GB2187990A - Surgical tools - Google Patents

Abstract

A surgical hand tool having a cutting edge and used for bone cutting, so that it can be of light weight with a cutting edge which will stand up well to prolonged use, is made of titanium or a titanium alloy. The tool including handle 10 is rough formed by closed die forging, and the cutting portion 12 is then hand- smithed, ground and polished. <IMAGE>

Description

SPECIFICATION Surgical tools This invention relates to surgical hand tools having a cutting edge and used for cutting bone. Examples of such tools are chisels, osteotomes and gouges, all of which are normally struck with a hammer, and also rongeurs which are used for nibbling bone by moving two parts together. The invention is also applicable to surgical reamers of the kind which are used for example in reaming out holes in bone when performing hip replacement operations. All of such tools have at least one cutting edge and the working part of the tool is made integral with a handle, or with a pair of handles in the case of rongeurs.

All of these surgical tools are conventionally made from surgical stainless steel.

The number of such surgical tools which are marketed by any one manufacturer is very considerable. There are numerous different designs performing very similar functions and one design may be produced in a Variety of sizes. Because of this the normal method of manufacture in the case of chisels, osteotomes and gouges is for the tools to be produced by hand smithing or, more usually, by employing a closed die forging technique to produce a handle with subsequent hand smithing to produce the working part of the tool on which the cutting edge is later formed. This combination allows the closed die forging, with its considerable tooling costs, to be used for a handle which would be common to a variety of products, yet avoids the considerable tooling costs which would be required if closed die forging was used for the entire forging operation.

Whichever method of forging is employed it leads to a blank of a precise shape and size which is then ground and polished to the completely finished shape.

We have now appreciated that it would be advantageous to make such surgical tools from a different material and surprisingly we have found that titanium can provide and retain a satisfactory cutting edge even though its absolute hardness is less.

Titanium has previously been used for small and very delicate instruments, for example small scale instruments used for neurosurgery.

This is however a category of surgical instruments where bone cutting is not involved and where it is commercially viable to make the tool by waste-removing machining which is the technique which has been employed.

According to one aspect of the invention, there is provided a bone-cutting tool formed from titanium. The titanium may be alloyed with up to 20% of alloying elements. The tool may have a cutting edge with an included angle of between 25 and 40 , ideally in the region of 30 .

According to another aspect of the invention, there is provided a method of making a bone-cutting hand tool of titanium or of a titanium alloy, the method including the forming of a tool blank by closed die forging and the subsequent working of the tool blank by hand smithing and a final grinding operation to apply a cutting edge. For reasons of economy of capital investment it is preferred to employ hand smithing for at least part of the fabrication process. The hand smithing of titanium to precise shape and size is itself novel.

Tools of the present invention have a number of advantages. They are lighter which of course means that it is less fatiguing for a surgeon holding the tool and working with it for a prolonged period of time. They have a duller finish which is therefore less fatiguing for the eyes of a surgeon working under the bright lights of an operating theatre for a prolonged period. They are not prone to brittle failure as can occur with steel tools and additionally titanium is biocompatible so that if a fragment of the tool did break off it might well not be essential to find and remove the fragment from the patient. By contrast any fragments of a steel tool must always be found and removed. A further advantage of the tools of this invention is that they have a lower thermal capacity as compared with steel tools.Consequently, if it does become necessary to resterilise the tool during the course of an operation the time for the sterile tool to cool to room temperature is less.

In order that the invention may be fully understood and readily carried into effect, an embodiment thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Figure 1 is a perspective view of a tool blank which has been produced by closed die forging, Figure 2 is a diagrammatic view illustrating a hand smithing operation in which the tool blank is being worked to produce a bone cutting surgical tool embodying the invention, and Figure 3 is a perspective view of a different type of bone cutting surgical tool embodying the invention.

Referring now to Figure 1 of the drawings, the tool blank there illustrated has been formed in a titanium alloy by closed die forging and comprises a handle part 10 and integral blade blank part 12. The closed die forging operation will have been carried out at a normal forging temperature for titanium alloy, that is to say at a temperature in the region of 910 C. At this stage the handle part is in substantially its finished shape, requiring only grinding and polishing, but the blade blank part is of a roughly rectangular shape and requires considerable further working to form the finished blade part, whatever the form of the required blade part might be.

In Figure 2 there is illustrated a hand smith ing operation being carried out, this comprising considerable working and re-heating before the finished blade is produced. This requires the considerable skill of a skilled hand forger such as currently required when working with steel. The workman will take care not to affect the properties of the material by raising the titanium to a temperature beyond a maximum value of 91 00C either by re-heating or by the working of the material at an excessiye rate. He can sufficiently closely control the temperature by observing the colour of the heated workpiece. The workpiece should be descaled and etched with acid between successive heating operations as is known per se for closed die forging of titanium.

It will be seen that in this illustrated example the form of tool which has been fashioned from the forged blank is a type of gouge.

Following the hand smithing operation, the finished shaped blade will be ground and the cutting edge applied by grinding. It has been found that the included angle of the cutting edge should be between 250 and 400 and preferably in the region of 30~. If the included angle is made substantially less than this, the cutting edge will be unlikely to stand up to prolonged use.

Referring now to Figure 3, this is a rather lighter form of tool, that is to say a small chisel, which again has been made of a titanium alloy. It has been found convenient to form this from titanium alloy bar by closed die forging, the tool then of course being ground and polished. This also has been found to cut cleanly into living bone and to stand up surprisingly well to prolonged use.

After grinding and polishing the tool to its finished shape it is preferably anodised in conventional manner for titanium alloy. Titanium alloy is self-colouring by anodising or heat oxidation, which not only makes the tools produced in this material of an attractive appearance but also reduces their reflectivity under the bright lights of an operating theatre. Selected parts of the tools can of course be acted on by brief exposure to acid to remove the anodising. We prefer to remove a portion of each tool adjacent its cutting edge and the surface of the handle which in use is to receive blows from a mallet. The acid used is acqueous hydroflouric acid with ferric sulphate dissolved in it and sufficiently diluted until the removal of anodising is not uncontrollably fast.

After anodising and removal of anodising no further treatment is necessary except perhaps a final wetting of the cutting edge.

Thus there is provided a bone cutting surgical tool which has been found to have a number of advantages over similar tools made from other materials, that is to say being of relatively light weight, having a duller surface finish than steel and being biocompatible.

Claims (7)

1. A bone-cutting hand tool formed from titanium.

2. A bone-cutting hand tool according to claim 1, the titanium being alloyed with up to 20% of alloying elements.

3. A bone-cutting hand tool according to either one of the preceding claims, the tool having a cutting edge with an included angle of between 250 and 400.

4. A bone-cutting hand tool according to claim 3, in which the included angle of the cutting edge is in the region of 300.

5. A method of making a bone-cutting hand tool of titanium or of a titanium alloy, the method including the forming of a tool blank by closed die forging, and the subsequent working of the tool blank by hand smithing and a final grinding operation to apply a cutting edge.

6. A bone-cutting hand tool, substantially as hereinbefore described.

7. A method of making a bone-cutting hand tool, substantially as hereinbefore described.