Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1993-08-18
2001-03-13
Thaler, Michael H. (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S170000, C606S184000
Reexamination Certificate
active
06200320
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to surgical instruments, and more particularly to surgical instruments used to bite out or cut portions of bone or cartilage.
2. Description of the Related Art
Rongeurs are surgical instruments for the cutting away of human tissue, and most commonly, cartilage and/or bone. At present there is a need for a rongeur having a less cumbersome and less intrusive foot plate which would make the instrument safer for use in the spinal canal and about the delicate neural structures and extend the range of use of the instrument by allowing it to be used in closer proximity to those same structures.
Attempts have been made in the past to provide a rongeur with a less cumbersome foot plate. For example, U.S. Pat. No. 4,990,148 issued to Worrick, III et al. (“Worrick”) on Feb. 5, 1991 teaches a means for allowing a limited reduction of the foot plate thickness by the addition of a groove placed at the junction of the foot plate to the shaft for the purpose of relieving crossed fields of stress. However, the foot plate of Worrick is still internally cupped to maintain a cutting edge, which thus limits any further reduction in the thickness of the foot plate.
Essentially flat foot plates had been in use earlier this century, but proved to be undesirable because spinal bone is markedly compressed during the biting process. When the foot plate is flat, the mass of bone bitten is forcefully compacted into the singularly cupped recess of the movable jaw such that it is extremely difficult to remove that bone after each bite.
At present, there is also a need for a rongeur with a capacity to remain within the wound and to repeatedly bite and to store the bone bitten until all the requisite bone removal has been completed without the need to continuously remove the rongeur from the wound for the purpose of removing the bone from the instrument to clear the cutting edges. A further and related need is for a rongeur that would collect and contain all of the bitten material such that the delicate neural structures would be protected from contact with the bitten material and/or any cogenerated inadvertent debris. In this regard, any rongeur can bite more than once, but not properly. That is, one could deliberately take several small bites, each of which would fail to fill the cup in the foot plate and the singularly cupped recess of the moveable jaw, in lieu of taking one full bite. However, once the cup and the cupped recess are filled further biting is not possible. Bone may be crushed as cups that are already full approach one another, but their contents will shield any further interposed bone from the cutting edges, thus making any further bone cutting impossible.
An example of a multibite rongeur is shown in U.S. Pat. No. 3,902,498 issued to Niederer on Sep. 2, 1975. Niederer teaches the use of a rongeur hollow at the tip such that it is possible to take several bites. Unfortunately, since the hollow tip is open to the wound at both ends, the further use of the instrument pushes the already bitten material out of the other end of the hollow tip and back into the depths of the surgical wound where it can cause great harm.
Finally, there is also a need for a surgical rongeur that will upon each use present a perfectly formed and razor sharp cutting edge, which will mate exactly, and close completely, to the opposed foot plate. In this regard, Niederer taught the use of a disposable cutting element but not the use of a disposable storage chamber for the cut pieces.
Of note is U.S. Pat. No. 5,026,375 issued to Linovitz et al. on Jun. 25, 1991 which claims a modification of Niederer's teaching wherein the tip is replaceable rather than disposable, in that it requires assembly and is secured with a screw, and wherein the tip has extending from its lower surface an inverted “T” shaped portion made to be inserted into and engage with a correspondingly internally disposed inverted “T” slot within a portion of the instrument shaft.
A further problem with the design of conventional rongeurs limiting further thinning of the foot plate so as to maintaining adequate strength is that since the opening of a conventional rongeur is much greater in its capacity than the sum volume of its cuts, in the process of biting with such a rongeur, the bone is not only bitten but is further compacted under tremendous pressure, that pressure being transmitted directly to the foot plate.
Conventional rongeurs by design have excursions beyond that needed to merely close the jaw completely when the rongeur is new. That is because the manufacturer must allow for the wear that will occur at the cutting edges, and yet still provide for the capacity of the instrument to still close fully later. Thus, when bone is bitten with a conventional rongeur, a force considerably greater than that necessary to cut or even compact the bone is additionally transmitted to the foot plate as the slidable member attempts further proximal migration in opposition to the foot plate.
SUMMARY OF THE INVENTION
The present invention is an ultra-thin foot plate, multi-bite rongeur with an integral storage chamber and cutting element that is replaceable and disposable. The integral storage chamber and cutting element of the present invention is removably locked to a central shaft and is removably engaged to a driving member. The integral storage chamber and cutting element slides along the shaft towards a foot plate at the distal end of the shaft in response to the movement of the driving member which may be hand operated or powered by a solenoid or a pneumatic means.
The ultra-thin foot plate of the present invention is made possible by the complete absence of a cup. The foot plate shaft junction area of the present invention is designed to mitigate the stress concentration of the junction. The foot plate of the present invention need not be as thick as that of a conventional rongeur since the only force applied to it is that sufficient to actually cut the bone being bitten. During use, the integral storage chamber and cutting element is closed at its proximal end and open at its distal end terminating in an ultra-sharp cutting surface. The interior cross sectional area of the storage chamber flares in both height and width from distal to proximal. Inasmuch as the cutting element storage chamber unit is hollow, rather than cupped, and the opposed surface of the foot plate is flat, the bone bitten is always driven rearward into the chamber portion. As the storage chamber is closed while in use except for the cutting entrance, it may be used to repeatedly bite bone without the danger of the bone bitten coming free and falling into the spinal canal.
When the present invention has completed its task and removed all of the bone as needed, the integral storage chamber and cutting element may be removed from the shaft of the rongeur and the bitten bone may be removed from the storage chamber and made available for use, as in performing a spinal fusion.
The present invention allows for the clean cutting of bone or cartilage without any compaction. Further, as the cutting element of the present invention is disposable and thus always fresh and sharp, less force is required during the actual cutting of the bone. In addition, since the integrated cutting element storage chamber unit is always fresh and sharp, edge wear is not a problem and the capacity for further excursion of the cutting element towards the foot plate is unnecessary and may be completely blocked, thereby sparing damage to the foot plate.
Finally, the present invention has an integrated cutting element and storage chamber unit that is truly disposable, rather than merely replaceable and requires no special assembly or the use of any tools. The integrated cutting element and storage chamber is simply placed onto the shaft whereby it is immediately locked into place by the use of the instrument itself.
OBJECTS OF THE PRESENT INVENTION
It is an object of the present invention to provide an improved surgical rongeur capable
Martin & Ferraro LLP
Thaler Michael H.
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