DE29805443U1 - Orthopedic compression screw modular system - Google Patents

Description

A 54 417 U AESCULAP AG & Co. KG

&zgr; - 248 , Am Aesculap-Platz

25 March 1998 78532 Tuttlingen

Orthopaedic compression screw modular system

The present invention relates to orthopedic instruments and is particularly, but not exclusively, concerned with orthopedic instruments of the compression screw type for creating compression between bone parts or for securing orthopedic implants in bone.

Currently, the use of orthopedic compression screws involves the process of compressing two bone parts together by using bone screws that are designed to be anchored in one bone part and to press the other bone part against it with the screw head, with or without the aid of the use of a washer. In addition, screws are used to secure internal fixation implants, such as intramedullary nails, in the bone. With the instruments currently used, the screw head protrudes from the bone and usually causes problems in the form of soft tissue irritation and pain. In addition, the screw is not securely connected to both bone parts and as a result, the screw-bone structure usually loses stability.

According to the present invention, an orthopedic instrument is provided which comprises two independent components, each of which comprises an externally threaded locking means for connection to a bone. The two externally threaded locking means may comprise threads,

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which have different geometrical characteristics from each other. The unthreaded part of one component is a solid tubular shaft which can be inserted into a hollow tubular shaft of the other component and secured in a manner that allows the two components to be rotated independently of each other. The two components thus together form an orthopaedic implant which can be inserted into a bone and create a compression between the bone parts or secure internal fixation implants, such as intramedullary nails, without any part of the implant protruding above the external surface of the bone.

Preferably, the threaded portion of each component is located substantially at one end of the component, whereby the remaining external surface of the component remains externally smooth.

Preferably, the hollow tubular component includes a locking means protruding from its inner hollow surface at the end of the non-threaded portion which prevents disassembly of the two components once assembled.

According to another embodiment of the invention, an elongated, thread-free shaft part of the solid component is extended by an elongated, thread-free shaft section with a different diameter, whereby a shoulder in the transition area between the shaft part and the shaft section

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cut is formed. This shoulder forms a stop for the hollow tubular component and prevents the hollow tubular component from being able to move in the axial direction. The hollow tubular component thus surrounds the elongated unthreaded shaft part of the solid component, which has a smaller diameter. This requires that the inner diameter of the hollow tubular component is larger than the smaller diameter of the solid component, but smaller than the large diameter of the solid component.

Preferably, the elongated unthreaded shaft section of the solid component is smaller in diameter than the elongated unthreaded shaft part and forms the end of the solid component. This design particularly facilitates the insertion of the solid component into the hollow tubular component, since the shaft section with the smaller diameter can be inserted into the hollow tubular component until it strikes the shoulder which is formed in the transition region between the shaft part and the shaft section of the solid component.

According to another preferred embodiment of the invention, the elongated unthreaded shaft portion of the solid component has a radial projection on its outer surface at its end. The projection, together with the shoulder at the transition region of the solid component, causes the hollow tubular component to be bent in the axial direction only within a certain range at any one time.

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is movable until it hits either the shoulder or the projection.

Preferably, the elongated shaft portion of the solid component has a longitudinal diametrical slot extending from one end of the solid component across the entire thickness, thereby allowing temporary compression during insertion of the elongated unthreaded shaft portion of the solid component into the hollow tubular component. The longitudinal slot is necessary to compress the elongated unthreaded shaft portion of the solid component to push the hollow tubular component over the projection, since the projection has a larger diameter than the inner diameter of the hollow component. For example, the free end can be compressed with the fingers. Furthermore, it is also possible to chamfer the end with the projection, whereby the hollow tubular component can slide on these inclined surfaces during assembly. This makes assembly significantly easier. In addition, this design makes it impossible for both components to be pulled apart due to axial tensile forces. Due to the design of the projection, axial tensile forces cannot be diverted into radial compressive forces that could cause the elongated threadless shaft section of the solid component to compress, causing the hollow tubular component to slide down. Another advantage is that the maximum outer diameter of the system is limited by the outer diameter of the elongated

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thread-free shaft part of the solid component. This allows the solid component to be inserted into a hole that has an inner diameter that corresponds to the maximum outer diameter of the solid component. Nevertheless, assembly is possible because the free end of the solid component can be compressed. This design is particularly advantageous when fixing medullary bone nails.

According to a further embodiment, the system has a hollow tubular component that fits precisely on the elongated unthreaded shaft section of the solid component between the projection and the shoulders. This can prevent any axial movement of the hollow tubular component, since the hollow tubular component strikes the shoulder and the projection simultaneously. In addition, disassembly, especially accidental disassembly, of the system is made more difficult by the fact that the radial projection can be designed to be narrow, whereby forces acting only on it can compress the free end of the solid component again.

Preferably, the entire surface of the hollow tubular component is provided with a screw thread. This offers the advantage that the hollow tubular component can have as short an overall length as possible. This increases the overall stability of the screw system, since the elongated thread-free shaft section of the solid component can therefore also be shorter, which makes higher axial tensile forces possible.

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This results in a higher possible
Compression of both bone parts.

According to another preferred embodiment of the invention, the hollow tubular component has a slot extending from
one end diametrically through its entire thickness
This makes it possible to
to use a tool to insert the hollow tubular
component. Since in this embodiment
both components have a slot, the use of a special tool allows the complete screw system to be rotated as a unit. To do this, the tool must engage in both slots of the respective component at the same time. Using another tool, it is possible to rotate the solid
component, regardless of any twisting of the hollow tubular component. This requires a tool that simply fits into the
slot of the solid component, with the
slot of the hollow tubular component but is not connected.

Although one can imagine that the screw threads
of the two components have different threads, according to a preferred embodiment of the invention both screw threads
the same gear difference.

Preferably, the diameter of both screw threads is the same. In this case, only one drill is needed to make a hole in the bone parts for inserting

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of the screw system, which can shorten the operation time.

The invention can be carried out in practice in many different ways, but two embodiments are described below by way of example with reference to the accompanying drawings. In the drawings:

Figure 1:
Figure 2:
Figure 3:
Figure 4:

Figure 5:

a side view of component A; a side view of component B; a sectional view of component B;

a side view of the two assembled components;

a side view of the Orthopaedic Compression Screw Modular System in use during insertion of the instrument through two pieces of bone;

Figure 6:

a side view of an orthopedic compression screw kit in use during the application of pressure between the two bone parts;

Figure 7:

a side view of the orthopedic compression screw modular system when used as a bone anchor for an orthopedic

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Intramedullary bone nail type implant;

Figure 8:

a side view of component C and a cross-sectional view of component D of another embodiment of the present invention during assembly of both components;

Figure 9:

a side view of the assembled components C and D with a tool to grip both components simultaneously and rotate them as a unit;

Figure 10:

a 90° enlargement of the left part of Figure 9 and

Figure 11:

a partial sectional view analogous to Figure 10 with a second tool to twist component C alone.

According to Figure 1, component A comprises a screw-threaded part 1, a conical neck part 2, a solid tubular shaft 3 and an end 4 which allows the reception of a suitable screwdriver for introducing the component into the bone.

As shown in Figure 2, component B comprises a hollow tubular shaft which is open at both ends 5 and 6. Component B has a smooth surface area 7 on the outside and a screw-threaded

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thread 8. Part of the externally smooth surface area 7 of the hollow tubular part of component B has a longitudinal slot 9 extending from the end 6 through the entire thickness of the tubular shaft to allow temporary expansion during insertion of the solid tubular shaft 3 of component A. The end 5 of the hollow tubular shaft is designed to receive a suitable screwdriver for inserting the component into the bone.

Referring to Figures 1, 2 and 3, the dimensions of the hollow inner surface 10 of component B are sufficiently large to accommodate the solid tubular shaft 3 of component A. The hollow inner surface 10 of component B includes a locking means 11 projecting inwardly from the hollow surface of the externally smooth surface area 7 of component B to prevent separation of components A and B once assembled.

As shown in Figures 1, 2 and 4, component A 12 and component B 13 are assembled by axially inserting the solid tubular shaft 3 of component A through the open end 6 of component B, thereby forming the orthopedic compression screw system.

The insertion procedure of the instrument is described below with reference to Figures 5, 6 and 7.

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As shown in Figure 5, once assembled, the orthopedic compression screw system can be inserted through a hole in two bone parts 14 and 15 with a screwdriver 16 which grasps both ends 4 and 5 of the respective components A and B and drives them in direction 17 by rotating the system clockwise 18.

Once the orthopedic compression screw system is fully inserted into both bone parts 14 and 15, another screwdriver 19, as seen in Figure 6, only grips the end 4 of the solid part of component A 12, which is accessible through the open end 5 of hollow component B 13. It is therefore possible for component A 12 to be rotated clockwise 20 while at the same time component B 13 does not rotate. This effect creates a compression 21 between the bone part 14 connected to the screw-threaded part of component A 12 and the bone part 15 connected to the screw-threaded part of component B 13.

According to this procedure, a strong compression is created between the two bone parts, and since both bone parts are securely held by a significant screw thread length, the fixation is safe and able to successfully withstand external loading forces. In addition, no part of the instrument protrudes above the bone surface and therefore no problems of soft tissue irritation are expected.

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Referring to Figure 7, another application of this invention is described. The orthopedic compression screw system 22 initially assembled in the manner described above can be inserted through a hole 23 of an orthopedic implant 24 of the intramedullary bone nail type and at the same time connected to bone tissue 25 and 26 on each side of the orthopedic intramedullary bone nail implant.

It should be noted that in the latter proposed application, increased stability of an orthopedic implant, such as an intramedullary bone nail, is achieved because high pressure is generated between adjacent bone areas and both bone areas are securely connected by a significant screw thread length. In addition, no part of the screw system used to secure an orthopedic implant, such as an intramedullary bone nail, protrudes beyond the outer bone surface and therefore no problems with soft tissue irritation are expected.

Figures 8 to 11 show a further embodiment of the present invention and will be described using the same reference numerals as those given for the first embodiment.

Figures 8 and 9 show that a component C has a solid tubular shaft 3 which has an external screw thread 1 at one end and another

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tapered end 50. Near the tapered end 50, the diameter of the solid tubular shaft 3 is reduced along the length of a shaft portion 53, thereby forming two radial shoulders 51 and 52 on either side of the shaft portion 53, which has the smaller diameter compared to the solid tubular shaft 3. The shaft portion 53 has a longitudinal diametrical slot 54 extending from the end 50 across the entire thickness of the shaft portion 53. In the axial direction, the slot 54 extends to a depth approximately equal to the length of the shaft portion 53 to allow temporary compression of the shaft portion 53 during insertion of the component C into a component D, as will be described in more detail below.

Component D comprises a hollow tubular shaft having two open ends 5 and 6 and an external screw thread 8 extending across the entire external surface of component D. A longitudinal diametrical screw slot 55 extends from end 5 of component D across the entire thickness of component D, allowing a screwdriver 16 to be connected to component D. However, screw slot 55 is not as deep as slot 54. The length of component D corresponds to the distance between shoulders 51 and 52, preventing relative axial movement of the two components C and D once they are assembled. Shoulders 51 and 52' form a locking device together with ends 5 and 6 of component D.

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The assembly of components C and D is explained in more detail using Figures 8 and 9. First, the end 6 of component D is moved towards the conical end 50 of component C. As soon as both components touch, the end 6 slides on the inclined surface of the conical end 50 and presses the conical end 50 and the shaft section 53 together as component D is pushed further forward. This is only possible because component C has the slot 54. This allows the two parts of the shaft section 53 to be moved towards or away from each other transversely to the longitudinal axis of the system. The inner diameter of component C corresponds to the outer diameter of the shaft section 53 of component C. Component D is now pushed forward along the longitudinal axis of the screw system until the end 6 of component D reaches the shoulder 51 of component C and stops there. At this moment, the conical end 50 emerges from the hollow interior of component D and the two parts of the shaft section 53 relax again. This fixes component D between shoulders 51 and 52. It is therefore important that the two parts forming shaft section 53 have such great elasticity that they can be pressed together by component D and expand again automatically when component D reaches its end position. The specialist achieves this by choosing the appropriate screw material or by using an appropriate slot width.

With reference to Figures 9, 10 and 11, the following describes in more detail how, with the help of special

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setting tools, the screw system is inserted into a hole prepared for it in the bone parts. However, the bone parts are not shown in these figures. In principle, they would correspond to the bone parts shown in Figures 5 and 6.

As already described above, a screwdriver 16 is used to engage the two ends 5 and 50 of the respective components C and D in order to advance them in a direction 17 by rotating the system clockwise 18. For this purpose, the screwdriver 16 has a two-part end. A first screw area 61 is wide enough to engage the screw slot 55 at the end 5 of the component D. The thickness of the screw area 61 corresponds to the width of the screw slot 55. The end 61 of the screwdriver 16 additionally has an extended engagement area 62, the width of which corresponds to the inner diameter of the component D. The different widths of the screw area 61 and the engagement area 62 at the end of the screwdriver 16 form a shoulder 63 on both sides, which forms a stop for inserting the screwdriver 16 into the screw slot 55 and the slot 54 of the two components C and D. After placing the screwdriver 16 on the screw system, it is now possible to turn both components C and D at the same time.

Figure 10 shows the inserted screwdriver 16 with the engagement area 62 fitting into the slot 54 and the wide screw area 61 fitting into the screw slot 55.

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Once the orthopedic compression screw system has been fully inserted into both bone parts (not shown here), as shown in Figure 11, after removing the screwdriver 16, another screwdriver 19 only engages the slot 54 in the component C via the conical end 50. This engagement in the component C is made possible through the open end 5 of the hollow component D. Unlike the screwdriver 16, the screwdriver 19 has only a single engagement area 71, which is comparable to the engagement area 62 of the screwdriver 16. Therefore, it is impossible for the screwdriver 19 to simultaneously engage the screw slot 55 of the component D. The engagement area 71 of the screwdriver 19 fits exactly into the longitudinal slot 54. This allows the component C to be rotated clockwise 20 while at the same time the component D is not rotated. As already described above, this effect creates pressure between the two bone parts.

Claims (14)

ft·« ·· · W &psgr; m W A 54 417 u &zgr; - 248 25 March 1998 - 16 - PROTECTION CLAIMS 1. Orthopaedic compression screw modular system for connecting a first and a second bone part, comprising: a shaft having a first component and a second component, the two components being able to be rotated independently of one another; a first external screw thread on the first component; a second external screw thread on the second component; a device connected to the second component and suitable for receiving a first drive tool for driving the screw system as a unit and further suitable for receiving a second drive tool for rotating the second component independently of the first component, and a retaining device that prevents relative axial movement of the two components, characterized in that the retaining device is designed in the form of a latching connection (2, 11; 5, 6, 51, 52). A 54 417 u &zgr; - 248 25 March 1998 - 17 - 2. Orthopedic screw system according to claim 1, characterized in that the first component (A; C) is formed by a solid tubular shaft with a first outer screw thread area (1) and an elongated smooth thread-free shaft part (3), that the second component (B; D) is formed by a hollow tubular shaft with a second outer screw thread (8) and a smooth inner cylindrical surface (10) which surrounds the elongated thread-free shaft part (3) of the first solid component (A; C), whereby the two components (A, B; C, D) can be rotated independently of one another. 3. Orthopedic screw system according to claim 2, characterized in that the hollow tubular component (B) has a free end (5) with a screw thread (8) and an elongated thread-free part (7). 4. Orthopaedic screw system according to claim 2 or 3, characterized in that the hollow tubular component (B) has a retaining means (11) which protrudes inwardly from its inner smooth surface (10), and that the solid component (A) has a conical neck part (2) on its elongated thread-free shaft part (3), with which the locking connection (2, 11) is formed together with the retaining means (11). •·♦· A 54 417 u &zgr; - 248 25 March 1998 - 18 - 5. Orthopaedic screw system according to one of claims 2 to 4, characterized in that the hollow tubular component (B) has a longitudinal slot (9) extending from one end (6) through its entire thickness to allow temporary expansion during insertion of the elongated unthreaded shaft part (3). 6. Orthopedic screw system according to claim 2, characterized in that the elongated, thread-free shaft part (3) of the solid component (C) is extended by an elongated, thread-free shaft section (53) which has a different diameter, whereby a shoulder (51) is formed in the transition region between the shaft part (3) and the shaft section (53). 7. Orthopedic screw system according to claim 6, characterized in that the elongated thread-free shaft section (53) is smaller in diameter than the elongated thread-free shaft part (3) and forms the end of the solid component (C). A 54 417 u &zgr; - 248 25 March 1998 - 19 - 8. Orthopaedic screw system according to claim 6 or 7, characterized in that the elongated thread-free shaft portion (53) of the solid component (C) has a radial projection (52) on its outer surface at its end (50). 9. Orthopedic screw system according to one of claims 2, 6 to 8, characterized in that the elongated unthreaded shaft portion (53) has a longitudinal slot (54) extending from the one end (50) of the solid component (C) across the entire thickness, thereby enabling temporary compression during insertion of the elongated unthreaded shaft portion (53) of the solid component (C) into the hollow tubular component (D). 10. Orthopedic screw system according to claim 9, characterized in that the hollow tubular component (D) fits exactly on the elongated thread-free shaft portion (53) of the solid component (C) between the projection (52) and the shoulder (51). 11. Orthopaedic screw system according to claim 10, characterized in that the entire outer surface of the hollow tubular component (D) is provided with a screw thread (8). A 54 417 u &zgr; - 248 25 March 1998 - 20 - 12. Orthopaedic screw system according to one of claims 2, 6 to 11, characterized in that the hollow tubular component (D) has a slot (55) which extends diametrically from the one end (5) through its entire thickness. 13. Orthopaedic screw system according to one of the preceding claims, characterized in that both screw threads (1, 8) have the same pitch difference. 14. Orthopaedic screw system according to one of the preceding claims, characterized in that the diameter of the two screw threads (1, 8) is the same.