BEAR ACL Surgery: A New Era for ACL Repair
‘You tore your ACL’ may be four of the most dreaded words an athlete knows. Those crippling words could be season-ending, but they are heard all too often. In the United States alone, around 200,000 ACL tears occur each year, according to Scott A. Rodeo, MD. They most commonly affect athletes in sports, namely football, soccer, and basketball, with high amounts of contact, pivoting, changing of direction, and jumping. The anterior cruciate ligament (ACL) is what connects the femur to the tibia and stabilizes the knee joint. A torn ACL creates an unstable knee prone to buckling and inhibits the abilities to jump, land, pivot, and accelerate, thus requiring surgery if the patient wants to play sports again. If the patient is not returning to sports, then surgery is not needed, as walking and running are still possible after some time. However, Nancy Novick from the Hospital of Special Surgery concludes that patients not undergoing surgery put themselves at greater risk of tearing their menisci, which puts them at a greater risk for developing osteoarthritis. If the patient wants to return to any activity requiring stability of the knee, surgery is the best option, although there are downsides to surgery currently available.
In the 1900s, ACL repair surgery involved reconnecting the two ends of the torn ACL through a suture. Dr. A. M. Kiapour and Dr. M. M. Murray report that this repair failed in more than 90% of the time, suggesting the ACL cannot regrow or heal itself. Surgeons transitioned from the unsuccessful suture repair technique to ACL reconstruction. Until recently, ACL reconstruction surgery involved taking the graft of another tendon in the body, usually hamstring, quadriceps, or patellar tendon, or a graft from a cadaver, and using it to replace the torn ACL. Surgeons actually remove the torn ligament and substitute the graft. Novick explains that this surgery uses arthroscopic techniques, including “fiber optics, small incisions, and small instruments.” Although endoscopic, a relatively large scar remains on the front of the knee and one from where the graft was taken. Using a graft from a cadaver, otherwise, increases the risk of disease transmission and rejection from the body (Kiapour 2014). Nonetheless, these athletes are more susceptible to a second knee injury and post-traumatic osteoarthritis, according to doctors Kiapour and Murray. They explain that the ligament replacement alters the joint mechanics of the knee, decreasing neuromuscular function, knee control and stability. The change in knee movement patterns and control rationalizes the increased risk of injury and development of osteoarthritis, onset of which holds a 66 to 100% risk post-reconstruction. In attempts to minimize the effects of altered knee mechanics and arthritis, doctors developed a “double-bundle reconstruction” as opposed to the standard single-bundle (Kiapour 2014). This development better restored joint stability, yet it provided no improvement to preventing osteoarthritis. Kiapour describes numerous novel methods of ACL treatment, including stem cell therapy, gene therapy, and use of bio-scaffolds, all of which demand further research to be tested in humans.
Recovery, consisting of mainly physical therapy, takes on average six to nine months, but it can take as long as twelve. Doctors and physical therapists evaluate range of motion, strength, control, and pain to determine when the knee reaches normal or close to normal function. Athletes can most often return to their sport, but for some, they can never play the way they did prior. On the other hand, many professional athletes, like Tom Brady, Alex Morgan, and Rob Gronkowski, have recovered from ACL surgery and surpassed all expectations by winning Super Bowls and World Cups. Those triumphs came only after a long six or more months of healing and determination to recover stronger. Not to mention, these athletes will most likely develop osteoarthritis in the future, inhibiting their active lifestyles.
Dr. Martha Murray is changing the course of ACL treatment. She created the less invasive Bridge-Enhanced ACL Repair (BEAR) procedure to effectively eliminate the need for a separate tendon graft. Domonique Foxworth reports that Murray developed a collagen bridge with which surgeons stitch together the two torn ends of the ACL to help the ligament heal more efficiently on its own. The bridge is essentially a sponge that is injected with the patient’s blood. The blood potentially increases blood flow and thus healing components of blood to the area and helps reduce inflammation in the knee, allowing space for the ligament to heal (Proffen, et al. 2016). Although still early in the clinical process, Murray proved that her BEAR technique healed the ACL equally well as ACL reconstruction surgery, effectively decreased the risk of osteoarthritis post-surgery, and minimized the recovery time.
Murray was a material science engineering student with no medical background whatsoever when she became intrigued by ACL reconstruction and healing. Her friend underwent ACL reconstruction, and she could not believe that the ligament couldn’t just be repaired and that they had to remove it completely. She took to the library in an attempt to understand this phenomenon and learned of the failed attempts to suture the ACL back together in the 1900s. In 1989, Murray left of her engineering graduate program at Stanford and enrolled in University of Pennsylvania’s medical school and then completed her residency at Harvard, determined to find a way to help the ACL heal without removing it. She got her foot in the door of this pursuit during her residency when she gained permission to sit in on ACL reconstruction surgery and collect the removed ACLs. The nurses gave her the nickname “Soup Lady” after joking that she was taking all those ACLs to make soup. With torn ACLs, Murray examined them using a microscope to find that they still had active cells and blood vessels, which meant the ligament was trying to heal itself. She discovered that the synovial fluid surrounding the ligament was washing away any blood clots formed. Blood clots serve as a connection between the torn tissue ends, supplying the blood components that heal wounds and regenerate tissue, like platelets and red and white blood cells (Murray, et al. 2016). Because the fluid in the knee joint was destroying the clots, Murray constructed a bridge to hold the clot and ligament ends in place to allow the healing process to continue uninterrupted. The bioactive bridge scaffold consists of normal ACL extracellular matrix proteins, which activate the platelets and clotting factors in the blood (Murray and Fleming 2013). According to Haslauer and her colleagues, including Murray, another reason for the ACL not being able to heal on its own is the decreased expression of collagen-regulating genes within weeks after the tear (2015). They concluded that this would inhibit repair of the ligament because collagen is required in rebuilding the tissue. So, Murray generated her bridge with collagen as a main component. She first created the bridge in 2008 from New Zealand cows and tested it out on pigs. Murray found that between six and eight weeks after surgery, the ACL regrows into the sponge and physically reconnects its ends. She and Dr. Braden Fleming performed a study released in 2013 showing the effectiveness of the Bridge-Enhanced ACL Repair. The pigs regrew their ACL and they had significantly less arthritis than those who received reconstruction surgery. Post-trial, she eventually earned funding to perform this repair in humans. In her first clinical trial, ten patients received BEAR treatment and ten received complete reconstruction surgery. Three months after surgery, the BEAR recipients’ ACLs were healing, they regained almost normal flexibility, and they recovered strength in the injured leg faster than the reconstruction patients (Murray, et al 2016). None of the patients who underwent BEAR surgery had any bad infections or knee stiffness after the surgery, and they regained their hamstring strength much quicker than those who underwent reconstruction, as BEAR does not require hamstring grafts (Springer 2016). Murray is currently conducting a trial of 100 patients in hopes of making the procedure available for widespread use. She is already thinking about expanding this surgery from just ACLs to labrum tears in the shoulder, rotator cuff tears, elbow ligament tears, and even arthritis. She dreams of invigorating stronger and more efficient recovery, using the body as the primary tool for healing.
Corey Peak, a young adult skier, was the first patient to receive Murray’s BEAR treatment in 2015. Three months post-surgery, Peak received an MRI to assess the healing process. Tears rolled down Dr. Martha Murray’s face as she got her first look at the success of her first BEAR trial surgery. She saw healing tissue in the space the ACL previously occupied. His range of motion looked great, his strength came back quicker than expected, and his ACL was growing back together. Springer reported that Peak is back to skiing, playing sports, biking to work, running 30 miles a week, and swimming, sometimes forgetting which knee was injured.
This incredible outcome could change the course of the ACL injury epidemic and decrease the recovery time needed to get athletes back in the game sooner than ever before. Another benefit of the BEAR procedure is that it actually “can restore the structural and anatomic properties of the torn ACL to those of the native ACL in an effort to minimize the risk of early-onset posttraumatic osteoarthritis” (Kiapour, et al 2017). In a previous study by Fleming and Murray, they found the average damaged cartilage area was significantly less in BEAR treated knees than in reconstructed ACLs after 12 months. More cartilage damage usually results in arthritis, so less damage in the BEAR trials supports the hypothesis that the BEAR procedure reduces the risk of developing arthritis. To confirm the hypothesis, studies on a much longer scale must be performed to understand if this novel surgery reduces osteoarthritis ten to twenty years post-surgery. Currently, there are no known downsides to this new repair, the only potential problem is if patients are allergic to cow protein, as the bridge is made of bovine collagen. There is currently no indication on how much this new surgery will cost in the future, but I imagine it will be comparable to current ACL surgery.
ACL surgeries and surgeries in general have improved tremendously over the past century, from having a less than 10% success rate, to the opposite, as high as a 97% success rate (Samitier, et al 2015). Yet even with improved technology and medicine, athletes still endure games and upon games and seasons upon seasons of sitting the bench because of an injury. An ACL injury will displace an athlete from his or her sport for 7 to 10 months, if not more. This debilitating circumstance could mean the end of a career for some athletes, not just the end of a season or two. The importance and relevance of new advancements in ACL repair for athletes like these cannot be emphasized enough. Dr. Martha Murray broke the glass ceiling of ACL repair and what is known about this ligament and the body. Her less-invasive Bridge-Enhanced ACL Repair surgery development changes the way athletes will view ACL injuries. As opposed to being completely disheartened by hearing the echoing pop of an ACL rupture, athletes can now interpret it as a mere speed bump, rather than the world’s longest stop sign, on their journey of playing the sport they love. Once the BEAR surgery completes the clinical trials and is available for ACL patients across the globe, athletes will look forward to a much faster recovery, only one incision and less trauma to the leg. Their remaining ACL tissue will also be preserved for closer to normal function, there will be less risk as is associated with cadaver grafts, and there will be a greatly decreased risk of developing osteoarthritis. These are the advantages understood after only the initial phases of the BEAR clinical trials; in the longer term, there could be many benefits that have yet to be discovered. These benefits all further separate the traditional ACL reconstruction surgery, which often requires two incisions and a longer recovery with greater risk of getting osteoarthritis, from the innovative BEAR surgery, which proves to be much more effective for competitive athletes.
Kiapour, Ata M., Braden C. Fleming, and Martha M. Murray. “Structural and Anatomic
Restoration of the Anterior Cruciate Ligament Is Associated With Less Cartilage Damage 1 Year After Surgery: Healing Ligament Properties Affect Cartilage Damage.” Orthopaedic Journal of Sports Medicine 5.8 (2017): 2325967117723886. PMC. Web. 1 Nov. 2017.
Foxworth, Domonique. “New ACL surgery could cut rehab and recovery time in half.” The
Undefeated, ESPN Internet Ventures, 21 Sept. 2016
Kiapour, A. M., and M. M. Murray. “Basic Science of Anterior Cruciate Ligament Injury and
Repair.” Bone & Joint Research 3.2 (2014): 20–31. PMC. Web. 1 Nov. 2017.
Murray, Martha M., et al. “The Bridge-Enhanced Anterior Cruciate Ligament Repair (BEAR)
Procedure.” Orthopaedic Journal of Sports Medicine, vol. 4, no. 11, 2016, p. 232596711667217. The Orthopaedic Journal of Sports Medicine, doi:10.1177/2325967116672176.
Murray, Martha M., and Braden C. Fleming. “Use of a Bioactive Scaffold to Stimulate ACL
Healing Also Minimizes Post-Traumatic Osteoarthritis after Surgery.” The American journal of sports medicine 41.8 (2013): 1762–1770. PMC. Web. 1 Nov. 2017.
Novick, Nancy. “ACL Tears: Tears of the Anterior Cruciate Ligament.” Hospital for
Special Surgery, Hospital for Special Surgery, 13 Oct. 2009, www.hss.edu/conditions_anterior-cruciate-ligament-acl-tears.asp.
Proffen, Benedikt L. et al. “Bridge-Enhanced ACL Repair: A Review of the Science and the
Pathway through FDA Investigational Device Approval.” Annals of biomedical engineering 43.3 (2015): 805–818. PMC. Web. 1 Nov. 2017.
Rodeo, Scott A, and Russell F Warren. “ACL Injuries: Partial and Complete Tears of the
Anterior Cruciate Ligament.” Hospital for Special Surgery, Hospital for Special Surgery, www.hss.edu/conditions_acl-injuries-partial-complete-tears.asp.
Samitier, Gonzalo et al. “Failure of Anterior Cruciate Ligament Reconstruction.” Archives of
Bone and Joint Surgery 3.4 (2015): 220–240. Web. 1 Nov. 2017.
Springer, Shira. “Childrens Hospital develops new surgery that could revolutionize knee
repairs.” Boston Globe, Boston Globe, 23 Mar. 2016, www.bostonglobe.com/sports/2016/03/23/new-surgery-could-revolutionize-knee-repairs/BJISuh60AYKYTKWPwaYFWP/story.html.