Rod template

A rod template for determining a curvature and a length of a spinal rod used for joining vertebrae in a spine fusion surgery in advance includes a core, a transparent outer tube, and a transparent filler. The core is made of metal and includes a scale on a surface thereof. The outer tube is made of silicone rubber and covers the core. The filler is made of liquid silicone rubber and inserted in a gap between the outer tube and the core to fill the gap.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Patent Application No. 2016-031029 filed on Feb. 22, 2016. The entire contents of the priority application are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a tool for a spinal fusion surgery.

BACKGROUND

A spinal fusion surgery that is one type of spine surgery has been known. In the spinal fusion surgery, vertebrae are joined together with spinal rods. The spinal fusion surgery is for spinal stenosis, spinal disc herniation, scoliosis, spinal cord trauma, spondylolisthesis or other spinal disorders.

A rod template may be used in the spinal fusion surgery. The rod template may include a core and an outer tube that covers the core. The rod template is used for determining a curvature and a length of the spinal rods that are used for joining the vertebrae. The core includes scale marks on the surface thereof. The length of the spinal rods is determined based on a measurement with the scale marks. The outer tube is used for restricting small metal pieces from spreading if cracking of the surface of the core occurs when the rod template is bent and such small metal pieces are produced from the cracking.

The outer tube is made of transparent material so that the scale marks on the core are visible through the outer tube. The known rod template may include a gap between the core and the outer tube. The gap may decrease visibility of the scale marks.

SUMMARY

The present invention was made in view of the foregoing circumstances. An object is to improve visibility of scale marks on a surface of a core of a rod template inserted in an outer tube.

A rod template for determining a curvature and a length of a spinal rod used for joining vertebrae in a spine fusion surgery in advance includes a core, a transparent outer tube, and a transparent filler. The core is made of metal and includes a scale on a surface thereof. The outer tube is made of silicone rubber and covers the core. The filler is made of liquid silicone rubber and inserted in a gap between the outer tube and the core to fill the gap.

According to technologies described herein, the visibility of the scale marks on the surface of the core of the rod template inserted in the outer tube improves.

DETAILED DESCRIPTION

An embodiment will be described according toFIGS. 1 to 14.

1. Configuration of Rod Template

A rod template10is a surgical tool for spinal fusion surgery. The rod template10is used for determining a curvature and a length of spinal rods81in advance. The spinal rods81are for joining vertebrae together in the spinal fusion surgery. The rod template10includes a core11that is a metal rod, an outer tube13, a filler15, and sealers17.

The core11is made of aluminum or aluminum alloy. The reason why the core11is made of aluminum or aluminum alloy is that an aluminum material is a soft metal material and thus the core11can be made more flexible and easier to deform in comparison to other metal material. The flexibility that the core11has allows the core11to be deformed into different shapes. An alumite treatment is performed on the core11to reduce corrosion. The surface of the core11is colored in black. The color of the surface of the core11is not limited to black. The surface of the core11may be colored other than black. The core11includes scale marks11aon the surface. The scale marks11aare at equal intervals in the axial direction. The scale marks11aare formed on the surface of the core11by scribing or printing.

The outer tube13is made of colorless and transparent biocompatible material, specifically, silicone rubber that is a material used for artificial blood vessels. The outer tube13covers and protects the core11. The outer tube13restricts small metal pieces from spreading if the surface of the core11cracks and such small metal pieces are produced when the rod template10is deformed. The outer tube13may have an outer diameter of 5 mm and an inner diameter of 3 mm. The core11may have a diameter of 3 mm. Silicone is a polymer including synthetic compound made up of repeating units of siloxane.

The filler15is made of liquid silicone rubber. The liquid silicone rubber is a kind of rubber having a property to turn into an elastomer with cross-links at a temperature in a range from room temperature to about 60° C., which is a relatively low temperature range. Before cross-lining occurs, the liquid silicone rubber has low viscosity and shows flowability. There are room-temperature curing-type and thermosetting-type liquid silicone rubbers classified according to response temperatures. The filler15in this embodiment is a room-temperature curing-type liquid silicone rubber, specifically, a one-component condensed-type room temperature vulcanizing (RTV) silicone rubber. The term “one-component” refers to a component including a base agent and a curing agent (a cross-linking agent) therein. The term “condensed-type” refers to a type that the curing agent (the cross-linking agent) is activated by moisture in the air and reaction progresses.

The filler15is inserted in the outer tube13to fill a gap between the inner surface of the outer tube13and the outer surface of the core11. The filler15is colorless and transparent, similarly to the outer tube13. The reason why the rubber is used for the outer tube13and the filler15is to restrict the outer tube13and the filler15from breaking when the core11is deformed. The outer tube13has flexibility that allows the outer tube13to curve along the core11together with the filler15when the rode template10is deformed into a different shape.

The sealers17are disposed at ends of the outer tube13, respectively, to seal the ends of the outer tube13. The sealers17are made of the liquid silicone rubber.

The rod template10is produced as follows. The filler15is applied to an entire surface of the core11. The core11with the filler15on the surface of the core11is inserted in the outer tube13. The filler15hardens at the room temperature in response to the moisture in the air and turned into a transparent elastomer. The filler15is integrated with the outer tube13in the process of curing. The filler15forms a transparent filling layer with which the gap between the outer tube13and the core11is filled (seeFIGS. 4 and 5).

After the core11is inserted in the outer tube13, the sealers17are fitted in the ends of the outer tube13from the outside. The fillers17harden in response to the moisture in the air and form sealing layers at the ends of the outer tube13. Then, the rod template10is complete.

2. Relationship Between the Filler15and the Visibility of the Scale Marks11

A rod template20illustrated inFIG. 6is an example comparative to the rod template10. The rod template20includes a core11and an outer tube13having the same configuration as those of the core11and the outer tube13of the rod template10. The rod template20does not include the filler15(or a filling layer), that is, a gap remains between the outer tube13and the core11without being filled.

As indicated with an arrow inFIG. 6, some rays of light reflected off the surface of the core11are reflected by the inner surface13aof the outer tube13because the gap remains between the outer tube13and the core11. Therefore, the rays of light are less likely to pass through the outer tube13. Because a smaller amount of light reaches viewer's eyes in comparison to the rode template10, the visibility of the scale marks11aon the core11is more likely to decrease.

As illustrated inFIG. 5, the rod template10includes the filler15(the filling layer) with which the gap between the outer tube13and the core is filled. Furthermore, the filler15and the outer tube13are made of the silicone rubbers including silicone polymers as base components. Namely, the base components of the filler15and the outer tube13are the same kind of base components.

With the filler15including the same base component as that of the outer tube13, refractive indexes of the outer tube13and the filler15are about equal to each other. Furthermore, the filler15integrates with the outer tube13as the filler15hardens. As illustrated inFIG. 5, some rays of light reflected off the surface of the core11are less likely to be reflected by the inner surface13aof the outer tube13. Namely, the rays of light are more likely to be passed through the outer tube13. A larger amount of light reaches the viewer's eyes and thus the visibility of the scale marks11aimproves.

3. Example of Spine Fusion Surgery

As illustrated inFIGS. 7 to 9, a lumber spine50includes the first lumber vertebra51, the second lumber vertebra52, the third lumber vertebra53, the fourth lumber vertebra54, and the fifth lumber vertebra55.

The spine fusion surgery is for joining some of the lumber vertebrae51to55with spinal rods81. A procedure of the spine fusion surgery for joining the second lumber vertebra52through the fourth lumber vertebra54will be described below.

In the spine fusion surgery, screws71are fixed to the target vertebrae of the lumber spine50. The screws71are made of titanium alloy or unalloyed titanium. As illustrated inFIG. 13, each screw71includes a shank73and a head75. The head75includes a holding portion75afor holding the spinal rod81. The holding portion75aincludes a U-shaped groove.

Specifically, as illustrated inFIG. 7, the screws71are fixed to the second lumber vertebra52through the fourth lumber vertebra54on the right side and the left side. As illustrated inFIG. 12, two screws71are screwed into each of the lumber vertebrae52through54from pedicles of vertebral arches63to a vertebral body61.

After the screws71are fixed, determination of a curvature and a length of the spinal rods81is performed using the rod template10. The curvature and the length of the spinal rods81are determined in advance to the joining of the lumber vertebrae52through54. Specifically, as illustrated inFIG. 8, the rod template10is bent to be fitted in the holding portions75aof the screws71that are fixed to the second lumber vertebra52through the fourth lumber vertebra54, the positions of which are corrected to proper positions. Furthermore, the length of the spinal rods81corresponding to a length from the second lumber vertebra52through the fourth lumber vertebra54is determined in advance according to reading of the scale marks11aon the rod template10. InFIG. 8, the core11is in white for an illustration purpose. However, the actual color of the core11is black.

The spinal rods81are made of titanium alloy or unalloyed titanium. The spinal rods81are straight before processed. The spinal rods81are bent by a bending machine (not illustrated) into a shape corresponding to the shape of the rod template10. Then, the spinal rods81are cut in the length determined in advance using the rod template10.

Two spinal rods81are used for fixing the right side and the left side of the lumber spine50. Two spinal rods81are prepared for fixing the right side and the left side of the lumber spine50. As illustrated inFIGS. 14A and 14B, spinal rods81A and81B having different lengths are prepared. The spinal rods81A or the spinal rods81B having the length closer to the length determined using the rod template10are used as the spinal rods81.

As illustrated inFIG. 9, the spinal rods81are fitted in the holding portions75aof the screws71fixed to the second lumber vertebra52through the fourth lumber vertebra54. Plugs85are fixed to the holding portion75aof the screws71. The plugs85are screwed into the holding portions75aand fixed.

With the plugs85fixed to the holding portion75a,the spinal rods81are less likely to be removed from the holding portions75a.This procedure is performed on the both sides of the lumber spine50. As a result, the second vertebra52through the fourth lumber vertebra54are joined with the spinal rods81.

The rod template10has a configuration including the gap that is filled with the filler15between the outer tube13and the core11. The filler15and the outer tube13are made of the silicone rubbers including the silicone polymers as the base components. Namely, the base components of the filler15and the outer tube13are the same. As illustrated inFIG. 5, some rays of light reflected off the surface of the core11are less likely to be reflected by the inner surface of the outer tube13and thus more rays of light are passed through the outer tube13. Therefore, the larger amount of light reaches the view's eyes. According to the configuration, the visibility of the scale marks11aimproves.

The filler15is made of the liquid silicone rubber having the flowability in the state before reacted to the moisture in the air. With the filler15, friction between the core11and the outer tube13decreases and the core11can be smoothly inserted into the outer tube13. Therefore, the core11is easily fitted in the outer tube13.

OTHER EMBODIMENTS

The scope of the present invention is not limited to the above embodiment. The following embodiments may be included in the scope of the present invention.

(1) The technology described herein can be applied to a thoracic spine100illustrated inFIG. 13and a cervical spine110illustrated inFIG. 14.

(2) The filler15may be made of two-component condensed-type RTV silicone rubber. The filler15may be made of any liquid silicone rubbers including a thermosetting liquid silicone rubber.

(3) The core11may be made of any plastically deformable metal materials, for example, stainless steel. The core11may be made of shape-memory alloy such as nickel titanium (Ni—Ti) alloy. Because the shape-memory alloy recovers its original shape when the shape-memory alloy is heated to a shape recovery temperature, it is preferable to use the shape-memory alloy for the rod template10that is repeatedly used. Namely, because the deformed rod template10recovers its original shape through heating, it is not necessary to manually reshape the rod template10. Furthermore, the rod template10is cleaned after use and a high-pressure steam sterilizing process (an autoclave sterilizing process) may be performed on the cleaned rod template10. If the shape recovery temperature is set below a sterilizing temperature at which the high-pressure steam sterilizing process is performed, the recovery of the shape of the rod template10can be complete in the sterilizing process. If the shape recovery temperature is set equal to the sterilizing temperature, whether a temperature of the steam is increased to a target temperature can be determined based on whether the rod template10recovers its original shape. Namely, if the original shape of the rod template10is observed, it can be assumed that the temperature of the steam has reached the target temperature.

(4) The sizes of the outer tube13and the core11are not limited to those described above. Furthermore, the outer tube13can be tinted as long as the outer tube13is transparent.

(5) The filler15may not be transparent before the filler15is cured. The filler15can be tinted as long as the filler15is transparent when the filler15is cured.