THE EFFECT OF KNEE EFFUSIONS ON KT-1000 ARTHROMETRY - A CADAVER STUDY

We studied five fresh-frozen lower extremity cadaveric specimens to as sess the effect of knee effusions on KT-1000 arthrometry, Part 1 consi sted of serial 10-ml injections (up to 100 mi) of saline into each kne e and measurements of midpatellar knee circumference and anterior disp lacement using the KT-1000 arthrometer at 67, 89, and 134 N after each 10-ml increment. Part 2 consisted of evacuation of the saline and tra nsection of the anterior cruciate ligament through a 2-cm medial parap atellar arthrotomy, Each knee again underwent the part 1 protocol, Seq uential injections in parts 1 and 2 showed incremental increases in kn ee circumference and KT-1000 arthrometer measurements for all three fo rce levels. A 3-mm increase in anterior translation compared with the value at 0-ml injection was obtained by the 70-ml injection point in b oth groups. At the 70-ml injection point, the patella was ballottable, thereby affecting anterior measurements-despite posterior force on th e patella sensor pad-because of the KT-1000 arthrometer reference leve l at midpatella. This increase in KT-1000 arthrometer readings could e rroneously imply anterior cruciate ligament disruption in the clinical situation of right-to-left comparison. We conclude that clinicians us ing the KT-1000 arthrometer should aspirate knees that have effusions and a ballottable patella to minimize false-positive readings.