Perthes Disease
CIM Case: Perthes Disease
Clinical Scenario
Patient: 6-year-old boy Presentation: 3-month history of progressive limp and intermittent left hip pain, referred to groin and anterior thigh, worse with activity Relevant history: No trauma, no recent illness, previously active and healthy, pain sometimes wakes him at night, no fever, no weight loss Examination findings:
- Antalgic gait with shortened stance phase on left
- Left leg held in slight flexion and external rotation
- Reduced hip flexion (100° vs 130°), limited internal rotation (10° vs 40°), limited abduction (20° vs 45°)
- Positive log roll test (pain with rotation)
- No leg length discrepancy currently
- Trendelenburg negative
- No muscle wasting
- Knee examination normal bilaterally
Investigations Provided
Laboratory Results
| Test | Result | Normal Range | Interpretation |
|---|---|---|---|
| Hb | 128 g/L | 115-135 g/L | Normal |
| WCC | 7.5 ×10⁹/L | 5-15 ×10⁹/L | Normal |
| Platelets | 298 ×10⁹/L | 150-400 ×10⁹/L | Normal |
| ESR | 8 mm/hr | <10 mm/hr | Normal (helps exclude infection/inflammation) |
| CRP | <3 mg/L | <5 mg/L | Normal |
Imaging
Image 1: AP Pelvis and Frog-leg Lateral Radiographs
Radiological features:
- Left femoral epiphysis smaller and denser than right (sclerosis)
- Widening of medial joint space (lateral subluxation)
- Crescent sign visible on lateral (subchondral fracture)
- Metaphyseal lucency present
- Physis appears horizontal
- Lateral pillar involvement - partial collapse (Herring B)
- Catterall Group III (50-75% head involvement)
Image 2: MRI of Pelvis (if obtained)
MRI findings:
- Low signal on T1 in anterolateral femoral epiphysis
- High signal on T2/STIR indicating oedema and revascularisation
- Extent of necrosis more clearly defined
- No physeal bar
- Labral changes minimal
Questions & Model Answers
Describe your approach to diagnosing and staging this child's hip condition.
What are the prognostic factors in Perthes disease?
What is the principle of containment and what are the treatment options?
How would you manage this child's reduced range of motion?
What is the natural history and what are the long-term outcomes?
What are the differential diagnoses and how would you distinguish them?
Key Teaching Points
Pattern Recognition
This pattern suggests Perthes Disease:
- School-age boy (4-8 years) with insidious limp
- Groin/thigh pain worse with activity
- Limited internal rotation and abduction
- Radiographs: small, dense, fragmented femoral head
Distinguish from Transient Synovitis:
| Feature | Perthes | Transient Synovitis |
|---|---|---|
| Onset | Insidious (weeks) | Acute (days) |
| Duration | Months-years | 1-2 weeks |
| X-ray | Abnormal | Normal |
| Age | 4-8 years | 3-6 years |
| Outcome | Permanent changes | Complete resolution |
Critical Management Points
- Age is the most important prognostic factor - younger is better
- Herring classification at fragmentation - determines treatment and prognosis
- ROM must be restored before surgery - stiff hip cannot be contained
- Disease is self-limiting - treatment optimises outcome, doesn't cure
- Head-at-risk signs indicate need for containment - lateral subluxation, Gage sign
- Long-term OA depends on Stulberg class - aspherical heads fare poorly
Common Examiner Follow-ups
Q: "When would you do an MRI?"
MRI indications in Perthes:
- Early diagnosis: X-ray equivocal but clinical suspicion high
- Extent of necrosis: Planning treatment, assessing lateral pillar
- Atypical presentation: Exclude other pathology (tumour, infection)
- Bilateral involvement: Consider MED or other skeletal dysplasia
- Poor response to treatment: Assess for complications
MRI provides earlier detection than X-ray and better defines extent of involvement.
Q: "This child is 9 years old with Herring C. What would you do?"
This is a "bad" Perthes with poor prognosis regardless of treatment:
- Expectation setting: Counsel family about likely outcome (Stulberg IV-V)
- ROM maintenance: Priority is preventing stiff hip
- Containment role limited: Evidence does not show containment helps Herring C at this age
- Observe: Serial X-rays, physiotherapy, activity modification
- Salvage surgery later if needed: Shelf acetabuloplasty, Chiari osteotomy, valgus osteotomy for hinge abduction, or eventual hip replacement
Surgery for poor prognosis Perthes is controversial - may not change outcome.
Q: "What is the evidence for containment surgery?"
Key evidence:
- Herring Prospective Study (2004, JBJS):
- Age >8 with Herring B/C: surgical containment better than non-operative
- Age <8 or Herring A: no benefit from surgery
- Systematic reviews: Weak evidence overall, no clear superiority of one surgical method
- Recent trends: Moving away from bracing, selective surgery based on age and classification
Bottom line: Surgery helps selected patients (older children with Herring B) but doesn't change outcome for very good or very poor prognosis groups.
Q: "What if this child has bilateral involvement?"
Bilateral Perthes (~10-12%):
- Usually asynchronous (different stages)
- Treat each hip according to its stage and classification
- If synchronous and symmetrical - consider MED or other skeletal dysplasia
- Order lateral spine X-ray (vertebral changes in MED)
- Consider genetics referral
Related Topics
- Developmental Dysplasia of the Hip
- Slipped Upper Femoral Epiphysis
- Transient Synovitis
- Paediatric Hip Fractures
- Proximal Femoral Osteotomy
- Pelvic Osteotomies