Low-intensity pulsed ultrasound increases the fracture callus strength in diabetic BB Wistar rats but does not affect cellular proliferation

Abstract

Type I diabetes mellitus (DM) is associated with impaired fracture healing. Specifically, DM affects multiple phases of fracture healing including early cellular proliferation and late phases resulting in inferior biomechanical properties. Recent studies demonstrated the utility of pulsed low-intensity ultrasound (US) to facilitate fracture healing. The current study evaluated the effects of daily application of US on mid-diaphyseal femoral fractures in DM and non-DM BB Wistar rats. Immunohistochemical staining for PCNA was used to evaluate cellular proliferation at 2, 4, and 7 days post-fracture. In concordance with previous findings. DM fracture callus demonstrated decreased cellular proliferation. Importantly, the application of US did not significantly alter the proliferation in either DM or control groups. However, mechanical testing revealed significantly greater torque to failure and stiffness in US-treated DM versus non-US-treated DM groups at six weeks post-fracture. Despite the inability of US to affect the early proliferative phase of fracture healing, its application clearly results in improved mechanical properties during the late phases of healing. These findings suggest a potential role of US as an adjunct for DM fracture treatment.