DDH Open Reduction (Medial & Anterior Approaches)

Surgical Indications

Open reduction is required when a concentric, stable reduction of the dislocated hip cannot be achieved or maintained by non-operative (closed) means, or when the child presents too late for those methods to succeed.

Principal Indications

• Failed Pavlik harness in the infant (persistent dislocation after ~3 weeks of harness, or the "Pavlik harness disease" of a posteriorly subluxed femoral head eroding the posterior acetabulum — abandon the harness)
• Failed closed reduction under anaesthesia — irreducible hip, or reducible only in an unsafe (extreme/forced) position outside the safe zone of Ramsey
• Unstable or non-concentric closed reduction — arthrogram shows excessive medial dye pool (greater than the contralateral side) indicating interposed soft tissue
• Late-presenting DDH — the walking child or any child presenting beyond the age at which closed methods reliably succeed (commonly cited beyond 18-24 months)
• Teratologic / syndromic dislocation — fixed antenatal dislocations (e.g. arthrogryposis, myelomeningocele) that are irreducible closed

Age-Based Strategy (a classic exam framework)

• 0-6 months: Pavlik harness (closed, dynamic). Open reduction rarely needed.
• 6-18 months: Closed reduction + arthrogram + spica under anaesthesia; if it fails or is non-concentric, OPEN reduction — medial approach is an option in this window.
• 18 months - 2/3 years: Open reduction, generally via the anterior approach (allows capsulorrhaphy ± pelvic osteotomy).
• Older than 2-3 years: Open reduction via the anterior approach + femoral shortening/derotation osteotomy and frequently a pelvic (Salter) osteotomy to address the dysplastic, anteverted, shallow acetabulum.

Contraindications / Cautions

Relative:

• A hip that achieves a safe, concentric, stable CLOSED reduction — do not open it
• The very high, long-standing bilateral dislocation in an older child where surgery may worsen function (individualised decision; some advocate leaving a painless bilateral dislocation)
• Active local infection; unfit for anaesthesia

Evidence and Principles

Why the head will not reduce — the obstacles

The literature (classically Salter, Tachdjian, and others) divides the obstacles into extra-articular (tight iliopsoas producing the hourglass capsular constriction; a contracted hip adductor mass) and intra-articular (inverted limbus/labrum, hypertrophied ligamentum teres, pulvinar, hypertrophied transverse acetabular ligament, and the redundant/constricted capsule). A concentric reduction is impossible until each relevant obstacle is dealt with.

The role of femoral shortening (rather than traction)

• Historically, pre-operative skin/skeletal traction was used to bring the head down to the level of the acetabulum and was believed to reduce AVN — modern evidence does NOT support routine traction as protective.
• Primary femoral shortening osteotomy has largely replaced traction in the older child: it decompresses the reduction, allows correction of femoral anteversion (derotation) and coxa valga (varus), and is associated with LOWER AVN rates than forcing a tense reduction.

Pelvic osteotomy as an adjunct

• In the older child the acetabulum is shallow and antero-laterally deficient. A redirectional Salter innominate osteotomy (or Pemberton/Dega acetabuloplasty) is added to provide anterolateral coverage and correct residual dysplasia once a concentric reduction is achieved.

Key Evidence

The Dysplastic Hip — Pathoanatomy

A chronically dislocated hip remodels in characteristic ways that the surgeon must understand to achieve and hold a reduction:

• The femoral head is displaced supero-laterally (and posteriorly), is smaller and often slightly flattened, with excessive femoral anteversion and coxa valga.
• The true acetabulum is shallow, anteverted and antero-laterally deficient; it is filled with pulvinar (fibrofatty tissue) and obscured by the hypertrophied ligamentum teres and transverse acetabular ligament.
• The labrum (limbus) is infolded ("inverted limbus"), blocking the entrance.
• The capsule is stretched and redundant superolaterally but constricted in the middle by the overlying iliopsoas tendon, producing the classic hourglass (figure-of-eight) deformity.

The Obstacles to Reduction — In Detail

Extra-articular

• Iliopsoas tendon — crosses anterior to the capsule at the level of the joint; tightens the waist of the hourglass. Released/recessed at the lesser trochanter.
• Capsular constriction (hourglass) — the mid-capsular narrowing produced by the psoas; the proximal pouch (true acetabulum) cannot accept the head until released.

Intra-articular

• Inverted limbus / labrum — infolded fibrocartilaginous rim; everted or radially incised (NOT routinely excised — it aids acetabular development).
• Hypertrophied ligamentum teres — elongated and thickened; usually excised to find the true acetabular floor (the fovea/cotyloid notch).
• Pulvinar — fibrofatty tissue in the depth of the acetabulum; cleared to allow medial seating.
• Transverse acetabular ligament (TAL) — the inferior continuation of the labrum across the cotyloid (acetabular) notch; hypertrophied and tight, it must be divided to open the inferomedial entrance.

Approach Anatomy

Medial approach — Ludloff and Ferguson

• Ludloff (anteromedial): interval anterior to adductor longus, developing the plane between pectineus (and the neurovascular bundle, anteriorly) and adductor brevis/iliopsoas.
• Ferguson (true medial): interval between adductor brevis (anterior) and adductor magnus (posterior), behind adductor longus.
• Both give a direct route to the inferomedial capsule, iliopsoas tendon, ligamentum teres and TAL — the obstacles that block reduction in the young child.
• Critical structure: the medial femoral circumflex artery runs between pectineus and iliopsoas in this region — the key reason the medial approach carries a recognised AVN concern. The anterior branch of the obturator nerve is also nearby.

Anterior approach — Smith-Petersen / bikini

• Superficial interval: between sartorius (femoral nerve) and tensor fasciae latae (superior gluteal nerve).
• Deep interval: between rectus femoris (femoral nerve) and gluteus medius (superior gluteal nerve).
• The iliac apophysis is split to expose the lateral ilium subperiosteally (for the pelvic osteotomy) and the medial wall.
• The lateral femoral cutaneous nerve lies near the ASIS and must be protected (meralgia paraesthetica if injured).
• The bikini incision is a low transverse cosmetic variant of the same approach.

Positioning and Preparation

Examination under anaesthesia (EUA) + arthrogram FIRST: confirm whether the hip reduces closed and is concentric. A "rose-thorn"/excessive medial pool of dye on arthrogram (greater than the normal contralateral side) indicates interposed soft tissue and the need for open reduction.

Position:

• Medial approach: supine, hip flexed, abducted and externally rotated ("frog-leg" for access only — NOT the casting position).
• Anterior approach: supine with a sandbag/bump under the ipsilateral buttock/flank; ipsilateral hemipelvis and whole leg prepped free; image intensifier available.

Consent: counsel specifically about avascular necrosis (the principal long-term risk), redislocation/loss of reduction, residual dysplasia needing later surgery, LFCN injury (anterior), MFCA injury (medial), infection, and the prolonged spica cast with hygiene implications.

Medial Approach (Ludloff) — Step-by-Step

Step 1: Incision and superficial dissection

Transverse incision over the adductor mass, distal to the groin crease. Identify adductor longus; the interval is developed anterior to it (Ludloff) toward pectineus, or between adductor brevis and magnus (Ferguson).

Step 2: Adductor and iliopsoas release

Perform an adductor longus tenotomy to improve access and reduce the deforming force. Follow the plane down to the lesser trochanter and identify the iliopsoas tendon; release/recess it — this relieves the hourglass constriction. Protect the MFCA in the pectineus-iliopsoas interval.

Step 3: Capsulotomy and clearing intra-articular obstacles

Open the inferomedial capsule. Excise the ligamentum teres (follow it to the true acetabular floor), clear the pulvinar, and divide the hypertrophied transverse acetabular ligament. Evert any inverted limbus.

Step 4: Reduce and assess stability

Reduce the head into the cleared true acetabulum. Confirm a concentric, stable reduction with a generous safe arc of motion. The medial approach does not permit capsulorrhaphy — stability relies on the cleared acetabulum and the cast.

Anterior Approach (Smith-Petersen / bikini) — Step-by-Step

Step 1: Incision and superficial interval

Bikini (transverse) or oblique incision below the iliac crest. Develop the interval between sartorius (medial) and tensor fasciae latae (lateral) — protect the lateral femoral cutaneous nerve medially.

Step 2: Deep interval and apophyseal split

Develop between rectus femoris and gluteus medius. Split the iliac apophysis and reflect periosteum/abductors subperiosteally off the lateral ilium; reflect the iliacus off the inner table to expose the anterior capsule.

Step 3: Iliopsoas tenotomy and T-capsulotomy

Identify and divide the iliopsoas tendon at the brim/lesser trochanter. Perform a T-shaped capsulotomy (along the femoral neck axis then along the acetabular rim) to fully expose the joint.

Step 4: Clear the obstacles and reduce

Excise the ligamentum teres and pulvinar, divide the TAL, and evert/incise the inverted limbus. Reduce the head into the true acetabulum and confirm concentricity and stability.

Step 5: Femoral shortening / derotation (older child)

If the head sits proximal or the reduction is tense, perform a femoral shortening osteotomy (subtrochanteric), removing a segment and correcting anteversion (derotation) and valgus (varus) as needed; fix with a paediatric plate. This decompresses the reduction and lowers AVN risk.

Step 6: Pelvic osteotomy (if dysplastic acetabulum)

Add a Salter innominate osteotomy (or Pemberton/Dega acetabuloplasty) to provide anterolateral coverage of the now-reduced head.

Step 7: Capsulorrhaphy

Excise redundant superolateral capsule and plicate (capsulorrhaphy) to reinforce the reduction — a defining advantage of the anterior approach.

Spica Cast — The Human Position

After reduction (by either approach) apply a hip spica holding the SAFE human position:

• ~95-100 degrees flexion, ~40-50 degrees abduction (moderate, NOT extreme), neutral-to-slight internal rotation.
• AVOID the extreme abducted frog-leg (Lorenz) position — it compresses the head and kinks the MFCA, the classic precipitant of AVN.
• Obtain post-reduction CT or limited MRI through the cast to confirm a concentric reduction (and that the head is not redislocated posteriorly).
• Typical immobilisation ~12 weeks (often 6 weeks, cast change/EUA, then 6 more), then an abduction orthosis as indicated.

Post-operative Protocol

Immediate Phase (Spica in situ)

• Spica cast in the human position for ~12 weeks total (commonly 6 weeks, then EUA/cast change and re-imaging, then a further 6 weeks).
• Confirm reduction with post-op CT or limited MRI through the cast (look specifically for posterior redislocation, which plain films miss).
• Cast care: meticulous skin and perineal hygiene, parental education, watch for pressure areas and soiling.
• Analgesia: simple analgesia; muscle spasm settles over the first days.

Cast Change / EUA (around 6 weeks)

• Examination under anaesthesia to confirm stability; arthrogram or imaging as needed.
• Reapply spica or transition to an abduction orthosis depending on stability and acetabular development.

After Cast Removal

• Transition to a removable abduction brace (e.g. nights and naps) for a period, as dictated by stability and surgeon preference.
• Gentle mobilisation: hips are stiff after prolonged casting — allow gradual return of motion; formal physiotherapy if slow.
• Encourage age-appropriate weight-bearing as the child resumes; full activity returns over weeks to months.

Surveillance Imaging (CRITICAL — long-term)

• Serial radiographs at intervals (e.g. 3-6 monthly initially, then yearly) to monitor:
  • AVN (ossific nucleus appearance/growth, fragmentation; Kalamchi-MacEwen grading)
  • Acetabular development (acetabular index trending down toward normal)
  • Concentricity and head coverage
• Follow to skeletal maturity — residual dysplasia may declare late and require pelvic osteotomy years after a "successful" reduction.

Special Situations

Bilateral DDH

• Stage the procedures or operate both with careful anaesthetic/positioning planning.
• A unilateral untreated dislocation creates obvious asymmetry; bilateral may present later (symmetrical gait masks the diagnosis).

Older child (greater than 3 years) / very high dislocation

• Plan for femoral shortening + derotation + pelvic osteotomy routinely.
• Counsel that AVN and residual dysplasia risks rise with age at reduction; there is an upper age at which open reduction of a long-standing bilateral dislocation may not be advisable.

Teratologic dislocation (arthrogryposis, myelomeningocele)

• Higher redislocation and stiffness rates; surgical plan and expectations are individualised.