DE20203439U1 - Surgical navigation screwdriver with fixing sleeve for screws with externally threaded heads has removable grip, integral tracker attachment sleeve for navigated computer-assisted applications - Google Patents

Abstract

The surgical navigation screwdriver has a screw-on screw fixing external sleeve for screws with externally threaded screw heads and a removable grip part with an integrated tracker attachment sleeve for navigated computer-assisted applications. The screwdriver's tip is designed for the different common screw versions.

Description

Navigation screwdriver with fixing sleeve for screws with external screw head thread

The invention relates to a screwdriver with an optional tracker attachment sleeve of the removable handle for use in conjunction with a navigation system with the option of fixing a screw with an external screw head thread via an external sleeve with a distal internal thread. By mounting and tightening the external sleeve onto the external screw head thread clockwise, the outer sleeve tightens further when attempting to remove the screw, which is firmly seated in the bone, in an anti-clockwise direction, thus providing an additional increase in the connection with the screw, which makes screw removal easier.

Background of the invention

In the field of surgical orthopedics and traumatology, it is common practice to fix bone fragments or osteosynthesis implants (e.g. plates, etc.) with screws after the desired repositioning has been achieved. The state of the art is, on the one hand, to make ever smaller surgical accesses (= incisions). This minimally invasive procedure is gentler on the patient and can significantly shorten their hospital stay and recovery time. Examples of this are laparoscopic gallbladder removal or arthroscopic meniscus removal. Numerous special anchoring systems and instruments have been developed especially for arthroscopic procedures, for example to fix soft tissue such as ligaments or tendons to bones.

On the other hand, the increasing use of computer technology has recently led to a previously unattainable level of operational precision. This completely

This new field in medicine is described with terms such as "computer-assisted surgery" or "navigated surgery". In principle, the surgeon is able to orient himself on the patient during an operation with the help of previously taken computer tomography or fluoroscopy X-ray images in order to be able to insert his instruments or implants precisely. The position of the patient and the instruments used are located by an infrared camera, for example. Other systems are based on the location of electromagnetic signals. This process is commonly referred to as "tracking". With optical tracking, the infrared camera can send out infrared (IR) signals, which are reflected back by reflector beads and can then also be located by the IR camera. These reflector beads are reversibly attached to a holding device in a defined geometric arrangement. This construction is generally referred to as a passive "tracker" because it does not emit any IR signals itself. Instead of reflector beads, an active tracker has its own IR LEDs, which "actively" send out IR signals to the IR camera. Active trackers currently have the disadvantage that they have a cable, which some surgeons may find annoying during the operation. For navigation, the position of the patient and the instrument used must be known, which is why both must be equipped with a tracker each. If the movement of separate parts of the patient's body is to be tracked (or "tacked"), it may be necessary to use more than one patient tracker. All current position information and the previously taken X-ray images of the patient are recorded and processed by a computer. Before successful navigation can take place, the previously recorded virtual patient image data must be compared with the real anatomical patient data, which is referred to as "registration".

When the navigation system is used intraoperatively, the surgeon is shown the previously created patient image data on the computer monitor with the instrument projected above it as a computer graphic. Theoretically, the doctor could rely entirely on the computer display during the operation without comparing the position of the instrument with the actual patient anatomy - as is normally the case.

The number of possible applications is constantly growing and requires new and modified instruments and tools to be fully utilized.

Simple screwdrivers without the option of fixation have the disadvantage that screws can be lost in the site before reaching the target location, meaning that the minimally invasive procedure that may have been started must be abandoned in order to remove the incorrectly placed screw. To avoid losing the screw and possible soft tissue damage to the surrounding tissue, a soft tissue protection sleeve can be used, as described in U.S. Pat. 5,904,685 and U.S. Pat. No. Des. 398,996.

Another simple solution is a holding clamp for the screw and screwdriver (e.g. U.S. Pat. No. 5,391,181). However, this is not suitable for minimally invasive procedures because the holding clamp must be held directly in the area of the screw entry area.

In computer-assisted surgery, instruments are represented as defined models in the computer. An intraoperative deviation from this can pose a threat to the patient, as the surgeon is shown an instrument location that does not correspond to reality. The instrument is defined in the computer as a rigid body. A screwdriver alone easily meets this requirement. However, if a screw is to be inserted into the patient, the screwdriver and screw must meet the principle of the "rigid body" in order to enable precise work. A conventional screwdriver without the option of screw fixation does not meet these requirements and therefore cannot be used effectively for minimally invasive or computer-assisted interventions. There is a need for a screwdriver with a mountable active or passive tracker attachment, as well as a screw fixation option.

After a bone fracture has healed, the previously inserted osteosynthesis material usually needs to be removed, as once it has fulfilled its holding function it only represents a foreign body for the patient and can cause various problems.

If the screw has grown firmly into the bone, it may be difficult to remove. Particularly if the screwdriver is not inserted completely orthograde into the screw head, the screw head may twist and the recessed socket may be destroyed. This makes it impossible to remove the screw with the screwdriver and requires more complex measures on the part of the surgeon, e.g. overdrilling the screw. In addition to the not insignificant additional trauma for the patient with possible resulting local instability, this procedure involves a considerable amount of additional time, which ultimately results in additional costs for the hospital.

Screwdrivers with holding devices are well known and widely used in everyday surgical practice. Most of these devices are designed for screws with conventional screw heads in order to fulfil their purpose of attaching the screw to the screwdriver. For example, in the following patents, a different type of outer sleeve is screwed or placed over the screwdriver shaft, which encloses and clamps the screw head: U.S. Pat. No. 6,189,422 Bl; U.S. Pat. No. 5,649,931; DE 37 14 994 Cl; DE 32 38 588 Al; DE35 39 502 Cl and DE 38 16 718 C2

In U.S. Pat. No. 5,056,387, the screw head is inserted through a lateral slot in an outer sleeve and screwed and clamped into the lower part of the outer sleeve from the proximal side.

Other designs require specially shaped screw types: U.S. Pat. No. 5,484,440 describes a screwdriver with a lockable screw holding sleeve for a bone screw, which has a trough-shaped recess in the screw head that runs through the screw head, similar to the pedicle screws used in spinal surgery. There, this recess is used to insert connecting rods.

U.S. Pat. No. 6,286,401 Bl has a lockable screw fixation outer sleeve that is placed on a hexagonal screw head shape.

A special system especially for the implantation of a bone screw in the cartilage-containing joint area, e.g. in the case of osteochondritis dissecans in the area of the distal femoral condyle, is presented by Huene in U.S. Pat. No. 4,693,144: The screw used for this does not have a recess in the middle of the screw head like conventional screws do, so that a conventional screwdriver can be inserted there. Rather, this smooth screw head shape is preferred in order to create the smoothest possible surface - ideally flush with the adjacent cartilage tissue - after insertion into the area near the joint. In order to be able to insert and tighten this screw, it has an external screw head thread. The screwdriver consists of an inner rod that sits on the flat screw head and an outer sleeve that can be screwed on proximally and which also has an internal thread distally in order to be able to accommodate the screw head with the milled external thread. In contrast to the invention presented, this construction does not represent a conventional screwdriver with an additional fixation sleeve and does not have a device for holding a tracker in order to be able to use it for navigation purposes.

U.S. Pat. No. 6,214,050 Bl and U.S. Pat. No. 5,531,792 also came from Huene. These similar constructions aim to achieve a stable anchoring in the bone by spreading the construction. For this purpose, a centrally located screw can be turned, which expands the surrounding outer sleeve after being placed in the bone when tightened. This anchor outer sleeve has an external thread at the proximal end, which is prevented from rotating and moving in the bone by a screw-on sleeve of the screwdriver. The construction is such that when the outer sleeve of the anchor construction is fixed, only the centrally located screw is turned to expand it and anchor it in the bone.

A conventional screw used in standard orthopedic and traumatological applications (e.g. cortical or cancellous bone screw) has a screw head that has a smooth-edged, roughly hemispherical or conical shape with an enclosed recess to accommodate, for example, a slotted, Phillips or Allen screwdriver.

A special type of screw, however, is used in the area of angle-stable osteosynthesis, for example. In order to create a firm connection between an inserted screw and an osteosynthesis plate, the screw head has a thread that fits into the plate hole, which also has a thread. An example of this type of angle-stable osteosynthesis in the spine area is U.S. Pat. No. 5,290,288. For mandibular applications, U.S. Pat. No. 6,325,803 describes an angle-stable plate osteosynthesis form.

Screws with externally threaded screw heads are also used as pedicle screws in spinal surgery, for example to attach connecting rods to the pedicle screw heads with a locking nut (e.g. U.S. Pat. No. 6,179,838). A special instrument for placing a nut on a pedicle screw with an externally threaded screw head is described in U.S. Pat. No. 5,352,231.

Screw heads with an internal thread are used in oral and maxillofacial surgery to attach implants (e.g. dentures) to them (e.g. U.S. Pat. No. 5,102,414).

The invention described here uses the screw type with an external screw head thread to reversibly connect the screwdriver presented here to the screw. This can also be cannulated in order to be used in minimally invasive, non-navigated applications. For this purpose, a Kirschner wire is drilled into the target area beforehand, over which the screw is inserted.

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Construction

Fig.l shows the assembled screwdriver with the (passive) optical tracker attachment attached.

Fig.2 shows the individual components in disassembled state. The numbering is valid for both drawings.

The screwdriver part is largely similar to that of a conventional screwdriver, consisting of a shaft 8, e.g. with a flat, cross or Allen tip 10. The entire screwdriver or just the screwdriver shaft 8 can also be cannulated, i.e. drilled through, for the use of cannulated screws 12. Cannulated screws are inserted after a Kirschner wire has been inserted into the bone. A self-tapping screw can then be inserted over this without first drilling a guide channel into the bone. In the proximal shaft area there is a circumferential ring-shaped expansion 6 _; which limits the movement of the outer sleeve 15 distally. This ring-shaped expansion 9 also exists distally in order to center the screwdriver shaft 8 in the fixation outer sleeve 15.

The removable screwdriver handle 1 can accommodate an outer sleeve 5 distally, to which, for example, an active (with infrared LEDs) or passive (with reflector beads) optical "tracker" 3 for a navigation system can be attached. This sleeve 5 has no fixed connection to the screwdriver shaft 8, unlike the main part of the screwdriver handle 1, and is particularly necessary for optical tracking systems, since there must be a permanent, unobstructed line of sight between the infrared camera and the tracker, which would no longer be possible with a tracker permanently mounted on the handle during the screwdriving process. The proximal end of the screwdriver shaft 7 can have a bayonet lock or similar mechanism in order to be firmly connected to the

Screwdriver handle. In the simplest case, the proximal end of the screwdriver shaft has a square shape 7, onto which the counterpart 2 in the screwdriver handle is placed.

The screw fixation outer sleeve 15, which can be attached to the screwdriver shaft 8, has a hollow cylinder shape that is open distally and has an internal thread at the distal opening 16 in order to be able to accommodate the screw head external thread of the special screw 12. The fixation sleeve 15 is prevented from being screwed onto the screw head 11 beyond what is necessary by the proximal end of the fixation sleeve 13 striking the prepared protuberance on the screwdriver shaft 6. A handle 14 is formed around the proximal end of the screw fixation outer sleeve, which makes it easier to screw the sleeve onto and off the screw head 11.

Application

First, assemble the screwdriver:

The screw fixation outer sleeve 15 is inserted from the proximal side over the screwdriver shaft 8.

For use with a navigation system, a tracker 3 is placed and secured on an attachment 4 provided for this purpose on the tracker sleeve 5 of the screwdriver handle 1. The screwdriver handle 1 with the previously mounted tracker 3 is now connected to the screwdriver shaft 8 with screw fixation outer sleeve 15.

To insert a screw into a bone, the screwdriver tip 10 is first inserted into the screw head. Then the screw fixation outer sleeve 15 is screwed clockwise (by the user) onto the screw head 11. The ring-shaped expansion on the proximal

Screwdriver shaft 6 limits the screwing on of the fixation sleeve beyond the distal end of the screw head. The ring-shaped expansion in the distal area of the screwdriver shaft 9 centers the shaft 8 in the outer fixation sleeve 15. This means that the outer sleeve 15 cannot become jammed once the screwdriver tip 10 is properly seated in the screw head 11. If the fixation sleeve 15 now sits firmly on the screw head 11, a stable connection between the screwdriver and the screw 12 is achieved.

Now screw 12 can be inserted by turning the screwdriver, usually also clockwise. While screwing it in, the tracker can be fixed with the left hand to ensure a line of sight to an infrared camera if necessary.

To remove the screw, first proceed as above:

It begins with inserting the screwdriver tip 10 into the screw head 11 and screwing the fixation sleeve 15 onto the screw head 11 in a clockwise direction. The screw 12 is then removed, usually by turning the screw anti-clockwise. If the screw 12 is firmly seated in the bone, twisting the screwdriver tip 10 in the screw head 11 with the screw fixation outer sleeve 15 screwed on is not possible under normal circumstances. In addition to the screwdriver tip 10, the external thread of the screw head 11 is now used to further increase the connection between the screwdriver and screw 12. Turning the screwdriver anti-clockwise with the screw 12 and fixation sleeve 15 fixed corresponds to further tightening the fixation sleeve 15 onto the screw head 11 in a clockwise direction.

The simple design allows the instrument to be easily cleaned and sterilized. For this purpose, the screwdriver can easily be disassembled into its few basic components mentioned above. The screwdriver presented here is also suitable for cases in which no special screws with an external screw head thread or cannulation are used. The use of a navigation system is also a basic requirement for using the screwdriver presented here.

Claims (12)

1. Screwdriver with screw-on screw fixation outer sleeve for screws with external screw head thread and removable handle with integrated tracker attachment sleeve for navigated computer-assisted applications. 2. Screwdriver according to claim 1, characterized in that the screwdriver tip is designed according to the various common screw designs. 3. Screwdriver according to one of claims 1-2, characterized in that the screwdriver or a part thereof can be cannulated to enable the use of cannulated screws over a Kirschner wire. 4. Screwdriver according to one of claims 1-3, characterized in that the screwdriver shaft has a proximal annular protuberance which limits the distal movement of the fixation outer sleeve. 5. Screwdriver according to one of claims 1-4, characterized in that the screwdriver shaft has an annular protuberance in the distal region proximal to the screwdriver tip in order to center it in the fixation outer sleeve. 6. Screwdriver according to one of claims 1-5, characterized in that the screwdriver shaft can be reversibly separated from the screwdriver handle. 7. Screwdriver according to one of claims 1-6, characterized in that a screw fixation outer sleeve is inserted from proximally over the screwdriver shaft and can be reversibly removed before the screwdriver handle is placed on the shaft. 8. Screwdriver according to one of claims 1-7, characterized in that the screw fixation outer sleeve has a distal internal thread which fits onto the associated screw head external thread. 9. Screwdriver according to one of claims 1-8, characterized in that the screw fixation outer sleeve has a cylindrical shape which is open towards the distal end and has a proximal passage opening for the screwdriver shaft which has a smaller diameter than the limiting ring in the region of the proximal screwdriver shaft. 10. Screwdriver according to one of claims 1-9, characterized in that the screwdriver shaft has an annular protuberance distally in order to center it in the fixation outer sleeve. 11. Screwdriver according to one of claims 1-10, characterized in that the screw fixation outer sleeve has a handle on the proximal outside to facilitate screwing and unscrewing it onto a screw head. 12. Screwdriver according to one of claims 1-11, characterized in that the removable handle has an outer sleeve for a navigation tracker attachment distally, which is rotatably and movably arranged around the handle.