孤立尺骨茎状突骨折の理解：偽関節および治癒転帰の後向き分析

Isolated ulnar styloid fractures (AO-Q1 or AO-OTA 2U3A1.1,2) are uncommon injuries often treated conservatively. However, the outcomes of such treatment are not well-studied. The aim of this study is to evaluate the radiological and functional outcomes of isolated ulnar styloid fractures, to compare case of nonunion and union, and to assess whether nonunion is associated with worse functional outcomes.

This retrospective study included 39 patients diagnosed with isolated ulnar styloid fractures (AO-Q1 or AO-OTA 2U3A1.2) between 2015 and 2022. The patients were divided into two groups, Group A (nonunion) and Group B (union), based on radiographic evidence obtained after a minimum follow-up period of 12 months. The functional outcomes were evaluated using the DASH score, Mayo Wrist Score, Visual Analogue Scale (VAS) pain scores, and DRUJ instability testing via the ballotment test.

Nonunion was observed in 51.3 % of patients (n = 20, Group A), while 48.7 % (n = 19, Group B) achieved union. Group A had significantly worse outcomes in supination, extension, flexion, and ulnar deviation (p < 0.05). VAS pain scores were higher in Group A (p = 0.012), and DASH and Mayo Wrist scores were also significantly lower in Group A (p < 0.001 for both). The incidence of DRUJ instability was higher in Group A, with a greater proportion of cases exhibiting positive results on the ballotment test (p = 0.011).

In this study of patients with isolated ulnar styloid fractures, nonunion was associated with reduced wrist motion, lower functional scores, and greater pain compared with union. These findings suggest that ulnar styloid nonunion may not always be associated with favorable outcomes, as ulnar styloid nonunions associated with distal radius fractures do. These findings, when considered in conjunction with future comprehensive studies, suggest that different approaches may be necessary in the treatment of isolated ulnar styloid fractures.