L5-S1 facet joint pathology in pelvic ring injuries.

Background: The authors believe that the L5-S1 facet joint injury in the setting of pelvic fractures is underappreciated by orthopedic traumatologists. The purpose of this study was to draw attention to the L5/S1 facet joint in the setting of pelvic ring injuries.

Methods: This was a retrospective comparative study of all patients greater than or equal to 18 years of age with an acute pelvic ring injury (AO/OTA 62 B to C) presenting to a single level I trauma center. The primary objective was to determine demographic and injury characteristics associated with L5-S1 facet joint injuries in patients with pelvic ring injuries. The secondary objective was to determine the proportion of L5-S1 facet joint injuries that were missed on initial radiographic workup.

Results: There were 476 patients included in the analysis, 53 (11.1%) of whom had an L5-S1 facet joint injury. Patients with an L5-S1 injury were more likely to be younger (44.1 vs. 53.2 years, p = 0.001) and experience a high energy mechanism of injury (95.0% vs. 78.0%, p = 0.002). Certain injury patterns were associated with L5-S1 facet joint injuries: any sacral fracture (96.2% vs. 73.8%, p < 0.001), Denis zone 2 fractures (43.4% vs. 20.1%, p  < 0.001), Denis zone 3 fractures (34.0% vs. 4.7%, p  < 0.001), bilateral displaced sacral fractures (18.9% vs. 3.5%, p  < 0.001), and L5 transverse process fractures (64.2% vs. 18.0%, p < 0.001). Only 16.0% of radiology reports identified an L5-S1 injury.

Conclusions: Orthopedic traumatologists should scrutinize imaging for L5-S1 facet joint injuries in the presence of pelvic ring injuries, especially in patients with certain sacral fracture patterns.