Comprehensive Orthopaedic Management of Cerebral Palsy: Spasticity and Hip Reconstruction

Introduction to Orthopaedic Management in Cerebral Palsy

Cerebral palsy (CP) represents a heterogeneous group of non-progressive, permanent disorders of the development of movement and posture, causing activity limitation, attributed to non-progressive disturbances that occurred in the developing fetal or infant brain. While the neurologic lesion is static, the musculoskeletal pathology is relentlessly progressive. The orthopaedic surgeon’s role is to manage the secondary musculoskeletal manifestations—namely spasticity, muscle contractures, altered bone growth, and joint instability—to optimize function, alleviate pain, and facilitate care.

The foundation of any surgical decision-making in CP relies heavily on the Gross Motor Function Classification System (GMFCS). Developed by Palisano and colleagues, the GMFCS stratifies patients into five levels based on self-initiated movement, providing a reliable prognostic indicator for ambulation and a framework for establishing realistic surgical goals.

Clinical Pearl: Surgical goals differ drastically across the GMFCS spectrum. In GMFCS Levels I-III, the primary goal is the preservation or enhancement of ambulation and gait efficiency. In GMFCS Levels IV-V, the focus shifts to pain prevention, facilitating perineal hygiene, and ensuring comfortable seating.

Medical and Neurosurgical Management of Spasticity

Before addressing fixed bony deformities, the dynamic component of spasticity must be managed. A multidisciplinary approach utilizing neuropharmacologic and neurosurgical adjuncts is essential to prevent the recurrence of orthopaedic deformities.

Botulinum Toxin Type A (BoNT-A)

Botulinum toxin type A acts by inhibiting the presynaptic release of acetylcholine at the neuromuscular junction, creating a reversible chemical denervation.
* Indications: Management of dynamic equinus, hamstring spasticity, and adductor spasticity in young children (typically under 6 years of age) before fixed contractures develop.
* Application: Often combined with serial casting to maximize muscle lengthening. Ultrasound or electromyographic (EMG) guidance enhances injection accuracy.

Selective Dorsal Rhizotomy (SDR)

SDR involves the selective sectioning of hyperactive sensory nerve rootlets in the cauda equina to interrupt the abnormal reflex arc responsible for spasticity.
* Indications: Ambulatory children (GMFCS II-III) with spastic diplegia, pure spasticity (no dystonia/athetosis), good underlying selective motor control, and adequate truncal strength.
* Orthopaedic Implications: SDR significantly reduces lower extremity spasticity but may unmask underlying weakness. Orthopaedic soft-tissue procedures are often required 1 to 2 years post-SDR to address residual fixed contractures.

Intrathecal Baclofen (ITB)

Baclofen is a GABA-B receptor agonist that inhibits monosynaptic and polysynaptic reflexes at the spinal cord level.
* Indications: Severe, generalized spasticity or mixed movement disorders (spasticity and dystonia), typically in non-ambulatory patients (GMFCS IV-V).
* Surgical Considerations: The pump is implanted in the abdominal wall with a catheter threaded into the intrathecal space. Orthopaedic surgeons must coordinate spinal deformity surgeries (e.g., posterior spinal fusion) carefully in patients with indwelling ITB catheters to avoid hardware infection or catheter transection.

Pathomechanics of the Spastic Hip

Hip displacement is the second most common orthopaedic manifestation in CP, following equinus deformity. The incidence of hip displacement is directly proportional to the GMFCS level, approaching 90% in GMFCS V patients.

Biomechanical Etiology

Normal hip development requires concentric seating of the femoral head within the acetabulum, driven by balanced muscle forces and normal weight-bearing. In CP, a profound muscle imbalance exists:
1. Overactive Flexors and Adductors: The iliopsoas, adductor longus, and gracilis overpower the relatively weak abductors (gluteus medius) and extensors (gluteus maximus).
2. Bony Deformity: This constant, unbalanced vector pulls the proximal femur proximally and laterally. The lack of normal weight-bearing and muscle pull prevents the normal physiologic decrease in femoral anteversion and neck-shaft angle.
3. Resultant Anatomy: The patient develops severe coxa valga, excessive femoral anteversion, and a posterosuperiorly directed subluxation vector. Over time, the acetabulum becomes dysplastic (shallow and deficient anterolaterally).

Surgical Warning: A dislocated spastic hip in a non-ambulatory patient is not merely a radiographic abnormality; it is a harbinger of severe pain, inability to sit, pelvic obliquity, and severe decubitus ulcers. Proactive surveillance and early intervention are mandatory.

Radiographic Evaluation

The gold standard for monitoring hip stability in CP is the anteroposterior (AP) pelvis radiograph.
* Reimers' Migration Percentage (MP): The percentage of the femoral head ossific nucleus that lies lateral to Perkin’s line. An MP > 30% defines a "hip at risk" and warrants close observation or soft-tissue intervention. An MP > 40-50% typically requires bony reconstruction.
* Acetabular Index (AI): Measures the slope of the acetabular roof. An AI > 25 degrees in an older child indicates significant dysplasia.
* 3D Computed Tomography (CT): Essential for preoperative planning in complex reconstructions to accurately quantify femoral anteversion and the exact location of acetabular deficiency.

Soft-Tissue Interventions: The Preventative Phase

Soft-tissue releases are indicated for dynamic contractures and early subluxation (MP 30-40%) in young children (typically 2-6 years old) before the onset of fixed bony deformity.

Adductor Release and Psoas Recession

• Indications: Hip abduction < 30 degrees in extension, MP between 30% and 40%, and absence of severe bony dysplasia.
• Positioning: Supine with the hips abducted to place the adductors under tension.
• Surgical Approach:
  1. A longitudinal incision is made over the adductor longus origin at the pubis.
  2. The adductor longus is isolated and transected near its tendinous origin.
  3. The gracilis is identified just posterior to the adductor longus and tenotomized.
  4. Controversy: The adductor brevis may be fractionally lengthened if severe contracture persists. Obturator neurectomy is largely abandoned in ambulatory patients due to the risk of excessive abduction weakness and subsequent pelvic instability.
  5. Psoas Recession: The iliopsoas tendon is identified over the pelvic brim. The tendinous portion is transected while preserving the underlying muscle belly to maintain active flexion for swing-phase clearance in ambulators.

Bony Reconstruction: The Corrective Phase

When the migration percentage exceeds 40-50%, or if significant coxa valga and acetabular dysplasia are present, soft-tissue releases alone will fail. Comprehensive bony reconstruction is required, typically consisting of a Varus Derotation Osteotomy (VDRO) combined with a pelvic osteotomy.

Proximal Femoral Varus Derotation Osteotomy (VDRO)

The VDRO is the workhorse of CP hip reconstruction. It directly addresses the coxa valga and excessive anteversion, redirecting the femoral head concentrically into the acetabulum.

• Indications: MP > 40%, coxa valga (neck-shaft angle > 140 degrees), excessive femoral anteversion (> 40 degrees).
• Positioning: Supine on a radiolucent table. The entire lower extremity is prepped free to allow intraoperative assessment of rotation.
• Step-by-Step Surgical Technique:
  1. Approach: A direct lateral approach to the proximal femur is utilized. The fascia lata is incised longitudinally.
  2. Exposure: The vastus lateralis is elevated off the lateral intermuscular septum and reflected anteriorly, exposing the proximal femoral shaft and the base of the greater trochanter.
  3. Guidewire Placement: Under fluoroscopic guidance, a guidewire is advanced up the femoral neck into the center of the femoral head. The angle of the wire determines the final neck-shaft angle (target: 110-120 degrees).
  4. Osteotomy: A transverse osteotomy is performed at the intertrochanteric level, just proximal to the lesser trochanter.
  5. Correction: The distal fragment is externally rotated to correct the anteversion (target residual anteversion: 10-15 degrees). The proximal fragment is allowed to fall into varus.
  6. Fixation: A pediatric locking proximal femoral plate or a fixed-angle blade plate is applied. Rigid fixation is paramount to allow early mobilization.
  7. Shortening: In cases of chronic dislocation, a 1-2 cm segment of the femur may be resected to decompress the joint and reduce the risk of avascular necrosis (AVN) and sciatic nerve palsy.

Pelvic Osteotomies in Cerebral Palsy

If the acetabulum is dysplastic (AI > 25 degrees) or if the femoral head remains uncovered anterolaterally after VDRO, a concomitant pelvic osteotomy is mandatory.

• Dega Osteotomy: An incomplete transiliac osteotomy that hinges on the triradiate cartilage and the intact inner table of the pelvis. It provides excellent anterolateral and lateral coverage, which is the primary site of deficiency in CP.
  • Technique: The outer table of the ilium is osteotomized from the AIIS to the greater sciatic notch. The osteotomy is levered down, and a triangular bone graft (often harvested from the femoral shortening) is impacted into the gap.
• San Diego Osteotomy: A modification of the Dega that includes the inner table posteriorly, providing even greater volume correction for severe dysplasia.

Pitfall: Failure to address acetabular dysplasia at the time of VDRO is the leading cause of recurrent hip dislocation in the cerebral palsy population. Always assess intraoperative coverage after the femur is repositioned.

Salvage Procedures for the Painful, Chronically Dislocated Hip

In older, non-ambulatory patients (GMFCS IV-V) who present with a chronically dislocated, painful hip with severe degenerative changes, reconstructive osteotomies are contraindicated due to poor bone stock, deformed femoral heads, and high failure rates. Salvage procedures aim to eliminate pain and restore perineal access.

Proximal Femoral Resection-Interposition Arthroplasty (Castle Procedure)

• Indications: Painful, stiff, chronically dislocated hip in a non-ambulatory patient where reconstruction is impossible.
• Biomechanics: Removes the mechanical articulation between the deformed femoral head and the false acetabulum, eliminating bone-on-bone pain.
• Surgical Technique:
  1. A generous lateral approach is utilized.
  2. The proximal femur is resected at the subtrochanteric level.
  3. To prevent proximal migration of the femoral shaft (which causes recurrent pain against the pelvis), the vastus lateralis is mobilized and interposed over the proximal stump of the femur.
  4. The capsule is closed securely over the acetabulum.
• Postoperative Care: Postoperative skeletal traction for 2-3 weeks was historically used, but modern protocols favor immediate use of an abduction orthosis to maintain length and alignment while the soft tissues heal.

Total Hip Arthroplasty (THA)

• Indications: Mature, ambulatory or highly functional non-ambulatory patients with painful osteoarthritis secondary to CP hip dysplasia.
• Challenges: THA in CP carries a significantly higher complication rate than in the general population, including dislocation (due to spasticity and poor muscle control), infection, and aseptic loosening.
• Surgical Considerations: Use of dual-mobility bearing surfaces or constrained liners is strongly recommended to mitigate the high risk of postoperative dislocation. Extensive soft-tissue releases (adductors, psoas) must be performed concurrently.

Postoperative Protocols and Rehabilitation

The success of orthopaedic surgery in CP is inextricably linked to meticulous postoperative care and aggressive rehabilitation.

1. Immobilization: Following bony reconstruction (VDRO/Pelvic osteotomy), patients are typically placed in a bilateral long-leg spica cast or a rigid abduction orthosis for 4 to 6 weeks to protect the osteotomies and soft-tissue repairs.
2. Pain Management: Muscle spasms are a primary source of postoperative pain. A multimodal regimen including diazepam, epidural analgesia, and scheduled NSAIDs is critical.
3. Physical Therapy: Once immobilization is discontinued, intensive physical therapy commences. The initial focus is on restoring passive range of motion, followed by active-assisted strengthening. For ambulatory patients, gait training with assistive devices is initiated as soon as radiographic healing is confirmed.
4. Long-Term Surveillance: CP is a lifelong condition. Patients require annual clinical and radiographic follow-up until skeletal maturity to monitor for hardware complications, recurrent subluxation, or the development of deformities in adjacent joints (e.g., knee flexion contractures or planovalgus foot deformities).

Conclusion

The orthopaedic management of the spastic hip in cerebral palsy is a complex, highly specialized endeavor requiring a deep understanding of altered biomechanics, neurophysiology, and pediatric bone growth. By utilizing a systematic approach—ranging from early neuropharmacologic tone management to preventative soft-tissue releases, and ultimately to definitive bony reconstructions—the orthopaedic surgeon can alter the natural history of the disease. Meticulous execution of procedures such as the Varus Derotation Osteotomy and Dega pelvic osteotomy ensures concentric joint reduction, prevents the devastating sequelae of chronic dislocation, and maximizes the functional potential and quality of life for patients with cerebral palsy.