Comparative study of lumbopelvic sagittal alignment between patients with and without sacroiliac joint pain after lumbar interbody fusion.

STUDY DESIGN: A retrospective case-control study.

OBJECTIVE: To elucidate the role of changes of lumbopelvic sagittal alignment in the pathogenesis of sacroiliac joint (SIJ) pain after posterior lumbar interbody fusion (PLIF) by comparing these values with the control, patients without SIJ pain.

SUMMARY OF BACKGROUND DATA: There has been no study specifically addressing the relation between lumbopelvic sagittal alignment and SIJ pain after PLIF.

METHODS: Among 346 patients who underwent PLIF between June 2009 and April 2012, patients with postoperative SIJ pain who responded to SIJ block were enrolled. For a control group, patients who were matched for sex, age group, the number of fused level, and fusion to sacrum were randomly selected. The patients were assessed using clinical and radiological parameters including age, sex, diagnosis, bone mineral density, body mass index, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt, and sacral slope. Target LL (PI + 9°), achieved rate of LL (postoperative LL/target LL × 100), and LL-PI mismatch (Δ) were also calculated and compared between 2 groups.

RESULTS: Twenty-three patients (9 males and 14 females) with SIJ pain and 46 patients (18 males and 28 females) without SIJ pain were assessed. Postoperatively, the SIJ pain group showed significantly greater pelvic tilt (19.88 ± 10.42°, P = 0.03), smaller achieved rate of LL (64.3%, P = 0.02), and substantial residual LL-PI mismatch (-14.45 ± 12.16°, P = 0.03) than the non-SIJ pain group (14.25 ± 7.68°, 73.2%, and -8.26 ± 9.12°, respectively). The degree of correlation between LL and PI in both the SIJ pain group and the non-SIJ pain group was positive preoperatively (r = 0.569; P = 0.003, r = 0.591; P = 0.000, respectively). Although correlation of the SIJ pain group remained positive postoperatively (r = 0.601, P = 0.002), it became strongly positive in the non-SIJ pain group (r = 0.856, P = 0.000).

CONCLUSION: This study indicates that lumbopelvic sagittal imbalance inferred from greater pelvic tilt and inadequately restored LL may play a central role in the development of SIJ pain after PLIF. Thus, it is important to restore lumbopelvic sagittal balance and to evaluate PI to determine the ideal LL that is needed to prevent postoperative SIJ pain.

LEVEL OF EVIDENCE: 3.