arthroplasty

Painful Total Hip Arthroplasty

advanced

6 min

18 marks

6 questions

Clinical Scenario

A 65-year-old male presents with progressive left groin pain 3 years after cemented THA for osteoarthritis. He initially had an excellent outcome with pain-free walking for 2 years. Now pain limits walking to 200m and disturbs sleep. He reports low-grade fevers. On examination, he walks with an antalgic gait, has limited hip rotation, and pain on axial loading.

$AP pelvis radiograph showing left cemented THA with progressive radiolucent line >2mm around acetabular component, cup migration, and cement mantle fracture. Femoral component appears well-fixed.$

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AP pelvis radiograph showing left cemented THA with progressive radiolucent line >2mm around acetabular component, cup migration, and cement mantle fracture. Femoral component appears well-fixed.

Source: Educational radiograph of cemented THA acetabular loosening • OrthoVellum Medical Education Team • OrthoVellum Educational Use

Questions

Question 1 (3 marks)

What are the key differential diagnoses for painful THA?

Question 2 (3 marks)

Describe your investigation approach including specific tests and thresholds.

Question 3 (3 marks)

Aspiration shows WCC 3,500/μL with 85% PMN. CRP is 25 mg/L. Cultures grow Staphylococcus epidermidis. How do you interpret these results and what are your management options?

Question 4 (3 marks)

If infection is excluded and CT shows significant acetabular osteolysis with 30% posterior column involvement, what is your management plan?

Question 5 (3 marks)

What factors influence your choice of acetabular reconstruction? Discuss the Paprosky classification.

Question 6 (3 marks)

What is the role of advanced imaging modalities in painful THA?

Exam Day Cheat Sheet

Must Mention

•MUST EXCLUDE PJI before any revision
•Groin pain = acetabular pathology (start-up, activity-related)
•Thigh pain = femoral pathology
•MSIS criteria: WCC >3000, PMN >80%, CRP >10, alpha-defensin positive
•Two-stage revision for chronic PJI (85-95% success)
•DAIR only for acute (<4 weeks) - NOT chronic
•Paprosky classification guides reconstruction

Common Pitfalls

•Antibiotics before aspiration
•DAIR for chronic PJI
•Missing infection (revision will fail)
•Not getting comparison X-rays
•Forgetting spine as pain source

Exam Tips

→PJI threshold: WCC >3000/μL, PMN >80%
→CRP threshold: >10 mg/L (chronic THA PJI)
→ESR threshold: >30 mm/h
→Two-stage success: 85-95%
→DAIR success: 60-80% (acute only)
→Radiolucent line >2mm = loosening
→Alpha-defensin: 98% specificity