Restoration of Stiffness During Fracture Healing at the Distal Radius, Using HR-pQCT and Finite Element Methods

Finite element analysis (FE) coupled with high-resolution peripheral quantitative computed tomography (HR-pQCT) allows for noninvasive in vivo assessment of fracture stiffness at peripheral locations including the distal radius. Previous studies have reported the ability of FE analysis to capture significant longitudinal changes in fracture stiffness. We hypothesized that continuum-based FE methods are necessary to capture significant changes in FE-estimated stiffness in men and women, with closed reductions and casting, over the course of their fracture healing process. The primary aim of the study was to evaluate the performance of 3 micro-FE (μFE) methods, 2 density-based (continuum) methods, and a homogeneous method. A total of 30 participants with stable distal radius fractures completed follow-ups at 2, 4, 6, 8, 12, and 26 weeks postfracture. Participants had their fractured wrist scanned using HR-pQCT at each follow-up; the contralateral wrist was also scanned at the initial assessment to represent baseline conditions. Images were used to generate continuum and homogeneous µFE models. Uniaxial compression and torsional tests were completed, with apparent stiffness determined as the primary outcome measure. Stiffness of the fractured wrist was compared to stiffness of the uninjured contralateral wrist to quantify the change in stiffness. Days since fracture significantly predicted change in stiffness for continuum and homogeneous µFE methods (p < 0.05). Continuum µFE methods appeared to account for partially mineralized tissues, resulting in a graduated recovery of stiffness (1% per week). Homogeneous µFE methods were more sensitive to stages of healing progression, resulting in a faster recovery of stiffness (3% per week). Our findings demonstrate the capability of µFE to capture the restoration of stiffness at the fractured side to prefracture stiffness in men and women, up to 6 months postfracture.