Load Sensor Balancer Instruments
Disclosed herein are apparatuses and methods for performing joint balancing procedures. The apparatus may have femoral paddle and a tibial paddle attached to a housing. The housing may include a distraction mechanism to vary the space between the femoral paddle and the tibial paddle. The tibial paddle may lie entirely within the femoral paddle in a closed position. A load sensor may be placed in the femoral paddle to measure ligament tension. The apparatus may be inserted into a knee joint and positioned to remain within the knee joint during flexion and extension of the knee without everting a patella.
1 . An apparatus for performing an orthopedic procedure on a knee, the apparatus comprising:
a femoral paddle defining a thickness, the femoral paddle having a proximal side and an opposite distal side, the proximal side including at least one proximal femoral recess, the distal side including a distal femoral recess;
a tibial paddle including a tibial proximal side and an opposite tibial distal side;
a load sensor disposed in the femoral recess to indicate a load on the femoral paddle; and
a housing coupled to the tibial paddle and the femoral paddle, the housing including a distractor to vary the distance between the tibial paddle and the femoral paddle,
wherein in a closed position the tibial paddle is disposed within the distal femoral recess such that a combined thickness of the femoral paddle, the tibial paddle and the load sensor in the closed position is substantially the same as the thickness.
2 . The apparatus of claim 1 , wherein the femoral paddle includes a plurality of tiered recesses within the distal femoral recess and the tibial paddle includes a plurality of tiered ribs on the tibial proximal side such that each of the plurality of tiered ribs is disposed within a corresponding tiered recess in the closed position.
3 . The apparatus of claim 2 , wherein at least one of the tiered ribs contact a distal surface of the corresponding tiered recess in the closed position.
4 . The apparatus of claim 1 , wherein the femoral paddle extends along a central femoral paddle axis, the femoral paddle axis separating the femoral paddle into a femoral medial side and a femoral lateral side, and the tibial paddle extends along a central tibial paddle axis, the tibial paddle axis separating the tibial paddle into a tibial medial side and a tibial lateral side.
5 . The apparatus of claim 4 , wherein the femoral paddle axis and the tibial paddle axis are parallel to each other and lie on a first plane.
6 . The apparatus of claim 5 , wherein a femoral paddle shaft couples the femoral paddle to the housing and a tibial paddle shaft couples the tibial paddle to the housing.
7 . The apparatus of claim 6 , wherein the femoral paddle shaft extends along a femoral paddle shaft axis and the tibial paddle shaft extends along a tibial paddle shaft axis.
8 . The apparatus of claim 7 , wherein the femoral paddle shaft axis and the tibial paddle shaft axis are parallel to each other and lie on a second plane.
9 . The apparatus of claim 8 , wherein the first plane is offset to the second plane.
10 . The apparatus of claim 1 , wherein the distractor includes a distraction screw to move the tibial paddle and/or the femoral paddle along a distraction axis transverse to the femoral paddle shaft axis and the tibial paddle shaft axis.
11 . The apparatus of claim 10 , wherein the tibial paddle includes an aperture for receiving an anti-rotation shaft extending from the housing to prevent rotation of tibial paddle about the tibial paddle shaft axis.
12 . The apparatus of claim 11 , wherein the housing includes an adjuster to translate the femoral paddle along an adjuster axis transverse to the distraction axis.
13 . The apparatus of claim 12 , wherein the femoral paddle shaft is rotatable about the femoral paddle shaft axis to rotate the femoral paddle with respect to the distraction axis.
14 . The apparatus of claim 9 , wherein a medial load center of a medial condyle in contact with the femoral medial side lies on a medial load center axis and a lateral load center of a later condyle in contact with the femoral lateral side lies on a lateral load center axis.
15 . The apparatus of claim 14 , wherein a medial offset distance measured between the medial load center axis and the femoral paddle shaft axis along the femoral paddle is less than a lateral offset distance measured between the lateral load center axis and the femoral paddle shaft axis along the femoral paddle.
16 . The apparatus of claim 15 , wherein the lateral offset distance allows the femoral paddle and tibial paddle to be placed between a femur and a tibia in posterior-anterior direction without everting a patella.
17 . An apparatus for performing an orthopedic procedure on a knee, the apparatus comprising:
a femoral paddle defining a thickness, the femoral paddle having a proximal side and an opposite distal side, the proximal side including at least one proximal femoral recess, the distal side including a distal femoral recess;
a tibial paddle including a tibial proximal side and an opposite tibial distal side; and
a housing coupled to the tibial paddle and the femoral paddle, the housing including a distractor to vary the distance between the tibial paddle and the femoral paddle,
wherein in a closed position the tibial paddle is disposed within the distal femoral recess such that a combined thickness of the femoral paddle and the tibial paddle in the closed position is equal to the thickness.
18 . The apparatus of claim 17 , further including a load sensor disposed in the femoral recess to indicate a load on the femoral paddle.
19 . A method of performing an orthopedic procedure on a knee, the method comprising the steps of:
resecting a proximal tibia;
placing a femoral paddle and a tibial paddle of a knee balancer in a closed position without everting a patella, the femoral paddle contacting an unresected distal femur and the tibial paddle contacting the resected proximal tibia in the closed position, the femoral paddle defining a thickness, the femoral paddle having a proximal side and an opposite distal side, the proximal side including at least one proximal femoral recess, the distal side including a distal femoral recess, the tibial paddle including a tibial proximal side and an opposite tibial distal side;
distracting the knee joint using a housing coupled to the tibial paddle and the femoral paddle, the housing including a distractor to vary the distance between the tibial paddle and the femoral paddle; and
measuring knee loads using a load sensor disposed in the femoral recess to indicate a load on the femoral paddle,
wherein the tibial paddle is disposed within the distal femoral recess such that a combined thickness of the femoral paddle, the tibial paddle and the load sensor in the closed position is substantially the same as the thickness.
20 . The method of claim 19 , further including the step of taking the knee joint through flexion and extension to measure knee gap and knee tension while the patella remains everted.