Predictors of postoperative sacroiliac joint dysfunction and distal failure after iliac and S2-alar-iliac spinopelvic...

Sacroiliac joint dysfunction is an underrecognized cause of lower back pain, particularly in patients with prior spinal fusion. The relationship between spinopelvic fixation and sacroiliac joint dysfunction requires further investigation. The authors compared outcomes among patients who underwent iliac and S2-alar-iliac (S2AI) pelvic fixation techniques.

The authors performed a retrospective analysis of patients who underwent index spinopelvic fixation with iliac or S2AI techniques between 2016 and 2022. Patients with < 2-year follow-up data, prior spinopelvic fixation, prior or concomitant sacroiliac joint dysfunction or sacroiliac joint fusion, > 1 pelvic screw per side, and inadequate postoperative standing radiographs were excluded. Summary statistics and univariate and multivariable analyses were performed.

Eighty-nine patients were included in the final analysis. The mean ± SD age was 63.49 ± 8.64 years and 58.4% of patients were female. Forty-two (47.3%) patients were former or current smokers, and 20 (22.5%) had preexisting diabetes. Patients underwent pelvic fixation for long construct fusion (> 3 levels), L5-S1 high-grade spondylolisthesis, and L5-S1 pseudarthrosis in 67 (75.3%), 2 (2.2%), and 20 (22.5%) cases, respectively. The mean number of fusion levels was 6.79 ± 3.86. Sixty-nine (77.5%) and 9 (10.1%) patients underwent posterior column osteotomy and 3-column osteotomy, respectively. Eighty-one (91.0%) patients underwent bilateral pelvic fixation, and 54 (60.7%) and 35 (39.3%) patients underwent iliac and S2AI techniques, respectively. Seventeen (19.1%) patients developed distal failure, defined as implant complication between L5-pelvis and/or L5-S1 pseudarthrosis, with 15 (16.9%) having reoperation. Fourteen (15.7%) patients had postoperative sacroiliac joint dysfunction diagnosed by sacroiliac joint injections, including 10 (11.2%) patients who underwent subsequent sacroiliac joint fusion. Head-to-head univariate comparison showed no difference in postoperative sacroiliac joint dysfunction between iliac and S2AI techniques. Multivariable analysis showed diabetes (p = 0.030) and higher postoperative pelvic tilt (p = 0.024) were significant predictors of sacroiliac joint dysfunction. Performing posterior column osteotomy predicted lower frequency of sacroiliac joint dysfunction (p = 0.006). After exclusion of patients with preexisting bony fusion at L5-S1, multivariable analysis showed that a greater number of fusion levels (p = 0.002) was an independent and significant predictor of distal failure. Pelvic fixation technique (iliac vs S2AI) did not predict distal failure.

There were no significant differences in sacroiliac joint dysfunction or the rates of distal failure following index pelvic fixation with either the iliac or S2AI technique. Higher postoperative pelvic tilt predicted sacroiliac joint dysfunction, and a higher number of fusion levels predicted distal failure.