Abstract
INTRODUCTION:
The use of tapered junctions in primary hip arthroplasty has excellent results. Large heads are being used to mitigate dislocation and optimize range of motion. The prevalence of larger heads, coupled with recent findings regarding corrosion artifacts at tapered surfaces, has spurred growing interest when considering revision rates. The purpose of this study was to determine if correlations exist between severity of corrosion artifacts and head size, head offset, time in vivo, orhead material in a 15 year retrieval database.
METHODS:
Retrieved hip arthroplasty devices with CoCrMo or oxidized zirconium (OxZr) heads were investigated for corrosion artifacts in this study. Female tapered surfaces were scored independently by a panel according to the Goldberg system for assessment of corrosion. Exclusion criteria included less than 1 week in vivo, ceramic taper, and modular proximal stem sleeves. Evaluation was performed on only stem/head taper junctions. SEM analyses and a newly developed method of vertical straightness deviation (VSD) were used on a subset of devices as an additional measure to quantify corrosion within the taper contact region by measuring depth of material loss.
RESULTS:
A total of 227 retrievals containing taper surfaces spanning 15 years were evaluated. Of these, 183 met the inclusion criteria (CoCrMo, n = 159; OxZr, n = 24). Time in vivo ranged from 1 week to 10 years. The majority of the head tapers were 12/14 in size. There was no correlation between head size and average Goldberg score (n = 183, R2 = 0.23). There was a parabolic correlation between head offset (9 offset sizes evaluated) and average Goldberg score (n = 156, R2 = 0.89), with the more negative offsets and the more positive offsets exhibiting higher scores. There was no correlation between time in vivo and Goldberg score (n = 104, R2 = 0.11). There was a correlation between head material and Goldberg score, with OxZr having a lower score as compared to CoCrMo heads (1.9 ± 0.6 vs. 2.5 ± 0.9, p = 0.002). VSD measurements made on CoCrMo heads with a Goldberg score of 4 showed that 5 of 6 CoCrMo heads had a measureable depth of material loss at the taper, with a maximum depth ranging from 8 to 103 microns. There were no OxZr heads with a Goldberg score of 4. SEM and VSD measurements corroborated scoring (Figures 1–3).
CONCLUSIONS:
CoCrMo heads have 20+ years of clinical success, but as shown in this study may still generate a quantifiable amount of taper corrosion. Though impaction force, taper cleanliness, patient factors and other myriad multi-factorial issues may contribute to taper corrosion, in this study no correlation was observed for head size or time in vivo and Goldberg score. A correlation was found between head offset and Goldberg score. The use of an OxZr head material exhibited decreased corrosion by-products as compared to the traditional CoCrMo head material used in hip arthroplasty.
