76 / 324
In case valgus 5 c_post is 0.8 cm longer than
predicted. Checking our other measurements
we can see that we lengthened the femur 1 cm
and also the difference between F-T pre and F-
T post is plus 0.8 cm. We therefore find the dif-
ference between c_post and _lies in a lengthe-
ning of the knee joint on the femoral side
(Table 4).
In case valgus 8 we also find the lengthening
in the knee joint. Here we measured a diffe-
rence of 0.8 cm between F-T pre and F-T post.
This time the lengthening is on the tibial side
as T-JL post is measured 1 cm longer than T-JL
pre. The joint line therefore was raised 1 cm
(Table 4).
In case valgus 9 c_post is 1.8 cm longer than
predicted, here we measured a lengthening of
the femur of 1.8 cm and a shortening of the
tibia (F-JL) of 0.2 cm. These two differences
lead to a lengthening in the knee joint of
1.6 cm. This is a near match to the measured
difference of 1.8 cm (Table 4).
CHANGES IN LENGTH AFTER TKA: ACCURACY OF A PREDICTIVE METHOD
75
Table 3: Preoperativ lengths compared with postoperative lengths and calculated
preoperative (c_pre calc) leg length. All measurements are given in cm.