DE8415145U1 - Twist drills for working on bones - Google Patents

Description

HOEGER

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A 45 970 u Applicant: AESCULAP-WERKE AG

^u ~ 183 formerly Jetter & Scheerer

March 1, 1984 " _Λ

7200 Tuttlingen

description

Twist drills for working on bones

The innovation concerns a twist drill for processing bones.

Twist drills are used in bone surgery, for example, to pre-drill screw holes for bone screws. The hole must have a high degree of dimensional and shape accuracy in order to hold the screws firmly for the duration of the entire healing process. When machining materials, the Most of the energy is converted into heat. This leads to an increase in temperature in the bone, which too damage to bone tissue. An egg-

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White coagulation already occurs at temperatures of 4 6 ⁰ C, and cell enzymes are already damaged if the cell temperature is raised by only 5 ⁰ C. In addition to the thermal damage, mechanical damage to the bone tissue also occurs during drilling, in particular due to the automatic retraction of the drill when it breaks through the cortex. Pieces of bone can be broken out, and microfractures and tears in the bone tissue occur.

It is the task of the innovation to design a twist drill in such a way that that with it accurately shaped drilled holes can be made in bone tissue, with the development of heat and the mechanical damage to the vicinity of the borehole is to be reduced.

This task is in accordance with the innovation in a twist drill solved in that it has a tip angle between 65 ° and 90 ° and a helix angle between 12 ° and 20 °. These values are compared to conventional twist drills, such as those used for machining metal or wood are used, much smaller, and it has surprisingly been found that by reducing both the point angle and the helix angle to the specified values a significantly more favorable Drilling behavior occurs when working on bone substance. It is not just that by choosing this angle Temperature increase in the drill hole area is reduced, but also the duration of the machining, i.e. with a given feed force can enter within a certain drilling time

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deeper hole to be drilled. Conversely, this means that the duration of the processing and thus the heating is reduced is, so that less heat is generated in the drilling area by this effect. Finally it turned out that the choice of this angle also the risk of automatic retraction when piercing the The cortex is significantly reduced, i.e. there are fewer mechanical injuries in the borehole area.

The temperature increase can be reduced even further if, according to a preferred embodiment, the core thickness between 9 and 15% of the drill diameter. These The core thickness is thus significantly below the core thickness of drills that are usually used for other materials will.

In preferred embodiments, the apex angles are between 70 ° and 80 °, in particular between 70 ° and IC 0

Particularly advantageous results can be achieved if the twist angle is between 14 ° and 18 °, preferably is between 15 ° and 16 °.

10 to 12% of the drill diameter have been found to be particularly favorable values for the core thickness.

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The following description of a preferred embodiment of the fire is used in conjunction with the drawing for a more detailed explanation. Show it:

Fig. 1 is a front view of a twist drill and

Figure 2 is a side view of the tip portion of a twist drill.

The twist drill shown in the drawing is basically constructed in the same way as any known double-edged drill Twist drill. The two main cutting edges 1 and 2 close together what is known as the point angle OO one that is relatively small and between 65 ° and 90 °, preferably between 70 ° and 80 ° and in particular between 70 ° and 75 °.

The pitch of the secondary cutting edges 3 and 4 is determined by the so-called helix angle, that is the angle that the secondary cutting edge includes with a radial plane passing through the axis of the twist drill. This helix angle is also much smaller compared to normal twist drills; it lies between "i2 ^c and 20 ^c, preferably between 14 ° and 18 ^C and more preferably between and 12 °.

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The two main cutting edges 1 and 2 are cut through the ^: $

called cross cutting edge 5 connected to one another, the length of which is I.

is indicated by the so-called core thickness K. This %

for the twist drill, which is particularly suitable for bone processing, values between 9 and 15% of the Bonrer diameter and especially at values between 10 and 12% of the drill diameter and is thus essential smaller than conventional twist drills.

The small point angle results in a favorable incision in the bone, so that the drill through the Operator is easier to handle. Due to the small helix angle, the flutes of the drill have a great slope. The chips are transported away from the cutting point and out of the borehole relatively quickly. As a result, the heat transfer between the chips and the bones will remain low. This also helps reduce the temperature to keep low in the drilling area.

The small helix angle also has the advantage that the drill is not able to operate automatically due to the small helix angle Tends to pull in when breaking through. This increases the risk of mechanical damage in the area of the borehole is significantly reduced. ■

The reduction in the core thickness of the drill reduces the drilling time compared to conventional drills urr, das Siebenbis Tenfold, i.e. the heat transfer time is also significantly reduced. The surgeon also needs less

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ger force to create a borehole of a certain depth with this drill.

Claims (7)

HOEGER1 STEL'lFteCffi ·;?. PARTNER pat ε Λ'.τ, ί'Ν * .λκ.τ * ε ·. UH.LANDSTRASSE Kc D 7ΟΟ0 STUTTGART A 45 970 u "Applicant: AESCÜLAP-WERKE AG u - 183 formerly Jetter & Scheerer '■ March 1984 7200 Tuttlingen Protection claims 1. Twist drill for machining bones, characterized in that it has a tip angle (cc) between 65 ° and 90 ° and a twist angle (ß) between 12 ° and 20 °. 2. Spiral drill according to claim 1, characterized in that the Ii Ksrndicke (K) 9 to 15% of the drill '"diameter. 3. Twist drill according to claim 1 or 2, characterized in that the point angle (CX) is between 70 ^e and 80 °. 4. Twist drill according to claim 3, characterized in that the point angle is between 70 ° and 75 °. A 45 970 u u - 183 March 1, 1984 5. Twist drill according to one of the preceding claims, characterized in that the helix angle between 14 ° and 18 °. 6. Twist drill according to claim 5, characterized in that the helix angle is between 15 ° and 16 °. 7. Twist drill according to one of claims 2 to 6, characterized in that the core thickness (K) between 10 and 12% of the drill diameter.