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Paediatric Orthopaedics
Paediatrics
General Practice

Perthes Disease (LCPD)

High EvidenceUpdated: 2025-12-26

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Red Flags

  • Stiff Hip in Child -> Rule out Septic Arthritis first
  • Loss of Abduction -> Hinge Abduction (Poor prognosis)
  • Lateral Pillar Collapse -> Urgent Surgery needed
Overview

Perthes Disease (LCPD)

1. Clinical Overview

Summary

Legg-Calvé-Perthes Disease (LCPD) is an idiopathic Avascular Necrosis (AVN) of the femoral head in children aged 4-8 years. The blood supply to the epiphysis is temporarily disrupted, causing the bone to die (necrosis), collapse (fragmentation), and then heal (re-ossification). The goal of treatment is Containment: keeping the "melting" femoral head inside the spherical acetabular mould so that it reforms as a round ball (Spherical congruency). If it extrudes, it heals as a flat mushroom (Coxa Plana - Incongruent), leading to early osteoarthritis. [1,2,3]

Key Facts

  • The "Hyperactive Short Boy": Classic patient profile is a small-for-age, hyperactive male (4-8 years).
  • Self-Limiting: The disease runs a 2-4 year course and heals itself. Our only job is to prevent deformity during the "soft" phase.
  • Prognostic Factors:
    • Age <6: Excellent prognosis (more time to remodel).
    • Age >8: Poor prognosis (stiff hip, less remodeling).

Clinical Pearls

"Knee Pain is Hip Pain": Always examine the hip in a child with knee pain. The obturator nerve refers pain from the hip to the medial knee.

"Containment is King": Think of the femoral head like a scoop of melting ice cream. If you keep it deep in the bowl (Acetabulum), it stays round. If it slips out the side, it flattens.

"The Crescent Sign": A subchondral fracture line on X-ray. It marks the beginning of the end for the bone structure.

2. Epidemiology

Demographics

  • Incidence: 1 in 1,200 children.
  • Age: 4-8 years (Peak). (Rare <2 or >12).
  • Gender: Male > Female (4:1).
  • Bilateral: 10-15% (but asynchronous - never at the same stage).
3. Pathophysiology

The 4 Stages (Waldenström)

  1. Initial (Necrosis): Blood supply stops. Bone dies. X-ray shows increased density (sclerosis) and small epiphysis.
  2. Fragmentation (Resorption): The "Soft Phase". Dead bone is resorbed by osteoclasts. The head is arguably structurally weakest here. CRITICAL PHASE for extrusion.
  3. Re-ossification: New bone is laid down.
  4. Remodelling: The head reshapes itself until maturity.

Classification (Herring Lateral Pillar)

Based on the height of the lateral 1/3 of the femoral epiphysis (The "Tent Pole").

  • Group A: No loss of height. (Good).
  • Group B: <50% loss of height. (Fair).
  • Group C: >50% loss of height. (Poor).

Head at Risk Signs (Catterall)

X-ray signs suggesting poor outcome:

  1. Lateral subluxation (Extrusion).
  2. Gage Sign (V-shaped defect laterally).
  3. Calcification lateral to epiphysis.
  4. Horizontal growth plate.
  5. Metaphyseal cysts.
4. Clinical Presentation

Symptoms

Signs

Painless limp
Often the first sign.
Pain
Groin, Thigh, or Knee. Worse with activity.
Stiffness.
Common presentation.
5. Investigations

Imaging

  • X-Ray Pelvis (AP & Frog Lateral):
    • Assess Waldenstrom stage.
    • Assess Herring Classification (AP view).
    • Crescent Sign: Subchondral fracture.
  • MRI:
    • Sensitive early (before X-ray changes). Shows marrow edema and loss of perfusion.
    • Assess cartilage shape (Is the head actually round despite flattened bone?).
6. Management Algorithm
                 DIAGNOSIS OF PERTHES
                        ↓
                  CHECK AGE & ROM
             ┌──────────┴──────────┐
          &lt; 6 YEARS             > 8 YEARS
       (Usually Good)         (Usually Bad)
             ↓                     ↓
        SYMPTOMATIC          LATERAL PILLAR?
     (Physio / Crutches)    ┌──────┴──────┐
             ↓             A              B/C
          MONITOR          ↓               ↓
        (X-rays 6mo)    OBSERVE         SURGERY
                                      (Osteotomy)
                                     (Containment)
7. Management Protocols

1. Conservative (Observation)

  • Indication: Age <6, Herring A.
  • Protocol:
    • Activity modification (No jumping/impact).
    • NSAIDS.
    • Physiotherapy (Maintain Abduction range).
    • "Supervised Neglect".

2. Surgery: Containment

  • Indication: Age >8 (or >6 with Head at Risk), Herring B or B/C border.
  • Goal: Put the head deep into the socket.
  • Options:
    • Femoral Varus Osteotomy (VDRO): Tilts the femoral neck to point the head inwards.
    • Pelvic Osteotomy (Salter): Tilts the roof to cover the head.

3. Surgery: Salvage

  • Indication: Hinge Abduction (Head is already flat and hits the edge of the socket).
  • Options:
    • Valgus Osteotomy (change the worn spot).
    • Shelf Acetabuloplasty (add a roof).
8. Complications

Coxa Magna / Coxa Plana

  • Coxa Magna: Broad head.
  • Coxa Plana: Flat head.
  • Both lead to incongruency and early osteoarthritis.

Osteochondritis Dissecans (OCD)

  • A loose fragment of bone/cartilage may separate late in the disease. Causes locking.
9. Evidence & Guidelines

The Herring Study (2004)

  • Multi-center prospective study.
  • Finding:
    • Herring A: Did well regardless of treatment.
    • Herring C: Did poorly regardless of treatment.
    • Herring B: The "Battleground". Surgery (Osteotomy) was superior to non-op in children >8 years.
10. Patient Explanation

What is Perthes?

The blood supply to the ball of the hip joint has temporarily stopped. The bone softens and can crumble, like a wet sugar cube.

Will it heal?

Yes, the blood supply always comes back, and the bone will regrow. The whole process takes 2-4 years.

What is the risk?

While the bone is soft, the weight of the body can squash it flat. If it heals flat (like a mushroom), it won't fit the round socket properly, leading to arthritis later in life.

The Treatment

We need to keep the hip strictly round while it heals. Sometimes we do this with exercises, but sometimes we need an operation to tilt the ball deep into the socket to use the socket as a mould.

11. References
  1. Herring JA, et al. Legg-Calve-Perthes disease. Part II: Prospective multicenter study of the effect of treatment on outcome. J Bone Joint Surg Am. 2004.
  2. Catterall A. The natural history of Perthes' disease. J Bone Joint Surg Br. 1971.
  3. Stulberg SD, et al. The natural history of Legg-Calve-Perthes disease. J Bone Joint Surg Am. 1981.
12. Examination Focus (Viva Vault)

Q1: What are the "Head at Risk" signs? A: Described by Catterall: Lateral Subluxation (Most important), Gage Sign (V-shaped lateral defect), Calcification lateral to epiphysis, Diffusely horizontal physis, Metaphyseal cysts. These predict a poor outcome.

Q2: Why is age such a critical prognostic factor? A: Younger bones remodel better. A 4-year-old has 10+ years of growth remaining to reshape a flattened head back into a sphere. An 8-year-old has much less time and plasticity. The acetabulum also remodels better in the young.

Q3: Explain the concept of "Hinge Abduction". A: In severe deformity, the femoral head is so flat/wide that it cannot slide inside the socket during abduction. Instead, the lateral edge of the head impinges against the edge of the acetabulum, and the hip "hinges" open like a book rather than rotating. This is painful and contraindicates containment surgery (as forcing it in would crush the cartilage).

(End of Topic)

Last updated: 2025-12-26

At a Glance

EvidenceHigh
Last Updated2025-12-26

Red Flags

  • Stiff Hip in Child -> Rule out Septic Arthritis first
  • Loss of Abduction -> Hinge Abduction (Poor prognosis)
  • Lateral Pillar Collapse -> Urgent Surgery needed

Clinical Pearls

  • **"Knee Pain is Hip Pain"**: Always examine the hip in a child with knee pain. The obturator nerve refers pain from the hip to the medial knee.
  • **"Containment is King"**: Think of the femoral head like a scoop of melting ice cream. If you keep it deep in the bowl (Acetabulum), it stays round. If it slips out the side, it flattens.
  • **"The Crescent Sign"**: A subchondral fracture line on X-ray. It marks the beginning of the end for the bone structure.

Guidelines

  • NICE Guidelines
  • BTS Guidelines
  • RCUK Guidelines