Page 107 - DOS Kongressen 2012 - Abstracts

67.
A novel method for assessment of polyethylene liner wear in
radiopaque tantalum acetabular cups: Clinical validation in patients
enrolled in a randomized controlled trial
Anders Troelsen, Dov Golvasser, Meridith Greene, David Ayers, Charles
Bragdon, Henrik Malchau
Clinical Orthopaedic Research Hvidovre Hvidovre University Hospital; Harris
Orthopaedic Laboratory, Massachusetts General Hospital, Boston; Harris
Orthopaedic Laboratory, Massachusetts General Hospital, Boston; Dept. of
Orthopaedics, University of Massachusetts Medical School; Harris
Orthopaedic Laboratory, Massachusetts General Hospital, Boston; Harris
Orthopaedic Laboratory, Massachusetts General Hospital, Boston
Background:
Radiostereometric analysis (RSA) is the gold standard for
assessment of wear in polyethylene (PE) liners in total hip replacement (THR).
When PE liners are used in conjunction with tantalum cups, conventional RSA
analysis of wear is not possible due to the radiopaque characteristics of
tantalum. Thus, clinical performance of PE liners can not be assessed.
Purpose / Aim of Study:
We propose a novel method for wear analysis and
evaluate it for clinical purposes.
Materials and Methods:
The study cohort consisted of 43 THR patients
previously enrolled in a randomized controlled trial receiving either titanium
or a tantalum cup with either a conventional or a highly cross- linked PE liner.
Femoral head penetration was assessed by gold standard RSA and the novel
method. Radiographs were taken postoperatively, at 6 months, and every year
up to 5 years. The novel "fictive head" method can estimate the center of the
femoral head. We assessed the accuracy and variation of the novel method,
and its ability to assess femoral head penetration.
Findings / Results:
Assessment of femoral head penetration by the novel
method was able to demonstrate a pattern of wear that was similar to that of
gold standard RSA in both conventional and highly cross- linked PE liners in
titanium cups. Little systematic error was introduced by the novel method
(
mean difference: 0.011 mm), however, it showed significantly (p=0.0006)
greater standard deviations for penetration measures compared with gold
standard RSA.
Conclusions:
The novel "fictive head" method offers accurate assessment and
can be a viable solution for assessment of femoral head penetration in
prospective studies on conventional and highly cross-linked PE liners, in
which the implantation of tantalum cups would otherwise make wear
assessment, and thus quality control of implants, impossible.