Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-11-10
2001-08-14
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06273893
ABSTRACT:
FIELD OF THE INVENTION
The field of art to which this invention relates is surgical instruments, in particular an applier for delivering an absorbable orthopaedic fastener. More specifically this invention relates to a single-shot rivet applier that drives an absorbable polymer rivet and pin for fixating of medical devices to bone, especially hard tissue of the cranium or face, for plastic or reconstructive surgical procedures.
BACKGROUND OF THE INVENTION
There are currently a variety of metallic fasteners and appliers or drivers to deliver the fastener for attaching bone plates to fracture and surgery repair sites; spinal, cranial, and maxillo-facial plates have all been fastened using metal screws. The disadvantage of metal screws and other fasteners is that they are permanent and may need to be removed through a second surgical procedure. If they remain in the body, tissue atrophy and subsequent loosening of the device may occur. In addition, metallic and especially plastic screws, including absorbable polymer screws, quite often require tapping threads into the bone; a laborious task that slows the surgical procedure and can lead to poor fixation from stripping of the threaded bone.
Metallic wire or suture can be used to attach plates to bone. This technique requires a tedious method of drilling numerous holes, guiding the wire through the holes, tying and bending the wire and then cutting excess wire away to prevent irritation of soft tissues.
Furthermore, several rivet patents relate to devices which are inserted into a hole and then deployed by driving a member upwards, or proximally, through or into a radially flexible portion of the device. This requires that the hole be deeper than the depth of the deployed device in order to leave enough room to fully insert the device with some type of driver before deployment. Such designs are undesirable for surgical applications where only a thin layer of bone is available for attachment or it is not possible to drill beyond the depth of the thin bone layer for fear of damaging underlying soft tissues, such as in cranial and maxillo-facial surgical procedures. In such cases, the required length of the fastener for adequate fastening strength is very close to the total thickness of the bone.
U.S. Pat. No. 4,590,928 describes an anchor consisting of an elongated cylindrical body with a tapered coaxial channel and radially flexible legs and a pin insertable into the end having the head, the proximal end. The body is placed into a hole formed in bone and the pin is inserted into the channel to expand the legs radially into the surrounding bone. The body and pin are of biocompatible material and the body contains carbon fibers embedded in and extending longitudinally along its interior. Since carbon fibers are not absorbed by or resorbed within the body, this fastener is only partially absorbable.
This U.S. Pat. No. 4,590,928, describes a fastener having a solid pin. It is well known that the material properties, such as Young's modulus of elasticity and is the material yield stress, of bone tissue change significantly with age and vary significantly among individuals of the same age and sex. Having a solid pin therefore limits the fastening ability of the device since the pin cannot deform if the surrounding bone is so stiff that the legs cannot expand radially outwards.
In such a case where the surrounding bone is stiffer than that for which the device was designed and the pin is solid, the large force required to drive the rigid pin into the tapered hole will be such that either the legs will be deformed and rendered useless or the pin will be crushed. A radially compressible or flexible pin that could deform radially inwards to fit the internal passage under high insertion load conditions would give the fastener better performance over a wider range of bone material properties.
U.S. Pat. No. 5,268,001 describes an apparatus for emplacement of a single bone fastener in a bone. The apparatus consists of a holder for holding an expandable sleeve in position within a pre-drilled hole in bone. A plunger moveable in relation to the holder forces a pin into the bore of the expandable sleeve. An attached means for separating the expandable sleeve from the holder (i.e. annular cutter) then cuts the expandable sleeve, thereby releasing the sleeve from the holder. Typical procedures require more than one fastener and varying amounts of application force.
Therefore, what is needed in the art is a novel absorbable fastener for cranial, maxillo-facial, and other reconstructive surgical applications in which the fastener is inserted into a hole having the same depth as the fastener and is deployed by driving a radially compressible member downwards, or distally, into a flexible body of the fastener from above. The current invention discloses an applier for such a device wherein the applier can fire a rivet fastener with minimum force thereby speeding and simplifying the procedure. The impact applier consists of a firing mechanism that can produce varying degrees of force required for different surgical applications.
SUMMARY OF THE INVENTION
We have discovered a rivet applier comprising of a handle with a central axis, hammer chamber, a hammer, biasing spring, a grip loader, a firing pin, and a receiver. The handle has a hammer chamber adjacent to the proximal end of the body and substantially parallel to the central axis. The hammer is slidably mounted within the hammer chamber of the handle. At the distal end of the applier is a receiver for retaining rivets. The receiver is in mechanical communications with a firing pin slidably mounted with the hammer in the applier in a central passage. The central passage provides mechanical communications between the hammer and the firing pin. Three stops, a hammer stop, a firing pin stop, and a firing pin guide stop are provided in the device which insure precise travel of the rivet pin upon firing. The grip loader is mechanically linked to the hammer and provides a means for moving the hammer. The proximal chamber opening is releasably capped to provide access to the spring.
Optionally a trigger mechanism may be provided. The trigger mechanism is composed of a trigger pin having a notch and a trigger spring for biasing the trigger notch. The trigger pin will generally be placed substantially perpendicular to the horizontal axis and is slidably mounted in this perpendicular direction The hammer is mechanically linked to a trigger mechanism for restraining the hammer in a first position and being capable of releasing the hammer in cooperation with the movement of the trigger to allow the hammer to move to a second position.
The rivet is manually loaded via a press-fit to the receiver at the distal end of the rivet applier. Firing the trigger advances the rivet out of the rivet applier and pushes the rivet pin into the rivet thereby securing the rivet in the patient.
REFERENCES:
patent: 4493205 (1985-01-01), Ramey
patent: 4590928 (1986-05-01), Hunt et al.
patent: 5268001 (1993-12-01), Nicholson et al.
patent: 5398861 (1995-03-01), Green
patent: 5662658 (1997-09-01), Wenstrom, Jr.
patent: 5741268 (1998-04-01), Schutz
patent: 5881942 (1999-03-01), Bergamini
patent: 5904284 (1999-05-01), Lin
patent: 2452892 (1980-12-01), None
Cooper Kevin L.
McAllen, III John
Overaker David W.
Ethicon Inc.
Robert Eduardo C.
Smith Jeffrey A.
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