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We have used the technique described below
for over 11 years in over 540 valgus knees with
a pre-operative deformity of ≥10 degrees. This
is a consecutive series in which a mobile
bearing LCS rotating platform was used in
every case irrespective of the degree of
deformity.
A midline incision with a medial approach
(Insall type [1]) was used in all cases. Exposure
of the proximal tibia is minimal – <10mm
below medial joint line, and as far posterior as
the mid-coronal plane. A “notch plasty”
(clearance of osteophytes) is performed and
both cruciates are excised. The tibial cut is
made perpendicular to the tibial mechanical
axis matching the posterior slope of medial
tibial condyle. The antero-posterior (AP)
femoral cuts are made using the femoral guide
positioner which sets femoral rotation off the
tibial axis.
After measuring the flexion gap a 5°
conservative distal femoral “pre-cut” is made
and the conservative extension gap is assessed
with the spacer block. If the gap is unbalanced
(trapezoidal gap) we use the algorithm in
figure 1 to balance the knee. If it is tight
laterally, and the difference between medial
and lateral gap is ≥2 and ≤5mm, the gap is
balanced by making a definitive cut in 60 or
more degrees. This does not elevate the joint
line but resects more bone from the tighter
lateral side. If the difference is >5mm then
this is too much to be corrected by a definitive
re-cut in greater valgus and therefore a
postero-lateral capsulotomy is required. The
postero-lateral capsulotomy is done with the
knee in full extension. The lateral joint space
is opened with laminar spreaders and the
popliteus tendon is identified (fig. 2). In our
experience the popliteus is never tight and is
never intentionally cut but its lateral border
locates the tight postero-lateral capsule. This
tight band which is about 10mm in width is
then divided using a small blade at which
point the lateral side of the joint will usually
visibly open. This corrects both the fixed
flexion and valgus deformity (fig. 2). Having
cut the posterior capsule the extension gap is
tested once more. If the difference between
the medial and lateral gap is now ≤2-5mm, the
gap can be balanced by making a definitive
cut in 60 or more degrees (fig. 1). In type II
valgus knees caution is required as the MCL
has become stretched. The knee should not be
fully balanced in extension, but with the
spacer block in place the extension gap should
stay closed medially unless a valgus stress is
applied.
We never resurface the patella but if necessary
a lateral patellar release is performed to allow
central tracking of the patella in the trochlear
Technical aspects of TKA in
the valgus knee.
Modified Surgical Technique to balance
the valgus knee and avoid instability
D. Beverland, E. Doran, S. O’Brien,
J. Hill, R. Pagoti