Mixing Metals During Operative Fixation and Reconstruction in the Appendicular Skeleton: Does Theoretical In Vivo Galvanization Cause Clinically Detrimental Outcomes?

Objective: Traditional training and teaching have advised against mixing varying metal types to avoid the potential for in vivo galvanization and corrosion. The objective of this study was to retrospectively analyze patients who have undergone operative reconstruction with mixed metal (MM) constructs to report any related complications.

Methods: Design: Retrospective case series.

Setting: Single Level II Trauma Center.

Patient selection criteria: Patients that underwent trauma and/or arthroplasty surgery at a single level II trauma center between 2017-2022 with 'mixed' fixation defined as contact and proximity within the bone (≤10mm) with complete radiographs and medical records and minimum 1 year follow-up was eligible for study inclusion.

Outcome measures and comparisons: The primary outcome measure were incidence of corrosion directly related to hardware related complications causing unplanned reoperation.

Results: The final analysis included 56 patients (67.9% female), with a mean age of 62.0±16.6 years, mean BMI of 28.9±8.4 kg/m2, and mean Charlson Comorbidity Index (CCI) of 2.5±1.8. Seventy-three percent of the MM implants had direct metal on metal contact, and the average distance between non contacting metals was 0.32±0.28cm. The most common combination of metals was titanium+stainless steel (69.6%). At an average postoperative follow-up of 25.9±19.6 months, hardware-related complications were observed in 15 (26.8%) of patients, with reoperation due to hardware-complications in 12 (21.4%) within 18.5±15.8 months. No evidence of metal-on metal galvanic corrosion was observed on radiographic evaluation at an average of 25.9±19.6 months.

Conclusion: Patients who received mixed metal implants showed no radiographic or clinical signs of corrosion. While theoretical concerns exist regarding use of mixed metal implants, these findings suggest that the consequence of such combinations in clinical practice may not be as significant.

Level of evidence: IV, Retrospective case series.