Notas / Notes - Active Congress.......

VIERNES / FRIDAY
192
and synovial attachments to the bone. When this lateral
tightness is associated with internal rotational contracture, the
popliteus tendon attachment to the femur also is released.
The iliotibial band and lateral posterior capsule should not be
released in this situation because they provide lateral stability
only in extension.
TIGHT LATERALLY IN FLEXION AND EXTENSION
The only structures that provide passive stability in flexion are
the LCL and the popliteus tendon complex, so knees that are
tight laterally in flexion and extension have popliteus tendon
or LCL release (or both). Stability is tested after adjusting tibial
thickness to restore ligament tightness on the lateral side of
the knee. Additional releases are done only as necessary to
achieve ligament balance. Any remaining lateral ligament
tightness usually occurs in the extended position only, and is
addressed by releasing the iliotibial band first, then the lateral
posterior capsule if needed. The iliotibial band is approached
subcutaneously and released extrasynovially, leaving its
proximal and distal ends attached to the synovial membrane.
TIGHT LATERALLY IN EXTENSION ONLY
In knees that initially are too tight laterally in extension, but
not in flexion, the LCL and popliteus tendon are left intact,
and the iliotibial band is released. If this does not loosen the
knee enough laterally, the lateral posterior capsule is released.
The LCL and popliteus tendon rarely, if ever, are released in
this type of knee.
Finally, the tibial component thickness is adjusted to achieve
proper balance between the medial and lateral sides of the
knee. Anteroposterior stability and femoral rollback are assessed,
and posterior cruciate substitution is done if necessary
to achieve acceptable posterior stability.
LONG TERM CLINICAL EXPERIENCE WITH
CRUCIATE RETAINING TKA
Jorge O. Galante, MD.
Rush Arthritis & Orthopaedic Institute St. Luke’s Medical
Center. Illinois (USA)
Design rationale in PCL retaining devices should include:
asymmetric femoral condyles, ability to reproduce the AP
dimensions of the femur, relatively flat unconstrained tibial
articulating surfaces, and a slope of 7 degrees on the tibial
cut. Preservation of bone stock is possible both in the femur
and in the tibia. The use of four small pegs in the tibial component
instead of a stem allows for limited intrusion on the
upper end of the tibia.
A critical issue is the tension in the posterior cruciate ligament,
a function of prosthetic design as outlined above and surgical
technique. We recommend the use of measured resection
technique and instrumentation. The possibility of restoring
the AP dimensions of the femur within 1 mm. makes restoration
of the flexion gap an easy task. In more contemporary designs,
improved kinematics at the patellofemoral joint and high
flexion designs provide additional valuable features to minimize
patellofemoral complications and improve the range of motion.
We have reported excellent long term results our first and
second generation designs. Our experience showed excellent
fixation with no loosening and no osteolysis at 15 years. Late
instability was not a problem.
We evaluated implant survivorship, reoperation rates, and
complication rates of a group of patients who had total knee
arthroplasty with a third-generation cemented cruciate-retaining
design at 10 to 12 years follow up.
One hundred and eighty six consecutive primary total knee
arthroplasties were performed at our institution during a 2year
period. Kaplan Meier survivorship using revision for any
reason as endpoint was 98% at 10 years. Three patients required
revision. One for deep infection, one for a periprosthetic
fracture and one for arthrofibrosis. No patients had reoperation
for problems related to the patellofemoral joint. Our results
show that with appropriate patient selection and meticulous
attention to surgical technique, excellent clinical and radiographic
results can be achieved.
The high prevalence of patellofemoral complications with the
original design was obviated by changes in the shape of the
patellofemoral articulation.
Cruciate retaining designs can provide excellent long-term
function when the appropriate design and surgical technique
are used.
FEMORAL COMPONENT POSITIONING IN
TKA. A 3-D PROBLEM
J. David Blaha, Ann Arbor
University of Michigan Medial School,
Michigan (USA)
Placing total knee components in the proper position in all
three planes (frontal, sagittal and transverse) is important for
correct functioning of the arthroplasty. Until relatively recently
little attention has been paid to positioning in the transverse
plane – often referred to as the “rotational” position of components.
There has been acceptance of the transepicondylar
axis (TEA) is a landmark by which the surgeon can align the
femoral component of a total knee replacement to achieve
proper rotation. Surgeons have experienced problems, however,
finding the epicondyles with certainty making this set
of landmarks difficult to use, and there is some concern that
the epicondyles do not always define a kinematically proper
placement. A line down the trochlear groove (AP axis – most