Hyperbaric oxygen therapy improves medial collateral ligament healing in a rabbit model

Purpose: Hyperbaric oxygen (HBO) therapy has been shown to enhance bone, muscle, skin, and wound healing, particularly in conditions of ischemia and low oxygen tension. Preliminary data show that HBO therapy may be beneficial in the treatment of muscle-tendon and ligament injury. However, the effects of HBO therapy on ligament healing have not been thoroughly investigated. The purpose of this study was to assess the effects of HBO on the healing of the medial collateral ligament (MCL) by using biomechanical and histological analyses in a rabbit model. Methods: We investigated the effects of intermittent HBO therapy on ligamentous healing in rabbits. Sixty-four male rabbits were divided into eight groups consisting of eight animals each. The experimental group (32 rabbits) was subjected to HBO at 2.5 atmospheres absolute for 2 hours per day, whereas the control group (32 rabbits) did not undergo HBO therapy. All animals underwent a standardized surgical severance of the right MCL, whereas the left MCL was not surgically lacerated. Rabbits from each group were euthanized at 2, 4, 8, and 12 weeks postoperatively for biomechanical testing (six rabbits) and histological analysis (two rabbits). Results: By using the intact left MCL as a control, the mean percentages of failure load calculated at 2, 4, 8, and 12 weeks in the HBO group were 20.6%, 49.1%, 63.9%, and 76.3%, respectively, whereas in the non-HBO group, the mean percentages of failure load at 2, 4, 8, and 12 weeks were 13.5%, 25.3%, 36.5%, and 57.3%, respectively. For all time intervals, the mean percent failure load of the severed MCLs from the HBO group was significantly higher than that from the non-HBO group. The mean percentages of regenerative collagen fibers in the HBO group at 2, 4, 8, and 12 weeks were 53.2%, 75%, 87.8%, and 95.1%, respectively, and 32.4%, 55.7%, 72.4%, and 82%, respectively, in the non-HBO group. For all time intervals, the HBO group showed a significantly higher amount of regenerative collagen fibers than the non-HBO group. Conclusion: The present study results suggest that the healing of the MCL is enhanced by intermittent HBO therapy. HBO therapy may be useful in shortening the healing time of the injured ligaments.