A biomechanical analysis of extra-articular distal radius fracture stability

Fractures of the distal end of the radius are common and have generated a vast body of medical and surgical literature dating back to the eighteenth century. Despite the frequency at which distal radius fractures occur, most would agree that achieving fracture stability is a prerequisite for attaining a satisfactory outcome. Unstable fractures are at increased risk for loss of reduction and subsequent malunion. Unfortunately, predicting fracture stability is a difficult task. The purpose of this study was to evaluate several factors considered to influence distal radius fracture stability. Specifically, the study investigated the impacts of (1) site and severity of comminution, (2) soft tissue injury, (3) bone quality and (4) fracture reduction.;A finite element model of the distal radius, distal ulna, scaphoid and lunate was created from CT scans of the distal forearm and wrist. A soft tissue envelope was incorporated, including key wrist ligaments. The finite element model was validated via laboratory experiments and published data. Once validated, parametric analyses were conducted to study the influence of bone comminution, soft tissue injury, bone quality, and fracture reduction on fracture stability. The results of these parametric analyses were evaluated to predict fracture instability. An instability table was implemented to categorize instability according to clinical measurements currently used by surgeons. The guidelines for the prediction of instability were based on radiographic measurements that correlate with clinical outcomes.;Comminution, soft tissue injury, quality of bone, and fracture reduction influenced fracture stability. The site and severity of fracture comminution played an important role in determining the initial instability of the fracture. The radiographic measurements incorporated in the instability tables showed a trend toward more instability as soft tissue injuries were implemented in the finite element models. Similar trends were associated with the degradation of bone quality and the alteration of fracture reduction.;Fracture stability was directly measured and further refinement of this study could result in optimization of injury treatment. The FE models presented in this study provided a platform to analyze the various instability factors and determine their biomechanical influence on the stability of extra-articular distal radius fractures.