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VIERNES / FRIDAY
280
dislocation, and popliteus tendon dysfunction
should be considered. If the pain developed
months or years after TKA, loosening,
progressive ligamentous incompetence or
hematogenously based infection. Physical
examination will differentiated between a
painful knee with or without reduced range
or motion. If fl exion is possible up to 90°,
stability assessment in both, extension and
fl exion is mandatory. Laxity measurements
in fl exion may be quantifi ed with stress fl uoroscopy
as described by Stähelin et al.1. It
may reveal a fl exion-extension gap mismatch
or an asymmetrical fl exion gap which is due
to insuffi cient ligament balancing or femoral
component malrotation2. The evaluation of
the position of the femoral component in the
transverse plane – often referred to as the
“rotational” position of the femoral component
– is performed using computer tomography3.
It is important to standardize the level above
the joint line of the computer tomography
image for reliable and reproducible measurement.
Our recent study demonstrates
that the best interobserver correlation was
found using the condylar twist angle (CTA) at
30 mm above the joint line4. The CTA is the
angular measurement subtended by the clinical
transepicondylar axes (TEA) which uses
the most prominent points of the medial and
lateral condyle and the posterior condylar line
(PCL). Excessive femoral internal malrotation
is responsible for lateral fl exion instability and
excessive femoral external malrotation is the
source of popliteus tendonitis. Plain radiographs
in the frontal plane will depict component
overhang which may irritate the joint
capsule and impinge with extraarticular soft
tissue such as the medial collateral ligament
(medial tibial overhang) or the medial patellofemoral
ligament (medial femoral overhang).
Plain radiographs in the sagittal plane are
useful for assessement of tibial component
slope and femoral fl exion-extension position.
Long standing x-rays are useful not only for
evaluation of component malalignment or
entire limb varus-valgus abnormalities but
also to detect distant pathologic conditions
such as tumors, stress fractures or simply
hip joint disease irradiating into the knee.
Detection of patellar problems such as lateral
patellofemoral hyperpression syndrome or
subluxation require patellofemoral axial view
radiographs. If the source of pain is suspected
in the patellofemoral joint assessment not
only of the femoral component rotaion but
also of the rotational position of the tibial tray
is required using transverse CT scans. Early
stages of loosening or failed osteointegration
(cementless TKA) can only be detected using
fl uoroscopically-assisted radiographs which
facilitate radiographic-beam placement perfectly
tangential to the fi xation interface5. Osteolysis
is most commonly detected by plain
radiographs, but may occasionally only be
suspected in technetium scans. Otherwise,
the role of nuclear medicine in evaluation
of painful TKA is unclear since sensitivity is
typically high but specifi ty is variable and in
addition, most scans demonstrate prolonged
increased uptake of the isotope. If the only
hot spot on the scan is on the patella it may
be indicating patellar necrosis or overuse in a
non-resurfaced patella. Magnetic resonance
imaging with metal subtraction software
may provide various diagnosis including
osteolysis, synovitis, bursitis, ligamentous or
tendinous injury, fat-ad scarring, pigmented
villonodular synovitis, and intramuscular
hematoma6. However, MRI is far from being
a diagnostic method of fi rst choice. Ultrasonography
has been reported to have the
ability to determine polyaethylen wear with
an accuracy of 0.5mm7.
Evaluation of the painful stiff knee
Physical examination is very important as
it categorizes the knee painful knee in two
groups: pain with and without reduced arc of
motion. Mechanical factors such as asymmetric
fl exion gap as a consequence of femoral
component malrotation, flexion-extension
gap mismatch, joint line elevation, femoral
component oversizing, patellofemoral joint
overstuffi ng, anterior tibial slope, inadequate
clearance between the posterior condyles of