8 Spinous Process Fixation Systems

Jordan A. Guntin, Benjamin Khechen, Brittany E. Haws, Kaitlyn L. Cardinal, and Kern Singh

8 Spinous Process Fixation Systems

8.1 Introduction

Spinous process fixation is another method utilized to provide spinal stability following interbody fusion. These devices are designed to provide additional stability through interspinous fusion. ¹ Many interspinous fixation devices (IFDs) also provide interspinous process spacing, which can provide further decompression. ¹ Additionally, the placement of this device only requires a single midline incision, which may make it a more expedient procedure compared to standard pedicle screw fixation. Surgical indications are presented in ▶ Table 8.1.

8.1.1 Interspinous Fixation Device Components

IFDs contain plates that clamp to the lateral aspects of adjacent spinous processes (▶ Fig. 8.1). ² The clamps are often fixed to the spinous processes through the use of rivets or spiked plates. By securing segment motion posteriorly, an IFD can provide rigidity to the two adjacent vertebrae to which it is secured. ² IFDs can be composed of a variety of materials, including polyetheretherketone (PEEK) and titanium.

**Table 8.1** Surgical indications for interspinous fixation devices
Indications
Posterior approach spinal fusion Thoracic procedures Lumbosacral procedures Degenerative disk disease Spondylolisthesis Spinal fracture/dislocation Spinal tumor

**Fig. 8.1** Interspinous fixation device with clamps fixated on the spinous processes of two adjacent lumbar vertebrae. (Adapted from Aspen® MIS Fusion System Surgical Technique Guide, Zimmer Biomet, 2014.)

8.1.2 Outcomes

Spinous process fixation has exhibited promising outcomes with regard to its efficacy. Previous studies have demonstrated similar fusion rates when utilizing either supplemental spinous process fixation or pedicle screw fixation. ¹ ^, ³ ^, ⁴ Additionally, IFDs have exhibited comparable rigidity to pedicle screws, especially in flexion–extension movements of the lumbar spine. ⁵ ^, ⁶ This is supplemented with evidence of reduced motion at adjacent segments, suggesting a reduced risk for adjacent segment disease when IFDs are utilized. ¹ However, the literature is limited regarding high-quality comparative studies. Few studies have examined the complication profile of IFDs. ¹ Furthermore, evidence regarding long-term outcomes and benefits of IFDs has not been addressed. ¹ As such, the literature is inadequate to identify the true advantages of IFDs over other methods of fixation.

8.2 Spinous Process Fixation Systems

**Table 8.2** Alphatec Spine BridgePoint® Spinous Process Fixation System
Design
Device type Fixed	Composition Titanium alloy	Specifications Angulating and telescoping plates enhance device fit and promote fusion

Modular aspects and variations
Widths Small: 35–40 mm Medium: 40–45 mm Large: 45–50 mm	Angulation ±14°	Compression/distraction Telescoping plates provide up to 5 mm adjustment

Procedures
MIS TLIF, MIS posterior decompression
Radiographs unavailable
Supplemental fixation system
Alphatec Spine Illico® Posterior Stabilization System

**Table 8.3** Globus Medical SP-Fix™ Spinous Process Fixation Plate
Design
Plate type Fixed	Composition Titanium and PEEK	Specification Zero-step locking mechanism expedites the implantation process

Modular aspects and variations
Rod sizes 25, 30, 35 mm	Barrel heights 8–20 mm (2-mm increments)	Plate lengths 35–47 (3-mm increments), 50, 55 mm	Angulation ±15°

Procedures
MIS TLIF, MIS posterior decompression
Radiographs unavailable
Supplemental fixation system
Globus Medical REVOLVE® Posterior Stabilization System

**Table 8.4** NuVasive Affix® II Spinous Process Plate Device
Design
Device type Fixed	Composition Titanium alloy	Plate lengths 35–55 mm (10-mm increments)	Specifications One-step insertion and self-locking mechanism

Procedures
MIS TLIF, MIS posterior decompression
Radiographs unavailable
Supplemental fixation system
NuVasive Precept® Posterior Stabilization System

**Table 8.5** OsteoMed PrimaLOK™ SP Interspinous Fusion System
Design
Device type Fixed		Composition Titanium alloy		Specifications Polyaxial movement facilitates anterior placement

Modular aspects and variations
Height (A) 8–12 mm (2-mm increments) 15–18 mm (3-mm increments)	Width (B) 5.5–13.5 mm 5.5–13.5 mm	Grip distance (C) 28 mm 34 mm	Length (D) 39 mm 45 mm	Width (E) 17 mm 17 mm	Central post length 25 and 30 mm 25 and 30 mm

Procedures
MIS TLIF, decompression
Radiographs unavailable
Supplemental fixation system
OsteoMed MIS Posterior Stabilization System

**Table 8.6** Paradigm Spine Coflex® Interlaminar Technology
Design
Device type Fixed	Composition Titanium alloy	Specifications In situ compressible in extension, which allows for flexion upon insertion

Modular aspects and variations
Available sizes 8–16 mm (2-mm increments)	Distal arm length 5–13 mm (2-mm increments)
Procedures
MIS TLIF, MIS posterior decompression

Supplemental fixation system
Paradigm Spine MIS Posterior Stabilization System

**Table 8.7** RTI Surgical BacFuse® Spinous Process Fusion Plate System
Design
Device type Fixed	Composition Titanium alloy	Specifications Torque-controlled locking mechanism confirms fixation

Modular aspects and variations
Caudal-cranial length	Maximum width	Barrel height	A/P length	Angulation
35–37 mm (0.5-mm increments)	12.5 mm	8–16 mm (2-mm increments)	16 mm	±10°

Procedures
MIS TLIF, MIS posterior decompression
Radiographs unavailable
Supplemental fixation system
RTI Surgical MIS Posterior Stabilization System

**Table 8.8** SeaSpine Spinous Process Fixation System
Design
Device type Fixed	Composition Titanium alloy	Available sizes 6–16 mm (2-mm increments)	Angulation ±10°

Procedures
MIS TLIF, MIS posterior decompression

Supplemental fixation system
SeaSpine Spinous Process MIS Posterior Stabilization System

**Table 8.9** Stryker UniVise® Spinous Process Fixation Plate System
Design
Device type Fixed	Composition Titanium alloy	Specifications Midline approach with centralized locking mechanism	Available sizes 35 and 40 mm

Procedures
MIS TLIF, MIS posterior decompression
Radiographs unavailable
Supplemental fixation system
Stryker UniVise® MIS Posterior Stabilization System

**Table 8.10** Zimmer Biomet ALPINE XC™ Adjustable Fusion System
Design
Device type Expandable	Composition Titanium	Specifications Adjustability allows in situ distraction and compression

Modular aspects and variations
Post length Medium (21 mm) Wide (24 mm)	Post height range 6–18 mm 10–18 mm	Ventral graft containment Medium: 6–12 mm Wide: 10–18 mm
Procedures
MIS TLIF, MIS posterior decompression

Supplemental fixation system
Zimmer Biomet MIS Posterior Stabilization System

**Table 8.11** Zimmer Biomet ASPEN® MIS Fusion System
Design
Device type Fixed	Composition Titanium and cobalt	Specifications Models designed for specific spinal levels

Modular aspects and variations
Type	Width options	Barrel length	Angulation	Offset
Standard	8–18 mm (2-mm increments)	21 mm	10°	–
Medium	6–14 mm (2-mm increments)	18 mm	10°	–
Flared 5–1 (special order)	8–18 mm (2-mm increments)	–	10°	45°

Procedures
MIS TLIF, MIS posterior decompression

Supplemental fixation system
Zimmer Biomet MIS Posterior Stabilization System