Hip Spica Cast Application

Indication. A hip spica holds the reduced dysplastic hip or an aligned paediatric femur in a fixed position while ligaments heal or bone unites. The three broad indications:

Contraindications. Absolute: active or suspected compartment syndrome, severe skin disease preventing casting, vascular insufficiency requiring monitoring, and a body habitus that prevents an adequate cast. Relative: age over about 6 years (a body spica becomes impractical by weight), severe respiratory disease (the abdominal window may not suffice), severe developmental delay, an inadequate home-care or social situation, and morbid obesity preventing immobilisation. Bilateral or unilateral? A bilateral spica is more stable — it prevents pelvic rotation — and is preferred for DDH and most fractures even when the pathology is unilateral. A unilateral spica is lighter and more mobile but only suits a very compliant, stable situation. A removable crossbar between the legs adds stability and allows diaper access. Consent for cast sores (the most common complication), skin breakdown and maceration around the perineum, the small but devastating risk of compartment syndrome, redislocation (DDH) or malunion (fracture), and — most important for DDH — avascular necrosis of the femoral head, which may not declare itself for months and has no treatment that alters the outcome. Setup. A spica table with a padded perineal post is preferred (the post prevents pelvic rotation during application); a flat padded table with two to three assistants works if no spica table is available. Have stockinette (6 inch trunk, 3-4 inch legs), generous cast padding (webril) with felt for bony prominences, 6-8 plaster or fibreglass rolls, and moleskin or tape for edge finishing ready. Position the child supine; for DDH the hips sit in the human position, for a fracture in less flexion.

The goal is to immobilise the reduced hip (or aligned fracture) in a position that holds reduction and protects the femoral head, while building a cast the child can breathe, feed and be cared for in. Positioning is the operation — set it first and hold it throughout — because once the plaster sets, the position cannot be changed without re-casting.

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Immediate monitoring (first 24-48 hours). Neurovascular checks every 2 hours while awake, as compartment-syndrome risk peaks in the first day. Expect mild discomfort controlled by paracetamol or ibuprofen; severe pain is a red flag and must not be masked with strong opioids. Position flat or at 30° elevation, avoiding prone initially, and turn every 2-3 hours. Follow-up schedule. Review at 24-48 hours (cast integrity, neurovascular status, skin and position on X-ray), then weekly for two weeks, then every two weeks until removal. Home care. Keep the cast clean and dry (sponge baths only, never submerged); change diapers frequently (at least every 2-3 hours), tucking the diaper edge inside the perineal window with barrier cream; blow-dry on cool if damp; never lift the child by the cast; never insert objects under the cast. Standard car seats are usually inadequate — a special car bed or modified larger seat is needed. Cast changes and removal. DDH: typically one planned change at 6 weeks (about 12 weeks total, range 8-16 weeks by age). Fractures: 6-8 weeks, with an earlier change at 3-4 weeks if loose; change any time the cast is soiled beyond cleaning, loose, or losing position. Remove by bivalving with an oscillating saw (demonstrate it on yourself first to reassure the child), then gentle skin care and moisturiser. After removal expect dry flaky skin, muscle atrophy and temporary stiffness that resolve over 1-2 weeks; DDH may need a night-time abduction brace for 3-6 months. Complications

Late issues. A cast loosens with growth and muscle atrophy (overwrap if minor, change if loose enough to lose position) and may crack if the child is lifted by it. Breakage from rough handling, and the psychological toll on child and family (frustration, regression, parental stress — involve child-life support), are common.

Where spica casting sits. A hip spica is the standard immobilisation after closed or open reduction of DDH, and the standard treatment for the femoral shaft fracture in children under about 5-6 years. Its safety rests on two ideas worked out a half-century apart: reduction is held by flexion with only moderate abduction (Ramsey safe zone, 1976), and forced abduction is itself a cause of femoral-head necrosis (Salter, 1969). The historical extreme-abduction frog position carried AVN rates as high as 30-50 percent in the worst series; modern perfusion-aware closed reduction reports AVN around 4 percent. Grading AVN — the Kalamchi classification. AVN after DDH treatment is graded I-IV by involvement of the ossific nucleus and, crucially, the proximal femoral physis (Kalamchi and MacEwen, 1980). Physeal damage — not change in the ossific nucleus alone — is the key predictor of residual growth deformity, with the severe (physeal, III-IV) forms driving long-term outcome. Severe AVN was most frequent when treatment began in the first six months, and preliminary traction plus reduction under anaesthesia reduced the severe forms. The modern nuance. The Gornitzky and Sankar perfusion-MRI cohort reframes the dogma: once femoral-head perfusion at reduction was normal, the spica abduction angle was not an independent predictor of later AVN. The practical lesson is to respect both a moderate position and femoral-head vascularity — confirm perfusion and re-cast a globally poorly perfusing hip — rather than chase a single magic abduction number.