Lateral Lumbar Interbody Fusion: A Review of the Current Clinical Outcomes of Different Supplemental Fixation Techniques

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Fig. 25.1
Preoperative radiographs. (a) AP, (b) lateral, (c) extension, and (d) flexion



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Fig. 25.2
Preoperative sagittal MRI


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Fig. 25.3
Postoperative radiographs. (a) AP, (b) lateral, (c) extension, and (d) flexion





25.3 Interspinous Fusion


Interspinous fusion devices are being evaluated as an alternative to bilateral and unilateral pedicle screw constructs in augmenting lumbar interbody fusion rates. The devices are designed to take advantage of the biomechanical loading processes of the posterior aspect of the vertebral column in order to immobilize the affected segment, thus stabilizing the spine. The interspinous devices are intended to create construct stability comparable to pedicle screws, while being less invasive, therefore reducing blood loss, risk of infection, and postoperative muscle pain [4245]. In contrast to interspinous process devices (IPDs), which primarily work as stand-alone decompressive materials (i.e., X-STOP), interspinous fusion devices (IFDs) are designed for fixation and fusion. Early attempts at interspinous fusion failed, as the pilot implants had a small surface area with the spinous processes, meaning all of the force due to the axial load of the superior spine was applied on a small area. Contemporary devices include paired plates with teeth or U-shaped device with wings that attach to the spinous process [46].

The US Food and Drug Administration (FDA) have approved a significant number of IFDs (Table 25.1). Despite the fact that they are composed of different designs and materials, they share similar indications and implantation techniques with the aim of maintaining a constant degree of distraction between the spinous processes and stabilize the spine in a minimally invasive manner [46]. As per 510 (k) premarket notifications, the indications for the use of these devices are to achieve supplemental fusion in the following conditions: degenerative disk disease (defined as back pain of discogenic origin with degeneration of the disk confirmed by history and radiographic studies), spondylolisthesis, trauma (i.e., fracture or dislocation), and/or tumor (510 K doc). These devices can be used in elderly patients or those with bone quality too poor for pedicle screw instrumentation. The vast majority of devices are implanted via a midline incision followed by muscle dissection lateral to the supraspinous ligament. The paraspinal muscles are then stripped off the laminae, and the interspinous ligament is sacrificed. Before implantation, a microsurgical decompression is performed (per manufacturer instruction manual).


Table 25.1
Partial list of interspinous fixation devices that have received clearance to market by the FDA














































































































































































#

Name

Company

510 (K) approval

Image

Material

Testing performed

Clinical study?

Additional

1

Spire™

Medtronic

November 2004

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Titanium

Cadaver testing: ±6.0 Nm nondestructive quasi-static loading in axial rotation, flexion/extension, and lateral bending with a constant displacement/rotation rate

X

Intended for use with autograft and/or allograft. For single use only

2

PrimaLOK™

OsteoMed

August 2010

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Titanium alloy

Static: compression, tension, and torsion

Dynamic: compression and torsion

X

Intended for use at one level, with bone graft material

3

Inspan™

Spine frontier

September 2010

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Titanium alloy

Static: compression and torsion

Dynamic: compression and torsion

X

Intended for use with bone graft material

4

Axle™

X-spine

November 2010

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Titanium alloy and PEEK

Cadaver testing

Static: compression

Bending, torsion

Fatigue compression bending
 
Intended for use with bone graft material

5

SP-Fix™

Globus

January 2011

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Titanium alloy and PEEK

Static: compression, torsion, plate dissociation, and tension

Dynamic: compression and plate dissociation
 
Intended for single level with bone graft material

6

BacFuse®

Pioneer surgical

March 2011

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Titanium alloy

Static: compression, tension, torsion, locking mechanism

Dynamic: flexion, extension, locking mechanism
 
For use at a single level. Intended for use with bone graft material

7

BridgePoint™

Alphatec

June 2011

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Titanium

Cadaver testing

Static and fatigue performance characteristics
 
Window allows for bone graft placement. Telegraphing plates allow for extension or compression

8

Octave™

Life spine

November 2011

Unavailable

Titanium alloy

Static: axial compression, torsion, axial pullout, axial grip strength

Dynamic: axial compression
 
Intended for use with bone graft material. Single-level use only

9

Coflex-F®

Paradigm spine

February 2012

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Titanium Alloy

Cadaver testing.

Static: compression, rotation/torsion

Dynamic: compression, tension

X

Intended for use at a single level

10

Aileron™

Life spine

March 2012

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Titanium

Static: axial grip

Engineering analysis, compression

Dynamic: compression
 
Intended for use with bone graft material. Single-level use only

11

Aspen™

Lanx, acquired by BioMet

September 2012

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Titanium

Cadaver testing

Static: compression bending, torsion

Fatigue compression bending

X

Intended for use with or without bone graft material

12

Interbridge

LDR spine

March 2013

Unavailable

Titanium

Static: axial, torsion, compression, pullout resistance, plate dissociation

Dynamic: axial compression bending
 
Intended for single-level use only

13

Affix™

NcixuVasive

July 2013

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Titanium

Static: axial compression, torsion, post distraction

Dynamic: axial compression

In progress

The FDA issued a warning letter for selling the device for uses not approved by its 510 (k) clearance [7]

14

Zip Mis

Aurora spine

November 2013

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Titanium alloy

Static: compression bending, torsion

Dynamic: compression bending

X

Intended for use with bone graft material

15

Minuteman™

Spinal simplicity

August 2015

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Titanium alloy with hydroxyapatite coating

Static: shear strength

Tensile strength

Solubility, dissolution products and rates, XRD pattern, and FTIR spectra

Recruiting

Can be placed under fluoroscopy through lateral or posterior MIS approach. Intended for use with bone graft material. Single-level use only


Information retrieved from device 510 (k) summary when possible. References for images included below

Currently, 15 IFDs have received clearance to market by the FDA. There are numerous designs to these implants as shown in Table 25.1, but each device claims the same advantages over the pedicle screw fixation including reduced risk of cerebrospinal fluid leakage and nerve damage, less muscle dissection and intraoperative estimated blood loss, shorter hospital stay and rehabilitation period, and reversibility of the surgical procedure that does not limit future surgical treatment options [47].

In contrast, while biomechanical studies indicate that IFDs may be similar to pedicle screw-rod constructs in limiting the range of flexion-extension, they may be less effective in reducing axial rotation and lateral bending [48]. Also, there is a potential for a negative impact on the interbody cage and bone graft due to focal kyphosis resulting from the interspinous device [48]. Due to the lack of long-term clinical studies and these uncertainties, further prospective clinical studies are needed to compare the functional outcomes between interspinous fusion devices and pedicle screw constructs.


25.3.1 Case Example


A 51-year-old male presented with worsening low-back and leg pain and paresthesia in his feet. He attempted multiple forms of conservative treatment including physical therapy, epidural steroid injections, acupuncture, and massage without significant relief of his symptoms. Figure 25.4 displays his preoperative plain radiographs, which confirm the presence of degenerative disk disease with narrowing at L4–L5, anterior and posterior osteophytes, and mild degenerative retrospondylolisthesis. A one-level X-LIF procedure and posterior bilateral fusion at L4–L5 with Coflex-F® stabilization were performed. Eleven months postoperatively, the patient reported complete improvement of his preoperative symptoms. Postoperative radiographs (Fig. 25.5), performed 11 months after surgery, demonstrated fusion at L4–L5, increased disk and foraminal height, and no motion with flexion.

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Fig. 25.4
Preoperative radiographic images of a 51-year-old male. From left to right: lateral view, AP, flexion, and extension. The flexion image shows a Cobb angle of 12.3°, whereas the extension shows a Cobb angle of 19.1°


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Fig. 25.5
Radiographic images at 11 month post-surgery. From left to right: lateral view, AP, flexion, and extension. A one-level X-LIF procedure and posterior bilateral fusion at L4–L5 with Coflex-F® stabilization was performed. Cobb angle in the flexion image (15.3°) is less than 1°, and then the Cobb angle in the extension image (16.2°) confirming the procedure decreased motion


25.4 Integrated Fixation Fusion


The combination of fixation integrated into interbody fusion cages provides greater segmental rigidity and more physiologic loading through the segment, promoting optimal stability. Although integrated designs are used extensively in anteriorly placed cages both in lumbar and cervical, there are possible drawbacks associated with the introduction of these supplemental devices from a lateral approach. Screw angle, screw fixation, and plate designs are quite different than an anterior approach. However, additional surgical approaches may lead to prolonged operating time, larger skin incisions, soft tissue injuries, and higher infection rates. Certain authors reported screw or plate dislodgments, higher incidences of adjacent level degenerations, and heterotrophic ossifications [49] in multiple approach procedures. If sufficient stabilization can be achieved in a single approach without supplemental fixation from a secondary approach, then it may avoid such adverse effects resulting from additional posterior surgery and minimize the hospitalization time. Integrated fixation cages are a recently developed technology to reduce adverse effects from procedures involving interbody fusion cages.

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Sep 23, 2017 | Posted by in NEUROLOGY | Comments Off on Lateral Lumbar Interbody Fusion: A Review of the Current Clinical Outcomes of Different Supplemental Fixation Techniques
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