Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-12-21
2001-07-24
Smith, Jeffrey A. (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
C606S104000
Reexamination Certificate
active
06264661
ABSTRACT:
This application claims priority of German Patent Application Number 198 59 135.7, filed Dec. 21, 1998, the entire disclosure of which is considered to be part of the present disclosure and is specifically incorporated by reference herein.
FIELD OF INVENTION
The present invention relates to a device by means of which an elongated wire pin, in particular a Kirschner wire, may be driven into bone material, comprising a propelling device that acts upon the wire pin which may be inserted into the device from the free front end thereof, said propelling device being moved by an impacting member which generates impact strokes and is in turn periodically moved.
BACKGROUND OF THE INVENTION
A medical instrument for driving a short headed nail into bone material is known from DE 195 27 529 A1. The propelling device described therein is designed as a transmitting piston which is biased by a return spring, and translationally driven by a drive piston. Said drive piston is moved pneumatically in a drive pipe until it abuts against the transmitting piston. The cylindrical, elongated head of the nail is inserted into a guide hole formed in the front end of the device, and pushed into the device until the head abuts against a pin formed at the transmitting piston. The nail is translatorily forced into the bone material by the impact applied upon the transmitting piston by the drive piston.
Devices for driving in a Kirschner wire are used in surgery, in particular for the treatment of bone fractures. The Kirschner wire, which is an elongated wire pin made of metal, for example, may easily and rapidly be driven into the bone portions without causing significant injury to the adjacent soft tissue
Such devices are known, for example, from EP 0 597 547 A and DE 27 35 563 A, according to both of which the strokes of the impacting member are transmitted to the wire pin via a receiving sleeve and a clamping device. In the device described in EP 0 597 547, the wire pin is inserted into the device from the rear end thereof, and applied with impact pulses in the form of vibrations which are transmitted via an eccentric clamping device so that the wire is driven to perform an oscillating motion that results in a translatory forward motion thereof. According to DE 27 35 563, the wire is inserted into the front end of the device and clampingly fixed therein. Similar to the operation of a percussion drill, the wire is periodically applied with impact pulses so that it successively advances together with the receiving sleeve, with the other portions of the device being subsequently taken along. The two above described prior art devices must be arranged as close to the bone material as possible so that the wire pin will perform a smooth translatory motion, i.e., the pin does not buckle. To still make sure that a sufficient length of wire material is driven into the bone material, the respective clamping device is designed as a silent ratchet which allows the wire pin to move out of the device, but prevents it from moving back into the device. Thus, the device may contain a sufficient supply of wire material which is successively supplied to be driven into the bone material. Because of their rather complex clamping and gripping devices, said prior art devices are expensive to manufacture. Further, they have a comparatively high energy consumption, which results from the fact that the impacts must be strong enough to move the entire clamping device together with the wire, and that the device must be relatively robust to withstand the extensive mechanical stresses and loads to which it is subjected. Moreover, the impact which may be transmitted to the wire pin itself is rather small.
SUMMARY OF THE INVENTION
The present invention provides a device of the initially mentioned type which may be used for driving a wire pin, in particular a Kirschner wire, into bone material, and which has a simple structure as well as low energy consumption.
In the device according to the present invention, the propelling device acts upon the wire pin without any clamping means being provided. Therefore, the inventive propelling device is designed as a transmission member transmitting elastic impact waves, against which the free end face of the wire pin may evenly abut so that the impact strokes applied by the impacting member are transmitted as periodically repeated impact pulses through the free end face of the wire pin and into the body thereof. Each impact transmitted into the wire pin propagates through the wire pin in the form of a compression wave so that the end thereof facing the bone material is displaced into the bone material, and gets lodged therein so that the rest of the wire pin follows up when the compression wave is being reflected at the bone facing end of the wire pin. Thus, the wire pin projecting from the free front end of the device is periodically and progressively driven into the bone material by periodically successive compression waves. After each impact pulse, the device is moved towards the bone material until the wire pin abuts again at the transmission member so that the device is ready for the next driving process.
According to the present invention and as opposed to conventional devices, the wire pin is driven into the bone material by means of continually applied impact pulses rather than by a translatory motion thereof. Further, the wire pin is not fixed at the propelling device at the time of impact transmission so that complex structures serving to automatically lock and release the wire may be dispensed with. Instead, the end face of the wire loosely abuts against the transmission member at any time of the operational process. As mentioned above, conventional devices have a supply of wire material provided therein which is successively moved out of the device by the propelling device which, during the operation of the device, engages the wire at different portions in the longitudinal direction thereof. In the device according to the present invention, however, the propelling device only engages the end face of the wire pin facing away from the bone material at any time of the process. Even if an elongate or slightly bent wire pin such as a Kirschner wire is used, there is no risk of buckling as the wire pin is not driven into the bone material by a generally translatory motion. The impact pulse transmitted into the wire pin according to the present invention is also able to propagate in the form of a compression wave through an elongate, curved wire pin, and causes the bone-facing end of the wire pin to be displaced into the bone material even if the wire is slightly curved. During each impact pulse, the wire pin is driven into the bone material by a stroke length of approximately 1 mm.
In the device according to the present invention, the transmission member is designed to transmit an impact pulse, into the wire pin and does not, or almost not, perform a translatory motion itself. Thus, no energy is consumed for the acceleration or moving of a clamping device, which results in a reduced energy consumption. The wire pin is formed as a waveguide capable of transmitting elastic longitudinal waves, therefore the impact pulse excites a longitudinal or compression wave in the wire pin which propagates through the wire pin so that the material thereof is locally expanded and compressed. Thus, the free end of the wire is displaced into the bone material by the incident elastic wave. The wave is being attenuated during travelling, and then reflected at the free end of the wire pin so that it causes the free wire portion to contract. However, since the free end portion of the wire is lodged in the bone material and cannot be pulled out thereof, the remaining portion of the wire is caused to follow up the displacement of the free end into the material.
The transmission of impact pulses into an elongate wave transmitting member having the form of a wire is already known from lithotripsy procedures as used, for example, for the crushing of kidney stones. From DE 196 18 972 A1, for example, a device is known
Jerger Thomas
Raabe Thorsten
Van Egmond Dirk Bernard
Ferton Holding SA
Griffin & Szipl, P.C.
Smith Jeffrey A.
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