Development and validation of a new approach for computer-aided long bone fracture reduction using unilateral external fixator

Abstract

An innovative computer-aided method to plan and execute long bone fracture reduction using Dynafix™ unilateral external fixator (EF) is presented and validated. A matrix equation, which represents a sequential transformation from proximal to distal ends, was derived and solved for the amount of rotation and translation required at each EF joint to correct for a displaced fracture using a non-linear least square optimization method. Six polyurethane-foam models of displaced fracture tibiae were used to validate the method. The reduction accuracy was quantified by calculating the residual translations (x r, y r, z r), the residual displacement (d r), and the residual angulations (α r, β r, γ r) based on the X-Y-Z Euler angle convention. The experiment showed that the mean±S.D. of α r, β r, γ r, x r, y r, z r and d r were 1.57±1.14°, 1.33±0.90°, 0.71±0.70°, 0.98±1.85, 0.80±0.67, 0.30±0.27, and 0.50±0.77 mm, respectively, which demonstrated the accuracy and reliability of the method. Instead of adjusting the fixator joints in-situ, our method allows for off-site adjustment of the fixator joints and employs the adjusted EF as a template to guide the surgeons to manipulate the fracture fragments to complete the reduction process. Success of this method would allow surgeons to perform fracture reduction more objectively, efficiently and accurately yet reduce the radiation exposure to both the involved clinicians and patients and lessen the extent of periosteum and soft tissue disruption around the fracture site.