U.S. patent application number 15/191346 was filed with the patent office on 2017-05-25 for catheter deliverable foot implant and method of delivering the same.
The applicant listed for this patent is Victor V. Cachia. Invention is credited to Victor V. Cachia.
Application Number | 20170143511 15/191346 |
Document ID | / |
Family ID | 35094755 |
Filed Date | 2017-05-25 |
United States Patent
Application |
20170143511 |
Kind Code |
A1 |
Cachia; Victor V. |
May 25, 2017 |
CATHETER DELIVERABLE FOOT IMPLANT AND METHOD OF DELIVERING THE
SAME
Abstract
Methods and devices are disclosed for manipulating alignment of
the foot to treat patients with flat feet, posterior tibial tendon
dysfunction and metatarsophalangeal joint dysfunction. An
inflatable implant is positioned in or about the sinus tarsi and/or
first metatarsal-phalangeal joint of the foot. The implant is
insertable by minimally invasive means and inflatable through a
catheter or needle. Inflation of the implant alters the range of
motion in the subtalar or first metatarsal-phalangeal joint and
changes the alignment of the foot.
Inventors: |
Cachia; Victor V.; (San Juan
Capistrano, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Cachia; Victor V. |
San Juan Capistrano |
CA |
US |
|
|
Family ID: |
35094755 |
Appl. No.: |
15/191346 |
Filed: |
June 23, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14258733 |
Apr 22, 2014 |
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15191346 |
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13164612 |
Jun 20, 2011 |
8747480 |
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14258733 |
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12325894 |
Dec 1, 2008 |
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13164612 |
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11068675 |
Mar 1, 2005 |
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12325894 |
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60549767 |
Mar 3, 2004 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2002/30904
20130101; A61F 2002/4627 20130101; A61B 2017/00557 20130101; A61F
2002/30841 20130101; A61F 2002/30873 20130101; A61F 2/30771
20130101; A61F 2002/4629 20130101; A61F 2002/30205 20130101; A61F
2/4606 20130101; A61F 2002/3021 20130101; A61F 2002/4223 20130101;
A61F 2002/30581 20130101; A61F 2/4202 20130101; A61B 17/562
20130101; A61F 2002/4628 20130101; A61B 17/844 20130101; A61F
2230/0067 20130101; A61B 2017/565 20130101 |
International
Class: |
A61F 2/46 20060101
A61F002/46; A61F 2/30 20060101 A61F002/30; A61F 2/42 20060101
A61F002/42 |
Claims
1-22. (canceled)
23. A method for treating a patient, comprising: identifying a cyma
line in a foot of a patient; smoothing said cyma line; and securing
said smoothing by inflating an implant in the sinus tarsi of said
foot with an inflation material.
24. The method of claim 23, wherein said material is a fluid.
25. The method of claim 23, wherein said material is a solid.
26. The method of claim 25, wherein said solid comprises
microspheres.
27. The method of claim 23, wherein the implant is inserted through
a cannula inserted into said sinus tarsi of said patient.
28. The method of claim 23, wherein the implant is inserted over a
guidewire inserted into said sinus tarsi of said patient.
29. The method of claim 28, further comprising combining multiple
agents to form said inflation material.
30. The method of claim 28, wherein said combining step is
performed before said inflating step.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application is a continuation of U.S. patent
application Ser. No. 14/258,733 filed on Apr. 22, 2014, which is a
continuation of U.S. patent application Ser. No. 13/164,612 filed
on Jun. 20, 2011 which is a continuation of U.S. patent application
Ser. No. 12/325,894 filed on Dec. 1, 2008, which is a continuation
of U.S. patent application Ser. No. 11/068,675 filed on Mar. 1,
2005, which claims priority under 35 U.S.C. .sctn.119(e) to U.S.
Provisional Application No. 60/549,767 filed on Mar. 3, 2004, the
disclosure of which are incorporated by reference herein in its
entirety.
BACKGROUND OF THE INVENTION
[0002] Field of the Invention
[0003] This invention relates generally to the field of subtalar
joint and first metatarsal-phalangeal implants for treating foot
conditions including flat feet, adult posterior tibial tendon
dysfunction and metatarsophalangeal joint dysfunction.
[0004] Description of the Related Art
[0005] Pes valgo planus, or flat foot, is a common condition where
the arch of a foot is weakened and is unable to properly support
the weight of the body. With a flat foot, shock absorption is
reduced and misalignment of the foot occurs. These changes may
eventually result in foot and ankle pain, tendonitis, plantar
fasciitis and hallux valgus, hallux limitus and functional
disorders of the knees, hips and back. Although there are several
causes of flat feet, one frequent cause is excessive motion in the
subtalar joint of the foot.
[0006] As early as 1946, surgeons have been attempting to apply the
arthroereisis concept to the subtalar joint. Arthroereisis is a
surgical procedure for limiting motion in a joint in cases of
excessive mobility. One early method was to remedy abnormal
excursion of the talus on the calcaneus with the talus contacting
the floor of the sinus tarsi by using an "abduction block"
procedure. During the abduction block procedure, a wedge-shaped
bone graft was impacted into the anterior leading edge of the
posterior facet of the calcaneus. Impacting such a bone graft
prevented excessive inferior displacement of the talus upon the
calcaneus, thus limiting the amount of excess pronation of the
subtalar joint.
[0007] A pronation limiting osteotomy in the form of a lateral
opening wedge of the posterior facet was developed for treatment of
"flatfoot" in cerebral palsy patients in 1964. In order to prevent
interfering with subtalar joint motion, a wedge-like bone graft was
used to improve the weight-bearing alignment of the calcaneus. In
1970, an accessory bone graft placed in the sinus tarsi was
developed as a corrective procedure. Later, the bone graft was
replaced with a silastic plug. As early as 1976, a high molecular
weight polyethylene plug was developed. The plug is cemented into
the calcaneal sulcus against a resected portion of the posterior
calcaneal facet. This procedure, known as "STA-peg" (subtalar
arthroereisis-peg), is a commonly used subtalar joint arthroereisis
procedure. STA-peg does not block excessive pronation, but rather
alters the axis of motion of the subtalar joint.
[0008] In addition, in 1976, a high molecular weight, polyethylene,
threaded device known as a "Valenti Sinus Tarsi Arthroereises
Device" was invented. The procedure used to implant the Valenti
device is commonly referred to as the "Valenti" procedure. Unlike
the STA-peg procedure, the Valenti procedure is an extra-articular
procedure that involves placing the Valenti device into the sinus
tarsi to block the anterior and inferior displacement of the talus.
Such placement of the Valenti device does not restrict normal
subtalar joint motion, but does block excessive pronation and
resulting sequelae. The Valenti device has a frusto-conical shape
and threads on the outer surface of the device, which allow it to
be screwed into the sinus tarsi. Because of the shape of the
Valenti device, the greater the penetration of the device into the
sinus tarsi, the more the sinus is dilated and the more calcaneal
eversion is eliminated.
[0009] However, several problems reduce the desirability of the
Valenti procedure and device. Because of its frusto-conical shape
and the manner in which it is inserted, the Valenti device is
difficult to precisely position in the subtalar joint and difficult
to ensure that the proper amount of calcaneal eversion has been
eliminated. Furthermore, it is generally difficult to locate the
device properly within the tarsal canal because the implant must be
threaded at least 3 to 5 millimeters medial to the most lateral
aspect of the posterior facet for correct placement. Because of its
polyethylene construction, the device cannot be imaged using
radiography (X-ray) to determine whether the proper position has
been achieved.
[0010] More recent attempts to control subtalar motion in the
hyperpronated foot include the Maxwell-Brancheau arthroereisis
(MBA), the Kalix subtalar prosthesis and the Futura arthroereisis.
The MBA is a titanium alloy implant where the implantation
procedure involves insertion "trial" implants to determine the
proper size of the actual implant used. The MBA implant procedure
requires either general anesthesia or local anesthesia with
sedation. It also requires up to a 3/4 inch incision on the lateral
portion of the foot. The MBA implant uses a metal guide pin for
positioning the implant. The guide pin must be positioned with
extreme care to prevent damage to the calcaneus. A two-week period
of crutch use and foot immobilization typically follows the
procedure. The Kalix implant is a cone-shaped implant with limited
expansion ability. The operator can use a double screwdriver to
increase the diameter of the implant. The Kalix implant requires
two weeks of non-weight bearing and three to four weeks of
immobilization following implantation of the device.
[0011] Another site of frequent foot problems is the first
metatarsal-phalangeal joint. The first metatarsal-phalangeal joint
(MTP) is a complex joint of the foot where bones, tendons and
ligaments work together to transmit and distribute the body's
weight, especially during movement. Bunions are the first MTP joint
disorder most frequently treated by podiatric surgeons. First-line
treatment involves educating patients about the condition and
evaluating their footwear. Providers can direct their patients to
wear wider, low-heeled shoes, use bunion pads, apply ice and take
over-the-counter analgesic medications. These options are designed
to relieve pain and make it easier to walk and engage in physical
activities, but they do not address the underlying cause of
bunions.
[0012] Bunions usually occur from inherited faulty biomechanics
that put abnormal stress on the first MTP joint. Contrary to
popular belief, bunions are aggravated, not caused, by shoes.
Various non-surgical approaches can help prevent aggravation of
bunions and other MTP-related problems. For some patients,
non-surgical treatment is sufficient, but surgical intervention is
considered if the bunions are progressive or if non-operative
treatments provide inadequate improvement.
[0013] Bunion surgery is performed to repair tendons and other soft
tissue and remove a small amount of bone. Procedures to correct
more severe bunions may involve removal of the bump or minor
realignment of the big toe joint. The most severe and disabling
bunions often require extensive joint realignment, reconstruction,
implants or joint replacement. Significant morbidity and
recuperation time is required for such procedures.
[0014] First MTP-related problems also occur from repetitive trauma
to the area and from arthritis. Over time, active persons can put
continuous stress on the first MTP joint that eventually wears out
the cartilage and lead to the onset of arthritis. This condition,
known as hallux rigidus, causes loss of movement and pain in the
joint. In most situations, non-operative treatments can be
prescribed to provide relief, but those with advanced disease might
need surgery, especially when the protective covering of cartilage
deteriorates, leaving the joint damaged and with decreased range of
motion. Again, significant morbidity results from these procedures
and an extended recovery time is required.
SUMMARY OF THE INVENTION
[0015] In one embodiment, the invention is a subtalar joint
implant, comprising an inflatable balloon adapted for positioning
in the sinus tarsi of a foot. In another embodiment, the invention
is a foot implant comprising an inflatable balloon, wherein the
inflatable balloon is adapted for extra-articular positioning in
the sinus tarsi of the foot.
[0016] In one embodiment of the invention, a method for treating a
patient is provided. The method comprises providing an inflatable
subtalar implant for the procedure, inserting the implant into the
sinus tarsi of a food, inflating the implant with an inflation
material and changing the alignment of the hindfoot. Furthermore,
the insertion of the implant into the sinus tarsi may be performed
through a cannula inserted into the sinus tarsi. The inflation
material may be a fluid or a solid. One example of a solid
inflation material are microspheres. In other embodiments of the
invention, multiple agents may be used to inflate the implant, such
as a substrate and catalyst capable of solidifying. In some
embodiments, the multiple agents are combined before inflation of
the implant. In other embodiments, the multiple agents are combined
during inflation of the implant.
[0017] In another embodiment of the invention, another method for
treating a patient is provided. This method comprises providing an
inflatable subtalar implant for the procedure, identifying a foot
having a first range of motion, inserting the implant into the
sinus tarsi of the foot and adapting the foot to a second range of
motion by inflating the implant.
[0018] In still another embodiment of the invention, another method
for treating a patient is provided. This method comprises providing
an inflatable subtalar implant, identifying a foot having a first
weight-bearing alignment, changing the foot to a second
weight-bearing alignment, inserting the implant into the sinus
tarsi of the foot and securing the foot in the second
weight-bearing alignment by inflating the implant. The first and
second weight-bearing alignments may be defined by the angle formed
between a first line connecting the edges of an articular surface
of the talus and a second line connecting the edges of an articular
surface of a navicular bone. Alternatively, the first and second
weight-bearing alignments may be defined by the angle between the
long axis of the talus and a second line along the long axis of the
first metatarsal bone. Still another alternative is to define the
first and second weight-bearing alignments by the angle between the
first line between most plantar point of a calcaneus and the most
inferior point of the distal articular surface of the calcaneus,
and a second line within a horizontal plane of the patient. Still
another alternative is to define the first and second
weight-bearing alignments by the angle between a first line along
the plantar border of the calcaneus and a second line along a first
midpoint in the body of a talus and a second midpoint in the neck
of the talus.
[0019] Several embodiments of the invention provide a minimally
invasive method for treating a patient. This method comprises
providing an inflatable subtalar implant, inserting the implant
into the sinus tarsi of a foot, inflating the implant, changing the
range of motion of the subtalar joint of the foot and conforming
the implant to the shape of the sinus tarsi thereby.
[0020] Some embodiments of the invention provide a method for
treating a patient, comprising identifying a cyma line in a foot of
a patient, smoothing the cyma line and securing the smoothing by
inflating an implant in the sinus tarsi of the foot.
[0021] In another embodiment of the invention, a method for
treating a patient is provided, comprising accessing the sinus
tarsi of a foot through an access path having a cross sectional
diameter of no more than about 0.5 inches, where the sinus tarsi
have a talus and calcaneus spaced apart by a first minimum
distance. The space between the talus and calcaneus is increased to
a second minimum distance and the talus and calcaneus is then
restrained at the second minimum distance.
[0022] In another embodiment, another method for treating a patient
is provided, comprising providing an inflatable first
metatarsal-phalangeal joint implant, inserting the implant into a
first metatarsal-phalangeal joint of a foot and inflating the
implant with a fluid.
[0023] Several embodiments of the invention provide these
advantages, along with others that will be further understood and
appreciated by reference to the written disclosure, figures, and
claims included herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The structure and method of making the invention will be
better understood with the following detailed description of
embodiments of the invention, along with the accompanying
illustrations, in which:
[0025] FIG. 1 is a superior elevation view of the calcaneus;
[0026] FIG. 2 is a lateral elevation view of the talo-calcaneus
relationship;
[0027] FIG. 3 is a lateral elevation view of the foot bones showing
the sinus tarsi;
[0028] FIG. 4 is dorso-plantar elevation view of the foot showing
the outline of the sinus tarsi;
[0029] FIG. 5A is a superior elevation view of the ligament
attachment sites to the calcaneus; FIG. 5B is a coronal
cross-section view showing the ligaments of the sinus tarsi;
[0030] FIGS. 6A and 6B depict the axis of rotation for the subtalar
joint;
[0031] FIGS. 7A and 7B are schematic views of the motion of the
subtalar joint as a mitered hinge joint;
[0032] FIGS. 8A and 8B are schematic views of subtalar joint motion
as a threaded screw joint;
[0033] FIGS. 9A and 9B are posterior cross-sectional views of a
neutrally aligned and a hyperpronated foot;
[0034] FIGS. 10A and 10B are lateral radiographs of the foot
illustrating the cyma lines in a neutrally aligned and misaligned
foot, respectively;
[0035] FIGS. 11A and 11B are AP radiographs of the foot
illustrating the cyma lines in a neutrally aligned and misaligned
foot, respectively;
[0036] FIGS. 12A and 12B are AP radiographs of the foot depicting
the talonavicular coverage angles in a neutrally aligned and
misaligned foot, respectively;
[0037] FIGS. 13A and 13B are lateral radiographs of the foot
depicting lateral talocalcaneal angles in a neutrally aligned and
misaligned foot, respectively;
[0038] FIGS. 14A and 14B are lateral radiographs of the foot
depicting the calcaneal pitch angles in a neutrally aligned and
misaligned foot, respectively;
[0039] FIGS. 15A and 15B are AP radiographs of the foot depicting
AP-talar-first metatarsal angles in a neutrally aligned and
misaligned foot, respectively;
[0040] FIGS. 16A and 16B are lateral radiographs of the foot
depicting the lateral talocalcaneal angles in a neutrally aligned
and misaligned foot, respectively;
[0041] FIGS. 17A and 17B are AP radiographs of the foot depicting
AP talocalcaneal angles in a neutrally aligned and misaligned foot,
respectively;
[0042] FIGS. 18A and 18B are schematic coronal cross-sectional
views of a neutrally aligned and hyperpronated foot, respectively.
FIG. 18C is a schematic view depicting the effect of material
placed within the sinus tarsi. FIG. 18D is a schematic view
depicting the tendency of the talus and calcaneus to cause
displacement of material in the sinus tarsi;
[0043] FIGS. 19A and 19B are schematic longitudinal cross-sectional
views of the talus and calcaneus in a hyperpronated foot before and
after insertion of material into the sinus tarsi;
[0044] FIGS. 20A and 20B are side elevation and cross-sectional
views of one embodiment of the implant;
[0045] FIGS. 21A through 21H depict side elevation views of various
embodiments of non-conforming implants;
[0046] FIGS. 22A and 22B are elevation and cross sectional views of
one embodiment of the invention having a ridged outer surface;
[0047] FIGS. 23A and 23B are cross-sectional views of the foot with
various embodiments of barbs for anchoring the implant;
[0048] FIGS. 24A and 24B represent various embodiments of the
invention comprising multiple inflatable compartments;
[0049] FIGS. 25A and 25B are elevation views of one embodiment of
the coupling interface and the distal end of a complementary
delivery catheter. FIG. 25C is a cross-sectional view of the
implant in FIGS. 25A and 25B attached to a delivery catheter;
[0050] FIGS. 26A and 26B are elevation views of another embodiment
of the coupling interface and the distal end of a complementary
delivery catheter. FIG. 26C is a cross-sectional view of the
implant in FIGS. 26A and 26B attached to a delivery catheter;
[0051] FIGS. 27A through 27C depict one embodiment of the delivery
system;
[0052] FIGS. 28A and 28B are schematic cross-sectional views of the
foot before and after inflation of the sizing catheter;
[0053] FIG. 29 is a side elevation view of a foot following
insertion of the delivery catheter;
[0054] FIGS. 30A and 30B are schematic cross-sectional views of the
foot with the implant inserted; FIG. 30A shows an uninflated
implant attached to the delivery catheter and FIG. 30B depicts an
inflated implant with the delivery catheter removed;
[0055] FIG. 31A is a front elevation view of one embodiment of a
first MTP joint inflatable implant and FIG. 31B is a side
cross-sectional view of the implant in FIG. 31A.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0056] The talus and calcaneus form the bones of the hindfoot. The
talus is a bone with no muscular attachments, but is stabilized by
ligaments and cradled by the tendons passing from the leg to the
foot. As shown in FIG. 1, the calcaneus 2 articulates with the
talus at the calcaneal anterior 4, middle 6 and posterior facets 8.
FIG. 2 depicts the relationship between the talus 10 and calcaneus
2 and the talo-calcaneal surfaces 12, 14 that articulate with the
midfoot bones. FIGS. 3 and 4 depict the midfoot bones, including
the navicular 16, cuboid 18 and cuneiform bones 20, 22, 24. The
sinus tarsi 26, also known as the talocalcaneal sulcus, is an
extra-articular anatomic space between the inferior neck 28 of the
talus 10 and the superior aspect of the distal calcaneus 2. The
space continues with the tarsal canal, a funnel or trumpet-shaped
space that extends medially to a small opening posterior to the
sustentaculum tali. Sinus tarsi 26 is oriented obliquely from a
lateral distal opening to proximal medial end. The canal is wider
laterally and narrower medially, but the lateral opening of the
canal is capable of widening with foot supination and narrowing
with pronation. Fat and ligaments occupy the space and are perfused
by the tarsal canal artery, a branch of the posterior tibial
artery.
[0057] FIG. 5A is a superior view of the calcaneus 2 showing the
ligament attachments within the tarsal canal, including the
inferior attachments 30, 32, 34 of the extensor retinaculum 36 of
the foot, the interosseous talocalcaneal ligament 38 and the
cervical ligament 40. The primary ligament is interosseous
talocalcaneal ligament 38, shown in a coronal cross section of the
foot in FIG. 5B. Its primary function is to maintain apposition of
the talus 10 to the calcaneus 2. The interosseous talocalcaneal
ligament 38 is anterior to the posterior subtalar joint and extends
from calcaneus 2 to talus 10. It forms a transverse partition
between the sulcus tali and the sulcus calcaneus, the two grooves
forming the sinus tarsi. Interosseus ligament 38 separates anterior
4 and middle facets 6 of the calcaneal portion of the anterior
subtalar joint from the posterior facet 8 of the posterior subtalar
joint and provides stability to the hindfoot. The cervical ligament
40, like the other ligaments of the tarsal sinus 26, is
extra-capsular. Cervical ligament 40 is larger than interosseous
talocalcaneal ligament 38. It attaches to the cervical tubercle of
the inferior and lateral aspects of neck 28 of talus 10 and the
dorsal aspect of calcaneus 2 medial to the origin of the extensor
digitorum brevis muscle. Cervical ligament 40 is flattened, its
width being four times greater than its thickness. The primary
function of cervical ligament 40, along with interosseous
talocalcaneal ligament 38, is to limit inversion of the hindfoot.
The inferior extensor retinaculum 36 is a Y-shaped strap of flat
thick connective tissue that crosses the proximal portion of the
foot. The stem of the "Y" is composed of superficial and deep
laminae that enclose the long extensor tendons and prevent bow
stringing of the long extensor tendons. Laterally, inferior
extensor retinaculum 36 is anchored to talus 10 and calcaneus 2 by
ligament-like roots that are located in the tarsal sinus and canal.
The medial 30, intermediate 32 and lateral roots 34 together
constitute the majority of the ligamentous material in the tarsal
sinus 26. Inferior extensor retinaculum 36 assists cervical
ligament 40 in limiting inversion of the subtalar joint. Medial
root 30 attaches to calcaneus 2 just anterior to the attachment
site of interosseous talocalcaneal ligament 38. Medial root 30 has
a secondary attachment site to talus 10 in common with interosseous
talocalcaneal ligament 38. Intermediate root 32 attaches to
calcaneus 2 posterior to the attachment site of cervical ligament
40. Lateral root 34 attaches to calcaneus 2 at the external aspect
of the tarsal sinus 26.
[0058] Subtalar motion is generally described as a rotational
motion of the talus around the calcaneus. FIGS. 6A and 6B depict
the subtalar axis of rotation 42, which typically extends upward
and forward at an angle of about forty-two degrees from the floor
at the heel. The axis deviates sixteen degrees medially from the
midline of the foot. Generally, the subtalar joint can be inverted
about twenty degrees and everted about five degrees. The average
range of motion throughout the stance phase of gait, however, is
only about six degrees. Longitudinal translation in both the
proximal and distal directions is also associated with the rotation
movement, but the direction and magnitude of this movement is
highly variable in each person. Some researchers have characterized
the motion of the subtalar joint as a mitered hinge joint 44, as
shown in FIGS. 7A and 7B. The vertical member 46 is analogous to
the leg and the horizontal member 48 is analogous to the foot.
Other researchers, however, have characterized the motion of the
subtalar joint as a screw joint, as shown in FIGS. 8A and 8B. The
differences between the characterizations of the subtalar joint
underscore the high degree of variation in the configuration of the
joint within the population.
[0059] When an excessive range of motion exists in the subtalar
joint, misalignment of the foot can occur. Compared to a person
with a neutrally aligned foot, shown in FIG. 9A, a person with flat
feet, shown in FIG. 9B, has a subtalar joint that is capable of
eversion up to about six degrees from a neutral talo-calcaneal
alignment. Excessive eversion places increased stress upon the foot
arch. Over time, foot or ankle disorders can develop from the
misalignment. Misalignment of the subtalar joint also affects the
alignment of the bones in the midfoot due to the dependence of
midfoot stability on hindfoot stability.
[0060] Alignment of the foot can be assessed on plain film x-ray
imaging by examining the cyma lines of the foot. The term "cyma
line" refers to the joining of two curved lines. A neutrally
aligned foot forms a smooth cyma line (shown with dots) between the
talonavicular joint and the calcaneocuboid joint on radiographs in
both the lateral and AP views, as shown in FIGS. 10A and 11A,
respectively. If the cyma line is broken, as shown in FIGS. 10B and
11B, this finding suggests misalignment of the talus 10 on the
calcaneus 2 as seen in patients with flat feet.
[0061] Other radiographic methods of assessing foot alignment are
also available. FIGS. 12A and 12B depict the evaluation of
talonavicular uncoverage. Talonavicular uncoverage is an indication
of forefoot abduction, a component of flatfoot. This measurement is
taken from a weight-bearing AP view. This angle represents the
degree of shift of navicular 16 on talus 10. Two lines are drawn,
one connecting the edges of the articular surface 52 of the talus
10, and one connecting the edges of the articular surface 54 of the
navicular 16. The angle formed by these two lines is the
talonavicular coverage angle, as seen in FIG. 12A. An angle of
greater than 7 degrees indicates lateral talar subluxation, shown
in FIG. 12B. A more direct measurement of pes planus, or collapse
of the longitudinal arch, is the talar-first metatarsal angle
(Meary's angle), shown in FIGS. 13A and 13B. This is an angle
formed between the long axis of the talus 2 and first metatarsal 56
on a weight-bearing lateral view. This line is used as a
measurement of collapse of the longitudinal arch 50. Collapse may
occur at the talonavicular joint, naviculo-cuneiform, or
cuneiform-metatarsal joints. In the normal weight-bearing foot,
shown in FIG. 13A, the midline axis of the talus 2 is in line with
the midline axis of the first metatarsal 56. An angle that is
greater than 4.degree. convex downward is considered pes planus. An
angle of fifteen to thirty degrees, as in FIG. 13B, is considered
moderate flat foot, and an angle greater than 30.degree. is
considered severe flat foot. FIGS. 14A and 14B depict radiographs
evaluating the calcaneal inclination angle, or calcaneal pitch. A
line is drawn from the plantar-most surface of the calcaneus 2 to
the inferior border of the distal articular surface. The angle
created between this line and the transverse plane, or the line
from the plantar surface of the calcaneus 2 to the inferior surface
of the fifth metatarsal head, is the calcaneal pitch, shown in FIG.
14A. A decreased calcaneal pitch is consistent with pes planus, as
represented in FIG. 14B. There have been differing opinions between
researchers concerning the normal range of calcaneal pitch.
Eighteen to twenty degrees is generally considered normal, although
measurements ranging from seventeen to thirty-two degrees have also
been reported to be normal. FIGS. 15A and 15B depict radiographs
evaluating the AP-talar-first metatarsal angle. A line drawn
through the mid-axis of the talus 10 should be in line with the
first metatarsal shaft 56, as in FIG. 15A. If the line is angled
medial to the first metatarsal 56 it indicates pes planus, as
illustrated in FIG. 15B. FIGS. 16A and 16B depict radiographs
evaluating the lateral talocalcaneal angle. The lateral
talocalcaneal angle is the angle formed by the intersection of a
first line bisecting the talus 10 with a second line along the
plantar border or through the long axis of the calcaneus 2. The
first line is drawn through two midpoints in talus 10, one at the
body and one at the neck. The angle is formed by the intersection
of these axes. As shown in FIG. 16A, the normal range is 25-45
degrees. An angle over 45 degrees indicates hindfoot valgus,
another component of pes planus, as depicted in FIG. 16B. FIGS. 17A
and 17B depict radiographs evaluating the AP talocalcaneal angle,
also known as Kite's angle. This is the angle formed by the
intersection of a line bisecting the head and neck of talus 10 and
a line running parallel with the lateral surface of calcaneus 2.
FIG. 17A depicts a foot within the range of normal for adults
between 15-30.degree.. Referring to FIG. 17B, an angle greater than
30.degree. indicates hindfoot valgus, another component of pes
planus.
[0062] FIGS. 18A and 18B are schematic cross-sectional
representations through the sinus tarsi of a neutrally aligned foot
compared to a hyperpronated foot, respectively. Due to ligament
laxity, the hyperpronated foot has a greater range of motion at
talus 10 and calcaneus 2, which causes a shift in load bearing
along the medial portion of the foot and tends to flatten the arch.
Insertion of material 58 into sinus tarsi 26, alters the range of
subtalar motion and limits the range of pronation. FIG. 18C shows
that material 58 positioned in sinus tarsi 26 can have a wedge-type
effect to position calcaneus 2 to a neutral alignment. FIG. 18D
illustrates, however, that over time, the configuration of talus 10
and calcaneus 2 also has a tendency to cause lateral displacement
of material 58 through forces exerted onto material inserted into
sinus tarsi 26. FIGS. 19A and 19B are schematic longitudinal
cross-sectional representations of a hyperpronated foot before and
after insertion of material 58 into sinus tarsi 26.
[0063] Accordingly, one embodiment of the present invention
provides an implant 60 which can be easily located within the
tarsal canal, which may or may not deform under post-operative
compressive forces, which would ensure that the desired amount of
calcaneal eversion has been provided after insertion of the implant
60 and which can be imaged using radiography to determine whether
the implant has been properly positioned during the procedure. By
placing a device into the tarsal space between talus 10 and
calcaneus 2, hindfoot motion and stability may be favorably
modified. Such a device may further provide midfoot stability
because midfoot-stability is co-dependent on hindfoot stability.
Dysfunction of the posterior tibial tendon that supports the foot
arch may also be treated by restoring the arch of the foot and
relieving the excessive tension on the tendon.
[0064] By developing a minimally invasive, catheter-deliverable
subtalar implant, disruption of the joint capsule and the
ligamentous structures in and around the lateral portion of the
foot can be reduced. Current subtalar implants require either
transaction of the ligaments overlying the sinus tarsi or the
dilation of an opening up to about 3/4 inch diameter through the
ligaments. Dilation of this magnitude will stretch and disrupt the
ligaments. In general, the implant in accordance with the present
invention may be advanced through a tissue opening of no greater
than about 7 mm, and preferably no greater than about 2 mm to about
3 mm.
[0065] The development of an inflatable, non-metallic implant will
allow the creation of an in-situ customized prosthesis that will
also minimize trauma to the surrounding tissue during the
implantation procedure and with long-term use. This will
considerably shorten the postoperative recuperation period compared
to existing devices and reduce postoperative pain and swelling.
Moreover, because the integrity of the tissue overlying the sinus
tarsi is preserved through minimally invasive implantation, the
intact tissue is able to assist in anchoring the implant in the
sinus tarsi. By customized, the inventor contemplates an implant
that is at least partially conformable to the anatomical cavity in
which it resides, at least prior to any polymerization or other
curing step.
[0066] In one embodiment of the invention, illustrated in FIGS. 20A
and 20B, the implant 60 comprises an inflatable compartment 64 and
an inflation port 66. Inflation port 66 provides access to
compartment 64 without compromising the integrity of compartment 64
and causing leakage. In one embodiment of the invention, implant 60
will form a custom shape that approximates the shape of sinus tarsi
26. The custom shape is defined on its superior-medial surface 61
by the inferior surface of talus 10, on its inferior-medial surface
63 by the superior surface of calcaneus 2, and on its lateral
surface 65 by soft tissue structures including the fascia. It is
preferred, but not required, that the shape have a large lateral
surface area 68. A large lateral surface takes advantage of the
intact ligaments and soft tissue along the lateral border of sinus
tarsi 26 to hold implant 60 in place. The implant has a lateral
surface area 68 of between about 2 square centimeters to about 5
square centimeters, preferably between about 3 square centimeters
to about 4 square centimeters, and more preferably about 3.8 square
centimeters. A custom-shaped implant 60 is also better adapted to
affect the highly variable anatomy of the subtalar joint and to
alter the highly variable geometry and motion of the joint. A
custom-shaped implant can be configured to have a greater contact
surface area with sinus tarsi 26 and can disperse the loading of
the subtalar joint across a greater surface area compared to
non-customized implants. The size and shape of sinus tarsi 26 is
also varies with foot position. Therefore, the surgeon will
position the foot during the procedure based upon the anatomy of a
particular patient and the characteristics of the selected implant.
One embodiment of the implantation procedure is described in detail
below.
[0067] Generally, the area of the lateral-proximal surface 68 of
the implant will be at least about twice the cross-sectional area
of the dilated tissue access tract. Often, the lateral surface area
will be at least 5.times., 8.times., 10.times. or 20.times. or more
than the access tract to resist migration of the implant.
[0068] In another embodiment, the implant is semi-customizable. The
surgeon is able to limit certain dimensions or features of the
semi-customizable implant by selecting a balloon having a shorter
length, diameter and/or volume. The implant shape is further
adjusted by allowing a variable degree of inflation. Variable
inflation may allow deeper positioning of the implant within the
sinus tarsi by providing implant 60 with a smaller diameter for
deeper insertion into the narrow tarsal canal.
[0069] In still another embodiment, the implant shape is
preselected by the surgeon. The implant is compressible onto a
catheter for minimally invasive delivery, but assumes a
preconfigured shape with inflation. A preconfigured shape may be
advantageously used to force a particular foot alignment or to
facilitate anchoring of the implant. One indication for this
implant and procedure is the hyperpronated, flexible and reducible
flatfoot. The most common patient with this indication is
pediatric, but adults with posterior tibial tendon dysfunction or
hyper-pronation in the absence of subtalar joint and mid tarsal
joint arthritis are also eligible. FIGS. 21A through 21H represent
implants of various possible shapes for nonconforming implants. The
implant can be spherical 70, cylindrical 72, conical 74,
frusta-conical 76, wedge-shaped 78, helical 80, polyhedral 82 or
any three-dimensional shape 84 capable of positioning in the sinus
tarsi. FIG. 21H is one embodiment of implant 60 advantageously
fitted to the sinus tarsi 26 of a left foot. The implant, when
inflated, may include a groove 86 or cavity dimensioned for fitting
around the cervical ligament 40 and a distal tip 88 for anchoring
implant 60 in a narrowing of the sinus tarsi 26 along the
interosseous ligament 38. A large lateral surface area 68 uses the
soft tissue at the lateral opening of the sinus tarsi 26 to
maintain the desired position of the implant. This implant has a
length of about fifteen millimeters to about twenty millimeters, a
lateral diameter of about ten to about fifteen millimeters and a
medial diameter of about six to about eight millimeters.
[0070] The outer surface 90 of implant 60 may be smooth, textured
or comprise any of a variety of protrusions or indentations to
reduce the risk of implant migration. FIGS. 22A and 22B show one
embodiment of the invention with a plurality of ridges 92 on the
outer surface. Texturing on the outer surface 90 of implant 60 may
provide an interference fit or increased friction between implant
60 and sinus tarsi 26 to resist displacement of implant 60 from its
desired position. In a further embodiment, the outer surface 90 may
further comprise cellular ingrowth regions that allow ingrowth of
the surrounding tissue and further resist displacement of the
implant. The pore size of the cellular ingrowth regions may range
from about 20 .mu.m to about 100 .mu.m or greater. Desirably, the
porosity of the cellular ingrowth regions ranges from 20 .mu.m to
50 .mu.m and, in many embodiments, the porosity of the cellular
ingrowth regions ranges from 20 .mu.m to 30 .mu.m.
[0071] If more aggressive anchoring of the implant is desired, the
inflatable member may be further configured to facilitate
attachment of implant 60 to soft tissue or bone. In one embodiment,
sutures, clips, staples, tacks, pins, hooks, barbs, or other
securing structures that can at least partially penetrate the
surrounding tissue or bone are used. These securing structures may
be made from a variety of materials, including metals, polymers,
ceramics or absorbable materials. Absorbable materials include but
are not limited to polylactic acid (PLA) or copolymers of PLA and
glycolic acid, or polymers of p-dioxanone and 1,4-dioxepan-2-one. A
variety of absorbable polyesters of hydroxycarboxylic acids may be
used, such as polylactide, polyglycolide and copolymers of lactide
and glycolide, as described in U.S. Pat. Nos. 3,636,956 and
3,297,033, which are hereby incorporated in their entirety herein
by reference. The use of absorbable materials allows the securing
structure to dissolve or resorb into human tissue after a known or
establishable time range, from a week to over a year.
[0072] In one non-limiting example, shown in FIG. 23A, a distal
anchor 94 with at least two or three or four or more barbs 96 is
attached to the medial surface 98 of implant 60 for anchoring at
the medial portion of the sinus tarsi 26. In another non-limiting
example in FIG. 23B, one or more short pointed barbs 96 are
integrally formed with implant 60 or secured thereto using any of a
variety of attachment techniques which are suitable depending upon
the composition of implant 60. As the implant is inserted into
sinus tarsi 26, barbs 96 penetrate the surrounding soft tissue,
bone or ligaments. Hooks may also be attached to or integrally
formed with implant, so that the implant can be hooked into the
surrounding tissue, possibly in combination with the use of a
bioadhesive. Such hooks and barbs may be formed from a
bioabsorbable or dissolvable material as has discussed above.
[0073] In one embodiment of the invention, implant 60 comprises any
of a variety of flexible materials that resist stretching. These
materials include but are not limited to polyethylene, polyolefins,
polyvinyl chloride, polyester, polyimide, polyethylene
terephthalate (PET), polyamides, nylon, polyurethane and other
polymeric materials. One skilled in the art can select the material
based upon the desired compliance, biocompatability, rated burst
pressure and other desired characteristics. In one embodiment, the
inflatable member has a wall thickness of about 0.001 cm to about
0.05 cm. In another embodiment, the inflatable member has a
thickness of about 0.02 cm to about 0.03 cm. Generally, the
inflatable member has a rated burst pressure of greater than 60
atmospheres (ATM) for resisting bursting and extrusion of inflation
material under physiologic loading. In another embodiment, the
inflatable member has a rated burst pressure of at least about
eight ATM or more. A lower burst pressure can be used where a
curable material is used to inflate the inflatable member and will
bear the loading of the subtalar joint. In a further embodiment of
the invention, implant 60 is integrally formed with deformable wire
supports within the material used to form the inflatable member.
One possible function of the wire support to provide some stiffness
to the implant during the insertion process to allow the operator
to insert the implant into distal sulci or crevices of the sinus
tarsi. A wire support can also comprise a shape memory metal, such
as nitinol. Upon insertion of the implant into the sinus tarsi, the
body heat of the patient will cause the wire support to change
shape and expand to the borders of the sinus tarsi. Those skilled
in the art understand that any of a variety of biocompatible,
deformable metals may be used to form the skeleton.
[0074] In addition to providing access to inflate the inflatable
compartment, the inflation port may comprise other features to
facilitate use of the implant. The inflation port may be
self-sealing or have a one-way valve to obviate the need for a
separate sealing of the implant after inflation. Valve
configurations include but not limited to hemostatic-type valves,
flap valves or duckbill valves. In some embodiments, a pierceable
septum may be used. A flap valve 100 is shown in FIG. 20B. The
flapper portion of the valve can be formed from silicone, rubber,
neoprene or any other flexible material known to those with skill
in the art. Less flexible materials may be used for the valve where
the inflation fluid is highly viscous or curable. One skilled in
the art can select the type of seal based upon the inflation
pressures of the implant, the viscosity of the inflation fluid,
curability and other characteristics. Inflation port 66 may be
further configured to minimize any leakage of material from either
implant 60 or the delivery system during the detachment process.
Inflation port 66 may include radio-opaque markers to allow a
clinician to later deflate or adjust implant 60 transcutaneously
with a hypodermic needle.
[0075] The material used to inflate inflatable compartment 62
includes any of a variety of biocompatible materials, including but
not limited to saline, silicone polymers, polyurethane polymers,
linear or branched polyols, PMMA or others known in the art. Solid
materials, such as small polymeric metallic microspheres,
microtubules or microdiscs can also be used as a filling agent. The
material can also be a combination of materials, such a curable
liquid substrate and a catalyst, that can solidify within implant
60. Several U.S. patents disclose various types of polymers or
proteins that, assertedly, can be injected into a joint as a liquid
or semi-liquid composition that subsequently harden into a
solidified material. For example, U.S. Pat. No. 5,556,429 (Felt
1996), herein incorporated by reference, discloses injection of a
fluidized mixture of a biocompatible polymer (such as a silicone or
polyurethane polymer) and a biocompatible "hydrogel" (a hydrophilic
polymer, formed by steps such as using an agent such as ethylene
dimethacrylate to cross-link a monomer containing a hydroxyalkyl
acrylate or methacrylate), into a space. After injection, the
polymer and hydrogel mixture can be set into solidified form by
means such as ultraviolet radiation, which can be introduced into
the space by a fiber optic device. Other articles on surgically
implantable polymers is contained in numerous published items;
recent review articles include Peppas et al 1994, Hubbell 1995,
Stokes 1995, Burg et al 1997, Lewis 1997, Kim and Mooney 1998, and
Ambrosio et al 1998, herein incorporated by reference. Other
discussions of biocompatible implantable materials are also
available in various textbooks, such as Silver 1994, herein
incorporated by reference. Other combinations of inflation
materials may include the addition of iodine, barium or other
radio-opaque component. One skilled in the art can select the
desired material based upon the viscosity, density, cure time,
degree of exothermic cure reaction, radio-opacity and other
characteristics. For curable materials, one skilled in the art may
consider the load-bearing strength, tensile strength, shear
strength, fatigue, impact absorption, wear characteristics and
other factors of the cured material.
[0076] In another embodiment, implant 60 has multiple inflation
ports and multiple compartments such that different portions of
implant 60 can be independently inflated. FIGS. 24A and 24B are
non-limiting examples of two-compartment inflatable members. The
delivery catheter for an implant comprising multiple compartments
may have multiple fluid ports to allow independent inflation of the
compartments. Different compartments may be inflated with different
materials having different characteristics. In one embodiment of
the invention, implant 60 has an inner compartment 104 and an outer
compartment 106. Outer compartment 106 may be inflated with a
curable material to provide a solid material at the surface of
implant 60. Inner compartment 104 may be inflated with a liquid
material to provide limited deformability to implant 60.
Alternatively, outer compartment 106 may be inflated with a liquid
material and inner compartment 104 is inflated with a curable
material. This particular embodiment may provide cushioning to the
joint surfaces by providing a compressible implant surface, yet the
curable core provides some resilience to complete compression.
[0077] Implant 60 further comprises a coupling interface 108 that
releasably attaches implant 60 to the delivery system. Coupling
interface 108 is generally located on or about inflation port 66
and allows for inflation of implant 60 through the delivery system
without leakage of material into the surrounding tissue. Coupling
interface 108 also allows transmission of force, including torque,
from the delivery system to the implant to facilitate positioning
of implant 60. Coupling interface 108 is configured to allow
detachment of implant 60 from the delivery system and, optionally
reattachment of the delivery system.
[0078] FIGS. 25A through 25C illustrate one embodiment of the
invention, where coupling interface 108 comprises a flange 110
surrounding inflation port 66. Flange 110 is capable of being
grasped by prongs 112 extending from the delivery catheter 114.
Coupling interface 108 further comprises a base 116 having a
polygonal or otherwise rotationally keyed cross-section. Base 116
may be positioned between coupling interface 108 and inflatable
compartment 64 and is capable of forming another mechanical
interfit with an outer sheath 146 over catheter 114. This
additional mechanical interfit provides further resistance to
dislodging or separation of implant 60 from delivery catheter 114
during implantation, especially from rotational forces. FIGS. 26A
through 26C depict another embodiment of coupling interface 108,
comprising base 116 and an internal threaded lumen 118 for
accepting a threaded core 120 extending from the delivery catheter
114. The attachment of coupling interface 108 to delivery catheter
114 is described in further detail below.
[0079] One embodiment of the delivery system is illustrated in
FIGS. 27A through 27C, comprising a cannula or sheath 122, a sizing
catheter 124 with an inflatable balloon tip 126 and delivery
catheter 114 attachable to implant 60. Cannula 122 is made from
plastic with radio-opaque markers to allow imaging of the cannula.
Cannula 122 can be introduced into the sinus tarsi over a needle
130. Cannula 122 has a length of about two inches to about six
inches and a diameter of about 12 gauge to about 18 gauge. A lumen
128 is provided in cannula 122 to allow passage of sizing catheter
124 and delivery catheter 114 with attached implant 60.
Alternatively, the cannula can be made of metal and has a distal
tip sufficiently sharp to pierce the skin, connective tissue and
ligaments overlying the sinus tarsi. A metal cannula with a sharp
tip would not require insertion of the cannula over a needle or
guidewire.
[0080] Sizing catheter 124, shown in FIG. 27B, has a length of
about two inches to about eight inches and a diameter capable of
passing through cannula 122. Sizing catheter 124 has radiographic
markers for determining its position in the foot during
radiographic imaging. The proximal end 132 of sizing catheter 124
comprises a Luer fitting 134 or other similar type of mechanical
lock for attaching a syringe 136. A lumen 138 within the sizing
catheter 124 provides a conduit from syringe 136 to sizing balloon
tip 126 at the distal end of sizing catheter 124. Sizing balloon
tip 126 has a length of about fifteen millimeters and a diameter of
about six to about twelve millimeters. Sizing balloon tip 126 can
have any of a variety of shapes similar to those described for
implant 60. Syringe 136 has markings so that the volume of fluid
inflated into sizing balloon tip 126 can be measured
quantitatively. Sizing catheter 124 is capable of performing a
number of functions. Insertion of sizing catheter 124 through
cannula 122 initiates the dilatation of sinus tarsi 26 and helps to
prepare the path for introduction of permanent implant 60. By
filling sizing catheter balloon 126, the surgeon is able to
determine the volume of non-compressible fluid required to fill
sinus tarsi 26 to the proper degree necessary for selection of the
configuration of permanent implant 60 capable of controlling
pronation within the proper range.
[0081] Alternatively, sizing balloon 126 may comprise a
high-compliance material that is capable of conforming to the
surrounding anatomical structures. By filling sizing balloon 126
with a radio-opaque fluid under fluoroscopy or with radiography,
the surgeon can determine the proper three-dimensional shape and of
the cavity 26. An implant 60 can be selected to correspond with the
predetermined shape and/or size. FIG. 28A is a cross-sectional
schematic of high-compliance sizing balloon 126 inflated in sinus
tarsi 26. As the balloon 126 is inflated in FIG. 28B, loose
ligaments and connective tissue will be displaced while balloon 126
conforms around taut structures. This shape information permits
selection or construction of an implant having a predetermined
shape or determination of the need for a semi-customizable or fully
customizable implant.
[0082] In an alternative embodiment of the delivery system, sizing
catheter 124 is omitted because the inflation characteristics of
the implant allow implant 60 to be adapted to structural variations
of the anatomy. Selection of a particular size or shape of implant
is not required in this alternative embodiment. In this embodiment,
the surgeon can partially inflate the implant, evaluate the effect
on the foot alignment and flexibility, and continue to inflate,
deflate and/or position the implant until a desired result is
achieved. The delivery catheter 114 may then be detached and
withdrawn, leaving the implant 60 in place.
[0083] FIG. 27C shows one embodiment of delivery catheter 114,
comprising a proximal end 140, a body 142, a distal end 144 and an
outer sheath 146. The delivery catheter has a length of about two
inches to about ten inches and has a diameter capable of passing
through cannula 122. Catheter 114 may contain radiographic markers
for determining its position in the foot with imaging. Proximal end
140 of delivery catheter 114 comprises at least one Luer fitting
134 or other similar type of mechanical lock for attaching a
syringe to inflate the implant with material. Body 142 of delivery
catheter 114 comprises at least one lumen 148 to provide a conduit
from the syringe or other source to implant 60 fastened to distal
end 144 of delivery catheter 114. A multi-lumen catheter may be
used where the implant has multiple compartments, or where multiple
reactive materials are used to inflate the implant. The use of
multiple lumens may prevent reactive components of the implant
material from reacting within the catheter and prevent clogging of
the catheter. For inflation materials that use ultra-violet light
for curing, a fiber-optic line can be inserted through the lumen
148 to provide the ultra-violet light. Outer sheath 146 comprises
an inner surface 150, an outer surface 152, a proximal portion 154
and a distal portion 156. Outer sheath 146 also has a retracted
position that exposes the distal end 144 of delivery catheter 114
and an extended position that covers distal end 144 of delivery
catheter 114.
[0084] Distal end 144 of delivery catheter 114 comprises an
inflation lumen 158 and a coupler for attaching to coupling
interface 108 of implant 60. In the embodiment of the invention
seen in FIG. 25A, where coupling interface 108 comprises flange
110, the coupler 160 of delivery catheter 114 comprises a plurality
of radially outward-biased graspers or prongs 112 extending
distally. Graspers 112 may comprise bent wires, thin arcuate
sheets, or any other configuration known to those with skill in the
art that is capable of engaging flange 110 and applying a
proximally directed force to flange 110. Referring back to FIG.
27C, when outer sheath 146 of delivery catheter 114 is in the
extended position, inner surface 150 of outer sheath 146 will
contact prongs 112 and apply radially inward forces against prongs
112. These forces move the prongs 112 closer together and allow the
prongs 112 to engage the edge of flange 110 on implant 60.
[0085] If outer sheath 146 is further extended, inner surface 150
of sheath 146 will contact base 116 of coupling interface 108. Base
116 of implant 60 has a polygonal cross-section capable of forming
a mechanical interfit with a polygonal cross-section of inner
surface 150 of outer sheath 146. Distal portion 156 of sheath 146
will also exert a distally directed counterforce on implant 60 in
opposition to the proximally directed force on the implant from the
prongs 112 to firmly attach implant 60 to the delivery catheter
114. If sheath 146 is retracted, the mechanical interfit with base
116 is relieved and radially inward forces on prongs 112 are
removed. Prongs 112 will resume their outward bias and distract
from flange 110 of implant 60, causing release of implant 60. As
previously mentioned, delivery catheter 114 shown in FIG. 26C, may
alternatively comprise a slideable inner core 161 within the
inflation lumen 158 of delivery catheter 114 that is capable of
extending through coupling interface 108 to engage inflation port
66 of implant 60. A lumen 162 in inner core 161 provides a conduit
to inflate attached implant 60 with material.
[0086] In the embodiment of implant 60 shown in FIG. 26A, where
coupling interface 108 comprises a threaded lumen 118, the delivery
catheter 114 comprises an outer sheath similar to the sheath
described above. The inner core of this embodiment of the delivery
catheter, however, comprises a lumen 166 and a threaded outer
surface 168 complementary to threaded lumen 118 of implant 60.
Implant 60 attaches to delivery catheter 114 by rotating inner core
120 into threaded lumen 118 of the implant. To resist rotation of
implant 60 from frictional forces during the attachment or
detachment of implant 60, the polygonal cross-section of inner
surface 150 of outer sheath 146 is capable of forming a mechanical
interfit with the polygonal cross-section of coupling base 116 on
implant 60 when outer sheath 146 is extended.
[0087] In an alternative embodiment of the delivery system, a
guidewire or guide pin having a diameter of about 0.010 inch to
about 0.038 inch and a length of about four inches to about eight
inches is provided for insertion into the sinus tarsi. The
guidewire is insertable through a needle inserted into the sinus
tarsi. The needle is withdrawn after the guidewire is positioned.
An introducer may be passed to further dilate the passage to the
sinus tarsi. The sizing and delivery catheters are adapted for
passage over the guidewire into the sinus tarsi. In this
embodiment, both catheters would each have at least two lumens. One
lumen is used to pass the catheter over the guidewire and the other
lumen would be used to inflate the sizing balloon or implant. These
lumens may be oriented in a dual concentric configuration or
adjacent to each other.
[0088] One indication for this embodiment of the implant and
implantation procedure is a reducible, hyperpronated, flexible
flatfoot. These patients are commonly pediatric, but adults with
posterior tibial tendon dysfunction and/or hyper-pronation in the
absence of subtalar joint and mid tarsal joint arthritis are also
potential candidates. FIG. 29 shows one procedure for using an
embodiment of the implant comprises positioning the patient on a
table and draping the lateral side of the foot in the usual sterile
fashion known in the art. The insertion site for the implant is
identified by palpation of bony markers, including but not limited
to the fibular head, cuboid, talus and calcaneus bones. The lateral
opening of the sinus tarsi is identified anterior, medial and
inferior to the lateral malleolus or distal head of the fibula.
Local anesthesia is injected into the skin and the connective
tissue overlying the insertion site. Anesthetics with epinephrine
may be used to limit bleeding at the insertion site. Alternatively,
regional or general anesthesia may be used. The surgeon places the
foot in a slightly supinated position to widen the lateral opening
of the sinus tarsi during the procedure. A needle is inserted at
the desired site and a small cannula is passed over the needle. The
desired depth of insertion is determined by markings on the cannula
and assisted by fluoroscopic imaging. The needle is then withdrawn.
The cannula may be of "peel-away" type as is known to those with
skill in the art. The foot with the inserted cannula is
radiographically imaged to facilitate positioning of the cannula in
the sinus tarsi. FIG. 28A illustrates sizing catheter 124 with an
attached, fluid-filled syringe inserted through cannula 122. The
foot is then repositioned and held in a generally neutral
alignment. Neutral alignment is defined as the foot position where
the lateral aspect of the heel becomes perpendicular to the leg and
the talonavicular joint feels congruous to palpation. Neutral
alignment is often, but not always, the position in the range of
motion where the foot is capable of two-thirds additional
supination and one-third additional pronation. Foot alignment can
also be checked radiographically by assessing changes to the cyma
lines in the AP and lateral views of the foot, as previously shown
in FIGS. 9A and 10A.
[0089] Referring to FIG. 28B, balloon tip 126 on sizing catheter
124 is inflated until significant resistance is met. The inflation
volume on the syringe is measured. The surgeon assesses the range
of motion and alignment of the foot with the inflated sizing
catheter in place. This allows the surgeon to estimate the
potential changes to the joint and to facilitate selection of the
permanent implant. The surgeon also checks the quality, range,
location and smoothness of joint motion. Radiographic imaging may
be performed for additional assessment of the joint. The cannula is
repositioned and/or the sizing balloon volume is adjusted to
achieve approximately four degrees of foot eversion. As noted
previously, approximately one third of the subtalar range should be
in the direction of pronation and two-thirds towards supination.
Balloon tip 126 is deflated and sizing catheter 124 is withdrawn.
FIG. 30A shows delivery catheter 114 with selected inflatable
implant 60 passed through cannula 122 and into sinus tarsi 26.
Cannula 122 is optionally peeled away from the foot. Implant 60 is
inflated with at least one material 58 to the desired volume based
upon the inflation volume measured with sizing catheter 124. Foot
alignment and range of motion is rechecked by physical exam and/or
radiographic imaging. The inflation volume of implant 60 may be
adjusted based upon the results of the exam and/or the imaging
until the desired talocalcaneal position is achieved. In one
embodiment, the surgeon uses the cyma line, in contradistinction to
an anterior displaced talonavicular joint, as an indication that a
pronated foot has been reduced to a more neutral alignment. Implant
60 is then sealed, if implant 60 is not self-sealing. Referring to
FIG. 30B, delivery catheter 114 is detached from implant 60 and
both catheter 114 and cannula 122 are withdrawn from the patient.
If necessary, the insertion site is closed by either suturing or
adhesives and dressed. A splint or cast is applied to the foot.
[0090] In an alternative implantation procedure, the material used
to inflate implant 60 to the desired volume is removed from the
implant and its volume is measured. An equal or similar volume of
another material having a different density or characteristics is
used to reinflate the implant. This alternative procedure may be
used to obtain a more accurate measurement of the sinus tarsi and
the volume of final inflation material to be used where the final
inflation material changes volume as it cures. The volume of the
initial fluid used to assess the sinus tarsi is used to calculate
the volume of uncured final inflation material to be delivered.
[0091] In another alternate method of implanting the device using a
guidewire, the patient is placed on a table and the lateral side of
the foot is draped in the usual sterile fashion known in the art.
The insertion site for the device is identified by palpation of
bony markers, including but not limited to the fibular head,
cuboid, talus and calcaneus bones. Local anesthesia is injected
into the skin and connective tissue overlying the insertion site.
Anesthetics with epinephrine may be used to limit bleeding at the
insertion site. A large bore needle is inserted at the desired site
and a guidewire is passed through the needle. Optionally, a small
dilator is passed over the guidewire for enlarging the pathway to
the sinus tarsi. The foot with the inserted guidewire is
radiographically imaged to confirm positioning of the guidewire in
the sinus tarsi. A catheter with the inflatable implant at the
catheter tip is passed over the guidewire and into the sinus tarsi.
The implant is inflated to the desired volume. The talo-calcaneal
relationship is checked by physical exam and/or radiographic
imaging. The inflation volume of the implant may be adjusted based
upon the results of the exam and/or the imaging until the desired
talo-calcaneal position is achieved. The surgeon may use the cyma
line, in contradistinction to an anterior displaced talo-navicular
joint, as an indication that a pronated foot has been reduced to a
more neutral alignment. The delivery catheter is detached from the
implant and both the catheter and guidewire are withdrawn from the
patient. The insertion site is closed by either suturing or
adhesives and dressed.
[0092] The implant and delivery system described above can also be
adapted for insertion into the first MTP joint of the foot.
Referring to FIGS. 31A and 31B, the implant shape for this
embodiment of the invention is preferably an implant comprising a
first concave surface 170 on a first side of the implant 172 and a
second concave surface 174 on a second side. First concave surface
170 is adapted to contact the distal end of the first metatarsal
and second concave surface 176 is adapted to contact the proximal
end of the first proximal phalanx of the foot. Other shapes,
however, can be used depending upon the particular anatomy and
disease of the first MTP joint. The delivery system will generally
have a shorter length because of the accessibility of the first MTP
joint.
[0093] While this invention has been particularly shown and
described with references to embodiments thereof, it will be
understood by those skilled in the art that various changes in form
and details may be made therein without departing from the scope of
the invention. For all of the embodiments described above, the
steps of the methods need not be performed sequentially.
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