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INTRODUCTION
A correct kinematic behaviour following a knee
reconstruction operation is a fundamental goal
to prevent abnormal wear, cartilage degenera-
tion and ligament damage [1]. Total knee
arthroplasty (TKA) is a surgical procedure used
to correct loss of motion and disability, and to
eliminate the pain associated with degenerative
pathologies like osteoarthritis. The motion pat-
terns following TKA may be different from the
kinematics of normal knees because TKA
causes substantial changes. The postoperative
kinematics is indeed affected by preoperative
clinical pathological conditions: a severe preo-
perative osteoarthritis could produce a postope-
rative abnormal kinematics and some out-
comes, related to the specific prosthetic design,
different from the expectations [1, 2].
A suitable understanding of the osteoarthritic
(OA) knees kinematics and a careful analysis
of the arthroplasty effects on the patterns of
motion, may improve implant design and sur-
gical techniques.
The main sources of information about the
kinematics of the osteoarthritic and reconstruc-
ted knees have been so far anatomical investi-
gations, postoperative radiographic analyses [3,
4], gait analysis [5, 6] and fluoroscopy [7, 8].
Tamaki
et al.
[8] used fluoroscopy to analyse,
on 13 patients, an in vivo kinematic pattern of
a posterior-stabilized mobile-bearing knee
prosthesis in an high flexion range (more than
120 deg). McClelland
et al.
[6] investigated
the knee kinematics of 40 patients, who have
undergone TKA, when walking at a self-selec-
ted comfortable and fast speeds using three
dimensional motion analysis.
Laidlaw
et al.
[3] studied knee kinematics with
an active flexion lateral radiograph to evaluate
whether it provide a simple, inexpensive,
quantitative measurement method of AP tibio-
femoral position and active knee flexion, and
whether it could be correlated with similar
information from more complex
in vivo
fluo-
roscopic kinematic studies.
A further method developed more recently to
analyse pre- and post-operative kinematic
behaviour of the knee, is the computer assisted
surgery (CAS) applied to TKA.
The CAS technology is based on bony land-
marks acquisitions during surgery; it provides
the surgeon with a set of parameters that allow
to verify, in real time, joints position and
motion and to quantify accurately implant
positioning and surgical gestures, thanks to an
higher precision of measurements than that of
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TOTAL KNEE REPLACEMENT KINEMATICS
ASSESSMENT BY CAS
S. ZAFFAGNINI, F. COLLE, S. BIGNOZZI, N. LOPOMO, C. SIGNORELLI,
G.M. MARCHEGGIANI MUCCIOLI, T. BONANZINGA, M. MARCACCI