Fretting and Corrosion Damage at the Head-Neck Taper is Reduced with Ceramic Femoral Heads : A Retrieval Study

Introduction: Modular head-neck total hip arthroplasty (THA) offers several benefits for orthopaedic surgeons, including intraoperative flexibility and the ability to change the head at revision surgery [1]. However, modularity at the head-neck taper, especially the use of metallic heads and stems, can lead to fretting and corrosion at the taper junction, leading to metal ions and debris released into the joint [2]. Adverse local tissue reactions from this taper junction have recently been reported [3]. There are comparatively few reports about taper corrosion with ceramic heads on metallic stems compared to cobalt-chromium alloy (CoCr) heads on metallic stems [4,5]. The purpose of this study is to determine whether the use of ceramic femoral heads resulted in less fretting and corrosion damage, relative to CoCr femoral heads, on the neck taper of titanium alloy femoral components. Methods: As part of our ongoing IRB-approved retrieval program, all available Quatro M and Quatroloc femoral stems (Ti-6-4 alloy; Signal Medical Corp.) that had been implanted for at least 6 months were included in this study (Table 1). All stems had been plasma sprayed with commercially pure titanium except for the oldest (13.3 years in vivo), which had a sintered bead coating, and were implanted without cement. The femoral stems had been implanted with zirconia (seven Mg-PSZ, Xylon; and two Y-TZP, CeramTec) or wrought CoCr (four, Signal Medical Corp.) femoral heads. Of the ceramic heads, seven were 28mm diameter and two were 32mm, while the CoCr heads included two that were 22mm in diameter (as part of a bipolar prosthesis), one 28mm, and one 32mm. The femoral neck tapers were divided into four quadrants (anterior, posterior, lateral, medial) and examined for fretting and corrosion damage under a dissection microscope at 10x-35x magnification. The neck tapers were characterized using the scoring technique described by Goldberg et al. with a score of 1 indicating no fretting or corrosion, and 4 indicating severe fretting or corrosion [6]. Each quadrant of the neck tapers were scored by the first three investigators to ensure consistency, then averaged together. Total score was calculated by adding the corrosion and fretting scores, where a total score of 8 would indicate no detectable fretting or corrosion, and a score of 32 would reflect severe corrosion and fretting in each quadrant. After sorting the data by femoral head material (ceramic vs. CoCr), average scores were compared by t-tests with p < 0.05 for significance. Total score was also correlated to time in vivo by linear regression, as the corrosion process at the neck-taper junction has been shown to progress with time [7].