Radiographic assessment of immediate postoperative lumbar lordosis redistribution after pedicle subtraction osteotomy with pre-contoured rods: A retrospective study.

BACKGROUND

Sagittal alignment is a major determinant of clinical outcomes in adult spinal deformity surgery. This study assessed the effect of pre-contoured rods (40°, 65°, or 90°) with a short-radius bend on postoperative lumbar lordosis after lumbosacral fusion with Pedicle Subtraction Osteotomy (PSO). This radiographic study was designed (1) to assess immediate postoperative redistribution in Global Lumbar Lordosis (LLGlobal) and L1S1 Lumbar Lordosis (LLL1S1) after L4 or L5 PSO with pre-contoured rods, (2) to quantify the mismatch (ΔL) between postoperative lordosis and rod curvature, (3) to test whether ΔL differed according to sex, revision status, osteotomy level, or fusion length, and (4) to evaluate correlations between ΔL and preoperative spinopelvic parameters.

HYPOTHESIS: Combining factory pre-contoured rods featuring a short-radius sagittal bend with L4 or L5 PSO effectively restores and redistributes lumbar lordosis.

PATIENTS AND

METHODS

This retrospective cohort included 51 patients (mean age 52 ± 14 years) who underwent L4 or L5 PSO with sacral fixation using 40°, 65°, or 90° factory pre-contoured rods. Preoperative and immediate postoperative EOS imaging was analysed. ΔLGlobal - rod and ΔLL1S1 - rod were calculated. The Spinal Lordosis Ratio (SLR), defined as the ratio between the upper and lower arc angles of lumbar lordosis, was also assessed." Paired comparisons, ANOVA, and Pearson correlations were performed.

RESULTS

LLGlobal increased by 5.3° ± 14.0° (9.8 %, p = 0.009) and LLL1S1 by 8.2° ± 15.3° (16.2%, p < 0.001). Spinal Lordosis Ratio (SLR) improved by 86.1% (p < 0.001). Postoperative lordosis remained lower than rod curvature, with average mismatches of -12° ± 15.7 (ΔLGlobal - rod) and -13.5 ± 16.8° (ΔLL1S1 - rod). No significant differences in ΔL were observed according to sex, revision status, osteotomy level, or fusion length. Rod angulation was the strongest predictor of ΔL (r = -0.593, p < 0.001), with higher angulations associated with greater absolute mismatch. Higher preoperative Pelvic Incidence (PI), Pelvic Tilt (PT), and Lumbar Lordosis (LL) also correlated with larger ΔL values.

CONCLUSIONS

PSOs at L4 or L5 combined with pre-contoured rods restore lumbar lordosis and redistribute sagittal alignment, but a persistent mismatch between rod curvature and postoperative alignment remains, more pronounced for strong angulations.

LEVEL OF EVIDENCE: IV; Retrospective, single-center observational cohort study.