CN214259417U - Individualized knee joint bone surface positioning osteotomy navigation system - Google Patents

Abstract

The utility model provides a personalized knee joint bone surface positioning osteotomy navigation system, which belongs to the technical field of knee joint osteotomy systems and comprises a four-in-one positioning osteotomy device, a far-end horizontal osteotomy device and a far-end drilling guider, wherein the four-in-one positioning osteotomy device is used for removing bone tissues in four directions of thighbone, the far-end horizontal osteotomy device is used for removing bone tissues in a far-end horizontal direction, and the far-end drilling guider is used for drilling a far-end bone surface; the four-in-one positioning osteotome is provided with four-in-one osteotome guide grooves and an inner and outer positioning plate connected with the four-in-one osteotome guide grooves, and a plurality of nail paths are arranged on the inner and outer positioning plates. The utility model discloses simple structure, it is convenient to fix a position, and not only positioning accuracy is high, has still reduced the design and the processing degree of difficulty of individualized location osteotomy system.

Description

Individualized knee joint bone surface positioning osteotomy navigation system

Technical Field

The utility model belongs to the technical field of the knee joint cuts bone system, especially, relate to a individualized knee joint bone face location cuts bone navigation.

Background

The existing individualized knee joint femur side positioning osteotomy technology basically abandons the mode of intramedullary positioning and adopts patient bone surface information as a positioning basis, thereby simplifying the operation process to a certain extent and reducing the operation trauma of the patient. On the other hand, however, the personalized navigation system is still based on the traditional surgical technique in the osteotomy method. In the knee joint replacement surgery, 5-direction osteotomies are usually performed on the femoral condyle, the horizontal osteotomy is performed in the osteotomy sequence, and then the multifunctional composite osteotomy instrument is used for performing subsequent osteotomy operation by taking the horizontal osteotomy surface as a reference.

According to the traditional operation scheme, a complex intramedullary positioning system is adopted to firstly determine the position of the osteotomy surface in the horizontal direction of the far end, and then an all-in-one osteotomy instrument is adopted to carry out subsequent osteotomy. The personalized operation scheme also adopts the same idea, firstly utilizes the bone surface information to position the osteotomy guide plate at the far end in the horizontal direction, and then can utilize the traditional instrument or continuously adopt the osteotomy instrument with personalized design to carry out subsequent osteotomy. The existing personalized surgical osteotomy scheme is still a surgical scheme which is planned by relying on the traditional positioning instrument, so that the flexibility of the personalized instrument is not effectively exerted. The personalized osteotomy navigation instrument needs to perform intraoperative positioning by means of bone surface information, and a traditional operation scheme is adopted to remove far-end bone tissues firstly, so that a large area of positioning area is removed, and the remaining femoral anterior condyle pulley groove surface has cartilage tissues with uneven thicknesses, thereby reducing the positioning precision of the personalized instrument to a great extent. In addition, the design concept of the existing individualized knee joint femur side osteotomy instrument is still developed towards multifunctional integration, so that the individualized surgical instrument tends to be complex in structure, the design difficulty is increased, the processing cost is increased along with the increase of the design difficulty, and the individualized surgical technology is not favorably developed.

SUMMERY OF THE UTILITY MODEL

In view of this, the utility model aims at providing an individualized knee joint bone face location cuts bone navigation system can solve above-mentioned problem.

In order to achieve the above purpose, the technical scheme of the utility model is realized like this: a personalized knee joint bone surface positioning osteotomy navigation system comprises a four-in-one positioning osteotomy device, a far-end horizontal osteotomy device and a far-end drilling guide device, wherein the four-in-one positioning osteotomy device is used for removing bone tissues in four directions of a femur, the far-end horizontal osteotomy device is used for removing bone tissues in a far-end horizontal direction, and the far-end drilling guide device is used for drilling a far-end bone surface; the four-in-one positioning osteotome is provided with four-in-one osteotome guide grooves and an inner and outer positioning plate connected with the four-in-one osteotome guide grooves, and a plurality of nail paths are arranged on the inner and outer positioning plates.

Further, four unification location osteotomies ware includes that four unification cut bone guide way, inboard locating plate, outside locating plate, inboard nail way and outside nail way to constitute, four unification cut bone guide ways respectively with inboard locating plate and outside locating plate are connected, simultaneously four unification cut bone guide ways are the closed structure of inside and outside, just four unification cut bone guide way's fluting runs through inboard locating plate and outside locating plate, inboard locating plate is provided with in the position that is close to its edge inboard nail way, the position that is close to its edge in the outside locating plate is provided with the outside nail way.

Further, the four-in-one osteotomy guide groove comprises an anterior condyle osteotomy guide groove, an anterior oblique osteotomy guide groove, a posterior oblique osteotomy guide groove and a posterior condyle osteotomy guide groove, and the osteotomy guide grooves in the four directions are connected in the anterior-posterior direction through a curved connecting plate.

Furthermore, the joint areas of the medial positioning plate and the lateral positioning plate respectively extend from the edge of the anterior condyle to the posterior condyle in the anterior-posterior direction, and respectively extend from the intercondylar to the edge in the medial-lateral direction.

Furthermore, the medial nail path comprises a medial first nail path, a medial second nail path and a medial third nail path, and the directions of the nail paths of the three nail paths are all inclined and point to the intercondylar; the lateral nail path comprises a first lateral nail path, a second lateral nail path and a third lateral nail path, and the nail path directions of the three nail paths are all inclined and point to the intercondylar.

Furthermore, the distal horizontal osteotome comprises a horizontal osteotome groove, a first front oblique positioning plate, a front condyle positioning plate and a front side nail way, wherein the horizontal osteotome groove is fixedly connected with the first front oblique positioning plate and the front condyle positioning plate respectively, the front side nail way is arranged on the front condyle positioning plate and comprises a front side first nail way, a front side second nail way and a front side third nail way, and the nail way directions of the three nail ways are all perpendicular to the front condyle positioning plate.

Further, the distal end drilling director comprises a second front oblique positioning plate, a distal end positioning plate, an inner rear oblique positioning plate, an outer rear oblique positioning plate, an inner drilling guide sleeve and an outer drilling guide sleeve, wherein the second front oblique positioning plate passes through the distal end positioning plate and the inner rear oblique positioning plate are connected, the distal end positioning plate is provided with the inner drilling guide sleeve and the outer drilling guide sleeve, and simultaneously, holes axially arranged on the inner drilling guide sleeve and the outer drilling guide sleeve are respectively penetrated through the distal end positioning plate.

Compared with the prior art, individualized knee joint bone face location osteotomy navigation have following advantage:

(1) the four-in-one positioning osteotome adopts a large-area bone surface area inside and outside the distal femur to perform intraoperative positioning, the guide plate has good fitting stability and higher positioning precision, and the position of the guide plate can be quickly found in the intraoperative setting process;

(2) the four-in-one positioning osteotome adopts an inner and outer side inclined nail placing mode, and realizes a stable fixing effect under the condition of not interfering an osteotomy route;

(3) the simple and accurate positioning can be realized by utilizing the osteotomy surfaces in different directions after the osteotomy of the four-in-one positioning osteotomy device is adopted, the remote horizontal osteotomy device adopted by the utility model has the advantages of simple structure, convenient positioning mode and high reliability;

(4) the utility model can adjust the sequence of osteotomy and drilling in the operation, simplify the structure of the guide plate and simultaneously improve the positioning precision of the osteotomy system, so that the operation in the operation is more convenient and smooth;

(5) the drilling step of the distal horizontal plane of the femur is separately stripped by adopting the distal drilling guider, so that the structure of the four-in-one osteotome is simplified, and the design difficulty and the processing difficulty of the whole personalized positioning osteotome system are reduced;

(6) each component of the system is of a thin plate type structure with uniform thickness, so that materials can be effectively saved;

(7) the system can be manufactured by 3D printing by adopting medical metal and high-strength medical non-metal materials.

Drawings

The accompanying drawings, which form a part hereof, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention without undue limitation. In the drawings:

fig. 1 is a schematic structural diagram of a personalized knee joint facet positioning osteotomy navigation system according to an embodiment of the present invention;

FIG. 2 is a schematic structural view of a four-in-one positioning osteotome according to an embodiment of the present invention;

FIG. 3 is a schematic view of the placement of a four-in-one positioning osteotome according to an embodiment of the present invention;

FIG. 4 is a schematic view of a distal osteotomy of a femur after a four-in-one osteotomy;

FIG. 5 is a schematic side view of a four-in-one positioning osteotome according to an embodiment of the present invention;

FIG. 6 is a schematic top view of a four-in-one positioning osteotome according to an embodiment of the present invention;

fig. 7 is a schematic view of the placement of a distal horizontal osteotome in accordance with an embodiment of the present invention;

FIG. 8 is a schematic view of the distal end of a femur after a distal horizontal resection;

fig. 9 is a schematic front view of a distal drill guide according to an embodiment of the present invention;

fig. 10 is a rear side view of a distal drill guide according to an embodiment of the present invention.

Description of reference numerals:

10. four-in-one positioning osteotome; 20. a distal horizontal osteotomy; 30. a distal drill guide;

110. a four-in-one osteotomy guide slot; 111. an anterior condyle osteotomy guide slot; 112. a front oblique osteotomy guide groove; 113. a posterior oblique osteotomy guide slot; 114. a posterior condylar osteotomy guide slot; 115. a curved surface connecting plate; 121. an inner side positioning plate; 122. an outer positioning plate; 130. an inner nail path; 131. a first nail path on the inner side; 132. an inner second nail path; 133. a third nail path on the inner side; 140. an outer nail path; 141. a first outer nail path; 142. a second outer nail path; 143. a third nail path on the outer side;

210. a horizontal osteotomy groove; 221. a first front inclined positioning plate; 222. a front condyle positioning plate; 230. a front side nail path; 231. a front first nail path; 232. a front second nail path; 233. a third nail path at the front side;

311. a second front inclined positioning plate; 312. a distal positioning plate; 313. an inner rear inclined positioning plate; 314. An outer rear inclined positioning plate; 321. drilling a guide cylinder on the inner side; 322. drilling a guide cylinder on the outer side;

01. a distal femur; 11. the anterior femoral condyle surface; 12. a femoral anterior slope; 13. a medial posterior slope of the femur; 14. a lateral posterior slope of the femur; 15. the medial femoral posterior condylar surface; 16. the lateral posterior condylar surface of the femur; 17. the distal femoral osteotomy face.

Detailed Description

It should be noted that, in the present invention, the embodiments and features of the embodiments may be combined with each other without conflict.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are used merely for convenience of description and for simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention. Furthermore, the terms "first", "second", etc. are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first," "second," etc. may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

In the description of the present invention, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.

As shown in fig. 1-10, the present invention relates to a personalized knee joint bone positioning osteotomy navigation system, which comprises a four-in-one positioning osteotomy device 10, a distal horizontal osteotomy device 20 and a distal drilling guide 30, wherein the four-in-one positioning osteotomy device 10 is used for removing bone tissues in four directions of femur, and the four-in-one positioning osteotomy device 10 is arranged at a position corresponding to the bone surface, because the inner and outer positioning plates 122 of the four-in-one positioning osteotomy device 10 are designed according to the bone surface shape of a patient, the arrangement position of the four-in-one positioning osteotomy device 10 is unique, and accurate positioning can be easily realized through manual adjustment in the operation; the distal horizontal osteotome 20 is used for removing bone tissue in the distal horizontal direction, the distal drilling guide 30 is used for drilling a distal bone surface, and the three are respectively used for different osteotomy procedures in the operation; the drilling step of the horizontal plane of the distal femur 01 is separated by adopting the distal drilling guider 30, the structure of the existing four-in-one osteotome is simplified, the design difficulty and the processing difficulty of the whole personalized positioning osteotome system are reduced, meanwhile, the sequence of osteotomy and drilling in the operation is adjusted by aiming at the effects of the four-in-one positioning osteotome 10, the distal horizontal osteotome 20 and the distal drilling guider 30, the positioning precision of the osteotome system is improved while the structure of the guide plate is simplified, the operation in the operation is more convenient and smoother, the four-in-one positioning osteotome 10 is provided with the four-in-one osteotome guide groove 110 and the inner and outer positioning plates 122 connected with the four-in-one osteotome guide groove, the inner and outer positioning plates 122 are provided with a plurality of nail paths, the four-in-one positioning osteotome 10 adopts the large-area of the inner and outer bone surfaces of the distal femur 01 to perform the positioning in the operation, and the fitting stability of the guide plate is good, the positioning accuracy is higher, and the guide plate position can be found more fast to the installation in the art.

Four unification location osteotomy device 10 includes that four unification osteotomy guide ways 110, inboard locating plate 121, outside locating plate 122, inboard nail way 130 and outside nail way 140 constitute, four unifications cut bone guide ways 110 respectively with inboard locating plate 121 and outside locating plate 122 are connected, simultaneously four unifications cut bone guide ways 110 and be the closed structure of inside and outside, can prevent that the pendulum from possessing the sliding-out osteotomy groove, just four unifications cut bone guide ways 110's fluting runs through inboard locating plate 121 and outside locating plate 122, do not receive the interference along the motion of cutting bone groove direction cutting bone pendulum utensil, inboard locating plate is provided with in the position that is close to its edge inboard nail way 130, the outside locating plate is provided with in the position that is close to its edge outside nail way 140.

The four-in-one osteotomy guide groove 110 comprises an anterior condyle osteotomy guide groove 111, an anterior oblique osteotomy guide groove 112, a posterior oblique osteotomy guide groove 113 and a posterior condyle osteotomy guide groove 114, the osteotomy guide grooves in the four directions are connected in the anterior-posterior direction through a curved surface connecting plate 115, the four osteotomy guide grooves correspond to the femoral prosthesis in the directions, and meanwhile, the groove walls of the osteotomy guide grooves in the four directions are uniform in thickness, so that materials can be effectively saved.

The groove wall thickness ranges of the anterior condyle osteotomy guide groove 111, the anterior oblique osteotomy guide groove 112, the posterior oblique osteotomy guide groove 113 and the posterior condyle osteotomy guide groove 114 are all 0.8mm to 3.5 mm; the width of the osteotomy guide groove in the four directions is 1.1 to 2 times of the thickness of the osteotomy cutter; the effective guide distance range of the osteotomy guide groove in four directions is 8mm to 40 mm.

The upper surfaces of the inner positioning plate 121 and the outer positioning plate 122 are individually designed according to the shape of the inner and outer bone faces of the distal femur end 01, the joint areas of the inner positioning plate 121 and the outer positioning plate 122 extend from the edge of the front condyle to the rear condyle in the front-back direction, the joint areas of the inner positioning plate 121 and the outer positioning plate 122 extend from the periphery of the front condyle to the periphery of the rear condyle in the inner-back direction, and the grooves along the direction of the osteotomy groove penetrate through the inner and outer positioning plates 122 to prevent interference with the osteotomy tool.

The medial nail path 130 comprises a medial first nail path 131, a medial second nail path 132 and a medial third nail path 133, and the directions of the nail paths of the three nail paths are all inclined and point to the intercondylar; the lateral nail path 140 includes a lateral first nail path 141, a lateral second nail path 142 and a lateral third nail path 143, the nail path directions of the three nail paths are all inclined and point to the intercondylar, the bone nails do not interfere with each other along the nail path directions, and the bone nails are the existing foundation. The inner nail path 130 and the outer nail path 140 form an included angle, and play a role in fixing and pressing the guide plate.

The nail path guide distance ranges of the inner nail path 130 and the outer nail path 140 are respectively 3mm to 6 mm.

The distal horizontal osteotome 20 comprises a horizontal osteotome groove 210, a first front oblique positioning plate 221, a front condyle positioning plate 222 and a front side nail path 230, wherein the horizontal osteotome groove 210 is fixedly connected with the first front oblique positioning plate 221 and the front condyle positioning plate 222 respectively, the front side nail path 230 is arranged on the front condyle positioning plate 222, the front side nail path 230 comprises a front side first nail path 231, a front side second nail path 232 and a front side third nail path 233, and the nail path directions of the three nail paths are all perpendicular to the front condyle positioning plate 222.

The effective navigation distance range of the horizontal osteotomy groove 210 is 12mm to 36mm, and the width of the inner lateral groove and the outer lateral groove of the horizontal osteotomy groove 210 is 0.6 to 1.2 times of the width of the inner lateral groove and the outer lateral groove of the horizontal osteotomy surface of the distal femur 01; the thickness of the first anterior oblique positioning plate 221 and the first anterior condyle positioning plate 222 are both in the range of 0.6mm to 2.5 mm.

The distal drill guide 30 comprises a second front inclined positioning plate 311, a distal positioning plate 312, an inner rear inclined positioning plate 313, an outer rear inclined positioning plate 314, an inner drill guide cylinder 321 and an outer drill guide cylinder 322, the second front inclined positioning plate 311 is connected with the inner rear inclined positioning plate 313 through the distal positioning plate 312, the distal positioning plate 312 is provided with the inner drill guide cylinder 321 and the outer drill guide cylinder 322, and holes axially arranged on the inner drill guide cylinder 321 and the outer drill guide cylinder 322 respectively penetrate through the distal positioning plate 312;

the size and the shape of each positioning plate of the far-end drilling guider 30 are determined by the size and the shape of each osteotomy surface of a patient femur far-end 01, the thickness range of each positioning plate is 0.6mm to 2.5mm, the inner side drilling guide barrel 321 and the outer side drilling guide barrel 322 correspond to the position of a femur prosthesis positioning column respectively, the inner diameter of the inner side drilling guide barrel 321 and the inner diameter of the outer side drilling guide barrel 322 are matched with the diameter of the femur prosthesis positioning column respectively, the thickness of the barrel wall of the inner side drilling guide barrel 321 and the outer side drilling guide barrel 322 are 0.6mm to 1.5mm, and the depth of the guide barrel of the inner side drilling guide barrel 321 and the outer side drilling guide barrel 322 is 5mm to 12 mm.

In the actual working process, the distal end 01 of the femur is exposed in the operation, the four-in-one positioning osteotome 10 is arranged at the position corresponding to the bone surface, and the inner side positioning plate 121 and the outer side positioning plate 122 of the four-in-one positioning osteotome 10 are designed according to the shape of the bone surface of a patient, so that the arrangement position of the four-in-one positioning osteotome 10 is unique, and the accurate positioning is easily realized through manual adjustment in the operation; after the position of the four-in-one positioning osteotomy device 10 is aligned, the four-in-one positioning osteotomy device 10 is fixed by placing nails along the inner nail path 130 and the outer nail path 140 respectively; then, the bone is cut in sequence along the bone cutting grooves in four directions, and the utility model does not limit the sequence of the bone cutting in four directions;

fourthly, a femur far end 01 after the completion of the resection cuts out a femur front condyle surface 11, a femur front inclined surface 12, a femur inner rear inclined surface 13, a femur outer rear inclined surface 14, a femur inner rear condyle surface 15 and a femur outer rear condyle surface 16; taking out the positioning nails at two sides of the four-in-one positioning osteotome 10, taking down the four-in-one positioning osteotome 10, then placing the distal horizontal osteotome 20, attaching the first front oblique positioning plate 221 to the femur front oblique surface 12, attaching the front condyle positioning plate 222 to the femur front condyle surface 11, and fixing the distal horizontal osteotome 20 by the nails, thus carrying out the distal horizontal osteotome operation;

after accomplishing distal end level and cutting the bone, take out the location nail, take off distal end level and cut bone ware 20, settle distal end drilling director 30, align distal end drilling director 30 and thighbone distal end and cut bone surface 17 edge after, drill along inboard drilling guide 321 and outside drilling guide 322 respectively, it needs to notice here that distal end drilling director 30 only is used for drilling, need not structurally to fix through the bone nail and can realize the drilling direction function.

The above description is only a preferred embodiment of the present invention, and should not be taken as limiting the invention, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. The utility model provides a individualized knee joint bone face location cuts bone navigation which characterized in that: the bone cutting device comprises a four-in-one positioning osteotome (10), a distal horizontal osteotome (20) and a distal drilling guide (30), wherein the four-in-one positioning osteotome (10) is used for removing bone tissues in four directions of a femur, the distal horizontal osteotome (20) is used for removing bone tissues in a distal horizontal direction, and the distal drilling guide (30) is used for drilling a distal bone surface; the four-in-one positioning osteotomy device (10) is provided with four-in-one osteotomy guide grooves (110) and inner and outer positioning plates (122) connected with the four-in-one osteotomy guide grooves, and a plurality of nail paths are arranged on the inner and outer positioning plates (122).

2. The system of claim 1, wherein the system comprises: four unification location osteotomy ware (10) constitute including four unification osteotomy guide ways (110), inboard locating plate (121), outside locating plate (122), inboard nail way (130) and outside nail way (140), four unifications osteotomy guide ways (110) respectively with inboard locating plate (121) and outside locating plate (122) are connected, simultaneously four unifications are cut bone guide ways (110) and are the closed structure of inside and outside, just four unifications are cut the fluting of bone guide ways (110) and are run through inboard locating plate (121) and outside locating plate (122), inboard locating plate is provided with in the position that is close to its edge inboard nail way (130), the outside locating plate is provided with in the position that is close to its edge outside nail way (140).

3. The system of claim 2, wherein the system comprises: the four-in-one osteotomy guide groove (110) comprises an anterior condyle osteotomy guide groove (111), an anterior oblique osteotomy guide groove (112), a posterior oblique osteotomy guide groove (113) and a posterior condyle osteotomy guide groove (114), and the osteotomy guide grooves in the four directions are connected in the anterior-posterior direction through a curved connecting plate (115).

4. The system of claim 2, wherein the system comprises: the attaching areas of the medial positioning plate (121) and the lateral positioning plate (122) respectively extend from the edge of the anterior condyle to the posterior condyle in the anterior-posterior direction, and extend from the intercondylar to the edge in the medial-lateral direction.

5. The system of claim 2, wherein the system comprises: the medial nail path (130) comprises a medial first nail path (131), a medial second nail path (132) and a medial third nail path (133), and the directions of the nail paths of the three nail paths are all inclined and point to the intercondylar; the lateral nail path (140) comprises a lateral first nail path (141), a lateral second nail path (142) and a lateral third nail path (143), and the directions of the nail paths of the three nail paths are all inclined and point to the intercondylar.

6. The system of claim 1, wherein the system comprises: the distal horizontal osteotome device (20) comprises a horizontal osteotome groove (210), a first front oblique positioning plate (221), a front condyle positioning plate (222) and a front side nail path (230), wherein the horizontal osteotome groove (210) is fixedly connected with the first front oblique positioning plate (221) and the front condyle positioning plate (222) respectively, the front side nail path (230) is arranged on the front condyle positioning plate (222), the front side nail path (230) comprises a front side first nail path (231), a front side second nail path (232) and a front side third nail path (233), and the nail path directions of the three nail paths are perpendicular to the front condyle positioning plate (222).

7. The system of claim 1, wherein the system comprises: distal end drilling director (30) constitute including oblique locating plate (311), distal end locating plate (312), inboard oblique locating plate (313) behind oblique locating plate (314) behind the second, inboard drilling guide cylinder (321) and outside drilling guide cylinder (322), preceding oblique locating plate (311) of second passes through distal end locating plate (312) with inboard oblique locating plate (313) behind is connected, be provided with inboard drilling guide cylinder (321) and outside drilling guide cylinder (322) on distal end locating plate (312), simultaneously the hole that axial setting was gone up on inboard drilling guide cylinder (321) and outside drilling guide cylinder (322) runs through respectively distal end locating plate (312).

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