Conditions for Achieving Postoperative Pelvic Incidence-Lumbar Lordosis < 10° in Circumferential Minimally Invasive Surgery for Adult Spinal Deformity

Abstract

This retrospective study aimed to evaluate the clinical outcomes of circumferential minimally invasive surgery (CMIS) using lateral lumbar interbody fusion (LLIF) and percutaneous pedicle screw (PPS) in adult spinal deformity (ASD) patients, and to clarify the conditions for achieving postoperative pelvic incidence-lumbar lordosis (PI-LL) < 10°. Demographics and other parameters of ASD patients who underwent CMIS and who were divided into groups G (achieved postoperative PI-LL < 10°) and P (PI-LL ≥ 10°) were compared. Of the 145 included ASD patients who underwent CMIS, the average fused level, bleeding volume, operative time, and number of intervertebral discs that underwent LLIF were 10.3 ± 0.5 segments, 723 ± 375 mL, 366 ± 70 min, and 4.0 segments, respectively. The rod material was titanium alloy in all the cases. The PI-LL significantly improved from 37.3 ± 17.9° to 1.2 ± 12.2° postoperatively. Pre- and postoperative PI, postoperative LL, preoperative PI-LL, PI-LL after LLIF, and postoperative PI-LL were significantly larger in group P. PI-LL after LLIF was identified as a significant risk factor of postoperative PI-LL < 10° by logistic regression, and the cut-off value on receiver operating characteristic curve analysis was 20°. Sufficient correction was achieved by CMIS. If PI-LL after LLIF was ≤20°, it was corrected to the ideal alignment by the PPS procedure.

Keywords: adult spinal deformity; circumferential minimally invasive surgery; lateral lumbar interbody fusion; lumbosacral fusion; percutaneous pedicle screw.

Figure 1

Illustration of various spinopelvic parameters. LL: lumbar lordosis; TK: thoracic kyphosis; PI: pelvic incidence; PT: pelvic tilt; SS: sacral slope; SVA: sagittal vertical axis.

Figure 2

Preoperative and postoperative LL and PI-LL. Values are presented as mean ± standard deviation. Wilcoxon signed-rank test. ** Statistically significant. PPS improved LL by 15.5° (4–42°). After CMIS, 60% of all patients met PI + 10° ≥ LL ≤ PI − 10° (blue range) and 90% met PI + 20 > LL > PI − 20 (green range). LL: lumbar lordosis; PI: pelvic incidence; PPS: percutaneous pedicle screw; LLIF: lateral lumbar interbody fusion. ** p < 0.001.

Figure 3

Correlation between various parameters. There was a low correlation between preoperative and postoperative LL (a) and between preoperative PI-LL and LL change using PPS (e). A high correlation was observed between PI-LL after LLIF and postoperative PI-LL (c) and between preoperative PI-LL and total LL change (d). A moderate correlation was observed between preoperative and postoperative PI-LL (b) and between PI-LL after LLIF and LL change with PPS (f). These findings indicate that greater correction is achieved in cases of greater deformity. LL: lumbar lordosis; ΔLL: change in LL; PI: pelvic incidence; LLIF: lateral lumbar interbody fusion; PPS: percutaneous pedicle screw.

Figure 4

The mechanism of correction surgery using LLIF and PPS. Spreading the intervertebral space with insertion of a LLIF cage also opens the facet joints and provides indirect decompression of the intervertebral foramen. Subsequently, by applying a rod, lordosis can be obtained by closing the facet joint. Therefore, even if PPS procedure without Ponte osteotomy was undertaken, sufficient correction is possible without causing nerve root impingement (a-1,a-2,a-3). The contracture facet joints were released and dilated with insertion of LLIF. LLIF procedure can dissociate not only the anterior element, but also the posterior element indirectly (b-1,b-2). LLIF: lateral lumbar interbody fusion; PPS: percutaneous pedicle screw.