Impact of decompression surgery without fusion for lumbar spinal stenosis on sagittal spinopelvic alignment: minimum 2-year follow-up

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OBJECTIVE

The importance of global sagittal alignment is well known. Patients with lumbar spinal stenosis (LSS) generally tend to bend forward to relieve their neurological symptoms, i.e., they have a positive sagittal vertical axis (SVA). We hypothesized that the positive SVA associated with LSS is symptom related and should improve after surgery. However, little is known about the changes in sagittal alignment in LSS patients after decompression surgery. In this study the authors aimed to evaluate midterm radiographical changes in sagittal spinopelvic alignment after decompression surgery for LSS and to determine the factors influencing the improvement in sagittal spinopelvic alignment.

METHODS

The authors retrospectively reviewed 89 patients who underwent lumbar decompression without fusion between January 2014 and September 2015 with a minimum follow-up of 2 years. Standing whole-spine radiographs at the preoperative stage and at the final follow-up were examined. We analyzed SVA, lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), thoracolumbar kyphosis (TLK), and thoracic kyphosis (TK).

RESULTS

LL and TK were significantly increased postoperatively. SVA and PI minus LL (PI-LL) were significantly decreased. There were no significant differences between the preoperative and postoperative PT, PI, SS, or TLK. Twenty-nine patients had preoperative sagittal malalignment with SVA > 50 mm. Thirteen of the 29 patients improved to SVA < 50 mm after decompression surgery. Lower ASA grade, preoperative higher LL, and lower PI-LL were related to patient improvement. A receiver operating characteristic curve for the preoperative PI-LL had an area under the curve value of 0.821, indicating moderate accuracy (p = 0.003). A cutoff value for preoperative PI-LL of 19.2° showed a sensitivity of 93.5% and a specificity of 71.4%.

CONCLUSIONS

Lumbar decompression can lead to a reactive improvement in the lumbar and global sagittal alignment. However, some of the sagittal malalignment in LSS was irreversible. Preoperative PI-LL was a useful predictor to distinguish reversible from irreversible sagittal malalignment.

ABBREVIATIONS ASA = American Society of Anesthesiologists; AUC = area under the curve; BMI = body mass index; EBL = estimated blood loss; LBP = low-back pain; LL = lumbar lordosis; LSPSL = lumbar spinous process–splitting laminectomy; LSS = lumbar spinal stenosis; NRS = numeric rating scale; PI = pelvic incidence; PI-LL = PI minus LL; PT = pelvic tilt; QOL = quality of life; ROC = receiver operating characteristic; SS = sacral slope; SVA = sagittal vertical axis; TK = thoracic kyphosis; TLK = thoracolumbar kyphosis.

Article Information

Correspondence Yoji Ogura: Japanese Red Cross Shizuoka Hospital, Shizuoka, Japan. yoji_totti1223@yahoo.co.jp.

INCLUDE WHEN CITING Published online February 15, 2019; DOI: 10.3171/2018.11.SPINE181092.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Flowchart of the study representing groups and numbers of patients. Eighty-nine patients with lumbar spinal stenosis were allocated into 6 groups based on preoperative and postoperative SVA.

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    ROC curve for the preoperative LL as a predictor for postoperative SVA improvement. The AUC was 0.766, indicating moderate accuracy. A cutoff value of 24.5° demonstrated a sensitivity of 78.6% and a specificity of 68.7%. Figure is available in color online only.

  • View in gallery

    ROC curve for the preoperative PI-LL as a predictor for postoperative SVA improvement. The AUC was 0.821, indicating moderate accuracy. A cutoff value of preoperative PI-LL of 19.2° demonstrated a sensitivity of 93.5% and a specificity of 71.4%. Figure is available in color online only.

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