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. 2023 Feb;17(1):17-24.
doi: 10.14444/8352. Epub 2022 Aug 2.

Fusion Mass Screws in Revision Spinal Deformity Surgery: A Simple and Safe Alternative Fixation

Ashish Mittal  1 , Alexander Rosinski  1 , Khalid Odeh  1 , Cristian Balcescu  1 , Victor Ungurean Jr  2 , Victor Ungurean Sr  3 , Dimitriy G Kondrashov  4
Affiliations

Fusion Mass Screws in Revision Spinal Deformity Surgery: A Simple and Safe Alternative Fixation

Ashish Mittal et al. Int J Spine Surg. 2023 Feb.

Abstract

Background: Revision spinal deformity surgery has a high rate of complications. Fixation may be challenging due to altered anatomy. Screws through a fusion mass are an alternative to pedicle screw fixation.

Objective: The purpose of this retrospective study was to further elucidate the safety and efficacy of fusion mass screws (FMSs) in revision spinal deformity surgery.

Design: Retrospective case series.

Methods: Fifteen freehand FMSs were placed in 6 patients with adult spinal deformity between 2016 and 2018 by the senior author. FMSs were combined with pedicle screws, at times at the same level. FMSs were used to save distal levels from fusion, assist in closing a 3-column osteotomy and provide additional fixation in cases of severe instability. Computed tomography (CT) was used to assess bone mineral density (BMD) and thickness of each fusion mass preoperatively along with accuracy of FMS placement postoperatively.

Results: The mean BMD of the fusion mass was 397 Hounsfield units (HU; range: 156-628 HU). The mean AP thickness of the fusion mass was 15.5 ± 4.8 mm (range: 8.6-24.4 mm). The mean FMS length was 35.3 ± 5.5 mm (range: 25-40 mm). There was no evidence of FMS loosening, breakage, or pseudarthrosis at latest follow-up (mean: 2.2 years, range: 1.4-3.1 years). No neurologic deficits were observed. 1/15 screws had a low-grade breach into the canal (<2 mm). No patients required revision surgery.

Conclusion: FMSs may be used to augment fixation in revision spinal deformity cases when pedicle screw placement may be challenging. FMSs may also provide an additional anchor at levels with pedicular fixation.

Keywords: extrapedicular fixation; fusion mass; pedicular dysplasia; revision; spinal deformity.

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Conflict of interest statement

Declaration of Conflicting Interests: Dimitriy G. Kondrashov reports receiving royalties and consulting fees from Spineart. The remaining authors have no relevant or material financial interests that relate to the research described in this paper.

Figures

Figure 1
Figure 1
(A) Intraoperative photograph of fusion mass screw cannulation lateral to medial immediately inferior to a chevron posterior column osteotomy using a Lenke probe. (B) Intraoperative photograph of polyaxial screw placement into the fusion mass.
Figure 2
Figure 2
Axial computed tomography image showing low-grade breach (<2 mm) into spinal canal of a f fusion mass screw placed at T12, Case 4.
Figure 3
Figure 3
Fusion mass screws (arrows) assisting in osteotomy closure and providing an additional anchor to save a distal fusion level below a 3-column osteotomy.
Figure 4
Figure 4
(A) Axial computed tomography (CT) image showing fusion mass screws (FMSs) placement at T12 through a thick fusion mass bed measuring 21.8 mm. (B) CT image showing right-sided FMS placement with a concurrent pedicle screw placement at L2.
Figure 5
Figure 5
(A-C) CT and (D) full-length standing radiograph images demonstrating fusion mass screw placement at T8 and T10 (arrows) distal to the vertebral column resection to assist in osteotomy closure. Concurrent pedicle screw placement is also shown at T8.
Figure 6
Figure 6
(A) Axial computed tomography images of Patient 6 demonstrating pedicular dysplasia in the setting of neurofibromatosis-1 and juvenile onset scoliosis. (B) Fusion mass screw placed at T12. Pedicle screw placement was avoided due to dysplasia and obscured landmarks intraoperatively. The pedicles were 2.2 and 3.9 mm in width at this level.
Figure 7
Figure 7
Intraoperative photograph demonstrating identification of the pedicle screw starting point using a quadrangulation technique as described by Kim et al.8
See this image and copyright information in PMC

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