Mid-Term Survivorship of a Novel Constrained Acetabular Device

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Background: Recurrent instability after total hip arthroplasty is a difficult complication. In certain cases, a constrained acetabular device is needed to address these issues. The purpose of this study is to report the midterm outcomes and survivorship of a single novel constrained liner device. Methods: A retrospective review as performed on all procedures (except first stage exchange for infection) in which a Freedom Constrained (Zimmer Biomet, Warsaw, IN) liner was used between December 2003 and November 2016. Patients with 2-year minimum follow-up or failure were included, yielding a cohort of 177 patients. Procedures were 130 aseptic revisions, 40 reimplantations following infection eradication, and 7 complex primaries. The constrained mechanism was implanted in 46 hips (26%) to treat active instability and 131 hips (74%) for increased risk of instability and intraoperative instability. Patients had on average 3.4 previous surgeries. Results: With an average 7.1-year follow-up, 11 hips dislocated (6.2%), and 13 hips (7.3%) were revised for acetabular aseptic loosening, resulting in an overall constrained aseptic or mechanical failure rate of 13.6%. Nineteen hips (10.7%) failed from infection with 58% of these having had a previous infection. Patients with active instability had significantly higher failure for dislocation than patients who were at risk (15.2% vs 3%, P = .01). All-cause survival rate at 7 years was 74.8%, aseptic survival was 83.6%, and survival for instability was 91.8%. Conclusion: Revision for instability remains challenging as many patients have had numerous previous surgeries and at-risk anatomy. Constrained inserts are one option to manage instability, but a high rate of recurrence can still occur.




Crawford, D. A., Adams, J. B., Brown, K. W., Morris, M. J., Berend, K. R., & Lombardi, A. V. (2020). Mid-Term Survivorship of a Novel Constrained Acetabular Device. Journal of Arthroplasty, 35(3), 859–863. https://doi.org/10.1016/j.arth.2019.09.049

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