JP7643864B2 - Percutaneous Total Endoscopic Discectomy Instruments - Google Patents

Description

The present invention relates to an instrument for removing intervertebral discs used in lumbar interbody fusion surgery using a percutaneous total endoscope.

There is a method of using a percutaneous total spinal endoscope in minimally invasive spinal surgery. As shown in Figures 1 and 2, the main body 901, which is the part inserted into the body, is a long and thin cylinder with an outer diameter of approximately 6 to 7 mm, inside which the telescope tube 902, light source path 903, irrigation water channel 904, and working lumen 905 are integrated. An outer tube 906 is inserted into the body from a skin incision S, and the main body 901 is inserted into it. Water is run through the irrigation water channel 904 to wash the area around the target, while an image from a connected camera is enlarged and displayed on a monitor, and an instrument such as a grasping forceps 800 inserted into the working lumen 905 is used to operate on the vertebrae B, intervertebral disc D, etc. The instruments that can be inserted into the working cavity 905 are those with a basic external shape of a thin cylinder with an outer diameter of about 2.5 mm to 4 mm and a length of about 200 mm to 400 mm, such as the grasping forceps shown in Figure 3, and are equipped with a handle 850, a fixed jaw 810, and a movable jaw 820 that opens and closes, etc., on a shaft 830. Instruments that are originally curved cannot be inserted.
The spine is an area where nerves are concentrated, and the routes for safely entering the intervertebral discs are limited to a specific, small area. The percutaneous total endoscope is a long, thin instrument that can pass through this small, safe area.

Lumbar interbody fusion, which is performed for lumbar spondylolisthesis and lumbar disc degeneration, is generally a procedure that involves interbody bone grafting and posterior screw fixation, as shown in Figure 4. Interbody bone grafting involves removing most of the intervertebral disc D between vertebral bodies B, inserting a box-shaped spacer called a cage 910 into the space, filling the cage with bone tissue for transplantation, and then performing bone grafting around the cage. Posterior screw fixation involves immobilizing adjacent vertebral bodies using a screw 911 inserted into the bone tissue of the vertebral arch L and vertebral body B, and an attached bar 912. Lumbar interbody fusion allows bone fusion between the vertebral bodies, alleviating symptoms. When performing interbody bone grafting, it is necessary to remove most of the intervertebral disc that inhibits bone fusion. To do this, a relatively sharp object must be pressed with great force against the boundary between the intervertebral disc and the bone and moved along the bone surface to peel the disc off the bone surface. The intervertebral disc is attached to the bone surface, so the instruments need to be strong and rigid.

There is a method of performing lumbar interbody fusion surgery using a percutaneous total endoscope (Non-patent paper 1 described below). Using a percutaneous total endoscope, surgery can be performed with much less invasiveness than conventional lumbar interbody fusion surgery, but as mentioned above, the instruments that can be used are long and slender, and therefore have limitations in strength and rigidity.
In addition, while it is necessary to remove a wide area of the intervertebral disc, the route to the intervertebral disc is smaller than that, and the movement of the percutaneous total endoscope is restricted by bones, muscles, fascia, etc., so the reachable range of the instrument is limited. Therefore, in order to expand the reachable range, it is conceivable to attach a mechanism that can be operated to move the blade part at the tip of the instrument, but the mechanism operated by multiple axes and cranks, such as the existing grasping forceps 800, is composed of small parts, which are fragile and can be damaged during operation.

Title of the paper: "Results of Percutaneous Lumbar Interbody Fusion (PELIF)" Name of the publication: Journal of Spine Research, Vol. 8, No. 7, Pages 1317-1320, 2017

The challenge for an intervertebral discectomy instrument is to have a structure that ensures strength and rigidity while being a long and slender instrument that can be inserted into the working cavity of a percutaneous total endoscope, with the blade portion being able to protrude to the side from the long axis of the instrument, and the extent of this protrusion being able to be instantly and appropriately changed using the handle. Furthermore, it is desirable for the structure to allow the protrusion to protrude to the side at the tip end.

The percutaneous fully endoscopic discectomy instrument of the present invention comprises a long, thin cylindrical shaft with a fenestration on one side of its tip, a bottom plate at the bottom (below) of the fenestration, and a stopper box distal to the fenestration, which has an inner cavity that leads to the fenestration as an extension of the shaft's inner cavity. The distal side of the inner cavity of the stopper box is closed. A rod that slides inside the shaft has one end of an elastic plate fixed to its tip. The elastic plate is a thin plate made of a plastic elastic material, its length is longer than the length of the fenestration and its width is narrower than the width of the fenestration. At the proximal end of the shaft there is a fixed handle and a movable handle that crosses it and is connected to it so as to be rotatable via a fulcrum axis. The movable handle has a recess into which the spherical portion of one end of the rod can be fitted, allowing the rod to be connected in a detachable manner and allowing movement.
The tip side of the inner cavity of the stopper box mentioned above is curved, and it is a curved circular arc surface with the corner of the tip of the fenestration as its center point. The tip of the fenestration is located sufficiently closer to the hand side than the tip of the inner cavity of the stopper box.
The movable handle has a bearing hole that accepts the fulcrum shaft of the fixed handle, and the bearing hole is an oval hole.

When the movable handle is gripped, the rod is pushed towards the tip and the elastic plate moves along the bottom plate towards the tip; when the tip of the elastic plate hits the tip of the stopper box lumen and is pushed further, the elastic plate bends, deviating from the fenestration and protruding to the side. The elastic plate hits the corner at the tip of the fenestration, and using this as a fulcrum, the tip of the elastic plate moves along the curved surface that continues from the tip of the stopper box lumen, and the tip of the elastic plate points significantly downward, causing the elastic plate to protrude further towards the tip. When the handle is released, the elastic plate returns to its original shape due to its plastic elasticity.
During surgery, the instrument is inserted into the intervertebral disc, and when the entire forceps is rotated while the elastic plate is bent, the corners on the sides of the elastic plate bite into the soft intervertebral disc and come into contact with the hard bone beyond, and by moving it from there, the disc can be detached from the bone. By rotating the instrument and reducing the deflection of the elastic plate, the blade can be moved along the flat bone surface, allowing continuous detachment. The detached disc pieces are grasped and removed using existing grasping forceps.

Even if a disc fragment becomes caught between the elastic plate and the bottom plate of the fenestration, causing the elastic plate to protrude irreversibly and become caught in the working cavity of the percutaneous total endoscope, making it impossible to remove the instrument from the body, the oval bearing hole in the movable handle allows the rod to be moved significantly toward the hand, and the elastic plate to be significantly retracted toward the hand, allowing the disc fragment to be removed from the fenestration.

Since it does not use a mechanism that operates using multiple axes and cranks, it has no weak points and is very strong. The elastic plate becomes rigid when bent, and is rigid enough to peel the intervertebral disc from the bone surface.
The protrusion of the elastic plate can be instantly changed as needed by manipulating the handle, so the circular motion of the instrument's rotation can be adapted to the flat bone surface to move the elastic plate, allowing continuous peeling over a wide area.
The structure of the stopper box cavity allows the tip of the elastic plate to be constrained while still being able to protrude laterally at the tip, making it possible to detach the disc as far as the instrument can reach.

Percutaneous total endoscope, outer tube, and grasping forceps in the lumbar axial plane during surgery. Oblique view of the percutaneous endoscope and the tip of the outer tube. Side view of an existing grasping forceps for percutaneous total endoscopy. Schematic diagram of lumbar interbody fusion surgery in sagittal section of the lumbar spine. Overall side view of embodiment 1. Sagittal cross-sectional view of the tip side of embodiment 1. 1 is a side view of the hand side of the first embodiment. 1 is a perspective view of the proximal side of the rod and the movable handle recess of the first embodiment. FIG. Sagittal section dynamics diagram of the tip side of embodiment 1. FIG. 2 is a perspective view of the tip side of the elastic plate of the first embodiment when protruding. Schematic diagram of dynamics in lumbar sagittal section during discectomy according to embodiment 1. A side view of the hand side of embodiment 1 (when the rod is pulled to the maximum). Sagittal section of a subtype of the stopper box lumen.

The first embodiment of the present invention will be explained using Figures 5 to 12. The shaft 130 is cylindrical with an outer diameter of 3-4 mm and a length of approximately 370 mm, and has a rectangular fenestration 131 on the upper UP of its tip side DI, through which the inner cavity of the shaft 130 opens to the outside. A bottom plate 132 is located at the bottom (lower DW) of the fenestration 131, and the upper surface of the bottom plate is flat. A stopper box 110 is located distal to the fenestration 131, and the stopper box 110 has an inner cavity that opens to the fenestration 131, and this inner cavity is located on an extension line of the inner cavity of the shaft 130. The distal side of the inner cavity of the stopper box 110 is closed. The rod 140 that slides within the inner cavity of the shaft 130 is a long, thin cylinder, and one end of the elastic plate 120 is fixed to its tip. The elastic plate 120 is a thin plate made of a plastic elastic material, about 0.5 mm thick, with a length longer than the length of the fenestration 131 and a width slightly smaller than the width of the fenestration 131. A fixed handle 150 is fixed to the proximal side PR of the shaft 130, and there is a single movable handle 160 that intersects with the fixed handle 150 and is connected to the fulcrum shaft 151 so that it can rotate . Although not shown, a cap is fixed to the fulcrum shaft 151 to prevent the movable handle 160 from coming off. The upper end 163 of the movable handle has a recess 164 into which one end of the rod 140 fits, and the rod 140 is connected so as to be detachable and allow movement, as described below. One end of the rod 140 has a spherical rod ball 142 attached, which fits into the cylindrical cavity of the recess 164 and is braked. However, the cavity of the recess 164 expands in the vertical direction at the tip side, allowing a small range of sliding and rotational movement on one plane (the vertical directions UP and DW in the figure).
Continuing from the tip 111 of the lumen of the stopper box 110 mentioned above is a curved surface 112 below it, which is a circular arc curved surface with the corner 113 at the tip of the fenestration as its center point (Figure 6). The corner 113 at the tip of the fenestration is located sufficiently closer to the hand than the tip 111 of the stopper box lumen.
The movable handle 160 has a bearing hole 161 that receives the fulcrum shaft 151 protruding from the fixed handle 150, and the bearing hole 161 is an oval hole. Similar to scissors, the fixed handle and the movable handle each have loops 152, 162 for inserting fingers. When the elastic plate 120 hits the tip of the stopper box inner cavity and begins to bend, the long axis of the movable jaw 160 becomes perpendicular to the long axis of the shaft 130, and in this state the fulcrum shaft 151 is located at the upper end of the bearing hole 161.

As shown in Figures 6, 9 and 10, when the movable handle 160 is gripped from the position shown in Figure 9a, the rod 140 is pushed towards the tip, and the elastic plate 120 moves towards the tip along the bottom plate 132, and when the elastic plate 120 hits the tip 111 of the stopper box lumen (Figure 9b) and is pushed further, the elastic plate 120 deviates from the fenestration 131 and bends upward UP (Figures 9c and 10). The elastic plate 120 hits the corner 113 at the tip of the fenestration, which acts as a fulcrum as the tip of the elastic plate moves along the curved surface 112 of the stopper box lumen, and the tip of the elastic plate 120 points significantly downward DW, causing the elastic plate to protrude upward further towards the tip. When the movable handle is loosened, the elastic plate 120 returns to its original shape due to its plastic elasticity.
The actual surgical procedure is as shown in Figure 11 (dynamic schematic diagram of a sagittal section of the lumbar spine), in which the instrument is inserted into intervertebral disc D between vertebral bodies B, and then the entire forceps instrument is rotated while gripping the handle and bending the elastic plate 120, so that the corners on the sides of the elastic plate 120 bite into the soft intervertebral disc D and come into contact with the hard bone of the vertebral body B beyond. By further rotating the instrument and reducing the bending of the elastic plate, the blade can be moved along the planar boundary surface between vertebral body B and intervertebral disc D, allowing the disc D to be continuously peeled off from vertebral body B. The peeled off intervertebral disc pieces are grasped and removed using existing grasping forceps.

Even if a disc fragment becomes caught between the elastic plate 120 and the bottom plate 132, causing the elastic plate 120 to protrude irreversibly and making it impossible to remove the instrument from the body, the bearing hole 161 of the movable handle 160 is an oval hole, so that by opening the movable handle 160 and shifting the fulcrum axis within the oval hole as shown in Figure 12, the rod 140 can be pulled significantly toward the hand, and the elastic plate 120 can be significantly retracted toward the hand to remove the disc fragment from the fenestration.

The shape of the stopper box cavity may be a simple straight cavity as shown in Fig. 13a as a variant. This will tightly restrain the tip of the elastic plate more than in embodiment 1, making it less likely to come loose during operation, but the elastic plate will be less likely to bend at the tip. Also, a slightly dug-in cavity as shown in Fig. 13b may be considered.
In order to limit misalignment due to the gap between the oval bearing hole 161 and the fulcrum shaft 151, a spacer that fills the gap is included but is removable.

S Skin incision L Bone (vertebral arch)
B bone (vertebral body)
D Intervertebral disc N Nerve UP Upper DW Lower DI Tip side PR Hand side

Claims (1)

A forceps instrument for percutaneous total endoscopy has a cylindrical, elongated shaft and a fenestration on one side of the tip, with a bottom plate at the bottom of the fenestration.
There is a stopper box on the distal side of the fenestration, and the stopper box has an inner cavity that is an extension of the shaft inner cavity and leads to the fenestration, the distal side of the inner cavity is closed, and the tip of the fenestration is located proximal to the tip of the stopper box inner cavity.
The lower part of the stopper box is curved, continuing from the tip of the cavity, and is a circular arc surface with the corner of the tip of the fenestration as its center point.
There is a rod that slides inside the shaft, and one end of an elastic plate is fixed to the tip of the rod. The elastic plate is a thin plate made of a plastic elastic material, and the length of the elastic plate is longer than the length of the fenestration, and the width of the elastic plate is narrower than the width of the fenestration.
A fixed handle is provided on the proximal side of the shaft, and a movable handle is connected to the fixed handle and rotatably connected to the fulcrum shaft. The proximal end of the rod can be connected to the movable handle.
The movable handle has a bearing hole that receives the fulcrum shaft of the fixed handle. The bearing hole is an oval hole.
An intervertebral disc resection instrument characterized in that an elastic plate is pushed out by operating a handle, hits the inner cavity of a stopper box, bends, and protrudes laterally from an opening.

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