Ulnar Resection Length: A Risk Factor for Nonunion in Ulnar Shortening Osteotomy.

Background: Nonunion rates following ulnar shortening osteotomy (USO) are reported up to 18% with few known risk factors. While resection length is variable in practice, little is known about the prognostic implications on healing. The purpose of this study was to evaluate whether longer resection lengths increased the odds of nonunion.

Methods: A retrospective review was performed on patients who underwent an elective USO at a single institution over a 6-year period. Demographic, social, comorbidity, and surgical data were reviewed. Ulnar resection length was obtained from operative notes and dichotomized into smaller (<5.5 mm) and larger (≥5.5 mm) groups. The primary outcome was the rate of nonunion. Univariate analyses and a multivariable logistic regression model were used to assess for significant predictors of nonunion.

Results: A total of 87 patients were included with a mean age of 45 years. Patient comorbidities included 12.6% with diabetes, 29.9% with an American Society of Anesthesiologists score of ≥ 3, 5.8% reporting current tobacco use, and 29.9% reporting former tobacco use. There were 55 patients (63.2%) with resection lengths < 5.5 mm and 32 patients (36.8%) with ≥ 5.5 mm resections. Multivariable analysis identified longer resection length (≥5.5 mm) and current tobacco use as independent risk factors for nonunion. Patients with a resection length of ≥ 5.5 mm had 20.2 times greater odds of nonunion compared with patients with smaller resections, and current smokers had 72.2 times greater odds of nonunion compared with nonsmokers.

Conclusion: Longer ulnar resection length (≥5.5 mm) significantly increases the risk of nonunion following USO.