EXPANDABLE INTRAVERTEBRAL IMPLANTS IN POST-TRAUMATIC VERTEBRAL NECROSIS - NEW CLASSIFICATION SUGGESTION

MOURA, DIOGO LINO; GABRIEL, JOSUÉ PEREIRA

doi:10.1590/1413-785220233104e262943

DIOGO LINO MOURA

contributed individually and significantly to the development of this article

substantial contribution to the conception

design, acquisition, analysis, and interpretation of data for the work

drafting and critically revising its intellectual content

final approval of the manuscript version to be published

agreeing to be accountable for all aspects of the work, ensuring that any issues related to the integrity or accuracy of any part of it are properly investigated and resolved

Centro Hospitalar e Universitario de Coimbra, Serviço de Ortopedia, Setor de Coluna Vertebral, Coimbra, Portugal.

Universidade de Coimbra, Faculdade de Medicina, Instituto de Anatomia e Clinica Universitaria de Ortopedia, Coimbra, Portugal.

Grant Medical Center, Spine Institute of Ohio, Columbus, OH, United States.

https://orcid.org/0000-0003-4037-2442

JOSUÉ PEREIRA GABRIEL

contributed individually and significantly to the development of this article

substantial contribution to the conception

design, acquisition, analysis, and interpretation of data for the work

drafting and critically revising its intellectual content

final approval of the manuscript version to be published

agreeing to be accountable for all aspects of the work, ensuring that any issues related to the integrity or accuracy of any part of it are properly investigated and resolved

Grant Medical Center, Spine Institute of Ohio, Columbus, OH, United States.

https://orcid.org/0000-0002-2129-1295

Correspondence: Diogo Lino Moura. Praceta Prof. Mota Pinto, Coimbra, Portugal, 3004561. dflcoluna@gmail.com

All authors declare no potential conflict of interest related to this article.

Figures (3)
Tables (2)

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Figure 1
Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow diagram. ⁽²⁸28. Page MJ, McKenzie JE, Bossuyt PM, Boutron I, Hoffmann TC, Mulrow CD, et al. The PRISMA 2020 statement: an updated guideline for reporting systematic reviews. BMJ. 2021;372:n71.

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Figure 2
Suggested post-traumatic vertebral necrosis evolution stages: Stage 0 - Initial fracture without necrosis; Stage 1i - Immobile (i) necrotic vertebra non-plana; Stage 1m - Mobile (m) necrotic vertebra non-plana; Stage 2i - Immobile necrotic vertebra plana; Stage 2m - Mobile necrotic vertebra plana; Highlighting the presence of intravertebral cleft only in the mobile vertebrae. Immobile vertebrae do not present intravertebral cleft. On the right side, note the vertebral body pseudarthrosis or mobile necrotic vertebra morphology and biomechanics.

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Figure 3
Suggested therapeutic and preventive algorithms for post-traumatic vertebral necrosis: Therapeutic algorithm for post-traumatic vertebral necrosis. Mobile vertebrae non-plana and plana - Armed kyphoplasty with VBS^®. After removal of pseudarthrosis region (the same as the intravertebral cleft) and proper intravertebral cleaning, the implants are expanded and filled with bone cement or graft; Immobile vertebra non-plana - Armed kyphoplasty with SpineJack^®. After proper intravertebral drilling, the implants are expanded and then bone cement or graft are applied around them; Immobile vertebra plana - the recommended treatment for young and active patients involves corpectomy and intersomatic fusion using a spacer (synthetic cage or structural allograft), along with fixation using a plate and pedicle instrumentation at adjacent levels. However, in older patients or cases where corpectomy is contraindicated, adjacent pedicular fixation with cemented screws and vertebroplasties at adjacent levels are indicated. Preventive algorithm for post-traumatic vertebral necrosis: 1 - For osteoporotic comminuted compression fractures, we recommend armed kyphoplasty with VBS^® filled with bone cement. In these patients the goal is interior replacement and reconstruction of the fragile vertebral body, fracture healing is not expected; 2 - For traumatic comminuted compression fractures (A4 from AOSpine classification), we recommend initial indirect reduction via adjacent pedicle instrumentation, followed by additional direct reduction and interior reconstruction of the vertebral body with VBS^® filled with cancellous bone graft. Highlighting the direct vertebral reduction that allows height restauration by elevation of the central depression of the upper vertebral endplate after expansion of VBS^® implants and their final filling with bone graft (yellow/brown final image representing the bone graft inside the stents).

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Table 1
Biomechanical characteristics of the two most commonly applied expansive intravertebral implants currently available, the Vertebral Body Stenting^® and the SpineJack^®.¹²12. Vanni D, Galzio R, Kazakova A, Pantalone A, Grillea G, Bartolo M, et al. Third-generation percutaneous vertebral augmentation systems. J Spine Surg. 2016;2(1):13-20.^{) (}²⁶26. Kerschbaumer G, Gaulin B, Ruatti S, Tonetti J, Boudissa M. Clinical and radiological outcomes in thoracolumbar fractures using the SpineJack device. A prospective study of seventy-four patients with a two point three year mean of follow-up. Int Orthop. 2019;43(12):2773-9.

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Table 2
Current studies regarding the application of intravertebral implants in the context of chronic compression vertebral fractures. ¹⁴14. Diel P, Röder C, Perler G, Vordemvenne T, Scholz M, Kandziora F, et al. Radiographic and safety details of vertebral body stenting: results from a multicenter chart review. BMC Musculoskelet Disord. 2013;14:233^)-(²⁷27. Premat K, Vande Perre S, Cormier E, Shotar E, Degos V, Morardet L, et al. Vertebral augmentation with the SpineJack(r) in chronic vertebral compression fractures with major kyphosis. Eur Radiol. 2018;28(12):4985-91.

Implant designation	Vertebral Body Stenting^®	SpineJack^®
Illustration
Illustration	http://synthes.vo.llnwd.net/o16/LLNWMB8/INT%20Mobile/Synthes%20International/SGT-EMEA-Agile/SE_818940AA/SE_818940AAeng.pdf	https://www.stryker.com/us/en/interventional-spine/products/spinejack-system.html
Morphology	Cylinder-shaped mesh (stent), two implants by transpedicular access	Similar to a car jack, with superior and inferior lamellas, and two implants by transpedicular access
Material	Chromium-cobalt	Titanium
Expansion direction	Centrifugal circumferential in the coronal plane (craniocaudal + lateral)	Bidirectional in craniocaudal or vertical direction
Expansion mechanism	Hydraulic mechanism, via a kyphoplasty balloon (controlled pressure and volume)	Mechanical mechanism
Expansion power	Maximum pressure = 30 Atm; Maximum expansion volumes: #small stent = 4 mL; #medium stent = 4.5 mL; #large stent = 5 mL	Expansion force = 500 Newtons; maximum expansion heights: #small implant 4.2 = 12.5 mm; #medium implant 5.0 = 17 mm; #large implant 5.8 = 20 mm
Objective	Vertebra reduction and space occupation	Vertebra reduction, preservation of unfractured trabeculae
Rationale	VBS^® is a reducing and space-occupying implant since it presents a multidirectional expansion (vertical and lateral). It is indicated for reconstruction or replacement of the vertebral body without the intention to wait for vertebral fracture natural healing. Stents are implants that, due to their expansion and impaction of the surrounding bone trabeculae, form two cavities inside the vertebral body, which are covered by an envelope of impacted trabeculae. These implants form cavities that, after being filled with bone cement or graft, replace a large part of the vertebral body, filling and stabilizing it. In addition, they minimize cement leakage by recreating the vertebral body walls by impacting bone trabeculae, thereby containing the cement inside	SpineJack^® is a more powerful reduction implant and preserver of unfractured native trabeculae. This implant is not as space occupant since it only expands vertically. In these cases, the goal is to reduce the fracture and wait for its healing, rather than replacing the vertebral body. This implant only reduces and supports the vertebral body, as it does not have a cavity shape or lateral expansion. Therefore, it does not destroy intact lateral trabeculae and does not create significant empty space within the vertebral body. Thus, this implant is useful in cases that demand fracture reduction and bone healing while preserving bone health. We consider that this implant is not ideal for replacing the comminuted, lytic, or porotic vertebral bodies with unstable interior content. Such cases require intrasomatic filling in addition to fracture reduction
Cement Distribution Pattern	Cavitary in the interior of the stents and trabecular at periphery	Trabecular, often joining the two implants in a horizontal pattern

Article	Premat et al. ⁽²⁷27. Premat K, Vande Perre S, Cormier E, Shotar E, Degos V, Morardet L, et al. Vertebral augmentation with the SpineJack(r) in chronic vertebral compression fractures with major kyphosis. Eur Radiol. 2018;28(12):4985-91.	Distefano et al. ⁽¹⁸18. Distefano D, Scarone P, Isalberti M, La Barbera L, Villa T, Bonaldi G, et al. The 'armed concrete’ approach: stent-screw-assisted internal fixation (SAIF) reconstructs and internally fixates the most severe osteoporotic vertebral fractures. J Neurointerv Surg. 2021;13:63-8.
Nature	Case series, prospective	Case series, retrospective
Fracture type	A3 compression chronic fracture (older than six weeks)	80 severe osteoporotic vertebral compression fractures - advanced collapse (Genant grade 3), high degree of osseous fragmentation (McCormack grade 2 and 3), burst morphology, pediculo-somatic junction fracture, and/or large osteonecrotic cleft.
Number of fractured vertebrae	19	Vertebrae with large osteonecrotic clefts in 56/80 levels (70%) of the sample
Intervention	Armed kyphoplasty with SpineJack^® implants	Stent-screw-assisted internal fixation (SAIF)
Mean follow-up	Six months	Six months
Symptoms (VAS)	Median VAS: 7 → 2 (p < 0.01)	VAS median 8 at preoperative → 3 at one month → 2 at six months (p < 0.05)
Function	57.9% of patients presented improvements in mobility, with nine patients (47.9%) able to fully ambulate without any help	PGIC Scale: 5.6 ± 0.9 at one month; 6.1 ± 0.9 at six months
Imaging	Parameters comparison from preoperative to postoperative: Mean kyphotic angulation: 24.4°± 4.1 → 11.7°± 6.7 (p < 0.01); Mean vertebral heights: anterior aspect 11.2 mm ± 3.1 → 16.3 mm ± 2.7(p < 0.01); middle aspect 11.5 mm ± 3.3 → 17.2 mm ± 2.7(p < 0.01); posterior aspect 23.4 mm ± 3.4 → 24.2 mm ± 3.5(p = 0.48); Modified Beck index 0.43 → 0.66 (p < 0.01)	Vertebral body reconstruction was evaluated by two external persons and considered satisfactory in 98.8% of levels, based on scores regarding correct placement and expansion of the implants, cement filling, and vertebral body height restoration.
Complications	21.1% of patients presented secondary adjacent level fractures correlated with kyphosis reduction; and 15.79% of patients presented minor PMMA	17.5% of patients presented painful adjacent vertebral fractures; 10% presented cement leakage detected on CT, with an epidural or foraminal location in 3.8%, all asymptomatic; 20.5% presented osseous subsidence around the VBS-cement complex, with mild to moderate secondary vertebral body height loss
Conclusion	Successful augmentation and reduction are reachable with SpineJack^® in chronic vertebral body fractures.	SAIF is a minimally invasive, safe, and effective treatment for severe osteoporotic vertebral compression fracture, including clefted vertebral bodies. VBS recreates the internal structure of the vertebral body, and favors a predictable and uniform cement distribution within the stents

[1] Correspondence: Diogo Lino Moura. Praceta Prof. Mota Pinto, Coimbra, Portugal, 3004561. dflcoluna@gmail.com

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EXPANDABLE INTRAVERTEBRAL IMPLANTS IN POST-TRAUMATIC VERTEBRAL NECROSIS - NEW CLASSIFICATION SUGGESTION

IMPLANTES INTRAVERTEBRAIS EXPANSÍVEIS NO TRATAMENTO DE NECROSE VERTEBRAL PÓS-TRAUMÁTICA - PROPOSTA DE NOVA CLASSIFICAÇÃO

ABSTRACT