TW201722371A - Supporting prosthesis of mandible - Google Patents

Abstract

A supporting prosthesis of mandible is disclosed for avoiding the bone plate of conventional mandible reconstruction surgery perforating soft tissue or skin of oral cavity. The supporting prosthesis of mandible comprises an insulation portion and two extension portions. The insulation portion includes a holding surface in a longitudinal direction. The holding surface has a sustaining portion means for sustaining a bone plate. The two extension portions couple with two ends of the insulation portion, respectively. Each extension portion extends a direction away from the insulation portion. Each extension portion includes a coupling portion coupling with the bone plate.

Description

Lower jaw support prosthesis

The present invention relates to a chin support prosthesis, and more particularly to a chin support prosthesis for repairing a mandibular defect.

In general, the defect of the mandible is usually caused by the removal of the mandible, the removal of the mandibular joint necessary for severe rheumatoid arthritis, or severe trauma. Please refer to Figure 1. After the defect of the humerus B, a bone plate 1 is usually used to fix the defect of the mandibular defect B1 caused by trauma or surgical resection. The bone plate 1 includes a plurality of locking holes 11 for the locking screw 12 to lock the bone plate 1 to a position where the lower jaw B is not missing.

However, the bone plate 1 is usually made of a material having a relatively high hardness such as titanium metal. Therefore, the bone plate 1 directly contacts and rubs against the soft tissue or the skin of the oral cavity, which causes the bone plate 1 to penetrate the soft tissue or the skin, resulting in inflammation and suppuration. In the case of infection, the surgeon must perform a second operation to remove the bone plate 1. After the soft tissue repair is performed, the squat reconstruction operation is performed again, which will greatly slow down the progress of the operation and cause a serious burden on the patient's body.

In view of the above, there is a problem that the bone plate 1 used in the present mandibular reconstruction surgery is "easy to break through the soft tissue or the skin of the mouth", and it is necessary to improve it.

The object of the present invention is to provide a chin support prosthesis for combining the outer periphery of a bone plate, and having a blocking portion capable of blocking a defect portion of the tibia and the bone plate to avoid oral soft tissue of the bone plate and the defect portion or Skin contact and friction.

In order to achieve the foregoing objectives, the technical contents applied by the present invention include: A chin support prosthesis, comprising: a blocking portion having a bearing surface in a longitudinal direction, the blocking portion being provided with a receiving portion on the bearing surface, the receiving portion for receiving a bone plate; The two extending portions are respectively disposed at two ends of the blocking portion, and the two extending portions respectively extend away from the blocking portion, and each of the extending portions has a joint portion for coupling the bone plate.

The two extending portions are respectively connected to the bearing surfaces of the two ends of the blocking portion, and the two extending portions and the blocking portion are respectively located on two sides of the bone plate in the longitudinal direction. Thereby, when the space above the upper edge of the humerus is larger, the two extensions will be formed above the bone plate, so that the two extensions can easily protrude into the patient's mouth, and the user can easily The extension is fixed to the upper edge of the lower jaw.

Alternatively, the blocking portion has a bottom surface opposite to the bearing surface in the longitudinal direction, and the two extending portions are respectively connected between the bearing surface and the bottom surface of the two ends of the blocking portion, and the two extending portions and the blocking portion are in the longitudinal direction The direction is on the same side of the bone plate. Thereby, when the space below the lower edge of the humerus is larger, the two extensions will be formed under the bone plate, so that the two extensions can easily protrude into the patient's mouth, and the user can easily The extension is secured to the lower edge of the mandible.

Each of the extending portions is further provided with a fixing hole through which a fixing screw is passed to fix the extending portion to the lower jaw bone, thereby fixing the two extending portions to the lower jaw bone to lift the lower jaw support. The combination of the prosthesis and the bone plate is stable.

The blocking portion and the two extending portions are formed in a curved shape corresponding to the two extending portions, and the blocking portion and the two extending portions are formed to form a concave portion, and each of the extending portions is further provided with a partition plate, and the partition plate is disposed at the extending portion Along one side of the recess, and the partition extends along the longitudinal direction, the partition shields the bone plate to prevent the bone plate from rubbing the soft tissue or skin of the mouth.

The iliac support prosthesis as described above, wherein the bone plate is provided with a locking hole, the baffle partially shielding the locking hole, a locking screw penetrating the baffle and passing the locking hole through the locking hole The bone plate is locked to the tibia. Thereby, the user of the partition plate fixes the extension portion together when the bone plate is locked, and the extension portion does not need to additionally provide the fixing hole, which can reduce the structural complexity of the chin support prosthesis and simplify the surgical procedure.

The blocking portion and the two extending portions are formed in a curved shape corresponding to the two extending portions, and the blocking portion and the two extending portions are formed to form a concave portion. The blocking portion is provided with a supporting piece, and the supporting piece extends toward the concave portion. Thereby, the support piece can cover the soft tissue of the defect of the tibia, and further avoid the contact and friction of the bone plate directly with the soft tissue of the defect.

The iliac support prosthesis as described above, wherein the bone plate is locked to the lower tibia, the lower tibia is received in the recess, the support piece is intended to extend into a defect portion of the lower tibia, and the lower tibia has a direction The defect surface of the defect portion, the end edge of the support piece is adapted to abut the defect surface. Thereby, the support piece can provide proper tension of the lower jaw bone and surrounding soft tissue, so that the lower jaw support prosthesis can support the lower jaw bone, further avoiding friction of oral soft tissue or skin contact of the defect part.

Wherein, the bone plate comprises a plurality of interconnected ring bodies, and the receiving portion of the blocking portion is provided with a plurality of consecutively arranged pockets, each of the receiving slots for receiving one of the ring bodies of the bone plate, so that the bearing portion The bone plate can be placed and positioned.

Wherein, the bone plate comprises a plurality of interconnected ring bodies, and the joint portion of each of the extending portions is provided with a plurality of consecutively arranged notches, each of the notches for abutting one of the ring bodies of the bone plate, so that the joint portion can Firmly bond the bone plate.

According to the above structure, each embodiment of the lower jaw support prosthesis of the present invention can be combined with a peripheral portion of the bone plate, and the barrier portion can block the defect portion of the tibia and the bone plate to avoid the soft tissue of the bone plate directly contacting the defect portion. Or skin contact and friction, which has the effect of preventing the bone plate from penetrating the soft tissue or skin of the mouth.

〔this invention〕

1‧‧‧ bone plate

1a‧‧‧Act

11‧‧‧Lock hole

12‧‧‧Locking screws

2‧‧‧ lower jaw support prosthesis

21‧‧‧Barrier

21a‧‧‧ bearing surface

21b‧‧‧ bottom

211‧‧‧ 承部

211a‧‧‧容容

212‧‧‧Support film

22‧‧‧Extension

221‧‧‧Combination Department

221a‧‧‧ Missing slot

222‧‧‧Fixed holes

223‧‧‧Baffle

23‧‧‧ fixing screws

X‧‧‧ longitudinal direction

R‧‧‧ recess

B‧‧‧ Lower jaw bone

B1‧‧‧Defected parts

[Use]

1‧‧‧ bone plate

11‧‧‧Lock hole

12‧‧‧Locking screws

Figure 1: Appearance of the bone plate used in the existing mandibular reconstruction surgery.

Fig. 2 is a perspective view showing the appearance of the first embodiment of the present invention.

Fig. 3 is a schematic view showing the appearance of a bone plate in combination with a first embodiment of the present invention.

Fig. 4 is a schematic view showing the appearance of the first embodiment of the present invention together with the bone plate fixed to the mandible.

Figure 5 is a schematic view showing the appearance of a second embodiment of the present invention.

Figure 6 is a schematic view showing the appearance of a second embodiment of the present invention in combination with a bone plate.

Figure 7 is a schematic view showing the appearance of the second embodiment of the present invention together with the bone plate fixed to the mandible.

Fig. 8 is a perspective view showing the appearance of a third embodiment of the present invention.

Figure 9 is a schematic view showing the appearance of a third embodiment of the present invention in combination with a bone plate.

Fig. 10 is a schematic view showing the appearance of the third embodiment of the present invention together with the bone plate fixed to the mandible.

The above and other objects, features and advantages of the present invention will become more <RTIgt; The first embodiment of the lower jaw support prosthesis 2 of the present invention, the lower jaw support prosthesis 2 is adapted to be coupled to a bone plate 1, and the lower jaw support prosthesis 2 comprises a barrier portion 21 and two extension portions 22, the two extensions The portions 22 are respectively disposed at two ends of the blocking portion 21.

The blocking portion 21 has a bearing surface 21a in a longitudinal direction X. The blocking portion 21 is provided with a receiving portion 211 on the bearing surface 21a. The receiving portion 211 is adapted to receive the bone plate 1.

The two extending portions 22 are respectively disposed at two ends of the blocking portion 21 , and the two extending portions 22 respectively extend away from the blocking portion 21 . In this embodiment, the two extending portions 22 can be respectively connected to the bearing surfaces 21a at the two ends of the blocking portion 21, whereby the two extending portions 22 and the blocking portion 21 have a height difference in the longitudinal direction X. . Each of the extensions 22 has a knot The joint portion 221 is adapted to be coupled to the bone plate 1.

Referring to FIG. 3, when the first embodiment of the lower jaw support prosthesis 2 is combined with a bone plate 1, the receiving portion 211 of the blocking portion 21 is adapted to receive the bone plate 1, and each of the extension portions The joint portion 221 of the 22 is also available for bonding to the bone plate 1, and therefore, the lower jaw support prosthesis 2 can be coupled to the outer circumference of the bone plate 1.

In this embodiment, the two extending portions 22 and the blocking portion 21 have a height difference in the longitudinal direction X. Therefore, when the lower jaw supporting prosthesis 2 is coupled to the bone plate 1, the two extending portions 22 are The blocking portion 21 may be located on both sides of the bone plate 1 in the longitudinal direction X. The blocking portion 21 is formed below the bone plate 1 (in terms of the drawing), and the two extending portions 22 are formed above the bone plate 1 (in terms of the drawing).

With the above structure, as shown in FIG. 4, when the first embodiment of the lower jaw support prosthesis 2 of the present invention is actually used, it can be coupled to the outer periphery of the bone plate 1, so that the bone plate 1 can be used to fix the tibia B. The bone plate 1 includes a plurality of locking holes 11 for the locking screw 12 to lock the bone plate 1 to a position where the lower jaw B is not missing. The obstruction portion 21 is located opposite to the defect portion B1 of the mandible B.

The sacral support prosthesis 2 can be coupled to the outer periphery of the bone plate 1. Since the barrier portion 21 can receive the bone plate 1, the blocking portion 21 can effectively block the defect portion B1 of the lower tibia B and the bone plate. 1. To avoid contact and friction between the bone plate 1 and the soft tissue or skin of the defect site B1.

In addition, the barrier portion 21 of the chin support prosthesis 2 and the outer edge of the second extension portion 22 can provide a smooth contact surface for abutting the lower tibia B, the oral soft tissue or the skin, so that the lower tibia B, The soft tissue or skin of the mouth has a large contact area with the bone plate 1 and the lower jaw support prosthesis 2 to further reduce the pressure experienced by the lower jaw bone B, oral soft tissue or skin in contact with the bone plate 1.

In this embodiment, the chin support prosthesis 2 is preferably made of a biocompatible material. The hardness of the chin support prosthesis 2 is less than the hardness of the bone plate 1. For example, the chin support prosthesis 2 can be made of a biocompatible material that conforms to the International Standard Organization (ISO) specification ISO 10993, and in general, the bone plate 1 is made of titanium metal. Made of a material, the hardness of the chin support prosthesis 2 is less than the hardness of the titanium metal. Thereby, the chin support prosthesis 2 is not easy to rub through the soft tissue or the skin, so the chin support prosthesis 2 can abut against the soft tissue or the skin to reduce the pressure on the soft tissue or the skin to contact the bone plate 1. .

Furthermore, each of the extending portions 22 can be further provided with a fixing hole 222, and the fixing hole 222 can pass through a fixing screw 23 to fix the extending portion 22 to a position where the lower tibia B is not broken. Thereby, the first embodiment of the chin support prosthesis 2 can be used to fix the joint stability of the chin support prosthesis 2 and the bone plate 1 by fixing the two extension portions 22 to the lower tibia B.

In addition, since the bone plate 1 is formed in a curved shape corresponding to the lower tibia B, the blocking portion 21 and the two extending portions 22 can collectively form a curved shape corresponding to the bone plate 1, so that the blocking portion 21 and the two extending portions are formed. The portion 22 can be formed around a recess R. The blocking portion 21 can be provided with a support piece 212, and the support piece 212 extends toward the concave portion R. Thereby, when the bone plate 1 is locked to the lower tibia B, the lower tibia B can be received in the concave portion R, and the support piece 212 can extend into the defect portion B1 of the lower tibia B to shield the defect portion. The oral soft tissue of B1 further prevents the bone plate 1 from directly contacting and rubbing with the soft tissue of the defect site B1. In addition, the lower tibia B has a defect surface B2 facing the defect portion B1, and the end edge of the support piece 212 can abut the defect surface B2 to provide proper tension of the lower tibia B and surrounding soft tissue, so that the chin support The first embodiment of the prosthesis 2 can support the mandible B, further avoiding the friction of the oral soft tissue or skin contact of the defect site B1, and maintaining the continuity of the shape of the mandibular B, contributing to the defect site B1. Complex.

On the other hand, please refer to the second and third figures, since the bone plate 1 can include a plurality of interconnected ring bodies 1a, each of the ring bodies 1a is provided with a locking hole 11 for locking screws. The locking portion 21 of the blocking portion 21 can be provided with a plurality of consecutively arranged cavities 211a corresponding to the ring body 1a of the bone plate 1. Each of the receiving grooves 211a can accommodate one of the ring bodies of the bone plate 1. 1a, such that the receiving portion 211 can receive and position the bone plate 1. Similarly, the joint portion 221 of each of the extending portions 22 can be provided with a plurality of consecutively arranged notches 221a corresponding to the ring body 1a of the bone plate 1, and each of the notches 221a can abut one of the ring bodies 1a of the bone plate 1. The joint portion 221 is configured to firmly bond the bone plate 1.

However, the embodiment of the lower jaw support prosthesis 2 of the present invention can provide a corresponding mounting portion 211 and a joint portion 221 structure corresponding to the form of the bone plate 1, for example, if the bone plate 1 has a rectangular strip shape. The receiving portion 211 can be formed into a long groove shape for receiving the edge of the bone plate 1. Accordingly, the present invention does not limit the detailed structure of the joint portion 211 of the blocking portion 21 and the joint portion 221 of each of the extending portions 22.

Referring to FIG. 5, which is a second embodiment of the lower jaw support prosthesis 2 of the present invention, which differs from the first embodiment in that the barrier portion 21 has the bearing surface in the longitudinal direction X. 21a is opposite to one of the bottom surfaces 21b, and the two extending portions 22 are respectively connected between the bearing surface 21a and the bottom surface 21b at both ends of the blocking portion 21, so that the blocking portion 21 and the two extending portions 22 can form a continuous curved surface. Thereby, the two extension portions 22 and the blocking portion 21 do not have a height difference in the longitudinal direction X.

Referring to FIG. 6 , since the two extension portions 22 and the blocking portion 21 do not have a height difference in the longitudinal direction X, when the lower jaw support prosthesis 2 is coupled to the bone plate 1, the two extensions The portion 22 and the blocking portion 21 may be located on the same side of the bone plate 1 in the longitudinal direction X. The blocking portion 21 and the two extending portions 22 are formed under the bone plate 1 (in terms of the drawing).

With the above structure, referring to FIG. 7, when the second embodiment of the lower jaw support prosthesis 2 of the present invention is actually used, it is also bonded to the outer periphery of the bone plate 1, so that the bone plate 1 can be used to fix the tibia B. . Among them, when the space below the lower edge of the tibia B is larger, the patient The two extending portions 22 and the blocking portion 21 may be located on the same side of the bone plate 1 in the longitudinal direction X. Therefore, the two extending portions 22 will be formed under the bone plate 1 so that the two extending portions 22 can be easily The patient extends into the patient's mouth and is convenient for the user (eg, a physician) to fix each of the extensions 22 to the lower edge of the mandible B with a set screw 23. In contrast, referring to FIG. 4, when the space of the upper edge of the tibia B is larger under the patient, the first embodiment of the chin support prosthesis 2 can be selected, by making the two extensions 22 The blocking portion 21 may be located on the two sides of the bone plate 1 in the longitudinal direction X, and the two extending portions 22 will be formed above the bone plate 1 so that the two extending portions 22 can easily protrude into the patient's mouth, and It is convenient for the user to fix the extension portions 22 to the upper edge of the lower tibia B by the fixing screws 23. In other words, the first and second embodiments of the lower jaw support prosthesis 2 of the present invention allow the user to freely select according to the patient's oral condition to ensure that the two extensions 22 can extend into the patient's mouth without excessively rubbing the patient's lower jaw. Tibia B, oral soft tissue or skin.

Referring to Figures 8 and 9, the third embodiment of the lower jaw support prosthesis 2 of the present invention is different from the foregoing embodiments in that each of the extensions 22 is further provided with a partition 223. The plate 223 may be disposed on a side of the extending portion 22 away from the concave portion R, and the partition plate 223 extends along the longitudinal direction X, whereby when the lower jaw supporting prosthesis 2 is coupled to the bone plate 1, the The partition 223 can shield the bone plate 1 to prevent the bone plate 1 from rubbing the soft tissues or skin of the mouth. In addition, as shown in FIG. 10 , the partition plate 223 directly shields the locking hole 11 of the bone plate 1 , so that a locking screw 12 can penetrate the partition plate 223 and pass the locking hole 11 through the locking hole 11 . The bone plate 1 is locked at a position where the lower tibia B is not damaged, whereby the extension portion 22 can be fixed together at a position where the lower tibia B is not deficient to lift the chin support prosthesis 2 and the bone plate The combination of 1 is stable. Accordingly, the extension portion 22 of the foregoing embodiments must be additionally provided with a fixing hole 222 for fixing the extension portion 22, and the third embodiment of the chin support prosthesis 2 can be locked by the user. When the bone plate 1 is fixed to the extension portion 22, the extension portion 22 does not need to be additionally provided with the fixing hole 222, which can reduce the structural complexity of the chin support prosthesis 2 and simplify the hand. Steps.

It should be noted that the bone plate 1 needs to select an appropriate length specification and bending curvature according to the size of the defect portion B1 of the patient's lower jaw B defect. Therefore, the embodiments of the lower jaw support prosthesis 2 of the present invention can also be used by the user according to the patient. The size of the defect portion B1 of the lower jaw B, the size and curvature of the barrier portion 21 and the two extension portions 22 are appropriately selected to ensure that the lower jaw support prosthesis 2 can be coupled to the outer circumference of the bone plate 1, and the obstruction portion is made 21 can effectively block the defect portion B1 of the lower jaw bone B. Similarly, in some embodiments of the present invention, the blocking portion 21 can be provided with a supporting piece 212. The size and shape of the supporting piece 212 can also be appropriately selected according to the size of the defect portion B1 of the patient's lower jaw B to ensure the size. The end edge of the support piece 212 may abut the defect surface B2 of the lower tibia B facing the defect portion B1.

According to the foregoing structure, each embodiment of the lower jaw support prosthesis 2 of the present invention is provided with a blocking portion 21 and two extending portions 22, and the two extending portions 22 are respectively disposed at two ends of the blocking portion 21, so that the lower jaw supporting prosthesis 2 The bone plate 1 can be combined with the bone plate 1 , and the barrier portion 21 can effectively block the defect portion B1 of the lower tibia B and the bone plate 1 to avoid the bone plate 1 Directly contacting and rubbing the soft tissue or skin of the defect site B1 has the effect of preventing the bone plate 1 from penetrating into the soft tissue or skin of the mouth to avoid infection or the like. Moreover, the chin support prosthesis 2 can enlarge the contact area between the lower tibia B, the oral soft tissue or the skin and the bone plate 1 and the chin support prosthesis 2 to further reduce the lower tibia B, oral soft tissue or skin The bone plate 1 is in contact with the pressure, and the hardness of the lower jaw support prosthesis 2 is smaller than the hardness of the bone plate 1. The lower jaw support prosthesis 2 is not easy to rub through the soft tissue or the skin, so the lower jaw support prosthesis 2 of the present invention Each of the embodiments does have the effect of preventing the bone plate 1 from penetrating the soft tissues or skin of the mouth.

In addition, in some embodiments of the present invention, the blocking portion 21 may be provided with a supporting piece 212. When the bone plate 1 is locked to the lower tibia B, the supporting piece 212 may extend into the defect portion B1 of the lower tibia B. To cover the soft tissue of the defect portion B1, and the support piece The end edge of 212 can abut the defect surface B2 of the lower tibia B toward the defect site B1 to provide proper tension of the lower tibia B and surrounding soft tissue, so that the first embodiment of the chin support prosthesis 2 can support the lower portion The tibia B further prevents the oral soft tissue or skin contact of the defect site B1 from rubbing, and maintains the continuity of the shape of the mandibular bone B, contributing to the complexation of the defect site B1.

In summary, in the embodiment of the present invention, the iliac support prosthesis can appropriately select the size and curvature of the obstruction portion and the two extension portions according to the size of the defect portion of the patient's lower jaw bone, so that the sacral support prosthesis can be combined. The outer periphery of the bone plate and the barrier portion can effectively block the defect portion of the lower jaw bone, and the effect of preventing the bone plate from penetrating the soft tissue or skin of the oral cavity can be achieved.

While the invention has been described in connection with the preferred embodiments described above, it is not intended to limit the scope of the invention. The technical scope of the invention is protected, and therefore the scope of the invention is defined by the scope of the appended claims.

1‧‧‧ bone plate

1a‧‧‧Act

11‧‧‧Lock hole

2‧‧‧ lower jaw support prosthesis

21‧‧‧Barrier

21a‧‧‧ bearing surface

211‧‧‧ 承部

211a‧‧‧容容

212‧‧‧Support film

22‧‧‧Extension

221‧‧‧Combination Department

221a‧‧‧ Missing slot

222‧‧‧Fixed holes

X‧‧‧ longitudinal direction

R‧‧‧ recess

Claims (10)

A chin support prosthesis, comprising: a blocking portion having a bearing surface in a longitudinal direction, the blocking portion being provided with a receiving portion on the bearing surface, the receiving portion for receiving a bone plate; The two extending portions are respectively disposed at two ends of the blocking portion, and the two extending portions respectively extend away from the blocking portion, and each of the extending portions has a joint portion for coupling the bone plate. The iliac support prosthesis according to the first aspect of the patent application, wherein the two extension portions are respectively connected to the bearing surfaces of the two ends of the blocking portion, and the two extending portions and the blocking portion are respectively located in the bone in the longitudinal direction. The two sides of the board. The haptic support prosthesis according to the first aspect of the invention, wherein the blocking portion has a bottom surface opposite to the bearing surface in the longitudinal direction, and the two extending portions are respectively connected to the bearing surface of the two ends of the blocking portion Between the bottom surfaces, the two extensions and the blocking portion are located on the same side of the bone plate in the longitudinal direction. The iliac support prosthesis as described in claim 1, 2 or 3, wherein each of the extensions is further provided with a fixing hole for a fixing screw to fix the extension to the lower tibia. . The iliac support prosthesis as described in claim 1, 2 or 3, wherein the barrier portion and the second extension portion form a curved arc corresponding to the two extension portions, and the barrier portion and the two extension portions form a concave portion Each of the extending portions is further provided with a partition plate disposed on a side of the extending portion away from the concave portion, and the partition plate extends along the longitudinal direction, and the partition plate shields the bone plate. The iliac support prosthesis as described in claim 5, wherein the bone plate is provided with a locking hole, the baffle is shielded by the locking hole, a locking screw is inserted through the baffle and the lock is passed through the baffle The solid hole locks the bone plate to the tibia. The iliac support prosthesis as described in claim 1, 2 or 3, wherein the obstruction portion and the second extension portion form a curved arc corresponding to the bone plate, and the obstruction portion and the two extension portions are surrounded by a shape Forming a recess, the blocking portion is provided with a support piece, and the support piece extends toward the recess. The iliac support prosthesis as described in claim 7, wherein the bone plate is locked to the lower tibia, and the lower tibia is received in the concave portion, and the support piece is inserted into a defect portion of the lower tibia, and The mandible has a defect surface facing the defect portion, and an end edge of the support piece abuts against the defect surface. The iliac support prosthesis as described in claim 1, 2 or 3, wherein the bone plate comprises a plurality of interconnected rings, and the receiving portion of the blocking portion is provided with a plurality of consecutively arranged pockets, each The receptacle is adapted to receive one of the rings of the bone plate. The iliac support prosthesis as described in claim 1, 2 or 3, wherein the bone plate comprises a plurality of interconnected rings, and the joint of each of the extensions is provided with a plurality of consecutively arranged vacancies, each The missing slot is for abutting one of the rings of the bone plate.