U.S. patent application number 11/068163 was filed with the patent office on 2005-07-07 for surgical retractor having low-friction actuating means and contoured blade arms.
Invention is credited to Cartier, Raymond, Paolitto, Anthony, Valentini, Valerio.
Application Number | 20050148826 11/068163 |
Document ID | / |
Family ID | 4162448 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050148826 |
Kind Code |
A1 |
Paolitto, Anthony ; et
al. |
July 7, 2005 |
Surgical retractor having low-friction actuating means and
contoured blade arms
Abstract
A retractor for performing surgery, for instance cardiac surgery
on the coronary organs of a patient, which has a driving member to
which the surgeon input is applied in the form of a mechanical
force or torque, a thoracic structure engaging member which
interfaces and retracts the patient's thoracic structure when
surgeon input is applied to the movable driving member, and a
surgeon input load-reducing and load-normalizing mechanism provided
in at least one mechanical interface between retractor components
where relative motion therebetween occurs. The load-reducing and
load-normalizing mechanisms are preferably non-lubricated, thereby
tending to ensure an inert and sterile environment during surgery.
The retractor is comprised of a locking arrangement allowing a
retractor spreader arm to be secured at any longitudinal position
along the rack bar, independently of the pinion's position. The
thoracic retractor according to this invention tends to improve the
efficiency and safety of surgery by reducing the surgeon input
required to achieve retraction, and by allowing said input to be
applied more uniformly and in a controlled manner free from sudden
movements through the normalization of retractor variables.
Inventors: |
Paolitto, Anthony; (St.
Leonard, CA) ; Valentini, Valerio; (Montreal, CA)
; Cartier, Raymond; (Montreal, CA) |
Correspondence
Address: |
Anthony PAOLITTO
c/o CORONEO
Suite 514
9250 Avenue du Parc
Montreal
QC
H2N 1Z2
CA
|
Family ID: |
4162448 |
Appl. No.: |
11/068163 |
Filed: |
March 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11068163 |
Mar 1, 2005 |
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10157836 |
May 31, 2002 |
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6896654 |
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10157836 |
May 31, 2002 |
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09740001 |
Dec 20, 2000 |
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6416470 |
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09740001 |
Dec 20, 2000 |
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PCT/CA99/00593 |
Jun 25, 1999 |
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Current U.S.
Class: |
600/232 |
Current CPC
Class: |
A61B 2017/0084 20130101;
A61B 17/0206 20130101 |
Class at
Publication: |
600/232 |
International
Class: |
A61B 001/32 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 26, 1998 |
CA |
2,237,877 |
Claims
We claim:
1. A surgical retractor for retracting generally opposed body
tissue edges away from each other so as to form a tissue opening
therebetween, said tissue opening extending generally in an opening
geometrical plane, each of said tissue edges intercepting a tissue
outer surface and a tissue inner surface, said surgical retractor
allowing the insertion of a surgical implement into said tissue
opening, said surgical retractor comprising: a generally elongated
guide member, said guide member defining a guide member first end
and a generally opposed guide member second end; a first spreader
arm and a second spreader arm, said first spreader arm defining a
first arm first end and a generally opposed first arm second end,
said second spreader arm defining a second arm first end and a
generally opposed second arm second end; said first and second
spreader arms being mechanically coupled to said guide member
adjacent said first and second arm first ends so that said first
and second arm second ends are unattached to one another and
positioned generally away from said guide member; said first and
second spreader arms being movable relative to each other along
said guide member between a first position wherein said first and
second spreader arms are in a generally adjacent relationship
relative to each other and a second position wherein said first and
second spreader arms are in a generally spaced apart relationship
relative to each other; a first retractor blade and a second
retractor blade respectively extending from said first and second
spreader arms, said first and second retractor blades respectively
defining a first and a second blade contacting surface for
respectively engaging said opposed body tissue edges during
retraction thereof away from each other; an actuator, said actuator
effecting relative movement of said first and second spreader arms
along said guide member; an interfacing member, said interfacing
member being mechanically coupled to either one of said first or
second spreader arms and providing a friction-reducing mechanical
interface between said actuator and either one of said first or
second spreader arm.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to the field of surgical
apparatus and more specifically, to retractors used in surgery.
BACKGROUND OF THE INVENTION
[0002] Retractors of all shapes and sizes have been present since
the dawn of surgery. A common type of retractor is the chest
retractor or thoracic retractor. Retractors of this category may
comprise sternum retractors, thoracotomy retractors,
mini-thoracotomy retractors, mini-sternotomy retractors, and
retractors used for the surgical harvesting of internal thoracic
arteries through a sternotomy or intercostal approach incision. For
instance, such internal thoracic arteries may comprise the left
internal mammary artery.
[0003] Sternum retractors are commonly used in cardiac surgery.
Cardiac surgery may take several forms. For instance, these forms
include traditional coronary artery bypass graft surgery (CABG)
requiring the heart-lung machine, CABG surgery performed directly
on a beating heart, minimally invasive direct coronary artery
bypass surgery (MIDCAB), heart valve repair surgery, heart valve
replacement surgery and surgery to correct a septal wall defect,
whether atrial or ventricular. Thoracic retractors serve to incise,
penetrate and retract the thoracic structure, namely the surface,
underlying tissue and bone structure of a patient, in order to
access the body organs and internal body tissue contained within
the patient's thorax. In the case of a sternum retractor, the
thoracic structure in question is the patient's sternum and entire
ribcage. The body organs and internal body tissue exposed by use of
a sternum retractor will comprise the coronary organs, which
include in particular the heart, the heart's arteries and veins,
the surrounding tissue and vessels, the pericardium, the thymus,
the pleura, and any other tissue within the mediastinum or the
space between the two lungs. Sternum retractors are typically used
in CABG surgeries or valve replacement surgeries.
[0004] The drive in recent years for less invasive cardiac surgery
has resulted in smaller chest incisions and consequently smaller
chest retractors as well. In minimally invasive cardiac surgery,
such as MIDCAB, mini-thoracotomy retractors were introduced to
laterally retract a pair of adjacent ribs and expose the underlying
coronary organs through the resultant intercostal space.
[0005] Most known chest retractors have an elongate rack bar and
two retracting arms, namely a fixed retracting arm and a movable
retracting arm. Both arms typically extend in a direction
substantially normal to the rack bar. The movable arm can be
displaced along the rack bar using a crank, which also acts as a
torque lever, to activate a pinion mechanism. Two blades are
provided, usually below the retractor arms, to interface with the
patient's sternum or skin, and which forms part of the thoracic
structure. The basic design and mechanism for separating the two or
more spreader members or retractor arms of chest retractors have
remained relatively unchanged since the first introduction of
retractors in cardiac surgery. Consequently, cardiac surgeons have
developed a manual proficiency in using the current retractors.
[0006] In all chest retractors, there is a resistance to retraction
by the patient's thoracic structure and by the retractor itself,
which the surgeon must overcome in deploying the retractor to
expose the coronary organs. The separating force the surgeon
applies is mainly a function of the geometry of the rack and pinion
mechanism, the length of the retractor arm, and the friction at the
interface between all moving components in the retractor assembly.
The separating force to overcome the resistance load on the
retractor may at times be excessive since:
[0007] a patient may be very corpulent;
[0008] a patient's bones may be very brittle, and therefore
especially resistant to rotation of the ribs about the spine;
[0009] the retractor blade design may result in concentrated loads
being generated at locations remote from the rack bar and pinion
mechanism;
[0010] friction in the retractor system may be high; and
[0011] wear may have occurred at the mechanical interface between
moving components.
[0012] The deployment of the retractor, and more specifically the
relative movement of the retractor arms, may at times be
intermittent, or "jerky" and not smooth, since:
[0013] the thoracic structure generally imposes variable loads on
the retractor as a function of its retracted opening;
[0014] the meshing of the crank and pinion mechanism of the
retractor may not be continuous, such that the load at the crank
handle may vary as a function of the pinion position within the
rack grooves and consequently as a function of the circumferential
orientation of crank handle;
[0015] the load to overcome friction between retractor components
to set retraction in motion is typically higher than the load to
keep said components in motion;
[0016] friction between moving retractor components may be subject
to variation given uneven wear in components; and
[0017] the friction forces associated with the operation of the
retractor are normally linked to the resistance force exerted by
the thoracic structure, which is itself variable as a function of
its retracted opening.
[0018] In most chest retractors, the pinion mechanism usually
consists of two pins which engage the rack teeth within grooves
formed therebetween in a variety of orientations depending on the
rotation of the pinion assembly (and the crank handle usually
attached to the pinion assembly). This results in a substantially
stable orientation when both pins are engaged with the rack teeth,
and a substantially unstable orientation when only one pin is
engaged with a rack tooth. This also results in an alternation of
discrete and substantially stable locked positions with unstable
unlocked positions of the retractor arms along the entire length of
the rack.
[0019] Based on the foregoing, it would therefore be advantageous
to provide a surgical retractor, for instance a sternum retractor,
with easier deployment in cardiac surgery.
[0020] Thus, it is one object of the present invention to attempt
to reduce the separating force and torque the surgeon must apply to
the retractor, to effect retraction in surgery.
[0021] It is a further object of the present invention to seek to
maintain more uniform separating loads by normalizing the variables
in chest retractor design discussed above and experienced during
deployment in surgery.
[0022] It is a further object of the present invention to aim to
reduce the risk of injury to a patient by providing improvements to
retractors, for instance sternum retractors, that allow the surgeon
to deploy said retractors in a controlled manner free from sudden
or intermittent movements.
[0023] It is a further object of the present invention to provide a
chest retractor, for instance a sternum retractor, which may more
readily be cleaned and sterilized.
[0024] It is a further object of the invention to provide a
retractor design which is intended to reduce concentrated loads
sometimes found at the extremities of a surgical incision, when
compared to certain prior art retractors, and for a given retracted
opening in the thoracic structure when measured at the mid length
location along the incision.
[0025] It is a further object of the present invention to provide a
chest retractor with contoured retractor blades adapted to more
closely conform to the ribcage halves along a sternotomy incision
as the thoracic structure is retracted.
[0026] It is an additional object of the present invention to
provide a retractor having a continuous variable range of lockable
open retracted positions.
[0027] It is an additional object of the present invention to
retrofit existing retractors, for instance sternum retractors, with
improvements that aim to reduce and normalize separating loads
which the surgeon must apply during retraction of the thoracic
structure therewith.
[0028] It is an additional object of the present invention to apply
the concepts and principles of this invention, as they relate to
chest retractors and more specifically to sternum retractors, to
other types of retractors.
[0029] These and other objects of the present invention will become
apparent from the description of the present invention and its
preferred embodiments which follows.
SUMMARY OF THE INVENTION
[0030] According to one broad aspect of the present invention,
there is provided a surgical retractor having an elongate guide
member, and having first and second spreader arms each extending
substantially transversely of the guide member and each extending
therefrom generally in the same direction, the first and second
spreader arms being disposed generally parallel to each other, the
first spreader arm being movable along the length of the guide
member from a first position, wherein the spreader arms are
adjacent one another, to a second position, wherein the spreader
arms are spaced apart from one another, to thereby effect
retraction of a surgical incision; characterized in that the
surgical retractor comprises: an actuator for effecting said
movement of the first spreader arm, the actuator being operatively
connected to the guide member and to the first spreader arm, and
wherein the actuator is translatable along the length of the guide
member; and a low friction interfacing member, the low friction
interfacing member being disposed between the actuator and the
guide member at a point of contact of said actuator with said guide
member.
[0031] With reference to preferred embodiments of the invention,
the low friction interfacing member may advantageously be connected
either to a pinion mechanism housing or be inserted in a slider
slot provided along the length of a corresponding rack bar. The low
friction interfacing member is preferably of an open configuration
which tends to facilitate sterilization and easy cleaning of blood
products from constituent elements prior to sterilization. As well,
the low friction interfacing member is preferably non-lubricated
tending to ensure inert and sterile environment during surgery.
[0032] The thoracic retractor may also advantageously provided with
a pinion arrangement having a friction reducing member. As well,
the driving member therefor may be provided with a friction
reducing member such as a bearing.
[0033] The retractor may also comprise a locking arrangement to
allow the adaptor to be secured at any longitudinal position along
the rack bar, independently of the pinion's position.
[0034] A low friction interfacing member according to the present
invention may also be used as a retrofit arrangement for existing
retractors.
[0035] The pinion arrangement preferably comprises two pinions, but
those skilled in this art will appreciate that more pinions may
also be provided.
[0036] All the foregoing features contribute to attempt to optimize
the operation and safety of the retractor.
[0037] The retractor according to the present invention seeks to
reduce the separating force and torque which the surgeon must apply
at the driving member of the retractor and thereby tends to
facilitate its deployment. As well, the retractor of the present
invention attempts to substantially normalize retraction loads;
that is, it is intended to allow the surgeon to sense more uniform
loads and to thereby result in a steadier deployment of the
retractor throughout its open range. Since a jerky deployment of
the retractor can lead to sudden retraction movements,
normalization may result in less risk of inadvertent tissue trauma
or sternum fracture. Thus the present invention describes a
low-friction interfacing member for providing load reduction and
load normalization in thoracic retractors.
[0038] In surgical interventions which obtain access to the
coronary organs via a midline sternotomy incision, the nature of
the surgical incision is substantially linear since the sternum or
breastbone is cut in two. The patient's thoracic structure usually
imposes the greatest resistance to retraction at the extremities of
the surgical incision, where tearing of tissue most often occurs.
This also tends to result in the highest concentration of
resistance load being applied to the retractor arms at the free
ends thereof, namely at the extremity of the incision location
which is furthest away from the rack and pinion mechanism of the
retractor. The retractor of this invention, with its arcuate
spreader arms and contoured thoracic structure engaging members is
expected to reduce these concentrated loads at the incision
extremities for a desired retracted opening in the thoracic
structure at the mid length location along the surgical incision.
This would therefore be advantageous since the overall separating
force the surgeon must apply will also be reduced for a given
opening in the thoracic structure.
[0039] In retracting a patient's thoracic structure subsequent to a
midline sternotomy, the two halves of the ribcage do not have a
tendency to spread apart in a parallel orientation along the
sternotomy incision. The top portion of the ribcage tends to go
from a generally cylindrical-shaped surface, when the incision is
not retracted, to a generally barrel-shaped surface when the
incision is retracted. That is, the center portion of the ribcage
along the sternotomy incision retracts more readily in an outward
and upward direction than the extremities of the incision, which
are somewhat restricted by the endpoints thereof at the patient's
abdomen and collarbone. This forms a lens-shaped opening for the
retracted incision. Many prior art retractors do not accommodate
this barrelling behaviour. The retractor of this invention, with
its contoured thoracic structure engaging members that interface
with the two halves of the patient's incised sternum and that
conform closely to this non-parallel barrelling of the ribcage
halves along the sternotomy incision during retraction, would offer
advantages in tending to minimize the likelihood of sternal
breakages and induced tissue trauma.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] For a better understanding of the present invention and to
show more clearly how it may be carried into effect, reference will
now be made by way of illustration and not of limitation to the
accompanying drawings, which show an apparatus according to
preferred embodiments of the present invention and in which:
[0041] FIG. 1A is an exploded perspective view illustrating a low
friction interfacing member, also termed a load-reducing and
load-normalizing member, for a sternum retractor, all according to
a first embodiment of the present invention;
[0042] FIG. 1B is an enlarged exploded view illustrating a
load-reducing and load-normalizing mechanism of the sternum
retractor of FIG. 1A;
[0043] FIG. 2A is a top plan view of the sternum retractor of FIG.
1, schematically illustrating an example of the forces acting on
the retractor system;
[0044] FIG. 2B is a top plan view of a pinion mechanism for the
retractor of FIG. 1, with a schematic representation of an example
of the forces acting thereon;
[0045] FIG. 2C is a top plan view of the pinion mechanism of FIG.
2B, showing a crank for deployment by a surgeon and an example of
the forces the surgeon must apply to the crank to achieve
retraction of a thoracic structure;
[0046] FIG. 3 is a side elevational view of a portion of the
retractor of FIG. 1A, illustrating the load-reducing and
load-normalizing mechanism of FIG. 1B;
[0047] FIGS. 4A to 4J illustrate top cross-sectional halves of
bearing variants, about their respective centerlines, which may be
adapted as the load-reducing and load-normalizing mechanism of FIG.
1B;
[0048] FIG. 5 is an enlarged exploded view illustrating a second
embodiment of a load-reducing and load-normalizing mechanism for
the sternum retractor of FIG. 1A, in the nature of a needle
bearing;
[0049] FIGS. 6A to 6D illustrate assembled views of the
load-reducing and load-normalizing mechanism of FIG. 5;
[0050] FIG. 7 is an exploded perspective view illustrating a third
embodiment of the load-reducing and load-normalizing mechanism for
the sternum retractor of FIG. 1A, in the nature of a sliding member
arrangement;
[0051] FIG. 8 is an exploded perspective view illustrating a fourth
embodiment according to this invention, comprising a
friction-reducing member for the pinion mechanism of the sternum
retractor of FIG. 1A;
[0052] FIG. 9 is an exploded perspective view illustrating a fifth
embodiment according to this invention, comprising a
friction-reducing member for the pinion mechanism of the sternum
retractor of FIG. 1A;
[0053] FIG. 10A is a partial cross-sectional view of the sternum
retractor of FIG. 1A, showing a sixth embodiment according to this
invention, and having a locking mechanism between the crank and
pinion mechanism of said retractor;
[0054] FIG. 10B is a side elevational view of the locking mechanism
of FIG. 10A illustrating a cam lock feature;
[0055] FIG. 10C is a partial cross-sectional view of a first
variant to the sixth embodiment of FIG. 10A, illustrating a locking
mechanism and hydraulic sleeve feature;
[0056] FIG. 10D is a partial cross-sectional view of a second
variant to the sixth embodiment of FIG. 10A, illustrating a locking
mechanism and wedge feature;
[0057] FIG. 11A is a partial perspective view of a seventh
embodiment according to this invention, illustrating the retrofit
of a load-reducing and load-normalizing mechanism to existing
retractors;
[0058] FIG. 11B is a partial side elevational view of the seventh
embodiment of FIG. 11A;
[0059] FIG. 12A is a top anterior view of the patient's thoracic
structure engaged with arcuate blades of the sternum retractor of
FIG. 1A prior to retraction of the thoracic structure, illustrating
an eighth embodiment according to this invention;
[0060] FIG. 12B is a cross-sectional view through the patient's
thoracic structure and through the sternum retractor of FIG. 12A,
illustrating the engagement of the thoracic structure in its
cylindrical-like configuration prior to retraction with respective
concave surfaces of the arcuate blades thereof;
[0061] FIG. 12C is a cross-sectional view of a spreader arm and
blade of the sternum retractor of FIG. 1A;
[0062] FIG. 13A is a top anterior view of the sternum retractor and
the patient's retracted thoracic structure of FIG. 12A, exposing
the coronary organs;
[0063] FIG. 13B is a partial cross-sectional view through the
patient's retracted thoracic structure and the sternum retractor of
FIG. 12A, illustrating the engagement of the thoracic structure in
its barrel-like configuration with portions of the arcuate blades
of the retractor which are adjacent lower longitudinal edges
thereof;
[0064] FIG. 14A is a top view of an arcuate spreader arm for the
sternum retractor of FIG. 1A;
[0065] FIG. 14B to 14D illustrate various sectional views along the
arcuate spreader arm of FIG. 14A, taken along the portion of the
spreader arm which is configured with an underlying blade;
[0066] FIG. 15A is a partially sectional view through the sternum
retractor of FIG. 1A and the patient's thoracic structure in its
cylindrical-like configuration prior to retraction; and
[0067] FIG. 15B is a sectional view through the sternum retractor
of FIG. 1A and the patient's thoracic structure in its barrel-like
configuration after retraction.
DETAILED DESCRIPTION OF THE INVENTION
[0068] The description which follows, and the embodiments described
therein, are provided by way of illustration of an example, or
examples, of particular embodiments of the principles of the
present invention. These examples are provided for the purposes of
explanation, and not of limitation, of those principles and of the
invention. In the description which follows, like parts are marked
throughout the specification and the drawings with the same
respective reference numerals. The drawings are not necessarily to
scale and in some instances proportions may have been exaggerated
in order to more clearly depict certain features of the
invention.
[0069] The features and principles of this invention can be
applied, in whole or in part, to many types of retractors, and more
particularly to chest retractors utilized in cardiac surgery. The
description of the preferred embodiments will be illustrated with
respect to sternum retractors, for instance those used to perform
multiple vessel CABG surgery and valve surgery through a midline
sternotomy incision.
[0070] In part, the preferred embodiments of this invention will
introduce enhancements and additional features to a retractor
described in copending Canadian patent application Serial No.
2,216,893 filed on Sep. 30, 1997 in the names of Cartier and
Paolitto and entitled "Sternum Retractor for Performing Bypass
Surgery on a Beating Heart", the contents of which are incorporated
herein by reference. This existing application has been assigned to
CoroNo Inc., the assignee of the present application.
[0071] By way of a general overview, FIG. 1 illustrates an exploded
view of the chest retractor apparatus according to a preferred
embodiment of the present invention. The sternum retractor 1
includes five major parts: (i) a guide member such as an elongated
rack bar 5, (ii) first and second retractor spreader arms 3 and 4,
with one retractor spreader arm 3 being preferably fixed to the
rack bar 5 and the other retractor spreader arm 4 being preferably
movable with respect to the rack bar 5, (iii) an actuator for
effecting movement of the retractor spreader arm 4, which
preferably comprises a pinion mechanism 6, and (iv) a low-friction
interfacing member in the nature of a friction-reducing, or a
load-reducing and load-normalizing mechanism 20.
[0072] Retractor arms 3 and 4 extend in a direction substantially
transversely with regard to the rack bar 5, extend generally in the
same direction therefrom and in parallel orientation with respect
to one another. The retractor arms 3 and 4 have a generally arcuate
orientation as explained in greater detail herebelow. The movable
arm 4 can be displaced along the rack bar 5, and relative to the
other arm 3, preferably through rotation of a pinion mechanism 6
activated by the surgeon through crank 64. The actuator is
operatively connected to the rack member and to the spreader arm 4,
and is translatable along the length of the rack member. This is
preferably achieved by the engagement of pinion mechanism 6 with
the rack teeth 51 on rack bar 5 through shaft 60. Two retractor
blades 7 and 8 are respectively provided with the retractor
spreader arms. Preferably, the retractor blades 7, 8 are disposed
below the rack bar 5 when the sternum retractor 1 is deployed on a
patient. The retractor blades 7, 8 serve to retract a portion of
the thoracic structure, thereby exposing the coronary organs to be
operated on. Blades 7 and 8 interface with the two halves of the
patient's sternum after the sternotomy incision, and thereby act as
thoracic structure engaging members.
[0073] The sternum retractor 1 advantageously comprises arcuate
rails 70 and 80 along the top of arcuate retractor spreader arms 3
and 4 respectively. A similar linear longitudinal rail 50 may also
be configured along the top of rack bar 5. These said rails form a
mounting perimeter that advantageously serves to engage a
positioning and articulation mechanism utilized to place a variety
of heart stabilizers during beating heart bypass surgery, as
described in the previously mentioned Canadian patent application
Serial No. 2,216,893. Alternatively, the positioning and
articulation mechanism may also be utilized to set a coronary organ
contacting member used in cardiac surgery, such as a valve tissue
retractor for example. As well, these rails can also be utilized to
engage other surgical apparatus, that need to be secured along the
perimeter of the chest retractor during cardiac surgery.
[0074] In broad terms, a typical example of the surgical procedure
for the set-up and deployment of sternum retractor 1 relating to
this invention consists of:
[0075] a) A full or partial sternotomy incision;
[0076] b) Cauterization of any bleeding vessels subsequent to the
sternotomy incision;
[0077] c) Insertion of sternum retractor blades 7, 8 along the
sternotomy incision, preferably with the portion of the blades
which are disposed farthest away from the rack 5 being inserted
first, and the remaining portion of the blades 7, 8 being
progressively introduced into the incision from the base of the
incision (closest to the abdomen) towards the top of the incision
(closest to collarbone);
[0078] d) Rotation of crank 64 to move spreader arms 3, 4 apart
from each other and gradually retract the patient's thoracic
structure exposing the coronary organs therewithin;
[0079] e) Performing the required surgical intervention;
[0080] f) Re-adjusting the opening of the retracted thoracic
structure during surgery, if required, by rotation of the
crank;
[0081] g) Closing the patient's thoracic structure after completion
of surgical intervention through opposite rotation of the
crank;
[0082] h) Removal of the sternum retractor;
[0083] i) Closing of the surgical incision.
[0084] FIGS. 2A to 2C illustrate schematically examples of the
loads exerted by the thoracic structure (labelled TS) on the
sternum retractor 1, and the resultant forces within the retractor
system. The thoracic structure resists retraction by imposing a
load F.sub.STERNUM on the blades 7 and 8 of the retractor. The load
is distributed along the entire length of the blades. Due to the
substantially linear nature of the typical surgical incision, the
thoracic structure normally imposes the greatest resistance to
retraction at the extremities of the incision, where the tearing of
tissue most often occurs. In some patients, where the ribcage is
very rigid and not easily rotatable about the spine axis, the
maximum load on the retractor blades can be anywhere along the
blade's arcuate length depending on the specific patient anatomy.
The resultant moment M.sub.STERNUM, on the retractor, depends on
the resistance force F.sub.STERNUM exerted on the retractor blades
7 and 8, and also on the length along the retractor arm L.sub.RA.
Thus, F.sub.STERNUM schematically represents the distributed
resistance load on the retractor blades 7 and 8 concentrated at one
location along the blade, and L.sub.RA represents the distance
between the line of action of F.sub.STERNUM and the mechanical
interface between spreader arm 3 and 4.
[0085] In the specific embodiment shown in FIGS. 1A, 2A and 3, the
pinion mechanism 6 is contained in an adaptor in the nature of a
crank housing 42. The crank housing 42 is described in greater
detail herebelow. Along the rack bar 5 and at the opposing ends of
the adaptor 42, the moment M.sub.STERNUM is reacted by the forces
F.sub.BRG and moment M.sub.BRG, which keeps the retractor arm 4
from rotating towards the retractor arm 3 at their free ends.
During translation of retractor arm 4 relative to retractor arm 3
along the rack bar 5, a friction force Ff.sub.SLIDER must also be
overcome (FIG. 2C). The friction force Ff.sub.SLIDER is a function
of the coefficient of friction between the two retractor arms; more
specifically in the illustrated example, between the rack 5 which
is integral with retractor arm 3 and the crank housing 42 which is
integral with arm 4. The friction force Ff.sub.SLIDER is also a
function of the component of force F.sub.BRG acting normal to the
sliding surface. A wider crank housing 42, with larger spacing
L.sub.BRG, will reduce the magnitude of forces F.sub.BRG at the
expense of a larger and perhaps heavier retractor, for a given
M.sub.STERNUM.
[0086] The force F.sub.STERNUM exerted on the retractor blades 7
and 8 is transferred to the rack bar 5, more specifically to rack
teeth 51 thereof, and to the pinion mechanism 6 as F.sub.PINION,
for a given F.sub.STERNUM as illustrated in the example of FIG. 2B.
Depending on the design of the retractor components, F.sub.PINION
may vary in magnitude. FIG. 2B schematically illustrates the forces
exerted from the rack teeth 51 on the pinion member 63. With each
half-turn rotation of the crank 64 and simultaneously of the shaft
60, pinion member 63 moves in and out of a slot 52 defined between
immediately adjacent rack teeth 51 of rack bar 5, in the case of a
dual pinion member arrangement. With the next half-turn rotation,
the other pinion member 63 engages an adjacent slot 52 and repeats
this motion. Each pinion member 63 engages alternate slots 52 in
the rack bar 5 to achieve the relative movement between retractor
spreader arms 3 and 4. As the pinion member 63 moves within a rack
slot 52, its perimeter surface 639 rotates and slides relative to
the mating surface 519 of the engaged rack tooth 51. A friction
force Ff.sub.PINION is thereby generated from this relative motion.
This friction force is a function of the coefficient of friction
between engaged rack tooth 51 and pinion member 63, and the normal
component of F.sub.PINION to mating surface 519. The friction force
Ff.sub.PINION may lead to wear at the rack tooth interface and
eventually the need for refurbishment or replacement of the
retractor.
[0087] FIG. 2C illustrates an example of the forces between the
pinion mechanism 6 and the retractor arm crank housing 42, and the
force and torque the surgeon must provide to retract the thoracic
structure through the crank handle 64. The force F.sub.PINION on
the pinion is reacted by an effective force F.sub.CRANK acting
between the crank housing 42 and pinion journals 61 and 62 (as best
shown in FIG. 3) of pinion mechanism 6. The spacing between pinion
members 63 determines the magnitude of F.sub.PINION acting between
the pinion members and the rack teeth 51, for a given
M.sub.STERNUM. A smaller F.sub.PINION is at the expense of a larger
tooth pitch rack with coarser travel of retractor arm 4 along the
rack bar 5; that is, a larger displacement of movable spreader arm
4 for each revolution of handle 64. The rotation of the pinion
mechanism 6 within the crank housing 42 generates a friction force
Ff.sub.CRANK along the circumference of top pinion journal 61 and
bottom pinion journal 62. This may lead to wear at the pinion
journal interfaces and eventually the need for refurbishment or
replacement of the retractor.
[0088] In conventional chest retractors, the surgeon applies force
F.sub.SURGEON and torque M.sub.SURGEON through the crank handle 64,
not only to overcome the resistance to retraction F.sub.STERNUM of
the thoracic structure, but also to overcome the friction forces
Ff.sub.SLIDER, Ff.sub.PINION and Ff.sub.CRANK. The longer the crank
length L.sub.CRANK, the easier is expected to be the surgeon input
at the expense of a heavier and perhaps less ergonomic handle. For
the purposes of this embodiment, the crank handle 64 is also the
movable driving member.
[0089] As illustrated in FIG. 1A and enlarged in FIG. 1B, a
load-reducing and load-normalizing mechanism 20, preferably in the
nature of a ball bearing, tends to operate in a fashion to reduce
the force F.sub.SURGEON and torque M.sub.SURGEON required to
retract the thoracic structure by overcoming the friction force
Ff.sub.SLIDER. This load-reducing and load-normalizing mechanism 20
will also tend to allow said force and said moment to be applied
more consistently and uniformly throughout the retraction range of
the apparatus, hence the reference to "load-normalizing" in
describing the mechanism.
[0090] The load-reducing and load-normalizing mechanism 20 may be
comprised of two ball bearings 24 which are each assembled to the
crank housing 42, for example, by a screw element 21 and a nut
element 23. In FIG. 1A, only the first of the two bearings 24 is
shown disassembled. The screw element 21 of the assembled second
bearing can be seen engaged within crank housing 42. Both bearings
are preferably, but not necessarily, of the same type. The two ball
bearings are spaced apart by L.sub.BRG such that the force couple
F.sub.BRG.times.L.sub.BRG can react the imposed moment
M.sub.STERNUM. This resultant force F.sub.BRG between retractor
arms 3 and 4 acts through each of the ball bearings 24 of the
load-reducing and load-normalizing mechanism 20, through the
interface of slider slot 501 of linear rail 50. Thus, a low
friction interfacing member is disposed between the actuator and
the guide member at a point of contact of the actuator with the
guide member.
[0091] With reference to FIG. 1B, bearing 24 is comprised of an
inner race 242, an outer race 241 and complement of rolling element
balls 243 spaced apart circumferentially by a cage 244. The items
comprising bearing 24 stay assembled as a whole after fabrication
of the bearing, and allow the free rotation of outer race 241
relative to inner race 242 through the complement of rolling
element balls 243 that roll within groove 248 in the inner race and
groove 249 in the outer race. These grooves 248, 249 also maintain
the axial position of the outer race while permitting its free
rotation relative to the inner race once the bearing 24 is
assembled during fabrication.
[0092] The bearing 24 is clamped through its inner race edges 245
and 246 between spacer 22 and nut element 23. Nut element 23 is
configured with a pilot diameter 233 to fit into inner diameter 247
of inner race 242. Shoulder 231 of the inner race axially clamps
bearing 24 through inner race edge 246 when internal thread 232
becomes engaged with threaded body 211. Spacer 22 is of a tubular
configuration to permit screw element 21 to pass through its center
and freely engage internal thread 232 of nut element 23. The
lateral faces 221 and 222 of spacer 22 contact the underside face
422 of crank housing 42 and inner race edge 245, respectively, when
the assembly of mechanism 20 is complete. Screw element 21 is
provided with a conical head portion 212 which sits within a
corresponding countersink feature 421 in crank housing 42, and
threaded body 211 for engaging internal thread 232 in nut element
23. A torque reaction feature 213, a hex drive recess for example,
is provided on screw element 21 and nut element 23 (not shown) to
enable fastening of the load-reducing and load-normalizing
mechanism 20 assembly to the crank housing 42.
[0093] Once all components are secured to crank housing 42 by
fastening threaded body 211 and nut element 23, only outer race 241
of bearing 24, and rolling element balls 243 along with their cage
244 are free to rotate about the centerline of the load-reducing
and load normalizing mechanism 20 assembly. All other components,
that is screw element 21, spacer 22, inner race 242 of bearing 24,
and nut element 23 are fixed in relation to crank housing 42, and
do not rotate.
[0094] The pinion mechanism 6 is insertable in the crank housing
42, where the top pinion journal 61 and bottom pinion journal 62
can rotate within port surface 461 (FIG. 1A). It is preferable to
have the free terminal end 53 of the rack bar configured without
any rack teeth, to enable the insertion of said pinion mechanism
after the two retractor arms are at least partially assembled with
bearing 24 simultaneously engaged within slot 501 of rack bar 5.
When the pinion member 63 is engaged with the rack teeth 51, the
pinion mechanism 6 is axially retained but free to rotate within
the crank housing 42, throughout the open range of the retractor
spreader arms 3 and 4.
[0095] As illustrated in FIG. 3, the spacer element 22 serves to
offset the two ball bearings 24 away from the underside face 422 of
the crank housing 42, such that only the cylindrical surface of the
outer race 241 engages with the slider slot 501 of linear rail 50.
In the illustrated example, the side surfaces of the bearing and
nut element 23 do not contact or rub against the sides of slider
slot 501, tending to achieve only substantially frictionless and
normalized sliding of the retractor arms when the bearing outer
race 241 rolls within the slider slot 501. This configuration also
results in the load-reducing and load-normalizing mechanism 20, in
the preferred nature of a ball bearing, being ergonomically stowed
within the said slider slot 501 throughout the entire open range of
the retractor spreader arms 3 and 4.
[0096] Advantageously, the two ball bearings 24 remain integral
with the crank housing 42, and do not have to be disassembled for
sterilization. The bearing design is of an open configuration; that
is, the rolling elements are non-shielded and non-sealed. The open
configuration tends to facilitate cleaning of the blood products
from the bearing elements prior to sterilization. The bearing
design does not require lubrication, tending to ensure inert and
sterile environment during cardiac surgery.
[0097] Although the first embodiment, as illustrated in FIGS. 1A,
1B and 3, employs an open configuration ball bearing 24 as part of
the load-reducing and load-normalizing mechanism 20, other
rolling-element-type bearings can also be employed to configure
alternative embodiments for the load-reducing and load-normalizing
mechanism. FIGS. 4A to 4I illustrate the top cross-sectional half
of rolling-element-type bearing variants, about their respective
centerlines CL. Suitable bearings may include but are not limited
to: (4A) open configuration ball bearing (also the illustrated
example in FIG. 1A); (4B) shielded ball bearing; (4C) sealed ball
bearing; (4D) external self-aligning ball bearing; (4E) double row
ball bearing; (4F) self-aligning ball bearing; (4G) straight roller
bearing; (4H) needle bearing; and (4I) tapered roller bearing. In
these figures, the bearing outer race is generically referred to as
OR, the inner race as IR, and the complement of rolling elements as
RE. FIG. 4J illustrates a flanged journal bearing.
[0098] The sealed ball bearing, illustrated in FIG. 4C, can be
either a dry non-lubricated cartridge which is limited in the
number of uses to which it can be put, or a self-contained
lubricated cartridge which either resists sterilization for
repeated uses or is replaced after every surgery.
[0099] FIG. 5 illustrates the second embodiment 120 for the
load-reducing and load-normalizing mechanism, in the nature of an
open configuration needle bearing. The spreader arms 3 and 4, the
pinion mechanism 6 and the rack bar 5 are the same as in the first
embodiment, and are not shown in FIG. 5. FIGS. 6A-6D illustrate
assembled views of this second embodiment without the crank housing
42.
[0100] The load-reducing and load normalizing mechanism 120 is
comprised of inner hub 123, outer race 126, retainer 127, screw
element 21, and a plurality of cylindrical pins 259 serving as the
bearing rolling elements. The annular gap between the inner
diameter 264 of the outer race 126 and the outer diameter of inner
race 237 is sized as a function of the desired number and diameter
of pins 259 to configure an annular cluster 125 (FIG. 6C) when said
cylindrical pins are assembled between said outer race and inner
hub. Slight circumferential gaps result between the cylindrical
pins 259 when assembled as a cluster 125 tending to facilitate the
rotation of outer race 126 about the inner hub 123. Cylindrical
pins 259 can be classified as to their diameter size in order to
allow for a selective close tolerance assembly of cluster 125
radially retained within annular gap formed between inner diameter
264 and inner race 237.
[0101] Guiding diameter 230 serves as a guide for the pilot
diameter 272 during the installation of retainer 127 onto inner hub
123. The diametrical fit between guiding diameter 230 and pilot
diameter 272 is preferably an interference fit. Swaging or stacking
can also be implemented between the retainer 127 and receiving
portion of inner hub 123, to further secure this assembly from
disengagement. Cluster 125 is limited in axial movement between hub
flange 239 and retainer flange 274, which serve to axially retain
the said cluster once the retainer flange 274 rests up against
abutment face 236 of inner hub 123. Axial movement of cluster 125,
or any of the cylindrical pins 259, is limited by gap 267 (FIG.
6D). Outer race 126, although free to rotate, is also limited in
axial movement between hub flange 239 and retainer flange 274.
Axial movement of outer race 126 is limited by axial gap 266. Axial
gap 266 is preferably smaller than axial gap 267.
[0102] Retainer 127 being fully seated against abutment face 236
results in an axial gap between recess face 234 of inner hub 123
and bearing face 273. The entire load-reducing and load-normalizing
mechanism 120 is secured to the crank housing 42 by screw element
21 which places retainer 127 in compression and in contact with
crank housing underside surface 422 (FIG. 3) through its bearing
face 273 when threaded body 211 engages inner hub internal thread
235. Guiding diameter 230 of inner hub 123 is in tension.
[0103] Retainer 127 serves to offset outer race 126 from underside
surface 422 and situate said outer race within slot 501 such that
preferably only the outer diameter 261 contacts and rolls along
lateral side faces of slot 501, as the spreader arm 4 moves along
rack bar 5 through the rotation of pinion mechanism 6. Cylindrical
pins 259 rotate about their axis and roll as a cluster between
inner race 237 of non-rotating inner hub 123 and inner diameter 264
of rotating outer race 126. F.sub.BRG is transferred from spreader
arm 3, more precisely lateral face of slot 501 of rack 5, to outer
race 126, to cylindrical pins 259, to inner race 237, and to crank
housing 42 of spreader arm 4 through retainer 127 clamped by
threaded interface between screw element 21 and inner hub 123.
[0104] Inner hub 123 is preferably configured with a hollow center
to provide internal thread 235 for engagement with screw element
21, to provide a passage to cylindrical pins 259 for cleaning
fluid, and to provide a hex drive socket 213 for fastening
purposes, preferably manufactured through a broaching
operation.
[0105] Subsequent to use in surgery, a flushing or cleaning
solution may be injected through the center of inner hub 123,
preferably with a standard syringe whose needle tip has been
removed, and that interfaces with countersink surface 215. The
solution then passes radially outwards through a series of radial
passages 240 where it enters the plenum created between inner hub
123 and outer race 126, which houses the cylindrical pins 259. The
cleaning solution is capable of circulating freely between any
circumferential space between said pins. While injecting cleaning
solution through the center of inner hub 123, the outer race 126
can also be rotated with the other hand to set the bearing rolling
elements into motion and assist in dislodging any blood products or
other contaminants to be flushed. The cleaning solution is
channeled through mechanism 120 via the following series of
passages: the axial gap 267 resulting between the height of pins
259 and the assembled dimension between retainer flange 274 and hub
flange 239; the axial gap 266 resulting between the axial stepped
width 262 of bearing outer race 126 and the assembled dimension
between retainer flange 274 and inner hub flange 239; annular gap
265 and 268 resulting from inner recess diameter 263 of outer race
126 and retainer flange diameter 271 or hub flange diameter
238.
[0106] This results in the load-reducing and load-normalizing
mechanism 120 in the nature of a needle bearing, capable of being
flushed from blood product or other contaminants prior to
sterilization without having to disassemble any of the constituent
components.
[0107] The material of components comprising the load-reducing and
load normalizing mechanisms 20 and 120, is preferably stainless
steel, or other non-oxidizing, non-corroding materials when exposed
to the environments of surgery, sterilization and the like. If a
stainless steel material is selected, one with a tempering
temperature above the range of temperatures seen during steam
sterilization or dry heat sterilization cycles is preferable to
avoid embrittlement of the component material.
[0108] FIG. 7 illustrates a third embodiment according to this
invention. The rack bar 5 and pinion mechanism 6 (not shown) are
the same as in the previous embodiment and are combined here with a
movable spreader arm 41. A load-reducing and load-normalizing
mechanism 121 is comprised of a sliding member 25 which replaces
the rolling element bearing system in the first and second
embodiments. The underside of the crank housing 43 is configured
with a protruding key feature 423, which can be integral with the
retractor arm or demountable. The key feature 423 preferably
consists of a depending member which is substantially transversely
disposed with respect to spreader arm 41 and has a web portion 423a
and flange portion 423b to form a substantially T-shaped
cross-section. The flange portion 423b defines two longitudinally
disposed lips 424a, 424b extending opposite one another from the
web portion 423a. Two corresponding components 252, 253 of sliding
member 25 are provided, each being configured with a backface slot
251 which mates with substantially half the outer profile of key
feature 423. Namely, each of the components 252, 253 mates with a
longitudinal face of web portion 423a and one of lips 424a, 424b.
When assembled onto key feature 423, the outside profile of the
components 252, 253 mates in sliding engagement with slot 501 in
the rack bar, which in this embodiment acts like a keyseat
slot.
[0109] When inserted into slot 501, the two components 252, 253 of
sliding member 25 are restrained transversally by said slot, and
are also retained axially relative to key feature 423 through their
engagement of backface slot 251. Consequently, the sliding member
25 moves together with the retractor arm 41 relative to rack bar 5
within slot 501, to provide for substantially frictionless sliding
motion and deployment of the retractor.
[0110] With most retractors being fabricated in stainless steel,
the material of the sliding member 25 is preferably teflon,
plastic, polymer, or any other material well-suited to mate with
the retractor material to provide a substantially frictionless
translation of one retractor arm relative to the rack and to the
other retractor arm. With lightweight aluminum retractors, the
sliding member 25 not only reduces sliding friction, but also acts
as a wear-resistant bushing to prevent wear between sliding
aluminum parts. If the material of sliding member 25 cannot be
sterilized, it must be replaced after every surgery.
[0111] If the sliding member 25 is fabricated with a process
similar to plastic injection, the two halves can be joined through
a flexible hinge arrangement, preferably along one of the backface
perimeter lengths 252. This would enable the two halves to be
angularly opened relative to each other, fitted and then closed
over key feature 423 with contact along perimeter 252.
[0112] In this third embodiment, feature 423 covered by sliding
member 25 forms a T-shaped key which slides within a T-shaped
keyseat slot 501 in the rack bar 5. Other variations of key and
keyslot geometry are possible which do not depart from the spirit
of this invention, such as: L-shape, dovetail, firtree and others
apparent to those skilled in this art.
[0113] FIG. 8 illustrates a fourth embodiment according to the
present invention. In order to reduce the friction force
Ff.sub.PINION, and consequently the force F.sub.SURGEON and torque
M.sub.SURGEON the surgeon must apply at the crank handle 641, a
friction-reducing member 631 is introduced as part of the pinion
mechanism 16.
[0114] In a first configuration of this fourth embodiment, feature
631 is a substantially cylindrical sleeve which is press-fit
(interference fit) onto pinion member 632. With the rotation of the
crank 641, the outer surface of sleeve feature 631 rotates as it
slides relative to the rack tooth 511 surface. The material of the
sleeve is either teflon, plastic, polymer, or any other material
well-suited to provide substantially frictionless movement of the
pinion relative to the rack. The sleeve tends not only to reduce
friction between the pinion member 632 and the rack tooth 511, but
also to reduce the wear at this interface. In most prior art
retractors, the pinion member and rack tooth are made of similar
materials, which is not ideal for minimizing wear. The sleeve can
also be replaced by a friction-reducing and wear-reducing coating
of dissimilar material properties to the rack tooth, like a plasma
coating or ion implantation coating. The spacing 521 between rack
teeth 511 may be modified accordingly to account for introduction
of sleeve feature 631.
[0115] In an alternative configuration of this fourth embodiment,
friction-reducing member 631 can act as a journal element. Journal
element 631 is assembled onto pinion member 632 with a loose fit.
With the rotation of the crank 641, the inner surface of journal
element 631 slides and rotates relative to the outer surface of
pinion member 632, and the outer surface of journal element 631
rolls on the surface of rack tooth 511. The friction-reducing
member 631 in the nature of a journal element can also be replaced
by a more conventional needle bearing or other bearing types as
illustrated in FIG. 4.
[0116] In both these configurations of the fourth embodiment, the
friction-reducing member 631 preferably lends itself to repeated
sterilization, or it must be replaced after every surgery or at
limited intervals.
[0117] FIG. 9 illustrates the fifth embodiment according to this
invention. In order to reduce the friction force Ff.sub.CRANK, and
consequently the force F.sub.SURGEON and torque M.sub.SURGEON the
surgeon must apply at the crank handle 642, a friction-reducing
member 613 is introduced to act between the pinion journal 612 and
counterbore recess 463 of crank housing 44. In the first
configuration of this embodiment, the friction-reducing member 613
is a ball bearing which can either be press-fit on the outer
diameter of the top pinion journal 612 to form an insertable
assembly with the pinion mechanism 116, or press-fit on the inner
diameter of a counterbore recess 463 to form an assembly with the
crank housing 44. Other bearing types as illustrated in FIG. 4 can
also be used in place of the ball bearing friction-reducing member
613.
[0118] In an alternative configuration of this fifth embodiment,
the friction-reducing member can be a cylindrical sleeve or journal
element (not shown) that is preferably assembled with at least one
loose fit, either with the pinion journal 612, the counterbore
recess 463 or the bore diameter in crank housing 44. The
friction-reducing member in the nature of a journal element may be
made of low-friction material compatible with the material of
pinion mechanism, preferably teflon, plastic, or a polymer
material. Rotation of the crank 642 is easier and smoother (lower
F.sub.SURGEON and M.sub.SURGEON) due to the substantially
frictionless rotational slip interface resulting between the
journal element and 612, between the journal element and the bore
diameter in crank housing 44 or between the journal element and
counterbore recess 463.
[0119] Similarly, a second friction-reducing member 613 can also be
incorporated between the bottom pinion journal 622 and the bore
diameter in crank housing 44. The friction-reducing member 613 acts
not only to reduce friction between a portion of the pinion
mechanism 116 and the crank housing 44, but also to reduce the wear
at this interface.
[0120] FIGS. 10A to 10D illustrate the sixth embodiment according
to this invention, which seeks to improve the deployment of chest
retractors by providing a locking mechanism 90, 91, or 92 capable
of achieving a substantially stable open retractor position,
throughout the entire variable range of open retractor arm
positions.
[0121] The pinion mechanism 9 usually consists of two pinion
members 634 which engage the rack teeth 512 in a variety of
orientations depending on the rotation of crank 643 of the pinion
mechanism. A substantially stable orientation results when both
pinion members 634 are longitudinally aligned and engaged within
rack teeth 512. A substantially unstable position results when only
one pinion member 634 is engaged with the rack teeth 512, with the
most unstable position occurring when both pinion members 634 are
transversally aligned relative to rack bar, and only the top pinion
member is in contact with the rack teeth (similarly illustrated by
pinion member 63 in FIG. 2B). Consequently, along the length of the
rack bar 55, there exists discrete settings of retractor arms which
are substantially stable, interspersed with relative settings that
are substantially unstable. An open retractor usually has a
tendency to close slightly from a substantially unstable position
to attain the closest substantially stable position.
[0122] The present invention provides a retractor that is capable
of locking the retractor arms in any desired open position, and
does not rely on the discrete orientation of pinion mechanism 9
relative to the rack teeth 512 to achieve stability.
[0123] In the first configuration of this sixth embodiment as
illustrated in FIGS. 10A and 10B, the locking mechanism 90 is
comprised of a cam lock feature 644. While the retractor is being
deployed by the rotation of the crank 643, said crank forms a
minimum non-locking angle .theta..sub.NL relative to the top
surface of crank housing 45 (FIG. 10B), to provide clearance for
the surgeon's or assistant's hand and fingers during cranking. Once
the desired open position of retractor arms 3 and 4 is achieved,
the crank 643 is stowed by pivoting it downward through the angle
.theta..sub.NL thereby engaging the cam lock feature 644. The cam
lock feature 644 imposes a compressive force F.sub.COMP acting on
the top surface of the crank housing 45, and reacted on the bottom
surface of the rack tooth 512 by the bottom pinion journal 623.
This motion locks the pinion mechanism relative to the rack, and
consequently the two retractor arms in the desired open
position.
[0124] FIG. 10C illustrates a variant to this sixth embodiment
whereby the locking mechanism 91 is comprised of a cam lock 646 and
a hydraulic sleeve feature 910. The pivoting of the crank 645
through angle .theta..sub.NL (as similarly illustrated in FIG. 10B)
results in a force F.sub.COMP acting on the top surface of the
hydraulic sleeve feature 910, which consequently causes an
expansion of the outer diameter and a contraction of the inner
diameter of the said hydraulic sleeve. A tight fit results between
the hydraulic sleeve 910, the top pinion journal 615, and the
counterbore recess 491 in the crank housing 46. This motion locks
the pinion mechanism relative to the rack, and consequently the two
retractor arms, in the desired open position.
[0125] FIG. 10D illustrates a variant of this sixth embodiment
where the locking mechanism 92 is comprised of a cam lock feature
648 and a wedge feature 626 on bottom journal pinion 625. The
pivoting of the crank 647 through angle .theta..sub.NL (as
similarly illustrated in FIG. 10B) results in the reaction of
F.sub.COMP through the wedge feature 626 and the tapered recess 471
in the crank housing 47.
[0126] Alternatively, this wedge principle can be applied between
the top pinion journal 616 and a tapered recess in crank housing
47.
[0127] As well, the wedge principle can be applied between the
pinion member 636 and the sides of rack teeth 514, whereby both
these features are substantially tapered in profile to achieve a
wedging action between them once cam lock feature 648 is
deployed.
[0128] FIG. 11A-11B illustrates a seventh embodiment of this
invention, whereby the principles of the first, second, and third
embodiments are applied to existing retractors as retrofit designs.
The load-reducing and load-normalizing mechanism 122 is comprised
of at least one rolling element bearing 29. In this example, two
bearings 29 are each assembled in slots 482 in the crank housing 48
by a screw element 292 and nut element 291, and at least one
sliding member 293 which is also inserted in a slot 485 or sits in
a recess within slot 483. Once assembled, the outer race of the
bearing 29 and the sliding member 293 extend inwardly into slot
483, and contact respectively with the top of rack bar 58 and rack
teeth 515 when said rack is inserted and slides through said slot.
As the retractor arm 114 moves relative to the rack bar 58, the
rolling of bearings 29 and low-friction slipping at interface with
sliding member 293 results in the friction force Ff.sub.SLIDER
being substantially reduced.
[0129] Rolling element bearing 29 can also be replaced by
variations as illustrated in FIGS. 4A-4I without departing from the
spirit of this embodiment. Bearing 29 can also be replaced with a
journal sleeve.
[0130] With most retractors being fabricated in stainless steel,
the sliding member 293 material is preferably a teflon, plastic,
polymer, or any other material well-suited to mate with retractor
material to provide substantially frictionless translation of one
retractor arm relative to the rack and other retractor arm.
[0131] The remaining FIGS. 12A to 12C, 13A, 13B, 14A to 14D, and
15A, 15B illustrate the eighth embodiment according to the present
invention. As already illustrated in FIG. 2A, the arcuate blades 7
and 8 of the sternum retractor 1 are advantageously configured with
a curvature that tends to minimize the trauma, tearing and
excessive retraction of the thoracic structure (labelled "TS" in
FIG. 13B) at the extremities of the incision (for instance the
topmost extremity thereof labelled "TEI"), for a given desired
opening at the mid-length location along the incision where the
surgical intervention will most likely be performed.
[0132] For the purposes of this present invention, the
cylindrical-like configuration is defined as the anatomical
configuration of the patient's thoracic structure when the ribcage
halves are in integral contact at the sternum prior to a midline
sternotomy incision, or immediately adjacent one another after the
sternotomy incision and prior to retraction. In both instances, the
ribcage is engaged with the patient's spine. After the sternotomy
incision, the cylindrical-like configuration implies that the two
halves of the incised sternum remain in close proximity,
substantially parallel to one another along the incision and
substantially in the same orientation with respect to one another
as they were prior to the sternotomy incision.
[0133] FIG. 2A shows an anterior aspect of the retracted thoracic
structure exposing the coronary organs. FIGS. 12A to 12C and FIG.
15A illustrate the engagement of the patient's thoracic structure
with the sternum retractor 1, in cylindrical-like configuration,
prior to retraction. FIGS. 13A to 13B and FIG. 15B illustrate the
engagement of the patient's thoracic structure with the sternum
retractor 1, in barrel-like configuration, after retraction. The
pinion mechanism 6, the screw elements 21, and part of the rack bar
are not shown in these figures.
[0134] As seen from above in FIGS. 12A, 13A and 14A, the arcuate
blades 7,8 and arcuate retractor spreader arms 3,4 are defined by
radius R1 in a plane P1 (FIG. 12B) through the innermost portion of
facing blades 7 and 8, and by a radius R2 in plane P2 (FIG. 12B)
defining the longitudinal centreline of arcuate rails 70 and 80.
Preferably, but not necessarily, the center of R1 and R2 are on the
same axis of revolution defining their curvature. These radii R1
and R2 are related to the overall length L1 of the spreader arm.
Proportional scaling of these dimensions can take place for smaller
and larger retractors as a function of L1. The arcuate
circumferential length ARC1 (FIG. 14A) of blades 7 and 8 can also
be varied proportionally for a constant R1, R2 and a given spreader
arm length L1, if shorter blades are desired as thoracic structure
engaging members, for instance.
[0135] Blades 7 and 8 are in contact at their free terminal ends
when the retractor is closed, as at contact points 79, 89. Contact
points 79 and 89 lie on plane P1 (FIG. 12B). At the closest
location to the rack bar 5, a gap G8 (FIG. 12A) between the blades
7 and 8 results. This achieves a rounded bowed profile in plane P1.
In other words, the blades 7, 8 being are in contact with one
another at contact points 79, 89, then progressively extend apart
from one another to a maximum gap G7 as rack bar 5 is approached,
and finally resume their convergence at the closest location to
rack bar 5, forming gap G8. This configuration tends to facilitate
insertion of the said retractor, more specifically the said blades,
by inserting the portion of the blades 7 and 8 which are in contact
into the base of the sternotomy incision closest to the abdomen,
and then by longitudinally sliding the retractor towards the top of
the sternotomy incision towards the patient's head with blades 7
and 8 engaged with opposing halves of the sternum and thoracic
structure. This motion progressively moves the sternal halves apart
to create the maximum opening G7 at approximately the mid-length
location along the incision prior to mechanical retraction of the
retractor. This mid-length location along the incision is also
usually the location where the maximum retraction of the thoracic
structure is preferably sought for exposure during surgery, and
also where the maximum barrelling of the thoracic structure is
likely to occur, as explained below.
[0136] FIG. 12B is a sectional view through the sternum retractor 1
and patient's thoracic structure at section line 12B-12B of FIG.
12A. The coronary organs are not shown. The sternum retractor 1 is
inserted into the sternotomy incision but is not yet retracted. Gap
G7 illustrates the slight spacing between the blades at this
section location, resulting by virtue of the engagement of concave
surface 73 and 83 of arcuate blades 7 and 8 with the sternal halves
of the thoracic structure.
[0137] Prior to retracting, the thoracic structure is still in its
cylindrical-like configuration; that is, both halves of the incised
sternum are disposed substantially parallel to one another along
the sternotomy incision. The two halves of the thoracic structure
substantially maintain their anatomical orientations with respect
to each other except for the lateral widening of the sternum
halves, to a varying degree along the arcuate blades 7 and 8, which
occurs subsequent to sternum retractor 1 being engaged with the
thoracic structure. At this point, the top surface of the thoracic
structure, on either half of the sternotomy incision, contacts the
substantially planar underside surface 72 and 82 of the retractor
spreader arms 3 and 4 (FIG. 12B). At the location closest to the
sternotomy incision, this top surface of the patient's thoracic
structure is in substantially parallel orientation with said
underside surfaces 72 and 82.
[0138] The foregoing is further illustrated in FIG. 15A, which is a
partially sectional view through the patient's thoracic structure
with the sternum retractor 1 engaged. The view is at section plane
15A-15A (FIG. 12A), which is located just left of the spreader arm
4 and perpendicular to the bisector of arcuate circumferential
length ARC1. The patient's thoracic structure is in its
cylindrical-like configuration and the top surface of the thoracic
structure is in substantial contact with the planar underside
surface 82 of spreader arm 4. The thoracic structure is
schematically represented with sectioned ribs (labelled SR). This
example illustrates that the thoracic structure is not in contact
with the surfaces 71 and 81 of blades 7 and 8 that are adjacent the
free longitudinal edges thereof. The degree of non-contact with the
extension portions 71 and 81 will depend on a patient's specific
anatomy and size of retractor selected. In this example, the
sternum retractor is illustrated to engage with the sternum
adjacent to rib nos. 2, 3, 4, and 5 (anatomical numbering). The
sternum retractor can be placed longitudinally along the sternotomy
incision to engage adjacent to other ribs, such as rib nos. 3 to 6
(anatomical numbering) for instance.
[0139] FIGS. 14B to 14D illustrate sectional views along the
arcuate spreader arm 4, through the portion of the spreader arm
which is configured with an underlying blade 8. The arcuate
portions of opposing spreader arm 3 and blade 7 are preferably
mirror image configurations of arcuate portions of spreader arm 4
and blade 8 about a plane normal to the longitudinal axis of rack
bar 5. FIG. 14B is the sectional view along 14B-14B (FIG. 14A),
which is adjacent the mid-arc length of the blade 8. This section
through blade 8 is preferably defined by a radius R11 and two
extensions L31 and L32. Each extension commences generally tangent
to R11 and divergently extends away from the center of R11
resulting in an angle .theta..sub.1 between said extensions. The
first extension L31 defines a portion of the arcuate spreader arm 4
containing arcuate rail 80. The other extension L32 defines a
portion of blade 8 which depends furthest away from the spreader
arm and comprises a portion of the free longitudinal edge of the
blade. The extensions L31 and L32 are preferably 0.6 to 0.8 times
as long as radius R11. This defines the profile of the concave
surface 83 at section 14B-14B.
[0140] The profile of the convex surface 84 (and similarly 74) is
defined by offsetting the concave profile 831 by thickness t for
uniform thickness blades. Alternatively, the blade thickness can be
variable from the extending-most portion of the blade to the
portion of the blade joining the spreader arm 4. The concave
surface 83 of the blade 8 yields a concave profile 831, 832, 833
when sectioned respectively at locations 14B-14B, 14C-14C, and
14D-14D. Concave surface 83 also yields a concave profile at any
other section therebetween. The convex surface 84 of the blade 8
yields a convex profile 841, 842, 843 when sectioned respectively
at locations 14B-14B, 14C-14C, 14D-14D. Convex surface 84 yields a
convex profile at any other section therebetween.
[0141] FIGS. 14C and 14D are sectional views adjacent the
longitudinal extremities of blade 8. These sections are defined by
R12 and R13, where R12 and R13 are preferably equal to R11 or more
preferably slightly larger than R11 (1.1 to 1.2 times R11). They
are also defined by .theta..sub.2 and .theta..sub.3 between
extensions L41 and L42, and L51 and L52, respectively, and where
.theta..sub.2 and .theta..sub.3 are each larger than .theta..sub.1
by 5 to 10 degrees. The configuration of blade 8 at location
14C-14C and 14D-14D is preferably, but not necessarily, the
same.
[0142] The portions of the blade 8 which span section 14B-14B to
section 14C-14C, and which span section 14B-14B to section 14D-14D,
are defined by progressively larger R11, or progressively larger
.theta..sub.1, or both, to attain the blade profile of the
extremity locations. Preferably, this progression is achieved with
a smooth transition. This construction tends to result in the
extending-most portion of blade 8 being capable of conforming to a
substantially cylindrical surface defined by radius R19 (FIG. 15A),
where R19 is best defined in a plane P3 (not shown) which is normal
to plane P2, which contains section plane 15A-15A and which bisects
the arcuate circumferential length ARC1. A larger R19 results if
R12 and R13 are of a dimension closer to dimension R11, or if
angles .theta..sub.2 and .theta..sub.3 are closer in value to angle
.theta..sub.1. A smaller R19 results if R12 and R13 are of a
dimension greater than dimension R11, or if angle .theta..sub.2 and
.theta..sub.3 are larger in value than angle .theta..sub.1.
[0143] The smaller the value of R19, then the greater the
curvature, and the greater the barrelling effect imposed on the
sternal halves during retraction for a given linear blade length L2
shown in true view in FIG. 15A. The barrelling effect produces the
result that the middle portion of the incised sternum extends
upwardly and laterally outwardly more than the extremities of the
incised sternum relative to the cylindrical-like configuration of
the thoracic structure prior to retraction. This promotion of a
barrelling effect in the patient's thoracic structure during
retraction is expected to induce less trauma to the tissue
surrounding the sternotomy incision. First, as previously
explained, the midportions of the retractor blades 7, 8 are each
characterized by a free terminal edge which is disposed higher than
the corresponding edge of each of the terminal longitudinal
portions of the blades, such that the tissue and bone structure
adjacent the two endpoints of the incision will not be urged
upwardly to the same degree as the tissue and structure adjacent
the midpoint of the incision. Second, as previously explained, the
midportions of each of the retractor blades 7, 8 are further apart
than are the terminal longitudinal portions thereof at any stage of
retraction, such that the tissue and bone structure adjacent the
two endpoints of the incision will not be urged apart to the same
degree as the tissue and bone structure adjacent the midpoint of
the incision.
[0144] In a specific example of a chest retractor for patients with
a smaller size thorax, the preferred blade 8 (and by mirror image
similarity blade 7) and spreader arm 4 (and by mirror image
similarity arm 3) definition is as follows: L1=6.25 in., R1=5.875
in., R12=7.0 in., R3=6.625 in., R11=0.625 in., R12=0.680 in.,
.theta..sub.1=30 degrees, .theta..sub.2=37.5 degrees,
.theta..sub.3=36 degrees, L31=L41=L51=0.375 in., L32=0.500 in.,
L42=0.650 in., L52=0.595 in., R19=5.00 in., t=0.125 in, ARC1=30
degrees.
[0145] In another specific example of a chest retractor for
patients with a larger size thorax, the preferred blade 8 (and by
mirror image similarity blade 7) and spreader arm 4 (and by mirror
image similarity arm 3) definition is as follows: L1=8.625 in.,
R1=7.625 in., R2=8.75 in., R3=8.375 in., R1=0.625 in., R12=0.680
in., R13=0.645 in., .theta..sub.1=30 degrees, .theta..sub.2=38
degrees 35 minutes, .theta..sub.3=35 degrees, L31=L41=L51=0.375
in., L32=0.500 in., L42=0.700 in., L52=0.600 in., R19=8.125 in.,
t=0.125 in., ARC1=30 degrees.
[0146] In another specific example, R11 may be constant and equal
to R12 and R13, and R11 is revolved around the centerline of R3 by
an angle of revolution of 30 degrees, to define ARC1 of blade 8 at
a distance R1 (FIG. 14A) from the centerline of this revolution.
The value of .theta..sub.1 in this example progressively increases
by 8 degrees to the value of .theta..sub.2 and .theta..sub.3 from
section 14B-14B to the respective extremity sections 14C-14C and
14D-14D. This results in concave surface, like 83, and convex
surface, like 84, of blade 8. As illustrated in FIG. 12C through
section 14B-14B of FIG. 14A, both these convex and concave surfaces
of the blade 8 can be offset by approximately {fraction (1/8)} of
an inch to create a volume V.sub.BLADE, within which can be
configured the most preferred blade design according to the present
invention. Although the blade definition has been defined by R1,
R3, R11, R12, R13, ARC1, .theta..sub.1, .theta..sub.2 and
.theta..sub.3 with reference to a circular geometry, it can also be
defined by elliptical geometries or any other spline geometry
provided the resultant concave and convex surfaces have boundaries
that generally fall within the volume V.sub.BLADE.
[0147] As illustrated in FIG. 13B, when retracted the thoracic
structure is in substantial contact with the substantially conical
extension portions 71 and 81 of blades 7 and 8, and is
substantially free from contact with planar surface 72 and 82. This
is also illustrated in FIG. 15B, which is a section view through
the thoracic structure at location 15B-15B of FIG. 13A, just left
of spreader arm 4. As previously explained, the thoracic structure
assumes a barrel-like configuration (labelled "TS-BLC") with the
middle portion of the incised sternum extending more upward from
the surgical table (not shown) and more laterally outward than the
extremities of the incision, and also with respect to its
orientation and position when it assumed a cylindrical-like
configuration (labelled "TS-CLC" in FIG. 15A) prior to
retraction.
[0148] FIG. 15B illustrates a bend 49 in the retractor spreader arm
4 (and similarly in spreader arm 3 not shown) which is intended to
facilitate the conformance of sternum retractor arms 3 and 4 to the
retracted thoracic structure when in its barrel-like configuration.
Thus, in tending to keep rack bar 5 close to patient's abdomen, and
preferably in contact therewith, the ergonomics of the surgical
worksite are expected to see improvement since the rack bar 5 will
be generally positioned below the arcuate arms 3, 4 during
operation of the retractor. As well, the stability of the sternum
retractor relative to a patient's retracted thoracic structure
during the surgical procedure should also be enhanced since the
rack bar 5 will tend to maintain its contact with the patient's
abdomen throughout retraction. A typical bend range for angle
.theta..sub.4 is 15 to 20 degrees.
[0149] As the sternum retractor 1 retracts the patient's thoracic
structure, the thoracic structure is displaced from its
cylindrical-like configuration to its barrel-like configuration.
The sternal halves typically move in a fashion whereby the top
surface of the thoracic structure is in substantial contact with
the planar underside surface 72 and 82 of retractor arm 3 and 4 at
the start of retraction, to the substantial contact of the inside
surface of the thoracic structure with the substantially conical
extensions 71 and 81 of blades 7 and 8.
[0150] The sternum retractor in the embodiments of this invention
is preferably designed with totally re-usable components and with
assemblies that can be dismantled, if necessary, for ease of
sterilization. All components are manufactured in surgical grade
stainless steel, titanium or any other re-usable sterilizable
material approved for surgical use. However, any number of
components can also be made in disposable surgical grade plastics,
if the case for disposable components is warranted.
[0151] The above description of the preferred embodiments should
not be interpreted in any limiting manner since variations and
refinements are possible without departing from the spirit and
scope of the invention. For instance, while the sternum retractor
has been described herein as being comprised of a fixed retractor
arm and a movable retractor arm, those skilled in the art will
appreciate that the retractor may be provided with two movable arms
if desired.
* * * * *