Legg-Calvé-Perthes Disease

Legg-Calvé-Perthes disease (also called Perthes disease or coxa plana) is idiopathic avascular necrosis of the femoral head in children. It is a self-limiting condition characterized by interruption of blood supply to the femoral epiphysis, followed by necrosis, fragmentation, revascularization, and remodeling.

Key features:

• Idiopathic AVN - cause unknown (unlike traumatic or sickle cell AVN)
• Self-limiting - natural history is 2-4 years from onset to healing
• Outcome depends on containment - maintaining head within acetabulum during healing
• Remodeling potential - younger children have excellent potential for recovery

Epidemiology:

Blood supply to the femoral head:

The pediatric femoral head receives blood from:

• Lateral epiphyseal vessels (branches of medial femoral circumflex) - primary supply
• Foveal vessels (from ligamentum teres) - minimal in young children
• Metaphyseal vessels - blocked by growth plate

Pathophysiology theories:

• Vascular occlusion - thrombosis of lateral epiphyseal vessels (? coagulopathy)
• Repetitive microtrauma - mechanical stress on vulnerable vessels
• Anatomical watershed - terminal vessels predisposed to ischemia
• Venous outflow obstruction - increased intraosseous pressure

Natural history - four stages:

The Containment Principle:

The biological rationale for containment:

• The femoral head is soft and moldable during reossification
• The acetabulum acts as a mold to shape the reossifying head
• If the head extrudes laterally (loses containment), it reossifies in a non-spherical, mushroom shape
• Maintained containment → spherical head → good long-term outcome
• Lost containment → aspherical head → early osteoarthritis

Multiple classification systems exist, but Herring lateral pillar is most reliable for prognosis and treatment decisions.

Typical presentation:

Physical examination findings:

Key findings in order of sensitivity:

1. Limited abduction - most sensitive early sign
2. Limited internal rotation - especially in flexion
3. Muscle spasm - protective spasm in hip flexors, adductors
4. Leg length discrepancy - apparent shortening from muscle spasm
5. Trendelenburg gait - abductor dysfunction

Differential diagnosis:

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Radiographic signs by stage:

Key radiographic measurements:

• Lateral pillar height: compare affected to normal side (Herring classification)
• Extrusion index: percentage of femoral head lateral to Perkin's line (normal less than 20%)
• Epiphyseal quotient: width of affected epiphysis / normal side (measures coxa magna)

Algorithm

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Treatment depends on age at onset and extent of involvement (Herring classification).

General principles:

• Goal: spherical, congruent femoral head at skeletal maturity
• Containment: maintain head within acetabulum during reossification
• ROM: maintain hip ROM to prevent stiffness
• Natural history: disease lasts 2-4 years regardless of treatment

Age Under 6Age 6-8Age Over 8

Management: Observation

Children under 6 have excellent prognosis regardless of classification due to high remodeling potential.

Treatment Protocol

DiagnosisInitial Management

• Reassure family: excellent prognosis at this age
• Activity: normal activity as tolerated, avoid high impact initially
• Analgesia: NSAIDs for pain (ibuprofen)

OngoingROM Exercises

• Goal: maintain abduction and internal rotation
• Method: physical therapy, swimming, cycling
• Avoid: prolonged immobilization (causes stiffness)

Every 3-4 monthsMonitoring

• X-rays: every 3-4 months until reossification complete
• Watch for: progression to Herring C, increasing extrusion
• Duration: follow for 2-4 years through all stages

Skeletal maturityOutcome

• Most achieve Stulberg I-II (excellent)
• Even Herring C at age under 6 often remodels well

Why Observation Under 6?

Children under 6 have tremendous remodeling potential. Even with significant collapse (Herring C), the acetabulum and femoral head remodel together over years, achieving sphericity by skeletal maturity. Surgery does not improve outcomes at this age.

Management: Selective Containment

Age 6-8 is the critical age where treatment decisions significantly affect outcome.

Treatment algorithm:

• Herring A: observation, ROM exercises
• Herring B: observation if younger than 7; consider containment if closer to 8
• Herring B/C or C: containment surgery recommended

Containment Surgery Decision

Fragmentation stageAssessment

• Classify Herring group at maximal fragmentation
• Assess extrusion: more than 20% extrusion = poor containment
• Check ROM: need adequate abduction for containment to work

If surgery indicatedContainment Options

Femoral osteotomy (varus +/- derotation):

• Creates containment by redirecting head into acetabulum
• Varus 10-15 degrees typically
• Advantage: addresses femoral side
• Disadvantage: limb shortening, Trendelenburg if excessive varus

Pelvic osteotomy (Salter):

• Redirects acetabulum over femoral head
• Improves lateral coverage
• Advantage: increases coverage without shortening
• Disadvantage: more extensive surgery

Combined (if severe extrusion)

After surgeryPost-operative

• Spica cast 4-6 weeks
• Early ROM exercises
• Protected weight-bearing 6-8 weeks
• Monitor reossification with serial X-rays

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Containment Prerequisites

Containment surgery only works if:

1. Head is still moldable (fragmentation or early reossification stage)
2. Adequate ROM (at least 30 degrees abduction)
3. Correct stage (not too early in necrosis, not too late in remodeling) If head is already spherical in reossification, surgery not needed. If already remodeled poorly, surgery won't help.

Management: Aggressive or Salvage

Children over 8 have limited remodeling potential. Even Herring B may have poor outcomes.

Treatment approach:

• Herring A: observation (uncommon to present this late with minimal involvement)
• Herring B: consider containment surgery (debated - some surgeons yes, some no)
• Herring C: poor prognosis - salvage options

Salvage procedures for Herring C over age 8:

• Valgus osteotomy: redirects head away from acetabulum to minimize impingement on activities
• Shelf procedure: augment lateral coverage with bone graft shelf
• Chiari osteotomy: medialize acetabulum for coverage
• Observation with activity modification: accept poor outcome, manage symptoms

Realistic Expectations Over Age 8

Be honest with families: children over 8 with Herring B/C or C have poor prognosis regardless of treatment. Goal is to minimize symptoms and delay arthritis, but most will need hip arthroplasty by age 40-50. Containment surgery is controversial and may not change long-term outcome.

Long-term outcomes:

• Stulberg I-II: excellent long-term function, low risk of OA
• Stulberg III: moderate risk of OA, typically after age 50-60
• Stulberg IV-V: high risk of early OA, often requiring THA by age 40-50

Post-surgical protocol varies by procedure type:

Key Rehabilitation Principles:

Follow-up Schedule:

• Surgical cases: 2 weeks (wound), 6 weeks (healing), 3 months, 6 months, then every 6 months until reossification complete
• Non-operative cases: Every 3-4 months until reossification complete
• Long-term: Annually until skeletal maturity (assess final Stulberg classification)
• Transition: To adult services for ongoing OA risk monitoring

Prognostic factors:

Favorable (good prognosis):

• Age at onset under 6 years (most important)
• Herring A or B classification
• Less than 50% lateral pillar collapse
• Minimal extrusion (less than 20%)
• Male gender
• Maintained ROM

Unfavorable (poor prognosis):

• Age at onset over 8 years (most important)
• Herring B/C or C classification
• More than 50% lateral pillar collapse
• Significant extrusion (more than 20%)
• Female gender (worse at same age/classification)
• Restricted ROM, especially abduction

Natural history without treatment:

• Under 6: most achieve good outcome (Stulberg I-III) even without surgery
• 6-8: variable, depends on extent (B/C and C often progress to Stulberg IV-V)
• Over 8: poor outcome common, especially Herring B/C or C

Effect of containment surgery:

• May improve outcome by 1 Stulberg class (IV → III) if done appropriately
• Most beneficial in age 6-8 with Herring B/C or C
• Limited benefit if too young (under 6) or too old (over 10)

Perthes disease has no single international clinical-practice guideline; management is guided by the prospective cohort evidence above and by paediatric-orthopaedic registries. The picture below is deliberately global rather than tied to any one health system.

Global epidemiology (population-based):

Reported incidence therefore varies several-fold worldwide (single figures to mid-teens per 100,000), with a consistent male predominance (roughly 3-5:1) and a robust association with socioeconomic deprivation. A Swedish national-register study also found increased rates of obesity, hypertension and other osteochondroses in affected children, supporting a possible systemic component (Hailer 2018, DOI).

Where management genuinely differs (and where it agrees):

Registry evidence: Several national paediatric-orthopaedic registries now capture Perthes prospectively, notably the Swedish Paediatric Orthopaedic Quality register (SPOQ) Perthes' register, which has been used to study comorbidity and outcome (Morlin 2021, DOI). Unlike arthroplasty, there is no implant-survival registry relevant here; registries instead inform incidence, risk factors and natural history rather than device performance.

Global practice variation: In high-resource settings the debate centres on which containment operation (femoral versus pelvic versus combined) and patient selection, supported by MRI/arthrography. In lower-resource settings, late presentation is more common, MRI access is limited, and management leans on plain radiographs with a higher proportion of salvage rather than early containment. Long-term surveillance to skeletal maturity, with transition to adult services for femoroacetabular impingement and early-osteoarthritis monitoring, is recommended everywhere.