Provisional tibial prosthesis system

A provisional tibial prosthesis system for a prosthetic knee joint for implantation in a natural knee, the provisional tibial prosthesis system capable of alternatively mimicking the geometry of a first final tibial prosthesis, a second final tibial prosthesis, and a third final tibial prosthesis, the natural knee comprising a proximal tibia and a distal femur and having a medial/lateral axis, an anterior/posterior axis, and a proximal/distal axis, the medial/lateral axis corresponding to a medial/lateral direction, the anterior/posterior axis corresponding to an anterior/posterior direction, and the proximal/distal axis corresponding to a proximal/distal direction, the provisional tibial prosthesis system comprising:

• a tibial base plate having a bone contacting surface and an opposing base plate superior surface;
• a tibial bearing component having a tibial bearing component height, said tibial bearing component attachable to said tibial base plate, said tibial bearing component height representing the first final tibial prosthesis;
• a first shim having a first shim height, said first shim slidable relative to both said tibial base plate and said tibial bearing component to be slidably receivable between said tibial base plate and said tibial bearing component in the anterior/posterior direction when said tibial base plate and said tibial bearing component are separated by a first distance along the proximal/distal axis equal to said first shim height, said first shim height cooperating with said tibial bearing component height to represent the second final tibial prosthesis;
• and
• a second shim having a second shim height, said second shim slidable relative to both said tibial base plate and said tibial bearing component to be slidably receivable between said tibial base plate and said tibial bearing component in the anterior/posterior direction when said tibial base plate and said tibial bearing component are separated by a second distance along the proximal/distal axis equal to said first shim height and said second shim height, said first shim height and said second shim height cooperating with said tibial bearing component height to represent the third final tibial prosthesis.

A method of determining a size of a final tibial prosthesis for a prosthetic knee joint for implantation in a natural knee, the natural knee comprising a proximal tibia and a distal femur and having a medial/lateral axis, an anterior/posterior axis, and a proximal/distal axis, the medial/lateral axis corresponding to a medial/lateral direction, the anterior/posterior axis corresponding to an anterior/posterior direction, and the proximal/distal axis corresponding to a proximal/distal direction, the method comprising:

• selecting a provisional tibial prosthesis system, comprising:
• a tibial base plate having a bone contacting surface and an opposing base plate superior surface;
• a tibial bearing component having a tibial bearing component height, the tibial bearing component attachable to the tibial base plate;
• and
• a first shim having a first shim height, the first shim slidable relative to both the tibial base plate and the tibial bearing component to be slidably receivable between the tibial base plate and the tibial bearing component in the anterior/posterior direction when the tibial base plate and the tibial bearing component are separated by a first distance along the proximal/distal axis equal to the first shim height;
• resecting the proximal tibia to form a resected proximal tibia surface;
• positioning the bone contacting surface of the tibial base plate on the resected proximal tibia surface;
• positioning the tibial bearing component on the tibial base plate;
• spacing the tibial bearing component from the tibial base plate by sliding the first shim between the tibial base plate and the tibial bearing component in the anterior/posterior direction, without distracting the femur from the tibia a distance greater than the first shim height;
• performing range of motion testing to verify proper sizing of the provisional tibial prosthesis system;
• and
• when the testing indicates that the provisional tibial prosthesis system is not properly sized,
• removing the first shim from between the tibial base plate and the tibial bearing component in the anterior/posterior direction;
• selecting a second shim having a second shim height, the second shim slidable relative to both the tibial base plate and the tibial bearing component to be slidably receivable between the tibial base plate and the tibial bearing component in the anterior/posterior direction when the tibial base plate and the tibial bearing component are separated by a second distance along the proximal/distal axis equal to the second shim height, the second shim height different than the first shim height;
• and
• spacing the tibial bearing component from the tibial base plate by sliding the second shim between the tibial base plate and the tibial bearing component in the anterior/posterior direction, without distracting the femur from the tibia a distance greater than the second shim height.

A method of determining a size of a final tibial prosthesis for a prosthetic knee joint for implantation in a natural knee, the natural knee comprising a proximal tibia and a distal femur and having a medial/lateral axis, an anterior/posterior axis, and a proximal/distal axis, the medial/lateral axis corresponding to a medial/lateral direction, the anterior/posterior axis corresponding to an anterior/posterior direction, and the proximal/distal axis corresponding to a proximal/distal direction, the method comprising:

• selecting a provisional tibial prosthesis system, comprising:
• a tibial base plate having a bone contacting surface and an opposing base plate superior surface;
• a tibial bearing component having a tibial bearing component height, the tibial bearing component attachable to the tibial base plate;
• and
• a first shim having a first shim height, the first shim slidable relative to both the tibial base plate and the tibial bearing component to be slidably receivable between the tibial base plate and the tibial bearing component in the anterior/posterior direction when the tibial base plate and the tibial bearing component are separated by a first distance along the proximal/distal axis equal to the first shim height;
• resecting the proximal tibia to form a resected proximal tibia surface;
• positioning the bone contacting surface of the tibial base plate on the resected proximal tibia surface;
• positioning the tibial bearing component on the tibial base plate;
• spacing the tibial bearing component from the tibial base plate by sliding the first shim between the tibial base plate and the tibial bearing component in the anterior/posterior direction, without distracting the femur from the tibia a distance greater than the first shim height;
• and
• performing range of motion testing to verify proper sizing of the provisional tibial prosthesis system;
• and
• when the testing indicates that the provisional tibial prosthesis system is not properly sized,
• selecting a second shim having a second shim height, the second shim slidable relative to both the tibial base plate and the tibial bearing component to be slidably receivable between the tibial base plate and the tibial bearing component in the anterior/posterior direction when the tibial base plate and the tibial bearing component are separated by a second distance along the proximal/distal axis equal to the first shim height and the second shim height;
• and
• spacing the tibial bearing component from the tibial base plate by sliding the second shim between the tibial base plate and the tibial bearing component in the anterior/posterior direction, without distracting the femur from the tibia a distance greater than the first shim height and the second shim height.