Method and apparatus for filling a cavity

Abstract

An implant for filling and / or distracting a body region, particularly a non-soft tissue cavity, has a plurality of segments wherein at least two of the segments are flexibly connected. The segments have a crush-strength sufficient to create and / or maintain the distraction of two or more non-soft tissue body surfaces, and to maintain the stability of the body region. The implant may be inserted into a cavity by an applicator having a cannula with a distal opening, and a rotary driver for applying force to move the implant within the cannula.

Description

FIELD [0001] Described here are non-soft tissue cavity implants, implant applicators, delivery devices, and methods for using them. In particular, the description relates to implants having a plurality of flexibly connected segments having a strength sufficient to support, to fill, to create, to maintain, or to distract a bone cavity such as might be found in a fractured vertebral body, and methods and devices for inserting implants into non-soft tissue cavities such as bone cavities. BACKGROUND [0002] Proper treatment of orthopedic conditions such as trauma, fractures, non-unions, tumors, cysts, and certain fusion procedures may involve filling a cavity that has been created by the pathology itself or by the action of a surgeon. Often the cavities are compressed, and require that the surfaces of the cavity be distracted from one another and then supported to return the bone structure to its anatomic position and form. Furthermore, because non-soft tissues such as bone have a struct...

AI Technical Summary

Benefits of technology

[0015] Broadly, described here are segmented implants for filling a non-soft tissue cavity, applicators for inserting implants, and methods of using the segmented implants and applicators to fill and / or distract tissue cavities. In particular, the implants described here may be used for filling and / or distracting non-soft tissue cavities such as a bone cavity. Generally, the segmented implants described here comprise a plurality of segments, where at least two of the segments are flexibly connected, and configured for insertion into a body region. The segments provide implant segment distractibility to the body region, and stability to the body region into which they are introduced. In some variations of the implant described herein, the segments have sufficient material strength to distract two or more non-soft tissue surfaces. In some versions, the material strength is crush strength, so that the segments of an implant have sufficient crush strength to allow and sustain the distraction of non-soft tissue surfaces. Thus, the implant is inserted into a cavity to distract, to expand, to reduce, or to support the cavity, typically filling the cavity and maintaining a desired shape.

[0024] The implant may comprise coated segments. The segments may have a medicinal coating. The segments may include pellets with a coating that allows them to crosslink with each other. The segments may be porous or solid. The segments may be imbedded or infused with any compound, for example a therapeutic or medicinal compound so long as the segments provide distractability and stability to the body region into which they are inserted, e.g. a bone cavity.

Problems solved by technology

Vertebral fractures may be painful and may deform the shape of the spine, resulting in unhealthy pressure on other parts of the body, loss of height, and changes in the body's center of gravity.

Untreated, such changes and the resulting discomfort can become permanent, since the bone heals without expanding the compression.

Existing methods of treating bone injuries such as compression fractures and bone voids may involve highly invasive or inadequate treatments.

When filling a bone cavity with bone filler using traditional vertebroplasty, fillers with lower viscosities may leak.

Further, even fillers having low viscosities may require the application of a high pressure to disperse the bone filler throughout the vertebral body.

However, application of high pressure also increases the risk of bone filler extravasation from the vertebral body.

Conversely, injecting a bone filler having a higher viscosity may provide an even greater risk of “leaking” bone filler into sensitive adjacent body areas.

Leaks or extrusion of the bone filler may be dangerous to a patient's health.

For example, posterior extravasation from a vertebral body may cause spinal cord trauma, perhaps resulting in paralysis.

Risk of leakage is even more acute when a bone filler is applied under pressure to expand a compression fracture, especially if the fracture has begun healing and requires substantial force to distract the cavity surfaces.

Furthermore, most bone cements and bone fillers are difficult to remove or to adjust.

Many bone cements, once set, are difficult or impossible to remove without further, highly invasive, surgery.

Even if the removal is attempted prior to the expiration of the setting time, the materials may have non-Newtonian flow characteristics requiring a substantial removal vacuum to achieve an initial and sudden movement.

However, the Grisoni device is not intended for distracting a non-soft tissue cavity, and has many disadvantages.

Calcium sulfate hemihydrate (Plaster of Paris) and similar materials have low crush strength, making them unreliable as materials to distract and later support a bone cavity, particularly during the early stages of the healing process.

Filling materials that are readily compressed or crushed, may shift within, or exit the bone cavity altogether, leading to detrimental changes in the shape of the corrected bone.

Materials with low crush strength (particularly those materials having crush strengths less than that of normal bone) are poor choices in withstanding the stress of distracting the bone surfaces, and may be unable to maintain the distracted shape of the bone after filling a bone cavity.

Because the Baumgartner implant is elastic, it may be less effective for filling and distracting body cavities benefiting from implants having some stiffness, such as non-soft tissue cavities.

However, Johnson's column of wafers is not amenable to providing uniform support to all surfaces of a bone cavity, when such support is needed.

Thus, these implants may be limited in strength and durability because of the inclusion of a releasable drug, as well as the properties and shape of the implant beads.

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