U.S. patent application number 13/827849 was filed with the patent office on 2013-08-08 for extra-articular implantable mechanical energy absorbing assemblies having two deflecting members and methods.
This patent application is currently assigned to Moximed, Inc.. The applicant listed for this patent is Moximed, Inc.. Invention is credited to Anton G. Clifford, Toru Mino, Alan C. Regala, Clinton N. Slone.
Application Number | 20130204378 13/827849 |
Document ID | / |
Family ID | 43879910 |
Filed Date | 2013-08-08 |
United States Patent
Application |
20130204378 |
Kind Code |
A1 |
Slone; Clinton N. ; et
al. |
August 8, 2013 |
EXTRA-ARTICULAR IMPLANTABLE MECHANICAL ENERGY ABSORBING ASSEMBLIES
HAVING TWO DEFLECTING MEMBERS AND METHODS
Abstract
Implantable assemblies for manipulating energy transferred by
members defining an anatomical joint, and methods of implanting and
using. The members of the anatomical joint collectively define a
path of motion. An assembly includes a first component configured
to be attached to a first member of the anatomical joint; a second
component configured to be attached to a second member of the
anatomical joint; and a joint joining the first and second
components. The first component includes a first flex member and
the second component includes a second flex member. The first and
second flex members are configured to flex to absorb energy
transferred by the members of the anatomical joint.
Inventors: |
Slone; Clinton N.; (San
Francisco, CA) ; Clifford; Anton G.; (Mountain View,
CA) ; Mino; Toru; (Somerville, MA) ; Regala;
Alan C.; (Seattle, WA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Moximed, Inc.; |
Hayward |
CA |
US |
|
|
Assignee: |
Moximed, Inc.
Hayward
CA
|
Family ID: |
43879910 |
Appl. No.: |
13/827849 |
Filed: |
March 14, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12582178 |
Oct 20, 2009 |
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13827849 |
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Current U.S.
Class: |
623/20.27 |
Current CPC
Class: |
A61B 2017/567 20130101;
A61F 2/3886 20130101; A61F 2002/0864 20130101; A61F 2/0811
20130101; A61F 2/38 20130101; A61B 17/56 20130101; A61F 2/384
20130101; A61F 2002/0888 20130101; A61F 2002/0829 20130101 |
Class at
Publication: |
623/20.27 |
International
Class: |
A61F 2/38 20060101
A61F002/38 |
Claims
1-27. (canceled)
28. A method for treating a knee joint having first and second
articular surfaces, comprising: implanting a first component to a
first anatomical member of the knee joint subcutaneously and
extra-capsularly on a lateral side of the knee joint; and reducing
the load experienced by the first articular surface during the knee
joint's higher loading positions and not reducing the load
experienced by the first articular surface during the knee joint's
lower load positions.
29. The method of claim 28, wherein in the step of reducing the
load comprises reducing the load transient variably experienced by
the first articular surface in the range of 1-40%.
30. The method of claim 29, wherein the load transient variably
experienced by the first articular surface is reduced in the range
of 5-30%.
31. The method of claim 28, further comprising attaching a second
component to a second anatomical member of the knee joint, wherein
a joint joins said first and second components.
32. The method of claim 31, wherein the first component includes a
first flex member and said second component includes a second flex
member.
33. The method of claim 32, further comprising flexing said first
and second flex members to transiently variably reduce load between
the first and second articular surfaces.
34. The method of claim 28, wherein the first component includes a
first flex member.
35. The method of claim 28, further comprising permitting at least
a limited amount of axial rotation between the first and second
articular surfaces of the knee joint.
Description
FIELD OF THE INVENTION
[0001] The present invention is directed towards systems and
methods for treating, tissue of a body and more particularly,
towards approaches designed to reduce mechanical energy transferred
between members forming an anatomical joint.
BACKGROUND OF THE INVENTION
[0002] An anatomical joint is the location at which two or more
bones make contact. They are constructed to allow movement and
provide mechanical support, and are classified structurally and
functionally. Structural classification is determined by how the
bones connect to each other, while functional classification is
determined by the degree of movement between the articulating
bones. In practice, there is significant overlap between the two
types of classifications.
[0003] There are three structural classifications of anatomical
joints, namely fibrous or immovable anatomical joints,
cartilaginous anatomical joints and synovial anatomical joints.
Fibrous/Immovable bones are connected by dense connective tissue,
consisting mainly of collagen. The fibrous joints are further
divided into three types: [0004] sutures which are found between
bones of the skull; [0005] syndesmosis which are found between long
bones of the body; and [0006] gomphosis which is an anatomical
joint between the root of a tooth and the sockets in the maxilla or
mandible.
[0007] Cartilaginous bones are connected entirely by cartilage
(also known as "synchondroses"). Cartilaginous joints allow more
movement between bones than a fibrous joint but less than the
highly mobile synovial joint. An example of a cartilaginous joint
is an intervertebral disc. Synovial joints have is space between
the articulating bones for synovial fluid. This classification
contains anatomical joints that are the most mobile of the three,
and includes the knee and shoulder. These are further classified
into ball and socket joints, condyloid joints, saddle joints, hinge
joints, pivot joints, and gliding joints.
[0008] Anatomical joints can also be classified functionally, by
the degree of mobility they allow. Synarthrosis joints permit
little or no mobility. They can be categorized by how the two bones
are joined together. That is, synchrondoses are anatomical joints
where the two bones are connected, by a piece of cartilage.
Synostoses are where two bones that are initially separated
eventually fuse together as a child approaches adulthood. By
contrast, amphiarthrosis joints permit slight mobility. The two
bone surfaces at the anatomical joint are both covered in hyaline
cartilage and joined by strands of fibrocartilage. Most
amphiarthrosis joints are cartilaginous.
[0009] Finally, diarthrosis joints permit a variety of movements
(e.g. flexion, adduction, pronation). Only synovial joints are
diarthrodial and they can be divided into six classes: 1. ball and
socket--such as the shoulder or the hip and femur; 2. hinge--such
as the elbow; 3. pivot--such as the radius and ulna; 4. condyloidal
(or ellipsoidal)--such as the wrist between radius and carps, or
knee; 5. saddle--such as the anatomical joint between carpal thumbs
and metacarpals; and 6. gliding --such as between the carpals.
[0010] Synovial joints (or diarthroses, or diarthroidal joints) are
the most common and most moveable type of anatomical joints in the
body. As with all other anatomical joints in the body, synovial
joints achieve movement at the point of contact of the articulating
bones. Structural and functional differences distinguish the
synovial joints from the two other types of anatomical joints in
the body, with the main structural difference being the existence
of a cavity between the articulating bones and the occupation of a
fluid in that cavity which aids movement. The whole of a
diarthrosis is contained by a ligamentous sac, the joint capsule or
articular capsule. The surfaces of the two bones at the anatomical
joint are covered in cartilage. The thickness of the cartilage
varies with each anatomical joint, and sometimes may be of uneven
thickness. Articular cartilage is multi-layered. A thin superficial
layer provides a smooth surface for the two bones to slide against
each other. Of all the layers, it has the highest concentration of
collagen and the lowest concentration of proteoglycans, making it
very resistant to shear stresses. Deeper than that is an
intermediate layer, which is mechanically designed to absorb shocks
and distribute the load efficiently. The deepest layer is highly
calcified, and anchors the articular cartilage to the bone. In
anatomical joints where the two surfaces do not fit snugly
together, a meniscus or multiple folds of fibro-cartilage within
the anatomical joint correct the fit, ensuring stability and the
optimal distribution of load forces. The synovium is a membrane
that covers all the non-cartilaginous surfaces within the joint
capsule. It secretes synovial fluid into the anatomical joint,
which nourishes and lubricates the articular cartilage. The
synovium is separated from the capsule by a layer of cellular
tissue that contains blood vessels and nerves.
[0011] Cartilage is a type of dense connective tissue and as noted
above, it forms a critical part of the functionality of a body
(anatomical) joint. It is composed of collagenous fibers and/or
elastin fibers, and cells called chondrocytes, all of which are
embedded in a firm gel-like ground substance called the matrix.
Articular cartilage is avascular (contains no blood vessels) and
nutrients are diffused through the matrix. Cartilage serves several
functions, including providing a framework upon which bone
deposition can begin and supplying smooth surfaces for the movement
of articulating bones. Cartilage is found in many places in the
body including the anatomical joints, the rib cage, the ear, the
nose, the bronchial tubes and between intervertebral discs. There
are three main types of cartilage: hyaline, elastic and
fibrocartilage.
[0012] Chondrocytes are the only cells found in cartilage. They
produce and maintain the cartilaginous matrix. Experimental
evidence indicates that cells are sensitive to their mechanical
(stress-strain) state, and react directly to mechanical stimuli.
The biosynthetic response of chondrocytes was found to be sensitive
to the frequency and amplitude of loading (Wong et al., 1999 and
Kurz et al., 2001). Recent experimental studies further indicate
that excessive, repetitive loading may induce cell death, and cause
morphological and cellular damage, as seen in degenerative joint
disease (Lucchinetti et al., 2002 and Sauerland et al., 2003).
Islam et al. (2002) found that continuous cyclic hydrostatic
pressure (5 MPa, 1 Hz for 4 hours) induced apoptosis in human
chondrocytes derived from osteoarthatic cartilage in vitro. In
contrast, cyclic, physiological-like loading was found to trigger a
partial recovery of morphological and ultra-structural aspects in
osteoarthritic human articular chondrocytes (Nerucci et al.,
1999).
[0013] Cancellous bone (also known as trabecular, or spongy) is a
type of osseous tissue which also forms an important aspect of an
anatomical joint. Cancellous bone has a low density and strength
but very high surface area, that fills the inner cavity of long
bones. The external layer of cancellous bone contains red bone
marrow where the production of blood cellular components (known as
hematopoiesis) takes place. Cancellous bone is also where most of
the arteries and veins of bone organs are found. The second type of
osseous tissue is known as cortical bone, forming the hard outer
layer of bone organs.
[0014] Various maladies can affect the anatomical joints, one of
which is arthritis. Arthritis is a group of conditions where there
is damage caused to the joints of the body. Arthritis is the
leading cause of disability in people over the age of 65.
[0015] There are many forms of arthritis, each of which has a
different cause. Rheumatoid arthritis and psoriatic arthritis are
autoimmune diseases in which the body is attacking itself. Septic
arthritis is caused by joint infection. Gouty arthritis is caused
by deposition of uric acid crystals in the joint that results in
subsequent inflammation. The most common form of arthritis,
osteoarthritis is also known as degenerative joint disease and
occurs following trauma to the anatomical joint, following an
infection of the joint or simply as a result of aging.
[0016] Unfortunately, all arthritides feature pain. Patterns of
pain differ among the arthritides and the location. Rheumatoid
arthritis is generally worse in the morning; in the early stages,
patients often do not have symptoms following their morning
shower.
[0017] Osteoarthritis (OA, also known as degenerative arthritis or
degenerative joint disease, and sometimes referred to as
"arthrosis" or "osteoarthrosis" or in more colloquial terms "wear
and tear"), is a condition in which low-grade inflammation results
in pain in the joints, caused by wearing of the cartilage that
covers and acts as a cushion inside joints. As the bone surfaces
become less well protected by cartilage, the patient experiences
pain upon weight bearing, including walking and standing. Due to
decreased movement because of the pain, regional muscles may
atrophy, and ligaments may become more lax. OA is the most common
form of arthritis.
[0018] The main symptoms of osteoarthritis is chronic pain, causing
loss of mobility and often stiffness. "Pain" is generally described
as a sharp ache, or a burning sensation in the associated muscles
and tendons. OA can cause a crackling noise (called "crepitus")
when the affected anatomical joint is moved or touched, and
patients may experience muscle spasm and contractions in the
tendons. Occasionally, the joints may also be filled with fluid.
Humid weather increases the pain in many patients.
[0019] OA commonly affects the hand, feet, spine, and the large
weight-bearing anatomical joints, such as the hips and knees,
although in theory, any anatomical joint in the body can be
affected. As OA progresses, the affected joints appear larger, are
stiff and painful, and usually feel worse, the more they are used
and loaded throughout the day, thus distinguishing it from
rheumatoid arthritis. With progression in OA, cartilage looses its
viscoelastic properties and its ability to absorb load.
[0020] Generally speaking, the process of clinical detectable
osteoarthritis is irreversible, and typical treatment consists of
medication or other interventions that can reduce the pain of OA
and thereby improve the function of the anatomical joint. According
to an article entitled "Surgical approaches for osteoarthritis" by
Klaus-Peter Gunther, MD, over recent decades, a variety of surgical
procedures have been developed with the aim of decreasing or
eliminating pain and improving function in patients with advanced
osteoarthritis (OA). The different approaches include preservation
or restoration of articular surfaces, total joint replacement with
artificial implants, and arthrodeses.
[0021] Arthrodeses are described as being reasonable alternatives
for treating OA of small hand and foot joints as well as
degenerative disorders of the spine, but were deemed to be rarely
indicated in large weight-bearing anatomical joints such as the
knee due to functional impairment of gait, cosmetic problems and
further side-effects. Total joint replacement was characterized as
an extremely effective treatment for severe joint disease.
Moreover, recently developed joint-preserving treatment modalities
were identified as having a potential to stimulate the formation of
a new articular surface in the future. However, it was concluded
that such techniques do not presently predictably restore a durable
articular surface to an osteoarthritic joint. Thus, the correction
of mechanical abnormalities by osteotomy and joint debridement are
still considered as treatment options in many patients. Moreover,
patients with limb malalignment, instability and intra-articular
causes of mechanical dysfunction can benefit from an osteotomy to
provide pain relief, with the goal being the transfer of
weight-bearing forces from arthritic portions to healthier
locations of an anatomical joint.
[0022] Joint replacement is one of the most common and successful
operations in modern orthopedic surgery. It consists of replacing
painful, arthritic, worn or diseased parts of the anatomical joint
with artificial surfaces shaped in such a way as to allow joint
movement. Such procedures are a last resort treatment as they are
highly invasive and require substantial periods of recovery. Some
forms of joint replacement are referred to as total joint
replacement indicating that all anatomical joint surfaces are
replaced. This contrasts with hemiarthroplasty (half arthroplasty)
in which only one bones anatomical joint surface is replaced and
unicompartinental arthroplasty in which both surfaces of the knee,
for example, are replaced but only on the inner or outer sides, not
both. Thus, arthroplasty, as a general term, is an operative
procedure of orthopedic surgery performed, in which the arthritic
or dysfunctional joint surface is replaced with something better or
by remodeling or realigning the anatomical joint by osteotomy or
some other procedure. These procedures are also characterized by
relatively long recovery times and are highly invasive procedures.
The currently available therapies are not condro-protective.
Previously, a popular form of arthroplasty was interpositional
arthroplasty with interposition of some other tissue like skin,
muscle or tendon to keep inflammatory surfaces apart or excisional
arthroplasty in which the joint surface and bone was removed
leaving scar tissue to fill in the gap. Other forms of arthroplasty
include resection(al) arthroplasty, resurfacing arthroplasty, mold
arthroplasty, cup arthroplasty, silicone replacement arthroplasty,
etc. Osteotomy to restore or modify joint congruity is also an
arthroplasty.
[0023] Osteotomy is a related surgical procedure involving cutting
of bone to improve alignment. The goal of osteotomy is to relieve
pain by equalizing forces across the joint as well as increase the
lifespan of the joint. This procedure is often used in younger,
more active or heavier patients. High tibial osteotomy (HTO) is
associated with a decrease in pain and improved function. However,
HTO does not address ligamentous instability--only mechanical
alignment. HTO is associated with good early results, but results
typically deteriorate over time.
[0024] Other approaches to treating osteoarthritis involve an
analysis of loads that exist at a joint. Both cartilage and bone
are living tissues that respond and adapt to the loads they
experience if an anatomical joint surface remains unloaded for
appreciable periods of time the cartilage tends to soften and
weaken. Further, as with most materials that experience structural
loads, particularly cyclic structural loads, both hone and
cartilage begin to show signs of failure at loads that are below
their ultimate strength. However, cartilage and bone have some
ability to repair themselves. There is also a level of load at
which the skeleton will fail catastrophically. Accordingly, it has
been concluded that the treatment of osteoarthritis and other
conditions is severely hampered when a surgeon is not able to
precisely control and prescribe the levels of anatomical joint
load. Furthermore, bone healing research has shown that some
mechanical stimulation can enhance the healing response and it is
likely that the optimum regime for a cartilage/bone graft or
construct will involve different levels of load over time, e.g.
during a particular treatment schedule. Thus, there has been
identified a need for devices which facilitate the control of load
on an anatomical joint undergoing treatment or therapy, to thereby
enable use of the anatomical joint within a healthy loading
zone.
[0025] Certain other approaches to treating osteoarthritis
contemplate external devices such as braces or fixators which
control the motion of the bones at an anatomical joint or apply
cross-loads at an anatomical joint to shift load from one side of
the anatomical joint to the other. Various of these approaches have
had some success in alleviating pain but stiller from patient
compliance or lack an ability to facilitate and support the natural
motion and function of the diseased anatomical joint. Notably, the
motion of bones forming an anatomical joint can be as distinctive
as a finger print, and thus, each individual has his or her own
unique set of problems to address. Therefore, mechanical approaches
to treating osteoarthritis have had limited applications.
[0026] Prior approaches to treating osteoarthritis have also been
remiss in acknowledging all of the basic functions of the various
structures of an anatomical joint in combination with its unique
movement. That is, in addition to addressing loads at an anatomical
joint and anatomical joint movement, there has not been an approach
which also acknowledges the dampening and energy absorption
functions of the anatomy, and taking a minimally invasive approach
in implementing solutions. Prior devices designed to reduce the
load transferred by the anatomical joint typically describe rigid
body systems that are incompressible. Mechanical energy is the
product of three (F) and displacement distance (s) of a given mass
(i.e., E=Fxs, for a given mass M). These systems have zero
displacement within their working body (s=0). Since there is no
displacement within the device it is reasonable to say that there
is no energy storage or absorption in the device. Such devices act
to transfer and not absorb energy from the anatomical joint. By
contrast the anatomical joint is not a rigid body but is comprised
of elements of different compliance characteristics such as bone,
cartilage, synovial fluid, muscles, tendons, ligaments, etc. as
described above. These dynamic elements act to both transfer and
absorb energy about the anatomical joint. For example cartilage
compresses under applied force and therefore the resultant force
displacement product represents the energy absorbed by cartilage.
In addition cartilage has a non linear force displacement behavior
and is considered viscoelastic. Such systems not only absorb and
store, but additionally act to dissipate energy.
[0027] Therefore, approaches to treating anatomical joint pain are
needed that address both anatomical joint movement and varying,
loads as well as dampening forces and energy absorption provided by
an articulating joint.
[0028] The present invention satisfies these and other needs.
SUMMARY OF THE INVENTION
[0029] The present invention provides implantable assemblies for
manipulating energy transferred by members defining an anatomical
joint, and methods of implanting and using the same.
[0030] An implantable assembly is provided, including a first
component configured to be attached to a first anatomical member of
an articulating anatomical joint; a second component configured to
be attached to a second member of the anatomical joint; and a joint
joining said first and second components; wherein the first
component includes a first flex member, the first flex member
configured to deflect, bend or twist to absorb energy transferred
from the first component to the second component when the distance
between the first and second components becomes smaller than an
implant-defined distance.
[0031] In at least one embodiment, the second component includes
second flex member.
[0032] In at least one embodiment, the first and second flex
members are configured to flex in a direction substantially normal
to a direction of bending of the anatomical joint.
[0033] In at least one embodiment, the first component further
comprises a first base configured to be attached to the first
member, and the first flex member is fixed to or integral with the
first base; and wherein the second component further comprises a
second base configured to be attached to the second member, and the
second flex member is fixed to or integral with the second
base.
[0034] In at least one embodiment, the joint comprises a compliance
member mounted between end portions of the first and second
components.
[0035] In at least one embodiment, the first component comprises a
ring shaped end and the second component comprise a shackle.
[0036] In at least one embodiment, the joint comprises a compliance
member within the ring shaped end and connected to the shackle.
[0037] In at least one embodiment; the compliance member comprises
an outside diameter that is much less than an inside diameter of
the ring-shaped end, thereby leaving space within a ring formed b
the ring-shaped end.
[0038] In at least one embodiment, the compliance member fills an
entire space of a ring formed by the ring-shaped end.
[0039] In at least one embodiment, the joint permits relative axial
rotations between the first and second components.
[0040] In at least one embodiment, the anatomical joint is a knee
joint, the first component is adapted to be fixed to a femur of the
knee joint and second component is adapted to be fixed to a tibia
of the knee joint.
[0041] In at least one embodiment, the first and second flex
members flex and absorb energy from the forces applied by the
members of the anatomical joint, thereby relieving at least a
portion of the load resultant from the forces from being
transferred through contacting surfaces of the anatomical
joint.
[0042] In at least one embodiment, the assembly relieves load on a
side of the anatomical joint to which the assembly is attached.
[0043] In at least one embodiment, the assembly includes a pin, and
the compliance member is attached to the shackle via, the pin.
[0044] In at least one embodiment, the compliance member is free to
rotate relative to the shackle, about the pin.
[0045] A method for treating an anatomical joint is provided that
includes: attaching a first component of an assembly to a first
anatomical member of the anatomical joint; and attaching, a second
component of the assembly to a second anatomical member of the
anatomical joint; wherein a joint of the assembly joins the first
and second components, the first component includes a first flex
member and the second component includes a second flex member; and
flexing the first and second flex members to transiently variably
reduce load between the first and second anatomical members of the
anatomical joint, wherein the assembly is implanted.
[0046] In at least one embodiment, the method further includes
permitting at least a limited, amount of axial rotation between the
first and second anatomical members of the anatomical joint.
[0047] In at least one embodiment, the first and second components
are attached at locations to place the joint adjacent to a location
of the anatomical joint that translates very little over a range of
motion of the anatomical joint, relative to other locations on the
anatomical joint.
[0048] In at least one embodiment, the anatomical joint is a knee
joint, and the location that translates very little is about the
midpoint of a Blumensaat's line of a femur of the knee joint.
[0049] In at least one embodiment, the method includes temporarily
fixing the joint at the location of the anatomical joint that
translates very little prior to the attaching a first component and
attaching a second component, and freeing the joint from the
temporarily fixing prior to completion of implantation of the
assembly.
[0050] These and other features of the invention will become
apparent to those persons skilled in the art upon reading the
details of the assemblies and methods as more fully described
below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] FIG. 1 is a front view, illustrated normal forces existing
in a joint.
[0052] FIG. 2 is a front view, depicting the effect an energy
manipulating assembly of the present invention has on the joint
shown in FIG. 1.
[0053] FIG. 3 is a graph of force versus displacement, illustrating
the energy characteristics of a prior art rigid structure applied
across a joint.
[0054] FIG. 4 is a graph of three versus displacement, illustrating
the energy characteristics of a linear spring system.
[0055] FIG. 5 is a graph of force versus displacement, illustrating
the energy characteristics of a spring and dampening system.
[0056] FIG. 6 is a graph, illustrating the flexion/extension angle
and joint force existing in a gait cycle.
[0057] FIG. 7 is a graph, illustrating one approach to energy
absorption on a gait cycle.
[0058] FIG. 8 is a graph, illustrating a second approach to energy
absorption on a gait cycle.
[0059] FIG. 9 is a graph,illustrating a third approach to energy
absorption on a gait cycle.
[0060] FIG. 10 is a graph, illustrating at approach to energy
absorption on a gait cycle.
[0061] FIG. 11 is a perspective view, depicting anatomy of a
typical knee joint.
[0062] FIG. 12 is a side view of one embodiment of an assembly
installed on a knee joint according to the present invention.
[0063] FIG. 13 is an anterior view of FIG. 12.
[0064] FIG. 14 is an enlarged partial sectional view of the joint
portion of the assembly of FIGS. 12-13.
[0065] FIG. 15A-15C illustrate the assembly of FIG. 12 at various
phases of flexion/extension of the knee joint. FIG. 15A also
illustrates an optional sheath provided over at least a portion of
the assembly of FIG. 12.
[0066] FIG. 16 is a side view of another embodiment of an assembly
according to the present invention, installed on a knee joint.
[0067] FIG. 17 is an enlarged partial sectional view of the joint
portion of the assembly of FIG. 16.
[0068] FIG. 18 illustrates the assembly of FIG. 16 when the knee
joint is in flexion.
[0069] FIG. 19A illustrates imaging the knee joint using
fluoroscopy according to a procedure implemented in at least one
embodiment of the present invention.
[0070] FIG. 19B illustrate use of a circle guide over the knee
joint with the center thereof configured at a midpoint of the
Blumensaat's line according to an embodiment of the present
invention.
[0071] FIG. 20 is a diagrammatic view, depicting motion patterns
and selected fixation points for energy manipulation devices
according to an embodiment of the present invention.
[0072] FIG. 21 illustrates a slit made superior to a K-wire placed
in the femur according to an embodiment of the present
invention.
[0073] FIG. 22 illustrates visualization of a base an assembly
under fluoroscopy in preparation for attaching it to the femur
according to an embodiment of the present invention.
[0074] FIG. 23 illustrates fluoroscopic visualization of a base of
an assembly having been attached to the femur according to an
embodiment of the present invention.
[0075] FIG. 24 illustrates slits formed superior and inferior to
the anatomical joint according to an embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0076] Before the present devices and methods are described, it is
to be understood that this invention is not limited to particular
embodiments described, as such may, of course, vary. It is also to
be understood that the terminology used herein is for the purpose
of describing particular embodiments only, and is not intended to
be limiting, since the scope of the present invention will be
limited only by the appended claims.
[0077] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower
limit, unless the context clearly dictates otherwise, between the
upper and lower limits of that range is also specifically
disclosed. Each smaller range between any stated value or
intervening, value in a stated range and any other stated or
intervening value in that stated range is encompassed within the
invention. The upper and lower limits of these smaller ranges ma
independently be included or excluded in the range, and each range
where either, neither or both limits are included in the smaller
ranges is also encompassed within the invention, subject to any
specifically excluded limit in the stated range. Where the stated
range includes one or both of the limits, ranges excluding either
or both of those included limits are also included in the
invention.
[0078] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which this invention belongs. Although
any methods and materials similar or equivalent to those described
herein can be used in the practice or testing, of the present
invention, the preferred methods and materials are now described.
All publications mentioned herein are incorporated herein by
reference to disclose and describe the methods and/or materials in
connection with which the publications are cited.
[0079] It must be noted that as used herein and in the appended
claims, the singular forms "a", "an", and "the" include plural
referents unless the context clearly dictates otherwise. Thus, for
example, reference to "a screw" includes a plurality of such screws
and reference to "the device" includes reference to one or more
devices and equivalents thereof known to those skilled in the art,
and so forth.
[0080] The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present invention is not entitled to antedate such publication
by virtue of prior invention. Further, the dates of publication
provided may be different from the actual publication dates which
may need to be independently confirmed.
[0081] Referring now to the drawings, which are provided by way of
example and not limitation, the present invention is directed
towards devices and methods for treating body tissues. In
applications relating to the treatment of body (anatomical) joints,
the present invention seeks to alleviate pain associated with the
function of diseased, overloaded or malaligned members forming an
anatomical joint. Whereas the present invention is particularly
suited to address issues associated with osteoarthritis, the energy
manipulation accomplished by the present invention lends itself
well to broader applications. Moreover, the present invention is
particularly suited to treating synovial joints such as the knee
and shoulder, as well as other synovial or articular, cartilaginous
joints of the body, such as those of the hips, fingers, wrist,
ankles and toes. However, it is also contemplated that the
apparatus and methods of the present invention can be employed to
treat other non-synovial, non-articular, non-cartilaginous joints
that are capable of motion in a flexion/extension direction that
exceeds forty-five degrees.
[0082] In one particular aspect, the extra articular energy
absorbing assemblies of the present invention seek to permit and
complement the unique articulating motion of the members defining
an anatomical joint or a patient while simultaneously manipulating
energy being experienced by both cartilage and osseous tissue
(cancellous and cortical bone). To minimize pain, transient
variable load reduction or absorption of 1-40% of forces, in
varying degrees, may be necessary. Transient variable load
reduction or absorption in the range or 5-30% can be a target for
certain applications. Transient variable load reduction or
absorption refers to the function of the energy manipulation
structure of the present invention reducing the load experienced by
the joint during the joint's higher loading positions and the
energy manipulation structure not reducing the load experienced by
the joints during lower or no load position. In certain specific
applications, transient distraction is employed in the energy
manipulation approach.
[0083] In order to implant the extra articular energy absorbing
assemblies of the present invention, conventional surgical or
minimally invasive approaches are used to gain access to an
anatomical joint or other anatomy requiring attention. Arthroscopic
approaches are contemplated when reasonable to both implant the
energy manipulation assembly as well as to accomplish adjusting an
implanted assembly. Biologically inert materials of various kinds
are employed in constructing the energy manipulation assemblies of
the present invention.
[0084] In one particular approach, an energy absorbing or
manipulating device is provided in which multiple components
deflect, bend side-to-side, or twist to manipulate or absorb
forces/load between body parts that are joined at an anatomical
joint, to which body parts the device is mounted. Thus, a device
utilizing elements that can absorb forces/load applied by the bones
that are joined by the joint may be desirable to treat afflictions
such as osteoarthritis, trauma, or other pain-causing conditions in
a joint. Preferably the embodiments of the present invention are
implanted subcutaneously and are extra-articular, peri-articular or
extra- or para-capsular of the treated anatomical joint.
[0085] The deflecting, bending or twisting of the energy absorbing
assembly is used in a novel way in the present invention to
accommodate the complex flexing, rotating and sliding motions of
articulating anatomical joints such as the knee while utilizing
fewer rotating or rubbing parts so as to decrease the generation of
wear debris over the useful life of the assembly.
[0086] Referring to FIGS. 1-2, forces occurring between members
forming an anatomical joint are described. The arrows 50 shown in
FIG. 1 represent forces occurring between adjacent members 6, 7 of
an anatomical joint lacking, an energy manipulation assembly 10 of
the present invention. However, as shown in FIG. 2, in body anatomy
incorporating the present invention, less threes/load are
transferred to the bones and cartilage of the members defining the
anatomical joint. Where the anatomical joint is treated with the
foregoing described energy manipulating assemblies of the present
invention, a portion of the forces/load between body members is
absorbed by the energy manipulating assembly 10 (depicted as arrows
54 in FIG. 2). Accordingly, with the energy manipulation assembly
10 in place, less force is placed on the joint than when the
assembly 10 is not present. The total load in FIG. 2 is shared
between the force/load 56 carried by the joint and the force/load
54 carried by the assembly 10.
[0087] The assembly 10 absorbs energy in the joint by application
of a force in the direction of the arrows 54, which are generally
in an axial direction of the joint in extension. The assembly 10
uses flex members to apply three in directions substantially
opposite to the directions of load applied by the first and second
members of the anatomical joint toward one another. This can also
be described as applying a three in a direction of distraction,
although actual distraction of the joint may or may not be
present.
[0088] Although the assembly 10 is schematically represented as
being installed on the medial side of the joint shown in FIG. 2,
the present invention is not limited to such an arrangement, as
assembly 10 can alternatively be installed on the lateral side of
the joint, or a pair of assemblies 10 can alternatively be
installed, one on the medial side of the joint and one on the
lateral side of the joint.
[0089] FIGS. 3-5 illustrate the relation between force (F) and
displacement (S) between members of an anatomical joint (where mass
is constant). In a rigid body system (FIG. 3) which does not
incorporate aspects of the present invention, there is no
displacement and no energy absorption. In an energy manipulating
system incorporating a single linear spring (FIG. 4), energy is
absorbed in proportion to a spring constant (spring stiffness). The
energy absorbed is represented by the shaded area 59 below the
curve. As shown in FIG. 5, where a spring and dampener are used in
combination, the energy absorbed 59 is a function of the spring
constant and the dampener. It is these relationships which are
considered in developing desired energy manipulating
characteristics for an energy absorbing assembly for a joint.
[0090] Also considered are the forces existing through the flexion
and extension through an articulation cycle of the particular joint
anatomy to be treated. Using the gait cycle of the legs of a human
as an example, both the joint three and flexion/extension angle in
degrees for a knee joint during walking can be plotted versus the
percentage of the gait cycle completed with the gait cycle
beginning at heel contact. A normal or expected relationship 60 of
vertical forces generated through the gait cycle is depicted in
each of FIGS. 6-10. Also depicted in FIGS. 6-10 is the
flexion/extension angle 62 of the knee throughout the gait cycle.
The expected relationship 60 of vertical forces during the gait
cycle can be altered using certain of the embodiments of the energy
manipulation assemblies of the present invention. As shown in. FIG.
7, an energy manipulation assembly 10 according to the present
invention can absorb energy by a substantially fixed proportion
during a portion of the gait cycle. This is reflected by curve 64
in FIG. 7. Moreover, energy can be both absorbed and dampened as
represented by curve 66 of FIG. 8 or alternatively, energy can be
absorbed only above a fixed value as represented by curve 68 of
FIG. 9. Additionally, as reflected by curve 70 of FIG. 10, energy
can be absorbed in a fixed portion of the gate cycle or though a
limited range of motion of the joint. It is to be recognized,
however, that each of or one or more of these types of energy
absorption can be combined in a desired system.
[0091] Referring now to FIG. 11, the medial side anatomy of a
typical knee joint is presented in a manner relating to an
implantation procedure. Such a procedure could ultimately involve
the implantation of devices such as those described below. Although
the knee joint is being described here, it is contemplated that
these devices can also be placed at other articular, cartilaginous
joints throughout the body, and some non-articular,
non-cartilaginous joints that are capable of motion in a
flexion/extension direction that exceeds forty-five degrees.
[0092] In a procedure seeking to transiently, variably reduce load
or manipulate forces at a knee joint, a proximal attachment site
(PAS) for to base of an energy manipulation device must be
identified. Similarly, a distal attachment site (DAS) must also be
selected. In a contemplated approach the medial proximal attachment
site (PAS) can be located on a femur 6 in a space defined by the
medial patellar retinaculum (MPR), the vastus medialis (VM) and the
tibial collateral ligament (TCL). The distal attachment site (DAS)
can be located on the tibia in the region defined by the medial
patellar retinaculum (MPR) and the pes anserinus (PA).
[0093] FIGS. 12-13 show a medial side view and an anterior view of
one embodiment of an energy absorbing assembly 10 according to the
present invention installed medially on a knee joint. Assembly 10
includes a first component 20 (in this example, first component 20
is a femoral component) and a second component 40 (in this example,
second component 40 is a tibial component). The femoral component
20 is configured to be attached to a distal end portion of a
patient's femur 6. The femoral component 20 includes a first base
22 that is configured to be anchored to a first bone that connects
at the joint, and second component 40 includes a second base 42
that is configured to be anchored to a second bone that connects at
the joint.
[0094] First component 20 includes a first flex member 24 that may
be integral with first base 22, but is preferably removably fixed
thereto at 26, such as by a dovetail connection with or without
locking screw, or other mechanical connection that can be locked
during, use, but unlocked at any such time as separation of the
base 22 and flex member 24 is desired. Likewise, second component
40 includes a second flex member 44 that may be integral with
second base member 42, but is preferably removably fixed thereto at
46.
[0095] The opposite ends of flex members 24 and 44 that are not
fixed to base members 22 and 42 are configured to form joint 30
such that the first and second components 20, 40 are joined at
joint 30. In the example shown in FIG. 12, first component 20 ends
as a ring member 32 that is integral with the end of flex member 24
that is opposite the end of flex member 24 fixed to base member 22.
Second component 30 ends as a shackle 34 that is pinned through
ring member 12, as shown. It is noted here that joint 30 need not
be configured to the specific arrangement shown in FIG. 12, as
alternative arrangements could be provided. For example, first
component 20 could be provided with shackle 34 and second component
40 could be provided with ring member 32. Further alternatively,
any other structures could be provided that would form a connection
between the two members 20 and 40 and perform as described below.
This connection, however, does not require constant contact between
the members forming the connection, as described in more detail
below.
[0096] A compliance member 36 is provided between ring and shackle
members 32 and 34. More specifically, in the embodiment shown,
compliance, member may be press fit, glued, or loosely it within
ring member 32 and pin 38 extends through an opening in compliance
member 36 to fix compliance member to shackle 34. Compliance member
36 can be connected to ring member 32 using any type of connection
that provides reliable "stack-up" height when needed to provide
support to the joint. For example, in the case of the knee joint,
as the knee joint is extended or loaded, the connection between
compliance member 36 and ring, member 32 is able to transmit force
therethrough. Outside of the anatomical joint angles where the
apparatus does not need to provided unloading to the anatomical
joint, compliance member 36 can be loose, e.g., not even in contact
with ring member 32, and this may facilitate maintenance of full
range of motion of the anatomical joint. Pin 38 is rigid and may be
made of the same material as components 20 and 40 (e.g., titanium,
stainless steel or other biocompatible metal or alloy). Note that
"fix" is used here to describe the fact the compliance member 36
cannot escape from its connection to shackle 34, as pin 38 prevents
this. However, pin 38 can allow rotation of compliance member 36
relative to shackle 34. Compliance member 36 may be provided with a
sleeve or hushing 37 surrounding the opening through which pin 38
is inserted, to prevent erosion of the elastomeric material of
compliance member 36 as it rotates relative to pin 38. Bushing 37
may be formed of any of the metals or alloys that can be used to
make members 20, 40, or other hardened, biocompatible material.
[0097] Compliance member 36 may be thrilled of an elastomeric
material for example and, in the example shown, is an elastomeric
disc. Examples of elastomeric materials include polymers such as
polyethylene, polyurethane, and polycarbonates, silicone,
polyester, and thermoplastics.
[0098] During loading of the anatomical joint (such as the knee
during, walking), the forces applied through assembly 10 cause flex
members 24 and 44 to bend (flex) in directions indicated by the
arrows A in FIG. 13. This results in joint 30 flexing out away from
the natural joint somewhat with the flexing members 24, 44 taking
up (absorbing) the distance change between components under loading
of the natural joint. This flexing absorbs some of the energy of
the threes, thereby reducing the amount of force/load that is
applied through the natural joint, as was described above. The
flexing of the members 24, 44 also alters the angle at which the
ring and shackle members 32 and 34 are oriented. The compliance
member 36 deforms (e.g. compresses on one side and extends on the
opposite side of the ring) to compensate for this change of angle.
Additionally, compliance member 38 can deform (e.g., twist) to
accommodate relative axial rotation between components 20, 40
(e.g., see arrows 35 in FIG. 14). During flexion of the natural
joint, the forces are also removed from flex members 24, 44 and
they relax from the bent or twisted configurations.
[0099] FIGS. 15A-15C illustrate the relative bending of the flex
member 24 and 44 at various ranges of flexion/extension of the knee
joint according to one embodiment of the present invention. In FIG.
15A, the knee is in full extension (i.e., 0 degrees flexion) and
the forces applied through assembly 10 cause flex members 24 and 44
to bend (flex) outwardly in directions indicated by the arrows B in
FIG. 15A. In this orientation, the compliance member 36 (not shown)
is also deformed to absorb load.
[0100] FIG. 15B shows the knee joint in a 10 degrees of flexion
orientation. In this embodiment, assembly 10 is configured to be
unloaded even at 10 degrees of flexion. Accordingly, in FIG. 15B
the flex members 24 and 44 are no longer bent or bowed outwardly,
like in FIG. 15A, but have returned to their resting (unbent)
configurations. The compliance member 36 is also unloaded or
substantially unloaded.
[0101] Likewise, in FIG. 15C, when the knee is flexed 90 degrees,
the flex members 24, 44 are also unflexed (unbent) and the
compliance member 36 is unloaded.
[0102] Note that in FIGS. 12-15, the terminal end portions of the
femur 6 and tibia 7 are depicted without surrounding tissue, for
purposes of simplicity and clarity. It is noted that the bases 22
and 42 are contoured to match potential mounting surfaces of the
femur and tibia.
[0103] Optionally, assembly 10 can be provided with a subcutaneous
tissue barrier in the form of a sheath 58 (represented in phantom
lines in FIG. 15A), preferably polytetrafluoroethylene (ePTFE),
which encloses various parts of the system, particularly the joint
30, and excludes surrounding tissue. It is contemplated that the
subcutaneous tissue barrier can be formed from or coated
alternatively with a tissue in-growth substance or for that matter,
substances which inhibit such in-growth. For example, it may be
desirable that one or more sides or portions of the assembly 10
enclosed by the sheath 58 be affixed to surrounding tissue whereas
it may be advantageous that other portions of the system be free to
move with respect to surrounding tissue. Of course, the flex
members 24, 44 and joint 30 would be left to move relative to the
sheath 84. Examples of some suitable sheaths are described in U.S.
patent application Ser. No. 10/113,186, which is incorporated
herein by reference in it's entirety.
[0104] FIGS. 16-17 illustrate another embodiment of an assembly 10
according to the present invention, with FIG. 16 showing, a side
view of assembly 10 installed on the medial side of a knee joint
and FIG. 17 showing a partial sectional view of assembly 10 taken
along line 17-17. Like the previous embodiment, assembly 10
includes a first component 20 (in this example, first component 20
is a femoral component) and a second component 40 (in this example,
second component 40 is a tibial component). The femoral component
20 is configured to be attached to a distal end portion of a
patient's femur 6. The femoral component 20 includes a first base
22 that is configured to be anchored to a first bone that connects
at the joint, and second component 40 includes a second base 42
that is configured to be anchored to a second bone that connects at
the joint.
[0105] First component 20 includes as first flex member 24 that may
be integral with first base member 22, but is preferably removably
fixed thereto at 26, such as by a dovetail connection with or
without locking, screw, or other mechanical connection that can be
locked during use, but unlocked at any such time as separation of
the base 22 and flex member 24 is desired. Likewise, second
component 40 includes a second flex member 44 that may be integral
with second base member 42, but is preferably removably fixed
thereto at 46.
[0106] The opposite ends of flex members 24 and 44 that are not
fixed to base members 22 and 42 are configured to form joint 30
such that the first and second components 20, 40 are joined at
joint 30. In the example shown in FIG. 16, first component 20 ends
as a ring member 32 that is integral with the end of flex member 24
that is opposite the end of flex member 24 fixed to base member 22.
Second component 40 ends as a shackle 34 that is pinned through
ring member 32, as shown. Compliance member 36 in this embodiment,
has an outside diameter that is much less than the inside diameter
of ring member 32, thereby leaving, space 32s within the ring 32
that is not occupied by compliance member 36. For example, the
outside diameter 36d of compliance member 36 may be about 75% or
less than the inside diameter 32d of ring 32, typically less than
about 50%, or even down to about 25% to about 33% of the inside
diameter 32d of ring member 32. In the example shown in FIG. 7,
outside diameter 36d is about 35% of inside diameter 32d.
[0107] Also, compliance member 36 has a curved outer surface
profile with a radius of curvature 36r of the outer surface in a
direction perpendicular to the plane of the circular shape formed
by compliance member 36, in contrast to the flat outer surface
profile in this dimension of the compliance member 36 of the
embodiment of FIG. 12. Thus, the compliance member 36 may form a
portion of a sphere, for example. Further alternatively, the member
36 in this embodiment may be formed of a non-compliant material
36n, such as rigid metal, rigid polymer, etc, as compliance can be
taken up by movement of the member 36n around the race formed by
the inner surface of ring member 32 in a manner as described
herein. Radius of curvature 36r of the outside of the compliance
member 32 is typically less than the radius of curvature 32r of the
inside surface of ring 32 in a direction perpendicular to the plane
of the circular shape formed by ring, member 32 to facilitate
relative axial rotational movements between the components 20 and
40. Note that the smaller the radius of curvature 36r is relative
to radius of curvature 32r, the less resistance is provided to the
relative axial rotational movements described above, but the
smaller the contact surface between compliance member 36 and ring
member 32, as a tradeoff. It is further noted, that when compliance
member 36 comprises a compliant material, the compliant nature of
the elastomer forming compliance member 36 allows it to twist, and
therefore some relative axial rotations between members 20 and 40
will still be permitted even when radius of curvature 36r equals
radius of curvature 32r in this case.
[0108] With the configuration of FIGS. 16-17, the position of
compliance member 36 relative to ring 32, and thus the location on
ring 32 where compliance member 36 contacts it (if at all) varies
over the gait cycle. In extension, as illustrated in FIG. 16,
compliance member 36 contacts ring 32 towards the top of the inner
surface of the ring member 32, (i.e. around the 12:00 position). As
the knee is flexed, the compliance member 36 moves clockwise (in
the example shown in FIG. 16, but this will vary depending upon
which side of the joint that the assembly 10 is installed on),
towards the 1:00, 2:00, 3:00, etc., positions until full flexion is
reached, and then compliance member travels back along, the inner
surface of ring member 32 to the positioning shown in FIG. 16 as
the knee moves from full flexion to full extension. In full
flexion, or even before full flexion is reached, compliance member
36 may pull away from the inner surface of ring member 32, so that
a gap exists between compliance member 36 and inner surface 32, at
which time, assembly 10 does not take up any forces between the
femur 6 and tibia 7. FIG. 18 illustrates a situation where, in full
flexion, compliance member 36 has pulled away from contact with the
inner surface 32 of ring 32 leaving a gap therebetween.
[0109] It is noted here that joint 30, like that in FIG. 12, need
not be configured to the specific arrangement shown in FIG. 16, as
alternative arrangements could be provided. For example, first
component 20 could be provided with shackle 34 and second component
40 could be provided with ring member 32. Further alternatively,
any other structures could be provided that would form a joint
between the two members 20 and 40 and perform as described
above.
[0110] Flex members 24, 44 when designed for use with an adult
human knee, are typically designed to flex a sufficient amount to
each take up about a one to about 2.5 mm change in length thereof,
typically about 1.5 mm each, for a combined compressibility of
about 2 to about 5 mm, typically about 3 mm. Typically, flex
members 24, 44 flex in a direction substantially normal to the
direction of flexing of the anatomical joint. Thus, for example, in
FIG. 13, the knee joint flexes substantially in the direction into
and out of the page, while flex members flex substantially in
directions aligned with the plane of the page. Assembly 10 can be
configured to resist compression to force all displacement to be
absorbed by the flex members 24, 44 or to absorb all forces, such
as by compliance member 36, for example. Note that these are the
extreme configurations over a range of configuration that can be
provided. Typically, the assembly 10 is configured to provide a
combination of resistance and absorption. For example, absorption
of about 1 to about 2 mm of compression is typically provided by
assembly 10.
[0111] Note that in FIGS. 16 and 18, the terminal end portions of
the femur 6 and tibia 7 are depicted without surrounding tissue,
for purposes of simplicity and clarity. It is noted that the bases
22 and 42 are contoured to match potential mounting surfaces of the
femur and tibia. The bases 22, 42 can be provided in one or more
shapes and size and in a variety of configurations to match the
femurs and tibias of a wide variety of patients. Some additional
examples of femoral and tibial base configurations are described in
detail in US Patent Publication No. 2008/0275562 which is
incorporated herein by reference in it's entirety.
[0112] Optionally, assembly 10 can be provided with a subcutaneous
tissue barrier in the form of a sheath 58, preferably ePTFE, which
encloses various parts of the system and excludes surrounding,
tissue as described above.
[0113] With reference now to FIGS. 19A-24, aspects of a
contemplated implantation approach are described. With the anatomy
of the knee joint in mind, a pre-operative or intra-operative
session with the patient is conducted. By employing two-dimensional
or three dimensional static or motion imaging techniques which are
available, such as x-ray, MRI or CT scans, the anatomy of the
interventional site is examined. A dynamic assessment can be
performed to map the articulating motion of the members defining
the particular joint.
[0114] The data collected during the pre-operative or
intra-operative session is logged and then compared to data sets
developed by the physician and/or the organization utilized to
store actual patient data as well as tested theoretical data
independently developed. Easily accessible and convenient to use
programs or charts can be developed and employed to automate the
comparison of a particular patients condition with previously
collected data. From this comparison, a specific treatment modality
is selected for the patient. Moreover, an expected device (assembly
10 or portions of assembly 10, e.g., base members 22, 42) selection
or multiple device selections are made from the various devices
contemplated to treat the patient.
[0115] The pre-operative session or an intra-operative session
further includes the collection of three-dimensional information
concerning an expected proximal attachment site (PAS) and as distal
attachment site (DAS). This lends itself to the selection of the
proper bases 22, 42 which may vary in shape and size and
particularly in regard to their surface curvatures/conformations
that are expected to conform to the bone surfaces to which they are
be attached.
[0116] Once the surgical intervention date is set and as it
approaches, the patient's health is continued to be closely
monitored. On the day of the procedure, the patient is prepared for
surgery in the conventional manner. In a particular application,
spinal anesthesia or general anesthesia can be used as a step to
prepare the patient.
[0117] Next, the knee or other joint being treated is imaged using
fluoroscopy (See FIG. 19A) or along, with three-dimensional
navigational software such as that available from Stryker,
Medtronic or Brainlab. The members defining the joint are placed in
a full lateral position and perpendicularly to the receiver of the
imaging device. The proximal joint member is then fixed using a
vacuum splint/sandbag (riot shown) or similarly effective device in
a preferred procedure to treat the knee joint, the Blumensaat's
line 85 of the femur boric 6 is used as a landmark for locating,
the various components of an energy manipulation device 10 as it
has been found to provide a convenient initial position marker for
ultimately achieving proper rotational positioning of the device.
Other referencing points can additionally be used and of course are
required when treating other joints.
[0118] Accordingly, it is further contemplated that other regions
can represent possible locations of a femoral rotation point on the
medial chondyle. In order to select such an alternative point, the
surface area of the medial chondyle is mapped to determine regions
corresponding to Changes in device length of a potentially
implanted energy manipulation assembly 10 while the joint is moved
from full extension to full flexion. Areas of device increasing
length and decreasing length can be mapped. Moreover, areas can
also be identified where there is an initial device length increase
then followed by a length decrease, and where there is an initial
length decrease followed by increasing length. Mapping of areas of
overlap between these various areas represent transitions from one
region to a nest. An area representing minimal displacement can
also be identified. This information is then employed to identify
the various points of rotation best suited for a particular energy
manipulation assembly implant 10. As device/assembly 10 rotates
only about joint 30 which is to be located over a location on the
femur, the fixation of both bases 22 and 42 are determined by the
location of "placement of the center of rotation of joint 30, which
is approximated as the central axis of pin 38. This is particularly
important with the embodiment of FIG. 12. The embodiment of FIG. 16
can accommodate some extension throughout flexion.
[0119] In one alternative embodiment, ring member 32 may not be
perfectly round. Ring member 32 operates, in conjunction with yoke
34 and members 36 and 38 to provide a force contact transmission
surface over some, but not all degrees of flexion.
[0120] Furthermore, an approach to proper implant placement can
involve observing changes resulting from changing, the proposed
location of pin 38. Trial flex members 24, 44 that are not
connected by pin 38 are move through the range of motion of the
anatomical joint. For example, at 90 degrees flexion, the distance
between the original location of the pin 38 and the resulting
location of the pin 38 at 90 degrees flexion is measured. By
repeating this process, each time rearranging the pin 38 at a new
location, the location of pin 38 and locations where the flex
members 24, 44 will be connected to the femur and tibia,
respectively (i.e., by bases 22 and 42, respectively), can be
chosen based on a shift of the location of pin 38 that provided
unloading, during flexion, but will not shift outside of the
constraints placed on the anatomical joint by the joint 30.
[0121] Alternatively as shown in FIG. 18B, a K-wire 87 can be
inserted into the femur at about a midpoint along, the Blumensaat's
line. Preferably, the K-wire, is inserted about 0.5-2 mm above and
anterior to the midpoint of Blumensaat's line.
[0122] By maintaining the joint 30 over this estimated rotation
point defined by the K-wire 87 and temporarily fixing bases 22 and
42 at the fixation locations on the femur 6 and tibia 7 dictated by
the placement of the joint 30, while the knee joint is in full
extension, the knee joint can then be manipulated through its range
of motion to simulate the gait cycle and observe the elongation of
the assembly 10. The assembly 10 should typically be at its most
compressed when the knee joint is in full extension and then should
gradually elongate over at least a portion of the gait cycle toward
full flexion. The best rotation point can be determined empirically
by moving the location of K-wire insertion until the actions of the
assembly over the course of the gait cycle have been optimized.
[0123] In an alternative approach, a circle guide 86 is placed over
the natural joint with the center thereof configured at a midpoint
of the Blumensaat's line 85 (FIGS. 19A and 19B), and as described
in US Patent Application Publication No. 2008/0275561 titled
"Extra-Articular Implantable Mechanical Energy Absorbing Systems
and implantation Method, which application is hereby incorporated
herein, in its entirety, by reference thereto. As shown in FIG. 20,
it has been found that when considering device elongation and
compression, along with anterior and posterior device positioning
as well as flexion degrees during a patients gait, that +/-5 mm
from a center point of a Blumensaat's line can be a starting
reference point. At this point, it is confirmed that the tibial
plateau at 90.degree. flexion is 1-2 rings outside of an initial
matching circle at 0.degree. flexion, if the assembly 10 selected
for the patient is only meant to extend during flexion. At a
mid-point of the Blumensaat's line and perpendicularly thereto, the
physician will then insert a rigid guide or K-wire 87 through a
center guide hole 88 of the circle guide 86 that has been
previously locked in place. The K-wire 87 includes a sharp terminal
tip for entering bone and thus the K-wire 87 can either be drilled
into the bone or tapped in by force. After the K-wire 87 has been
fixed perpendicularly to the bone, the circle guide 86 is removed
and the K-wire is shortened leaving approximately one inch of wire
protruding through the skin. Assembly 10 may then be placed over
the K-wire 87 and the locations of fixation of bases 22 and 42 can
be estimated in the manner described above, while using remote
image techniques.
[0124] With specific reference to FIG. 21, once the rotation point
has been located and fixation locations of the bases 22, 42 have
been estimated, assembly 10 can be removed off of K-wire 87 and an
incision 89 is made superior to the K-wire 87. Additionally, an
incision 93 is made inferior to the K-wire 87, see FIG. 24. Fascia
and tissue are then manipulated to expose bone periostium in the
region of anticipated base attachments to the femur 6 and tibia 7.
A subcutaneous channel is then formed either by hand or with blunt
instrumentation to connect the two incisions 89, 93 and accommodate
the joint 30. Alternatively, only one incision 89 or 93 can be used
from which to form a subcutaneous channel of equal length to the
one described above that connect incisions 89 and 93. Further
alternatively, one long incision can be formed with a length of the
previously described subcutaneous channel. Further alternatively, a
single small incision can be made at the center (e.g., location of
K-wire 87) and a tunnel can be formed to extend superiorly and
inferiorly therefrom. In any case, assembly 10 is inserted either
into the elongated incision, or through the subcutaneous tunnel to
place the joint 30 over the rotation point having been previously
determined. In instances where K-wire 87 is present joint 30 may be
centered over the same. For example, pin 38 nay be provided with an
annulus or axially extending central through hole (not shown)
configured and dimensioned to allow K-wire 87 to pass therethrough.
In this case, pin 38 is slid down over K-wire 87 to temporarily fix
joint 30 at the desired rotation point.
[0125] The bases 22, 42 can next be fixed to the femur 6 and tibia
7 at the previous located fixation locations, the fascia, tissue
and periosteum having been previously manipulated to expose the
fixation locations on the bone. FIG. 22 illustrates visualization
of base 22 under fluoroscopy in preparation for attaching it to the
femur 6. The bases 22 and 42 are affixed to the femur 6 and tibia
7, respectively, using bone screws 91 as schematically represented
in FIG. 23 and which may be accomplished under fluoroscopic
visualization, for example. Prior to completely turning the screws
to fix the bases 22, 42, further adjustment may be performed. Once
the screws 91 have been fully torqued down to fix the positions of
bases 22, 42, K-wire 87, if present, can be removed from joint 30.
It is to be further recognized that various angles of insertion of
the bone screws 91 can be used to aid in providing attachment
support in a multitude of directions. Moreover, hi-cortical
penetration of one or more of the bone screws is contemplated for
certain applications.
[0126] In one approach, it is contemplated that bicortical screws
can be polyaxial because their trajectory will be fixed by the
bicortical purchase. Their trajectories can either diverge or
converge by about 15 to 30 degrees to improve pull out strength but
the exact angle is not critical so the technique can be simplified
by letting them rotate in a small cone. Further, the unicortical
screws can have fixed trajectories. This will increase their
stability that they may lack because of the unicortical purchase.
The trajectories should either converge or diverge as above but the
angles will be set. It may further be desirable to use a resorbable
bone void tiller under the bases to eliminate gaps and prevent
ingrowth of fibrous tissues. An anti back-out feature is
contemplated for the screws in certain applications. Examples of
anti back-out features include locking screws with heads threaded
into the bases or rotating locking mechanisms on the bases which
partially cover the heads of the screws.
[0127] Once the energy manipulation device assembly 10 is
completely implanted, the incisions are dosed and allowed to heal.
Subsequent post-operative steps are taken to verify proper
placement and to accomplish any necessary adjustment. In this
regard, two or three-dimensional motion imaging techniques can be
used to observe effectiveness.
[0128] Further details of methods described above, as well as
alternative techniques and methods for locating, orienting,
positioning and implanting assembly/device 10 can be found in
Application Publication No. 2009/0014016 filed Apr. 30, 2008, which
application is hereby incorporated herein, in its entirety, by
reference thereto.
[0129] The bone contacting surfaces of any of the bases 22, 42
described herein can be modified to induce bone growth.
Osteointegration can be obtained through mechanical interlocking or
as a result of chemical loading. For example, the bone contacting
surfaces may be coated with bone morphogenic protein 2 (BMP-2),
hydroxyapatite (HA), titanium, cobalt chrome beads, or any other
osteo-generating substance. According to one embodiment, a titanium
plasma spray having a thickness of approximately 0.033 in .+-.0.005
in. is applied to the inner surface 28. In another embodiment, a HA
plasma spray having a thickness of approximately 35 .mu.m.+-.10
.mu.m is applied alone or in combination with the titanium plasma
spray coating to facilitate osteo-integration.
[0130] Each of the embodiments described herein can incorporate or
cooperate with sensing mechanisms adapted to provide loading
information concerning the tissues being treated. Thus, it is
contemplated that the various pressure sensing mechanisms available
can be placed upon the devices of the present invention. Such
sensors can be configured to provide information about the efficacy
of the energy manipulating device of the present invention and
whether adjustments are necessary. Similarly, sensors can be placed
on anatomy to provide information regarding loads being placed on
the tissues themselves.
[0131] Furthermore, it is contemplated that drugs can be delivered
to the interventional site targeted for energy manipulation. In
this regard, the entirety of the subject matter disclosed in U.S.
Publication No. 2007/0053963 is hereby incorporated herein, by
reference thereto.
[0132] While the present invention has been described with
reference to the specific embodiments thereof, it should be
understood by those skilled in the art that various changes may be
made and equivalents may be substituted without departing from the
true spirit and scope of the invention. In addition, many
modifications may be made to adapt a particular situation,
material, composition of matter, process, process step or steps, to
the objective, spirit and scope of the present invention. All such
modifications are intended to be within the scope of the claims
appended hereto.
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