We assessed the difference in hospital based and early clinical
outcomes between the direct anterior approach and the posterior
approach in patients who undergo total hip arthroplasty (THA). The outcome was assessed in 448 (203 males, 245 females) consecutive
patients undergoing unilateral primary THA after the implementation
of an ‘Enhanced Recovery’ pathway. In all, 265 patients (mean age:
71 years (49 to 89); 117 males and 148 females) had surgery using
the direct anterior approach (DAA) and 183 patients (mean age: 70
years (26 to 100); 86 males and 97 females) using a posterior approach.
The groups were compared for age, gender, American Society of Anesthesiologists
grade, body mass index, the side of the operation, pre-operative
Oxford Hip Score (OHS) and attendance at ‘Joint school’. Mean follow-up
was 18.1 months (one to 50).Aims
Patients and Methods
Plasma levels of cobalt and chromium ions and
Metal Artefact Reduction Sequence (MARS)-MRI scans were performed
on patients with 209 consecutive, unilateral, symptomatic metal-on-metal
(MoM) hip arthroplasties. There was wide variation in plasma cobalt
and chromium levels, and MARS-MRI scans were positive for adverse reaction
to metal debris (ARMD) in 84 hips (40%). There was a significant
difference in the median plasma cobalt and chromium levels between
those with positive and negative MARS-MRI scans (p <
0.001).
Compared with MARS-MRI as the potential reference standard for the
diagnosis of ARMD, the sensitivity of metal ion analysis for cobalt
or chromium with a cut-off of >
7 µg/l was 57%. The specificity was
65%, positive predictive value was 52% and the negative predictive
value was 69% in symptomatic patients. A lowered threshold of >
3.5 µg/l for cobalt and chromium ion levels improved the sensitivity
and negative predictive value to 86% and 74% but at the expense
of specificity (27%) and positive predictive value (44%). Metal ion analysis is not recommended as a sole indirect screening
test in the surveillance of symptomatic patients with a MoM arthroplasty.
The investigating clinicians should have a low threshold for obtaining
cross-sectional imaging in these patients, even in the presence
of low plasma metal ion levels.
