Sequelae of Hylan G-F 20 Viscosupplementation of the Knee

To The Editor: We recently read Granulomatous Inflammation After Hylan G-F 20 Viscosupplementation of the Knee. A Report of Six Cases (2002;84:1142-7), by Chen et al., which involved five patients (six knees) who had a granulomatous reaction after intra-articular injections of hyaluronate in the knee. Because we believe that it is important for orthopaedic surgeons to be aware of the possible risks of various therapeutic modalities, we have several queries and comments concerning the findings reported in this article. First, this is not the first report of an inflammatory reaction in soft tissue after injectionsof Hylan G-F 20 or hyaluronate derivatives. A number of previous reports have documented similar reactions 1-5. However, there is no reported evidence that this observed reaction represents a class effect for all preparations of hyaluronate. Unlike other approved hyaluronate-derived products, Hylan G-F 20 is chemically cross-linked to increase the molecular weight of and to stabilize the natural hyaluronate 5,6. Chemical cross-linking may enhance the immunogenicity of components. Because the cross-linking of hylan occurs in the presence of proteins and other components of the rooster comb (the source of all hyaluronate products), such an enhancement of immunogenicity is possible. Second, the prevalence of this adverse reaction is unclear. It would be useful to know how many injections were given without a reaction; how many patients received injections without arthroscopy and had a reaction with evidence of a granulomatous inflammation; and how frequently incidental findings of granulomatous inflammation were noted in patients who were not treated with injections, particularly in those …