A 66-year-old woman with recurrent instability after primary total hip arthroplasty, and known high risk of dislocation due to abductor weakness, undergoes revision. Which acetabular construct is specifically designed to reduce dislocation risk in such patients?
- A Standard hemispherical cup with a 28 mm femoral head
- B Ceramic-on-ceramic bearing with elevated rim liner
- C Dual mobility cup with a large polyethylene head articulating within a metal shell ✓
- D Constrained tripolar liner with a 22 mm head
Correct answer: C. Dual mobility cup with a large polyethylene head articulating within a metal shell
Explanation
The dual mobility concept uses a small head inside a mobile polyethylene liner that also articulates with the metal shell, giving two articular junctions and a large effective head diameter, which raises the jump distance and impingement-free range. It is favoured for recurrent dislocation and abductor deficiency. Constrained liners restrict motion and transmit forces to the locking ring, with higher loosening rates.
Reference: Miller's Review of Orthopaedics, 8th ed.
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