Hyaluronan Injections Show No Histologic Evidence of Adverse Tissue Effects

BACKGROUND: The safety of hyaluronan intra-articular injections is mostly based on animal studies and clinical evidence rather than histologic studies from human administration. OBJECTIVE: This study analyzed the histologic effects of viscosupplementation with sodium hyaluronate on the synovium and articular cartilage of human knee specimen status post total knee arthroplasty within 3 years of viscosupplementation. METHODS: Twenty-four specimens from total knee arthroplasties from April 2012 to August 2016 at NYU Winthrop Hospital were selected for microscopic analysis. All cases had a diagnosis of end-stage osteoarthritis at the time of surgery. Thirteen of the cases had 3 viscosupplementation injections of the knee with Euflexxa, a hyaluronate-based viscosupplementation agent, within 3 years preceding a total knee replacement. The remaining 11 did not receive viscosupplementation and were incorporated as controls. Upon histologic review, synovium was categorized by degree of hyperplasia and inflammation and the presence or absence of foreign material and giant cell reactions. Residual articular cartilage was categorized by staining intensity, and the presence or absence of crystals, foreign material, and giant cell reactions. RESULTS: No significant difference was found between these groups for degree of synovial hyperplasia (P = .33) or for cartilage staining density (P = .42). None of the samples displayed evidence of foreign material, crystals, or giant cell reactions. CONCLUSION: In this cohort of patients, we demonstrated that Euflexxa was administered without any discernible microscopic adverse tissue effects.