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A Novel, Minimally-Invasive Approach to Repair Degenerative Disk Disease in an Ovine Model Using Injectable Polymethyl-Methacrylate and Bovine Collagen (PMMA/BC)

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ABSTRACT

Background :

The natural, inflammatory repair processes of an injured intervertebral degenerative disc can propagate further injury and destruction. While there are many different treatment modalities of the pain related to degenerative disc disease, none are actually reparative in nature. Treatment strategies to repair a degenerative disc without inducing a destructive inflammatory milieu have been elusive. 

Purpose:

The purpose of this experiment is to discover the feasibility of reconstructing an injured intervertebral disc using an injected, inert polymer as the foundation for endogenous collagen growth.

Study Design:

In this ovine model of six subjects in total, we introduce a modality where a large inert polymer, polymethyl methacrylate (PMMA), in conjunction bovine collagen (BC) is injected into the intervertebral disc. Following six months of observation, histologic specimens were evaluated macroscopically and microscopically for evidence of a benefit of the injectable PMMA/BC.

Methods:

We obtained six merino sheep for this study. Concentric injuries were made to four of their lumbar intervertebral discs. Two of those levels were treated with a percutaneous injection of 0.3 cc of PMMA/BC. The remaining lumbar levels were left untreated and were our controls. After six months, all subjects were sacrificed. Their four levels were extracted and were examined macroscopically and microscopically.

Results:

All subjects tolerated the lumbar injury and percutaneous injection of PMMA/BC well. After the six month interval, all subjects have demonstrated an intact architecture of their lumbar disc height at the macroscopic and microscopic level. Microscopically, there was no evidence of external migration of the PMMA/BC microspheres, nor was there any evidence of an inflammatory response by its presence. Notably, the PMMA/BC microspheres were well-incorporated into the concentric disc tears and had undergone endogenous collagen formation in its environment. Treatment levels were revealing for maintenance of disc height without evidence of an ongoing degeneration. The controlled levels were revealing for continued disc degeneration with loss of disc height and evolving injury at the level of the concentric tear.

Conclusions:

This ovine model demonstrates a novel and promising technique for prevention and arrest of lumbar intervertebral disc degeneration.

No MeSH data available.


Illustration of a concentric annular injury, where the normal scalloping of the annulus fibrosus is expanded between the concentric lamellar architecture.
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FIG1: Illustration of a concentric annular injury, where the normal scalloping of the annulus fibrosus is expanded between the concentric lamellar architecture.

Mentions: A healthy intervertebral disc has four distinct tissue types: the annulus fibrosus, the transition zone, the nucleus pulposus, and the endplate [14-15]. The annulus fibrosus, a strong material that makes up the perimeter of the disc, is composed primarily of type I collagen which exhibits robust tensile strength. The outer portion of the annulus fibrosus is composed of about 30-90 layers of collagen fibrils called lamellae. A less-dense inner portion of the annulus fibrosus contains fibroblast-like cells and lacks organization. The annulus is often the first site to be injured in the onset of DDD, after which scar tissue resulting from the healing of small tears can cause progressive weakening of the disc [12]. An injured annulus is represented by a concentric annular tear, where the normal scalloping of the layers of the annulus fibrosus is expanded by an injury. Figure 1 illustrates this type of injury. 


A Novel, Minimally-Invasive Approach to Repair Degenerative Disk Disease in an Ovine Model Using Injectable Polymethyl-Methacrylate and Bovine Collagen (PMMA/BC)
Illustration of a concentric annular injury, where the normal scalloping of the annulus fibrosus is expanded between the concentric lamellar architecture.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5016043&req=5

FIG1: Illustration of a concentric annular injury, where the normal scalloping of the annulus fibrosus is expanded between the concentric lamellar architecture.
Mentions: A healthy intervertebral disc has four distinct tissue types: the annulus fibrosus, the transition zone, the nucleus pulposus, and the endplate [14-15]. The annulus fibrosus, a strong material that makes up the perimeter of the disc, is composed primarily of type I collagen which exhibits robust tensile strength. The outer portion of the annulus fibrosus is composed of about 30-90 layers of collagen fibrils called lamellae. A less-dense inner portion of the annulus fibrosus contains fibroblast-like cells and lacks organization. The annulus is often the first site to be injured in the onset of DDD, after which scar tissue resulting from the healing of small tears can cause progressive weakening of the disc [12]. An injured annulus is represented by a concentric annular tear, where the normal scalloping of the layers of the annulus fibrosus is expanded by an injury. Figure 1 illustrates this type of injury. 

View Article: PubMed Central - HTML - PubMed

ABSTRACT

Background :

The natural, inflammatory repair processes of an injured intervertebral degenerative disc can propagate further injury and destruction. While there are many different treatment modalities of the pain related to degenerative disc disease, none are actually reparative in nature. Treatment strategies to repair a degenerative disc without inducing a destructive inflammatory milieu have been elusive. 

Purpose:

The purpose of this experiment is to discover the feasibility of reconstructing an injured intervertebral disc using an injected, inert polymer as the foundation for endogenous collagen growth.

Study Design:

In this ovine model of six subjects in total, we introduce a modality where a large inert polymer, polymethyl methacrylate (PMMA), in conjunction bovine collagen (BC) is injected into the intervertebral disc. Following six months of observation, histologic specimens were evaluated macroscopically and microscopically for evidence of a benefit of the injectable PMMA/BC.

Methods:

We obtained six merino sheep for this study. Concentric injuries were made to four of their lumbar intervertebral discs. Two of those levels were treated with a percutaneous injection of 0.3 cc of PMMA/BC. The remaining lumbar levels were left untreated and were our controls. After six months, all subjects were sacrificed. Their four levels were extracted and were examined macroscopically and microscopically.

Results:

All subjects tolerated the lumbar injury and percutaneous injection of PMMA/BC well. After the six month interval, all subjects have demonstrated an intact architecture of their lumbar disc height at the macroscopic and microscopic level. Microscopically, there was no evidence of external migration of the PMMA/BC microspheres, nor was there any evidence of an inflammatory response by its presence. Notably, the PMMA/BC microspheres were well-incorporated into the concentric disc tears and had undergone endogenous collagen formation in its environment. Treatment levels were revealing for maintenance of disc height without evidence of an ongoing degeneration. The controlled levels were revealing for continued disc degeneration with loss of disc height and evolving injury at the level of the concentric tear.

Conclusions:

This ovine model demonstrates a novel and promising technique for prevention and arrest of lumbar intervertebral disc degeneration.

No MeSH data available.