Surgery – Instruments – Orthopedic instrumentation
Patent
1989-09-14
1992-04-28
Hafer, Robert A.
Surgery
Instruments
Orthopedic instrumentation
606 80, 173 91, A61F 504, B25D 900
Patent
active
051084007
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a striking tool for surgical instruments with a sleeve-shaped gripping part, a tool holder which is slidingly displaceable in the latter in the longitudinal direction thereof, and an oscillatingly driven piston which is slidingly displaceable in the gripping part in the longitudinal direction thereof and has two striking surfaces which strike corresponding contact surfaces of the tool holder and thereby act upon the latter with impulses acting in opposite directions.
Striking tools are used in surgery, for example, to drive rasps into the marrow cavity of a bone and to thus prepare this marrow cavity for receiving an endoprosthesis, or to insert prosthesis shafts into the marrow cavity of bones. In this connection, it is known to use as striking tools, for example, tools which have an oscillatingly driven striking piston which with each stroke of its motion strikes against a tool holder and hence delivers a blow to the tool holder to drive the tool into the bone. This piston can be oscillatingly driven, for example, pneumatically by valves being correspondingly reversed.
It is, furthermore, known to so design such an instrument that with each stroke of the striking piston, not only a blow acting upon the instrument in the forward direction is delivered to the instrument driven into the bone but also a blow acting in the opposite direction so with each stroke, the instrument is also loosened again relative to the bone cavity (EP-B1 144 005). In the known construction, this is achieved by the piston striking against oppositely arranged stop faces on the tool holder at the end of its motion and by the instrument being axially immovably connected to the tool holder. With each stroke, blows acting in opposite directions are thereby transmitted to the instrument.
Such an instrument is suitable for driving in rasps, prosthesis shafts, etc., but not for pulling out such instruments, for example, for pulling out a rasp which is firmly seated in the marrow cavity of a bone.
On the other hand, striking hammers which operate with a flying piston are used in various technical fields. In a known pneumatic chisel for automobile bodies, one compressed air channel each is connected to the front and to the rear cylinder chamber. The compressed air channels are alternately connected to a source of compressed air via a flutter valve. Arranged in the front region of the rear cylinder chamber is an air-release bore which during forward drive is initially closed by the flying piston and is opened shortly before the axially displaceably mounted chisel is struck, the pressure head forming in front of the piston escaping through a clearance between the chisel pin and the guide bore in the housing. Once the air-release bore is exposed, the flutter valve changes over as a result of the drop in pressure so the front cylinder chamber is now subjected to compressed air and drives the piston rearwardly, i.e., away from the tool. When the air-release valve is then closed again by the piston, there is a build-up of pressure again in the rear cylinder chamber which finally reverses the two-way acting valve and initiates the next forward stroke. In this construction, the flying piston does not strike the cylinder housing. The device is, however, unsuitable for medical purposes, above all, because the tool is acted upon only in the direction towards the object, i.e., a rasp could not be pulled out.
There is, furthermore, known from DE 32 29 309 C 2 a hydraulic striking hammer provided with a flying hollow piston which has a striking pin designed as a piston and acting upon a tool axially displaceably mounted therein. By means of a certain guidance of the hydraulic medium and a two-way acting valve, the hollow piston and the piston-type striking pin are alternately driven against an intermediate piston abutting on the tool. This device operates only when the tool is pressed against the object. Here, too, use for the performance of operations in the medical field is excluded.
Bone surgery also includes driving in and ou
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Appel Hans-Gunter
Hausler Rainer
Heymeyer Thorsten
Laabs W. A.
Wolfle Wilfried
Aesculap AG
Brown Michael
Hafer Robert A.
Lipsitz Barry R.
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