Single Versus Double Screw Fixation for the Treatment of Scaphoid Waist Fractures: Finite Element Analysis and Preliminary Clinical Results in Scaphoid Nonunion

Abstract

Objectives: This study aims to compare the single versus doublescrew fixation of scaphoid waist fractures using finite elementanalysis, and to present the preliminary clinical results of doublescrew fixation in a consecutive series of patients with scaphoidnonunion.Patients and methods: A transverse scaphoid waist fracture(Herbert type B2) model was fixed with either single or doublecannulated compression screws. Displacement and rotation of thefragments were performed using three-dimensional finite elementanalysis in three different wrist positions. A retrospective reviewwas performed on 13 male patients (mean age 31.6±12.8 years;range, 17 to 64 years) who underwent double screw fixation for anestablished scaphoid nonunion in our clinic between January 2015and December 2017. Assessment of union was established withserial plain radiographs in eight patients and with wrist computedtomography in five patients. Clinical evaluation was performedusing the Mayo wrist score and visual analog scale (VAS).Results: In all wrist positions, the displacement of the fracture gapin double screw fixation in all planes (x, y, and z) was less than insingle screw fixation. Similarly, rotation of the fracture fragmentsaround the longitudinal axis of the scaphoid was lower in doublescrew fixation. Complete union was obtained in all patients. Themean time to union was 5±0.75 months (range, 4 to 6 months).The mean VAS was 0.8±0.9 (range, 0 to 3). Mayo wrist score was91±6.9 (range, 80 to 100) at the final follow-up.Conclusion: Double-screw fixation technique may be a solution toreduce the rate of scaphoid nonunion in unstable type B2 scaphoidfractures or nonunion.