WO2009023971A1

WO2009023971A1 - Trial insert for use in orthopaedic surgery

Info

Publication number: WO2009023971A1
Application number: PCT/CA2008/001524
Authority: WO
Inventors: Yvan Petit; Julio Fernandes; Jean-Sébastien MERETTE; Mathieu Dansereau; Victor Songmene; Mathieu Carrier
Original assignee: Socovar Societe En Commandite; Valorisation Recherche Hopital Sacré-Coeur De Montreal
Priority date: 2007-08-21
Filing date: 2008-08-21
Publication date: 2009-02-26

Abstract

A trial insert (28) for selecting between a first hip prosthesis (10) and a second hip prosthesis (10), the selected hip prosthesis (10) being fitted to a patient, the patient having a femur (16) and a pelvis (12), the pelvis (12) defining an acetabulum (14), the first hip prosthesis (10) including a first acetabular cup (20) attachable to the acetabulum (14) and a first replacement femoral head (24) attachable to the femur (16), the first acetabular cup (20) defining a substantially spherical first cup shell (21), the first cup shell (21) defining a first shell inner radius, the second hip prosthesis (10) including a second acetabular cup (20) attachable to the acetabulum (14) and a second replacement femoral head (24) attachable to the femur (16), the second acetabular cup (20) defining a substantially spherical second cup shell (21), the second cup shell (21) defining a second shell inner radius, the first shell inner radius being smaller than the second shell inner radius, the trial insert (28) comprising: a body (30); a head mount (34) for mounting the first and second replacement femoral heads (24) thereto, the head mount (34) being mechanically coupled to the body (30); and an insert-to-cup coupler (32) mountable to the first and second acetabular cups (20), the insert-to- cup coupler (32) being mechanically coupled to the body (30) and configurable between a smaller configuration in which the insert-to-cup coupler (32) is mountable to the first acetabular cup (20) and a larger configuration in which the insert-to-cup coupler(32) is mountable to the second acetabular cup (20).

Description

TITLE OF THE INVENTION

TRIAL INSERT FOR USE IN ORTHOPAEDIC SURGERY

FIELD OF THE INVENTION

[0001] The present invention relates to the art of surgical devices. More specifically, the present invention is concerned with a trial insert for use in orthopaedic surgery.

BACKGROUND

[0002] Referring to Fig. 1 , there is shown a hip prosthesis 10 for replacing a hip articulation 11. The hip prosthesis 10 is usable in a patient having a pelvis 12 defining an acetabulum 14. The patient also has a femur 16 defining a femur head 18. In Fig. 1 , one of the hip articulations 11 of the patient 11 is shown intact, while the other hip articulation 11 is undergoing hip replacement.

[0003] The prosthesis 10 includes an acetabular cup 20, the acetabular cup 20 being attachable to the acetabulum 14. The acetabular cup 20 typically defines a substantially spherical cup shell 21 defining a shell inner radius. The prosthesis 10 also includes a femoral component 22 attachable to the femur 16 and a replacement femoral head 24. Typically, the replacement femoral head 24 has a substantially spherical configuration and is removably attachable to the femoral component 22. Finally, the prosthesis 10 includes an insert 26, which is typically made out of a polymer. The insert 26 is insertable inside the acetabular cup 20 and receives the replacement femoral head 24. In other words, the insert 26 couples the replacement femoral head 24 to the acetabular cup 20 and allows rotation of the replacement femoral head 24 relatively to the acetabular cup 20 in all directions, thereby forming a ball-and-socket joint replacing the natural hip articulation 11 in the patient.

[0004] Due to morphologic differences between patients and to imprecisions in the surgical technique used to attach the prosthesis 10, a surgeon typically needs to proceed iteratively to select the optimal dimensions of the acetabular cup 20, insert 26 and the replacement femoral head 24. To that effect, the surgeon typically attaches the acetabular cup 20 to the acetabulum 14, attaches a femoral component 22 to the femur 16 and attaches a replacement femoral head 24 having a first dimension to the femoral component 22. Once the dimensions of the replacement femoral head 24 and of the acetabular cup 20 have been selected, only an insert 26 having specific dimensions is usable to couple the replacement femoral head 24 to the acetabular cup 20. The only variation that remains in conventional hip prostheses is the presence or absence of a stabilizing lip (not shown in Fig. 1) onto the insert 26.

[0005] Once these dimensions have been selected, the surgeon then inserts the replacement femoral head 24 into the acetabular cup 20 using a trial insert 26 and examines the range of motion obtained with this trial insert 26 and this replacement femoral head 24. The surgeon also ascertains the likelihood of dislocation of the hip articulation 11 by looking at a tendency of the replacement femoral head 24 and trial insert 26 assembly to lose contact with the internal surface of the acetabular cup 20 as the hip articulation 11 is manipulated by the surgeon. If the selected replacement femoral head 24 and trial insert 26 prove to be unsatisfactory, the surgeon may then remove the replacement femoral head 24 and trial insert 26 and repeat the above-mentioned operations with a replacement femoral head 24 and a trial insert 26 having different dimensions. [0006] Since the surgeon typically cannot plan the exact dimensions of the replacement femoral head 24, insert 26 and acetabular cup 20 that will be needed during the surgery, there is a need to sterilize inserts 26 having various dimensions, the number of inserts 26 depending on the number of differently sized replacement femoral heads 24 and differently sized acetabular cups 20 available to the surgeon. In a conventional hip replacement kit, there may be a need to sterilize more than 100 different trial inserts 26, which proves costly and time- consuming.

[0007] Accordingly, there is a need in the industry to provide an improved trial insert for use in orthopaedic surgery. An object of the present invention is therefore to provide such a trial insert.

SUMMARY OF THE INVENTION

[0008] In a broad aspect, the invention provides a trial insert for selecting between a first hip prosthesis and a second hip prosthesis, the selected hip prosthesis being fitted to a patient, the patient having a femur and a pelvis, the pelvis defining an acetabulum, the first hip prosthesis including a first acetabular cup attachable to the acetabulum and a first replacement femoral head attachable to the femur, the first acetabular cup defining a substantially spherical first cup shell, the first cup shell defining a first shell inner radius, the second hip prosthesis including a second acetabular cup attachable to the acetabulum and a second replacement femoral head attachable to the femur, the second acetabular cup defining a substantially spherical second cup shell, the second cup shell defining a second shell inner radius, the first shell inner radius being smaller than the second shell inner radius, the trial insert comprising: a body; a head mount for mounting the first and second replacement femoral heads thereto, the head mount being mechanically coupled to the body; and an insert-to-cup coupler mountable to the first and second acetabular cups, the insert-to-cup coupler being mechanically coupled to the body and configurable between a smaller configuration in which the insert-to-cup coupler is mountable to the first acetabular cup and a larger configuration in which the insert-to-cup coupler is mountable to the second acetabular cup. The insert-to-cup couplers is usable for fitting the selected hip prosthesis to the patient with the first and second hip prostheses including respectively the first and second acetabular cups defining different shell inner radii.

[0010] Therefore, the proposed trial insert is mountable to acetabular cups having different dimensions without requiring the removal, addition or replacement of parts. Advantageously, the proposed trial insert reduces the number of trial inserts required during the course of conventional orthopaedic surgery, therefore minimizing acquisition costs, sterilization requirements and storage space required to store the trial insert.

[0011] In some embodiments of the invention, the head mount is removably attachable to the body and replaceable by a head mount having a different inner dimension. This allows the proposed trial insert to receive femoral heads having different dimensions.

[0012] In some embodiments of the invention, the proposed trial insert includes an insert-to-cup coupler that has retractable arms. Varying the position of the arms allows for mounting the insert-to-cup coupler to acetabular cups having different dimensions.

[0013] Advantageously, the proposed trial insert is also relatively easily manufactured using known materials and techniques. Furthermore, since the proposed trial insert is manufacturable using a relatively small quantity of material as compared to the conventional set of trial inserts, the proposed trial insert may be commercialized at relatively low costs.

[0014] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 , already described, in a front partially exploded cross-sectional view, illustrates a conventional hip prosthesis attachable to a pelvis and a femur;

[0016] Figure 2, in a perspective view, illustrates a trial insert in accordance with an embodiment of the present invention, the trial insert being shown attached to a conventional acetabular cup, the acetabular cup being shown in phantom lines;

[0017] Figure 3, in a perspective exploded view, illustrates the trial insert shown in Fig. 2;

[0018] Figure 4, in a perspective view, illustrates the trial insert shown in Figs. 2 and 3, the trial insert being shown in a smaller configuration;

[0019] Figure 5, in a perspective view, illustrates the trial insert shown in Figs. 2 to 4, the trial insert being shown in an intermediate configuration; [0020] Figure 6, in a perspective view, illustrates the trial insert shown in Figs. 2 to 5a, the trial insert being shown in a larger configuration;

[0021] Figure 7, in a top plan view, illustrates the trial insert shown in Figs. 1 to 5b;

[0022] Figure 8, in a side cross-sectional view along the line A-A shown in Fig. 6, illustrates the trial insert shown in Figs. 1 to 6;

[0023] Figure 9, in a side elevation view, illustrates an actuator, the actuator being part of the trial insert shown in Figs. 1 to 7;

[0024] Figure 10, in a bottom plan view, illustrates the actuator shown in Fig. 8;

[0025] Figure 11 , in a side cross-sectional view along the line AA-AA of Fig. 9, illustrates the actuator shown in Figs. 8 and 9;

[0026] Figure 12, in a perspective view, illustrates an arm, the arm being part of the trial insert shown in Figs. 1 to 7;

[0027] Figure 13, in an alternative perspective view, illustrates the arm shown in Fig. 11 ;

[0028] Figure 14, in a top elevation view, illustrates a head mount, the head mount being part of the trial insert shown in Figs. 1 to 7; [0029] Figure 15, in a side elevation view, illustrates the head mount shown in Fig. 13;

[0030] Figure 16, in a top elevation view, illustrates a body, the body being part of the trial insert shown in Figs. 1 to 7;

[0031] Figure 17, in a side cross-sectional view along the line B-B of Fig. 15, illustrates the body shown in Fig. 15; and

[0032] Figure 18, in a side-elevation view, illustrates the body shown in Figs. 15 and 16.

DETAILED DESCRIPTION

[0033] Referring to Fig. 2, there is shown a trial insert 28 in accordance with an embodiment of the present invention, the trial insert 28 being shown mounted to an acetabular cup 20, shown in phantom lines. The trial insert 28 is usable in an orthopaedic surgery aiming at replacing a hip articulation 11 (shown in Fig. 1) with a prosthesis in a patient. For example, the prosthesis 10 is substantially similar to the prosthesis 10 described with reference to Fig. 1. More specifically, the trial insert 28 is usable for selecting between two hip prostheses 10 in which the acetabular cup 20 thereof define different shell inner radii.

[0034] The trial insert 28 includes a body 30. The trial insert 28 also includes an insert-to-cup coupler 32 for coupling the trial insert 28 to the acetabular cup 20, shown in phantom lines in Fig. 2, and a head mount 34 for receiving the replacement femoral head 24. The head mount 34 is mechanically coupled to the body 30 and the insert-to-cup coupler 32 is mechanically coupled to the body 30 and couplable to acetabular cups 20 having different dimensions for mounting thereto.

[0035] The insert-to-cup coupler 32 is mountable to the acetabular cup 20 and, as shown respectively in Figs. 4 and 6, is configurable between a smaller configuration and a larger configuration. When in the larger configuration, the insert-to-cup coupler 32 is attachable to acetabular cups 20 having larger dimensions, and more specifically larger inner radii, than when in the smaller configuration. Figure 5a illustrates the trial insert 28 with the insert-to-cup coupler 32 configured in an intermediate configuration occurring between the smaller and larger configurations.

[0036] Referring to Fig. 2, the acetabular cup 20 typically defines a cup shell 21 , as already mentioned previously. The cup shell 21 defines a cup inner surface 36 and a cup outer surface 38. The acetabular cup 20 also defines a cup peripheral edge 40 having a substantially annular configuration. In some embodiments of the invention, at least one, and typically two attachment pins 42 extend from the cup peripheral edge 40. The attachment pins 42 are usable to secure the trial insert 28 to the acetabular cup 20, as described in further details hereinbelow. However, in some embodiments of the invention, no attachment pin 42 is present.

[0037] Referring to Fig. 3, the insert-to-cup coupler 32 includes at least one, and typically more than one, arms 44 mechanically coupled to the body 30 and to an actuator 46. The arms 44 are operatively coupled to the body 30 so as to be movable between an arm retracted position, as seen in Fig. 4, and an arm extended position, as seen in Fig. 6. When the arms 44 are in the arm retracted position, the trial insert 28 is in the smaller configuration, and when the arms 44 are in the arm extended position, the trial insert 28 is in the larger configuration. The arms 44 are described in further details hereinbelow. The actuator 46 is operatively coupled to the arms 44 for moving the arms 44 between the arm retracted and extended positions

[0038] In some embodiments of the invention, as better seen in Fig. 16, the body 30 has a substantially annular configuration. Referring to Fig. 17, the body 30 defines a body radially outwardmost surface 48, a body radially inwardmost surface 50, a body first end surface 52 and body second end surface 54. The body first and second end surfaces 52 and 54 are substantially opposed to each other. The body radially inwardmost and outwardmost surfaces 50 and 48 extend between the body first and second end surfaces 52 and 54. As seen in Fig. 17, the body 30 defines a body longitudinal axis 31 and a body aperture 55 extending substantially longitudinally through the body 30 between the body first and second end surfaces 52 and 54.

[0039] The body 30 defines at least one arm mounting channel 57 extending from the body radially outwardmost surface 48. For example, the body 30 defines four arm mounting channels 57 circumferentially spaced apart from each other around the body 30. The arm mounting channel 57 extend substantially obliquely relatively to the body radially outwardmost surface 48 towards the body radially inwardmost surface 50. The arm mounting channels 57 are usable for mounting the arms 44 thereto, as described in further details hereinbelow.

[0040] In some embodiments of the invention, each arm mounting channel 57 defines an arm receiving passageway 56 located between the body first and second end surfaces 52 and 54. The arm receiving passageways 56 are typically substantially parallel to the body first end surface 52. In the specific embodiment of the invention illustrated in the drawings, the arm receiving passageways 56 extend in an anti-clockwise direction when the body 30 is seen from a viewpoint pointing towards the body first end surface 52. The arm receiving passageways 56 are usable for receiving a portion of the arms 44.

[0041] A respective body slit 58 extends between the body first end surface 52 and at least a portion of each of the arm receiving passageways 56. The body slit 58 is substantially elongated and laterally narrower than the arm receiving passageway 56. In some embodiments of the invention, the body slit 58 defines at least two, and typically a series of substantially longitudinally spaced apart necks 60. as seen in Fig. 16. The body slit 58 is wider between the necks 60 than substantially adjacent the necks 60.

[0042] As seen in Fig. 16, the body radially inwardmost surface 50 defines a body ledge 62 extending substantially radially inwardly into the body aperture 55 substantially adjacent the body second end surface 54. Head mount locking protrusions 64 extend substantially radially inwardly from the body radially inwardmost surface 50 into the body aperture 55. As seen in Fig. 17, head mount locking protrusions 64 are substantially longitudinally spaced apart from the body ledge 62 and define a gap 66 extending therebetween. Also, the body 30 defines a substantially annular actuator mounting flange 53 located substantially adjacent to the body radially inwardmost surface 50 and extending substantially away from the body first end surface 52.

[0043] Figs. 12 and 13 illustrate one of the arms 44. Each of the arms 44 is substantially elongated and defines an arm proximal end 68 and a substantially opposed arm distal end 70. The arm distal end 70 is located further away from the body longitudinal axis 31 (not shown in Figs. 12 and 13) than the arm proximal end 68 when the arms 44 are mounted to the body 30. Each of the arms 44 includes an arm-to-body coupling portion 72 for mechanically coupling the arm 44 to the body 30, an arm-to-cup coupling portion 74 for mounting the arm 44 to the acetabular cup 20, and an arm-to-actuator coupling portion 76 for mechanically coupling the arm 44 to the actuator 46 and allowing the actuator 46 to move the arm 44 between the arm retracted and extended positions.

[0044] In the specific embodiment of the invention shown in Figs. 12 and 13, the arm-to-body coupling portion 72 is substantially elongated and slidably mounted into the arm mounting channel 57, and more specifically into the arm receiving passageway 56, so as to be movable therealong. The arm-to-body coupling portion 72 extends from the arm proximal end 68 towards the arm distal end 70.

[0045] The arm-to-cup coupling portion 74 is located substantially adjacent the arm distal end 70. The arm-to-cup coupling portion 74 is further away from the body longitudinal axis 31 when the arm 44 is in the arm extended position than when the arm 44 is in the arm retracted position The arm-to-cup coupling portion 74 defines a coupling recess 78, the coupling recess 78 being provided for receiving one of the attachment pins 42. For example, the coupling recess is substantially C-shaped and extends substantially radially inwardly when the arm 44 is mounted to the arm receiving passageway 56.

[0046] In addition, the arm-to-cup coupling portion 74 defines a coupling flange 80 extending substantially perpendicularly to the arm-to-body coupling portion 72. More specifically, the coupling flange 80 extends substantially parallel to the body longitudinal axis 31 at a location intermediate the arm proximal and distal ends 68 and 70 for abutting against the cup shell 21 when the arm-to-cup coupling portion 74 is mounted to the cup shell 21. The coupling flange 80 extends towards the acetabular cup 20 when the trial insert 28 is mounted to the acetabular cup 20. The coupling flange 80 defines a substantially arcuate abutment surface 82 provided for substantially abuttingly contacting the cup inner surface 36, for example in acetabular cups lacking the attachment pin 42. The abutment surface 82 is the radially outwardmost surface of the coupling flange 80 when the arm 44 is mounted to the arm receiving passageway 56.

[0047] The arm-to-actuator coupling portion 76 takes the form of a coupling pin extending substantially parallel to the body longitudinal axis 31 from the arm-to- body coupling portion 72. When the arm 44 is mounted to the body 30, the arm-to- actuator coupling portion 76 extends towards the actuator 46 with the actuator 46 operatively coupled to the arm-to-actuator coupling portion 76 for moving the arm- to-actuator coupling portion 76 along the body slit 58 upon being actuated so as to move the arm 44 between the arm retracted and extended positions.

[0048] The arm-to-actuator coupling portion 76 defines a pin distal flange 88 spaced apart from the arm-to-body coupling portion 72 and a pin neck 86 extending between the arm-to-body coupling portion 72 and the pin distal flange 88. When the arm 44 is mounted to the body 30 through the arm receiving passageway 56, the arm-to-actuator coupling portion 76, and more specifically the pin neck 86 extends through the body slit 58 and the pin distal flange 88 is operatively coupled to the actuator 46 for allowing the actuator 46 to slidably move the arm 44 into the arm receiving passageway 56, thereby allowing for the movement of the arm 44 between the arm retracted and extended configurations upon actuation of the actuator 46.

[0049] Typically, the arm-to-actuator coupling portion 76 extends through the body slit 58 and protrudes outwardly from the body first end surface 52. In embodiments of the invention in which the body slit 58 defines the series of substantially longitudinally spaced apart necks 60, the necks 60 are each configured and sized for at least partially impeding longitudinal movements of the arm-to-actuator coupling portion 76 along the body slit 58.

[0050] In some embodiments of the invention, the arm-to-body coupling portion 72 has a substantially uniform cross-section and a reinforcement ridge 84 (not seen in Fig. 13) extends along at least a portion thereof to reinforce the arm 44 and make it more resistant to deformation upon the action of external mechanical forces.

[0051] Figs. 9 to 11 illustrate the actuator 46. Referring to Fig. 9, the actuator 46 defines a substantially annular actuator base 47. The actuator base 47 defines a base first end surface 92 and a substantially opposed base second end surface 94. A base radially outwardmost surface 96 and a base radially inwardmost surface 98 (seen in Fig. 10) each extend between the base first and second end surfaces 92 and 94. The actuator 46 defines an actuator aperture 105 that extends also between the base first and second end surfaces 92 and 94, the actuator aperture 105 being delimited by the base radially inwardmost surface 98.

[0052] The actuator second end surface 94 is substantially adjacent to the body first end surface 52 when the actuator 46 is mounted to the body 30. The actuator 46 is being mounted to the body 30 with the actuator mounting flange 53 inserted in the actuator aperture 105 and the actuator base 47 rotatable about the actuator mounting flange 53. In some embodiments the invention, this is achieved by having an actuator mounting flange 53 having an outer diameter substantially similar to a diameter of the actuator aperture 105.

[0053] In some embodiments of the invention, the base first end surface 92 defines a handle section 107. The handle section 107 is topographically different than substantially adjacent portions of the base first end surface 92. In other words, the handle section 107 defines protrusions, recesses, combinations of protrusions and recesses or textured areas that facilitate actuation of the actuator 46. For example the handle section 107 includes a protrusion 108, the protrusion 108 providing a surface against which a surgeon (not shown in the drawings) can exert a force to rotate the actuator 46 relatively to the body 30.

[0054] The base second end surface 94 defines pin receiving channels 99 extending thereinto, each pin receiving channel 99 corresponding to one of the arm receiving channels 57. The arm mounting channel 57 and the pin receiving channel 99 intersect each other an intersection location 101. The arm-to-actuator coupling portion 76 is received in the pin receiving channel 99 so as to be movable therealong. Typically, as seen in Fig. 11 , the pin receiving channel 99 defines an actuator passageway 100 extending substantially obliquely from the base radially outwardmost surface 96 towards the base radially inwardmost surface 98. The actuator passageway 100 is located between the base first and second end surfaces 92 and 94. An actuator slit 102 extends between the base second end surface 94 and the actuator passageway 100, the actuator slit 102 being laterally substantially narrower than the actuator passageway 100. [0055] As better seen in Fig. 8, when each of the arms 44 is inserted in a respective arm receiving passageway 56 and coupled to the actuator 46, the pin neck 86 extends through both the actuator slit 102 and the body slit 58. In this configuration, the pin distal flange 88 is mounted into the actuator passageway 100.

[0056] Returning to Fig. 10, the pin receiving channel 99 has a substantially V- shaped configuration and defines a radially inwardmost channel main section 106 and a radially outwardmost channel auxiliary section 104 extending from the channel main section 106 at an acute angle relatively thereto. The channel main and auxiliary sections 106 an 104 intersect each other at an apex 109. The apex 109 defines a circumferential extremity of the pin receiving channel 99.

[0057] The arm mounting channel 57 and the pin receiving channel 99 are angled relatively to each other along at least a portion of the pin receiving channel 99. Typically, the channel main section 106 and the arm mounting channel 57 are angled relatively to each other and are oriented circumferentially in generally opposite directions when going from larger radial locations to smaller radial locations.

[0058] Referring to Figs. 3, 14 and 15, there is shown in better details the head mount 34. As shown in Fig. 3, the head mount 34 is removably attachable to the body 30. This allows for providing head mounts 34 having various head mount elements, each similar to the head mount 34 but having different dimensions, so as to be able to receive replacement femoral heads 24 (shown in Fig. 1) having different dimensions when alternatively mounting each of the head mount elements to the body 30. [0059] Still referring to Fig. 3, the head mount 34 defines a substantially spherical head mount shell 110 for receiving the replacement femoral head 24 and a receiving portion-to-body attachment 112 mechanically coupled to the receiving head mount shell 110. The receiving portion-to-body attachment 112 is provided for attaching the head mount 34 to the body 30, for example by mounting the head mount 34 into the body aperture 55.

[0060] In some embodiments of the invention, the head mount shell 110 is shaped substantially similarly to a substantially hemispherical shell and defines a head mount shell inner surface 113, an opposed head mount shell outer surface 114 and a head mount shell peripheral edge 115. The head mount shell inner surface 113 defines a head mount shell cavity 116 for receiving the replacement femoral head 24.

[0061] The receiving portion-to-body attachment 112 takes the form of a substantially annular head mount peripheral flange 118 extending substantially radially outwardly from head mount shell 110 substantially adjacent to the head mount shell peripheral edge 115. The head mount peripheral flange 118 defines at least one, and typically many, peripheral flange recesses 120 extending substantially radially inwardly into the head mount peripheral flange 118.

[0062] In some embodiments of the invention, as seen in Fig. 3, the head mount 34 defines a head mount lip 122 extending substantially away from the head mount shell peripheral edge 115. The head mount lip 122 122 has a substantially arcuate configuration and corresponds to a stabilizing lip present in some conventional inserts 26 (seen in Fig. 1 , with the stabilizing lip omitted). [0063] Typically, the trial insert 28 includes at least two head mounts 34, each of the head mounts 34 being selectively attachable to the body 30, the head mounts 34 differing from each other by the presence or the omission of the head mount lip 122, by the radii of curvature of their head mount inner surfaces 113, or both by the presence or the omission of the head mount lip 122 and by the radii of curvature of their head mount inner surfaces 113. To be attachable to a single body 30, the head mounts 34 including head mount shell inner surfaces 113 having different radii of curvatures include head mount peripheral flanges 118 having different widths, but all having a substantially similar outer diameter.

[0064] As seen in Fig. 15, in some embodiments of the invention, a stopper 124 extends substantially away from the head mount shell 110. Typically, the stopper 124 is radially outwardly located relatively to the head mount lip 122. The stopper 124 is usable to stop a rotation of the head mount 34 relatively to the body 30 and, therefore, locks the head mount 34 inside the body 30, as described in further details hereinbelow.

[0065] In use, the trial insert 28 is assembled as follows. After a surgeon has attached a specific acetabular cup 20 in the acetabulum 14 of the patient, the surgeon selects a trial size for the replacement femoral head 24. Once these components have been selected, there is only one combination of outer and inner dimensions of the trial insert 28 that will suitably couple the replacement femoral head 24 to the acetabular cup 20.

[0066] To achieve these dimensions, the trial insert 28 is assembled so that the arms 44 are slidably received within the arm mounting channels 57 and the arms 44 are each coupled to the actuator 46 through a respective pin neck 86 and a respective pin distal flange 88. The pin distal flange 88 prevents the actuator 46 from moving in a longitudinal direction away from the body 30.

[0067] In some embodiments of the invention, each channel auxiliary section 104 is substantially parallel to a respective arm receiving passageway 56, which facilitates entry of the pin distal flange 88 into the actuator passageway 100. Once the pin distal flange 88 reaches the channel main section 106, which extends circumferentially in a direction opposite to the direction in which the arm receiving passageways 56 extend, the arms 44 can only be moved relatively to the body 30 if the actuator 46 is rotated relatively to the body 30. Indeed, there is only one intersection location 101 , seen in Fig. 8, at which the pin neck 86 can extend from the arm 44 to the actuator 46 for each position of the actuator 46 relatively to the body 30, which is the position at which the actuator slit 102 and the body slit 58 intersect each other. Rotating the actuator base 47 and the body 30 relatively to each other about the body longitudinal axis 31 moves the intersection location 101 radially relatively to the body longitudinal axis 31 so as to move the arms 44 between the arm retracted and extended positions.

[0068] In embodiments of the invention wherein the body slit 58 defines the necks 60, the necks 60 provide discrete increments in the longitudinal position of the arm 44 relatively to the arm receiving passageway 56, thereby guiding the positioning of the arms 44 relatively to the body 30, and consequently guiding in discrete steps a distance between the body 30 and the arm-to-cup coupling portion 74. Therefore, by rotating the actuator 46 to a suitable angle, the pin neck 86 of each arm 44 engages a predetermined location between 2 adjacent necks 60 corresponding to an acetabular cup 20 having a predetermined diameter. [0069] Optionally, the body 30 includes inscriptions indicative of an acetabular cup diameter substantially adjacent the necks 60 to guide the surgeon for suitably positioning the arms 44 relatively to the arm receiving passageways 56. In these embodiments, the actuator 46 is made out of a transparent material. In other embodiments of the invention, a series of templates corresponding to acetabular cups 20 having various diameters is provided. Adjusting the position of the actuator 46 such that the trial insert 28 is mountable to a template corresponding to the acetabular cup 20 attached to the acetabulum 14 of the patient allows for selecting a configuration that will be used when inserting the trial insert 28 in the patient.

[0070] With reference to Fig. 7, the head mount 34 is then attached to the body 30 by sliding the head mount 34 through the actuator aperture 105 and through the body aperture 55. The head mount 34 is slid through the actuator aperture 105 and the body aperture 55 until the head mount peripheral flange 118 abuts against the body ledge 62. To that effect, the peripheral flange recesses 120 and the head mount locking protrusions 64 must be configured, located and dimensioned such that the head mount locking protrusions 64 are movable through the peripheral flange recesses 120 when the head mount 34 is inserted in the body aperture 55 with the head mount locking protrusions 64 and the peripheral flange recesses 120 substantially in register with each other (this configuration not being shown in Fig. 7).

[0071] Afterwards, the head mount locking protrusions 64 substantially prevent relative longitudinal movements between the head mount 34 and the body 30 when the head mount peripheral flange 118 abuts against the body ledge 62 and the head mount 34 and the body 30 have been rotated relatively to each other about the body longitudinal axis 31 so that the head mount locking protrusions 64 and the peripheral flange recesses 120 are substantially circumferentially offset from each other. In some embodiments of the invention, the stopper 124 stops this rotation of the head mount 34 relatively to the body 30 before each peripheral flange recess 120 becomes adjacent another head mount locking protrusions 64. Therefore, the head mount peripheral flange 118 and the head mount locking protrusions 64 form a head mount lock for selectively locking the head mount 34 and the body 30 to each other.

[0072] By selecting a suitably dimensioned head mount 34, in other words, a head mount 34 having a head mount shell cavity 116 of a diameter substantially similar to the diameter of the replacement femoral head 24, the replacement femoral head 24 may then be coupled to the trial insert 28.

[0073] Afterwards, the trial insert 28 is inserted into the patient, mounted to the acetabular cup 20 and positioned to receive the replacement femoral head 24. If, for any reason, the surgeon needs to try a replacement femoral head 24 having a different dimension, or switch the presence or the absence of the head mount lip 122, the surgeon removes the trial insert 28 from inside the patient, replaces the head mount 34 and, if required, the replacement femoral head 24, and reinserts the trial insert 28 in the patient for further trials.

[0074] Although the present invention has been described hereinabove by way of preferred embodiments thereof, it can be modified, without departing from the spirit and nature of the subject invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A trial insert for selecting between a first hip prosthesis and a second hip prosthesis, the selected hip prosthesis being fitted to a patient, said patient having a femur and a pelvis, said pelvis defining an acetabulum, said first hip prosthesis including a first acetabular cup attachable to said acetabulum and a first replacement femoral head attachable to said femur, said first acetabular cup defining a substantially spherical first cup shell, said first cup shell defining a first shell inner radius, said second hip prosthesis including a second acetabular cup attachable to said acetabulum and a second replacement femoral head attachable to said femur, said second acetabular cup defining a substantially spherical second cup shell, said second cup shell defining a second shell inner radius, said first shell inner radius being smaller than said second shell inner radius, said trial insert comprising: -a body;

-a head mount for mounting said first and second replacement femoral heads thereto, said head mount being mechanically coupled to said body; and

-an insert-to-cup coupler mountable to said first and second acetabular cups, said insert-to-cup coupler being mechanically coupled to said body and configurable between a smaller configuration in which said insert-to- cup coupler is mountable to said first acetabular cup and a larger configuration in which said insert-to-cup coupler is mountable to said second acetabular cup;

-whereby said insert-to-cup couplers is usable for fitting said selected hip prosthesis to said patient with said first and second hip prostheses including respectively said first and second acetabular cups defining different shell inner radii.

2. A trial insert as defined in claim 1 , wherein said insert-to-cup coupler includes an arm, said arm defining an arm-to-cup coupling portion for mounting said arm to said first and second acetabular cups, said arm being operatively coupled to said body so as to be movable between an arm retracted position and an arm extended position, said arm being in said arm retracted position when said insert-to-cup coupler is in said smaller configuration and said arm being in said arm extended position when said insert-to-cup coupler is in said larger configuration.

3. A trial insert as defined in claim 2, wherein said body defines a body longitudinal axis, said arm-to-cup coupling portion being further away from said body longitudinal axis when said arm is in said arm extended position than when said arm is in said arm retracted position.

4. A trial insert as defined in claim 3, wherein said insert-to-cup coupler includes an actuator operatively coupled to said arm for moving said arm between said arm retracted and extended positions.

5. A trial insert as defined in claim 4, wherein said body has a substantially annular configuration and defines

-a body first end surface and a substantially opposed body second end surface;

-a body radially inwardmost surface and a body radially outwardmost surface each extending between said body first and second end surfaces; and

-an arm mounting channel extending from said body radially outwardmost surface towards said body radially inwardmost surface; -said arm defining an arm-to-body coupling portion slidably mounted in said arm mounting channel so as to be movable therealong.

6. A trial insert as defined in claim 5, wherein said arm mounting channel defines an arm receiving passageway located between said body first and second end surfaces, said arm-to-body coupling portion being slidably mounted in said arm receiving passageway.

7. A trial insert as defined in claim 6, wherein

-said arm mounting channel defines a body slit extending between said body first end surface and said arm receiving passageway; and -said arm defines a coupling pin extending from said arm-to-body coupling portion, said coupling pin extending through said body slit and protruding outwardly from said body first end surface.

8. A trial insert as defined in claim 7, wherein said body slit is laterally narrower than said arm receiving passageway.

9. A trial insert as defined in claim 7, wherein said body slit defines at least two longitudinally spaced apart necks each configured and sized for at least partially impeding longitudinal movements of said coupling pin along said body slit.

10. A trial insert as defined in claim 7, wherein said actuator is operatively coupled to said coupling pin for moving said coupling pin along said body slit upon being actuated so as to move said arm between said arm retracted and extended positions.

11. A trial insert as defined in claim 10, wherein said actuator defines a substantially annular actuator base, said actuator base defining

-a base first end surface and a substantially opposed base second end surface, said base second end surface being substantially adjacent to said body first end surface; and

-a base radially outwardmost surface and a base radially inwardmost surface, said base radially outwardmost and inwardmost surfaces extending between said base first and second end surfaces;

-said base second end surface defining a pin receiving channel extending thereinto, said arm mounting channel and said pin receiving channel intersecting each other an intersection location, said coupling pin being received in said pin receiving channel so as to be movable therealong.

12. A trial insert as defined in claim 11 , wherein

-said arm mounting channel and said pin receiving channel are angled relatively to each other along at least a portion of said pin receiving channel; and

-said actuator base and said body are rotatable relatively to each other about said body longitudinal axis;

-whereby rotating said actuator base and said body relatively to each other about said body longitudinal axis moves said intersection location radially relatively to said body longitudinal axis so as to move said arm between said arm retracted and extended positions.

13. A trial insert as defined in claim 12, wherein said pin receiving channel has a substantially V-shaped configuration and defines a radially inwardmost channel main section and a radially outwardmost channel auxiliary section extending from said channel main section at an acute angle relatively thereto, said channel main and auxiliary sections intersecting each other at an apex, said apex defining a circumferential extremity of said pin receiving channel.

14. A trial insert as defined in claim 12, wherein

-said pin receiving channel defines an actuator passageway located between said base first and second end surfaces and an actuator slit extending between said base second end surface and said actuator passageway, said actuator slit being laterally substantially narrower than said actuator passageway;

-said coupling pin defines a pin distal flange spaced apart from said arm-to- body coupling portion and a pin neck extending between said arm-to-body coupling portion and said pin distal flange, said pin distal flange being mounted in said actuator passageway, said pin neck extending through both said actuator slit and said body slit.

15. A trial insert as defined in claim 11 , wherein said base first end surface defines a handle section, said handle section being topographically different than substantially adjacent portions of said base first end surface.

16. A trial insert as defined in claim 11 , wherein

-said actuator base defines an actuator aperture extending between said base first and second end surfaces, said actuator aperture being delimited by said base radially inwardmost surface;

-said body defines a substantially annular actuator mounting flange substantially adjacent to said body radially inwardmost surface and extending substantially away from said body first end surface, said actuator being mounted to said body with said actuator mounting flange inserted in said actuator aperture and said actuator base rotatable about said actuator mounting flange.

17. A trial insert as defined in claim 3, wherein said first cup shell defines a first cup shell peripheral edge, said first acetabular cup defining a first attachment pin extending from said first cup shell peripheral edge, said arm-to-cup coupling portion defining a substantially radially inwardly extending coupling recess for receiving said attachment pin thereinto.

18. A trial insert as defined in claim 3, wherein said arm defines an arm distal end and a substantially opposed an arm proximal end, said arm distal end being located further away from said body longitudinal axis than said arm proximal end, said arm-to-cup coupling portion defining a coupling flange extending substantially parallel to said body longitudinal axis at a location intermediate said arm proximal and distal ends for abutting against said first and second cup shells when said arm-to-cup coupling portion is mounted to said first and second cup shells.

19. A trial insert as defined in claim 2, wherein said insert-to-cup coupler includes at least two arms, each of said arms defining a respective arm-to-cup coupling portion mountable to said first and second acetabular cups, each of said arms being operatively coupled to said body so as to be movable between a respective arm retracted position and a respective arm extended position, each of said arms being in said respective arm retracted position when said insert-to-cup coupler is in said smaller configuration and each of said arms being in said respective arm extended position when said insert-to-cup coupler is in said larger configuration.

20. A trial insert as defined in claim 19, wherein said at least two arms are substantially circumferentially spaced apart from each other around said body.

21. A trial insert as defined in claim 1 , wherein said head mount includes a first head mount element and a second head mount element, said first and second head mount elements being configured and sized for receiving respectively said first and second femoral heads with said first and second femoral heads having different dimensions, said first and second head mount elements being alternatively mountable to said body.

22. A trial insert as defined in claim 1 , wherein said body has a substantially annular configuration and defines a body aperture extending substantially longitudinally therethrough, said head mount being mountable into said body aperture.

23. A trial insert as defined in claim 22, further comprising a head mount lock for selectively locking said head mount and said body to each other.

24. A trial insert as defined in claim 22, wherein said head mount defines a substantially spherical head mount shell.

25. A trial insert as defined in claim 24, wherein

-said head mount shell defines a head mount shell peripheral edge, said head mount defining a substantially annular head mount peripheral flange extending substantially radially outwardly from said head mount shell substantially adjacent said head mount shell peripheral edge; and -said body defines a body ledge extending substantially radially inwardly into said body aperture; -said head mount peripheral flange abutting against said body ledge when said head mount is mounted to said body.

26. A trial insert as defined in claim 25, wherein

-said body defines a head mount locking protrusion extending substantially radially inwardly into said body aperture from said body radially inwardmost surface, said head mount locking protrusion being substantially longitudinally spaced apart from said body ledge; and -said head mount peripheral flange defines a peripheral flange recess extending substantially radially inwardly into said head mount peripheral flange;

-said head mount locking protrusion is movable through said peripheral flange recess when said head mount is inserted in said body aperture with said head mount locking protrusion and said peripheral flange recess substantially in register with each other, and said head mount locking protrusion substantially prevents relative longitudinal movements between said head mount and said body when said head mount peripheral flange abuts against said body ledge and said head mount and said body have been rotated relatively to each other about said body longitudinal axis so that said head mount locking protrusion and said peripheral flange recess are substantially circumferentially offset from each other.