O2106: Physeal Fractures of the Distal Ulna: Incidence and Risk Factors for Premature Growth Arrest

Background: Fractures involving the distal radius and ulna are among the most common pediatric fracture. Premature physeal closure is a relatively rare complication with rates of growth arrest of the distal radius between 1-10%. Literature on fractures of the distal ulnar physis is sparse and primarily limited to case reports. The aim of this study is to assess the rate of traumatic ulnar physeal arrest and to identify risk factors for premature ulnar epiphyseal closure.

Methods: A retrospective review of patients with a distal ulnar physeal fracture was performed at a single tertiary-care children’s hospital. Patients without a minimum 6-month follow-up were excluded. Patient demographics, injury characteristics, treatment, and outcomes were abstracted from medical records. Fractures were classified by the Salter-Harris (SH) classification system. All follow-up radiographs were reviewed for changes in ulnar variance or signs of premature physeal arrest. Descriptive statistics and Fisher’s Exact Tests were performed.

Results: Fifty-six children (35 males) with an average age of 10.7  3.3 years were included with a mean follow-up of 1.9 years. The most common fracture pattern was a SH II (52.7%), with 29.1% SH I, 9.1% SH III, and 9.1% SH IV. Over two-thirds of patients (69.6%, 39/56) had a concomitant distal radius fracture, 12.5% (7/56) an additional extraphyseal ulnar styloid fracture, and 8.9% (5/56) additional injuries to the ipsilateral upper extremity. 41.1% (23/56) of the distal ulnar physeal fractures were displaced (mean translation 40.2  38.3% and angulation 24.8  20.9 degrees). In this cohort, 32.1% (18/56) underwent closed reduction and 12.5% (7/56) underwent open reduction and internal fixation.

19.6% (11/56) demonstrated radiographic signs of growth disturbance, including 3 patients (5.4%) with growth disturbance but continued longitudinal growth (Figure 1) and 8 patients (14.3%) with a complete growth arrest (Figure 2A). Average maximal ulnar variance was -3.4 mm. Three patients (27.3%) underwent subsequent surgical reconstruction including ulnar lengthening with external fixator (Figures 2B and 2C), distal ulna completion epiphysiodesis with distal radius epiphysiodesis, and ulnar corrective osteotomy. Patients with displaced distal ulnar fractures and SH III or IV fractures were more likely to develop a growth disturbance (34.8% vs. 3.2%, p = 0.003; 50.0% vs. 11.1%, p = 0.012 respectively). Children with less than 2 years of skeletal growth remaining at time of injury had a higher risk of growth disturbance (46.2% vs. 9.5%, p = 0.007). Other complications included symptomatic ulnar styloid nonunion (n=2), triangular fibrocartilage complex injury (n=2), and DRUJ subluxation (n=1).

Conclusion: Intra-articular physeal fractures (SH III and IV) of the distal ulna are relatively common. Growth disturbance or growth arrest occurs in approximately 20% of distal ulnar physeal fractures. Displaced and intra-articular distal ulnar physeal fractures and older children are at increased risk of growth arrest.