatively to determine the need for calcaneal osteotomy.

 

ii. A soft-tissue procedure will not be sufficient if the hindfoot deformity is rigid.

 

iii. In rigid feet, soft-tissue and bone procedures are both needed.

 

3. Equinovalgus arises from gastrocnemius-soleus and peroneal spasticity with tibialis posterior weakness.

 

a. Weight-bearing AP radiographs of the ankles must be obtained because ankle valgus may also contribute to deformity.

 

b. Nonsurgical treatment includes SMO or AFO bracing and PT for ROM, and may include botulinum toxin injection.

 

c. Surgical treament

 

i. Calcaneal osteotomies preserve ROM and are preferred when feasible. Calcaneal lengthening with peroneus brevis lengthening is preferred because it can restore the anatomy. Avoid peroneus longus lengthening because this can cause increased first ray dorsiflexion. Calcaneal (medial) sliding osteotomy brings the calcaneus in line with the weight-bearing axis of the tibia.

 

ii. Subtalar arthrodesis is rarely needed but may be necessary in the presence of marked deformity or ligamentous laxity.

 

iii. Triple arthrodesis is rarely required.

 

4. Hallux valgus

 

a. Occurs frequently with pes valgus, equinovalgus, and equinovarus feet

 

b. Toe straps added to AFOs or nighttime hallux valgus splinting may be helpful.

 

c. Severe hallux valgus should be treated with a fusion of the first metatarsophalangeal (MTP) joint.

 

d. Pes valgus must be simultaneously corrected to avoid recurrence.

 

e. Pitfalls—At the time of hallux valgus correction, consider that the patient will often also have valgus interphalangeus, which should be treated with a proximal phalanx (Akin) osteotomy.

 

5. Dorsal bunion

 

a. Overview/etiology

 

i. Dorsal bunion is a deformity in which the great toe is flexed in relation to an elevated metatarsal, causing a prominence over the uncovered metatarsal head, which can be painful with shoe wear.

 

ii. Dorsal bunion may be iatrogenic, occurring after surgery to balance the foot.

 

iii. The deformation may either be caused by an overpowering tibialis anterior or an overpowering flexor hallucis longus (FHL).

 

b. Treatment

 

i. Nonsurgical treatment is with shoes with soft, deep toe boxes.

 

ii. Surgical treatment is needed in recalcitrant cases. Flexible deformities are treated with lengthening or split transfer of the anterior tibialis and transfer of the FHL to the plantar aspect of the first metatarsal head. Osteotomies of the medial column are rarely needed. Rigid deformities require fusion of the first MTP joint and lengthening or split transfer of the anterior tibialis. Osteotomies are rarely needed.

 

L. Upper extremity problems specific to CP

 

1. General information

 

a. Upper extremity involvement is typical in patients with hemiplegia and quadriplegia. Commonly, the hand is fisted, the thumb is in the palm, the forearm is flexed and pronated, the wrist is flexed, and the shoulder is internally rotated.

 

b. Nonsurgical treatment

 

i. OT is useful in early childhood for ADL, stretching, and splinting.

 

ii. Botulinum toxin is useful for dynamic deformities.

 

iii. Constraint-induced therapy (splinting of the uninvolved upper extremity to encourage use of the involved arm) in patients with hemiplegia is gaining popularity but does not have a long track record.

 

c. Surgical treatment

 

i. Surgical treatment is undertaken primarily for functional concerns, hygiene, and sometimes for appearance.

 

ii. If shoulder adduction and internal rotation contractures are interfering with hand function, they may be treated with subscapularis release and pectoralis major lengthening. A proximal humeral derotational osteotomy is rarely necessary.

 

iii. Elbow flexion contractures may be treated with lacertus fibrosis resection, biceps and brachialis lengthening, and brachioradialis origin release.

 

iv. Elbow pronation contractures should be treated with pronator teres release. Transfer of the pronator teres to an anterolateral position (to act as a supinator) may cause a supination deformity, which is not preferable to pronation.

 

v. Radial head dislocation is uncommon and, if symptomatic, may be treated with radial head excision when the patient reaches maturity.

 

vi. Wrist deformities usually include flexion contracture with ulnar deviation and are associated with weak wrist extension and a pronated forearm. If finger extension is good and there is little wrist flexion spasticity, the flexor carpi ulnaris (FCU) or flexor carpi radialis (FCR) should be lengthened. Releasing the wrist and finger flexors and the pronator teres from the medial epicondyle of the humerus weakens wrist and finger flexion but is nonselective. In severe spasticity, an FCU transfer is recommended. If grasp is good, release is weak, and the FCU is active in release, it should be transferred to the extensor digitorum communis (EDC). If grasp is weak with the wrist flexed, release is good, and the FCU is active in grasp, it should be transferred to the extensor carpi radialis brevis (ECRB). A concurrent FCR release should not be performed, to avoid overweakening wrist flexion.

 

2. Hand deformities

 

a. Thumb-in-palm—Caused by metacarpal adduction contracture with metacarpophalangeal (MCP) flexion or extension contracture, sometimes with interphalangeal (IP) joint flexion contracture.

 

b. Clawing of the fingers, with wrist flexion and MCP hyperextension, can be treated with FCR or FCU transfer to the ECRB.

 

c. Finger flexion contracture is treated with flexor digitorum sublimis (FDS) and flexor digitorum longus (FDL) lengthening or tenotomies.

 

d. Swan-neck deformities of the fingers are a result of intrinsic tightness and extrinsic overpull. These deformities are sometimes caused by wrist flexion or weak wrist extensors and can sometimes be helped by correcting the wrist flexion deformity.

 

M. Fractures specific to CP

 

1. Nonambulatory patients are at risk for fracture due to low bone mineral density.

 

2. Intravenous (IV) pamidronate should be considered for children with three or more fractures and a dual-energy x-ray absorptiometry (DEXA) Z-score <2 SD.



II. Myelodysplasia

A. Overview/epidemiology

 

1. Myelodysplasia is congenital malformation of the spinal column and spinal cord due to failure of closure of neural crests 3 to 4 weeks after fertilization, causing motor and sensory deficits.

 

2. Myelodysplasia is the most common major birth defect, affecting 0.9 per 1,000 live births.

 

3. Prenatal diagnosis via maternal serum α-fetoprotein is 60% to 95% accurate.

 

4. Diagnosis can also be made by ultrasound or amniocentesis.

 

5. Women of child-bearing age should be encouraged to have adequate folic acid intake. Supplementation with folic acid decreases the risk of myelodysplasia, but only if taken in the first weeks following conception. This has also been addressed by the addition of folic acid to many foods, such as breads and cereals.

 

B. Risk factors

 

1. History of previously affected pregnancy

 

2. Low folic acid intake

 

3. Pregestational maternal diabetes

 

4. In utero exposure to valproic acid or carbamazepine

 

C. Classification

 

1. Motor level and functional status are given in

Table 5.

 

2. L4 level or lower (active quadriceps) is considered necessary for community ambulation.

 

D. Treatment—The long-term medical and skeletal issues associated with myelodysplasia are often best addressed by multidisciplinary teams.

 

1. Nonsurgical treatment

 

a.

Frequent skin checks for pressure sores and well-fitting braces and wheelchairs are important because these patients often have significant sensory deficits.

b.

Urologic and gastrointestinal issues, including detrusor malfunction and abnormal sphincter tone, make early catheterization and bowel regimens important. Kidney reflux and pyelonephritis cause significant morbidity and mortality.

c.

Latex allergies are common, so latex precautions should be exercised for all patients with myelodysplasia.

d.

Rehabilitation efforts should include early mobilization,

 

[Table 5. Motor Level and Functional Status for Myelomeningocele]

 

PT, bracing, and functional wheelchair fitting.

e.

Bracing

i. Hip-knee-ankle-foot orthoses (HKAFOs), knee-ankle-foot orthoses (KAFOs), or AFOs are frequently used to support stance and/or to prevent contracture.

 

ii. As the child grows, bracing and crutch requirements may decrease as the child gains skills or increase if the child gains weight or a deformity develops.

 

2. Surgical

 

a.

Spine—Neurosurgeons perform closure of myelomeningocele within 48 hours with a shunt for hydrocephalus. Later issues can develop with the shunt, a tethered cord, or syrinx, so diligent neurologic examinations need to be repeated and documented.

i. Tethered cord can cause progressive scoliosis, change functional levels, or cause spasticity.

 

ii. Syrinx, shunt problems, or new hydrocephalus can cause new upper extremity symptoms such as weakness or increasing spasticity.

 

iii. Arnold-Chiari malformation is often addressed with shunting in infancy but may require later decompression.

 

iv. Scoliosis and kyphosis may be progressive. 90% of patients with thoracic myelodysplasia may require kyphectomy and posterior fusion; 10% of patients with L4 myelodysplasia may require surgery. Prior to kyphectomy, it is important to check shunt function, because shunt failure can result in acute hydrocephalus and death when the spinal cord is tied off during the kyphectomy.

b.

Hip

i. Flexion contractures are common but are often not severe. If the contracture is >40° in patients with lower lumbar level involvement, they may require flexor release.

 

ii. Hip dysplasia and/or dislocation occur in four of five patients with midlumbar level involvement. Currently, the trend in treatment is not to reduce a dislocated hip in any child with myelodysplasia, but flexion deformity may be addressed for functional reasons. The rare exception to this may be the child with a unilateral hip dislocation who has a low-level lesion (ie, a community ambulator), but the recurrence rate is high and therefore the procedure is controversial.

c.

Knee

i. Flexion contracture >20° should be treated with hamstring lengthening, capsular release, and/or distal femoral extension osteotomy.

 

[

Table 6. Muscular Dystrophies]

 

 

There is, however, a significant rate of recurrence after extension osteotomy in growing children.

 

ii.

Extension contracture can be treated with serial casting or V-Y quadriceps lengthening.

 

iii.

Knee valgus, often with associated external tibial torsion and femoral anteversion, is common in patients with midlumbar level involvement because they lack functional hip abductors and have a significant trunk shift when walking with AFOs. This can be addressed by the use of KAFOs or crutches with AFOs.

 

iv.

External tibial torsion can be addressed with a distal tibial derotational osteotomy.

d.

Foot

i. About 30% of children with myelodysplasia have a rigid clubfoot.

 

ii. With surgical treatment, a portion of the tendons (eg, Achilles, posterior tibialis, FHL, flexor digitorum communis [FDC]) may be resected rather than lengthened to decrease the risk of recurrence.

 

iii. Equinus contracture is common in patients with thoracic and high lumbar level involvement.

 

iv. Calcaneus foot position can occur with unopposed tibialis anterior (L3-L4 level).

 

v. Equinovarus, equinus, and calcaneal foot deformities often are best treated with simple tenotomy rather than tendon transfer, achieving a flail but braceable foot.

 

vi. Valgus foot deformities are common in L4-L5 level patients. If surgery is necessary to achieve a plantigrade foot, fusion should be avoided to maintain foot flexibility and to decrease the risk of pressure sores.

 

E. Fractures in children with myelodysplasia

 

1. In these children, fractures often present with erythema, warmth, and swelling in insensate patients.

 

2. A child with myelodysplasia who presents with a red, hot, swollen leg should be assumed to have a fracture until proven otherwise.



III. Muscular Dystrophies

A. Overview

 

1. Muscular dystrophies are genetically based muscle diseases causing progressive weakness (Table 6).

 

2. Pseudohypertrophy of the calf is classic for DMD, although it is present in only approximately 85% of patients (

Figure 3).

 

3. Although genetically based, new mutations are frequent; for example, one third of cases of Duchenne muscular dystrophy (DMD) are the result of new mutations that arise during spermatogenesis on the patient's mother's paternal side.

 

B. Treatment of DMD

 

1. Nonsurgical

 

a. Corticosteroid therapy

 

i. Prolongs ambulation, slows progression of scoliosis, and slows the deterioration of forced vital capacity (FVC).

 

[Figure 3. Clinical photograph of a 5-year-old boy with Duchenne muscular dystrophy. The marked pseudohypertrophy of the calves is a common physical finding.]

ii. The optimum age for beginning therapy is 5 to 7 years.

 

iii. Treatment carries a high risk of complications and side effects including osteonecrosis, weight gain, cushingoid appearance, GI symptoms, mood swings, headaches, short stature, and cataracts.

 

b. Nighttime ventilation significantly prolongs survival.

 

c. Rehabilitation includes PT for ROM, adaptive equipment, power wheelchairs, and nighttime bracing.

 

2. Surgical

 

a. Lower extremity surgery is controversial in children with DMD.

 

i. If surgery is performed, the focus should be on early postoperative mobilization and ambulation to prevent deconditioning and deterioration.

 

ii. If performed, contracture release surgery (in the form of hip abductor, hamstring, Achilles tendon, posterior tibialis lengthening) should be performed while the child is still ambulatory.

 

b. Spine—Scoliosis develops in 95% of patients after they transition to a wheelchair (usually around age 12 years).

 

i. Bracing is contraindicated because in most patients progression occurs relentlessly after 20°. Bracing can also interfere with respiration.

 

ii. Early posterior instrumented fusion (at 20°) is recommended before loss of FVC occurs due to respiratory muscle weakness and progressively decreasing cardiac output.

 

iii. Stiff curves may require anterior and posterior fusion.

 

c. Malignant hyperthermia is common intraoperatively and is pretreated with dantrolene at surgery.



IV. Spinal Muscle Atrophy

A. Overview

 

1. Spinal muscle atrophy (SMA) is the most common genetic disease resulting in death during childhood, with an incidence of 1 in 10,000 live births.

 

2. The inheritance pattern of SMA is autosomal recessive.

 

3. Progressive weakness starts proximally and moves distally.

 

B. Classification

 

1. SMA I (Werdnig-Hoffmann) has onset at birth with severe involvement. Death occurs from respiratory failure by age 2 years.

 

2. SMA II has onset at age 6 to 18 months, and function diminishes with time.

 

a. Hip dislocations, scoliosis, and joint contractures are common.

 

b. Life expectancy is 15+ years.

 

3. SMA III has onset at age >18 months with physical manifestations similar to SMA II, but patients can stand independently. Life expectancy is normal.

 

C. Pathoanatomy

 

1. C5 mutations cause deficient survival motor neuron (SMN) protein resulting in progressive loss of α-motor neurons in the anterior horn of the spinal cord and progressive weakness.

 

2. There are two genes—SMN-I and SMN-II.

 

a. All patients with SMA lack both copies of SMN-I.

 

b. Severity is determined by the number of functional copies of SMN-II. (Patients with SMA I have one copy, patients with less severe forms have more than one.)

 

D. Treatment—No effective medical treatment (such as steroids) is available.

 

1. Scoliosis is very common, occurs by age 2 to 3 years, and is progressive.

 

a. A thoracolumbosacral orthosis (TLSO) improves sitting balance but does not stop progression.

 

b. Flexible curves; often can be fused posteriorly only

 

c. The patient should be evaluated for lower extremity contractures to ensure seating balance.

 

d. A vertical expandable prosthetic titanium rib (VEPTR) for thoracic insufficiency in young patients with SMA II with curves >50° has had good results.

 

e. Fusion may cause an ambulatory child to lose the ability to walk (and may cause temporary loss of upper extremity function) because of loss of trunk motion.

 

2. Hip dislocation

 

a. May be unilateral or bilateral

 

b. Rarely symptomatic and surgery rarely indicated

 

3. Lower extremity contractures occur commonly.

 

a. Hip and knee contractures >30° to 40° are not generally treated surgically. In lesser contractures, hamstring lengthening may sometimes be considered in patients who are strong enough with a strong motivation to walk.

 

b. Foot deformities such as equinovarus occur commonly. Rarely, if the patient is ambulatory and retains strength, then gastrocnemiussoleus, posterior tibialis, FDL, and FHL tenotomy may be performed to maintain standing and walking.



V. Hereditary Motor Sensory Neuropathies

A. Overview/pathoanatomy/types

 

1. Hereditary motor sensory neuropathies (HMSNs) are chronic progressive peripheral neuropathies. They are common causes of cavus feet in children, but they may not be diagnosed before age 10 years.

 

2. HMSN I (myelinopathy Charcot-Marie-Tooth disease)

 

a. HMSN I is the most common HMSN (1 in 2,500 children).

 

b. Peripheral myelin degeneration occurs with decreased motor nerve conduction.

 

c. HMSN I is commonly caused by a mutation in 17p11 (PMP-22) or X-linked connexin 32.

 

d. Autosomal dominant inheritance is most common, but can also be autosomal recessive, X-linked, or sporadic.

 

e. The age at onset is the first to second decade of life.

 

f. EMG is slow (<38 mm/s).

 

3. HMSN II (neuropathy Charcot-Marie-Tooth disease)

 

a. The myelin sheath is intact, but wallerian axonal degeneration, with decreased motor and sensory conduction, occurs.

 

b. Autosomal dominant inheritance is most common, but it can also be autosomal recessive, X-linked, or sporadic.

 

c. The age at onset is the second decade of life or later.

 

d. EMG is normal or slightly prolonged.

 

4. HMSN III (Dejerine-Sottas disease)

 

a. HMSN III is characterized by peripheral nerve demyelination with severely decreased motor nerve conduction.

 

b. Autosomal recessive inheritance is common, with the mutation in the MPZ gene.

 

c. HMSN III presents in infancy.

 

d. It is characterized by enlarged peripheral nerves, ataxia, and nystagmus. The patient stops walking by maturity.

 

5. Other peripheral nerve abnormalities include polyneuritis and small muscle atrophy.

 

B. Treatment

 

1. HMSN commonly presents as distal weakness, affecting intrinsic and extrinsic muscles.

 

2. Decreased sensation and areflexia may also be present.

 

3. Hip dysplasia (5% to 10%) develops from weak hip abductors and extensors.

 

a. Hip dysplasia requires treatment, even if it is not symptomatic.

 

b. Acetabular reconstruction is usually performed before VDRO.

 

4. Cavus foot (

Figure 4)

 

a. Cavus foot develops from contracted plantar fascia, weak tibialis anterior, weak peroneals, and tight foot intrinsic muscles with normal FDL and FHL.

 

[Figure 4. Drawings contrasting a normal and a cavus foot. A, Normal foot with normal height of the arch (double arrow) during standing. B, Cavus foot with increased height of the arch (double arrow) as a result of metatarsophalangeal joint hyperextension (curved arrow), such as occurs at toe-off and as seen in the windlass effect of the plantar fascia.]

b. The peroneus longus is generally somewhat stronger than the peroneus brevis and anterior tibialis.

 

c. Surgery for cavus feet aims to balance the muscle forces and maintain flexibility.

 

i. Surgery typically involves plantar release and posterior tibial tendon transfer to the dorsum or split posterior tibial tendon transfer.

 

ii. Forefoot equinus should be corrected with plantar release and possibly midfoot osteotomies.

 

iii. Achilles tendon lengthening is occasionally needed, but only if there is true hindfoot equinus.

 

iv. Osteotomies to correct bony deformities in adolescence include a calcaneal osteotomy (Dwyer) for fixed hindfoot varus (determined by Coleman block test).

 

v. Fusions should be avoided to maintain flexibility.

 

5. Claw toes may become rigid and require treatment, such as IP fusion, often in conjunction with Jones transfers of the extensor tendons to the metatarsal heads.

 

6. Scoliosis or kyphoscoliosis is seen in 15% to 37% of children with HMSN and up to 50% of patients with HMSN who are skeletally mature—more commonly in HMSN I and girls.

 

a. Bracing arrests progression in the minority of cases.

 

b. Surgery with posterior fusion is effective.

 

c. Intraoperative somatosensory cortical-evoked potentials may show no signal transmission because of the underlying disease.

 

7. Hand intrinsics, thenar, and hypothenar muscles may also show wasting, creating clawing of the thenar and hypothenar eminences, limiting thumb abduction, and compromising pinch power. Surgically, sometimes transfer of the FDS, nerve decompression, contracture releases, and joint arthrodesis may be helpful.



VI. Neurofibromatosis

A. Overview

 

1. Two forms of neurofibromatosis (NF)—NF1 and NF2

 

2. NF1 is the most common single gene disorder (1 in 3,000 births).

 

B. Pathoanatomy

 

1. The mutation in NF is in the neurofibromin gene.

 

2. Neurofibromin regulates cell growth by modulating Ras signaling

 

3. Malignant transformation to neurofibrosarcoma is possible if there is a second mutation in the remaining normal gene.

 

C. Evaluation (

Table 7)

 

D. Treatment

 

1. Anterolateral bowing of the tibia (

Figure 5) is often treated with prophylactic bracing with total contact orthosis to prevent pseudarthrosis. 50% of patients with anterolateral bowing have NF, but only 10% of children with NF have anterolateral bowing.

 

2. Pseudarthrosis may be treated with bone graft and intramedullary rodding and sometimes later will require vascularized bone graft or bone transport by distraction osteogenesis. Amputation is rarely necessary.

 

[Figure 5. Congenital pseudarthrosis of the tibia. A, Lateral radiograph of the tibia and fibula in a child with neurofibromatosis demonstrating anterolateral bowing of a dystrophic tibia. B, Lateral radiograph of the same child after the tibia has progressed to a true pseudarthrosis.]

3. Plexiform neurofibromas (in 40% of patients with NF1) may cause limb overgrowth. Limb equalization procedures are indicated for children with projected limb-length discrepancies >2 cm.

 

4. Scoliosis

 

a. Scoliosis is common in patients with NF.

 

b. Nondystrophic scoliosis in NF is treated like adolescent idiopathic scoliosis.

 

c. Dystrophic scoliosis is short (4 to 6 levels), with sharp curves, and often occurs in children younger than age 6 years.

 

i. It is characterized by scalloping end plates, foraminal enlargement, and penciling of ribs.

 

ii. 87% of curves rapidly progress when three or more ribs are penciled.

 

iii. Dystrophic scoliosis in NF is resistant to brace treatment.

 

iv. Dystrophic scoliosis in NF is treated with early anterior and posterior fusion.

 

v. A preoperative MRI scan should be obtained to rule out dural ectasia and intraspinal neurofibromas.



VII. Friedrich Ataxia

A. Overview

 

1. Friedrich ataxia (FA) is the most common form of the uncommon spinocerebellar degenerative diseases. It occurs in 1 in 50,000 births.

 

[Table 7. Diagnostic Criteria for Neurofibromatosis 1]

2. Onset is before age 25 years, with ataxia, areflexia, positive plantar response, and weakness. Often the gluteus maximus is the first muscle involved.

 

3. Death usually occurs by the fourth or fifth decade of life.

 

4. Nerve conduction velocity studies are decreased in the upper extremities.

 

B. Pathoanatomy

 

1. The FA mutation is GAA repeats in 9q13, causing a lack of the frataxin protein.

 

2. The age of onset of the disease is related to the number of GAA repeats.

 

C. Treatment

 

1. Pes cavovarus is progressive and rigid, resistant to bracing.

 

a. Ambulatory patients may be treated with lengthenings and transfers.

 

b. For rigid deformities, arthrodesis is needed to achieve a plantigrade foot.

 

2. Scoliosis occurs frequently and will usually progress if onset of the disease occurred before age 10 years and scoliosis occurred before age 15.

 

3. Posterior instrumented fusion is effective and does not need to be to the pelvis.



Top Testing Facts

Cerebral Palsy

1. The CNS lesion in cerebral palsy is static, but the peripheral manifestations of CP often change over time.

 

2. Botulinum toxin blocks the presynaptic release of acetylcholine and generally relaxes the muscle(s) into which it is injected for 3 to 6 months.

 

3. Scoliosis occurs in >50% of patients with quadriplegia and ~1% of patients with hemiplegia.

 

4. The most common causes of intoeing in children with CP are femoral anteversion and internal tibial torsion. Varus foot deformities commonly cause intoeing in patients with hemiplegia but not in patients with diplegia or quadriplegia.

 

5. Varus foot deformities are due to overactivity of the anterior tibialis, posterior tibialis, or both. Dynamic electromyography (EMG) is helpful in distinguishing the etiology.

 

6. Soft-tissue transfers alone will not suffice to correct a rigid foot deformity. Bone surgery will be needed in such cases as well.

 

Myelodysplasia

1. Supplementation with folic acid decreases the risk of myelodysplasia, but only if taken in the first weeks following conception.

 

2. Serial neurologic examinations are critical. Changes in strength and/or spasticity are early signs of a tethered cord.

 

3. Prior to kyphectomy surgery, ventriculoperitoneal (VP) shunt function must be checked. If the VP shunt is not working, tying off the spinal cord at the time of surgery can cause death due to acute hydrocephalus.

 

4. Hip dislocations in children with myelodysplasia rarely require treatment.

 

5. Fusions should be avoided during foot surgery to decrease the risk of pressure sores.

 

6. A child with myelodysplasia who presents with a red, hot, swollen leg should be assumed to have a fracture until proven otherwise.

 

Muscular Dystrophies

1. Pseudohypertrophy of the calf is classic for DMD, although present in only about 85% of patients.

 

2. Steroids, when tolerated, slow the progression of DMD. Unfortunately, they are often poorly tolerated because of their significant side effects.

 

3. Early posterior instrumented fusion (curves ≥ 20°) is recommended in DMD because 95% of such curves are progressive and because of progressive cardiopulmonary deterioration as children age.

 

4. Malignant hyperthermia is common in children with muscular dystrophy and should be treated with dantrolene.

 

Spinal Muscle Atrophy

1. The course and prognosis of SMA are directly related to the age at onset.

 

2. Scoliosis progression is not impacted by use of a TLSO.

 

3. Spine fusion may cause an ambulatory child to lose the ability to walk (and may cause temporary decrease of upper extremity function) because of loss of trunk motion.

 

4. Hip dislocation rarely requires treatment.

 

Hereditary Motor Sensory Neuropathies

1. The most common cause of bilateral cavus feet is Charcot-Marie-Tooth disease.

 

2. If foot surgery is required, soft-tissue balancing and avoidance of fusions are important.

 

3. Scoliosis is very common and often does not respond to brace treatment.

 

Neurofibromatosis

1. Many patients have cafe-au-lait spots. Six or more (of the noted size) are required as a criterion for NF.

 

2. Although 50% of congenital pseudarthroses of the tibia cases are due to NF, only 10% of patients with NF have congenital pseudarthrosis of the tibia.

 

3. Scoliosis in patients with NF is often dystrophic (short and sharply angular curve). Surgical success is much higher with combined anterior and posterior fusions.

 

4. 87% of curves rapidly progress when three or more ribs are penciled.

 

5. A preoperative MRI scan should be obtained to rule out dural ectasia and intraspinal neurofibromas.



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