WO2006053212A2

WO2006053212A2 - Hydrogel bone void filler

Info

Publication number: WO2006053212A2
Application number: PCT/US2005/040915
Authority: WO
Inventors: Jill M. Embry
Original assignee: Medtronic, Inc.
Priority date: 2004-11-12
Filing date: 2005-11-09
Publication date: 2006-05-18
Also published as: US20060106392A1; US8663225B2; WO2006053212A3

Abstract

A bone void filler material, including a hydrogel component provided by microparticulates of pre-set hydrogel material dispersed within a carrier component to maintain the microparticulates substantially proximate to one another so that the resulting fill material is rendered as a substantially flowable mass.

Description

HYDROGEL BONE VOID FILLER

FIELD OF THE INVENTION

This invention relates generally to bone treatment agents. More

particuTarly, this invention relates to bone treatment agents for introduction into bone

voids and particularly compressed vertebral bodies for maintaining the height of

compressed vertebral bodies and inhibiting further collapse.

BACKGROUND AND SUMMARY OF THE INVENTION

Vertebroplasty and kyphoplasty are examples of surgical procedures for

treating fractured and diseased bones. In these procedures a bone void fill material or

filler, such as a bone cement, is introduced, as by injection, into the fractured bone, e.g.,

the vertebral body. Improvement is desired in the composition of bone void fillers.

In this regard, the invention relates to a bone void filler material that

incorporates a hydrogel component provided by microparticulates made of a pre-set,

e.g., fully polymerized, hydrogel, dispersed within a carrier component, preferably

provided by an adhesive, to maintain the hydrogel particulates proximate to one another

so that the fill material is a substantially cohesive and flowable mass. The bone void

fill material may be introduced, such as via a needle, into a void of a bone, such as a

cavity within a vertebral body during a vertebroplasty procedure.

The microparticulates of the hydrogel component are substantially a solid,

but swell upon exposure to body fluids to substantially fill the vertebral body. The carrier component helps to maintain the microparticulates proximate to one another and

yield a flowable, injectable mass that remains cohesive within the bone void.

In another aspect, the invention relates to a method of filling a bone void. The

methocfincludes the steps of providing microparticulates of apre-sethydrogel material;

providing a flowable carrier; dispersing the microparticles within the carrier

component to render a substantially flowable mass; and flowably introducing the mass

of microparticles dispersed within the carrier component into a bone void.

DETAILED DESCRIPTION

The invention relates to bone treatment agent, preferably a bone void

filler, that is suitable for use in filling voids in bony structures and for treatment of

fractured bone. In particular, the treatment agent is configured for use in surgical

procedures wherein the agent is introduced into compressed vertebral bodies for

treatment of the compressed vertebral bodies to fill void areas and aid in at least

partially restoring the height of the patient and for inhibiting further collapse of the

vertebral body. In particular, the treatment agents of the invention are preferably

utilized in conjunction with vertebral lift devices such as described in U.S. Applications

Serial No. /Op^ fJO. entitled IMPLANTABLE VERTEBRAL BODY LIFT and

filed concurrently herewith.

In a preferred embodiment, the invention provides a biocompatible bone

void fill material that includes a pre-set or pre-solidified hydrogel component and an

carrier component. In this regard, it will be understood that the hydrogel component

- ? . is provided by microparticulates of pre-set or polymerized hydrogel material and the

carrier component, preferably an adhesive, maintains the microparticulates substantially

proximate so that the resulting fill material is rendered as a substantially flowable mass.

The bone void fill material may be flowably introduced, such as via a

needle, into a void of a bone, such as a cavity within a vertebral body during a

vertebroplasty procedure. The hydrogel microparticulates swell upon exposure to body

fluids to substantially fill the vertebral body. The carrier component helps to maintain

the hydrogel components proximate to one another to yield a flowable composition and

to provide a substantially cohesive fill material.

In this regard, and with reference to FIG. 1, there is shown a vertebral

body, such as a vertebra lumbalis 10, having a void 12. A quantity of fill material 14

is shown within the void 12. The fill material 14 includes a hydrogel component

provided by microparticulates 16 made of pre-set hydrogel material and a carrier

component 18. An enclosure of mesh 20 is preferably also provided within the void

12 for receiving the fill material 14.

Hydrogels are networks of polymer chains that are set or solidified so as

to form a three-dimensional structure that is substantially insoluble in water and which

is highly hydrophillic so that when exposed to water it absorbs water and swells. The

polymers may be natural or synthetic polymers and setting or solidification of the

polymeric chains may be accomplished by various well-known mechanisms, such as

by crosslinking and by coagulation. Thus, it will be understood that the hydrogel components utilized in the bone void fill material of the invention are pre-set or pre-

solidified or polymerized prior to their introduction into the body.

The hydrogel component is preferably made of non-biodegradable

polymέrs, examples of which include polyacrylic acid polymers, polyethylene glycol

polymers such as polyethylene glycol co polyethylene oxide, hydrophillic segmented

urethanes, polyvinylpyrrolididone, polyvinylacrylate, polymethacrylic acid and

polymethacrylates, and PLA-PEG copolymers. The hydrogel component may also

preferably be made of biodegradable polymers, examples of which inlude poly(α-

hydroxyesters), ρoly(L-lactic acid), poly(DL-lactic acid), andpoly(dl-lactic-co-glycolic

acid).

The pre-set hydrogel components for use in the present invention are

preferably provided as microparticles, such as microspheres, preferably ranging in size

from about 50 to about 500 microns.

Preparation of hydrogel microparticles such as microspheres and the like

may be accomplished by well known techniques such as solvent emulsion or solvent

^■ evaporation, microdispersion, interfacial polymerization, coacervation, cryogenic

grinding, and suspension. For example, in solvent emulsion or evaporation, the

polymer is dissolved in an organic solvent and suspended in an aqueous phase that

contains a surface active agent. The resulting emulsion is stirred as the organic solvent

evaporates, leaving solid microspheres. The carrier component is preferably provided by an adhesive material,

most preferably cellulose and/or bioadhesive polymers such as cyanoacrylate and

flowable gelatin hydrogels including gelatin-gluteraldehyde, gelatin-poly (L-glutamic

acid) (PLGA), and gelatin-alginate-carbodiimide. In the case of the use of gelatin

hydrogels as carrier agents, these materials may be polymerized or subsequently

polymerized after introduction into the body. The carrier component is formulated as

a suspension into which the pre-set hydrogel component may be dispersed.

In a preferred embodiment, the bone void fill material preferably contains

the pre-set hydrogel component and the carrier component in amounts such that the

percentage (by weight) of the carrier component to the hydrogel component ranges

from about 5 to about 15 percent. The resulting bone void fill material preferably has

an elastic modulus of from about 15 to about 25 Gpa and a compressive strength of

from about 5 to about 20 Mpa.

The pre-set hydrogel component and the carrier component may be

combined as by pre-mixing in a syringe or via a dual-barrel syringe that mixes the

streams at the syringe/needle interface. In the event unpolymerized gelatin hydrogel

is selected as the carrier material, the gelatin hydrogel material may be suspended in an

alginate solution and combined with a sodium chloride solution introduced into the

syringe to initiate a crosslinking reaction to polymerize the carrier component in situ.

The bone void fill material may also preferably include additives such as

biocompatible fibrous materials, such as carbon fibers, to provide mechanical reinforcement to the bone void filler material. Other preferred fibrous materials for use

as additives include nitinol fibers and coils, polyurethane fibers and coils, stainless steel

fibers and nylon. Preferred fibers have a length of from about 200 microns to about 1

mm, and a width of from about 25 microns to about 50 microns. The fibers are

preferably incorporated when combining the hydrogel and adhesive components.

In addition, if it is desired to render the filler material radiopaque, a

radiopacifϊer material may be included. Examples of radiopacifier materials include

gold, tantalum, and barium compositions such as barium sulfate. The radiopacifier

materials are generally available in a powder form and may be encapsulated into the

pre-set hydrogel microparticles or mixed in with the adhesive suspension.

Other preferred additives include pharmacological agents such as growth

factors, proteins, amino acids, polysaccharides, and antibiotics and other

pharmaceutics. Preferred growth factors include fibroblast growth factors (FGF), bone

morphogenetic growth factors (BMP), and platelet-derived growth factors (PDGF).

Preferred proteins include collagen and herapin. Preferred polysaccharides include

glycosaminoglycon (GAG). Preferred pharmaceutics include biophosphates such as

^' pamidronate. These additives may be encapsulated or crosslinked to side chains of the

pre-set hydrogel microparticles.

Accordingly, the foregoing description of certain exemplary embodiments

of the present invention has been provided for purposes of illustration only, and it is

understood that numerous modifications or alterations may be made in and to the illustrated embodiments without departing from the spirit and scope of the invention

as defined in the following claims.

Claims

WHAT IS CLAIMED IS:

Claim 1. A bone void filler material, comprising:

a hydrogel component provided by microparticulates of pre-set

hydrogel material dispersed within a carrier component to maintain the

microparticulates substantially proximate to one another so that the resulting fill

material is rendered as a substantially flowable mass.

Claim 2. The filler material of claim 1 , wherein the microparticles range in

size from about 50 to about 500 microns

Claim 3. The filler material of claim 1 , wherein the microparticles are non¬

biodegradable polymers

Claim 4. The filler material of claim 1 , wherein the microparticles are non¬

biodegradable polymers selected from the group consisting of polyacrylic acid

polymers, polyethylene glycol polymers, hydrophillic segmented urethanes,

polyvinylpyrrolididone, polyvinylacrylate, polymethacrylic acid andpolymethacrylates,

and PLA-PEG copolymers.

Claim 5. The filler material of claim 1, wherein the microparticles are

biodegradable polymers.

Claim 6. The filler material of claim 1, wherein the microparticles are

biodegradable polymers selected from the group consisting of poly(α-hydroxyesters),

poly(L-lactic acid), poly(DL-lactic acid), and poly(dl-lactic-co-glycolic acid).

Claim 7. The filler material of claim 1 , wherein the carrier component

comprises an adhesive suspension.

Claim 8. The filler material of claim 1, wherein the carrier component

comprises a cellulose.

Claim 9. The filler material of claim 1, wherein the carrier component

comprises an alginate.

Claim 10. The filler material of claim 1 , wherein the percentage (by weight)

of the carrier component to the hydrogel component is from about 5 to about 15

percent.

Claim 11. The filler material of claim 1 , wherein the filler material has an

elastic modulus of from about 15 to about 25 Gpa and a compressive strength of from

about 5 to about 20 Mpa.

- Q -

Claim 12. The filler material of claim 1, wherein the filler material further

comprises one or more additives selected from the group consisting of biocompatible

fibrous materials, radiopacifier materials, and pharmacological agents.

Claim 13. A method of filling a bone void, the method comprising the steps

of:

providing microparticulates of a pre-set hydrogel material;

providing a flowable carrier;

dispersing the microparticles within the carrier component to render a

substantially flowable mass; and

flowably introducing the mass of microparticles dispersed within the

carrier component into a bone void.