Polyethylene Shows No Concerning Evidence of Material Changes or Stress Cracking After Exposure to Chlorhexidine Gluconate and Povidone‐Iodine Irrigation Solutions

Chlorhexidine-gluconate (CHG) and povidone-iodine (PI) are used as irrigation solutions to prevent infection in arthroplasty. This study to aimed to determine whether exposing ultra-high molecular weight polyethylene (UHMWPE) implants to different concentrations of CHG or PI solutions would result in material or mechanical changes. This in vitro study assessed 30 specimens at low and high concentrations of povidone-iodine (0.35%, 10%), chlorhexidine-gluconate (0.05%, 4%) and ultrapure water. A Bell test was conducted on 25 specimens, followed by gross and microscopic assessment for cracking and/or discoloration. Five additional specimens underwent dynamic mechanical analysis (DMA). No gross evidence of environmental stress cracking was found across all irrigation solutions and concentrations. One specimen (submerged in 0.35% povidone-iodine) demonstrated gross non-localized discoloration. Under 200× magnification, there was a significant difference in the diameter of localized discoloration at the notched tip (H(4) = 18.18, p = 0.001). Significant differences between 10% PI and water (p = 0.029), and 0.35% PI and water (p = 0.001) solutions were noted. Though statistically significant, differences in discoloration are unlikely of clinical relevance. Notch depth did not vary across groups (p = 0.625). DMA demonstrated a significant difference across groups (p = 0.0035) with post hoc pairwise comparisons demonstrating a significant difference between 4% CHG and water (p = 0.035). Analysis of viscoelasticity demonstrated minor decreases in the relaxation time of the polymer, with the exception of 4% CHG that had an increased relaxation time and a second relaxation mode. This study demonstrates no concerning evidence of material changes that impact the integrity of UHMWPE secondary to CHG or PI irrigation solutions. STATEMENT OF CLINICAL SIGNIFICANCE: Findings of this study reassure surgeons that the use of chlorhexidine gluconate and povidone-iodine as irrigation solutions in total joint arthroplasty is most likely a safe practice. To bring these findings from bench to bedside, future prospective studies assessing the efficacy of irrigation solutions in preventing prosthetic joint infection in total joint arthroplasty may consider additional follow-up studies assessing long-term implant survivorship.