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Conclusion:The dual mobility cup is a highly effective option to manage unstable total hip arthroplasty.Unlike constrained devices, such components provide encouraging radiologic results regardingthe potential for loosening and osteolysis. Longer follow up is needed to confirm these results.FiguresFriday, October 8, 2010, 7:30-8:30Session B9: Complications in ArthroplastyConstrained Implants for Total Hip Arthroplasty Instability: Analysis ofFailuresIntroduction:*Olivier Guyen - Edouard Herriot Hospital - Lyon, FranceDavid Lewallen - Mayo Clinic - Rochester, USAMiguel Cabanela - Mayo Clinic - Rochester, USA*Email: oguyen@hotmail.comRecurrent instability after total hip arthroplasty remains a serious and somewhat frequentproblem. Constrained implants have proven effective to manage instability. This has led to aliberal utilization of these devices. However, sporadic mechanical failures have been reported.This report analyzes the failures of a single constrained device at our institution.Materials and Methods:Forty-three constrained implants (Stryker Constrained Liner TM ) in 34 patients were revised outof total 390 similar implants performed at our institution. There were 24 females and 10 males.Constrained implant was inserted at the first revision in 6 hips and after an average of threesurgeries (1-6) in 37 hips. Seven different methods of constrained liner fixation were observed.Eight different theoretical failure mechanisms were identified: six are mechanical devicefailures at each of the implant interfaces, infection and catastrophic polyethylene wear being theother two.Results:Average time to failure was 28.4 months (1-78). Several failure mechanisms were operating inmost cases. The predominant mechanism was infection in 12 (28%), type I (failure of fixation tofile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]