– by Shail M. Vyas, MD; Freddie H. Fu, MD, DSc.(Hon) DPs
The core principle of anatomic
double-bundle reconstruction is to reproduce the native
anatomy of the ACL. Anatomic double-bundle ACL reconstruction continues to gain
interest as it has been shown to better restore native kinematics of the knee
when compared to traditional single bundle techniques.
The principle of double-bundle ACL reconstruction is fourfold. First and
foremost, the native anatomy of the ACL is reproduced. Second, this is done by
appropriately identifying the femoral and tibial insertion sites of both the
anteromedial (AM) and posterolateral (PL) bundles. Third, the implanted bundles
can match the measured dimensions of the patient’s native ligament to
individualize ACL reconstruction for that patient. Finally, these bundles can
be independently tensioned to act as the native ligament does at varying
degrees of knee flexion and rotation.
The patient is positioned supine on the operating table with the
affected knee secured in a leg holder and bent over the end of the table,
allowing at least 120° of knee flexion. The contralateral limb is
positioned in the high lithotomy position away from the surgical field. We
prefer the use of a pneumatic tourniquet.
three portals utilized in double-bundle ACL reconstruction are shown here:
The high anterolateral portal (LP), the central medial portal (CMP), and
accessory medial portal (AMP).
Images: Fu FH
A three-portal technique is utilized to optimize visualization (Figure
1). First, the high anterolateral portal is created at the intersection between
the inferior pole of the patella and the lateral border of the patellar tendon.
This portal gives us an excellent “birds-eye” view of the tibial
insertion site. Next, under direct visualization, a low central medial portal
and an accessory medial portal are both created. The low central medial portal
gives an excellent view of the lateral wall of the femoral notch. Using the
central medial portal as viewing portal obviates the need for a notchplasty as
the whole lateral wall of the notch can be seen from this angle. Furthermore,
it allows visualization of the fine anatomical details of the lateral wall of
The tibial insertion site is evaluated with the camera looking down the
anterolateral portal. The tibial stump of the ACL is carefully dissected and
debrided identifying the AM and PL bundles. Using a cautery device, the center
of the AM and center of the PL insertion sites are marked. The length of the
total insertion site is measured as well as the size of the individual bundles
with an arthroscopic ruler. At least 14 mm are required to accommodate a
double-bundle reconstruction. The insertion site diameter for each bundle is
the same size that is used when the graft is being prepared to individualize
bundle size for each patient.
Freddie H. Fu
While directly viewing the lateral wall of the notch through the central
medial portal, the femoral insertion site is cleared with a cautery device
through the accessory medial portal. Both the AM and PL bundle femoral
insertion sites are carefully dissected and the intercondylar ridge is
visualized. This ridge runs from superior to inferior — and appears
transverse with the knee in the flexed operating position — and marks the
most anterior border of the ACL. In the operating position with the knee flexed
90°, the intercondylar ridge is the upper limit of the ACL femoral
insertion site. A second ridge, the lateral bifurcate ridge, runs anterior to
posterior and is seen as a vertical ridge in the operating position, and marks
the boundary between the femoral AM and PL insertion sites (Figure 2). The
width of the femoral notch is measured with an arthroscopic ruler. A minimum of
12 mm of notch width is required to accommodate double-bundle reconstruction.
Then, the total length of the femoral insertion site is measured. A minimum of
14 mm is required to accommodate two tunnels for double-bundle reconstruction.
A pointed awl is then used to mark the center of both the AM and PL tunnels.
The femoral PL tunnel is then drilled over a guidepin through the accessory
medial portal. This tunnel is drilled with the knee flexed maximally (at least
110°). This knee flexion angle allows for maximum tunnel length and allows
the tunnel to exit anterior to the peroneal nerve. The tunnel is drilled to 20
mm by a power acorn reamer, and then by hand to the appropriate depth required
for suspensory femoral fixation.
A standard anteromedial skin incision is made over the proximal tibia
centered between the anterior tibial crest and the medial tibial crest. We
prefer a “tip-directed” tibial tunnel aiming guide to advance our
guide pins. The tibial tunnel aiming guide is set to 45° and the tip of the
guide is placed in the center of the tibial PL bundle footprint. A guide pin is
advanced starting from a more medial position on the anteromedial tibia. The
guide is reset to 55° and the tip of the guide is placed in the AM bundle
footprint. Starting from a more lateral position on the anteromedial tibial
surface, a second guide pin is advanced. On the tibia, the pins should be
sufficiently apart such that when the tunnels are drilled, there remains at
least a 10 mm bone bridge on the anteromedial tibial surface. The tunnels are
then drilled, PL tunnel first, to the pre-determined size based on the diameter
of the patient’s tibial insertion sites.
Double bundle ACL
reconstruction begins with identification of the tibial (A) and femoral (B)
insertion sites of the AM and PL bundles. Once the four tunnels are drilled
(C), the grafts are passed and fibrin clot is inserted between the two bundles
The AM tunnel can be drilled with the knee at 90° in three ways. It
can be drilled through the tibial AM tunnel, through the tibial PL tunnel, or
through the accessory medial portal. In our experience, approaching the femoral
AM insertion site through the tibial PL tunnel is successful over 60% of the
time whereas approaching the femoral AM insertion site through the tibial AM
tunnel is successful only approximately 10% of the time. The femoral tunnel is
then drilled to a depth of 20 mm and then further hand-drilled per suspensory
femoral fixation specifications.
The soft tissue graft is prepared to meet the anatomical specifications
of the individual patient based on pre-measured insertion sites. The PL bundle
soft tissue graft is then advanced from the tibial PL tunnel through the
femoral PL tunnel. It is then secured on the femoral side with a suspensory
fixation device. Next, the AM bundle soft tissue graft is advanced from the
tibial AM tunnel through the femoral AM tunnel. It too is secured on the
Magnetic resonance image of the reconstructed
ACL with the double bundle technique (A). Three dimensional computed
tomography scan identifies the femoral and tibial tunnels created during double
bundle reconstruction (B). SOURCE
The graft is then checked for impingement on both the notch and the
posterior cruciate ligament. Ideally, with an anatomic ACL reconstruction,
there should be no impingement as we have recreated the pre-existing anatomy of
the native ACL. With tension on both grafts, the knee is cycled 20 times
through a full range of motion, from full extension to maximum flexion. The PL
bundle is then fixed in full extension and next, the AM bundle is fixed in
45°. We prefer biointerference screws for our tibial fixation (Figure 3).
The anatomical details of the lateral
wall of the notch are appreciated through the medial portal when the
femoral stump of the ACL is debrided. The lateral intercondylar ridge marks the
anterior limit of the ACL while the lateral bifurcate ridge demarcates the
transition from the anteromedial (AM) to postlateral (PL) bundle femoral
Recently, we have added the concept of the
fibrin clot to our double-bundle ACL reconstruction to
augment biologic healing of the graft. During the operation, 50 to 60
milliliters of blood are drawn from the patient and stirred in a beaker until a
clot forms. Part of this clot is sutured within the proximal and distal ends of
the soft tissue graft of both bundles. The remainder of the clot is placed
between the two reconstructed bundles. Once both bundles are fixed on the
femoral side and the PL bundle is fixed on the tibial side, the AM bundle (not
yet fixed on tibial side) is pulled apart from the PL bundle with a suture
around its waist. A cannula is then introduced through the accessory medial
portal and the clot is deposited through the cannula and into the gap created
between the bundles. The suture around the AM bundle is then released and the
AM bundle is fixed, resulting in a “sandwich” effect of the clot
between the two bundles (Figure 4).
Currently, in 30% of all cases, we perform matched anatomic single
bundle reconstructions. Indications are a small native femoral or tibial
insertion site — less than 14 mm, a severe lateral femoral condyle bone
bruise, open physes, significant arthritic changes, a narrow notch,
multi-ligamentous knee injury, and a one bundle tear (AM or PL). Understanding
the double bundle principle is helpful in placing the single bundle tunnels in
the correct anatomic position.
Postoperatively, the patient’s knee is immobilized in a knee
immobilizer locked in full extension. The patient is abled to ambulate with
crutches with the braced locked until the first postoperative visit 1 week
after surgery. The brace may be removed for ROM exercises at home. The brace
can be unlocked after the first postoperative week. The brace is typically
discontinued after 6 weeks. The focus of the first 6 weeks is to regain ROM.
Subsequently, strengthening protocols are gradually integrated into the
postoperative regimen. We prefer a gradual return to activity. Inline
activities are permitted between 3 and 6 months. Cutting activities are
permitted between 9 and 12 months. A prophylactic ACL brace is utilized for the
initial period of return to sport.
- Freddie H. Fu, MD, can be reached at The University of Pittsburgh
Department of Orthopaedic Surgery, 3471 Fifth Ave., Pittsburgh, PA 15213;
412-605-3203; e-mail: email@example.com.