L4-sparing versus L4-L5 spinopelvic fixation in traumatic spinopelvic dissociation: A randomized controlled trial.

BACKGROUND

Traumatic spinopelvic dissociation (SPD) requires surgical stabilization, traditionally with L4-L5-iliac fixation. Recent biomechanical evidence suggests L4 fixation may be unnecessary. This randomized controlled trial compared clinical and radiological outcomes of L5-iliac versus L4-L5-iliac constructs in SPD patients.

METHODS

Between January 2020 and December 2023, 112 patients with traumatic SPD (Roy-Camille type II/III) were randomized to L5-iliac with transiliac-transsacral (TTS) screws (intervention, n = 56) or L4-L5-iliac with TTS screws (control, n = 56). Primary outcome was residual vertical displacement at 24 months. Secondary outcomes included operative time, blood loss, neurological recovery (Gibbons score), functional outcomes (Iowa Pelvic Score and Majeed Score), complications, and implant failure. Follow-up rate at 24 months was 85.7% (96/112).

RESULTS

At 24 months, mean vertical displacement was 3.1 mm (standard deviation [SD] 1.7) in the L5-iliac group versus 3.3 mm (SD 1.8) in the control group (mean difference -0.2 mm; 95% confidence interval [CI] -0.9 to 0.5), demonstrating noninferiority (upper CI limit 0.9 mm < noninferiority margin of 2.0 mm; p for noninferiority = 0.008). Operative time was significantly shorter in the L5-iliac group (91.4 vs. 108.7 minutes; mean difference -17.3 minutes; 95% CI -24.1 to -10.5; p < .001). Blood loss was reduced (298 vs. 387 mL; p < .001). Implant failure (rod or screw breakage) occurred in 2 patients (4.1%) in the L5-iliac group versus 1 patient (2.1%) in the control group (p = .58). No significant differences were observed in neurological recovery, functional scores, or other complication rates.

CONCLUSIONS

L5-iliac fixation with adjunctive TTS screws is noninferior to traditional L4-L5-iliac fixation for traumatic SPD, with significantly shorter operative time and reduced blood loss. The 4.1% implant failure rate in L4-sparing constructs appears acceptable. L4 fixation may be safely omitted.