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. 2022 Oct-Dec;13(4):454-459.
doi: 10.4103/jcvjs.jcvjs_120_22. Epub 2022 Dec 7.

Compensatory mechanisms in adult degenerative thoracolumbar spinal deformity - Radiographic patterns, their reversibility after corrective surgery, and the influence of pelvic morphology

Nicholas Dietz  1 , Basil Erwin Gruter  2 , Edin Nevzati  3 , Samuel K Cho  4 , Mazda Farshad  5 , Brian Williams  1 , Peter Hollis  6 , Alexander Spiessberger  6
Affiliations

Compensatory mechanisms in adult degenerative thoracolumbar spinal deformity - Radiographic patterns, their reversibility after corrective surgery, and the influence of pelvic morphology

Nicholas Dietz et al. J Craniovertebr Junction Spine. 2022 Oct-Dec.

Abstract

Objective: Loss of lumbar lordosis (LL) in degenerative deformity activates spinal compensatory mechanisms to maintain neutral C7 sagittal vertical axis (C7SVA), such as an increase in pelvic tilt (PT) and decreased thoracic kyphosis (TK). We study the extent to which PT increase and TK reduction contribute to the compensation of pelvic incidence (PI)-LL mismatch.

Methods: A cohort of 43 adult patients with adult degenerative thoracolumbar deformity were included in this retrospective study. Radiographic spinopelvic measurements were obtained before and after corrective surgery. Pearson correlations were calculated.

Results: Preoperative PI-LL mismatch significantly correlated with an increase in PT and a decrease in TK in the whole cohort r = +0.66 (95% confidence interval [CI] 0.44-0.8) and r = -0.67 (95% CI - 0.81--0.47), respectively, at a relative rate of 0.37 (standard deviation [SD]: 0.07) and - 0.57 (SD: 0.09), respectively. In patients with low PI, only TK showed a significant correlation with PI-LL mismatch, r = -0.56 (95% CI - 0.8 to - 0.16), at a rate of - 0.57 (SD: 0.19). The high PI subgroup showed a significant correlation with PT, TK, and C7SVA, r = 0.62 (95% CI 0.26-0.82), r = -0.8 (95% CI - 0.9--0.58), and r = 0.71 (95% CI 0.41-0.87) at rates of 0.48 (SD: 0.11), -0.72 (SD: 0.12), and 0.62 (SD: 1.27).

Conclusions: Decreased TK represented a more consistent compensatory mechanism in patients with high and low PI when compared to an increase in PT. PI-LL mismatch induced more pronounced changes in TK than did PT in both subgroups. Patients with high PI relied more on increases in PT and a relative decrease in TK to compensate for PI-LL mismatch than patients with low PI.

Keywords: Adult spinal deformity; pelvic incidence; pelvic tilt; sagittal balance; thoracolumbar deformity.

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Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1
Figure 1
Correlations between preoperative PI-LL and perioperative change in PI-LL and sagittal spinopelvic parameters in the whole patient cohort as well as low and high PI subgroups. PI-LL - Pelvic incidence-lumbar lordosis, (a) PI-LL preoperative measures for whole cohort, (b) Change in lumbar lordosis for whole cohort, (c) PI-LL preoperative measures for low PI subgroup, (d) Change in lumbar lordosis preoperative measures for low PI subgroup, (e) PI-LL preoperative measures for high PI subgroup, (f) Change in lumbar lordosis preoperative measures for high PI subgroup
Figure 2
Figure 2
Mechanisms involved in reduction of TK (inlet a): Erector spinae activation, and increase in PT (inlet b): Rectus abdominis and gluteal muscle activation. PT - Pelvic tilt, TK - Thoracic kyphosis
See this image and copyright information in PMC

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