U.S. patent application number 14/459959 was filed with the patent office on 2014-12-04 for methods of implanting transcutaneous joint unloading devices.
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, Michael E. Landry, Joshua Makower.
Application Number | 20140358231 14/459959 |
Document ID | / |
Family ID | 47437623 |
Filed Date | 2014-12-04 |
United States Patent
Application |
20140358231 |
Kind Code |
A1 |
Landry; Michael E. ; et
al. |
December 4, 2014 |
Methods of Implanting Transcutaneous Joint Unloading Devices
Abstract
Various methods for treating a joint are disclosed herein.
According to one method, a joint is surgically treated by
performing a surgical repair treatment on tissue within the joint
capsule; implanting a load reducing device at the joint and
entirely outside of the joint capsule to reduce load transmitted by
the treated tissue to allow for the tissue within the joint capsule
to heal; and partially unloading the joint during healing of the
surgical repair site.
Inventors: |
Landry; Michael E.; (Austin,
TX) ; Clifford; Anton G.; (Mountain View, CA)
; Makower; Joshua; (Los Altos, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Moximed, Inc. |
Hayward |
CA |
US |
|
|
Assignee: |
MOXIMED, INC.
Hayward
CA
|
Family ID: |
47437623 |
Appl. No.: |
14/459959 |
Filed: |
August 14, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13495440 |
Jun 13, 2012 |
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14459959 |
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61504886 |
Jul 6, 2011 |
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Current U.S.
Class: |
623/14.12 |
Current CPC
Class: |
A61B 17/6425 20130101;
A61B 17/56 20130101; A61B 17/683 20130101; A61B 17/80 20130101;
A61B 17/86 20130101; A61B 2017/564 20130101; A61B 2017/567
20130101 |
Class at
Publication: |
623/14.12 |
International
Class: |
A61B 17/68 20060101
A61B017/68; A61B 17/56 20060101 A61B017/56; A61B 17/86 20060101
A61B017/86; A61B 17/80 20060101 A61B017/80; A61B 17/64 20060101
A61B017/64 |
Claims
1-22. (canceled)
23. A method of treating a joint, comprising: attaching a first
anchor portion of a first percutaneous anchor to a first member of
the joint; attaching a second anchor portion of a second
percutaneous anchor to a second member of the joint; and attaching
a load absorber to the first and second anchors so that a load
absorbing portion of the load absorber is disposed externally of a
user's skin by attaching a first and a second mating portion of the
load absorber to first and second anchor mating portions of the
first and second anchors, the load absorbing portion being disposed
between the first and the second mating portions, the load
absorbing portion comprising a single load absorbing pivot, the
load absorber being attached so that the load absorbing pivot is
pivotable at least about an axis substantially aligned with an axis
of rotation of the first and second members of the joint.
24. The method of claim 23, wherein the load absorbing portion
comprises an absorber and an arm pivotably attached to the absorber
at a pivot point of the load absorbing pivot, the method comprising
adjusting a position of the pivot point relative to the first and
second members of the joint by changing an attachment between the
first mating portion and the first anchor mating portion.
25. The method of claim 24, wherein the first anchor comprises
upper and lower screws and upper and lower links adjustably
attached at first ends thereof to the upper and lower screws,
respectively, and, at second ends thereof, to the arm, and wherein
the lower link is lockable relative to the arm at one of a
plurality of locking points, the position of the pivot point being
adjusted by changing a locking point of the lower link relative to
the arm.
26. The method of claim 24, wherein the first anchor comprises
upper and lower screws and upper and lower links adjustably
attached at first ends thereof to the upper and lower screws,
respectively, and, at second ends thereof, to the arm, wherein the
upper and lower links are adjustably attached to the upper and
lower screws and adapted to pivot about the longitudinal axes of
the upper and lower screws, and wherein the upper and lower links
are locked to the arm so that the upper and lower links form a
plurality of pairs of upper and lower link angles relative to the
arm, the position of the pivot point being adjusted by changing the
upper and lower link angles.
27. The method of claim 23, comprising attaching a second load
absorber to the first and second anchors so that the second load
absorbing portion is disposed externally of a user's skin by
attaching a first and a second mating portion of the second load
absorber to second first and second anchor mating portions of the
first and second anchors, the second load absorber having a load
absorbing portion disposed between the second first and the second
mating portions.
28. The method of claim 23, comprising attaching the first anchor
and the second anchor to the first and second members of the joint
so that the first and second mating portions are at least partially
subcutaneous.
29. The method of claim 23, wherein the joint is a knee joint.
30. (canceled)
31. A method of treating a joint, comprising: attaching a first
anchor portion at a first end of a first percutaneous anchor to a
first member of the joint; attaching a second anchor portion at a
first end of a second percutaneous anchor to a second member of the
joint; and attaching a load absorber to the first and second
anchors so that a load absorbing portion of the load absorber is
disposed externally of a user's skin by attaching a first and a
second mating portion of the load absorber to first and second
anchor mating portions of the first and second anchors at second
ends of the first and second anchors opposite the first ends of the
first and second anchors, the load absorbing portion being disposed
between the first and the second mating portions, and the first
ends of the first and second anchors being disposed
subcutaneously.
32. (canceled)
33. A method of treating a joint, comprising: attaching a first
anchor portion of a first percutaneous anchor to a first member of
the joint; attaching a second anchor portion of a second
percutaneous anchor to a second member of the joint; and attaching
a single load absorber to the first and second anchors so that a
load absorbing portion of the load absorber is disposed externally
of a user's skin only on one side of the joint by attaching a first
and a second mating portion of the load absorber to first and
second anchor mating portions of the first and second anchors, the
load absorbing portion disposed between the first and the second
mating portions.
34. (canceled)
35. A method of treating a joint, comprising: attaching a first
anchor portion of a first percutaneous anchor to a first member of
the joint; attaching a second anchor portion of a second
percutaneous anchor to a second member of the joint; and attaching
a load absorber to the first and second anchors so that a load
absorbing portion of the load absorber is disposed externally of a
user's skin by attaching a first and a second mating portion of the
load absorber to first and second anchor mating portions of the
first and second anchors, the load absorbing portion disposed
between the first and the second mating portions, wherein the first
and the second mating portions and the first and second anchor
mating portions comprise quick-disconnect couplings.
36-38. (canceled)
39. A method of treating a joint, comprising: attaching a first
anchor portion of a first percutaneous anchor to a first member of
the joint by at least one bone screw; attaching a second anchor
portion of a second percutaneous anchor to a second member of the
joint by one bone screw; and attaching a load absorber to the first
and second anchors so that a load absorbing portion of the load
absorber is disposed externally of a user's skin by attaching a
first and a second mating portion of the load absorber to first and
second anchor mating portions of the first and second anchors, the
load absorbing portion disposed between the first and the second
mating portions.
40. The method of claim 39, comprising affixing the first anchor
portion to the first member of the joint by two bone screws.
41. The method of claim 39, comprising affixing the second
percutaneous anchor to a tibia of a knee joint.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application claims the benefit of U.S. Application Ser.
No. 61/504.886, filed Jul. 6, 2011, the entire disclosure of which
is expressly incorporated herein.
BACKGROUND AND SUMMARY
[0002] The present invention relates to a joint unloading device
and, more particularly, to a transcutaneous joint unloading
device.
[0003] Joint replacement is one of the most common and successful
operations in modern orthopaedic surgery. It consists of replacing
painful, arthritic, worn or diseased parts of a joint with
artificial surfaces shaped in such a way as to allow joint
movement. Osteoarthritis is a common diagnosis leading to joint
replacement. Such procedures are a last resort treatment as they
are highly invasive and require substantial periods of recovery.
Total joint replacement, also known as total joint arthroplasty, is
a procedure in which all articular surfaces at a joint are
replaced. This contrasts with hemiarthroplasty (half arthroplasty)
in which only one bone's articular surface at a joint is replaced
and unincompartmental arthroplasty in which the articular surfaces
of only one of multiple compartments at a joint (such as the
surfaces of the thigh and shin bones on just the inner side or just
the outer side at the knee) are replaced. Arthroplasty as a general
term, is an orthopaedic procedure which surgically alters the
natural joint in some way. This includes procedures in which the
arthritic or dysfunctional joint surface is replaced with something
else, procedures which are undertaken to reshape or realigning the
joint by osteotomy or some other procedure. As with joint
replacement, these other arthroplasty procedures are also
characterized by relatively long recovery times and are highly
invasive procedures. A previously popular form of arthroplasty was
interpositional arthroplasty in which the joint was surgically
altered by insertion of some other tissue like skin, muscle or
tendon within the articular space to keep inflammatory surfaces
apart. Among other types of arthroplasty are resection(al)
arthroplasty, resurfacing arthroplasty, excisional arthroplasty,
mold arthroplasty, cup arthroplasty, silicone replacement
arthroplasty, and osteotomy to affect joint alignment or restore or
modify joint congruity. When it is successful, arthroplasty results
in new joint surfaces which serve the same function in the joint as
did the surfaces that were removed. Any chondrocytes (cells that
control the creation and maintenance of articular joint surfaces),
however, are either removed as part of the arthroplasty, or left to
contend with the resulting joint anatomy. Because of this, none of
these currently available therapies are chondro-protective.
[0004] Other approaches to treating osteoarthritis involve an
analysis of loads which exist at a joint. Both cartilage and bone
are living tissues that respond and adapt to the loads they
experience. Within a nominal range of loading, bone and cartilage
remain healthy and viable. If the load falls below the nominal
range for extended periods of time, bone and cartilage can become
softer and weaker (atrophy). If the load rises above the nominal
level for extended periods of time, bone can become stiffer and
stronger (hypertrophy). Finally, if the load rises too high, then
abrupt failure of bone, cartilage and other tissues can result.
Accordingly, it has been concluded that the treatment of
osteoarthritis and other bone and cartilage conditions is severely
hampered when a surgeon is not able to precisely control and
prescribe the levels of 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 is a need for devices which facilitate the control of load on
a joint undergoing treatment or therapy, to thereby enable use of
the joint within a healthy loading zone.
[0005] Certain other approaches to treating osteoarthritis
contemplate external devices such as braces or fixators which
attempt to control the motion of the bones at a joint or apply
cross-loads at a joint to shift load from one side of the joint to
the other. A number of these approaches have had some success in
alleviating pain but have ultimately been unsuccessful due to
patient discomfort or the inability of the devices to facilitate
and support the natural motion and function of the diseased
joint.
[0006] One new approach to treating osteoarthritis involves
implantation of an extra-articular implantable joint unloading
device which is positioned alongside the painful joint and bears
some of the load normally borne by the joint. This unloading device
reduces pain by cushioning the joint from excessive loading. Since
the device is extra-capsular and extra-articular, no bone,
ligament, or cartilage is removed and future treatment options,
such as joint replacement, are still available if needed. However,
for some patients a more temporary solution may be more attractive.
Patients and physicians may also be interested in providing an
unloading device in which a portion of the device is external for
ease of adjustment and removal.
[0007] With the foregoing applications in mind, it has been found
to be desirable to develop temporary joint unloading structures for
mounting to body anatomy with at least a portion of the unloading
structure external and removable. Such structures should conform
generally to body anatomy and cooperate with body anatomy to
achieve desired load reduction, energy absorption. energy storage,
and energy transfer. For these implant structures to function
optimally, they must not cause an adverse disturbance to joint
motion. Therefore, what is needed is an approach which addresses
both joint movement and varying loads as well as complements
underlying or adjacent anatomy.
[0008] Briefly and in general terms, the present disclosure is
directed towards treating diseased or mal-aligned body joints,
typically affected by osteoarthritis, using a transcutaneous joint
unloading device without limiting the range of motion of the
patient's articulating joint. The devices of the present invention
accomplish one or more of: absorbing energy during normal gait,
reducing load on at least a portion of the natural joint, load
transferring or bypassing, energy cushioning, and load sharing,
unloading or load redistribution. In addition, both energy
dampening and shock absorption are considered in effecting such
load manipulations. Further, the particular anatomy of a patient is
considered in the contemplated approaches in that loads on desired
portions of anatomy are manipulated without overloading healthy
surfaces. In a preferred aspect, the present invention adds an
energy absorber to the joint to reduce energy transferred through
the natural joint. One aspect includes a system for manipulating or
absorbing energy transferred by members defining a joint.
[0009] According to an aspect of the present invention, a
transcutaneous unloading device for a joint comprises a load
absorber having a first and a second mating portion, a load
absorbing portion disposed between the first and the second mating
portions, and the load absorbing portion comprising a single load
absorbing pivot, a first percutaneous anchor having a first anchor
portion configured to be affixed to a first member of the joint,
and a first anchor mating portion for mating with the first mating
portion, and a second percutaneous anchor having a second anchor
portion configured to be affixed to a second member of the joint,
and a second anchor mating portion for mating with the second
mating portion, wherein the first and second mating portions and
the first and second anchors are configured so that the load
absorbing portion is disposed externally of a user's skin and so
that the load absorbing pivot is pivotable at least about an axis
substantially aligned with an axis of rotation of the first and
second members of the joint.
[0010] According to another aspect of the present invention, a
method of treating a joint comprises attaching a first anchor
portion of a first percutaneous anchor to a first member of the
joint, attaching a second anchor portion of a second percutaneous
anchor to a second member of the joint, and attaching a load
absorber to the first and second anchors so that a load absorbing
portion of the load absorber is disposed externally of a user's
skin by attaching a first and a second mating portion of the load
absorber to first and second anchor mating portions of the first
and second anchors, the load absorbing portion being disposed
between the first and the second mating portions, the load
absorbing portion comprising a single load absorbing pivot, the
load absorber being attached so that the load absorbing pivot is
pivotable at least about an axis substantially aligned with an axis
of rotation of the first and second members of the joint.
[0011] According to another aspect of the present invention, a
transcutaneous unloading device for a joint comprises a load
absorber having a first and a second mating portion and a load
absorbing portion disposed between the first and the second mating
portions, a first percutaneous anchor having, at a first end
thereof, a first anchor portion configured to be affixed to a first
member of the joint, and, at a second end thereof, a first anchor
mating portion for mating with the first mating portion, and a
second percutaneous anchor having, at a first end thereof, a second
anchor portion configured to be affixed to a second member of the
joint, and, at a second end thereof, a second anchor mating portion
for mating with the second mating portion, wherein the first and
second mating portions and the first and second anchors are
configured so that the load absorbing portion is disposed
externally of a user's skin, and first ends of the first and second
anchors are disposed on opposite ends of the first and second
anchors from the second ends of the first and second anchors and
are configured to be disposed subcutaneously.
[0012] According to another aspect of the present invention, a
method of treating a joint, comprises attaching a first anchor
portion at a first end of a first percutaneous anchor to a first
member of the joint, attaching a second anchor portion at a first
end of a second percutaneous anchor to a second member of the
joint, and attaching a load absorber to the first and second
anchors so that a load absorbing portion of the load absorber is
disposed externally of a user's skin by attaching a first and a
second mating portion of the load absorber to first and second
anchor mating portions of the first and second anchors at second
ends of the first and second anchors opposite the first ends of the
first and second anchors, the load absorbing portion being disposed
between the first and the second mating portions, and the first
ends of the first and second anchors being disposed
subcutaneously.
[0013] According to another aspect of the present invention, a
transcutaneous unloading device for a joint comprises a single load
absorber having a first and a second mating portion and a load
absorbing portion disposed between the first and the second mating
portions, a first percutaneous anchor having a first anchor portion
configured to be affixed to a first member of the joint, and a
first anchor mating portion for mating with the first mating
portion, and a second percutaneous anchor having a second anchor
portion configured to be affixed to a second member of the joint,
and a second anchor mating portion for mating with the second
mating portion, wherein the first and second mating portions and
the first and second anchors are configured so that the load
absorbing portion is disposed externally of a user's skin only on
one side of the joint.
[0014] According to another aspect of the present invention, a
method of treating a joint comprises attaching a first anchor
portion of a first percutaneous anchor to a first member of the
joint, attaching a second anchor portion of a second percutaneous
anchor to a second member of the joint, and attaching a single load
absorber to the first and second anchors so that a load absorbing
portion of the load absorber is disposed externally of a user's
skin only on one side of the joint by attaching a first and a
second mating portion of the load absorber to first and second
anchor mating portions of the first and second anchors, the load
absorbing portion disposed between the first and the second mating
portions.
[0015] According to another aspect of the present invention, a
transcutaneous unloading device for a joint comprises a load
absorber having a first and a second mating portion and a load
absorbing portion disposed between the first and the second mating
portions, a first percutaneous anchor having a first anchor portion
configured to be affixed to a first member of the joint, and a
first anchor mating portion for mating with the first mating
portion, and a second percutaneous anchor having a second anchor
portion configured to be affixed to a second member of the joint,
and a second anchor mating portion for mating with the second
mating portion, wherein the first and second mating portions and
the first and second anchors are configured so that the load
absorbing portion is disposed externally of a user's skin, and
wherein the first and the second mating portions and the first and
second anchor mating portions comprise quick-disconnect
couplings.
[0016] According to another aspect of the present invention, a
method of treating a joint comprises attaching a first anchor
portion of a first percutaneous anchor to a first member of the
joint, attaching a second anchor portion of a second percutaneous
anchor to a second member of the joint, and attaching a load
absorber to the first and second anchors so that a load absorbing
portion of the load absorber is disposed externally of a user's
skin by attaching a first and a second mating portion of the load
absorber to first and second anchor mating portions of the first
and second anchors, the load absorbing portion disposed between the
first and the second mating portions, wherein the first and the
second mating portions and the first and second anchor mating
portions comprise quick-disconnect couplings.
[0017] According to another aspect of the present invention, a
transcutaneous unloading device for a joint comprises a load
absorber having a first and a second mating portion and a load
absorbing portion disposed between the first and the second mating
portions, a first percutaneous anchor having a first anchor portion
configured to be affixed to a first member of the joint by at least
one bone screw, and a first anchor mating portion for mating with
the first mating portion, and a second percutaneous anchor having a
second anchor portion configured to be affixed to a second member
of the joint by one bone screw, and a second anchor mating portion
for mating with the second mating portion, wherein the first and
second mating portions and the first and second anchors are
configured so that the load absorbing portion is disposed
externally of a user's skin.
[0018] According to another aspect of the present invention, a
method of treating a joint comprises attaching a first anchor
portion of a first percutaneous anchor to a first member of the
joint by at least one bone screw, attaching a second anchor portion
of a second percutaneous anchor to a second member of the joint by
one bone screw, and attaching a load absorber to the first and
second anchors so that a load absorbing portion of the load
absorber is disposed externally of a user's skin by attaching a
first and a second mating portion of the load absorber to first and
second anchor mating portions of the first and second anchors, the
load absorbing portion disposed between the first and the second
mating portions.
[0019] Other features of the unloading device and device will
become apparent from the following detailed description, taken in
conjunction with the accompanying drawings, which illustrate, by
way of example, the principles of the embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The features and advantages of the present invention are
well understood by reading the following detailed description in
conjunction with the drawings in which like numerals indicate
similar elements and in which:
[0021] FIG. 1 is a perspective view of a joint unloading device
according to an aspect of the present invention;
[0022] FIG. 2 is a side view of the joint unloading device of FIG.
1;
[0023] FIG. 3 is a front view of the joint unloading device of FIG.
1 showing a bilateral version;
[0024] FIG. 4 is a rear view of the joint unloading device of FIG.
1 showing a unilateral version;
[0025] FIG. 5 is a top view of the joint unloading device of FIG.
1;
[0026] FIG. 6 is a bottom view of the joint unloading device of
FIG. 1;
[0027] FIG. 7 is a side view of the joint unloading device of FIG.
1 in a flexed condition;
[0028] FIG. 8 is a schematic, cross-sectional view of a joint
unloading device according to another aspect of the present
invention;
[0029] FIG. 8A is a side view of one example of an anchor;
[0030] FIG. 9A is a side view of another embodiment of the joint
unloading device; and
[0031] FIG. 9B is a side view of the joint unloading device of FIG.
9A is a flexed condition.
DETAILED DESCRIPTION
[0032] Referring now to the drawings, which are provided by way of
example and not limitation, the disclosed embodiments are directed
to apparatus and methods for treating the knee joint. However,
these embodiments may also be used in treating other body joints,
and to alleviate pain associated with the function of diseased or
misaligned members forming a body joint while preserving range of
motion of the joint. The embodiments described below relate to
apparatuses and methods for reducing the amount of load carried by
the natural joint anatomy.
[0033] Certain of the embodiments include joint unloading devices
designed to minimize the loading of the anatomy of the body, such
as that found at a body joint. It has been postulated that to
minimize pain, unloading or load absorption of 1-40% of the forces
on the joint, in varying degrees, may be necessary. Variable
unloading or energy absorption in the range of 5-20% can be a
target for certain applications.
[0034] It has also been found that a medial compartment of a knee
of an average person with osteoarthritis can benefit from an
absorber set for compression between 1 mm and 10 mm, and preferably
3-6 mm with a spring or absorber element that accommodates a range
from 20-60 pounds, preferably 20-40 pounds. In a preferred
embodiment, the absorber is set for about 4 mm of such compression
and a pre-determined load of about 30-40 pounds.
[0035] When a joint unloading device is attached to a joint as
described below, less force is transferred through the bones and
cartilage of the joint, and a degree of the force between bones of
the joint is absorbed by the unloading device. In one embodiment,
the joint unloading device can be initially configured to
eliminate, variably reduce or manipulate loads at a first desired
amount, and to be later adjusted or altered as patient needs are
better determined or change to a second desired amount. The
unloading device can be adjusted periodically or can be
automatically adjusting based on feedback provided by the
device.
[0036] In applications to the knee joint, the unloading device can
be positioned only on the medial side of the knee and designed to
absorb medial compartment loads in a manner that completely
preserves the articulating joint and capsular structures. In other
application, the unloading device can be positioned and designed
for unloading the lateral compartment of the knee joint or both the
medial and lateral compartments of the knee.
[0037] One embodiment of the present invention is a transcutaneous
knee unloading device comprised of an external kinematic load
absorber including at least one spring attached to transcutaneous
bone anchors. Although the illustrated embodiment is designed for
use with a knee joint, the device can be applied to the ankle, hip,
and other joints.
[0038] A transcutaneous knee unloading device 21 according to an
aspect of the invention for a knee joint 1 is seen in FIGS. 1-8.
The knee joint 1 comprises a first member 2, which may be a femur,
and a second member 3. which may be a tibia. The device 21 shown in
FIGS. 1-8 is shown as having an external component on a medial side
of a left knee joint 1, but it will be appreciated that an external
component of the device may be disposed on the lateral side of the
joint, or on a right joint. As shown in phantom in FIG. 3. an
external component of the device 21 may be disposed bilaterally,
i.e., on both the lateral and medial sides of the joint 1.
[0039] The device 21 comprises a load absorber 23 that is
ordinarily entirely or at least substantially outside of the user's
skin. The load absorber 23 has a central load absorbing portion
disposed between first and the second mating portions. The device
21 further comprises first and second transcutaneous anchors 33 and
35 in the form of bone screws each having a first threaded end
configured to be affixed to the first member 2 of the knee joint 1,
and a mating end for mating with the first mating end of the load
absorber 23. The device also comprises a third transcutaneous
anchor 37 having a threaded end configured to be affixed to the
second member 3 of the knee joint 1. and a mating end for mating
with the second mating end of the load absorber 23.
[0040] The load absorber 23 and the first, second and third anchors
33, 35 and 37 are configured so that at least a portion of the load
absorber is disposed externally of a user's skin S (shown by dotted
lines in FIG. 3). Thus, the load absorber 23 can be attached and
detached from the first, second and third anchors 33, 35 and 37
which are secured in the bone. The attachment and detachment of the
load absorber 23 can be accomplished by the patient or physician
and depending on the type of attachment can be done with or without
tools. The patient may remove the absorber 23 during times of
inactivity, such as when sleeping, bathing or sitting at a desk and
may attach the absorber during all waking hours or only during
active time periods.
[0041] As the bone anchors 33, 35 and 37 are designed to traverse
the skin of the patient, certain precautions can be implemented to
prevent the transmission of microorganisms at the skin penetration
site. In one embodiment, the anchors 33, 35 and 37 can have a
coating to reduce the possibility of infections, for example,
titanium anchors can be provided with a silver anti-infective
coating. Other known coatings and precautionary methods can also be
used. Other precautions for prevention of infection can include
specific cleaning and maintenance steps to be performed by the
patient. For example, adhesive coverings may be provided for the
exposed ends of the bone anchors when they are not in use.
[0042] In another embodiment, a porous tissue cuff can be secured
around the bone anchors 33, 35, 37 to prevent infection at the
tissue penetration site. A tissue cuff 95 as shown in FIG. 8A is
secured to the bone anchor 37 and promotes skin growth into the
cuff to provide a barrier to microorganisms. Attachment of the skin
to the tissue cuff 95 can be initially preformed by suturing,
followed by tissue growth. The secure attachment between the cuff
95 and the skin eliminates pathways for microorganisms to enter the
body. Examples of materials for use in the tissue cuff 95 include
ePTFE, PTFE and other materials used for synthetic vascular grafts.
The material of the tissue cuff 95 should be flexible and avoid
irritation of adjacent tissue.
[0043] The bone anchors can also include flanges or other anchoring
structures which allow suturing to the skin. The flanges 77 shown
on each of the anchors are arranged to lie just below the surface
of the patient's skin. The flanges 77 can be provided with small
openings to accommodate sutures for securing the skin around the
anchors. Alternatively, other known skin securing systems can be
used to secure the skin to the anchors.
[0044] The bone anchors 33, 35 and 37 as shown in the present
application are designed to have a top surface which do not
protrude from the surface of the skin to prevent any discomfort of
protruding parts when the device is removed. Alternately, other
anchor structures can be used which protrude somewhat from the
bone, however, preferably the bone anchors do not protrude more
than about 5 mm from the skin surface.
[0045] The unloading device 21 comprises an energy absorber 23 and
an arm 45 that are pivotably attached to each other via one or more
pivot links. A first pivot link 47, shown in FIG. 1, is mounted in
a recess in the lower end of the arm 45 and also includes a pivot
post 47a that extends in an anterior direction and is secured in
and pivotable relative to an opening 50 in the energy absorber 23.
The first pivot link 47 permits pivoting of the arm 45 relative to
the energy absorber 23 in two dimensions including about a first
axis normal to the user's coronal plane and a second axis
perpendicular to the first axis direction.
[0046] As shown in FIG. 1 first pivot link 47 includes the pivot
post 47a which permits angulation of the external surfaces of the
arm 45 and absorbing portion 43 with respect to one another.
Rotation about the pivot post 47a accommodates varus/valgus
angulation of the joint. The first pivot link 47 also provides
relative pivoting of the absorber 23 and the arm 45 at least about
a pivot post 49 which is arranged along an axis substantially
normal to the user's sagittal plane and extends through the pivot
link 47. The pivot, post 49 allows flexion/extension motion of the
joint 1 and provides the largest range of motion of the unloading
device 21. The pivot post 49 is ordinarily arranged to be located
substantially parallel with an axis of rotation of the first and
second members 2 and 3 of the joint 1. Positioning the pivot post
49 directly on the axis of rotation of the joint provides for
unloading force throughout rotation of the joint and throughout the
gait of the patient. However, the device 21 facilitates positioning
the pivot point 49 in a variety of locations relative to the axis
of rotation of the knee joint 1 to obtain various unloading
responses. A pivot point 49 just slightly anterior and superior of
the axis of rotation of the joint provides an unloading device
which unloads the joint in full extension and provides no unloading
when the knee is beyond some predetermined amount of flexion. Other
locations of the pivot point 49 can be used to achieve other
unloading profiles during the motion of the joint.
[0047] It is presently believed that the first pivot link 47 should
be arranged to permit at least 20 degrees or more of hyperextension
of the knee joint 1 and at least 140 degrees or more of flexion, it
being further believed that 30 degrees of hyperextension and
150-160 degrees of flexion will be sufficient for the vast majority
of users and still allow for significant surgical variation. The
first pivot link 47 also allows for varus/valgus rotation of the
knee joint of at least 10 degrees and preferably at least 30
degrees.
[0048] The first and second anchors or bone screws 33 and 35 are
connected to the arm 45 by upper and lower links 55 and 57. The
lower link 57 is rotatably attached at a first end thereof to the
lower screw 35 and at a second end is adjustably attached to the
arm 45. The upper link 55 is rotatably attached at a first end
thereof the upper screw 33 and at a second end is rotatably
attached to the arm 45. The first ends of the upper and lower links
55 and 57 are ordinarily attached to the upper and lower screws 33
and 35 in a manner such the links are substantially unable to
transmit moment to the upper and lower screws, such as that the
links are attached in a manner so that they are freely rotatable
relative to the screws. The links are also preferably detachable
from the bone screws 33 and 35 to allow the unloading device to be
removed from the bone anchors. One such connection will be
described in further detail below with reference to FIG. 8.
[0049] The links 55 and 57, shown most clearly in FIG. 2, may be
the same length but, ordinarily, are of different lengths an allow
adjustment of unloading device to a particular patient. Ordinarily,
it is desirable for a longitudinal axes of the arm 45 and the femur
2 to be parallel, as shown in FIG. 2, and the device is adjustable
to achieve this arrangement as will be described below.
[0050] The lower link 57 is adjustable and lockable relative to the
arm 45 at one of a plurality of locking points. As shown in FIG. 2,
the arm 45 comprises a longitudinal slot 59 and the lower link 57
comprises fastener 63 at the second end of the lower link. The
fastener extends through the slot 57 and threads into an internally
threaded hole in the lower link 57 to secure the link 57 to the arm
45 at any locking position along the length of the slot.
Ordinarily, the fastening arrangement between the arm 45 and the
lower link 57 will be one that will prevents relative angular
between the longitudinal axes of the arm and the lower link once
the fastener 63 has been tightened. Changing the locking point of
the lower link 57 relative to the arm 59 changes a location of the
absorber pivot point 49 relative to the knee joint 1 and can change
the overall function of the device.
[0051] While locking the lower link 57 to the arm 45 in this
fashion can serve to also set the relative position of the upper
link 55 relative to the arm, ordinarily, the upper link is also
locked to the arm, such as by a threaded fastener 65 extending
through the upper end of the arm 45 and into a threaded hole in the
upper link 55. When at least the lower link 57 is locked relative
to the arm 45, the upper and lower links 55 and 57 form a plurality
of pairs of upper and lower link angles relative to the arm.
Changing the upper and lower link angles ordinarily changes a
location of the pivot point 49 relative to the first and second
members 2 and 3 of the knee joint 1. Selection of the length of the
lower link 57 relative to the length of the upper link 55 can
impact the variety of angles that the arm 45 can form with the
first member 2 of the knee joint 1 and the position of the pivot
point 49. Longitudinal axes of the upper and lower links 55 and 57
ordinarily extend substantially perpendicularly to longitudinal
axes of the upper and lower screws 33 and 35 when the screws are
parallel.
[0052] The energy absorber, also called a load absorber 23 is
ordinarily pivotably attached to the third anchor 37, by a second
pivot link 69 that permits pivoting of the absorber relative to the
second anchor in two dimensions. Similar to the first pivot link
47, the second pivot link 69 has a pivot post 73 which extends in
an anterior direction from the third anchor 37 and is received in
an opening in the lower end of the energy absorber 23. The pivot
post 73 pivotably connects the second pivot link 69 to the energy
absorber allowing varus/valgus rotation of the joint.
[0053] Ordinarily, the second pivot link 69 is removably attached
to the third bone anchor screw 37 in a manner that at least
substantially precludes transmission of moment to the screw 37,
i.e., the second pivot link is ordinarily freely rotatable relative
to the anchor screw. It is desirable for the second pivot link 69
to be easily attached to and detached from the anchor screw 37,
such as by providing suitable quick-release fittings as discussed
below with reference to FIG. 8. The second pivot link 69 can be
provided in different sizes to facilitate offsetting the absorber
23 a desired distance from a user's skin.
[0054] The bone screws 33, 35 and 37 are ordinarily bicortical
screws which pass through the cortical (harder exterior bone) on
two opposite sides of the bone to achieve secure and lasting
fixation. Although the screws are shown extending out of the
opposite side of the bone in FIG. 1, they do not need to pass out
of the bone. In the case of the bilateral embodiment of FIG. 3, the
screws 33, 35 and 37 pass through the bones and are provided with a
fitting to allow securing of the absorber on both sides of the
joint with the same bone screws.
[0055] The load absorber 23 ordinarily comprises a spring 79 and a
telescoping piston and arbor assembly. Alternatively, the spring 79
can serve as the arbor with a piston translating in the interior
bore of the spring to accommodate the variable distance between the
bones of the joint during rotation. U.S. Patent Application
Publication Nos. US20080275565 and US2008/0275555 and U.S. patent
application Ser. No. 12/843,381 are incorporated herein by
reference and disclose embodiments of spring, piston and arbor
assemblies that are suitable for use in. connection with the
present invention. The load absorber 23 is arranged so that as a
user applies load to the knee joint 1, such as by standing, walking
or running, the spring 79 will tend to absorb some or all of the
force and thereby reduce load on the knee joint.
[0056] As seen in FIG. 7, when the knee joint is bent, a piston 83
and arbor (beneath the spring) telescope to allow the absorber 23
to extend to accommodate an increasing distance between the first
pivot link 47 and the second pivot link 69. Thus, the absorber
spring 79 acts in compression to apply a force when the knee joint
is in extension and the spring applies no force to the bones in
tension when the joint is positioned in flexion as shown in FIG.
7.
[0057] The absorber 23 can be provided with quick connection
mechanisms (not shown) at both ends for quick attachment to and
removal from corresponding connection mechanisms in the upper and
lower pivot links 47 and 69 to facilitate changing the absorber 23
for a particular user. For example, absorbers may be provided in
different lengths and different spring forces depending on the
patient anatomy.
[0058] In the bilateral embodiment, as seen in FIG. 3, the
unloading device 21 is positioned on the medial side of the knee
joint 1 while a second unloading device 121 is positioned on the
lateral side of the joint. The bone screw anchors 33, 35 and 37
extend through the bone and are attached to the corresponding upper
and lower links 155 and 157 and pivot link 169. A second absorber
123 and second arm 145 can be formed with the same features as
those in the medial side device or can be modified for the lateral
side of the joint.
[0059] FIG. 8 illustrates one example of a quick disconnect fitting
for connection to the bone anchors in a removable manner. It is
desirable for the upper and lower links 55 and 57 and the pivot
link 69 to each be easily attached to and detached from the
corresponding bone anchors 33, 35 and 37 either by a physician or a
patient. Fittings such as quick-disconnect fittings can be provided
to facilitate attachment and removal of the external load absorber
23 from the bone anchors by the user with or without assistance.
Examples of quick disconnect fittings include snap lock fittings,
taper lock fittings and interference fittings. In one example, as
shown in FIG. 8, the quick-disconnect fitting for attaching the
pivot link 69 to the bone screw 37 secured in the tibia includes a
tapering central bore 85 in the external end of the screw 37 and a
corresponding tapered peg 87. The tapered peg 87 also has a mating
end for rotatably mating with the pivot link 69. The connections to
the first and second bone screws 33 and 35 can also include similar
quick connections with tapered pegs 91 and 93. In the event that a
physician prefers for the unloading device to be removed only in
the doctor's office, more secure fasteners including screws or
locking screws can be used.
[0060] FIGS. 9A and 98B illustrate an alternative embodiment of an
unloading device 121 in which an external cam base 123 is secured
to the femur 2 by one or more transcutaneous anchors 125. The cam
base 123 cooperates with a follower 127 provided on a follower base
129 which is also positioned external of the knee and secured to
the tibia 3 by transcutaneous anchors 131. The follower 127 is
shown in the form of a small roller, however, other moving and
non-moving followers may also be used. The follower 127 is mounted
on the end of an absorber 133 which operates in a manner similar to
the absorbers described above to absorb a portion of the forces
normally transmitted by the natural knee joint. The cam and
follower unloading device 121 provides an external discontinuous
unloading device in which one or both bases 123, 129 can be removed
to deactivate the device.
[0061] A method of treating a knee joint 1 is described with
reference to the device 21 shown in FIGS. 1-7. According to the
method, first and second transcutaneous anchors 33 and 35 is
attached to a first member 2 of the knee joint 1, such as by
screwing upper and lower screws 33 and 35 into holes that have been
drilled in a femur. A third transcutaneous anchor 37 is attached to
a second member 3 of the knee joint 1, such as by screwing into a
hole drilled in a tibia. Although two anchors are illustrated on
the femur and one on the tibia, other numbers and types of anchors
can also be used. The positions of the anchors may be determined by
one or more templates or by using the absorber 23 and arm 45 as a
guide to determine the proper positioning for the anchors.
[0062] A load absorber 23 is attached to the anchors 33, 35 and 37
so that the load absorbing portion is disposed externally of a
user's skin. The position of the pivot point 49 relative to the
axis of rotation of the first and second members 2 and 3 of the
knee joint 1 is adjusted by changing an angle of the lower link 57
in the manner described above.
[0063] Because the femur has six degrees of freedom relative to the
tibia, it is desirable that a load absorbing device have at least
four degrees of freedom, and preferably at least six degrees of
freedom. The device 21 according to an aspect of the invention has
six degrees of freedom as follows. The two pivot links 47 and 69
with each provide two degrees of freedom; about the pivot posts
47a, 49 and 73 and about the peg 87: linear movement of the piston
83 relative to the spring 79 provides one degree of freedom; and
rotational movement of the piston 83 relative to the spring and
arbor provides one degree of freedom. While the device 21
illustrated in FIGS. 1-8 provides motion with rotational joints, it
will be appreciated that other types of joints and bearings, such
as three degree of freedom spherical bearings, can be used
instead.
[0064] The unloading device 21 according to an aspect of the
invention can be useful where the bones proximate the knee joint
limit the locations in which femoral and tibial anchors can be
provided. Even if it is necessary to provide the anchors at a
distance from a location at which they would normally be installed,
simple external adjustments can ensure that the pivot points of the
device will be at desired locations. These adjustments can be
accomplished after attachment of the anchors. In this case, the arm
45. links 55 and 57, pivot link 69, and absorber 79 can be selected
among elements provided in varying lengths.
[0065] The unloading device 21 according to an aspect of the
invention can be versatile. The device shown in FIGS. 1-8 is
illustrated used on a left medial knee, however, it could also be
used on a right medial knee with the same parts rotated about
various pivots. A device for use on left or right lateral knees,
such as the device 121 of FIG. 3, will be similar to the device 21,
however, somewhat different anatomical considerations may require
alterations.
[0066] The unloading device 21 according to an aspect of the
invention can be used as a more temporary version of devices that
are normally provided subcutaneously. This can be particularly
useful for temporary unloading of the knee joint after another
surgical procedure including cartilage repair or regeneration to
allow the surgical site to heal under reduced loading conditions.
The device may also be useful for users who are hesitant to undergo
a procedure to have a fully implantable system. The device can be
implanted minimally invasively with only a few load bearing screws
inserted into the bone.
[0067] The device can be intraoperatively or post-operatively
adjusted. For example, the device can be adjusted post-operatively
as further or less load manipulation becomes necessary. Moreover,
the device can be activated and adjusted to absorb energy to
desired degree or can be deactivated so that no energy absorbing
occur, such as just subsequent to implantation during a period of
healing. In this way, a natural healing process where tissue and
bone at the interventional site grows to help in fixation of the
structure can be allowed to progress prior to activating the load
manipulating capabilities of the absorber.
[0068] The device can be used to provide load manipulation
throughout a wide spectrum of joint unloading from complete
unloading and even distraction of the joint to lower levels of
partial unloading depending on the clinical situation of the
patient. Advantageously, the external unloading device allows for
changing clinical needs during the healing process or progression
of a clinical condition. For patients seeking pain relief from
osteoarthritis pain in a joint, it has also been found that a
medial compartment of a knee of an average person with
ostcoarthritis can benefit from an absorber element that unloads
the joint in a range from 20-60 pounds, preferably 20-40 pounds.
However, this unloading may be adjusted further depending patient
specific factors including patient size, pain level and activity
level. Adjustments can be made by periodically by a physician to
address patient reported pain or can be made by the patient at a
physician's instruction during changing daily activity. For pain
relief, the unloading is desired through only a portion of the gait
cycle including the stance phase of the gait cycle.
[0069] The device can also be used for temporarily for complete
unloading or distraction to facilitate tissue regeneration in
patients recovering from joint surgery or trauma. Although
permanent complete unloading would be negative to joint vitality,
temporary unloading of 100% of the joint forces or even distraction
of the joint can facilitate biological regeneration. When
distraction is provided, unloading sufficient to provide a space of
about 0.5 to 5.0 mm between the regenerating joint tissues is
desired. The 100% unloading or distraction can be maintained for a
period of about 2-4 months, preferably about 3 months to allow
regeneration without significant negative effects on joint
vitality. This complete unloading or distraction should be followed
by a reduction in the percent of unloading (joint reloading) over
the subsequent 1-3 years. The gradual reloading of the joint can be
done in a gradual or stepwise manner with the goal of eliminating
the unloading device completely over a period of time. Although
complete unloading or distraction are described for promoting
tissue regeneration, less than 100% unloading may also be used to
promote tissue regeneration. In one example 60% to 100% unloading
can be provided to promote tissue regeneration.
[0070] In the case of complete or near complete unloading to allow
tissue regeneration. unloading may be needed throughout the entire
gait cycle or for only a portion of the gait cycle depending on the
location of the damaged tissue within the joint. Examples of use of
load reducing devices, such as the external unloading devices 21
and 121 of the present invention for load reduction during healing
from other surgical procedures is described in U.S. patent
application Ser. No. ______ (attorney docket no. 83456.0078)
entitled "Methods and Devices for Partial Joint Offloading During
Healing of Joint Tissue," filed on even date herewith and
incorporated herein by reference in its entirety.
[0071] The device can also incorporate an adjustable energy
absorber which can be easily adjusted as the patient's need for
unloading of the joint changes. Examples of adjustable energy
absorbing devices are described in U.S. Patent Publication No.
2008/0275565 which is incorporated herein by reference in its
entirety. Such adjustable absorbers allow the patient of physician
to adjust the energy absorbing or absorption device to alter the
load manipulating or absorbing function of the device. For example,
the physician may adjust the device 21 based on external or
internal measurement of the load on the joint or on the absorber.
Alternatively or additionally, the patient may adjust the absorber
based on a current activity level, leaving the device on a low
unloading setting while sitting at a desk and changing to a high
unloading setting when exercising.
[0072] Moreover, feedback systems can be incorporated into the
device to indicate the past performance of the device and help in
adjustment for better performance. For example, the device may
record data including loading, cycling and time worn.
[0073] In each of the disclosed embodiments, various features can
be incorporated such as audible and textile feedback sub-systems
can be incorporated to both indicate translation of load adjustment
structure as well as to exhibit locking and unlocking of
subcomponents.
[0074] Moreover, the device can include springs machined to provide
desirable energy absorbing which varies as the spring is compressed
during various degrees of flexion and extension of joint markers to
which the unloading device is attached.
[0075] The term "spring" is used throughout the description but it
is contemplated to include a variety of conventional springs
including coil springs. leaf springs and other springs as well as
other energy absorbing structures, such as resilient materials can
be used to accomplish the functions of the invention. Magnetic,
hydraulic, pneumatic or piezoelectric systems can also serve the
unloading function of the spring.
[0076] In the present application, the use of terms such as
"including" is open-ended and is intended to have the same meaning
as terms such as "comprising" and not preclude the presence of
other structure, material, or acts. Similarly, though the use of
terms such as "can" or "may" is intended to be open-ended and to
reflect that structure, material, or acts are not necessary, the
failure to use such terms is not intended to reflect that
structure, material, or acts are essential. To the extent that
structure, material, or acts are presently considered to be
essential, they are identified as such.
[0077] While this invention has been illustrated and described in
accordance with a preferred embodiment, it is recognized that
variations and changes may be made therein without departing from
the invention as set forth in the claims.
* * * * *