Effects of hyperbaric oxygen treatment on tendon graft and tendon-bone integration in bone tunnel: biochemical and histological analysis in rabbits

Abstract

Despite moderate success in clinical applications, outcome of tendon grafts employed for anterior cruciate ligament (ACL) reconstruction remains unsatisfactory. This study investigated the effects of hyperbaric oxygen (HBO) on neovascularization at the tendon-bone junction, collagen fibers of the tendon graft, and the tendon graft-bony interface incorporated into the osseous tunnel in rabbits. Forty rabbits were assigned to two groups. The HBO group was exposed to 100% oxygen at 2.5 atmospheres pressure for 2 h daily, 5 consecutive days in a week. The control group was maintained in cages exposed to normal air. Histological studies of 12 rabbits were performed postoperatively at 6, 12, and 18 weeks. Biomechanical studies of 24 rabbits were conducted postoperatively at 12 and 18 weeks. Electron microscopy (EM) analyses of four rabbits were performed postoperatively at 18 weeks. Experimental results demonstrated that a higher number of Sharpey's fibers bridged the newly formed fibrocartilage and graft in the HBO group than in the control group. In addition, HBO treatment increased neovascularization and enhanced the incorporation of the progressive interface between tendon graft and bone. Biomechanical analysis showed that the HBO group achieved higher maximal pullout strength than the control group. Examination by EM showed that HBO treatment resulted in regenerated collagen fibers with increased compaction and regularity. Based on experimental results, HBO treatment is a treatment modality that potentially improves outcome following ACL reconstruction.