Force sensing distal femoral alignment system and method of use

Abstract

Devices, systems, and methods are provided for facilitating the aligning and balancing of the knee during total knee replacement surgery. A femoral assembly is engaged with a distal femur. The positions of medial and lateral portions of the femoral assembly relative to a stationary portion of the femoral assembly can be separately adjusted to adjust the alignment of the knee. A force sensor will be provided to sense the forces in the medial and lateral portions of the knee, and the medial and lateral portions of the femoral assemblies will be adjusted so that the sensed forces are balanced. The alignment of the knee is visually verified using a knee alignment verification member coupled to the femoral assembly. The knee alignment verification member may emit laser beams along the mechanical axes of the femur and tibia, or the knee alignment verification member may couple to alignment rods aligned along these axes.

1 . A system for aligning the knee during a surgical procedure on the knee, the system comprising:
 a femoral assembly removably engagable with a distal femur, the femoral assembly including a stationary femoral portion, an adjustable medial femoral portion coupled to the stationary femoral portion, and an adjustable lateral femoral portion coupled to the stationary femoral portion;   a knee alignment verification member coupleable with the stationary femoral portion of the femoral assembly and providing visual confirmation of a femoral and tibial mechanical axes of the knee; and   a force sensor coupleable with the stationary femoral portion of the femoral assembly, the force sensor comprising a medial portion for sensing a first force in a medial portion of the knee and a lateral portion for sensing a second force in a lateral portion of the knee.   
   
   
       2 . The system of  claim 1 , wherein the knee alignment verification member means includes a laser knee alignment verification member coupleable to the stationary femoral portion and providing a first laser beam oriented along the femoral axis of the knee and a second laser beam oriented along the tibial axis of the knee. 
   
   
       3 . The system of  claim 1 , wherein the knee alignment verification member includes a mechanical knee alignment verification assembly, the mechanical knee alignment verification assembly comprising:
 a knee alignment hub;   a first rod coupleable with the knee alignment hub to be oriented along the femoral axis of the knee; and   a second rod coupleable with the knee alignment hub to be oriented along the tibial axis of the knee.   
   
   
       4 . The system of  claim 1 , wherein the adjustable medial portion comprises a medial paddle, and the adjustable femoral portion comprises a lateral paddle. 
   
   
       5 . The system of  claim 1 , wherein the position of the adjustable medial femoral portion relative to the stationary femoral portion is adjustable, and the position of the adjustable lateral femoral portion relative to the stationary femoral portion is adjustable. 
   
   
       6 . The system of  claim 5 , wherein the adjustable medial femoral portion and the adjustable lateral femoral portion are separately adjustable. 
   
   
       7 . The system of  claim 5 , wherein a medial rotatable screw couples the adjustable medial femoral portion with the stationary femoral portion, and a lateral rotatable screw couples the adjustable lateral femoral portion with the stationary femoral portion. 
   
   
       8 . The system of  claim 7 , wherein rotating the medial rotatable screw adjusts the position of the adjustable medial femoral portion relative to the stationary femoral portion, and rotating the lateral rotatable screw adjusts the position of the adjustable lateral femoral portion relative to the stationary femoral portion. 
   
   
       9 . The system of  claim 1 , wherein the force sensor comprises a force sensing element selected from the group consisting of piezoelectric sensors, force sensing resistors, force sensing capacitors, strain gages, load cells, and pressure sensors. 
   
   
       10 . The system of  claim 1 , further comprising:
 a processor coupled with the force sensor for processing sensed force data into usable data for providing to a user; and   a visual display coupled with the processor and adapted to display the usable data.   
   
   
       11 . The system of  claim 10 , wherein the visual display displays usable data representing a first force sensed in the medial portion of the knee and a second force sensed in the lateral portion of the knee. 
   
   
       12 . The system of  claim 1 , further comprising a plurality of locating pins, and wherein the stationary femoral portion defines at least one medial aperture for positioning a first at least locating pin on the distal femur and at least one lateral aperture for positioning a second at least one locating pin on the distal femur. 
   
   
       13 . The system of  claim 12 , further comprising a cutting guide removably engagable with the distal femur, the cutting guide being positioned relative to the distal femur based on the position of at least one first locating pin and the at least one second locating pin. 
   
   
       14 . The system of  claim 1 , wherein the force sensor is removably coupleable to a thickness adapter, the adapter configured to fill the space between the femur and tibia. 
   
   
       15 . The system of  claim 1 , wherein the adjustable medial femoral portion and the adjustable lateral femoral portion include a medial fulcrum and lateral fulcrum, the fulcrums positionable against the provisionally cut distal femur when the distal femoral alignment assembly is mounted against the distal femur. 
   
   
       16 . The system of  claim 15 , wherein a bone interface plate is disposed between the fulcrums and the distal femur. 
   
   
       17 . A method for aligning the knee during a surgical procedure on the knee, the method comprising:
 engaging a femoral assembly with a distal femur, the femoral assembly including a stationary femoral portion, an adjustable medial femoral portion coupled to the stationary femoral portion, and an adjustable lateral femoral portion coupled to the stationary femoral portion;   coupling a force sensor with the stationary femoral portion of the femoral assembly;   sensing a first force in a medial portion of the knee and a second force in the lateral portion of the knee using the coupled force sensor;   separately adjusting the position of the adjustable medial femoral portion relative to the stationary femoral portion and the position of the adjustable lateral femoral portion relative to the stationary femoral portion based on the sensed first and second forces to align a femoral and tibial mechanical axes of the knee; and   visually confirming the alignment of the femoral and tibial mechanical axes of the knee using a knee alignment verification assembly coupleable with the stationary femoral portion of the femoral assembly.   
   
   
       18 . The method of  claim 17 , further comprising:
 coupling a mechanical knee alignment verification assembly with the stationary femoral member of the femoral assembly;   aligning a first alignment rod of the mechanical knee alignment verification assembly along the femoral axis of the knee; and   aligning a second alignment rod of the mechanical knee alignment verification assembly along the tibial axis of the knee,   wherein visually confirming the alignment of the femoral and tibial mechanical axes of the knee comprises visually confirming the alignment of the first alignment rod and the second alignment rod relative to each other.   
   
   
       19 . The method of  claim 17 , further comprising:
 coupling a laser knee alignment verification member with the stationary femoral member of the femoral assembly;   aligning a first laser beam from the laser knee alignment verification member along the femoral mechanical axis of the knee; and   aligning a second laser beam from the laser knee alignment verification member along the tibial mechanical axis of the knee along the tibial axis of the knee,   wherein visually confirming the alignment of the femoral and tibial mechanical axes of the knee comprises visually confirming the alignment of the first laser beam and the alignment of the second laser beam relative to each other.   
   
   
       20 . The method of  claim 17 , wherein the positions of the adjustable medial femoral portion relative to the stationary femoral portion and of the adjustable lateral femoral portion relative to the stationary femoral portion are adjusted based on the sensed first force and the sensed second force so that the first and second forces are balanced. 
   
   
       21 . The method of  claim 17 , wherein sensing a first force in a medial portion of the knee and a second force in a lateral portion of the knee using the coupled force sensor comprises:
 transmitting a voltage to a sensor element of a thin force sensing portion of the force sensor;   measuring the voltage after it has passed through the sensor element;   determining a percentage of the voltage passed through the sensor element relative to the voltage transmitted to the sensor element; and   deriving the measured force from the percentage.   
   
   
       22 . The method of  claim 17 , further comprising displaying the sensed first force and the sensed second force with a visual display coupled to the force sensor. 
   
   
       23 . The method of  claim 17 , where separately adjusting the position of the adjustable medial femoral portion relative to the stationary femoral portion and the position of the adjustable lateral femoral portion relative to the stationary femoral portion comprises rotating at least one of a lateral rotatable screw coupling the adjustable lateral femoral portion to the stationary femoral portion and a medial rotatable screw coupling the adjustable medial femoral portion to the stationary femoral portion. 
   
   
       24 . The method of  claim 17 , wherein the stationary femoral portion defines at least one medial aperture and at least one lateral aperture, the method further comprising positioning a first at least one locating pin on the distal femur based on the at least one medial aperture and positioning a second at least one locating pin on the distal femur based on the at least one lateral aperture. 
   
   
       25 . The method of  claim 24 , further comprising disengaging the femoral assembly with the distal femur and engaging a distal femoral cutting guide with the distal femur, the distal femoral cutting guide being positioned relative to the distal femur based on the positioned first and second at least one locating pins. 
   
   
       26 . The method of  claim 25 , further comprising making cuts on the distal femur based on the position of the distal femoral cutting guide. 
   
   
       27 . A method for aligning a leg having a femur and a tibia during knee surgery, the femur having a mechanical axis, a distal end and a proximal end and the tibia having a mechanical axis, a distal end and a proximal end, the method comprising:
 engaging a femoral assembly with the provisionally cut distal end of the femur, the femoral assembly including a stationary femoral portion, an adjustable medial femoral portion having a medial pivot fulcrum coupled to the stationary femoral portion, and an adjustable lateral femoral portion having a lateral pivot fulcrum coupled to the stationary femoral portion;   coupling a force sensor with the stationary femoral portion of the femoral assembly;   reversibly coupling a medial posterior member to the medial side of the stationary femoral portion;   reversibly coupling a lateral posterior member to the lateral side of the stationary femoral portion;   abutting the medial member against the medial posterior femur;   abutting the lateral member against the lateral posterior femur;   sensing a first force in a medial portion of the knee and a second force in the lateral portion of the knee using the coupled force sensor;   separately adjusting the position of the adjustable medial femoral portion relative to the stationary femoral portion and the position of the adjustable lateral femoral portion relative to the stationary femoral portion based on the sensed first and second forces to align the femoral and tibial mechanical axes of the knee; and   visually confirming the alignment of the femoral and tibial mechanical axes of the knee using a knee alignment verification assembly coupleable with the stationary femoral portion of the femoral assembly.   
   
   
       28 . The method of  claim 27 , wherein the abutting occurs with the leg in full extension. 
   
   
       29 . The method of  claim 27 , wherein the medial and lateral fulcrums determine fixed distance points to adjust an angle. 
   
   
       30 . The method of  claim 27 , wherein a bone interface plate is disposed between the adjustable medial and lateral femoral portions and the distal femur.