an Markers Injected Into a Single- oop Anterior Cruciate igament Graft Define the Axes of the ibial and Femoral Tunnels? A adaveric Study Using Roentgen tereophotogrammetric Analysis

engthening of a soft-tissue anterior cruciate ligament (ACL) raft construct over time, which leads to an increase in anterior axity following ACL reconstruction, can result from relative moions between the graft and fixation devices and between the fixaion devices and bone. To determine these relative motions using oentgen stereophotogrammetry (RSA), it is first necessary to dentify the axes of the tibial and femoral tunnels. The purpose of his in vitro study was to determine the error in using markers njected into the portions of a soft-tissue tendon graft enclosed ithin the tibial and femoral tunnels to define the axes of these unnels. Markers were injected into the tibia, femur, and graft in ix cadaveric legs the knees of which were reconstructed with ingle-loop tibialis grafts. The axes of the tunnels were defined by arker pairs that were injected into the bones on lines parallel to he walls of the tibial and femoral tunnels (i.e., standard). By sing marker pairs injected into the portions of the graft enclosed ithin the tibial and femoral tunnels and the marker pairs aligned ith the tunnel axes, the directions of vectors were determined by sing RSA, while a 150 N anterior force was transmitted at the nee. The average and standard deviations of the angle between he two vectors were 5.5 3.3 deg. This angle translates into an verage error and standard deviation of the error in lengthening uantities (i.e., relative motions along the tunnel axes) at the sites f fixation of 0.6 0.8 %. Identifying the axes of the tunnels by