Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-10-20
2001-03-27
Smith, Jeffrey A. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S017110
Reexamination Certificate
active
06206924
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a three-dimensional structure for use as a bone mass replacement or fusion augmentation device. In particular, this structure is specifically engineered from interconnecting, non-random metallic segments so as to minimize the volume of the metal to void and thereby maximize potential volume for reconstructive bone growth. The metallic segments or filaments are joined to form regular repeating geometric shapes to provide maximum strength and minimize potential shear planes through the structure. A particularly favored geometric shape is a modified dodecahedron based on pentagons. The resulting structure may have a general rectangular block configuration, a cylindrical configuration which can include a larger defined void area in the center.
SUMMARY OF THE INVENTION
The present invention provides an engineered three-dimensional structure, which has a goal of providing a structure for bone to grow through for fusion or reconstructive surgery. The structure is further intended to be strong enough to provide support to the skeletal and muscular structure during bone rehabilitation, i.e. during the healing process when bone reconstruction occurs.
Thus, it is a goal of the present invention to provide a structure which is self-supporting meaning that no further substrate or support is required to provide the necessary support characteristics during rehabilitation. This contrast with implants such as acetabular cups having porous coatings. Likewise, these coatings can also be distinguished since the pores tend to be random and substantially distinguished since the pores tend to be random and substantially smaller (by at least a magnitude or more of size) than the pores of the present invention.
Further, the structure is constructed of discrete subcomponents which are repeating geometric shapes, constructed of filamentary elements so as to provide regular intersticial pores and/or voids of an appropriate shape and size to allow for bone. Thus, while the filamentary segments are providing structural support, slow in-growth can occur into the void area. This growth, can be encouraged and/or augmented through the use of bone graft or bone substitutes. By “regular” it is meant that the component parts are uniform, or of the same kind or structure or shape or size, or having repeating units of the same size and/or angle. By “geometric” it is meant that at least some of the component parts are formed of straight lines, bars, or crosses. By “ordered” it is meant that the shapes are arranged in a sequence or pattern which is not random but which possesses symmetry and/or repetition. In a further embodiment the structure has a central void area to accommodate the bone graft or bone substitute.
An additional aspect of the invention is the provision of a structure, which is “space-filling” meaning that structure can be expanded to any size and will maintain its shape as a repeating structure. Thus, the structure is ordered and not random. It is homogeneous and provides multiple planes of symmetry.
The implant is preferably constructed from a bio-compatible cast metal such as titanium or a titanium alloy so as to maximize strength and minimize the metal artifact which would appear on sectional CT scans. The structure can be modified to generate the desired implant stiffness for a variety of applications. The structure can also be modified to increase its strength and resistance to fatigue as is necessary. Further, once the fundamental structure has been established by constructing the component repeating shapes, individual filamentary members may be modified or eliminated to provide for functional structures including for example voids for bone growth voids or means to attach fasteners.
Potential applications include spinal fusions such as posterior lumbar inter-body fusion (“PLIF”), anterior lumbar and inter-body fusion (“ALIF”), inter-body fusion ring, long-bone reconstruction such as humoral or femoral reconstruction, tibial-plateau reconstruction, cranial facial applications including mixillo-facial reconstruction, and pelvic-defect reconstruction. Thus, in general, the present structure has many orthopaedic applications for reinforcing weak, bony tissue.
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Hudak & Shunk Co.
Robert Eduardo C.
Shunk Laura F.
Smith Jeffrey A.
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