Summary

Variability is relatively large when using transportal technique comparing to using transtibial technique with guiding system, it is necessary to build an objective system for accurate femoral entry position in transportal technique.

Abstract

Introduction

Anatomical reconstruction is known to be an effective way to reproduce the original ACL femoral insertion. Therefore, ACL reconstruction using trasportal technique for anatomical femoral tunnel position has recently been performed often, but there is high possibility that femoral tunnel position is not made at the planned position due to the absence of objective guiding system in femoral tunnel drilling. In ACL reconstruction using transtibial technique, femoral tunnel is less likely to be located at anatomical position than using transportal technique, but it has also been reported that anatomical reconstruction can be achieved using modified transtibial technique. Femoral tunnel guide at modified transtibial technique can reduce intersurgeon variability by positioning femoral tunnel at the planned position.

Purpose

The purpose of this study is to compare femoral tunnel entry position in ACL reconstruction using transportal technique and modified transtibial technique, and to figure out the variability of femoral tunnel entry in each technique.

Methods

Eighty-six patients (86 knees), who underwent arthroscopic anatomical ACL reconstruction using transportal (43 knees) and transtibial (43 knees) technique by two different orthopedic surgeons from 2014 to 2018, were included. For all patients, 3D computed tomography were taken after ACL reconstruction and reconstructed using Mimics program. Bernard's quadrant method was used to measure femoral tunnel entry. Variability in one surgeon and the mean value between two surgeons were compared using independent two-sample t-test.

Result
The mean values of relative depth of femoral tunnel from posterior wall was 27.12% in tranportal technique and 33.58% in modified transtibial technique, and the mean value of relative height of femoral tunnel from Blumensaat line was 26.09% in tranportal technique and 17.14% in modified trantibial technique, with significant differences between the two surgeons. Height difference from Blumensaat line (8.95%) was greater than difference in depth from posterior wall (6.46%) (p <0.05). Range of measured values using standard deviation was quite wide, with values from posterior wall to femoral tunnel in each surgeon being 27.12±3.92 in tranportal technique and 33.58±3.54% in modified trantibial technique, and those from Blumensaat line to femoral tunnel in each surgeon being 26.09±5.82% in tranportal technique and 17.14±3.85% in modified trantibial technique. These results showed that the range of relative height of femoral tunnel from Blumensaat line was greater. There were significant differences in the mean values of femoral tunnel placement in each technique, and variability in each surgeon was large in tranportal technique.

Conclusion

Although anatomical femoral entry is made at the closest position to surgeon’s planning using tranportal technique, variability of tunnel point in one surgeon is large. On the other hand, variability in modified trastibial technique using femoral tunnel guide is relatively low. Therefore, it is necessary to make efforts to reduce variability and build an objective system for accurate femoral entry position in transportal technique.