Traumatic Separation of the Distal Ulnar Physis in Children: A New Classification for Displaced Volar-Flexion Injuries.

ABSTRACT

OBJECTIVES: To propose a new fracture classification according to the direction of epiphysis displacement and to compare clinical findings and surgical outcomes between these subtypes. DESIGN: Retrospective study. SETTING: A tertiary referral hospital. PATIENTS Twelve adolescents (mean age, 13.4 ± 1.3 years) who experienced separation of the distal ulnar physis were identified from the pediatric trauma database. INTERVENTION Closed reduction was attempted for all injuries. If a satisfactory alignment could not be achieved, an open reduction was performed. MAIN OUTCOME MEASUREMENTS The clinical outcome was evaluated with Mikic's criteria (union, alignment, length, distal radioulnar joint subluxation, limitations of elbow/wrist function, and degree of supination/pronation). The impacts of fracture patterns and locations of wrist abrasions on treatment decisions and clinical outcomes were tested with Fisher exact tests (unadjusted) and logistic regression analyses (adjusted for age and gender) with the bootstrap method. Five orthopedic surgeons used the new classification, and the reproducibility was tested with multirater kappa. RESULTS: The injury patterns included 6 dorsally-tilted distal ulnas (type 1) and 6 volarly-tilted distal ulnas [type 2-A (n = 1), type 2-B (n = 3), and type 2-C (n = 2)]. All type 1 fractures were successfully treated with closed reduction. Five of 6 cases with type 2 injuries failed closed reduction because of entrapment of the extensor carpi ulnaris tendon in the fracture site. Eleven of the patients' outcomes were excellent. One patient with a type 2-C injury experienced ulnar growth arrest. The multirater kappa for the new classification equals to 0.94, and P < 0.001. CONCLUSIONS: A majority of volar-flexion injuries require surgery to reduce the entrapped soft tissue. This new classification is easy to understand with a good interrater reproducibility. It is useful in identifying the injury mechanism and correlated with the likelihood of open reduction. LEVEL OF EVIDENCE Prognostic Level IV. See Instructions for Authors for a complete description of levels of evidence.