Hip Arthroplasty: Hemi vs Total
Hip replacement surgery is one of the most successful operations in medicine. Choosing between Hemiarthroplasty and Total Hip Replacement (THR) depends on the patient's age, activity level, and condition of the acetabulum.
[Image of Total Shoulder vs Reverse Shoulder Replacement]1. Types of Arthroplasty
- Hemiarthroplasty: Replaces only the femoral head. The native acetabulum is left intact.
- Indications: Displaced Neck of Femur fractures in elderly, low-demand patients.
- Types: Monopolar (Head fixed to stem) vs Bipolar (Head moves within a shell).
- Total Hip Replacement (THR): Replaces both the femoral head and the acetabulum.
- Indications: Osteoarthritis, Rheumatoid Arthritis, AVN, Active elderly with fractures.
2. Fixation Methods
- Cemented: Bone cement (PMMA) acts as grout. Allows immediate full weight bearing. (Best for osteoporotic bone).
- Uncemented (Press-fit): Rough surface allows bone ingrowth. (Best for young, good bone quality).
3. Surgical Approaches & Precautions
Posterior Approach (Most Common):
Risk: Posterior Dislocation.
Precautions: No Flexion > 90°, No Adduction (crossing legs), No Internal Rotation.
Anterior Approach:
Risk: Anterior Dislocation (rare).
Precautions: No Extension + External Rotation.
Risk: Posterior Dislocation.
Precautions: No Flexion > 90°, No Adduction (crossing legs), No Internal Rotation.
Anterior Approach:
Risk: Anterior Dislocation (rare).
Precautions: No Extension + External Rotation.
25 Practice MCQs
Q1. Hemiarthroplasty is indicated for:
Answer: A). If the acetabulum is damaged (OA/RA), you need a THR.
Q2. Total Hip Replacement replaces:
Answer: A). Both sides of the joint.
Q3. Which approach has the highest risk of Posterior Dislocation?
Answer: A). Because the posterior capsule/rotators are cut.
Q4. The danger position for Posterior Approach THR is:
Answer: A). Sitting on a low chair or crossing legs.
Q5. Cemented fixation allows:
Answer: A). Cement hardens in 10 minutes.
Q6. Uncemented (Press-fit) stems rely on:
Answer: A). Takes 6-12 weeks for solid integration.
Q7. Bipolar Hemiarthroplasty has:
Answer: A). Reduces wear on the acetabulum compared to monopolar.
Q8. Trendelenburg gait after THR is usually due to:
Answer: A). Or superior gluteal nerve injury.
Q9. Deep Vein Thrombosis (DVT) prophylaxis includes:
Answer: A). Standard of care.
Q10. Foot drop after THR indicates injury to:
Answer: A). Usually from excessive traction or retractor placement.
Q11. Acetabular erosion is a long-term complication of:
Answer: A). Metal head rubbing against native cartilage eventually wears it down.
Q12. Which bearing surface has the lowest wear rate?
Answer: A). But risks squeaking or fracture.
Q13. Leg length discrepancy is:
Answer: A). Often functional due to muscle tightness or true lengthening for stability.
Q14. Using a toilet seat raiser helps prevent:
Answer: A). Essential for posterior precautions.
Q15. Heterotopic Ossification (HO) is:
Answer: A). NSAIDs (Indomethacin) can prevent it.
Q16. Revision THR is:
Answer: A). Done when the primary hip fails.
Q17. An Abduction Pillow is used to:
Answer: A). Prevents dislocation in bed.
Q18. The Anterior Approach ("Direct Anterior") spares:
Answer: A). Quicker recovery, lower dislocation risk, but harder learning curve.
Q19. Aseptic Loosening is caused by:
Answer: A). Macrophages eat particles and release enzymes eating bone.
Q20. Antibiotic prophylaxis is given:
Answer: A). To prevent prosthetic joint infection (PJI).
Q21. Austin Moore is which type?
Answer: A). Thompson prosthesis is the cemented version.
Q22. Before discharge, patient must be able to:
Answer: A). Basic independence.
Q23. Resurfacing Arthroplasty (Birmingham) preserves:
Answer: A). A metal cap is placed over the trimmed head. Good for young males.
Q24. Girdlestone procedure results in:
Answer: A). Salvage for infected THR.
Q25. Stair climbing rule:
Answer: A). Up with the good, down with the bad (operated).
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