Bone Screws Have Advantages in Repair of Experimental Osteochondral Fragments

Abstract

Cartilage defects are created on intraarticular osteochondral fragments at the entrance holes of fixation devices when these fragments are fixed to the original sites. Conventional fixation devices hinder repair of these defects and there is a latent risk of secondary osteoarthritis. We therefore developed a novel fixation device system consisting of bone screws made of cortical bone for osteochondral fragments to improve repair of these surface defects. We asked whether bone screws had advantages over poly-L-lactic acid (PLLA) screws in terms of (1) gross assessment of the surface, (2) volume and histologic quality of the repair tissue, and (3) biomechanical assessment of the tissue stiffness. We examined gross morphology, microCT, histology, and stiffness of the repaired tissue with PLLA (n = 32) and bone (n = 32) screws in a rabbit model of osteochondral fracture, compared with normal controls (n = 16). Gross morphology and histology revealed better quality with bone screws than with PLLA screws. Mean repaired volumes in microCT were 70.6% ± 14% with bone screws and 50.3% ± 15% with PLLA screws. Average stiffness values for PLLA screws, bone screws, and normal cartilage were 1.67 ± 0.54 N/mm, 2.63 ± 0.42 N/mm, and 3.15 ± 0.49 N/mm, respectively. Our results show better repaired tissue was observed for quality and quantity when chondral fractures were treated with bone screws than when treated with PLLA screws. Bone screws made of cortical bone may have applications in clinical situations for the fixation of intraarticular osteochondral fragments.