Mobilization versus displacement on lateral stress radiographs for determining operative fixation of minimally displaced lateral compression type I (LC1) pelvic ring injuries.

PURPOSE: Operative fixation of minimally displaced lateral compression type I (LC1) pelvic ring injuries is considered by some if the patient is unable to mobilize or displacement is seen on stress radiographs. The purpose of this study was to compare these methods of determining operative fixation.
METHODS: A retrospective study of a prospectively gathered registry of LC1 injuries was performed before and after the adoption of a mobilization protocol. Fixation was considered if the patient was unable to mobilize 15 feet on the second day of admission. Prior to this protocol, all patients with displacement of ≥ 10 mm on stress radiographs were offered fixation. All patients received lateral stress radiographs (LSR), an anteroposterior pelvis radiograph in the lateral decubitus positions without sedation, to assess stability.
RESULTS: There were 21 and 18 patients treated under the stress radiograph and mobilization protocols. Displacement ≥ 10 mm was present in 12 (57%) and six (33%) patients in the LSR and mobilization groups. Under the mobilization protocol, patients with ≥ 10 mm of displacement on LSR all had incomplete sacral fractures and were less likely to mobilize (2 (33%) vs. 11 (92%); 95% confidence interval of the difference (CID) - 86 to - 9%). The mobilization protocol did not identify all cases of occult instability and resulted in an increased time to surgery compared to the LSR protocol (5 vs. 2 days, 95% CID 1 to 5).
CONCLUSION: Under the mobilization protocol, unstable LC1 injuries were less likely to mobilize and the time to surgery was increased.