R. Nagamine et al., EFFECT OF ROTATIONAL MALPOSITION OF THE FEMORAL COMPONENT ON KNEE STABILITY KINEMATICS AFTER TOTAL KNEE ARTHROPLASTY, The Journal of arthroplasty, 10(3), 1995, pp. 265-270
Excessive external rotation of the femoral component can cause an abno
rmally tight popliteus tendon complex, which induces loss of rotationa
l laxity of the knee in the late phase of knee flexion after total kne
e arthroplasty. This study evaluated the effect of popliteus tendon re
lease on rotational and varus-valgus laxity of implanted knees with an
excessively externally rotated femoral component. Rotational and varu
s-valgus laxity was measured with a knee kinematics testing device bef
ore and after total knee arthroplasty. External rotational positions o
f the femoral component of 5 degrees and 8 degrees were compared, and
the effects of popliteus tendon release on rotational and varus-valgus
laxity were evaluated. To further investigate this question, the effe
ct of a conforming articular design was compared with that of a hat ti
bial surface. External rotational position of 5 degrees did not change
rotational or varus-valgus laxity of the knee. With an 8 degrees exte
rnal rotational position, however, external rotational laxity signific
antly decreased in knees with a conforming surface at angles of 30 deg
rees, 45 degrees, 60 degrees, and 90 degrees. After popliteus tendon r
elease, external rotational laxity significantly improved at 90 degree
s flexion and was identical to that of the normal knee. Internal rotat
ional range was similar before and after popliteus tendon release. Pop
liteus tendon release did not affect the varus-valgus laxity (stabilit
y) with either articular surface.