Durability of Constrained Liners in Revision THA
The indications for treating total hip arthroplasty (THA) dislocations by cementing a constrained polyethylene liner into a well-fixed, retained acetabular component at the time of revision are narrow. That’s largely due to concerns about the durability of the resulting acetabular construct. Now, thanks to a study by Brown et al. in the April 3, 2019 issue of JBJS, hip surgeons have some hard data about the long-term outcomes of this approach.
After reviewing 125 cases in which a constrained liner was cemented into a retained, osseointegrated acetabular component during revision THA, with a mean follow-up of 7 years, the authors found that:
- Survivorship free from revision for instability was 86% at 5 years and 81% at 10 years. The cumulative incidence of instability at 7 years was 18%.
- Survivorship free from aseptic acetabular component revision was 78% at 5 years and 65% at 10 years. The most common failure mechanism was dissociation of the constrained liner from the retained component.
- Harris hip scores (HHS) did not improve significantly after revision. This finding is consistent with prior research that shows better post-revision HHS scores in patients whose revisions include the entire acetabular component.
- Position of the retained cup did not affect implant survivorship or risk of dislocation.
The authors mention alternative strategies for reducing the risk of dislocation after revision THA, such as the use of large-diameter heads and dual-mobility constructs. Still, they conclude that this constrained-liner approach, in the setting of a relatively well-positioned acetabular component, is a viable and durable THA revision option, especially for those “with a compromised abductor mechanism, recurrent instability, [and] a well-fixed and well-positioned acetabular component, for whom an acetabular revision would not be tolerated.”