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R. Badet, S. Piedade
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Coronal knee
malalignment and
correction
The objectives of UKA is to correct bone wear
and restore the patient’s original alignment,
however, with no correction of the knee
constitutional deformity. Therefore, the axis
correction is individual and, for each patient a
residual valgus deformity will be predicted
after than the bone wear had been compensated.
Hence, the final knee alignment should be in
valgus for the lateral UKA and in varus for
medial UKA. On the other hand, patients with
no malalignment will have a final knee
alignment of 180°.
Thus, the surgical procedure should leave
persist a hypocorrection, with a residual knee
deformity. In the cases of important
constitutional deformities (higher than 10°),
particularly when the knee is fixed, the UKA
should be contra-indicated.
Ligament status:
central pivot and
peripheral ligaments
UKA : no lesion of cruciates ligaments and no
lésion of peripherals ligaments. The cruciates
and peripheral ligaments should be intact and
an anterior cruciate ligament tear is a classical
contra-indication to the UKA. Moreover, the
presence of medial laxity with a medial
retraction (which could attest to medial
collateral ligament insufficiency secondary to
distension or to rupture) presents a contra-
indication to UKA because it has an important
risk of failure.
In clinical practice, the non-compliance of
these major rules could lead to failures and to a
bad results.
Patient-related
factors (minor rules)
A
ge
:
Currently, the UKR has an ideal indication
to elderly patients (> 70 years old).
L
evel
of
activity
:
It is usually associated to
age. Classically, the UKA has been indicated
for patients with low level of activity.
W
eight
:
Many authors have recommended a
BMI < 30, but, others studies have found no
influence of the patient´s weight on the
outcomes.
The remodeling knee osteoarthritis with no
medial tibiofemoral and patelofemoral
compartment narrowing
could influence the
outcomes of the lateral UKA.
In practice, each minor rules alone does not
present a real contra-indication to this
procedure.
It is very important to integrate these data in a
overall context. The goal of the integration of
these data should be to limited the possible risk
of failure secondary to wear and loosening.
Hence, the ideal patient should be 70-year old
or more, no overweight and low level of
activity.
Technical factors
(components)
Femoral component
The complexity of the anatomy of the femoral
condyles (Fick’s multicenter model or Frain’s
spiral logarithmic monocentric model) clearly
seen on the knee lateral view where the design
of the implant is formed by two circles: one
large anterior curve, the other, smaller posterior
radius.