Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-03-10
2001-06-12
O'Connor, Cary (Department: 3736)
Surgery
Instruments
Orthopedic instrumentation
C606S057000
Reexamination Certificate
active
06245071
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a device for fixation of bone, and in particular to an external fixation device for a long bone.
BACKGROUND OF THE INVENTION
The clinical success of external fixation of bones has been well documented in the orthopaedic literature. However, external fixation at or near a joint can be problematic due to biomechanical requirements. For example, because the wrist has degrees of freedom which allow rotation, flexion, adduction, and abduction, external fixation near the wrist should be adjustable to ensure that proper fracture alignment is achieved. Furthermore, in order to avoid damage to the tendons and nerves that surround the wrist, the pins which are used to couple the fixation device to the body are usually placed on opposite sides of the wrist in the metacarpal bone and the radius. As a result, the fixation device must be sufficiently articulated to reduce the fracture using the forces transmitted through the wrist.
In order to address these, as well as other complications associated with fixation at or near a joint, a number of fixation devices have been developed. Examples include those disclosed in U.S. Pat. Nos. 4,554,915, 4,611,586, 4,628,919, 4,782,842, 4,919,119, 4,922,896, Re. 34,985, 5,122,140, 5,152,280, 5,304,177, 5,320,622, 5,437,667, 5,545,162, 5,601,551, 5,683,389, and 5,743,898. One particular problem common to these, as well as other prior art devices, is the need to have both large scale distraction to facilitate implantation and precisely controlled distraction to ensure proper fracture reduction. Some of these patents attempt to overcome this dilemma by requiring assembly and/or disassembly of multiple parts. U.S. Pat. No. 5,662,649 to Huebner discloses an external fixator for repairing fractures of the distal radius and wrist which allows both rapid gross distraction and finely controlled distraction without the need for intraoperative assembly or disassembly. However, the nut and thread assembly which permits both types of movement can be cumbersome to use and unintentional switching between the movement modes is possible.
As the discussion above illustrates, there is a need for an improved external fixation device for bone.
SUMMARY OF THE INVENTION
The present invention relates to a device for fixation of a bone fracture. The device comprises at least one distal pin having a mounting end for insertion into the bone on a distal side of the fracture, at least one proximal pin having a mounting end for insertion into the bone on a proximal side of the fracture, a distal member attached to the distal pins, a proximal member attached to the proximal pins and slideably connected to the distal member for reducing or distracting the bone fracture, and a distraction assembly for controlling the sliding movement between the proximal and distal members. The distraction assembly has two modes of operation: an active configuration and an inactive configuration. In the active configuration, incremental relative sliding movement between the proximal and distal members is allowed, and, in the inactive configuration, free relative sliding movement between the proximal and distal members is allowed. The free sliding movement is useful in installation of the device and the incremental relative sliding movement is useful for finely manipulating the relative positions of the proximal and distal members.
The device also includes a removable engagement element operatively engaging the distraction assembly in the inactive configuration. Removal of the engagement element places the distraction assembly in the active configuration. Once the engagement element is removed, it cannot easily be replaced. As a result, the distraction assembly cannot inadvertently be placed in the inactive configuration.
Preferably, the distraction assembly comprises a gear rack on a wall of the proximal member body cavity, an intermediate gear engageable with the gear rack to cause the incremental relative sliding movement between the proximal and distal members upon rotation of the intermediate gear, a worm gear engageable with the intermediate gear so that rotation of the worm gear causes rotation of the intermediate gear, and a resilient member which biases the worm gear into engagement with the intermediate gear. The removable engagement element may be a pin located between the intermediate gear and the worm gear to prevent engagement between the intermediate gear and the worm gear.
In one embodiment, the device also includes a distal mounting blocks for attaching the distal pins to the distal member and a proximal mounting block for attaching the proximal pins to the proximal member. Each pin, which may be Schanz screws or any other suitable fastener, fits into a channel in the proximal and distal mounting blocks and a locking screw secures the respective pin to the channel. In order to avoid interference with anatomical structures, the channel may be oriented at an angle of about 45° with respect to the longitudinal axis of the device.
In a preferred embodiment, at least one of the distal and proximal mounting blocks includes a ball joint for allowing rotational movement of the mounting blocks with respect to the rest of the device. The distal and proximal mounting blocks may include a plurality of set screws for securing the mounting blocks at a desired position with respect to the proximal and distal members. In a further preferred embodiment, two set screws oriented perpendicular to each other are used for each ball joint.
In a different embodiment, the distal mounting block has an arm for connection with the distal member and the distal member has a head with a track for receiving the arm. The arm is movable in the track to vary the position of the distal mounting block with respect to the distal member. The track may be curved with teeth which engage a gear on the arm upon rotation of the gear to move the distal mounting block. Preferably, a locking element is provided to prevent rotation of the gear and fix the position of the distal mounting block.
In order to have the sliding movement between the proximal and distal members, the proximal member may include a body and a linking section. The body has a cavity for slideably receiving the distal member. In addition, the linking section may be slideably connected to the body so that sliding motion between the linking section and the body occurs in a direction perpendicular to the direction of the sliding motion between the proximal and distal members. The sliding motion between the linking section and the body is coplanar to the sliding motion between the proximal and distal members. In a preferred embodiment, a distal end of the linking section includes a pair of slots and the proximal end of the body includes a cutout. The cutout slides in the slots to produce the sliding motion between the linking section and the body. In a further preferred embodiment, a lead screw connects the linking section to the body. Turning of the lead screw moves the linking section relative to the body.
In another embodiment, the proximal member has a tail pivotably connected to the linking section. The tail has a worm gear and the linking section has a curved gear rack. The worm gear engaging the gear rack to produce the pivotal movement between the tail and the linking section.
REFERENCES:
patent: Re. 34985 (1995-06-01), Pennig
patent: 4040129 (1977-08-01), Steinemann et al.
patent: 4554915 (1985-11-01), Brumfield
patent: 4611586 (1986-09-01), Agee et al.
patent: 4628919 (1986-12-01), Clyburn
patent: 4662365 (1987-05-01), Gotzen et al.
patent: 4782842 (1988-11-01), Fietti, Jr.
patent: 4919119 (1990-04-01), Jonsson et al.
patent: 4922896 (1990-05-01), Agee et al.
patent: 4978348 (1990-12-01), Ilizarov
patent: 4988349 (1991-01-01), Pennig
patent: 5122140 (1992-06-01), Asche et al.
patent: 5152280 (1992-10-01), Danieli
patent: 5207676 (1993-05-01), Canadell et al.
patent: 5304177 (1994-04-01), Pennig
patent: 5320622 (1994-06-01), Faccioli et al.
patent: 5376091 (1994-12-01), Hotchkiss et al.
patent: 54376
O'Connor Cary
Pennie & Edmonds LLP
Synthes (U.S.A.)
LandOfFree
External fixation device for bone does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with External fixation device for bone, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and External fixation device for bone will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2479743