Source: https://patents.justia.com/patent/20080039841
Timestamp: 2020-01-26 12:06:32
Document Index: 367836401

Matched Legal Cases: ['art 18', 'art 18', 'art 18', 'art 44', 'art 43', 'art 44', 'arts 39', 'art 39', 'art 41', 'art 39']

US Patent Application for DISTANCE MEASURING INSTRUMENT FOR PEDICLE SCREWS Patent Application (Application #20080039841 issued February 14, 2008) - Justia Patents Search
Justia Patents US Patent Application for DISTANCE MEASURING INSTRUMENT FOR PEDICLE SCREWS Patent Application (Application #20080039841)
Oct 2, 2007 - ZIMMER GMBH
The invention relates to a distance measuring instrument for pedicle screws which detects the spacing between two pedicle screws (3, 3′) with the ends (26, 27) of two crossing limbs (11, 12) and displays it on a crossbar (25) fixedly connected to one of the limbs at a scale (22). Since the second limb (12) is divided into a pointer (16a) and into a flexural spring extending parallel to it at which a pronounced thumb grip (21a) is fastened, and since the thumb grip is connected to a scale (24) via which a pre-determined pre-tension can be read off relative to the pointer (16a), a spacing measurement can take place under a controlled pre-tension.
The two limbs 11, 12 cross at an axis of rotation 13. A cross bar 25 made of plastic is screwed to the first limb 11 opposite to its end 26 and first projects laterally as a scale part 18 with a curvature in the form of an arc of a circle with the axis of rotation 13 as the centre point and merges into a handle 20. The two limbs 11, 12 are made of metal, for example of a non-rust steel. The first limb is fastened to the crossbar 25 by screws 19. The second limb 12 is guided in an elongate slot 32 of the crossbar 25 and split in its longitudinal direction into two components, a pointer 16a and a flexural spring 15 which are both captured in the elongate slot 32. The flexural spring 15 extends parallel to the pointer 16a, is fastened to the second limb 12 by screws (not shown), for example, and is fixedly connected at its upper end to a thumb grip 21a projecting above the crossbar 25. The pointer 16a has at its upper end an arrow marking 23 which indicates the spacing of the two ends 26, 27 on a scale 22 of the arc-shaped scale part 18. When the handle 20 is gripped by the hand and the flexural spring 15 is drawn towards the hand by the thumb grip 21a, a pre-tension arises at the ends 26, 27 of the limbs 11, 12 which corresponds in a tactile manner to a feedback on the contacting of the ends 26, 27 at the pedicle screws 3, 3′, with the spacing of the ends being able to be read off at a pre-determined pre-tension because a scale 24 has been attached to the thumb grip 21a at which the pre-tension can be read off relative to the arrow marking 23 of the pointer 16a. An advantage of the device consists of the fact that it can be operated with one hand and leaves the second hand free for the surgeon for additional manipulations such as the holding back of tissue parts standing in the way.
A further embodiment is shown in FIGS. 4 to 9 in which further improvements to the embodiment of FIG. 3 are included. The same reference numerals have been used as in FIG. 3. The elongate slot 32 (FIGS. 5 and 9) divides the curved scale part 18 of the crossbar 25 into a front part 44 and into a rear part 43. A continuous, curved groove 33 has been applied in the front part 44 and a key 14, which itself has a friction brake, is displaceably supported in this in order to be taken along in the spreading direction as a trailing pointer 17 by the pointer 16a. For this purpose (FIG. 9), a dog 45 is attached to the key 14 which projects into the elongate slot 32 and is taken along by the pointer 16a. The actual key 14 is, for example, inserted from the side of the elongate slot 32 and secured from the front by a trailing pointer 17 screwed on as a securing plate. On the drawing of the thumb grip 21a, the trailing thermometer 17 is taken along by the pointer 16a. If the ends 26, 27 now meet the resistance of the pedicle screws, the flexural spring can be pre-tensioned so much via the thumb grip until a pre-determined tension has been reached. At this tension, the largest spacing also occurs between the two pedicle screws 3, 3′. On the subsequent relief of the thumb grip, the trailing pointer remains at the position of the largest spacing and thus stores the measured value without any influencing taking place on the further moving together of the tips 26, 27, for example for the releasing of centring projections 36 from the passage bores 31 of pedicle screws.
The scale 24 for the reading of the pre-tension is attached to a hook 28 bent out of the thumb grip 21a which is partly guided around the pointer 16a in order to avoid over-straining of the flexural spring 15 in that the hook 28 abuts the pointer 16a. This means that the pointer 16a must be so stable that it is also not plastically deformed on non-professional handling of the thumb grip 21a. In FIGS. 6, 7 and 8, alternatives are shown in the region of the ends 26, 27 of the limbs 11, 12. Both limbs 11 and 12 are cranked toward the end and have projections 29, 30 offset laterally relative to the spreading direction which each form the end. The lateral offset has the advantage that the whole distance measuring instrument is arranged laterally offset relative to the pedicle screws and does not take up the space directly above the pedicle screws for itself. Furthermore, the projections 29, 30 have opened guiding forks 34, 35 in the spreading direction with which they can be guided from the outside up to the head of the pedicle screw at a slight pre-tension along centring parts 39 or along tubular tools which sit at the head of the pedicle screw. Such a centring part 39 is shown with its under end in FIG. 6. It has been screwed into the thread provided for a clamping screw 6 and tapers from a cylindrical start via a cone 40 up to a flexurally elastic central part 41. The cable 7 is already fixed by a clamping screw 6 in FIG. 8. A tubular mating holder having an internally guided screwdriver which is described in a parallel application can be used for the fixing. Such a mating holder is supported in a shape matched manner in notches 10 of the head 4 and is continued upwardly in tubular shape. If this mating holder is left in position after the screwing in of the clamping screw 6, it can be used like the centring part 39 for the guiding of a lateral projection 30 with a guiding fork 35 on its way to the pedicle screw. The end 26 is made to form a fork 42 which is centred at the drawn in cable 7. The pre-tension to the pedicle screw is applied via pressure zones 38 which are arranged at both sides of the cable 7 at the fork 42.
16a pointer
21a thumb grip
11. A distance measuring instrument for pedicle screws, comprising first and second limbs which cross at an axis of rotation and whose ends can be positioned at two pedicle screws screwed into adjacent spinal vertebrae, with the first limb including a scale part at its opposite end, the scale part being formed as a first pointer to display a spacing between two pedicle screws with the first pointer at a first scale of the scale part, wherein the second limb includes a second pointer and a spring and wherein the scale part is incorporated into a handle configured to produce a spreading force at the ends via the spring, the spreading force being readable relative to the second pointer via a second scale.
12. A distance measuring instrument in accordance with claim 1, wherein the scale part includes an arc-shaped crossbar of the first limb.
13. A distance measuring instrument in accordance with claim 1, wherein the spring is a flexural spring.
14. A distance measuring instrument in accordance with claim 1, wherein the first limb includes an elongate slot, the second limb being guided relative to the first limb in the elongate slot.
15. A distance measuring instrument in accordance with claim 1, wherein the scale part includes a groove and the second pointer includes a key defining a trailing pointer guided along the groove, the trailing pointer showing the spacing of the ends of the first and second limbs on the first scale, the key remaining in place at a maximum spacing measured.
16. A distance measuring instrument in accordance with claim 1, wherein at least one of the ends of the first and second limbs is designed as a fork configured to be centered at a band or cable drawn through a head of a pedicle screw.
17. A distance measuring instrument in accordance with claim 1, wherein at least one of the ends of the first and second limbs includes a hemispherical projection configured to be centered at a passage bore in a head of a pedicle screw.
18. A distance measuring instrument in accordance with claim 1, wherein the first and second limbs define respective first and second axes, the first and second limbs including respective first and second projections respectively laterally offset relative to the first and second axes.
19. A distance measuring instrument in accordance with claim 18, wherein the projections define adapter pieces pushable onto the limbs.
20. A distance measuring instrument in accordance with claim 18, wherein each of the projections includes a guide fork oriented in a spreading direction, the projections configured to guide the respective ends of the first and second limbs to a head of a pedicle screw along a centering part thereof screwed into the head of the pedicle screw.
21. A distance measuring instrument in accordance with claim 1, wherein the second limb includes a thumb grip, the second scale being configured for reading of pre-tension and being attached to a hook that engages behind the second pointer to prevent overstraining of the spring by the thumb grip.
22. A distance measuring instrument in accordance with claim 1, wherein the first limb includes a crossbar having a plastic, the first and second limbs including a metal.
23. A method of measuring a distance between pedicle screws, comprising:
providing a distance and force measuring instrument, the distance and force measuring instrument comprising:
first and second limbs which cross at an axis of rotation, with the first limb including a scale part, the scale part being formed as a first pointer to display a spacing with the first pointer at a first scale of the scale part, wherein the second limb includes a second pointer and a spring; and wherein the scale part is incorporated into a handle configured to produce a spreading force via the spring, the spreading force being readable relative to the second pointer via a second scale;
coupling ends of the instrument to at least two pedicle screws;
applying a spreading force to the pedicle screws via the spring of the handle;
reading the spreading force indicated by the second pointer on the second scale; and
reading the spacing indicated by the first pointer on the first scale.
selecting an implant based on the spacing indicated by the first pointer on the first scale.
25. A method in accordance with claim 24, wherein the implant includes at least one of a cable and an element for bridging the distance between the pedicle screws.
26. An intervertebral implantation system comprising:
first and second pedicle screws configured for implantation into adjacent vertebrae;
a bridging element configured for coupling to the first and second pedicle screws; and
an instrument for measuring a distance between the first and second pedicle screws, the instrument including first and second limbs which cross at an axis of rotation and whose ends can be positioned at the first and second pedicle screws screwed into the adjacent vertebrae, with the first limb including a scale part at its opposite end, the scale part being formed as a first pointer to display a spacing between the pedicle screws with the first pointer at a first scale of the scale part, wherein the second limb includes a second pointer and a spring and wherein the scale part is incorporated into a handle configured to produce a spreading force at the ends via the spring, the spreading force being readable relative to the second pointer via a second scale.
27. A system in accordance with claim 26, wherein the bridging element is flexible.
Publication number: 20080039841
Patent Grant number: 8257362
Inventors: Simon Casutt (Gossau), Nimrod Meier (Schaffhausen), Marc Huber (Turbenthal)
Application Number: 11/866,197
Current U.S. Class: 606/61.000; 606/102.000