CN106923895B

CN106923895B - Hip stretching device

Info

Publication number: CN106923895B
Application number: CN201511016471.2A
Authority: CN
Inventors: 吴健华; 秦岭; 麦福达; 郑玉臣; 邓宁; 周泳豪; 张健森
Original assignee: Chinese University of Hong Kong CUHK
Current assignee: Chinese University of Hong Kong CUHK
Priority date: 2015-12-29
Filing date: 2015-12-29
Publication date: 2020-10-16
Anticipated expiration: 2035-12-29
Also published as: CN106923895A

Abstract

A hip distraction device includes an external ball joint, an upper fixation unit pivotally coupled to a front side of the external ball joint and securable to a hip bone, and a lower fixation unit coupled to a bottom end of the external ball joint and securable to a femur. The external ball joint includes a slider housing defining a rail shaped to have a curved channel along the curvature of which the rail is movable up and down in the slider housing relative to the upper fixation unit such that the femur abducts or adducts relative to the hip bone.

Description

Hip stretching device

Technical Field

The present disclosure relates to orthopedic hip distraction devices. In particular, the present disclosure relates to orthopedic hip distraction devices that allow multiplanar motion. The present disclosure also relates to orthopedic hip distraction devices that enable other orthopedic fixation devices to provide improved multiplanar and guided motion.

Background

Avascular necrosis of the femoral head is a form of hip joint disorder, in which case avascular necrosis causes osteomalacia and fragmentation. This leads to distortion of the femoral head and loss of function of its ball and socket joint. The patient may not be able to bear weight, walk and stand. The hip joint will subluxate and become incompatible, and will lose mobility. If this condition is not treated effectively, permanent subluxation will cause permanent distortion. Hip distraction devices are used to distract the hip joint to repair normal bone by reducing subluxation and constraint of the hip of a skeletal immature patient, removing some of the load on the hip joint, which will improve synovial circulation for better recovery.

However, existing devices for hip distraction allow only flexion movement of the hip in one plane and do not allow movement in other planes as is normally allowed by a healthy ball and socket hip. This limitation greatly impairs the mobility of the patient.

Disclosure of Invention

At least one of the disclosed embodiments allows for two-plane motion of the hip distractor device, which thus allows the patient to perform hip flexion/extension and abduction/adduction motions without dislocating the bone, while the hip distractor remains fixed to the patient's hip joint during rehabilitation. In addition, the device may also be connected to other orthopedic external fixators or devices and allow multi-planar movement of the hip distraction device.

A hip distraction device according to embodiments of the present application can include an external ball joint, an upper fixation unit pivotally coupled to a front side of the external ball joint at a lower rear side of the upper fixation unit, and a lower fixation unit coupled to a bottom end of the external ball joint. The upper fixation unit may be fixed to the hip bone and the lower fixation unit may be fixed to the femur. The external ball joint may include a slider housing defining a rail having a channel. The guide rail may be shaped to have a curvature along which the external ball joint can move up and down in the slider housing with respect to the upper fixing unit so that the femur abducts or adduces with respect to the hip bone.

According to an aspect of the present application, a channel is formed in the rail for defining a path of the rail with a plurality of first bearing assemblies passing through the channel. The first bearing assembly is arranged to secure the rail in the slider housing. The hip distractor device may undergo adduction and adduction motions as the guide track moves in a clockwise direction with the curvature of the lower stationary unit along its path. However, if the guide rail moves with the lower stationary unit in a counterclockwise direction along the curvature of its channel, the hip distraction device will perform a abduction motion. When the upper fixation unit and the external ball joint are rotated relative to each other, the hip distraction device will perform an extension or flexion movement.

According to another aspect of the present application, the external ball joint may further include a slider housing including a left housing and a right housing combined with the left housing. The guide rail may be sandwiched between the left and right side housings to avoid tilting in the slider housing. The guide rail may be locked in the slider housing, for example, by a plurality of second bearing assemblies.

According to aspects of the present application, the guide rail may be configured with a channel for defining a path of movement of the guide rail with the plurality of first bearing assemblies passing through the channel. The spacing for sandwiching the guide rail between the left and right housings may be adjustable by a plurality of second bearing assemblies. Each of the left and right side housings includes a plurality of first fixed settings to press against the second bearing assembly to adjust the second bearing assembly to contact the rail whereby the position of the rail in the slider housing can be adjusted.

According to an aspect of the present application, the external ball joint may be configured to have a front hole in the slider housing, and the upper fixing unit is coupled to the external ball joint through a third bearing assembly embedded/disposed in the front hole of the slider housing.

According to another aspect of the application, the upper stationary unit may comprise a pin platform and the third bearing assembly may comprise a shaft arranged to string the pin platform. The shaft and pin platform are rotatably secured together such that the pin platform, guide rail and slider housing are free to rotate along the axis of the shaft. The upper fixation unit may be fixed to the hip bone by a coupling assembly, which may include a cube placed on a pin platform, a sleeve inserted into the cube, and a pin retained by the cube.

According to aspects of the present application, the lower fixation unit may include an extendable distraction unit to adjust the length of the lower fixation unit along the femur. After extending the distraction unit, the hip distraction device can be implemented to accommodate distraction of different patients.

According to another aspect of the present application, the lower fixing unit may include a ball combined with the guide rail by a second positioning bearing assembly, wherein one end of the second positioning bearing assembly may be screwed into the guide rail and the other end thereof may be screwed into the ball.

According to another aspect of the present application, the lower fixing unit may further include a first cylinder, an insert inserted into the first cylinder, a cap, and a socket placed at an upper end of the insert and forming a space with the cap to receive the ball.

According to still another aspect of the present application, the lower fixing unit may further include an eccentric bolt inserted into the insertion body. The outer ball joint is fixed with the lower fixing unit after rotating the eccentric bolt.

According to another embodiment of the present application, an external ball joint is disclosed. The external ball joint may include a slider housing including a left side housing and a right side housing combined with the left side housing. The guide rail may be sandwiched between the left and right side housings to avoid tilting in the slider housing. The guide rail may be configured with a channel for defining a path of movement of the guide rail with a plurality of first bearing assemblies passing through the channel. The spacing for sandwiching the guide rail between the left and right housings may be adjustable by a plurality of second bearing assemblies. Each of the left and right side housings may include a plurality of first fixed settings to press against the second bearing assembly to adjust the first bearing assembly into contact with the guide rail. By providing an external ball joint as described above in the hip distractor, the hip distractor may assist the user in abduction/adduction movements along the curvature of the tunnel.

According to aspects of the present application, the external ball joint may be configured with a front aperture in the slider housing to retain the third bearing assembly. The third bearing assembly may be used to couple the upper fixation unit to secure the external ball joint to the hip bone.

A method for assembling a hip distraction device is disclosed according to yet another embodiment of the present application. The hip distraction device may include an upper fixation unit, an external ball joint, and a lower fixation unit. The upper fixing unit may be fixed to the hip bone, and the lower fixing unit may be fixed to the femur. The method can comprise the following steps: pivotally coupling an upper fixing unit to a front side of the external ball joint; coupling a lower fixing unit to a bottom end of the external ball joint; the external ball joint may include a slider housing defining a rail having a channel. The guide rail may be shaped to have a curvature along which the external ball joint can move up and down in the slider housing with respect to the upper fixing unit so that the femur abducts or adduces with respect to the hip bone.

The structures and methods as disclosed in this application allow flexion/extension motion to add some degree of hip abduction or adduction motion. The limb secured to the hip retractor will not dislocate during hip abduction or adduction.

In addition, the disclosed devices can be connected to other orthopedic external fixators or devices to treat various diseases (e.g., avascular necrosis and bone fractures) and allow for multiplanar motion.

Drawings

Exemplary, non-limiting embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. The drawings are illustrative and are not generally drawn to the precise scale of the elements shown therein. The same or similar elements in different drawings are denoted by the same reference numerals.

Fig. 1 is a schematic diagram illustrating a hip distractor consisting of an external ball joint and a fixation unit according to one embodiment of the present application.

Figure 2 illustrates an overview of an example structure of a hip retractor according to one embodiment of the present application.

FIG. 3 is an isometric exploded view of an external ball joint according to one embodiment of the present application.

FIG. 4 is a cross-sectional view of an external ball joint according to one embodiment of the present application.

FIG. 5 is a set of bearing assemblies placed inside a slider structure according to one embodiment of the present application.

FIG. 6 is a set of bearing assemblies rolling in a rail according to one embodiment of the present application.

FIG. 7 is an exploded side view of a bearing assembly that allows rotation in an external ball joint according to one embodiment of the present application.

FIG. 8 is a cross-sectional view of an upper pin securing structure according to one embodiment of the present application.

FIG. 9 is a transparent view of the connection between the upper guide rail and the lower ball joint according to one embodiment of the present application.

Figure 10 is a diagrammatic view of the underlying structure of a hip retractor according to one embodiment of the present application.

Figure 11 is an exploded view of a distraction unit of a hip distractor according to one embodiment of the present application.

Fig. 12 is a cross-sectional view of a ball joint of a quick releasable clamping unit according to an embodiment of the present application.

Figure 13 is a diagram illustrating a hip joint secured to a hip distractor according to one embodiment of the present application.

Detailed Description

Exemplary embodiments according to the present application will be described below with reference to the accompanying drawings. The same reference numbers will be used throughout the drawings to refer to the same or like parts, as appropriate.

Figure 1 illustrates a hip distractor 1000 according to one embodiment of the present application. Hip distractor 1000 may comprise an external ball joint 100, an upper fixation unit 200 and a lower fixation unit 300. The upper fixing unit 200 may be pivotally coupled at one end thereof to the front side of the external ball joint 100 and may be fixed at the other end thereof to the hip bone. The lower fixing unit 300 may be coupled at one end thereof to a bottom end of the external ball joint and may be fixed at the other end thereof to the femur.

Figure 2 illustrates an overview of an example structure of a hip retractor according to one embodiment of the present application. As shown in fig. 1 and 2, the external ball joint 100 constitutes the main structure of the hip distractor 1000, since it is capable of allowing motion in two planes. Referring to fig. 2, external ball joint 100 and upper fixing unit 200 may constitute an upper half of hip distractor 1000, and lower fixing unit 300 may constitute a lower half of hip distractor 1000, wherein the upper half facilitates movement of hip distractor 1000 in two planes, and the lower half is capable of providing distraction. A plurality of bearing assemblies may be provided which may be used for different functions. For example, three sets of bearing assemblies may be provided to provide different functions, as will be discussed below.

FIG. 3 illustrates an isometric exploded view of an external ball joint 100 according to one embodiment of the present application. In this embodiment, the upper fixing unit 200 may be pivotally coupled to the external ball joint 100 by a connection member, which may be a bearing assembly, for example. The bearing assembly may, for example, comprise a shaft and a screw. Thus, the upper fixing unit 200 and the external ball joint 100 may rotate with respect to each other. As shown in fig. 3, the external ball joint 100 may include a slider housing 50 defining a guide rail 1. The shape of the guide rail may be designed to have a curvature, and the external ball joint may move up and down in the slider housing 50 with respect to the upper fixing unit along the curvature of the guide rail. The guide rail may be configured with a channel, which may have the shape of a groove or slot, for example, to define a path of movement of the guide rail with the plurality of first bearing assemblies passing through the channel. External ball joint 100 may also include a plurality of first bearing assemblies 70 configured to pass through the passages to support the rails and define the position of the rails relative to slider housing 50. A hole (not shown) may be designed at the front side of the slider housing 50 to receive the connection member. The upper fixation unit 200 may be used to anchor the hip distractor 1000 to the hip bone. The external ball joint 100 is movable up and down in the slider housing 50 with respect to the upper fixing unit 200 to abduct or adduct the femur with respect to the hip bone. When the user intends to perform adduction, the guide rail 1 may be configured to move downward with respect to the hip bone. Accordingly, the rail 1 may be configured to move upwardly relative to the hip bone when the user intends to perform abduction movement. As shown in fig. 3, this means that when the guide rail 1 moves in a clockwise direction along the curvature of its channel together with the lower fixing unit 300, the hip retractor 1000 can perform adduction movement. However, if the guide rail 1 moves with the lower stationary unit 300 in a counterclockwise direction along the curvature of its channel, the hip distraction device 1000 will perform a abduction motion. Furthermore, when the upper fixation unit 200 and the external ball joint 100 are rotated relative to each other, the external ball joint 100 will rotate relative to the hip bone coupled with the upper fixation unit 200, thereby enabling the hip distraction device 1000 to perform an extension or flexion motion.

As shown in fig. 3, the slider housing 50 may include a left side housing 3 and a right side housing 11 for forming a space to arrange the guide rail 1 in place. A plurality of second bearing units 60 may be inserted into the left and

right housings

3 and 11 to ensure that only the guide rail 1 can move along its path.

Fig. 5 shows the structure of the second bearing assembly. As shown, the rod 4 may string the shim 6 and the bearing 5 together to form a bearing assembly. Preferably, six sets of bearing assemblies are inserted into the concave housings of the left and

right housings

3 and 11, respectively. The second bearing unit 60 may contact with a side surface of the guide rail 1 and serves to resist a side force to prevent the guide rail 1 from being inclined inside the left and

right housings

3 and 11. Therefore, the second bearing assembly 60 can ensure that the left and

right housings

3 and 4 rotate together with the guide rail 1 without changing their relative positions.

The left side housing 3 and the right side housing 11 may be joined together by a fixed arrangement, for example a plurality of screws 22 which may include a band 29 and a washer 6 to form a slider structure capable of abduction and flexion movements.

Referring again to fig. 3, a plurality of fixing members 7 such as set screws are inserted into the left and

right housings

3 and 11, respectively. When the set screws are screwed into the left and

right housings

3 and 11, the set screws 7 may contact the rod 4 and press against the rod 4. The set screws 7 can thus be used to adjust the second bearing assembly 60 as shown in fig. 5 and bring them into contact with the side surface of the guide rail 1.

FIG. 4 illustrates a cross-sectional view of an external ball joint according to one embodiment of the present application. As shown in fig. 4, at least two sets of bearing assemblies 70 may roll in the channels (i.e., grooves or slots). Fig. 6 shows the structure of the bearing assembly 70, wherein the rod 12 may string two spacers 15, two bearings 14 and the sleeve 13 to form the bearing assembly 70. The washer 15 and the sleeve 13 may be in contact with the inner ring of the bearing 14. The washer 15 and the sleeve 13 prevent the bearing 14 from sliding along the rod 12. The bearing 14 is rotatable about the rod 12. One end of the bearing assembly may be inserted into the left side housing 3 and the other end thereof may be inserted into the right side housing 11.

Fig. 7 shows an exploded side view of a bearing assembly in the external ball joint that allows upper fixing unit 200 to rotate relative to external ball joint 100. In fig. 7, the shaft 17 may string together two bearings 19, two shims 18, and a shim 16 to form a bearing assembly 80. Two shims 18 may be placed between the two bearings 19 and in contact with the outer ring of the shaft 17. The two spacers 18 prevent the two bearings 19 from contacting each other. The bearing assembly 80 may be positioned in the front hole of the slider housing 50 to be connected with the upper fixing unit 200. The cover 20 may be secured with the slider housing 50 by a plurality of securing arrangements (e.g., 4 screws 21). The diameter of the inner annular edge of the cover 20 is adapted to receive the shim 16 therein and prevent the bearing 19 from passing through the cover 20. The inner ring of the bearing 19 may be in contact with the shaft 17 and the washer 16 and may be rotatable about the axis of the shaft 17.

Returning to fig. 3, the upper fixing unit 200 may further include a pin platform 2 having a plurality of holes for inserting pins or screws to fasten the cube 31 (fig. 8) thereto by means of screws. As shown in fig. 3, a number of holes are arranged in the pin platform 2 to accommodate patients of different sizes. A plurality of securing elements 21, such as screws, may be used to secure cover 20 to external ball joint 100 with bearing assembly 80. When cover 20 is secured to external ball joint 100 with bearing assembly 80, the shim is sandwiched between pin platform 2 and bearing 19. The shaft 17 may also string the pin platforms 2 and may also be fastened together by screws 23 and washers 30. Thus, as shown in fig. 4, the pin platform 2, the guide rail 1 and the slider structure can freely rotate along the axis of the shaft 17.

Referring to fig. 1 to 7, the upper fixing unit 200 may rotate with respect to the external ball joint 100 and the guide rail 1 may move up and down in the slider housing 50 along the curvature of the passage. In case the hip joint is to perform flexion/extension as well as adduction movements, the guide rail 1 will move downwards (i.e. clockwise) along the curvature of the channel while the upper fixation unit 200 and the external ball joint 100 rotate relative to each other. In case the hip joint will perform flexion/extension as well as abduction movements, the guide rail 1 will move upwards (i.e. counter clockwise) along the curvature of the channel while the upper fixation unit 200 and the external ball joint will rotate relative to each other. Specifically, flexion and extension movement of the external ball joint 100 is achieved by relative rotation between the bearing assembly 80 passing through a front aperture in the slider housing 50 and the slider housing 50. When the outer ball joint 100 performs a flexion-extension movement, only the bearing assembly 80 rotates without the rail 1 moving up/down.

Thus, hip distractor 1000, in conjunction with external ball joint 100, may allow flexion, extension, adduction, and abduction motions. That is, the device according to the present embodiment is capable of movement in two planes and allows 360 degrees of movement.

Figure 8 shows a cross-sectional view of an upper pin fixation structure for use in securing the hip distractor to the hip bone. Referring to fig. 8 and 2, a cube 31 may be located on the pin platform 2. The screws 24 can pass through the bottom countersunk slots of the pin platform 2 and serve to fix the cube 31. The bore diameters of the cube 31 and the sleeve 32 may be, for example, 8 mm and 6 mm, respectively. The sleeve 32 may be manufactured with different hollow diameters to hold different pins 33 with corresponding diameters. One end of the pin 33 is inserted into the sleeve 32 and the other end of the pin 33 is secured to the hip bone. With such a cube and sleeve system, the cube 31 can hold bone pins of different sizes with corresponding sleeves. A fixation unit (e.g., screw) 28 may be used to secure the cube 31, sleeve 32 and pin 33 together so that the upper fixation unit may be secured to the hip bone.

Figure 9 shows a transparent view of the connection between the guide rail of the upper half and the ball joint in the lower half. In fig. 9, a set screw 8 may join the guide rail 1 with a ball 37. One end of the set screw 8 can be screwed into the guide rail 1 and the other end thereof can be screwed into the ball 37. To secure the set screw 8, two set screws 9 may be used to compress the set screw 8 and prevent the set screw 8 from becoming loose.

Figure 10 shows an overview of the lower half of the hip retractor. The body of the lower half of the hip retractor may include a barrel 44 and an insert 45. The barrel 44 may include a clamping arrangement for securing to other parts. The lower half of the hip retractor may also include a clamping device 48 that is tightened by two screws 27 against the fixed clamping device of the barrel 44.

With reference to fig. 2 and 10, the shaft of the pin 33 can be placed in the receiving seat of the clamping device 48. The pin 33 can be inserted into the femur and clamped by the fixed cylinder 44 and the clamping device 48. Thus, the hip retractor can be safely applied to the bone of a patient. The insertion body 45 may be vertically inserted into the cylinder 44. The insert body 45 may have a groove thereon. As shown in fig. 2, the central body locking screw 47 may protrude into the groove. The barrel 44 and the insert 45 may then be secured against rotation relative to each other during displacement of the other parts.

The lower half of the hip retractor may also include a distraction unit 301 for applying pressure or tension to the joint. Hip distraction is a surgical procedure that uses a hip distractor to distract the hip joint. By providing a distraction unit 301 in hip distractor 1000, a surgical procedure for hip distraction can be achieved. As shown in fig. 10, the bolt 39 and the bolt 40 of the tension unit 301 may be inserted into the cylinder 44 and the insertion body 45, respectively, to engage with the cylinder 44. The bolt 39 and the bolt 40 may be designed to include an annular groove around the axis of the bolt at the end of the insertion cylinder 44.

Figure 11 illustrates an exploded view of a distraction unit of a hip distractor according to one embodiment of the present application. As shown in fig. 11, the tension unit 301 may include a collar 42 to which the bolt 39 is fixed, a hollow cylinder 38, a screw 25, and a ring 43, wherein the bolt 40 and the mounting 41 are fixed at the upper end of the hollow cylinder 38. The collar 42 may be attached to the shaft of the screw 25 and the external threads of the screw 25 may engage the internal threads of the hollow cylinder 38. The ring 43 may hold the collar 42 in place without impeding rotation of the collar 42. The ring 43 may include holes in its perimeter to receive set screws 10 for locking the position of the ring 43. An O-ring 49 may be placed in the groove of the bolt 39 and the bolt 40. The O-ring 49 prevents the tension unit from sliding off the barrel 44.

Thus, the distraction unit 301 can be connected to the body of the lower half of the hip distractor 1000 by

bolts

39 and 40 and can be used for distraction. After attachment of the distraction unit 301, the hip distractor can be distracted by the elongate distraction unit 301. That is, when the stretching is required, the relative position of the hollow cylinder 38 and the screw 25, and thus the relative position of the cylinder 44 and the insertion body 45, can be adjusted. The central body locking screw 47 may be tightened to lock the barrel 44 and the insert 45 after distraction.

Thus, the lower half of hip distractor 1000 with distraction unit 301 can provide distraction to accommodate different patients.

Fig. 12 shows a cross-sectional view of a ball joint of a quick releasable clamping unit according to an embodiment of the present application.

As shown in fig. 12, the eccentric bolt 35 may be inserted into the insertion body 45. A ball 37 may be held between the hemispherical cup socket 34 and the cap 36. After turning the eccentric bolt 35 to a certain extent, the socket 34 is pushed upwards and it will clamp against the ball 37 contained in the joint. Accordingly, as shown in fig. 4, the external ball joint may be connected with the lower fixing unit 300 and fixed to the lower fixing unit 300.

For example, in the embodiment, the eccentric bolt 35 has the shape of an eccentric rectangular parallelepiped, and the socket 34 is pushed upward by rotating the eccentric bolt 35 by a right angle, thereby connecting the lower fixing unit with the external ball joint.

Figure 13 is a schematic view illustrating a hip joint secured to a hip distractor according to one embodiment of the present application.

As shown in fig. 13, the bone pin may be securely inserted into the bone. The hip distractor 1000 provided with the clamping device may be firmly screwed over the bone pins, e.g. about 10mm from the skin. The axis of rotation of the hip retractor may be precisely aligned with the axis of flexion/extension of the hip joint. As shown in fig. 3, the guide rail 1 may be of an arc-shaped configuration and an imaginary center of the guide rail 1 must be located at the hip joint rotation center. This means that the guide rail 1 must be concentric with the hip joint. Otherwise, the limb to which the hip retractor is attached will be dislocated during hip abduction or adduction.

In the foregoing description, aspects, steps or portions are described in one embodiment, but this disclosure should not be read as requiring that all of the above-described disclosure be required by the claimed subject matter. What is claimed as part of the specification, including the claims, is also included to provide further understanding of the invention, and are incorporated in and constitute a part of this specification.

Further, it will be apparent to those skilled in the art from consideration of the specification and practice of the present disclosure that various modifications and changes may be made to the disclosed systems and methods without departing from the scope of the present disclosure as defined in the following claims. It is intended, therefore, that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.

Claims

1. A hip distraction device comprising:

an external ball joint;

an upper fixing unit pivotally coupled to a front side of the external ball joint and fixable to a hip bone; and

a lower fixing unit coupled to a bottom end of the external ball joint and fixable to a femur,

wherein the external ball joint includes a slider housing defining a guide rail shaped to have a curved channel and capable of following the curvature of the curved channel, moving up and down in the slider housing relative to the upper fixation unit to abduct or adduct the femur relative to the hip bone, and

wherein the upper fixation unit and the external ball joint are coupled to be rotatable relative to each other to enable the femur to move in flexion/extension motion relative to the hip bone simultaneously.

2. The hip distraction device of claim 1, wherein the rail is movable with the lower fixation unit along the curvilinear channel in a clockwise direction to adduct the femur relative to the hip bone; and

the guide rail is movable in a counterclockwise direction along the curved channel with the lower fixation unit to abduct the femur relative to the hip bone.

3. The hip distraction device of claim 1, wherein said external ball joint comprises a slider housing, said slider housing comprising:

a left side housing; and

a right side housing coupled to the left side housing;

wherein the guide rail is sandwiched between the left and right side cases.

4. The hip distraction device of claim 3,

the curved channel is configured to define a path of movement of the rail with a plurality of first bearing assemblies passing therethrough,

the interval for sandwiching the guide rail between the left and right housings can be adjusted by a plurality of second bearing units, an

Each of the left and right side housings includes a plurality of first fixed settings to press against the second bearing assembly to adjust the second bearing assembly into contact with the guide rail.

5. The hip distraction device of claim 4, wherein said external ball joint has a front aperture on its slider housing, said upper fixation unit being coupled to said external ball joint by a third bearing assembly embedded/disposed in said front aperture of said slider housing.

6. The hip distraction device of claim 5, wherein the upper fixation unit comprises a pin platform, the third bearing assembly comprising a shaft arranged to string the pin platform, the shaft and the pin platform being rotatably secured together to enable the pin platform, the guide rail and the slider housing to freely rotate along the axis of the shaft.

7. The hip distraction device of claim 6, wherein said upper fixation unit is securable to the hip bone via a coupling assembly, said coupling assembly comprising:

a cube disposed on the pin platform;

a sleeve inserted into the cube; and

a pin retained by the cube.

8. The hip distraction device of claim 1, wherein the lower fixation unit comprises an extendable distraction unit to adjust the length of the lower fixation unit along the femur.

9. The hip distraction device of claim 1, wherein the lower fixation unit comprises a ball coupled to the rail by a second fixation arrangement, and one end of the second fixation arrangement is fixed in the rail and the other end of the second fixation arrangement is fixed in the ball.

10. The hip distraction device of claim 9, wherein the lower fixation unit comprises:

a first cylinder;

an insertion body inserted into the first cylinder,

a cover; and

a socket provided at an upper end of the insert body and forming a space with the cap to receive the ball.

11. The hip distraction device of claim 10, wherein the lower fixation unit further comprises an eccentric bolt inserted into the insert body, and

wherein the external ball joint is connected with and fixed to the lower fixing unit after rotating the eccentric bolt.

12. An external ball joint, comprising:

a slider housing, the slider housing comprising:

a left side housing;

a right side housing coupled to the left side housing; and

a guide rail sandwiched between the left side case and the right side case,

wherein the slider housing is pivotally coupled at a front side to an upper fixation unit that is fixed to a hip bone; and

the guide rail is coupled at a bottom end to a lower stationary component that is fixed to a femur,

wherein the guide rail is provided with a curved passage for defining a movement path of the guide rail together with a plurality of first bearing units passing through the passage, the guide rail is movable up and down in the slider housing along the curvature of the curved passage with respect to the upper fixing unit to abduct or adduct the femur with respect to the hip bone, and the upper fixing unit and the slider housing are coupled to be rotatable with respect to each other to enable the femur to simultaneously move in flexion/extension movements with respect to the hip bone,

13. The external ball joint of claim 12, wherein said external ball joint is configured with a front bore in said slider housing for holding a third bearing assembly for coupling an upper fixation unit that secures a hip bone to said external ball joint.

14. A method of assembling a hip distraction device, wherein said hip distraction device comprises at least an upper fixation unit, an external ball joint and a lower fixation unit,

wherein the upper fixing unit is fixable to a hip bone and the lower fixing unit is fixable to a femur,

wherein the method comprises the following steps:

pivotally coupling the upper fixing unit to a front side of the external ball joint;

coupling the lower fixing unit to a bottom end of the external ball joint;

configuring the external ball joint to have a slider housing defining a rail, wherein the rail is shaped to have a curved channel and is capable of moving up and down in the slider housing relative to the upper fixation unit along the curvature of the curved channel to abduct or adduct the femur relative to the hip bone; and

coupling the upper fixation unit and the external ball joint to be rotatable relative to each other to enable the femur to move in flexion/extension motion relative to the hip bone simultaneously.