Outside-in vs. Transportal Technique for ACL reconstruction
Computed Tomography Analysis of the Femoral Tunnel Position and Aperture Shape of Transportal and Outside-In ACL Reconstruction: Do Different Anatomic Reconstruction Techniques Create Similar Femoral Tunnels?Am J Sports Med. 2013 Nov;41(11):2512-20
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80 patients who had experienced a primary unilateral anterior cruciate ligament (ACL) injury were randomly assigned into 1 of 2 groups to compare femoral tunnel aperture shape and femoral tunnel position. Patients received either a transportal (group 1) or outside-in (groups 2) technique for ACL reconstruction. The results of the study indicated that the transportal (TP) technique led to a more ellipsoidal anteromedial (AM) femoral tunnel aperture than the outside-in (OI) technique, and that mean posterolateral femoral tunnel position with the OI technique was significantly shallower, with more variable/perpendicular aperture axis angle to the femoral shaft axis than the TP technique.
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
Inclusion / Exclusion
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Recent interest regarding anatomic anterior cruciate ligament (ACL) reconstruction has led to further research on the anatomy and biomechanics of the native ACL. Current anatomic ACL reconstruction techniques place tunnels in the center of the native femoral and tibial insertion sites with the goal of restoring physiological function of the native ACL. Due to certain restraints with the conventional non-anatomic ACL reconstruction (through the transtibial technique), popularity of the transportal (TP) and outside-in (OI) techniques has risen, because of their focus on independent drilling to form the femoral tunnel. Previous studies have compared non-anatomic to anatomic ACL reconstruction techniques and have demonstrated favourable results for ACL reconstruction with the use of anatomic techniques, but no studies have thoroughly compared TP to OI techniques in terms of femoral tunnel aperture.
What was the principal research question?
How does the femoral tunnel aperture shape and femoral tunnel position compare between transportal and outside-in techniques when performing anterior cruciate ligament reconstruction?
What were the important findings?
- Average H/W ratio of the AM femoral tunnel was 1.35 +/- 0.16 in the TP group and 1.22 +/- 0.16 in the OI Group, demonstrating a significantly more elliptical aperature in the TP group than the OI Group (p=0.008).
- No significant differences in PL femoral tunnels was found between the two groups (H/W ratio = 1.32 +/- 0.23 in the TP group vs. 1.35 +/- 0.29 in the OI group) (p=0.99).
- Mean aperture axis angle in the PL femoral tunnel of the OI group (23.3 degrees +/- 27.1 degrees) was more perpendicular to the femoral shaft axis and had a larger variable range than the TP group (8.09 degrees +/- 7.70 ) (p=0.007).
- No significant differences in AM femoral tunnels were found between the groups regarding axis angle (TP group = 17.5 degrees +/- 17.3 vs. 18.4 degrees +/- 23.5) (p=0.87).
- Mean distance of the AM and PL femoral tunnel positions parallel to the Blumensaat line were 23.6% +/- 3.7 and 33.9% +/- 5.8 in the TP group respectively, and 24.6% +/- 4.4% and 37.5% +/- 5.0 in the OI group respectively, along the line measured from the posterior border of the medial wall of the lateral condyle.
- Mean distance of the AM and PL femoral tunnel positions perpendicular to the Blumensaat line were 19.1% +/- 8.8 and 49.5% +/- 7.8 in the TP group respectively, and 21.1% +/- 9.7and 51.1% +/- 9.5% in the OI group respectively, along the line measured from Blumensaat line.
- No significant differences in AM femoral tunnel position between the two groups were found. However, mean PL femoral tunnel position parallel to the Blumensaat line in the OI group was shallower in the arthroscopic view than in the TP group (p=0.06).
What should I remember most?
The mean height/width ratio of the AM femoral tunnels in the TP group was significantly greater than the OI group. No difference between the groups in PL tunnels regarding height/width ratio was found. Mean aperture axis angle of the PL femoral tunnels was significantly more perpendicular to the femoral shaft axis and had more variable range in the OI group when compared to the TP group. Mean PL femoral tunnel position in the OI group was significantly shallower and slightly higher than the TP group.
How will this affect the care of my patients?
The findings of the study would suggest that a TP technique may be more advantageous than OI in terms of graft coverage, due to a more ellipsoidal AM femoral tunnel and horizontal/consistent PL aperture axis angle. However, it may be useful to take into account the shallower PL femoral tunnel positions that occur when using the OI technique. Further research on this topic, with standardised starting positions, must be completed to verify these results. Also, whether these differences result in better clinical outcome with either technique should also be determined.
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