Radiographic outcome and complications after single-level lumbar extended pedicle subtraction osteotomy for fixed sagittal malalignment: a retrospective analysis of 55 adult spinal deformity patients with a minimum 2-year follow-up

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OBJECTIVE

Fixed sagittal spinal malalignment is a common problem in adult spinal deformity (ASD). Various three-column osteotomy techniques, including the extended pedicle subtraction osteotomy (ePSO), may correct global and regional malalignment in this patient population. In contrast to the number of reports on traditional PSO (Schwab grade 3 osteotomy), there is limited literature on the outcomes of ePSO (Schwab grade 4 osteotomy) in ASD surgery. The objective of this retrospective study was to provide focused investigation of radiographic outcomes and complications of single-level lumbar ePSO for ASD patients with fixed sagittal malalignment.

METHODS

Consecutive ASD patients in whom sagittal malalignment had been treated with single-level lumbar ePSO at the authors’ institution between 2010 and 2015 were analyzed, and those with a minimum 2-year follow-up were included in the study. Radiographic analyses included assessments of segmental lordosis through the ePSO site (sagittal Cobb angle measured from the superior endplate of the vertebra above and inferior endplate of the vertebra below the ePSO), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence and LL mismatch, thoracic kyphosis (TK), and sagittal vertical axis (SVA) on standing long-cassette radiographs. Complications were analyzed for the entire group.

RESULTS

Among 71 potentially eligible patients, 55 (77%) had a minimum 2-year follow-up and were included in the study. Overall, the average postoperative increases in ePSO segmental lordosis and overall LL were 41° ± 14° (range 7°–69°, p < 0.001) and 38° ± 11° (range 9°–58°, p < 0.001), respectively. The average SVA improvement was 13 ± 7 cm (range of correction: −33.6 to 3.4 cm, p < 0.001). These measurements were maintained when comparing early postoperative to last follow-up values, respectively (mean follow-up 52 months, range 26–97 months): ePSO segmental lordosis, 34° vs 33°, p = 0.270; LL, 47.3° vs 46.7°, p = 0.339; and SVA, 4 vs 5 cm, p = 0.330. Rod fracture (RF) at the ePSO site occurred in 18.2% (10/55) of patients, and pseudarthrosis (PA) at the ePSO site was confirmed by CT imaging or during rod revision surgery in 14.5% (8/55) of patients. Accessory supplemental rods across the ePSO site, a more recently employed technique, significantly reduced the occurrence of RF or PA on univariate (p = 0.004) and multivariable (OR 0.062, 95% CI 0.007–0.553, p = 0.013) analyses; this effect approached statistical significance on Kaplan-Meier analysis (p = 0.053, log-rank test). Interbody cage placement at the ePSO site resulted in greater ePSO segmental lordosis correction (45° vs 35°, p = 0.007) without significant change in RF or PA (p = 0.304). Transient and persistent motor deficits occurred in 14.5% (8/55) and 1.8% (1/55) of patients, respectively.

CONCLUSIONS

Extended PSO is an effective technique to correct fixed sagittal malalignment for ASD. In comparison to traditional PSO techniques, ePSO may allow greater focal correction with comparable complication rates, especially with interbody cage placement at the ePSO site and the use of accessory supplemental rods.

ABBREVIATIONS ASD = adult spinal deformity; ePSO = extended PSO; FSM = fixed sagittal spinal malalignment; LL = lumbar lordosis; PA = pseudarthrosis; PI = pelvic incidence; PSO = pedicle subtraction osteotomy; PT = pelvic tilt; RF = rod fracture; SVA = sagittal vertical axis; TK = thoracic kyphosis.

Article Information

Correspondence Thomas J. Buell: University of Virginia Health System, Charlottesville, VA. tjb4p@hscmail.mcc.virginia.edu.

INCLUDE WHEN CITING Published online November 9, 2018; DOI: 10.3171/2018.7.SPINE171367.

C.I.S. and J.S.S. share senior authorship.

Disclosures Dr. C. I. Shaffrey has been a consultant for Medtronic, Nuvasive, Zimmer Biomet, and K2M; has received royalties from Medtronic, Nuvasive, and Zimmer Biomet; is a stock holder in Nuvasive; and has received grants from the NIH, Department of Defense, and the North American Clinical Trials Network for non–study-related effort. Dr. Smith has received royalties from Zimmer Biomet; has been a consultant for Zimmer Biomet, Cerapedics, Nuvasive, K2M, and AlloSource; has received honoraria from Zimmer Biomet, Nuvasive, and K2M; has received support from DePuy Synthes for the study described; has received support from DePuy Synthes and ISSGF for non–study-related effort; and has received fellowship support from the NREF and AOSpine.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    A: The classic or traditional PSO technique, which is classified as Schwab grade 3 osteotomy.35 The posterior closing bony wedge resection respects the superior endplate of the index vertebra and adjacent superior disc space. Also note the ePSO technique (Schwab grade 4 osteotomy), which was utilized by the two senior authors (C.I.S., J.S.S.) in this study. The wedge resection is extended superiorly to include the adjacent disc space for radical discectomy. B: An interbody cage spacer can be placed at the osteotomy site to act as a fulcrum for additional lordosis or to increase the contact surface area for arthrodesis. C: Preoperative (left) and postoperative (right) long-cassette standing scoliosis radiographs for a 65-year-old woman who presented with thoracolumbar kyphoscoliosis above a previous L3–S1 dynamic stabilization system. She underwent surgical correction with an ePSO at L3, interbody cage placement at the ePSO site, and re-instrumentation for fusion from T10 to iliac. In this case, the L3 ePSO segmental lordosis is the sagittal Cobb angle measured between the L2 superior endplate and L4 inferior endplate. The early postoperative change in ePSO segmental correction measured 41°.

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    This case demonstrates postoperative bilateral RFs at L2–3 after T10-iliac posterior instrumentation and fusion with L2 ePSO for adult idiopathic scoliosis. Approximately 3 years after the index operation, the patient presented with increasing low-back pain and muscle spasms. Note the bilateral RFs (arrows) at L2–3 adjacent to the ePSO (A and B). The patient underwent revision surgery with replacement of both primary rods and placement of two accessory supplemental rods across the original osteotomy level (C). During surgery, PA was noted at the L2–3 osteotomy level. The patient recovered from the revision operation without complication, and symptoms resolved.

  • View in gallery

    The protective effect of accessory supplemental rods to avoid RF or PA approached statistical significance on Kaplan-Meier analysis (p = 0.053, log-rank test). The figure demonstrates Kaplan-Meier curves or probability distribution functions for all patients dichotomized based on the use of accessory supplemental rods.

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