Growing rod for treating spinal deformities and method for using same

A growing rod adapted to be secured along a length of a spine for treating deformities of the spine. The growing rod comprises a base rod, an extendible rod having a proximal portion that is slidably coupled to the base rod and arranged with a gear rack, and a distraction unit. The distraction unit includes a housing attached to the base rod, a rotatable drive interface accessible by an external driver from outside of the housing, and a drive gear mechanism housed within the housing and coupled to the rotatable drive interface and the gear rack such that rotation of the rotatable drive interface causes linear movement of the extendible rod through the gear rack.

FIELD OF THE INVENTION

The present invention relates generally to a growing rod for treating spinal deformities, and more particularly to a growing rod that can be secured to a spine of a patient and manually extended to grow with the patient's spine.

BACKGROUND OF THE INVENTION

Scoliosis is a term used to describe any abnormal, sideway curvature of the spine. The most common form of scoliosis for patients between the age of 10 and 18 years is termed adolescent idiopathic scoliosis (AIS). Although the particular cause of this type of scoliosis is still unknown, advancements in the medical field have enabled doctors to increase the likelihood of successfully treating scoliosis is children and adolescents.

Studies have shown that curvatures in the spine progress during the rapid growth period of children. Because of this, children suffering from scoliosis are generally recommended by their doctor to undergo surgical treatment to prevent curve progression and to obtain some curve correction.

One type of spinal surgery for treating scoliosis in children is the use of implantable rods that allow for continued growth of the spine. One or two rods are implanted into the child through the back of the spine. The rods are then secured to the spine above and below the curve using hooks or screws. Because the child will continue to grow after the spinal surgery, the child will be required to return every few months to have the rods lengthened to keep up with his/her growth.

There thus exists a need to provide improved growing rods.

SUMMARY OF THE INVENTION

The present invention cures some of the deficiencies in the prior art by providing a growing rod that is less complex and that can be manually extended by a user.

The growing rod of the illustrative embodiment of the present invention is adapted to be subcutaneously implanted and secured along a length of a spine of a patient. The growing rod comprises a base rod, an extendible rod having a distal portion that is slidably coupled to the base rod and arranged with a gear rack, and a distraction unit.

The distraction unit provides one or more mechanical elements to facilitate linear movement of the extendible rod relative to the base rod. In general, the distraction unit comprises: (i) a housing attached to the base rod, (ii) a rotatable drive interface accessible by an external driver from outside of the housing, and (iii) a drive gear mechanism housed within the housing and coupled to the rotatable drive interface and the gear rack such that rotation of the rotatable drive interface causes linear movement of the extendible rod through the gear rack.

Because the patient is likely to continue to grow after implantation of the growing rod, the patient will be required to return to the doctor (e.g., two months, four months, six months, etc., after each doctor's visit) to have the growing rod extended in order to keep up with the patient's growth. This can be accomplish by making a small incision on the patient's back to access the rotatable drive interface with an external driver. The rotatable drive interface is adapted to be physically coupled to and manually rotated by the external driver employed by the doctor. As the doctor rotates the rotatable drive interface in a first direction (e.g., clockwise), it causes linear movement of the extendible rod through the gear rack. The linear movement is a result of a gear in the drive gear mechanism cooperating with the gear rack to linearly move the extendible rod relative to the base rod. A latching mechanism housed within the housing is configured to latch onto the drive gear mechanism to prevent the rotatable drive interface from being able to rotate in a second direction (e.g., counter-clockwise) for retracting the extendible rod. The latching mechanism also provides a means to prevent the drive gear mechanism from causing the extendible rod from retracting under pressure of the spine; for example, when the patient is sitting up, standing, walking, etc.

To unlatch the latching mechanism, provided is a rotatable cam interface arranged on the outside of the housing. The doctor can access the rotatable cam interface by using an external cam driver. Rotating the rotatable cam interface using the driver causes a cam housed within the housing to unlatch the latching mechanism from the drive gear mechanism, thereby allowing the doctor to rotate the rotatable drive interface in the second direction. This feature allows the doctor to fine tune the overall length of the growing rod if the extendible rod has been extended too much.

By providing a manually operated implant that is less complex, like the growing rod of the illustrative embodiment, fewer elements and moving parts can be used to extend and retract the implant without the need of a power source.

In an alternative embodiment of the present invention, different types of gears and gear configurations are employed to extend the extendible rod relative to the base rod.

In a further alternative embodiment of the present invention, the extendible rod is extended relative to the base rod by means of applying fluid pressure through a fluid intake coupled to a fluid connection body of the growing rod. The fluid pressure enters the connection body and forces a piston forwards to extend the extendible rod.

In yet another alternative embodiment, a growing rod is adapted to be extended by incrementally pushing a toggling switch on the surface of a patient's skin.

These advantages of the present invention will be apparent from the following disclosure and the appended claims.

DETAILED DESCRIPTION

FIG. 1shows a growing rod100in a collapsed configuration in accordance with an illustrative embodiment of the present invention. The growing rod comprises: base rod102, extendible rod104, and distraction unit106. Each of these elements that form growing rod100can be constructed from a biocompatible plastic, metal, metal alloy, or a combination thereof. The biocompatible metals and metal alloys can be, for example, and without limitation, titanium, titanium alloy, stainless steel, cobalt chrome, or any combination thereof. However, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which some of the elements of growing rod100is made from a durable thermoplastic polymer, such as polyether ether ketone (PEEK).

In accordance with the illustrative embodiment, extendible rod104has a proximal portion that is slidably coupled to base rod102and arranged with a gear rack. The extendible rod may be constructed to have a slightly smaller diameter than that of base rod102in order to allow the extendible rod to telescopically slide in and out of the base rod. It will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which base rod102can be adapted to slide in and out of extendible rod104.

FIG. 2shows growing rod100in a fully extended configuration in accordance with an illustrative embodiment of the present invention. In this figure, extendible rod104has been fully extended relative to base rod102in response to a doctor manually rotating a rotatable drive interface that is arranged on the outside of distraction unit106. The doctor can also fine tune the length of growing rod100by retracting extendible rod104to a desired distraction length. The doctor can achieve this by manually rotating a rotatable cam interface arranged on the outside of distraction unit106in the opposite direction. The illustrative embodiment of extendible rod104is adapted to allow for a minimum of three and a half years growth before replacement or removal is required. However, it will also be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which extendible rod104is adapted for more or less than three and a half years growth before replacement or removal is required. These features of the present invention will be described in more detail below, with respect toFIGS. 3 and 4.

FIG. 3is a perspective view of the outside of distraction unit106in accordance with an illustrative embodiment of the present invention. The distraction unit comprises: housing302, rotatable drive interface304, guide wall306, recess308, rotatable cam interface310, and cover plate312. Each of these elements of distraction unit106can be constructed from a biocompatible plastic, metal, metal alloy, or combination thereof. The biocompatible metals and metal alloys can be, for example, and without limitation, titanium, titanium alloy, stainless steel, cobalt chrome, or any combination thereof.

As shown in the figure, rotatable drive interface304is arranged on the outside of housing302and is accessible to a doctor via an external driver. The rotatable drive interface304is hexagon-shaped and is adapted to be received in a correspondingly shaped recess of the external driver. The rotatable drive interface304can be, for example, and without limitation a 35 mm hex drive interface. Although rotatable drive interface304is depicted as hexagon-shaped, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which rotatable drive interface304can have any shape and size, so long as it can be received by the recess of the external driver.

As further shown in the figure, rotatable drive interface304is surrounded by guide wall306, which has a pair of oppositely positioned recesses308arranged on the outer surface of the guided wall. Only one recess308is shown in the figure, but it will be clear to those skilled in the art, after reading this disclosure, that one half of guide wall306is substantially a mirror image of the other half of the guide wall. In accordance with the illustrative embodiment, each recesses308is adapted to receive a correspondingly shaped and sized protrusion, hook, etc., arranged on the external driver. Once received, the external driver is locked to guide wall306such that lateral movement of the external driver is prevented. This mechanism helps prevent the external driver from dislodging from rotatable drive interface304as the doctor is rotating it. The physical structure of guided wall306also has the added benefit of helping the doctor determine where rotatable drive interface304might be located underneath the skin.

Housing302also includes rotatable cam interface310, which is coupled to a cam housed within housing302. Although the figure depicts rotatable cam interface310as having a slotted head for receiving a corresponding shaped external cam driver, it will be clear to those skilled in the art, after reading this disclosure, that rotatable cam interface310can have any shape and size, so long as it can receive the external cam driver. As will be discussed in more detail below, with reference toFIG. 4, rotating interface310causes a cam housed within housing302to disengage a latch from a drive gear mechanism so that a doctor can retract extendible rod104.

FIG. 4is a cross-sectional view of the interior of distraction unit106, thus housing302, in accordance with an illustrative embodiment of the present invention. The interior of the distraction unit comprises: drive gear402, idler gear404, pinion406, cam408, and latch410. Like all of the elements that form growing rod100, elements402to410can be constructed from a biocompatible plastic, metal, metal alloy, or combination thereof. The biocompatible metals and metal alloys can be, for example, and without limitation, titanium, titanium alloy, stainless steel, cobalt chrome, or any combination thereof.

Removing cover plate312from housing302reveals a drive gear mechanism that is coupled to rotatable drive interface304and gear rack412. The gear rack412is preferably arranged on a proximal portion of extendible rod104, but it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which gear rack412is arranged along the length of extendible rod104.

In accordance with the illustrative embodiment, the drive gear mechanism comprises drive gear402, idler gear404, and pinion406. These gears are coupled to one another as shown in the figure to form a “simple gear train”. The gear ration between drive gear402and pinion406is preferably 2-to-1 (i.e., 2:1 ratio). What this means is that pinion404has twice as many teeth as drive gear402. However, those skilled in the art will appreciate after reading this disclosure that distraction unit106can be configured to have any number of gears and different gear ratio ranges without departing from the scope of the invention. For example, the gear ratio range can have a lower limit of 1.5 and an upper limit of 10.

Furthermore, althoughFIG. 4only depicts the drive gear mechanism as having three gears, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which the drive gear mechanism has fewer or more gears than depicted. For example, and without limitation, the drive gear mechanism can have one gear, two gears, ten gears, etc., without departing from the scope of the present invention. It will also be clear to those skilled in the art that other types of gears and gear trains could be used without departing from the scope of the present invention. Other types of gears may include, for example, and without limitation, spur gears, helical gears, herringbone gear, face gears, screw gears, etc., or a combination thereof. Other types of gear trains may include, for example, and without limitation, compound gear trains, reverted gear trains, epicyclic gear train, etc., or a combination thereof. Lastly, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which distraction unit106can be configured to have different number of gears and different gear ratios without departing from the scope of the invention.

As briefly described above, rotatable drive interface304is adapted to be accessed by an external driver from outside of housing302. The rotatable drive interface is also adapted to be physically coupled to and manually rotated by the external driver for extending and retracting the extendible rod relative to the base rod. More specifically, rotating interface304in a first direction (e.g., clockwise) rotates drive gear402in the same direction. In response to the rotational movement of drive gear402, idler gear404will also begin to rotate, but in the opposite direction, while pinion406will rotate in the same direction as drive gear402. Thus, gears402,404, and406are coupled to rotatable drive interface304in such a way that rotation of the rotatable drive interface causes each of the gears to simultaneously rotate. The rotational movement from gears402,404, and406is then translated into linear movement by coupling pinion406to gear rack412.

The coupling between pinion406and gear rack412is made possible by coupling housing302of distraction unit106to base rod102as shown inFIGS. 2 and 3. More specifically, and as shown inFIG. 5A, the outer surface of base rod102is machined with an opening502. The opening502is arranged at a distal portion of base rod102. The opening502can also be seen inFIG. 4. Similarly, housing302has an opening504arranged on one side of the housing. The opening504of housing302is shown inFIG. 5B. In accordance with the illustrative embodiment, the teeth508of pinion406extend slightly outside of opening504of housing302. This allows the teeth508of pinion406to extend through opening502of base rod102to engage the teeth506of gear rack412when housing302is coupled to base rod102, thereby forming a rack-and-pinion configuration. As discussed above, rotational movement of pinion406is translated into linear movement by gear rack412such that extendible rod104can be either extended or retracted, depending on which direction rotatable drive interface304is rotated.

Referring back toFIG. 4, the latching mechanism housed within housing302is adapted to latch onto a gear of the drive gear mechanism such that rotation of rotatable drive interface304is prohibited in a direction (e.g., in a counter-clockwise direction) that retracts extendible rod104. In accordance with the illustrative embodiment, the latching mechanism comprises latch410, which is biased to lock the drive gear mechanism. As shown in the figure, latch410is biased to latch onto and lock idler gear404. Although latch410is biased to lock idler gear404in the illustrative embodiment, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which latch410is biased to lock drive gear402or pinion406instead.

Continuing with the illustrative embodiment, latch410is sized and shaped to be received between a pair of adjacent teeth of idler gear404. Latch410is spring-loaded in the illustrative embodiment and is adapted to ratchet back and forth as rotatable drive interface304is rotated in the clockwise direction for extending rod104. However, the size and shape of latch410relative to the root/pitch of idler gear404prevents latch410from being able to ratchet back and forth when rotatable drive interface304is rotated in the counter-clockwise direction for retracting rod104. That is, latch410will not be dislodged from between the pair of adjacent teeth of idler gear404when rotatable drive interface304is rotated in a direction that retracts extendible rod104. This feature of the present invention is advantageous in that downward pressure exerted on the spine (e.g., when the patient is sitting up, standing, etc.) after implantation of growing rod100will not cause gears402,404,406to unintendedly rotate and inadvertently retract rod104.

FIG. 6shows latch410unlatched from between the pair of adjacent teeth of idler gear404in accordance with the illustrative embodiment. To unlatch latch410, rotatable cam interface310is provided. The rotatable cam interface is accessible by an external cam driver from outside of housing302. The rotatable cam interface310is coupled to cam408such that rotation of the rotatable cam interface causes the latching mechanism to either prohibit or allow the drive gear mechanism to rotate in a direction that retracts or extends the extendible rod104.

Specifically, rotatable cam interface310is adapted to be physically coupled to and manually rotated by external cam driver310such that rotation of rotatable cam interface310causes a tip of cam408to engage or be free from physical contact with latch410. The rotatable cam interface310is rotatable from outside of housing302in a first direction (e.g., counter-clockwise) until the tip of cam310abuts against lever602of latch410and pins it against stopper604. This causes latch410to be unlatched from between the pair of adjacent teeth of idler gear404. This also holds latch410in the unlatched position so that the doctor can rotate interface304to retract extendible rod104to a desired length. After reaching the desired length, the doctor can use the external cam driver to rotate interface310in a second direction (e.g., clockwise) to position latch410between a pair of adjacent teeth of idler gear404, thereby locking gears402,404, and406from rotating in a direction that retracts extendible rod104.

Having described the elements of growing rod100in particular detail, an example of using growing rod100will now be described. After growing rod100has been implanted into a patient, the patient may be required to return to the doctor every few months to have growing rod100extended to keep up with his/her growth. To extend growing rod100, the doctor uses his hands to feel for where distraction unit106is located; in particular, where guide wall306is located underneath the patient's skin. Once located, a small incision is made on the patient's back near guide wall306. An external driver is inserted through the small incision and then physically coupled to rotatable drive interface304from outside of housing302. Once coupled, the doctor may manually rotate rotatable drive interface304using the coupled external driver. As discussed above, with respect toFIGS. 3-6, rotating interface304also rotates drive gear402, idler gear404, and pinion406, since each of these gears are either physically or indirectly coupled to rotatable drive interface304. The rotational movement of these gears is then translated into linear movement through the rack-and-pinion configuration created by coupling pinion406to gear rack412. The linear movement of gear rack412causes extendible rod104to linearly extend relative to base rod102. Likewise, rotating interface304in the opposite direction causes extendible rod104to linearly retract relative to base rod102, as discussed above, with respect toFIGS. 3-6.

It should be noted that “manual” rotation of rotatable drive interface304includes, for example, and without limitation, physically coupling the external driver to rotatable drive interface304and then having the doctor manually rotate the physically coupled external driver in a clockwise or counter-clockwise direction. In this embodiment, the external driver is similar to, for example, and without limitation, a socket wrench that is not electrically driven.

In alternative embodiments, “manual” rotation of rotatable drive interface304includes, for example, and without limitation, physically coupling the external driver to rotatable drive interface304and then actuating one or more buttons to electrically power the physically coupled external driver. In this embodiment, a power source provides electricity of the physically coupled external driver to manually rotate interface304.

FIGS. 7A and 7Bdepict an alternative embodiment of extendible rod104discussed above.FIG. 7Adepicts one side of housing302of distraction unit106with cover plate312removed. Housed within housing302in this alternative embodiment are four gears—namely, drive gear702, a compound gear formed by a larger gear704having a smaller gear706coupled on one side of the larger gear, and pinion708. The smaller gear706is shown inFIG. 7B.

In accordance with this alternative embodiment, drive gear702is coupled to larger gear704(as shown inFIG. 7A) and smaller gear706is coupled to pinion708(as shown inFIG. 7B). Pinion708in turn is coupled to gear rack412, as discussed above, with respect toFIGS. 3-5B. The gear configuration in this alternative embodiment has, for example, and without limitation, a gear ratio of 4-to-1 (i.e., 4:1 ratio). However, those skilled in the art will appreciate after reading this disclosure that distraction unit106can be configured to have different number of gears and different gear ratios without departing from the scope of the invention.

To extend or retract extendible rod104relative to base rod102, rotatable drive interface304can be respectively rotated in a clockwise or a counter-clockwise direction, as discussed above, with respect toFIGS. 3-5B. As interface304rotates drive gear702, the larger gear704and smaller gear706also rotate, but in the opposite direction of drive gear702. The coupling between smaller gear706and pinion708causes linear movement of extendible rod104through gear rack412, as discussed above. AlthoughFIGS. 7A and 7Bdo not depict the latching mechanism (e.g., latch410, rotatable cam interface310, cam408, stopper604, etc.) discussed above, those skilled in the art will appreciate that this alternative embodiment can be configured to include the latching mechanism. The advantage of having a gear train that includes a compound gear is the ability to more easily meet the distraction force for extending extendible rod104.

FIG. 8Ashows a growing rod800in a collapsed configuration in accordance with an alternative embodiment of the present invention. The growing rod comprises: base rod802, extendible rod804, fluid connector body806, fluid intake808, piston810, spring-loaded ball812, fluid seals814, end seal816, input tube818, and port820.

FIG. 8Bshows growing rod800in a fully extended configuration in accordance with an alternative embodiment of the present invention. As will be discussed in more detail below, with respect toFIG. 9, extendible rod804has been fully extended relative to base rod802in response to fluid pressure being applied through fluid intake808to force piston812forwards.

Turning now toFIG. 9, and in accordance with this alternative embodiment, growing rod800is implanted along a spine of a patient and can be expanded after implantation to keep up with the growth of the patient. More specifically, growing rod800can be expanded by making a small incision on the patient's back to access an input tube818arranged on fluid intake808, which fluid intake is coupled to connector body806of growing rod800. Once accessible, a fluid hose coupled to a fluid delivery device is connected to input tube818of fluid intake808. The fluid delivery device is then operated to apply fluid pressure (e.g., saline fluid, etc.) through fluid intake808. The fluid pressure exits port820and forces piston812forwards, thereby extending rod804relative to base rod802. Although three fluid seals are shown in the figures, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments of the present invention in which piston810has more or less fluid seals than depicted. It should also be noted that growing rod800has an end seal816that prevents extendible rod804from being able to extend too far and decoupling from connector body806.

Once extendible rod804has reached a desired distraction length, extendible rod804will be under load pressure. This load pressure will force extendible rod804to retract backwards on itself. At this time, spring-loaded ball812is forced up a ramp arranged within a recess of on piston810. This causes ball812to press up against the side of fluid connector body806, thereby stopping any further retraction of extendible rod804. Once extendible rod804has been stopped from retracting on itself, the fluid pressure can be relieved from an access port to empty fluid connector body806of the fluid pressure.

The design of growing rod800is advantageous because it has a small diameter and is of minimal design complication. Growing rod800is also advantageous because the fluid pressure will not be in effect during implantation—that is, fluids and pressure will only be introduced when extendible rod804is being extended relative to base rod802. From this design, growing rod800is able to be a passive growth mechanism. As the spine grows, growing rod800can be advanced within the patient without the aid of external manipulation. The fact that growing rod800can be both passive and manipulative (if required) reduces the need of additional surgeries for the patient.

FIG. 10depicts a further alternative embodiment of the present invention. Growing rod1000comprises: extendible rod1002, coupling1004, toggling switch1006, spring1008, and base rod1010. Each of these elements that form growing rod1000can be constructed from a biocompatible plastic, metal, metal alloy, or a combination thereof. The biocompatible metals and metal alloys can be, for example, and without limitation, titanium, titanium alloy, stainless steel, cobalt chrome, or any combination thereof. However, it will be clear to those skilled in the art, after reading this disclosure, how to make and use alternative embodiments in which some of the elements of growing rod1000can be made from a durable thermoplastic polymer, such as polyether ether ketone (PEEK).

In accordance with this alternative embodiment, the outer surface of extendible rod1002is arranged with threads1030. Preferably, only a portion of the outer surface of extendible rod1002is threaded with threads1030. However, in other embodiments, the entire length of extendible rod is arranged with threads1030. The proximal portion of extendible rod1002is adapted to be received within and threaded into the distal portion of coupling1004.

Coupling1004has a through-hole for receiving extendible rod1002and base rod1010. As shown inFIG. 12, the inner surface of the distal portion of coupling1004is arranged with threads1040. These threads of coupling1004allow extendible rod1002to be received within and threaded into the distal portion of coupling1004. The inner surface of the proximal portion or intermediate portion of coupling1004is arranged with a groove1012. The groove is adapted to receive a retaining ring1014coupled to base rod1010for preventing the base rod from being able to slide in and out of the through-hole of coupling1004.

As further shown inFIGS. 11 and 13, the proximal portion of coupling1004is arranged with teeth1050that are adapted to mesh with the teeth1060of toggling switch1006to form a one-way, sliding, sawtooth clutch. The teeth of coupling1004and toggling switch1006are chamfers having a symmetrical sloping edge, as shown in the figures. The sloping edge allows teeth1050of coupling1004to slide along the sloping edge of the teeth1060arranged on toggling switch1006. The angle of the sloping edge of the teeth of elements1004and1006can be, for example, and without limitation, 10°, 45°, 65°, etc. As will be discussed in more detail below, the one-way, sliding, sawtooth clutch allows coupling1004to rotate and cause linear movement of extendible rod1002.

Toggling switch1006is arranged with a through-hole for receiving base rod1010. The inner surface of the through-hole of toggling switch1006has a cutout that is adapted to receive spring1008. Toggling switch1006is also arranged with a first toggle1016and a second toggle1018that can be operated by a user (e.g., a doctor, nurse, etc.) to cause linear movement of extendible rod1002relative to coupling1004.

The distal portion of base rod1010is arranged with a groove1020for receiving retaining ring1014. As discussed above, retaining ring1014is adapted to prevent base rod1010from being able to slide in and out of the through-hole of coupling1004when seated within groove1012. The proximal portion of base rod1010is arranged with a circular protrusion having an underside that is adapted to abut against spring1008.

The method of using growing rod1000will now be described. After growing rod1000has been implanted along the spine of a patient, the growing rod will need to be periodically extended to keep up with the patient's growth. Unlike the other embodiments described in this disclosure, this alternative embodiment does not require making any incisions on the patient's back access a mechanism for extending the length of growing rod1000. Instead, the doctor can simply use his hands and feel where toggling switch1006is located underneath the patient's skin on his/her back. Once the doctor has located toggling switch1006, the first toggle1016or the second toggle1018can be operated by the doctor to lengthen growing rod1000. For the purpose of this discussion, and without limitation, the first toggle1016will be used to lengthen growing rod1000.

More specifically, the doctor can press on the first toggle1016one or more times on the surface of the patient's skin. This pressing action causes toggling switch1006to incrementally rotate in the same direction in which the first toggle1016is pressed; for example, in a clockwise direction. As toggling switch1006incrementally rotates in a clockwise direction, the teeth1060of toggling switch1006will abut against the teeth1050of coupling1004, thereby driving the coupling to rotate as well. Because coupling1004is threaded to base rod1002, rotating coupling1004in this way causes extendible rod1002to back out of the through-hole of the coupling, thus extending the length of growing rod1000.

However, it should be noted that pressing on the second toggle1018will not cause coupling1004to rotate in the opposite direction; in other words, a counter-clockwise direction. This is because the teeth1050of coupling1004and the teeth1060of toggling switch1006cooperatively form a one-way, sliding, sawtooth clutch. More specifically, as the second toggle1018is pressed by the doctor, the sloping edge of the teeth1060of toggling switch1006slide along the sloping edge of the teeth1050of coupling1004. This causes toggling switch1006to be pushed away from coupling1004and compress against spring1008. Spring1008is then compressed against the underside of circular protrusion1022until the teeth1060of toggling switch1006is once again meshed with the teeth1050of coupling1004.

As noted above, this alternative embodiment is advantageous in that no incisions are required to extend the growing rod.

FIG. 14is a top perspective view of an alternative growing rod in accordance with some embodiments. The growing rod1100is a manually driven growing rod that advantageously uses a worm gear to extend the length of the growing rod. The advantageous of using such a worm gear is that it prevents inadvertent rotation of any particular gears, thereby reducing the risk of undesired movement of the growing rod.

The growing rod1100comprises a fixed rod1102and an expansion or extendible rod1104, wherein the extendible rod1104is capable of extending in length away from the fixed rod1102. The growing rod1100further comprises a housing1112operably connected to a cover plate1142for receiving the fixed rod1102and/or extendible rod1104therein. The cover plate1142is further designed to house one or more gears as part of a gear set1106for causing extension and/or retraction of the extendible rod1104.

As shown inFIG. 14, the growing rod1100comprises a fixed rod1102and an extendible rod1104. In some embodiments, the fixed rod1102comprises a shaft that is configured to have a fixed length relative to the housing1112and/or cover plate1142. The fixed rod1102comprises an end cap1103that is operably attached to the cover plate1142. In contrast, the extendible rod1104is configured to have an adjustable length relative to the housing1112and/or cover plate1142. The extendible rod1104is capable of expansion via rotation of a rotatable drive interface1107in a first direction, and retraction via rotation of the rotatable drive interface1107in a second direction opposite the first direction. In some embodiments, the extendible rod1104comprises an outer threaded portion (shown as reference numeral1321inFIG. 21) that is configured to engage an inner threaded portion of an inner threaded sleeve1132. This engagement between the threaded portions accommodates lateral movement of the extendible rod1104upon rotation of the inner threaded sleeve1132.

The extendible rod1104is received in the hollow shaft of an inner threaded sleeve1132(shown inFIG. 15), which itself is received in the hollow shaft of housing1112. The housing1112comprises a hollow body which advantageously encloses a portion of the extendible rod1104, thereby protecting it from interference with tissue and other objects in the body. On a first end of the housing1112, an extendible rod1104extends there through. On a second end of the housing1112, a cover plate1142is operably attached to the housing1112. The cover plate1142is designed to house and protect a gear set1106.

In the present embodiment, the gear set1106comprises a worm gear set. The worm gear set1106comprises a worm in the form of a rotatable drive interface1107that is engaged to worm gear1108(shown inFIG. 15). Advantageously, a worm gear helps to hold the position of the growing rod1100so that it does not inadvertently retract. Rotation of the rotatable drive interface1107in a first direction causes rotation of the worm gear1108to rotate around a longitudinal axis of the growing rod1100. The rotatable drive interface1107is visible through an eyelid1114that is formed in the cover plate1142of the growing rod1100. In some embodiments, the worm gear1108is attached to the inner threaded sleeve1132. In some embodiments, the worm gear1108is welded to the inner threaded sleeve1132. Accordingly, rotation of the rotatable drive interface1107in a first direction causes the worm gear1108to rotate, which in turn causes rotation of the inner threaded sleeve1132. As the inner threaded sleeve1132is engaged with the extendible rod1104via threading, this causes the extendible rod1104to translate linearly (e.g., extend or expand). Rotation of the rotatable drive interface1107in a second direction causes the worm gear1108to rotate in the opposite direction, which in turn causes linear translation of the extendible rod1104in an opposite, retracted direction.

FIG. 15is a top perspective view of the alternative growing rod ofFIG. 14with portions of the housing removed. In addition to the housing1112, the cover plate1142has also been removed, thereby exposing the gear set1106. From this view, one can see the inner threaded sleeve1132which threadingly engages the threaded portion of the extendible rod1104. From this view, one can also see how rotation of the rotatable drive interface1106causes rotation of the worm gear1108, which in turn causes rotation of the inner threaded sleeve1132and translation of the extendible rod1104.

FIG. 16is a close up view of the gear set of the alternative growing rod ofFIG. 14. The gear set1106comprises a worm gear set including a worm in the form of a rotatable drive interface1106and a worm gear1108. As shown in this figure, the worm gear1108is attached to the inner threaded sleeve1132(e.g., via welding). As such, rotation of the worm gear1108causes rotation of the inner threaded sleeve1132, which thereby causes linear translation of an extendible rod1104therein.

In some embodiments, the growing rod1100can incorporate a pre-lordosed housing1112and extendible rod1104. Such a design can also incorporate a flexible inner threaded sleeve1132. Advantageously, by providing a pre-lordosed growing rod1100, this removes the flexural forces that can incur between the housing1112and extendible rod1104, and can further allow for more beneficial contouring of the growing rod1100to a patient's anatomy.

In some embodiments, the growing rod1100can be affixed to a spine via one or more bone screws. The growing rod1100can be implanted in either up or down position and can be used singularly or in pairs. In some embodiments, the growing rod1100can be engaged through a small incision with a hexalobular drive interface. In some embodiments, the worm gear set1106provides a reduction ration of 6:1, 8:1, 10:1 or more. In some embodiments, the worm gear set1106provides a reduction ratio of 10:1 such that the rotatable drive interface1107is rotated 6 complete revolutions to achieve 1 mm of growing rod1100expansion or contraction, with the amount of growth based upon a goal measure of 1.8 cm to 2.4 cm per year. Advantageously, a surgeon can fine tune the amount of expansion by either increasing or decreasing the amount of rotations. If a surgeon feels too much distraction has been incorporated, the growing rod1100can be reduced by simply reversing the direction of the driver.

Advantageously, the growing rod1100and previous designs can be implanted via use of existing pedicle screws. In some embodiments, the growing rod1100will have the strength of a conventional rod, and can be adjusted via minimal incision. Per the worm gear set1106, a controlled adjustment can be accomplished and distraction forces can be easily met. In some embodiments, the growing rod1100can be manufactured using a metal, such as steel, cobalt chrome, or titanium.

FIG. 17is a top perspective view of another alternative growing rod in accordance with some embodiments. The present growing rod1200includes a number of similar features to the growing rod1100inFIG. 14, including a fixed rod1202, an extendible rod1204, a housing1212, a cover plate1242, and a worm gear set1206. In addition to these features, the growing rod1200includes an O-ring cover seal1219and a snubber, which will be discussed in more detail below.

The growing rod1200comprises a fixed rod1202and an extendible rod1204. In some embodiments, the fixed rod1202is fixed relative to the housing1212and cover plate1242, while the extendible rod1204is changeable in length relative to the housing1212and cover plate1242. In some embodiments, the fixed rod1202comprises an end cap1203that is operably connected to the cover plate1242.

Like the growing rod1100, the cover plate1242of the growing rod1200covers a worm gear set1206. The worm gear set1206comprises a rotatable drive interface1207that is accessible via a driver through an eyelid1214of the cover plate1242. Rotation of the rotatable drive interface1207causes rotation of a worm1209(shown inFIG. 18). As the worm1209is attached to an inner threaded sleeve1232(shown inFIG. 18), it causes the inner threaded sleeve1232to rotate. As the extendible rod1204is attached to the inner threaded sleeve1232by a threaded engagement, it translates laterally, thereby causing expansion or contraction of the extendible rod1204.

FIG. 18is a top perspective view of the alternative growing rod ofFIG. 17with portions of the housing removed. From this view, one can see the O-ring cover seal1219, which extends around the extendible rod1204. The O-ring cover seal1219advantageously helps to seal the housing1212from the migration of blood or bodily fluids. In addition, the growing rod1100can include an optional snubber that helps to control any backlash from the gear set1206.

FIG. 19is a close up view of the gear set of the alternative growing rod ofFIG. 17. From this view, one can see the worm gear set1206which includes the worm in the form of a rotatable drive interface1207and the worm gear1209. In some embodiments, the worm gear1209can include a hex portion that is welded to the inner threaded sleeve1232, which is not visible inFIG. 19. As the worm gear1209is attached to the inner threaded sleeve1232, rotation of the worm gear1209causes the inner threaded sleeve1232to rotate, thereby causing translation of the extendible rod1204.

In some embodiments, the growing rod1200can incorporate a pre-lordosed housing1212and extendible rod1204. Such a design can also incorporate a flexible inner threaded sleeve1232. Advantageously, by providing a pre-lordosed growing rod1200, this removes the flexural forces that can incur between the housing1212and extendible rod1204, and can further allow for more beneficial contouring of the growing rod1200to a patient's anatomy.

In some embodiments, the growing rod1200can be affixed to a spine via one or more bone screws. The growing rod1200can be implanted in either up or down position and can be used singularly or in pairs. In some embodiments, the growing rod1200can be engaged through a small incision with a hexalobular, or hex, drive interface. In some embodiments, the worm gear set1206provides a reduction ration of 6:1, 8:1, 10:1 or more. In some embodiments, the worm gear set1206provides a reduction ratio of 10:1 such that the rotatable drive interface1207is rotated 6 complete revolutions to achieve 1 mm of growing rod1200expansion or contraction, with the amount of growth based upon a goal measure of 1.8 cm to 2.4 cm per year. Advantageously, a surgeon can fine tune the amount of expansion by either increasing or decreasing the amount of rotations. If a surgeon feels too much distraction has been incorporated, the growing rod1200can be reduced by simply reversing the direction of the driver.

FIG. 20is a top perspective view of a growing rod including a magnet in accordance with some embodiments. The growing rod1300advantageously comprises a combined magnet and worm gear set1306that can extend the length of the growing rod either by an external magnet or via a small incision with a manual driver. The surgeon thus has the option to extend the growing rod via the magnet, manual driver or both options, depending on the needs of a particular patient. In addition to this advantage, the worm gear itself helps to prevent inadvertent rotation (e.g., reverse rotation) of the gear set, thereby providing a stable growing rod1300. In some embodiments, the growing rod1300further includes a planetary reduction gear1319. The advantage of providing the planetary reduction gear1319(shown close up inFIG. 23) is that it provides greater gear reduction per rotation.

The growing rod1300comprises a housing1312attached to a cover plate1342. The growing rod1300further comprises an extendible rod1304extendible through the housing1312and a fixed rod1302. The extendible rod1304is capable of extending relative to the housing1312and cover plate1342, while the fixed rod1302is fixed relative to these two components. The fixed rod1302comprises an end cap1303that is operably attached to the cover plate1342. The cover plate1342encases the gear set1306, which in the present case advantageously includes both a magnet1308and a worm gear with a rotatable drive interface1307, as will be discussed in more detail below

FIG. 21is a top perspective of the growing rod ofFIG. 20with portions of the housing removed. From this view, one can see the inner threaded sleeve1332that is received in the housing1312. In some embodiments, the inner threaded sleeve1332has a first end and a second end, wherein the first end is operably attached to the worm gear1309. In some embodiments, the inner threaded sleeve1332is welded to the worm gear1309. In addition, the inner threaded sleeve1332includes inner threads that engage with a threaded portion1321formed on the body1322of the extendible rod1304. Advantageously, the worm gear1307can be rotated either magnetically or manually via a driver. Rotation of the worm gear1307causes the inner threaded sleeve1332(to which it is attached) to be rotated. As the extendible rod1304is threadingly engaged with the inner threaded sleeve1332, the extendible rod1304will thus rotate and linearly translate, thus allowing the growing rod1300to extend in length. Rotation of the worm gear1307in an opposite direction causes the extendible rod1304to retract.

The gear set1306comprises a number of components including a magnet1308, a worm including a rotatable drive interface1307, a worm gear1309and a planetary gear1319. The magnet1308is designed to extend radially from a longitudinal axis of the growing rod1300. The magnet1308can be engaged via an external magnet that causes rotation of the magnet1308and worm1307. By providing such a magnet, this advantageously provides a means for non-invasive growth of the growing rod1300. The worm including the rotatable drive interface1307comprises an interface that can be engaged by an external driver (e.g., a hex driver). By providing such a rotatable drive interface1307, this advantageously provides a means for minimally invasive growth of the growing rod1300. As shown inFIG. 21, the magnet1308and the rotatable drive interface1307will rotate together, whether via magnet or manual driver. As these components rotate, the worm gear1309will also be rotated around the longitudinal axis of the growing rod1300. As shown inFIG. 21, the worm gear1309can be operably attached to the planetary gear1319. The planetary gear1319advantageously allows for greater expansion of the growing rod1300with less rotations of the worm gear1309, thereby allowing the surgeon to expend less work during the procedure. In some embodiments, as shown inFIG. 21, a seal1329(e.g., an O-ring seal) can be received over the extendible rod1304to seal the housing1312from any migration of blood or bodily fluids.

FIG. 22is a close up view of the gear set of the growing rod ofFIG. 19. From this view, one can see the magnet1308, the cover plate eyelid1306housing the worm including the rotatable drive interface1307, the worm gear1309and the planetary gear1319. The worm gear1309and/or planetary gear1319can be attached to the inner threaded sleeve1332(not shown inFIG. 22), which is threadingly engaged with the extendible rod1304.

FIG. 23is a close up view of a planetary gear of the growing rod ofFIG. 19. The planetary gear1319comprises a gear hub1339engaged to a series of miniature gears1338a,1338b,1338c. Rotation of the gear hub1339causes the miniature gears1338a,1338b,1338cto rotate, thus causing the overall planetary gear1319to rotate.

In some embodiments, the growing rod1300can be implanted in either an up or down position and can be used singularly or in pairs. In some embodiments, the magnet1308and worm1306can be rotated 12, 14, 16, or 18 revolutions to achieve 1 mm of rod expansion or contraction, with the amount based upon a goal measure of 1.8 cm to 2.4 cm per year. The advantage of the growing rod1300is that it is designed to be implanted via use of bone screws (e.g., pedicle screws) as would a standard rod. The growing rod1300can be adjusted non-invasively with the magnet or via minimal incision. By providing a worm gear1309in conjunction with a planetary gear1319, a controlled adjustment can be accomplished and distraction forces more easily met. In some embodiments, the growing rod1300can be made of a metal such as stainless steel, cobalt chrome, or titanium.

It is to be understood that the disclosure describes a few embodiments and that many variations of the invention can easily be devised by those skilled in the art after reading this disclosure and that the scope of the present invention is to be determined by the following claims.