FACTORS AFFECTING ISOMETRY OF ENDOSCOPIC ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION - THE EFFECT OF GUIDE OFFSET AND ROTATION

Eight normal cadaveric knee specimens were used to evaluate the effect s of femoral and tibial tunnel positions on length excursions of a sin gle wire and bone-patellar tendon-bone graft as measured by an isomete r. Femoral attachment sites were varied by using a commercially availa ble femoral pin guide with either a 5.5- or 7.0-mm offset and by aimin g with the guide oriented vertically (12:00 notch position) or rotatin g 45 degrees toward the lateral condyle (1:30 or 10:30 notch position depending on right or left knee), Tibial isometry was altered by testi ng the wire against the posterior tunnel wall or 5-mm anterior using a custom centering device. Isometry was measured from 0 degrees to 120 degrees for each position tested, A 7-mm offset guide rotated to the 1 2:00 position yielded the best single fiber and graft excursion patter ns (P <.05). A 5.5-mm offset guide yielded inferior single fiber and g raft excursion patterns. Single fiber and graft isometry were found to be similar, but not identical in endoscopic anterior cruciate ligamen t reconstruction. Centering the single fiber in the tibial tunnel had little effect on excursion patterns, showing that the mon posterior ti bial positions needed for endoscopic reconstruction are acceptable fro m an isometry standpoint.