US3763855A

US3763855A - Device for fixation of bone fractures

Info

Publication number: US3763855A
Application number: US00234849A
Authority: US
Inventors: Atee R Mc
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-03-15
Filing date: 1972-03-15
Publication date: 1973-10-09
Anticipated expiration: 1990-10-09

Abstract

A medical assembly is provided for the positive fixation of fractures of the ulna, one of the forearm bones, in cases where it is broken at or near the elbow joint. One element of the assembly is secured to the distal (remote from the body) part of the ulna, and another threaded element is independently tightened up to impact the bone fragments. The first element may be a metal element or unit inserted from the side through the cortex, or hard outer part of the forearm bone, below the break. This metal element, referred to as the cortical fixation unit, extends into the soft center channel of the bone and has a transverse threaded hole near its end, opening to the center channel of the bone. The other element may be a flexible bolt or pin formed of a threaded stiff wire about six inches long having a bolt head at one end, and will be referred to as a ''''pin'''' in the present specification. This flexible bolt or pin is pushed through a drilled hole in the elbow fragment of the bone, down the bone channel and engaged with the threaded hole at the end of the cortical fixation unit. By tightening up the bolt head on the flexible bolt or pin, the elbow fragment is positively set in its proper position in engagement with the remaining distal portion of the ulna.

Description

United States Patent [19:

McAtee [4 Oct. 9, 1973 DEVICE F OR FIXATION OF BONE FRACTURES [76] Inventor: Richard M. McAtee, 355 South G St, Oxnard, Calif. 93030 [22] Filed: V Mar. 15, 1972 [21] Appl. No.: 234,849

Primary Examiner-Richard A. Gaudet Assistant Examiner-J. Yasko Attorney-Alan C. Rose [5 7 ABSTRACT A medical assembly is provided for the positive fixa tion of fractures of the ulna, one of the forearm bones, in cases where it is broken at or near the elbow joint. One element of the assembly is secured to the distal (remote from the body) part of the ulna, and another threaded element is independently tightened up to impact the bone fragments. The first element may be a metal element or unit inserted from the side through the cortex, or hard outer part of the forearm bone, below the break. This metal element, referred to as the cortical fixation unit, extends into the soft center channel of the bone and has a transverse threaded hole near its end, opening to the center channel of the bone. The other element may be a flexible bolt or pin formed of a threaded stiff wire about six inches long having a bolt head at one end, and will be referred to as a pin in the present specification. This flexible bolt or pin is pushed through a drilled hole in the elbow fragment of the bone, down the bone channel and engaged with the threaded hole at the end of the cortical fixation unit. By tightening up the bolt head on the flexible bolt or pin, the elbow fragment is positively set in its proper position in engagement with the remaining distal portion of the ulna.

8 Claims, 6 Drawing Figures 1 DEVICE FOR FIXATION OF BONE FRACTURES BACKGROUND OF THE INVENTION This invention relates to an improved medical assembly for the fixation and impaction of bone fragments.

The principal bones in the arm include the upper arm bone, or humerus, and the two forearm bones, the ulna which is the bone having its lower or distal end alined with the smallest finger of the hand, and the radius which has its distal end alined with the thumb. The elbow joint includes a crescent-shaped recess in the ulna and a corresponding matching convex surface at the lower end of the humerus.

The medical term for the crescent-shaped recess is the semi-lunar notch, and the enlarged end of the ulna at the elbow is called the olecranon. The medical convention of referring to the end of a bone closest to the body as the proximal" end, in constract to the distal" or farther end will be followed in this specification.

When the ulna is broken near its proximal end, at or close to the semi-lunar notch, the triceps muscles tend to pull the bone fragment upward away from the main distal portion of the bone and it is difficult to set the bones in their proper relative positions for mending.

It has previously been proposed to use a sort of screw which extends through a hole drilled in the end of the bone fragment and which is provided with screw threads which are directed into the soft center channel, known as the medullary canal, of the main distal portion of the ulna. However, this procedure does not always accommodate different bone shapes and sizes and types of breaks. More specifically, it is not always possible to have the screw reach the desired tightness just as the head of the screw brings the bones into the properly set or reduced position, without repeated insertions and removals of the screw, either with modifications, or using a different length screw.

It has also been proposed to set the ulna bone fragments, or reduce the fracture, by using metal wires or plates or absorbable material such as catgut, kangaroo tendon or the like. However, such techniques are frequently complicated by the pull of the triceps muscles, which are located on the back of the humerus, or upper arm bone. These triceps muscles normally pull on the olecranon or upper end of the ulna to extend the forearm. When the ulna is broken near the elbow, the upper or distal bone fragment is pulled upward, away from its normal position, by these powerful triceps muscles.

In view of the problems of reducing the fracture against the force of the triceps muscles, it has also frequently been proposed to completely excise or remove the broken bone fragment near the elbow. However, this widely used technique gives rise to severe instability of the joint and a decrease in triceps power, and has many disadvantages as can readily be appreciated.

SUMMARY OF THE INVENTION Against the foregoing background, the present invention contemplates securing a metal element or cortical fixation unit into the main lower or distal portion of the ulna, and the screwing in of another member (relative to the cortical fixation unit) which bears on the olecranon to hold the bone fragments firmly in place against the strong pull of the triceps muscles.

As set forth in the Abstract of the Disclosure," a first hole is preferably drilled transversely through the cortex, or hard outer wall, of the main part of the ulna into the soft medullary channel. Another hole is drilled through the olecranon at the upper end of the elbow bone fragment. The cortical fixation unit is pushed through the first hole in the cortex, this unit being provided with a transverse threaded hole alined with the medullary channel. A long flexible threaded wire or pin is then inserted through the hole in the olecranon, down the medullary canal and into the threaded hole in the short transverse cortical fixation unit, and the pin is tightened up until it impacts the bones firmly and properly secures the bone fragments together.

The method has the advantage of providing easily adjustable impaction of the fragments of the broken bone, in a positive way against the separating force of the triceps muscle, and independent of the problem of securing the assembly to the main distal portion of the ulna.

Other advantages and features of the invention will become apparent from the following detailed description and from the drawings, in which:

FIG. 1 is a drawn fron an X-ray to show relative bone positions following a fracture of the upper end of the ulna;

FIG. 2 shows the ulna with the broken bones set or reduced, in accordance with the principles of the invention;

FIGS. 3 and 4 are two views of the cortical fixation unit having a threaded hole, which is one part of the assembly;

FIG. 5 is a side view of the elongated threaded wire, or flexible pin, and the cortical fixation unit, which are used as shown in FIG. 2; and

FIG. 6 shows a holder which is used in inserting the unit shown in FIGS. 3 and 4 into a position such as that shown in FIG. 2.

Referring more particularly to the drawings, FIG. 1 is taken from an X-ray of the elbow region taken following a fracture of the ulna 12 near the elbow. The bone fragment 14 is in engagement with the humerus, or upper arm bone 16. The other forearmbone 18, the radius, is shown above the ulna 12.

The triceps muscle on the back of the upper arm is secured through a tendon to the upper or proximal end of the ulna. The force applied to the upper end of the ulna bythe triceps must be powerful, in view of the short moment arm" or distance from the end of the elbow to the effective turning point of the ulna.

This powerful force of the triceps pulls the bone fragment 14 up to the indicated position, and exerts a continuing force on the bone fragment tending to pull it away from the remainder of the ulna 12 when the bones are set. The present invention is directed to the solution of this problem.

FIG. 2 shows the ulna in greater detail, and also shows the assembly for fixation of the fracture. In FIG. 2 the ulna 12 of a left arm is shown with the distal end 20 to the right and the proximal end to the left. The ulna 12 is fractured along a break 22 extending to the semi-lunar notch 24, with the bone fragment l4 including the olecranon or elbow protruberance 25 of the ulna.

The assembly for fixation of the fracture includes a cortical fixation unit 32, provided with a threaded transverse opening 34 (as shown in FIG. 3), and a long flexible bolt or threaded pin 38 having a bolt head 40,

and a washer 42. The mode of insertion of the fixation assembly will be set forth in some detail below.

FIGS. 3 and 4 are side and top views, respectively, of the cortical fixation unit 32. It is provided with a tapped hole 34 near one end. The other end is provided with a head 36 of a configuration which can readily be mechanically held, and which will indicate alinement with the tapped hole 34. As shown in FIG. 4, the head 36 has two flat sides alined with opening 34 and a central recess for use with the holding device shown in FIG. 6. The shank of the cortical fixation unit 32 may have a diameter of 0.200 inch, and it may be about twenty three-sixty fourths inch in length, although an assortment of lengths are desirable for use with different bone dimensions.

The long flexible medullary (or marrow) pin is shown in the assembly view of FIG. 5. The shank of the pin may be three-thirty seconds in diameter, and it is provided with threads starting about I 1% inches from its head which may bave a pitch of 48 turns per inch. These threads should match those in the threaded hole 34 in the cortical fixation unit 32, of course. To facilitate starting the threads of the flexible pin 32 in the threaded hole 34, the end of the medullary pin 32 is provided with a rounded and slightly tapered unthreaded end portion 44 of reduced diameter which is about one-fourth inch long or slightly longer to extend through the threaded hole 34 in the cortical fixation unit and properly aline the parts. With this arrangement, problems in starting the threading where the threaded hole is not visible, are minimized.

The washer 42 serves to avoid abrasion and facilitate tightening of the medullary pin 38 as the hexagonal head 40 is tightened.

FIG. 6 is a cross-sectional view of a simple holder 52 for the cortical fixation unit 32. The holder 52 includes two parts 54 and 56 which may be longitudinally adjusted to engage the cortical fixation unit 32 by relative rotation about threads 58. The part 56 has two

fingers

60 and 62 which extend around the flat sides of the head 36 of the cortical fixation unit 32; and the other part 54 of the holder 52 has a pointed central shaft 64 which engages the recess 37 in the head of the unit, to positively hold it in place.

In FIG. 2, the position of the fixation device or

assembly

32, 38 is shown relative to the fractured ulna. The medical procedure for applying the assembly will now be briefly set forth.

After standard preparation for an arm operation, a posterior incision is made at the elbow in the usual manner, curving the incision slightly toward the lateral side at the olecranon bursa, to avoid injuring the bursa (which permits freedom of movement of the skin over the elbow). Over the distal fragment the incision is carried through the periosteum (or covering of bone), then' the bone is exposed by subperiosteal dissection approximately three quarters of an inch distal to the fracture site. Care is taken to remove all small fragments of bone and tissue tags that may invert into the fracture site. The lateral and medial aspects of the fracture site are adequately exposed to detect any frag ments which may prevent adequate approximation (or pulling together of the bones). A towel clip (or clamp) is then placed through the tendon of the triceps proximal to the olecranon and in this manner the proximal fragment can be easily controlled while reducing the fracture. The fracture is reduced carefully.

A small cruciate incision is made through the triceps tendon at the tip of the olecranon and a hole is drilled through the olecranon, alined with the marrow canal of the ulna. The drill hole should be about nine-sixty fourths inch in diameter size to avoid any possible binding of the flexible medullary pin (preferably of threethrity seconds inch diameter) in the olecranon fragment. The medullary pin 32 is first assembled with the washer 42 and is then driven through the drill hole in the olecranon and into the marrow canal with a gentle tap of a mallet.

A second incision is made over the shaft of the ulna an inch to two inches distal to the fracture site. By subperiosteal dissection the flexor surface of the ulna is exposed. (The flexor side of the forearm is the inner surface which continues into the plam of the hand.) At this level the cross section of the ulna is triangular in shape and the flatter surface is on the flexor aspect. A onequarter inch hole is drilled through the flexor surface of the ulna entering into the marrow canal. The hole is drilled through the marrow, and a few millimeters into the opposite cortex (the hard outer part of the bone).

When the tip 44 of the medullary pin 38 is seen through the lateral drill hole, the tip is withdrawn slightly so that the cortical fixation unit 32 can be placed in the hole and with its threaded hole 34 alined with the tip of the medullary pin. Technically, this is the more difficult part of the procedure, but it is made eas ier if one chooses the unit 32 of the right length, and if the drill hole into the opposite cortex is adequate to allow some leeway in manipulation of the fixation unit 32. Once they are joined, the smooth section on the tip 44 of the medullary pin slides into the threaded hole in the unit 32, alining the threads accurately. A small socket wrench fitted to a handdrill is the most convenient instrument for threading the flexible medullary pin 38 through the hole 34 in the unit 32 and down the shaft of the ulna. This gives very positive control in approximating the fragments, and almost any desired degree of impaction can be accomplished in this manner. If the fracture line is oblique the fragments tend to override with impaction. This distortion can be prevented by holding the fracture reduced and then inserting a Kirschner wire across the fracture site parallel to the pin. The fragments are then impacted by tightening the flexible medullary bolt while the more rigid Kirschner wire keeps the bone fragments alined. The wounds are closed in the usual manner and the arm is dressed with gentle compression. A posterior molded splint is applied for patients comfort during the first several post-operative days. After wound healing and removal of the sutures, gentle active motion is begun. Other circumstances such as extensive comminution, loss of fragments of bone, or other fractures about the elbow or forearm may mitigate against early motion.

Concerning other aspects of the invention, it is of course necessary that the fixation assembly be made of biologically inactive material. A number of materials are used for this purpose in surgical implant work and one such material, a stainless steel, is identified as ASTM Designation: F55 and is made of iron alloyed with the following metals in the indicated quantities:

Chromium HBO-20.00% Nickel l0.00-l4.00% Molybedenum ZOO-4.00%

The following metals shall not be present in excess of the following levels:

Carbon 0.08% Max. Manganese 2.00% Max Phosphorus 0 03% Max Sulfur 0.03% Max Silicon 0.75% Max.

The arrangements described in detail above in connection with the drawings represent the preferred mode of implementing the present invention. It is useful, however, to consider alternative arrangements which would. realize many of the advantages of the preferred arrangements. Broadly from one aspect, the invention contemplates first securing one part of the bone fixation assembly against longitudinal movement relative to the main distal portion of the ulna, and then in a second step exerting fixation force on the olecranon bone fragment.

These two steps can be implemented in a number of ways, including an assembly similar to that used in bicycle wheels. Using this concept, holes would be drilled in the two bone fragments similar to those discussed hereinabove. But instead of the unit 32 as shown in FIGS. 3 and 4 of the drawings, a curved cortical fixation element having a head and a central threaded aperture would be employed, similar to those used to secure bicycle spokes in place. This curved element would be inserted in the lateral hole in the distal part of the ulna, with the curved end pointing toward the elbow fragment, so that a flexible medullary bolt could be threaded into it.

Another technique would be to use a semi-flexible medullary screw threaded on its front end to engage the inner surface of the ulna, and threaded on its other end to engage matching threads on a nut. The medullary screw could be provided with a slot for rotational driving,-with the drilled hole through the olecranon being oversize to permit clearance. After the flexible medullary screw is seated in the distal portion of the ulna, a washer and a nut would be threaded to the other (exposed) end of the screw for fixation, and the extra length of screw threads protruding from the olecranon would subsequently be cut off.

Components serving the function of nuts or other internally threaded elements are sometimes formed in various ways to provide a ratchet-like action so that assembly with a bolt or notched member is facilitated in that, for assembly in one direction, rotation of the bolt is not required. Such elements could of course be employed in place of the internally threaded elements described hereinabove.

The various described embodiments including the foregoing alternatives are all considered to provide advantages over prior methods by separating the steps of first, securing the bone fixation assembly against longitudinal movement, and secondly, impacting the bone fragments and firmly securing them together. However, the described alternatives to the preferred method have mechanical complexities and procedural steps which make them less attractive than the preferred method disclosed in detail herein.

What is claimed is:

1. An assembly for the fixation and impaction of a bone fragment relative to the main part of a fractured bone comprising:

a first structurally rigid unitary member of biologically inactive material including means for engagement with and prevention of longitudinal movement of said first member relative to the main part of the broken bone, said first member also being provided with means engaging another member of the assembly;

means including a second structurally rigid unitary member of biologically inactive material, for entering locking engagement with said first engaging means upon relative movement of said members, and for applying force to a bone surface of the bone fragment to firmly and positively impact the fractured bone surfaces; and

both said first and second members having enlarged portions for bearing on the exterior surface of the bone at one of their respective ends and having mutually locking engagement 'means of reduced size near their other ends, whereby the two members can be manipulated from outside of the bone into direct locking engagement with each other within the bone.

2. A bone fixation assembly primarily for fractures of the upper ulna comprising:

a first member of biologically inactive material including means for engagement with and prevention of longitudinal movement relative to the distal portion of the ulna, said first member being provided with a first set of threads;

means including a second member of biologically inactive material having threads engaging said first set of threads, for applying force to the upper end of the bone surface of the olecranon to finnly and positively impact the fractured bone surfaces; and

said first member being a cortical fixation unit having a head bearing on the outer surface of the bone and a hole engaging the second member within the medullary canal of the bone.

3. A bone fixation assembly as defined in claim 2, wherein said first member is a short cortical fixation unit having a head for bearing on the outer surface of the ulna at one end, and a threaded hole near its other end.

4. A bone fixation assembly'as defined in claim 3 wherein the second member is an elongated flexible medullary pin having external threads matching the internal threads of said threaded hole at one end, and a head at its other end.

5. A bone fixation assembly as defined in claim 4 wherein said pin has a rounded end of reduced crosssection less than the internal diameter of the threaded hole for starting threaded engagement with said cortical fixation unit.

6. A bone fixation assembly as defined in claim 3 wherein the head of the cortical fixation unit is asymmetric and indicates the orientation of said threaded hole.

7. A bone fixation assembly as defined in claim 6 wherein the head of said cortical fixation unit has two flat sides for engagement by a holding device and for designating the orientation of said threaded hole.

8. A bone fixation assembly as defined in claim 4 wherein said assembly further includes a washer of biologically inactive material on said pin adjacent the head of said pin to transmit force to the olecranon along the axis of said pin as said pin is tightened up.

Claims

1. An assembly for the fixation and impaction of a bone fragment relative to the main part of a fractured bone comprising: a first structurally rigid unitary member of biologically inactive material including means for engagement with and prevention of longitudinal movement of said first member relative to the main part of the broken bone, said first member also being provided with means engaging another member of the assembly; means including a second structurally rigid unitary member of biologically inactive material, for entering locking engagement with said first engaging means upon relative movement of said members, and for applying force to a bone surface of the bone fragment to firmly and positively impact the fractured bone surfaces; and both said first and second members having enlarged portions for bearing on the exterior surface of the bone at one of their respective ends and having mutually locking engagement means of reduced size near their other ends, whereby the two members can be manipulated from outside of the bone into direct locking engagement with each other within the bone.

2. A bone fixation assembly primarily for fractures of the upper ulna comprising: a first member of biologically inactive material including means for engagement with and prevention of longitudinal movement relative to the distal portion of the ulna, said first member being provided with a first set of thReads; means including a second member of biologically inactive material having threads engaging said first set of threads, for applying force to the upper end of the bone surface of the olecranon to firmly and positively impact the fractured bone surfaces; and said first member being a cortical fixation unit having a head bearing on the outer surface of the bone and a hole engaging the second member within the medullary canal of the bone.

4. A bone fixation assembly as defined in claim 3 wherein the second member is an elongated flexible medullary pin having external threads matching the internal threads of said threaded hole at one end, and a head at its other end.

5. A bone fixation assembly as defined in claim 4 wherein said pin has a rounded end of reduced cross-section less than the internal diameter of the threaded hole for starting threaded engagement with said cortical fixation unit.