Perthes Containment Surgery (Femoral & Pelvic Osteotomy)

Pathophysiology

Legg-Calvé-Perthes disease (LCPD) is an idiopathic avascular necrosis of the proximal femoral epiphysis in the growing child. The interruption of blood supply (predominantly via the lateral epiphyseal vessels of the medial femoral circumflex artery) leads to a self-limiting but staged sequence of necrosis, revascularisation, collapse, and repair. The vulnerable window is the period of necrosis and fragmentation, during which the softened, plastic epiphysis can deform under load.

• Typical age: 4-8 years; male predominance (approximately 4-5:1)
• Bilateral in up to 10-15% (usually asynchronous — synchronous bilateral symmetrical disease should prompt consideration of epiphyseal dysplasia or hypothyroidism)
• Presentation: Painless or mildly painful limp, restricted abduction and internal rotation, occasionally referred knee pain
• The biological principle exploited by surgery is that the plastic head will remodel to the shape of whatever it is moulded against — hence containment within the spherical acetabulum

Waldenström Radiographic Stages

Key timing principle: Containment surgery is effective only in stages 1-2 while the head is plastic and reducible. By stage 3-4 the final shape is largely set.

Lateral Pillar (Herring) Classification

Assessed on the AP radiograph in the fragmentation stage by the height of the lateral pillar (lateral 15-30% of the epiphysis) compared with the contralateral side. It is the strongest radiographic prognostic factor.

Catterall Classification

Based on the extent of epiphyseal involvement (4 groups: I = anterior only, II = anterolateral, III = most of epiphysis with small intact medial/posterior, IV = whole epiphysis). Less reproducible than lateral pillar and assessed retrospectively, but historically important and the source of the head-at-risk signs.

Stulberg Classification (Outcome / Sphericity-Congruence)

Applied at skeletal maturity to predict long-term osteoarthritis based on head sphericity and joint congruence.

Principle: Congruence (a round head in a matching socket, or a flat head in a flat socket — "aspherical congruency") matters more than absolute sphericity. The goal of containment is to achieve a Stulberg I-III hip.

The Decision-Making Framework

The aim of all treatment is containment — keeping the femoral head within the acetabulum during the plastic phase so it remodels spherically and congruently. Not every Perthes hip needs surgery; the decision integrates age, lateral pillar grade, range of motion, and head-at-risk signs.

Prognostic Factors (Decision Drivers)

• Age at onset — the single most important factor. In the Herring study no treatment effect was seen below a chronological age of 8 years (or a skeletal age of 6 years), so younger children usually do well non-operatively; children older than 8 years at onset remodel poorly and are more likely to benefit from surgery.
• Lateral pillar grade — A (good regardless), B/B-C (benefits from surgery if older), C (poor regardless).
• Head-at-risk signs — especially lateral subluxation — favour intervention.
• Loss of containment / extrusion and progressive loss of abduction.
• Hinge abduction — if present, varus containment is contraindicated.

Non-Operative Containment — Largely Abandoned

• Abduction bracing / casting (e.g. Petrie casts, Scottish-Rite orthosis) was historically used to hold the hip abducted and contained.
• High-quality evidence (including the Herring multicentre study) showed bracing is ineffective at altering outcome and is poorly tolerated — it is no longer recommended as a containment strategy.
• Modern non-operative management focuses on symptomatic care: activity modification, physiotherapy to maintain range of motion (especially abduction and internal rotation), analgesia, and observation — appropriate for the younger child and lateral pillar A.

Indications for Surgical Containment

Best-Supported Indication

• Chronological age older than 8 years at onset with lateral pillar B or B/C — this is the group with demonstrated benefit from operative containment (femoral or pelvic osteotomy) in the Herring multicentre prospective study. (Wiig used a chronological-age threshold of 6 years with greater than 50% head necrosis to recommend femoral varus osteotomy.)

Additional Indications

• Progressive subluxation / extrusion of the head (head-at-risk signs) with loss of containment
• Failure to maintain containment with conservative measures in an at-risk hip
• Lateral pillar B/B-C in the early (initial/fragmentation) stage while the head is still reducible and congruent in abduction

Contraindications to Containment (Varus/Salter)

• Healed or late reossification stage — head no longer plastic, deformity fixed
• Hinge abduction confirmed on dynamic arthrogram — abduction worsens congruity (needs valgus osteotomy or shelf)
• Uncontainable head (markedly enlarged coxa magna that cannot be seated) — consider lateral shelf / Chiari salvage
• Stiff, incongruent hip with fixed deformity

Prerequisite Assessment Before Surgery

• Dynamic arthrogram under anaesthesia — the key planning step. Confirms the head reduces and is congruent in abduction and internal rotation and excludes hinge abduction.
• Restore range of motion first if the hip is stiff (traction, adductor release / physiotherapy) — a hip must abduct before it can be contained.

Overview of Surgical Options

Containment can be achieved on the femoral side (redirect the head into the socket by reorienting the proximal femur), the pelvic side (redirect the acetabulum to cover the head), or both. Salvage procedures (shelf, Chiari) are used when the head is too large or uncontainable, or when hinge abduction is present.

Femoral Varus Derotation Osteotomy (VDRO)

Principle

A subtrochanteric (intertrochanteric) osteotomy introduces varus (and often derotation to correct excessive anteversion) so that the femoral head is directed more deeply into the acetabulum, improving cover anterolaterally.

Technique Outline

• Position: Supine, radiolucent table, image intensifier available; lateral hip exposure.
• Approach: Lateral approach to the proximal femur (split vastus lateralis off the lateral intermuscular septum).
• Fixation: Pre-contoured paediatric blade plate or proximal femoral locking plate. The blade is inserted along the planned proximal fragment trajectory.
• Correction: Aim for a neck-shaft angle of about 105-110 degrees (avoid excessive varus, which causes a Trendelenburg gait and does not remodel well in the older child). Derotate to correct excess anteversion.
• Avoid over-shortening: Resect a wedge sufficient to obtain contact and the desired varus without excessive shortening.

Salter Innominate (Pelvic Redirectional) Osteotomy

Principle

A complete osteotomy through the innominate bone above the acetabulum, hinging on the symphysis pubis, redirects the acetabulum anterolaterally to cover the extruded anterolateral femoral head. A bone graft wedge (from the iliac crest) is interposed and fixed with threaded wires.

Technique Outline

• Approach: Anterior (bikini / Smith-Petersen) approach to the iliac wing and hip.
• Osteotomy: Straight cut from the sciatic notch to the anterior inferior iliac spine.
• Redirection: Distal fragment (with acetabulum) rotated anterolaterally and held with a tricortical iliac wedge graft and two threaded Kirschner wires.
• Requirement: Needs a mobile, congruent, concentrically reducible hip — the Salter does not increase coverage of an incongruent hip and slightly increases joint contact pressure.

Salvage and Hinge-Abduction Procedures

• Shelf acetabuloplasty / lateral shelf: For the large (coxa magna) or older child where the head cannot be fully contained anatomically, or with mild hinge — augments lateral coverage with a bone shelf.
• Chiari osteotomy: Medialising salvage for an incongruent / uncontainable hip; provides coverage by capsular metaplasia.
• Valgus osteotomy (+/- extension): The procedure of choice for hinge abduction — the head is congruent in adduction, so a valgus osteotomy brings the congruent medial portion under the acetabulum, relieves the hinge, and improves abduction and gait.

Post-operative Care (General)

• Femoral osteotomy: Hip spica or protected weight-bearing depending on fixation rigidity; plate removal commonly at 6-12 months once united.
• Salter osteotomy: Single hip spica for approximately 6 weeks, then mobilise; remove threaded wires once healed.
• Rehabilitation: Regain abduction and internal rotation; physiotherapy; monitor for trochanteric overgrowth and leg-length discrepancy to maturity.

Determinants of Outcome

The long-term outcome of Perthes is determined chiefly by the final shape and congruence of the femoral head (Stulberg class). Treatment aims to achieve a spherical or aspherical-congruent (Stulberg I-III) hip and to avoid an incongruent (IV-V) hip, which leads to early osteoarthritis.

Most Important Prognostic Factors

• Age at onset — younger remodels better; older than 8 years (chronological) at onset is the high-risk group with proven surgical benefit
• Lateral pillar (Herring) grade — strongest radiographic predictor (A good, C poor)
• Final head sphericity and congruence (Stulberg) — predicts adult OA
• Head-at-risk signs (especially lateral subluxation/extrusion)
• Range of motion maintained throughout the disease

Evidence for Surgical Containment

• Herring et al. multicentre prospective study (PMID 15466720, J Bone Joint Surg Am 2004) — the landmark study (438 patients, 451 hips, ages 6.0-12.0 years at onset). Key findings:
  • Lateral pillar A: good outcome regardless of treatment
  • Lateral pillar B and B/C border in children older than 8 years (skeletal age): significantly better outcomes with surgery (femoral or Salter osteotomy) than non-operative treatment
  • Lateral pillar C: poor outcome regardless of treatment
  • Children under 8 years with pillar B: did well irrespective of treatment
• This study established the modern indication: operate on the older child with pillar B/B-C.

Femoral vs Salter — Outcome Comparison

• Comparative series show no consistent difference in final sphericity or congruence (Stulberg outcome) between femoral and Salter osteotomy when the hip is congruent and reducible — both achieve containment.
• In the most-cited direct comparison (Kitakoji et al., 2005), the two procedures produced equivalent head sphericity and hip congruity, but the Salter group had a neck-shaft angle, acetabular coverage, and articular-trochanteric distance closer to normal, and avoided the surgical scarring and coxa vara seen after femoral osteotomy.
• Femoral osteotomy: simpler, familiar, but shortens the limb and risks trochanteric overgrowth/Trendelenburg and coxa vara.
• Salter osteotomy: avoids shortening (slight lengthening), redirects anterolateral cover, but raises joint pressure and needs a congruent mobile hip.
• Choice is guided by deformity pattern, surgeon experience, and limb-length considerations.

Long-Term and Natural History

• Many patients function well into adulthood; significant osteoarthritis typically presents in the 5th-6th decade, correlating with Stulberg class.
• Stulberg I-II: minimal long-term OA risk.
• Stulberg III: moderate; OA in middle age.
• Stulberg IV-V: high risk of early, severe OA requiring joint-preserving osteotomy or arthroplasty.
• Counselling should be realistic: containment improves the odds of a congruent hip but cannot guarantee a normal hip, especially in older children and lateral pillar C.