JPH0551303B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION This invention relates generally to the field of femoral prostheses, and more particularly to an improved femoral head and neck prosthesis.

Industrial Applications Changes in the stress distribution across the femur (femoral bone) after implantation of a prosthesis lead to a number of complications, such as further bone deterioration. According to Wolff's law, if the stress distribution in bone changes, eventually
Significant changes occur in the internal structure of the bone. For example, if a portion of the femur is isolated from the stresses that would normally occur, that portion is more likely to deteriorate. On the other hand, parts of the femur that are subjected to greater stress tend to correspondingly become thicker. Of course, if stress were to increase excessively, bone cells would probably be killed (gangrene).

Conventional "intraosseous" femoral head-neck style implants, i.e., implants with long stems that are fixed in the medullary canal of the femur, are typically Because it is insulated from the stress of
The femur will deteriorate. As a result, the expected lifespan of endosseous prostheses is relatively short, at least when applied to young patients. Additionally, patients receiving endosteal grafts may experience a substantially reduced level of activity. One of the studies aimed at solving this problem is the extraosseous prosthetic joint disclosed by A. Huggler in US Pat. No. 4,129,903. This prosthesis is a type of prosthesis described by Hagler and H. Jacob, ``The Uncemented Thrust-Plate Hip Prosthesis
Prosthesis) and Schleiba (A.
Schreiber), Jacob, Suezawa (Y.Suezawa)
and Hagler, “First Results with the Thrust Plate Total Hip Prosthesis”
“Thrust Plate” Total Hip Prosthesis” and these are discussed in “The Cementless
Fixation of Hip Endoprosthesis 125−132 [E.
Morscher ed. 1984]). (Hereinafter, each document will be referred to as "Thrust Plate Prosthesis" and "First Results.") Hagler's prosthesis consists of a tension or connection hole that penetrates the bone, a pressure disk that contacts the femoral neck, and a pressure disk that contacts the femoral neck. and a back plate disposed on the outside of the. One of the advantages of this type of prosthesis is that there is sufficient bone to support the endosteal graft should it become necessary to replace it.

However, even with Hagra's prosthesis,
There are many undesirable effects. For example, during walking, when the femur changes between loaded and unloaded conditions, the tension plate tends to move slightly relative to the bone. (Micromotion) This is due to the fact that the elastic modulus of the bone and the connecting rod are different from each other. As a result, the connecting rod wears almost constantly on the bone and the back plate. In some cases, the connecting rod may crack at the contact surface between the connecting rod and the back plate.

The study by Hagler included placing the thrust plate perpendicular to the longitudinal axis of the femoral neck and placing the connecting rod along the longitudinal axis of the femoral neck (e.g., 35 degrees from the horizontal). It includes: According to Hagler, movement of the connecting rod relative to the bone and dorsal plate can be avoided by placing the connecting rod along the central axis of the femoral neck.
More specifically, the more vertical the connecting rod is in the installation state using the hooker, the more the end of the connecting rod will move within the back plate. (This means more micromovements.) However, because Hagler's prosthesis is aligned along the central longitudinal axis of the femoral neck, the connecting rods are placed in a generally vertical direction on the femur. It is not placed in parallel (or near parallel) to the loads, ie, the loads that occur on the femur due to normal activities, such as walking. Therefore, when the femur is loaded, the connecting rod is subject to bending moments that can cause the connecting rod to crack. This is believed to be the cause of the connecting rod cracking discussed on page 127 of ``Thrust Plate Prosthesis''.

Furthermore, the Hagler prosthesis is mounted at a relatively high neck (proximal) on the lateral side of the femoral shaft. In this location, the cortical bone is relatively thin. This means that three patients treated with a prosthesis
This is because one in five patients complain of pain during the first 6 to 8 months (although, according to Wolff's Law, this pain will subside significantly when the cortical bone becomes sufficiently thick). (No. 130 of “First Results”
page). Another cause of this pain is the combination of the high position of the dorsal plate and its relatively high profile, which can cause inflammation in the muscles or tendons. vinegar.

SUMMARY OF THE INVENTION Some objects of the present invention are to provide a femoral head-neck prosthesis that loads the femur in a manner similar to the native femoral head and neck; To provide a prosthesis that protects a femur from movement of a ball and a stem portion replacing the femur with respect to the femur in a state in which a load is applied and a state in which no load is applied; To provide a prosthesis that allows a person affected by the disease to carry out a more normal daily life, to provide a prosthesis that reduces pain experienced by the person wearing the prosthesis, and to provide a prosthesis that is durable, economical, and long-lasting. The objective is to provide a prosthesis that has

Further described herein is a method of installing a prosthesis as described above, which reduces complexity and failure during installation, facilitates positioning of such a prosthesis, and provides an advantage to the patient. minimizes the amount of trauma caused by the process, minimizes trial and error when installing such prostheses, and avoids the generation of excessive frictional heat that can kill bone cells, which can occur during operation, especially during cutting and drilling of the femur. A method for reducing this is shown.

Generally speaking, the extraosseous femoral head according to the invention -
The neck prosthesis is implanted into the femur. The femur has a substantially vertically extending trunk and a neck medially at the upper end of the shaft. The prosthesis includes a side plate and means for securing the side plate to the femoral shaft on the lateral side of the femur. A cylindrical body extends obliquely upward from the side plate and has an open upper end.
The tubular body is configured to be inserted into a hole extending obliquely upwardly from the lateral side of the femoral shaft through the femoral shaft to the femoral neck. The prosthesis includes a sphere assembly including a stem coaxially inserted into and slidably received through the open upper end of the tube. The stem portion is sized to fit within the cylindrical body with a relatively small clearance. A neck is provided at the upper end of the stem portion for facing engagement with the neck of the femur. The sphere is attached to its neck. Restraining means are provided to hold the stem against upward movement when the stem is received in the tube.

Generally speaking, the method of implanting the extraosseous femoral head-neck prosthesis of the present invention into the femur includes:
Cut the neck of the femur to create a generally flat surface;
A hole is drilled through the shaft of the femur so that the hole extends diagonally from the neck of the femur to the outside of the shaft. In this case, it is preferable that the angle is approximately 30 degrees with respect to the central axis in the longitudinal direction of the trunk of the femur. A cylindrical body having an open end is inserted into the hole with the open end facing upwardly and fixed in a fixed position within the hole. The stem of the ball assembly is coaxially inserted into the barrel and the generally planar surface of the ball assembly is brought into facing engagement with the planar surface of the neck of the femur.

Other objects and features will be made clear and pointed out in the following description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, an extraosseous femoral head-neck prosthesis according to the invention is generally designated by the reference numeral 1. FIG. The femur, roughly marked 3, is the trunk 5
and a neck 7 at the upper end of the shaft on the medial side of the femur, into which the femoral head-neck prosthesis is configured. The femur has a hard layer of cortical bone 9 adjacent to the surface of the bone;
Relatively soft bone network inside the femur 1
Contains 1.

Referring to FIG. 1, the prosthesis 1 generally includes a side plate formed in the form of an elongated member 13, and a cylindrical body 15 integrally attached to the side plate and extending obliquely upward. There is. The cylindrical body 15 has an open upper end 17, and the femoral trunk 5
It extends from the lateral part 21 of the femur into a hole 19 which extends diagonally upwardly through its trunk 5 into the neck 7 of the femur.

The central axis AX-1 in the longitudinal direction of the cylindrical body 15 is
Preferably, the longitudinal center axis AX of the side plate 13
-5 at an angle A1 (Fig. 1) of approximately 150 degrees. Further, the longitudinal axis AX-2 of the femoral neck 7 and the longitudinal axis AX-1 of the hole 19 and the cylindrical body 15 are the same as the longitudinal central axis AX-3 of the femoral trunk 5. It exists substantially within the plane P-1, so that the load applied to the femur acts in a state as close to normal as possible (the state before the prosthesis is implanted).

Referring to FIG. 2, the side plate 13 is attached to the femoral trunk 5.
Means are provided for securing to the side plate 13 so that the side plate 13
will extend along the trunk 5 at the lateral part 21 of the femur. For example, a tuft pin screw 23 may pass through the lower portion 24 of the side plate 13 to secure the side plate to a thick cortical bone portion of the trunk 5.

The prosthesis includes a sphere assembly 25 that is inserted into the tube 15.
5 includes a stem portion 27 configured to be inserted coaxially through the open upper end 17 of 5. The stem portion 27 has a flat surface 28 that engages a flat portion (not shown) of the tubular body 15, thereby preventing the stem portion 27 from rotating within the tubular body 15. The stem portion 27 is sized to fit within the tubular body 15 with a relatively small clearance, and the stem portion 27 is slidably received within the tubular body 15. . The collar part 31 at the upper end of the stem part 27 faces and engages the neck part 7 of the femur, covering the entire cut surface of the neck part 7 of the femur, and applying pressure only to a certain part of the neck part. Avoid concentrating. A sphere 33 is removably attached to neck 29 on collar 31 and has dimensions 7 and 35.
The lengths of the neck and head of the femur are respectively shown in . (The head of the femur is shown in FIG. 4.) Preferably, the central longitudinal axis AX-1 of the stem 27 of the ball assembly 25 is at the longitudinal center of the neck 29 of the ball assembly 25. It is inclined at an angle A2 (Fig. 1) of about 25 degrees with respect to the axis AX-4, and the center C of the sphere is aligned with the longitudinal axis AX-1 of the stem portion 27.
It will be offset inward from the point. (It is offset to the left in FIG. 1.) Stem portion 27
is inserted into the cylindrical body 15, the central axis AX-
4, i.e., the longitudinal axis of the neck 29 of the sphere is about 125 with respect to the longitudinal axis AX-5 of the side plate 13
The neck 2 of such a sphere extends at an angle of
9 will be placed approximately on the same straight line as the axis AX-2 of the neck 7 of the femur.

Collar portion 31 of sphere assembly 25 has a downwardly facing generally flat surface 37 .
extends approximately at right angles to the longitudinal central axis AX-1 of the stem portion 27. The surface 37 is adapted for face-to-face engagement with an abutting surface or sheet 39 on the neck 7 of the femur, such engagement being accomplished by, for example, providing a metal bead or a "porous covering" on the surface. The tissue is composed of surface 3
This allows for growth into the gap between 7 and 7.

It will be appreciated that the load is applied to the tubular body 15
and acting generally along the stem axis AX-1, which is perpendicular to the flat surface 37, so that the load will be carried by the surface 37. As a result, the bone is subjected to substantially the same loads by the prosthesis 1 as were applied by the original femoral neck. Furthermore, the neck 29 of the prosthesis will have no tendency to slide on the neck 7 of the femur. because,
This is because the joint surface between the neck of the sphere and the neck of the femur is generally perpendicular to the direction of the load applied to the femur. Furthermore, excessive bending moments acting on the stem portion 27 are avoided. This is because the loads acting on the axis AX-1 of the cylindrical body 15 and the stem portion of the prosthesis and the femur are approximately parallel to each other. It will be appreciated that the respective meeting surfaces 37, 39 of the collar 31 and femoral neck 7 may have configurations other than flat shapes without departing from the perspective of the present invention. . For example, the seat 39 on the neck of the femur may be configured in the shape of a dish, forming a socket, and the surface 37 on the collar 31 may have a corresponding convex shape.

Restraint means are provided which hold the stem portion 27 against upward movement within the tubular body 15 and which restrain the neck of the prosthesis opposite the neck 7 of the femur. 29 to apply compression or preload to the neck 7 of the femur. For example, the restraining means may include a set screw 4 screwed into the lower end 43 of the stem portion 27 when the stem portion 27 is inserted into the cylindrical body 15.
1 may be included. The head of the set screw 41 is
The stem portion 27 is configured to be able to engage with the lower end of the cylindrical body 15 in order to hold the stem portion 27 from moving upward within the cylindrical body 15.

It will be appreciated that the set screw 41 merely holds the stem in the barrel 15 and compresses the neck of the femur, and does not support the weight of the patient. The femur 3, including the neck 7, supports the weight of the patient in a near normal state, thereby avoiding the phenomenon of bone atrophy.

Further, since the stem portion 27 is slidably received in the cylindrical body 15, the friction or wear caused by the movement of the stem portion 27 relative to the cylindrical body 15 or the bone is caused by the friction or wear caused by the movement of the stem portion 27 and the cylindrical body. This will occur between the body 15 and the body 15. Thus, the bone is a cylindrical body15
will be protected by. It will therefore be appreciated that micromotion and resulting wear on the femur will be reduced or eliminated by this particular barrel 15 and stem configuration.

FIG. 3 shows another embodiment of the invention, which generally corresponds to the embodiment of FIGS. 1 and 2, with the fundamental difference being that the side plate, indicated at 13A, is cylindrical. It has an upper portion 45 above the joint between the body 15A and the side plate, and further includes a cylindrical body 15A.
The lower part 24 is located below the joint between the side plate 13A and the side plate 13A.
The point is that it has A. The upper and lower portions 45 and 24A each have a hole 47 through the side plate 13A which receives a fastener (e.g. tuft pin screw 49) to secure the side plate to the femoral shaft 5.

Although there are a number of devices useful for implanting femoral head-neck prostheses, the particular device shown generally at 51 in FIGS. 4-7 specifically includes:
removably fixed to the shaft of the femur, with multiple
It is suitable for holding cutting, drilling and reaming accessories in place on the femur.

Referring to FIG. 4, the retention device 51 includes a body 53 configured to be removably attached to the femoral shaft 5 in facing engagement (e.g., by a stop 55); Body 5 on one side
3 and an arm or outwardly extending portion 57 extending upwardly and outwardly from the body at an angle (e.g., approximately 150 degrees relative to the body). arm part 57
The upper end 59 is configured to be centered at the base of the femoral neck 7. In the position shown,
When the arm portion 57 is fixed, the arm portion 57 is
It is arranged at an angle of approximately 150 degrees with respect to the central axis AX-3 in the longitudinal direction of the femoral shaft 5.

As shown in FIG. 6, the body 53 of the holding device 51 includes a tubular guide member 61, which includes a starter drill.
drill) (not shown) through the member 61. The tubular guide member 61 is arranged at an angle of approximately 90 degrees with respect to the central longitudinal axis AX-3 of the femoral shaft 5 when the retaining device is attached to the femoral shaft 5.
It is configured to be placed at the desired position.

Preferably, the retaining device 51 includes a guide sleeve 63 for guiding a drill-tipped guide pin 65 into the femoral shaft 5 . The guide sleeve 63 is aligned with the central axis AX in the longitudinal direction of the femoral shaft 5.
It is placed at an angle of approximately 30 degrees to -3. The guide sleeve 63 is configured to be slidably received in a guide tube 67 which is preferably formed as an integral part of the body 53 of the retaining device 51 . The guide sleeve 63 is a guide cylinder 6
7 so that, after the guide pin 67 has penetrated the femoral neck 7, the guide sleeve 63 can be removed, leaving the guide pin in place.

As mentioned above, the holding device 51 is configured to hold various different accessories used in implanting the prosthesis 1 of the present invention. One such accessory is a saw guide 69 that is removably attached to the upper end 59 of the arm portion 57 and guides the saw teeth to cut the femoral neck 7 and form the surface 39. . As shown in Figure 4,
Saw guide 69 has a saw cutting slot 71 oriented generally perpendicular to the central longitudinal axis of arm portion 57 and, in this configuration, retaining device 51
is installed in the position shown, slot 7
1 is the longitudinal central axis AX- of the femoral shaft 5;
It is now approximately 60 degrees to 3. Slot 71 is also configured to be generally perpendicular to the central longitudinal axis of arm portion 57. The saw guide 69 is slidably adjusted along the arm portion 57 and adjusted to bring it into proper position relative to the femoral neck 7. A set screw 73 is provided to secure the saw guide 69 in its adjusted position.

At 75, a retention device 51 for the femur 3
Another attachment is shown that limits the position of the . Attachment 75 is the surface 3 of the femoral neck.
The arm portion 57 is slidably adjusted along the arm portion 57 so that the arm portion 57 is in an appropriate position relative to the arm portion 9.

Attachment 75 cannot rotate relative to arm portion 57. A set screw 79 is provided to removably secure accessory 75 in its adjusted position. The attachment 75 is a relatively thin flat member 80.
, with member 80 extending laterally and outwardly in a position located just above surface 39 and in a plane generally parallel thereto. The member 80 also has an opening 81 located along the central axis of the guide sleeve 63. The opening 81 indicates the position on the cutting surface 39 of the femoral neck through which the guide pin 65 is to pass, so that the position of the retaining device 51 is precisely ascertained prior to drilling. It will be appreciated that the arm portion 57 of the retaining device is preferably parallel to the central longitudinal axis of the guide sleeve 63 and the guide tube 67, so that the guide sleeve 63 and the guide tube Shape 6
The axis of 7 will be parallel to the opening 81 regardless of the position of the attachment 75 along the arm portion.

A hollow reamer 83 (FIG. 7) is sized to be slidably received within the guide tube 67. Center axis hole 84 passing through reamer 83
is sized to slidably receive a guide pin 65 therein. It will be appreciated that the reamer 83 is configured to slide into the guide tube 67 over the guide pin 65 so that the guide pin and tube are A reamer is guided to enlarge the hole 85 that has been formed. The reamer 83 may rotate around the guide pin 65 while the guide pin 65 is fixed, or the reamer and the guide pin may rotate together.
It will be appreciated that the guide pin 65 projects through the opening 81 in the end member 80 during the reaming process. This stabilizes the position of the guide pin 65 when the femur is being reamed.

To install the prosthesis 1 in the femur, the hip joint and the lateral part of the femur (the right side in the figure) are first surgically exposed. The vertical plane P-1, which includes the central longitudinal axis AX-2 of the femoral neck 7, typically coincides with the central longitudinal axis AX-2 of the femoral trunk 5, as shown in FIG. It forms an angle of approximately 15 degrees anteriorly with respect to plane P-2 which passes through P-3 and extends from the lateral to the medial portion of the femur. This angle is commonly referred to as the "anteversion" of the femoral neck 7. Therefore, the holding device 51 is attached to the plane P-1 in which the vertical axis of the main body 53 is at an angle of about 15 degrees rearward from the plane P-2.
radially mounted on the femur such that it is set within the femur. (This is because the main body 53 has an axis AX-
3 is on the outside, and the femoral neck 7 is on the inside. ) In this position, the vertical plane P-3 containing the arm portion 57 must be parallel to the plane P-1. Furthermore, the retaining device 51 is placed in a proximal-to-distal direction (proximal-distal direction) on the femur;
The upper end 59 of the arm portion 57 becomes centered at the base of the femoral neck 7, as shown in FIG. The retaining device 51 is then attached to the stopper 5
5 on the shaft 5 of the femur.

As shown in FIG. 4, the saw guide 69 is inserted into the arm so that the slot 71 is located adjacent to the root of the femoral neck 7 and juxtaposed with the upper surface of the femoral cortex 87 on the lateral side of the femur. Located on portion 57 (in proximal-distal direction). In this position, slot 7
1 must be set at an angle of approximately 60 degrees with respect to the longitudinal axis AX-3 of the femoral shaft 5. Set screw 73 is then tightened to securely attach saw guide 69 to arm portion 57.

With the saw guide 69 in place, the femoral neck 7 is inserted into the slot 71 using an oscillating saw.
is cut to form a surface 39 extending from the lateral femoral cortex 87 at an angle of approximately 60 degrees to the central longitudinal axis AX-3 of the femoral shaft 5. . Saw guide 69 is removed from arm portion 57 and femoral head 35 is removed, leaving retainer 51 in its original position and attached to the femoral shaft.

If the entire hip joint is to be replaced (ie, replacing the femoral head 35 and the acetabulum [not shown]), the acetabulum would be treated after this.

As shown in FIGS. 6 and 7, an opening 81 in member 80 of attachment 75 is centered on surface 39 and secured to arm portion 57. Opening 8 to the surface of the femoral neck
It may be necessary to adjust the holding device 51 appropriately so that 1 is centered. This is accomplished by removing the stop 55 and adjusting the body 53 of the retaining device 51. For example, if the opening 81 is too medially (towards the left in the figure), the retention device 51 must be set in a more proximal position on the femoral shaft 5 (towards the left in the figure). above). And if opening 81 is too lateral (towards the right in the figure), the pin must be placed in a more distal position on the femoral shaft. Furthermore, if the opening 81 is anterior or posterior to the center of the surface 39, the anteversion may be adjusted by slightly rotating the retaining device 51 on the femoral shaft 5.

With opening 81 centered in surface 39, a drill (not shown) is inserted through annular guide member 61 to drill a relatively short starting hole (not shown) in the lateral femoral cortex. Without a starting hole, the acute angle of incidence of the guide pin 65 would make it easier for the guide pin 65 to move or "walk" along the lateral femoral cortex, or at the correct angle to penetrate the femur. (for example, 30 degrees). The guide sleeve 63 is then inserted into the guide tube 67 of the holding device 51 .

A drill-tipped guide pin 65 is then inserted into the guide tube 67 and a hole 85 is drilled through the outer femoral cortex and through the cutting surface 39 of the femoral neck 7 . The bore 85 extends obliquely from the femoral neck 7 to the lateral side of the femoral shaft at an angle of approximately 30 degrees to the central longitudinal axis of the femoral shaft. The guide pin 65 is an accessory 75
should protrude from the cutting surface of the femoral neck 7 through the opening 81 of the femoral neck 7.

If the guide pin 65 is significantly off center (eg more than 5 mm), the retaining device 51 must be adjusted. For example, guide pin 65
If it is too medial (to the left in the figure), the retaining device 51 must be placed in a more proximal position on the femoral shaft 5 (upward in the figure).
If the guide pin 65 is too lateral (to the right in the figure), the guide 65 must be placed in a more distal position on the femoral shaft. Furthermore, if the guide pin 65 is located in front of or behind the opening 81, the surface 39
If the holding device 51 extends through the femoral shaft 5, the anteversion may be adjusted by slightly rotating the holding device 51 on the femoral shaft 5. However, it should be noted that retaining device 51 reduces or eliminates the trial and error process discussed in this paragraph.

If the guide pin 65 is in the correct position, the guide sleeve 63 is removed from the guide tube 67, leaving the guide pin and attachment 75 in its place. As mentioned above, attachment 75 stably supports the proximal end of guide pin 65.

As shown in FIG. 7, the hollow reamer 83
is then inserted into the guide tube 67 so as to cover the guide pin 65, and a hole is inserted through the outer femoral cortex at an angle of about 30 degrees to the longitudinal central axis AX-3 of the femoral shaft 5. form 19. Holding device 5
Since the body 53 of 1 is anteverted about 15 degrees about the femur, the hole 19 will lie in the plane P-1 (and the hole 19 will lie in the lateral direction of the knee parallel to the plane P-2). tilted approximately 15 degrees forward relative to the axis). Retainer 51 is then removed from the femur. In the next step of the implantation process, the cylindrical body 15 of the prosthesis 1
is inserted into the hole 19 with its outer end 17 facing upward. The pin sleeve 89 (FIG. 8) is attached to the cylindrical body 15.
The guide pin 65 is inserted into the sleeve and the position of the hole 19 relative to the center of the femoral neck surface 39 is checked again. The radial direction or anteversion of the hole 19 is confirmed. The longitudinal axis AX-2 of the femoral neck 7 and the axis AX- of the hole 19
1 is the central axis AX-3 in the longitudinal direction of the femoral shaft 5
must be contained within the same vertical plane P-1. This plane is set at an angle of approximately 15 degrees to the lateral axis of the knee (not shown) parallel to plane P-2.

If the position of the prosthesis 1 is satisfactory, the side plate 13 is installed in its place and the pin sleeve 89 and guide pin 65 are removed. hole 91
is drilled through a screw hole in the rear side plate 13, and has a tuft pin screw 2 having an appropriate length.
3 is inserted through the side plate 13 and tightens the side plate to the femoral shaft 5, thereby fixing the tubular body 15 in the designated position within the hole 19.

After attaching the side plate 13 and the cylindrical body 15 to the femur, a trunnion 93 (planing
trunnion) is inserted into the cylindrical body 15 and properly fixed so as not to move in the rotational or axial direction with respect to the cylindrical body 15, as shown in FIG.
Projects upwardly from the surface 39 of the femoral neck 7. For example, the trunnion 93 is connected to the prosthesis tube 15.
It is fixed against rotational movement by a corresponding flat surface on the inside of and axially by a set screw 95. A high speed motor-driven surface smoothing device in the form of a femoral neck planer 97 is then placed on the trunnion 93, thereby causing a planer on the axis AX-1 of the tubular body 15. The rotation is stabilized, and the surface 39 of the femoral neck 7 is flattened (smoothed) in a direction perpendicular to the axis of the cylindrical body 15 by applying pressure evenly to the planer.
It will be done. The planing surface of the planing machine corresponds to the desired shape of the sheet 39 (e.g., flat, dished, etc.), and the most important consideration is that the sheet 39 is smoothed and aligned with the axis AX-1.
to ensure that uniform pressure distribution and wear occur. After planarization, planer 97 and trunnion 93 are removed.

A trial assembly (similar to sphere assembly 25) having a neck, collar and stem is then inserted into the femoral neck and tube 15. The collar of this assembly (similar to collar 31) is pulled against the surface 39 of the femoral neck by tightening a set screw (similar to set screw 41). The lower surface of the collar includes a pressure sensing indicator (eg, pressure sensitive paper) to determine load uniformity. If the distribution of the load acting on the surface 39 of the femoral neck 7 is not uniform, a planer 97 is used to smooth out the raised areas causing the non-uniform distribution.

It will be appreciated that the planing process described above may also be accomplished by other methods. For example, the smoothing device or planer 97 may be formed with coaxially extending shafts on both sides of the planer, one of the shafts being associated with a drive that rotates the planer at high speed. The other shaft (equivalent to trunnion 93) may rotate within the tube 15 of the trial side plate and tube assembly;
This flattens the sheet 39. After the smoothing process is completed, the trial assembly is removed and replaced by an assembly with side plates and tube 15 that will be used permanently.

Once the femoral neck 7 has been sufficiently flattened (smoothed), the stem portion 2 of the ball assembly 25 of an appropriate size is
7 is coaxially inserted through the femoral neck and into the tubular body 15, and the generally flat surface 37 of the sphere assembly 25
is engaged facing the flat surface 39 of the femoral neck with which it meets. A set screw 41 is inserted through the side plate 13 into the cylindrical body 15 and tightened tightly with a screw driver (not shown) having a torque gauge. When the set screw 41 is tightened tightly, the femoral neck 7 is sufficiently compressed and the prosthesis 1 and the femur 3 are compressed.
Limit the minute movements between the Over-tightening of screws must be avoided. This is because excessive compression causes gangrene (necrosis) of the bone.

The sphere 33 of the prosthesis 1 is then placed into the acetabulum (not shown) and the surgically created opening is closed.

It is understood from the above that the prosthesis can be placed in the proper position relative to the femur with a minimum of trial and error, and that the load placed on the femur by the prosthesis is close to normal. This reduces patient pain and avoids deterioration of the femur even after implantation of the prosthesis.

In view of the above, the above-mentioned objects of the present invention have been achieved,
Other benefits will also be obtained.

Various modifications may be made to the structure and method described above without departing from the scope of the invention, and what is shown in the above description and accompanying drawings is intended to be illustrative only and not limiting. It doesn't mean anything.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a femoral head-neck prosthesis according to the present invention attached to a femur.

FIG. 2 is a partial side view of the prosthesis of FIG. 1, showing the side plates that secure the prosthesis to the femur.

FIG. 3 is a view similar to FIG. 2, showing the side plate of another embodiment of the femoral head-neck prosthesis according to the invention.

FIG. 4 is a side view of an apparatus used in installing a femoral head-neck prosthesis according to the present invention, showing the saw guide being held to cut the neck of the femur.

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG.

Figure 6 shows Figure 4 holding other accessories for mounting a femoral head-neck prosthesis according to the present invention.
FIG. 3 is a side view of the device.

FIG. 7 is a side view of the retention device of FIGS. 4-6 showing the femur being reamed.

FIG. 8 is a side view of the side plate and barrel of the prosthesis of FIG. 1 placed on the femur.

Figure 9 is a front view of the bone being implanted.

1... Prosthesis, 3... Femur, 5... Femoral shaft, 7... Femoral neck, 13... Side plate, 15
... Cylindrical body, 17 ... Open upper end, 19 ... Hole, 23
... Tatsu pin screw, 25 ... Ball assembly, 27 ...
... stem part, 29 ... neck part, 31 ... collar part,
33... Sphere, 41... Set screw.

Claims (1)

[Scope of Claims] 1. An extraosseous femoral head-neck prosthesis configured to be implanted in a femur having a trunk and a neck, comprising: a side plate; means for fixing the side plate to the trunk; a cylindrical body having an open upper end and extending diagonally upward from the side plate, the body extending from the outside of the trunk to the neck of the femur; a cylindrical body configured to be inserted into a hole extending obliquely upward through the trunk; and a cylindrical body inserted coaxially into the cylindrical body through the open upper end of the cylindrical body. a stem portion configured to be slidably received within a body with a relatively narrow clearance; a collar portion disposed at an upper end of the stem portion for facing engagement with the neck of the femur; A sphere assembly comprising: a neck formed on the neck; and a sphere provided on the neck;
a sphere assembly in which the central axis of the neck is inclined with respect to the central axis of the stem, thereby displacing the center of the sphere inwardly from the central axis of the stem; restraint means for holding the stem against upward movement of the stem. 2. The extraosseous femoral head-neck prosthesis of claim 1, wherein the side plate is an elongated member having a central longitudinal axis, and the side plate is an elongated member having a central longitudinal axis, An extraosseous femoral head-neck prosthesis configured to extend. 3. The extraosseous femoral head-neck prosthesis according to claim 2, wherein the central axis of the cylindrical body extends at an angle of approximately 150 degrees with respect to the longitudinal central axis of the side plate. External extraosseous femoral head
Cervical prosthesis. 4 In the extraosseous femoral head-neck prosthesis according to claim 3, when the stem portion is inserted into the cylindrical body, the central axis of the neck portion is aligned with the central axis of the stem portion. The extraosseous femoral head-neck prosthesis is tilted at an angle of approximately 25 degrees. 5. The extraosseous femoral head-neck prosthesis according to claim 1, wherein the constraining means is screwed into the lower end of the stem when the stem is inserted into the cylindrical body. an extraosseous femoral head-neck, the set screw being engaged with the tubular body to retain the stem portion from substantially upward movement within the tubular body; prosthesis. 6. The extraosseous femoral head-neck prosthesis according to claim 1, wherein the central axis of the neck is inclined at an angle of 25 degrees with respect to the central axis of the stem. Femoral head-neck prosthesis. 7. The extraosseous femoral head-neck prosthesis according to claim 1, wherein the side plate has an upper portion above a branching point between the cylindrical body and the side plate; An extraosseous femoral head-neck prosthesis having a lower portion below the bifurcation of the side plate. 8. An extraosseous femoral head-neck prosthesis according to claim 1, wherein the collar portion has a downwardly facing generally flat surface extending generally perpendicular to the central axis of the stem portion. an extraosseous femoral head-neck prosthesis having a surface configured for face-to-face engagement with an upwardly facing engagement surface on the neck of the femur.