Cerebral Palsy. Paralytic Hip Dislocation. Paralytic Foot.

Introduction and Definitions

Cerebral palsy (CP) is a non-progressive disorder of movement and posture arising from injury to the immature developing brain. By international consensus the diagnosis requires three features: the disorder must be of central origin, the brain injury must be non- progressive (although the clinical manifestations may evolve as the child grows), and the brain injury must occur in the developmental period — most narrowly before age 2 years, with broader definitions extending into early childhood. The condition is the commonest cause of motor disability in childhood, with an incidence of approximately 2-3 per 1,000 live births in developed countries. The orthopedic manifestations of CP — paralytic hip dislocation, contractures, paralytic foot deformities, scoliosis — are progressive secondary consequences of the underlying motor disorder, and they constitute one of the principal areas of pediatric orthopedic practice. This chapter synthesizes content from Tachdjian’s Pediatric Orthopaedics, Apley & Solomon’s, Miller’s Review, and Netter’s Concise Orthopaedic Anatomy to address the etiology and classification of CP, the assessment of motor function (GMFCS), the principal orthopedic manifestations (gait abnormalities, hip subluxation and dislocation, foot deformities, upper-limb deformities, scoliosis), the principles of management including botulinum toxin injection, selective dorsal rhizotomy, single-event multilevel surgery (SEMLS), and the long-term issues of adult life with CP.

Etiology and Classification

Etiology The causes of cerebral palsy vary by gestational age at the time of injury. Prematurity is the strongest single risk factor, with periventricular leukomalacia (white matter injury near the lateral ventricles) being the typical pathological substrate in very-low-birth-weight infants. Other causes include hypoxic-ischemic encephalopathy at term (cerebral palsy from acute intrapartum hypoxia accounts for approximately 10-20% of cases, less than was historically attributed), intracerebral hemorrhage, congenital brain malformations, intrauterine infections (TORCH organisms: toxoplasmosis, rubella, cytomegalovirus, herpes simplex, others), kernicterus, postnatal infection (meningitis, encephalitis), trauma, and the various rare genetic and metabolic causes. In a substantial fraction of cases, no clear cause can be identified, and the term “idiopathic CP” applies. Classification by Motor Pattern Spastic CP — the commonest pattern — accounts for approximately 75% of cases. The clinical features include increased muscle tone, hyperreflexia, clonus, positive Babinski sign, and progressive contractures from continuous unopposed muscle pull on growing bones. The spastic pattern is further subdivided by distribution: spastic diplegia (predominant lower-limb involvement, the classical pattern of premature birth), spastic hemiplegia (one side of the body, often associated with focal lesions), spastic quadriplegia

(all four limbs, often with severe associated cognitive and other impairments), and the less commonly used terms spastic monoplegia and triplegia. Dyskinetic CP (approximately 15%) is characterized by involuntary movements: chorea (rapid, irregular, jerky movements), athetosis (slow, writhing movements), or dystonia (sustained muscle contractions producing twisting postures). The pathology typically involves the basal ganglia, often resulting from kernicterus or severe hypoxic-ischemic injury at term. Ataxic CP (approximately 5%) is characterized by impaired balance, coordination, and gait, with normal muscle tone. The pathology typically involves the cerebellum. Mixed CP (approximately 5%) combines features of two or more of the above patterns. Gross Motor Function Classification System (GMFCS) The Gross Motor Function Classification System (GMFCS), introduced by Rosenbaum, Palisano, and others in the 1990s, has transformed pediatric orthopedic care for CP by providing a reproducible, prognostically useful classification of motor function. The five levels are: GMFCS Level I: Walks without limitations; can run, jump, navigate stairs, perform community ambulation without assistive devices. GMFCS Level II: Walks with limitations; can walk in most settings but with limitations on stairs, uneven surfaces, and long distances; may use a handrail for stairs. GMFCS Level III: Walks using a hand-held mobility device (cane, crutch, walker); uses wheeled mobility for long distances. GMFCS Level IV: Self-mobility with limitations; uses powered or pushed wheelchair for community mobility; may stand with support and take a few steps with assistance. GMFCS Level V: Transported in a manual wheelchair; no self-mobility; severe limitations in head and trunk control. The GMFCS level predicts the likely lifelong motor function (children at Level II at age 5 typically remain Level II throughout life) and informs treatment planning, particularly the decision-making for surgical intervention. Hip surveillance protocols, scoliosis surveillance, and the timing and type of orthopedic surgery are all guided by GMFCS level.

Pathophysiology of Orthopedic Deformity in CP

The orthopedic manifestations of CP arise from the interaction of three processes: (1) spasticity, the velocity-dependent increase in muscle tone that produces sustained or rhythmic over-contraction of affected muscles; (2) muscle imbalance, where spastic muscles overpower their normally toned antagonists, producing characteristic patterns of deformity; (3) bone growth, where the immature, growing bone progressively adapts to the persistent abnormal muscle forces, producing both contractures (soft-tissue shortening) and bony deformity (angular or rotational malalignment).

The classical example is the spastic hip: the hip flexors and adductors are typically more spastic than the extensors and abductors, producing a flexed, adducted hip position; over years, the femoral head migrates laterally and superiorly under the pull of these muscles, the acetabulum fails to develop normal coverage, the femoral neck remains in excessive anteversion and valgus (because the muscle forces do not produce the normal molding of the proximal femur), and the hip progresses through subluxation to dislocation. Similar patterns of muscle imbalance produce equinus foot, crouch gait, scissor gait, and other characteristic abnormalities.

Gait Analysis and Common Gait Patterns

Three-Dimensional Computerized Gait Analysis Three-dimensional computerized gait analysis, available in specialized centers, has transformed the understanding and management of gait abnormalities in CP. The analysis combines kinematic data (joint angles through the gait cycle), kinetic data (forces and moments at each joint), electromyographic data (timing of muscle activation), and energy expenditure measurements. The output is a comprehensive description of the gait that guides decisions about which interventions — soft-tissue lengthenings, tendon transfers, bony osteotomies, orthotics — will produce the desired improvement. Common Gait Patterns in Spastic Diplegia The Rodda classification of gait in spastic diplegia recognizes five sagittal-plane patterns: Type I — Apparent equinus: The ankle is in equinus from a tight gastrocnemius-soleus complex, with relatively preserved knee and hip kinematics. Type II — True equinus: Equinus combined with hyperextended knees and increased hip flexion. Type III — Jump knee gait: Equinus combined with flexed knees and flexed hips during stance, with the knee extending at terminal stance. Type IV — Apparent crouch: Equinus combined with flexed knees and flexed hips throughout stance. Type V — Crouch: Calcaneus ankle (typically iatrogenic from overly aggressive Achilles tendon lengthening), flexed knees, and flexed hips throughout stance. Crouch gait is the most problematic pattern: it produces excessive energy expenditure, accelerates knee joint degeneration, and is poorly responsive to treatment once established.

Common Gait Patterns in Spastic Hemiplegia The Winters, Gage, and Hicks classification of hemiplegic gait recognizes four types: Type I: Drop foot during swing phase from anterior tibialis weakness, with normal stance phase. Type II: Persistent equinus in stance and swing from gastrocnemius-soleus spasticity.

Type III: Type II features combined with limited knee flexion in swing from rectus femoris spasticity. Type IV: Type III features combined with hip flexion and adduction.

Hip Subluxation and Dislocation in CP

Pathogenesis and Epidemiology Hip subluxation and dislocation are among the most consequential orthopedic complications of CP. The risk correlates strongly with GMFCS level: GMFCS I patients have minimal risk (1-2%), while GMFCS V patients have a lifetime risk of approximately 70-90%. The pathogenesis combines the muscle imbalance described above with the absence of normal weight-bearing forces in non-ambulatory patients, which fails to provide the mechanical stimuli necessary for normal acetabular development. The progression from a normally located hip in infancy through subluxation to dislocation typically occurs over several years. Hip Surveillance Hip surveillance programs — systematic radiographic assessment of all children with CP — are now standard practice in many centers and have transformed the management of CP hip disease. The Australian Hip Surveillance program is one of the largest and best- documented, with clear protocols based on GMFCS level: children at GMFCS I require radiographic screening only if they show abnormal hip examination; GMFCS II require initial and intermittent screening; GMFCS III-V require radiographic assessment from age 2-3 years at intervals dictated by their level (every 6-12 months for GMFCS V). The Reimers migration percentage is the standard radiographic measurement: the percentage of the femoral head not covered by the acetabular roof, measured on the AP pelvis radiograph. A migration percentage of less than 33% is considered acceptable; 33- 50% indicates subluxation requiring monitoring and intervention; greater than 50% indicates significant subluxation requiring treatment; complete dislocation has migration percentage of 100%.

Treatment of CP Hip Disease The principles of CP hip management are: prevention of dislocation (the dislocated hip is markedly more difficult to treat than the subluxing hip); muscle balance (adductor and iliopsoas tenotomy to release the pull of the spastic flexor-adductors); bony reconstruction (varus-derotation osteotomy of the proximal femur, pelvic osteotomy to deepen the acetabulum); and salvage procedures for the painful dislocated hip in the older non- ambulatory patient. Soft-tissue surgery alone — typically adductor tenotomy with or without iliopsoas tenotomy — is considered for early subluxation (migration percentage <40%) in the younger child. The procedure releases the spastic flexor-adductor pull and allows the hip to return to a more centered position, providing the bony anatomy permits.

Bony reconstruction — varus-derotation femoral osteotomy combined with pelvic osteotomy (typically Dega or Pemberton for the bony defect of CP hip, both of which can correct posterior and lateral acetabular dysplasia) — is indicated for established subluxation (>40-50% migration) or for failed soft-tissue surgery. The combination of femoral and pelvic correction produces durable reduction in most cases, particularly when combined with adductor and iliopsoas releases. Salvage procedures for the painful dislocated hip in the non-ambulatory older patient include proximal femoral resection (Castle procedure) and valgus osteotomy with femoral head excision (Schanz, McHale procedures). Total hip arthroplasty has been performed in selected ambulatory patients with dislocation but is technically challenging and has higher complication rates than primary THA in non-CP patients.

Foot Deformities in CP

The paralytic foot in CP varies with the underlying motor pattern. The principal deformities are: Equinus: Plantarflexed ankle from gastrocnemius-soleus spasticity or contracture. Treatment is initial conservative (stretching, ankle-foot orthosis), with botulinum toxin injection for spasticity, and surgical lengthening (gastrocnemius recession or formal Achilles tendon lengthening) for established contracture. The single most important principle is to avoid over-lengthening, which produces calcaneus gait and crouch — a calcaneus ankle is among the most disabling iatrogenic outcomes in CP orthopedics. Equinovarus: Plantarflexed and inverted foot, typically from spasticity of both the gastrocnemius-soleus and the tibialis posterior (or sometimes the tibialis anterior). The deformity is common in hemiplegic CP. Treatment combines lengthening of the contracted tendons (gastrocnemius recession, tibialis posterior or tibialis anterior lengthening or transfer) and bony correction in cases of established bony deformity. Equinoplanovalgus: Plantarflexed at the ankle but pronated at the subtalar joint, with hindfoot valgus and forefoot abduction. The deformity is common in diplegic CP. The combination produces a complex multi-axial problem requiring multi-component correction: Achilles or gastrocnemius lengthening for the equinus, peroneus brevis-to- longus tendon transfer or other muscle balancing for the valgus, calcaneal lengthening (Evans) or arthrodesis for the bony correction. Crouch foot: Calcaneus ankle from over-lengthened Achilles combined with knee flexion contracture, often progressing to bony deformity at the hindfoot. The deformity is among the most difficult to correct and emphasizes the importance of conservative initial intervention with the Achilles tendon.

Knee and Hip Deformities

Crouch Gait Crouch gait, in which the patient walks with flexed hips and knees and either neutral or calcaneus ankles, is one of the most difficult problems in ambulatory CP. The mechanism combines knee flexion contracture, hamstring spasticity or contracture (producing the flexed knee), hip flexor spasticity or contracture (producing the flexed hip), and weak quadriceps or hip extensors (limiting the corrective capacity). Treatment combines hamstring lengthening (medial hamstrings: semitendinosus, semimembranosus, gracilis; lateral hamstrings: biceps femoris), distal femoral extension osteotomy (in patients with established knee flexion contracture), patellar tendon advancement (to address patella alta and improve quadriceps function), iliopsoas release, and rectus femoris transfer to address the stiff-knee component. The procedures are typically combined in a single-event multilevel surgery (SEMLS). Stiff-Knee Gait Stiff-knee gait, characterized by limited knee flexion during swing phase, is produced by overactivity of the rectus femoris during swing. Rectus femoris transfer (to a knee flexor — sartorius, gracilis, semitendinosus, or iliotibial band — improving knee flexion in swing) is the standard surgical treatment.

Spinal Deformity in CP

Scoliosis develops in approximately 70% of GMFCS V patients and in lower percentages at higher functional levels. The curves are typically long C-shaped neuromuscular curves with pelvic obliquity. Bracing has a limited role (it may improve sitting balance but does not reliably prevent progression). Surgical management — long instrumented fusion T2-pelvis — is indicated when the curve produces functional sitting difficulty or when it is progressing rapidly. The complication rates are substantial (10-20% for major complications including infection, pulmonary problems, and instrumentation failure), and the perioperative care must be multidisciplinary.

Upper-Limb Deformities

Upper-limb involvement in CP is most pronounced in hemiplegic patients but is present in many spastic diplegic and quadriplegic patients. The classical deformity pattern is: shoulder internally rotated and adducted, elbow flexed and pronated forearm, wrist flexed and ulnar-deviated, fingers flexed, thumb-in-palm deformity. The Zancolli classification grades the wrist and finger function. Treatment options include splinting, botulinum toxin injection of overactive muscles, tendon transfers (flexor carpi ulnaris to extensor carpi radialis brevis to address the wrist flexion-ulnar deviation), and selective lengthenings or releases. The functional goals are improvement of grasp, release, and hygiene; cosmetic improvement is secondary.

Principles of Management

Botulinum Toxin Botulinum toxin type A, injected into spastic muscles, produces temporary chemodenervation lasting 3-6 months. The injection is used to reduce spasticity, facilitate stretching and bracing, and as a “trial intervention” to assess the response that might be expected from definitive surgical lengthening. Doses are weight-based, with maximum total doses limited to avoid systemic effects. The principal indications are gastrocnemius-soleus spasticity, hamstring spasticity, adductor spasticity, and upper-limb dynamic deformities. Selective Dorsal Rhizotomy Selective dorsal rhizotomy (SDR) is a neurosurgical procedure in which a fraction of the dorsal sensory rootlets of the lumbosacral spinal cord are selectively transected, based on intraoperative electrophysiological identification of abnormal motor responses. The procedure reduces spasticity in the lower extremities permanently. The classical indication is the ambulatory diplegic patient (GMFCS II-III) aged 3-8 years with isolated lower- extremity spasticity and good underlying strength. The procedure is followed by intensive rehabilitation. The long-term outcomes in carefully selected patients are very good, with sustained reduction of spasticity and improved gait. Intrathecal Baclofen Intrathecal baclofen pump therapy delivers baclofen directly to the spinal cord via an implanted reservoir and catheter. The treatment is used for severe spasticity in non- ambulatory patients (GMFCS IV-V), reducing tone, facilitating positioning and care, and improving comfort. The pump requires refill every 1-3 months and replacement every 5-7 years; complications include catheter problems, infection, and pump dysfunction. Single-Event Multilevel Surgery (SEMLS) Single-event multilevel surgery — the principle of addressing all the deformities of the lower extremity at a single operation rather than in serial operations — has become the standard for ambulatory CP children requiring orthopedic intervention. The procedure is typically planned in late childhood or early adolescence (age 7-12) after computerized gait analysis, and combines bony osteotomies (femoral derotational osteotomy for excessive anteversion, supramalleolar osteotomy for tibial torsion, calcaneal lengthening) with soft- tissue procedures (gastrocnemius lengthening, hamstring lengthening, psoas lengthening over the brim). The patient undergoes a single major operation followed by intensive rehabilitation over 6-12 months, with substantial gains in gait quality compared with serial operations performed over years (the “birthday-syndrome” of pre-SEMLS practice in which patients underwent annual operations through childhood and adolescence). Orthoses Ankle-foot orthoses (AFOs) are central to the orthotic management of CP gait. Static AFOs hold the ankle at a fixed angle (typically 0-5° dorsiflexion); ground-reaction or floor-

reaction AFOs convert the forefoot ground-reaction force into a knee extension moment, useful for crouch gait; articulated AFOs permit dorsiflexion but limit plantarflexion. The selection depends on gait pattern, contractures, and treatment goals.

Adult Life with CP

Adults with CP, particularly those at lower GMFCS levels, face a distinct set of orthopedic and medical problems: progressive arthritis (particularly in the knees and hips), back pain (from sagittal imbalance and degenerative spine disease), painful contractures, pressure sores in non-ambulatory patients, increased fall risk, and progressive functional decline beginning in the third to fifth decade of life. The “adult CP gait deterioration” — a worsening of gait pattern after the third decade — is well-recognized and reflects the cumulative effects of contracture, weakness, and degenerative joint disease. The transition from pediatric to adult orthopedic care is a recognized challenge, with relatively few adult orthopedic surgeons trained in the specific issues of adult CP.

Summary and Take-Home Points

Cerebral palsy is a heterogeneous group of motor disorders arising from non-progressive injury to the immature brain, producing characteristic patterns of spasticity, weakness, and progressive secondary musculoskeletal deformity. The Gross Motor Function Classification System (GMFCS) provides the unifying framework for assessment, prognosis, and treatment planning. The principal orthopedic manifestations are hip subluxation and dislocation (managed by hip surveillance with the Reimers migration percentage, adductor and iliopsoas releases for early subluxation, femoral and pelvic osteotomy for established subluxation, and salvage procedures for the painful dislocated hip in the older non- ambulatory patient), foot deformities (equinus, equinovarus, equinoplanovalgus, crouch), gait abnormalities (analyzed by Rodda and Winters-Gage-Hicks classifications and best assessed by computerized gait analysis), upper-limb deformities, and progressive neuromuscular scoliosis. Treatment combines pharmacological measures (botulinum toxin for focal spasticity, intrathecal baclofen for global spasticity), selective dorsal rhizotomy in carefully selected ambulatory patients, single-event multilevel surgery for the comprehensive orthopedic management of the ambulatory child, and orthotic management. The principle of avoiding over-lengthening of the Achilles tendon — to prevent calcaneus and crouch gait — is one of the great teaching points of CP orthopedics. Adult life with CP brings progressive orthopedic and medical problems that require ongoing multidisciplinary care.