Composites and methods for treating bone

Abstract

A system and method for treating bone abnormalities including vertebral compression fractures and the like. In one vertebroplasty method, a fill material is injected under high pressures into cancellous bone wherein the fill material includes a flowable bone cement component and an elastomeric polymer component that is carried therein. The elastomer component can further carry microscale or mesoscale reticulated elements. Under suitable injection pressures, the elastomeric component ultimately migrates within the flowable material to alter the apparent viscosity across the plume of fill material to accomplish multiple functions. For example, the differential in apparent viscosity across the fill material creates a broad load-distributing layer within cancellous bone for applying retraction forces to cortical bone endplates. The differential in apparent viscosity also transitions into a flow impermeable layer at the interface of cancellous bone and the flowable material to prevent extravasion of the flowable bone cement component.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims benefit of Provisional U.S. Patent Application Ser. No. 60 / 578,182 filed Jun. 9, 2004 (Docket No. S-7700-030) titled Scaffold Composites and Methods for Treating Abnormalities in Bone, the entire contents of which are hereby incorporated by reference in their entirety and should be considered a part of this specification.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to bone implant materials and methods and more particularly to composite materials including an elastomer component for treating abnormalities in bones such as compression fractures of vertebra, necrosis of femurs, joint implants and the like. An exemplary method includes introducing a flowable composite material into the interior of a bone wherein increasing pressures result in the elastomer component causing a differential apparent viscosity within selected regions across the flowable material to thereby ...

AI Technical Summary

Benefits of technology

[0019] The invention provides systems and method of treating bone abnormalities including vertebral compression fractures, bone tumors and cysts, avascular necrosis of the femoral head and the like. In one embodiment, the invention comprises a bone infill system or implant system with a fill material that includes a flowable component and an elastomeric polymer component that is deformable in-situ (FIG. 1A). In one embodiment, the elastomer component comprises a matrix of base elastomer and a filler of microscale or mesoscale reticulated elements (FIG. 1B). The elastomeric component corresponding to the invention performs multiple functions, for example, (i) forming a load-distributing structure between a bone fill material or structure and the elastomer component; (ii) mechanically creating a seal at the interface of cancellous bone and bone fill material or structure to prevent extravasion of a flowable material, (iii) creating a substantially porous layer around the surface of non-porous bone fill material or structures and / or (vi) creating an insulative layer around the surface of an exothermic bone fill material. The elastomer component can be used in bone support treatments or in treatments to move apart cortical bone surfaces as in treating vertebral compression fractures.

Problems solved by technology

Medical advances aimed at slowing or arresting bone loss from aging have not provided solutions to this problem.

Osteoporosis affects the entire skeleton but most commonly causes fractures in the spine and hip.

Spinal or vertebral fractures also have serious consequences, with patients suffering from loss of height, deformity and persistent pain which can significantly impair mobility and quality of life.

Osteoporosis describes a condition of decreased bone mass that leads to fragile bones which are at an increased risk for fractures.

In an osteoporotic bone, the sponge-like cancellous bone has pores or voids that increase in dimension, making the bone very fragile.

In an elderly patient, bone resorption can surpass bone formation thus resulting in deterioration of bone density.

The bilateral transpedicular approach is typically used because inadequate PMMA infill is achieved with a unilateral approach.

Since the PMMA needs to be forced into cancellous bone, the technique requires high pressures and fairly low viscosity cement.

Since the cortical bone of the targeted vertebra may have a recent fracture, there is the potential of PMMA leakage.

Leakage of PMMA during vertebroplasty can result in very serious complications including compression of adjacent structures that necessitate emergency decompressive surgery.

The exothermic reaction of PMMA carries potential catastrophic consequences if thermal damage were to extend to the dural sac, cord, and nerve roots.

Vertebroplasty patients often return with new pain caused by a new vertebral body fracture.

Leakage of cement into an adjacent disc space during vertebroplasty increases the risk of a new fracture of adjacent vertebral bodies.

Another life-threatening complication of vertebroplasty is pulmonary embolism.

The vapors from PMMA preparation and injection are also cause for concern.

Another disadvantage of PMMA is its inability to undergo remodeling—and the inability to use the PMMA to deliver osteoinductive agents, growth factors, chemotherapeutic agents and the like.

Yet another disadvantage of PMMA is the need to add radiopaque agents which lower its viscosity with unclear consequences on its long-term endurance.

In both higher pressure cement injection (vertebroplasty) and balloon-tamped cementing procedures (kyphoplasty), the methods do not provide for well controlled augmentation of vertebral body height.

Thus, the reduction of a vertebral compression fracture is not optimized or controlled in high pressure balloons as forces of balloon expansion occur in multiple directions.

Expansion of the balloon under high pressures close to cortical bone can fracture the cortical bone, or cause regional damage to the cortical bone that can result in cortical bone necrosis.

Such cortical bone damage is highly undesirable and results in weakened cortical endplates.

Kyphoplasty also does not provide a distraction mechanism capable of 100% vertebral height restoration.

Further, the kyphoplasty balloons under very high pressure typically apply forces to vertebral endplates within a central region of the cortical bone that may be weak, rather than distributing forces over the endplate.

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