Patent Application
20130277261
The packaging of the femoral component used in the orthopedic knee arthroplasty procedure has traditionally involved the use of inserts to stabilize the femoral component within the package and these inserts have been tailored to the size of a particular femoral component. Femoral components are currently available in a substantial number of sizes with some manufacturers offering as many as ten sizes in order to better meet the needs of individual patients.
The traditional packaging of sterile medical devices such as implants including femoral components has involved a system of an inner tray within an outer tray. Each tray is typically an open mouthed cavity with a peripheral rim to which a film is adhesively adhered to create a sealed package. The outer tray simply contains the inner tray which in turn contains the medical device, commonly stabilized within the tray with closed cell foam pieces. The pieces of foam are commonly selected to have configurations adapted to the particular device being packaged. Thus in the case of femoral components different pieces of foam are required in progressing across the size range of such components. The two tray system provides some assurance that if the integrity of the outer tray is breached in shipping and handling, the sterility of the packaged medical device is preserved by the inner tray.
This two tray system has some disadvantages. The foam used for stabilization within the inner tray is friable and, particularly with orthopedic implants with roughened surfaces to enhance bonding to living tissue, typically bone, it has been observed to abrade, creating a particulate contaminate. In addition, because the peripheral rim of the inner tray typically carries residual adhesive after the removal of the lid stock, it may not be placed on the surgical tray adjacent to the surgeon implanting the device. Consequently, the medical device must be fully removed from its protective packaging well before its use and is thus exposed to damage and being splashed with bodily fluids and tissue while awaiting implantation.
Thus there are benefits to be gained from a packaging approach in which a single system can be used across the size range of at least a single line of femoral components of a given design or from a single manufacturer. There are further benefits to be obtained from a unitary package which can be removed from an inner tray and placed on a surgical tray thus providing protection for the packaged component until it is used and providing a convenient manner of presenting the component to the surgical team.
The present invention involves a package which is adapted to securely hold any of a series of femoral components of artificial knee joints which have an approximate common thickness dimension but vary in size. This package is configured to provide a clearance which captures and closely approximates this approximate common thickness dimension. One convenient way to provide this clearance is to provide a base portion which is adapted to support the inside of the major arch of a femoral component, to provide a second structural member which has a portion that has a contour similar to at least a portion of the exterior major arch of the femoral component and to provide additional structure which holds the base portion a fixed distance from the second structural member which carries the contour. In a preferred embodiment the base portion has a quadrilateral bottom periphery and one or more vertical projections with the tallest vertical project being tall enough to support the largest of the femoral components in the series for which the package is designed. In other words, the top of this tallest vertical projection contacts the inside of the major arch of this largest femoral component in such a way that the two extreme edges of this major arch are suspended above the horizontal plane which includes the quadrilateral bottom periphery, of the base portion. In a particularly preferred embodiment the bottom of periphery of the base portion is generally rectangular in shape and the top of the tallest vertical projection is generally rectangular in shape. In an especially preferred embodiment the base portion has a series of vertical projections with their long edges parallel with the long edges of the bottom periphery of the base portion and configured as steps between the bottom periphery and the top of the tallest vertical projection. In one preferred embodiment one edge of the top surface of the tallest vertical projection is connected to an edge of the bottom periphery of the base portion by a wall which slants outwardly away from the center of the base portion.
One approach to holding the base portion and the second structural member in a fixed spacial relationship when retaining a femoral component is to have both of them part of a unitary structure. In a preferred embodiment the base portion is hingedly connected to two side portions via two opposing sides of its bottom periphery such that these side portions can be rotated toward each other. It is convenient to have at least a portion of the surface of one or both of these side portions which face the base portion have a contour similar to a portion of the exterior major arch of the largest femoral component of the series the package is to accommodate. It is preferred that a portion of the top surface of the tallest vertical projection of the base and a portion of the facing surface of one of the side portions define the clearance that captures the approximate common thickness dimension of the series of femoral components the package is to accommodate. In a particularly preferred embodiment each side portion has a quadrilateral, more preferably a rectangular, base with a generally vertical wall rising from each of the three sides not hinged to the base portion. Each of these generally vertical walls has the same height as the other two and terminates in a horizontal ledge which extends inwardly. From each of these horizontal ledges an interior wall extends downwardly to the base of the side portion. In an especially preferred embodiment the interior wall which extends from the middle horizontal ledge has an arcurate shape. It is convenient if at least a portion of the arcurate wall of one of the side portions has a contour similar to at least a portion of the exterior major arch of the largest femoral component in the series for which the package is designed.
One preferred embodiment of this unitary structure is a clamshell trifold in which a central portion has a generally rectangular base with a hinged connection along each of its long edges to a side portion with the external shape of a rectangular prism which lacks a wall arising from its hinged connection with the central portion, a bottom surface and most of its top surface. Each side portion does have a peripheral top surface which extends inward from its three side walls and terminates in a set of downwardly directed walls which define the interior of the side portion. The downwardly directed walls attached via the top surface to the short edges are generally vertical while the downwardly directed wall attached via the top surface to the long edge distal from the hinged connection has an arcurate shape. The partial top surfaces of the side portions are adapted to meet each other when the side portions are rotated about their hinged connections to the central portion and preferably these surfaces carry engaging means such as detents and mating projections so that the two top surfaces can be removably affixed to each other. The central portion is the base portion with the at least one vertical projection with a general rectangular top surface adapted to support the inner surface of the major arch of the femoral components for which the package is designed.
Another approach to holding the base portion and the second structural member in a fixed spacial relationship when retaining a femoral component is to have both of them affixed to an inner tray of the type traditionally used in the packaging of medical implants. The tray has a quadrilateral bottom surface with a generally vertical side wall arising from each of its four peripheral edges to define a cavity adapted to contain the base portion, a femoral component and the second structural member. The tray typically has a horizontal ledge surrounding the periphery of its open mouth. In a preferred embodiment the tray has a generally rectangular bottom surface. The bottom surface carries means for removable attachment to the base portion. One convenient approach is to have this bottom surface carry an upward projection with a periphery which is similar to the periphery of the interior periphery of the bottom of the base portion. The top surface of the tallest vertical projection of the base portion may conveniently carry a central projection adapted to lie between and closely adjacent to the condyles of the femoral components for which the package is designed. The second structural member may conveniently have a generally quadrilateral, preferably rectangular, peripheral shape which carries one or more arcurate surfaces which have contours which approximate the outer major arch of the femoral components for which the package is designed. In a preferred embodiment the second structural member also carries a downward projection adapted to fit between the condyles of the femoral components for which the package is designed. Means are provided for affixing the second structural member to the tray at a fixed distance from the base portion. One convenient means is a peripheral horizontal ledge on the second structural member which mates with the peripheral horizontal ledge of the tray. To provide for this mating without interfering with the ability to seal a film across the mouth of the tray, it is convenient for this horizontal ledge to have a depressed inner periphery with which to mate with the horizontal ledge on the second structural member. A portion of one or more of the arcurate surfaces of the second structural member and a portion or all of the top surface of the tallest vertical projection of the base portion establishes the clearance adapted to the approximate common thickness of the series of femoral components for which the package is designed.
It is convenient to provide the package with venting means such that every surface of the package, as well as any femoral component that it may enclose, can be exposed to the sterilizing gases used in the preparation of sterile packaging of medical implants. In the case of the clamshell approach the trifold may be designed so that the three portions mate imperfectly leaving a gap so that these gasses can penetrate the interior, vents can be specifically provided or both approaches can be used together. In the case of the tray approach the second structural member may be provided with a vent passage such as a gap in its surface and the base portion may be affixed to the bottom of the tray in such a way that the gasses can pass into the bottom of the base portion such as providing detents which cross the perimeter of the projection over which the base portion fits.
The present invention involves the design of packaging for a series of femoral components of various sizes for artificial knee joints which have an approximate common thickness dimension. The common thickness dimension does not require that all the components in the series have an identical thickness dimension but just that this dimension does not so greatly vary over the size range as to make a common package impractical. The invention also involves the concept of designing such a common package with a clearance which captures this common dimension but also accommodates a range of sizes in the other dimensions of the femoral components.
It is advantageous to construct the packaging such that the surfaces which contact the inner surfaces of the femoral component have a high abrasion resistance. In this regard, femoral components are typically constructed with a generally convex configuration with the inner surfaces of the major arc having a fairly rough surface to promote adhesion to the bones which will carry them when they are implanted. One type of surface with advantageous abrasion resistance is based upon thermoplastic aromatic polyether polyurethane. Deerfield Urethanes, a subsidiary of Bayer, markets suitable thermoplastic aromatic polyether polyurethane films under the trademark Dureflex® with grade PT9400 being particularly suitable. It is also advantageous to use this polyurethane surface to protect to the exterior polished treated surface typical of femoral components.
It is also advantageous to construct the packaging out of materials which can be readily thermoformed into packages of suitable rigidity to support the largest femoral component of the series for which the packaging is designed. The typical packaging material for medical implants including femoral components has been films of polyethylene terephthalate glycol (PETG) because they have adequate rigidity and mechanical strength and good thermal formability. However, it is desirable to have greater abrasion resistance than this material offers. It is convenient to laminate these films to films of thermoplastic aromatic polyether polyurethane and configure the packaging such that it is the polyurethane surface which faces the rough surfaces of the femoral component. The laminate is conveniently formed by melt laminating the polyurethane to the PETG. A preferred PETG for this lamination is Eastman's Eastar 6763 PETG resin. The thicknesses for both films should be compatible with both thermoforming the package configuration and providing adequate mechanical strength. A convenient range for the polyurethane is between about 0.01 and 0.025 inches while for the PETG it is between about 0.015 and 0.04 inches.
The packages with which the present invention is concerned can be conveniently designed using computer-aided design (CAD). One approach is to create three dimensional depictions of all the femoral components in a given series such as the size range offered by a given manufacturer and then overlay them to determine the location and size of a common dimension. Commonly, this is the thickness at the top of the major arch. Then a package can be designed which provides a clearance which closely approximates this common dimension and also accommodates the largest size femoral component in the series.
The clearance which is used to capture the common thickness dimension is preferably between about 0 and 0.125 inches, more preferably between about 0.010 and 0.050 inches. The minimum design clearance between a packaged femoral component and the package preferably ranges between about 0 and 0.0325 inches.
One approach to the packaging of a series of femoral components is illustrated in
The unitary package 10 is adapted to be placed into an inner tray of the type common in medical implant packaging. Because it carries no contaminates such as residual adhesive from the lid stock and can be readily sterilized and kept sterile in an appropriate inner tray, it can be placed on the surgical tray for ready access by the clean surgical team. Thus it can serve to protect the femoral component which it contains from damage or any bodily fluid or tissue spatter during an operation until the component is accessed for insertion. The unitary package 10 also provides a convenient presentation of the femoral component to the clean surgical team.
Another approach to the packaging of a series of femoral components is illustrated in
The retainer 50 cooperates with the base portion 20 to create a clearance for capturing the common thickness dimension of the series of femoral components for which the package is adapted. In particular, the arcurate walls 52 of the retainer 50 are held a constant distance from the tallest vertical projection 22 of the base portion 20 to establish this clearance. These arcurate walls 52 have a contour which approximates that of a portion of the outside surface of the major arch of the femoral components belong to this series. The retainer 50 also has a vent 54 which facilitates the circulation of sterilizing gasses about the contents of the inner tray 60 and also serves as a finger grip with which to remove the retainer 50 from the inner tray 60. In addition, it has a central groove 56 which is adapted to engage the condyles of the femoral components by fitting between them. It also a peripheral locking surface 58 which cooperates with the peripheral locking surface 66 of the inner tray 60 to hold the retainer 50 in place. Finally it has a supporting ledge 59 which cooperates with the supporting ledge 64 of the inner tray 60 to support its weight.
The inner tray 60 holds the base portion 20 and the retainer 50 in a fixed spacial relationship to create a package interior which accommodates a series of femoral components of different sizes and provides a clearance which approximates the approximate common thickness dimension of this series. It also has the traditional sealing surface 62 which accommodates the adhesive sealing of a film across the open mouth of the inner tray 60. It additionally has vents 69 which provide access to the interior of the base portion 20 for the sterilizing gasses.
In both approaches it is contemplated that the inner tray will in turn be placed in an outer tray 70 as illustrated in
A unitary package 10 was constructed of a melt lamination of 0.01 inch thick Duraflex®PT 9400 aromatic polyether polyurethane onto 0.02 inch thick Eastar® 6763 PETG by thermoforming. The overall package had a length of 10″ when open with each side portion 30 having a length of 2.571″ and the base portion 20 having a length of about 4.86″. The side portions 30 each had a height of 1.750″ and the tallest vertical projection 22 of the base portion 20 had a height of 1.750″ as well. There were three vertical projections 24 with heights of 0.364″, 0.680″ and 0.800″. The post recesses were about 0.468″ in depth. The package had an overall width of approximately 5″. The top wall of the tallest vertical projection 22 had a width of about 2.963″ The hinges 40 were grooves about 0.125″ wide.
This unitary package could accommodate a range of sizes of femoral components such that each was held in the closed package rather tightly with minimal readily noticeable movement within the package on shaking.
A base portion 20 configured as an insert and a retainer 50 were each constructed of a melt lamination of 0.01 inch thick Duraflex®PT 9400 aromatic polyether polyurethane onto 0.025 inch thick Eastar® 6763 PETG by thermoforming. The base periphery 21 of the base portion was an approximate rectangle 3.5″ by 2.59″. Its tallest vertical projection 22 had a height of about 1.875″. The top wall projection 28 was approximately a rectangle 0.624″ by 0.661″ and had a height of about 0.095″. It had a series of vertical projections 24 of lesser height on either side of the tallest vertical projection 22. The recesses 23 for the posts were about 0.42″ in diameter and about 0.542″ deep measured from the top of the tallest vertical projection 22. The retainer 50 had a roughly rectangular shape of 4.733″ by 3.826″. It had arcurate walls 52 of about 2.96″ in the plane of the retainer 50 parallel to the shorter side. These arcurate walls 52 rose above the plane of the retainer 50 to a maximum height of 0.564″. The distance from the plane of the retainer 50 to its supporting ledge 59 was about 0.564″.
An inner tray 60 was constructed of 0.04 inch thick Eastar® 6763 PETG by thermoforming. It had a height of about 2.318″ with a step down to its supporting ledge 59 of about 0.125″. Its cavity viewed from the top was approximately a rectangle 4.551″ by 3.640″. When the base portion 20 and the retainer 50 were affixed to it, it held them in a fixed special relationship to each other.
This three piece structure was used to package a series of femoral components of different sizes and each size component was rather tightly held with minimal readily noticeable movement within the package on shaking. The closest clearance of the assembled package was a gap of about 0.3256″ between the top of the tallest vertical projection 22 of the base portion 20 and the arcurate walls 52 of the retainer 50. For the largest of the femoral components in the series this left a clearance of about 0.009″ when this component was placed in the package and for the smallest of the femoral components in the series this left a clearance of about 0.0102″. The femoral components in this series ranged in size from about 1.902″ to 2.8795″, viewing the components oriented like a letter “C” and measuring between the highest and lowest points on the “C”.
CAD modeling established that a single package was able to accommodate forty different femoral components comprising left and right hand versions of two styles and ten sizes within each style.
The above disclosure is for the purpose of illustrating the present invention and should not be interpreted as limiting the present invention to the particular embodiments described but rather the scope of the present invention should only be limited by the claims which follow and should include those modifications of what is described which would be readily apparent to one skilled in the art.
