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

VIERNES / FRIDAY
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MEASURED RESECTION VERSUS GAP
BALANCING TECHNIQUE
Douglas A. Dennis, M.D
Adjunct Professor, Dept. of Biomedical Engineering, University
of Tennessee; Assistant Clinical Professor, University of
Colorado Health Sciences Center; Clinical Director, Rocky
Mountain Musculoskeletal Research Laboratory
Denver, Colorado (USA)
Controversy persists regarding the most favourable method
to determine accurate femoral component rotation during
total knee arthroplasty (TKA). Some favour a measured resection
technique in which bone landmarks (femoral epicondyles,
posterior femoral condyles, or the anteroposterior
axis) are the primary determinants of femoral component
rotation. Others recommend a gap balancing methodology
in which the femoral component is positioned parallel to the
resected tibia with each collateral ligament equally tensioned.
Recent research has documented that accurate surgeon
identification of bone landmarks is frequently NOT obtained
which can result in flexion gap asymmetry. To test this hypo-
thesis, two hundred twelve patients underwent a total knee
arthroplasty utilizing a computer navigation system (Ci Navigation
System; Depuy, Warsaw, IN). The transepicondylar,
anteroposterior, and the posterior condylar axes were registered.
CAS optimized femoral rotation (gap balancing) was
then compared to use of the anatomic bony landmarks to
evaluate the accuracy of these landmarks in determining rotation
of the femoral component. Comparing the gap balancing
method to the anatomic landmarks, use of the epicondylar
axis for determination of femoral component rotation was
a mean 0.9º externally rotated (range, 12º internal to 16º external),
with the flexion gap balanced (+/- 3º) 43% of the
time. The posterior condylar axis was a mean of 0.4º internally
rotated (range, 15º internal, 13º external), with the flexion gap
balanced 58% of the time. The anteroposterior axis was a
mean of 1.9º externally rotated (range 13º internal, 18º external),
with the flexion gap balanced 39% of the time.
An additional fluoroscopic analysis of TKA performed utilizing
either measured resection vs. gap balancing methods demonstrated
a significantly lower incidence of femoral condylar
lift-off when a gap balancing technique was used, further
confirming the superiority of use of the gap balancing technique
in obtaining a balanced flexion gap.
CONCLUSION
Surgeons have been shown to be inaccurate in locating the
anatomic landmarks recommended for femoral component
rotation. When anatomic landmarks were used to determine
femoral component rotation, an asymmetric, trapezoidal flexion
gap was frequently observed with an increased incidence
of femoral component lift-off. Rotation of the femoral component
using a gap balancing technique results in better gap
symmetry, which should create more favourable knee kinematic
patterns and reduced polyethylene wear.
REFERENCES
1. Fehring TK. Rotational malalignment of the femoral component
in total knee arthroplasty. Clin Orthop Relat Res.
2000;Nov(380):72-9.
2. Poilvache PL, Insall JN, Scuderi GR, Font-Rodriguez DE.
Rotational landmarks and sizing of the distal femur in total
knee arthroplasty. Clin Orthop Relat Res. 1996;Oct(331):35-
46.
3. Whiteside LA, Arima J. The anteroposterior axis for femoral
rotation alignment in valgus total knee arthroplasty. Clin
Orthop Relat Res. 1995;Dec(321):168-72.