U.S. patent application number 15/976100 was filed with the patent office on 2018-09-13 for apparatus for fixing sheet-like materials to a target tissue.
This patent application is currently assigned to Rotation Medical, Inc.. The applicant listed for this patent is Rotation Medical, Inc.. Invention is credited to Charles L. Euteneuer.
Application Number | 20180256162 15/976100 |
Document ID | / |
Family ID | 45768311 |
Filed Date | 2018-09-13 |
United States Patent
Application |
20180256162 |
Kind Code |
A1 |
Euteneuer; Charles L. |
September 13, 2018 |
APPARATUS FOR FIXING SHEET-LIKE MATERIALS TO A TARGET TISSUE
Abstract
A device for attaching a sheet-like implant to a target tissue.
The device includes a fastener push rod including a first portion,
a second portion and a force limiting mechanism operably coupled
between the first portion and the second portion. A fastener is
carried by the second portion of the fastener push rod. The force
limiting mechanism transmits longitudinal movement of the first
portion to the second portion while the forces applied to the
fastener by the fastener push rod are less than a predetermined
value such that longitudinal movement of the first portion of the
fastener push rod causes substantially equivalent longitudinal
movement of the second portion. The force limiting mechanism allows
relative longitudinal motion between the first and second portions
while the forces applied to the fastener are equal to or greater
than the predetermined value such that the application of undue
forces to the fastener is prevented.
Inventors: |
Euteneuer; Charles L.; (St.
Michael, MN) |
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Applicant: |
Name |
City |
State |
Country |
Type |
Rotation Medical, Inc. |
Plymouth |
MN |
US |
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|
Assignee: |
Rotation Medical, Inc.
Plymouth
MN
|
Family ID: |
45768311 |
Appl. No.: |
15/976100 |
Filed: |
May 10, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14711351 |
May 13, 2015 |
9993247 |
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15976100 |
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13397573 |
Feb 15, 2012 |
9033201 |
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14711351 |
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61443180 |
Feb 15, 2011 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61F 2/08 20130101; A61B
17/0684 20130101; A61B 17/072 20130101; A61B 2017/0645 20130101;
A61F 2/0063 20130101; A61B 17/07207 20130101; A61B 2017/00398
20130101; A61F 2/0811 20130101; A61B 17/00234 20130101; A61B
17/0401 20130101; A61B 17/0644 20130101; A61B 17/0682 20130101;
A61B 2017/07214 20130101; A61B 90/03 20160201; A61F 2002/0852
20130101; A61B 17/0642 20130101; A61B 17/0686 20130101 |
International
Class: |
A61B 17/068 20060101
A61B017/068; A61F 2/08 20060101 A61F002/08; A61B 17/064 20060101
A61B017/064; A61B 17/072 20060101 A61B017/072; A61F 2/00 20060101
A61F002/00 |
Claims
1. A method for attaching a sheet-like implant to a target tissue,
comprising the steps of: positioning a sheet-like implant adjacent
to a tissue to be repaired; advancing a fastener fixation tool to
contact the sheet-like implant, wherein the fastener fixation tool
comprises: a sheath having a proximal end and a distal end; a
fastener push rod disposed at least partially within the sheath,
the fastener push rod including a first portion and a second
portion; a fastener disposed at least partially within the sheath
and distal of the fastener push rod second portion, wherein the
distal end of the sheath of the fastener fixation tool contacts the
sheet-like implant in a nominally perpendicular orientation; and an
actuator assembly coupled to the fastener push rod first portion,
the actuator assembly configured and adapted to apply a force to
the fastener push rod first portion upon activation of the actuator
assembly; activating the actuator assembly, thereby advancing the
fastener push rod first portion, wherein when the force applied to
the fastener push rod first portion is below a force threshold the
fastener push rod second portion is translated with the applied
force and when the force applied to the fastener push rod first
portion is equal to or above a force threshold the fastener push
rod second portion is translated with the force threshold;
advancing the fastener distally from the sheath to penetrate the
sheet-like implant and tissue to be repaired.
2. The method for attaching a sheet-like implant to a target tissue
of claim 1, wherein advancing the fastener distally from the sheath
creates at least one pilot hole in the target tissue.
3. The method for attaching a sheet-like implant to a target tissue
of claim 1, wherein advancing the fastener distally from the sheath
creates a second pilot hole in the target tissue.
4. The method for attaching a sheet-like implant to a target tissue
of claim 2, wherein further advancing the fastener into the target
tissue engages one or more flukes of the fastener with the target
tissue adjacent to the at least one pilot hole thereby preventing
withdrawal of the fastener from the at least one pilot hole.
5. The method for attaching a sheet-like implant to a target tissue
of claim 1, wherein the fastener push rod first portion is operably
coupled to the fastener push rod second portion by a force limiting
mechanism.
6. The method for attaching a sheet-like implant to a target tissue
of claim 5, wherein the force limiting mechanism comprises a
constant force spring a first end of which is coupled to the
fastener push rod first portion and a second end of which is
coupled to the fastener push rod second portion.
7. The method for attaching a sheet-like implant to a target tissue
of claim 5, wherein the fastener push rod first portion includes a
first tubular member and a portion of the fastener push rod second
portion is slideably received within the first tubular member.
8. The method for attaching a sheet-like implant to a target tissue
of claim 5, wherein the fastener push rod second portion includes a
second tubular member and a portion of the fastener push rod first
portion is slideably received within the second tubular member.
9. The method for attaching a sheet-like implant to a target tissue
of claim 5, wherein the fastener push rod first portion and the
fastener push rod second portion do not rotate relative to each
other.
10. The method for attaching a sheet-like implant to a target
tissue of claim 1, wherein the fastener comprises a first arm
having a proximal end and a distal end and a second arm having a
proximal end and a distal end.
11. The method for attaching a sheet-like implant to a target
tissue of claim 10, wherein the fastener further comprises a bridge
extending from the proximal end of the first arm to the proximal
end of the second arm.
12. The method for attaching a sheet-like implant to a target
tissue of claim 1, wherein the fastener push rod second portion
contacts and engages the fastener.
13. The method for attaching a sheet-like implant to a target
tissue of claim 12, wherein the fastener push rod second portion
comprises a fork.
14. The method for attaching a sheet-like implant to a target
tissue of claim 13, wherein the fork comprises two stakes.
15. The method for attaching a sheet-like implant to a target
tissue of claim 1, further comprising withdrawing distal end of the
sheath of the fastener fixation tool from the sheet-like implant.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. application Ser.
No. 14/711,351, filed on May 13, 2015, which is a continuation of
U.S. application Ser. No. 13/397,573 filed on Feb. 15, 2012, now
U.S. Pat. No. 9,033,201, which claims benefit to U.S. Provisional
Patent Application No. 61/443,180, filed on Feb. 15, 2011. The
disclosures of each of which are herein incorporated by reference
in their entirety.
FIELD
[0002] The present invention relates generally to orthopedic
medicine and surgery. More particularly, the present invention
relates to methods and apparatus for delivery and fixation of
sheet-like materials, such as for treating articulating joints.
BACKGROUND
[0003] The glenohumeral joint of the shoulder is found where the
head of the humerus mates with a shallow depression in the scapula.
This shallow depression is known as the glenoid fossa. Six muscles
extend between the humerus and scapula and actuate the glenohumeral
joint. These six muscles include the deltoid, the teres major, and
the four rotator cuff muscles. As disclosed by Ball et al. in U.S.
Patent Publication No. US 2008/0188936 A1 and as illustrated in
FIG. 1 the rotator cuff muscles are a complex of four muscles.
These four muscles are the supraspinatus, the infraspinatus, the
subscapularis, and the teres minor. The centering and stabilizing
roles played by the rotator cuff muscles are critical to the proper
function of the shoulder. The rotator cuff muscles provide a wide
variety of moments to rotate the humerus and to oppose unwanted
components of the deltoid and pectoralis muscle forces.
[0004] The four muscles of the rotator cuff arise from the scapula
12. The distal tendons of the rotator cuff muscles splay out and
interdigitate to form a common continuous insertion on the humerus
14. The subscapularis 16 arises from the anterior aspect of the
scapula 12 and attaches over much of the lesser tuberosity of the
humerous. The supraspinatus muscle 18 arises from the supraspinatus
fossa of the posterior scapula, passes beneath the acromion and the
acromioclavicular joint, and attaches to the superior aspect of the
greater tuberosity 11. The infraspinatus muscle 13 arises from the
infraspinous fossa of the posterior scapula and attaches to the
posterolateral aspect of the greater tuberosity 11. The teres minor
15 arises from the lower lateral aspect of the scapula 12 and
attaches to the lower aspect of the greater tuberosity 11.
[0005] The mechanics of the rotator cuff muscles 10 are complex.
The rotator cuff muscles 10 rotate the humerus 14 with respect to
the scapula 12, compress the humeral head 17 into the glenoid fossa
providing a critical stabilizing mechanism to the shoulder (known
as concavity compression), and provide muscular balance. The
supraspinatus and infraspinatus provide 45 percent of abduction and
90 percent of external rotation strength. The supraspinatus and
deltoid muscles are equally responsible for producing torque about
the shoulder joint in the functional planes of motion.
[0006] The rotator cuff muscles 10 are critical elements of this
shoulder muscle balance equation. The human shoulder has no fixed
axis. In a specified position, activation of a muscle creates a
unique set of rotational moments. For example, the anterior deltoid
can exert moments in forward elevation, internal rotation, and
cross-body movement. If forward elevation is to occur without
rotation, the cross-body and internal rotation moments of this
muscle must be neutralized by other muscles, such as the posterior
deltoid and infraspinatus. The timing and magnitude of these
balancing muscle effects must be precisely coordinated to avoid
unwanted directions of humeral motion. Thus the simplified view of
muscles as isolated motors, or as members of force couples must
give way to an understanding that all shoulder muscles function
together in a precisely coordinated way--opposing muscles canceling
out undesired elements leaving only the net torque necessary to
produce the desired action. Injury to any of these soft tissues can
greatly inhibit ranges and types of motion of the arm.
[0007] With its complexity, range of motion and extensive use, a
fairly common soft tissue injury is damage to the rotator cuff or
rotator cuff tendons. Damage to the rotator cuff is a potentially
serious medical condition that may occur during hyperextension,
from an acute traumatic tear or from overuse of the joint. With its
critical role in abduction, rotational strength and torque
production, the most common injury associated with the rotator cuff
region is a strain or tear involving the supraspinatus tendon. A
tear in the supraspinitus tendon 19 is schematically depicted in
FIG. 2. A tear at the insertion site of the tendon with the
humerus, may result in the detachment of the tendon from the bone.
This detachment may be partial or full, depending upon the severity
of the injury. Additionally, the strain or tear can occur within
the tendon itself. Injuries to the supraspinatus tendon 19 and
recognized modalities for treatment are defined by the type and
degree of tear. The first type of tear is a full thickness tear as
also depicted in FIG. 2, which as the term indicates is a tear that
extends through the thickness of the supraspinatus tendon
regardless of whether it is completely tom laterally. The second
type of tear is a partial thickness tear which is further
classified based on how much of the thickness is tom, whether it is
greater or less than 50% of the thickness.
[0008] The accepted treatment for a full thickness tear or a
partial thickness tear greater than 50% includes reconnecting the
tom tendon via sutures. For the partial thickness tears greater
than 50%, the tear is completed to a full thickness tear by cutting
the tendon prior to reconnection. In contrast to the treatment of a
full thickness tear or a partial thickness tear of greater than
50%, the treatment for a partial thickness tear less than 50%
usually involves physical cessation from use of the tendon, i.e.,
rest. Specific exercises can also be prescribed to strengthen and
loosen the shoulder area. In many instances, the shoulder does not
heal and the partial thickness tear can be the source of chronic
pain and stiffness. Further, the pain and stiffness may cause
restricted use of the limb which tends to result in further
degeneration or atrophy in the shoulder. Surgical intervention may
be required for a partial thickness tear of less than 50%, however,
current treatment interventions do not include repair of the
tendon, rather the surgical procedure is directed to arthroscopic
removal of bone to relieve points of impingement or create a larger
tunnel between the tendon and bone that is believed to be causing
tendon damage. As part of the treatment, degenerated tendon may
also be removed using a debridement procedure in which tendon
material is ablated. Again, the tendon partial tear is not
repaired. Several authors have reported satisfactory early post
operative results from these procedures, but over time recurrent
symptoms have been noted. In the event of recurrent symptoms, many
times a patient will "live with the pain". This may result in less
use of the arm and shoulder which further causes degeneration of
the tendon and may lead to more extensive damage. A tendon repair
would then need to be done in a later procedure if the prescribed
treatment for partial tear was unsuccessful in relieving pain and
stiffness or over time the tear propagated through injury or
degeneration to a full thickness tear or a partial thickness tear
greater than 50% with attendant pain and debilitation. A subsequent
later procedure would include the more drastic procedure of
completing the tear to full thickness and suturing the ends of the
tendon back together. This procedure requires extensive
rehabilitation, has relatively high failure rates and subjects the
patient who first presented and was treated with a partial
thickness tear less than 50% to a second surgical procedure.
[0009] As described above, adequate treatments do not currently
exist for repairing a partial thickness tear of less than 50% in
the supraspinatus tendon. Current procedures attempt to alleviate
impingement or make room for movement of the tendon to prevent
further damage and relieve discomfort but do not repair or
strengthen the tendon. Use of the still damaged tendon can lead to
further damage or injury. Prior damage may result in degeneration
that requires a second more drastic procedure to repair the tendon.
Further, if the prior procedure was only partially successful in
relieving pain and discomfort, a response may be to use the
shoulder less which leads to degeneration and increased likelihood
of further injury along with the need for more drastic surgery.
There is a large need for surgical techniques and systems to treat
partial thickness tears of less than 50% and prevent future tendon
damage by strengthening or repairing the native tendon having the
partial thickness tear.
SUMMARY OF THE DISCLOSURE
[0010] The disclosure is directed to devices for attaching a
sheet-like implant to a target tissue. One embodiment includes a
fastener push rod including a first portion, a second portion and a
force limiting mechanism operably coupled between the first portion
and the second portion. A fastener is carried by the second portion
of the fastener push rod. An actuator assembly coupled to the first
portion of the fastener push rod is provided. The actuator assembly
is capable of creating longitudinal movement of the first portion.
The force limiting mechanism transmits longitudinal movement of the
first portion to the second portion while the forces applied to the
fastener by the fastener push rod are less than a predetermined
value such that longitudinal movement of the first portion of the
fastener push rod causes substantially equivalent longitudinal
movement of the second portion. The force limiting mechanism allows
relative longitudinal motion between the first portion and the
second portion while the forces applied to the fastener are equal
to or greater than the predetermined value such that the
application of undue forces to the fastener is prevented.
[0011] Another embodiment includes a pronged sheath. The pronged
sheath defines a lumen. The pronged sheath includes at least a pair
of prongs extending distally beyond a distal end of the lumen such
that the prongs form pilot holes when a distal portion of the
pronged sheath is pressed against the target tissue. A fastener
push rod extends into the lumen defined by the pronged sheath. The
fastener push rod includes a first portion, a second portion and a
force limiting mechanism operably coupled between the first portion
and the second portion. A pair of stakes are disposed at a distal
end of the second portion of the fastener push rod. The pair of
stakes carries a fastener. An actuator assembly is coupled to the
first portion of the fastener push rod and capable of creating
longitudinal movement of the first portion of the fastener push rod
relative to the pronged sheath. The force limiting mechanism
transmits longitudinal movement of the first portion to the second
portion while the forces applied to the fastener by the fastener
push rod are less than a predetermined value such that longitudinal
movement of the first portion of the fastener push rod causes
substantially equivalent longitudinal movement of the second
portion. The force limiting mechanism allowing relative
longitudinal motion between the first portion and the second
portion while the forces applied to the fastener are equal to or
greater than the predetermined value such that the application of
undue forces to the fastener is prevented. In some embodiments, the
fastener comprises a staple and each stake has a distal portion and
a proximal portion with each distal portion being dimensioned to
extend into a passage defined by the staple. Each proximal stake
portion has a width larger than a width of each distal portion so
that a shoulder of each proximal portion contacts a proximal
surface of the staple to apply pushing forces thereto.
[0012] In some exemplary embodiments, the force limiting mechanism
comprises a constant force spring. A first end of the constant
force spring may be coupled to the first portion of the fastener
push rod and a second end of the constant force spring may be
coupled to the second portion of the fastener push rod.
[0013] In some exemplary embodiments, the first portion of the
fastener push rod includes a first tubular member, the second
portion of the fastener push rod includes a second tubular member,
and a portion of one tubular member is slidingly received in a
lumen defined by the other tubular member such that the first
tubular member and the second tubular member can translate relative
to each other. For instance, the first portion of the fastener push
rod may include a first tubular member, the second portion of the
fastener push rod may include a second tubular member, and a
portion of the first tubular member may be slidingly received in a
lumen defined by the second tubular member such that the first
tubular member and the second tubular member can translate relative
to each other. In some exemplary embodiments, the second tubular
member defines a slot and the first tubular member carries a pin
that is slidingly received in the slot such that relative rotation
between the first tubular member and the second tubular member is
prevented. The force limiting mechanism may include a constant
force spring having a first end coupled to the first tubular member
and a second end coupled to the second tubular member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a simplified perspective view of the human rotator
cuff and associated anatomical structure;
[0015] FIG. 2 is a schematic depiction of a full thickness tear in
the supraspinatus tendon of the rotator cuff of FIG. 1;
[0016] FIG. 3 is a stylized anterior view of a patient with a
shoulder of patient being shown in cross-section for purposes of
illustration;
[0017] FIG. 4 is a stylized anterior view of a shoulder including a
humerus and a scapula. The head of the humerus is shown mating with
the glenoid fossa of the scapula at a glenohumeral joint and a
sheet-like material is fixed to the tendon;
[0018] FIG. 5 is a stylized perspective view illustrating an
exemplary procedure for treating a shoulder of a patient;
[0019] FIG. 6 is a stylized perspective view of a shoulder
including a supraspinatus having a distal tendon with a sheet-like
material fixed thereto. A proximal end of the supraspinatus is
fixed to the scapula and the distal tendon of the supraspinatus is
fixed to the humerus;
[0020] FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views
illustrating an exemplary staple in accordance with the present
detailed description;
[0021] FIG. 8 is a perspective view further illustrating the staple
shown in the previous Figure;
[0022] FIG. 9 is a perspective view showing a staple push rod that
may be used in conjunction with the staple shown in the previous
Figure;
[0023] FIG. 10A and FIG. 10B illustrate multiple plan views of an
exemplary fixation tool in accordance with the present detailed
description;
[0024] FIG. 11A is a further enlarged partial cross-sectional view
of a distal portion of the fixation tool shaft shown in the
previous Figure;
[0025] FIG. 11B is an additional partial cross-sectional view
showing a staple carried by a staple push rod and a fixation tool
shaft disposed about the staple push rod;
[0026] FIG. 12A through FIG. 12C are a sequence of plan views
illustrating an exemplary method and apparatus in accordance with
the present detailed description;
[0027] FIG. 13A, FIG. 13B, FIG. 13C and FIG. 13D are multiview
projections illustrating a fixation tool shaft shown in the
previous figures;
[0028] FIG. 14 is an enlarged axial view of the fixation tool shaft
shown in the previous Figure;
[0029] FIG. 15 is an additional enlarged axial view of the fixation
tool shaft shown in the previous Figure;
[0030] FIG. 16 is an exploded isometric view of an exemplary
fixation tool in accordance with the detailed description;
[0031] FIG. 17 is a perspective view showing an illustrative
fixation tool assembly with overlying shaft removed in accordance
with this detailed description;
[0032] FIG. 18A and FIG. 18B are plan views further illustrating
the operation of the fixation tool assembly shown in the previous
figure also with overlying shaft removed;
[0033] FIG. 19 is a perspective view showing an illustrative
fixation tool assembly in accordance with this detailed description
with overlying shaft removed; and;
[0034] FIG. 20A and FIG. 20B are plan views further illustrating
the operation of the fixation tool assembly shown in the previous
figure also with overlying shaft removed.
DETAILED DESCRIPTION
[0035] The following detailed description should be read with
reference to the drawings in which similar elements in different
drawings are numbered the same. The drawings, which are not
necessarily to scale, depict illustrative embodiments and are not
intended to limit the scope of the invention.
[0036] As used herein, the term "tissue" refers to soft tissue,
such as a tendon, and/or bone tissue, depending on the context in
which it is used.
[0037] FIG. 3 is a stylized anterior view of a patient 20. For
purposes of illustration, a shoulder 22 of patient 20 is shown in
cross-section in FIG. 3. Shoulder 22 includes a humerus 14 and a
scapula 12. In FIG. 3, a head 24 of humerus 14 can be seen mating
with a glenoid fossa of scapula 12 at a glenohumeral joint. With
reference to FIG. 3, it will be appreciated that the glenoid fossa
comprises a shallow depression in scapula 12. The movement
othumerus 14 relative to scapula 12 is controlled by a number of
muscles including: the deltoid, the supraspinatus, the
infraspinatus, the subscapularis, and the teres minor. For purposes
of illustration, only the supraspinatus 26 is shown in FIG. 3.
[0038] With reference to FIG. 3, it will be appreciated that a
distal tendon 28 of the supraspinatus 26 meets humerus 14 at an
insertion point. Scapula 12 of shoulder 22 includes an acromium 32.
In FIG. 3, a subacromial bursa 34 is shown extending between
acromium 32 of scapula 12 and head 24 of humerus 14. In FIG. 3,
subacromial bursa 34 is shown overlaying supraspinatus 26.
Subacromial bursa 34 is one of the hundreds ofbursae found the
human body. Each bursa comprises a fluid filled sac. The presence
of these bursae in the body reduces friction between bodily
tissues. Injury and/or infection of the bursa can cause it to
become inflamed. This condition is sometimes referred to as
bursitis.
[0039] The exemplary methods and apparatus described herein may be
used to fix tendon repair implants to various target tissues. For
example, a tendon repair implant may be fixed to one or more
tendons associated with an articulating joint, such as the
glenohumeral joint. The tendons to be treated may be tom, partially
tom, have internal micro-tears, be untom, and/or be thinned due to
age, injury or overuse. Applicants believe that the methods and
apparatus of the present application and related devices may
provide very beneficial therapeutic effect on a patient
experiencing joint pain believed to be caused by partial thickness
tears and/or internal microtears. By applying a tendon repair
implant early before a full tear or other injury develops, the
implant may cause the tendon to thicken and/or at least partially
repair itself, thereby avoiding more extensive joint damage, pain,
and the need for more extensive joint repair surgery.
[0040] FIG. 4 is a stylized anterior view of a shoulder 22
including a humerus 14 and a scapula 12. In FIG. 4, a head 24 of
humerus 14 is shown mating with a glenoid fossa of scapula 12 at a
glenohumeral joint. A supraspinatus 26 is also shown in FIG. 4.
This muscle (along with others) control the movement of humerus 14
relative to scapula 12. A distal tendon 28 of supraspinatus 26
meets humerus 14 at an insertion point 30.
[0041] In the embodiment of FIG. 4, distal tendon 28 includes a
first damaged portion 36. A number of loose tendon fibers 40 in
first damaged portion 36 are visible in FIG. 4. First damaged
portion 36 includes a first tear 42 extending partially through
distal tendon 28. First tear 42 may therefore be referred to as a
partial thickness tear. With reference to FIG. 4, it will be
appreciated that first tear 42 begins on the side of distal tendon
28 facing the subacromial bursa (shown in the previous Figure) and
ends midway through distal tendon 28. Accordingly, first tear 42
may be referred to as a bursal side tear.
[0042] With reference to FIG. 4, it will be appreciated that distal
tendon 28 includes a second damaged portion 38 located near
insertion point 30. In the embodiment of FIG. 4, second damaged
portion 38 of distal tendon 28 has become frayed and a number of
loose tendon fibers 40 are visible in FIG. 4. Second damaged
portion 38 of distal tendon 28 includes second tear 44. With
reference to FIG. 4, it will be appreciated that second tear 44
begins on the side of distal tendon 28 facing the humerus 14.
Accordingly, second damaged portion 38 may be referred to as an
articular side tear.
[0043] In the embodiment of FIG. 4, a sheet-like implant 50 has
been placed over the bursal side of distal tendon 28. With
reference to FIG. 4, it will be appreciated that sheet-like implant
50 extends over insertion point 30, first tear 42 and second tear
44. Some useful methods in accordance with this detailed
description may include placing a tendon repair implant on the
bursal side of a tendon regardless of whether the tears being
treated are on the bursal side, articular side or within the
tendon. In some cases the exact location and nature of the tears
being treated may be unknown. A tendon repair implant may be
applied to the bursal side of a tendon to treat shoulder pain that
is most likely caused by one or more partial thickness tears in the
tendon. In the embodiment of FIG. 4, sheet-like implant 50 is fixed
to distal tendon 28 and to humerus 14 by a plurality of staples 100
as described herein in detail.
[0044] FIG. 5 is a stylized perspective view illustrating an
exemplary procedure for treating a shoulder 22 of a patient 20. The
procedure illustrated in FIG. 5 may include, for example, fixing
tendon repair implants to one or more tendons of shoulder 22. The
tendons treated may be tom, partially tom, have internal
micro-tears, be untom, and/or be thinned due to age, injury or
overuse.
[0045] Shoulder 22 of FIG. 5 has been inflated to create a cavity
therein. In the exemplary embodiment of FIG. 5A, a fluid supply 52
is pumping a continuous flow of saline into the cavity. This flow
of saline exits the cavity via a fluid drain 54. A camera 56
provides images from inside the cavity. The images provided by
camera 56 may be viewed on a display 58.
[0046] Camera 56 may be used to visually inspect the tendons of
shoulder 22 for damage. A tendon repair implant in accordance with
this disclosure may be fixed to a bursal surface of the tendon
regardless of whether there are visible signs of tendon damage.
Applicants believe that the methods and apparatus of the present
application and related devices may provide very beneficial
therapeutic effect on a patient experiencing joint pain believed to
be caused by internal microtears, but having no clear signs of
tendon tears. By applying a tendon repair implant early before a
full tear or other injury develops, the implant may cause the
tendon to thicken and/or at least partially repair itself, thereby
avoiding more extensive joint damage, pain, and the need for more
extensive joint repair surgery.
[0047] A delivery system 60 can be seen extending from shoulder 22
in FIG. 5. Delivery system 60 comprises a sheath that is fixed to a
handle. The sheath defines a lumen and a distal opening fluidly
communicating with the lumen. In the embodiment of FIG. 5, the
distal opening of the sheath has been placed in fluid communication
with the cavity created in shoulder 22.
[0048] A tendon repair implant is at least partially disposed in
the lumen defined by the sheath of delivery system 60. Delivery
system 60 can be used to place the tendon repair implant inside
shoulder 22. Delivery system 60 can also be used to hold the tendon
repair implant against the tendon. In some embodiments, the tendon
repair implant is folded into a compact configuration when inside
the lumen of the sheath. When this is the case, delivery system 60
may be used to unfold the tendon repair implant into an expanded
shape.
[0049] The tendon repair implant may be fixed to the tendon while
it is held against the tendon by delivery system 60. Various
attachment elements may be used to fix the tendon repair implant to
the tendon. Examples of attachment elements that may be suitable in
some applications include sutures, tissue anchors, bone anchors,
and staples. In the exemplary embodiment of FIG. 5, the shaft of a
fixation tool 70 is shown extending into shoulder 22. In one
exemplary embodiment, fixation tool 70 is capable of fixing the
tendon repair implant to the tendon with one or more staples while
the tendon repair implant is held against the tendon by delivery
system 60.
[0050] FIG. 6 is a stylized perspective view of a shoulder 22
including a supraspinatus 26 having a distal tendon 28. With
reference to FIG. 6, it will be appreciated that a tendon repair
implant 50 has been fixed to a surface of distal tendon 28. Tendon
repair implant 50 may comprise, for example, various sheet-like
structures without deviating from the spirit and scope of the
present detailed description. In some useful embodiments, the
sheet-like structure may comprise a plurality of fibers. The fibers
may be interlinked with one another. When this is the case, the
sheet-like structure may comprise a plurality of apertures
comprising the interstitial spaces between fibers. Various
processes may be used to interlink the fibers with one another.
Examples of processes that may be suitable in some applications
including weaving, knitting, and braiding. In some embodiment, the
sheet-like structure may comprise a laminate including multiple
layers of film with each layer of film defining a plurality of
micro-machined or formed holes. The sheet-like structure can
comprise collagen material having a porous structure such as
reconstituted bovine collagen. The sheet-like structure of the
tendon repair implant may also comprise a plurality of electro-spun
nanofiber filaments forming a composite sheet. Additionally, the
sheet-like structure may comprise a synthetic sponge material that
defines a plurality of pores. The sheet-like structure may also
comprise a reticulated foam material. Reticulated foam materials
that may be suitable in some applications are available from
Biomerix Corporation of Freemont, Calif. which identifies these
materials using the trademark BIOMATERIAL.TM..
[0051] Various attachment elements may be used to fix tendon repair
implant 50 to distal tendon 28 without deviating from the spirit
and scope of this detailed description. Examples of attachment
elements that may be suitable in some applications include sutures,
tissue anchors, bone anchors, and staples. In the exemplary
embodiment of FIG. 6, a plurality of staples 100 are fixing tendon
repair implant 50 to distal tendon 28. In some exemplary methods, a
plurality of staples 100 may be applied using a fixation tool. The
fixation tool may then be withdrawn from the body of the patient.
Distal tendon 28 meets humerus 14 at an insertion point 30. With
reference to FIG. 6, it will be appreciated that sheet-like implant
50 extends over insertion point 30. Tendon repair implant may be
applied to distal tendon 28, for example, using the procedure
illustrated in the previous Figure.
[0052] FIG. 7A, FIG. 7B, and FIG. 7C are multiple plan views
illustrating an exemplary staple 100 in accordance with the present
detailed description. FIG. 7A, FIG. 7B, and FIG. 7C may be
collectively referred to as FIG. 7. It is customary to refer to
multi-view projections using terms such as front view, top view,
and side view. In accordance with this convention, FIG. 7A may be
referred to as a front view of staple 100, FIG. 7B may be referred
to as a side view of staple 100, and FIG. 7C may be referred to as
a bottom view of staple 100. The terms top view, side view, and
bottom view are used herein as a convenient method for
differentiating between the views shown in FIG. 7. It will be
appreciated that the staple shown in FIG. 7 may assume various
orientations without deviating from the spirit and scope of this
detailed description. Accordingly, the terms top view, side view,
and bottom view should not be interpreted to limit the scope of the
invention recited in the attached claims. A proximal direction is
illustrated with an arrow P in FIG. 7. A distal direction is
illustrated with a second arrow Din FIG. 7.
[0053] Staple 100 comprises a first arm 102A, a second arm 102B,
and a bridge 104 extending from the proximal end of first arm 102A
to the proximal end of second arm 102B. The distal end of first arm
102A abuts the proximal end of a first fluke 106A. Similarly, the
distal end of second arm 102B abuts the proximal end of a second
fluke 106B. In FIG. 7, first fluke 106A and second fluke 106B are
shown extending distally from first arm 102A and second arm 102B,
respectively. With reference to FIG. 7, it will be appreciated that
first fluke 106A has a lateral extent that is larger than a lateral
extent of first arm 102A. First fluke 106A is mounted eccentrically
to first arm 102A in the embodiment of FIG. 7. Second fluke 106B is
mounted eccentrically to second arm 102B and second fluke 106B has
a lateral extent that is larger than a lateral extent of second arm
102B. First fluke 106A includes a first proximal surface 108A
projecting at an outward angle in a proximal direction away from
the distal end of first arm 102A. Second fluke 106B includes a
second proximal surface 108B projecting at an outward angle in a
proximal direction away from the distal end of second arm 102B.
[0054] With reference to FIG. 7A, it will be appreciated that first
fluke 106A includes a first point 120A and a first barb 122A.
Second fluke 106B includes a second point 120B and a second barb
122B. The first barb 122A and second barb 122B each have a cleft
barb with two points and a valley there between. In FIG. 7, first
point 120A and second point 120B are shown generally pointing in
the distal direction indicated by arrow D. Also in FIG. 7, first
barb 122A and second barb 122B are shown generally pointing in the
proximal direction indicated by arrow P.
[0055] With reference to FIG. 7A it will be appreciated that first
fluke 106A defines a first passageway 124A and second fluke 106B
defines a second passageway 124B. In the exemplary embodiment of
FIG. 7, first passageway 124A extends through first fluke 106A and
second passageway 124B extends through second fluke 106B. It will
be appreciated, however, that first passageway 124A may extend
through other portions of staple 100 in some embodiments.
Similarly, second passageway 124B may extend through other portions
of staple 100 in some embodiments. With reference to FIG. 7B it
will be appreciated that, first passageway 124A and second
passageway 124B each have a generally rectangular or square
cross-sectional shape. It will be appreciated, however, that first
passageway 124A and second passageway 124B may have various
cross-sectional shapes without deviating from the spirit and scope
of the present detailed description. Further, each passageway can
extend partially through the length of each fluke rather than all
the way through to provide a cavity rather than a passageway.
[0056] With reference to FIG. 7C, it will be appreciated that first
barb 122A of first fluke 106A defines a first notch 126A. In the
exemplary embodiment of FIG. 7, first notch 126A divides first barb
122A into a first sub-barb and a second sub-barb. Second barb 122B
of second fluke 106B defines a second notch 126B. In the exemplary
embodiment of FIG. 7, second notch 126B divides second barb 122B
into a first sub-barb and a second sub-barb. The barbs are thus
clefted to form two points for greater retention in tissue.
[0057] FIG. 8 is a perspective view showing staple 100 depicted in
the previous Figure. Staple 100 comprises a first arm 102A, a
second arm 102B, and a bridge 104 extending from the proximal end
of first arm 102A to the proximal end of second arm 102B. The
distal end of first arm 102A abuts the proximal end of a first
fluke 106A.
[0058] With reference to FIG. 8 it will be appreciated that first
fluke 106A defines a first passageway 124A. In the exemplary
embodiment of FIG. 8, first passageway 124A has a generally
rectangular or square cross-sectional shape. It will be
appreciated, however, that first passageway 124A may have various
cross-sectional shapes without deviating from the spirit and scope
of the present detailed description.
[0059] A second fluke 106B extends distally from second arm 102B
with the proximal end of second fluke 106B abutting the distal end
of second arm 102B. With reference to FIG. 8, it will be
appreciated that second fluke 106B has a lateral extent that is
larger than a lateral extent of second arm 102B. Second fluke 106B
is mounted eccentrically to second arm 102B in the embodiment of
FIG. 8. Similarly, first fluke 106A is mounted eccentrically to
first arm 102A and first fluke 106A has a lateral extent that is
larger than a lateral extent of first arm 102A.
[0060] A proximal direction is illustrated with an arrow P in FIG.
8. A distal direction is illustrated with a second arrow D in FIG.
8. With reference to FIG. 8A, it will be appreciated that first
fluke 106A of first arm 102A includes a first point 120A and a
first barb 122A. Second fluke 106B includes a second point 120B and
a second barb 122B. In FIG. 8, first point 120A and second point
120B are shown generally pointing in the distal direction indicated
by arrow D. Also in FIG. 8, first barb 122A and second barb 122B
are shown generally pointing in the proximal direction indicated by
arrow P. With reference to FIG. 8, it will be appreciated that
first fluke 106A includes a first proximal surface 108A projecting
at an outward angle in a proximal direction away from the distal
end of first arm 102A. Second fluke 106B includes a second proximal
surface 108B projecting at an outward angle in a proximal direction
away from the distal end of second arm 102B.
[0061] FIG. 9 is a perspective view showing a staple push rod 130
that may be used in conjunction with staple 100 shown in the
previous Figure. Staple push rod 130 includes a shaft 132 and a
pair of stakes 134 extending distally beyond a distal end of shaft
132. The distal direction is indicated with an arrow Din FIG. 9.
Stakes 134 include a first stake 134A and a second stake 134B.
First stake 134A and second stake 134B form a fork 136.
[0062] In the embodiment of FIG. 9, each stake 134 has a distal
portion 138 and a proximal portion 140. In some useful embodiments,
each distal portion 138 is dimensioned to extend into a passage
defined by a staple. In the embodiment of FIG. 9, each proximal
portion 140 has a width larger than a width of each distal portion
138 so that a shoulder of each proximal portion 140 contacts a
proximal surface of the staple to apply pushing forces thereto.
First stake 134A comprises a first shoulder 142A and second stake
134B comprises a second shoulder 142B. Although depicted as a
shoulder to provide pushing force to the staple, other designs can
be utilized. For example, any larger cross section proximal portion
can provide a pushing force, such as a conical increase in profile.
In the embodiment of FIG. 9, proximal portion 140 of first stake
134A and the proximal portion 140 of second stake 134B diverge from
one another as they extend in distal direction D away from shaft
132. In some applications, this arrangement may cause pushing
forces applied to two flukes of a staple to have a laterally
outward component.
[0063] In FIG. 9, first stake 134A and second stake 134B are shown
assuming a substantially unstressed state. It will be appreciated
that first stake 134A and second stake 134B can be resiliently
urged to assume shapes other than the shape shown in FIG. 9. For
example, first stake 134A and second stake 134B may be urged
together so that fork 136 can be inserted into a lumen having a
diameter smaller than the distance between the distal points of
first stake 134A and second stake 134B shown in FIG. 9.
[0064] FIG. 10A and FIG. 10B illustrate multiple plan views of an
exemplary fixation tool 144 in accordance with the present detailed
description. Fixation tool 144 incorporates staple push rod 130 and
is useful in delivering staple 100. FIG. 10A and FIG. 10B may be
referred to collectively as FIG. 10. It is customary to refer to
multi-view projections using terms such as front view, top view,
and side view. In accordance with this convention, FIG. 10 A may be
referred to as a top view of fixation tool 144 and FIG. 10B may be
referred to as a side view of fixation tool 144. The terms top view
and side view are used herein as a convenient method for
differentiating between the views shown in FIG. 10. It will be
appreciated that the elements shown in FIG. 10 may assume various
orientations without deviating from the spirit and scope of this
detailed description. Accordingly, the terms top view and side view
should not be interpreted to limit the scope of the invention
recited in the attached claims.
[0065] In the embodiment of FIG. 10, fixation tool 144 comprises a
fixation tool shaft 146 that is attached to a handle 148. Fixation
tool shaft 146 comprises a wall 150 defining a lumen 152. With
reference to FIG. 10, it will be appreciated that fixation tool
shaft 146 includes a first prong 154A and a second prong 154B that
extend distally beyond a distal end 158 of lumen 152.
[0066] In FIG. 10, a staple 100 can be seen residing in lumen 152
of fixation tool shaft 146. For purposes of illustration, a distal
portion of fixation tool shaft 146 is enlarged in FIG. 10 to better
show staple 100. Staple 100 comprises a first arm 102A, a second
arm 102B, and a bridge 104 extending from the proximal end of first
arm 102A to the proximal end of second arm 102B. The distal end of
first arm 102A abuts the proximal end of a first fluke 106A.
Similarly, the distal end of second arm 102B abuts the proximal end
of a second fluke 106B. In FIG. 10, first fluke 106A and second
fluke 106B are shown extending distally from first arm 102A and
second arm 102B, respectively.
[0067] Staple push rod 130 includes a shaft 132 and a pair of
stakes 134 extending distally beyond a distal end of shaft 132. The
distal direction is indicated with an arrow D in FIG. 10. Stakes
134 include a first stake 134A and a second stake 134B. In FIG. 10,
a distal portion of each stake 134 extends into a passageway
defined by staple 100. In the embodiment of FIG. 10, a trigger 160
is pivotably coupled to handle 148 of fixation tool 144. Trigger
160 is operatively coupled to or in contact with staple push rod
130. In operation, staple push rod 130 will be advanced and/or
retracted in an axial direction when trigger 160 is pivoted
relative to handle 148.
[0068] FIG. 11A is a further enlarged top view of a distal portion
of fixation tool shaft 146 shown in the previous Figure. For
purposes of illustration, fixation tool shaft 146 is shown in
partial cross-section in FIG. 11A so that staple 100 is visible
residing in lumen 152. With reference to FIG. 11A, it will be
appreciated that staple 100 is disposed on a distal portion of
staple push rod 130. Staple 100 comprises a first arm 102A, a
second arm 102B, and a bridge 104 extending from the proximal end
of first arm 102A to the proximal end of second arm 102B. The
distal end of first arm 102A abuts the proximal end of a first
fluke 106A. Similarly, the distal end of second arm 102B abuts the
proximal end of a second fluke 106B. In FIG. 11, first fluke 106A
and second fluke 106B are shown extending distally from first arm
102A and second arm 102B, respectively.
[0069] First fluke 106A and second fluke 106B define a first
passageway 124A and a second passageway 124B, respectively. In FIG.
11A, distal portion 138 of first stake 134A of staple push rod 130
extends into first passageway 124A defined by first fluke 106A. A
distal portion 138 of second stake 134B of staple push rod 130
extends into a second passageway 124B defined by second fluke 106B
of staple 100. In FIG. 11A, a first shoulder 142A of first stake
134A is shown contacting proximal surface 108 of first fluke 106A.
A second shoulder 142B of second stake 134B is shown contacting
proximal surface 108 of second fluke 106 in FIG. 11A. The distal
portion 138 of first stake 134A extends distally of first shoulder
142A and proximal portion 140 of first stake 134A extends
proximally of first shoulder 142A. The distal portion 138 of second
stake 134B extends distally of second shoulder 142B and a proximal
portion 140 of second stake 134B extends proximally of second
shoulder 142B.
[0070] With reference to FIG. 11A, it will be appreciated that
there is a gap G between staple push rod 130 and bridge 104 of
staple 100. In some applications, gap G allows staple 100 to be
placed in tension without bridge 104 contacting staple push rod
130. Staple 100 may be placed in tension, for example, as staple
100 is advanced into a target tissue.
[0071] FIG. 11B is an additional top view showing a distal portion
of fixation tool shaft 146, staple push rod 130, and staple 100. By
comparing FIG. 11A and FIG. 11B, it will be appreciated that staple
push rod 130 and staple 100 have been advanced in a distal
direction D relative to fixation tool shaft 146. In FIG. 11B,
staple 100 is shown extending out of lumen 152 defined by fixation
tool shaft 146.
[0072] In FIG. 11B, a distal portion 138 of first stake 134A of
staple push rod 130 extends into a first passageway 124A defined by
first fluke 106A of staple 100. In FIG. 11B, a first shoulder 142A
of first stake 134A is shown contacting proximal surface 108 of
first fluke 106A. Distal portion 138 of first stake 134A extends
distally of first shoulder 142A and proximal portion 140 of first
stake 134A extends proximally of first shoulder 142A. In some
useful embodiments, the proximal portion of first stake 134A has a
first width and the distal portion of first stake 134A has a second
width different from the first width. In some particularly useful
embodiments, the first width is greater than the first width. The
arrangement allows the proximal portion of stake to engage a
proximal surface of the staple to apply pushing forces to the
staple.
[0073] In FIG. 11B, a distal portion 138 of second stake 134B of
staple push rod 130 extends into a second passageway 124B defined
by second fluke 106B of staple 100. In FIG. 11B, a second shoulder
142B of second stake 134B is shown contacting proximal surface 108
of second fluke 106B. In the embodiment of FIG. 11B, proximal
portion 140 of second stake 134B may apply pushing force to
proximal surface 108 of second stake 134B. Proximal portion 140 of
second stake 134B extends proximally of second shoulder 142B and
distal portion 138 of second stake 134B extends distally of second
shoulder 142B. In the embodiment of FIG. 11B, proximal portion 140
of second stake 134B has a width larger than the width of distal
portion 138 of second stake 134B so that the shoulder 142 of second
stake 134B contacts proximal surface 108 of second fluke 106B to
apply pushing forces thereto.
[0074] In the embodiment of FIG. 11B, first stake 134A and second
stake 134B are in a substantially unstressed state. It will be
appreciated that first stake 134A and second stake 134B can be
resiliently urged to assume shapes other than the shape shown in
FIG. 11. For example, first stake 134A and second stake 134B may be
urged together so that fork 136 of staple push rod 130 and staple
100 can be inserted into lumen 152 defined by fixation tool shaft
146.
[0075] With reference to FIG. 11B, it will be appreciated that
there is a gap G between staple push rod 130 and bridge 104 of
staple 100. In some applications, gap G allows staple 100 to be
placed in tension without bridge 104 contacting staple push rod
130. In some applications, placing staple 100 under tension may
urge first fluke 106 and second fluke 106 into orientations which
lock staple 100 into a target tissue. For example, first fluke 106A
and second fluke 106B may be rotated so that a barb of each fluke
engages the target tissue. When this is the case, the tension on
the staple may keep first fluke 106A and second fluke 106B in the
rotated position. Also when this is the case, the barbs of the
rotated flukes may inhibit staple pullout.
[0076] FIG. 12A through FIG. 12C are a sequence of plan views
illustrating an exemplary method in accordance with the present
detailed description. FIG. 12A, FIG. 12B, and FIG. 12C may be
collectively referred to as FIG. 12. The exemplary method
illustrated in FIG. 12 may be used, for example, to fix a tendon
repair implant 50 to a target tissue T using a staple 100.
[0077] At FIG. 12A, a fixation tool 144 has been used to form a
first pilot hole 162A and a second pilot hole 162B in target tissue
T. In the embodiment of FIG. 12, fixation tool 144 includes a
fixation tool shaft 146 comprising a wall 150 defining a lumen 152.
With reference to FIG. 12, it will be appreciated that fixation
tool shaft 146 includes a first prong 154A and a second prong 154B
that extend distally beyond a distal end 158 of lumen 152. In the
embodiment of FIG. 12A, first prong 154A and second prong 154B have
been urged into tissue T to form first pilot hole 162A and second
pilot hole 162B. In FIG. 12A a distally directed force F applied to
fixation tool shaft 146 is illustrated using an arrow. Force F may
be produced, for example, by pushing on a handle that is fixed to a
proximal portion of fixation tool shaft 146. It will be appreciated
that in some embodiments, such as the embodiment depicted in FIG.
6, one of the first and second pilot holes may be formed through
the sheet-like implant and the target tissue, and the other pilot
hole may be formed directly in the target tissue without passing
through the sheet-like implant. In other words, in various
embodiments staples may straddle the perimeter edge of the
sheet-like implant (as shown in FIG. 6), may be applied adjacent to
the perimeter, and/or be applied to a central region of the
implant. In some embodiments, the staples may be used to attach the
implant to soft tissue and/or to bone. In FIG. 12A, a staple 100
can be seen residing in lumen 152 of fixation tool shaft 146. For
purposes of illustration, fixation tool shaft 146 is shown in
partial cross-section in FIG. 12A so that staple 100 is visible
residing in lumen 152.
[0078] With reference to FIG. 12, it will be appreciated that
staple 100 is carried by a fork 136 comprising a first stake 134A
and a second stake 134B. In FIG. 12A, a distal portion of first
stake 134A of staple push rod 130 extends into a first passageway
defined by first fluke 106A. A distal portion of second stake 134B
of staple push rod 130 extends into a second passageway defined by
second fluke 106B of staple 100.
[0079] In some useful embodiments, each stake is positioned
relative to a prong along an inner surface of fixation tool shaft
146 so that the stakes advance into the pilot holes when the stakes
are moved in a distal direction. Staple push rod 130 is slidably
disposed within lumen 152 defined by fixation tool shaft 146.
Fixation tool 144 includes a mechanism that is capable of creating
relative axial motion between staple push rod 130 and fixation tool
shaft 146 so that staple push rod 130 slides along fixation tool
shaft 146.
[0080] At FIG. 12B, relative motion has been created between staple
push rod 130 and fixation tool shaft 146 while distally directed
force F has been continuously applied to fixation tool shaft 146.
By comparing FIG. 12B and FIG. 12A, it will be appreciated that
first stake 134A and second stake 134B have been advanced in a
distal direction D. With reference to FIG. 12, it will also be
appreciated that first stake 134A and second stake 134B have
advanced into first pilot hole 162A and second pilot hole 162B,
respectively. In FIG. 12B, first fluke 106A is shown residing in
first pilot hole 162. Second fluke 106B is residing in second pilot
hole 162 in the embodiment of FIG. 12B.
[0081] At FIG. 12C, additional relative motion has been created
between staple push rod 130 and fixation tool shaft 146 while
distally directed force F has been continuously applied to fixation
tool shaft 146. By comparing FIG. 12C and FIG. 12B, it will be
appreciated that the relative motion between staple push rod 130
and fixation tool shaft 146 has moved fixation tool shaft 146 in a
proximal direction P.
[0082] By comparing FIG. 12C and FIG. 12B, it will also be
appreciated that first arm 102A of staple 100 has been bent and
first fluke 106A has been rotated to a toggled position. Inthe
exemplary embodiment of FIG. 12C, force applied to first fluke 106A
by first shoulder 142A has caused first fluke 106A to rotate. With
continuing reference to FIG. 12C and FIG. 12B, it will be
appreciated that second arm 102B of staple 100 has been bent and
second fluke 106A has been rotated to a toggled position. Inthe
exemplary embodiment of FIG. 12C, force applied to second fluke
106b by second shoulder 142B has caused second fluke 106B to
rotate.
[0083] With reference to FIG. 12C, it will be appreciated that a
first through hole 164A and a second through hole 164B have been
formed in tendon repair implant 50. In the embodiment of FIG. 12,
first through hole 164A and a second through hole 164B were created
by urging first prong 154A and second prong 154B of fixation tool
shaft 146 through tendon repair implant 50.
[0084] FIG. 13A, FIG. 13B, and FIG. 13C are multiview projections
illustrating a fixation tool shaft 146 shown in the previous
Figures. FIG. 13D is a cross-sectional view of fixation tool shaft
146 sectioned along cutting plane D-D illustrated in FIG. 13C.
These Figures may be collectively referred to as FIG. 13. Fixation
tool shaft 146 of FIG. 13 comprises a wall 150 defining a lumen
152. A first prong 154A and a second prong 154B of fixation tool
shaft 146 extend distally beyond a distal end 158 of lumen 152.
[0085] With reference to FIG. 13, it will be appreciated that
fixation tool shaft 146 comprises a proximal portion 170, a distal
portion 168 and an intermediate portion 166 disposed between
proximal portion 170 and distal portion 168. In the embodiment of
FIG. 13, distal portion 168 has an axial extent DA, a major lateral
extent LA and a minor lateral extent LB. With reference to FIG. 13,
it will be appreciated that axial extent DA is greater than both
minor lateral extent LB and major lateral extent LA.
[0086] FIG. 14 is an enlarged axial view of fixation tool shaft 146
shown in the previous Figure. With reference to FIG. 14, it will be
appreciated that proximal portion 170 of fixation tool shaft 146
comprises a wall 150 having an outer surface 172. In FIG. 14, outer
surface 172 is illustrated using a circle. Thus, it will be
appreciated that proximal portion 170 of fixation tool shaft 146
has a generally cylindrical outer shape in the exemplary embodiment
of FIG. 14. In the exemplary embodiment of FIG. 14, fixation tool
shaft 146 has a generally uniform wall thickness. Accordingly, the
shape of proximal portion 170 may be generally described as a
cylindrical tube. The shape of distal portion 168 may be described
as a cylindrical-tube that has been partially flattened. In the
exemplary embodiment of FIG. 14, distal portion 168 of fixation
tool shaft 146 has a major lateral extent LA and a minor lateral
extent LB. With reference to FIG. 14, it will be appreciated that
major lateral extent LA is greater than minor lateral extent
LB.
[0087] FIG. 15 is an additional enlarged axial view of fixation
tool shaft 146. With reference to FIG. 15, it will be appreciated
that distal portion 168 of fixation tool shaft 146 comprises a
first major side SA, a second major side SB, a first minor side SC,
and a second minor side SD. In the exemplary embodiment of FIG. 15,
each minor side has a first central radius RA and each major side
has a second central radius RB. With reference to FIG. 15, it will
be appreciated that second central radius RB is greater than first
central radius RA. In the exemplary embodiment of FIG. 15, first
major side SA, second major side SB, first minor side SC, and
second minor side SD each have a generally convex shape. In the
exemplary embodiment of FIG. 15, each minor side is generally more
convex than each major side.
[0088] FIG. 16 is an exploded isometric view showing an exemplary
fixation tool 144 in accordance with this detailed description. In
the embodiment of FIG. 16, fixation tool 144 comprises a fixation
tool shaft 146 and a handle 144. In FIG. 16, handle 148 is exploded
into two pieces. A proximal portion of fixation tool shaft 146 is
fixed to handle 148 when fixation tool 144 is in an assembled
state. Fixation tool 144 also comprises a staple push rod 130. A
distal portion of staple push rod 130 extends into a lumen 152 of
fixation tool shaft 146 when fixation tool 144 is in the assembled
state.
[0089] Fixation tool shaft 146 comprises a wall 150 defining a
lumen 152. With reference to FIG. 16, it will be appreciated that
fixation tool shaft 146 includes a first prong 154A and a second
prong 154B that extend distally beyond a distal end 158 of lumen
152. In some useful embodiments, first prong 154A and second prong
154B form pilot holes in a target tissue when the distal portion of
fixation tool shaft 146 is pressed against the target tissue.
[0090] A staple 100 of fixation tool 144 is carried by a fork 136
in the embodiment of FIG. 16, as with prior embodiments. A fluke of
staple 100 may be advanced into each pilot hole formed by the
prongs of fixation tool shaft 146. Fork 136 of fixation tool 144
comprises a first stake 134A and a second stake 134B. First stake
134A and second stake 134B are fixed to a distal end of a staple
push rod 130 in the embodiment of FIG. 16.
[0091] Staple push rod 130 includes a first tubular member 182, a
second tubular member 184 and a force limiting mechanism 186
operably coupled between first tubular member 182 and second
tubular member 184. The proximal end of first tubular member 182 is
coupled to a lever 174. Lever 174 is coupled to a trigger 160.
Trigger 160 is pivotably supported by handle 148 of fixation tool
144 when fixation tool 144 is in an assembled state. Trigger 160
and lever 174 form part of an actuator assembly 176 that is capable
of creating longitudinal movement of first tubular member 182 of
staple push rod 130 relative to fixation tool shaft 146. In
operation, first tubular member 182 of staple push rod 130 will be
advanced and/or retracted in an axial direction when trigger 160 is
pivoted relative to handle 148. In some cases, the motion produced
by actuator assembly 176 is transferred to staple 100 carried by
fork 136.
[0092] Actuator assembly 176 may be used to control the motion of
first tubular member 182. In the embodiment of FIG. 16, force
limiting mechanism 186 will transmit longitudinal movement between
first tubular member 182 and second tubular member 184 as long as
the forces applied to staple 100 by staple push rod 130 are less
than a predetermined value. If the forces applied to staple 100 are
equal to or greater than the predetermined value, then force
limiting mechanism 186 will allow relative longitudinal motion
between first tubular member 182 and second tubular member 184. In
some useful embodiments, this function of force limiting mechanism
186 prevents the application of undue forces to staple 100. Once
the force applied to staple 100 reaches a pre-selected threshold,
further rotation of trigger 160 will result in relative motion
between first tubular member 182 and second tubular member 184 and
will not result in the application of additional force to staple
100. Force limiting mechanism 186 is represented by a block in FIG.
16 and may comprise various force limiting arrangements without
deviating from the spirit and scope of this detailed
description.
[0093] FIG. 17 is a perspective view showing an illustrative
fixation tool assembly 181 in accordance with this detailed
description. In the embodiment of FIG. 17, fixation tool assembly
181 comprises a staple push rod 130 and a fixation tool shaft 146.
A distal portion of staple push rod 130 extends into a lumen 152
defined by fixation tool shaft 146 when fixation tool assembly 181
is in an assembled state. Staple push rod 130 includes a first
tubular member 182, a second tubular member 184 and a force
limiting mechanism 186 operably coupled between first tubular
member 182 and second tubular member 184.
[0094] In the exemplary embodiment of FIG. 17, a distal portion of
first tubular member 182 is slidingly received in a lumen defined
by second tubular member 184 such that first tubular member 182 and
second tubular member 184 can translate relative to each other.
Second tubular member 184 defines a slot 194. First tubular member
182 carries a pin 196 that is slidingly received in slot 194 such
that relative rotation between first tubular member 182 and second
tubular member 184 is prevented.
[0095] An actuator assembly 176 is coupled to the proximal end of
first tubular member 182. Actuator assembly 176 is capable of
creating longitudinal movement of first tubular member 182 of
staple push rod 130 relative to fixation tool shaft 146. In the
embodiment of FIG. 17, actuator assembly 176 comprises a lever 174
and a trigger 160. Lever 174 is pivotably coupled to a proximal end
of first tubular member 182. Trigger 160 engages lever 174 such
that rotation of trigger 160 causes rotation of lever 174.
[0096] In operation, first tubular member 182 of staple push rod
130 will be advanced and/or retracted in a longitudinal direction
when trigger 160 and lever 174 are rotated. Under certain
circumstances, the longitudinal motion of first tubular member 182
is transferred to second tubular member 184 by force limiting
mechanism 186. When certain conditions are met, however, force
limiting mechanism 186 does not transfer the longitudinal motion of
first tubular member 182 to second tubular member 184.
[0097] A staple 100 is disposed at a distal end of second tubular
member 184. In the embodiment of FIG. 17, force limiting mechanism
186 will transmit the longitudinal movement of first tubular member
182 to second tubular member 184 as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value. Accordingly, longitudinal movement of first tubular member
182 of staple push rod 130 will cause substantially equivalent
longitudinal movement of second tubular member 184 as long as the
forces applied to staple 100 by staple push rod 130 are less than
the predetermined value. If the forces applied to staple 100 are
equal to or greater than the predetermined value, then force
limiting mechanism 186 will allow relative longitudinal motion
between first tubular member 182 and second tubular member 184. In
some useful embodiments, this function of force limiting mechanism
186 prevents the application of undue forces to staple 100. Once
the maximum desired force is applied to staple 100, further
rotation of trigger 160 will result in relative motion between
first tubular member 182 and second tubular member 184 and will not
result in the application of additional force to staple 100.
[0098] In the embodiment of FIG. 17, force limiting mechanism 186
comprises a spring 188. A first end of spring 188 is pivotably
coupled to first tubular member 182 at a first joint 190A. A second
end of spring 188 is pivotably coupled to second tubular 184 member
at a second joint 190B. In some particularly useful embodiments,
spring 188 comprises a constant force spring. Spring 188 may
comprise various constant force springs without deviating form the
spirit and scope of the present invention. One constant force
spring that may be suitable in some applications is disclosed in
U.S. Pat. No. 2,630,316. With reference to FIG. 17 it will be
appreciated that spring 188 comprises a plurality of wire turns
arranged to extend along a longitudinal axis 198. With reference of
to FIG. 17, it will be appreciated that the wire turns of spring
188 are arranged so that spring 188 extends along a straight
longitudinal axis in the illustrated embodiment. Spring 188 will
maintain the straight shape shown in FIG. 17 as long as the forces
applied to staple 100 by staple push rod 130 are less than a
predetermined value. In operation, spring 188 will transmit the
longitudinal movement of first tubular member 182 to second tubular
member 184 as long as the forces applied to staple 100 by staple
push rod 130 are less than the predetermined value. If the forces
applied to staple 100 are equal to or greater than the
predetermined value, then spring 188 will bend such that the wire
turns of spring 188 extend along a curvilinear longitudinal axis.
When spring 188 bends, spring 188 allows relative longitudinal
motion between first tubular member 182 and second tubular member
184.
[0099] With reference to FIG. 17, it will be appreciated that
staple 100 is carried by a pair of stakes 134 that extend distally
beyond a distal end of second tubular member 184. The distal
direction is indicated with an arrow D in FIG. 17. Stakes 134
include a first stake 134A and a second stake 134B. In FIG. 17, a
distal portion of each stake 134 extends into a passageway defined
by staple 100. Staple 100 comprises a first arm, a second arm, and
a bridge 104 extending from the proximal end of the first arm to
the proximal end of the second arm. The distal end of the first arm
abuts the proximal end of a first fluke 106A of staple 100.
Similarly, the distal end of the second arm abuts the proximal end
of a second fluke 106B.
[0100] In the embodiment of FIG. 17, a distal portion of first
stake 134A extends into a first passageway defined by first fluke
106A. Similarly, a distal portion of second stake 134B extends into
a second passageway defined by second fluke 106B of staple 100. A
first shoulder of first stake 134A contacts a proximal surface of
first fluke 106A in the embodiment of FIG. 17. A second shoulder of
second stake 134B contacts a proximal surface of second fluke
106B.
[0101] Fixation tool shaft 146 of FIG. 17 comprises a wall 150
defining a lumen 152. With reference to FIG. 17, it will be
appreciated that fixation tool shaft 146 includes a first prong
154A and a second prong 154B that extend distally beyond a distal
end 158 of lumen 152. In some useful embodiments, first prong 154A
and second prong 154B form pilot holes in a target tissue when the
distal portion of fixation tool shaft 146 is pressed against the
target tissue. A fluke of staple 100 may be advanced into each
pilot hole formed by the prongs of fixation tool shaft 146.
[0102] FIG. 18A and FIG. 18B are plan views further illustrating
the operation of fixation tool assembly 181 shown in the previous
figure. FIG. 18A and FIG. 18B may be collectively referred to as
FIG. 18. Fixation tool assembly 181 comprises a staple push rod 130
including a first tubular member 182, a second tubular member 184
and a force limiting mechanism 186 operably coupled between first
tubular member 182 and second tubular member 184. In the exemplary
embodiment of FIG. 18, a distal portion of first tubular member 182
is slidingly received in a lumen defined by second tubular member
184 such that first tubular member 182 and second tubular member
184 can translate relative to each other.
[0103] An actuator assembly 176 including a lever 174 is coupled to
the proximal end of first tubular member 182. Actuator assembly 176
is capable of creating longitudinal movement of first tubular
member 182 of staple push rod 130. In operation, first tubular
member 182 of staple push rod 130 will be advanced and/or retracted
in a longitudinal direction when lever 174 of actuator assembly 176
is rotated. Under certain circumstances, the longitudinal motion of
first tubular member 182 is transferred to second tubular member
184 by force limiting mechanism 186. When certain conditions are
met, however, force limiting mechanism 186 does not transfer the
longitudinal motion of first tubular member 182 to second tubular
member 184.
[0104] A staple 100 is disposed at a distal end of second tubular
member 184. In the embodiment of FIG. 18, force limiting mechanism
186 will transmit the longitudinal movement of first tubular member
182 to second tubular member 184 as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value. Accordingly, longitudinal movement of first tubular member
182 of staple push rod 130 will cause substantially equivalent
longitudinal movement of second tubular member 184 as long as the
forces applied to staple 100 by staple push rod 130 are less than
the predetermined value. If the forces applied to staple 100 are
equal to or greater than the predetermined value, then force
limiting mechanism 186 will allow relative longitudinal motion
between first tubular member 182 and second tubular member 184. In
some useful embodiments, this function of force limiting mechanism
186 prevents the application of undue forces to staple 100. Once
the maximum desired force is applied to staple 100, further
rotation of lever 174 will result in relative motion between first
tubular member 182 and second tubular member 184 and will not
result in the application of additional force to staple 100.
[0105] In the embodiment of FIG. 18, force limiting mechanism 186
comprises a spring 188. A first end of spring 188 is pivotably
coupled to first tubular member 182 at a first joint 190A. A second
end of spring 188 is pivotably coupled to second tubular 184 member
at a second joint 190B. In some particularly useful embodiments,
spring 188 comprises a constant force spring. Spring 188 may
comprise various constant force springs without deviating form the
spirit and scope of the present invention. One constant force
spring that may be suitable in some applications is disclosed in
U.S. Pat. No. 2,630,316. With reference to FIG. 18 is will be
appreciated that spring 188 comprises a plurality of wire turns
arranged to extend along a longitudinal axis 198.
[0106] In the embodiment of FIG. 18A, the wire turns of spring 188
are arranged so that spring 188 extends along a straight
longitudinal axis. Spring 188 will maintain the straight shape
shown in FIG. 18A as long as the forces applied to staple 100 by
staple push rod 130 are less than a predetermined value. In
operation, spring 188 will transmit the longitudinal movement of
first tubular member 182 to second tubular member 184 as long as
the forces applied to staple 100 by staple push rod 130 are less
than a predetermined value.
[0107] In the embodiment of FIG. 18B, spring 188 is bent so that
the wire turns of spring 188 are arranged with spring 188 extending
along a curvilinear longitudinal axis. If the forces applied to
staple 100 are equal to or greater than the predetermined value,
then spring 188 will bend such that the wire turns of spring 188
extend along a curvilinear longitudinal axis. The resistance to
additional bending offered by spring 300 remains substantially
constant as spring 300 is bent from the shape shown in FIG. 18A to
the shape shown in FIG. 18B. When spring 188 bends, spring 188
allows relative longitudinal motion between first tubular member
182 and second tubular member 184. Dimension lines are used to
illustrate an overall length LA and an overall length LB in FIG.
18A and FIG. 18B, respectively. With reference to FIG. 18, it will
be appreciated that overall length LB is shorter than overall
length LA. In the embodiment of FIG. 18, the difference between
overall length LB and overall length LA is due to relative
longitudinal motion between first tubular member 182 and second
tubular member 184.
[0108] FIG. 19 is a perspective view showing an illustrative
fixation tool assembly 180 in accordance with this detailed
description. In the embodiment of FIG. 19, fixation tool assembly
180 comprises a staple push rod 130 and a fixation tool shaft 146.
A distal portion of staple push rod 130 extends into a lumen 152
defined by fixation tool shaft 146 when fixation tool assembly is
in an assembled state. Staple push rod 130 includes a first tubular
member 182, a second tubular member 184 and a force limiting
mechanism 186 operably coupled between first tubular member 182 and
second tubular member 184. A staple 100 is disposed at the distal
end of second tubular member 184 and a lever 174 is connected to
the proximal end of first tubular member 182.
[0109] Staple 100 is carried by a fork 136 that extends distally
beyond the distal end of second tubular member 184. The distal
direction is indicated with an arrow D in FIG. 19. Fork 136
includes a first stake 134A and a second stake 134B. In FIG. 19, a
distal portion of each stake extends into a passageway defined by
staple 100. Staple 100 comprises a first arm, a second arm, and a
bridge 104 extending from the proximal end of the first arm to the
proximal end of the second arm. The distal end of the first arm
abuts the proximal end of a first fluke 106A of staple 100.
Similarly, the distal end of the second arm abuts the proximal end
of a second fluke 106B.
[0110] In the embodiment of FIG. 19, a distal portion of first
stake 134A extends into a first passageway defined by first fluke
106A. Similarly, a distal portion of second stake 134B extends into
a second passageway defined by second fluke 106B of staple 100. A
first shoulder of first stake 134A contacts a proximal surface of
first fluke 106A in the embodiment of FIG. 19. A second shoulder of
second stake 134B contacts a proximal surface of second fluke
106B.
[0111] Fixation tool shaft 146 of FIG. 19 comprises a wall 150
defining a lumen 152. With reference to FIG. 19, it will be
appreciated that fixation tool shaft 146 includes a first prong
154A and a second prong 154B that extend distally beyond a distal
end 158 of lumen 152. In some useful embodiments, first prong 154A
and second prong 154B form pilot holes in a target tissue when the
distal portion of fixation tool shaft 146 is pressed against the
target tissue. A fluke of staple 100 may be advanced into each
pilot hole formed by the prongs of fixation tool shaft 146.
[0112] An actuator assembly 176 is operably coupled to first
tubular member 182 of staple push rod 130. Actuator assembly 176 is
capable of moving first tubular member 182 in a longitudinal
direction relative to fixation tool shaft 146. In the embodiment of
FIG. 19, actuator assembly 176 comprises a lever 174 and a trigger
160. With reference to FIG. 19, it will be appreciated that lever
174 is pivotably coupled to the proximal end of first tubular
member 182. Trigger 160 engages lever 174 in such a way that
rotation of trigger 160 causes rotation of lever 174. In operation,
first tubular member 182 of staple push rod 130 will be advanced
and/or retracted in a longitudinal direction when trigger 160 and
lever 174 are rotated.
[0113] In the embodiment of FIG. 19, force limiting mechanism 186
will transmit the longitudinal movement of first tubular member 182
to second tubular member 184 as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value. Accordingly, longitudinal movement of first tubular member
182 of staple push rod 130 will cause substantially equivalent
longitudinal movement of second tubular member 184 as long as the
forces applied to staple 100 by staple push rod 130 are less than
the predetermined value. If the forces applied to staple 100 are
equal to or greater than the predetermined value, then force
limiting mechanism 186 will allow relative longitudinal motion
between first tubular member 182 and second tubular member 184. In
some useful embodiments, this function of force limiting mechanism
186 prevents the application of undue forces to staple 100. Once
the maximum desired force is applied to staple 100, further
rotation of trigger 160 will result in relative motion between
first tubular member 182 and second tubular member 184 and will not
result in the application of additional force to staple 100.
[0114] In the embodiment of FIG. 19, force limiting mechanism 186
comprises a spring 300. Spring 300 of FIG. 19, comprises ribbon 312
that forms a roll 314 when ribbon 312 is in an unstressed state.
When fixation tool assembly 180 is in an assembled state, roll 314
is supported by a roller 316 that extends through a center opening
of roll 314. Roller 316 is rotatably supported by a bracket that is
fixed to second tubular member 184 when fixation tool assembly 180
is in an assembled state. Second tubular member 184 defines a slot
194. First tubular member 182 carries a pin 196 that extends
through slot 194. When fixation tool assembly 180 is in an
assembled state, free end 318 of spring 300 is affixed to pin 196.
In the embodiment of FIG. 19, the arrangement of pin 196 extending
through slot 194 prevents relative rotation between first tubular
member 182 and second tubular member 184.
[0115] When spring 300 is in an unstressed state, ribbon 312 forms
a roll 314 as illustrated in FIG. 19. Spring 300 will maintain the
rolled shape shown in FIG. 19 as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value. In operation, spring 300 will transmit the longitudinal
movement of first tubular member 182 to second tubular member 184
as long as the forces applied to staple 100 by staple push rod 130
are less than a predetermined value. If the forces applied to
staple 100 are equal to or greater than the predetermined value,
then spring 300 will unroll. When spring 300 unrolls, spring 300
allows relative longitudinal motion between first tubular member
182 and second tubular member 184. As ribbon 312 of roll 314 is
unrolled, the force produced by spring 300 comes primarily from the
portion of ribbon 312 near roll 314. Because the geometry of that
region remains nearly constant as ribbon 312 unrolls, the resulting
force is nearly constant.
[0116] FIG. 20A and FIG. 20B are plan views further illustrating
the operation of fixation tool assembly 180 shown in the previous
figure. FIG. 20A and FIG. 20B may be collectively referred to as
FIG. 20. Fixation tool assembly 180 comprises a staple push rod 130
including a first tubular member 182, a second tubular member 184
and a force limiting mechanism 186 operably coupled between first
tubular member 182 and second tubular member 184. In the exemplary
embodiment of FIG. 20, a distal portion of first tubular member 182
is slidingly received in a lumen defined by second tubular member
184 such that first tubular member 182 and second tubular member
184 can translate relative to each other.
[0117] An actuator assembly 176 including a lever 174 is coupled to
the proximal end of first tubular member 182. Actuator assembly 176
is capable of creating longitudinal movement of first tubular
member 182 of staple push rod 130 relative to fixation tool shaft
146. In operation, first tubular member 182 of staple push rod 130
will be advanced and/or retracted in a longitudinal direction when
lever 174 of actuator assembly 176 is rotated. Under certain
circumstances, the longitudinal motion of first tubular member 182
is transferred to second tubular member 184 by force limiting
mechanism 186. When certain conditions are met, however, force
limiting mechanism 186 does not transfer the longitudinal motion of
first tubular member 182 to second tubular member 184.
[0118] A staple 100 is disposed at a distal end of second tubular
member 184. In the embodiment of FIG. 20, force limiting mechanism
186 will transmit the longitudinal movement of first tubular member
182 to second tubular member 184 as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value.
[0119] Accordingly, longitudinal movement of first tubular member
182 of staple push rod 130 will cause substantially equivalent
longitudinal movement of second tubular member 184 as long as the
forces applied to staple 100 by staple push rod 130 are less than
the predetermined value. If the forces applied to staple 100 are
equal to or greater than the predetermined value, then force
limiting mechanism 186 will allow relative longitudinal motion
between first tubular member 182 and second tubular member 184. In
some useful embodiments, this function of force limiting mechanism
186 prevents the application of undue forces to staple 100. Once
the maximum desired force is applied to staple 100, further
rotation of lever 174 will result in relative motion between first
tubular member 182 and second tubular member 184 and will not
result in the application of additional force to staple 100.
[0120] In the embodiment of FIG. 20, force limiting mechanism 186
comprises a spring 300. Spring 300 of FIG. 20, comprises ribbon 312
that forms a roll 314 when ribbon 312 is in an unstressed state.
When fixation tool assembly 180 is in an assembled state, roll 314
is supported by a roller 316 that extends through a center opening
of roll 314. Roller 316 is rotatably supported by a bracket that is
fixed to second tubular member 184. First tubular member 182
carries a pin 196 that extends through a slot defined by second
tubular member 184. Free end 318 of spring 300 is affixed to pin
196 in the embodiment of FIG. 20.
[0121] When spring 300 is in an unstressed state, ribbon 312 forms
a roll 314 as illustrated in FIG. 20A. Spring 300 will maintain the
rolled shape shown in FIG. 20A as long as the forces applied to
staple 100 by staple push rod 130 are less than a predetermined
value. In operation, spring 300 will transmit the longitudinal
movement of first tubular member 182 to second tubular member 184
as long as the forces applied to staple 100 by staple push rod 130
are less than a predetermined value. If the forces applied to
staple 100 are equal to or greater than the predetermined value,
then spring 300 will umoll. When spring 300 umolls, spring 300
allows relative longitudinal motion between first tubular member
182 and second tubular member 184. In the embodiment of FIG. 20B,
spring 300 has been partially umolled relative to the unstressed
state of spring 300. Dimension lines are used to illustrate an
overall length LA and an overall length LB in FIG. 20A and FIG.
20B, respectively. With reference to FIG. 20, it will be
appreciated that overall length LB is shorter than overall length
LA. In the embodiment of FIG. 20, the difference between overall
length LB and overall length LA is due to relative longitudinal
motion between first tubular member 182 and second tubular member
184. As ribbon 312 of roll 314 is unrolled, the force produced by
spring 300 comes primarily from the portion of ribbon 312 near roll
314. Because the geometry of that region remains nearly constant as
ribbon 312 unrolls, the resulting force is nearly constant.
[0122] While exemplary embodiments of the present invention have
been shown and described, modifications may be made, and it is
therefore intended in the appended claims and subsequently filed
claims to cover all such changes and modifications which fall
within the true spirit and scope of the invention.
* * * * *