Abstract
Total knee arthroplasty belongs today to one of the standard operation in orthopaedic surgery. During the last years the number of the total knee arthroplasty has dramatically increased. The prognosis for the future have shown also an increasing tendence. The Swedish Regiter Study and others showed that the results after total knee replacement not almost dependant on the design of the prothesis. More important are patient selection, operation technique and the postoperative therapy.
The goals of modern knee replacement surgery are restoring mechanical alignment, preserving of the joint line, balancing ligament with a well balanced extension and flexion gap to reach maximum stability and movement. Bone resection is the simple part of a total knee operation. Ligament balancing with equal extention and flextion gap represents a major chalange for the surgeon which may consequantly affect the stability both in extention and flextion. Stability of total knee arthroplasty is dependant on correct and percise rotation of the femoral component. Femoral component malrotation has been associated with numerous adverse sequelae, including patellofemoral and tibiofemoral instability, knee pain, arthrofibrosis, and abnormal knee kinematics. A great number of early revision today are due to malrotation of the femoral component.
Multiple differing surgical techniques are currently utilized to perform TKA.
femur first (measured resection)
tibia first (gap balancing)
In the classic femur first technique the excision of the bone done indepentaly after one another followed by ligament balancing in flextion and extension. There are 4 bony landmarks deciding the rotational position of the femur. The epicondylar line, whiteside line, the dorsal condyles and anetroir-posterior axis. All these landmarks are associated with problems and failure to define exactly these bony landmarks intraoperatively. This may lead not seldom to malrotation of the femural component, consequently instability, limitation of function and increased wear.
In the tibia first technique excision of the femur especially for flexion done dependant on the excision of the tibia. This carried out using a tensor. With using this technique the rotation of the femur will be oriented mainly at the ligament balancing espcialy in flexion. Flexion instability and patellae maltacking will be avoided.
We present our preferrd tibia first technique using a new tensor system. With this system it is possible to reach a well balanced extension and flextion gap. A 3° release is only needed in special cases. The rotation position of the femur depend primerly on the released soft tissue in extension. Also an exact reconstruction of the dorsal offset as well as an exact anterior or posterior referencing can be guaranteed with the instruments by infinitely variable ap movement. The use of bony landmarks also possible.
we think our new tensor present a step forwards in understanding the biomechanics of the knee and offer a new development of the instruments used in knee replacement. This could be useful especialy in cases of revision.
