Invention (Patent Application Publication): Mansmann
KA. Tendon-sparing implants for arthroscopic replacement of hip cartilage. WO2012162571A1 (2012).
WO2012162571A1S US
Inventor: Kevin A. Mansmann
Worldwide applications 2012 WO
Application PCT/US2012/039481 events:
2012-05-24 Application filed by Mansmann Kevin A
2012-11-29 Publication of WO2012162571A1
Tendon-sparing implants for
arthroscopic replacement of hip cartilage
Kevin A. Mansmann
Abstract
Surgical implant devices are
disclosed which will allow completely arthroscopic resurfacing of the
acetabular socket, and the femoral head, in hip joints, in both humans, and in
animals such as dogs. Such devices, made of flexible polymers with smooth articulating
surfaces and porous anchoring surfaces, can be provided with centered openings,
to allow a surgeon to spare the major ligament (the ligamentum teres) which
connects the femoral head to the pelvis. Various
anchoring means are also disclosed.
Description
BACKGROUND
This invention is in the field of orthopedic surgery, and
relates to surgical implant devices designed for use in the arthroscopic
(minimally invasive) replacement of damaged cartilage in hip joints, in animals
or humans.
Extensive background information on the tools, devices, and
methods that are used for repairing injured, degenerated, or otherwise damaged
cartilage in hip joints is contained in numerous medical school textbooks,
review articles, vendor catalogs and training materials, and other reference
works that are well-known to surgeons. Well-known medical school texts which
describe and illustrate this type of surgery include Campbell 's Operative
Orthopaedics (a multi-volume set which was last issued in paper as the 11th
edition in 2007, with online updating since then) and Wheeless ' Textbook of
Orthopaedics (which is available in a "dynamic online" form which is
extensively illustrated, at www.wheelessonline.com/ortho).
In addition, numerous orthopedic supply companies (including
Stryker, Zimmer, Smith & Nephew, and various others) sell surgical implants
used for so-called "hip replacement" surgery, which is one of the
most common and well-known types of orthopedic surgery. All such manufacturing
companies and vendors have published detailed information, for surgeons, on how
to surgically implant their products. Furthermore, detailed information on such
implants also is available to the public via a website run by the U.S. Food and
Drug Administration (FDA), which uses panels of impartial experts to review any
applications that are submitted by companies to test or use any new type of
surgical implant in human patients.
Additional
background information on new types of cartilage-replacing implants which are
flexible, and which are specifically designed for arthroscopic implantation, is
available in various issued patents and published applications that were
invented or … Mansmann (i.e., the same applicant herein), an orthopedic surgeon
whc …
Such prior published applications include:
Serial number 12/067654, published as 2009/132047,
"Anchoring systems and interfaces for flexible surgical implants for
replacing cartilage";
Serial number 11/471090, published as 2007/293947,
"Multi-part implants for combined repair of hyaline and meniscal cartilage
in joints";
Serial number 11/390539, published as 2007/224238,
"Implants for replacing hyaline cartilage, with hydrogel reinforced by
three-dimensional fiber arrays";
Serial number 11/105677, published as 2005/287187,
"Hydrogel implants for replacing hyaline cartilage, with charged surfaces
and improved anchoring";
Serial number 10/677444, published as 2004/133275,
"Implants for replacing cartilage, with negatively-charged hydrogel
surfaces and flexible matrix reinforcement";
Serial number 10/011933, published as 2002/183845,
"Multi-perforated non-planar device for anchoring cartilage implants and
high-gradient interfaces";
Serial number 10/071930, published as 2002/173855,
"Cartilage repair implant with soft bearing surface and flexible anchoring
device"; and,
Serial number 09/818811, published as 2002/022884,
"Meniscus-type implant with hydrogel surface reinforced by three-dimensional
mesh".
Because of the different anatomic structures of the knees
and hips, in humans, the cartilage segments in knee joints are much closer to
the skin surfaces, and are much more easily accessible to surgeons without
having to cut deep into soft tissues, compared to cartilage segments in hip
joints. In addition, by alternately bending and extending a knee joint while it
is being surgically repaired, various parts and surfaces of the cartilage
segments in a knee can be made even more accessible, to the surgeon repairing
that joint. Accordingly, the research to date by Mansmann (including the
development of implant devices that are fully suited for testing in large
animals, such as sheep and goats) has focused primarily on implant devices that
are sized, shaped, and designed for implantation in knee joints.
Now that that work is firmly on a pathway which includes
testing in large animals, Dr. Mansmann has turned his attention to the
challenges of implants designed for hip repairs, as described below. Based on a detailed understanding of
the "technology … developing over the past 10 years, for creating implant
devices contain … polymers that are designed and suited for arthroscopic repair
of knee joints, the Applicant herein has determined that the time has arrived
to begin doing focused and targeted work to modify and redesign those types of
implant devices, so that they will be suited for replacing injured, diseased,
or otherwise damaged cartilage in hip joints, in humans.
In addition, the Applicant has recognized that there is a
potentially very large and unmet need for hip repairs that are minimally
invasive, and completely arthroscopic, in dogs. Due to historical patterns of dog breeding
which generally can be encompassed by the term … "in-breeding", many
breeds of dogs are prone to severe congenital hip problems. Accordingly,
the Applicant has recently recognized that the technology and designs he has
been developing and refining over the past decade, for flexible
cartilage-replacing implants, have reached a point where they can be adapted
and optimized for insertion and emplacement in four-legged animals such as
dogs, using arthroscopic methods and tools. By adapting this technology to
provide arthroscopic hip repairs in dogs (which can be directly adapted for
other types of four-legged animals), this approach can minimize the pain and
discomfort that will be suffered by an animal, both immediately after surgery,
and during a longer recovery period. For animals that cannot talk, and that
cannot understand why they must suffer at the hands of humans, this can greatly
improve the nature, quality, and caliber of hip repair surgery.
It should be noted that this work, to create flexible
implants that can be used to arthroscopically replace hip cartilage, does not
merely involve reshaping and resizing the implant devices that are disclosed
herein. Instead, these new designs arise after careful study and analysis of:
(i) the natural patterns of lubrication of a healthy hip joint, by native
synovial fluid; and, (ii) the major and even drastic alteration in the pattern
of lubrication which occurs, when a "conventional" hip replacement is
performed.
Most "conventional" hip replacements that are
performed in human patients, at the current time, use two "loading"
surfaces which are both made of hard and rigid materials. At least one surface,
in essentially all implants used in humans today, is made of an extremely hard
and rigid material, such as a titanium or cobalt steel alloy, or a ceramic. In most implants used today, the
surface which covers the convex "head" or "ball" at the
upper end of the femur bone (i.e., the long bone that passes from the hip to
the knee), is made of tha … The other cartilage-replacing implant surface, in a
hip replacem … surface known as the "acetabular socket", which is
part of the pelvic bone. In a human pelvis, the two acetabular sockets
face generally forward, somewhat downward, and in a somewhat
"lateral" or "outward" direction (the term
"lateral" indicates the direction away from an imaginary vertical
"center plane" of a human or animal; by contrast, the term
"medial" indicates an orientation or movement toward the center
plane). In most hip implants being used in humans today, the implant component
which replaces the acetabular socket is made of a very hard and effectively
rigid polymer, most commonly a material called "ultra-high molecular-
weight polyethylene", abbreviated as UHMWPE. Some implants in the past
used "metal-on-metal" interfaces; however, those tended to suffer
from problems of degradation and leaching, over time, leading to unhealthy
levels of cobalt or other unusual minerals in a patient's blood and tissues.
Because the very hard and rigid materials used in
conventional hip replacements are machined and finished in ways which make them
extremely smooth, and because the sizes, shapes, and nature of those types of
hip-replacing implants effectively requires that the native femur-pelvic
interface must be completely removed and replaced, conventional hip
replacements are designed to not require constant lubrication. Therefore, they
severely disrupt the flow and distribution of "synovial fluid" (i.e.,
the natural fluid which lubricates mammalian joints), in a hip joint, after hip
replacement surgery. Instead of being designed to sustain and promote the
normal presence (and the distribution and flow patterns) of synovial fluid, as
a liquid which will coat and lubricate the "articulating surfaces" of
the cartilage-replacing materials in hip implants, conventional hip implants
are designed to function without such lubrication.
It also should be noted that conventional hip implants
completely remove and eliminate a major physiological structure which is
present in healthy hip joints, called the ligamentum teres. The medical term
"ligament" refers to specialized bands, sheets, or segments of
connective tissues which connect two different structures to each other (the
term "tendon" is similar, but it is limited to the specialized
connective tissues that connect muscles, to other types of tissues). The
specific ligament which is called the ligamentum teres directly couples the
acetabular socket (i.e., part of the pelvic bone) to the femur bone (i.e., the
thigh bone, where the ligamentum teres occupies and is attached to a dimple, or
depression, which generally is in the very center of the "femoral
ball", also called the "femoral head". In a conventional hip re … ligamentum teres is
simply cut out and removed, in its entirety.
Conventional cartilage replacement surgery, in hip joints,
requires "open joint" surgery. In this type of surgery, the term
"minimally invasive" is often used; however, instead of referring to
arthroscopic surgery, it refers to methods for limiting the longest skin
incision to only about 3 inches long (about 8 cm), in humans, and that does not
qualify as "arthroscopic" surgery.
In addition, numerous articles can be found which describe
arthroscopic surgery, on hips; two moderately recent reviews include Katz et
al, "Advances in arthroscopic surgery," Curr Opin Rheumatol. 19(2): 106-10 (2007) and Larson et
al, "Advanced techniques in hip … arthroscopy," Instr Course Lect.
58: 423-36 (2009). However, those types of arthroscopic surgery do not
involve or include what is commonly known as a "hip replacement" or
"hip resurfacing", in which the cartilage surfaces on both a femoral
head, and an acetabular socket, are completely replaced.
Accordingly, the Applicant herein has focused on the
development of flexible implants which will: (i) enable complete replacement of
both the acetabular and femoral cartilage, in hip joints, using entirely
arthroscopic methods and tools; and, (ii) much more closely emulate, mimic, and
function in the same ways as the natural cartilage surfaces they are replacing.
As a final matter of Background information, it should be
noted that the cartilage segment of an acetabular socket includes more than
just a thin layer of hyaline cartilage which is directly bonded to a hard
surface of pelvic bone. Instead, the cartilage in an acetabular socket also
includes a component called a "labrum" (the adjective is
"labral"). That term comes from the same root word as
"lip", and it refers to a somewhat thicker and enlarged ring (or rim)
of cartilage, which generally surrounds the acetabular socket.
The cartilage which forms the labral segment does not have
the same internal fibrous structure as hyaline cartilage. The internal
structure of hyaline cartilage is optimized to form a relatively thin layer,
which clings directly and tightly to an underlying and supporting bone. The
structure and strength of hyaline cartilage is provided by relatively short
fibers of collagen, which is the main type of fibrous connective protein in the
soft tissues of animals.
By contrast, the larger and thicker cartilage segment which
forms the labral portion of a hip socket uses a more complex type of anchoring
system and internal structure. Even
though it is bonded mainly to the rim of the acetabular socket, its
substantially gi … (compared to a thin layer of hyaline cartilage) requires its
internal struc … collagen fibers that
are much longer than the short collagen fibers found in thin layers of hyaline
cartilage. Accordingly, the labral segments in hip joints are made of a
specialized type of cartilage called "fibrocartilage".
Since labral segments are substantially thicker than the
thin-layered hyaline cartilage which covers most of an acetabular socket, and
since they have a different type of anchoring system than hyaline cartilage,
the labral cartilage in a hip joint poses an additional set of challenges and
complications, to anyone who seeks to replace injured or diseased cartilage in
a hip, with anything other than "classic" hip implants made of hard
alloys and hard plastics.
Nevertheless, due to an innovative anchoring system
described herein, which has been developed only recently by the Applicant
herein, the new types of implants disclosed herein are able to meet and satisfy
that challenge.
Accordingly, one object of this invention is to disclose the
design and structure of surgical implants that: (i) are sized, shaped, and
suited for replacing damaged cartilage in hip joints; and, (ii) are made of
flexible materials that will enable the surgical emplacement of such implants,
into hip joints, using entirely arthroscopic methods and tools, to minimize
damage to surrounding tissues.
Another object of this invention is to disclose the design
and structure of surgical implants for replacing injured or diseased cartilage
in hips joints, in a manner which:
(i) spares, retains, and protects the so-called ligamentum
teres, i.e., the large and important ligament which, in a normal and healthy
joint, directly connects the femoral head to the acetabular socket; and,
(ii) preserves and sustains the normal and natural patterns
of synovial fluid distribution and wetting, in a hip joint.
To the best of the Applicant's knowledge and belief, the
implants disclosed herein are the first feasible and practical implants ever
disclosed, for completely replacing the injured or diseased cartilage in a hip
joint that requires resurfacing, which can indeed spare and protect the
ligamentum teres, and which can also preserve the normal and natural patterns
of synovial fluid distribution, in a hip joint. Another object of this invention is to disclose
the design and stt … implants that are especially well-suited for
minimally-invasive hip rep£ … animals, notably including dogs, which suffer
from frequent and severe hip problems. These implants can enable better
forms of surgical hip repair for dogs (and for other four-legged companion
animals, and for livestock as well), since the minimally-invasive nature of
these implants will substantially reduce the pain and discomfort suffered by
the animal, and will also reduce the convalescent and recovery period,
following surgery.
These and other objects of the invention will become more
apparent through the following summary, drawings, and detailed description.
SUMMARY OF THE INVENTION
Structures and designs are disclosed for surgical implants
that are sized, shaped, and suited for replacing damaged cartilage in hip
joints. In general, they will be sold and implanted in sets, and/or as matched
pairs; one implant will be used to resurface the acetabular socket in a pelvic
bone, while the other implant will be used to resurface the ball (head) of a
femoral bone. In a preferred embodiment, these implants will contain flexible
polymeric materials to enable entirely arthroscopic implantation. One side of
each implant will provide a smooth but durable "articulating
surface", which will be kept wet and lubricated by natural synovial fluid,
after implantation. The opposing side of each implant device will be covered by
a layer of porous material which will encourage tissue ingrowth into the
implant, to provide greater long-term strength and stability.
These are believed to be the first types of hip repair
implants which can entirely replace the ball-and-socket cartilage segments in a
hip, while using a central vacancy and an access channel to allow a surgeon to
spare and preserve a major ligament, called the ligamentum teres, which
directly connects a femoral head to a pelvic socket. They also are believed to
be the first hip repair implants which will preserve and sustain the normal
flow and distribution of synovial fluid, which will lubricate a repaired hip
joint. In addition, these implants include enlarged labral rim structures,
which closely resemble and emulate the enlarged labral cartilage rims that
occur in the acetabular sockets of natural hip joints.
These
implants can be manufactured in a range and assortment … of which will be
designed and suited for humans, while others are designed and suited for
various types of four-legged animals, such as dogs. Their design, and
the anchoring means that will be used to secure them to the bones in a hip
joint, will enable surgical emplacement using entirely arthroscopic methods and
tools, to minimize pain, damage to surrounding tissues, and the time required
for recovery and convalescence.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a perspective view which depicts the anchoring
surface and the outer rim of a flexible C-shaped implant, which will replace
both the hyaline surface and the labral rim of a damaged cartilage segment in
the acetabular socket of a hip joint. The central opening in the "C"
shaped structure of this implant leaves room for the "ligamentum
teres" (which couples the acetabular socket to the femur bone) to remain
intact and in its normal position, in a repaired joint.
FIGURE 2 is a perspective view which depicts the same
C-shaped flexible implant shown in FIGURE 1. This drawing also depicts, in a
partial cutaway segment, a portion of a flexible cable, with a loop of suture
material wrapped around it; these components will provide part of the anchoring
means that will be used to anchor the implant to a pelvic bone.
FIGURE 3 is a perspective view which depicts the same
C-shaped flexible implant shown in FIGURE 1 , and which generally shows the
anchoring surface that will be pressed directly against a prepared pelvic bone
surface from which the cartilage has been removed. The anchoring surface will
be made of a porous material, to promote tissue ingrowth into the anchoring
surface, to provide a strong and permanent anchoring attachment. This drawing
also depicts two protrusions (which can also be called prominences, extensions,
fingers, pegs, or similar terms) which will fit into accommodating holes that
will be drilled into the pelvic bone, to help anchor and stabilize the implant.
FIGURE 4 is a perspective view which depicts the same sides
and components of the C-shaped flexible implant shown in FIGURE 3, from a
different angle.
FIGURE 5 is
a perspective view of a generally hemispherical ir … the "ball"
condyle at the upper end of a femur bone, in a hip joint. This implant
has a continuous ring which surrounds a central opening; accordingly, it is designed
for repairing a hip in which the ligamentum teres has been severed, or damaged
to a point where it does not need to be spared, during insertion of the
implant.
FIGURE 6 is a perspective view of the "underside"
of the femoral ball implant shown in FIG. 5. This view depicts a porous
anchoring surface, which will be pressed directly against the femoral bone, and
which will promote tissue ingrowth into the anchoring surface, to create a
stronger anchoring attachment.
FIGURE 7 is a perspective view of a "split"
implant for resurfacing a femoral cartilage surface. This "split"
implant has a seam or juncture which will allow the implant to be
"opened", while it is being emplaced on the surface of a femoral
ball, so that the surgeon will not need to sever and subsequently reconstruct
an intact and functioning ligamentum teres.
FIGURE 8 is a flow chart which summarizes the major steps
that will be performed, during a hip resurfacing operation which uses the
implant components shown in FIGS. 1-7.
DETAILED DESCRIPTION
As briefly summarized above, structures and designs are
disclosed for surgical implants that are designed and suited for replacing
injured, diseased, or otherwise damaged or defective cartilage, in hip joints.
These implants will be offered and made available: (i) to surgeons, in a first
range of sizes that are designed, sized, and suited for use in human patients;
and, (ii) to veterinarians, in second and additional size and shape ranges that
are designed, sized, and suited for use in specific types of animals, notably
including dogs, which suffer from frequent and widespread hip problems, and
which have hip joints that are relatively close to the surface, and which are
easily accessible.
In a first embodiment, which is strongly preferred at least
for use in humans, these types of implants will be made of materials which have
sufficiently flexibility to allow them to be rolled into generally cylindrical
configurations, so that they can be inserted into hip joints via arthroscopic
insertion tubes. Accordingly, these including:
(1)
flexible polymer components, which will provide smooth ar … wettable, and
actually lubricated when in use) articulating surfaces, which will replace the
articulating surfaces previously provided by hyaline cartilage segments that
require replacement due to injury, disease, congenital defects, or other
problems;
(2) flexible anchoring components, such as flexible
multi-stranded cables, or rings or segments made of super-elastic and/or
shape-memory materials (such as nitinol, a metal alloy that becomes softer and
more pliable when chilled, as just one example), embedded within or otherwise
coupled to the flexible polymer component. In a preferred embodiment, an
anchoring cable or ring can be embedded within an enlarged molded component
which surrounds the periphery (outer rim) of an implant. That enlarged molded
component can be designed and sized to settle and "seat", in a snug
and conforming manner, into a groove or trench that can be machined into the
bone surface, immediately before the implant device is inserted into the joint.
A plurality of anchoring
screws or pegs, and/or suture strands or cerclage wires, can be wrapped around
an anchoring cable, ring or segment, and the "free ends" of the strands
or wires, which emerge from the molded polymer, can provide a surgeon with
means to anchor the implant to a bone surface; and,
(3) a
flexible layer of porous mesh or similar material, which will be affixed to the
"anchoring" surface of the implant, and which will be designed to
promote tissue ingrowth into the porous anchoring surface of the implant, to
promote stronger and more durable anchoring of an implant to a bone surface.
Damage to either cartilage surface in a hip joint almost
always leads, fairly rapidly, to abrasion of and damage to the other cartilage
surface, since the two cartilage surfaces must press, rub, and slide against
each other. As a result, in essentially all cases of interest, a pelvic implant
and a femoral implant will be implanted as a "matched pair", in which
the two implant devices will be inserted into a single joint, during a single
operation. One implant will replace the concave cartilage surface (including
both the hyaline cartilage, and the labral rim) of an acetabular socket, in a
pelvic bone. The other implant will replace the convex cartilage surface on a
femoral ball. However, since these two types of implant devices will
manufactured and packaged separately, they can be handled, sold, and shipped
separately, if desired. Because
of their design, and because the largest components of … made of flexible
materials, these implants will enable a "complete" hip … entire
hyaline and labral cartilage segment of an acetabular socket will removed and
replaced, and the entire cartilage surface on a femoral ball also will be
removed and replaced), in a manner which can be done arthroscopically (i.e.,
using minimally-invasive tools and methods, to minimize disruption of, and
damage to, surrounding tissues and blood vessels).
However, even though these implants will enable arthroscopic
emplacement, they will not require arthroscopic implantation. For example, if
an orthopedic surgeon determines that a non-arthroscopic approach would be
preferable for a specific repair procedure (such as on a patient who was
injured in an accident, fall, etc., and who will require reconstructive surgery
to repair one or more broken bones), the surgeon will be able to emplace and
anchor these implants, using non-arthroscopic methods and tools.
Each such implant will have both an articulating surface,
and an anchoring surface. In an acetabular implant 100 as illustrated in FIGS.
1-4 (which will replace the cartilage in an acetabular socket in a pelvic
bone), the articulating surface 110 will have a generally concave shape. By
contrast, in a femoral implant 200 as illustrated in FIGS. 5 and 6 (which will
replace the cartilage layer that coats the ball or head of a femur), the
articulating surface 210 will have a generally convex shape.
As described in various prior patents and published patent
applications by the same inventor here, which are listed in the Background
section, the articulating surface of either type of implant will be made of a
flexible polymer which is hydrophilic, and which will provide a very smooth but
durable and lubricious articulating surface. In vertebrate animals, the smooth
and wet "articulating" surface of a hyaline cartilage segment in any
articulating joint (this excludes spinal joints, and certain other types of
joints which do not involve sliding and running of cartilage surfaces across
and against each other) will press, rub, and slide against the corresponding
surface of a different hyaline cartilage segment, which covers the surface of a
different bone in that joint. Accordingly, each cartilage-replacing implant
described herein will have a smooth and wettable surface on the
"articulating" side or surface of that implant.
These types of smooth and wettable articulating surfaces can
be manufactured, in flexible form, by using certain well-known types of
polymers. An extended
description of polymer technology is not required herein to adequately disclose
or enable this i … skilled in the art, since these types of options and
features are well witt … specialize in making these types of polymers. Briefly,
such polymers contain long polymeric chains (often called "backbone"
chains), which have certain selected types of hydrophilic pendant groups bonded
to those backbone chains, at a desirable density (or spacing, or similar
terms). The "backbone" chains typically are manufactured, in desired
lengths which will impart a suitable balance of hardness and flexibility to a
polymer, by selecting precursor compounds (usually called monomers) that will
react with each other in a controllable manner, to form large numbers of
selected types of bonds which can repeat an endless number of times, in a
backbone chain. To control the lengths of the backbone chains, a small quantity
(usually 1% or less) of one or more "terminating" agents (which will
effectively create a non-reactive "cap" or "terminus" at
the end of a long chain) can be incorporated into the reaction mixture, during
the polymerization reaction. In addition, the spacing and density of the
hydrophilic side chains (or pendant groups, moieties, or similar terms) can be
controlled, by selecting and incorporating one or more types of monomers which
will provide those types of side chains (also called side groups, pendant
groups, moeties, etc.) at a desired density and spacing. As mentioned above, these aspects of polymer
technology are well known to those skilled in this particular art, and can be
used to create any of numerous types of well-known polymers, which usually are
named based on the types of molecular bonds in the backbone chains (such as polyacrylics,
polyvinyls, polyacrylonitriles, polyurethanes, etc.).
If desired, known methods can be used to create polymers
that will contain and hold a quantity of water, within the molecular matrix of
the polymer. If this approach is used, the final polymer, once it has been
fully hydrated (i.e., saturated with water), can be classified and labeled as a
"hydrogel", if it is flexible (since the terms "gel" and
"gelatinous" imply nonrigid behavior). Hydrogel polymers are of particular
interest, and are generally preferred for use herein, for two reasons:
(1) since natural cartilage is a polymeric hydrogel (where
collagen, the fibrous protein in animal tissue, provides the molecular strands
that hold the cartilage polymer together and give it structure and strength),
synthetic polymers manufactured in hydrogel form can more closely emulate the
structural, mechanical, and behavioral traits of natural cartilage, compared to
other types of polymers that are not hydrogels;
(2) in addition, since the process of hydration (i.e., adding wate ... cause a volumetric swelling of the polymer, it may be possible to insert, into a joint, an implant containing a polymer component that is not yet hydrated, or which is only partially hydrated. This approach may be able to reduce the volume of an implant, while it is being inserted into a joint via an arthroscopic insertion tube.
PELVIC IMPLANT, FOR ACETABULAR SOCKET
Referring to the drawings, FIGS. 1-4 depict a "pelvic
implant" 100 which is designed, sized, and suited for replacing both the
hyaline and labral cartilage in an acetabular socket, on the left or right side
of a pelvic bone.
The implant has a central component 110, which provides: (i)
an unoccupied "access channel" 112, which leads to a "central
vacancy" 114. The term "access channel" 112 (either with or
without the adjective, "unoccupied") indicates that a segment of
twine or rope (or, in practical terms, an undamaged ligamentum teres which
remains fully attached, at both ends, to large bones) can be moved into the
central vacancy 114, via the access channel 113, without having to be
"threaded into the hole" from either above or below the device, and
without having to breach or violate the material that flanks and brackets the
access channel.
Accordingly,
this implant device has a shape that can be called a "horseshoe" … configuration,
or which resembles the letter "C", or the letter "U". This
shape generally emulates the shape of the hyaline cartilage surface in a normal
and healthy acetabular socket, in which the ligamentum teres directly passes
from a centered location in the acetabular socket, into a small depression in
the center of the femoral ball. Accordingly, the access channel 112 of implant
100 will allow the implant to be physically inserted into the acetabular
socket, even if that ligament is present, in a manner which causes the ligament
to pass through the access channel. Once the implant reaches the desired
"depth", in the gap between the pelvic bone and the femoral head, it
will be rotated, around the ligament, until the access channel reaches a
desired orientation, which generally will be pointed slightly away from a vertically
downward direction (at least, in a human patient), in a manner which will
emulate the orientation of an acetabular cartilage segment (which also has a
"horseshoe" shape) in a healthy hip joint. The implant will then be
anchored to the pelvic bone, in that position.
As
mentioned above, central component 110 will have a smootl … surface 118, on one
side of the component 110. The side with the articulating surface 118
can be called the "front" of the implant, if desired, especially for
implants designed for humans, since it will face in the anterior direction,
after implantation in a human pelvis. In implants designed for four-legged
animals, the side with the articulating surface 118 can be called the
"lateral" side (a term which indicates that something points
outwardly, either left or right, away from the vertical center plane of the
animal, as distinct from the "medial" direction, which indicates an
inward direction or orientation, toward the animal's center plane).
This
implant design is believed by the Applicant to be the first such implant
design, for hip replacement implants, which will closely emulate the physiology
and behavioral … performance of native cartilage in an acetabular socket. In
specific, the geometry and shape of this type of implant will both: (i) enable
a surgeon to spare and preserve an intact ligamentum teres, so that the joint
will continue to function in a more normal and natural manner, after the
surgery; and, (ii) permit and promote the same types and patterns of synovial
fluid secretion, flow, and distribution, within a hip joint, that occur in a
normal and healthy hip joint. For an implant in a weight-bearing hip joint
which provides a relatively soft and flexible bearing surface, similar to
cartilage (and different from the types of super-hard alloy implants used in
conventional hip resurfacing), sustained lubrication by synovial fluid will be
critical to enabling the implant to last for multiple years or even decades.
As indicated in FIGS. 2-4, a porous anchoring surface 150 is
located on the opposite side of the implant (which can be called the back or
posterior side, in a human hip implant, and which can be called a medial (as
opposed to lateral) surface, in most types of four-legged animals). After
implantation, the porous anchoring surface will be pressed directly against a
bone surface from which any native cartilage has been removed. After a surgeon
has removed the native cartilage, he or she usually will perform a scraping,
abrading, or similar procedure, on the bone surface; this is frequently
referred to as a "freshening" step, by orthopedic surgeons, since it
primes and activates various natural repair mechanisms which will help
accelerate tissue regrowth and repair, after surgery has been completed. The anchoring layer 150 may be made
of a flexible mesh (made of thin strands of titanium steel or other
biocompatible metal, or made of a stranded polymer or similar material, if
desired) which will actively … the anchoring surface, after the device has been
implanted into an anim … If desired, the porous anchoring surface 150 can be
coated, embedded, or otherwise treated so that it will carry or contain one or
more types of cells and/or bioactive compounds, either before or during
implantation. For examples, various types and mixtures of … growth-stimulating
hormones (including bone-stimulating hormones, often referred to as osteogenic
hormones) stromal precursor cells (i.e., partially-mature cells which are
capable of differentiating into various types of connective tissue cells), and
platelet cells (i.e., specialized white blood cells which play key roles in the
repair and regeneration of injured tissues) have begun to play important roles
in orthopedic surgery, and in various types of medical
interventions which involve little or no cutting (commonly
referred to, among practitioners and specialists, as "sports
medicine" and/or "regenerative medicine"). These and various
other known bioactive agents can be used to create liquefied mixtures which can
be coated onto (and/or embedded within, with the help of centrifugation or
similar force-generating procedures) a porous anchoring surface of an implant
as described herein.
Each of FIGS. 1-4 also depicts an enlarged and generally
curving cylindrical component 120 positioned around the outer rim of implant
100. That enlarged rim structure will replace the "labral rim"
component of a damaged acetabular socket, described in the Background section.
The enlarged rim component 120 also provides a useful and
convenient anchoring means. As depicted in the partial cutaway segment shown in
FIG. 2, the smooth-surfaced polymeric material which will provide the wettable
articulating surface of the implant has been molded around an anchoring cable
122, which may be made of thin and flexible twisted or braided strands of a
biocompatible metal (such as a stainless steel alloy) or polymer (such as
nylon, ultra-high molecular- weight polyethylene, etc.). A strand of suture
material 124 also is shown; it has been wrapped around cable anchoring 122, using
several "turns" to reduce any risk of sliding or other displacement.
Each of the two protruding (or free) ends of suture strand 124 can be affixed
by the surgeon to a nearby location on the pelvic bone, to provide additional
anchoring for the implant.
Any desired
number of these types of anchoring strands can be affixed to the embedded
anchoring cable, around the periphery of the implant; the preferred number will
depend on factors such as: (i) the size of the implant; and, (ii) the type,
size, and … human that the device will be implanted in. If desired, the two
"free … coupled to "racheting" anchors (i.e., anchoring devices
that will allow a strand to be pulled in one direction, so that the anchoring
strand can be conveniently tightened at an appropriate time, during the
surgery, and which will prevent any travel of the strand in the opposite
direction), or to any of various types of "lockable" anchoring
mechanisms. The two ends of an anchoring strand can be positioned and
anchored separately, or they can be kept together as a coupled pair.
As indicated in FIGS. 2-4, the enlarged rim component 120
truncates, at each end, in anchoring components 132 and 134. The two anchoring
components 132 and 134 will provide suitable means for securely attaching the
implant, at those two locations, to prepared surfaces in the pelvic bone. For
example, these devices can provide "snap cap" attachments, with a
metallic or other stiff-but-yielding "split ring" component that can
be pressed down onto the rounded head of an anchoring screw. That is one
preferred mode of attachment, since it will allow each of the two anchoring
screws to be emplaced in the pelvic bone, at appropriate locations, after the
damaged native cartilage has been removed from the bone surface, but before the
implant device is inserted into the joint, while the available working space is
relatively open and uncluttered. Alternately, the two anchoring attachments can
be in the forms of eyelets or similar devices, which will allow an anchoring
screw to be driven through each eyelet and then covered by a protective
covering layer or device; this can avoid any risk of misalignment of the
implant with the anchoring screws.
Alternately, the two anchoring components 132 and 134 can be
designed and used as protrusions (which can also be called pegs, fingers,
extensions, prominences, or similar terms) which will fit into accommodating
holes which can be drilled or otherwise prepared in the receiving bone, before
the implant is inserted into the hip joint that is being repaired. If this
approach is used, the two protrusions 132 and 134, rather than containing a
"snap cap" or similar device which will be coupled to the head of an
anchoring screw, will simply have paired or multiple anchoring sutures emerging
from each of the two protrusions 132 and 134. This design is likely to be
preferred, for example, for implants designed for medium-sized or small dogs,
where: (i) the amount of weight and compressive forces that will be loaded onto
the implant will not be great; and (ii) there may not be sufficient thickness,
in the pelvic bone at the anchoring site, to accommodate the shaft of an
anchoring screw.
FEMORAL IMPLANT
FIGS. 5 and 6 depict a femoral implant 200, which is
designed, sized, and shaped to replace damaged cartilage on the convex surface
of the ball (also called the head) of a femur (i.e., the long bone inside the
thigh). As with the pelvic implants, these femoral implants will have a smooth
and wettable articulating surface 210 on one side. That side can be called the
outside (or outer surface, or similar terms) of a femoral implant, since its
generally hemispherical shape clearly gives it an outer (external) surface.
The other side (which can be called the inside, interior, or
similar terms) of femoral implant 200 will provide a porous anchoring surface
220. As with the pelvic
implants, this anchoring layer will directly contact a "freshened"
bone surface after the surgery, it will be designed to promote tissue ingrowth
into the anchoring layer, and it can be coated or embedded with growth factors,
platelet cells, stromal precursor cells, or other biologically active … compounds.
For simplicity of illustration, the femoral implant 200 in
FIGS. 5 and 6 is depicted with a continuous outer ring 202, surrounding a
somewhat off-center opening (or orifice, vacancy, or similar terms) 204.
Vacancy 204 is designed to allow passage of a ligamentum teres (mentioned
above) through vacancy 204, following surgery, as described in more detail
below. In addition, vacancy 204 enables and facilitates the flow and
distribution of synovial fluid across the articulating surfaces of the
acetabular and femoral implants, as they press, rub, and slide against each
other. To the best of the Applicant's knowledge and belief, no prior hip
replacement implants provide for sparing of the ligamentum teres, and no prior
hip replacement implants enable or promote the normal and natural flow and
distribution of synovial fluid, to lubricate a completely resurfaced joint.
If desired, an "elevated ring" of material 230 can
be provided, around the anchoring surface of femoral implant 200. This
"elevated ring" can be designed to settle into a groove which has
been machined, by the surgeon, into the entire circumference (or any desired
and controlled portion) of the femoral head, to provide a "snap-on"
type of emplacement fitting, which can give additional strength and stability
to the implant. Although not
shown in the drawings, a femoral implant can … molded within the polymeric
component, in a manner which surrounds … the device, and a plurality of suture
strands can be wrapped around the cable. These components will be
directly comparable to the anchoring cable 122 and anchoring suture strands
124, which are shown in FIG. 2 for a pelvic implant, and the same teachings and
comments above, for anchoring cables strands in pelvic implants, also apply to
femoral implants.
If a continuous outer ring 202 surrounds the center vacancy
204, the implant 200 cannot be moved into position over a ligamentum teres
which is intact. Therefore, these types of implants are designed for use in
animals or patients in which the ligamentum teres has already been severed, or
has become damaged or degraded so badly that a surgical reconstruction is
advisable. That is the condition which exists in most dogs that have been
suffering from hip problems for sustained periods of time; accordingly, this
class of implants will generally be advisable for use, in dogs (and human
patients) with severed or badly damaged center ligaments.
By contrast, FIG. 7 depicts a "split" femoral
implant 300, which has a seam or juncture 310, which can be opened temporarily.
This seam or juncture 310 provides an access channel to an somewhat
off-centered vacancy 312, and it will allow implant 300 to be opened somewhat,
while it is being placed and positioned on the surface of a femoral ball, so
that the surgeon will not need to sever and subsequently reconnect an intact
and functioning ligamentum teres.
If desired, seam 310 (which can also be referred to as
access channel 310, since the seam can indeed be opened, when needed, to
convert it into an access channel) can be provided with a "tongue and
groove" or "chevron" design which does not require any flexure,
when being closed. This would be comparable to various types of planks or
sheets, made of wood or similar non-rubbery materials, that are used in
cabinet-making, flooring, and other types of carpentry.
Alternately, since the polymers that will be used to make
these devices will be made of elastomeric materials, the "tongue"
component can have an enlarged "head" on a slightly smaller
"neck", in a manner comparable to the types of rounded protrusions
that are present on conventional jigsaw puzzle pieces. This would require an
assembly step that would require the use of a moderate compressive force, to
"snap" the tongue component into the corresponding groove, which in
turn will impart a somewhat higher level of strength and stability to the
juncture that will result from that type of closure step. Accordingly, a design which requires some level
of compressive force, so that closure of the seam or juncture … reinforced, is
regarded as generally preferable to a non-snapping tongu … used for materials
such as wood.
Alternate and/or additionally, other designs and mechanisms
can be incorporated into a "split" implant, to help ensure a tight,
reliable, and secure closure. For example, a securing mechanism can be
provided, on a component such as a peripheral anchoring cable, which will allow
a surgeon to adjust the level of tensile force on that component, in an
adjustable manner, such as by rotating a threaded component, or by pulling a
suture strand through a gripping or anchoring device which contains a ratchet
mechanism.
Thus, there has been shown and described a new and useful
class of flexible implants, designed for surgical replacement of damaged
cartilage in hip joints. Although this invention has been exemplified for
purposes of illustration and description by reference to certain specific
embodiments, it will be apparent to those skilled in the art that various
modifications, alterations, and equivalents of the illustrated examples are
possible. Any such changes which derive directly from the teachings herein, and
which do not depart from the spirit and scope of the invention, are deemed to
be covered by this invention.
Claims:
1. An implant device for
replacing cartilage in an acetabular socket in a mammalian hip joint,
comprising at least one component having a smooth articulating surface which
emulates the size and shape of a native cartilage segment which covers an
acetabular socket in said mammalian hip joint,
wherein said implant device
contains both a central vacancy, and an access channel which provides access to
said central vacancy, wherein said central vacancy and said access channel are
sized and suited to enable:
a. surgical implantation of
said implant device, into an acetabular socket from which native cartilage has
been removed, in a manner which does not require alteration of a ligamentum
teres which is connected to said acetabular socket; and,
b. natural patterns of
distribution of synovial fluid across articulating surfaces within said hip
joint.
2. The implant device of Claim
1, wherein said implant has sufficient flexibility to enable said implant to be
rolled into a cylindrical configuration having a diameter which will allow
insertion of said implant device, into a joint that requires surgical repair,
through an arthroscopic insertion tube.
3. The implant device of Claim
1, which also comprises at least one anchoring component selected from the
group consisting of:
a. a flexible multi-stranded
cable which is embedded, within a molded polymer component, around at least a
portion of an outer peripheral rim of said implant device;
b. a flexible reinforcing
component which is embedded, within a molded polymer component, around at least
a portion of an outer peripheral rim of said implant device, and which is made
of a shape-memory material and/or a super-elastic material;
c. at least one coupling attachment,
embedded within or connected to said implant, which will enable said implant
device to be securely attached to at least one a
been driven into a pelvic
bone; and,
d. a plurality of flexible
strands or wires which emerge from said implant device, and which have free
ends which can be attached to anchors that can be embedded within a bone.
4. The implant device of Claim
1, wherein said articulating surface contains an enlarged rim component which
is sized and shaped to emulate labral cartilage in a hip joint.
5. The implant device of Claim
1, wherein said implant device is designed, sized, and suited for implantation
in a dog hip.
6. The implant device of Claim
1, wherein said implant device is designed, sized, and suited for implantation
in a human hip.
7. An implant device for
replacing hyaline cartilage in a mammalian hip joint, comprising:
a. at least one polymeric
component having a smooth articulating surface which emulates the size and
shape of a natural hyaline cartilage segment in a hip joint of a patient or
animal suited to receive such implant;
b. at least one anchoring
surface comprising a layer of material which is porous, and which is designed
and suited to promote tissue ingrowth after surgical implantation; and,
c. a plurality of anchoring
components which, acting together, enable surgical anchoring of said implant to
a hip bone from which native cartilage has been removed;
wherein said implant device
has sufficient flexibility to enable said implant to be rolled into a
cylindrical configuration which will allow insertion of said implant device
into a joint that requires surgical repair, through an arthroscopic insertion
tube,
and where said implant is
sized, designed, and suited to replace a hyaline cartilage surface in a
mammalian hip joint.
8. The implant device of Claim
7, wherein said anchoring components are selected from the group consisting of:
a. a flexible multi-stranded
cable which is embedded, within a … component, around at least a portion of an
outer peripheral rim of said implant device;
b. a flexible reinforcing
component which is embedded, within a molded polymer component, around at least
a portion of an outer peripheral rim of said implant device, and which is made
of a shape-memory material and/or a super-elastic material;
c. at least one coupling
attachment, embedded within or connected to said implant, which will enable
said implant device to be securely attached to at least one anchoring screw
which has been driven into a pelvic bone; and,
d. a plurality of flexible strands
or wires which emerge from said implant device, and which have free ends which
can be attached to anchors that can be embedded within a bone.
9. The implant device of Claim
7, wherein said articulating surface contains a central vacancy and an access
channel which are sized and shaped to enable a surgeon to insert and emplace
said implant device around an intact ligamentum teres without altering said
ligamentum teres.
10. An implant device for
replacing hyaline cartilage on an femoral head in a mammalian hip joint,
comprising at least one component having a smooth convex articulating surface
with a size and shape which emulates femoral hyaline cartilage in a hip joint
of patient or animal suited to receive such implant, and wherein said implant
device contains a central vacancy which is sized, positioned, and suited to
coexist, after implantation, with an intact ligamentum teres which is connected
to said femoral head.
11. The implant device of
Claim 10, wherein said implant device is provided with an access channel which
leads to said central vacancy, wherein said access channel can be temporarily
opened, during surgical implantation, to allow said implant device to be
emplaced upon a femoral head which is being resurfaced, around a ligamentum
teres which remains connected to said femoral head, without requiring any
alteration of saic…
12. The implant device of
Claim 10, which also coemprises anchoring components selected from the group
consisting of:
a. a flexible multi-stranded
cable which is embedded, within a molded polymer component, around at least a
portion of an outer peripheral rim of said implant device;
b. a flexible reinforcing
component which is embedded, within a molded polymer component, around at least
a portion of an outer peripheral rim of said implant device, and which is made
of a shape-memory material and/or a super-elastic material;
c. at least one coupling
attachment, embedded within or connected to said implant, which will enable
said implant device to be securely attached to at least one anchoring screw
which has been driven into a pelvic bone; and,
d. a plurality of flexible
strands or wires which emerge from said implant device, and which have free
ends which can be attached to anchors that can be embedded within a bone.
External links
Mansmann KA. Tendon-sparing implants for arthroscopic
replacement of hip cartilage. WO2012162571A1 May 24, 2012. 2012. patents.google
Authors & Affiliations
Kevin A. Mansmann – Paoli, Pa (US)
Keywords
ligamentum capitis femoris, ligamentum teres, ligament
of head of femur, endoprosthesis, prosthesis,
invention, unipolar, subtotal, bipolar, total
NB! Fair practice / use: copied for the purposes of criticism, review, comment, research and private study in accordance with Copyright Laws of the US: 17 U.S.C. §107; Copyright Law of the EU: Dir. 2001/29/EC, art.5/3a,d; Copyright Law of the RU: ГК РФ ст.1274/1.1-2,7
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