Abstract
Trunnionosis is an important failure mechanism of total hip arthroplasties as has recently been reported by the England and Wales national joint registry. Adverse local tissue reaction has also recently been associated with total hip arthroplasty (THA) with metal on polyethylene and ceramic on polyethylene articulations. The contributing factors in the mechanism of this failure pattern have not been elucidated, however they are likely multifactorial to include corrosion, fretting, taper design, implantation time, metal particulate debris, and wear at the metal on metal interface. Furthermore, dissimilar metallic combinations have been shown to exacerbate tribocorrosion. Authors have also reported on the use of ceramic heads to reduce trunniononis, however, tribocorrosion is still present. The majority of the literature regarding modular head neck taper fretting and corrosion involves cobalt chrome (CoCr) alloy. Little is known about head neck fretting corrosion with Oxinium femoral heads.
To measure fretting, corrosion, and wear on the female tapers of retrieved Oxinium femoral heads and to determine how demographic and device factors affect these measurements.
Ninety-two (92) retrieved 12/14 Oxinium heads were graded using the modified Goldberg score for subjectively grading corrosion and fretting on the taper surface. A novel silicone molding technique was validated, then applied to the female tapers of the retrievals and of two pristine Oxinium femoral heads, sizes 32+0 and 32+4. The molds were scanned using a Konica Minolta 3D laser scanner for reconstruction of the topography, dimensions, and surface features of the tapers. Geomagic software was used to align the retrieved to the pristine 3D models, allowing measurement of surface deviations (from wear) that had occurred while the heads were implanted. Patient demographic and implant data were correlated with Goldberg scores and wear deviations.
The mean Goldberg score was 1.6. Goldberg scores of 1 (minimal), 2 (mild), and 3 (moderate) were present in 41 of the 92 heads (45%), 43 heads (47%), and 8 heads (8%) respectively. No implants received a score of 4 (severe). A positive significant correlation was found between length of implantation and increased female taper fretting (R = 0.436, p < 0.01). Wear deviations were significantly greater with 36mm heads compared to 32mm heads (p < 0.01) and with +4 offsets compared to 0 offsets (p = 0.013).
Similar to previous work analyzing ceramic heads, Oxinium heads demonstrated predominately mild tribocorrosion grades, however do not eliminate tribocorrosion. Tribocorrosion was increased with large heads and increased offsets. This finding is consistent perhaps with greater mechanical burden that larger implants with increased offsets experience. Further investigation is needed to elucidate if Oxinium femoral heads reduce fretting and corrosion when compared to CoCr femoral heads.
