WO2008064059A2

WO2008064059A2 - Sliding hip helical implant

Info

Publication number: WO2008064059A2
Application number: PCT/US2007/084780
Authority: WO
Inventors: Alberto A. Fernandez Dell'oca
Original assignee: Synthes(U.S.A.); Synthes Gmbh
Priority date: 2006-11-17
Filing date: 2007-11-15
Publication date: 2008-05-29
Also published as: WO2008064059A3

Abstract

A device for treating fractures comprises an intramedullary member (1) sized and shaped for insertion along a longitudinal axis of a bone within a medullary canal thereof, the intramedullary member including a bore extending laterally there through and a lateral implant (3) sized for insertion into the bone through the bore, a distal portion of the lateral implant including a plurality of substantially helical blades in combination with a sleeve (4) slidably received over a proximal portion of the lateral implant, the sleeve being non-rotatably received on the proximal portion of the lateral implant and a locking member for locking the sleeve in a desired position within the bore.

Description

SLIDING HIP HELICAL IMPLANT

Inventor(s): Alberto A. Fernandez DelFOca

Field of the Invention

[0001] The present invention relates to a device for use in osteosynthesis to treat femoral fractures, in particular fractures of the proximal femur including, for example, fractures of the femoral neck, pertrochanteric, subtrochanteric and the intertrochanteric regions of the femur.

Background of the Invention:

[0002] Implants have been developed to treat proximal femoral fractures based on a hip nail or screw inserted from the side of the femur through the neck and into the femoral head. Afterwards this nail or screw is fixed either to an intramedulary implant (e.g., an intramedullar nail) within the femoral shaft, or to a side plate positioned on the outside of the femoral shaft.

[0003] Intramedullary rod and cross nail assemblies as disclosed, for example, in U.S. Pat. No. 3,433,220 include a hip nail fixed to an intramedullary nail inside the femoral shaft. Although such devices permit adequate fixation and rotational control of the fracture, at times fragments of the fractured bone may slide along the hip nail rendering contact between the fractured surfaces of the bone insufficient to support the patient's weight. This intensifies stresses applied to the implanted hip nail and increases the risk of bending or breaking of the hip nail. Depending on the shape of the hip nail, these increased stresses may exceed the strength of the femoral neck and head bone tissue potentially moving the fragments of the fractured bone out of a desired alignment with one another or causing the implant to cut through the chancellous tissue of the femoral neck or head in a condition known as "cut out."

[0004] Collapsible implants as disclosed, for example, in U.S. Pat. No. 5,176,681 were developed to in which a hip nail or screw is passed through a bore in a side plate or intramedullary nail, binding to this anchor to draw the bone fragments toward each other, reducing the fracture as weight is placed on the fractured limb. However, such implants often contact bone tissue over only a small surface area so that, when weight is put on the bone, the implant may cut through the cancellous bone of the femoral head, causing the implant to rupture the femoral surface and/or no longer maintaining a desired alignment of the fracture. Moreover, such implants may permit unwanted rotation of the femoral head around the hip nail or screw.

[0005] Thereafter, complete helical blades were developed (such as Neufelds' Subtrochanteric Nail described in US Pat. No. 4.103.683; and Friggs' Fixation Plate disclosed in U.S. Pat No. 4.978.349) which include a single helical blade inserted through the femoral neck into the femoral head, so that when the insertion is completed the distal end of the blade lies in a vertical position passing through a vertical slot in the intramedullary nail; while the proximal end lies in a horizontal position, permitting the load over the femoral head to act on a larger, substantially Hat surface, diminishing pressure on the bone tissue and reducing the tendency of the implant to cut out.

[0006] To obtain the necessary sliding (minimizing the implants' breaking risk while permitting compression of bone fragments), and to avoid the cutting-out problem of complete helical implants, partial helical implants were developed. Examples of these implants are the Two-part Angle Plate invented by Frigg US Pat. No. 5.300.074, and Bresinas^" Helical Implant US Pat. No. 5.908.422. In this devices the hip implant consist in a proximal helical blade at the front portion of the implant (which increases the surface over which the load acts, preventing the cut-out), followed by a distal shaft at the rear portion of the implant which is able to slide back through the bore in the intramedullary nail or side plate.

Summary of the Invention

[0007] The present invention is directed to an intramedullary ostesynthetic device for treating proximal femoral fractures which minimizes the risk of cut out through cancellous femoral bone tissue and which is rotationally stable while allowing sliding back of the hip implant to permit the approaching of bone fragments toward one another. [0008] The present invention is further directed to an insertion tool to facilitate insertion of the implant.

[0009] The present invention is further directed to a hip implant that permits easy removal by a single lateral approach.

[0010] The Hip helical implant is a partial helical implant that consists of a frontal helical portion, and a rear substantially smooth shaft. The frontal helical portion is provided with at least two helically twisted blades and a rear (proximal) smooth shaft fit within a sliding sleeve, permitting the sliding-back of the implant through the sleeve. The shaft has a flat that abuts an internal flat in the sliding sleeve, which prevents rotation of the shaft of the hip helical implant inside the sliding sleeve maintaining rotational stability of the fractured segments of the bone.

[0011] The intramedullary nail has at least one oblique slotted bore angled in the direction of the femoral neck and designed to accommodate the sliding sleeve which slidably passes through it. Under this oblique bore, and in communication with it, the intramedullary nail is provided of a threaded notch to accommodate a lateral set screw, which provides fixation of the sliding sleeve to the intramedullary nail by a threaded mechanism.

J0012] An insertion tool facilitating the insertion procedure includes a cannulated shaft connected with a striking cap, a driving sleeve which slides over the cannulated shaft and a rear slotted insert which also slides over the cannulated shaft. A guiding sleeve slides over the rest of the assembly.

[0013] During the insertion procedure the cannulaated shaft is hammered pushing the helical assembly forward through the oblique bore of the intrmedullary nail (previously introduced in the medullary canal) toward the femoral head.

[0014] Once the required depth has been achieved, the rear slotted insert is removed and the helical implant is pushed far into the femoral head until its final position is achieved.

[0015] Thereafter, the lateral set screw is inserted in the notch of the intramedullary nail affixing the sliding sleeve to the nail. [0016] The present invention is further directed to a device for treating fractures comprising an intramedullary member sized and shaped for insertion along a longitudinal axis of a bone within a medullary canal thereof, the intramedullary member including a bore extending laterally therethrough and a lateral implant sized for insertion into the bone through the bore, a distal portion of the lateral implant including a plurality of substantially helical blades in combination with a sleeve slidably received over a proximal portion of the lateral implant, the sleeve being non-rotatably received on the proximal portion of the lateral implant and a locking member for locking the sleeve in a desired position within the bore.

Brief Description of the Drawings

[0017] Fig 1 shows a front view of the disassembled implant and insertion instruments;

Fig 2 shows a cross-section of the implant and insertion instruments of Fig. 1 showing cross-sections in planes perpendicular to the overall cross-section of selected portions of portions of the implant and insertion instruments;

Fig 3 shows a front view of the implant and insertion instruments of Fig. 1 assembled with the guiding sleeve shown at the side;

Fig 4 shows a cross-section of the implant inserted to a position required to place the holding sleeve in its final position;

Fig 5 shows the implant inserted as in Fig 4 after removal of the slotted insert;

Fig 6 shows the implant in its final position;

Fig 7 shows the implant in the final position of Fig. 6 with a lateral set screw inserted and the insertion instruments removed;

Fig 8 shows a cross-section of the implant in its final position with a lateral set screw in place; and

Fig 9 shows a cross-section of an implant similar to that of Fig. 8 in its final position with an axial set screw used in place of the lateral set screw.

Detailed Description

[0018] The present invention, which may be further understood with reference to the following description and the appended drawing, relates to devices for treating fractures and, in particular, relates to internal fixation devices for treating fractures. It is noted that, although the exemplary embodiments of the present invention are described below with respect to the treatment of fractures of the femur, the description is not meant to limit the application of the invention to such fractures as the invention may be employed in the treatment of fractures of other bones including, for example, the humerus.

[0019] To improve the performance of intramedullary ostesynthetic devices in the treatment of proximal femoral fractures (e.g., in the femoral neck or femoral head), embodiments of the present invention provide hip implants and intramedullary nails which substantially eliminate relative rotational movement between the hip implant and the intramedullary nail and which, consequently, minimize relative rotational motion between the fractured elements of the femur.

[0020] Figs. 1 and 2 show an exemplary embodiment of a device of the present invention. The device comprises an intramedullary nail 1 with at least one oblique bore 16 to slidably receive therein a sliding sleeve 4 of a helical hip implant 3 as will be described in more detail below. An insertion tool for use with the implant according to the invention comprises an insertion shaft 8, a driving sleeve 6, a guiding sleeve 7, and a rear slotted insert 9. The device further comprises a locking member for fixing the position of the sliding slee\e 4 relative to the nail 1. As will be described in more detail below, the locking mechanism may comprise, for example, an axial set screw 15 inserted to the bore 16 through a proximal hole 2 extending axially into the nail 1 and/or a lateral set screw 5 inserted into a set screw bore 14 adjacent to the bore 16,

[0021] The nail 1 may, for example, be a cannulated intramedullary nail generally shaped and sized for insertion into the medullar canal of a femur as would be understood by those skilled in the art. The oblique bore 16 is angled to be substantially parallel to an axis of the trochanter of the femur when the nail 1 is inserted to a desired position in the medullary canal and is sized to slidably receive the sliding sleeve 4 therein. The diameter of the helical implant 3 is preferably selected to be no greater than that of the sliding sleeve 4 so that the implant 3 may be passed through the bore 16 as well. The set screw bore 14 extends through a portion of the nail 1 substantially parallel to the bore 16 immediately adjacent thereto and in communication with the bore 16. That is, the set screw bore 14 is open to the bore 16 so that the thread of a set screw 5 inserted therein may engage surface features of the sliding sleeve 4. For example, a portion of threads of the sliding sleeve 4 may engage any of a series of raised circular ridges 19 formed on an outer surface of the sliding sleeve 4 so that the set screw 5 which is locked in the set screw bore 14 by its threads locks the position of the sliding screw 4 relative to the bore 16. As would be understood by those skilled in the art, the nail 1 may include additional laterally extending bores 18 toward a distal end thereof for receiving lateral screws to stabilize the nail 1 within the femur.

[0022] A distal end of the helical hip implant 3 comprises at least two helically twisted blades 17 while a shaft 20 extends proximally therefrom to a proximal end including a threaded opening 21. The helical blades 17 extend around a longitudinal axis of the implant 3 along a substantially helical path with a helix angle Θ between 70° and 90° with the angle Θ preferably being between approximately 75° and 85°. The sliding sleeve 4 slides over the shaft 20 allowing the implant 3 to slide along the axis of the bore 16 relative to the sliding sleeve 4.

[0023] As shown in the cross-sectional view of Fig. 2, the shaft 20 and the sliding sleeve 4 are keyed relative to one another to prevent rotation of the shaft 20 relative to the sliding sleeve 4 about the axis of the bore 16. That is, a first portion 21 of the circumference of the shaft 20 is substantially cylindrical while a second portion 22 forms a flat surface extending along the length of the shaft 20 to engage a flat surface 23 on an inner surface of a lumen 24 of the sliding shaft 4 so that the angular orientation of the shaft 20 within the lumen 24 is fixed. It will be understood by those in the art that any of a variety of other key systems may be used so long as the rear shaft of implant 3 and the sliding sleeve 4 are able to slide relative to one another without rotating relative to one another about their longitudinal axes. For example, the implant 3 and the inner lumen of the sliding sleeve 4 may be hexagonal. [0024] The threaded opening 21 of the helical implant 3 is sized to threadably receive therein a threaded distal end 25 of the insertion shaft 8. The insertion shaft 8 includes an elongated body 26 and a annular shoulder 27 extending radially outward from a proximal end of the body 26. The driving sleeve 6 includes a lumen sized to slidably receive therein the shaft 20 and the body 26 which preferably have diameters substantially equal to one another. When assembling the insertion tool, the driving sleeve 6 is slid over the insertion shaft 8 prior to coupling the shaft 8 to the implant 3. This assembly is then slid into the sleeve 7. The driving sleeve 6 is slidable over the shaft 20 of implant 3 until the distal end of the shaft 8 abuts the proximal end of the sliding sleeve 4. The driving sleeve 6 may continue to move distally along the implant 3 pushing the sliding sleeve 4 distally therealong until the distal end of the sliding sleeve 4 abuts a shoulder 29 at a proximal end of the blades 17. At this point, the sliding sleeve 4 and the sleeve 6 can move no further distally over the shaft 20. The length of the shaft 8 is preferably selected relative to the lengths of the shaft 20, the sliding sleeve 4 and the driving sleeve 6 so that, at the point when the sliding sleeve 4 and the sleeve 6 are moved to their distal-most position on the implant 3, a gap between a proximal end 30 of the sleeve 6 and the annular shoulder 27 along the longitudinal axes of these shafts is at least equal to a distance by which it is desired to drive the implant 3 into the femur. That is, the annular shoulder 27 must be free to advance distally by a distance required to drive the implant 3 through the bore 16 to a desired depth in the bone.

[0025| A rear slotted insert 9 is preferably formed as a slotted spacer with a length selected to be substantially equal to the distance by which it is desired to drive the implant 3 into the bone. The slot 31 allows the insert 9 to be slid over and removed from the shaft 8 between a proximal end of the guiding sleeve 7 and the annular shoulder 27 to maintain the desired separation therebetween. As shown in Fig. 3, when the insert 9 is placed over the driving sleeve 6 and slid proximally thereover, it abuts the shoulder 27 of the shaft 8. The guiding sleeve 7 is slidable over the driving sleeve 6 such that a distal end of the guiding sleeve 7 abuts the end of sleeve 4 and a proximal end of the guiding sleeve 7 abuts an end of the rear slotted insert 9.

[0026] As shown in Figs. 4-7, the system according to the invention further comprises an aiming block 1 1 which, during insertion of the implant 3, is coupled to the proximal end 13 of the nail 1 and extends out of the leg (not shown) and downward so that a lumen 32 therethrough aligns with the bore 16. The sleeve 7 is sized so that, when inserted through the lumen 32 until its distal end 33 abuts the femur as shown in Fig. 5, the proximal end 34 thereof extends out of the lumen 32 with a shoulder formed at the proximal end 34 separated from the shoulder 27 of the shaft 8 by the distance it is desired to drive the implant 3 into the bone. At the point shown in Fig. 4, the sliding sleeve 4 is received within the bore 16 and the implant 3 has been partially hammered into the femur with the blades 17 extending a slight distance into the bone on the opposite side of the nail 1. The insert 9 is then removed from the shaft 8 so that the implant 3 may be driven into the bone (e.g., by hammering) as would be understood by those skilled in the art. As the shoulder 8 is hammered distally, the proximal end of the implant 3 and the blades 17 are driven into the bone with the helical shape of the blades 17 causing the implant 3 and the sliding sleeve 4 to rotate together about the axis of the bore 16. As would be understood by those skilled in the art, the helix of the blades 17 is preferably wrapped around the axis of the implant 3 in a direction opposite that of the thread of the threaded end 25 of the shaft 8 so that the connection between the shaft 8 and the implant 3 is not loosened by this rotation.

[0027] When the shoulder 27 abuts the shoulder at the proximal end of the sleeve 7, the user knows the implant has been driven to the desired depth in the bone. The user then removes the sleeve 7 from the aiming block 11 and removes the aiming block from the proximal end 13 of the nail 1. The user then locks the sliding sleeve in place (preventing movement axially and rotationally) within the bore 16 inserting an axial set screw 15 into the proximal hole 2 until a distal end thereof engages the sliding sleeve 4 (e.g., between adjacent features 19 and/or a lateral set screw 5 inserted into the set screw bore 14. The user then unscrews the threaded end of the shaft 8 from the implant 3 and removes the shaft 8 and sleeve 6 and installation of the implant 3 is completed.

[0028] If no axial set screw 15 has been used, the lateral set screw 5 may facilitate removal of the implant 3 should it be required. The lateral set screw 5 is simply removed from the set screw bore 14 by turning the screw 5 and loosening the screw mechanism. Once removed, the implant 3 may be removed by using the insertion tool. The insertion shaft 8 may be attached to the implant 3 via the screw mechanism. The shoulder of the insertion shaft 8 may then be pulled and rotated to dislodge the implant 3 from the oblique bore 16. Thus the sliding rotationally locked femoral neck implant according to the invention may be removed through a single incision. [0029] Since the sliding sleeve 4 is securely locked in place within the oblique bore 16 and the helical portion of the implant 3 is lodged in the femoral head, the implant 3 is able to slide within the sliding sleeve 4, without rotating relative to the sliding sleeve 4. The device allows relative axial sliding between the nail 1 and the implant 3 while preventing relative rotation between the trochanter and the shaft of the femur. Thus, fragments of the femur are able to move axially relative to one another (along the axis of the bore 16) when the patient is walking, supporting the patient's weight and preventing any cutting through of the cancellous tissue within the femoral neck or head as well as any breaking or bending of the implant 3.

[0030] It will be apparent to those skilled in the art that various modifications and variations can be made in the structure and methodology of the present invention, without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims and their equivalents.

Claims

What is claimed is:

1. A device for treating fractures comprising:

an intramedullary member sized and shaped for insertion along a longitudinal axis of a bone within a medullary canal thereof, the intramedullary member including a bore extending laterally therethrough;

a lateral implant sized for insertion into the bone through the bore, a distal portion of the lateral implant including a plurality of substantially helical blades;

a sleeve slidably received over a proximal portion of the lateral implant, the sleeve being non-rotatably received on the proximal portion of the lateral implant; and

a locking member for locking the sleeve in a desired position within the bore.

2. The device of claim 1, wherein the sleeve and the proximal portion of the lateral implant are keyed to one another such that the sleeve is non-rotatably received over the proximal portion of the lateral implant.

3. The device of claim 1 , wherein the locking member comprises a set screw for engaging the sleeve.

4. The device of claim 3, wherein the set screw is a lateral set screw for insertion substantially parallel to the bore.

5. The device of claim 3, wherein the set screw is an axial set screw for insertion along an axis of the intramedullary member.

6. The device of claim 1, wherein the sleeve includes a plurality of projections along its length.

7. The device of claim 1, wherein a proximal end of the lateral implant includes a feature for coupling to an insertion member.

8. The device of claim 1 , wherein a helix angle of the blades is between 70° and 90°.

9. The device of claim 1 , wherein a helix angle of the blades is between 75° and 85°.

10. A system, comprising:

a sleeve slidably received over a proximal portion of the lateral implant, the sleeve being non-rotatably received on the proximal portion of the lateral implant;

a locking member for locking the sleeve in a desired position within the bore; and

an insertion apparatus for inserting the lateral implant into the bone through the bore, the insertion apparatus including:

a shaft engaging a proximal end of the lateral implant and including an annular shoulder at a proximal end thereof; and

a guiding sleeve sized such that, when a distal end of the guiding sleeve abuts the bone, a difference in length between the shoulder of the shaft and a proximal end of the guiding sleeve substantially equals a depth to which the implant is to be driven into the bone.

1 1 . The system of claim 10, further comprising an aiming block including a distal end coupleable to a proximal end of the intramedullary member and a proximal end extending out of a body with a lumen extending therethrough, such that when coupled to the intramedullary member the lumen aligns with the bore.

12. The system of claim 10, further comprising a spacer slidable over the shaft between the shoulder and the proximal end of the guiding sleeve.

13. The system of claim 10, wherein a length of the guiding sleeve is selected so that, when the distal end of the guiding sleeve abuts the bone, the proximal end of the guiding sleeve extends out of the lumen of the aiming block.

14. A method, comprising the steps of:

inserting an intramedullary member along a longitudinal axis of a bone within a medullary canal thereof, the intramedullary member including a bore extending laterally therethrough;

inserting a lateral implant into the bone through the bore, a distal portion of the lateral implant including a plurality of substantially helical blades and a proximal portion of the lateral implant being slidably and non-rotatably received within a sleeve; and

locking the sleeve in a desired position within the bore using a locking member permitting the implant to move relative to the intramedullary member along a longitudinal axis of the implant without rotating relative thereto.

15. The method of claim 14, further comprising using an insertion apparatus to insert the lateral implant, the insertion apparatus having a shaft engaging a proximal end of the lateral implant and including an annular shoulder at a proximal end thereof and a guiding sleeve sized such that, when a distal end thereof abuts the bone, a difference in length between the shoulder of the shaft and a proximal end of the guiding sleeve equals a depth to which the implant is to be driven into the bone.

16. The method of claim 15, further comprising the step of coupling a distal end of an aiming block to a proximal end of the intramedullary member, a proximal end extending out of a limb in which the bone resides such that a lumen extending through the aiming block aligns with the bore.

17. The method of claim 16, further comprising the step of selecting a guiding sleeve length such that when the distal end abuts the bone, the proximal end extends out of the lumen short of the shoulder by a distance equal to a depth to which the implant is to be driven into the bone.

18. The method of claim 17, further comprising the step of providing a spacer over the shaft between the shoulder and the proximal end of the guiding sleeve to prevent relative movement therebetween.

19. The method of claim 18, further comprising the step of removing the spacer to permit relative movement between the shaft and the guiding sleeve.

20. The method of claim 17, further comprising the step of driving the implant into the bone by a depth substantially equal to the distance between the shoulder and the proximal end of the guiding sleeve.

21. A device for treating fractures comprising:

a lateral implant sized for insertion into a bone transverse to a medullary canal of the bone through a bore in a prosthesis received within the medullary canal, a distal portion of the lateral implant including a plurality of substantially helical blades;

a locking member for locking the sleeve in a desired position within the bore.