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MATERIALAND
METHODS
We choosed patients with varus or valgus
malalignment greater than 10° and patients
with normal alignment that underwent TKA.
The patients were randomly chosen out of a
pool of over 2,400 operated patients.
Exclusion criteria
Patients with an extension deficiency greater
than 5° to avoid false results in leg length mea-
surements in the AP-view were excluded [1].
Preoperative assessment and planing
As this study is a retrospective analysis all the
patients included were preoperatively exami-
ned as usual in our clinic. The radiological
documentation included standard knee radio-
graphs, a standing AP view, a lateral view,
stress XRays, a patella view in 45° flexion and
an AP long-leg weight-bearing view. The range
of passive motion was measured with a gonio-
meter and the IKS knee score was calculated.
Postoperative follow-up
The usual postoperative follow-up was classi-
cal with physiotherapy and full weight bea-
ring. Radiographic follow up was performed at
6 Weeks and one year. The radiological docu-
mentation included standard knee radiographs,
a standing AP view, a lateral view, a patella
view in 45° flexion and an AP long-leg weight-
bearing view. The range of passive motion was
again measured with a goniometer and the IKS
knee score was calculated.
Material
We decided to study the change in leg length
in three groups. The groups were formed as
follows.
• Group 1
(n1=10) varus malalignment >10°
(AFTm >170°)
• Group 2
(n2=10) valgus malalignment >10°
(AFTm >190°)
• Group 3
(n3=10) normal aligned (AFTm ±2°)
Measurements
Measurements were accomplished as following
(fig. 1). Our first method was to measure leg
length on preoperative AP long-leg weight-
bearing radiographs. We defined the leg length
(c) as the distance between the centre of the
femoral head (CFH) and the centre of the
ankle (B), this line is equal to the mechanical
axis and also known as the Mikulic line. We
then measured the distance (b) between the
centre of the femoral head and a tangent to the
femoral condyles (TC) on a line going
through the CFH and the interconylar point.
The crossing point of (b) with TC was marked
C. Then we measured the distance (a) between
the centre of the ankle (B) and point C. It sho-
wed that in our groups a was identical with to
the mechanical tibial axis. In this way we
created a triangle with the angle gamma on
the medial side of the knee in the corner/point
of C which we compared with the same tri-
angle drawn on the postoperative radiograph.
In this way we had a direct comparison of all
three sides of this triangle and the angle
gamma. Then we compared the measured leg
length (c) postoperative with the predicted leg
length calculated out of
γ
gamma postoperati-
vely and a and b preoperatively.
We also measured the length of centre ankle (B)
to joint line (JL), femoral length (LF) on the ana-
tomical axis by measuring the distance between
the crossing point of the femoral anatomical axis
(FAA) with the tangent to the femoral condyles
and a point D on the femoral axis which is the
crossing point of a perpendicular line to the ana-
tomical axis going through the CFH.
We then developed a second way to measure a
possible lengthening in the knee joint by crea-
ting a fix-point on tibia (T) and femur (F) as
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