Double-Bundle Anterior Cruciate Ligament Reconstruction With Primary Repair and Hamstring Autograft Augmentation

The optimal treatment of a ruptured anterior cruciate ligament (ACL) restores the patient’s native anatomy and biomechanics as close to normal as possible. The purpose of this technical note is to describe an ACL reconstruction technique in which a double-bundle concept is used, wherein one bundle contains repaired ACL tissue and the second bundle contains a hamstring autograft, and each bundle is tensioned independently. Even in chronic cases, this technique allows for incorporation of the native ACL because, more often than not, there is sufficient tissue of good quality available for repair of one bundle. By augmenting the ACL repair with an autograft sized to the fit the individual anatomy, the patient’s ACL tibial footprint can be closely restored to normal, and the potential benefits of tissue preservation are combined with the biomechanical strengths of an autograft double-bundle ACL reconstruction.


Introduction
S ingle-bundle autograft reconstruction is the standard of care for a complete rupture of the anterior cruciate ligament (ACL) in young, active patients. However, single-bundle ACL reconstruction fails to normalize knee biomechanics and does not prevent osteoarthritis. 1 Even short-to-midterm patient-reported and radiographic outcomes have been similar between some young, active patients who were treated with rehabilitation alone and those who underwent singlebundle ACL reconstruction. 2 The quest for the optimal ACL reconstruction is, therefore, ongoing. Anatomic double-bundle ACL reconstruction was introduced to approximate the patient's original anatomy more closely and, thereby, improve the postoperative kinematics. Despite the biomechanical advantage in early laboratory studies, 3 double-bundle ACL reconstruction has not replaced single-bundle reconstruction as the gold standard. The doublebundle technique is technically challenging, requires more autograft tissue, and its early clinical outcomes have not been overwhelmingly superior to singlebundle reconstruction. Primary ACL repair is a promising alternative to single-bundle ACL reconstruction. ACL repair restores the ligament's original anatomy and (conceivably) its biomechanical and proprioceptive function. Unfortunately, ACL repair is limited to a small subset of patientsdthose with acute, proximal avulsions of the ACL. Even in these select cases, the failure rate following ACL repair with suture augmentation was 10 times higher compared to ACL reconstruction in adolescents. 4 Biological augmentation of the repair with a protein implant decreased the failure rate, but the repair remained restricted to acute injuries with at least 50% of the length of the ACL attached to the tibia. 5 In acute cases with insufficient remnant tissue, hamstring augmentation has been performed to create a more robust single-bundle ACL repair, 6,7 reminiscent of the primary ACL repair techniques with semitendinosus augmentation performed in the early 1990s. 8 The purpose of this technical note was to describe an ACL reconstruction technique in which a double-bundle concept is used wherein the first bundle contains repaired ACL tissue, and the second bundle contains a hamstring autograft, and each bundle is tensioned independently.

Surgical Technique
In this technique description (Video 1), the posterolateral (PL) bundle is repaired and the anteromedial (AM) bundle of the ACL is reconstructed. The surgical steps for AM reconstruction and PL repair are not shown in the present technique description, but follow the same principles as outlined below. The decision on which bundle to repair and which bundle to reconstruct depends on the individual ACL remnant characteristics (Table 1).

Surgical Approach
Preoperative MR imaging is used to measure the ACL tibial footprint (Table 1). Following general anesthesia and bilateral knee examination, arthroscopy is performed with standard anterolateral (AL) and AM portals; any meniscal and/or cartilaginous pathology is addressed.
Switching between AM and AL portals, the ACL tear characteristics are evaluated using a probe ( Table 1, Fig  1A). A partial release of the ACL remnant is performed with a combination of probe, arthroscopic scissors, and prudent use of a shaver (Fig 1B). On the basis of the remnant characteristics, either AM or PL bundle is repaired. In the present technique description, the PL bundle is repaired, and the AM bundle is reconstructed. A shoulder Scorpion suture passer (Arthrex, Naples, FL) is used to place a 25-mm FiberRing with preattached shuttle loop (Arthrex) at the base of the ACL remnant (Fig 2A). For additional fixation strength and maximum approximation of the remnant to the femoral wall to avoid cyclops formation, a 1.3-mm SutureTape (Arthrex, Naples, FL) is placed more proximally in the remnant. The FiberRing shuttle loop and SutureTape ends are then docked out of the AM portal. With tension on these sutures, the ACL remnant is now completely released from its surroundings, leaving its tibial attachment intact ( Fig 2B).
The semitendinosus tendon is harvested in the standard fashion. On the basis of the preoperative MR imaging and intraoperative measurements, the graft is either doubled, tripled, or quadrupled, and, if necessary, supplemented with a gracilis tendon, so that the combined final graft diameter plus the remnant tibial   DOUBLE BUNDLE ACLR e641 footprint diameter approximate that of the native ACL tibial footprint. The graft is secured with TightRope RT devices (Arthrex).
Looking from the AM portal, the femoral drill guide is entered through the AL portal and positioned at the anatomic location of the femoral AM attachment   3, A and B). A longitudinal incision is placed over the lateral aspect of the distal femur, with sharp incision through the fascia. A FlipCutter (Arthrex) is advanced outside-in, opened to the diameter of the graft, and a 20-mm socket is created in a retrograde fashion at the location of the AM femoral attachment. A cannulated stick with draw suture (Fiber-Stick; Arthrex) is advanced into the socket (Fig 3C). The FiberStick, draw suture, and drill sleeve are left in place to avoid tunnel convergence. The location of the native femoral PL attachment is defined. A pointto-point drill guide is entered through the AL portal (Fig 3D), and a 3.0-mm cannulated drill is drilled outside-in at the location of the PL femoral attachment site. The central stylus is removed from the cannulated drill and a nitinol loop is advanced through the cannula (Fig 3E). The repair sutures within the ACL remnant, together with the nitinol loop, are first pulled outside the knee through the AL portal and then shuttled through the femoral tunnel using the nitinol loop (Fig 4).
Looking from the AL portal, a guide pin is advanced from the anteromedial aspect of the tibia using the hamstring harvesting incision through the center of the anatomic AM bundle attachment of the native ACL (Fig 5, A and B). The guide pin is overdrilled with a reamer with the size determined by the graft diameter. The femoral draw suture that was left in place in the femoral AM socket is now pulled outside the knee through the tibial tunnel (with care to stay anterior to  Frequently, especially in more chronic cases, the bulk of the ACL remnant is stuck down onto the PCL. Placement of the repair sutures in the ACL remnant is easier if a partial release is performed initially with some proximal remnant tissue left attached. Once the repair sutures are secured, tension on these sutures helps with the complete release of the ACL remnant. A shoulder Scorpion suture passer (Arthrex, Naples, FL) works better than the knee suture passer for penetrating the ACL remnant tissue at its base to place the 25-mm FiberRing (Arthrex, Naples, FL). For additional fixation strength and maximum approximation of the remnant to the femoral wall to avoid cyclops formation, a 1.3-mm SutureTape (Arthrex) is placed more proximally in the ACL remnant. The ACL remnant can make visibility of the femoral wall cumbersome. When entering the femoral drill guide, an assistant maintains tension of the sutures placed in the ACL remnant and docked out of the AM portal to improve visibility. To avoid tunnel convergence during drilling of the femoral PL repair tunnel, the FiberStick, draw suture, and drill sleeve of the AM femoral socket are left in place.
To avoid damage to the ACL remnant during tibial tunnel drilling, the reamer is advanced in an oscillating manner through the proximal tibial cortex, while an assistant holds some tension on the repair sutures. Suture management is critical during this procedure. Stay anterior to the ACL repair sutures when pulling the ACL graft femoral draw suture outside the knee through the tibial tunnel. Irrigation with saline over the ACL Repair TightRope implant (Arthrex) assembly card helps with pulling the leader suture through the button. the ACL repair sutures in the PL femoral tunnel) (Fig 5C). Using the femoral draw suture, the surgeon docks the graft into its femoral socket (Fig 5D).
After cycling of the knee, the graft is tensioned using the TightRope RT with extension button for tibial fixation, with the knee in extension plus a combined posterior and external rotation vector (Fig 6, A and B). The FiberRing within the ACL remnant is attached to an ACL Repair TightRope implant (Arthrex, Naples, FL) using the sequential passing sutures on the assembly card ( Fig 6C). The SutureTape ends in the proximal ACL stump are passed through the empty lateral eyelets of the button. With the knee in extension and neutral rotation, the ACL repair is tensioned using the Tight-Rope cinch stitches, and the SutureTape ends are tied over the button (Fig 6D).

Postoperative Management
A standardized ACL reconstruction protocol under the guidance of a physical therapist is prescribed. Weight bearing is as allowed as tolerated unless meniscal repair was performed. A brace is not routinely used.

Discussion
The concept of ACL repair with autograft augmentation is not new. Open repair of an acute ACL injury with semitendinosus tendon augmentation, often supplemented with a lateral extra-articular reinforcement, provided good to excellent results in active patients. 8 However, with the advent of arthroscopically assisted ACL reconstruction, only few surgeons continued augmented ACL repair (and lateral extra-articular tenodesis). Despite improved clinical outcomes and decreased morbidity compared to the open ACL surgical techniques, graft failure and persistent rotational instability were also seen in patients after single-bundle autograft ACL reconstruction.
Preservation of ACL remnant during ACL reconstruction was found to enhance graft revascularization and integration, with greater initial graft coverage with ACL remnant tissue, resulting in greater postoperative stability. Primary ACL repair results in the greatest degree of remnant preservation, and with advances in fixation and tensioning devices, its use has seen a resurgence. However, even when the repair was restricted to adolescents with acute, proximal avulsions of the ACL, failure rate of ACL repair with suture augmentation was significantly increased relative to ACL reconstruction. 4 To provide additional strength to the ACL repaird especially when insufficient tissue for a complete repair is presentdprimary repair has been augmented with a single-bundle autograft, resulting in a single-bundle ACL construct containing both preserved and reconstructed tissue. 6,7 In these augmented repairs, the central portion of the ACL remnant has to be debrided to allow for graft placement, and the lack of rotational control seen in singlebundle ACL reconstruction might persist.
The current surgical technique incorporates the novel ACL repair methods in a double-bundle procedure, wherein one bundle contains repaired ACL tissue, and the second bundle contains a hamstring autograft, and each bundle is tensioned independently. The advantage of this technique is that the possible benefits of ACL remnant preservation are combined with the biomechanical advantages of two individually tensioned bundles for the control of rotational laxity. The technique is less challenging than a four-tunnel, two-graft double-bundle reconstruction. However, the technique is undeniably more demanding than a standard singlebundle ACL reconstruction, with decreased visibility due to obstruction of the preserved ACL tissue, risk of femoral tunnel convergence, and intricate suture management. Nevertheless, these technical challenges can be minimized as detailed in Table 2. Clinical followup studies of the technique are needed to determine whether the added complexity results in improved outcomes compared to the standard single-bundle ACL reconstruction.
The current surgical concept can be individualized to the patient's ACL anatomy and surgeon's preference. The described steps could be followed to incorporate a quadriceps or bone-patellar tendon-bone autograft instead of a hamstring autograft, or semitendinosus tendon with its tibial insertion left attached, into the double-bundle ACL.
In conclusion, by augmenting the ACL repair with an autograft sized to the fit the individual anatomy, the patient's ACL tibial footprint can be closely restored to normal and the potential benefits of tissue preservation are combined with the biomechanical strengths of an autograft double-bundle ACL reconstruction.