A variety of traumatologic devices for reduction of bone segments are known in the art. For example external bone fixation devices (commonly referred to as external fixators) are known. Typically external fixators are used to reduce fractures of the long bones in the human body. These devices are always placed in position under anesthesia. In order to reduce the duration of the anesthesia, fixator devices have been developed to allow positioning at every possible angle, while still allowing easy adjustment by a surgeon.
The early development of external fixator devices, such as that exemplified by U.S. Pat. No. 2,250,417 to Ettinger, was aimed at producing a simple and lightweight fracture reduction device which is practical to leave in place to serve as a retention device, thereby rendering a cast unnecessary. As disclosed, the Ettinger device allows two separate sets of dual bone pins or screws, each transcutaneously installed in the bone on either side of a fracture, to be connected and fixed at variable points to a single bone fixation rod running roughly parallel to the longitudinal axis of the affected bone. This resultant connection of opposing pin/screw sets provides the immobilization necessary to allow proper healing of, the fracture. Ettinger discloses the use of multiple sleeve and post connections between the bone pins/screws and the bone fixation rod to allow the bone pins or screws to be installed at varying angles relative to the bone fixation rod. Ettinger additionally discloses the use of a rod and sleeve configuration whereby one of the two bone pin/screw couplings is fixed to the bone fixation rod, while the second comprises an internally threaded sleeve that is threaded over the opposite end of the bone fixation rod, and whose position is adjustable relative to the fixed coupling via rotation of the bone fixation rod.
Later improvements on the Ettinger design, such as that disclosed by U.S. Pat. No. 4,135,505 to Day, allow for the installation of an increased and/or variable number of bone pins on each side of the fracture. This provides the advantage of giving the practitioner more options in the spacing of pins, and of avoiding installing a pin at a particular point on the bone if such placement was undesirable. The Day device additionally discloses a bone pin clamp incorporating a ball and socket connection to allow for varying bone pin installation angles.
Further improvements such as those disclosed by U.S. Pat. No. 5,160,335 to Wagenknecht, U.S. Pat. No. 5,219,349 to Krag, U.S. Pat. No. 5,624,440 to Huebner, U.S. Pat. No. 5,891,144 to Mata et al., and U.S. Pat. No. 6,022,348 to Spitzer disclose bone pin/screw clamps which incorporate more modern universal joint assemblies to allow easier adjustment of the distance between bone pin clamps along the length of the bone fixation rod when the attached bone pins/screws are installed at multiple angles relative to the immobilization rod. Moreover the Krag, Huebner, Mata et al., and Spitzer devices provide easier means to adjust the relative distance between bone pin couplings on opposing sides of a fracture (accomplished by simple sliding in the Krag, Huebner, Mata et al., and Spitzer devices, and by incremental rotation of an attached screw and nut combination in the Day and Wagenknecht devices). Yet a further improvement is disclosed in the Wagenknecht patent, which provides springs between the bone pin clamp faces to spread the faces and thereby facilitate introduction of the bone pins.
The difficulty with the Huebner, Krag, Wagenknecht and Day devices is that their means of fixing the bone pin clamp to the bone fixation rod is by way of a closed hole and screw combination. To facilitate installation of these fixators, the bone pin clamps must be threaded onto the bone fixation rod from one end of the rod, making installation cumbersome. The Mata et al., and Spitzer devices address this problem by providing bone pin clamps that attach to the bone fixation rod utilizing open-face jaws. This design allows the device to be engaged with the rod by simply placing it onto the desired location along the length of the rod, without the need for threading as in the Mata et al. and Spitzer devices. The difficulty with the Mata et al. and Spitzer devices is that their open-faced bone pin clamp jaws are two-piece designs which by their nature cannot be self-sprung and so require the use of an additional piece, such as a coil or compression spring, to maintain the jaws in an open position during installation onto the bone fixation rod. Additionally, the two piece nature of their design increases unit fabrication difficulty and cost.
Accordingly, there is a need in the art to provide a simpler design bone pin clamp assembly that minimizes the total number of steps an operator must take to engage the clamp assemblies and bone fixation rod, while still providing maximum flexibility to the operator in adjusting the distance between bone pin clamps on either side of a fracture.