After the hardware was removed, it was analyzed to determine the elemental composition of the plate and screws, and the patient was then patch tested with the major metal components of the implant: aluminum chloride hexahydrate 2.0% pet, elemental titanium 10.0% pet, titanium dioxide 10.0% pet, titanium (III) nitride 5.0% pet, titanium (III) oxalate decahydrate 5.0% pet, elemental vanadium 5.0% pet, and vanadium (III) chloride 1.0% pet. She demonstrated a 1+ reaction (erythema and induration) to vanadium trichloride at 72 and 96 hours.
The plate and screws removed from the patient were sterilized and submitted for analysis. Electron microprobe analysis confirmed that the major elemental composition of the plate and screws essentially matched the manufacturer’s listing (Table 1). The trace elements were determined using laser ablative inductively coupled mass spectroscopy, which demonstrated that the screws were of different metal composition from the plate (Table 2). Electron microprobe analysis also was used to determine the microstructure of the plate and screws. The plate had 2 distinct phases consisting of a titanium-aluminum phase and a vanadium phase, whereas the screw was much more homogeneous. Basic electrochemical studies were performed in a salt solution replicating the tissue of the foot. These studies showed that galvanic corrosion could have occurred between the plate and screws due to the differences of composition.