Jodi Richards and Jessica McCartyTOTAL KNEE REPLACEMENT PROCEDURE
INTRODUCTION TO TKR In this presentation we will go over a step by step procedure of how a total knee replacement (TKR) is performed. Knee replacements are performed on people that have severely damaged knees from degenerative changes and sports injuries. A knee replacement is mainly performed to allow a person to be more active, improve function of the knee, and to relieve pain. When a TKR is performed the surgeon removes the damaged tissues and cartilage and replaces it with a man-made metal or plastic replacement. A TKR is performed using many different types of equipment. These include: tourniquet, nitrogen tank for power instrument, foot holder or foot bump, suction, and electrical surgical unit (cauterization). Basic instruments used will also be discussed. These include: basic orthopedic drill set, power drill, gauges, total knee specialty instrument sets, power oscillating saw, osteotomes, and drill bits.
THE BEGINNING • The Incision: • An incision is made in the middle and front of the knee with the knee positioned in flexion. • Another approach is a medial parapatellar approach. • The middle side of the knee is then exposed by removing the anteromedial knee capsule and medial collateral ligament from the tibia using a curved osteotome. • The leg is then extended and the patella is everted, then the lateral patellofemoral plicae is removed with mayo scissors. • The knee is once again flexed and the medial meniscus and anterior cruciate ligament are removed using mayo scissors and a rongeur.
THE FEMORAL SEGMENTFemoral preparation: Femoral Resection: A 3x8 drill bit is used to create an The distal femoral resection is performed. opening in the femoral canal. The IM reamer and valgus angle alignment In order to reduce the risk of developing guide are removed. a fat embolism, a intramedullary (IM) The appropriate sized saw blade is then reamer is inserted into the femoral canal used to resect the distal femur using the while irrigating. standard resection guide.Femoral Alignment: The pins or drill bits along with the The valgus alignment guide is then used crosshead are removed. and attached to the IM reamer. It then Femoral Sizing: rests and is secured on the distal femoral The anterior-posterior femoral sizer is then condyle. placed against the resected distal femur The guide is locked into pace by and is adjusted so that the feet rest tightening a large screw. against the posterior condyles and so that The distal resection crosshead is locked the point of the stylus hardly touches the on the valgus alignment guide using a anterior cortex proximal to the anterior hexagonal screwdriver. condyles. The surgeon then checks the alignment. The holes that were already made in the 1x8 pins or drill bits are then placed into distal femur are then re-drilled for the the holes of the crosshead fixing the fixation pegs of the femoral resection block. anterior femur into place.
THE RESECTIONAnterior and Posterior Resection Trochlear Groove Resection The fixation pegs and pins are The trochlear resection guide is used to hold the cutting block secured to the femur with pins against the distal femur. The and the final femoral resection is calipers are used to measure performed. the size of the femoral resection The appropriate size saw blade is block. used for the resection. The appropriate sized saw The cutting guide is removed. blade is then used to make the anterior, posterior, and chamfer cuts. The cutting block is then removed.
TIBIAL PREPARATION• The ankle is positioned and secured against the lower portion of the leg proximal to the malleolus.• The tibia resection guide is secured with pins after it is positioned and centered on the proximal tibia.
CONTINUATION OF TIBIAL PREPARATION Extra-medullary Tibial Tibial Sizing Resection A tibial trial handle is attached to the The medial/lateral adjustment screw trial base which is placed against the that is placed at the ankle is used to proximal tibial surface. align the resection guide parallel Alignment is confirmed through the with the tibia. handle in order to check the The stylus is then attached to the alignment to the ankle by inserting crosshead and the crosshead knob the alignment rod. is turned to raise or lower it until the The keel punch guide is then level resection is indicated by the attached to the keel punch handle stylus. and is secured at the trial base. Pins are then used to fix the The keel punch on the keel punch crosshead to the proximal tibia. handle is hammered into place using To check alignment to the ankle an the mallet through the guide until the alignment rod is used. punch is fully seated. An appropriate size saw blade is When the punch is seated the keel then used for the tibial resection. punch handle is removed. This leaves the tibial trial base and stem in place for trial reduction.
PATELLAR PREPARATION First the patella is laterally retracted with the articular surface facing in the upward position Calipers are then used to determine the size of the patella along with the amount of bone that will be removed. The patella cutting guide is then placed to ensure the proper cut of the patellar apex. The appropriate size saw is then used to make the patellar cut. The patellar peg holding guide is then placed on the resected patella and the peg holes are then drilled.
FINISHING THE TKR Trial Reduction: Implant Insertion: With the knee flexed, using the The femoral impactor and mallet is mallet and femoral impactor the used to insert the femoral implant appropriate femoral trial is placed The tibial base impactor and mallet on the distal femur. are used to insert the metal tibial The tibial trial insert is then snapped base. into place on the trial base. The patellar implant is secured with The knee is then put through a bone cement and held in place using series of motions to confirm normal the parallel patellar recessing clamp. movement and alignment. The tibial polyethylene insert is The trial components are then seated and locked into place on the removed after the correct fit is metal tibial base. confirmed. The cement is hardened with the leg The joint is then irrigated with a placed in 35 degrees of flexion. pulse lavage. The cement is then injected on the cut bone surfaces and the prostheses are then placed.
WOUND CLOSURE AND DRESSING The wound is thoroughly irrigated. The tourniquet is then removed and the bleeding is stopped using electrocautery. The surgeons preference is used to then determine if a closed-suction drainage device will be needed. The wound is then closed in layers and a compressive dressing is placed on the knee.
WORKS CITEDFrey, K.B. Surgical Technology for the Surgical Technologist. Clifton Park, NY. DelMar Cengage Learning. 2007. Print. (897-902).