IL120243A - Bone fixation and stabilization device and method of using same - Google Patents

Description

BONE FIXATION AND STABILIZATION DEVICE BONE FIXATION AND STABILIZATION DEVICE AND ME HOD OF USING SAME FIELD OF THE INVENTION This invention relates to a bone fixation and stabilization device for maintaining bones or bone sections in a fixed position to promote healing. The invention also relates to a method for insertion of the device into a bone cavity, for example the medullary canal of a fractured bone, to promote healing of the fracture.

BACKGROUND OF THE INVENTION Treatment of bone fractures was at one time based exclusively on long term traction, i.e. stretching, wherein the fractured limb is held in traction for an extended period of time, with the patient confined to his bed for a long time. Such long confinement in bed may cause various complications, such as pneumonia, urinary tract infections and pressure sores. These complications can sometimes even result in death.

Modern treatment of bone fractures involves operations in which the fractured bone is aligned, fixated and stabilized. This can be done either externally or internally. External fixation of fractured bones can sometimes be satisfactorily achieved with casts or splints. In cases where casts cannot achieve proper alignment and union of the fracture, there are sometimes used external fixation devices consisting of stainless steel percutaneous pins, which are fixed proximally and distally of the fracture. Alternatively, there are also used internal fixation devices. These can consist of stainless steel plates positioned directly on the bone and fixed in place with screws through the plate and bone. Such implants are, however, difficult to manipulate to achieve the desired compressive force and the operation necessitates a large cut and scraping the (periost) , increasing the risk of wound infection and loss of blood during the operation. Furthermore, the pins or screws weaken the bone and may cause local infection. They are also difficult to remove because of callus and in the case of the humerus their removal may damage the ratial nerve. . Moreover, this procedure generally necessitates another operation to remove the implant. The plates may also be inconvenient for the patient. Another internal fixation method is known as intramedullary fixation. This method is considered more effective and has now become the treatment of choice for treating fractures of long bones because of its numerous advantages. It lowers the infection rate, permits earlier mobility of the patient, often after only 24 hours, heals more rapidly and enables earlier weight bearing. This method involves an intramedullary nail or rod that is inserted in the bone canal traversing the fracture. In this procedure the bone marrow and/or soft 3 bone tissue is reamed out of or evacuated from the bone canal and the intramedullary nail is inserted into the cavity. The nail is generally fixed in position by locking screws inserted through the bone and nail to prevent relative rotation of the fractured bone segments. The intramedullary nails method involves making a relatively small cut with a minimum exposure of bone and relativley small loss of blood. Its main medical disadvantages are 1) the risk of fat embolism caused by the reaming procedure, 2) high exposure of the medical team to X-ray radiation during the operation while monitoring the positioning of the nail and locking screws, and 3) the need for subjecting the patient to a further procedure requiring general anaesthesia when extracting the nail. Numerous patents were obtained for special construction of fixation means for intramedullary nail, as for example, U.S. Patents Nos. 4,204,531; 5,041,114 and 5,057,103.

U.S. Patent No. 4,637,396 discloses a balloon catheter where a balloon is attached to a catheter tube. The expandable and collapsible balloon is reinforced by knitted fabric, so that the balloon cannot expand beyond a predetermined diameter regardless of the internal pressure applied to the balloon. This balloon catheter was disclosed as being suitable for use in the dilation of blood vessels which have been partially or entirely blocked by deposits on the inside wall of the blood vessel. The procedure involves inflating the balloon for a very short time only, while dilating the blood vessel, and then removing the deflated balloon and catheter tube shortly thereafter as part of the same procedure.

In general, the surgical technique for treating fractures such as for example a femural fracture, with an intramedullary nail is as follows. A patient is positioned on a fracture table, either in the supine or lateral position. Closed reduction of the fracture is easily achieved in the supine position and problems of rotational alignment are less frequently encountered this way than in the lateral position. Satisfactory reduction of fracture must be obtained in all dimensions before preparing and draping the limb. Any residual minor displacement of the fractured fragments can be achieved intra-operatively.

A lateral incision, about 1 cm, is made distal to the tip of the greater trochanter, extending superiorly 8-10 cm. The fascia lata and the fibers of the gluteus maximus are divided in line with the skin incision. The interval between the abductor tendon incision on the greater trochanter and the piriformis tendon is identified and the gluteus medius and minimus are freed from the underlying hip capsule. The trochanteric or piriformis fossa is exposed by retracting the abductor muscle anteriorly. A diamond tipped awl is inserted into the marrow of the bone and visualized in both planes fluoroscopically . The proximal fragment is reamed or evacuated with a 6-9 mm hand reamer or by other means. A bulb-tipped guide pin is then inserted into the open femural canal and passed into the distal fragment by small incremental maneuvers until fully inserted. This can be measured by subtracting from the total length of the guide pin the distance of the remaining pin from its tip to the trochanter. At the completion of reaming, the bulb-tipped guide pin is exchanged for a straight guide pin via a plastic medullary tube. A preselected nail is then driven over the straight guide pin into the proximal fragment. Perfect fracture alignment is required as the nail is passed across the fracture into the distal fragment. The nail should be aligned properly with the anterior bow of the femur. Once the nail has entered the distal fragment for about 3-4 cm, the rotary alignment of the limb is checked and traction adjusted to restore normal femural length. The nail is then driven fully into the distal fragment until the lateral flange of the driver impacts the tip of the greater trochanter. Proximal locking is performed readily using a proximal targeting device that firmly attaches to the proximal tip of the nail. Distal locking can be done by various techniques as referred to above in the background of the invention.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a bone fixation and stabilization element for internal implants that can be employed to treat a number of different fracture patterns involving a simple uncomplicated surgical procedure in which surgical invasiveness and operation time are minimized.

Another object of the invention is to provide a method of implanting a simple bone fixation and stabilization device to help heal fractures.

In accordance with this invention there is thus provided a bone fixation and stabilization device comprising an expandable fixation element made of biocompatible elastomer or other expandable material, providing an expandable and collapsible chamber that can fill the space in a bone canal, said fixation element comprising a distal end including a radiopaque portion and a tube for introducing pressurized fluid into said fixation element chamber.

The device of this invention may preferably include reinforcing means to restrict radial and optionally axial expansion of the fixation element so that it will not burst if by accident too much pressure is applied to the fluid. The reinforcing means also provide bend resistance to the device. Such reinforcing means could be rods or strips that are embedded axially in the elastomeric walls of the fixation element. These rods or strips may or may not be interconnected. Alternatively, the reinforcement could comprise netting or knitted fabric either embedded in the balloon wall or surrounding it from the outside.

The biocompatible elastomer can be any material that is expandable and that can be shaped into a form and having the physical properties required for expanding and contracting with the introduction therein of pressurized fluid. The fixation element can have round, rectangular or other shaped cross section.

The expandable wall of the fixation element may have an outer surface that is made rough or that has protrusions to better and more firmly grasp the surface against which it is pressed. The fixation element is thus able to fill the void of a bone canal and anchor therein better and more completely, even if the canal does not have a symmetrical cavity.

In a preferred embodiment, the fixation and stabilization device is made of silicone rubber.

The tube for conducting pressurized fluid into the fixation element preferably has a pressure valve inlet so that the valve can be closed after the pressurized fluid is introduced into the fixation element, preventing backflow of fluid. 8 It is also preferable that the distal end of the device have some reinforcement, so that it is also restricted in its expandability/ yet be able to expand fully into the larger cavity near the distal end of a bone, providing further stability to the bone.

The invention will be better understood with reference to the drawings in which - Figure 1 illustrates in cross-sectional view an expandable fixation device and insertion rod in accordance with this invention; and Figure 2 is a cross-sectional view of an alternative embodiment of an expandable fixation device in accordance with this invention.

Figure 3 is a cross-sectional view of yet another embodiment of the present invention.

Figure 4 is an expanded blown-up perspective view of the device in Figure 3.

Referring now to Figure 1, there is shown a fixation element 10 comprised of an elastomeric annular walled tube 12 which has a distal sealed end 14 and a proximal sealed end 16. The fixation element 10 thus creates a chamber 18 which can be expanded and collapsed. Along one side of the elastomeric tube wall 12 runs a filling tube 20 having an outlet 22 into the fixation element chamber 18 and a filling pressure valve 24 outside of the fixation element. The distal seal 14 has on its inner surface 26 a radiopaque portion for X-ray monitoring, to help guide the fixation element into the proper location in the bone cavity. The proximal seal 16 contain a self-sealing aperture 28 into which a leader rod or tube 30 can be inserted to help guide the fixation element 10 into position in the bone canal. Rigid reinforcing rods 32 are embedded axially in the elastomeric annular wall 12 to limit the expansion of the cavity 18 beyond a predetermined level, thereby preventing the potential bursting of the fixation element. The reinforcing rods 32 possess outward facing projections 34 judiciously placed along the rods 32 to press against the walls of the bone canal when the fixation element is filled with pressurized fluid, thereby preventing radial and axial movement of the fixation element once it is fixed in place. This is very important to provide proper fixation and stabilization of fractured bone sections.

In accordance with the present invention, using an expandable fixation element for intramedullary fixation and stabilization, as illustrated in Figure 1 a patient is prepared initially in the same manner as for conventional metal rod or nail intramedullary fixation. The patient is positioned in a lateral position and the approach is through the piriformis fosa into the femural canal. An opening is cut in the bone and the marrow and/or soft bone is reamed or evacuated clearing the bone canal. The deflated fixation element 10, together with a leader rod 30 inserted therein through self-sealing aperture 28, is introduced into the cavity of the bone canal and incrementally advanced with the assistance of moderate fluoroscopic monitoring until the distal tip comes to the end of the cavity of the distal fracture. The distal tip of the fixation element should reach the epiphyseal line of the distal femur. Pressurized sterile fluid such as saline solution is pumped into the fixation element through pressure valve 24 and filling tube 20 to expand the fixation element chamber 18 to a predetermined level. The projections 34 of the reinforcing rods 32 are pressed against the bone canal walls, fixing the fixation element 10 in position and immobilizing the fractured sections. The distal seal end 14, which is larger in diameter than the main chamber 18, may therefore expand to a greater extent than the fixation element walls 12 because the cavity in the bone at this end is generally larger than the axial bone canal. Thus the expansion of the distal sealed end 14 further helps stabilize the balloon in position and prevent axial movement. The fluid inlet pressure valve is closed and disconnected from the pump and may be buried under the subcutaneous tissue. It is also possible to have a proximal end similar to the distal end 14.

The deflated fixation element can be extracted after the fracture is healed usually without requiring general anaesthesia. All that is required is that a small cut be made in the skin to find the location of the fluid inlet pressure valve and empty the pressurised fluid from the fixation element cavity. In most cases this can be done under local anaesthesia. In the intramedullary nail procedure, the removal of the nail and locking screws requires the patient to be under full anaesthesia. In its empty form the fixation element collapses when the fluid is withdrawn and can be pulled out from the bone cavity with little resistance. The patient is thus spared the discomfort and danger that would otherwise be required if a conventional metal nail were to be used. This procedure is also beneficial to the medical personnel by reducing their exposure to the radiation which normally emanates during the fluoroscopic monitoring.

Figure 2 illustrates an alternative embodiment of a fixation device in accordance with the invention. The fixation element 40 is similar to element 10 illustrated in Figure 1, and comprises elastomeric walls 42, forming an expandable chamber 44, a distal sealed cap 46, and a radiopaque ring 48 near the distal cap 46. The fixation element 40 also has a self-sealing aperture 50 in the proximal sealed end 52. In this embodiment the fluid filling tube 54 passes within the fixation element wall 42 and has its outlet 56 closer to the proximal end 52 of the balloon 40. A fluid sealing pressure valve 58 terminates the fluid filling tube 54. In this embodiment the elastomeric walls 42 of the fixation element 40 are reinforced with a knitted fabric tube 59 embedded therein which prevents radial expansion of the fixation element chamber 44 beyond the predetermined level.

Referring now to Figures 3 and 4, there is shown an alternative fixation element 60. The element comprises an annular double walled tube having an outer wall 62 and an inner wall 64 with a sealed chamber 66 formed between walls 62 and 64. The inner wall 64 surrounds a hollow space 68 extending axially through the entire inside of the fixation element 60. At the distal end of the fixation element 60 the inner and outer walls 62 and 64 respectively form a crown chamber 70 continuous with chamber 66 and which can expand radially beyond the diameter of the outer wall 62. The inner wall 64 is terminated at its distal end with apertured 76 disk 79 integrally formed with fixation element 60. At the proximal end a disk 74 with aperture 78 terminates and seals together walls 62 and 64. The apertures 76 and 78 and hollow space 68 alalow the fixation element 60 to be slipped over a guide rod 94 in the bone canal .

The distal and optionally proximal terminal disks 72 and 74 respectively have inner surfaces 82 and 84 respectively that are radiopaque to allow X-ray monitoring of insertion of the fixation element 60 into the proper position in the bone cavity. Within the inner wall 64 there runs a filling tube 88 having an outlet 90 into the chamber 66 and a filling pressure valve 92 outside the fixation element 60. Rigid reinforcing rods 86 are embedded axially in the outer wall 62 to limit radial expansion of the device in the bone cavity and thus avoid rupturing the expandable fixation element. The reinforcing rods 86 preferably have outward facing projections 96 judiciously positioned on the rods 86 to press against the walls of the bone canal when the fixation device is expanded with pressurized fluid. This prevents radial and axial movement of the bone fragments with respect to one another .

When the fixation element 60 is expanded by introducing pressurized fluid into the chamber 66, the outer wall 62 expands outward and the inner wall 64 expands inward, decreasing the diameter of the hollow space 68. Moreover, the crown chamber 70, which does not have restraining rods, expands more fully laterally and thus fixes the distal position of the fixation device in the enlarged cavity section of the bone canal.

The device 60 of this embodiment is introduced into the bone cavity by first inserting into the bone cavity a guide rod 94 and aligning the fractured sections properly. Then the unexpanded fixation device 60 is slipped into the bone canal over the guide rod 94 via the inner hollow space 68 with the distal and proximal apertures 76 and 78 14 respectively providing entry and exit points for rod 94. Once the fixation element is in place in the bone canal, pressurized fluid is introduced in the chambers 66 and 70 in tube 88. The outer walls 62 of the fixation deivce 60 expand axially up to a predetermined level determined by the reinforcing rods 86, or by a web material embedded in the outer wall 62 (not shown) similar to that in Figure 2. The protrusions 96 press against the bone cavity wall assuring a tight contact. The crown chamber 70, which is not reinforced, expands more than the outer wall 62 and fills the distal layer bone cavity, providing further fixation against rotational or axial movement of respective fracture sections.

The expandable fixation device of the present invention may also have use in addition to intramedullary applications, where for example, spinal vertebrae are collapsed. A small expandable fixation element may be inserted into the vertebra body and expanded to provide an anatomic structure form to prop up the vertebra. Such an element can then be collapsed and removed after the vertebra bone has healed enough to function properly.

It will be appreciated by persons skilled in the art that the scope of the present invention is not limited to what has been shown and described hereinabove, merely by way of example. Rather, the scope of the invention is limited solely by the claims which follow.

Claims (14)

C L A I M S

1. A fixation and stabilization device for inserting into a bone cavity comprising an expandable fixation element made of biocompatible expandable material, providing an expandable and collapsible chamber that can fill the space in a bone canal said fixation element comprising a distal end including a radiopaque portion and means for introducing and removing pressurized fluid into and from said chamber.

2. A fixation and stabilization device as in Claim 1 wherein said means for introducing comprises a tube with a pressure valve inlet.

3. A fixation and stabilization device as in Claims 1 and 2 wherein said chamber has exterior walls provided with means to grasp the bone firmly upon expansion of said chamber in said bone cavity.

4. A fixation and stabilization device as in Claim 3, wherein said means are roughened exterior protrusions or surfaces.

5. A fixation and stabilization device as in Claim 1 and wherein said chamber comprises exterior walls with reinforcing means therewith to restrict the chamber from expanding radially and optionally axially beyond a predetermined distance.

6. A fixation and stabilization device as in Claim 5 wherein said reinforcing means are axially embedded rods .

7. A fixation and stabilization device as in Claim 5 wherein said reinforcing means are selected from netting or knitted fabric tube embedded in or at least partially enveloping the fixation element outer wall.

8. A fixation and stabilization device as in Claim 6 wherein said rods further comprise outward facing protrusions.

9. A fixation and stabilization device as in any of the previous claims, wherein the expandable material is an elastomer.

10. A fixation and stabilization device as in Claim 9, wherein the elastomer is silicone rubber.

11. A fixation and stabilization device as in any of the previous claims, having a throughgoing hollow tube for Sliding said device over a guide rod in the bone cavity.

12. A fixation and stabilization device as in any of the previous claims, comprising a radiopaque distal surface .

13. A fixation and stabilization device as in any of the previous claims, comprising a non-reinforced distal expandable and collapsible crown chamber continuous with reinfoeced cylindrical chamber.

14. An intramedullary fixation and stabilization kit comprising a device as in Claims 1-13 and guide rod for guiding said device into a bone canal over said guide rod.