The assignee for this patent application is
Reporters obtained the following quote from the background information supplied by the inventors: "The present invention is related to the general surgical repair of separated body tissues, and more particularly to internally fixating and stabilizing such body tissues, specifically bones.
"In the present state of the art, there are a number of systems available to repair biological tissues separated in surgery or by injury. These products serve to approximate and stabilize the tissues so that healing may commence and provide compression in the interface to promote healing. Compression and stability are critical for proper anatomical healing of tissue. With the correct amount of compression applied to the interface of the tissue portions to be joined, signals are sent to the tissue, thus allowing the tissue to remodel in proper anatomical position. The amount of compression applied to the tissue interface needs to be appropriate to the type of tissue that is being healed.
"Twisted wires are also typically used to keep bone fragments together so they may heal. Twisted wires only hold tension as long as the twisted wire pair remains stable. Often the wires untwist too soon failing to keep the bone fragments together so that they may heal. Wires can also cut into the bone fragments allowing them to separate so that healing is difficult.
"When it is necessary to access the thoracic cavity for a medical procedure, for example, it is required to cut the sternum into two pieces using a rib spreader. Once the procedure is completed within the thoracic cavity, the sternum must be repaired. For such repairs, it is known to use a dynamic compression device. Some of the drawbacks of this typical device, and others which are used include:
"In addition, the current banding systems have stiff bands that are not compliant with bony undulations. Flat sutures are used, but are tedious to tie and do not hold reliably.
"The banding systems of the present invention are therefore attractive for use in sternal closure because they offer some distinct advantages over the twisted wires most commonly used in the procedure.
"Bands address the issues wires have, as noted in the preceding discussion. A band, by defmition, is wide. In being wide, a band distributes its forces over a wider surface area. This inhibits the band from digging into the bone. In being wide, a band affords a larger cross-sectional area whereby more material may be realized, thus presenting the opportunity to offer as much strength in the construct as is necessary to hold the bone fragments together. As such, bands address wires two main weaknesses, namely, digging into the bone fragments being held together and not having sufficient cross-sectional area.
"Bands ring in other attributes other than strength and reduced pressure on the bone. Some of these attributes are difficult to manage. With strength comes stiffness, as mentioned elsewhere herein. The larger cross-section of the band significantly increases the stiffness of the band. While stiffness and rigidity are good attributes in that they can stabilize the bone union, these attributes can also prevent the band from following the contours of the bone when inserted. This can lead to capturing tissues underneath the band that ultimately destabilize the union as the tissue continue to compress and disappear over time.
"Binding the band ends together can also impose some problems. Generally, this involves a mechanism on one band end that interfaces with holes or slots or contours on the other band end. This creates a tensioning system that is incremental in nature. As in the twisted wire system, this mechanical interface of the two ends is the weakest link in the system. This mechanical interface becomes stronger as the incremental steps become larger. But larger incremental steps are not conducive to fine tuning the tension, so this is problematic. Flat sutures have been used to tie tissues together, but the residual tension supplied in such a knotted structure is insufficient for optimum healing. There is a lot of fuss/time associated with trying to keep and hold a desirable tension with these flat sutures. What is needed is an attachment approach that provides variable tensioning.
"Another problem associated with banding systems is that their tension holding capabilities are insufficient for the environment in which they operate. Tension holding ability can be increased or enhanced by increasing friction at the binding interface of the band. What is needed, however, is a banding system with the ability to hold tension by selectively increasing friction at the binding interface during locking and/or after locking without increasing friction while tensioning.
"What is needed, therefore, are improved devices and techniques for holding two tissue portions in a state of compression and tension that address and overcome these shortcomings in an innovative way."
In addition to obtaining background information on this patent application, NewsRx editors also obtained the inventors' summary information for this patent application: "There is disclosed, in one aspect of the invention, a dynamic tissue holding device for dynamically holding two tissue portions in contact with one another, which comprises a resilient body and a band adapted for extending about the tissue portions to be held together. The band has a first end for attachment to a first attachment portion on the resilient body and a second end for attachment to a second attachment portion on the resilient body. The band establishes a path of tension along its length and extends linearly between the two ends of the band. The resilient body comprises a spring, a first stop having a first opposing surface, and a second stop having a second opposing surface. The resilient body may be pre-compressed to a predetermined limit of compression wherein the first and second opposing surfaces of the first and second stops, respectively, are in substantial contact with each other, such that the pre-compression of the spring applies a predetermined level of tension to the band without strangulating the tissue.
"An additional stop is provided which contacts the spring when the spring is expanded a predetermined amount, so that the contact of the additional stop and the spring prevents further expansion of the spring, thereby establishing a predetermined limit of expansion of the spring. This additional stop preferably comprises a portion of one of the first and second stops, and more preferably a portion of each of the first and second stops. In one illustrated embodiment, the additional stop comprises a side surface of the first stop and a side surface of the second stop.
"The spring comprises a spring portion on each of opposing sides of the resilient body, and the first and second stops each comprise generally hemispherical or horseshoe-shaped structures, in the illustrated embodiment. The first stop comprises a pair of first opposing surfaces, and the second stop comprises a pair of second opposing surfaces. A gap is disposed between the first and second opposed stop surfaces when the surfaces are not in contact, the gap being at a maximum length when the spring is expanded to the aforementioned predetermined amount. Advantageously, both the stops and the gap may be sized to establish the predetermined limits of expansion and of compression of the spring, which may comprise a leaf spring in a currently preferred embodiment.
"Advantageously, the device of the invention is formed of two different materials. In one such embodiment, the resilient body comprises metal and the band bio-absorbable suture. Because of a desire to prevent the resilient body from floating within the patient's body once the suture is absorbed, in one embodiment the suture advantageously comprises a hybrid of materials, including an absorbable portion and a non-absorbable portion woven into the absorbable portion, wherein the non-absorbable suture portion will remain after absorption to provide sufficient anchoring for the resilient body to prevent migration.
"In another embodiment, rather than using a hybrid suture, an eyelet is disposed on the resilient body, for receiving a fastener for attaching the resilient body to adjacent bone.
"In another aspect of the invention, there is provided a dynamic tissue holding device for dynamically holding two tissue portions in contact with one another, which comprises a resilient body comprising a spring, and a band adapted for extending about the tissue portions to be held together. The band has a first end for attachment to a first attachment portion on the resilient body and a second end for attachment to a second attachment portion on the resilient body, and establishes a path of tension along its length and extending linearly between the two ends of the band. Stops are disposed on portions of the resilient body for limiting both the compression and expansion of the spring. Preferably, the compression of the spring is limited by engagement of two of the stops with one another and the expansion of the spring is limited by engagement of at least one of the stops with the spring.
"Preferably, as well, the resilient body comprises metal and the band comprises bio-absorbable suture. In one embodiment, the suture comprises a hybrid of materials, including an absorbable portion and a non-absorbable portion woven into the absorbable portion. In another, alternative embodiment, the resilient body comprises an eyelet disposed on the resilient body, for receiving a fastener for attaching the resilient body to adjacent bone.
"The invention, together with additional features and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying illustrative drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
"FIG. 1 illustrates a broken femur on which has been installed an implant constructed in accordance with the principles of the present invention;
"FIG. 1a is a detail view of the portion of FIG. 1 denoted by the circle A, illustrating the inventive implant in its initial state;
"FIG. 1b is a detail view similar to FIG. 1a, illustrating the inventive implant in its expanded state; and
"FIG. 2 is a view showing a modified embodiment of the inventive implant."
For more information, see this patent application: Allen, Drew; Foerster,
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