CA2151555A1 - Sternal closure device - Google Patents

Abstract

A surgical device and method are disclosed for closing the sternum following a median sternotomy. Instead of using stainless steel wire or a flat steel band, a strand of flexible suture material is used which is compressible in its radial dimension, but which resists compression and seeks to return to its full diameter in an elastic manner when radially compressed. Despite its radial compressibility, the strand must also be strong and relatively inelastic in its longitudinal dimension. This combination of traits can be provided by a hollow tubular shape, a foam-type or other compressible outer layer surrounding an inelastic core, or other suitable design.
When not compressed, the sternal closure strand has a diameter slightly larger than the diameter of the needle used to emplace the strand in position around the sternal halves, between the ribs. After insertion, the expandable suture material will provide gentle pressure against the surrounding tissue, to minimize bleeding in the needle track. The soft suture material will also help cushion, distribute, and minimize the stresses and damage inflicted on the sternum or ribs during postoperative ambulation; this can provide major benefits, especially among elderly and infirmpatients who require open-chest surgery. An optional fastener device which provides additional advantages is also disclosed.

Description

2 i.~l555 SIERNAL CLOSURE DEVIOE
BACKGROUND OF THE INVENTION
This invention is in the fie]d of surgical devices. It relates to surgery on the heart or lungs, and to other tlloracic ~lv~dul~b that require opening of thesternum (the breast bone).
Most surgical ~v~dul~ imvolving the heart or lungs are performed through a rnidline sternal incision, widely referred to as a "median ~ vlv~y The breast bone is comprised of the smaller u~al~ubl;u~ u~iv~ly (which is locdted near the neck) and the la}ger sternum inferiorly; the composite bone structure is usually referred to as the sternum. After an incision is made thlrough the skin, the sternum is cut longitudinally using ~iali~d power saws. The cut extends the entire length of the sternum, from the sternal notch, at the neck, to the xiphoid (the srnall ~JIVLl ~ . of bone at the solar plexus).
This midline cut allows the two tlalves of the sternum and the anterior portion of the ribcage to be spread several inches apart, giving the surgeons access to the healrt and lungs. During surg~ry, the two halves of the sternum are held apart by lll~ ' '^Al retractors.
2 0 At the end of the surgery, the sternum must be closed, or vidllldl~d.~ In the vast majority of cases, surgeons use stainless steel wire closure devices. These closu]re devices alre composed of a thin stainless steel wire with a diameter of about 1-1.5 mrn, coupled to a curved needle. The composite device is formed by inserting one end of the stainless steel wire into a hollow cavity in the non ~ d end of the curved needle, and then crimping the hollow needle tightly to secure the wire to it.
When this closure device i~ passed to the surgeon by a sc rub nurse, the firee end of the stainless steel wir~ is usually controlled by seculring it with a small surgical clamp. The needle is used to pass the wire through the sternum 3 0 or around the sternal halves, betvveen the ribs, which connect to the sternal halves at roughly right angles. T~le path of each of the six wires used for a typical sternal closure is as follo~s: 1) around and behind the left sternal half (between the ribs at each level) alld 2) behind and up around the right sternal half (once again, between the ribs at each level). In the upper portion of the closure, where the manubrium portion of the sternal bone is relah~vely wide, the needle is usually pushed &a~ugh the bone. Below the l..a...ll,.;ul,., the needle is usually passed through "IJ~.;..t~lllal" hssue (i.e., tissue which surrounds the sternum) and usually does not penetrate the sternal bone except 5 when the sternum is excephonally wide.
After the wire is properly placed around the two sides using the needle, the needle is cut off and the wire is clamped at the cut end. This leaves a piece of wire that passes around arld bl~hind each of the sternal halves, with some excess wire attached to a clamp a~n each side of the sternum. This EJ.v~dul~ is 10 repeated unhl the desired number of wire segments (usually six) have been inserted into the peristernal hssu~ around the sternal halves. Each segment is usually posihioned between two ribs, so that the wire does not have to penetrate the bones which conshtute the ribs or the sternum (except at the wide manubrium).
After all of the wire segments have been properly ~UDiLiUll~d~ the clamps of each wire are .cf~q~ nh~lly picked up by the surgeon and the wires are twisted around each other to sec~lre them inihally. The ends are then trimmed, and the twisted junchures are twi~;ted again using a heavy needle driver, usually several more times, to create an extra-snug closure that will ensure that the sternal bones are pressed hghtly against each other to minimize bleeding and ensure proper fusing of the sternal halves into an intact sternum, to promote healing in a manner corrlparable to the healing of a broken bone.
Normally, the wire loops are left in place ~.u~ lly. Unless problems arise which require a second surgical operation to remove the wires, they remain in place for the remaindel of the pahent's life, even after the sternal halves have fused together again.
Despite their widespread use, stainless steel wires can be highly vbl~ l ic both during surgery, and afterward. The problems associated with stainless steel wire closure of the sternum include:
3 0 1. The free end of a sternal wire can stab a surgeon, assistant, or scrub nurse during preparation or applicahon. This problem is aggravated by the fact that the wire is typically cut usin~, a wire cutter with relahvely blunt blades,Li-~g a chiseled point that is typically quite sharp. To reduce the risk of stab wounds to surgeons and the~ir assistants (such wounds have become of - major concern since the onset of the AIDS epidemic), clamps are used to secure the free ends of any wires in the patient's chest. Such clamps clutter the operating field, especially near the end of an operation, when at least a doæn clamps will be attached to the six wire loops. The clamps are tedious and time-g to work with and arollnd, and even when they are properly attached to the wires, it is very c<)mmon for exposed wire tips (or the clamps themselves) to tear surgical gloves and/or cause stab wounds. Such clamps may even promote operator injury, by holding the stiff wire in a fixed and 10 unyielding position which the op~rator or assistants may brush against duringthe course of the operation. Thes-! sharp wire points and clamps expose the operating team to blood-borne diseases, including AIDS and hepatitis, and may break proper sterile technique anld expose the patient to infection. Kjaergard et al, "Accidental Injuries and Blood Exposure to Cardiothoracic Surgical Teams,"
European Joumal of Cardio-T1~on2cic Surgery 6: 215-217 (1992) reported that in a large study of cardiac surgical ~ ases, stab wounds and glove lacerations caused by steel wires during sternal closure l~ ' one of the most common causes of operator exposure to blood from a patient. Therefore, steel closure wires pose dangerous risl~s to cardiothoracic surgeons and their 2 0 assishnts, as well as to their patients.
2. The stiff, unyielding characteristic of stainless steel wire (compared to flexible plastics) make it unwieldy and difficult to manage in the operative field. After each wire is placed, t]ne segment that sits below the sternal halves may press down on the heart or coronary artery bypass grafts while the other 2 5 wires are being placed. Injury to these soft tissues can occur from these stiff wire segments during the norma] course of sternal closure, further endangering the patient.
3. The wires are smaller in diameter than the needles that are used to pass the wires through or around the sternal halves. Thus, bleeding (supplied 3 0 by the intercostal blood vessels or sternal marrow) oft~n occurs in the needle tracks (i.e., the tunnels which are made when a needle passes through tissue or bone), since the diameter of the ~ire is not sufficient to press out in a radialmanner to compress the small bl~!eding vessels. This results in ~ ly 21~155~
blood loss and visual obshruction of the operative field; occasionally, a return to the operating room becomes imp~rative to conhrol internal ll~.,..,..l, ~,;..g 4. r~,~,lv~laliv~ sh:ess on the closure loops may cause the thin wires to cut into and through the bone of the sternum. The result is further loosening ofthe sternal closure, which can lead to painful instability of the two sternâl halves, with ~ Jilaluly VIII~lVlllli~ and ultimately sternal d~ (i.e., complete separation of the sternal bones). Elderly patients or patients who havethin or highly porous bones (-,.,t~,~o u,is) are particularly :,us.~,lil,le to this complication. Instability of the sterrlal closure can also result in internal bleeding and can increase the risk of infection. E a second operation for sternal rewiring is required, it is made e~7en more difficult by the fact that the sternal halves are often sliced into many pieces by the st~inless steel wires.

5. Sternal wires occasionall~y break after an operation. Such breakage can be secondary to the thinning and d~r~ llalivll of the steel shrand by the excessive torsion shresses that are sl~m~hmf~s applied to the loops during routine closure (especially as the ~)perator h~7ists the two ends tighter to effect a more secure dlJ~JIvxilllaliul~ of the sternal halves). E a broken loop causes discomfort and/or prohrudes towi~rd or through the skin, a second surgical operation can be required to remove the wire.

6. For the rest of the patient's life, the stainless steel sternal wires interfere with any c~,ll.~uLeli~d axial tomography (CAT) or magnetic resonance imaging (MRI) scans of the chest. Unlike an X-ray, where steel loops generate clear and distinct images within a larger pichure, steel closure loops can disrupt the enffre image generated in a CAT or MRI scan.
Despite their obvious disadvantages, stainless steel closure wires are used in the uv~vvl~ g majority of the hundreds of thousands of median ~I~IIIVlVILIL::l pelrVlll~d each year As described below, at least two efforts have been made to create better tools or ~hniqll~c for sternal closure;
however, neither of these modifications has succeeded in displacing st~inless steel wires from their ~ lll position in achual practice.
One prior art effort to create an improved ste~nal closure device is described in US patent 4,730,615 (~ h~rlJ~n~l and Vasconcellos, 1988). This patent describes a flat band made of metal and coated with plastic, which 21 ,~ 5~
slides through a fastener device which was referred to in the '615 patent as a - buckle. The band contains protrulling serrations (~u~ alable to sawtooth ~Vj~Liulls which extend out from a flat surface) which interact in a ratcheting manner with an angled tang in the buckle. This allows the band to be pulled tight while the tang slides across the raised serrations. S~ ly, if tension is exerted which tries to expand c~r open the loop, the angled tang presses against the shoulder of a serratio~l, thereby ~.~v~"li~.~, the band from moving in the opposite direction. This holds the band in the tightened position.
This allall~ ll1 suffered from a fairly clear limitation: the sawtooth ~lVtlUDiVlls extending outward from the surface of the band can injure tissue orbone, as the band is being pulled through a patient's scernum or FPri~ n~
tissues. AL~VlVill~,ly, a modified closure device which avoided that specific problem is described in US patenlt 4,813,416 (Pollak and Blasnik 1989), which described a flat stainless ~cteel band with notches rather than serrations. The notches interact with bumps in a buckle device, to hold the band securely after it has been pulled tight. Except for the fact that they are made of steel, both of the foregoing devices are similar ~:o various plastic bands that are widely usedto bundle various types of merchcmdise, or to take up slack in electrical cords attached to hol.c~hA,I~I a~lia~ s.
2 0 These devices offer certain i~ v~ L over the standard sternal closure using wires; however, the~y suffer from various limitations which limit tlleir utility. For example, the flat shape of these bands results in relativelysharp side edges, which can slice into the Du~lvulldi-lg tissues or bone like a blade when they are pulled through a needle track, behind the needle. These edges, if ul-l~lul~ d, also have c.mci~lPrAhle potential to slice into the fingers of the operating surgeon or assist~mts. In addition, both devices are made of stiff, unyielding metal which, as ~ith stainless steel wires, makes these bands unwieldy and capable of inflicting injury to the soft tissues below the sternum during closure.
3 0 It is also known, fronl anec,dotal reports, that a number of cardiothoracicsurgeons (including the Applicant) have tested various woven tapes, such as Mersilene tape, which is somewhalt similar to a flattened shoe lace. Since this typ~ of tape i- relatively wide andl llat, lt helps ~ listribute the ~sses 21~1555 imposed on the sternal bone. As each loop is completed, the ends of the tape are usually tied together by hand.
In another field of prior art that is related only peripherally to sternal or other bone closures, various type~; of suture materials created for use in 5 suturing soft tissues have certain types of surface porosity, to ~ UUId~;~ thegrowth of cells into the suture strands. For example, US patent 4,034,763 (Frazier) teaches the use of sutur~s made of "woven or expanded" material in lig,....~ . joints or to repair Achilles tendons. The purposes of using "woven or expanded" material on the sur~ace of the suture is to allow ingrowth of 10 newly formed li~,d-~ . tissue:~ into the porous suture material. Such tissuescan Du~ and reirlforce ancl may eventually replace the holding action of the suture.
One type of suture described by Frazier is hollow, to allow ingrowth of tissue. Although radial compressibility is not taught or mPn~ionf~ by Frazier, 15 his hollow suture would appear to be radially compressible, due to its hollowtubular structure and to the flexil~ility of the material used to make it.
However, this type of suture doe~; not resist radial ~UIII,U~D~iUII to any ci~"~;ri~ ,...1 degree, and does not seek to return to its original diameter after ~U~ Da;U14 if someone flattens or ~UI11lUI~DD~ it, it simply stays flat, or 2 0 ~VI~ DD~d, like a piece of tubular cloth. Since these sutures do not try toreturn to their original diameter after compression, they would not provide a useful and gentle l_UUl~ DDiilg action to minimiæ bleeding, as provided by the sutures described herein.
Another type of suture material with a porous outer surface was described in US patent 4,880,002 (MacGregor). These sutures are made of an outer layer of p~lll.edl,le and compressible materia~ (to promote cell growth into the suture material in a manrler similar to the Frazier patent) DUllVUllllill~S
an inner l~l~lfUl~,illg strand. Due b~ their inbended use, which does not involve stemal closure in any way, the sulures taught by MacGregor must also be lon~ lin~lly elastic (i.e., they mllst be stretchable in the lon~ih~in~l direction). This lon~itll~lin~l stretchability would render them unsuibed for sternal closure use; as described below, stemal closure sutures must be 21~il5~5 . ~
sub-~n~ 1y inelastic in the lon~lib.rlinal dimensior4 to provide secure closure of sternal bones.
It should also be noted that sutures taught for other (non-sternal) purposes are much smaller im di~meter than the sternal closure strands 5 described herein. For example, M~acGregor teaches sutures which "typically"
have diameters of about l/20th cf a ~ t.. or less; the largest suture size mentioned by MacGregor is a USP size 2 suture, which has a diameter of about 0.6 mrn. Even that is too thin to ~Ise as a sternal closure strand, since it would pose a grave risk of wearing and cutting through the sternal bones of the 10 patient. By contrast, sternal closu~re strands preferably should have a thickness of at least about 2 mm.
The Applicant has created a sternal closure device and method which differ cllhc~nh~lly from any known items of prior art, and which offer a number of advantages not availal~le from the prior art The subject invention 15 uses a thin, flexible suture material which has a circular cross-section, such as a clear, soft plastic which is strong and inelastic in its longitudinal liLIle~
while ~ soft and compressible in its radial dimension. The suture remair s compressible in its radia]l dimension because of its hollow tubular shape; alternately, it can be composed of a radially compressible soft spongy 2 0 material, reinforced by a stronger material such as nylon fibers.
When not compressed, a sllture strand according to the current invention should have a diameter slightly larger than the diameter of the needle which is used to insert the suture through the sternal bone or ~.; ,~t ...al tissue. Unlike a stainl~ss steel wire or band, this suture material will 25 expand gently and outwardly in l~he radial direction after insertion, therebycreating gentle pressure agairlst tl~e tissue that surrounds the needle track. This causes the suture material to act ~LS a compress, to minimiæ bleeding in the needle track.
In addition, unlike a steel l~ire or band, this type of suture material will 3 0 help cushion4 distribute, and miniimiæ the torsion and other stresses that are inflicted on the stemal bones duriing normal post-operative ambulation. These advantages can be obtained with no loss of lon~ih~lir al strength by using 21~il55~
selected materials such as polyvillyl chloride, or by using an internal materialwith high tensile strength such aE; nylon to reinforce a soft material.
In addition to the advanta~es which arise from the selection and design of the suture material, this inven~ion also disdoses a fastener device which 5 provides additional advantages described below.
Au u~diu~E,ly, one object of this invention is to provide a sternal closure device which uses a strand of fle ~ible mate~ial which can be radially ~u...~ d and which is slightly thicker than the needle used to insert the strand through the sternal bone c~r ~el;D~elllal tissue, so that after insertion, the material will expand gently and ]?rovide mild pressure against the ~UIIUUIIIIillg tissue, to minimize bleeding.
Another object of this invention is to provide sternal closure suture material having a relatively thick and preferably round cross-section which does not have any thin or squared edges or thin-diameter cross-sections, which therefore evenly distributes stresses and ~ injury to bone or tissue surfaces that contact the suture materia~.
A third object of this inverltion is to disclose a sternal suture fastener device which offers an improved gripping ~ulll~ullelll for securing the suture material.
These and other advantages will become apparent from the following summary and detailed descriptio]- of the invention and from the a..ulllpallying drawings.
SUMM~R'I~ OF THE INVENTION
A surgical device and metllod are disclosed for closing the sternum following a median b~e...o~u...y. Irlstead of using stainless steel wire or a flat steel band, a strand of flexible sul~ure materiall is used which is compressible in its radial diullelL~;ul4 but which r~sists culll~le~;ull and seeks to return to its full diameter in an elastic mannel when radially ~ le~d. Despite its radial 30 compressibility, the strand must a~lso be strong and relatively inelastic in its lon~itu~inal dimension. This combination of traits can be provided by a hollow tubular shape, a foam-type or other compressible outer layer surrounding an inelastic core, or other suitable design. When not ~ulll~le~ed~ the sternal 2~.51~
-closure strand has a diameter sLighLLy larger than the diameter of the needle used to emplace the strand in po<;ition around the sternal halves, between the ribs. After insertion, the expandal~le subure materiaL will provide gentle pressure 2gainst the ~u~lvullvLi~ tissue, to minimize bleeding in the needle track. The soft suture material will aLso help cushion, distribute, and minimizethe sbresses and damage irlfLicted on the sternum or ribs during puc.lvlu~l~liveambulation; this can provide major benefits, especiaLly among elderly and infirm patients who require open-chest surgery. An optional fastener clevice which provides additional advan~ages is also disclosed.

BRIEF DESCa~[PllON OF THE FIGUF~ES
FIGURE I depicts the flexible strand of this invention coupled to a curved needle at one end, and to a securing device at the other end.
FIGUF~ES 2, 3, and 4 depict ~hree types of radially compressible subure materiaL.
FIGUF~E 5 is a cross-sectiollal side view of a fastener device in the open position, showing a suture (in crc)ss-section) passing through an orifice in thefastener.
FIGURE 6 is a cross-sectiollal side view of a fastener in the closed 2 0 position, showing the suture stra]ld crimped and held securely in place.
FIGURE 7 is a different sicLe view of a fastener device in an open position, showing two extendible fixation prongs which will secure the fastener in the soft tissues adjacent to the sternum and prevent migration of the subure and fastener around the sternum.
FIGURE 8 is a side view oE a fastener device in the closed position, showing the fixation prongs in the extended position.
FIGURE 9 is a ~l~ e~live view of the cylinder and base of the fastener dev*e.
FIGURE 10 depicts a need]e, subure, and fastener assembly enclosed within a sterile package.
FIGURE 11 depicts the sublre strands of this invention emplaced around a sternum.
_g_ 21 5155~
~'IION OF THE I'IW~kI~IWL~ EMBOD~ENTYi Referring to the drawings, number 10 in Fig. 1 refers to a sternal closure assembly ~UIII~ ;III7 a curved needle 12, a compressible suture strand 20, and A suture strand fastener device 3~. This assembly can be used to close the 5 sternum following a median Dt~IIIuI~IIII.y. It ccm also be used following any other type of thoracic operation ~hich involves cutting the sternal bone into two or more divided segments, or to repair a sternum which has been broken due to accidental injury or other ,causes.
The curved needle 12 can Ibe a conventional sternal needle, wllich 10 typically has a semi-circular shape, made of suitably hard metal alloy such as stainless steel. CoI~v~ al stern~al needles have a blIdl~ ed proximal end 14 and a hollowed-out tubular struc~ure 16 at the distal end which allows . ~1..1.,.,~1 to the suture material. In prior art needles attached to stainless steel wires, the cylindrical wall of the tubular structure 16 is crimped around the 15 wire, as described in the Background section. Such needles can be readily adapted to this invention by inselrting one end of the suture strand 20 into tubular end 16, and crimping the tubular end 16 around the flexible strand. The needle diameter, typically about 1.25 ~..illi,...-l. . ~ (mm) for conventional sternal closures, should be ci~nifi~Hn~ly smaller than the diameter of the suture strand2 0 when the suture is relaxed and f~llly expanded. A suitable suture material, when relaxed, should have a diameter in the range of about 2 to about 3 mm if used with a 1.25 mm needle.
The Hl~ of suture strand 20 to needle 12 does not need to be excessively strong; it comes into play on~y after the needle has been pushed 2 5 through the bone or tissue, as the needle pulls the strand through the needle track. The needle will be cut off after the loop has been created, so the mode of ,.11-.1".,~.,1 of the suture strand 20 to needle 12 will have no bearing on whathappens after an operation is corrlpleted. A~ lbly, any suitable c ~
means, such as biocompatible glue, can be used. Alternately, if a suture 30 material is used which has a flexible coating DUI~UII lillg a l~ Ul~illg strand, the porous coating can be strippe,d off of a short length of the I~ iIIg strand, and the I~ , strand can be passed through the eye of a needle.

21315~
. ~
The suture strand 20 is made of a radially compressible material. This feature allows the suture materia]~ to pass through the narrow needle track caused by passage of the narrow~r sternal needle. The suture material thereby expands slightly in the track afte]- placement. This creates gentle pressure 5 against the tissue which surrouncls the needle track. This gentle pressure ...;,.;,..:"-~ bleeding, in a manner similar to a compress or tamponade. By contrast, when stainless steel wir~s are used for sternal closure, the wire is smaller in diameter than the neeclle which made the hole. Therefore, any bleeding source which the needle passed through remains free to bleed; unlike 10 the sutures of the subject inventic~n, steel wires do nothing to help suppress or control such bleeding.
Despite its radial compressibility, the suture must have a high level of lon~it~ inAl strength, and a relatively low level of longitudinal yield; it mustnot stretch a substantial amount ~hen subjected to tensile forces of the 15 m~g,nih1de that are generated du]ing post-operative ambulation. Otherwise, itwould not be able to hold the tw,~ halves of the stemum tightly enough to promote proper healing of the bone. Any slippage of the two bone segments relative to each other when they ;~re in a state of partial healing would act, in effect, as a new break in the bone; it would delay and prolong the healing 20 process, and it could lead to miP~ nmqnt of the sternal halves when they fuse together again. This ~ Ui~ a~J~R~ ly is the primary reason why stainless steel wires are used in tlle vast majority of sternal closures. Steel wires suffer from numerous problems, but they have one thing in their favor: they will not stretch lon~ 1inAlly during post-operative ambulation. That factor 25 a~,~R.~.,lly has been sufficient to ensure their widespread use despite their dangers and disadvantages.
However, several other tyE~es of material can be used to provide sternal sutures having a desired level of flexibility and radial compressibility withoutFq-rif~ in~ longitudinal strength, iif they are properly designed. For example, a 30 hollow tube 100, shown in FIG. 2, made of polyvinyl chloride or other flexible plastic and having an external di~lmeter in the range of about 2 to 3 mm can be used. Alternately, a pliable material 110 having a moderately dense foam structure can be coated onto the c~utside of an internal single- or multi-filament 21~555 strand of material 112 such as nylon or polypropylene, as shown in FIG. 3. As another alternative, a hollow ~ tube 120 can be provided by strands of strong fibers 122, such as nyloll, woven in a manner ~ulll~al ' l~ to the external shielding in a coaxial cal~le or a reinforced hose; these Itil~..il~, strands 122 can be impregnated ~vith, or coated by, a second material 124 having foam-like or other flexible ~llala~L~ lics~ as shown in FIG. 4. In a similar fashion, the wall of the hollow soft plastic tube shown in FIG. 2 can besupported by nylon or other l~iluru..il.g strands as demonstrated in FIG. 4 to improve lon~ihldin-l strength. Tlle ~. l llm~ inn of blood or other tissue inside 10 these tubular structures is unlikely since in practice they will be closed at both ends by the method of their application.
These a~lua~ can be used to create sutures which will not stretch or yield significantly in the longitudinal direction, but which are radially compressible. It is also likely thal similar results could be achieved using 15 specially designed polymers having controlled molecular structures whidh can be stretched or ~u.~ d in one direction but not the other; however, the designs discussed above can be carried out using relatively i~ ive shrting materials.
A numerical value for the acceptable limits of lon~ihldin~l yield (which 20 can be expressed as a modulus Olr elasticity) can be generated, if desired, by evaluating materials such as Mer.~ilene tape, which has sufficiently low elasticity to render it useful for slernal closure. To provide an d~ ..ation, itis anffcipated that suture material which stretches less than about 2 to 3 percent (i.e., less than about 2 or 3 mm per 10 cm length) when subjected to a 5 2 5 kilogram load is sufficiently inelzlstic to render it suitable for use as described herein.
Various flexible l,;o~ alible materials have been developed which are good ~ in~ ~c for use as sternal closure sutures as described herein. Non-absorbable materials indude plastics such as polyvimyl chloride amd other 3 0 polymers, and fabrics sold under trademarks such as DACRON and GORETEX.
It may also be possible, in some ]~atients, to use absorbable sutures, if they provide sufficient tensile strength for a sufficient period of time (these traits ~vill depend on suture diameter zLs well as the material used) to allow the 2~155~
sternal halves to uv~ t ly heal and close together by I~Lllbli~
pc~lllldll~ bone sbructure. Cdndidate materials which are currently used as absorbable sutures include polyg.llactin (sold under brademarks such as VICRYL) and polyglycolic acid (sold under brademarks such as DEXON).
During sternal closure, near bhe complebion of open-chest surgery, a needle 12 attached to a suture sbrand 20 is passed bhrough or around bhe sternal halves, drawing the sutur~ sbrand 20 into posibion. Under routine , bhe needle inibiall~ penebrates bhe anterior chest wall either through or around bhe left side Ol~ bhe sternum, between each set of ribs as they approach the sternum at roughly right angles. It emerges beneath bhe left sternal half into bhe midline incision which was used to separate left and rightsternal halves. It is bhen passed bluough below and around bhe right side of bhesternum, and it emerges on the right side of the sternum where it exits the chest wall.
The round cross-secbion and the compressibility of a suture sbrand 20 will help it pass smoobhly and abrAl~m~it Ally bhrough ~-; ~ lldl bissue, and bhrough any bone which is ~ LI 1 To make inserbion even easier, the suture sbrand (or selected suture ~sbrands, such as specific sbrands which will pass through bhe llla~.u~l;u..l) call be lubricated by a low-friction coabing such 2 0 as polytebrafluoroebhylene (PTFE, sold under bhe brademark TEFLON) or by a biologically absorbable gel or fluid which would funcbion as a lubricant. Such suture coabings are taught in, for example, US patent 3,187,752 (Glick).
After bhe inibial pldu~ lll is completed for all of the suture sbrands, the operative team usually checks tht! underside of each sternal half to see how 25 much bleeding is coming bhroug~l bhe suture holes. Wibh stainless steel wires, there typically are multiple bleeding sources including intercostdl or internal mammary arteries and veins and sternal marrow. Since steel wires are smaller in diameter bhan the needles usetl to place bhem~ any bissue which is bleeding due to needle damage remains fr2e to bleed unbil clot formabion ~v~lllually 30 stops the bleeding or other meastlres are taken by bhe surgeon to stop bhe bleeding. By conbrast, in the subj~ct invenbion, bhe tubular suture has a largerdiameter than the needle, and ex]E~ands against the bissue which surrounds the needle brack. This ~Ulllpl~DSt~ an~l tamponades any bleeding source.

21~15~5 It should also be noted that the tubular sutures used herein do not have relatively sharp side edges, whicll are a problem with steel bands having flat cross-sections, disclosed in US patents 4,813,416 and 4,730,615 (~
above). The sharp side edges of flat steel bands are likely to cut through tissue 5 Iying along the sides of the band i, causing increased tissue trauma and bleeding. In addition, the spine modification clescribed in patent 4,730,615 hasprotruding serrations that must be pulled through the ~ ..al tissue, causing frank tissue disruption altd aggravated bleedirlg. That is not a problemin the subject invention; the needles and suture surfaces are ~ul~ ~ly smooth.
10 In addition, the soft and complia]tt suture strands used herein are much easier to handle than steel wires or banlls, and because of their flexible characteristics, they are much less likely to injure cardiac or vascular structures beneath or around the sternal halves during or after closure.
It should also be noted that the needle is cut off i",-..~ y after encircling the sternum and passirlg it tltrough the orifice 44 in the plunger 40 of the fastener device 30. There are, therefore, no exposed sharp wire ends, which can cut or tear surgical gloves or injure any of the operative team when steel wires are used. This invention thereby avoids a significant risk of LlCLll~ .iUII
of blood-borne infections.
In addition, it is not necessary to secure the ends of the multiple suture strands with surgical clamps after the strands have been placed in their iltitial position, before final tightening and closure. Therefore, the multiple clamps which normally lay in the surgic.~l field when stainless steel wires are used are not necessary in this invention ar~d will not clutter the operative field or cut the gloves or fingers of the operative team.
If desired, an alternative rllethod can be used to insert the suture strands around the sternal halves without using a sternal closure needle. In this alternative method, a tool such a~, a hemostat or needle-nosed clamp is insertedthrough the intercostal (between the ribs) space on the anterior chest wall justlateral to the left sternal half and into the patient's chest beneath the left half of the sternal bone. A surgeon holdiing the end of the suture strand with another needle-nosed clamp inserts the elld of the suture into the patientls chest through the midline incision. It is then grasped by the needle-nosed clamp ~ 21~15~
which was inserted through the i]ttercostal muscle. The clamp is then withdrawn, thereby drawing the suture strand around the left sternal half. This ~IV~eVU~: is then repeated by inserting the other end of the suture into the rltidline incision and beneath the right half of the sternum, so it can be grasped and drawn through by a clamp illserted in a similar manner through the intercostal space on the right side of the sternum.
The Fastener Device If desired, the sternal closulre strands can be secured into loops, after ~ Ia~ , by tying the two e]tds of a strand in a conventional manner.
Alternately, a loop can be closed using a fr~c ~n~lin~ hm~qnt device such as the clip shown in US patent 5,l~78,731 (Hayhurst).
In an alternate preferred ~ hoflimtqn~ a fastener device 30 shown in FIGS. 5 through 8 can be coupled to the distal end of the suture 20. The bottom end of cylinder ~UIII,UUII~ 32 is ~ ly secured to the end of suture strand 20 by means such as a l,;v~ull.rudlible glue. The top end of the cylinder32 is firmly attached to a relatively flat ~vll.luul.~, referred to herein as the fastener base 34. Cylinder 32 enc] oses a plunger 40 which is attached to a plunger cap 42. An orifice 44 passes through the shaft of plunger 40.
2 0 When the needle has com~leted its path during insertion of a suture strand, the suture strand 20 is dritwn all the way through, until the fastener base 34 of the fastener 30 (which is attdched to the distdl end of the suture 20) seats firmly against the anterior surface of the sternuTn or peristernal tissues.
This leaves the cylinder 32 tqmhq~ d in the sternal or peristernal tissues. The size and shape of the fastener 30 prevents it from being pulled all the way through the sternum or soft peristernal tissue.
In a normal sternal closur~!, six sutures are used; each suture is positioned between two ribs. All six suture pieces are placed in the proper inittal position, circling around and behind the sternum. The needle is passed 3 0 through the orifice 44 in the plurlger 40 of the fastener device 30 that isattached to that suture, thereby d~rawing the suture through the orifice. This closes tlte stemal closure loop, arld the needle should be cut off as soon as possible, to eliminate any risk of inadvertent stab wounds. The fastener orifice ~151~55 --44 preferably should be slightly srnaller in diameter than the suture strand; this - will allow it to temporarily hold the suture strand in place while the other sutures are placed. The suture is left long enough to allow easy manipulation of the two sternal halves as the r~st of the sternal sutures are placed.
When the iniHal ~la.~ steps are completed for all of the suture strands, the Hghterling procedure is ready to begin. For each suture strand, thefree end 25 of the suture strand 2.0 is inserted through the fastener orifice 44 if this has not already been perforrlled as each individual suture was placed. Thisorifice 44 passes through the plullger 40. When a suture strand has been tightened to a desired tension, thl~ plunger 40 is pushed down. This squeezes and tightly crimps the suture stralnd 20 between the roof of orifice 44 and the surface of fastener base 34, as shc~wn in FIG. 6 (along ~he axis of suture strand 20) and FIG. 8 (perpendicular to suture strand 20). The plunger 40 is held in the crimped position, tightly gripping the suture 20, by means of two locking devices 36 mounted inside the barrel of cylinder 32. These locking devices 36 engage A~ ~omm~rlaHn~ slots 46 ill the sides of plunger 40. The plunger 40 and/or the cylinder 32 are made of a slightly deformable plastic, allowing the plunger to be pressed down desF~ite the resistance generated by the locking devices 36.
2 0 If desired, the cylinder barrel 32 can also be fitted with one or more extendable fixaHon prongs 50, sh~awn in FIGS. 7 and 8. Before plunger 40 is pushed down, fixation prongs 50 are in a retracted position, as shown in FIG.

7, and are coupled to the cylinde.r barrel 32 by means of pivoting athrhmPnh 52 at or near the lower end of th~! cylinder barrel 32. These pivoting Ai~
2 5 points can be provided by mP~l- 1 hinges, or by thin deformable plastic junctures between the cylinder bclrrel and the fixaHon prongs. When the plunger 40 is pushed downward, the plunger presses against the sloped upper region of the fixation prongs, which pushes the fixaffon prongs in an outward direction, into the soft peristernal tissue as shown in FIG 8. This causes the fixation prongs to secure and stal~ilize the position of the fastener device 30 in the p~l;.t~llal Hssue. The extended prongs prevent outward migration of the fastener 30 around the sternum, elong the path of the suture loop, while the fastener base 34 prevents migratil~n into the chest cavity. The fastener device 21~
therefore remains seated next to the sternum, typically on the patient's left side, nestled ulwbLIu~;vely between t~o ribs.
By contrast, conventional stainless steel wire closures, and the prior art banding devices disclosed in US ]~atents 4,813,416 and 4,730,615 do not have any comparable method for t~l~Vl~ illg migration of the fixation device. The result is that the wire twist-closule, the "buckle" described in patent 4,813,416, or the "head" described in patent 4,730,615 can migrate around the sternal bone.Usually, migration tends to bring the wire loop closure devices to an anterior position and places them on top of the front of the sternum, where they may become annoying and can cause di~u~rul~, and occasionally require corrective surgery The fastener device 30 sholuld have a size which is as small as possible consistent with its function and ~ith the need for dire~t handling by surgeons wearing surgical gloves. For exarnple, the fastener base 34 should have a diameter of less than about 1 cm; a diameter of about 5 or 6 mm is preferred for use with sutures having diameters up to about 3 mm. The height from cap to barrel end when the plunger is depressed, should also be less than 1 cm and ably should be in the rangt of about 5 to 7 mm.
In addition, FIG. 9 shows ~:wo .'. ~ h in the fastener base 34 2 0 ~hich can be used to further red~uce the profile of the fastener after uL~ ion. A groove 60 which Pr- mm~ the suture strand 20 will allow the suture strand to be ~u~ u~ d to a very low profile when the fastener is in the closed (crimping) position; this low suture profile is indicated in FIGS. 6 and 8. If desired, the surface of t]le groove (and the top surface of the plunger orifice 44) can be serrated slightl~ or otherwise provided with a rough surface,to improve their ability to grip t~le suture material without slippage. In addition, a second groove 62 can be provided in the top of the fastener base 34.After closure, this second groove will serve as a cutting guide to help the surgeon trim the free end of the ~suture strand.
If desired, the fastener de~ice can be provided with a means for releasing the plunger after it has been depressed, in case the length of the suture needs to be adjusted. One way to allow such release would be to provide ramps on the sides of th~ slots 46 which hold the locking members 36.

~ 21'il55~
These would allow rotation of th~- plunger 40 relative to the cylinder 32, to release the locking members 36. l'his would not create a substantial danger of D~JUIlL~l~eUUD release, since the suture strand siWng in groove 60 will resist any such rohtion.
The fastener design descri~)ed above is only one possible designi other fastener ~u. figulaLions could be llsed so long as they allow effective sternal closure. For e%ample, a fastener d~evice could be provided with two separate orifices, or with a single orifice ~ ide enough to hold two suture strands side-by-side. If such fasteners were used, they would not need to be affixed to one end of the suture strand, and a single sternal needle coupled to a single long piece of suture material would b~! sufficient to close the entire sternum if sixfastener devices were enclosed in the sterile pouch holding the needle and suture strand.
After all of the sutures ha~e been tightened, secured, and trirnmed, the fascial closure is ~fu~æd in th~ usual manner, to cover the devices ~u~ t~ly, then sub. ..t-~PU..c arld skin closure is carried out using a conventional routine.
Routine poDLu~.a~ive care of cardiothoracic patients requires a~ t,D;Ye pulmonary rehabilitation includillg early ambulation. The coughing, deep 2 0 breathing and l,.vv~ requirecl to attain these goals imposes substantial stresses on the sternal closure. In conventional sternal closures, this results in tension of the stainless steel wires against the bone of the sternum. The end result, particularly in patients who are elderly or who suffer from u~L~u~ulvDisor other degeneration of the sterrlum, is that the narrow stainless steel wires 25 can cut through the bone. This loosens the sternal a~.v~i-,.aLion, and leads to undesired l..v~ ..L of the sternal halves against the wires. This often leads toincreased incisional pain, and in the some cases to complete sternal separation and/or sternal infection. These llLaDLlu,ulLc complications often mandate further surgery in an attempt to ~;ecure the sternal closure.
3 0 The subject invention will lessen the chance of these complications. The suture materials described herein, allow more than enough lon~ib~iinsll strength with minimal longitudirlal deformation, thereby allowing firm fixation of the sternal halves. At the sam~! time, the increased diameter of the sutures 2151~55 ~, .
described herein, compared to conventional stainless steel wires, allow any tensile stresses to be evenly distributed across a larger area, which decreases the chances of the sutures cut~ing into the sternal bone and loosening the sternal d~u,~ ation. In addition~ even when sternal healing takes place with 5 a stainless steel wire closure, son ~e of the wires may break (which can occuryears after the original operation)l, and the sharp ends of the broken wire can injure internal tissue and protrude through or against the skin requiring another surgical procedure to remove them. Most such wire breaks occur where a wire has been twisted, since twisting of a steel wire weakens the wire.
10 This v~ nin~ effect does not al ise with the compliant suture material as described herein, and there is little or no danger of suture breakage under the subject invention. In addiffon, ev~n if a suture described hereirl were to break, the free end would not protrude into the alllluulldi~ tissues.
15 Articles of 1\~ - .. . r, l .. . ~ ~
In addition to a surgical method, this invention also discloses an article of ..~ U---~ ;I.g a needle, a radially ~UIII~I~bb;bl~: suture strand as described above, amd a fastener, ~rherein the needle and the fastener are coupled to the ends of the suture strand.
In addition, this invention also discloses a kit which includes one or more needle/suture/fastener asb~lllbl;~b which are contained inside a sealed package which maintains the ster~ility of the assembly. A preferred kit could include a single assembly; alternately, it can include several (such as three orsix) assemblies.
This article of l"~ 200 is depicted in FIG. 10. In this drawing, pA( l~gjn~ device 210 contains a rleedle, suture, and fastener assembly 220. Thepackage 21û preferably is an airtight, watertight sealed plastic pouch A
llallb~a~ front layer 212 (which is shown partially opened at one corner, for illustration purposes) enables the user to quickly identify or confirm the contents. Until the package is opened, the front layer 212 is sealed around the entire periphery of the package t~ a back layer 214, which can be either opaque or t[cula~ lL The two sealed la~ers form a relatively flat envelope which is impervious to water, air, bacteria, and viruses. Most sterile kits intended for , = ==. .

21!~1~5~
use during surgery are achually double-sealed; they have an external sealed pouch which keeps out dirt, and ,an mternal sealed pouch as well. As soon as the outside pouch is opened, the ~internal pouch is removed, posihioned over a sterile hble in the operating roor~l, and cut open so that the contents spill out, 5 without being touched, onto the sterile hble An alternative preferred article of m~n--f~ hlre comprises a sternal closure needle (which preferably ~hould be semi-circular in shape) coupled to a radially compressible suture material, wherein the needle and suhure assembly is enclosed within a sealed sterilized package. As described above, the suture 10 material can be coupled together by means of fastener devices which are not iniffally attached to the suture material, or by tying bwo free ends together.
Yet another arhcle of ,.. ...r, ~ which is disclosed by the subject invention comprises a suhure shralld as described herein, enclosed within a sealed sterilized package. As mentioned above, a suhure shrand can be 15 positioned around and behind the sternal halves following a median LY using tools such as a l~emostat or needle-nosed clamp. Although this ~Id~ means is not preferred, it is enhrely feasible. A~u~ 61y, this invention discloses a suture material having radial compressibility but little or no lon~ibl-lin~l yield, enclosed wiithin a sealed and sterilized package, without 2 0 requiring that a sternal closure needle must be coupleLI to the suhure strand.
Any type of packaging material which is conventionally used to store sterile surgical ill:~LlU111~1~6 or deviices can be used, such as plashc which is permeable to a sterilizing gas sucll as ethylene oxide, or plastic which will withstand the ~Illp~ldlul~ used iin autoclaves. The packaging material and 25 enclosed items can be sterilized ir any manner suitable to render the enclosed items safe for use during surgery, such as by means of ethylene oxide, by high UII:~, or by ionizing radiation, provided that the method used will not seriously degrade the shrength of ihe suhure material or any fastener devices.
After sterilizaffon, the sealed package will maintain the sterility of the enclosed 3 0 items even if the outside of the pa.ckage becomes soiled.
Fig. 11 illushrates a pluralib~ of suhure strands 20 that have been emplaced around a sternal bone 300, which was divided into halves 302 and . ~
304 during open-chest surgery. As shown, each str_nd 20 is posihoned between adjacent ribs 30æ
Indushrial Utility This invenhon has industrial uhlity, since it discloses a new and highly useful item of m-nllfa.~hlre and cc~mmerce, which will need to be man.lfarhlred in ,~,e~ialia~d and highly sterile fabrication and packaging facilihes, for sale to hospitals where open-chest surge,ry is ~.ru,.,.ed. It also has industrial uhlityby disclosing a sllhrl-nhally imploved device and method for reducing hospital stays, medical expenses, recovery times, and other costs and losses that are inflicted on workers and their er~ployers when open-chest surgery is needed to cope with a major injury or disease.
Thus, there has been shown and described an improved device and method for closing a sternum following a median 71~1lIUlUll.~. Although this invenhon has been ~x~ d for purposes of illustration and descriphon by reference to certain specific embodiments, it will be apparent to those skilled in the art that various modificahons, alterations, and equivalents of the illustrated examples are possible. Any such,changes which derive directly from the teachings herein~ and which do not depart from the spirit and scope of the invention, are deemed to be covered by this invention, which is limited only by the clairns below.

Claims (16)

1. An article of manufacture useful for surgical closure of sternal bone segments following a median sternotomy, comprising:
(a) at least one strand of suture material suitable for securing closure of surgically-divided sternal bone segments without damaging the sternal bone segments during post-operative ambulation, wherein the suture strand has a diameter of at least about 2 mm and is made of a flexible material which will not stretch significantly in the longitudinal direction but which is radially compressible and which will attempt to expand radially after compression, thereby allowing the suture material, after emplacement in a needle track created by a needle having a diameter smaller than the suture strand, to provide gentle pressure against tissue surrounding the needle track, to minimize bleeding in such tissue; and, (b) a packaging enclosure which encloses the suture material, and which has been sealed and sterilized, and which maintains sterility of the suture strand.

2. The article of manufacture of Claim 1 wherein the package also contains at least one surgical needle which is firmly coupled to the suture material, wherein the surgical needle has a thickness which is sufficiently less than the diameter of the suture strand to allow the radially compressible suture strand to exert pressure against peristernal tissue surrounding the needle track, to minimize bleeding of said tissue.

3. The article of manufacture of Claim 1 wherein the package also contains at least one fastener device capable of securely gripping the suture strand in amanner that will not allow significant slippage of the suture strand during post-operative ambulation after the suture strand has been used to reapproximate sternal bones during thoracic surgery.

4. The article of manufacture of Claim 3 wherein the suture strand fastener device comprises a cylinder and a plunger which is slidably enclosed within said cylinder, wherein the plunger contains an orifice through which a suture strand can pass, and wherein the suture strand passing through the orifice is crimped and held securely when the plunger is depressed, and wherein the cylinder and plunger are provided with interacting means to hold the plunger in a depressed position after the plunger is depressed to crimp the suture strand passing through said orifice.

5. The article of manufacture of Claim 4, wherein the suture strand fastener device is provided with at least one extendable fixation prong which is forced into an extended position when the plunger is depressed, and wherein the fixation prong reduces the likelihood of migration of the suture strand though peristernal tissue after said fixation prong has been extended.

6. A method of surgically reapproximating a sternal bone which has been divided into two or more segments, comprising the following steps:
a. providing a surgical needle and a radially compressible suture strand which is firmly coupled to the needle, wherein the needle has a size and shape suitable for positioning the suture strand around a sternal bone that has been divided into two or more sections, and wherein the thickness of the suture strand is greater than the thickness of the needle;
b. inserting the needle through tissue surrounding the sternal bone, thereby creating a needle track through said tissue;
c. emplacing the radially compressible suture strand in the needle track in a manner that (1) forms a loop around the sternal bone which has been divided, and (2) causes the radially compressible suture strand to exert gentle pressure against surrounding tissue, to minimize bleeding;
d. forming a plurality of such loops around the sternal bone; and, e. securing the loops at a level of tension suitable for maintaining closure and healing of the sternal bone segments.

7. The method of Claim 6 wherein the suture strand is made of a flexible material having a hollow tubular shape.

8. The method of Claim 6 wherein the suture strand is made of an outer layer of compressible material which surrounds at least one inner reinforcing strand.

9. The method of Claim 6 wherein the suture strand is coated with a compound that can reduce friction as the suture strand is emplaced in the needle track.

10. The method of Claim 6 wherein the securing step further comprises:
a. providing a suture strand fastener device comprising a cylinder, a plunger which is slidably enclosed within said cylinder, and securing means to hold the plunger in a depressed position after the plunger is depressed, wherein the plunger contains a plunger orifice through which the suture strand can pass;
b. passing the suture strand through the orifice;
c. depressing the plunger into the cylinder in a manner which crimps the suture strand passing through the plunger orifice; and, d. engaging the securing means, to secure the plunger in a depressed position which secures the crimped suture strand passing through the plunger orifice.

11. The method of Claim 10 wherein the securing step further comprises providing the suture strand fastener device with at least one extendable fixation prong which is forced into an extended position when the plunger is depressed, wherein the fixation prong when forced into an extended position reduces the likelihood of migration of the suture strand through peristernal tissue after said fixation prong has been extended.

12. A method of closing the sternum following a thoracic surgical operation which involves cutting the sternal bone into two or more divided segments, comprising the following steps:
a. using a needle having a first thickness to draw a suture strand having a second thickness into position around the divided segments of the sternal bone, wherein the needle creates a needle track through peristernal tissue, and wherein the suture strand occupies the needle track after passage of the needle;and, b. securing the suture strand in a manner which forms a secure loop which encircles the divided segments of the sternal bone, wherein the suture strand is made of a flexible radially compressible material having a thickness larger than the thickness of the needle, wherein theradial compressibility is sufficient to allow the suture strand to exert gentle pressure on tissue which encloses the needle track, thereby allowing the suture strand to help reduce bleeding generated by such tissue.

13. The method of Claim 12 wherein the suture strand is made of a flexible material having a hollow tubular shape.

14. The method of Claim 12 wherein the suture strand is made of an outer layer of compressible material which surrounds at least one inner reinforcing strand.

15. The method of Claim 12 wherein the suture strand is coated with a compound that can reduce friction as the suture strand is pulled through bone or peristernal tissue.

16 The method of Claim 12 wherein the securing step further comprises:
a. providing a suture strand fastener device comprising a cylinder, a plunger which is slidably enclosed within said cylinder, and securing means to hold the plunger in a depressed position after the plunger is depressed, wherein the plunger contains a plunger orifice through which the suture strand can pass;
b. passing the suture strand through the orifice;
c. depressing the plunger into the cylinder in a manner which crimps the suture strand passing through the plunger orifice; and, d. engaging the securing means, to secure the plunger in a depressed position which secures the crimped suture strand passing through the plunger orifice.