Introduction
Drilling the femoral tunnel via the tibial tunnel (transtibial tunnel drilling or TTTD) has been the standard technique since the early days of anterior cruciate ligament reconstruction (ACLR) and has produced excellent results with both hamstring and patellar tendon grafts. The groundbreaking work of Stephen Howell showed that a coronal angle of 65 degrees is optimal, and this has been universally felt to be easily achievable with TTTD. More recently there has been a trend toward transmedial portal drilling (TMPD) of the femoral tunnel. This trend started in response to the transient trend toward double-bundle reconstruction, which necessitated placing one of the tunnels far down on the wall of the femoral intercondylar notch, which cannot be done transtibially. While meta-analyses have shown marginally overall better results from double-bundle ACLR, other reports have shown no difference, and morbidity and surgical difficulty have been recognized to be greater with double-bundle. Thus most orthopaedic surgeons have now reverted to anatomic single-bundle reconstruction, placing the femoral tunnel in the middle of the femoral footprint of the anterior cruciate ligament (ACL), instead of at the bottom.
Additionally, a recent landmark paper from the lab of Andrew Amis has shown that “66% to 84% of the resistance to tibial anterior drawer arose from the ACL fibers at the central-proximal area of the femoral attachment…corresponding to the anteromedial bundle…The central area resisted 82% to 90% of the anterior drawer force; …and the posterior fan-like area, 11% to 15%.” These findings from arguably the world’s leader in studies of this kind argue powerfully in favor of the easier traditional transtibial drilling of the femoral tunnel rather than the more difficult medial portal technique, since there is now excellent anatomical and biomechanical evidence that drilling near the bottom of the femoral wall is unnecessary and indeed not physiologic.
Transtibial Femoral Tunnel Drilling Advantages
Comfortable Knee Flexion Angle
TTTD can be carried out with the knee flexed to its natural position of roughly 70 degrees as routine arthroscopy is conducted. This technique and the intra-articular view provided are familiar to most orthopaedic surgeons.
Adequate Tunnel Length
TTTD drilling routinely allows femoral tunnels of at least 3 cm in length.
Decreased Graft Abrasion at the Femoral Outlet
One of the original perceived advantages of TTTD is that the graft has a relatively straight course as it enters the femoral tunnel. The tibial and femoral tunnels are essentially colinear with the TTTD technique. This decreases abrasion of the graft at the femoral outlet since the graft is not bent around its entrance point.
Transtibial Femoral Tunnel Drilling Advantages
Comfortable Knee Flexion Angle
TTTD can be carried out with the knee flexed to its natural position of roughly 70 degrees as routine arthroscopy is conducted. This technique and the intra-articular view provided are familiar to most orthopaedic surgeons.
Adequate Tunnel Length
TTTD drilling routinely allows femoral tunnels of at least 3 cm in length.
Decreased Graft Abrasion at the Femoral Outlet
One of the original perceived advantages of TTTD is that the graft has a relatively straight course as it enters the femoral tunnel. The tibial and femoral tunnels are essentially colinear with the TTTD technique. This decreases abrasion of the graft at the femoral outlet since the graft is not bent around its entrance point.
Trans Femoral Tunnel Disadvantages
Difficult Knee Flexion Angle
In TMPD, drilling must be done with the knee hyperflexed to over 110 degrees. Such hyperflexion provides both reduced visibility and a view that is unfamiliar to most orthopaedic surgeons as they search for femoral footprint landmarks. Such hyperflexion can also be difficult to maintain in lower extremities of large girth, which has become increasingly common in patients.
Shorter Femoral Tunnel Length
TMPD has the further disadvantage that it tends to produce shorter femoral tunnels, which may be too short for proper fixation with buttons or cross-pins.
Increased Graft Femoral Tunnel Abrasion
TMPD causes the graft to enter the femoral tunnel at a significant angle, since the femoral tunnel is drilled at a different angle (i.e., more horizontally) than the tibial tunnel. This angle subjects the graft to greater abrasive stresses than are seen with TTTD.
Related posts:
Risk of Anterior Cruciate Ligament Injury as a Function of Type of Playing Surface
Hamstring Harvest Technique for Anterior Cruciate Ligament Reconstruction
Intraoperative Fluoroscopy for Anterior Cruciate Ligament Tunnel Placement
Arthrex TightRope Fixation of a Soft Tissue Graft
Sonographically Guided Anterior Cruciate Ligament Injection: Technique and Potential Use for the Treatment of Partial Anterior Cruciate Ligament Tear
Factors Associated with Increased Allograft Failure Rate in Anterior Cruciate Ligament Reconstruction
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