Pulsed ultrasound and moderate exercise accelerate bone healing in an experimental tibial fracture model: biochemical, radiological and biomechanical evidence

Abstract

Currently, therapeutic strategies involving mechanical stress play a key role in fracture consolidation. However, no literary evidence exists regarding the combined effects of low-intensity pulsed ultrasound (LIPUS) and moderate aerobic exercise. This study aimed to investigate the effects of LIPUS and moderate aerobic exercise on bone consolidation in 48 male Wistar rats. The animals were divided into four groups (n = 12 per group): Bone Fracture (BF); BF + LIPUS; BF + Exercise (Ex); BF + Ex + LIPUS. A transverse osteotomy with Kirschner wire fixation was performed, followed by therapeutic interventions for 19 days, three times a week. LIPUS was applied for 10 min (1.5 MHz, 0.4 W/cm², 3 cm² area), and aerobic exercise lasted 30 min/day with progressive speed. Radiographic analyses were conducted on days 1, 12, and 24 post-fracture, and euthanasia occurred 72 h after the final session. The combined group exhibited improved radiographic scores and increased birefringent collagen fibers. IL-4, IL-10, and TGF-β levels were significantly higher in treated groups, particularly the combined intervention. Additionally, oxidative stress markers showed reduced nitrite levels, controlled sulfhydryl oxidation, and enhanced SOD and GSH activity. Biomechanically, the combined group tolerated higher loads and demonstrated superior deformation capacity and tissue elasticity. The combination of aerobic exercise and LIPUS enhanced radiographic healing, modulated inflammation, reduced oxidative stress, and improved mechanical properties, supporting its potential for fracture rehabilitation.