MUSCULOSKELETAL DISORDERS

Foot/Ankle

Foot deformities in CP are typically caused by an imbalance of the muscles that control segmental foot and ankle alignment. This imbalance may be a consequence of spasticity, disrupted motor control, or impaired balance function (87). Equinus deformity, due to increased tone or contractures of the gastrocsoleus complex, is the most common musculoskeletal deformity in CP. Equinovarus foot deformity is primarily due to a combination of spasticity of the posterior tibialis muscle and the gastrocsoleus complex, resulting in inversion and supination of the foot and a tight heel cord (Figure 14.10). This deformity is most common in a child with hemiparesis. In children with diplegia, the varus will often overcorrect into valgus (88). Equinovalgus foot deformity is due to spasticity of the gastrocsoleus complex and the peroneal muscles, as well as weakness in the posterior tibialis muscle. This deformity is most common in older children with spastic diparesis and quadriparesis. Piano valgus foot deformities begin with the lateral displacement of the navicular, causing the talar head to become uncovered and prominent in the mid-foot (88). Hallux valgus deformities are associated with valgus deformities of the foot, which may lead to a painful bunion at the head of the first metatarsal.

Knee

Knee flexion contractures are common due to spasticity in the hamstring muscles and static positioning in a seated position. If a severe knee flexion is present, hip flexion will be limited, resulting in lumbar kyphosis in the seated position. Flexion contractures at the knee are associated

Equinovarus foot in a child with CP.

FIGURE 14.10 Equinovarus foot in a child with CP.

with hip and ankle flexion contractures and patella alta. Genu valgus may also occur, and is most commonly associated with excess femoral anteversion.

Hip

Acquired hip dysplasia is common in CP and often leads to progressive subluxation and possible dislocation. Hip subluxation can begin as early as age 2 years (89) and should be monitored closely by exam and serial radiographs. On exam, passive hip abduction of less than 35 degrees and a hip flexion contracture of more than 20 degrees are concerning signs of hip instability (90). On x-ray, hip subluxation is typically defined as a migration percentage greater than 30%. Close surveillance of hip migration with intermittent serial hip radiographs is recommended once hips have subluxed (91). Details of consensus-based hip surveillance programs have been published and include a baseline anterior-posterior (AP) pelvic radiograph at ages 12 to 24 months for all children with CP (92).

The reported incidence of dislocation in untreated hips varies, but 25% to 35% is the average estimate from most large series (91,93). Causative factors include persistent excessive femoral anteversion, a dysplastic acetabulum, and muscle imbalance from overactive hip adductors and flexors. These factors cause the hip to be adducted, flexed, and internally rotated, placing it at risk for posterior dislocation. A large population-based sample of children revealed a linear relationship between the incidence of hip displacement and level of gross motor function on the GMFCS (91). The incidence of hip displacement for each GMFCS level was as follows: I 0%, II 15%, III 41%, IV 69%, and V 90%. The natural history of hip dislocation has not been well described. Early osteoarthritis and difficulty with positioning and hygiene are not uncommon. The reported incidence of pain associated with a dislocated hip varies, but is commonly felt to be present in at least 50% of patients with dislocations (93).

Children with CP may also develop a "windswept deformity" of their hips, described as an adduction deformity of the elevated hip and an abduction deformity of the opposite hip, which also tends to be externally rotated and commonly results in pelvic obliquity (Figure 14.11). The hip on the elevated side is at significant risk for dislocation, and positioning can be challenging. Hip dislocation with pelvic obliquity is often associated with scoliosis, but any potential causative relationship remains unproven.

Windswept hip deformity in a child with CP.

FIGURE 14.11 Windswept hip deformity in a child with CP.

Spine

Spinal deformities, including kyphosis, lordosis, or scoliosis, are common in children with CP. Kyphosis is often seen in conjunction with significant weakness of the spinal extensor muscles and tightness in the hamstrings, leading to a posterior pelvic tilt. Lordosis is frequently associated with hip flexion contractures. The likelihood of scoliosis increases with the severity of CP. An overall incidence of approximately 20% (94) has been reported, with an incidence as high as 68% in children with spastic quadriparesis (95). Curves greater than 40 degrees tend to progress, regardless of the patienf s skeletal maturity (95). The risk of progression is greatest for patients with quadriparesis, increased spasticity, a larger curve, a younger age, poor sitting balance, or pelvic obliquity (90).

Upper Extremity

Spasticity and muscle imbalances can often lead to joint deformities in the UE. The shoulder is often positioned in an adducted and internally rotated position. Spasticity in the biceps, brachioradialis, and the brachialis frequently result in elbow flexion contractures. Elbow flexion contractures less than 30 degrees rarely have functional significance. Forearm pronation deformities are common and can significantly affect functional use of the hand. The most common deformity of the wrist is flexion, typically with ulnar deviation (Figure 14.12). The most common finger deformities are flexion and swan neck deformities due to hand intrinsic muscle spasticity. A thumb-in-palm deformity is commonly seen with adduction at the carpometacarpal joint, which may be associated with hyperextension of the metacarpophalangeal and interphalangeal joints.

Wrist and finger flexion and ulnar deviation in a child with CP

FIGURE 14.12 Wrist and finger flexion and ulnar deviation in a child with CP.

GAIT IMPAIRMENTS

A wide variety of gait classification systems have been developed to assist in diagnosis and clinical decision making, and to facilitate communication among health care providers. A systematic review of the literature, however, concluded that no single classification system appeared to reliably and validly describe the full magnitude or range of gait deviations in CP (96).

The following is a description of the more common gait deviations associated with CP (Table 14.1). At the hip, increased hip adduction tone can cause scissoring and difficulty advancing the limb in swing phase. Increased tone in the iliopsoas can lead to increased hip flexion, resulting in an anterior pelvic tilt and a crouched gait. Increased femoral anteversion can contribute to in-toeing. At the knee, tight hamstrings can inhibit the knee from extending during stance phase, further contributing to a crouched gait. Spasticity of the rectus femoris may limit knee flexion during the swing phase, causing a stiff-knee gait pattern. At the ankle, spasticity of the plantarflexors can lead to toe walking, difficulty clearing the foot during swing phase, or genu recurvatum (due to limited dorsiflexion in stance phase creating an extension moment at the knee). Spasticity of the ankle invertors, most commonly seen in spastic hemiparesis, can lead to supination of the foot and weight-bearing on the lateral border of the foot. Weight-bearing on the talar head is more common in spastic diparesis or quadriparesis, and is associated with an equinovalgus deformity. Malrotation of the leg can interfere with stability during stance phase and

TABLE 14.1 COMMON GAIT DEVIATIONS IN CP

LOCATION

IMPAIRMENT

POTENTIAL EFFECTS

Hip

Increased adductor tone

Scissoring; difficulty advancing leg in swing phase

Increased iliopsoas tone

Anterior pelvic tilt; increased lumbar lordosis; crouched gait

Increased femoral anteversion

In-toeing; false genu valgus; compensatory external tibial torsion

Abductor weakness

Trendelenburg's gait

Knee

Decreased hamstring range of motion

Crouched gait

Hamstring/quadriceps cocontraction

Stiff-knee gait

Ankle

Increased gastrocsoleus tone or contracture

Toe walking; genu recurvatum; difficulty clearing foot during swing

Internal tibial torsion

In-toeing; ineffective pushoff

External tibial torsion

Out-toeing; ineffective pushoff

Varus

Increased ankle supination in stance or swing

Valgus

Increased pronation in stance or swing; mid-foot break

effective pushoff. Internal rotation is more common with a varus deformity and external rotation with a valgus deformity.

 
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