Notched Surgical Pin And Breaking Tool Therefor

Abstract

A surgical pin formed of rigid material for joining bone sections in an area of fracture. Following insertion of the pin into the bone sections, a breaking tool in the form of a handle-equipped tube is fitted over the free end portion of the pin and the pin is then broken externally of the bone and along a transverse plane defined in part by any one of a series of notches formed in the pin. The notches of the series are angularly offset about the axis of the pin to provide an arrangement which facilitates breaking of the pin only at a selected notch.

Description

BACKGROUND OF THE INVENTION

The use of metal pins to hold bone sections together as they heal is a well known practice, particularly for fractures near the upper joint of the femur, commonly called hip fractures. The usual procedure is to form an incision, drill a hole into the exposed bone to receive a hip pin, insert the threaded pin into the hole, and then, with a suitable shearing tool, cut away the remainder of the pin in a severing action which resembles a conventional wire-cutting operation. For such a pin-cutting step, it is essential that the jaws of the cutting instrument be as close as possible to the bone; therefore, a relatively large incision must be made. Because such an incision extends through a substantial amount of muscle and ligament structure, a prolonged period of recuperation, is required simply to allow healing of the soft tissue. Especially where the patient is elderly, as is often the case with hip fractures, extended periods of complete immobilization may be accompanied by a risk of pneumonia and other serious complications.

SUMMARY OF THE INVENTION

The present invention is concerned with a device, or a combination of devices, which eliminate the need for making the usual incision during a surgical pinning operation and, in consequence, greatly reduce the length of time required for healing. Where in the past bed confinement for seven or eight weeks has been quite common, in order to permit healing about the area of incision, the surgical technique permitted by the structure of the present invention may reduce the period of such confinement.

The surgical technique is a "blind" one to the extent that no incision is formed to expose the bone. Furthermore, there is no direct view of the surgical pin at the point where it enters the femur. The pin is inserted into the bone by a threading action and the excess portion of it removed with minimal damage to soft tissue and, because of the reduced operating time, at substantially lower risk to the patient.

A characteristic feature of the pin is the provision of a longitudinal series of notches or weakened portions which define predetermined planes of transverse weakness. Most desirably, each of the notches extends transversely through a side portion of the pin and is radially angularly offset relative to adjacent notches of the series. Each notch extends inwardly to a base line which is substantially parallel with a diameter of the pin. If the pin is then subjected to localized bending forces in a plane normal to the base line, fracture of the pin at the selected notch will readily occur.

Localization of the bending forces is achieved by utilizing a tool which has a tubular body portion slidably receiving the pin. As the tubular body is pivoted laterally to bend the pin, pin fracture occurs in a transverse plane passing through the selected notch.

Other advantages and objects of the invention will become more apparent as the specification proceeds.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a somewhat simplified sectional view illustrating the step of breaking off the excess portion of a hip pin following insertion thereof;

FIG. 2 is a side elevational view of a pin embodying the present invention;

FIG. 3 is an enlarged front elevational view of the pin taken along line 3--3 of FIG. 2;

FIGS. 4-7 are cross sectional views of the pin taken along lines 4-7 of FIG. 2;

FIG. 8 is a side elevational view of a tube breaking tool embodying the present invention.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, the invention will be described in conjunction with a hip pinning operation as illustrative of one operative procedure for which the structure of the invention is especially well suited. It is to be understood, however, that no limitations are to be inferred from the particular operative procedure selected and that the structure of this invention is believed to have utility for a wide range of surgical procedures in which bone sections are to be joined by one or more pins.

Referring to FIG. 2, the numeral 10 generally designates a surgical pin embodying this invention. The pin 10 is straight and is of substantially uniform diameter throughout its entire extent except for the extreme front end 11 which is pointed and provided with one or more cutting edges 12. Three such edges are shown in FIG. 3. Directly behind the pointed front end, the pin is provided with threads 13. The threads 13 are preferably rolled threads where the exterior diameter of the threads are equal to or greater in diameter than the diameter of the remaining elongated part of the pin 10. Such specific thread formation while not essential to proper function does add additional strength to the pin 10.

The intermediate portion 14 of the pin is provided with a series of longitudinally shaped weakened portions or notches 15-20, inclusive. The notches are preferably spaced apart a distance within the range of approximately one fourth to one half of an inch and, as most clearly shown in FIGS. 4-7, each notch extends inwardly from one side of the pin to a transverse line short of the axis 21 of the pin. Thus, notch 15 extends downwardly from the top side of the pin to a line 15a spaced above axis 21.

Of particular significance is the fact that each of the notches is radially angularly offset relative to the notch or notches adjacent thereto. Thus, notch 16 is offset 90 degrees from notch 15, and notch 17 is staggered 90 degrees relative to notches 16 and 18. Notches 19 and 20 are identical to notches 15 and 16 except that they are disposed a greater distance from the front end of the pin. An offset of 90 degrees has been found particularly effective although other angular variations, say 120 degrees, might conceivably be used. Also, while a total of six notches are shown, it is to be understood that a greater or smaller number might be provided in the series.

FIG. 8 illustrates the breaking tool 22 used for fracturing pin 10 at any selected notch. The tool comprises a rigid tube 23 equipped at one end with a handle 24. The opposite end of the tube terminates in a free edge 25 extending in a plane generally perpendicular to the axis of the tube. The bore 26 is slightly larger than the diameter of pin 10; therefore, the tool may be easily slipped over the rear end of the pin as indicated in FIG. 1.

Pin 10 may be formed of titanium or any other suitable material which has similar properties of strength, fracturability in response to bending forces, and acceptability, without undue reaction, by the body of the patient. The pin must not be brittle to the extent that brittleness suggests a lack of strength. However, it must be capable of fracturing in response to concentrated or localized bending forces exerted in the manner which will now be described.

FIG. 1 illustrates three pins 10a, 10b and 10c inserted through the neck of femur 27 to secure the head 28 of the femur in position following a fracture at 29. Pins 10a and 10b are already fully in place, having been implanted by a procedure which involves the steps of first drilling through the tissue and into both sections of the bone, then (before removal of the drill) slipping a guide tube (not shown) over the exposed end of the drill until the tube contacts the bone, then withdrawing the drill and inserting pin 10 through the guide tube and into the hole in the bone. The pins are fixed in place by a threading operation.

Another surgical procedure which is used is that the pin 10 acts as its own drill. In such case, after a small incision is made in the tissue, the pin 10 is then inserted through the tissue to the bone and an instrument (not shown) clamps the end of the pin and by turning the instrument the pin is threaded through the bone for proper insertion. With such procedure the pin furnishes its own mechanical holding strength.

After each pin is securely in place, a substantial portion of it projects outwardly from the bone and through the patient's muscle and skin. The surgeon then simply slips tube 23 of tool 22 over the exposed end of the pin and, using an image intensifier to view the movement of the parts, urges the tube 23 towards the bone until the free end 25 of the tube is aligned with the first notch external to bone 27. Handle 24 is then urged laterally in the manner indicated by arrow 30 in FIG. 1. Bending movement of 15 degrees or less in a direction which tends to spread the selected notch is all that is needed to break the pin. The rear end portion of the pin is extracted through the small hole in the patient's soft tissue, leaving the pin in place in the manner generally represented by pins 10a and 10b in FIG. 1.

It will be observed that the transverse line at the base of each notch or weakened portion becomes the line about which the bending force is exerted upon the pin. The metal pin and its notches are readily visible on an image intensifier screen and from the intensified image a surgeon may readily determine the direction of proper movement of the handle 24 to cause spreading of the selected notch, flexure of the pin about the base line of that notch, and fracture of the pin in that localized area. Because of the angular staggering of the notches, breakage of the pin at some point other than at the selected notch is extremely unlikely. Thus, breakage of pin 10c at the adjacent notch disposed just beneath the surface of the bone would not occur because the lifting action of the handle necessary to produce fracture of the selected notch in the manner illustrated is not the movement necessary to cause fracture of the notch beneath the bone surface. To cause fracture of the pin at the notch within the bone, handle 24 would have to be moved in a different direction, specifically, one at 90 degrees to the direction indicated.

By having a plurality of notches the surgeon may select a proper notch for the breaking that will allow enough of the pin to extend beyond the femur 27 so that when it is desired to remove the pin 10 upon mending of the bone there is a sufficient exposed portion to be grasped by a tool to remove the pin.

While in the foregoing we have disclosed an embodiment of the invention in considerable detail for purposes of illustration, it will be understood by those skilled in the art that many of these details may be varied without departing from the spirit and scope of the invention.

Claims

I claim:

1. A surgical pin for use in joining bone section, said pin being formed of a rigid material capable of fracturing when exposed to localized bending forces of predetermined magnitude and being of circular cross section along substantially its entire length, said pin having a pointed forward end, and having first, second and third sections, said first section extending from said pointed end to said second section, said second section extending from said first section to said third section, said third section extending from said second section to the rearward end of said pin, said first section including a threaded portion adjacent said pointed end and otherwise being uninterrupted along its length, said third section also being uninterrupted along its length, said first and third sections being at least as long as said second section, said second section being interrupted by a series of longitudinally spaced transverse notches, the bottom of each notch defining a chord of the circular cross section and the notch reducing the mass of the pin opposite the notch forming a weakened section, each notch having a maximum depth to said chord less than the radius of said pin, whereby localized bending force at any selected notch of said series causes break off of said pin generally along the weakened section of said selected notch, said third section being of a length accessible outside the bone surface of a patient in the region where the pin is installed for manipulation and discarding after break off, said third section having a diameter throughout its length no greater than that of said second section whereby said second and third sections are adapted to receive a break off tool.

2. The surgical pin of claim 1 in which said pointed end of said pin is provided with cutting edges.

3. A surgical pin for use in joining bone sections, said pin being formed of a rigid material capable of fracturing when exposed to localized bending forces of predetermined magnitude, said pin being pointed at its forward end and having an intermediate portion provided with a series of longitudinally spaced notches, each of said notches extending transversely to a side portion of said pin and being radially angularly offset relative to adjacent notches of said series, whereby the notches of said series are staggered to permit pin breakage at any selected notch, by localized bending of said pin at such selected notch, without at the same time risking pin fracture at a different point therealong.

4. The structure of claim 3 in which said pointed end of said pin is provided with cutting edges.

5. The structure of claim 3 in which said pin is roll threaded immediately adjacent said pointed end.

6. The structure of claim 3 in which each notch extends to an inner base line substantially parallel with a diameter of said pin, said localized bending of said pin to produce breakage thereof occurring about the base line of a selected notch.

7. The structure of claim 6 in which each notch has a maximum depth to the base line thereof less than the radius of said pin.

8. The structure of claim 3 in which each of the successive notches of said series is radially angularly offset approximately 90 degrees from the preceding notch.

9. The structure of claim 3 in which said notches of said series are longitudinally spaced apart a distance within the range of one fourth to one half of an inch.