Double-Bundle Anterior Cruciate Ligament
DEFINITION
Anterior cruciate ligament (ACL) tears have been described in detail in Chapter 49.
Any patient with functional instability or pivoting of the knee is considered to have an ACL insufficiency. Anatomic ACL reconstruction is defined as the functional restoration of the ACL to its native dimensions, collagen orientation, and insertion sites.18
ANATOMY
The ACL is an intra-articular, extra-synovial ligament of nonparallel collagen fibers that arise from the posterior aspect of the lateral femoral condyle and insert on the tibial plateau between the medial and lateral tibial
spines2,7,8 (FIG 1).
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, the anteromedial (AM) and posterolateral (PL) bundles, named according to their relative insertion sites on the tibia.12,15
At the femoral insertion site, the lateral intercondylar ridge (“residents ridge”) represents the upper (anterior) limit of the ACL, whereas the lateral bifurcate ridge divides the AM and PL bundle insertion sites and is perpendicular to the intercondylar ridge.9,10
The AM and PL bundle are synergistic according to knee flexion angle and control anterior and rotational stability of the knee. The AM bundle remains constant through knee flexion but attains peak tension between 45 and 60 degrees of knee flexion. The PL bundle is tightest in extension and loosens with knee flexion, thereby
allowing rotation.6,11
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FIG 1 • Anatomy of the ACL with the anteromedial (AM) and posterolateral (PL) bundles marked by arrows.
PATHOGENESIS
The majority of ACL ruptures, approximately 70%, occur via a noncontact injury mechanism. Females are approximately seven times more likely to suffer an ACL injury than males.17
NATURAL HISTORY
The natural history of an ACL rupture is multifactorial and depends on patient age, activity level, concomitant injury, and degree of functional instability.
The majority of athletic patients suffering an ACL rupture will be unable to perform cutting and/or pivoting activities without surgical reconstruction of the ACL.
A small percentage of carefully identified patients may be able to undergo successful nonoperative rehabilitation. However, the patient should be aware that repeated episodes of instability is likely to induce secondary damage to the knee in the form of meniscal and/or cartilage pathology.
In the long-term, patients are likely to develop some form of osteoarthritis after an ACL rupture regardless of conservative or surgical treatment.
PATIENT HISTORY AND PHYSICAL FINDINGS
A noncontact valgus pivoting injury followed by an effusion of the knee is highly suspicious of an ACL rupture. If an ACL rupture has occurred, patients are typically unable to return to the same athletic competition.
The physical examination and methods for examination of the ACL are covered in Chapter 49.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Radiographs should include the following views:
Thirty-degree flexion weight-bearing posteroanterior (PA) view Lateral
Sunrise (Merchant) view of the patella
Long-leg alignment view in the case of suspected coronal angular deformity
Magnetic resonance imaging (MRI) should be ordered to confirm a suspected ACL tear and evaluate potential rupture pattern, including partial ACL tears. MRI is also used to evaluate potential associated injuries of the chondral surfaces, menisci, and other ligamentous structures.
The sagittal MRI can be used to measure the length of the tibial insertion site of the ACL in the AP dimension as well
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as the inclination angle and length of the ACL. These measurements can be used in individualized ACL reconstruction and are discussed in the following text. Moreover, the thickness of both the quadriceps and patellar tendons can be used to provide the surgeon with an approximation for graft size prior to harvest.
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FIG 2 • The tibial insertion site of the ACL (left) and intercondylar notch width are measured intraoperatively using an arthroscopic ruler.
Computed tomography scan should be ordered in revision cases to assess for factors such as tunnel widening. The images can also be reconstructed three-dimensionally for an accurate assessment of primary tunnel placement for preoperative planning of revision surgery.
An instrumented laxity test (eg, KT-1000 arthrometer) to assess anteroposterior knee laxity can be performed to determine absolute translation and side-to-side translation difference.
DIFFERENTIAL DIAGNOSIS
Contusion Meniscal tear
Osteochondral injury
Patellar dislocation, which may mimic the initial presentation of an ACL injury Collateral ligament injury (eg, medial collateral ligament, lateral collateral ligament) Multiple ligament injury
NONOPERATIVE MANAGEMENT
Potential nonoperative treatment candidates and rehabilitation protocol are detailed in Chapter 49.
SURGICAL MANAGEMENT
Indications
The indications for anatomic double-bundle ACL reconstruction are similar to those for traditional singlebundle 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 that the remaining bundle is incompetent.
Measurements of the tibial footprint (FIG 2) and notch preand intraoperatively help guide individualized ACL reconstruction to better reproduce native anatomy.
Tibial footprint length
14 mm or less—single-bundle reconstruction
14 to 18 mm—single- or double-bundle reconstruction More than 18 mm—double-bundle reconstruction
Notch width
12 mm or less—single-bundle reconstruction More than 12 mm—double-bundle reconstruction
Contraindications
Tibial footprint length 14 mm or less Notch width 12 mm or less
PREOPERATIVE PLANNING
Graft Options
Anatomic double-bundle reconstruction can be performed using quadriceps tendon autograft with patella bone block, or soft tissue graft, including hamstrings autograft and allograft. Bone-patellar tendon-bone (BPTB) grafts
cannot be used for double-bundle reconstruction.
The quadriceps tendon autograft with patella bone block is a versatile option16 (FIG 3).
The quadriceps tendon can be used for a single-bundle graft or split longitudinally through a natural plane into its rectus femoris and vastus interomedialis portions to create a double-bundle graft.
The smaller rectus portion is used to reconstruct the PL bundle and the larger vastus portion for the AM bundle.
Soft tissue grafts
Two separate tibialis anterior or tibialis posterior tendon allografts can be used.
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FIG 3 • A single-bundle (top) and double-bundle (bottom) quadriceps tendon autograft.
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These grafts are usually 24 to 30 cm in length, and we fold each tendon graft to obtain 12 to 15 cm doublestranded grafts.
The AM tendon double-stranded graft is typically 8 mm and the PL graft is 7 mm. These sizes can be individualized to the patient based on the native anatomy.
Semitendinosus and gracilis autografts can be harvested (see Chap. 49) and used for reconstruction.
ACL graft preparation is done during the arthroscopic procedure on the back table.
Exam under Anesthesia
Range of motion is compared to the contralateral knee Ligamentous exam
Lachman and anterior drawer Pivot shift
Varus and valgus stress
Dial test
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.
The operative leg is positioned in an arthroscopic leg holder to ensure intraoperative knee flexion up to 120 degrees and then sterilely prepped and draped.
A pneumatic tourniquet is applied around the upper thigh of the operative leg, the operative limb is exsanguinated with an Esmarch bandage, and the tourniquet is insufflated to 250 to 300 mm Hg, depending on patient size.
Approach
The portals used for this procedure are slightly different from standard arthroscopy portals (FIG 4). Three portals are used for reconstruction: lateral, central, and medial portals.
The lateral portal is placed slightly above the level of the inferior pole of the patella and just lateral to its border to avoid the infrapatellar fat pad.
The central portal is placed low adjacent or through the medial aspect of the patella tendon such that it provides a head on view of the knee notch.
The medial portal is placed medial to the central portal just above the AM meniscus. It is established under direct visualization with a spinal needle to ensure proper trajectory to the femoral ACL footprint and 3 to 4 mm of clearance from the medial femoral condyle.
The arthroscope is placed in the central portal during femoral tunnel placement for excellent visualization of the intercondylar notch and femoral ACL footprint.
The arthroscope is placed in the lateral portal for visualization of the tibial ACL footprint and tunnel placement.
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FIG 4 • The three-portal approach with lateral (LP), central (CP), and medial (MP) portals made in a representative case.
TECHNIQUES
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Diagnostic Arthroscopy
Thorough inspection of the joint compartments particularly for loose bodies and meniscal and chondral pathologies, including the following:
Patellofemoral compartment
Medial compartment, meniscus, and gutter Lateral compartment, meniscus, and gutter Posterior cruciate ligament
ACL
Any associated meniscal or chondral lesions are addressed prior to ACL reconstruction.
The ACL injury pattern is carefully examined. There are 25 different patterns which may include the following:
Tear or stretch of one or both bundles
Injury at femoral insertion, tibial insertion, and/or midsubstance
The torn ACL is carefully dissected, preserving the native anatomy of the AM and PL bundles using a thermal device (TECH FIG 1).
Bony landmarks are visualized and identified including the intercondylar ridge and the lateral bifurcate ridge.
Anatomic insertion sites of the AM and PL bundles on the tibia and femur are marked with a thermal device.
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Measurements using a flexible arthroscopic ruler are taken to ascertain whether the patient may be a candidate for doublebundle reconstruction. These measurements are correlated to MRI measurements.
Tibial AM and PL footprint length and width Notch width and height
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TECH FIG 1 • Dissection and marking of the femoral insertion of the ACL with a thermal device.
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Double-Bundle Anterior Cruciate Ligament Reconstruction
Technical Order of Steps
Steps of reconstruction are graft dependent: quadriceps autograft with bone block versus soft tissue grafts The femoral side is addressed first. One tunnel is created for the quadriceps autograft with bone block.
Two tunnels are created for soft tissue allograft or hamstrings autograft.
Tibial tunnels are then created, PL first followed by AM. Grafts are passed after all tunnels are created.
Quadriceps autograft is passed into the femoral tunnel followed by passage of each bundle into the tibial tunnels anterograde.
Soft tissue grafts, PL first, are passed retrograde through the tibial tunnels into the respective femoral tunnels.
Tibial fixation is then performed with the PL bundle tensioned at full extension and AM bundle at 45 degrees flexion.
Femoral Tunnel—Quadriceps Autograft
A single femoral tunnel for the quadriceps bone block is to be drilled.
The position of the femoral tunnel is between the anatomic AM and PL bundles. Based on bony landmarks, the position is below the intercondylar ridge and at the lateral bifurcate ridge.
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TECH FIG 2 • A. A Steadman awl is used to mark the desired tunnel location on the femoral side. B. A single femoral tunnel was drilled at the native insertion site.
Viewing from the central portal, a Steadman awl is inserted through the medial portal to create a small hole, thereby marking the starting point for the guidewire between the AM and PL bundle footprints (TECH FIG 2A).
A curved guide is used to place the tip of the flexible guidewire into the starting point. A straight guide can be used as well, but care must be taken when used to protect the medial femoral condyle while reaming the tunnel by hyperflexing the knee.
Tunnel size may vary depending on the graft and patients native anatomy, although 10 mm is usually drilled. Again, care should be taken to flex the knee as necessary to protect the medial femoral condyle as the reamer is passed over the guidewire (TECH FIG 2B).
The femoral tunnel is drilled to a depth of 25 to 30 mm.
The far cortex is breached with a 4.5-mm EndoButton (Smith & Nephew, Andover, MA) drill and the distance to the far cortex is measured with a depth gauge.
Femoral Tunnels—Soft Tissue Grafts
Two femoral tunnels, AM and PL, for allograft or hamstrings autograft are used for double-bundle reconstruction.
The PL femoral tunnel is created first.
Viewing from the central portal, a Steadman awl is inserted through the medial portal to create a small hole
for a starting point at the PL femoral insertion site.
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TECH FIG 3 • A. Placement of a guide pin into the femoral AM bundle insertion site. B. Appearance of the AM and PL femoral tunnels at 90 degrees after drilling to 8 and 7 mm diameter, respectively.
A curved guide is used to place the tip of the flexible guidewire into the PL femoral starting point. The guidewire is passed out the lateral femoral cortex and skin.
The tunnel is drilled with typically a 7-mm flexible reamer with the knee in hyperflexion to protect the medial femoral condyle articular cartilage from the drill.3
The PL tunnel is drilled to a depth of 25 to 30 mm.
The far cortex is then breached with a 4.5-mm EndoButton drill and the distance to the far cortex is measured with depth gauge.
An 8-mm AM tunnel is then established in a similar fashion at the center of the AM footprint posterior to the bifurcate ridge (TECH FIG 3).
Alternatively, a transtibial technique can also be used if the AM femoral footprint can be reached with the transtibial guide.
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 previously marked with a thermal device.
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TECH FIG 4 • A. Placement of ACL tibial guide on the tibial PL bundle insertion site through the central portal. B. Placement of ACL tibial guide on the tibial anteromedial (AM) bundle insertion site through the central portal. C. Appearance of guide pins in the AM and PL tibial insertions of the ACL. D. Dilators demonstrating the locations of the tibial tunnels drilled within the native tibial footprint of the ACL.
After the guidewire is inserted in the anatomic AM femoral position, an 8-mm reamer is inserted over the guidewire and drilled to a depth of 35 to 40 mm.
Again, the far cortex of the AM femoral tunnel is breached with a 4.5-mm EndoButton drill, and the distance to the far cortex is measured.
Tibial Tunnels—Quadriceps and Soft Tissue Grafts
To establish the two tibial tunnels, a 4-cm skin incision is made over the AM surface of the tibia at the level of the tibial tubercle.
The tibial ACL footprint is viewed from the lateral portal. The PL tunnel guide pin is placed first.
A tibial ACL guide is set to 45 degrees and placed through the central portal onto the tibial PL footprint previously marked with a thermal device (TECH FIG 4A).
On the tibial cortex, the PL tunnel starts just anterior to the superficial medial collateral ligament fibers.
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TECH FIG 5 • The graft in its final fixed position with the knee in 90 degrees of flexion.
A 3.2-mm guidewire is then passed into the stump of the PL tibial footprint and left in place.
The AM tunnel guide pin is drilled with the tibial ACL guide set to 55 degrees and placed through the central portal. The tip of the drill guide is placed on the tibial AM footprint previously marked.
The AM tunnel starting point on the tibial cortex is more central and distal than the PL tunnel starting point.
A 3.2-mm guidewire is passed into the stump of the AM tibial footprint, and placement of both guidewires is assessed for anatomic position at the footprint and adequate pin spread of at least 1 cm at the tibial cortex.
The tibial tunnels are then overdrilled with 7- and 8-mm reamers for the PL and AM tunnels, respectively (TECH FIG 4B).
Graft Passage—Quadriceps Autograft
The medial portal is enlarged to facilitate passage of the entire quadriceps tendon patella bone block autograft.
The smaller rectus femoris portion of the tendon is colored with a marker to help facilitate orientation of the graft.
A Beath pin with a long looped suture attached to the eyelet is passed through the medial portal out the femoral tunnel and lateral aspect of the thigh.
The bone block is passed through the medial portal into the femoral tunnel and the EndoButton is flipped in the standard fashion establishing femoral fixation. Appropriate orientation of the bone block within the femoral tunnel to recreate AM and PL anatomy is confirmed prior to flipping the EndoButton (TECH FIG 5).
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TECH FIG 6 • Arthroscopic view from the lateral portal during passage of the PL graft. A. The PL graft is passed first, followed by the AM graft. B. Arthroscopic view from the central portal following passage of the AM and PL grafts, completing the anatomic doublebundle ACL reconstruction.
Flexible wires are passed retrograde through the appropriate tibial tunnels and retrieved through the central portal.
The sutures for the PL portion of the graft are passed through the medial portal into the notch and out the central portal. This suture is then shuttled with the flexible wire out the PL tibial tunnel.
The PL bundle is passed under direct visualization with the arthroscope and assisted with arthroscopic instruments.
The AM bundle is passed in a similar fashion.
Graft Passage—Soft Tissue Grafts
The PL bundle graft is passed first. A Beath pin with a long looped suture attached to the eyelet is passed through the central portal and out the PL femoral tunnel and lateral aspect of the thigh.
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 6).
Next, A Beath pin loaded with a looped suture is passed through the AM femoral tunnel either through the medial portal or transtibial depending on technique used.
The looped suture can be retrieved out of the AM tibial tunnel with a suture grasper if passed through the medial portal.
The AM graft is passed and the EndoButton is flipped in standard fashion to establish femoral fixation of the AM bundle graft.
Tibial Fixation—Quadriceps and Soft Tissue Grafts
Prior to tibial fixation, preconditioning of the grafts are performed by flexing and extending the knee through a range of motion from 0 to 120 degrees approximately 20 to 30 times.
Interference screw fixation is used for each graft, and if necessary, the graft sutures can be tied over a cortical screw post for backup.
The PL bundle graft is tensioned and fixed at full extension, and the AM bundle graft is tensioned and fixed at 45 degrees of flexion.
After the fixation is complete, the knee is tested for stability and full range of motion. The arthroscope is reintroduced to confirm graft placement and no notch impingement with full extension. The wounds are closed in standard fashion and the leg locked in full extension in a hinged knee brace with a Cryo/Cuff (Aircast, Summit, NJ) placed under the brace.
Grafts
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We prefer quadriceps autograft.
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AM bundle graft: 7-8 mm
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PL bundle graft: 5-7 mm
Examination of injury
pattern
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Inspection for tear or stretch of one or both bundles
Portals
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Three portals are used.
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The femoral ACL footprint is visualized through the central portal.
Tunnel placement
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Marking anatomic insertion sites
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Single femoral tunnel for quadriceps autograft
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Soft tissue grafts—PL tunnel placed first, AM femoral tunnel based on PL tunnel
Fixation
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Femoral side: EndoButton
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Tibial side: interference screw
Postoperatively
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Early range of motion
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PEARLS AND PITFALLS
POSTOPERATIVE CARE
The authors' postoperative rehabilitation follows the same standard protocol used for patients undergoing ACL singlebundle 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. In cases where concomitant procedures are performed, the protocol is adjusted accordingly.
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 9 to 12 months postoperatively.
OUTCOMES
No current long-term studies on the results of anatomic double-bundle ACL reconstruction have been published.
Aglietti et al1 performed a prospective randomized singleblinded clinical trial comparing anatomic singlebundle and double-bundle ACL reconstruction with minimum of 2-year follow-up. Double-bundle ACL reconstruction had significantly lower anterior tibial translation (1.2 mm vs. 2.1 mm), less residual pivot shift (14% vs. 26%), as well as better Visual Analog Scale (VAS) and final subjective International Knee Documentation Committee (IKDC) scores.
Hussein et al13 reported on 3- to 5-year follow-up of 245 patients prospectively randomized to anatomic single-bundle and double-bundle ACL reconstruction. Double-bundle reconstruction was found to have significantly lower side-toside difference in anterior translation (1.2 mm vs. 1.6 mm) and more negative pivot shift testing (93.1% vs. 66.7%). However, no significant difference was found in Lysholm and subjective IKDC clinical outcomes scores.
A comprehensive systematic review performed by Bjornsson et al5 found 60 level I to III papers meeting their criteria comparing single-bundle and double-bundle ACL reconstruction for primary ACL rupture. Double-bundle reconstruction was found to have less anteroposterior and rotational laxity as well as fewer reruptures. No significant difference was found in short-term patient-reported outcomes.
COMPLICATIONS
Double-bundle ACL reconstruction is a technically challenging.
Traditional complications for single-bundle ACL reconstruction apply in double-bundle reconstruction, including graft failure, hardware complications, stiffness, and infection.
Multiple clinical studies comparing single-bundle and doublebundle ACL reconstruction have not found a significant difference in complication rates.
Specific complications for double-bundle reconstruction include the following: Risk of femoral condyle fracture
Graft impingement
Tunnel enlargement Incorrect tunnel placement
Difficulty with revision surgery
Bell et al4 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.
Multiple studies comparing single-bundle and double-bundle ACL reconstruction have shown no significant difference in range of motion due to graft impingement, whereas some have even shown improved range of motion with doublebundle reconstruction.
Kawaguchi et al14 measured tunnel widening after singlebundle and double-bundle ACL reconstruction in 169 patients. Double-bundle reconstruction was found to have significantly lower incidence and degree of tunnel enlargement.
Proper tunnel location is achieved by marking the anatomic sites for each bundle prior to ACL débridement.
Revision surgery after double-bundle ACL reconstruction can be challenging and requires flexibility and a repertoire of different graft options and reconstruction techniques. Careful preoperative planning and intraoperative assessment is necessary for proper management.
REFERENCES
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Bell K, Egan M, Fu FH, et al. Femoral fracture risk analysis of singeand double-bundle ACL reconstruction. Paper presented at: 52nd Annual Meeting of Orthopaedic Research Society; March 19-22, 2006; Chicago, IL.
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Bjornsson H, Desai N, Musahl V, et al. Is double-bundle anterior cruciate ligament reconstruction superior to single-bundle? A comprehensive systematic review [published online ahead of print September 15, 2013]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-013-2666-x.
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Kawaguchi Y, Kondo E, Kitamura N, et al. Comparisons of femoral tunnel enlargement in 169 patients between single-bundle and anatomic double-bundle anterior cruciate ligament reconstructions with hamstring tendon grafts. Knee Surg Sports Traumatol Arthrosc 2011;19(8):1249-1257.
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