Force dissipating impactor device

Abstract

A force dissipating impactor device is comprises a bar member including a hollow shaft, a first end, and a second end. The first end of the impactor device provides an impaction surface and the opposite second end of the impactor device provides an implant engagement surface. The implant engagement surface is contoured to mate with a surface of the implant member. The impaction surface is configured to be struck with a mallet or other tool. A plurality of holes are provided in the shaft and penetrate the surface of the bar member. The plurality of holes provided on the shaft surface of the bar member may be arranged such that a line passing axially along the shaft surface intersects at least one of the plurality of holes. Further, the plurality of holes may be arranged in a staggered matrix around the shaft surface.

Description

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an exemplary prior art humeral implant;

FIG. 2 shows a diagram of the humeral head, humeral stem, and insert for the humeral implant of FIG. 1;

FIG. 3 shows a perspective view of a force dissipating impactor device;

FIG. 4 shows a side view of the impactor device of FIG. 3;

FIG. 5 shows a perspective view of the impactor device of FIG. 3 from an end portion of the impactor device;

FIG. 6 shows a side view of an alternative embodiment of the impactor device of FIG. 3;

FIG. 7 shows a cross-sectional view of the impactor device along line VII-VII of FIG. 6;

FIG. 8 shows a cross-sectional view of the impactor device along line VIII-VIII of FIG. 6;

FIG. 9 shows a cross-sectional view of the impactor device along line IX-IX of FIG. 6; and

FIG. 10 shows an expanded polar coordinate view of the shaft portion of the impactor device of FIG. 3 with the holes arranged in a staggered matrix.

DESCRIPTION

With reference to FIGS. 3-5, an impactor device 50 is disclosed. The impactor device 50 is provided as an elongated bar member 52 that includes a shaft portion 54, a grip 55, a first end 56, and a second end 58. The first end 56 provides an impaction surface and the second end provides a force distributing surface in the form of an implant engagement surface. A plurality of holes 60 are formed in the shaft portion 54.

In the embodiment of FIGS. 3-5, the shaft portion 54 of the impactor device 50 is generally cylindrical in shape. The shaft portion 54 is hollow with a channel 62 extending axially along the center of the shaft portion. The channel 62 is surrounded by an exterior wall 62. Although the exterior wall 62 is cylindrical in the embodiment of FIGS. 3-5, one of skill in the art will recognize that the exterior wall may be any of numerous other shapes, such as box-shaped.

A plurality of holes 60 extend through the exterior wall 62 of the shaft portion 54 and into the axial channel 62, resulting in a perforated shaft portion 54. In the embodiment of FIGS. 3-5, the plurality of holes 60 are arranged on the shaft portion 54 such that any given line passing axially along the surface of the exterior wall will intersect at least one of the plurality of holes 60. To obtain this result, the holes 60 on the shaft portion 54 may be arranged in a staggered matrix around the shaft.

FIG. 10 shows an expanded polar coordinate view of the shaft portion 54 further displaying the staggered matrix arrangement of the holes. This view shows the shaft portion 54 “unwrapped” along the central axis such that the leftmost position is a zero degree position and the right most position is a three hundred sixty degree position radially relative to the central axis of the shaft. As shown in FIG. 10, the holes 60 are arranged in a staggered matrix such that the holes 60 in one row are offset from the holes in an adjacent row. In the disclosed embodiment, seven rows of holes 60 are provided with four holes in each row. The holes 60 overlap in the axial direction such that a line extending axially along the shaft portion, such as line 90, will intersect one or more of the holes 60. With this arrangement, the holes in each row are situated at ninety degree increments around the shaft, as can be seen from FIGS. 8 and 9. In other words, the center of a hole in a row is ninety degrees removed from the center of an adjacent hole in the row. In the disclosed embodiment, the diameter of each hole is 0.379 inch.

With reference again to FIGS. 3-5, the grip 55 of the impactor device 50 is provided next to the shaft portion 54, toward the first end 56 of the impactor device 50. The grip 55 includes a plurality of fins 72 that extend axially along a length of the shaft surface. The fins 72 are separated by axial indentations 74. The fins 72 and indentations 74 provide a knurled surface that provides an aid in gripping the impaction device 50.

The first end 56 of the bar member 52 provides the impaction surface and is configured to receive a blow from a mallet or other striking device. In the embodiment of FIGS. 3-5, it can be seen that the impaction surface is generally flat. This flat surface helps prevent the surgeon or surgical assistant from hitting the impactor device off axis. FIGS. 6-9 show a similar embodiment to that of FIGS. 3-5, and identical reference numerals are used to identify the same parts. However, in the embodiment of FIGS. 6-9, the impaction surface on the first end 56 of the bar member is convex. In this embodiment, the force of striking tool used by the surgeon is generally concentrated on a smaller area of the impaction surface.

The second end 58 of the bar member is positioned opposite the first end. The second end 58 of the bar member provides a force distributing surface. The force distributing surface is configured to engage an implant member, and thus serves as an implant engagement surface. If the implant member that will be contacted by the implant engagement surface is contoured, the implant engagement surface may be similarly contoured to mate with the surface of the implant member in a congruent fashion. The implant engagement surface shown in FIGS. 3-5 is designed to engage a convex rounded surface, such as the spherical humeral head of a humeral implant. Thus, the implant engagement surface on the second end 58 of the bar member 52 provides a concave rounded surface.

In one embodiment, the impactor device 50 is designed to be somewhere between five and nine inches in length. This length generally facilitates ease of handling by the surgeon along with a sufficient size for many human implant devices. In one embodiment for use with a humeral implant, the impactor device 50 is about seven inches in length. Of course, one of skill in the art will recognize that the impactor device is not limited to a particular length and the impactor device may be designed to any number of different lengths.

The impactor device 50 may be comprised of any of several different materials. Preferably, the material will be moldable, offer high flexural fatigue strength, rigidity, low wear, toughness and resistance to repeated impact. In one embodiment, the impactor device 50 is comprised of an acetal copolymer such as Celcon®. The simplicity of the impactor device design and use of appropriate material will also allow the impactor device to be easily cleaned through autoclaving.

The impactor device 50 is used by a surgeon or other surgical personnel to assemble a prosthetic device to be implanted in a patient. To this end, the surgeon first chooses an appropriate design and size for the various components of the implant device based on the size and needs of the patient. The implant device comprises a first implant component and a second implant component to be connected by a Morse taper or similar arrangement where the implant components are configured for connection by forcing connection features on the first component into engagement with connection features on the second component.

After selecting appropriate implant components, the surgeon selects an impactor device as set forth above. The impactor device includes a shaft portion, a grip portion, a first end with an impact surface and a second end with an implant engagement surface. A plurality of holes are formed in the axial wall of the shaft portion. The implant engagement surface of the impactor device is configured to engage a surface of the first implant component in a congruent fashion.

The surgeon aligns the connection features of the first implant component with the connection features of the second an implant component. Next, the surgeon holds the impactor device by the grip portion 55 and brings the implant engagement surface 58 into contact with the first implant component (e.g., the head 12 of the humeral implant of FIGS. 1 and 2). The axis of the impactor device is oriented on the first implant component such that a force transmitted through the impactor device will force the first implant component into full engagement with the second implant component. After properly aligning the impactor device, the surgeon strikes the impaction surface 56 on the impactor device, thus transmitting a force through the impaction device and to the first implant component (e.g., the plug 19 into engagement with the recess 28 in FIG. 2). This force is intended to bring the connection features on the first implant component into engagement with the connection features on the second implant component. The surgeon may be required to strike the impaction surface 56 one or more times to bring the connection features on the first implant component into full engagement with the connection features on the second implant component.

When the surgeon strikes the impactor device, the impactor device dissipates the force transmitted through the bar member and to the implant. In particular, the holes 60 in the impactor device 50 provide voids in the shaft portion 54 so that the shaft portion 54 can compress and expand to dissipate energy. Furthermore, the orientation of the holes 60 not only limits the amount of force that is transmitted down the shaft portion, but also helps to maintain the integrity of the impactor device, such that the impactor device does not fracture, degrade or otherwise fail when struck with a mallet or other striking device.

The staggered matrix orientation and size of the holes on the shaft portion can effectively dissipate about forty percent of the impaction force imparted by a striking device. Thus, even if a five thousand pound force is delivered by a mallet strike, the impactor device 50 will reduce that force to around three thousand pounds, which would be more than enough force to cause the humeral head to engage the humeral insert for most implants. At the same time, the reduced force is much less likely to result in disengagement of or damage to the intermediate components in the implant device.

Although the present invention has been described with respect to certain preferred embodiments, it will be appreciated by those of skill in the art that other implementations and adaptations are possible. For example, the impactor may take the form of different shapes than those shown in the figures, may include different features, may be differently sized, or may be comprised of different materials than those disclosed herein. Moreover, there are advantages to individual advancements described herein that may be obtained without incorporating other aspects described above. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred embodiments contained herein.

Claims

1. An impactor device configured to impact an implant member, the impactor device comprising: a bar member including a shaft surface, a first end, and a second end, the first end including an impaction surface and the second end including an implant engagement surface; anda plurality of holes provided in the shaft surface of the bar member.

2. The impactor device of claim 1 wherein the shaft surface of the bar member is cylindrical in shape.

3. The impactor device of claim 1 wherein the bar member is hollow.

4. The impactor device of claim 1 wherein the implant engagement surface is contoured to mate with a surface of the implant member.

5. The impactor device of claim 4 wherein the implant engagement surface is rounded and concave and the surface of the implant member is rounded and convex.

6. The impactor device of claim 1 wherein the bar member is between five and nine inches in length.

7. The impactor device of claim 6 wherein the bar member is about seven inches in length.

8. The impactor device of claim 1 wherein the plurality of holes are arranged on the shaft surface of the bar member such that any line passing axially along the shaft surface intersects at least one of the plurality of holes.

9. The impactor device of claim 1 wherein the plurality of holes are staggered on the shaft surface of the bar member.

10. The impactor device of claim 9 wherein the plurality of holes are arranged in a staggered matrix around the shaft surface.

11. The impactor device of claim 1 wherein the plurality of holes are arranged in a plurality of rows around the shaft surface of the bar member.

12. The impactor device of claim 11 wherein each row of the plurality of rows comprises four holes, and wherein with each hole in each row is situated ninety degrees relative to an adjacent hole in the row.

13. The impactor device of claim 1 wherein the bar member comprises an exterior wall and the shaft surface is provided on the exterior wall.

14. An impactor device configured to deliver an impact force, the impactor device comprising: a hollow perforated shaft;an impaction surface located on one end of the perforated shaft; anda force distributing surface on the opposite end of the perforated shaft.

15. The impactor device of claim 14 wherein the perforated shaft includes a plurality of holes arranged in a pattern upon the shaft.

16. The impactor device of claim 15 wherein the plurality of holes are arranged in a staggered matrix upon the shaft.

17. The impactor device of claim 15 wherein the pattern of the plurality of holes is such that all lines extending axially along a surface of the shaft will contact at least one of the plurality of holes.

18. The impactor device of claim 14 wherein the force distributing surface comprises an implant engagement surface which is contoured to mate with a component of an implant.

19. A method of assembling an implant, the method comprising the steps of: a) providing a first implant component and a second implant component, the first implant component and second implant component configured for connection by forcing connection features on the first component into engagement with connection features on the second component;b) providing an impactor device comprising a shaft including an axial wall, and impaction surface, and an implant engagement surface, wherein a plurality of holes are formed in the axial wall of the shaft;c) aligning the connection features of the first implant component with the connection features of the second an implant component;d) contacting the implant engagement surface of the impactor device with the first implant component; ande) striking the impaction surface of the impactor device in order to deliver a force through the impactor device to the first implant component which brings the connection features on the first implant component into engagement with the connection features on the second implant component.

20. The method of claim 19 wherein the first implant component comprises a convex surface, and wherein the implant engagement surface of the impactor device is concave and configured to engage the convex surface in a congruent fashion.