Elsevier

The Spine Journal

Volume 18, Issue 4, April 2018, Pages 648-654
The Spine Journal

Clinical Study
Comparison of S2-Alar and traditional iliac screw pelvic fixation for pediatric neuromuscular deformity

https://doi.org/10.1016/j.spinee.2017.08.253Get rights and content

Abstract

Background Context

Many pelvic fixation options exist for posterior spinal fusion of pediatric neuromuscular scoliosis, including standard iliac screws (SISs) or a more recently introduced S2-Alar (S2A) technique. However, little data exist comparing the clinical and radiographic outcomes of these techniques.

Purpose

This study aimed to dentify differences in clinical and radiographic outcomes for pediatric neuromuscular scoliosis patients treated with SIS or S2A pelvic fixation.

Study Design/Setting

This was a retrospective cohort study at a pediatric orthopedic clinic.

Patient Sample

Patients aged 8–19 years undergoing posterior spinal fusion to the pelvis for neuromuscular scoliosis using SIS or S2A technique, with Gross Motor Function Classification System (GMFCS) Level 4 or 5 were included.

Outcomes Measures

Postoperative complication rates associated with pelvic fixation method were the outcome measures.

Methods

Charts and radiographs were reviewed for demographics, intra- and postoperative course, levels of instrumentation, operative correction, and implant failure (IF). Postoperative complications were classified according to the Accordion scale.

Results

We studied 50 patients (28 SIS, 22 S2A) aged 14.0±2.8 years and an average follow-up of 3.5±1.7 years. The average number of levels fused was 16.5±1.1 with an average curve correction of 48°±21° postoperatively. A significant difference in radiographic IF rates was noted between SIS and S2A groups (57% vs. 27%, p=.02). No difference was noted between groups for frequency or severity of postoperative complications, inclusive of wound infections. Subgroup analysis demonstrated equivalent IF rates when comparing the S2A group with the SIS group with cross-links.

Conclusions

The S2A group generally demonstrated improved rates of radiographic IF compared with the SIS group, but the rates became equivalent when a cross-link was added to an SIS construct. Further, no difference in postoperative complication rates were identified between SIS and S2A groups.

Introduction

Progressive neuromuscular scoliosis (NMS) can compromise the ability of non-ambulatory pediatric patients to comfortably seat in a wheelchair and tolerate activities of daily living. Spinal fusion with instrumentation to the pelvis is used to correct and stabilize the spinal deformity, level pelvic obliquity, and improve sitting balance. Since the development of the Luque-Galveston technique in 1984, numerous pelvic constructs have been described with various short to mid-tem success rates [1], [2], [3], [4]. In the current era of spinal instrumentation, modular iliac screws have become widely used as they have eliminated the need for the technically demanding three-dimensional Galveston rod bending and offer greater pull-out strength than smooth rod fixation [5]. The S2-Alar (S2A) screw fixation technique has more recently been developed and uses a more medial starting point than traditional iliac screws. The alteration in starting point obviates the need for offset connectors to connect to the primary rods, potentially improving the implant profile of the construct and limiting soft tissue dissection [2], [6], [7].

Although S2A fixation has theoretical benefits for wound management and implant stability, there are sparse data comparing the radiographic and clinical outcomes of this pelvic construct with the more traditional iliac screw method in a pediatric neuromuscular population [8]. The current study examines the clinical and radiographic outcomes of pediatric patients with NMS treated with either standard iliac screws (SISs) or S2A constructs.

Section snippets

Materials and methods

This study was approved by the Connecticut Children's Institutional Review Board. A single institution, retrospective chart and radiograph review was performed of all patients who underwent spinal instrumentation between November 2003 and October 2014. Inclusion criteria consisted of age between 8 and 20 years of age, diagnosis of NMS, Gross Motor Function Classification System Level 4 or 5, received posterior spinal instrumentation with extension to the pelvis using SIS or S2A technique, and

Demographics

A total of 68 NMS patients underwent posterior spinal fusion to the pelvis during the study period, and 50 of these patients met inclusion criteria. Nine patients were excluded for incomplete follow-up of less than 1 year, and the remainder was excluded for incomplete medical records. Twenty-nine patients were male (58%) and 21 were female (42%), with an average age of 14.0 years at surgery (range 9.8–19.6) and an average length of follow-up of 3 years (range 1–10 years) (Table 1). Twenty-eight

Discussion

The surgical management of NMS remains challenging, given the high overall postoperative complication rates for this population and the technical difficulty of extending a long spinal construct into the pelvis, which has been identified as an independent risk factor for postoperative morbidity [11]. The choice of pelvic fixation has demonstrated notable variability throughout literature and has changed over time. More modern variations of the pelvic fixation concept have stressed modular

Conclusion

In summary, S2A screws were generally found to offer lower IF rates when compared with SISs, without conferring an advantage in correction of the main Cobb angle or in decreasing postoperative complications. However, IF rates are equivalent when S2A screws are compared with iliac screws with a single cross-link at any point in the construct. Although S2A fixation has gained popularity, modular iliac screws remain a viable option and may offer the same clinical outcomes in a pediatric NMS

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Cited by (33)

  • Comparison of Complications and Revisions After Sacral 2 Alar Iliac Screw and Iliac Screw Fixation for Sacropelvic Fixation in Pediatric and Adult Populations: Systematic Review and Meta-Analysis

    2019, World Neurosurgery
    Citation Excerpt :

    A previous meta-analysis28 including 5 comparative studies found that S2AI screw fixation in adults has a significantly lower mechanical failure and complication rate than does IS fixation. However, this meta-analysis did not consider fixation in other diseases (e.g., neuromuscular scoliosis or pediatric scoliosis) and other relevant outcomes such as complications,3,20,29 publication bias, and sources of heterogeneity (e.g., age, sex, disease, and level of fixation) were not assessed. The risk bias assessment for comparative studies was not assessed.

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FDA device/drug status: Approved (pedicle/modular screws used in the pediatric spine/sacrum).

Author disclosures: MCL: Nothing to disclose. CJ: Nothing to disclose. MJS: Nothing to disclose. JT: Nothing to disclose.

There was no funding associated with this study, and there are no conflicts of interest.

The current study received IRB approval from Connecticut Children's Medical Center.

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