Abstract
Background:
Anterior cruciate ligament (ACL) injuries are incredibly common, with an annual incidence of 68.6 per 100,000. The Bridge-Enhanced ACL Restoration (BEAR) is a relatively novel technique that combines suture repair of the ligament and a bioactive scaffold implant to bridge the gap between the torn ligament ends. Since the adoption of the BEAR technique, several modifications have been made to the original technique. These modifications are being prospectively studied within the Bridge registry.
Indications:
ACL tears amenable to repair.
Technique Description:
The described technique demonstrates 2 common modifications to the original BEAR technique. The first technique passes 2 luggage tag-style sutures onto the ACL stump. These are then passed into a tensionable suture loop and button assembly. This is passed through a femoral tunnel, securing the ACL stump to the femoral footprint. Bridging sutures are attached to the button, passed through the BEAR Implant, and brought through a tibial tunnel. The second demonstrated technique again passes 2 luggage tag style sutures through the ACL stump and secures them to the femoral footprint using a knotless anchor. Bridging sutures are passed through the BEAR Implant, out a tibia tunnel, and fixed to the tibia with another knotless anchor. In both techniques, the preparation of the BEAR Implant is the same and is completed without arthroscopic visualization.
Results:
In our experience, patients undergoing BEAR with real-world technique modifications have achieved successful outcomes. The Bridge registry has prospectively followed these patients and has published their early results. With the first 100 patients, they showed an ACL retear rate of 5% at 2 years. Furthermore, there has been a low rate of adverse events, and 61% of patients have been able to return to sport at 9 months.
Discussion/Conclusion:
Several technical modifications have been developed for the use of the BEAR Implant in ACL repair. These approaches demonstrate promising early outcomes and enable surgeons to tailor the procedure according to their preferences and level of expertise.
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 of approval from the patient(s) with this submission for publication.
This is a visual representation of the abstract.
Keywords
Video Transcript
This video demonstrates various technique modifications using the Bridge-Enhanced Anterior Cruciate Ligament Restoration Implant for ACL restoration.
Background
Dr. Martha Murray developed the Bridge-Enhanced ACL Restoration (BEAR) Implant. The goal is to create a fibrin clot, which is imperative for extra-articular ligament healing. She found that bovine collagen had the ideal characteristics of being hemostatic, supporting cell adhesion, clotting, and resisting synovial degradation. The anterior cruciate ligament (ACL) will not heal on its own because the ACL is an intra-articular ligament. Unlike the medial collateral ligament, a clot or bridge at the wound site is unable to form as enzymes within the synovial fluid break that clot down.
The BEAR Implant itself is decellularized, and during preparation for implantation, the patient's autologous blood is used to hydrate it. Biologically, the hydrated graft forms a fibrin-platelet clot that bridges the gap between the torn ends of the ACL. It coats the ends of the healing ACL, protecting it from synovial enzymes. By 8 weeks, the BEAR Implant is replaced with native tissue, collagen, and blood vessels. Over time, the new tissue remodels and becomes stronger. There have been many BEAR Implant clinical trials. BEAR I was a feasibility trial, which showed a 0% retear rate. 3 BEAR II was the Food and Drug Administration pilot study, which demonstrated a 13.8% retear rate. 2 BEAR III expanded the label use of the BEAR Implant. BEAR MOON has enrolled 150 participants comparing BEAR with bone-patellar tendon-bone, and most recently, the Bridge Registry has opened up the use of the BEAR Implant to many different technical modifications to study post-market real-world evidence of the BEAR Implant. 1 Initial results indicate about a 5% retear rate. With this video, we will demonstrate and discuss several technical modifications seen in the Bridge registry.
Technique Description
Overview
In the classic technique, Vicryl sutures are passed through the ACL stump and brought out through a tunnel just anterior to the femoral footprint. Ethibond sutures are used as the bridging sutures, which are then brought out through a tibial tunnel and fixed with a button. The sutures are tightened in extension.
In Modification 1, a tibial anchor is used for fixation instead of a button. In Modification 2, the repair suture is altered to use a high-tensile suture passed through the ACL as a luggage tag, rather than the Bunel-style stitch. In Modification 3, the bridging suture is altered to use a high-tensile suture. This can either have 2 or 4 strands. In Modification 4, a knotless femoral anchor is used instead of a femoral tunnel with a button for the fixation. In Modification 5, a tensionable femoral suture loop and button are constructed. This allows for the ACL repair to be retensioned after the BEAR Implant is inserted. Furthermore, many different combinations of these modifications being used in real-world applications, all of which are captured and studied in the Bridge Registry.
Demonstrations
First, we will demonstrate the modification with the tensionable femoral suture loop and button. This utilizes high tensile strength sutures. The ACL stump is first assessed for adequacy and appropriateness of repair. The stump can be mobilized if needed, as there often are adhesions to the posterior cruciate ligament. A limited notchplasty should be performed to provide a healing surface, taking care not to disrupt the femoral footprint.
The femoral tunnel is then placed. This is done via an outside-in point-to-point guide. The guide is inserted through a lateral portal while viewing through a medial portal. The tunnel should enter the notch at the anterior aspect of the ACL footprint. This does require a percutaneous distal lateral femoral incision. The arthroscope is then positioned back in the lateral portal. A flexible cannula is inserted into the medial portal to facilitate suture passage.
A self-retrieving suture passer is then used to place 2 or 3 small loop sutures in a luggage tag style into the ACL stump. Each of these sutures is preloaded with an additional shuttling suture that is later used to pass one end of a tensionable suture loop assembly. In this technique, the FiberRing (Arthrex) is used. The free limb of the yet-to-be assembled tensionable suture loop and button construct is sequentially loaded onto each of these fiber rings. This needs to be done in the same direction: either all top-down, as in this video, or bottom-up. Outside of the joint, the tensionable suture construct can now be fully assembled using the preloaded card. The leading suture end is unwound and passed sequentially through the card. Once loaded, the suture ends are pulled out of the card, now attached to the button and ready for passing. The suture button is then prepared to be shuttled into the medial portal. The lead suture is then used to shuttle the button up into the notch and out of the femoral tunnel. Arthroscopically, we see the button being fed up into the notch and then through our femoral tunnel. The bridging sutures are suspended by the femoral button left behind in the medial portal, spanning the joint. The suture is preliminarily tensioned to tighten the repair.
The tibial tunnel is then drilled just anterior to the ACL footprint. This is done using another point-to-point guide inserted through the medial portal. In this case, we use a cannulated drill bit so that a lasso can be passed and retrieved from the anterior-medial portal. This concludes the arthroscopic portion of the procedure.
Outside of the body, the BEAR Implant is prepared for passage into the knee. This process is the same for all technique modifications. The firmest end of the BEAR Implant is first selected as the inferior end, as it will be used to push the implant through the extended medial portal into the notch. Using a Keith needle, the bridging sutures are passed through the implant from superior to inferior. Using 15 to 30 mL of autologous blood, the implant is then hydrated on the superior portion and sides. The inferior portion is minimally hydrated, so it remains firm for pressing into the notch through the extended medial portal. Once the implant is inserted into the notch, the knee is brought up into an extended position. The tibial sutures are then tensioned and fixed to the tibia. In this modification, a knotless anchor is used for fixation to the tibia.
The second technique we will present is the knotless anchor technique. In this technique, instead of drilling a tunnel, a knotless anchor is placed at the femoral footprint. Again, to begin this procedure, the ACL tissue quality is assessed for repair, and it is mobilized if needed. A limited notchplasty is performed as seen here. Multiple luggage tags are placed into the ACL. The hole for the anchor is punched and tapped. This is done with the knee in flexion. The anchor is placed just anterior and superior to the ACL footprint so that when the luggage tags with the ACL tissue are loaded onto the anchor, they pull the ACL to its native footprint. Four limbs from this anchor or 2 limbs of an internal brace are parked in the medial portal and later used as bracing sutures for the BEAR Implant.
A tibial tunnel is drilled just anterior to the ACL stump using a point-to-point guide. A passing suture is then placed through the tibial tunnel. The passing suture and the bracing sutures are then all retrieved through the medial portal.
Results/Discussion
All modifications to the original BEAR technique are included in the Bridge Registry. The Bridge Registry is a post-market clinical study that will continue collecting data on patients treated with the BEAR Implant in a commercial setting. The inclusion-exclusion criteria are unrestricted so that investigators are not required to adhere to the original technique. A total of 300 patients were enrolled, of whom 161 reached 2-year outcomes.
For the first 100 enrolled patients, 1-year data analysis was completed in September 2024, and 2-year data analysis was completed in June 2025. 4 Interim results demonstrate that at 1 year, the retear rate was 0%, and at 2 years, it was 5%. The overall reoperation rate was 18.2% at 2 years. There has been continued technical variation for real-world BEAR Implant utilization.
Conclusion
Overall, there have been no differences in safety outcomes between classic and modified techniques. Continuing to follow these patients in the BRIDGE Registry will shed light on any potential long-term complications and retear rates.
Footnotes
One or more of the authors has declared the following potential conflict of interest or source of funding: B.C.L. has received consulting fees from Miach Orthopaedics. J.R.W. has received consulting fees from Miach Orthopaedics. J.M.B. has received a paid presenter fee from Miach Orthopaedics. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.
