Preventing Acetabular Component Migration in Revision THA
Revision total hip arthroplasty (THA) is a challenging procedure for many reasons, not the least of which is the risk of aseptic loosening leading to re-revision, especially in patients with severe acetabular defects. Acetabular components made of porous tantalum have a developed a good reputation for lower rates of re-revision, relative to components made of other materials. In the November 21, 2018 issue of The Journal of Bone & Joint Surgery, Solomon et al. bolster the evidence base regarding the success of porous tantalum acetabular components in revision THA.
The authors conducted a single-center prospective cohort study that used radiostereometric analysis (RSA) to accurately measure acetabular component migration in 55 revision THAs that involved a porous tantalum acetabular component. Over a mean follow-up of 4 years, 48 of the 55 components migrated <1 mm, the threshold that, based on previous findings in the literature, the authors defined as predicting later loosening. Five of the 7 components that exceeded the threshold were re-revised for loosening related to patient symptoms.
The RSA data for the 5 components that required re-revision revealed large proximal translations and sagittal rotations that increased over time until re-revision, although the RSA readings revealed that the majority of the migration occurred in the first 6 weeks. Among the components that did not exceed the 1 mm threshold for migration at 2 years, none have been subsequently re-revised for loosening.
The authors also analyzed fixation methods in this cohort. They found that, at 2 years, the median proximal translation of components that used inferior screw fixation was significantly lower than that of components without inferior screw fixation. The take-home messages from this study seem to be as follows:
- Porous tantalum acetabular components really do perform well in revision THA.
- When indicated, inferior screw fixation lowers the risk of component migration.
- Early component migration is a good predictor of long-term component survivorship.