Must-Know MCQs for the FRCS Orth- Hip Arthroplasty

Courtesy: Zaid Al-Rub, Founder and CEO, OrthoPass

1. Periprosthetic Joint Infection (PJI)

Clinical Scenario

• Elderly patient with persistent pain following total hip replacement.

Diagnostic Criteria (International Consensus Meeting – ICM)

Minimum criteria suggesting infection (>6 weeks after surgery):

• ESR > 30 mm/hr
• CRP > 10 mg/L
• Synovial WBC count > 3000 cells/µL
• Synovial PMN percentage > 80%

Key Point

• Diagnosis of PJI relies on combination of clinical, laboratory, and synovial fluid findings.

2. Periprosthetic Femoral Fracture – Vancouver Classification

Clinical Scenario

• Patient with fracture around femoral stem after fall.

Vancouver Classification

Type A

• Fracture around trochanters

Type B

• Fracture around stem
• Subtypes:
  • B1 – Stem stable
  • B2 – Stem loose with good bone stock
  • B3 – Stem loose with poor bone stock

Type C

• Fracture distal to stem

Case Answer

• Vancouver B2
  • Loose stem
  • Adequate bone stock

Management

• Revision arthroplasty + fracture fixation
• Options:
  • Cemented revision
  • Uncemented revision

3. Core Decompression in Avascular Necrosis (AVN)

Key Concept

• Core decompression is a joint-preserving procedure.

Best Indication

• Early AVN before femoral head collapse

Ficat–Arlet Classification

• Stage I – Normal X-ray, MRI positive
• Stage II – Sclerosis/cysts, no collapse
• Stage III – Crescent sign (subchondral collapse)
• Stage IV – Secondary osteoarthritis

Important Point

• Core decompression is most successful before Stage III
• Therefore effective up to Stage II

4. Bone Cement Implantation Syndrome (BCIS)

Definition

Clinical features occurring during cemented arthroplasty:

• Hypoxia
• Hypotension
• Loss of consciousness
• Cardiac collapse (severe cases)

Timing

Occurs during:

• Cementation
• Prosthesis insertion
• Joint reduction
• Tourniquet release (occasionally)

Most Accepted Pathophysiology

• Embolization to pulmonary circulation
  • Fat
  • Bone marrow
  • Cement particles
  • Air
  • Platelet–fibrin aggregates

Historical Theory (Less Supported)

• Methyl methacrylate monomer toxicity

5. Risk Factors for Hip Dislocation after THR

Major Risk Factors

• Neuromuscular disorders
• Component malposition
• Small femoral head size
• Posterior surgical approach

Example Question

Most significant risk factor:

Parkinson’s disease

Reason:

• Abnormal muscle tone
• Poor motor control
• Increased instability

Safe Zone for Acetabular Component (Lewinnek)

• Inclination: ~40°
• Anteversion: ~15°

6. Total Hip Arthroplasty in Paget Disease

Expected Findings

• Acetabular protrusio
• Increased blood loss
• Hard sclerotic bone
• High-output cardiac state

Bone Deformity

• Varus deformity of femoral neck

Important Surgical Considerations

• Increased vascularity
• Difficult reaming
• Higher intraoperative bleeding

MCQ Key Point

• Valgus deformity is NOT typical
• Correct answer: Valgus neck deformity

7. Iliopsoas Impingement after THR

Clinical Features

• Groin pain
• Pain with resisted hip flexion
• Often due to prominent or retroverted acetabular cup

Investigation Findings

• Normal infection markers
• Radiographs may show cup retroversion

Most Appropriate Management

• Ultrasound-guided steroid injection into iliopsoas bursa

Incidence

• Occurs in approximately 4% of THR patients

8. Vascular Injury in Posterior Hip Approach

Artery at Risk

Inferior gluteal artery

Origin

• Branch of anterior division of internal iliac artery

Clinical Significance

• Injury can cause severe bleeding
• Vessel may retract into pelvis
• May require laparotomy to ligate internal iliac artery

9. Follow-up of Metal-on-Metal Hip Resurfacing

Example

• Birmingham Hip Resurfacing (BHR)

ODEP Rating System

• Implant benchmark for long-term performance.

10A rating

• ?10 years follow-up
• Low revision rate

10A*

• Excellent performance compared with other implants

Follow-up Recommendation

For asymptomatic patients with high-rated implants:

• Year 1
• Year 7
• Every 3 years thereafter

High-Risk Patients (Require Annual Follow-up)

• Females
• Femoral head size <48 mm
• Recalled implants

10. Micromotion in Uncemented Femoral Stems

Maximum Micromotion

• 150 µm

If micromotion >150 µm:

• Bone ingrowth fails
• Fibrous fixation occurs

Other Important Parameters

Optimal pore size

• 50–150 µm

Maximum implant–bone gap

• 50 µm

Optimal implant porosity

• 40–50%

Hydroxyapatite coating thickness

• ~50 µm

Key Examination Tips

• Many FRCS MCQs require knowledge beyond textbooks, including current literature and guidelines.
• Important concepts frequently tested:
  • Vancouver fracture classification
  • Ficat AVN staging
  • PJI diagnostic criteria
  • Arthroplasty biomechanics
  • Metal-on-metal surveillance guidelines.