High-yield overview

Incomplete pericapsular reshaping osteotomies for the dysplastic acetabulum in DDH | advanced

Surgical Imaging

Pemberton acetabuloplasty technique — Pemberton acetabuloplasty: a curved pericapsular cut hinging on the open triradiate cartilage levers the acetabular roof down and forward, reducing acetabular volume — reshaping rather than redirecting.Credit: AI-generated medical image · OrthoVellum

Dega transiliac osteotomy technique — Dega osteotomy: an incomplete transiliac cut preserving the posterior and medial cortex as a flexible hinge, with stacked grafts directing coverage anterolaterally — useful for posterosuperior deficiency.Credit: AI-generated medical image · OrthoVellum

Pemberton, Dega and Salter compared — Acetabular osteotomies compared: Pemberton (triradiate hinge), Dega (posterior-cortex hinge) and Salter (complete cut, symphyseal hinge). The hinge point is the key exam discriminator.Credit: AI-generated medical image · OrthoVellum

Critical Danger Structures and Exam Traps

Triradiate Cartilage — Must Be Open

The trap: Both osteotomies depend on the triradiate cartilage. Pemberton hinges directly ON it; Dega relies on the cartilage and medial cortex to remain intact as the hinge. A closed (fused) triradiate cartilage is a contraindication.

The fix: Confirm an open triradiate on the pre-operative radiograph and intra-operatively. Operating on a closed/closing triradiate risks osteotomy propagation into the joint, premature fusion and acetabular growth arrest.

Sciatic Notch / Greater Sciatic Foramen

Location: The posterior limb of the Dega osteotomy and the posterior extent of the Pemberton cut approach the greater sciatic notch. The sciatic nerve and superior gluteal vessels lie at the notch.

Risk: Driving the osteotome too far posteriorly out of the bone risks the sciatic notch contents. Stay within the bone, keep a finger/retractor in the notch, and do NOT complete the cut through the posterior cortex (this is the hinge).

Lateral Femoral Cutaneous Nerve

Location: The LFCN crosses near the anterior superior iliac spine (ASIS), close to the anterior (Smith-Petersen / bikini) approach used for both osteotomies.

Risk: Retraction or direct injury at the interval between sartorius and tensor fasciae latae causes anterolateral thigh numbness (meralgia paraesthetica). Identify and protect it; develop the interval just lateral to sartorius.

Pemberton vs Salter — Reshape vs Redirect

Pemberton / Dega (reshape): Incomplete osteotomy hinging on cartilage/cortex; changes acetabular SHAPE and reduces VOLUME; no pelvic discontinuity; usually no metalwork.

Salter (redirect): Complete innominate osteotomy hinging on the symphysis pubis; redirects the whole acetabulum antero-laterally without changing its shape or volume; needs a graft and K-wire/screw fixation.

Over-Coverage and Joint Stiffness

Why different: Because Pemberton reduces acetabular volume the most, hinging too aggressively can create acetabular over-coverage (a pincer-type deformity) and a tight, stiff joint, especially if the femoral head is not truly concentrically reduced.

Implications: Reduce only enough to give a congruent, stable hip with an acceptable acetabular index. Over-correction risks stiffness, impingement and chondrolysis — assess congruency intra-operatively before grafting.

Concentric Reduction is a Prerequisite

Why it matters: Reshaping a roof over a head that is not concentrically reduced (residual subluxation, inverted limbus, hypertrophic ligamentum teres, capsular constriction) just buttresses a malreduced hip.

The fix: Ensure a concentric, stable closed or open reduction first. Acetabuloplasty is an adjunct to reduction (plus or minus femoral shortening/derotation), NOT a substitute for it.

Mnemonic

P.E.M.B.E.R.TPEMBERTON — Key Features of the Pericapsular Osteotomy

Mnemonic

D.E.G.ADEGA — Transiliac Reshaping Osteotomy

Surgical Indications

Core Indication

Residual acetabular dysplasia in DDH with a concentrically reducible femoral head and an open triradiate cartilage (typically age 18 months to 7-8 years)
Persistently high acetabular index after reduction, where the acetabulum is capacious / globally deficient and reshaping (volume reduction) is required

Pemberton — Preferred When

The acetabulum is large and capacious with generalised (multidirectional) deficiency
Maximum reduction of acetabular volume is desired
A single hinged correction in almost any direction is needed (the triradiate hinge allows anterior, lateral or global redirection of the roof)

Dega — Preferred When

Posterosuperior deficiency predominates (classically the neuromuscular / cerebral palsy hip and posterior DDH)
Selective, directional correction is wanted while preserving the medial wall and inner cortex
A more forgiving, "tunable" osteotomy is preferred (depth and posterior extent of the cut titrate the correction)

Contraindications

Absolute:

Closed (fused) triradiate cartilage — reshaping osteotomies depend on the open triradiate as the hinge
Non-concentric / irreducible hip — reshaping a roof over a subluxated head is futile; achieve concentric reduction first
Active hip sepsis

Relative:

Severe incongruity of the joint surfaces (a redirectional osteotomy such as Salter, or a salvage shelf/Chiari procedure, may be more appropriate)
Marked femoral-sided deformity requiring a primary femoral osteotomy (often combined rather than a contraindication)
Older child near triradiate closure — diminishing remodelling potential

The Central Concept: Reshape vs Redirect

Reshaping osteotomies (Pemberton, Dega) change the shape of the acetabulum and reduce its volume by hinging the roof down on cartilage (triradiate) or cortex (posterior/medial). They do not move the acetabulum as a whole and create no pelvic discontinuity.
Redirectional osteotomies (Salter, periacetabular/Ganz, triple) move the entire acetabulum as a unit to improve coverage without changing its intrinsic shape or volume.
Salvage osteotomies (Chiari, shelf) augment coverage with non-articular bone/fibrocartilage when the joint is incongruent.

Evidence and Outcomes

Pemberton

Pemberton PA (1965), J Bone Joint Surg Am (PMID 14256975): Original description of the pericapsular osteotomy of the ilium hinging on the triradiate cartilage; demonstrated reliable correction of the acetabular index in DDH.
Large reductions of acetabular index are achievable in a single procedure (mid-term series report acetabular index falling from the low-40s to under 20 degrees). The principal trade-offs are joint stiffness and the risk of avascular necrosis when the femoral head is over-reduced (excessive inferior displacement), with a theoretical risk of premature triradiate fusion.

Dega

Dega W (1964/1969): Description of the incomplete transiliac acetabuloplasty using the intact inner/posterior cortex as a hinge, allowing directional correction (original Polish-language papers; no PubMed-indexed PMID).
Widely adopted for neuromuscular hip displacement; series in cerebral palsy report effective correction of posterosuperior deficiency, with the migration percentage and acetabular index reliably normalised when the modified Dega is combined with open reduction and femoral varus-derotation/shortening osteotomy (single-event multilevel surgery).

Combined Procedures

Acetabuloplasty is frequently combined in a single sitting with open reduction and, where the head is high or anteverted, a femoral shortening/varus-derotation osteotomy to achieve a concentric, stable, low-pressure reduction.

Reshaping vs Redirectional Osteotomies — Exam Comparison

Key Evidence

Pericapsular osteotomy of the ilium for treatment of congenital subluxation and dislocation of the hip

Level IV

Pemberton PA • J Bone Joint Surg Am

Clinical Implication: The foundational technique paper defining the triradiate-cartilage hinge and the reshaping concept that distinguishes Pemberton/Dega from the Salter redirectional osteotomy.

Verify on PubMed (PMID 14256975)

Analysis of osteonecrosis following Pemberton acetabuloplasty in developmental dysplasia of the hip: long-term results

Level III

Wu KW, Wang TM, Huang SC, Kuo KN, Chen CW • J Bone Joint Surg Am

Clinical Implication: Do not over-reduce: avoid excessive inferior displacement of the head when levering the roof down, as it compresses the lateral epiphyseal vessels and is the dominant driver of avascular necrosis after Pemberton acetabuloplasty.

Verify on PubMed (PMID 20810858)

Mid-term results of Pemberton pericapsular osteotomy

Level IV

Balioglu MB, Oner A, Aykut US, Kaygusuz MA • Indian J Orthop

Clinical Implication: Confirms durable correction of the acetabular index into the normal range across the 18-month to 8-year age window when Pemberton is combined with concentric (open) reduction and selective femoral shortening.

Verify on PubMed (PMID 26229162)

One-stage correction of the spastic dislocated hip: use of pericapsular acetabuloplasty to improve coverage

Level IV

Mubarak SJ, Valencia FG, Wenger DR • J Bone Joint Surg Am

Clinical Implication: In the neuromuscular hip, address all three levels in one sitting - soft-tissue release, femoral varus-derotation/shortening and a directional (Dega-type) acetabuloplasty - to durably contain a spastic dislocated hip.

Verify on PubMed (PMID 1429790)

Early results of one-stage correction for hip instability in cerebral palsy

Level IV

Kim HT, Jang JH, Ahn JM, Lee JS, Kang DJ • Clin Orthop Surg

Clinical Implication: The Dega osteotomy is tunable to the direction of acetabular deficiency demonstrated on 3D-CT, supporting its use for the variably (often posterosuperiorly) deficient cerebral palsy hip within a single-event multilevel reconstruction.

Verify on PubMed (PMID 22662300)

Clinical Decision Scenarios

Use these scenarios to practise clinical reasoning and management decisions

CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"A 3-year-old child has residual acetabular dysplasia following previous closed reduction for DDH. The acetabulum is capacious and globally deficient, the triradiate cartilage is open, and the femoral head is concentrically reduced. Which pelvic osteotomy would you choose and why? Contrast it with the alternatives."

PRACTICAL APPROACH

In a 3-year-old with an open triradiate cartilage, a concentrically reduced head and a capacious, globally deficient acetabulum, I would choose a reshaping (volume-reducing) osteotomy — specifically a Pemberton pericapsular osteotomy. **Rationale**: The pathology here is a roomy, oversized socket. A reshaping osteotomy decreases acetabular volume and improves coverage by hinging the roof down. The Pemberton hinges directly on the open triradiate cartilage, which allows the largest single-procedure reduction in acetabular volume and lets me direct the correction in essentially any direction to address the global deficiency. **Prerequisites I would confirm first**: A truly concentric, stable reduction — if there is any residual subluxation or an inverted limbus, I would perform an open reduction (excise ligamentum teres and pulvinar, divide the transverse acetabular ligament and limbus) before reshaping. Reshaping a roof over a malreduced head simply buttresses a subluxation. **Contrast with the alternatives**: - A Dega osteotomy is also a reshaping option but is most useful for selective posterosuperior deficiency (classically the neuromuscular hip); it hinges on the intact posterior/medial cortex and is more 'tunable' but reduces volume less aggressively than a Pemberton. - A Salter innominate osteotomy redirects the whole acetabulum on the symphyseal hinge without changing its shape or volume — better suited to milder dysplasia with a congruent, normally-sized socket, and it requires graft and K-wire fixation. - A periacetabular (Ganz) or triple osteotomy is for the older child/adolescent with a closed or closing triradiate, so it is inappropriate at age 3. **Technique points**: Anterior bikini approach protecting the LFCN, subperiosteal exposure of both iliac tables to the sciatic notch, curved pericapsular cut toward (not through) the triradiate, lever the roof down checking congruency, impact corticocancellous graft, and spica.

CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"What is the fundamental difference between the Pemberton and Dega osteotomies, and how does each differ from the Salter innominate osteotomy?"

PRACTICAL APPROACH

All three are pelvic osteotomies for the dysplastic hip, but they differ fundamentally in what they do to the acetabulum and where they hinge. **Pemberton and Dega are reshaping (volume-reducing) osteotomies** — they are incomplete pericapsular cuts that change the SHAPE of the acetabulum and reduce its volume by levering the roof down. They do not move the acetabulum as a unit and create no pelvic discontinuity, so they generally do not need internal fixation. **The key difference between them is the hinge**: - The Pemberton is a curved pericapsular cut from the AIIS region toward the triradiate cartilage, and it hinges on the OPEN TRIRADIATE CARTILAGE. Because the hinge is the cartilage, it reduces volume the most and can correct deficiency in almost any direction — ideal for a globally capacious DDH socket. Its trade-offs are stiffness, over-coverage and a theoretical risk of premature triradiate fusion. - The Dega is an incomplete transiliac cut that hinges on the intact POSTERIOR (and medial) ILIAC CORTEX, preserving the medial wall. By varying the depth and posterior extent of the cut, the surgeon tunes the direction of correction, which makes it ideal for the posterosuperior deficiency of the neuromuscular (cerebral palsy) hip. **The Salter innominate osteotomy is fundamentally different — it REDIRECTS rather than reshapes.** It is a COMPLETE innominate osteotomy that hinges on the SYMPHYSIS PUBIS and rotates the entire acetabulum antero-laterally without changing its shape or volume. Because the segment is completely freed, it requires a bone graft and K-wire or screw fixation. It is best for milder dysplasia with a congruent, normally-sized acetabulum. **The one-liners**: Pemberton hinges on the triradiate; Dega hinges on the posterior/medial cortex; Salter hinges on the symphysis. Pemberton and Dega reshape and reduce volume; Salter redirects and preserves volume.

CLINICAL SCENARIOAdvanced

CLINICAL PROMPT

"You are performing a pericapsular osteotomy and are working at the posterior extent of the cut near the sciatic notch. What structures are at risk, and how do you protect them? What other intra-operative errors threaten the result of a reshaping osteotomy?"

PRACTICAL APPROACH

The posterior extent of both the Pemberton and Dega osteotomies approaches the greater sciatic notch, where the sciatic nerve and the superior gluteal neurovascular bundle lie immediately deep to the bone. **Protecting the sciatic notch**: I keep my exposure strictly subperiosteal on both the inner and outer tables of the ilium and place blunt retractors (e.g. curved Hohmann or a blunt elevator) into the notch on each side. The retractor both protects the neurovascular structures and guides the depth of my osteotome. Critically, I do NOT exit the posterior cortex — for the Dega this posterior cortex is the hinge, and for the Pemberton I am hinging on the triradiate, so in neither case should the osteotome be driven out through the back of the bone into the notch. **Other key intra-operative errors that threaten the result**: 1. Propagating the cut into the triradiate cartilage or the joint — risks premature triradiate fusion, growth arrest and intra-articular damage. I keep the cut directed toward but not through the triradiate. 2. Entering the joint capsule — these are pericapsular osteotomies; I stay above the capsule. 3. Reshaping over a non-concentric reduction — I confirm a concentric, stable reduction first. 4. Over-correction — over-hinging (especially a Pemberton) produces an over-covered, tight, stiff hip; I correct only to a congruent, stable hip and check congruency before grafting. 5. Inadequate graft impaction — a poorly held roof loses correction; I impact solid corticocancellous wedges and immobilise in a spica. 6. Anteriorly, traction injury to the lateral femoral cutaneous nerve — I identify and protect it during the approach.