Differential outcomes of ulnar shortening osteotomy in idiopathic ulnar impaction syndrome and distal radius malunion–associated ulnar impaction

To compare the clinical outcomes of ulnar shortening osteotomy (USO) in patients with idiopathic ulnar impaction syndrome (IUIS) and ulnar impaction secondary to distal radius (DR) fracture malunion. This retrospective, single-center matched cohort study included 65 eligible patients with extra-articular distal radius malunion who underwent ulnar shortening osteotomy (USO). These patients were individually matched at a 1:1 ratio with 65 patients who underwent USO for idiopathic ulnar impaction syndrome (IUIS) during the same study period, based on identical age and sex. Clinical outcomes included the visual analog scale (VAS) for pain, QuickDASH score, wrist range of motion, and grip strength. Radiographic parameters and intraoperative arthroscopic findings and procedures were also evaluated. VAS scores decreased in both groups after ulnar shortening osteotomy. Postoperative VAS and QuickDASH scores were lower in the idiopathic ulnar impaction syndrome group than in the distal radius malunion group. Wrist range of motion improved in both cohorts, with a significantly greater postoperative pronation–supination arc observed in the idiopathic group, while other motion parameters and grip strength were comparable. The magnitude of ulnar shortening and postoperative ulnar variance correction were similar between groups. Patients with distal radius malunion showed significantly altered preoperative distal radius alignment and a higher prevalence of reverted distal radioulnar joint morphology and radiographic distal radioulnar joint osteoarthritis at final follow-up. Arthroscopic findings and procedures did not differ significantly between groups. USO was associated with reductions in pain scores and improvements in functional scores in both groups. However, patients with distal radius malunion demonstrated less favorable postoperative outcomes than those with idiopathic ulnar impaction syndrome. Residual distal radius deformity and DRUJ congruity should be considered when selecting surgical treatment for patients with distal radius malunion. III, Retrospective cohort study.