Bridge-Enhanced Anterior Cruciate Ligament Restoration: Surgical Technique

Abstract

Background:

Anterior cruciate ligament (ACL) repair has historically had poor outcomes and fell out of favor in the 1980s with the majority of surgeons opting to do an ACL reconstruction instead due to the high failure rate. The Bridge-Enhanced ACL Restoration or BEAR technique utilizes a de-cellularized, bovine-derived, type I collagen implant to aid in the ACL repair. The device is implanted to augment the healing of the ACL.

Indications:

The BEAR technique is indicated to augment ACL repair in cases of complete rupture where there is a residual tibial stump of sufficient length and good tissue quality.

Results:

In our experience to date, patients undergoing an ACL repair with BEAR recover range of motion quickly and have less quadriceps atrophy and less postoperative swelling than those undergoing ACL reconstruction requiring autograft harvest. We will continue to follow up our patient cohort to assess for re-rupture rate as they return to sport.

Conclusion:

The BEAR technique is a promising development that enables ACL repair as an alternative option to reconstruction. This article describes our approach including tips and tricks to successfully perform this procedure.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

We present a surgical technique for a Bridge-Enhanced Anterior Cruciate Ligament restoration.

Anterior cruciate ligament (ACL) tears are one of the most common sporting injuries with 120,000 ACL injuries occurring per year and accounting for 60% of knee injuries in high school athletes. ³ ACL repair has historically had poor outcomes and fell out of favor in the 1980s, with the majority of surgeons opting to do an ACL reconstruction instead due to the high failure rate. Newer literature, however, has shown improved results, especially with proximal injuries.^6,7

The Bridge-Enhanced ACL Restoration, or BEAR technique, utilizes a de-cellularized, bovine-derived, type I collagen implant to aid in the ACL repair. ⁴ The device is implanted to augment the healing of the ACL. ²

Previous research has been done to demonstrate the effectiveness of this technique and device. Murray et al ⁵ conducted a pilot small-cohort study with 10 patients undergoing a BEAR and a further 10 undergoing a standard ACL reconstruction using a hamstring allograft. Inclusion criteria were a complete ACL tear within 3 months of the surgery and no prior history of knee surgeries. The study demonstrated that the two groups had similar patient-reported outcome measures and stability at 24 months as well as a similar quantity and severity of adverse events.

In 2020, a randomized control trial with a total of 100 patients was conducted to compare BEAR to standard ACL reconstruction with autograft. ⁴ In this study, patients were within 45 days from injury, had a complete ACL tear, and had at least 50% of ACL length remaining. Sixty-five patients were assigned to the BEAR group, and 35 to the ACL reconstruction group. The study demonstrated noninferiority between the two groups with a similar re-rupture rate at 2 years. In addition, the BEAR group had earlier return to activity and sport. While these studies are promising, there is a risk of type II error due to the small sample size.^1,2,4,8

Here is a case presentation and demonstration of our technique. We have a 30-year-old female presenting with a left knee injury sustained while skiing 3 weeks prior to presentation. She reports that she felt a pop with immediate left knee swelling and associated anterior and medial knee pain. She has continued to have instability symptoms since her injury. On clinical examination, she has a 1+ effusion and full range of motion (0° to 135°), with a grade IIb Lachmann and a grade 2 pivot shift. She otherwise has a stable ligamentous examination with no evidence of collateral ligament or posterolateral corner injury. Radiographs were unremarkable. A representative water-weighted sagittal magnetic resonance imaging (MRI) sequence shows a complete ACL rupture with residual tibial stump and no significant meniscal injury. The tibial stump is closely inspected on the mid-sagittal slice at the intercondylar notch looking for at least 50% of the fibers to be well defined and longitudinal, and the stump is therefore presumed to be of good quality, indicating the patient is a potential candidate for BEAR. It remains an intraoperative decision to ensure the fibers can hold sutures and be approximated to the femoral footprint. It is an area of active research to better define preoperative imaging appearances that are predictive of tibial stump quality intraoperatively.

Surgical options for this patient include a nonoperative approach with a period of rehabilitation emphasizing hamstring strengthening, a standard ACL reconstruction, or a BEAR. Indications for a BEAR are ongoing instability in an ACL-deficient knee, presenting with sufficient time for surgery, that is, within 60 days from injury, and adequate length of the tibial stump of the ACL. Contraindications include inadequate length or tissue quality of the ACL stump which, in our experience, is usually discovered intraoperatively by visualization during the diagnostic arthroscopy prior to repair or after probing the ACL repair prior to implanting the device. If this is discovered, we change to performing a standard ACL reconstruction with the choice of graft based on individual patient characteristics and discussion.

We will now present our surgical technique. The patient is positioned supine on a radiolucent table with all bony prominences well padded. A post is placed lateral to the surgical knee to enable the surgeon to place valgus stress on the knee and open the medial compartment for access during arthroscopy. The surgical knee is flexed over the side of the bed with a towel bump in place.

We begin with an examination under anesthesia to confirm the diagnosis, assess for the grade of pivot shift, and rule out any other ligamentous instability that may need addressing. If there is a high-grade pivot shift, we consider adding a lateral extra-articular tenodesis procedure.

We then proceed to a standard diagnostic arthroscopy establishing and utilizing an anterolateral viewing portal. An anteromedial portal is established under direct visualization. During the diagnostic arthroscopy, any meniscal or chondral injuries are evaluated and addressed as needed. In addition, the residual ACL is assessed, and if the tissue quality and length appears suitable, the decision is made to continue with the BEAR procedure rather than change to an ACL reconstruction at this stage.

Next, any fat pad and ligamentum that is present is cautiously debrided to enhance visualization and access through the anteromedial portal without debriding any of the ACL tissue. The femoral footprint for the ACL is prepared using the shaver on burr mode to create a bleeding surface to promote healing. Notchplasty is performed to ensure there is sufficient room for the implant. If needed, the interval between the ACL and posterior cruciate ligament (PCL) is developed with an arthroscopic elevator to mobilize the ACL stump and enable it to be advanced onto the femoral condyle.

Two luggage tag 1.3-mm suture tapes are placed through the ACL stump using a shoulder scorpion device. The surgeon needs to ensure that these have adequate hold and are placed in the appropriate position on the ACL stump such that it can be advanced to the femoral condyle with the optimum tension. To create the luggage tag, the center of the suture is placed into the scorpion device to facilitate this. The suture is placed with the free ends of suture pulled through the loop to create the luggage tag. This is then repeated with a second suture tape so that you have 2 luggage-tag sutures through your ACL stump.

These suture tapes are loaded into a double-loaded 4.75-mm SwivelLock Anchor (Arthrex), and a punch is used to create a pilot hole for the anchor. The punch is used rather than drill to avoid capture of suture or ACL tissue. Tapping is not performed. The anchor is placed within the anatomic footprint of the ACL. After the anchor has been placed, the suture tapes are cut while ensuring the 4 sutures from within the anchor are maintained. These 4 sutures are then brought out the anteromedial portal.

Next, the tibial tunnel is created with a 3.0 drill using a standard ACL tibial tunnel guide. A fiberstick is used to place a passing suture which is retrieved from the anteromedial portal, and a snap is placed on both ends of this suture. The loop is out the anteromedial portal, and a ring grasper is used to ensure there is no tissue bridge between this loop and the 4 sutures from the SwivelLock anchor.

The anteromedial portal is enlarged, and an arthrotomy created. To ensure that we have enough access, we prefer a finger check by placing a gloved finger through the enlarged portal and visualize this with the arthroscope which allows us to make sure that the BEAR implant can be appropriately placed into the notch.

A Keith needle is used to place the 4 sutures from the femoral anchor (exiting from the anteromedial portal) through each quadrant of the BEAR device (Miach Orthopedics). It is important to ensure gloves and surfaces are dry prior to handling the BEAR implant. The patient's autologous blood is taken from a peripheral blood draw by the anesthesia team and used to soak the BEAR implant. It is important to ensure that there is enough blood to cover the BEAR scaffold while ensuring that the scaffold is not completely soaked as it may lose its structure. This will ensure that the integrity of the scaffold is kept during the passage into the joint through the anteromedial arthrotomy. Fluid from the knee is drained prior to placement of the BEAR scaffold. The 4 sutures are pulled through the tibial tunnel using the passing suture to shuttle them through, and the BEAR scaffold is placed through the anteromedial arthrotomy with a combination of pushing on the implant and pulling the tibial sutures until implant is in the notch. The knee is then extended and elevated onto the operating table. The knee is kept in extension from this point forward.

The sutures are then fixed to the tibia with a second 4.75-mm SwivelLock Anchor with the knee in extension. It is not possible to view the position of the BEAR implant after it has been inserted into the knee as it is important not to introduce any arthroscopic fluid into the joint after the implant has been placed. The correct position of the implant is confirmed with palpation by the operating surgeon who can feel that it is within the intercondylar notch with their finger.

Wounds are closed with a 0 vicryl suture to the anteromedial arthrotomy followed by standard wound closure with a 2-0 vicryl and 3-0 running prolene suture.

It is important to discuss a backup graft with the patient and be prepared to perform a reconstruction if necessary. With regard to the femoral preparation, we empathize that we use a punch rather than a drill, and we do not tap. Suture management is important, and it may be necessary to place proximal sutures if there are significant femoral fibers remaining in order to oppose the two ends of the ACL. With regards to BEAR implantation, it is important that you have easy access through the anteromedial portal and that you do not oversaturate the BEAR implant.

With regard to postoperative rehabilitation, initially, the patient has 0 to 4 weeks of touch-down weightbearing with crutches, and then the protocol reverts to one consistent with standard ACL rehabilitation. The overall rehabilitation for patients undergoing a BEAR procedure is similar to that for patients undergoing standard ACL reconstruction. However, anecdotally we have noticed patients tend to do well in the early postoperative period due to the absence of pain secondary to autograft harvest. Average return-to-sport duration is between 9 and 12 months.

At the 6-month follow-up, this patient underwent an MRI. This sagittal sequence shows that ACL fibers are present and inserted on the lateral femoral condyle, indicating that there was successful repair and healing of the ACL in this case. This still MRI image demonstrates that the ACL fibers are in the correct orientation and that the BEAR implant has reabsorbed with no evidence of a cyclops lesion. Arrows highlight the path of the ACL.

Thank you for your interest.