BEAR ACL Repair: Understanding the Novel Bridge-Enhanced Technique

What is the Bear ACL repair?

The BEAR® (Bridge-Enhanced ACL Repair) Implant is an innovative surgical procedure designed to facilitate the healing of a torn anterior cruciate ligament (ACL) rather than replacing it, as is done in traditional ACL reconstruction. This technique uses a resorbable collagen-based implant to bridge the gap between the torn ends of the ACL, providing a scaffold for the body's own blood and cells to form a clot and regenerate the native ligament tissue.

Understanding ACL Injuries

The anterior cruciate ligament (ACL) is one of the four major ligaments in the knee, playing a critical role in stabilizing the joint, particularly in preventing the tibia (shin bone) from sliding too far forward relative to the femur (thigh bone) and limiting rotational movements. ACL injuries are common, especially in sports involving sudden stops, changes in direction, jumping, and landing (e.g., soccer, basketball, skiing). When the ACL tears, it typically disrupts the blood supply to the ligament ends, preventing natural healing. For many, especially active individuals, surgical intervention is often recommended to restore knee stability and function.

Traditionally, ACL repair involves reconstruction, where the torn ligament is removed and replaced with a graft, typically taken from another part of the patient's body (autograft) or from a deceased donor (allograft). While highly effective, this method introduces donor site morbidity (if autograft) and does not preserve the native ACL structure.

The BEAR® Implant: A Novel Approach

The Bridge-Enhanced ACL Repair (BEAR®) Implant represents a significant advancement in ACL injury management. Developed by researchers at Boston Children's Hospital, the BEAR® Implant received FDA approval in 2020, offering an alternative to traditional ACL reconstruction for specific types of tears.

Unlike reconstruction, the BEAR® procedure aims to heal the patient's own torn ACL. It does this by providing a scaffold that acts as a bridge between the torn ends of the ligament. This scaffold is filled with the patient's own blood, which forms a clot within the implant. This blood clot is rich in healing factors and cells that are essential for tissue regeneration. Over time, the scaffold is naturally absorbed by the body as the native ACL heals and regrows, eventually restoring the ligament's original structure and function.

How the BEAR® Procedure Works

The BEAR® procedure is performed arthroscopically, meaning it involves small incisions and specialized instruments guided by a camera.

• Preparation: The surgeon first assesses the torn ACL. The torn ends of the ligament are prepared to encourage healing.
• Implant Insertion: The BEAR® Implant, a small, sponge-like collagen scaffold, is carefully placed between the torn ends of the ACL.
• Blood Introduction: A small amount of the patient's own blood is drawn and injected into the BEAR® Implant. This blood saturates the scaffold, forming a clot that bridges the gap between the torn ligament ends.
• Suture Fixation: Sutures are used to secure the torn ends of the ACL to the BEAR® Implant, ensuring proper alignment and stability during the initial healing phase.
• Healing Process: The blood clot within the scaffold provides a biological environment conducive to healing, encouraging the body's own cells to grow into the scaffold and form new ligament tissue. As the new tissue forms, the BEAR® Implant gradually resorbs over approximately 8 weeks.

Advantages of the BEAR® Implant

The BEAR® Implant offers several potential benefits compared to traditional ACL reconstruction:

• Preservation of Native ACL: The primary advantage is the ability to heal and preserve the patient's original ACL, which may retain more of its natural anatomy, proprioception (sense of joint position), and vascularity.
• No Graft Harvest Morbidity: Since no graft is taken from another part of the patient's body, there is no pain or weakness associated with graft harvest sites (e.g., hamstring or patellar tendon).
• Potentially Faster Initial Recovery: Some studies suggest that patients may experience less pain and a quicker return of quadriceps strength in the early post-operative period compared to traditional reconstruction.
• Maintained Proprioception: By preserving the native ligament, there's a theoretical advantage in maintaining the sensory nerve endings within the ACL, which contribute to proprioception and reflex muscle activation for joint stability.

Potential Disadvantages and Considerations

While promising, the BEAR® Implant also has considerations:

• Newer Technology: It is a relatively new procedure, meaning long-term outcomes beyond a few years are still being studied and accumulated.
• Specific Tear Types Only: The BEAR® Implant is not suitable for all ACL tears. It is primarily indicated for acute, mid-substance ACL tears where both ends of the torn ligament are still present and can be approximated. It is generally not recommended for chronic tears, avulsion injuries (where the ligament pulls off the bone), or tears with extensive damage.
• Re-rupture Risk: Like traditional ACL reconstruction, there is still a risk of re-rupture with the BEAR® Implant, though current data suggests similar re-rupture rates to traditional methods.
• Rehabilitation Protocol: While early recovery may differ, the overall rehabilitation protocol for the BEAR® Implant is very similar in duration and intensity to traditional ACL reconstruction, typically lasting 6-9 months or more before a full return to sport.

Who is a Candidate for BEAR®?

Ideal candidates for the BEAR® Implant typically meet the following criteria:

• Acute ACL Tear: The injury must be recent, usually within weeks of the tear (often within 50 days of injury).
• Mid-Substance Tear: The tear must be in the middle portion of the ligament, allowing the two ends to be brought together.
• Intact Ligament Ends: Both the femoral and tibial stumps of the torn ACL must be present and of sufficient length to allow for repair.
• Age: While initial studies focused on younger patients (e.g., 12-35 years old), candidacy is increasingly determined by tear type and activity level rather than strict age cutoffs.
• Overall Health: Good general health and no contraindications to surgery.

A thorough evaluation by an orthopedic surgeon specializing in knee injuries is essential to determine if the BEAR® procedure is appropriate.

Recovery and Rehabilitation

Recovery after a BEAR® procedure follows a structured, multi-phase rehabilitation program, similar to traditional ACL reconstruction. The timeline and specific exercises are tailored to protect the healing ligament while gradually restoring strength, range of motion, and function.

• Phase 1: Protection and Early Motion (Weeks 0-6): Focus on protecting the healing ligament, managing swelling and pain, and regaining full knee extension. Crutches are typically used, and a brace may be prescribed.
• Phase 2: Progressive Strengthening and Balance (Weeks 6-12): Gradually increase weight-bearing, introduce strengthening exercises for the quadriceps, hamstrings, and glutes, and begin balance training.
• Phase 3: Advanced Strengthening and Agility (Months 3-6): Progress to more dynamic exercises, including light jogging, plyometrics, and sport-specific drills, under strict supervision.
• Phase 4: Return to Sport (Months 6-9+): Gradual return to full activity and sport, contingent upon meeting specific strength, balance, agility, and functional performance criteria, often after comprehensive testing.

Adherence to the rehabilitation program is crucial for successful outcomes, as the healing ligament needs time and appropriate stress to regain its strength and integrity.

Comparing BEAR® to Traditional ACL Reconstruction

Conclusion

The BEAR® Implant represents a significant step forward in ACL injury management, offering a biologically-driven approach to heal the native ligament. For select patients with acute, mid-substance ACL tears, it provides an alternative to traditional reconstruction, potentially offering benefits such as preserved native anatomy and reduced donor site morbidity. As with any surgical procedure, careful consideration of individual patient factors, tear characteristics, and a thorough discussion with a qualified orthopedic surgeon are paramount to determining the most appropriate course of treatment and ensuring the best possible outcomes.