Surgery – Instruments – Orthopedic instrumentation
Patent
1990-09-20
1992-02-11
Thaler, Michael H.
Surgery
Instruments
Orthopedic instrumentation
606177, 301233, 83169, 83171, A61B 1714
Patent
active
050872613
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a saw-blade for sawing living human bone during surgical operations.
DISCUSSION OF RELATED TECHNOLOGY
Operations in orthopedic surgery often involve shortening, cutting, cleaving or otherwise working bone structures. This is done by chisel, drill, sometimes by milling cutters and sometimes, where straight cuts or planar bone surfaces are desired, by saws. To ensure precision in sawing very high speeds on the order of 20,000 rpm are used, so the saw "vibrates" in a stable manner. This way of working the bone is customary at operations involving artificial joints (joint prostheses), especially in the knee joint. However, also when operations are made in the hip joint and joints in the upper extremity, use is made of sawing.
Artificial joints are fixed to the bone tissue by means of so-called bone cement (acrylic plastic) or by promoting growth of bone directly into the prosthesis. Such anchoring at present is the greatest problem in prosthesis surgery; if the prostheses comes loose from the bone tissue, another operation is required. A corresponding problem exists at operations not involving a prosthesis, i.e. where bone is sawn off and screwed together at another angle. In some cases, the bone does not heal after such operation.
With the use of extant saws, high temperatures develop. By way of example, there have been measured in the clinical situation, at an operation involving an artificial joint in the knee joint, temperatures ranging between 45.degree. and >100.degree. C., the average value being about 70.degree. C. The critical temperature for bone tissue is considered to lie at 47.degree. C. The conclusion is that the bone around the saw cut is killed during the operation. This may be one of the reasons why prostheses come loose and, respectively, that healing sometimes does not occur in the contemplated manner.
During sawing at this kind of operations it is customary to cool the bone by supply of liquid dropwise to the saw-blade or by spraying liquid thereonto. In laboratory tests as well as under clinical conditions, it has proved that such cooling has no effect at all; the problem of heat development on sawing in orthopedics is still unsolved at present.
In patent literature there are some specifications that treat of the supply of coolant to the saw-blade for the cooling thereof. Thus U.S. Pat. No. 4,008,720 describes a saw-blade having three coolant passages. At the rear portions of the saw-blade said passages connect onto a coolant supply conduit and extend in a forward direction along the saw-blade, opening at a distance from the saw teeth in one of the saw-blade sides which run in parallel with the plane of oscillation of the saw-blade. The passages opening at a distance from the saw teeth, the coolant will not contact said teeth, which implies that they are not cooled directly. Instead, the heat has time to spread rearwardly in the saw-blade until it reaches cooled portions thereof, and the harm is done already. Moreover, since the passages open into those sides of the saw-blade which run in parallel with the plane of oscillation of the saw-blade, the exiting coolant jets will not be directed outwardly away from the saw-blade for efficiently carrying off saw residues in a direction away from the saw teeth.
BRIEF SUMMARY OF THE INVENTION
The object of the present invention is to provide a saw-blade in which the above-mentioned problems are eliminated. This is achieved, according to the invention, by using a saw blade presenting on at least one side at least two saw portions and the saw blade having at least one inner space through which coolant is intended to flow for cooling the saw blade during sawing.
As the coolant space in the saw-blade according to the invention extends all the way to the saw portions, coolant can get in direct contact with said portions for efficient direct cooling thereof. Moreover, as coolant can emerge between the saw teeth, the coolant is able to flush away saw residues from the saw teeth, which will pr
REFERENCES:
patent: 4008720 (1977-02-01), Brinckmann et al.
Bertilsson-Lindstrand Anders O.
Ryd Leif E. S. H.
Toksvik-Larsen Soren
Mit AB
Thaler Michael H.
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