Salter Innominate Osteotomy

Core indication. The Salter innominate osteotomy is a single redirectional pelvic osteotomy used to improve femoral head coverage in a concentrically reduced but dysplastic hip. It rotates an intact, adequately shaped acetabulum to improve anterior and lateral cover in developmental dysplasia of the hip (DDH) and residual acetabular dysplasia. Specific indications.

• Residual acetabular dysplasia in DDH after closed or open reduction, with a persistently high acetabular index in a child roughly 18 months to 6 years of age.
• Primary treatment of DDH in the walking child (commonly combined with open reduction in the older or higher hip).
• Anterolateral acetabular deficiency with a congruent, spherical femoral head and a concentric reduction.
• Neuromuscular or syndromic dysplasia in selected cases where the symphysis remains mobile (often combined with femoral surgery). Prerequisites — all must be satisfied.
• Concentric reducibility — the head must sit congruently in the acetabulum.
• Spherical, congruent femoral head — redirection of an incongruent joint worsens load distribution.
• Open triradiate cartilage and a mobile symphysis pubis — the symphysis must rotate as the hinge.
• A correctable deficiency within about 15 degrees — the limit of a single Salter. The one decision that matters. Choose the osteotomy by the hinge and what it does to volume:

Absolute contraindications.

• Irreducible or non-concentric hip without prior or concurrent open reduction.
• Stiff symphysis pubis (typically an older child or adolescent) — a single Salter cannot rotate.
• Markedly incongruent or aspherical femoral head (consider a reshaping or salvage procedure). Relative contraindications.
• Deformity requiring more than about 15 degrees of correction (combine with a femoral osteotomy or choose a periacetabular or reshaping procedure).
• Severe fixed adduction contracture (release the adductors first).
• Active infection. When NOT to choose a Salter.
• Stiff symphysis pubis (older child or adolescent): a single Salter can no longer rotate — consider a triple innominate osteotomy while the triradiate cartilage is still open, or a Ganz periacetabular osteotomy (PAO) once the triradiate has closed (the PAO requires triradiate closure to avoid disrupting growth). A salvage shelf or Chiari procedure is reserved for an incongruent or aspherical hip.
• Need for more than about 15 degrees of correction: choose a reshaping (Pemberton or Dega) or a procedure with greater corrective capacity.
• Aspherical or incongruent head: a redirectional osteotomy worsens load transfer — consider a salvage augmentation (shelf, Chiari) that relies on fibrocartilaginous metaplasia rather than congruent reorientation. The older or higher hip. Beyond about 3 to 4 years, or with a high dislocation, the femur is often too long and the reduction too tight for a safe Salter alone. A femoral shortening (and frequently derotation or varus) osteotomy is added to reduce pressure on the femoral head (lowering AVN risk), allow a tension-free concentric reduction, and correct excessive femoral anteversion. The Salter then redirects the acetabulum over a head that is concentrically and tension-free reduced. Bilateral disease is typically managed with staged procedures, each planned to the individual deficiency and the child's age and symphyseal mobility. Consent. Counsel specifically about avascular necrosis of the femoral head, redislocation or loss of reduction, graft displacement and pin migration, sciatic and lateral femoral cutaneous nerve injury, over- or under-correction, a slight leg-length change (lengthening), the need for pin removal, and possible cast immobilisation. Setup. Supine with a small sandbag or bump under the ipsilateral buttock to elevate the hemipelvis; the whole limb, hemipelvis and iliac crest are prepped and draped free to allow intra-operative manipulation and on-table imaging. General anaesthesia with an image intensifier available; an arthrogram may be used to confirm a concentric, congruent reduction before committing to the osteotomy.

The goal: expose the ilium through an anterior approach, make a complete transverse cut from the greater sciatic notch to just above the anterior inferior iliac spine (AIIS), rotate the distal acetabular fragment forward, downward and laterally about the symphysis pubis hinge, and hold the corrected position with an iliac crest bone-graft wedge and two threaded pins. Because the entire acetabulum rotates as a unit, its volume and shape are preserved — only its orientation changes.

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Post-operative protocol.

• Immobilisation: a hip spica cast for about 6 weeks, positioned in a safe, stable zone that avoids extremes of abduction and internal rotation. Routine cast care, neurovascular checks and skin surveillance.
• Pin and cast removal: threaded pins are removed at about 6 to 8 weeks (often at the time of cast change or removal), usually as a short day-case procedure. Radiographs confirm union of the osteotomy, maintained correction and a concentric reduction.
• Mobilisation and rehabilitation: gradual mobilisation after cast removal with protected weight-bearing progressing as the osteotomy unites; physiotherapy restores range of motion and strength.
• Long-term surveillance: follow to skeletal maturity — residual dysplasia, growth disturbance and AVN can declare late. Document the acetabular index and centre-edge angle at each review to confirm durable correction. Complications.

Bilateral disease. Bilateral dysplasia is typically managed with staged procedures, with correction direction and magnitude planned independently for each hip based on the deficiency and the child's age and symphyseal mobility.

Reported outcomes. Good to excellent results are reported in roughly 75 to 90 percent of appropriately selected hips operated before significant secondary changes, with improvement in the acetabular index and centre-edge angle. Outcomes decline with increasing age at surgery and with pre-existing avascular changes or incongruity; series consistently show better results when reduction and osteotomy are achieved before about 4 years of age. The acetabular index typically improves by roughly 10 to 15 degrees, reflecting the about 15-degree correction ceiling. The osteotomy corrects the direction of the acetabulum (anterolateral) rather than its depth. Original description and principle. Salter (1961) described the complete cut from the sciatic notch to the AIIS, rotation of the distal fragment about the symphysis pubis, and a bone-graft wedge held by two pins — establishing the concept of redirecting rather than reshaping the acetabulum. Salter and Dubos (1974) confirmed superior outcomes when reduction and osteotomy are performed in the younger child and emphasised concentric reduction as the prerequisite.

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Further reading. 1. Salter RB (1966). Role of innominate osteotomy in the treatment of congenital dislocation and subluxation of the hip in the older child. J Bone Joint Surg Am 48:1413-39. PMID 5921797. — Extends the technique to the older child and details combined open reduction. 2. Pemberton PA (1965). Pericapsular osteotomy of the ilium for treatment of congenital subluxation and dislocation of the hip. J Bone Joint Surg Am 47:65-86. PMID 14256975. — Description of the reshaping pericapsular osteotomy hinging on the triradiate cartilage, the key contrast to the Salter. 3. Sutherland DH, Greenfield R (1977). Double innominate osteotomy. J Bone Joint Surg Am 59:1082-91. PMID 591540. — Adds a pubic osteotomy to increase rotation and coverage in the older child, where a single Salter is insufficient.