Revisiting predictors of instability in pelvic ring injuries: are lumbar transverse process fractures significant?

objectivesThere has been significant controversy in the literature surrounding the significance of lumbar spine transverse process (LSTP) fractures in the context of concomitant injuries of the pelvic ring. We hypothesized that LSTP fractures are a harbinger of instability in patients with concomitant pelvic ring injuries.

methodsDesign: Retrospective Cohort.

settingUrban/Suburban Academic Level I Trauma Center. Patient selection criteria: Subjects were identified using a retrospective search for AO/OTA type A, B, C pelvic ring injuries. Patients were included if they were age 18 or older, suffered a pelvic ring injury, and had a CT obtained of the full lumbar spine at the time of injury. Patients were excluded if they were skeletally immature, had suffered an associated injury to the spine other than lumbar spine transverse process fractures, had undergone previous lumbosacral spine procedures, or had anomalous lumbosacral anatomy. Outcome measures and comparisons: The status of all available lumbar spine vertebrae visualized on advanced imaging was recorded. Assessment for correlation of LSTP fractures with pelvic ring instability was made between stable (LC I, LC II injuries stable on examination under anesthesia, all APC I injuries) and unstable (APC II, APC III, LC III, LC II and LC I injuries unstable on examination under anesthesia) pelvic ring injury patients, as well as severity of injury using the Young-Burgess classification.

results741 patients met inclusion criteria. LSTP fractures were significantly more common in patients who underwent operative management 60.6% (186/306) compared to those treated nonoperatively 23.7% (103/435), (p < 0.001). The mean number of LSTP fractures was significantly higher in the unstable group (2.52 ± 1.56) compared to the stable group (0.58 ± 1.00; P < 0.001). Patients with complete sacral fractures sustained significantly more LSTP fractures compared to those with ala-type fractures (mean 1.11 ± 1.43 vs. 0.40 ± 1.00, P = 0.002).

conclusionsA positive association was identified between LSTP fractures and pelvic ring instability, including when comparison was made between stable and unstable LC I pelvic ring injury patients. The presence of multiple transverse process fractures was a sign of pelvic ring instability. This study provides a radiographic marker of pelvic ring instability, even amongst patients with LC I pelvic ring injuries.