Range of flexion improvement in degenerative stages of the first metatarsophalangeal joint (Hallux rigidus) witk cross-linked hyaluronic acid: A cadaveric study

Background: Viscosupplementation consists of intraarticular hyaluronic acid injections applied to treat pain and improve joint mobility. The objective of the study was to analyze the improvement of the range of mobility of the first metatarsophalangeal joint with a single dose of cross-linked hyaluronic acid. Methods: Ten fresh frozen specimens of feet sectioned below the knee were selected. Before and after the infiltration procedure, the range of flexion was calculated for all specimen's metatarsophalangeal joints. To detect complications due to the procedure, five feet were dissected and five were sectioned with a diamond saw. Results: The range of the first metatarsophalangeal joint flexion differences between the preoperative and the postoperative period was as follows: (1) 47° (range, 37-51.5) to 58° (range, 49-69.5) degrees of loaded dorsiflexion (p > 0.006); (2) 41° (range, 40-51.5) to 58° (range, 52.5-66.5) degrees of unloaded dorsiflexion (p > 0.009); and (3) 14° (range, 10.5-24.25) to 16° (range, 14.25-28.5) degrees of unloaded plantarflexion (p > 0.083). No injuries of anatomical structures were observed either by anatomical dissection or in the anatomical sections. Conclusions: The results obtained in this viscosupplementation study demonstrate the improvement of the range of mobility of the first metatarsophalangeal joint without evidence of extravasation and lesions of the periarticular anatomical structures.