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Primary Anterior Cruciate Ligament Single-Bundle Repair With Augmentation for a Partial Anterior Cruciate Ligament Tear

Although anterior cruciate ligament (ACL) reconstruction remains the gold standard for the treatment of ACL tears, repair is regaining popularity as a treatment option for proximal or distal ACL avulsions. Historically, ACL repairs had poor outcomes. To remedy this, techniques were developed using graft-based augmentation but never gained widespread popularity. Recently, there has been a renewed interest in primary ligament repairs, with newer techniques incorporating modern synthetic materials to augment the repair site. The term “internal bracing,” or ligament repair with augmentation, has been used to describe the new philosophy for primary ligament repair and augmentation. We present our technique for arthroscopic primary ACL repair with augmentation for a proximal posterolateral bundle tear. The advantages of this technique include preservation of the intact fibers of the anteromedial bundle, intuitive suture augmentation with standard ACL tunnel placement techniques, and the ability to calibrate ligament tension.

S ingle-bundle autograft anterior cruciate ligament (ACL) reconstruction is the current gold standard treatment for an ACL tears; however, there are associated morbidities and complications. [1][2][3][4] Research into the treatment of ACL injuries has focused on optimizing reconstructions with modifications in parameters such as graft choice and tunnel placement. 5 Reconstruction has remained the procedure of choice due to unsatisfactory historical results with primary ACL repair. 6 However, ACL repair has the potential to preserve ligament orientation, knee kinematics, and native proprioception. [7][8][9] New technical modifications could allow us to reach satisfactory biomechanics, making primary repair a viable option. There are reported strategies for improving ACL repair outcomes with graft augmentation, but this has not gained widespread use except in the form of remnant-preserving ACL reconstructions. [10][11][12][13] The advent of new, high tensile strength suture materials has created the potential for synthetic augmentation. ACL repair with suture-based augmentation has been described and is of increasing popularity. 14, 15 We present our technique for arthroscopic primary repair of the native ACL with augmentation. A diagnostic arthroscopy is performed. In this case, it shows a proximal rupture of the majority of the posterolateral bundle and the leading edge of the anteromedial bundle of the ACL. Distally the ACL is intact. In general, we reserve repair for proximal or distal avulsions with some ligament fibers in continuity. If diagnostic arthroscopy shows a mid-substance tear or poor integrity of the native ligament, we proceed with reconstruction rather than repair.

Surgical Technique
Once the tear is identified, a passport cannula (Arthrex, Naples, FL) is placed in the medial portal while viewing through the lateral portal. A scorpion suture passer (Arthrex) is then used to pass 4 FiberLinks (Arthrex), each color-coded (2 blues, 2 whites, alternating), into the remnant ACL. The suture passer is aimed so the needle deploy toward the lateral femoral condyle. This will result in the sutures exiting the lateral aspect of the ligament. This allows for appropriate orientation of the ligament when repaired back native ACL origin off of the lateral aspect of the intercondylar notch. A locking stitch is easily created by the use of a FiberLink No. 2 suture (Arthrex). All passed sutures are then brought outside the cannula.

Preparing the Femoral Origin
The native posterolateral bundle origin is lightly debrided with a shaver, taking care not to injure the origin of the intact anteromedial bundle fibers or the native ligament. Gently pulling medial tension on the newly placed sutures within the native ACL stump can assist in exposing the ACL femoral footprint. Next, while viewing through the medial portal and instrumenting through the lateral portal with an ACL FlipCutter guide (Arthrex) set on approximately 110 , the guide is placed in the avulsed portion of the ACL where the fibers originated from. A small incision in the distal lateral thigh is then made through the skin and subcutaneous tissues, and underlying iliotibial band to drill with the FlipCutter. Of note, we use this to drill but do not flip the blade. A No. 2 fiberstick Fiberwire (Arthrex) is brought out of the lateral portal and is then used to shuttle a total of 2 color-coded FiberLoop stitches for transport.

Returning ACL to Its Origin
While viewing through the lateral portal, the sutures within the ACL stump (which have been sitting outside of the medial portal for storage) are brought back into the medial cannula and loaded into one of the colorcoded femoral transport sutures (which had been stored outside of the lateral portal). The ACL stump sutures are then transported back into the knee and into the femoral tunnel. This puts tension back into the    ACL, recreating the ACL contour, and returning the ACL back to its origin in the intercondylar notch.

Creating and Preparing the Tibial Tunnel
With the ACL back in place, an ACL tibial guide set at 55 to 60 is inserted at the ACL footprint. Using the Flipcutter without deploying it, the tibial tunnel is then drilled, taking care not to injure the body of the ACL. Next, a No. 2 fiberstick (Arthrex) is passed through this tunnel to bring in a passing suture.

Augmentation of the Primary Repair
A No. 2 FiberTape is looped and passed up into the femoral tunnel through the second color-coded Fiber-Link passing suture passed into the tibial tunnel using the tibial transport suture.

Securing the Construct
On the femur, the looped end of the No. 2 FiberTape is secured by looping it over an ABS Dog Bone fixation device (Arthrex). The repair sutures (the 4 color-coded No. 2 FiberLinks) from the ACL stump are then organized by color on the opposite sides of the button to eventually be tied down to each other (blue to blue, white to white). The Dog Bone is then placed on the femur while holding the sutures in place and the knee is cycled for 30 repetitions of flexion and extension for preconditioning.
The knee is placed in 20 degrees of flexion with a posterior drawer. The ACL stump sutures are then tied down in a total of 2 separate knots over the button (blues to blues, whites to whites). Next, the knee is cycled again for 30 more repetitions. The knee is then placed in near full extension with a gentle posterior drawer, whereas the tibial portions of the augmentation sutures are secured in a SwiveLock suture anchor, just distal to the tibial tunnel orifice. Care is taken not to over tension the augmentation sutures as it is meant to merely reinforce the ACL primary repair. The ACL repair with augmentation is now complete and spans the entire distance of the ligament (Figs 10 and 11).

Rehabilitation
The rehabilitation protocol uses no brace or crutches and attempts facilitate return to activity as quickly and safely as possible. During the first postoperative week, we allow full weight bearing as tolerated and full range of motion with the goal of maintaining full passive extension. During the second week, we begin formal physical therapy with quadriceps isometrics, straight leg raises, active flexion, and active-assisted extension exercises. We allow return to work at this time for desk jobs or light duty. During the third and fourth weeks, we progress to strengthening with quad sets, straight leg raises, partial squats, toe raises, stationary bike, elliptical machine, leg presses, and leg curls. We also have a goal of flexion to 120 by this point. In the 4-to 6-week span, we continue strengthening and progress to balance exercises. Starting at week 12, we introduce jogging as well as light running and agility drills. Finally, we allow return to sport at 24 weeks if quadriceps and hamstring strength is at least 80% of the    normal leg, there is full motion, no swelling, good stability, and the patient is able to complete a running program.

Discussion
Single-bundle autograft ACL reconstruction is the current gold standard treatment for an ACL tear, but ACL repair may have the potential to improve outcomes in a select group of patients. Primary repair of the native ligament, with or without augmenting, allows for a less invasive approach while preserving the native anatomy and biology. The biologic benefit was shown by a prospective comparative study by Young et al. 16 that evaluated mechanoreceptor reinnervation. In that study, biopsies were taken and stained for neurofilament protein (NFP) and compared with the native ACL. There was no difference in NFP analogs when comparing autograft with allograft, but there was a significant decrease in NFP in autograft and allograft compared with native ACL tissue, implying improved proprioception with native tissue.
Arthroscopic primary ACL repair was recently repopularized by DiFelice et al. 17 in 2015. The authors reported promising early short-term results (minimum 2-year follow-up) with primary ACL repair in a small group (n ¼ 11) of carefully selected patients with proximal ACL avulsions and good quality tissue. Achtnich et al. 18 compared primary ACL repair with suture anchor to single-bundle ACL reconstruction. They had a failure rate in the primary repair group of 15% compared with 0% in the reconstruction group; however, this was not statistically significant. They found no significant differences in Lachman testing, pivot shift testing, objective International Knee Documentation Committee score, and KT-1000 scores. Both DiFelice and Achtnich used suture anchors for the femoral fixation. Augmentation provides biomechanical protection to reduce tension on healing ligamentous tissue. In 2016, MacKay et al. 14 Table 1 for the advantages and disadvantages, and Table 2 for the pearls and pitfalls of ACL repair with suture augmentation.
Video 1 is a narrated step-by-step guide to our arthroscopic technique for ACL repair with suture augmentation. The whole video is from the same case in a right knee. The viewing portal is indicated in the top-left corner throughout.