101 / 242
Bicruciate-retaining TKA: A Concept Worth Exploring
101
Intuitively, one may think that knees with a
larger pre-operative coronal misalignment are
more difficult to balance during surgery and are
less likely to have a good outcome after
bicruciate-retaining TKA. In our series,
however, severe pre-operative coronal
misalignment, defined as more than ten degrees
of varus or valgus, did not appear to negatively
affect the results of bicruciate-retaining
arthroplasty; on the contrary, knees with a
severe misalignment seemed to benefit more
from their surgery than those with a lesser
misalignment with regard to the Knee Society
and KOOS scores. Tourniquet times were five
minutes longer with severely misaligned knees,
either varus or valgus, reflecting the time
necessary to perform ligament releases, but
otherwise no difference was found between
more severe and lesser misalignments. These
groups may eventually prove to have different
knee kinematics and/or a different long-term
outcome but this remains to be seen. As of now
there is no evidence that pre-operative coronal
alignment of the knee has an influence on the
outcome of bicruciate-retaining TKA.
Knees with a pre-operative flexion of
130 degrees or more lost in average 12 degrees
of flexion after a bicruciate-retaining TKA and
8 degrees after a posterior-stabilized TKA,
while knees with less than 130 degrees of
flexion before surgery lost an average of
4 degrees after a bicruciate-retaining TKA but
gained an average of 13 degrees after a
posterior-stabilized TKA. This is significant, as
this may lead to more patients not able to flex
their operated knee to 110 degrees, the
commonly cited flexion angle required to climb
down stairs fluently. Indeed, knees with
decreased pre-operative flexion were more
likely to have less than 110 degrees of flexion
after surgery if a bicruciate-retaining TKA was
performed (21 out of 46, or 46%) compared to
a posterior-stabilized TKA (14 out of 63, or
22%). Flexion of less than 110 degrees was a
rare occurrence after both types of TKA when
pre-operative flexion was 130 degrees or more:
2 out of 54 cases for bicruciate-retaining TKA
(4%) and one out of 37 cases for posterior-
stabilized TKA (3%).
When a knee flexion contracture was noted
pre-operatively, it was more likely to recur
after surgery if a bicruciate-retaining arthro
plasty was performed instead of a posterior-
stabilized prosthesis. More specifically, 50% of
knees with a pre-operative flexion contracture
of 5 degrees or more (8 out of 16) had a post-
operative flexion contracture of 5 degrees or
more if a bicruciate-retaining TKA was
performed, compared to 18% (5 out of 28) if a
posterior-stabilized TKA was done. When
considering a pre-operative knee flexion
contracture of 10 degrees or more, the rate of
persistent post-operative flexion contracture
climbed to 71% if a bicruciate-retaining TKA
was performed (5 out of 7), but was essentially
the same if a posterior-stabilized TKA was
done (20%, 3 out of 15). When no pre-operative
flexion contracture was present, it was
nonetheless found in 11% of bicruciate-
retaining knees (9 out of 84) and in 4% of
posterior-stabilized knees (3 out of 72).
Based on the presented results, and until we
understand better what causes some knees to
lose flexion after bicruciate-retaining TKA, we
think that this procedure should probably be
avoided if, before surgery, maximal knee flexion
is less than 130 degrees and a flexion contracture
of 5 degrees or more is present. Otherwise, as
long as the ACL is functional and that the bone
stock is not compromised, bicruciate-retaining
TKA can be safely performed.
Conclusion
Bicruciate-retaining total knee arthroplasty is a
bone-preserving surgery that results in good
clinical outcomes and a good long-term
survivorship. Its biggest drawback seems to be
a decrease in post-operative flexion compared
to posterior-stabilized TKA, which we think is
explained in part by a lesser tolerance for slight
technical errors. New tools are available to
identify the benefits of this technique and to
better understand how to do it: patient-reported
outcome scores like the new Knee Society
score [16] and the Forgotten Joint Score [17],
kinematic analysis devices like the KneeKG
TM
,