Vol.:(0123456789) 1 3 Knee Surgery, Sports Traumatology, Arthroscopy https://doi.org/10.1007/s00167-018-5150-9 KNEE Proximal fxation anterior to the lateral femoral epicondyle optimizes isometry in anterolateral ligament reconstruction Brian Forsythe 1  · Avinesh Agarwalla 1  · Drew A. Lansdown 2  · Richard Puzzitiello 1  · Nikhil N. Verma 1  · Brian J. Cole 1  · Bernard R. Bach 1  · Nozomu Inoue 1 Received: 5 June 2018 / Accepted: 19 September 2018 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2018 Abstract Purpose Concomitant anterolateral ligament (ALL) injury is often observed in patients with an anterior cruciate ligament injury leading some to recommend concurrent ALL reconstruction. In ligament reconstruction, it is imperative to restore desirable ligament length changes to prevent stress on the graft. The purpose of this investigation is to identify the optimal femoral and tibial locations for fxation in ALL reconstruction. Methods 3D computerized tomography (CT) knee models were obtained from six fresh-frozen, unpaired, cadaveric human knees at 0°, 10°, 20°, 30°, 40°, 90°, 110°, and 125°of knee fexion. Planar grids were projected onto the lateral knee. Isometry between each tibial and femoral grid point was calculated at each angle of fexion by the length change in reference to the length at 0° of knee fexion. The mean normalized length change over the range of motion was calculated for each combina- tion of points at all angles of fexion were calculated. Results Fixation of the ALL to the lateral femoral epicondyle or 5 mm anterior to the epicondyle with tibial fxation on the posteroinferior aspect of the tibial condyle (14–21 mm posterior to Gerdy’s tubercle and 13–20 mm below the joint line) provided the lowest average length change for all possible ALL tibial insertion points. Minimal length change for all femoral fxation locations occurred from 20° to 40° of fexion, which identifes the angle of fexion where graft tensioning should occur intraoperatively. Conclusion With the use of 3D reconstructed models of knee-CT scans, we observed that there was no ALL fxation point that was truly isometric throughout range of motion. Fixation of the anterolateral ligament on the lateral femoral epicon- dyle or anterior to the lateral femoral epicondyle and on the inferoposterior aspect of the tibial condyle restores isometry. Additionally, minimal length change was observed between 20° and 40° of fexion, which is the most appropriate range of knee fexion to tension the graft. Reproducing isometry reduces stress on the graft, which minimizes the risk of graft failure. Keywords Anterolateral ligament · Isometry · Anterior cruciate ligament · Anterolateral ligament reconstruction · 3-Dimensional knee model Introduction Concomitant anterolateral ligament (ALL) injury has been observed in 33–90% of patients with an anterior cruciate ligament (ACL) injury [3, 9, 14]. The ALL functions as an internal rotation stabilizer, especially at knee fexion angles greater than 35°, where the contribution of the ALL exceeds that of the anterior cruciate ligament [4, 27, 29]. Intra-artic- ular ACL reconstruction restores anterior–posterior kin- ematics; however, internal laxity may remain, most likely due to the defciency of the anterolateral ligament [18, 26]. Concomitant anatomical anterolateral ligament reconstruc- tion during ACL reconstruction reduces internal laxity, and has recently shown to provide satisfactory patient outcomes [38]. Given the association between ALL injury with a posi- tive pivot-shift examination following ACL reconstruction, this has led some to recommend concurrent ALL reconstruc- tion [26, 35]. * Brian Forsythe forsythe.research@rushortho.com 1 Midwest Orthopaedics at Rush, Rush University Medical Center, Chicago, IL, USA 2 University of California, San Francisco, San Francisco, CA, USA