Clinical Application of N+7 Method for the Solution of Graft: Tibial Tunnel Discrepancy in Anterior Cruciate Ligament Reconstruction

ABSTRACT

PURPOSE: The purpose of this study is to prevent the graft-tunnel mismatching by N+7 method and to present the experience of the authors in anterior cruciate ligament reconstruction, using the patellar ten- don by N+7 method. MATERIALS AND METHODS: Authors analyzed 34 cases who had taken the anterior cruciate ligament reconstruction from April 1998 to July 1999, at Asan Medical Center, by N+7 method. By measuring the patellar tendon length(N), tibial guide was set an angle of N+7 degree. We analyzed the results by dividing the cases into 3 groups by the degree of extrusion of the bone plug from the tibial tunnel. RESULTS: Clinical results were acceptable in 79.4%(27 cases), protrusion in 8.8%(3 cases) and recession in 11.8%(4 cases). When the angle of tibial tunnel was less than 50 degrees, there wasn't a protruded case in 19 cases. Comparing with 15 cases of the angle which was larger than 50 degrees, there were three protruded cases. CONCLUSION: Clinical results of anterior cruciate ligament reconstruction using the patellar tendon, with N+7 method is superior to empirical methods which was performed by authors, previously at the point of positioning of ideal tibial tunnel and conveniency of the technique. Especially, if the graft tendon length is shorter than 43mm, N+7 method is preferable.