Outcomes for cemented dual mobility cup to treat recurrent instability; A UK case series.

Objectives: Recurrent dislocation of Total Hip Replacement (THR) is often multifactorial and remains a significant surgical challenge with a significant risk of further instability. Dual Mobility Cups (DMC) have been used widely with good long term results in France with few studies in the British literature, especially assessing their use for recurrent instability. We set out to assess whether recurrent instability can be successfully treated solely with revision of acetabular component to a dual mobility cup.

Methods: We retrospectively reviewed a prospectively collected electronic database for all consecutive dual mobility cups implanted to address recurrently instability in THR. Radiological and clinical data have been analysed.

Results: From September 2013 to September 2017 54 dual mobility cups have been implanted, mean age 78 (range 49-97). 47 were 1st time revision procedures, 7 were following previous revisions including 5 failed PLADs. Average time post primary was 10 years (range 8 months-23 years). Twenty cases are cement in cement revisions which has become our primary technique for revision of cemented cups. Mean follow up is 1.9 years (range 6 months-5 years), 37 cases have 2 year follow up available. 8 patients have died. There have been no episodes of further instability. One patient has had reoperation for infection (1st stage revision).

Conclusions: This series demonstrates satisfactory early to mid-term results for the use of dual mobility cups to treat recurrent instability. The technique is particularly useful when femoral components are well fixed and can be used with monoblock implants such as the Charnley stem. Cement in cement revision is a convenient technique and potentially reduces complications and cost. Further analysis of longer term data is required but these results suggests this could be a valid solution to a complex problem.