CT Scan Assessment of Femoral Tunnel Location in ACL Reconstruction Performed During Initial Phase of the Learning Curve

Abstract

Introduction:During anterior cruciate ligament (ACL) reconstruction, femoral tunnelling is one of the most imperative stage. The success of surgical reconstructions of the ACL depends on the accurate restoration of its anatomy. The significance of the location of the hole drilled in femur has been repeatedly highlighted in ACL reconstruction. Incorrect tunnel placement is not infrequent, and even with diligent training, and aids, surgeons may still have difficulty in correctly positioning tunnels intra-operatively. Usually susceptible are surgeons in initial phase of the learning curve.Objective:To determine the susceptibility of surgeons in initial phase of learning curve while drilling femoral tunnel.Methods:All patients diagnosed with ACL rupture at a single institution between August 2018 and September 2019 were considered for the study. The surgeons who were relatively new out of their fellowship and training programmes (average of less than one years of independent practice) performed all surgical reconstructions, the number of reconstructions done independently was also taken into consideration (average of less than five independent procedures done before commencement of this study). We used anatomic free hand technique using bony and anatomic indicators as our markers, assisted by ruler, to drill femoral tunnel. Every subject had an 128 slice 3D CT-Scan done in immediate post-op period. High resolution 3-Dimensional view was created of the knee to evaluate the tunnel location. The position of the femoral tunnel was evaluated using the Bernard and Hertel quadrant method. The Femoral tunnel location was expressed in terms of its distance from the notch and posterior wall of condyle, the results were expressed in terms of percentage.Results:A net total of 32 patients were included who underwent single bundle ACL reconstruction. In our study, measurement of femoral tunnel placement was - depth 37.1% and height 24.6%, represented as percentage depth (deep to shallow (t)) and height (high to low (h)). Our results were compared with other established studies. The value of height was near to that mentioned in literature; whereas the value of depth was shallower (or distal) when compared to established literature with average location being 10.7% shallower (or distal) to anteromedial bundle insertion mentioned in study by Colombet et al and 4.8% shallower when compared to study by Zantop et al. When compared to study by Bernard and Hertel the location is 12.3% shallower. The reason for comparison with anteromedial bundle is that in single bundle anatomical reconstruction Pearle et al , Segawa et al and Simmons et al advocate it to be anteromedial.Conclusion:The surgeons in initial phase of their learning curve may be more prone to shallow (non anatomic) location of femoral tunnel during single bundle ACL reconstruction. We infer that this discrepancy in proximal (deep) to distal (shallow) orientation is due to fear of posterior wall blow out, that is the violation of the posterior femoral cortex, a known intraoperative complication in ACL reconstruction.