Abstract
Introduction
The possibility of corrosion at the taper junction of hip replacements was initially identified as a concern of generating adverse reactions in the late 1980s. Common clinical findings of failure are pain, clicking, swelling, fluid collections, soft tissue masses, and gluteal muscle necrosis identified intra operatively.
Methodology
The joint replacement surgery was performed utilizing a posterior approach to the hip joint. The data from all surgical, clinical and radiological examinations was prospectively collected and stored in a database. Patients were separated into two groups based on bearing material, where group 1 had a CoC bearing and ABG modular stem whilst group 2 had a MoM bearing and SROM stem, with each group having 13 cases. Pre-operative revision surgery and post-operative blood serum metal ion levels we collected. Cup inclination and anteversion was measured using the Ein-Bild-Roentgen-Analyse (EBRA) software. A range of 2–5 tissue sections was examined per case. 2 independent observers that were blinded to the clinical patient findings scored all cases. The tissue grading for the H&E tissue sections were graded based on the presence of fibrin exudates, necrosis, inflammatory cells, metallic deposits, and corrosion products. The corrosion products were identified into 3 groups based on visible observation and graded based on abundance. A scanning electron microscope (SEM) Hitachi S3400 was used to allow for topographic and compositional surface imaging. Unstained tissue sections were used for imaging and elemental analysis. X-Ray diffraction was the analytical technique used for the taper debris that provided identification on the atomic and molecular structure of a crystal.
Result
Group 1 patients showed a significant reduction (p = 0.0002) in the Co, however the decrease of Cr ion concentration had no statistical significance (p = 0.48). The Co (p = 0.001) and Cr (p = 0.02) levels significantly reduced after revision surgery for patients within group 2. The largest differences in the abundance between the two groups were for the brown/red corrosion particles where group 2 is highly significant (p<0.001) compared to group 1. The specific identification was determined using a mapping technique that showed the red/brown colour consisted of evenly scattered Ti (green) and Cr (red) particles (figure 1). Elemental analysis of the green shards showed chromium as a major metallic element with traces of cobalt (figure 2). The ABG modular collected debris matched the peaks of the following crystaline strucutes: chromium oxide (CrO), titantium oxide (TiO2), and chromium oxide (Cr2O3), and iron titanium oxide (Fe2Ti3O9) (figure 2). The peaks from the XRD scan were assessed against these possible elements which showed the most were aluminium nitride and chromium oxide (Cr2O3). Both implant configurations produced an ALTR response indicative from the tissue sections graded and visually observed.
Conclusion
This study has characterized the corrosion products produced at taper junctions. The histology presented with similar results across the two groups suggestive that due to the same corrosion products found between both groups this was expected.
