Abstract:
The present invention is related to an artificial hip joint prosthesis. Also, it can be decreased the time of medical treatment and administered medicine easily. Besides, it can be applied an Oriental having small pelvis.

Description:
TECHNICAL FIELD 
   The present invention relates, in general, to an artificial hip joint prosthesis and, more particularly, to an artificial hip joint prosthesis for connecting a pelvis with a femur, which is improved in its construction. 
   BACKGROUND OF THE INVENTION 
   As well known to those skilled in the art, among a number of joints in the human body, the pelvis and the femur can be rotated relating to one another within a predetermined angle. To this end, between the pelvis and the femur, there is intervened a hip joint for connecting the pelvis and the femur with each other in a rotatable manner. 
   The hip joint may be adversely influenced by stand-up walking, or may be injured by inherited factors, due to excessive exercise or through an accident. In the case that the hip joint is adversely influenced or injured, pain is caused at a boundary region where the pelvis and the femur are connected with each other. In order to replace the injured hip joint and ensure smooth rotation of the hip, an artificial hip joint prosthesis is provided. The artificial hip joint prosthesis has mainly been researched at the West with the progress in medical science, and therefore, fabricated in conformity with a body structure of a Westerner who has a larger physique and bone size than an Oriental. 
   Hereafter, several of the conventional artificial hip joint prostheses disclosed in the art will be briefly described. 
   The conventional artificial hip joint prosthesis shown in  FIG. 16  comprises a pelvis-contacting element  110  fastened to a pelvis, a stem  150  fastened to a femur, a head  120  integrally formed at a distal end of the stem  150 , a flexible joint member  130  which is coupled to the pelvis-contacting element  110  and in which the head  120  is accommodated in a freely rotatable manner, and a release prevention member  160  for preventing release of the flexible joint member  130  from the pelvis-contacting element  110 . 
   The release prevention member  160  is meshed with the flexible joint member  130  along a circumferential direction through engagement between prominences and depressions (see the section ‘A’). An inner surface of the pelvis-contacting element  110  is defined with a groove  170 , and the release prevention member  160  is formed with a projection  161  which is engaged into the groove  170 . 
   The conventional artificial hip joint prosthesis constructed as mentioned above suffers from defects in that, since the flexible joint member  130  and the release prevention member  160  are formed as separate component parts, not only the number of component parts is increased, but also appreciable wear may take place due to rotation occurring therebetween. 
   Also, because the flexible joint member  130  and the release prevention member  160  are decreased in thickness at a region wherein they are meshed with each other through engagement between the prominences and the depressions, when the artificial hip joint prosthesis is used for an extended period of time, the region cannot but be weakened. Further, when the release prevention member  160  and the flexible joint member  130  are meshed with each other, since a height of a release preventing configuration of the release prevention member  160  is substantial, the stem  150  integrally rotated with the head  120  is likely to come into collision with the release prevention member  160 . Therefore, if this collision occurs, as the rotation of the head  120  is interfered with, inordinate force can applied to the pelvis-contacting element  110 , whereby the possibility of the pelvis to be adversely influenced is increased. Moreover, even with the flexible joint member  130  inserted into the pelvis-contacting element  110 , positional fluctuation occurs due to play existing between the release prevention member  160  and the pelvis-contacting element  110  and the flexible joint member  130  and play existing between the flexible joint member  130  and the head  120 , so that collision may easily occur between respective component parts. 
   Another conventional artificial hip joint prosthesis as shown in  FIG. 17  also has the flexible joint member  130   a  inserted into the pelvis-contacting element  110   a . The flexible joint member  130   a  is formed with six coupling portions  160   a  through  160   f  which are separated one from another in the circumferential direction and each of which is defined with a groove  161   a.    
   In this type of conventional artificial hip joint prosthesis, because the six coupling portions  160   a  through  160   f  are formed separately one from another, flexibility of the flexible joint member  130   a  is increased. However, when it is necessary to disassemble the flexible joint member  130   a  from the pelvis-contacting element  110   a , all of the six coupling portions  160   a  through  160   f  should be simultaneously and resiliently contracted radially inward. Hence, where it is necessary to perform an operation again for the hip joint after decoupling the flexible joint member  130   a  and the pelvis-contacting element  110   a  from each other, inconvenience is caused. 
   Furthermore, in order to ensure decoupling of the flexible joint member  130   a  from the pelvis-contacting element  110   a , the groove  161   a  must be defined on each of the coupling portions  160   a  through  160   f  in the circumferential direction. Thus, when the head (not shown) is, inserted into a flexible joint member  130   a  of increased size and rotated, the stem (not shown) is apt to collide with the flexible joint member  130   a.    
   Still another conventional artificial hip joint prosthesis as shown in  FIG. 18  also has the head  120   b , which is integrally formed at the distal end of the stem  150   b . After the flexible joint member  130   b  is inserted into the pelvis-contacting element  110   b , the head  120   b  is inserted into the flexible joint member  130   b  along with a support piece  162  which is placed around the head  120   b . Then, a fixed locking piece  160   b  is fitted between the pelvis-contacting element  110   b  and the support piece  162  to allow the support piece  162  to be biased against the head  120   b  and thereby properly support the rotation of the head  120   b . By the cooperation of the fixed locking piece  160   b  with the support piece  162 , release of the head  120   b  and flexible joint member  130   b  from the pelvis-contacting element  110   b  is prevented. 
   Nevertheless, the conventional artificial hip joint prosthesis having been just described above encounters a problem in that, after the head  120   b  is inserted into the flexible joint member  130   b , there exists a space C between the flexible joint member  130   b  and the fixed locking piece  160   b , in which the support piece  162  can be moved, whereby collision may still occur between the head  120   b  and the flexible joint member  130   b . Also, since the support piece  162  should be separately prepared, the entire manufacturing procedure is complicated. Further, since the increased number of component parts, that is, the flexible joint member  130   b , the fixed locking piece  160   b  and the support piece  162  must be assembled in the pelvis-contacting element  10   b , assemblability is deteriorated. 
   The above-described conventional artificial hip joint prostheses additionally have a disadvantage in that, since sizes of the artificial hip joint prostheses are substantial, difficulties are encountered when installing them. In other words, because the region where ends of the pelvis and femur are positioned is narrow, if assembling and disassembling operations are made complicated, difficulties cannot but be encountered when installing the artificial hip joint prostheses. In addition, because the conventional artificial hip joint prostheses are initially developed for Westerners who have large physiques and bone sizes, they cannot be appropriately adapted to Orientals. 
   Besides, in each of the conventional artificial hip joint prostheses, since the play in which the head can be moved to and for exists, collision frequently occurs between the head and the flexible joint member, whereby drawbacks associated with abrasion and wear of the component parts may be caused. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention solves the above problems occurring in the prior art. An, object of the present invention is to provide an artificial hip joint prosthesis that can be more easily installed utilizing a shorter installation time. 
   Another object of the present invention is to provide an artificial hip joint prosthesis which can be optimally adapted even to Orientals having relatively small physiques and bone sizes. 
   Another object of the present invention is to provide an artificial hip joint prosthesis which can minimize interference and ensure its smooth rotation, thereby preventing the pelvis and femur of the human body from being injured. 
   Still another object of the present invention is to provide an artificial hip joint prosthesis which allows assembly and disassembly of component parts to be easily performed and which minimizes radial movement of a rotating head so that collision does not occur between the component parts and drawbacks associated with abrasion and wear of the component parts are not caused, while release of the head is properly prevented. 
   Yet still another object of the present invention is to provide an artificial hip joint prosthesis which is less complex to manufacture while maintaining structural integrity, thus reducing manufacturing costs. 
   In order to accomplish the above objects, the present invention provides an artificial hip joint prosthesis installed between a pelvis and a femur to allow the femur to be rotated relative to the pelvis, comprising: a pelvis-contacting element fixed to the pelvis and having a truncated hollow sphere-shaped configuration; a stem fixed to the femur; a head integrally coupled to a distal end of the stem and having a truncated sphere-shaped configuration; and a flexible joint member interposed between the pelvis-contacting element and the stem to accommodate and rotatably support the head, the flexible joint member capable of being resiliently deformed outward and inward in a radial direction to be coupled to and decoupled from the pelvis-contacting element along with the head. 
   Here, the flexible joint member may comprise a body part having a configuration of a hollow hemisphere; a resilient part formed at an entrance of the body part to have a predetermined thickness, the resilient part possessing a ring-shaped configuration; and a depressed part (also known hereinafter as a middle part) depressed radially inward by a predetermined depth between the body part and the resilient part to extend at least partially in a circumferential direction. 
   At this time, for providing proper elasticity to the resilient part, it is preferred that the depressed part is formed on an outer surface of the flexible joint member to have the predetermined depth and extends in the circumferential direction. 
   At least one through-hole is defined through the depressed part. The through-hole is defined in the form of a slot which is rounded at both ends thereof so that cracks are not formed in the depressed part due to a stress generated in the through-hole when the resilient part undergoes contraction and expansion. Also, it is preferred that a pair of through-holes are defined through the depressed part such that they are opposite to each other. 
   A pair of slits are defined in the resilient part at regions corresponding to the through-holes, such that the resilient part is divided into a pair of unit resilient portions which are separated by a predetermined distance and symmetrical with each other. 
   A pair of flattened portions are formed on an outer surface of the resilient part at regions corresponding to the slits each to extend through a predetermined angle in the circumferential direction. 
   Preferably, a pair of decoupling grooves are defined on the outer surface of the resilient part to be aligned on a line which is orthogonal to another line connecting the slits and thereby spaced apart from the slits by 90° in the circumferential direction, so that the flexible joint member can be decoupled from the pelvis-contacting element by pressing radially inward the resilient part in the decoupling grooves. The pair of decoupling grooves serve as tool passage openings so that a tool can be placed between the pelvis-contacting element and the flexible joint member when the flexible joint member is coupled to the pelvis-contacting element. 
   Projecting ribs are formed on one of an inner surface of the pelvis-contacting element and the outer surface of the resilient part, and engaging grooves in which the projecting ribs are to be engaged are defined on the other of the inner surface of the pelvis-contacting element and the outer surface of the resilient part. By this feature, it is possible to securely couple the pelvis-contacting element and the flexible joint member with each other. 
   At this time, it is preferred that the projecting ribs project radially outward from the outer surface of the resilient part and extend in the circumferential direction, and the engaging grooves are defined adjacent to an entrance of and on the inner surface of the pelvis-contacting element and have a preselected depth. 
   In order for ensuring easy decoupling of the flexible joint member from the pelvis-contacting element, it is preferred that each projecting rib is formed in a manner such that its height is gradually decreased from the decoupling groove toward the slit. 
   Each projecting rib has a first inclined surface which is inclined downward by a preselected angle when viewed in a direction where the flexible joint member is inserted into the pelvis-contacting element. By this feature, the flexible joint member can be inserted into the pelvis-contacting element with reduced force. 
   The resilient part is formed to have an outer diameter which is greater than a diameter of the entrance of the pelvis-contacting element, whereby the resilient part is prevented from being released after being inserted into the pelvis-contacting element. The resilient part is formed to have an inner diameter which is less than a diameter of the head, whereby unintentional release of the head from the resilient part is prevented. 
   An inner edge of each unit resilient portion is formed with a second inclined surface which has an inclination substantially corresponding to a surface curvature of the head to allow easy insertion and removal of the head into and out of the flexible joint member. 
   A pair of indented portions are defined on an inner surface of the flexible joint member in a manner such that they are diametrically opposite to each other and define a diameter which is greater than the diameter of the head, to ensure smooth insertion and removal of the head into and out of the flexible joint member. The indented portions create spaces of a predetermined size between the flexible joint member and the head when the head is inserted into the flexible joint member. When the flexible joint member is inserted along with the head into the pelvis-contacting element, the indented portions are biased radially inward so that the spaces created between the flexible joint member and the head are removed, to thereby appropriately support the head while preventing the head from being unintentionally released from the flexible joint member. 
   The flexible joint member has an inner diameter which corresponds to the diameter of the head, to minimize abrasion and wear of the component parts due to collision. 
   Meanwhile, a plurality of through-holes may be defined through the depressed part in a manner such that they are spaced apart one from another by a predetermined interval. In another embodiment of the present invention, the through-hole may not be defined in the form of a slot so long as a space for ensuring resilient deformation of the resilient part is provided in the flexible joint member and a dummy portion for additionally supporting the head inserted into the flexible joint member is produced in the depressed part. 
   In still another embodiment of the present invention, it can be envisaged that the projecting ribs project radially inward adjacent to the entrance of and from the inner surface of the pelvis-contacting element and have the preselected depth, and the engaging grooves are defined on the outer surface of the resilient part and extend in the circumferential direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a view schematically illustrating a state wherein an artificial hip joint prosthesis in accordance with a first embodiment of the present invention is installed; 
       FIG. 2  is an exploded perspective view of the artificial hip joint prosthesis shown in  FIG. 1 ; 
       FIG. 3  is a perspective view illustrating a partially assembled state of the artificial hip joint prosthesis shown in  FIG. 2 ; 
       FIG. 4  is a plan view illustrating a state wherein a pelvis-contacting element and a flexible joint member are assembled with each other; 
       FIG. 5  is an enlarged perspective view of the flexible joint member; 
       FIG. 6  is a side view of  FIG. 5 ; 
       FIG. 7  is an enlarged perspective view of the pelvis-contacting element; 
       FIG. 8  is a partially enlarged schematic sectional view illustrating a state wherein the pelvis-contacting element and the flexible joint member are assembled with each other; 
       FIG. 9  is a sectional view taken along the line IX—IX of  FIG. 3 ; 
       FIG. 10  is a sectional view taken along the line X—X of  FIG. 3 ; 
       FIG. 11  is a transverse sectional view illustrating a main part of  FIG. 3 ; 
       FIG. 12  is a side view similar to  FIG. 6 , illustrating a flexible joint member in accordance with a second embodiment of the present invention; 
       FIG. 13  is a plan view similar to  FIG. 4 , illustrating a flexible joint member in accordance with a third embodiment of the present invention; 
       FIG. 14  is a partially enlarged schematic sectional view similar to  FIG. 8 , illustrating a state wherein a pelvis-contacting element and a flexible joint member in accordance with a fourth embodiment of the present invention are assembled with each other; 
       FIG. 15  is a plan view similar to  FIG. 4 , illustrating a state wherein a pelvis-contacting element and a flexible joint member in accordance with a fifth embodiment of the present invention are assembled with each other; and 
       FIGS. 16 through 18  are views respectively illustrating the conventional artificial hip joint prostheses. 
   

   DESCRIPTION OF THE INVENTION 
   Reference should now be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same or similar component parts. Hereafter, a first embodiment representative of the present invention will be described in detail, and as for the other embodiments, only the features which are different from those of the first embodiment will be described. 
   As shown in  FIG. 1 , an artificial hip joint prosthesis  1  in accordance with a first embodiment of the present invention is installed between a pelvis  8  and a femur  9  to connect the femur  9  to the pelvis  8  so that the femur  9  can be rotated relative to the pelvis  8 . 
   As can be readily seen from  FIGS. 2 through 4 , the artificial hip joint prosthesis  1  comprises a pelvis-contacting element  10  and a stem  50  which are respectively fixed to the pelvis  8  and the femur  9 , and a flexible joint member  30  which is interposed between the pelvis-contacting element  10  and the stem  50  to rotatably connect the pelvis-contacting element  10  and the stem  50  with each other. 
   The pelvis-contacting element  10  may be formed of a metallic material, for example, stainless steel, alloyed steel, etc. The pelvis-contacting element  10  is formed to have a configuration of a truncated hollow sphere which has a volume slightly greater than that of a hollow hemisphere. The pelvis-contacting element  10  is inserted into the pelvis  8  in a manner such that an entrance  10   a  thereof faces the femur  9 . 
   Engaging grooves  10   b  (see  FIG. 7 ) in which projecting ribs  44  of the flexible joint member  30  are to be engaged, as will be described later in detail, are defined on an inner surface of the pelvis-contacting element  10  to have a preselected depth. The engaging grooves  10   b  are positioned adjacent to the entrance  10   a  between the entrance  10   a  and a center of the pelvis-contacting element  10 . 
   The entrance  10   a  of the pelvis-contacting element  10  is formed to have an inner diameter which is less than a diameter of the flexible joint member  30 , so that the flexible joint member  30  accommodated in the pelvis-contacting element can be prevented from being unintentionally released. Due to the fact that a height of the pelvis-contacting element  10  which is measured from the entrance  10   a  is less than a diameter of the pelvis-contacting element  10 , it is possible to decrease a relative height of the flexible joint member  30 . As a consequence, it is possible to manufacture an artificial hip joint prosthesis which can be adapted even to Orientals having relatively small physiques and bone sizes, install the artificial hip joint prosthesis in an easy and convenient manner, and shorten an installation time. Further, as will be described later in detail, since smooth rotation of the head  20  is ensured and interference between the pelvis-contacting element  10  and the head  20  is minimized, it is possible to prevent the pelvis including a cartilage and the femur of the human body from being injured. 
   The stem  50  has a long rod-shaped configuration and is fixed to the femur  9  along a lengthwise direction thereof. The stem  50  is integrally coupled at a distal end thereof with the head  20  which is to be inserted into the flexible joint member  30 . The head  20  has a truncated sphere-shaped configuration to be freely rotated in the flexible joint member  30 . The head  20  is defined with a hole  21  in which the distal end of the stem  50  is press-fitted. 
   The flexible joint member  30  can be resiliently deformed in radial inward and outward directions. As a consequence, the flexible joint member  30  can accommodate therein and support the head  20  so that the head  20  can be freely rotated, and can be coupled to and decoupled from the pelvis-contacting element  10  along with the head  20 . 
   An outer surface of the flexible joint member  30  is contoured in conformity with the inner surface of the pelvis-contacting element  10  to be in surface contact therewith. The flexible joint member  30  has a resilient part  40  formed at an entrance thereof. The resilient part  40  has a diameter which is greater than the inner diameter of the entrance  10   a  of the pelvis-contacting element  10 . By this fact, after the flexible joint member  30  is accommodated in the pelvis-contacting element  10  with the resilient part  40  resiliently contracted radially inward, the resilient part  40  can be resiliently expanded again radially outward to prevent the flexible joint member  30  from being unintentionally released from the pelvis-contacting element  10 . 
   As can be readily seen from  FIGS. 5 through 10 , the flexible joint member  30  comprises a body part  35 , the resilient part  40 , and the depressed part  38  (also known hereinafter as a middle part). The body part  35  has a configuration of a hollow hemisphere. The resilient part  40  is formed at the entrance  30   a  of the body part  35  to have a predetermined thickness and possesses a ring-shaped configuration. The depressed part  38  is depressed radially inward on the outer surface of the flexible joint member  30  by a predetermined depth to extend at least partially in a circumferential direction between the body part  35  and the resilient part  40 . 
   In this first embodiment of the present invention, the depressed part  38  is formed on the outer surface of the flexible joint member  30  in such a way as to continuously extend along the circumferential direction of the flexible joint member  30 . At this time, it is preferable to determine a depth of the depressed part  38  so that the resilient part  40  can be reliably supported by the body part  35  and the flexible joint member  30  does not lose its resiliency even though it is repeatedly contracted and expanded. 
   A pair of through-holes  38   a  and  38   b  are defined through the depressed part  38  each to extend at least partially in the circumferential direction. Each of the through-holes  38   a  and  38   b  is defined in the form of a slot which is rounded at both ends thereof so that cracks are not formed in the depressed part  38  due to repeated contraction and expansion. The pair of through-holes  38   a  and  38   b  are defined through the depressed part  38  such that they are opposite to each other. The through-holes  38   a  and  38   b  are not necessarily defined in the depressed part  38 . 
   In order to ensure that the flexible joint member  30  is resiliently deformed in an easy manner while the flexible joint member  30  accommodates the head  20  or is inserted by itself into the pelvis-contacting element  10 , the resilient part  40  is divided into a pair of unit resilient portions  40   a  and  40   b  which are separated by a predetermined distance H and symmetrical with each other. The pair of unit resilient portions  40   a  and  40   b  are formed by the fact that a pair of slits  41   a  and  41   b  are defined in the resilient part  40  at regions where the through-holes  38   a  and  38   b  are respectively defined. 
   A pair of flattened portions  42   a  and  42   b  are formed on an outer surface of the resilient part  40  at regions where the slits  41   a  and  41   b  are respectively defined, so that each of the flattened portions  42   a  and  42   b  extends through a predetermined angle in the circumferential direction. The flattened portions  42   a  and  42   b  are formed to ensure that the pair of unit resilient portions  40   a  and  40   b  can be biased toward each other by a small level of force. 
   In cooperation with the material used for forming the flexible joint member  30  which may be, for example, silicon, ceramic and thermoplastic synthetic resin, the depressed part  38 , the through-holes  38   a  and  38   b  and the slits  41   a  and  41   b  play an important role of determining a flexibility of the flexible joint member  30  which repeatedly undergoes contraction and expansion. If the flexible joint member  30  has excessive flexibility, coupling of the flexible joint member  30  with the head  20  and the pelvis-contacting element  10  can be easily effected, but the likelihood of the flexible joint member  30  to be released therefrom is increased. On the contrary, if the flexible joint member  30  has insufficient flexibility, coupling of the flexible joint member  30  with the head  20  and the pelvis-contacting element  10  cannot be easily effected. Accordingly, the depressed part  38 , the through-holes  38   a  and  38   b  and the slits  41   a  and  41   b  must be defined to have appropriate contours and sizes. 
   With the flexible joint member  30  coupled to the pelvis-contacting element  10 , in order to allow the flexible joint member  30  to be decoupled from the pelvis-contacting element  10 , a pair of decoupling grooves  43   a  and  43   b  are defined on the outer surface of the resilient part  40 . 
   The pair of decoupling grooves  43   a  and  43   b  are defined on the outer surface of the resilient part  40  in a manner such that they are aligned on a line which is orthogonal to another line connecting the slits  41   a  and  41   b  with each other and thereby are spaced apart from the slits  41   a  and  41   b  by 90° in the circumferential direction. The pair of decoupling grooves  43   a  and  43   b  serve as tool passage openings so that a tool can be placed between the pelvis-contacting element  10  and the flexible joint member  30  when the flexible joint member  30  is coupled to the pelvis-contacting element  10 . Actually, when performing an operation, as occasion demands, decoupling of the head  20  formed at the distal end of the stem  50  from the flexible joint member  30  or decoupling of the flexible joint member  30  having the head  20  inserted therein from the pelvis-contacting element  10  may be needed or not. In consideration of this fact, in a fifth embodiment of the present invention, the pair of decoupling grooves  43   a  and  43   b  may be or may not be defined on the outer surface of the resilient part  40 . 
   If the flexible joint member  30  can be easily decoupled from the pelvis-contacting element  10 , when performing an operation, convenience can be improved and a required time can be shortened. Therefore, it is preferred that the decoupling grooves  43   a  and  43   b  are normally defined on the outer surface of the resilient part  40 . 
   Here, the tool for decoupling the flexible joint member  30  from the pelvis-contacting element  10  may have a configuration such as of a pair of long-nose pliers. In this case, after placing the respective actuating arms of the pliers into the pair of decoupling grooves  43   a  and  43   b , by pressing grip portions of the pliers toward each other, the flexible joint member  30  can be easily decoupled from the pelvis-contacting element  10 . If a tool is not separately prepared, the flexible joint member  30  can be decoupled from the pelvis-contacting element  10  using two screwdrivers. 
   The projecting ribs  44  are formed in a manner such that they project radially outward from the outer surface of the resilient part  40  and extend in the circumferential direction of the resilient part  40 . When the flexible joint member  30  is accommodated in the pelvis-contacting element  10 , the projecting ribs  44  are engaged into the engaging grooves  10   b  which are defined on the inner surface of the pelvis-contacting element  10 . 
   When it is necessary to decouple the flexible joint member  30  from the pelvis-contacting element  10 , by pressing the resilient part  40  radially inward in the decoupling grooves  43   a  and  43   b  using a separate tool, the resilient part  40  is contracted along the circumferential direction. At this time, in the regions where the slits  41   a  and  41   b  are defined to divide the resilient part  40  into the pair of unit resilient portions  40   a  and  40   b , since contraction occurs to a slight extent, it is not easy to decouple the flexible joint member  30  from the pelvis-contacting element  10 . 
   To cope with this problem, as shown in  FIG. 11 , the projecting ribs  44  are formed in a manner such that their height is gradually decreased from the decoupling grooves  43   a  and  43   b  toward the slits  41   a  and  41   b . Due to this fact, in the regions where the slits  41   a  and  41   b  are defined in the resilient part  40  and contraction occurs to a slight extent, the projecting ribs  44  can be easily disengaged from the engaging grooves  10   b.    
   Each projecting rib  44  has a first inclined surface  44   a  which is inclined downward by a preselected angle when the surface  44   a  is viewed in a direction along which the flexible joint member  30  is inserted into the pelvis-contacting element  10 . Thus, when the flexible joint member  30  is inserted into the pelvis-contacting element  10 , due to the presence of the first inclined surface  44   a , the flexible joint member  30  can be slidingly guided at the entrance  10   a  of the pelvis-contacting element  10 . Thereafter, the projecting ribs  44  are respectively engaged into the engaging grooves  10   b . At this time, after the engagement is effected between the projecting ribs  44  and the engaging grooves  10   b , the projecting ribs  44  are respectively brought into contact with bottom surfaces of the engaging grooves  10   b  in a vertical direction, whereby the flexible joint member  10  is prevented from being unintentionally released in a direction opposite to the direction along which the flexible joint member  30  is inserted into the pelvis-contacting element  10  (see the enlarged part in  FIG. 8 ). 
   The resilient part  40  which is divided into the pair of unit resilient portions  40   a  and  40   b  is formed to have an outer diameter which is greater than a diameter of the entrance  10   a  of the pelvis-contacting element  10 . By this fact, when the flexible joint member  30  is accommodated in the pelvis-contacting element  10 , the pair of unit resilient portions  40   a  and  40   b  are contracted radially inward, and the projecting ribs  44  are inserted and engaged into the engaging grooves  10   b , respectively. When the insertion of the projecting ribs  44  into the engaging grooves  10   b  is completed, the pair of unit resilient portions  40   a  and  40   b  are expanded radially outward so that the projecting ribs  44  can be held securely engaged in the engaging grooves  110   b.    
   Further, the resilient part  40 , which is divided into the pair of unit resilient portions  40   a  and  40   b , is formed to have an inner diameter which is less than a diameter of the head  20 . By this fact, when the head  20  is accommodated in the flexible joint member  30 , the pair of unit resilient portions  40   a  and  40   b  are expanded radially outward. When the insertion of the head  20  into the flexible joint member  30  is completed, the pair of unit resilient portions  40   a  and  40   b  are contracted radially inward to properly support the head  20 . At this time, an inner edge of each unit resilient portion  40   a  and  40   b  is formed with a second inclined surface  45 , which has an inclination substantially corresponding to a surface curvature of the head  20  to allow easy insertion and removal of the head into and out of the flexible joint member  30 . 
   While the flexible joint member  30  is formed to have the diameter which is substantially the same as the diameter of the head  20  so that collision does not occur between the component parts and abrasion and wear are not caused, a pair of indented portions  46   a  and  46   b  are defined on an inner surface of the flexible joint member  30  in a manner such that they define a diameter which is greater than the diameter of the head  20 , to ensure smooth insertion and removal of the head  20  into and out of the flexible joint member  30 . The pair of indented portions  46   a  and  46   b  are defined to be diametrically opposite to each other. 
   The indented portions  46   a  and  46   b  (see  FIG. 8 , where the dotted lines show the indented portions when the flexible joint member  30  is not placed in the pelvis-contacting element  10 ) create spaces of a predetermined size between the flexible joint member  30  and the head  20  when the head  20  is inserted into the flexible joint member  30 . When the flexible joint member  30  is inserted into the pelvis-contacting element  10  along with the head  20  accommodated therein, the indented portions  46   a  and  46   b  are biased radially inward. In this way, as the contraction is effected in the flexible joint member  30  having accommodated therein the head  20 , the spaces created between the head  20  and the flexible joint member  30  due to the presence of the indented portions  46   a  and  46   b  are removed, whereby collision does not occur and the head  20  can be securely supported in the flexible joint member  30 . 
   Hereinafter, a procedure for installing the artificial hip joint prosthesis  1  according to the present invention, constructed as mentioned above, will be described. 
   First, a position and a status of the pelvis  8  into which the pelvis-contacting element  10  is to be inserted are checked. Then, after fixing the stem  150  to the femur  9 , the head  20  is coupled to the distal end of the stem  50 . 
   Next, the head  20  coupled with the stem  50  is inserted through the entrance  30   a  of the flexible joint member  30 . By doing this, as the head  20  is guided along the second inclined surface  45  which is formed on the inner edge of each unit resilient portion  40   a  and  40   b , the head  20  is inserted into the flexible joint member  30  which is resiliently expanded outward in the radial direction. 
   That is to say, the pair of unit resilient portions  40   a  and  40   b  are expanded radially outward due to the presence of the depressed part  38 , through-holes  38   a  and  38   b  and slits  41   a  and  41   b  which are formed on or defined in the flexible joint member  30 . When the head  20  is completely inserted into the flexible joint member  30 , the pair of unit resilient portions  40   a  and  40   b  are contracted radially inward. 
   By the fact that the pair of indented portions  46   a  and  46   b  are defined on the inner surface of the flexible joint member  30  in a manner such that they define the diameter which is greater than the diameter of the head  20 , if the head  20  is completely inserted into the flexible joint member  30 , the spaces of the predetermined size are created between the inner surface of the flexible joint member  30  and the outer surface of the head  20 . 
   If the coupling of the head  20  with the flexible joint member  30  is completed, the flexible joint member  30  having accommodated therein the head is inserted into the pelvis-contacting element  10 . Thereupon, due to the presence of the depressed part  38 , through-holes  38   a  and  38   b  and slits  41   a  and  41   b , the pair of unit resilient portions  40   a  and  40   b  are resiliently contracted radially inward, by which the flexible joint member  30  is inserted into the pelvis-contacting element  10 . After the insertion of the flexible joint member  30  into the pelvis-contacting element  10  is completed, the pair of unit resilient portions  40   a  and  40   b  are expanded radially outward again. 
   At this time, the projecting ribs  44  are respectively engaged into the engaging grooves  10   b . Since an expansion degree of the flexible joint member is less than a contraction degree thereof, if the flexible joint member  30  is completely inserted into the pelvis-contacting element  10 , the spaces created between the outer surface of the head  20  and the inner surface of the flexible joint member  30  are removed. Consequently, the head  20  can be held securely supported in the flexible joint member  30 , and at the same time, the flexible joint member  30  can be securely supported in the pelvis-contacting element  10 . Thereafter, the combination of the head  20 , flexible joint member  30  and pelvis-contacting element  10  which are coupled one with another is positioned in place on the pelvis  8 . 
   As apparent from the above description, in the present invention, since it is possible to operatively connect the head  20  and the pelvis-contacting element with each other by virtue of resiliency of the flexible joint member  30  which comprises a single component which allows a user to easily and simply manipulate the joint member  30 , it is possible to conveniently install the artificial hip joint prosthesis and shorten an installation time. 
   Further, in the present invention, because it is possible to decrease relative heights of the pelvis-contacting element  10  and the flexible joint member  30 , the artificial hip joint prosthesis can be easily and conveniently adapted even to Orientals having relatively small physiques and bone sizes. Also, since smooth rotation of the head  20  is ensured and interference between the pelvis-contacting element  10  and the head  20  is minimized, it is possible to prevent the pelvis including a cartilage and the femur of the human body from being injured. 
   Moreover, in the present invention, the pelvis-contacting element  10 , the head  20  and the flexible joint member  30  can be easily coupled to and decoupled from one another, and collision and interference between component parts are minimized. In addition, it is possible to prevent the respective component parts from being unintentionally released from one another. Because the flexible joint member  30  comprises a single component, manufacture of the artificial hip joint prosthesis can be conveniently implemented and a manufacturing cost can be reduced. 
   In the above-described embodiment, it was explained that the through-holes  38   a  and  38   b  of the flexible joint member  30  are defined in the form of a slot. However, as shown in  FIG. 12 , instead of defining the through-holes  38   a  and  38   b  in the form of a slot, the through-hole  38   b  can be defined in a manner such that a space for ensuring resilient deformation of the resilient part  40  is sufficiently provided in the flexible joint member  30  and a dummy portion  47  for additionally supporting the head  20  inserted into the flexible joint member  30  is formed on the depressed part  38 . 
   Also, as shown in  FIG. 13 , the configuration of the flexible joint member  30 ′ can be partially changed. In other words, the unit resilient portions  40   a ′ and  40   b ′ can be formed to have a polygonal configuration, and the associated parts such as the slits  41   a ′ and  41   b ′, the projecting ribs  44 ′, the flattened portions  42   a ′ and  42   b ′ and the through-holes  38   a ′ and  38   b ′ can be defined or formed to have a corresponding contour or configuration. 
   Furthermore, in the above-described embodiment, it was explained that the projecting ribs  44  are formed on the resilient part  40  and the engaging grooves  10   b  are defined in the pelvis-contacting element  10 . However, in another embodiment of the present invention as shown in  FIG. 14 , the projecting ribs  44 ″ can project radially inward adjacent to the entrance of and from the inner surface of the pelvis-contacting element  10 ″ and have the preselected depth, and the engaging grooves  10   b ″ can be defined on the outer surface of the resilient part  40 ″ of the flexible joint member  30 ″ and extend in the circumferential direction. 
   When selectively decoupling the head  20  and the stem  50  from their corresponding component elements, it is not always necessary to decouple the flexible joint member  30  from the pelvis-contacting element  10 . Accordingly, as shown in  FIG. 15 , within the scope of the present invention, the decoupling grooves may not be defined in the unit resilient portions  40   a ′″ and  40   b ′″ of the flexible joint member  30 . 
   INDUSTRIAL APPLICABILITY 
   As described above, the present invention provides an artificial hip joint prosthesis in which interference and collision are minimized between component parts and which ensures smooth rotation of a head and is constructed in such a way as to be easily installed and shorten an installation time. 
   The artificial hip joint prosthesis according to the present invention can be optimally adapted even to Orientals having relatively small physiques and bone sizes, and can minimize the interference and collision between the component parts to thereby prevent the pelvis including a cartilage and the femur of the human body from being injured. 
   The artificial hip joint prosthesis according to the present invention allows assembly and disassembly of component parts to be easily performed and minimizes radial movement of the head so that collision does not occur between the component parts, while release of the head is properly prevented. As the present artificial hip joint prosthesis is constructed to render partial structural integration, it is possible to simplify a manufacturing procedure and reduce a manufacturing cost.