Salter Innominate Osteotomy

Surgical Indications

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 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 (must ALL 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 mobile symphysis pubis — the symphysis must rotate as the hinge
• A correctable deficiency within ~15 degrees — the limit of a single Salter

Contraindications

Absolute:

• Irreducible or non-concentric hip without prior/concurrent open reduction
• Stiff symphysis pubis (typically older child / adolescent) — single Salter cannot rotate
• Markedly incongruent or aspherical femoral head (consider reshaping or salvage procedure)

Relative:

• Deformity requiring greater than ~15 degrees of correction (combine with femoral osteotomy or choose periacetabular / reshaping procedure)
• Severe fixed adduction contracture (release adductors first)
• Active infection

Evidence and Outcomes

Original Description and Principle

• Salter (1961): Original description of the innominate osteotomy — a 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. Established the concept of redirecting rather than reshaping the acetabulum (see EvidenceCard below for the verified reprint citation).
• Salter & Dubos (1974): Long-term review confirming superior outcomes when reduction and osteotomy are performed in the younger child and emphasising concentric reduction as the prerequisite.

Reported Outcomes

• Good to excellent results in roughly 75-90% of appropriately selected hips operated before significant secondary changes, with improvement in 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/osteotomy is achieved before about 4 years of age
• Acetabular index typically improves by roughly 10-15 degrees, reflecting the ~15-degree correction ceiling
• The osteotomy also corrects the direction of the acetabulum (anterolateral) rather than its depth

Verified Evidence

The Innominate Bone and the Osteotomy Plane

Course of the Osteotomy

The Salter osteotomy is a complete transverse cut through the innominate bone running from the greater sciatic notch posteriorly to a point just above the anterior inferior iliac spine (AIIS) anteriorly. The cut passes between these two landmarks in a straight line, dividing the ilium completely so that the distal fragment (carrying the acetabulum, pubis and ischium) remains connected to the rest of the pelvis only through the pubic symphysis.

The Symphysis Pubis Hinge

Because the distal acetabular fragment stays tethered at the symphysis pubis, the symphysis acts as the hinge (fulcrum) about which the fragment rotates. As the surgeon levers the distal fragment forward, downward and laterally, the acetabulum reorients to cover the anterior and lateral aspects of the femoral head. The mobile, cartilaginous symphysis of the young child is what permits this rotation — once it ossifies, the rotation is lost.

Why Volume Is Unchanged

Because the entire acetabulum rotates as a unit on its symphyseal hinge, the shape and volume of the acetabulum are preserved — only its orientation changes. This is the fundamental distinction from the Pemberton and Dega osteotomies, which hinge through the triradiate cartilage and physically reshape (and reduce the volume of) the acetabulum.

Neurovascular Anatomy and Danger Zones

Sciatic Notch and Sciatic Nerve

• The posterior limb of the cut emerges at the greater sciatic notch, where a Gigli saw is passed subperiosteally around the notch
• The sciatic nerve lies immediately posterior — protected by keeping the dissection strictly subperiosteal and seating a curved retractor in the notch
• The superior gluteal vessels and nerve also exit at the notch and can bleed if the periosteal sleeve is breached

Anterior Approach Structures

• The lateral femoral cutaneous nerve (LFCN) crosses near the ASIS in the anterior (bikini / Smith-Petersen) approach interval — at risk of stretch or division (meralgia paraesthetica)
• The interval is developed between sartorius/tensor fasciae latae superficially and the iliac apophysis; the apophysis is split to expose both tables of the ilium subperiosteally
• The femoral neurovascular bundle lies medially, protected by staying subperiosteal on the inner table of the ilium

Femoral Head Vascularity

• The medial femoral circumflex artery (MFCA) is the dominant blood supply to the femoral head; the lateral femoral circumflex contributes anteriorly
• Avascular necrosis arises chiefly from pressure on the reduced head (forced abduction/internal rotation, tight reduction) rather than the pelvic cut itself — a tension-free, concentric reduction protects the supply

Landmarks for the Cut

• Posterior landmark: greater sciatic notch (Gigli saw exit point)
• Anterior landmark: just above the anterior inferior iliac spine (AIIS)
• The line connecting these two is the osteotomy; the distal fragment swings on the symphysis pubis

Positioning and Preparation

Patient position: Supine with a small sandbag/bump under the ipsilateral buttock to elevate the hemipelvis. The whole limb, hemipelvis and iliac crest are prepped and draped free to allow intraoperative manipulation and on-table imaging.

Anaesthesia and imaging: General anaesthesia; image intensifier available. An arthrogram may be used to confirm a concentric, congruent reduction before committing to the osteotomy.

Consent: Counsel specifically about avascular necrosis of the femoral head, redislocation/loss of reduction, graft displacement and pin migration, sciatic and lateral femoral cutaneous nerve injury, over- or under-correction, leg-length change (slight lengthening), need for pin removal and possible cast immobilisation.

Step-by-Step Technique

Step 1: Approach and Adductor Assessment

Use an anterior bikini (transverse) or Smith-Petersen approach. If a fixed adduction contracture is present, perform an adductor tenotomy first. Develop the interval, identify and protect the lateral femoral cutaneous nerve medially.

Step 2: Iliac Apophysis Split and Subperiosteal Exposure

Split the iliac apophysis longitudinally and reflect the periosteum off both the inner and outer tables of the ilium subperiosteally, down to the greater sciatic notch posteriorly. Stay strictly subperiosteal to protect the nerves and vessels at the notch.

Step 3: Open Reduction (if required)

In a child with an irreducible or high hip, perform a formal open reduction: T-capsulotomy, clear obstacles to reduction (inverted limbus, pulvinar, hypertrophied ligamentum teres, transverse acetabular ligament, and a tight psoas via release), and reduce the head concentrically.

Step 4: Pass the Gigli Saw and Make the Cut

Pass a Gigli saw subperiosteally around the greater sciatic notch under retractor protection. Direct the cut from the sciatic notch anteriorly to just above the AIIS, producing a complete osteotomy of the innominate bone. Keep the saw straight and the periosteum protected throughout.

Step 5: Rotate the Distal Fragment

Grasp the distal fragment (a towel clip or bone hook on the AIIS) and rotate it forward, downward and laterally, hinging on the symphysis pubis. Sometimes a controlled greenstick of the symphysis is felt. This brings the acetabular roof over the anterior and lateral femoral head.

Step 6: Harvest and Insert the Bone Graft Wedge

Harvest a wedge of bone (often a triangular full-thickness segment) from the anterior iliac crest and insert it into the open osteotomy to hold the corrected position. The wedge should be sized to maintain the rotation without over-distraction.

Step 7: Fixation with Threaded Pins

Pass two threaded Kirschner wires / pins from the proximal fragment across the graft into the distal fragment to stabilise the construct. Confirm pin position and the corrected acetabular orientation on the image intensifier. Pins are left outside or beneath the skin for later removal.

Step 8: Closure, Reduction Check and Immobilisation

Repair the capsule (if open reduction performed) and re-approximate the iliac apophysis over the crest. Confirm a stable concentric reduction through a full safe range. Close in layers and apply a hip spica cast (typically ~6 weeks) for protection.

Combined Procedures in the Older or Higher Hip

In a child older than ~3-4 years, or with a high dislocation, the femur is often too long and the reduction too tight for a safe Salter alone. In these hips a femoral shortening (and frequently derotation / varus) osteotomy is added to:

• Reduce pressure on the femoral head (lower AVN risk)
• Allow a tension-free concentric reduction
• Correct excessive femoral anteversion

Post-operative Protocol

Immobilisation Phase

• Hip spica cast for approximately 6 weeks to protect the reduction and osteotomy
• Position the hip in a safe, stable zone (avoid extremes of abduction/internal rotation that threaten the femoral head blood supply)
• Routine cast care, neurovascular checks, and skin surveillance

Pin and Cast Removal

• Threaded pins removed at ~6-8 weeks (often at the time of cast change/removal), usually as a short day-case procedure
• Radiographs to confirm union of the osteotomy, maintained correction and a concentric reduction

Mobilisation and Rehabilitation

• Gradual mobilisation after cast removal; protected weight-bearing progressing as the osteotomy unites
• Physiotherapy to restore range of motion and strength
• Serial radiographs to monitor acetabular index, centre-edge angle, head ossification and any signs of AVN

Long-term Surveillance

• Follow to skeletal maturity — residual dysplasia, growth disturbance and AVN can declare late
• Document acetabular index and CE angle at each review to confirm durable correction

Special Case: The Older or Higher Dislocated Hip

• Beyond ~3-4 years, or with a high dislocation, a single Salter alone is usually inadequate and unsafe
• Combine with open reduction and a femoral shortening / derotation osteotomy to detension the reduction (reducing AVN risk) and correct anteversion
• The Salter then redirects the acetabulum over a head that is concentrically and tension-free reduced

Special Case: When NOT to Choose a Salter

• Stiff symphysis pubis (older child/adolescent): single Salter cannot 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 / Chiari procedure is reserved for an incongruent / aspherical hip
• Need for greater than ~15 degrees correction: choose a reshaping (Pemberton/Dega) or a procedure with greater corrective capacity
• Aspherical / incongruent head: a redirectional osteotomy worsens load transfer — consider salvage augmentation (shelf, Chiari) that relies on fibrocartilaginous metaplasia rather than congruent reorientation

Special Case: Bilateral Disease

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