WO2012093287A2

WO2012093287A2 - Stabilization of a wrist fracture using an implantable device

Info

Publication number: WO2012093287A2
Application number: PCT/IB2011/003359
Authority: WO
Inventors: David Wilson; Michael Dunbar; Andrew Allan
Original assignee: Dalhousie University
Current assignee: Dalhousie University
Priority date: 2010-12-17
Filing date: 2011-12-19
Publication date: 2012-07-12
Anticipated expiration: 2013-06-17
Also published as: WO2012093287A3

Abstract

Methods and apparatuses are provided to stabilize a wrist fracture using minimally invasive devices and techniques. Methods and devices for inserting a fracture stabilizing implant device are also provided.

Description

STABILIZATION OF A WRIST FRACTURE USING AN IMPLANTABLE DEVICE

FIELD OF THE INVENTION

[0001] The present disclosure relates to methods and compositions for repairing a fracture in a patient's wrist using a minimally invasive surgical technique. The invention provides an implantable device, tools for inserting the implantable device, methods for healing fractures, and methods for inserting the implantable device.

BACKGROUND OF THE INVENTION

[0002] Fracture of the distal radius (wrist) is the single most common fracture, with over 500,000 occurrences a year in the U.S. alone, and is commonly associated with osteoporosis (Brogren, Petranek et al, 2007). Treatment of these wrist fractures can be conservative (i.e., casting) or surgical. Conservative treatment is the traditional option on simple fractures that can be readily reduced (e.g., aligned) without instability. However, long term casting has its drawbacks (i.e. loss of reduction, muscle atrophy, etc.). If the fracture is unstable, surgery is necessitated. Surgical fixation has traditionally been performed with Kirshner wires (k- wires) being placed across the fracture gap and fixated on either side. More recent techniques include both locking and non-locking plate fixation.

[0003] There are problems with all available surgical treatments for these fractures. K-wire fixation can be done with a limited exposure, can be done quickly, and can be done without subspecialist training. However, this technique only provides minimal stability and requires that the patient be immobilized with a cast for six weeks after the procedure. This can lead to loss of range of motion and atrophy of the musculature of the forearm. Plate fixation can be locked or non-locked. Non-locking plates are screwed directly to the bone and rely on the compression of the plate to the bone to maintain fixation. The problems with these plates in osteoporotic bone have been well documented. Locking plates are a relatively new surgical option. These have shown relatively good clinical results and allow for early mobilization. However, the procedure is technically difficult, time consuming and requires a large incision.

[0004] Minimal invasive surgical (MIS) techniques rely on navigation technologies to visualize the fracture area through small incisions, rather than exposing the entire fracture area to open surgery. MIS techniques are cost effective and show improved outcomes for patients. SUMMARY OF THE INVENTION

[0005] The present disclosure addresses long-felt needs in the field of orthopedic tools by providing compositions and methods for minimally invasive surgical treatment of distal radial fractures. In one embodiment, an implantable device for stabilizing a fracture comprises a shaft having a proximal end and a distal end, wherein the distal end comprises an optionally detachable sharpened tip and the proximal end comprises a blunt end, wherein the shaft defines a longitudinal axis and comprises a V-shaped cross section along at least a portion of the longitudinal axis, and wherein the shaft comprises a metal. In another embodiment, the V-shape of the cross section has a bend angle of 90°. In still another embodiment, the V-shape of the cross section has a bend angle selected from a group consisting of: about 30°, about 35°, about 40°, about 45°, about 50°, about 55°, about 60°, about 75°, about 80°, about 85°, about 90°, about 95°, about 100°, about 105°, about 110°, about 115°, about 120°, about 125°, about 130°, and about 135°. In some embodiments, the shaft comprises a foamed metal. In other embodiments, the shaft is coated with a foamed metal. In one aspect, the foamed metal is titanium or tantalum, pure or alloyed. In still other embodiments, the shaft comprises a solid metal. In one aspect, the solid metal is stainless steel or a titanium alloy. In another aspect, the solid metal comprises a roughened surface. In a further aspect, the roughened surface is formed by etching the surface.

[0006] In one aspect, the shaft and the sharpened tip is part of a continuous, single piece. In another aspect, the sharpened tip of the shaft is on a first portion of the shaft and the blunt end of the shaft is on a second portion of the shaft, and wherein the first portion of the shaft is detachable from the second portion of the shaft. In a further aspect, the sharpened tip comprises one or more tab inserts and wherein the proximal end of the shaft comprises one or more slots. In an alternative further aspect, the proximal end of the shaft is tapered and wherein the sharpened tip comprises one or more slots. In one embodiment, the shaft comprises a means for interfacing with and fixedly attaching the sharpened tip to the proximal end of the shaft. In another embodiment, the sharpened tip comprises at least one tab or at least one slot for interfacing with the proximal end of the shaft. In yet another embodiment, the proximal end of the shaft comprises at least one tapered end or at least one slot for interfacing with the sharpened tip.

[0007] In one embodiment, the sharpened tip is aligned with a center of the V-shaped cross section of the shaft. In another embodiment, the sharpened tip is aligned with an edge of the V-shaped cross section of the shaft. In still another embodiment, the shaft comprises rounded edges along a longitudinal axis of the shaft. In yet another embodiment, the sharpened tip is a blade.

[0008] In certain aspects, a system is used for inserting a biological implant into a wrist of a patient, the system comprising a distal end, a distal component, a proximal end, and a proximal component wherein the distal end comprises an opening for receiving the biological implant into the attached distal component, wherein the distal component is cannulated for holding a biological implant, wherein the proximal end comprises a blunt surface for interfacing with a device for providing force and is attached to a proximal component, wherein the proximal component interfaces with an end of the biological implant, and wherein the proximal component and the distal component are engaged. In one aspect the opening is V-shaped. In another aspect, the opening allows parallel passage of a k-wire and a V-shaped implantable device. In still another aspect, the device for providing force is a hammer, i.e., a pneumatic hammer or an electric hammer.

[0009] In some embodiments, an apparatus is provided for inserting a biological implant into the wrist of a patient, the apparatus comprising a horizontal surface for resting a fractured wrist, an arm clamp attached to the horizontal surface having means for securing the fractured wrist to the surface, and a traction device linked to the horizontal surface. In one aspect, the apparatus further comprises an implant guide affixed to the horizontal surface. In a further aspect, the implant guide comprises a hole for alignment of the biological implant. In another further aspect, the implant guide comprises a height guide for adjusting the level at which the implant is inserted into the wrist of the patient. In yet another further aspect, the implant guide comprises an angle guide for adjusting the angle at which the implant is inserted into the wrist of the patient. In still another further aspect, the implant guide comprises a thumb screw for adjusting the height or angle of the implant guide.

[0010] In one embodiment, the apparatus further comprises a system for inserting a biological implant into a wrist of a patient, the system comprising a distal end, a distal component, a proximal end, and a proximal component, wherein the distal end comprises an opening for receiving the biological implant into the attached distal component, wherein the distal component is cannulated for holding a biological implant, wherein the proximal end comprises a blunt surface for interfacing with a device for providing force and is attached to a proximal component, wherein the proximal component interfaces with an end of the biological implant, and wherein the proximal component and the distal component are engaged. [0011] In another aspect, the apparatus further comprises an implantable device for stabilizing a fracture, the device comprising a shaft having a proximal end and a distal end, wherein the distal end comprises a sharpened tip and the proximal end comprises a blunt end, wherein the shaft defines a longitudinal axis and comprises a V-shaped cross section along at least a portion of the longitudinal axis, and wherein the shaft comprises a metal. In one aspect, the sharpened tip is detachable. In a further aspect, the sharpened tip is a blade.

[0012] In one embodiment, the traction device of the apparatus for inserting a biological implant device into the wrist of a patient comprises a traction tray. In another embodiment, the traction device of the apparatus comprises a pulley. In a further embodiment, the pulley is attached to a medical finger trap. In another aspect, the traction device comprises an angle alignment guide. In still another aspect, the traction device comprises a height alignment guide. In one aspect, the traction device provides rotational control of the wrist, e.g., to obtain anteroposterior and lateral images of the wrist. In yet another aspect, the traction device comprises a ratcheting extension mechanism. In a further aspect, the ratcheting extension mechanism has sliding rails.

[0013] In one embodiment, the horizontal surface of the apparatus comprises a surgical board. In another embodiment, the arm clamp comprises a strap. In still another

embodiment, the apparatus further comprises a fluoroscopic imaging unit. In one aspect, the fluoroscopic imaging unit is a c-arm imaging device.

[0014] In further aspects, a method is provided for stabilizing a fracture in bone tissue of a patient comprising: stabilizing a fractured bone of a patient using a fracture stabilizing implant device, the device comprising a shaft having a proximal end and a distal end, wherein the distal end comprises a sharpened tip and the proximal end comprises a blunt end;

reducing the fracture; and inserting the fracture stabilizing implant device into the bone tissue so that the fracture stabilizing implant device lies across the fracture to stabilize the fracture. In one embodiment, the sharpened tip is detachable. In another embodiment, the sharpened tip is a blade.

[0015] In one aspect of the method, the fracture is a distal radius fracture. In further aspect, the distal radius fracture is a Colles fracture. In another aspect, inserting the fracture stabilizing implant device comprises passing the fracture stabilizing implant device through the radial styloid process of the wrist and across the fracture, and resting the fracture stabilizing implant device near the medial cortex of the wrist. In another aspect, the implant device is passed through the medial cortex to provide bicortical fixation. In still another aspect, the shaft comprises a foamed metal. In a further aspect, the shaft comprises a solid metal, such as stainless steel or titanium alloy. In another aspect, the implantable device comprises a roughened surface. In yet another aspect, the shaft defines a longitudinal axis and consists of a V-shaped cross section along at least a portion of the longitudinal axis.

BRIEF DESCRIPTION OF THE FIGURES

[0016] Figures 1 A-C illustrate embodiments of a fracture stabilizing implant device.

[0017] Figures 2A-D illustrate an embodiment of a modular design of the fracture stabilizing implant device.

[0018] Figure 3A-D illustrate another embodiment of a modular design of the fracture stabilizing implant device.

[0019] Figures 4A-D illustrate another embodiment of a modular design of the fracture stabilizing implant device.

[0020] Figure 5 is a schematic diagram of an entry path for insertion of the fracture stabilizing implant device into a distal radius of a wrist to stabilize a Colles fracture, in accordance with an embodiment of the invention.

[0021] Figures 6 A and B illustrate a countersink tool for inserting the fracture stabilizing implant into a wrist, in accordance with an embodiment of the invention.

[0022] Figure 7 is an exploded view of the embodiment of a countersink tool of Figure 6.

[0023] Figure 8A and B illustrate an embodiment of the countersink tool for use with k-wire.

[0024] Figure 9 provides additional angles of an embodiment of the countersink tool for use with k-wire.

[0025] Figure 10 is an exploded view of the embodiment of a countersink tool of Figures 8 and 9.

[0026] Figure 11 is a schematic diagram of the assembly of an embodiment of a countersink tool with an embodiment of the implantable device and k-wire.

[0027] Figure 12 and 13 illustrate a device for securing a patient's distal radius and inserting a fracture stabilizing implant device, in accordance with an embodiment of the invention.

[0028] Figure 14 illustrates a positioned arm of a patient in a traction device for inserting a fracture stabilizing implant device, in accordance with an embodiment of the invention.

[0029] Figure 15 illustrates a device for securing a patient's distal radius and inserting a fracture stabilizing implant device, in accordance with an embodiment of the invention.

[0030] Figure 16 illustrates a device for securing a patient's distal radius and inserting a fracture stabilizing implant device and having a rectangular arm board, in accordance with an embodiment of the invention. [0031] Figure 17 illustrates a device for securing a patient's distal radius and inserting a fracture stabilizing implant device and having an angular arm board, in accordance with an embodiment of the invention.

[0032] Figure 18 illustrates a device for securing a patient's distal radius and inserting a fracture stabilizing implant device and designed to be coupled with an fluoroscopic imaging unit , in accordance with an embodiment of the invention.

[0033] Figure 19 illustrates the device of Figure 18 coupled with an fluoroscopic imaging unit , in accordance with an embodiment of the invention.

[0034] Figure 20 illustrates the device of Figure 19 in an "extended" position.

[0035] Figure 21 illustrates the device of Figure 19 having additional support legs.

[0036] Figure 22 illustrates the device of Figure 19 coupled with an optional guide for implantation.

[0037] Figures 23 and 24 are schematic diagrams of the optional guide for implantation.

[0038] Figure 25 illustrates a top-down view of the clamping device, with a patient's arm positioned in the device for inserting a fracture stabilizing implant device, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0039] The following terms, unless otherwise indicated, shall be understood to have the following meanings:

[0040] "About" as used herein when referring to a measurable value such as an amount, a temporal duration, and the like, is meant to encompass variations of ±20% or ±10%, more preferably ±5%, even more preferably ±1%, and still more preferably ±0.1% from the specified value, as such variations are appropriate to perform the disclosed methods.

[0041] Throughout this specification and claims, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0042] The term "solid metal" refers to a metal such as stainless steel or titanium. In one embodiment, the solid metal is used in the implantable device of the present invention. In another embodiment, the solid metal has a roughened surface (e.g., a surface that has been etched) for increasing friction with the bone tissue and providing enhanced stability.

[0043] The term "foamed metal" refers to a cellular structure consisting of a solid metal, containing a large volume fraction of gas-filled pores. The pores can be sealed (closed-cell form), or they can form an interconnected network (open-cell form). A defining characteristic of metal foams is a high porosity, typically 75-95% of the volume consists of void spaces. Foamed metal has unique properties that make it suitable for biological implantation. Examples of foamed metal include porous titanium and foamed tantalum. Properties of the foamed metal, such as the type of metal used and the porosity of the metal, can be adjusted to provide desirable properties for a biological implant, such as coefficient of friction and tensile strength.

[0044] The term "fracture" refers to the condition of a broken or cracked bone or torn cartilage. Fractures can be divided into many subgroups depending on type and location, i.e., Colles fracture, comminuted fracture, compound fracture, greenstick fracture, and impacted. The examples of the specification provide, but are not limited to, methods and compositions for treating a Colles fracture of the distal radius.

[0045] The term "reduction" refers to the positioning of a bone or bones to their normal position after a fracture or dislocation. The goals of a reduction are to restore position (alignment, rotation, and length) to the bone or joint, to decrease pain, to prevent later deformity, and to encourage healing and normal use of the bone and limb. In the case of a fracture, it is also important for the bone ends to meet correctly (apposition).

[0046] The term "fracture stabilizing" refers to an action taken that reduces the probability of dislocation or movement of a fracture. This is useful for after a fracture has been reduced, as fracture stabilization is important to allow time for the bone to heal in the proper alignment.

[0047] The term "implant device" is a medical device manufactured to replace a missing biological structure, support a damaged biological structure, or enhance an existing biological structure. In the present disclosure, the term is primarily used to refer to an implant device that supports a damaged biological structure, e.g. fractured bone tissue, to allow proper healing. In one embodiment, the implant device is an "elongate stabilizing implant," which refers to a specific type of implant device that is primarily used to support a damaged biological structure, and which has notably more length than width. In another embodiment of the invention, the elongate stabilizing implant is V-shaped for additional structural stability, and is implanted across a fracture to provide stability to fractured bone tissue for proper healing.

[0048] The term "modular cutting blade" refers to a sharpened apparatus made for cutting through material and designed to attach to a complementary modular part. In one example, the modular cutting blade is attached to the elongate stabilizing implant, providing a mechanism for insertion of the elongate stabilizing implant into bone tissue. [0049] The term "patient" refers to a person having fractured bone tissue (e.g., a fractured distal radius) and is therefore in need of treatment.

[0050] The term "distal radius" refers to the segment of the radius bone in the forearm of the human body that is proximal to the wrist. The distal radius is the site of a common bone fracture, requiring casting or surgery.

[0051] The term "radial styloid process" refers to a projection of bone on the lateral surface of the distal radius bone. It extends obliquely downward into a strong, conical projection. The lateral surface is marked by a flat groove for the tendons of the Abductor pollicis longus and Extensor pollicis brevis.

[0052] The term "aiming jig" refers to a device used to aid in alignment of the implant device into the aligned fracture site for insertion and stabilization.

[0053] The term "minimally invasive surgical (MIS) technique" is any surgical technique that is less invasive than open surgery used for the same purpose. A minimally invasive surgery results in minimal damage of biological tissues at the point of entrance of the instruments.

[0054] The term "fluoroscopic imaging unit " refers to a device having an X-ray source and image intensifier. A fluoroscopic imaging unit provides real time X-ray images. It can be used to provide a surgeon with intra-operative feedback for positioning a device such as an implant. In one embodiment, a fluoroscopic imaging unit refers to a C-arm. One embodiment of the invention comprises a C-arm which is used to image the bone fracture and/or to visualize the implantation of the implantable device across the fracture. A C-arm is a mobile fluoroscopy unit capable of obtaining real time x-ray images.

[0055] Various aspects of a fracture stabilizing implant device 100 in accordance with an embodiment of the present disclosure are shown in Figures 1-5. Figure 1 shows a general diagram of a fracture stabilizing device 100, which in one aspect of the present disclosure may be implanted into bone tissue to stabilize a reduced fracture. The fracture stabilizing device 100 includes a shaft 120 defining a longitudinal axis, a distal end 130, and a proximal end 110. The proximal end 110 has a blunt end for applying force to the fracture stabilizing implant device for implantation into bone tissue. The longitudinal axis of the shaft intersects and stabilizes the bone fracture. The distal end has a sharpened tip 130 for displacing bone and other tissue for insertion of the fracture stabilizing device 100 into a bone fracture. In one embodiment, the sharpened tip is a blade. In another embodiment, the sharpened tip is triangular. Alternatively, the device 100 may include a sharpened tip 131 that is shaped for insertion into a distal radial fracture of the right hand, as shown in Figure IB or the device 100 may include a sharpened tip 132 for insertion into a distal radial fracture of the left hand, as shown in Figure 1C.

[0056] The proximal end 110 of the device 100 has a blunt end for applying force to the device 100 for insertion into a bone fracture. The proximal end 110 may also be shaped for integration with a tool for hammering the implantable fracture stabilizing device 100 (i.e., the countersink tool 300 shown in Figures 6 and 7 and described, e.g. in Example 2). The longitudinal axis of the shaft 120 is designed to pass across a reduced bone fracture to provide stabilization of the fracture to allow proper healing.

[0057] In one embodiment, the cross section of the shaft 120 along the longitudinal axis of the fracture stabilizing implant device 100 is V-shaped 120. This shape provides additional structural strength to prevent deformation upon insertion into the bone. In one embodiment, the angle of the bend of the V-shaped device is 90°. This embodiment is provided in Figure 1 A-C as shown in the cross-sectional view 122 of the fracture stabilizing implant device. In other embodiments, the angle of the bend of the V-shaped device is about 30°, about 35°, about 40°, about 45°, about 50°, about 55°, about 60°, about 75°, about 80°, about 85°, about 90°, about 95°, about 100°, about 105°, about 110°, about 115°, about 120°, about 125°, about 130°, or about 135°. In other embodiments, the implantable device is U-shaped or flat. Additionally, the size of the implantable device may vary according to the size of the fracture or bone that it is to be inserted into.

[0058] A modular design of the fracture stabilizing implant device 100 is shown in Figures 2- 4. The modular design features a sharpened tip or blade 130 that can be attached to and separated from the shaft 120 having a blunt end 110. The modular design of the fracture stabilizing device features a means for interfacing the blade 130 with the distal end of the shaft 120. In the modular embodiment shown in Figure 2, the shaft 120 features one or more slots 141 for accepting one or more tab inserts 142 of the sharpened tip or blade 130. The sharpened tip or blade of the modular device can be designed for insertion into a right wrist 131 or a left wrist 132. In another modular embodiment shown in Figure 3, the shaft 120 features a distal end for interfacing with a separate blade having the edge shaved down a specific depth to match the sharpened tip or blade 130. The sharpened tip or blade contains slots 152 cut into the back to match the interfacing distal end 151 of the shaft 120. The sharpened tip or blade of the modular device can be designed for insertion into a right wrist 131 or a left wrist 132. In another modular embodiment shown in Figure 4, the fracture stabilizing implant device 100 features a shaft 120 with a rounded edge 170, and a distal end for interfacing with a separate blade having the edge shaved down a specific depth to match the sharpened tip or blade 130. The sharpened tip or blade contains slots 162 cut into the back to match the interfacing distal end 161 of the shaft 120. The sharpened tip or blade of the modular device can be designed for insertion into a left wrist or a right wrist.

[0059] The material used for the implantable device is selected for optimal coefficient of friction with bone tissue (i.e., a low enough friction for ease of insertion and a high enough friction for good stabilization), high tensile strength, and compatibility with bone growth and repair. In one embodiment, a solid metal, such as stainless steel or titanium alloy is used. In another embodiment, the implantable device has a roughened surface to enhance the coefficient of friction with the bone tissue. In still another embodiment, a porous metal is used. In yet another embodiment, the porous metal is foamed metal. In a further preferred embodiment, the foamed metal is selected from titanium and tantalum. In another embodiment, the implantable device is stainless steel or ceramic. In still another

embodiment, the implantable device comprises cobalt or titanium. There are several biocompatible materials, ceramics, metals, and other polymers known to one of skill in the art that can provide the proper strength, flexural, tensile, and friction coefficient properties useful for the application of embodiments of the disclosed invention.

[0060] Foamed metal used as a material for the implantable device can have a range of porosities that provide a balance between the coefficient of friction and the tensile strength of the implantable device. In one embodiment, the implantable device has 80% porosity. In other embodiments, the foamed metal of the implantable device has 60, 65, 70, 75, 85, 90, or 95% porosity. In still other embodiments, the foamed metal of the implantable device has porosity in the range of 60-65%, 65-70%, 70-75%, 75-80%, 80-85%, 85-90%, 90-95%, or 95-100%. In general, thinner designs are made with a foamed metal with lower porosity, since there is a tradeoff between porosity and tensile strength. Solid metal having a roughened surface can also be used to provide friction while enhancing tensile strength.

[0061] Although as described herein, the implantable device is used in stabilizing fractures of the distal radius, it is contemplated that embodiments of the device can also be used with other fractured bones with proper sizing of the implant so as to permit its entry and passage within the respective fractured bone. For instance, the device can also be used to stabilize fractures of the distal ulna, scaphoid, lunate, triquetrum, hamate, capitates, trapezoid, trapezium, lateral epicondyle, medial epicondyle, humerus, tubercle, clavicle, lateral and medial malleolus, tibia, fibula, femur, patella, lateral epicondyle, lateral femoral and tibial condyles, intercondylar eminence, medial femoral condyle, patella, talus, sternum, etc. In one embodiment, the implantable device comprises perforated tabs which allow the implant to be easily cut to the desired length prior to implantation. In another embodiment, the implantable device is provided in a range of selected lengths to allow the user to select an appropriate size for implantation. In still another embodiment, a cannulated measuring sleeve is provided to pass over the k-wire to determine the necessary length of the implantable device.

[0062] A method for insertion of the fracture stabilizing implant device 100 along an entry path 240 into a Colles fracture 210 of the distal radius 200 is shown in Figure 5, showing the device in situ. In this drawing, the fracture has been reduced, and is stabilized by inserting the fracture stabilizing implant device 100 across the fracture 210. The entry path 240 shows that the fracture stabilizing implant device 100 is passed into the distal radius through the radial styloid process 220, moves across the Colles fracture 210 and comes to rest near the medial cortex 230. In another aspect, the device is passed through the medial cortex to achieve a bicortical fixation. The material of the implantable device 100 provides a coefficient of friction sufficient to stabilize the separate pieces of the fractured distal radius 200. In one embodiment of the invention, the implantable device stimulates bone growth or repair. In another embodiment, the implant device 100 is permanently integrated into the structure of the repaired bone.

[0063] The present disclosure also provides various embodiments of a device useful for inserting the implantable device into a fracture. Examples of these devices and elements of these devices are shown in Figures 6-14, showing embodiments of a countersink tool of the present invention, and in Figures 15-25, showing embodiments of the invention useful for clamping the patient's arm, reducing the fractured distal radius and inserting the implantable device.

[0064] Various aspects of a countersink tool 300 in accordance with one embodiment are shown in Figures 6 and 7. Figure 6 shows a general diagram of an embodiment of the countersink tool 300, which may be used, for example, to hammer the fracture stabilizing implant device 100 into bone tissue to stabilize a reduced fracture. The countersink tool 300 includes a distal component 312 comprising a distal end 310, a fastener cap 320, and a proximal component 332 comprising a proximal end 330. The distal end 310 contains a notch 340 designed so that the blunt end 110 of the fracture stabilizing implant device 100 will fit into the notch and lie below the surface of the distal end 310. In one embodiment, the notch 340 is shaped and sized to match the cross sectional profile of the fracture stabilizing device implant 100. In one aspect, the notch 340 is V-shaped. The proximal end 330 is sized to mate with a device used to pound the implant into the bone, such as an electric hammer or a pneumatic hammer. The fastener cap 320 passes over the proximal component 332 and screws onto the distal component 312 providing fixation.

[0065] The internal components of an embodiment of the countersink tool 300 are shown in Figure 7. The distal end 310 contains a notch 340 that fits over the fracture stabilizing implant device 100. A compression spring 350 is optionally placed over the protrusion and sits in a circular groove 362 cut into the proximal component 332. A matching groove is located inside the distal component 312 for the other end of the spring 350 to sit in. An implant interfacing segment 360 comprises a distal face 361 for resting or pushing against the proximal end 110 of the implant device 100. The implant interfacing segment 360 pushes the implant device 100 out of the V-shaped notch 340 during insertion of the implant device 100 into the patient. The distal component 312 of the countersink tool slides over the proximal component 332 of the countersink tool with a spring 350 and implant interfacing segment 360 contained within the distal component 312. In one embodiment, the distal component 312 comprises a hollow bore for accepting the spring 350 and implant interfacing segment 360. The fastener cap 320 is hollow and is used to hold the proximal component 332 in place by passing over the proximal component 332 and interfacing with the protrusion 363 of the proximal component 332. The attachment of the fastener cap 320 to the distal component 312 while holding the proximal component 332 fastens the distal component 312 and the proximal component 332. In one embodiment, this fastening maintains a slight compression in the spring 350.

[0066] Another embodiment of the countersink tool 300 is shown in Figures 8-11. In this embodiment, the countersink tool 300 is adapted to slide the fracture stabilizing implant device 100 along a kirschner wire (k-wire) which has been implanted into the fracture. The notch 340 at the distal end 310 is adapted to fit both the implant device 100 and k-wire, as shown in the cross-sectional view of the countersink tool 300 in Figure 8B. The distal component 312 is cannulated to allow the countersink tool 300 to thread over the top of the k- wire and to fully encase the implant. The distal end 310 is concave to align with the radial styloid process. The distal component 312 may be supplied with different concave shapes at the distal end 310 to allow selection of the best suited shape for each patient. As shown in Figure 9, the proximal end 330 is adapted to interface with a device for applying force (e.g., an electric hammer or a pneumatic hammer) to the countersink tool 300 to push the implantable device 100 along a k-wire 370 and into a radial styloid for stabilization of a distal radial fracture. An exploded view of the countersink tool 300 is shown in Figure 10. In this embodiment, no spring is used. The proximal component 332 passes through a linear bearing for smooth and controlled travel into the distal component 312. The device in combination with the k-wire and implant is shown in Figure 11.

[0067] Various aspects of a clamping device 400 that stabilizes the distal radius fracture for insertion of the fracture stabilizing implant device 100 in accordance with an embodiment of the present disclosure are shown in Figures 12-14. Figure 12 shows a general diagram of the clamping device 400, which may be used, for example, to hammer the fracture stabilizing implant device 100 into a patient's fractured distal radius. The arm clamp 413 is used to clamp the patient's arm once it is placed in the correct position for insertion of the fracture stabilizing implant device 100. In one embodiment, the arm clamp 413 is selected from a screw mechanism, a telescoping rod with a locking device, or a strap that tightens the arm to the table. An embodiment of a traction device 410 as shown in Figure 12 provides additional stabilization of the patient's arm. The implant guide 420 interfaces with the countersink tool 300 and implant device 100 to guide the implant into the fracture. Figure 13 shows a frontal view of the clamping device 400 including an implant guide 420. The implant guide 420 comprises a height guide 421, a hole for the countersink tool 422, an angle alignment guide 423, and a thumb screw 424. The height and angle of the implant guide is adjusted using the thumb screw 424. The height guide 421 is an attachment that adjusts the level at which the implant is inserted into the bone. In one embodiment, the height guide 421 is radio opaque. The angle alignment guide 423 is an attachment that adjusts the angle at which the implant is inserted into the bone. In one embodiment, the angle alignment guide 423 is radio-opaque. The traction device 410 consists of a traction tray 411 that pivots out from the main component. In one embodiment, the traction tray 411 is held in place using a push-release latch. In another embodiment, the traction tray 411 is located on both sides, making the instrumentation ambidextrous. In yet another embodiment, the traction tray 411 comprises a groove allowing a pulley 412 to be positioned within it. The clamping device can be used with a standard medical finger trap 431 that is placed on the patient's index and middle fingers (Figure 14). The finger traps 431 are connected to a counterweight that hangs from a cable running over the pulley 412, providing traction on a patient's wrist 250 for easy implantation of the fracture stabilizing implant device 100.

[0068] Another aspect of the clamping device 400 is shown in Figures 15-17. Figure 15 shows an adjustable clamping device having an embodiment of a traction device 430 attached to a wrist securing board 444 attached to a surgical board interface 451. The traction device 430 comprises means for securing and adjusting a finger trap comprising an angle alignment guide 434, height alignment guide 435, rotational alignment guide 436, rotational alignment lever 437, and rotational alignment lever push pin 438. The angle alignment guide 434 is used to adjust the angle of the finger trap and is secured in place by a latching swivel pin 440. The angle alignment guide 434 can be adjusted in height along the height alignment guide 435. The orientation of the angle alignment guide 434 as shown in Figure 15 is for treatment of a left distal radius fracture. The angle alignment guide may also be flipped and inserted along the height alignment guide 435 in the opposite orientation for treatment of a right distal radius fracture. The rotational angle of the wrist may be adjusted using the rotational alignment lever 437. A rotational alignment lever push pin 438 is used to secure the rotational alignment lever 437 along the rotational alignment guide 436 for the finger trap. The distance of the finger clamp is adjusted via extension of the sliding rails of the ratcheting extension mechanism 432 out from the wrist securing board 444. The sliding rails have a saw-tooth ratcheting mechanism, which is locked in place via spring loaded latches 433. The sliding rails can be retracted by pulling on the spring loaded latches 433. This extension mechanism can be used to provide locked tension to the patient's wrist. Push locking pins 439 are provided to allow quick assembly and disassembly of the sliding rails of the ratcheted extension mechanism. The wrist securing board optionally has an arm strap, e.g., a Velcro arm strap, which is placed through the wrist securing board slots 443. The wrist securing board is optionally attached to a surgical board via a surgical board interface 451 comprising arm board clamps 441. In figure 15, the arm board clamps 441 are shown in the open or unlocked position. Figure 16 provides an embodiment of the invention which comprises a surgical board 450. The surgical board of figure 16 is rectangular, and is attached via arm board clamps 441 shown in the closed or locked position in figure 16. Figure 17 provides an additional embodiment of the invention comprising a surgical board 450 that is angular. [0069] Another aspect of the clamping device 400 coupled with a c-arm device 500 is shown in Figures 18-21. Figure 18 provides a diagram of an embodiment of the clamping device 400 for coupling with a c-arm device. In this embodiment, a traction device 430, as described in the paragraph above, is attached to a c-arm interface board 460. The c-arm interface board comprises wrist securing board slots 443 (for, e.g., a Velcro arm strap), means for attaching a c-arm device to the c-arm interface board, such as e.g., thumb screws 461, and a vulcrom pin 462 inserted into the bottom of the board 460. The vulcrom pin 462 is used as a vulcrom to gain leverage when adjusting the angle of the patient's wrist with the angle alignment guide 434. The position of the vulcrom pin 462 in relation to the patient's left wrist is shown in Figure 25. A vulcrom pin hole 463 is shown in Figure 18 opposite to the vulcrom pin 462 to be used in the case of a right distal radius fracture. Figure 19 depicts the clamping device 400 interfaced with a c-arm device 500. The c-arm device 500 is useful for imaging the patient's arm and implant device for reducing the patient's fracture and inserting the implantable device 100. Also shown in figure 19 is the finger clamps 431 attached to the latching swivel pin 440. Tension is applied to the arm of the patient by extending the finger clamps 431 from the c-arm interface board 460 using the ratcheting extension mechanism 432. An extended version of the device from figure 19 is shown in figure 20. Finally, means for supporting the traction device 430 extending from the c-arm interface board 460 are provided, for example, by the embodiment as diagrammed in figure 21, showing traction device support legs 442 attached to the traction device 430.

[0070] An optional implant guide 600 for guiding the implantable device 100 into the patient's wrist is also provided. In one embodiment, as shown in Figure 22, the implant guide 600 is placed atop the clamping device 600. One aspect of the implant guide 600 is shown in Figures 23-24. In this aspect, the implant guide is used to assist in the k-wire and implant placement. The guide clamps against the patient's arm proximal to the fracture and offers angular and height alignment via a height and angle guide 603. In one embodiment the height and angle guide is radio-opaque. The clamping device of this aspect also comprises thumb screws 601 for clamping the implant guide 600 over the top of the patient's wrist, a countersink tool interface 602 for attaching the implant guide 600 to the countersink tool 300, and a vulcrom pin 462 to gain leverage when adjusting the angle of the patient's wrist with the angle alignment guide 434. [0071] The insertion of the implantable device 100 into a patient's wrist using an embodiment of the present invention is shown in figure 25. This figure depicts a top-down view of an embodiment of the clamping device 400 coupled with a c-arm device 500.

Stabilization of a Distal Radius Fracture Using a Fracture Stabilizing Implant Device

[0072] In one embodiment, a fracture stabilizing implant device 100 is used for minimally invasive surgical treatment of distal radial fractures. This device is inserted in the radial styloid process and passed across the fracture. The high coefficient of friction of the foamed metal results in early fixation of the implant to the bone without any screws, allowing early mobilization and providing stabilization of the reduced fracture. A solid metal having a roughened surface can also be used to provide an implantable device having an improved coefficient of friction. A biocompatible material can be used with the implantable stabilizing device to allow it to become fully integrated into the bone. The device can be inserted into the patient manually, or with the aid of specialized instrumentation.

Hammering a Fracture Stabilizing Implant Device into a Distal Radius Fracture

[0073] An embodiment of the countersink tool 300 shown in Figures 6 and 7 is used to hammer the fracture stabilizing implant device into the distal radius fracture. The V-shape slot in the distal end 340 is sized to match the profile of the implant. The implant is inserted a depth of 10mm into the slot to provide stability during implantation. The proximal end of the tool 330 is sized to mate with an electric hammer or pneumatic hammer used to pound the implant into the bone.

[0074] When the distal face of the tool makes contact with the surface of the patient's skin, the pressure applied to the face causes the spring 350 to compress. As the spring compresses, the angled face of the proximal component protrudes through the slot in the distal component. As it protrudes, it hammers the implant below the surface of the skin a desired amount.

[0075] Another embodiment of the countersink tool 300 a shown in Figures 8-11 is used to guide the fractures stabilizing implant device along a k-wire and into a distal radius fracture. The slot 340 at the distal end of the device is shaped to allow passage of the implantable device 100 and k-wire into and through the distal component 312. The implant is inserted completely into the countersink tool 300 to allow the distal end 310 to rest against the patient's radial styloid process 220. In this embodiment, the use of a spring is not necessary. Instead, the proximal component 332 passes through a linear bearing for smooth and controlled travel into the distal component 312. Method of Securing a Patient's Arm and Inserting a Fracture Stabilizing Implant Device

[0076] The surgeon positions the patient's arm having a distal radius fracture into a clamping device 400 (Figures 12, 13, 15-22, and 25) and manipulates the bone fragments into anatomically correct positions to reduce the fracture. In one embodiment, an implant guide 420 is used to guide the passage of the implantable stabilizing device 100 into an optimal position with the distal radius 200 (for example, see Figure 5). In another embodiment, an implant guide 600 (see Figures 22-24) is optionally used to guide the passage of the implantable device 100 along a k-wire and into the distal radius fracture. Alternatively, the implantable device 100 is manually inserted into the patient's distal radius without the use of an implant guide.

[0077] In one embodiment, the patient's wrist is placed in a supinated position beneath the adjustable arm clamp 413 (Figure 12). The surgeon aligns the wrist so that the implant guide 420 aligns the implant correctly with the distal radius fracture. Once in the correct position, the arm clamp 413 is tightened onto the patient's arm. Once the traction tray 411 and pulley 412 are in place, standard medical finger traps are placed on the patient's index and middle fingers 431 (Figure 14). The finger traps are connected to a counterweight that hangs from a cable running over the pulley 412. This provides the necessary traction on the patient's wrist 250 and allows correct positioning for easy implantation. Finally, the implant is inserted with the countersink tool 300 (Figures 6 and 7) through the hole for the countersink tool 422 in the implant guide 420 of the clamping device 400 (Figure 13).

[0078] In an alternative embodiment, a patient's arm is positioned in the clamping device as depicted in Figures 15-17. The patient's arm is optionally strapped against the wrist securing board 444 and surgical board 450, with the patient's wrist lying near the edge of the wrist securing board 444 towards the traction device 430. The patient's fingers are placed in a finger trap 431 attached to the traction device 430. The angle and height of the finger traps are then adjusted to reduce the patient's fracture and the traction device 430 is extended away from the wrist securing board 444 to provide tension. If a decrease in tension is desired, spring loaded latches 433 are pulled on both sides to slide the traction device 430 towards the wrist securing board 444. Anatomical reduction is then verified by imaging the patient's wrist in selected anteroposterior (AP) and lateral views, as oriented in the clamping device 400. The patient's wrist can be moved to the AP and lateral views using the rotational alignment guide 436 and lever 437. Once reduction is verified, a k-wire is inserted into the distal radius across the fracture. The implantable device 100 is then manually inserted along the k-wire into the distal radius across the fracture. Alternatively, the k-wire and implantable device 100 are inserted using the implant guide 600 shown in Figures 22-24.

[0079] In one aspect, the implant guide 600 clamps against the patient's arm proximal to the fracture and offers angular and height alignment via a height and angle guide 603. One embodiment of the implant guide 600 is shown in Figures 22-24. Two thumb screws 601 tighten to clamp the top of the implant guide 600 over the top of the patient's wrist. The angle and height of the guide are adjusted using a height and angle guide 603 to ensure the k- wire and implant will be positioned accurately. Once in position, a k-wire insert can be used to guide the k-wire insertion as shown in Figures 23 and 24. Once the k-wire is in place, the implant can then be inserted by passing the countersink tool 300 through the countersink tool interface 602 in the implant guide 600.

[0080] In another embodiment, the clamping device 400 is coupled with a c-arm fluorescence imaging device 500 to enable imaging of the patient's arm and insertion of the implantable device 100. One such embodiment is depicted in Figures 18-22 and 25. In this embodiment, the patient's arm is positioned on top of a c-arm interface board 460 and attached to the finger clamp 431 attached to the traction device 430. The patient's distal radius fracture is reduced by adjusting the angle alignment guide 434 and height alignment guide 435The patient's distal radius is imaged using the c-arm imaging device 500 to insure reduction of the fracture. An implantable device 100 is inserted into the patient's distal radius and across the fracture, as shown in Figure 25. The proper orientation of the implantable device 100 can also be guided by fluoroscopic images from the c-arm imaging device 500.

[0081] The patient's wrist is immobilized for a brief period (i.e. no longer than 10 days) postoperatively to allow for early tissue in-growth. The patient is then mobilized slowly with full function achieved at 6 weeks. The unique properties of foamed metal or a solid metal having a roughened surface allows for fixation without any screws, and early mobilization. The implanted material is osteo-integrated completely and does not require removal.

[0082] In the preceding detailed description, reference has been made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the present invention may be practiced. These embodiments, and certain variants thereof, have been described in sufficient detail to enable those skilled in the art to practice embodiments of the present invention. It is to be understood that other suitable embodiments may be utilized and that logical, mechanical, chemical and electrical changes may be made without departing from the spirit or scope of such inventive disclosures. To avoid unnecessary detail, the description omits certain information known to those skilled in the art. The preceding detailed description is, therefore, not intended to be limited to the specific forms set forth herein, but on the contrary, it is intended to cover such alternatives, modifications, and equivalents, as can be reasonably included within the spirit and scope of corresponding claims.

[0083] It should be noted that the language used herein has been principally selected for readability and instructional purposes, and it cannot have been selected to delineate or circumscribe the inventive subject matter. Accordingly, the disclosure is intended to be illustrative, but not limiting, of the scope of claimed methods.

[0084] Any terms not directly defined herein shall be understood to have the meanings commonly associated with them as understood within the art of the present disclosure. Certain terms are discussed herein to provide additional guidance to the practitioner in describing the compositions, devices, methods and the like of aspects of the present disclosure, and how to make or use them. It will be appreciated that the same thing can be said in more than one way. Consequently, alternative language and synonyms can be used for any one or more of the terms discussed herein. No significance is to be placed upon whether or not a term is elaborated or discussed herein. Some synonyms or substitutable methods, materials and the like are provided. Recital of one or a few synonyms or equivalents does not exclude use of other synonyms or equivalents, unless it is explicitly stated. Use of examples, including examples of terms, is for illustrative purposes only and does not limit the scope and meaning of the aspects of the present disclosure herein.

Claims

What is claimed is:

1. An implantable device for stabilizing a fracture, the device comprising a shaft having a proximal end and a distal end, wherein the distal end comprises a sharpened tip and the proximal end comprises a blunt end, wherein the shaft defines a longitudinal axis and comprises a V-shaped cross section along at least a portion of the longitudinal axis, and wherein the shaft comprises a metal.

2. The device of claim 1, wherein the V-shape of the cross section has a bend angle of 90°.

3. The device of claim 1, wherein the V-shape of the cross section has a bend angle selected from a group consisting of: about 30°, about 35°, about 40°, about 45°, about 50°, about 55°, about 60°, about 75°, about 80°, about 85°, about 90°, about 95°, about 100°, about 105°, about 110°, about 115°, about 120°, about 125°, about 130°, and about 135°.

4. The device of claim 1, wherein the shaft comprises a solid metal.

5. The device of claim 4, wherein the solid metal comprises stainless steel or titanium alloy.

6. The device of claim 1, wherein the shaft comprises a foamed metal.

7. The device of claim 1, wherein the shaft is coated with a foamed metal.

8. The device of claim 6 or 7, wherein the foamed metal is selected from titanium and tantalum.

9. The device of claim 1, wherein the shaft comprises a roughened surface.

10. The device of claim 9, wherein the roughened surface is formed by etching the

surface.

11. The device of claim 1 , wherein the shaft and the sharpened tip are part of a

continuous, single piece.

12. The device of claim 1 , wherein the sharpened tip of the shaft is on a first portion of the shaft and the blunt end of the shaft is on a second portion of the shaft, and wherein the first portion of the shaft is detachable from the second portion of the shaft.

13. The device of claim 12, wherein the first portion of the shaft comprises one or more tab inserts, and wherein the second portion of the shaft comprises one or more slots configured to receive the tab inserts.

14. The device of claim 12, wherein the first portion of the shaft is tapered, and wherein the second portion of the shaft comprises one or more slots for receiving the first portion.

15. The device of claim 1, wherein the shaft comprises a means for interfacing with and fixedly attaching the first portion of the shaft to the second portion of the shaft.

16. The device of claim 1, wherein the sharpened tip comprises at least one tab or at least one slot for interfacing with the proximal end of the shaft.

17. The device of claim 1, wherein the proximal end of the shaft comprises at least one tapered end or at least one slot for interfacing with the sharpened tip.

18. The device of claim 1 , wherein the sharpened tip is aligned with a center of the V- shaped cross section of the shaft.

19. The device of claim 1, wherein the sharpened tip is aligned with an edge of the V- shaped cross section of the shaft.

20. The device of claim 1, wherein the shaft comprises rounded edges along a

longitudinal axis of the shaft.

21. The device of claim 1 , wherein the sharpened tip is a blade.

22. A system for inserting a biological implant into a wrist of a patient, the system

comprising a distal end, a distal component, a proximal end, and a proximal component wherein the distal end comprises an opening for receiving the biological implant into the attached distal component, wherein the distal component is cannulated for holding a biological implant, wherein the proximal end comprises a blunt surface for interfacing with a device for providing force and is attached to a proximal component, wherein the proximal component interfaces with an end of the biological implant, and wherein the proximal component and the distal component are engaged.

23. The system of claim 22, wherein the opening is V-shaped.

24. The system of claim 22, wherein the opening allows parallel passage of k-wire and a V-shaped implantable device.

25. The system of claim 22, wherein the shape of the distal end matches the profile of a distal styloid radius.

26. The system of claim 22, wherein the device for providing force is a hammer.

27. The system of claim 26, wherein said hammer is selected from a pneumatic hammer and an electric hammer.

28. An apparatus for inserting a biological implant into the wrist of a patient, the

apparatus comprising:

a horizontal surface for resting a fractured wrist;

an arm clamp attached to the horizontal surface having a means for securing the fractured wrist to the surface; and

a traction device linked to the horizontal surface.

29. The apparatus of claim 28, wherein the apparatus further comprises an implant guide affixed to the horizontal surface.

30. The apparatus of claim 29, wherein the implant guide comprises a hole for alignment of the biological implant.

31. The apparatus of claim 29, wherein the implant guide comprises a height guide for adjusting the level at which the implant is inserted into the wrist of the patient.

32. The apparatus of claim 29, wherein the implant guide comprises an angle guide for adjusting the angle at which the implant is inserted into the wrist of the patient.

33. The apparatus of claim 29, wherein the implant guide comprises a thumb screw for adjusting the height or angle of the implant guide.

34. The apparatus of claim 28, further comprising a system for inserting a biological implant into a wrist of a patient, the system comprising a distal end, a distal component, a proximal end, and a proximal component wherein the distal end comprises an opening for receiving the biological implant into the attached distal component, wherein the distal component is cannulated for holding a biological implant, wherein the proximal end comprises a blunt surface for interfacing with a device for providing force and is attached to a proximal component, wherein the proximal component interfaces with an end of the biological implant, and wherein the proximal component and the distal component are engaged.

35. The apparatus of claim 28, further comprising an implantable device for stabilizing a fracture, the device comprising a shaft having a proximal end and a distal end, wherein the distal end comprises a sharpened tip and the proximal end comprises a blunt end, wherein the shaft defines a longitudinal axis and comprises a V-shaped cross section along at least a portion of the longitudinal axis, and wherein the shaft comprises a metal.

36. The apparatus of claim 35, wherein the sharpened tip is detachable.

37. The apparatus of claim 35, wherein the sharpened tip is a blade.

38. The apparatus of claim 28, wherein the traction device comprises a traction tray.

39. The apparatus of claim 28, wherein the traction device comprises a pulley.

40. The apparatus of claim 39 wherein the pulley is attached to a medical finger trap.

41. The apparatus of claim 28, wherein the traction device comprises an angle alignment guide.

42. The apparatus of claim 28, wherein the traction device comprises a rotational

alignment guide

43. The apparatus of claim 28, wherein the traction device comprises a height alignment guide.

44. The apparatus of claim 28, wherein the traction device comprises a ratcheting

extension mechanism.

45. The apparatus of claim 44, wherein the ratcheting extension mechanism has sliding rails.

46. The apparatus of claim 28, wherein the horizontal surface is attached to a surgical board.

47. The apparatus of claim 28, wherein the arm clamp comprises a strap.

48. The apparatus of claim 28, further comprising a fluoroscopic imaging unit attached to the apparatus.

49. The apparatus of claim 48, wherein the fluoroscopic imaging unit is a c-arm imaging device.

50. A method for stabilizing a fracture in bone tissue of a patient, the method comprising: stabilizing a fractured bone of a patient using a fracture stabilizing implant device, the device comprising a shaft having a proximal end and a distal end, wherein the distal end comprises a sharpened tip and the proximal end comprises a blunt end, reducing the fracture, and

inserting the fracture stabilizing implant device into the bone tissue so that the fracture stabilizing implant device lies across the fracture to stabilize the fracture.

51. The method of claim 50, wherein the sharpened tip is detachable.

52. The method of claim 50, wherein the sharpened tip is a blade.

53. The method of claim 50, wherein the fracture is a distal radius fracture.

54. The method of claim 53, wherein the distal radius fracture is a Colles fracture.

55. The method of claim 53, wherein inserting the fracture stabilizing implant device comprises passing the fracture stabilizing implant device through the radial styloid process of the wrist and across the fracture.

56. The method of claim 55, wherein the method further comprises passing the fracture stabilizing implant through the medial cortex of the wrist.

57. The method of claim 50, wherein the shaft comprises a solid metal.

58. The method of claim 57, wherein the solid metal comprises stainless steel or titanium alloy.

59. The method of claim 57, wherein the shaft comprises a roughened surface.

60. The method of claim 50, wherein the shaft comprises a foamed metal.

61. The method of claim 50, wherein the shaft defines a longitudinal axis and comprises a V-shaped cross section along at least a portion of the longitudinal axis.