INSTRUMENTED ANALYSIS OF THE PIVOT SHIFT PHENOMENON AFTER RECONSTRUCTION OF THE ANTERIOR CRUCIATE LIGAMENT

The pivot shift was analysed using an electrogoniometer linkage (OSI, CA, USA) in 27 patients 18 to 24 months after reconstruction of the an terior cruciate ligament (ACL). The static passive AP-displacement of the tibia was also measured by a laxity tester in 20(.) of knee flexio n with a load of 90N. All patients had a positive pivot shift on manua l examination before surgery. At follow-up 18 patients had normal subj ective knee function according to the Lysholm score and 18 patients ha d returned to their preinjury, competitive activity level. Only three patients had a positive pivot shift on manual testing. In contrast a p ivot shift curve was registered with the electrogoniometer in 18/27 in the operated knee. Their mean maximum tibial translation in the opera ted knee during the pivot shift test was 8.1 +/- 4.3 mm. In 10 of thes e patients a pivot shift-like motion pattern was recorded also in the non-operated knee. Generally patients with passive sagittal A-P displa cement difference of the tibia of > + 2 mm in comparison to the non-op erated knee also had positive instrumented pivot shift tests. In six c ontrol subjects without previous knee injury the electrogoniometer rev ealed no pivot shift curve and the mean maximum sagittal translation w as only 3.4 +/- 1.3 mm. It seems that pathologic knee motions can be p rovoked manually in many patients two years after reconstruction of th e ACL in spite of a generally good clinical result. In some patients a lso 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 tes ting. These findings are in line with results previously found in vitr o.