JP7758455B2 - Bone Plate Device - Google Patents

Description

Article 30, Paragraph 2 of the Patent Act was applied. Presented at Luncheon Seminar 49, a co-sponsored seminar of the 96th Annual Meeting of the Japanese Orthopaedic Association, held on May 14, 2023.

The present invention relates to a bone plate device for use in high tibial osteotomy (HTO).

The bone plate device used in HTO consists of a bone plate that is placed and fixed to the medial surface of the tibia, and a fastener for fixing the bone plate to the tibia.

As a conventional bone plate constituting a bone plate device, the following Patent Document 1 proposes a generally T-shaped bone plate 1, as shown in Figure 6, which includes a long, strip-like distal portion (main body portion) 3, a short proximal portion (transverse portion) 4, and a connecting portion (intermediate portion) 5 connecting these, with the distal portion 3 twisted relative to the proximal portion 4 around an axis parallel to the longitudinal axis of the distal portion 3.

As shown in the figure, through holes 6a to 6d are arranged along the longitudinal direction of the distal portion 3, and through holes 7a to 7c are arranged along the longitudinal direction of the proximal portion 4 (a direction intersecting the longitudinal direction of the distal portion 3), and through hole 7d is formed on the distal side thereof.
The distal and proximal portions 3 and 4 are positioned on the medial surfaces of the diaphysis and epiphysis of the tibia, respectively, and are fixed to the tibia by fasteners fitted in the through holes 6a-6d and 7a-7d.

Furthermore, protruding portions 8 are provided around the through-holes 7 a, 7 c, and 7 d of the proximal portion 4.
This raised portion 8 is said to be able to prevent the corners of the head 2b of the fastener 2, which is inserted at an angle relative to the normal to the tangent plane of the lower surface of the proximal portion 4, from protruding from the upper surface of the proximal portion 4, as shown in Figure 7.
Furthermore, since the corners of the head 2b of the fastener 2 (part of the male thread) are covered with the raised portion 8, the contact area between the head 2b and the proximal portion 4 is increased, thereby increasing the fixing strength of the fastener 2 to the proximal portion 4 of the bone plate.

International Publication No. 2021/250853

However, the bone plate described in Patent Document 1 has the following problems.
(1) When the bone plate is placed on the medial surface of the tibia, the distal portion 3 and part of the intermediate portion 5 may interfere with the pes anserine, which is the attachment point of the tendons of the muscles (sartorius, semitendinosus, and gracilis), and the bone plate 1 fixed to the tibia may inhibit the expansion and contraction of these muscles.

(2) The shank 2a of the fastener 2 inserted through the through-holes 6a-6d of the distal portion 3 is typically inserted perpendicularly into the inner surface of the diaphysis with which the underside of the distal portion 3 is in contact. At this time, the tip of the inserted shank 2a may penetrate the diaphysis of the tibia and reach the area where the deep peroneal nerve or artery passes, potentially damaging these nerves or arteries.

(3) As shown in Figure 7, although the raised portion 8 prevents the corners of the head 2b of the fastener 2 inserted at an angle from protruding from the upper surface of the proximal portion 4, the corners of the head 2b still protrude from the lower surface of the proximal portion 4. As a result, the number of engagement pitches with the female thread formed in the through hole is insufficient, reducing the fixation strength of the fastener 2 to the proximal portion 4 of the bone plate, and ultimately the fastening strength of the bone plate to the epiphysis of the tibia.

The present invention has been made based on the above circumstances.
A first object of the present invention is to provide a bone plate device in which, when the bone plate is positioned and fixed on the medial surface of the tibia, the distal and middle portions of the bone plate do not interfere with the pes anserine.

The second object of the present invention is to provide a bone plate device that, when the bone plate is placed and fixed on the medial surface of the tibia, prevents the tip of the shank of the fastener inserted through the distal through-hole from reaching the area where the deep peroneal nerve or artery passes.

The third object of the present invention is to provide a bone plate device that, when the bone plate is positioned and fixed to the medial surface of the tibia, prevents the corners of the heads of the fasteners inserted through the through-holes in the proximal portion from protruding from the upper and lower surfaces of the proximal portion, thereby ensuring sufficient fastening strength of the fasteners to the proximal portion of the bone plate, and ultimately the fastening strength of the bone plate to the epiphysis of the tibia.

(1) The bone plate device of the present invention is a bone plate device for high tibial osteotomy, comprising a bone plate that is placed with its underside facing the medial surface of the tibia, and a plurality of fasteners for fixing the bone plate to the tibia,
The fastener has a shank on which a screw thread is formed and a head on which a male screw thread is formed and which is larger in diameter than the shank,
The bone plate includes a strip-shaped distal portion extending in a proximal-distal direction so as to be disposed on the medial surface of the diaphysis, a curved plate-shaped proximal portion extending in an anterior-posterior direction so as to be disposed on the medial surface of the epiphysis, and an intermediate portion connecting the distal portion and the proximal portion;
The distal portion has a plurality of through holes arranged along the longitudinal direction (proximal-distal direction) of the distal portion, and the proximal portion has a plurality of through holes arranged along the longitudinal direction (front-rear direction) of the proximal portion, each of the through holes being capable of inserting the shank, and each of the through holes has a female thread formed therein to be threadedly engaged with the male thread formed on the head portion,
when viewed from above, all of the through holes arranged along the longitudinal direction of the proximal portion are located posterior to an extension line of a posterior side surface of the distal portion;
When viewed from above, the anterior surfaces of the intermediate portion and the proximal portion lie on a straight line that slopes more anteriorly as it approaches the distal side, and the angle α between the straight line and an extension of the anterior surface of the distal portion is 25° or greater .

With a bone plate device configured in this way, the distal portion is located in front of the through-holes arranged in the proximal portion of the bone plate, and the proximal and distal portions of the bone plate are sufficiently spaced apart in the anterior-posterior direction. Therefore, when the bone plate is positioned and fixed to the medial surface of the tibia, it is possible to prevent the distal and middle portions of the bone plate from interfering with the pes anserine.

Furthermore, with the bone plate device configured in this manner, the proximal and distal portions of the bone plate can be spaced apart sufficiently in the anterior-posterior direction.

(2) In the bone plate device of the present invention, it is preferable that the proximal portion has at least one through hole formed distal to the through holes arranged along the longitudinal direction of the proximal portion.

(3) In the bone plate device of the present invention, it is preferable that the shaft portion of the fastener inserted into the through-hole in the distal portion and extending from the underside of the bone plate is inclined forward by 20°±5° relative to the axis (Z-axis) extending vertically (the central axis of the female thread of the through-hole is inclined).

A bone plate device configured in this way prevents the shank of the fastener from being directed toward the area where the deep peroneal nerve or artery passes, so when the bone plate is placed and fixed to the medial surface of the tibia, the tip of the shank will not reach said area.

(4) In the bone plate device of (3) above, it is preferable that a protruding portion on which a partial internal thread is formed is provided around the upper opening of the through hole formed in the distal portion.

With a bone plate device configured in this way, when the bone plate is positioned and fixed to the medial surface of the tibia, the fixation strength of the distal portion of the fastener, whose shank is inserted obliquely through the through-hole, and ultimately the fastening strength of the bone plate to the diaphysis of the tibia, can be sufficiently ensured.

(5) In the bone plate device of the present invention, it is preferable that a protruding portion having a partial internal thread is provided around each of the upper and lower openings of at least one of the through holes formed in the proximal portion.

With a bone plate device configured in this way, protrusions are provided not only around the upper opening of the through hole but also around the lower opening of the through hole. This ensures sufficient fixation strength to the proximal portion of the fastener, whose shank is inserted at an angle through the through hole, when the bone plate is positioned and fixed to the medial surface of the tibia, and ultimately ensures sufficient fastening strength of the bone plate to the epiphysis of the tibia.

According to the bone plate device of the present invention, when the bone plate constituting the device is positioned and fixed on the medial surface of the tibia, the distal and middle portions of the bone plate do not interfere with the pes anserine.
Furthermore, according to the bone plate device of the present invention, the shaft of the fastener extending from the underside of the bone plate is inclined forward by 20°±5° relative to the Z-axis extending up and down, so that when the bone plate is positioned and fixed on the medial surface of the tibia, the tip of the shaft of the fastener inserted through the distal through-hole will not reach the area where the deep peroneal nerve or artery passes.
Furthermore, according to the bone plate device of the present invention, in which protrusions are provided around each of the upper and lower openings of the through hole formed in the proximal portion of the bone plate, when the bone plate is positioned and fixed to the medial surface of the tibia, the fixing strength of the fastener to the proximal portion of the bone plate, and ultimately the fixing strength of the bone plate to the epiphysis of the tibia, can be sufficiently ensured.

1 is a perspective view of a bone plate device according to one embodiment of the present invention; 2 is a perspective view showing a fastener that constitutes the bone plate device shown in FIG. 1. FIG. 2 is a plan view (top view) showing a bone plate constituting the bone plate device shown in FIG. 1; FIG. 2 is a bottom view (underside view) showing a bone plate constituting the bone plate device shown in FIG. 1; FIG. FIG. 2 is a side view (rear side view) showing a bone plate constituting the bone plate device shown in FIG. 1 . 2 is an explanatory view of the bone plate device shown in FIG. 1 as seen from the distal side. FIG. 2 is a cross-sectional view of the bone plate device (proximal portion of the bone plate) shown in FIG. 1. FIG. 3E is a detailed cross-sectional view of a portion of FIG. 3E. 2 is a perspective view showing the proximal portion (top surface side) of a bone plate constituting the bone plate device shown in FIG. 1. FIG. 2 is a perspective view showing the proximal portion (lower surface side) of the bone plate constituting the bone plate device shown in FIG. 1. FIG. 2 is an explanatory diagram showing a schematic view of the bone plate constituting the bone plate device shown in FIG. 1 not interfering with the anserine pes; FIG. FIG. 2 is an explanatory diagram showing, in a schematic manner, that the tip portion of the shaft of the fastener constituting the bone plate device shown in FIG. 1 is not directed toward the area through which the deep peroneal nerve or artery passes. FIG. 1 is a plan view showing a conventional bone plate. FIG. 7 is a cross-sectional view showing a main part of the bone plate shown in FIG. 6 .

The bone plate device of this embodiment shown in Figure 1 is a bone plate device for high tibial osteotomy, consisting of a bone plate 10 placed with its lower surface 10B facing the medial surface of the tibia, and eight fasteners 20 for fixing the bone plate 10 to the tibia. The fasteners 20 have a shaft 21 on which a screw thread 23 is formed, and a head 22 with a larger diameter than the shaft 21 and on which a male thread 24 is formed. The bone plate 10 has a strip-shaped distal portion 13 extending in the proximal-distal direction (X direction) so as to be placed on the medial surface of the diaphysis, and a strip-shaped distal portion 14 extending in the anterior-posterior direction (X direction) so as to be placed on the medial surface of the epiphysis. The distal portion 13 has through holes 16a to 16d arranged along the longitudinal direction (X direction) of the distal portion 13, and the proximal portion 14 has through holes 17a to 17c arranged along the longitudinal direction (approximately the Y direction) of the proximal portion 14, with through hole 17d formed on the distal side thereof. A shank 21 of a fastener 20 can be inserted through each of the through holes 16a to 16d and 17a to 17d, and a head 22 of the fastener 20 can be inserted through each of the through holes 16a to 16d and 17a to 17d. and a female thread 19 is formed to threadably engage with a male thread 24 formed in the distal portion 13; in a top view of the bone plate 10, the anterior surfaces of the intermediate portion 15 and the proximal portion 14 are substantially on a straight line L1, and the angle (α) between this straight line L1 and an extension line L2 of the anterior surface of the distal portion 13 is 25° or more, and all of the through holes 17a to 17c arranged along the longitudinal direction of the proximal portion 14 are located posterior to the extension line L3 of the posterior surface of the distal portion 13; fasteners are inserted into the through holes 16a to 16d of the distal portion 13 and extend from the underside 10B of the bone plate 10. The shaft 21 of the proximal portion 14 is inclined forward by 20°±5° relative to the Z axis extending in the vertical direction (Z direction); a raised portion 18A with a partial internal thread 19A is provided around the opening on the upper surface 10A of the through holes 17a and 17d formed in the proximal portion 14, and a raised portion 18B with a partial internal thread 19B is provided around the opening on the lower surface 10B of the through holes 17a and 17d; a raised portion 18A with a partial internal thread 19B is provided around the opening on the upper surface 10A of the through holes 16a to 16d formed in the distal portion 13.

The bone plate device of this embodiment consists of a bone plate 10 and eight fasteners 20 for fixing the bone plate 10 to the tibia.

As shown in Figure 2, the fastener 20 consists of a shank 21 and a head 22 with a larger diameter than the shank 21. A screw thread 23 is formed on the shank 21 of the fastener 20, and a male thread 24 is formed on the head 22.

The bone plate 10 shown in FIGS. 3A to 3H is a plate for the tibia of the left leg, and is composed of a distal portion 13, a proximal portion 14, and an intermediate portion 15.
When placed on the medial surface of the tibia, the bone plate 10 has a lower surface 10B that faces the medial surface and an upper surface 10A on the opposite side. Therefore, the up-down direction (thickness direction) of the bone plate 10 corresponds to the medial-lateral direction of the tibia to which it is fixed.

The distal portion 13 of the bone plate 10 is the portion that is placed on the medial surface of the diaphysis of the tibia and is a strip-like plate extending in the proximal-distal direction (X direction). Here, the "proximal-distal direction" of the bone plate 10 corresponds to the proximal-distal direction of the tibia to which it is fixed, and therefore the distal portion 13 is positioned along the proximal-distal direction of the diaphysis.

Four through holes 16a to 16d are arranged along the longitudinal direction of the distal portion 13. Each of the through holes 16a to 16d has an inner diameter that allows the shank 21 of the fastener 20 to be inserted therethrough, and each of the through holes 16a to 16d has a female thread 19 formed therein that meshes with a male thread 24 formed on the head 22 of the fastener 20.
The width (length in the Y direction) of the distal portion 13 is set to 13 to 16 mm, and a preferred example is 14 mm.

The proximal portion 14 of the bone plate 10 is positioned on the medial surface of the epiphysis of the tibia, which protrudes medially relative to the diaphysis, and extends in the anterior-posterior direction (approximately the Y direction) while curving. Here, the "anterior-posterior direction" of the bone plate 10 corresponds to the anterior-posterior direction of the tibia to which it is fixed, and therefore the proximal portion 14 is positioned along the anterior-posterior direction of the epiphysis.

Three through holes 17a to 17c are arranged along the longitudinal direction of proximal portion 14, and through hole 17d is formed distally thereto. Each of through holes 17a to 17d has an inner diameter that allows shank 21 of fastener 20 to be inserted therethrough, and each of through holes 17a to 17d is formed with female threads 19 that mesh with male threads 24 formed on head 22 of fastener 20.
The length of the proximal portion 14 (length in the Y direction) is set to 25 to 30 mm, and a suitable example is 28 mm.

The intermediate portion 15 of the bone plate 10 connects the distal portion 13 and the proximal portion 14, and does not have a through-hole for attaching the fastener 20. The intermediate portion 15 is placed in the enlarged osteotomy site.

In the top view of the bone plate 10 shown in FIG. 3A, the anterior surfaces of the intermediate portion 15 and the proximal portion 14 are substantially on a single straight line L1, and this straight line L1 is inclined so as to approach the "anterior side" as it approaches the "distal side."
The angle α formed by this straight line L1 and an extension line L2 of the front side surface of the distal portion 13 is preferably 25° or more, more preferably 25 to 45°, and a suitable example is 37°.

By setting this angle α to 25° or more, the proximal portion 14 and the distal portion 13 of the bone plate 10 can be sufficiently spaced apart in the front-to-back direction (Y direction).
Furthermore, by ensuring a sufficient distance between the proximal portion 14 and the distal portion 13 in the anterior-posterior direction, all of the through holes 17a to 17c arranged along the longitudinal direction of the proximal portion 14 are located behind the extension line (extrapolated line) L3 of the rear side surface of the distal portion 13.

In this way, in the bone plate device of this embodiment, the distal portion 13 and intermediate portion 15 of the bone plate 10 that constitutes it can be positioned at a position that is significantly spaced forward from the position where the proximal portion 14 is positioned.
As a result, as shown in Figure 4, the distal portion 13 and/or part of the intermediate portion 15 do not interfere with the pes anserine, which is located distal to the position of the proximal portion 14 (position indicated by G in the same figure), and therefore the fixed bone plate 10 does not inhibit the expansion and contraction of the muscles (sartorius, semitendinosus, and gracilis).

As shown in Figure 3D, in the bone plate device of this embodiment, the fasteners 20 are inserted into the through-holes 16a to 16d in the distal portion 13 of the bone plate 10, and the female threads 19 formed in the through-holes are threadedly engaged with the male threads 24 formed in the head 22. The shanks 21 of the fasteners 20 extend downward from the underside 10B of the bone plate 10 and are inclined forward by 20° relative to the axis extending vertically (the Z-axis, which is normal to the X-Y plane).

As a result, as shown in Figure 5, the shank 21 of the fastener 20 can be prevented from being directed toward the area where the deep peroneal nerve and artery pass (the area indicated by N in the figure). Therefore, when the bone plate 10 is positioned and fixed to the medial surface of the tibia, the tip of the shank 21 is positioned in the center of the tibia without reaching the area.

As shown in Figure 3A, raised portions 18A with partial internal threads are provided around the openings of the upper surface 10A of the through holes 16a to 16d formed in the distal portion 13. These raised portions 18A are provided on the side where the central axis of the internal threads 19 formed in the through holes 16a to 16d forms an obtuse angle with the X-Y plane, i.e., the front side.

This prevents the corners of the heads 22 (part of the male threads 24) of the fasteners 20 inserted through the through holes 16a-16d formed in the distal portion 13 from protruding from the top surface of the distal portion 13, and ensures sufficient fixation strength of the fasteners 20 to the distal portion 13 of the bone plate 10, and ultimately the fastening strength of the bone plate 10 to the diaphysis of the tibia.

As shown in Figures 3A, 3F, and 3G, a raised portion 18A with a partial internal thread 19A is provided around the opening of the upper surface 10A of the through holes 17a and 17d formed in the proximal portion 14.

As shown in FIGS. 3B, 3F, and 3H, protrusions 18B on which partial internal threads 19B are formed are also provided around the openings of the lower surface 10B of the through holes 17a and 17d.
During surgery, the bone plate 10 is placed between the medial collateral ligaments (the deep and superficial medial collateral ligaments). Specifically, only the superficial medial collateral ligament is cut, and the bone plate 10 is placed on top of the deep medial collateral ligament. The cut superficial medial collateral ligament is then reattached and sutured. Furthermore, when inserting the fastener 20 into the bone plate 10, the fastener 20 penetrates the deep medial collateral ligament located on the lower surface 10B while avoiding the superficial medial collateral ligament located on the upper surface 10A, thereby securing the bone plate 10 to the epiphysis. Therefore, when the knee is moved after surgery, the upper surface of the bone plate 10 rubs against the superficial medial collateral ligament. If the protruding portion 18A is extremely convex, the protruding portion may rub against the ligament, potentially damaging the ligament. However, since the protuberance 18A of the bone plate 10 has a gentle slope and a smooth shape, when the knee is moved after surgery, there is very little friction resistance between the protuberance 18A and the superficial medial collateral ligament, preventing damage to the ligament.
Furthermore, because blood flows inside bones, if protrusions or bumps on a metal plate are pressed against the bone, blood flow in that area may be obstructed, slowing bone regeneration. For this reason, no protrusions are provided on the underside of the distal portion 13 of the bone plate 10 (a portion that may come into contact with the diaphysis). On the other hand, unlike the diaphysis where the distal portion 13 is located, the epiphysis where the proximal portion 14 is located has soft tissue (the deep medial collateral ligament). Therefore, even if a protrusion 18B is provided on the underside 10B, which is located on the medial surface of the epiphysis, the protrusion 18B will not obstruct blood flow.

In this way, raised portions 18A are provided around the openings on the upper surface 10A of the through holes 17a and 17d, and raised portions 18B are also provided around the openings on the lower surface 10B of the through holes 17a and 17d, thereby ensuring a sufficiently high fixation strength of the fastener 20 to the proximal portion 14 of the bone plate 10.

10 Bone plate 10A Upper surface of bone plate 10B Lower surface of bone plate 13 Distal portion 14 Proximal portion 15 Middle portion 16a to 16d Through holes formed in the distal portion 17a to 17d Through holes formed in the proximal portion 18A Raised portion formed on the upper surface of the bone plate 18B Raised portion formed on the lower surface of the proximal portion of the bone plate 19 Female thread 19A, 19B Partial female thread 20 Fastener 21 Shank 22 Head 23 Screw thread 24 Male thread

Claims (5)

A bone plate device for high tibial osteotomy, comprising a bone plate arranged with its lower surface facing the medial surface of the tibia, and a plurality of fasteners for fixing the bone plate to the tibia,
The fastener has a shank on which a screw thread is formed and a head on which a male screw thread is formed and which is larger in diameter than the shank,
The bone plate includes a strip-shaped distal portion extending in a proximal-distal direction so as to be disposed on the medial surface of the diaphysis, a curved plate-shaped proximal portion extending in an anterior-posterior direction so as to be disposed on the medial surface of the epiphysis, and an intermediate portion connecting the distal portion and the proximal portion;
The distal portion has a plurality of through holes arranged along the proximal-distal direction, which is the longitudinal direction of the distal portion, and the proximal portion has a plurality of through holes arranged along the anterior-posterior direction, which is the longitudinal direction of the proximal portion, each of the through holes being capable of inserting the shank, and each of the through holes has a female thread formed therein to be threadedly engaged with the male thread formed on the head,
when viewed from above, all of the through holes arranged along the longitudinal direction of the proximal portion are located posterior to an extension line of a posterior side surface of the distal portion;
A bone plate device characterized in that, when viewed from above, the anterior surfaces of the intermediate portion and the proximal portion lie on a straight line that slopes more anteriorly as it moves distally, and the angle α between this line and an extension of the anterior surface of the distal portion is 25° or more . 2. The bone plate device according to claim 1, wherein the proximal portion has at least one through hole formed distal to the through holes arranged along the longitudinal direction of the proximal portion. 2. The bone plate device according to claim 1, wherein the shank of the fastener inserted through the through-hole of the distal portion and extending from the underside of the bone plate is inclined forward by 20°±5° relative to an axis extending vertically. 4. The bone plate device according to claim 3 , wherein a protuberance having a partial internal thread is provided around the upper opening of the through-hole formed in the distal portion. The bone plate device according to claim 1, characterized in that a protruding portion having a partial internal thread is provided around each of the upper and lower openings of at least one of the through holes formed in the proximal portion.