Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1999-12-17
2002-04-16
Milano, Michael J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S013110, C623S023570
Reexamination Certificate
active
06371985
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to prostheses. More particularly, this invention relates to new prostheses and methods for safely and effectively restraining such prostheses using a combination of direct immediate attachment to stabilize the prostheses while attachment to native connective tissue by ingrowth to the prostheses proceeds naturally over time.
BACKGROUND OF THE INVENTION
Implants or prostheses are employed for restoring damaged upper and lower extremity bones such as fingers, wrists, elbows, knees and ankles of human patients. These prostheses are especially useful in the reconstruction of joints which, for example, have been damaged by pathological conditions such as rheumatoid arthritis, degenerative arthritis, aseptic necrosis, and for treating trauma which may have a debilitating effect on articular joints.
Extra articular bone segment replacement includes long bones replaced after destruction processes, such as trauma and tumors. For example, if a segment of femur (thigh) or radius (forearm) bone shafts is being destroyed by malignant tumor, it may be replaced by a transplanted cadaver bone graft of that segment. Native tendons with connected muscles may be reattached to that bone graft to preserve the function of limb motion. Similarly, a synthetic bone replacement, such as one made of ceramic or metal, could be used to replace those segments.
Unfortunately, some joint implant designs available currently or described in the past have drawbacks arising from their construction and design. For example, current and past scaphoid and lunate carpal bone replacements generally cannot reproduce the normal and vital kinematics of that joint, normally dictated by native ligamentous restraints.
Joint replacement designs or arthroplasties which rely solely on man-made mechanical restraint mechanisms of various types (e.g. semi-constrained elbow arthroplasties), also may fail to properly simulate or replace native ligamentous and capsular restraints. Many arthroplasties also attempt to change the native biomechanical properties of the replaced joint instead of reproducing the native properties. New prostheses which restore native biomechanical properties are discussed and claimed in the present inventor's U.S. Pat. Nos. 5,702,468 and 5,888,203, which are incorporated by reference.
There are three types of arthroplasties: 1) unconstrained, 2) semi-constrained and 3) fully constrained. A common flaw with all of these current joint replacement designs is the inability to reconstruct and re-attach the replaced joint's vital native capsular and ligamentous restraints, which dictate, in large measure, the behavior and stability of the joint (i.e., its kinematics).
The present invention may apply to any synovial or diarthroidial human joint, or to extra-articular bone segment replacement. One preferred application of the invention is to joints whose motion and stability are both quantitatively and qualitatively significant and therefore functionally important.
The definitions of “joints” and “articulations”, adopted from
Stedman's Medical Dictionary,
1982, pp. 126-7 and p. 737, refer to three types of “articulations”: fibrous, cartilaginous, and synovial. The synovial articulation is the preferred application of this invention. A synovial articulation (or diarthrodial joint) is a joint allowing various amounts and types of motion in which the bony surfaces are covered with a layer of hyaline or fibrous cartilage. There is a joint cavity containing synovial fluid and lined with a synovial membrane, reinforced by a fibrous capsule and by ligaments.
In order to better explain the vital importance of the natural capsular and ligamentous restraints in a synovial joint, and to illustrate the shortcomings of arthroplasties which do not reconstruct these native restraints, replacement of wrist carpal bones will be discussed below. This discussion will illustrate the anatomy, function and kinematics of the carpus with an emphasis on demonstrating the necessity and unique contribution of the invention as it applies to replacing the scaphoid and lunate carpal bones. This invention, however, is not limited to scaphoid and lunate prostheses but rather extends to all upper and lower extremity arthroplasties in any synovial or diarthroidial joints which are functionally important, as well as to extra-articular bone segment replacement.
Wrist movement is apportioned between the radiocarpal and midcarpal joints in a very complex manner. Accordingly, it is essential that a carpal implant be restrained in a manner as close as possible to that achieved with the native carpal bones and native capsule and ligaments in order to maintain the normal kinematics of the carpus. This serves to preserve the shape of the implant and to prevent wear, fracture, dislocation and particulate synovitis.
To date, a satisfactory technique for reconstruction of native restraints (capsule, ligament and tendon) with arthroplasties has not been achieved. The present invention is uniquely designed to allow the surgeon to accurately and predictably replace native connective tissue restraints and thus prevent the above-mentioned causes of failure.
Accordingly, an object of the present invention is to provide an improved method and prostheses for replacing upper or lower extremity bone(s) in a joint of a human.
A further object of the present invention is to provide an improved method and prostheses for replacing extra-articular bone segments, that is, segments of bones outside of human bone joints.
It is another object of the present invention to provide prostheses for replacing upper or lower extremity bone(s) of a joint in which the prostheses are further restrained using ingrown native ligament, capsule, and tendon.
It is yet another object of the present invention to provide prostheses for replacing upper or lower extremity bone joints as well as extra-articular bone segments in which the reconstruction of native connective tissue restraints encourages normal joint global kinematics, and tendon-muscle function, respectively.
It is a further object of the present invention to provide a method and prostheses for replacing upper or lower extremity bone joints as well as extra-articular bone segments by direct immediate attachment to ligament, capsule, bone, or tendon adjacent the bone or portion of which is to be replaced by the prosthesis while ingrowth adhesion from native ligament, capsule, or tendon to discrete ingrowth receptive zones of the prosthesis proceeds naturally over time, preferably with substantial vascularized tissue ingrowth at the ingrowth receptive zones.
These and other objects and advantages of the invention will appear hereinafter.
SUMMARY OF THE INVENTION
The present invention accomplishes the foregoing objects by providing a surgically implantable bone prosthesis including a body member, means for direct immediate attachment of the body member, and at least one ingrowth receptive stationing site on and/or within the body member for delayed ingrowth adhesion naturally over time. The direct immediate attachment of the body member as well as the ingrowth which proceeds over time is to adjacent native connective tissue (ligament, capsule or tendon).
The body member is made totally or partially from any appropriate material including but not limited to a bio-compatible, medically inert material such as ceramic, titanium, a stainless steel alloy, a non-ceramic substrate with a ceramic or other biocompatible, medically inert coating, or an open-celled lattice tantalum metal-carbon foam composite material. The body member may comprise a single component or body member as illustrated in
FIGS. 1-15
a,
or it may be made up of at least two components or body members (e.g.
FIGS. 16-18
) contoured to resemble the shape of a bone, bones or a portion of a bone or bones which are to be replaced by the prosthesis.
In order to achieve the desired tissue ingrowth over time, the body member must be buttressed and affixed to adjacent connective tissue. Mooring means are provided to dra
Michael Best & Friedrich LLC
Milano Michael J.
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