Scaphoid Malunion: Incidence, Predictors, and Outcomes.

Background  Scaphoid malunion is rarely reported. Previous literature has attributed loss of carpal height and degenerative changes to scaphoid malunion, but the percentage of asymptomatic malunions remains unknown. Purpose  The authors of this study aim to define predictors of malunion and outcomes associated with scaphoid malunion. Methods  Institutional board review was obtained prior to evaluating medical records of patients 18 years and older who were treated for scaphoid fractures and/or nonunion between 2000 and 2020. The following data were collected for each patient: age, gender, fracture location, surgical technique, time to union, and whether malunion resulted. Malunion was defined using a lateral intrascaphoid angle (LISA) >45 degrees and height-to-length ratio (HLR) >60. Pain scores, range of motion (ROM), and secondary surgery were also evaluated. Results  Overall, 355 scaphoid injuries, including 196 acute fractures and 159 nonunions, were evaluated in this analysis. Of these, 55 scaphoids (15%) met the definition of malunion. Of these patients, 23% were female. The mean age at the time of injury was 29 years. Nonunion cases were more likely than acute cases to be associated with malunion. Proximal pole fractures were more likely to associated with malunion than waist fractures. When controlling for nonunion and fracture location, malunited scaphoids were not associated with any significant difference in pain score, ROM, or secondary surgery, compared with nonmalunion cases. A total of 10 patients (3.3%) without malunion and 2 patients (3.6%) with malunion went on to a secondary surgery. Final extension/flexion was 67/67 degrees and 56/59 degrees in nonmalunion and malunion groups, respectively, but these differences were not significant. Conclusion  Compared with scaphoid injuries that do not result in malunion, scaphoid injuries that heal into malunion have similar outcomes. While scaphoid malunion in a single case or series may be associated with poor outcomes, this study suggests that scaphoid malunions do not have worse functional outcomes. Level of Evidence  This is a Level IV study.