Effects of Intra-Epiphyseal Vascularized Muscle Flap and Platelet Derived Growth Factor in Regeneration of Articular Cartilage of Lyophilized Humeral Head in Rabbits

Park, Sang Eun; Kwon, Soon Yong; Chung, Do Hyun; Lee, Jun Seok; Lim, Young Wook; Rhee, Seung Koo

Abstract

PURPOSE
The regeneration of injured articular cartilage is one of the most interesting things in orthopedic field. The aim of this study is to assess whether the degree of regeneration of a lyophilized autografted articular cartilage and the union capacity on osteotomized site could be improved by implanting a vascularized muscle flap into the epiphysis of autografted proximal humerus and applying platelet derived growth factor (PDGF) that stimulates the growth of chondrocytes in vitro into the reconstructed joint. MATERIALS AND METHODS: Nine rabbits were used in the experiment. A hemijoint reconstruction using a lyophilized autografted proximal humerus was done in 3 rabbits for control, and combined with a vascularized muscle flap using lateral thoracic artery into the epiphysis of proximal humerus and PDGF injection (0.25 mg/ml/kg) into the reconstructed joint for another 6 rabbits in experimental group. One rabbit in control group and two rabbits in experimental group on each the 3rd, 6th and 9th week after experiments were sacrificed. In both group, articular cartilage regeneration and union process of implanted autograft were followed by serial plain radiographs at the 3rd, 6th and 9th week and MRI at the 9th week after implantation. The histological investigations were followed at the same time. RESULTS: Radiologically, the control group showed delayed union in osteotomized site and sclerosis and collapse on articular surface as time goes, but the experimental group showed solid union by huge callus formation in osteotomized site and smooth articular surface. Histologically, the cartilage surface was irregular and the chondrocytes are completely destroyed with empty lacunae and revealed with severe osteoarthritic changes in whole layers in control groups, but the cartilagenous erosions and their arthritic changes are also noted with somewhat regeneration of chondrocytes in deep layer more prominently in experimental groups. CONCLUSIONS: These results suggest that an intra-epiphyseal vascularized muscle flap and injection of PDGF into the reconstucted joint can improve the functional results of lyophilized autograft by providing stimulation for bony union on osteotomized site and partial regeneration of injured articular cartilge.