Abstract
Background
Recurrent instability and dislocation after total hip arthroplasty are difficult complications. In certain cases, a constrained acetabular device can address these issues. The purpose of this study is to report the midterm outcomes and survivorship of a single 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 to November 2016. Patients with 2-year minimum follow-up or failure were included, yielding a cohort of 177 patients. Procedures were 130 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 or 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 aseptic loosening of the acetabular component, resulting in an overall constrained mechanism aseptic or mechanical failure rate of 14.1%. 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=0.01). 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 still occurs.
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