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JUEVES / THURSDAY
234
in extension after total knee arthroplasty fi rst
should have release of the posterior oblique
fi bers of the medial collateral ligament, and
release of the posterior capsule if medial contracture
persists in extension. This procedure
leaves the anterior portion of the medial collateral
ligament intact to stabilize the knee.
Tight Medially in Flexion and Extension
In many cases with a long-standing varus
deformity and medial ligament contracture,
the knee is tight medially both in fl exion and
extension. This indicates that the entire MCL
is contracted. The posterior capsule and PCL
also may be contracted, but the primary contracture
is the MCL in these cases. The PCL
and posterior capsule cannot be evaluated
until the MCL contracture has been corrected.
Knees that are tight in fl exion and extension
have release of the anterior and posterior portions
of the medial collateral ligament. This is
done by fi rst stripping the anterior portion of
the medial collateral ligament in line with the
tibial long axis, then directing the osteotome
posteriorly to release the posterior portion of
the ligament. Those knees that remain tight
in full extension after release of the posterior
oblique medial collateral ligament have
release of the posterior medial capsule from
the femur and tibia. If inappropriate posterior
femoral rollback occurs, or if medial ligament
tightness remains in fl exion after release of
the anterior portion of the medial collateral
ligament, the posterior cruciate ligament is
released from its tibial attachment.
Tight Popliteus Tendon
Occasionally the popliteus tendon and its surrounding
structures are tight in the varus knee
after the medial side has been corrected.
This often is diffi cult to detect, but rotational
stability testing of the tibia demonstrates that
the tibia is held anteriorly on the lateral side
and pivots around the lateral edge of the tibial
component. The popliteus tendon is released
from its bone attachment when the knee is
fl exed. It is found just distal and posterior
to the lateral collateral ligament (LCL) at-
tachment, and care must be taken to avoid
release of the LCL during this procedure.
Compensatory Lateral Release—Extension
Only
Occasionally, after full MCL release, the knee
is excessively loose on the medial side in
extension, and tight laterally. Compensatory
lateral release corrects the imbalance, and a
thicker tibial component brings the knee to
correct stability.
Compensatory Lateral Release—Flexion
and Extension
In some cases after full release of the MCL,
the secondary stabilizers are inadequate to
provide medial stability in fl exion and extension,
and the knee is too loose medially after
the tibial component has been sized to bring
the lateral ligaments to their normal tension.
In those cases the LCL and popliteus tendon
are released to create more laxity both in
fl exion and extension, and a thicker tibial
component is used to tension the medial
structures.
THE IMPACT OF
LIGAMENT BALANCING IN
TOTAL KNEE ARTHROPLASTY
J. Romero, M.D.
Endoclinic Zurich, Center for Arthroplasty
and Joint Surgery,
Klinik Hirslanden, Switzerland
Symmetrically balanced collateral soft tissues
in extension and in fl exion 1, 2 and alignment of
the tibial and femoral components perpendicular
to the mechanical axis in the coronal plane 3 are
major surgical goals in total knee arthroplasty.
Erroneous resection of the tibial plateau and
distal femoral condyles or inadequate soft tissue
release for varus or valgus contracture will result
in an asymmetric extension gap. Extension gap
imbalance due to insuffi cient soft tissue release
may cause polyethylene edge overload 4 and