Alignment guide

An orthopedic joint prosthesis assembly which comprises:

• a. a head part of an orthopedic joint prosthesis component, which has a spherical bearing surface for articulation with a corresponding joint surface, and an assembly surface having a bore formed in it for receiving a spigot on another part of the orthopedic joint prosthesis, said bore having a first axis that extends perpendicular to the assembly surface, and in which there is a discontinuity at an interface between the bearing surface and the assembly surface, the said assembly surface being arranged on a plane which is parallel to, or contains, a plane which is defined by the opening to the bore in the head part when the head part is viewed from one side in cross-section, and
• b. an alignment guide comprising an axial portion defining a second axis coincident with the first axis, such when an impaction force is applied along the second axis the force is directed along the first axis, the axial portion comprising:
• a plain bore sleeve;
• and
• a pair of arms that extend from a distal portion of the sleeve such that a space is formed between each arm,
• wherein each arm comprises a proximal end, a distal end and an inner surface that has a contact surface shaped to substantially correspond to the bearing surface of the head part of the orthopedic joint prosthesis, such that when the head part is mounted within the guide a nesting fit is formed between the bearing surface of the head part and the contact surface of each arm, and
• wherein the distal end of each arm joins to form a U-shaped bracket which carries a U-shaped assembly surface seating member configured to engage the assembly surface of the head part of the orthopedic joint prosthesis when the head part is mounted within the guide.

An orthopedic joint prosthesis assembly comprising:

• a part of an orthopedic joint prosthesis having a spigot a head part of an orthopedic;
• a joint prosthesis component, which has a spherical bearing surface for articulation with a corresponding joint surface, and an assembly surface having a bore formed in it for receiving the spigot on another part of the orthopedic joint prosthesis, said bore having a first axis that extends perpendicular to the assembly surface, and in which there is a discontinuity at an interface between the bearing surface and the assembly surface, the said assembly surface being arranged on a plane which is parallel to, or contains, a plane which is defined by the opening to the bore in the head part when the head part is viewed from one side in cross-section;
• b. an alignment guide comprising an axial portion defining a second axis coincident with the first axis, such when an impaction force is applied along the second axis the force is directed along the first axis, the axial portion comprising:
• a plain bore sleeve;
• and
• a pair of arms that extend from a distal portion of the sleeve such that a space is formed between each arm;
• wherein each arm of the alignment guide comprises a proximal end, a distal end and an inner surface that has a contact surface shaped to substantially correspond to the bearing surface of the head part of the orthopedic joint prosthesis, such that when the head part is mounted within the guide a nesting fit is formed between the bearing surface of the head part and the contact surface of each arm, and
• wherein the distal end of each arm joins to form a U-shaped bracket which carries a U-shaped assembly surface seating member configured to engage the assembly surface of the head part of the orthopedic joint prosthesis when the head part is mounted within the guide.

A method of assembling an orthopedic joint prosthesis, which comprises:

• a. providing an assembly comprising:
• a part of an orthopedic joint prosthesis having a spigot;
• a head part of an orthopedic joint prosthesis component, which has a spherical bearing surface for articulation with a corresponding joint surface, and an assembly surface having a bore formed in it for receiving the spigot, said bore having a first axis that extends perpendicular to the assembly surface, and in which there is a discontinuity at an interface between the bearing surface and the assembly surface, the said assembly surface being arranged on a plane which is parallel to, or contains, a plane which is defined by the opening to the bore in the head part when the head part is viewed from one side in cross-section;
• an alignment guide comprising an axial portion defining a second axis coincident with the first axis, such when an impaction force is applied along the second axis the force is directed along the first axis, the axial portion comprising:
• a plain bore sleeve;
• and
• a pair of arms that extend from a distal portion of the sleeve such that a space is formed between each arm,
• wherein each arm of the alignment guide comprises a proximal end, a distal end and an inner surface that has a contact surface shaped to substantially correspond to the bearing surface of the head part of the orthopedic joint prosthesis, such that when the head part is mounted within the guide a nesting fit is formed between the bearing surface of the head part and the contact surface of each arm, and
• wherein the distal end of each arm joins to form a U-shaped bracket which carries a U-shaped assembly surface seating member configured to engage the assembly surface of the head part of the orthopedic joint prosthesis when the head part is mounted within the guide;
• and
• b. mounting the head part of the orthopedic joint prosthesis component within the alignment guide so that the distal portion of each arm is engaged with the assembly surface of the head part and the contact surface of each arm contacts the bearing surface of the head part,
• c. locating the spigot on the other part of the prosthesis component in the bore in the head part, and
• d. applying an impaction force to the head part through the axial portion, so that when the impaction force is applied along the second axis the force is directed along the first axis.