Training or no training : Does early post- operative exercise influence the mechanical properties of bone around bioresorbable implants?

Physical exercise is a well-known method for maintaining a healthy musculoskeletal system. Conducting detailed preclinical research on the effects of physical exercise on bone healing kinetics could significantly enhance the rehabilitation process following fracture treatment and bone remodeling. Our objective was to assess the impact of early post-operative exercise on the mechanical properties of rat bones around bio-resorbable implants, utilizing nanoindentation. Bio-resorbable ulra-high-purity Magnesium (XHP-Mg) implants were inserted into both femurs of male Sprague Dawley rats, followed by continuous treadmill training (TR) over two weeks, while another group was designated as the non-training (NT) control. Both trained and non-trained animals were randomly assigned to different euthanasia time points, specifically 2-, 4-, and 6-weeks post-implantation. Trained interface bone at 4 and 6 weeks exhibited higher Young’s modulus and hardness values compared to non-trained new bone. However, at 2 weeks non-trained bone had higher values. These findings further the knowledge about the influence of post-operative exercise on bone tissue mechanics and bone remodeling after placing implants, indicating that longer healing times and exercise contribute to enhanced mechanical properties. Post-operative exercise continues to influence the mechanical properties of bone even after the training protocol has concluded.