arthroplasty
Leg Length Discrepancy After THA
intermediate
6 min
18 marks
5 questions
Clinical Scenario
A 54-year-old woman presents 6 weeks after primary right THA for osteoarthritis. She complains that her operated leg feels "too long." She has developed a limp and low back pain. Preoperatively her legs were equal length. Nerve function is normal but she reports a tight feeling in the groin. On examination, she walks with a shortened stride on the left.
AP pelvis radiograph showing right THA with the operated leg measuring approximately 15mm longer than the left. Measurement from lesser trochanter to teardrop confirms discrepancy. Components appear well-positioned.
Image source: Open Access medical literature (NIH/PubMed Central) • CC-BY License
Questions
Question 1 (3 marks)
How would you assess leg length discrepancy clinically and radiographically?
Question 2 (4 marks)
What are the causes of perceived and actual leg length inequality after THA?
Question 3 (4 marks)
How would you manage this patient at 6 weeks post-operatively?
Question 4 (4 marks)
How can leg length discrepancy be prevented during THA?
Question 5 (3 marks)
What are the medicolegal implications of LLD after THA?
Exam Day Cheat Sheet
Must Mention
- •True LLD: ASIS to medial malleolus
- •Apparent LLD: umbilicus to malleolus
- •Measure: lesser trochanter to teardrop on XR
- •<10mm usually accommodated over time
- •Shoe lift first line; surgery rarely indicated
- •Intraop: shuck test, Steinman pin technique, navigation
- •LLD is common cause of litigation
Common Pitfalls
- •Early revision for LLD
- •Not distinguishing true from apparent
- •Not counselling about accommodation time
- •Missing contracture resolution as cause
- •Poor documentation for medicolegal protection