Correlation Between Metal Allergy and Treatment Outcomes After Ankle Fracture Fixation
Reference: So S., Harris I.A., Naylor J.M., et al. (2011) Correlation Between Metal Allergy and Treatment Outcomes After Ankle Fracture Fxation. Journal of Orthopaedic Surgery, 19(3), 309-313.
Scientific Literature Review
Reviewed by: Danielle R. McKenna, DPM
Residency Program: Grant Medical Center, Columbus, Ohio
Long term outcomes for open reduction and internal fixation of ankle fractures have been shown to be good to excellent; however, there is a subset of these patients that have persistent pain, stiffness, and swelling. A possible cause for these complications could be an allergy to the implant utilized for the procedure. Although the study population in this prospective study is small, it evaluates the possibility of a metal allergy or hypersensitivity as a possible cause of long-term pain.
106 out of 205 (52 percent) patients that underwent open reduction and internal fixation of an ankle fracture with a stainless steel implant responded to a phone call or questionnaire on an average of 26 months after their surgery. This document contained 10 questions regarding past medical history, problems or outcomes of the stainless steel implant, and history of metal sensitivity. A 25 question American Academy of Orthopaedic Surgeons (AAOS) foot and ankle score was also sent to measure functional outcome and pain at the level of the ankle. Out of the 106 patients that responded, 27 then underwent patch testing for sensitivity to nickel, iron, chromium, manganese, and molybdenum. The International Contact Dermatitis Research Group guidelines were utilized to score this test. The results were then analyzed.
It was noted that the AAOS score was not associated with any variables except for irritation around the surgical scar and a history of metal hypersensitivity, specifically to dental implants. Additional analysis was utilized to identify that a poorer AAOS score was only associated with irritation around the surgical scar. Five of the 27 patients that underwent patch testing were positive. Of those 27 patients that underwent the patch testing, eight complained of itching, irritation, redness/rash around the surgical scar; however only one of those eight was positive for metal hypersensitivity. Of the 19 patients that had negative results, four complained of similar symptoms as above. Two of the 27 patients developed eczema around their surgical scar, but only one had a positive patch test. One of the 27 patients reported a history of metal sensitivity, but had a negative patch test.
As we know, stainless steel is commonly used for internal fixation. We have all seen the metal corrosion that takes place when metal comes into contact with biological fluids. These ions that leach into the surrounding deep tissue are not antigenic but can stimulate a metal hypersensitivity. It was discussed that one reason for the correlation between irritation around the surgical scar and poorer AAOS scores is an allergic contact dermatitis in the skin overlying the implant. Other studies have shown an association between metal hypersensitivity and functional outcomes of metal implants. This study did not show a correlation between poor AAOS scores and history of metal hypersensitivity or positive patch testing. It should be remembered that cutaneous sensitivity may not necessarily reflect deep-tissue sensitivity. Patients with a negative patch test may exhibit a moderate to strong inflammatory reaction in peri-implant tissue.