Steven B. Cohen and Freddie H. Fu
DEFINITION
Anterior cruciate ligament (ACL) tears have been described in detail in Chapter SM-41.
Any patient with functional instability or pivoting of the knee is considered to have an ACL insufficiency.
ANATOMY
To fully understand the principles of ACL reconstruction, it is important to understand the complex anatomy of the ACL, which is composed of two major bundles.
These bundles are named relative to their relation to the tibial footprint: the posterolateral (PL) bundle is posterior and lateral on the tibial footprint, whereas the anteromedial (AM) bundle is anterior and medial on the tibial footprint.
The PL bundle originates more distally and anteriorly relative to the AM bundle on the wall of the intercondylar notch.
The femoral insertion site of ACL changes based on flexion angle (FIG 1).
With the knee in full extension, the alignment of the AM and PL bundle insertion sites on the femur is vertical.
With the knee in 90 degrees of flexion, the insertion sites are horizontal, with the PL bundle insertion site anterior to that of the AM bundle.
Measurements of individual bundles have found the AM bundle to be, on average, 38.5 mm long and 7.0 mm wide, whereas the PL bundle is 19.7 mm long and 6.4 mm wide.4,5,8
When the knee is extended, the PL bundle is under tension and the AM bundle is moderately lax.
With knee flexion, the AM bundle tightens and the PL bundle becomes lax.
With internal and external rotation of the tibia at 90 degrees of flexion, the PL bundle tightens.
BIOMECHANICAL STUDIES
ACL single-bundle reconstruction using either patellar tendon or quadrupled hamstring autograft successfully limits anterior tibial translation but provides insufficient control of the combined rotatory load of internal and valgus torque.9
In a single-bundle ACL reconstruction, rotatory stability was improved with the use of the 2 o'clock or 10 o'clock femoral tunnel position compared with the 1 o'clock or 11 o'clock position. Neither the 10 o'clock nor the 11 o'clock tunnel position could restore the kinematics and the in situ forces of the intact knee, however.6
PATIENT HISTORY AND PHYSICAL FINDINGS
The history of a noncontact valgus pivoting injury followed by an effusion of the knee is highly suspicious for an ACL tear.
The physical examination and methods for examination of the ACL are covered in Chapter SM-41.
Patients with a partial or single-bundle tear may have either a positive pivot shift or positive Lachman test. For example, an intact AM bundle and torn PL bundle may have a normal Lachman and positive pivot shift, whereas an intact PL bundle and a torn AM bundle may have a normal pivot shift and an increased Lachman test.
IMAGING AND DIAGNOSTIC STUDIES
Radiographs should include the following views.
30-degree flexion weight-bearing posteroanterior view
Lateral
Sunrise view of the patella
Long-leg alignment view in the case of coronal angular deformity
FIG 1 • Anatomy of the anterior cruciate ligament (ACL). The femoral insertion of the anteromedial (AM) and posterolateral (PL) bundles varies based on degree of flexion. At 0 degrees, the femoral insertion is vertical, with the AM bundle superior to the PL bundle (A), whereas at 90 degrees, the femoral insertion is horizontal, with the PL bundle anterior to the AM bundle (B).
MRI should be used to confirm the suspicion of an ACL tear and look for associated injuries of the chondral surfaces (including bone bruises), meniscus, patella, and other ligamentous structures.
A KT-1000 arthrometer test is performed to determine absolute translation and side-to-side translation difference.
DIFFERENTIAL DIAGNOSIS
Meniscal tear
Osteochondral injury
Contusion
Patellar dislocation
Other ligament/capsular injury (eg, medial collateral ligament, lateral collateral ligament, posterolateral corner, multiple ligament injury)
It is important to remember that patella dislocation may mimic the initial presentation of ACL tear.
NONOPERATIVE TREATMENT
Potential nonoperative candidates and rehabilitation protocol are detailed in Chapter SM-41.
SURGICAL TREATMENT
Indications
The indications for anatomic double-bundle ACL reconstruction are similar to those for traditional single-bundle reconstruction.
Patients with recurrent instability or episodes of giving way or those who are unable to return to activities of daily living or sports are appropriate for surgical reconstruction.
Patients with complaints of instability and a single-bundle or “partial” tear may benefit from single-bundle augmentation, or double-bundle reconstruction in the event the remaining bundle is incompetent.
Double-bundle reconstruction has been useful in the revision setting, particularly when the previous femoral tunnel placement was in the traditional “over the top” position, which is too high in the femoral notch. This allows anatomic placement of the two femoral tunnels without interfering with the previous tunnel.
Contraindications
We have not found any contraindication to this procedure in the skeletally mature patient.
Neither the height of the patient nor the size of the knee has been a factor when performing the surgery.
Evaluation Under Anesthesia
Range of motion in comparison to the contralateral knee
Ligamentous examinatio.
Lachman
Pivot shift
Varus and valgus stress
Anterior and posterior drawer
Positioning
The patient is positioned supine on the operating table, and the nonoperative leg is placed in a well-leg holder in the abducted lithotomy position.
A pneumatic tourniquet is applied around the upper thigh of the operative leg, the operative limb is exsanguinated by elevation for 3 minutes, and the tourniquet is insufflated to 300 to 350 mm Hg, depending on patient size.
The operative leg is positioned in an arthroscopic leg holder and prepared and draped.
Approach
The portals used for this procedure3 are slightly different from standard arthroscopy portals (FIG 2).
The anterolateral portal is placed more superior, at the level of the inferior pole of the patella, just lateral to the patella tendon.
A central anteromedial portal is placed just below the inferior pole of the patella, approximately 1 cm lateral to the medial edge of the patella tendon (intratendinous central portal).
An accessory anteromedial portal is established using direct visualization with an 18-gauge spinal needle, which is inserted medially and distally to the inferomedial portal, just above the anterior medial meniscus.
The accessory medial portal is used for better access to the lateral wall of the intercondylar notch when placing the femoral PL tunnel and femoral AM tunnel if transtibial tunnel location placement is unacceptable.
The arthroscope is placed in the central anteromedial portal during femoral tunnel placement for better visualization of the intercondylar notch.
The arthroscope is placed in the anterolateral portal for tibial tunnel placement.
FIG 2 • Portal placement for anatomic double-bundle ACL reconstruction.
TECHNIQUES
DIAGNOSTIC ARTHROSCOPY
Thorough inspection of the joint, including.
Patellofemoral joint compartment
Lateral compartment and meniscus
Medial compartment and meniscus
Posterior cruciate ligament
ACL
Any associated meniscal or chondral lesions are addressed before the ACL reconstruction.
The torn ACL is dissected carefully using a thermal device to determine the injury pattern and with special attention to the anatomic footprints of the two ACL bundles, on the lateral wall of the intercondylar notch and on the tibial insertion (TECH FIG 1).
Injury patterns may include the following.
Tear or stretch of one or both bundles
Injury from femoral insertion, tibial insertion, and midsubstance
There are 25 different injury patterns.
Anatomic insertion sites of the AM and PL bundles on the tibia and femur are marked.
The tibial footprints are left intact because of their proprioceptive and vascular contributions.
TECH FIG 1 • Dissection and marking of the femoral insertion of the ACL with a thermal device.
POSTEROLATERAL FEMORAL TUNNEL
The PL femoral tunnel is the first tunnel to be drilled.
A 3/32 Steinmann pin is inserted through the accessory anteromedial portal.
The tip of the guidewire is placed on the femoral footprint of the PL bundle on the lateral wall of the intercondylar notch adjacent to the articular surface (TECH FIG 2A).
Once the tip of the guidewire is placed in the correct anatomic position (8 mm from anterior and 5 mm from distal articular cartilage), the knee is flexed to 120 degrees and the guidewire is manually tapped into the femur.
Hyperflexion is performed while placing the PL femoral tunnel to avoid injury to the peroneal nerve when passing a Beath pin.
The guidewire is over-drilled with a 7-mm acorn drill, taking care to avoid injury to the medial femoral condyle articular cartilage.
The PL tunnel is drilled to a depth of 25 to 30 mm (TECH FIG 2B).
The far cortex is then breached with a 4.5-mm EndoButton drill (Smith & Nephew, Andover, MA), and the depth gauge is used to measure the distance to the far cortex.
TECH FIG 2 • A. Insertion of a guide pin in the femoral insertion of the PL bundle through the accessory anteromedial portal. B. PL femoral tunnel drilled to 7 mm diameter.
TIBIAL TUNNELS
To establish the two tibial tunnels, a 4-cm skin incision is made over the anteromedial surface of the tibia at the level of the tibial tubercle.
First the PL tunnel is drilled.
An Accufex (Smith & Nephew, Andover, MA) ACL tibial tunnel tip drill guide set to 55 degrees is placed through the accessory medial portal intra-articularly on the tibial footprint of the PL bundle, which was previously marked using a thermal device (TECH FIG 3A).
On the tibial cortex, the tibial drill starts just anterior to the superficial medial collateral ligament fibers.
A 3.2-mm guidewire is then passed into the stump of the PL tibial footprint.
The AM tibial tunnel is drilled with the tibial drill guide set at 45 degrees and placed through the anteromedial portal, and the tip of the drill guide is placed on the tibial footprint of the AM tunnel (TECH FIG 3B).
The starting point of the AM tunnel on the tibial cortex is more anterior, central, and proximal than the starting point of the PL tunnel.
The 3.2-mm guidewire is passed into the stump of the AM tibial footprint, and placement of both guidewires is assessed for satisfactory position (TECH FIG 3C).
The tibial tunnels are then overdrilled with 7- and 8-mm compaction drill reamers for the PL and AM tunnels, respectively.
TECH FIG 3 • A. Placement of ACL tibial guide (set on 55 degrees) on the tibial PL bundle insertion site through the accessory anteromedial portal. B. Placement of ACL tibial guide (set on 45 degrees) placed on the tibial anteromedial (AM) bundle insertion site through the central anteromedial portal. C. Appearance of guide pins in the AM and PL tibial insertions of the ACL.
ANTEROMEDIAL FEMORAL TUNNEL
The femoral AM tunnel is the last tunnel to be drilled.
A transtibial technique is used most commonly, in a similar fashion to that of a femoral tunnel for ACL singlebundle reconstruction (TECH FIG 4A).
A guidewire is passed through the AM tibial tunnel, and the tip of the guidewire is placed on the femoral footprint of the AM bundle, which was marked previously with a thermal device.
At 90 degrees, the location is directly posterior to the PL femoral tunnel.
If the location of the guidewire tip is unacceptable, the accessory medial portal is used to insert the guidewire in the proper location.
After the guidewire is inserted in the desired position, an 8-mm acorn drill is inserted over the guidewire, and the AM femoral tunnel is drilled to a depth of 35 mm to 40 mm (TECH FIG 4B).
The far cortex of the AM femoral tunnel is breached with a 4.5-mm EndoButton drill, and the depth gauge is used to measure the distance to the far cortex.
TECH FIG 4 • A. Placement of a guide pin into the femoral AM bundle insertion using the transtibial technique. B. Appearance of the AM and PL femoral tunnels at 90 degrees after drilling to 8 mm and 7 mm diameter, respectively.
GRAFT CHOICE
During the arthroscopic procedure, the ACL grafts are prepared on the back table.
We prefer to use two separate tibialis anterior or tibialis posterior tendon allografts.
These grafts usually are 24 cm to 30 cm in length, and we fold each tendon graft to obtain 12- to 15-cm double-stranded grafts (TECH FIG 5).
The AM tendon double-stranded graft typically is 8 mm, and the PL double-stranded graft is 7 mm.
Alternatively, autogenous semitendinosus and gracilus grafts can be harvested (see Chap. SM-41) and used for the reconstruction.
The ends of the tendon grafts are sutured using a whipstitch with no. 2 Ticron sutures (Tyco, Waltham, MA).
TECH FIG 5 • Double-looped tibialis anterior allografts. An 8-mm graft is used for the AM graft and looped through a 15-mm EndoButton loop. A 7-mm graft is used for the PL graft and is placed through an EndoButton loop.
GRAFT PASSAGE
The PL bundle graft is passed first. A Beath pin with a long looped suture attached to the eyelet is passed through the accessory anteromedial portal and out the PL femoral tunnel and lateral aspect of the thigh.
Hyperflexion of the knee is performed to protect the peroneal nerve.
The looped suture is visualized within the joint and retrieved with an arthroscopic suture grasper through the PL tibial tunnel.
The graft is passed, and the EndoButton is flipped in standard fashion to establish femoral fixation of the PL bundle graft (TECH FIG 6A).
Next, the AM bundle graft is passed using the transtibial technique and out the anterolateral thigh with a Beath pin loaded with a looped suture (TECH FIG 6B).
If the transtibial technique is not used for the AM femoral tunnel, then the graft is passed in a similar fashion to the PL bundle graft.
The EndoButton is flipped in standard fashion to establish femoral fixation of the AM bundle graft.
Preconditioning of the grafts is performed by flexing and extending the knee through a range of motion (ROM) from 0 to 120 degrees approximately 20 to 30 times.
TECH FIG 6 • A. Arthroscopic view from the anterolateral portal of the passage of the PL bundle graft. The PL graft is passed first, followed by the AM graft. B. Arthroscopic view from the central anteromedial portal following passage of the AM and PL grafts, completing the anatomic double-bundle ACL reconstruction.
FIXATION
Each graft is looped around an EndoButton.
The length of the EndoButton loop is chosen according to the measured length of the femoral tunnels.
On the tibial side, we prefer the use of a bioabsorbable interference screw fixation combined with Richards staple fixation (Smith & Nephew Richards, Memphis, TN) for each graft (TECH FIG 7).
The PL bundle graft is tensioned and fixed at full extension, and the AM bundle graft is tensioned and fixed at 60 degrees of flexion.
After the fixation is complete, the knee is tested for stability and full ROM. The wounds are closed in standard fashion, and the leg locked in full extension in a hinged knee brace with a Cryocuff (Aircast, Summit, NJ) placed under the brace.
TECH FIG 7 • Postoperative AP radiograph after anatomic double-bundle ACL reconstruction. The femoral fixation uses an EndoButton for each graft, and tibial fixation is obtained using a bioabsorbable interference screw and Richards staple for each graft.
POSTOPERATIVE CARE
The authors' postoperative rehabilitation follows the same standard protocol used for patients undergoing ACL single-bundle reconstruction using soft tissue grafts.
Patients wear a hinged knee brace for 6 weeks.
For the first week, the brace is locked in extension.
Continuous passive motion is started immediately after surgery, from 0 to 45 degrees of flexion, and is increased by 10 degrees per day.
Patients use crutches for 4 weeks postoperatively.
From the first postoperative day, patients are allowed full weight bearing as tolerated.
Non-cutting and non-twisting sports such as swimming, biking, and running in a straight line are allowed at 12 weeks after surgery.
Return to full activity level usually is allowed at 6 months postoperatively.
OUTCOMES
No current long-term studies on the results of anatomic double-bundle ACL reconstruction have been performed.
Several short-term studies and multiple prospective studies currently are ongoing in Japan, France, Italy, and the United States.
Muneta et al7 reported on 54 patients 2 years after doublebundle ACL reconstruction using autogenous hamstring and found a trend toward improved anterior stability compared with the single-bundle technique.
Zaricznyj11 found 86% good or excellent results at 3.6 years follow-up in 14 patients after using doubled hamstring autograft for ACL reconstruction with one femoral and two tibial tunnels. Rotational stability was achieved in each patient, as demonstrated by a negative pivot shift.
In a case series with 57 consecutive patients, Yasuda et al10 demonstrated that anatomic ACL double-bundle reconstruction appears to be a safe technique with satisfactory outcomes. They evaluated functional outcomes at 24 to 36 months follow-up and compared their results with historic data on ACL single-bundle reconstruction. Patients undergoing anatomic ACL double-bundle reconstruction trended toward better AP knee stability, as measured by the KT-2000, compared with the single-bundle group.
In a prospective, randomized clinical trial including 108 patients, Adachi et al1 compared the outcomes of anatomic ACL double-bundle reconstruction with the ACL single-bundle technique at an average follow up of 32 months. Their outcome measures included AP knee stability, as measured by the KT-2000, and the joint position sense of the knee. These authors did not find any difference between the ACL doublebundle and the ACL single-bundle group.
COMPLICATIONS
Traditional complications for single-bundle reconstruction include graft failure, hardware complications, and infection.
In our series, we have had three graft failures, all occurring after returning to sports.
Two failures were sustained during contact injuries while playing collegiate football. The third occurred in a noncompliant patient 3 months after reconstruction when she returned to playing high school basketball without a brace.
Four patients have undergone staple removal for symptomatic hardware.
Specific complications for double-bundle reconstruction include:
Risk of femoral condyle fracture
Graft impingement
Incorrect tunnel placement
Tunnel enlargement
Difficulty with revision surgery
We have performed 186 double-bundle ACL reconstructions and have had no fractures and no radiographic signs of femoral condylar avascular necrosis or tunnel widening.
Bell et al2 performed biomechanical and computer modeling studies comparing single and double femoral tunnels and the risk of femoral condyle fracture.
Results of these studies have shown that fracture risk increased significantly for the single tunnel versus the native condyle procedure, but no significant increase in fracture risk was found for one versus two tunnels.
ROM studies are in progress. Preliminary results have shown earlier return to full extension and symmetric flexion to the contralateral knee by 3 months after surgery.
Proper tunnel location is achieved by marking the anatomic sites for each bundle prior to ACL débridement.
Prospective studies measuring for radiographic tunnel enlargement are ongoing. Thus far, no significant tunnel enlargement has been found; however, follow-up has been short-term only.
Revision surgery has not been compromised in the two patients in our cohort who have undergone repeat ACL surgery following traumatic re-tear after double-bundle reconstruction.
REFERENCES
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2. Bell KM, Egan M, Fu FH, et al. Femoral fracture risk analysis of singeand double-bundle ACL reconstruction. Orthopaedic Research Society Annual Meeting, Chicago, March 19–22, 2006.
3. Cohen SB, Fu FH. The three portal technique for ACL reconstruction: use of a central anteromedial portal—Technical note. Arthroscopy 2007;23:325.
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7. Muneta T, Sekiya I, Yagishita K, et al. Two-bundle reconstruction of the anterior cruciate ligament using semitendinosus tendon with endobuttons: operative technique and preliminary results. Arthroscopy 1999;15:618–624.
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9. Woo SL, Kanamori A, Zeminski J, et al. The effectiveness of reconstruction of the anterior cruciate ligament with hamstrings and patellar tendon: a cadaveric study comparing anterior tibial and rotational loads. J Bone Joint Surg Am 2002;84A:907–914.
10. Yasuda K, Kondo E, Ichiyama H, et al. Anatomic reconstruction of the anteromedial and posterolateral bundles of the anterior cruciate ligament using hamstring tendon grafts. Arthroscopy 2004;20:1015–1025.
11. Zaricznyj B. Reconstruction of the anterior cruciate ligament of the knee using a doubled tendon graft. Clin Orthop Relat Res 1987;220: 162–175.