Skull tong

Abstract

A skull tong for rigid engagement with the skull, comprising a rigid frame which has a pair of arm members and a transverse member forming a region between the members which is open at one end to receive a skull. A first and a second threaded passage is disposed in respective first and second arm members, and a third threaded passage is formed in one of the members spaced from the other two passages. All of the passages open into the region, and a respective engagement rod is threaded into each of them. Each engagement rod carries a drill adapted to cut its way into the skull when the engagement rod is rotated, so that the engagement means is self-drilling. Preferably, at least a 180.degree. portion of the periphery of the drill is formed as a smooth, non-cutting bearing surface, and the cutter means for cutting the skull is disposed outside of this portion. First and second lock means is carried by the first and second arm for engaging the first and second engagement rods to hold them in selected angular positions. The frame may be placed over a skull with the engagement rods retracted sufficiently to clear the skull. The engagement rods are rotated to advance them into the region and against the skull, further turning of the engagement rods causing the drills to drill respective holes in the skull to receive them as they advance into the skull. When the first and second engagement rods are fully engaged to the skull, the smooth portion of the drill may be faced toward the transverse member, so that the cutter means will not cut the skull when the transverse member is pulled in a direction away from the arm members.

Parent Case Text

This is a continuation of application Ser. No. 334,701, filed Feb. 22, 1973, now abandoned.

Description

This invention relates to a skull tong for rigid engagement with the skull.

There are applications in orthopedic surgery and in neurosurgery wherein the head must be engaged by a skull tong to be held in a predetermined manner. Skull tongs for this purpose are known, but they lack the capacity to retain themselves to the skull reliably for long periods of time without pulling out of the skull or otherwise adversely affecting the skull structure. Further, it has not heretofore been possible rigidly to attach a skull tong to the skull in such manner that, with the patient in traction, a pull on the skull tong can exert not only a pulling force on the head, but also a torque to pull it in an angular direction so as, for example, to elevate the top of the head and depress the chin, or to depress the top of the head and elevate the chin.

It is an object of this invention to provide a skull tong which can quickly and reliably be engaged to the skull so as to be rigidly attached thereto, and so that the skull tong will not pivot relative to the skull. In so doing, it is unnecessary to engage anything but the top and sides of the skull.

It is a further object of this invention to provide an engagement rod for the skull tong which is provided with a drill which cuts its own hole. The engagement rod is, therefore, precisely located and firmly engaged to the skull. As an optional objective, the drill may be pointed so as to puncture the scalp without requiring a previous incision in, or shaving of, the scalp.

It is an optional object of this invention to provide lock means which can hold the engagement rods in such manner that a smooth portion of the engagement rod will provide a non-cutting buttress when the skull tong is locked in place and pulled.

A skull tong according to this invention comprises a rigid frame having a first and a second arm member, and a transverse member joining the arm members together. The members lie in substantially the same plane, and the arm members extend in the same general direction away from the transverse member. They are spaced apart from one another so as to form a region between the members which is open at one end to receive a skull. A first and a second threaded passage is formed in the respective first and second arm members, and a third threaded passage is formed in one of the arm members, which third passage is spaced from the other threaded passages. All of these passages open into the region, and each has a respective central axis. A first, second and third engagement rod is threadedly engaged in each of the first, second and third passages. Each of these engagement rods carries a drill on its end concentric with the respective central axis, which drill includes cutter means. A first and a second lock means is carried by the first and second arm, respectively, for engaging the first and second engagement rods to hold them in selected angular positions.

According to preferred but optional features of this invention, the drill bears a point which can pierce the scalp without a prior incision, and has a smooth portion devoid of cutter means to act as a buttressing, non-cutting bearing surface between the engagement rod and skull.

According to still another preferred but optional feature of the invention, a limit shoulder is formed on each of the engagement rods adjacent to the drill point, whereby to limit the penetration of the drill point into the skull.

According to still another preferred but optional feature of the invention, a lock surface is formed on each of the first and second adjustment rods in such angular relationship to the cutter means that, when the lock means is engaged to the lock surface, the cutter means is directed away from the transverse member.

The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which:

FIG. 1 is a top view, partly in cutaway cross-section, showing the presently preferred embodiment of the invention;

FIG. 2 is a fragmentary cross-section taken at line 2--2 of FIG. 1;

FIG. 3 is a right-hand side view of a portion of FIG. 1, taken at line 3--3 therein; and

FIGS. 4 and 5 are two schematic views showing features of the skull tong when engaged to a skull.

A skull tong 10 according to the invention is shown in FIG. 1. It includes a rigid frame 11 having a first arm member 12, a second arm member 13, and a transverse member 14. The arms lie in the same plane (see FIG. 3), extend in generally the same direction away from the transverse member, and are spaced apart from one another so as to form a region 15 which is open at one end 16 to receive a skull 17 for engagement by the skull tong. The frame may be made of a bent rod, or if a lighter weight is desired, of a length of tubing provided with appropriate inserts to supply threads where needed.

The three members preferably form a continuous U-shaped structure, and in such a construction there is no precise boundary between them. For convenience, the arm members are defined as those portions in brackets 18, 19 which extend generally axially in FIG. 1, and the transverse member by the portion enclosed in bracket 20 which extends generally transversely, all relative to a tong axis 21, which is the central axis of the geometrically symmetrical frame. It is evident that structures other than curves may be used, for example frames formed by straight arms extending at right angles from a straight transverse member. However, all constructions have in common a pair of arms and a transverse member bounding a region into which the skull can be received for engagement by the tong.

A first passage 25, second passage 26, and third passage 27 are formed in the first arm member, second arm member, and transverse member, respectively. Each passage is at least partly bounded by a respective thread 28, 29, 30, which is coaxial with the central axis 31, 32, 33 of the respective passage. In the preferred embodiment of the invention, axes 31 and 32 are co-linear (coaxial). Also in the preferred embodiment, the third passage is disposed in one of the arm members, although it may be usefully disposed in the transverse member.

A first engagement rod 34, second engagement rod 35, and third engagement rod 36 are provided in the respective first, second and third passages. These rods have respective threads 37, 38, 39, which extend coaxially about the central axis of the engagement rod, which axis is co-linear with the respective passage axis when threads 37, 38 and 39 are engaged to threads 28, 29 and 30.

Knurled heads 40, 41 and 42 are formed on the ends of the engagement rods outside of the frame so that the engagement rods can readily be turned. The first, second and third engagement rods carry respective drills 45, 46, 47. The drills are best shown in FIGS. 1 and 2, and they are all alike, so that only drill 45 will be shown in detail. The drill is composed of three basic sections, the first being point 47a, the second being a smooth, non-cutting portion 48 which extends peripherally for at least 180.degree. of the periphery around the central axis as a smooth, continuous surface of revolution, which preferably is the fragment of a cone generated around the central axis, or a smooth surface representing the relieved rake of a drill, and the third section comprises cutter means 49, in the form of a sharp edge 50, that is formed by the intersection of a relief 51 and portion 48. Rotation of the engagement means in a counterclockwise (assuring a right-hand thread) direction relative to FIG. 2 will cause the point to perforate the scalp 52, without a previous incision, and will next cause the cutter means to form a hole in the skull by a scraping action, which is a form of drilling or abrading. It is evident that shapes than conical may be provided for the portion 48, and that a plurality of edges 50 may be provided if desired.

In the preferred embodiment as shown, portion 48 is a fragment of a conical surface of revolution, and because the cutter means is formed as an intersection with it, it does not project radially beyond a theoretical continuation of the surface of revolution. A cutting action will occur because endwise force against the smooth portion causes a lateral deflection toward the cutting edge. A cone is a single example of a suitable surface of revolution. Other types of surfaces of revolution, both concave and convex, or a combination of concave and convex, could be used. The term "surface of revolution" is used to denote the surface cut by revolving a cutting edge that generates the surface. Because the cutting surface advances as it cuts, the surface will differ a little from a true cone, or from a true surface of revolution of the type generated by an edge which does not advance along the axis of rotation, but the difference is quite small in view of the fine thread pitch involved, and the term "surface of revolution" appears suitably to describe the surface. Also, cylindrical drills can be used any may be conventionally fluted and raked. They may or may not carry a sharp point.

A conical surface provides optimum surface-to-surface contact between the engagement rod and the wall of the hole in the skull. However, other forms of smooth, non-cutting portions 48 can be provided, such as a gently spiraling (raked) relieved surface which trails the cutting edge. With such a relieved smooth portion 48 (relative to the cutting edge), the cutting edge projects beyond the smooth portion, and there is a slight possibility that the cutting edge may gall in the hole, which possibility does not exist when a conical portion is used and the edge does not project radially beyond it. However, the risk is small and its effects can readily be overcome by exerting a sufficient torque on the engagement rod. Also, there is a less perfect surface-to-surface contact of the engagement rod against the wall of the hole in the skull, but this can be tolerated.

Furthermore, multiply-fluted drills of common construction can be used. A smooth portion 48 is therefore optional, because a full surface-to-surface bearing contact is not necessary. although it is desirable.

Similarly, the point is optional, because an incision can be made by a separate instrument. It is preferable, however, because the incision it makes is correctly located and minimal in size.

A limit shoulder 55 is formed adjacent to the drill point to limit penetration of the drill point into the skull.

A lock surface 60, 61, 62 is formed on respective first, second and third engagement rods. The lock surface 62 is optional on the third engagement rod, but it is desirable. Lock means 63, 64, 65 comprise headed set screws 66, 67, 68, which are threaded into threaded holes 69, 70, 71 and are disposed so that access can be had to slots 72, 73, 74 in their respective heads. The location of the set screws in the frame, and the location of the lock surfaces relative to the edge 50, are so selected that, when a set screw is brought against its respective back surface portions 48 face toward the transverse member, i.e., away from open end 16, and edge 50 faces away from it, i.e., toward the open end 16 of the frame. The lock surfaces are optional, and are used only when some portion of the drill is to be aligned. If such a feature is not provided, then the lock means can bear against any part of the engagement rods, and the lock surfaces will be eliminated.

The included conical angle at the point on the drills may conveniently be between about 25.degree. and 35.degree., and the pitch of the thread and the cutting capacity of edge 50 (or edges) are so interrelated that the edge 50 will cut away skull material at such a rate relative to the advance of the adjustment rod that no substantial compressive expansive forces are exerted on the skull material which might tend to crack it. This is a matter of design, and in usage it has been found that a fine thread pitch is needed in order that the cutter means can remove material as fast as the engagement rod advances. When a single cutting edge is used, a pitch representing at least about 80 thread convolutions per axial inch is found as a practical matter to be needed, and an even greater number of convolutions per inch is advantageous, provided that the thread does not become so fine as to be impractical. Between about 80 and about 190 convolutions per inch appears to represent an ideal range of thread pitches. The cutting edge will be designed to cut material at a rate at least as fast as the engagement rod advances. The thread range recited is suitable for cutting into the bony skull.

Attachment means 80 conveniently may be in the form of an eyelet 81. This means is attached to the frame and is adapted to be engaged by a link of a chain 82 or by an end loop of some other type of flexible member, such as cord. The usage of the skull tong should be evident from the foregoing. However, to recapitulate, when the skull tong is to be engaged to the skull, the engagement rods will be retracted sufficiently to clear the skull as the frame is placed over it, with the arm members on opposite sides thereof. When the frame is properly located, the engagement rods are rotated so that their points penetrate the scalp and the cutter means drills into the skull as they advance. The engagement rods are rotated either successively in increments, or substantially simultaneously, until the desired degree of attachmemt is obtained which might consist of the engagement of the limit shoulders against the bony material of the skull or a lesser penetration. At this time, the first and second engagement rods will be stopped where the set screws may be brought firmly against the lock surfaces (when they are used) so as properly to orient the portions 48, as shown in the drawings, preferably without backing off the engagement rods. Such an arrangement of portion 48 is not as important for the third engagement rod as it is for the other two engagement rods, but it is convenient should the third rod be disposed other than in direct alignment with axis 21. For this reason, when lock means is provided for this third engagement means, the third engagement rod may conveniently also include a lock surface as shown, although for this engagement rod, direct engagement against a continuous uninterrupted thread instead of against a lock surface would perform many of its same functions when alignment of the rod is not necessary.

With the skull tong installed as shown, the skull may be manipulated with the tong as a "handle" for any purpose. When it is used on a patient in traction, then the benefits of other advantages of this tong will be obtained. It is known that a person in traction must often have his head propped in place by pillows and the like in order to provide a desired flexure at the neck. This can constitute a source of considerable discomfort for the patient, and also requires frequent adjustment and meddling. In contradistinction, by utilizing this invention, flexure in either direction can be caused by appropriate location of the skull tong on the skull. Should a force tending to elevate the chin relative to the chest be desired, then the skull tong will be applied with the transverse member tilted farther forward on the head, as shown in FIG. 4. THen, a linear force 85, such as might be exerted by a cord pulled by a traction weight over a pulley, will exert not only the typical linear traction force 85, but also a torque 86 tending to elevate the chin.

On the other hand, should depression of the chin be desired, then the skull tong will be inserted with the transverse member tilted farther back along the skull (in both cases, the first and second engagement rods being located in the same places). Then a linear traction force 87 will exert a torque 88 tending to depress the chin. Forces and torques 85-88 are schematically illustrated by the arrows in FIGS. 4 and 5.

Similarly, the tong may be attached centrally, and the force applied in the desired direction by changing the angle of the cord or chain relative to the horizontal to provide the same result.

The invention thereby provides a skull tong for rigid attachment to a skull which is readily attached without requiring an incision, and in which the engagement rods cut their own holes in the skull and, if desired, exert their force against the bony material of the skull through a smooth, non-cutting surface. In the preferred arrangement of FIG. 1, wherein axes 31 and 32 are co-linear, it will be noted that a maximum buttressing area of portions 48 faces in the direction of pull so as to give maximum resistance to pull-out. Engagement rod 36 also may be so oriented, if desired.

Prior art devices have tended to require pre-drilled holes in the skull, and the introduction of their sloppily-fitting pins have a tendency to gall and pull out of the skull, and also to fit poorly in them because, in order for the pins assuredly to enter into already-drilled holes, the drilled holes must be made oversized relative to the pin because of the near-impossibility of aligning the same. In this device, the alignment is automatic because each engagement rod drills its own hole, and for the same reason each makes a tight fit which is not subject to excessive loosening and play, thereby overcoming the problems of excessive galling and working of the rods in the hole. Should this device loosen somewhat for any reason, it is only necessary to rotate the engagement rods a bit more to tighten them down farther, and usually there will be sufficient thickness of the skull relative to the selected length of the drill point that this can be accomplished without untoward effect on the surrounding structure. In fact, in the usual case, the distance of the limit shoulder 55 from the tip end of the drill point will be such that the limit shoulder will not be engaged to the skull during the intended usage of the device, at least initially. The parts are shown in substantially full scale in the drawings as submitted. For reference purposes, the distance between the inside edges 89 anad 90 of the first and second arms is approximately 7-3/8 inches, and the diameter 91 of the rod used to make the frame is about 1/2 inch.

As a further comparison to the prior art, it has been found that attempts to pierce the skull with unfluted points have required an endwise force on the order of 60 pounds to penetrate even slightly, which is a dangerous load, and even so, the penetration is so small that the structure is readily pulled off the skull.

This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of illustration and not of limitation, but only in accordance with the scope of the appended claims.

Claims

I claim:

1. A skull tong for rigid engagement with a skull, comprising: a rigid frame comprising a first and a second arm member, and a transverse member joining the arms together, the members lying in substantially the same plane, and the arm members extending in the same general direction away from the transverse member and being spaced apart from one another so as to form a region between the members which is open at one end to receive a skull; a first and a second passage in the respective first and second arm members, and a third passage in one of said members, which third passage is spaced from the other passages, all of said passages opening into said region and each having a respective central axis; a thread in each of said passages; a first, second and third engagement rod, each rod having a respective central axis of rotation coaxial with the central axis of the respective passage; a thread on each of said engagement rods coaxial with the central axis of the rod, said engagement rods being threadedly engaged to the thread in the respective first, second and third passages, whereby rotating said rods moves the rods along their respective central axes into and out of said region, the threads of the respective passages and of the engagement rods which are threadedly engaged thereto having a dimension of pitch; a first, second and third lock means carried by the first and second arm members and by the transverse member, respectively, for engaging the respective engagement rods to hold them in a respective selected angular position; a drill on the end of each engagement rod concentrically with the respective central axis said drill comprising cutter means and a non-cutting portion which is axially aligned with the cutter means, said non-cutting portion providing a surface for engagement with the wall of a hole in the skull which is cut by the respective cutter means, the cutter means comprising an intersection with the said portion, and said portion comprising a fragment of a surface of revolution, whereby the frame may be placed over a skull with the engagement rods retracted sufficiently to clear the skull, and then the engagement rods may be rotated so as to advance them into the region and against the skull, further turning of the engagement rods causing the cutter means to drill respective holes in the skull to receive them, the pitch of the threads and the cutting capacity of the cutter means being so inter-related that the cutter means will cut a hole in the skull at a rate sufficient to enable the drill to enter the skull without substantial compression of the skull adjacent thereto, and engagement of the engagement rods by the respective lock means holding them in a selected position in the respective hole, thereby to keep the skull tong engaged to the skull.

2. A skull tong according to claim 1 in which a point is formed on the end of each engagement rod which faces said region, for making an incision in the scalp.

3. A skull tong according to claim 1 in which the first and second lock means comprises a lock surface formed on each of the first and second adjustment rods in such angular relationship to the cutter means that, when the lock means is engaged to the respective lock surface, the respective cutter means is directed away from the transverse member.

4. A skull tong according to claim 3 in which the lock means comprises a screw threaded into a respective member.

5. A skull tong according to claim 1 in which a limit shoulder is formed on each of the engagement rods adjacent to the drill whereby to limit the penetration of the drill into the skull.

6. A skull tong according to claim 1 in which said surface of revolution is a cone.

7. A skull tong according to claim 1 in which the said first and second threaded passages are coaxial.

8. A skull tong according to claim 1 in which attachment means is provided on the transverse member to for attaching an element to the frame which exert a pull thereon.

9. A skull tong according to claim 3 in which attachment means is provided on the transverse member for attaching an element to the frame which exert a pull thereon.

10. A skull tong according to claim 3 in which a point is formed on the end of each engagement rod which faces said region, for making an incision in the scalp.

11. A skull tong according to claim 1 in which the lock means is a screw threaded into a respective member.