WO2005053545A2

WO2005053545A2 - Rod for the neck of the femur and instrument set for inserting the rod

Info

Publication number: WO2005053545A2
Application number: PCT/EP2004/013139
Authority: WO
Inventors: Paolo Trentani; Claudio Trentani
Original assignee: Trentani, Federico; Zella, Adriana
Priority date: 2003-11-20
Filing date: 2004-11-18
Publication date: 2005-06-16
Also published as: ITBO20030698A1; WO2005053545A3

Abstract

A rod (1) for the neck (12) of the femur (4) and an instrument set for insertion, which has a substantially tubular shape, is adapted to be inserted from below and from outside toward the inside of the articulation substantially in axial alignment with the neck (12) of the femur (4) through an opening (2b) that passes through the cortex (2) of the femur (4), which has a tapered front insertion end (7) and is crossed by a plurality of through holes (5).

Description

ROD FOR THE NECK OF THE FEMUR AND INSTRUMENT SET FOR INSERTINGTHEROD Technical Field The present^' invention relates to a rod for the neck of the femur and to the instrument set for inserting the rod. Background Art As a good standard of quality of life becomes widespread and as discoveries in the medical field advance, there is a constant increase in lifespan expectation. Accordingly, the number of elderly people increases every year in the population of the most industrialized countries. One of the consequences of this longevity is that some diseases, which previously affected only a minimal fraction of the population, are currently more widespread (and it is presumable that there will be further increases in the number of people affected by these diseases in the future). One of the diseases that most affects elderly people (but also people of other age groups affected by specific primary and secondary diseases) is the increase in bone fragility (osteoporosis). Rarefaction of bone tissue entails reduced structural strength: accordingly, bones fracture more easily both due to external traumatic actions and due to degenerations that lead to inability to bear the normal load (the bones are no longer capable of bearing the weight of the body). A very high percentage of the fractures that occur following this bone rarefaction (approximately 30%) affects the neck of the femur. This neck is in practice the portion that connects the greater trochanter to the head (epiphysis), which in turn is articulated in the acetabular cavity of the pelvis. Due to its shape, the neck of the femur is subjected to a rather intense load: while the remaining part of the femur is subjected almost exclusively to compression (axial load), the neck is subjected to a mixed load, in which it is possible to identify a compression component and an important shearing component, which entails the presence of a moment of flexure. The presence of these components is due to the shape of the neck of the femur, which forms an angle of approximately 128° with the diaphysis of the femur. There are extremely sophisticated diagnostic methods (which employ tests such as X-rays, bone densitometry, computerized axial tomography, nuclear magnetic resonance) which allow to determine very precisely the porosity of a bone and in particular can identify the presence of rarefactions of the tissue or the presence of regions in which the tissue is completely altered and predict with considerable accuracy the risk of fracture of the neck of the femur. Currently, once a high risk of femur neck fracture has been diagnosed, there are no preventive surgical strategies. The administration of drugs is in fact unable, on its own, to prevent the risk of fracture. On the other hand, it is not conceivable to suggest to the patient in whom damage, but not yet a f acture, has been detected to perform an invasive surgical procedure (osteosynthesis or arthroprosthetics). Such procedures are complicated and require long hospitalization times, the risk of severe complications, and blood transfusions and deep anesthesias. Accordingly, performing such a preventive procedure is a choice that is unlikely to be acceptable for the patient, for his relatives and for the health service. Disclosure of the Invention The aim of the present invention is to obviate the cited drawbacks and to meet the mentioned requirements, by providing a rod for the neck of the femur and an instrument set for insertion that allow to reinforce the neck of the femur with a technique that is simple, mini-invasive, in day-hospital conditions and allowing immediate loading of the treated limb. Advantageously, an object of the present invention is to allow to insert substances that have a medicinal or curative function directly inside the bone. This aim and this and other objects that will become better apparent hereinafter are achieved by the present rod for the neck of the femur and by the present instrument set for inserting said rod, characterized in that it has a substantially tubular shape, is suitable to be inserted f om the fossa of the greater trochanter from below and from the outside toward the acetabular cavity, substantially in axial alignment with the neck of the femur through an opening that passes through the cortex of the femur, which has a tapered front insertion end and is crossed by a plurality of through holes. Brief description of the Drawings Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a rod for the neck of the femur and of the instrument set for insertion, illustrated by way of non-limiting example in the accompanying drawings, wherein: Figure 1 is a side view of a rod and of the corresponding instrument set according to the invention, assembled together; Figure 2 is a side view of a stem of a rod according to the invention; Figure 3 is a side view of a milling cutter for providing an opening in the cortex in order to insert a rod according to the invention; Figure 4 is a sectional side view of a rod according to the invention; Figure 5 is a side view of a thread protecting plug of a rod according to the invention; Figure 6 is a sectional side view of an extension of a rod according to the invention; Figure 7 is a sectional side view of a bush of a rod according to the invention; Figure 8 is a partially sectional side view of the insertion of a stem in a femur with rarefied bone tissue; Figure 9 is a partially sectional side view of the insertion of the rod and of the extension with the aid of the bush on the stem previously arranged in a femur with rarefied bone, tissue; Figure 10 is a partially sectional side view of the removal of the bush previously arranged in a femur with rarefied bone tissue; Figure 11 is a partially sectional side view of the removal of the stem, previously arranged in a femur with rarefied bone tissue; Figure 12 is a partially sectional side view of the injection of material through the extension and the rod in a femur with rarefied bone tissue; Figure 13 is a partially sectional side view of the distribution of material and of the position of the rod once the operation has been completed.

Ways of carrying out the Invention With reference to the figures, the reference numeral 1 generally designates a rod for the neck of the femur. The rod 1 is a tubular element that is shorter than the distance between the internal surface of the cortex 2 of the head (epiphysis) 3 of the femur 4 and the outer surface of the trochanteric cortex 2 of the femur 4. The length of the rod 1 is preferably variable between 80 and 110 mm, and the rod is provided in all the intermediate sizes, with length steps of 5 mm between one size and the next, so as to have available a rod 1 that is suitable for every size of femur 4 (which of course depends on various parameters, including the height of the patient). The cross-section of the rod 1 is preferably circular, with an outside diameter comprised, by way of example, between 8 and 10 mm and a diameter of the internal channel 6 that is comprised between 6 and 8 mm. Each rod 1 is provided with through holes 5, which are arranged symmetrically and distributed uniformly, radially and longitudinally: the holes 5 are preferably provided in a number comprised between 4 and 8, and have a diameter of preferably 4 mm and are mutually offset substantially by a right angle. The front end 7 of the rod 1 is tapered, in order to facilitate its insertion in the ^' femur 4, after milling the outer cortex 2 with an appropriately provided instrument 2a, while the rear end 8 is provided with means 9 for coupling to an extension 10. The coupling means 9 are constituted by a female thread, which is suitable to be associated with a male thread 11 provided at the front end of the extension 10 or with other elements described hereinafter. The rear end 8 may also be provided with an end flaring (not shown in the figure), which is suitable to prevent the penetration of the rod 1 in the femur 4. The outer surface of the rod 1 is normally smooth, since this solution facilitates its insertion in the neck 12 of the femur 4: it can be convenient to provide rods 1 with a rough outer surface, coated with osteoinducing ceramic materials (for example alumina, hydroxyapatite and trabecular metal), or provided with crests (optionally arranged at a specific angle, for example 60°, in order to constitute a grip thread) in order to provide better anchoring of the rod 1. Optionally, the rod 1 can have a polygonal (preferably polygonal) cross-section, so that it cannot rotate about its own axis of symmetry due to geometric interference with the bone that accommodates it. The extension 10 also is a tubular element, which has a length that can vary on average between 150 and 200 mm, and is chosen according to the physical characteristics of the patient in order to be able to work percutaneously (from the outside) in the easiest way. The outside and inside diameters of the extension 10 are substantially the diameters of the rod 1; the outer surface is smooth. The extension 10 has, at its rear end, a female thread 13 for coupling to a bush 14 (cannulated handle). The extension 10 further has an end flaring 13a, which is suitable for coupling to an injector, which is generally made of polyethylene (not shown in the figure). The bush 14 (cannulated handle) is provided longitudinally with two mutually opposite elongated slots 15 in order to assess the insertion of the rod 1 in the femur 4 and has, at the front end, a male thread 16 for coupling to the extension 10. A metallic stem 17 (guiding wire) is substantially a slender element that is slightly longer (by approximately 2 or 3 mm) than the overall length of the rod 1, of the extension 10 and of the cannulated portion of the bush 14 when mutually coupled, and has a diameter that is slightly smaller than the inside diameter of the rod 1 and of the extension 10 (the diameter is on the order of 3-4 mm). The stem 17 (guiding wire) is provided, at the front, with a piercing sharp end 18. The rod 1, the extension 10, the bush 14 (cannulated handle) and the stem 17 (guiding wire) are preferably made of titanium or other metallic materials, such as for example surgical steel. Optionally, the materials can be combined, adopting more noble materials (such as titanium) to provide the rod 1 and other materials (such as surgical steel) for the other elements of the instrument set. The rod 1 can be made of a particular material and then be coated with other materials, obtaining composite materials (for example a rod 1 made of titanium coated with a layer of hydroxyapatite or alumina or trabecular metal et cetera). A polyethylene injector, not shown in the figure, can be connected to the outer rear end of the extension 10, particularly to the flaring 13 a, and it is possible to insert through said injector, and through the extension 10 inside the rod 1, and therefore inside the neck 12 and the head 3 of the femur 4, different materials, such as acrylic cement (with the aim of structurally reinforcing the neck 12 of the femur 4), substances that have a substantially local action (stem cells, platelet gel, chemotherapy substances) or radioactive isotopes. The operation of the invention is as follows: once the patient has been subjected to valid diagnostic methods such as X-rays, bone densitometry, computerized axial tomography and nuclear magnetic resonance, it is possible to determine very precisely the state of osteoporosis of a bone. In particular, it is possible to identify, within the intact bone tissue 19, the presence of rarefactions 20 of the tissue or the presence of regions in which the tissue is completely absent (neoplastic disorder) and predict with good precision the risk of fracture of the neck 12 of the femur 4. The patient is then subjected to local anesthesia and an incision of approximately 10 mm is produced at the trochanteric fossa. The stem 17 is inserted through the incision (as shown in Figure 6) inside the femur 4 until the sharp end 18 arrives in the vicinity of the internal cortex 2 of the head 3 of the femur 4. The direction along which the stem 17 (guiding wire) is to be inserted is visualized by using an image intensifier (this is a device that is normally present in facilities that perform orthopedic surgical treatments). An opening 2b is provided in the subtrochanteric cortex 2 by means of the appropriately provided instrument 2a, which is substantially a milling cutter provided with an axial channel and with a shoulder at a distance of approximately 15 mm from the tip in order to prevent excessive removal of material, having a diameter comprised between 8 and 10 mm, following the stem 17 (guiding wire) for a depth of approximately 15 mm. Once the rod 1, the extension 10 and the bush 14 (cannulated handle) have been mutually assembled, the rear end of the stem 17 (guiding wire) is inserted in the front opening of the rod 1 (so that the stem 17 acts as a guide) and by percussion, by using a hammer (not shown in the figure) against the percussion end of the bush 14 (cannulated handle), the rod 1 is inserted (as shown in Figure 7) inside the femur 4 until it is inserted completely (as shown in Figure 8). The stem 17 (guiding wire) can be seen through the slot 15 of the bush 14 (cannulated handle); by unscrewing the bush 14 (cannulated handle) from the extension 10 (as shown in Figure 8), it is possible to remove the stem 17 (as shown in Figure 9). By connecting by pressure the injector to the flaring 13a of the extension 10, it is possible to introduce material in the extension 10 and in the rod 1 (and therefore in the neck 12 of the femur 4). In order to keep the outer rear thread 9 of the rod 1 free, in case of removal, it is possible, once the material has been introduced, to insert axially in the rod 1 a guiding wire that has a diameter of approximately 1 mm, while the cement is still soft, and then a cannulated male plug that has the same pitch and size as the thread 9 of the rod 1, and fasten it by means of a cannulated hexagonal screwdriver. The plug 21 can preferably be frustum-shaped and can have a length preferably on the order of 10 to 15 mm, in which the thread affects only an end portion that is no more than 6-8 mm long. If acrylic cement or other compounds are injected in order to improve structural strength, these compounds, through the holes 5 and the front opening 7, spread inside the neck 12 and the head 3 of the femur 4 and distribute mainly in the regions 20 where the bone tissue is rarefied, helping to reinforce them and couple them rigidly to the rod 1. The result is an increased solidity of the neck 12 of the femur 4, reducing the risk of fracture. If fractures occur after the insertion of the rod 1, such rod can be extracted easily by connecting to its thread 9, after removing the thread protection plug 21, the extension 10 and the bush 14 (cannulated handle) and engaging the bush 14 (cannulated handle) from the slot 15 by means of an extractor. If pertrochanteric fractures occur, the application of plates and screws would be possible through the rod 1 with telescopic coupling, providing a pertrochanteric synthesis. It should be noted that the rod 1 may have an end flaring, in order to prevent it from entering the femur 4 completely; if this flaring is not provided, it is possible to consider applying the plug 21 fixed to the thread 9 of the rod 1, which has or not a rear end provided with a shoulder. The time required for insertion of the rod 1, stabilization thereof and skin suture are on the order of 15-20 minutes and the patient can walk immediately by placing his weight normally on the treated limb. If a patient suffers breakage of the neck 12 of the femur 4 and must be subjected to an osteosynthesis or prosthetic procedure on that femur 4 (for example the left one), he can be advantageously subjected, during the same operating session, to the insertion of a rod 1 according to the invention in the other femur 4 (the right one), which is certainly at risk (since its condition is certainly similar to the condition of the fractured femur, which is the left one in this example). After the procedure, the patient can plate all of his body weight on the limb in which the rod 1 has been implanted (for example the right limb), ensuring greater stability of contralateral support. It is also possible to insert in the bone, by means of the injector, drugs that have a local action: one example can be the administration of chemotherapy drugs. This type of treatment subjects the patient to considerable discomfort and to problems of various kinds: by being able to localize their administration to the affected part, it is possible to reduce their side effects on the patient. Likewise, it is possible to introduce radioactive isotopes in the bone in order to subject the patient to localized radiotherapy (brachytherapy). These radioactive isotopes can be removed, and the part can then be filled with acrylic cement. It has thus been shown that the invention achieves the intended aim and object. The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. It should be noted that it is necessary to include in the instrument set also a sort of cleaning rod, which can have substantially two functions. Once the cement has been injected, it can be used to push into the rod 1 the cement that is present in the extension 10. Once injection has occurred and the extension 10 has been extracted, it is possible to clean said extension by using the cleaning rod so as to be able to reuse it in future procedures. All the details may further be replaced with other technically equivalent ones. In the illustrated embodiments, individual characteristics, given in relation to specific examples, may actually be interchanged with other different characteristics that exist in other embodiments. Moreover, it is noted that anything found to be already known during the patenting process is understood not to be claimed and to be the subject of a disclaimer. In practice, the materials used, as well as the shapes and the dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims. The disclosures in Italian Patent Application No. BO2003A000698 from which this application claims priority are incorporated herein by reference.

Claims

CLAIMS 1. A rod (1) for the neck (12) of the femur (4) and an instrument set for inserting said rod, characterized in that it has a substantially tubular shape, is adapted to be inserted from the fossa of the greater trochanter from below and from the outside toward the acetabular cavity, substantially in axial alignment with the neck (12) of the femur (4) through an opening (2b) that passes through the cortex (2) of the femur (4), which has a tapered front insertion end (7) and is crossed by a plurality of through holes (5).

2. The rod according to claim 1, characterized in that it is shorter than the distance between the internal surface of the cortex (2) of the head (3) of the femur (4) and the outer surface of the cortex (2) of the femur (4), in which it will be inserted.

3. The rod according to claim 1, characterized in that said instrument set comprises a tubular handling extension (10), the outside and inside diameters of which are substantially identical to those of said rod (1), said extension having, at its front end, means (11) for detachable coupling to the rear end (9) of said rod (1).

4. The rod according to one or more of the preceding claims, characterized in that said handling extension (10) has, at its rear end, means (13) for detachable coupling to an instrument set that selectively comprises a hollow percussion handle bush (14) or an injector of substances of various kinds.

5. The rod according to one or more of the preceding claims, characterized in that said instrument set comprises a guiding stem (17), which is slightly longer than the total length of the rod (1), the extension (10) and the cannular portion of the bush (14), when mutually coupled, and has a diameter that is slightly smaller than the inside diameter of the rod (1) and of the extension (10) and is provided with a sharp end (18), which is suitable to be inserted and guided, with the aid of radiographic means, through the subtrochanteric fossa within, and in axial alignment with, the neck (12) of the femur (4) up to the vicinity of the internal surface of the cortex (2) of the head (3) of the femur (4), the rod (1) being made to penetrate in the femur (4) along said guide, after milling, said rod being coupled to said extension (10) and to said bush (14) by percussion by means of a sort of hammer against the end of the percussion bush (14).

6. The rod according to one or more of the preceding claims, characterized in that said percussion bush (14) is provided longitudinally with two mutually opposite elongated slots (15), through which it is possible to view the rear end of the guiding stem (17) when the rod (1) is proximate to its end insertion portion, in order to avoid overshooting into the pelvis.

7. The rod according to one or more of the preceding claims, characterized in that said detachable coupling means (9, 11, 13, 16) are constituted by female thread portions of the rear ends of said rod (1) and of said handling extension (10), which are suitable to cooperate with male thread portions of the front ends of said handling extension (10), of said bush (14) and of a plug (21) for closing the rod (1) inserted in the bone.

8. The rod according to one or more of the preceding claims, characterized in that said percussion bush (14) is suitable to act as an extractor through said elongated slots (15).

9. The rod according to one or more of the preceding claims, characterized in that said injector, provided with elements for connecting a front tubular portion thereof to the rear end, provided with an appropriate flaring (13a), of said handling extension (10), is adapted to introduce material through said extension (10) and said rod (1) inside the neck (12) and the head (3) of the femur (4).

10. The rod according to claim 9, characterized in that said introduced material is substantially of the type of acrylic cement, suitable to fill any cavities (20) that are present, strengthening them, and to anchor the rod (1) to the bone.

11. The rod according to claim 7, characterized in that said introduced material is a locally-acting substance.

12. The rod according to claim 7, characterized in that said introduced material is a radioactive isotope (brachytherapy).

13. The rod according to claim 1, characterized in that said through holes (5) are arranged symmetrically and are distributed radially and longitudinally.

14. The rod according to claim 1, characterized in that said rod (1) can have a rear end (8) that is provided with an end flaring suitable to prevent the penetration of said rod (1) in the femur (4).

15. The rod according to one or more of the preceding claims, characterized in that said rod (1) is made of a material such as titanium.

16. The rod according to one or more of the preceding claims and as an alternative to claim 13, characterized in that said rod (1) is made of a material such as surgical steel.

17. The rod according to one or more of the preceding claims and as an alternative to claim 13, characterized in that said rod (1) is made of a composite material, such as a metal with an osteoinducing ceramic coating.

18. The rod according to one or more of the preceding claims, characterized in that said handling extension (10), said stem (17) and said bush (14) are made of a material such as titanium.

19. The rod according to one or more of the preceding claims, characterized in that said handling extension (10), said stem (17) and said bush (14) are made of a material such as surgical steel.

20. The rod according to one or more of the preceding claims, characterized in that said rod (1) has a smooth outer surface.

21. The rod according to one or more of the preceding claims, characterized in that said rod (1) has a rough outer surface.

22. The rod according to one or more of the preceding claims, characterized in that said rod (1) has an outer surface provided with distributed crests.

23. The rod according to claim 22, characterized in that said crests are distributed so as to constitute an anchoring thread.

24. The rod according to one or more of the preceding claims, characterized in that said rod (1) preferably has a length that is variable between 80 and 110 mm and is provided in all the intermediate sizes, with length steps of 5 mm between one size and the next.

25. The rod according to one or more of the preceding claims, characterized in that said rod (1) has an outside diameter comprised between 8 and 10 mm and a diameter of the internal channel (6) that is comprised between 6 and 8 mm.

26. The rod according to one or more of the preceding claims, characterized in that said holes (5) are 4 to 8, have a diameter of 4 mm and are substantially mutually offset by a right angle.

27. The rod according to one or more of the preceding claims, characterized in that it has a substantially polygonal cross-section.

28. The rod according to claim 27, characterized in that it has an octagonal cross-section.