POSITIONING OF THE TIBIAL TUNNEL FOR ANTERIOR CRUCIATE LIGAMENT RECONSTRUCTION

Two mechanisms of unintentional anterior tibial tunnel axis shift can occur despite accurate placement of the guide wire within the proximal tibia. The first results from using a short-block reamer head joined to a shaft of smaller diameter. If the tibial tunnel is drilled obliqu ely, it is possible for the reamer head to displace anteriorly in the knee joint before completion of the posterior portion of the tibial tu nnel. The second mechanism of anterior shift involves using two sequen tial drills to create the tibial tunnel. To delineate the causes of th is unwanted shift, cadaveric studies and special roentgenographic stud ies were undertaken. Results demonstrated that the shift is related di rectly to the presence of high-density bone in the tibial plateau. In an effort to minimize this effect, various drill designs were tested, and it was determined that a drill-head length of 25 mm was most effec tive at reducing the shift without sacrificing the freedom of movement necessary to obtain precise endosteal placement of the femoral tunnel . Along with these experimental studies, a retrospective 7-year review of anterior cruciate ligament (ACL) reconstruction failures was perfo rmed to assess the clinical significance of inadvertent anterior posit ioning of the tibial tunnel.