The pivot shift was analysed using an electrogoniometer linkage (OSI, CA, USA) in
27 patients 18 to 24 months after reconstruction of the anterior cruciate ligament
(ACL). The static passive AP-displacement of the tibia was also measured by a laxity
tester in 20° of knee flexion with a load of 90N. All patients had a positive pivot
shift on manual examination before surgery. At followup 18 patients had normal subjective
knee function according to the Lysholm score and 18 patients had returned to their
preinjury, competitive activity level. Only three patients had a positive pivot shift
on manual testing. In contrast a pivot shift curve was registered with the electrogoniometer
in 18/27 in the operated knee. Their mean maximum tibial translation in the operated
knee during the pivot shift test was 8.1 ± 4.3 mm. In 10 of these patients a pivot
shift-like motion pattern was recorded also in the non-operated knee. Generally patients
with passive sagittal A-P displacement difference of the tibia of > + 2 mm in comparison
to the non-operated knee also had positive instrumented pivot shift tests. In six
control subjects without previous knee injury the electrogoniometer revealed no pivot
shift curve and the mean maximum sagittal translation was only 3.4 ± 1.3 mm. It seems
that pathologic knee motions can be provoked manually in many patients two years after
reconstruction of the ACL in spite of a generally good clinical result. In some patients
also the non-operated knee shows a pathologic motion pattern that could not be demonstrated
in normal subjects. Computerized registration of the pivot shift phenomenon was more
sensitive than ordinary manual testing. These findings are in line with results previously
found in vitro.
Key words
Knee - ligament reconstruction - motion analysis - pivot shift - electrogoniometry
