In a „true“ valgus knee the lateral femoral condyle is smaller in both the vertical and anteroposterior dimensions and lateral soft tissue structures are contracted. In a „false“ valgus knee there is no mismatch between anteroposterior dimensions of both condyles. The aim of the study was to preoperatively analyse patterns of passive movement of valgus knees with imageless navigation system to optimise surgical approach during subsequent total knee replacement (TKR). TKR were prospectively performed in 50 valgus knees. After the data registration process, the kinematic analysis was performed by passive movement of the knee. The mechanical axis was recorded at 0°, 30°, 60°, 90°, and 120° of flexion. The valgus deformity persistent through the whole range of motion was called „true“ and the valgus deformity passing into varus with flexion was called „false“. The pre-operative valgus deformity in extension ranged from 13° to 4° (mean 7.8°). We observed „true“ valgus type deformity during passive range of movement in 34 cases (68%) and „false“ type of kinematics in 16 cases (32%). The average value of valgus deviation in extension in „true“ group was 7.9° (range 13° to 4°) and in „false“ group 7.5° (range 9° to 6°). The mean difference between axis deviation in 0° to 120° range of flexion was 5.5° (range 10° to 1°) in the „true“ valgus group. In the „false“ valgus group the varus deviation was observed in 90° of flexion in all cases and mean difference between axis deviation in 0° to 120° range of flexion was 12.0° (range 14° to 10°). Computer navigation can easily help to identify the character of valgus deformity („true“ or „false“) just before skin incision. In „true“ valgus deviation lateral approach may be necessary for appropriate soft tissue balancing during TKR surgery.
Valgus knee deformity is associated especially with differences in anatomy between medial and lateral femoral condyles. Vertically smaller lateral condyle and more distally located medial condyle cause valgus deformity in extension. The anteroposterior dimensions of both condyles influence the knee axis in flexion. In a „true“ valgus knee there is a mismatch between both condyles in both the vertical and anteroposterior dimensions, the lateral condyle is generally smaller. In a „false“ valgus knee there is no mismatch between anteroposterior dimensions of both condyles, the knee axis changes from valgus into varus with increased degree of flexion and lateral soft tissue structures are that's why not so contracted as in „true“ valgus knee deformity, where the knee stays in valgus deviation during the whole range of motion. The aim of the study was to preoperatively identify and analyse patterns of passive movement of osteoarthritic valgus knees with imageless navigation system to optimise surgical approach and intra-operative tissue handling during subsequent total knee replacement (TKR) surgery. TKR were prospectively performed in 50 valgus knees. Cases with severe bony destruction and enormous soft tissue laxity were excluded from the study. The kinematic navigation system used was OrthoPilot® (Aesculap, Tuttlingen, Germany). It is designed to produce a numerical output of varus/valgus deviation of the knee against the degree of flexion. Before skin incision for TKR surgery, active markers were attached percutaneusly to the femur and the tibia with bicortical screws to create two ‘rigid bodies’. After the registration process the kinematic analysis was performed by passive movement of the knee. The mechanical axis was recorded at 0°, 30°, 60°, 90°, and 120° of flexion. The valgus deformity persistent through the whole range of motion was called „true“ and the valgus deformity passing into varus with flexion was called „false“. In „true“ valgus knees the lateral approach according to Keblish was used, in „false“ valgus knees we used standard medial parapatellar approach.Introduction
Material and Methods
