Femoral stem including an anchor to facilitate assembly and implantation

An orthopedic prosthesis for use in a hip replacement surgery. The orthopedic prosthesis includes an elongated stem component that has a proximal body, a neck extending superiorly and medially from the proximal body and a tapered stem extending inferiorly from the proximal body. An anchor is positioned on the neck and is configured to be engaged by a surgical instrument. A system for use in assembling the orthopedic prosthesis and a method of assembly are also disclosed.

TECHNICAL FIELD

The present disclosure relates generally to orthopaedic prostheses, and particularly to orthopaedic prostheses for use in hip replacement surgery.

BACKGROUND

Joint arthroplasty is a well-known surgical procedure by which a diseased and/or damaged natural joint is replaced by a prosthetic joint. The prosthetic joint may include a prosthesis that is implanted into one or more of the patient's bones. Many hip prostheses include a femoral prosthesis that is implanted into a patient's femur. A femoral prosthesis typically includes an elongated stem component that is received in the medullary canal of the patient's femur and a spherically-shaped head component that bears against the patient's acetabulum or a prosthetic replacement acetabular cup.

The elongated stem implant may be cemented into the medullary canal or may have a porous coated surface for allowing the bone to heal directly to the implant. In some prostheses, the head is attached to a neck of the elongated stem via a taper connection. It is important to assemble the head to the neck with enough force so as to limit micromotion between the head and neck. The acetabulum of the patient may also be reamed to receive a shell and liner. A polyethylene, metal or ceramic liner with a metal shell is inserted into the acetabulum and acts as socket for receiving the head on the stemmed implant.

SUMMARY

According to one aspect of the disclosure, an orthopaedic prosthesis is disclosed. The orthopaedic prosthesis comprises an elongated stem component. The elongated stem component includes a proximal body and a neck extending superiorly and medially from the proximal body. The neck has a longitudinal axis and is configured to receive a femoral head component. The stem component also includes a tapered stem extending inferiorly from the proximal body, and an anchor positioned on the neck. The anchor extends orthogonal to the longitudinal axis of the neck.

In some embodiments, the anchor may include a first flange positioned on an anterior side of the neck and a second flange positioned on a posterior side of the neck. In some embodiments, the first flange may extend outwardly from the anterior side of the neck, and the second flange may extend outwardly from the posterior side of the neck. Additionally, in some embodiments, a first opening may be defined in the anterior side of the neck, and the first flange may include a first inner wall extending inwardly from the first opening.

In some embodiments, a second opening may be defined in the posterior side of the neck, and the second flange may include a second inner wall extending inwardly from the second opening.

In some embodiments, the first flange and the second flange may include engagement surfaces that are positioned in an imaginary plane extending orthogonal to the longitudinal axis of the neck.

In some embodiments, the neck may include a first opening defined in an anterior surface, a second opening defined in a posterior surface, and the anchor may include an inner wall that extends between the first opening and the second opening.

In some embodiments, the inner wall may include a substantially planar medial surface and a curved surface connected to the substantially planar medial surface. Additionally, in some embodiments, the neck may extend from a superior tip to an inferior end attached to the proximal body, and the anchor may be positioned on the medial side of the inferior end of the neck.

In some embodiments, the anchor may include a medial collar extending outwardly from the inferior end of the neck. In some embodiments, an opening may be defined in the inferior end of the neck, and the anchor may include an inner wall that extends inwardly from the opening.

In some embodiments, the proximal body may have a first opening defined in an anterior side and a second opening defined in a posterior side adjacent to the neck. The neck may include a first inner wall that extends inwardly from the first opening and a second inner wall that extends inwardly from the second opening. The anchor may include the first inner wall and the second inner wall.

In some embodiments, the orthopaedic prosthesis may include the femoral head component including a tapered bore. The neck may include a tapered trunnion sized to receive the tapered bore.

According to another aspect, a system for hip orthopaedic surgery is disclosed. The system includes a femoral head component, an elongated stem component, and a surgical instrument. The elongated stem component includes a proximal body, a neck extending superiorly and medially from the proximal body, a tapered stem extending inferiorly from the proximal body, and an anchor positioned on the neck and extending orthogonal to the longitudinal axis of the neck. The neck is configured to receive the femoral head component.

The surgical instrument includes a plate configured to engage the femoral head component, an arm configured to engage the anchor to secure the surgical instrument to the elongated stem component, and an actuator configured to move the plate along an axis to apply a force to the femoral head component.

In some embodiments, the anchor may include a first flange positioned on an anterior side of the neck and a second flange positioned on a posterior side of the neck. The arm of the surgical instrument may be a first arm configured to engage the first flange, and the surgical instrument may include a second arm configured to engage the second flange.

In some embodiments, the proximal body may have a first opening defined in an anterior side and a second opening defined in a posterior side adjacent to the neck. The neck may include a first inner wall that extends inwardly from the first opening and a second inner wall that extends inwardly from the second opening. The anchor may include the first inner wall and the second inner wall.

According to another aspect, an orthopaedic prosthesis comprises a femoral head component and an elongated stem component. The elongated stem component comprises a proximal body, a neck that is configured to receive the femoral head component and extending superiorly and medially from the proximal body, and a tapered stem extending inferiorly from the proximal body. A first opening is defined an anterior surface of the neck, a second opening is defined in a posterior surface of the neck, and a pair of inner walls extend inwardly from the first opening and the second opening. Each inner wall includes a medial surface positioned in an imaginary plane extending orthogonal to the longitudinal axis of the neck.

In some embodiments, the pair of inner walls may define a single inner wall extending from the first opening between the second opening.

DETAILED DESCRIPTION OF THE DRAWINGS

Terms representing anatomical references, such as anterior, posterior, medial, lateral, superior, inferior, etcetera, may be used throughout the specification in reference to the orthopaedic implants or prostheses and surgical instruments described herein as well as in reference to the patient's natural anatomy. Such terms have well-understood meanings in both the study of anatomy and the field of orthopaedics. Use of such anatomical reference terms in the written description and claims is intended to be consistent with their well-understood meanings unless noted otherwise.

Referring toFIG. 1, an orthopaedic prosthesis is illustratively embodied as a femoral orthopaedic implant10of a hip prosthesis. The femoral orthopaedic implant10(hereinafter implant10) includes a head component12and an elongated stem component14that is configured to be inserted into an intramedullary canal16of a patient's surgically-prepared femur18. In particular, the femoral stem component14is implanted into a surgically prepared (e.g., broached) intramedullary canal16of the patient's femur18.

The head component12includes a spherical outer surface20configured to engage a patient's natural acetabulum (not shown) or a prosthetic acetabular cup implanted into the patient's pelvic bone. The head component12may be constructed with an implant-grade biocompatible metal, although other materials may also be used. Examples of such metals include cobalt, including cobalt alloys such as a cobalt chrome alloy, titanium, including titanium alloys such as a Ti6Al4V alloy, and stainless steel. The head component12also includes a distal surface22having an opening24defined therein, and an inner wall extends inwardly from the opening24to define a tapered bore28in the head component12.

The head component12is secured to a trunnion30formed in the end32of the elongated neck34of the stem component14. As shown inFIG. 1, the elongated neck34has a longitudinal axis36that extends through the trunnion30. In the illustrative embodiment, the head component12is advanced along the longitudinal axis36to advance the tapered trunnion30of the stem component14may be advanced into the tapered bore28of the head component12to taper lock the trunnion30(and hence the stem component14) and the femoral head component12to one another. When installed on the stem component14, the femoral head component12is positioned to bear on either the patient's natural acetabulum or a prosthetic socket which has been implanted into the patient's pelvis to replace his or her acetabulum. In such a manner, the orthopaedic hip prosthesis10and the natural or artificial acetabulum collectively function as a system which replaces the natural joint of the patient's hip

As shown inFIG. 1, the elongated neck34extends medially and superiorly from an inferior end38attached to a proximal body40of the elongated stem component14. As described in greater detail below, the elongated stem component14also includes a tool engagement feature or anchor42that is positioned on the neck34. A tapered stem44extends inferiorly away from the opposite end of the proximal body. The tapered stem44has a rounded distal end46that defines the inferior-most surface of the femoral stem component14.

In the illustrative embodiment described herein, the stem component14is embodied as a “fit and fill” type of femoral stem. As such, the stem component14is embodied as a monolithic metal structure. The stem component14may be constructed with an implant-grade biocompatible metal, although other materials may also be used. Examples of such metals include cobalt, including cobalt alloys such as a cobalt chrome alloy, titanium, including titanium alloys such as a Ti6Al4V alloy, and stainless steel. Such a metallic femoral stem component14may also be coated with a surface treatment, such as hydroxyapatite, to enhance biocompatibility. Moreover, the surfaces of the femoral stem component14that engage the natural bone, such as the outer surface of the proximal body40, may be textured to facilitate securing the component to the bone. Such surfaces may also be porous coated to promote bone ingrowth for permanent fixation.

As shown inFIGS. 2A and 2B, the anchor42of the elongated stem component14is defined in an anterior surface50and a posterior surface54. The anterior surface50of the stem component14extends from the inferior end38of the neck34to the base of the trunnion30, and an opening52is defined in the anterior surface50adjacent to the inferior end38of the neck34. The posterior surface54extends from the inferior end38of the neck34to the base of the trunnion30. Another opening56is defined in the posterior surface54adjacent to the inferior end38of the neck34. In the illustrative embodiment, the anchor42includes an inner wall60that extends inwardly from the openings52,56. As shown inFIGS. 2A and 2B, the inner wall60defines a passageway62through the elongated neck34.

The inner wall60includes a medial surface64and a curved lateral surface66that extend between the openings52,56. In the illustrative embodiment, the medial surface64is substantially planar and extends orthogonal to the longitudinal axis36of the elongated neck34. In other embodiments, the medial surface64(and hence the anchor42) may merely extend transverse to the axis36. Additionally, as shown inFIGS. 2A and 2B, the medial surface64extends between a superior edge68and an inferior edge70that are connected to the lateral surface66. In the illustrative embodiment, the longitudinal axis36intersects the medial surface64at a midpoint72on the surface64between the edges68,70. It should be appreciated that in other embodiments the axis36may be offset from the midpoint72

Referring now toFIG. 3, a surgical instrument100for use in securing the femoral head component12to the elongated stem component14is shown. The surgical instrument100includes a body102, an actuator104configured to engage the femoral head component12, and a pair of elongated arms106configured to engage the anchor42of the elongated stem component14. The body102of the instrument100includes an elongated bore108that extends from a distal end110to a proximal end112. In the illustrative embodiment, the elongated bore108is internally-threaded at the distal end110.

The actuator104of the instrument100has a shaft114that extends through the elongated bore108and an engagement plate116that is attached to the distal end118of the shaft114. The distal end118of the shaft114includes a plurality of external threads120that are configured to engage the internally-threaded bore108of the body102. A handle122is secured to the shaft114at the end opposite the distal end118. As described in greater detail below, the handle122is operable to rotate the shaft114and move the engagement plate116along an axis124defined by the shaft114.

As shown inFIG. 3, the engagement plate116includes a base126that is secured to the distal end118of the shaft114. The plate116also includes a distal surface128that is configured to engage the femoral head component12. In the illustrative embodiment, the distal surface128is concave to define a recess130that receive the spherical outer surface20of the femoral head component12. The engagement plate116is illustratively formed from a polymeric material such as a hard plastic. It should be appreciated that in other embodiments the plate116may be partially or fully formed from a metallic material. In other embodiments, the plate116may also include a gasket formed from an elastomeric material, which is configured to engage the head component12.

As described above, the instrument100also includes a pair of elongated arms106configured to engage the anchor42of the elongated stem component14. Each arm106includes an elongated body132that extends from a distal end134to a proximal end136. An engagement pin138extends outwardly from the distal end134of each arm106in a direction perpendicular or orthogonal to the axis124defined by the actuator104. As shown inFIG. 3, the engagement pins138are shaped to be received in the passageway62defined in the elongated stem component14.

The elongated arms106are coupled to the body102of the instrument100such that the arms106(and hence the engagement pins138) may be repositioned relative to the axis124. In the illustrative embodiment, the body102has a pair of channels140defined therein on each side of the elongated bore108. Each channel140is sized to receive a corresponding proximal end136of one of the arm bodies132. It should be appreciated that in other embodiments the instrument may include other combinations of tabs, openings, channels, or passageways to attach the arms to the body.

The instrument100also includes an adjustment mechanism142configured to permit the arms106to be selectively moved relative to the body102(and hence the axis124). In the illustrative embodiment, the adjustment mechanism142includes a pair of screw clamps144,146that may be operated by the user to independently position and fix each of the arms106at a desired position relative to the axis124. It should be appreciated that in other embodiments the adjustment mechanism may include other fasteners, screws, tabs, and so forth configured to permit the arms to be selectively moved.

During a surgical procedure, the elongated stem component14may be inserted into a surgically-prepared intramedullary canal16of a patient's femur18, as shown inFIG. 4. To attach a femoral head component12, the surgeon may align the selected head component12with the trunnion30of the elongated stem component14. The surgeon may advance the head component12along the longitudinal axis36such that the trunnion30is received in the tapered bore28defined in the head component12.

A user, such as a surgeon or a surgical assistant, may then use the surgical instrument100to apply controllably a sufficient, quasistatic axial force to join the head component12to the stem component14. A quasistatic axial force as used herein refers to an axial force that is applied gradually, increasing from a low to a high, peak magnitude. Conversely, a quasidynamic axial force as used herein refers to a high axial force that is applied, more or less, instantaneously, such as like a hammer strike.

To attach the surgical instrument100, the user may operate the screw clamps144,146to disengage the clamps144,146from the proximal ends136of the elongated arms106, thereby releasing the arms106for movement relative to the axis124. The user may then pull the arms106away from the axis124, which moves the engagement pins138apart. The engagement plate116may be advanced into the contact with the spherical outer surface20of the femoral head component12, and the axis124aligned with the longitudinal axis36of the elongated neck34of the stem component14.

As shown inFIG. 6, the engagement pins138may be aligned with the passageway62defined in the stem component14. The user may then advance the pins138into the passageway62. When the pins138are positioned at the desired location, the user may operate the clamps144,146to lock the elongated arms106(and hence the pins138) into position. With the instrument100positioned as shown inFIG. 6, the user may rotate the handle122to advance the head component12along the aligned axes36,124in the direction indicated by arrow150. To exert the quasistatic axial force on the components12,14, the engagement pins138of the instrument100engage the medial surface64of the anchor42of the stem component14such that the actuator104applies a force to the components12,14along the axes36,124when the handle122is rotated.

In the illustrative embodiment, the instrument100is configured to apply at least a peak axial force of about 4 kN. It should be appreciated that in other embodiments the instrument may include a force gauge or other sensor to measure the force applied to the components12,14. After the user has applied a desired amount of force to secure the head component12to the stem component14, the user may reverse actuator the instrument100and remove the instrument from the surgical area.

While the instrument100is illustrative hand-operated, it should be appreciated that in other embodiments the instrument100may include a motor or other drive mechanism to apply the axial force. Other surgical instruments configured to apply a quasistatic axial force are disclosed in U.S. Patent Application Ser. No. 62/103,611 entitled “ASSEMBLY TOOL,” which is filed concurrently with this application. Such surgical instruments may be configured for use with specific, compatible types of anchors but may be adapted for use with the anchor42of the stem component14. In other embodiments, the stem component may include other anchor configurations similar to those illustrated inFIGS. 7-13, which are described in greater detail below. Some features of the embodiments illustrated inFIGS. 7-13are substantially similar to those discussed above in reference to the embodiment ofFIGS. 1-6. Such features are designated inFIGS. 7-13with the same reference numbers as those used inFIGS. 1-6.

Referring now toFIGS. 7-8, another elongated stem component (hereinafter stem component214) is shown. Similar to the embodiment ofFIGS. 1-6, the stem component214includes a trunnion30formed in the end32of the elongated neck234of the stem component214. The elongated neck234also has a longitudinal axis36that extends through the trunnion30. As shown inFIG. 7, the elongated neck234extends medially and superiorly from an inferior end38attached to a proximal body240of the elongated stem component214. Similar to the embodiment ofFIGS. 1-6, a tapered stem (not shown) extends inferiorly away from the opposite end of the proximal body.

The elongated stem component214also includes a tool engagement feature or anchor242that is positioned on the neck234. The anchor242of the elongated stem component214is defined in an anterior surface250and a posterior surface254. The anterior surface250of the stem component214extends from the inferior end38of the neck234to the base of the trunnion30, and an opening252is defined in the anterior surface250adjacent to the inferior end38of the neck234. The posterior surface254extends from the inferior end38of the neck234to the base of the trunnion30. Another opening256is defined in the posterior surface250adjacent to the inferior end38of the neck34. In the illustrative embodiment, the anchor242includes an inner wall258that extends inwardly from the opening252and another inner wall260that extends inwardly from the opening256.

As shown inFIGS. 7-8, the inner wall258is one of a plurality of inner walls262that extend from the opening252to a base surface264. The base surface264and the inner walls262cooperate to define a closed aperture266in the anterior surface250. Similarly, the inner wall260is one of a plurality of inner walls270that extend from the opening256to a base surface272. The base surface272and the inner walls270cooperate to define a closed aperture274in the posterior surface254. In the illustrated embodiment, the apertures266,274are square-shaped. In other embodiments, the apertures may be rectangular, circular or other geometric shape.

In the illustrative embodiment, the inner walls258,260include medial surfaces278that are substantially planar and are positioned in a common imaginary plane that extends through the elongated neck234orthogonal to the longitudinal axis36. In other words, the medial surfaces278, like the medial surface64of the stem component14, extend orthogonal relative to the axis36.

The anchor242of the stem component214may be engaged by an appropriately-shaped surgical instrument in a manner similar to that described above in regard toFIGS. 1-6. For example, the engagement pins138of the surgical instrument100may be shaped to be received in the closed apertures266,274of the stem component214and thereby engage the anchor242. In other embodiments, other surgical instruments may be used.

Referring now toFIG. 9, another embodiment of an elongated stem component (hereinafter stem component314) is shown. Similar to the embodiments ofFIGS. 1-8, the stem component314includes a trunnion30formed in the end32of the elongated neck334of the stem component314. The elongated neck334also has a longitudinal axis36that extends through the trunnion30. As shown inFIG. 9, the elongated neck334extends medially and superiorly from an inferior end38attached to a proximal body340of the elongated stem component314. A tapered stem (not shown) extends inferiorly away from the opposite end of the proximal body.

The elongated stem component314also includes a tool engagement feature or anchor342that is positioned on the neck334. In the illustrative embodiment, the neck334has an opening344defined in a medial surface346at its inferior end38. A number of inner walls348extend inwardly from the opening344to base surface350. A closed pocket352is defined by the surfaces350and the inner walls348. In the illustrated embodiment, the closed pocket352is rectangular-shaped. In other embodiments, the apertures may be square, circular or other geometric shape.

The anchor342includes a superior surface354of one of the inner walls348. The superior surface354extends orthogonal to the longitudinal axis36. In other embodiments, the surface354(and hence the anchor342) may merely extend transverse to the axis36. The superior surface354may be engaged by an appropriately-shaped surgical instrument in a manner similar to that described above in regard toFIGS. 1-8. For example, the surgical instrument100may be configured with only a single engagement pin138that is shaped to be received in the closed pocket352of the stem component314and thereby engage the superior surface354of the anchor342. In other embodiments, other surgical instruments may be used.

Referring now toFIG. 10, another embodiment of an elongated stem component (hereinafter stem component414) is shown. Similar to the embodiments ofFIGS. 1-8, the stem component414includes a trunnion30formed in the end32of the elongated neck434of the stem component414. The elongated neck434also has a longitudinal axis36that extends through the trunnion30. As shown inFIG. 10, the elongated neck434extends medially and superiorly from an inferior end38attached to a proximal body440of the elongated stem component414. A tapered stem (not shown) extends inferiorly away from the opposite end of the proximal body.

The elongated stem component414also includes a tool engagement feature or anchor442that is positioned on the neck434. In the illustrative embodiment, the neck434has a collar444that extends outwardly from a medial surface446at its inferior end38. As shown inFIG. 10, the collar444has a slot448extending from a superior opening450to an inferior opening (not shown) and a curved outer surface452. The slot448is sized to receive an appropriately sized surgical instrument. In other embodiments, the slot may be omitted.

The collar444extends orthogonal to the longitudinal axis36, and may be engaged by an appropriately-shaped surgical instrument in a manner similar to that described above in regard toFIGS. 1-9. For example, the surgical instrument100may be configured with only a single engagement pin138that is shaped to engage the collar444of the anchor442. In other embodiments, other surgical instruments may be used.

Referring now toFIGS. 11-12, another elongated stem component (hereinafter stem component514) is shown. Similar to the embodiments ofFIGS. 1-10, the stem component514includes a trunnion30formed in the end32of the elongated neck534of the stem component214. The elongated neck534also has a longitudinal axis36that extends through the trunnion30. As shown inFIG. 11, the elongated neck534extends medially and superiorly from an inferior end38attached to a proximal body540of the elongated stem component514. A tapered stem (not shown) extends inferiorly away from the opposite end of the proximal body.

The elongated stem component514also includes a tool engagement feature or anchor542that is positioned on the neck534. The anchor542of the elongated stem component514includes a pair of flanges544,546that extend outwardly from an anterior surface550and a posterior surface554, respectively. As shown inFIG. 11, the anterior surface550of the stem component514extends from the inferior end38of the neck534to the base of the trunnion30, and the flange544extends outwardly from the surface550adjacent to the inferior end38of the neck534. The flange544includes an elongated body556that extends orthogonal to the axis36. The flange544also includes a superior surface558and an inferior surface560.

As shown inFIG. 12, the posterior surface554extends from the inferior end38of the neck534to the base of the trunnion30. The flange546extends outwardly from the surface554adjacent to the inferior end38of the neck534. The flange546includes an elongated body566that extends orthogonal to the axis36. The flange546also includes a superior surface568and an inferior surface570.

In the illustrative embodiment, the inferior surfaces560,570are substantially planar and are positioned in a common imaginary plane that extends through the elongated neck534orthogonal to the longitudinal axis36. In other words, the inferior surfaces560,570, like the medial surface64of the stem component14, extend orthogonal relative to the axis36.

The anchor542(i.e., the flanges544,546) of the stem component514may be engaged by an appropriately-shaped surgical instrument in a manner similar to that described above in regard toFIGS. 1-10. For example, the engagement pins138of the surgical instrument100may be shaped to engage the flanges544,546. In other embodiments, other surgical instruments may be used.

Referring now toFIG. 13, another elongated stem component (hereinafter stem component614) is shown. Similar to the embodiments ofFIGS. 1-12, the stem component614includes a trunnion30formed in the end32of the elongated neck634of the stem component614. The elongated neck634also has a longitudinal axis36that extends through the trunnion30. As shown inFIG. 11, the elongated neck234extends medially and superiorly from an inferior end638attached to a proximal body640of the elongated stem component214. A tapered stem644extends inferiorly away from the opposite end of the proximal body640to a distal end646.

The elongated stem component614also includes a tool engagement feature or anchor642. In the illustrative embodiment, the anterior surface650of the proximal body640has an opening652defined therein. An inner wall654extends inwardly from the opening652to define a closed aperture656in the body640. As shown inFIG. 13, the aperture656has an open end658that is closed by an inferior surface660of the elongated neck634.

The anchor642includes the inferior surface660. The anchor642also includes another inferior surface (not shown) defined on the posterior side662of the stem component614. In the illustrative embodiment, the inferior surfaces660are substantially planar and are positioned in a common imaginary plane that extends through the elongated neck634orthogonal to the longitudinal axis36.

The anchor642of the stem component614may be engaged by an appropriately-shaped surgical instrument in a manner similar to that described above in regard toFIGS. 1-6. For example, the engagement pins138of the surgical instrument100may be shaped to be received in the closed apertures656of the stem component614and thereby engage the anchor642. In other embodiments, other surgical instruments may be used.

It should be appreciated that the anchors of the stem components described above may be configured for use in other parts of the orthopaedic surgical procedure. For example, a surgeon may use the anchors to grip the stem during implantation and extraction, thereby eliminating the need for a separate feature to perform that step.