Pediatric lateral patellar dislocation: is there a role for plain radiography in the emergency department?

Osteochondral fractures are reported to complicate patellar dislocations in 5-95% of patients. For this reason, post-reduction radiographs are recommended for the routine evaluation of patellar dislocations in all patients. To date, no data have been reported regarding the impact plain radiography has on the Emergency Department (ED) management of pediatric patients with lateral patellar dislocations.

To estimate the incidence of fractures detected by post-reduction plain radiographs in pediatric patients presenting with unreduced lateral patellar dislocations and to examine differences in ED management between patients with and without radiographically apparent fractures.

Retrospective review of records for pediatric patients who presented to an ED, received a diagnosis of lateral patellar dislocation, and underwent a reduction procedure.

Of 80 patients who met criteria for inclusion in the study, 8 patients (10%; 95% CI 3-17) had a fracture identified. All patients, regardless of their radiographic findings, had their dislocation reduced uneventfully and were discharged with knee immobilization and a plan for outpatient follow-up. There were no statistically significant differences between those patients who had a detected fracture as compared to those without in terms of intravenous line placement (p = 1.000), parenteral analgesic administration (p = 0.965), procedural sedation administration (p = 0.922), ED length of stay (p = 0.706), or provision of a prescription for an oral analgesic upon discharge (p = 0.103).

Osteochondral fractures were detected by plain radiography in 10% of patients presenting with lateral patellar dislocation and did not alter ED management. Pediatric patients with lateral patellar dislocations may be candidates for discharge from the ED after reduction without plain radiography. The modality by which to best determine the presence of a complicating osteochondral fracture (i.e., plain radiography, computed tomography, magnetic resonance imaging, or arthroscopy) may be left to the discretion of the orthopedic surgeon accepting the child in follow-up. Further study is needed to determine if forgoing plain radiographs in the ED decreases length of stay and reduces patient costs.