A Simple Radiographic Sign of Vertical Anterior Cruciate Ligament Tunnel Placement

The purpose of this study is to describe a novel radiographic sign indicative of vertical tunnel placement following anterior cruciate ligament (ACL) reconstruction. We reviewed 190 consecutive ACL reconstructions. Operative records, patient charts, arthroscopic images, and preoperative and postoperative orthogonal plain radiographic images were reviewed. We made special note of the operative technique. Note was made of tunnel position and whether the posterior (proximal) aspect of Blumensaat line was violated on standard lateral knee radiographic images. Of 190 patients, 17 patients did not have postoperative imaging and were excluded. Of the 173 remaining knees, 163 were primary ACL reconstructions and 10 were revision ACL reconstructions. We found that no anatomically placed ACL femoral tunnel violated Blumensaat line. In all revision cases exhibiting violation of Blumensaat line, a new femoral tunnel was able to be drilled while completely avoiding the previously placed, nonanatomic ACL femoral tunnel. The principal findings of our study demonstrate that violation of Blumensaat line following ACL reconstruction is an indicator of vertical, nonanatomic femoral tunnel placement. Furthermore, presence of this radiographic sign indicates that an anatomically placed femoral tunnel may be drilled while completely avoiding the existing femoral tunnel during cases of revision ACL reconstruction.