A New Technique for Repairing a Torn ACL Shows Promise

Clinical, functional, and patient-reported outcomes were similar 2 years after surgery in patients with a torn anterior cruciate ligament (ACL) who underwent either a bridge-enhanced ACL repair (BEAR) procedure with the experimental BEAR implant or a standard ACL reconstruction with a 4-stranded hamstring autograft, according to the results of a Phase I, first-of-its-kind study in humans.

The study was presented at the Arthroscopy Association of North America/American Orthopaedic Society for Sports Medicine 2019 Specialty Day and also has been published in the Orthopaedic Journal of Sports Medicine.

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The BEAR implant is a proprietary, bioengineered bridging scaffold. This scaffold is surgically placed between the torn ends of the ACL and then 5 to 10 mL of the patient’s blood is injected into it. The scaffold holds the blood to stimulate healing of the torn ACL. The goal is to restore more normal anatomy and function of the knee.

“We wanted to find a way to encourage the ACL to heal itself,” said Martha Murray, MD, who invented the procedure. She’s a professor of orthopaedic surgery at Harvard Medical School and an orthopaedic surgeon in the Sports Medicine Division at Boston Children’s Hospital.

“We hoped we could find a better way than removing the torn ACL and replacing it with perfectly normal tissue from somewhere else, so we started working on a protein-based scaffold.”

After decades of laboratory research, a human trial was approved by the US Food and Drug Administration (FDA) to assess the safety and early efficacy of the BEAR implant. The researchers included 10 patients age 18 to 35 in each arm of the non-randomized, 2-arm, Phase I study:

  • Patients in the BEAR group had a complete ACL tear sustained less than 1 month prior to study enrollment and had at least 50% of the length of the ACL attached to the tibia according to MRI.
  • Patients in the standard group had a complete ACL tear sustained within 3 months prior to enrollment.

Patients in the 2 groups had similar patient-reported outcomes, physical examination findings, and functional outcomes 2 years after the procedure, the researchers found. None of the patients who received the BEAR implant developed an infection or severe inflammatory reaction, arthrofibrosis, or a reaction that required scaffold removal. In addition, manual and instrumented measures suggested comparable stability of the knee after both procedures.

“At 24 months, 9 of the 10 repaired subjects and 7 of the 10 reconstructed patients completed a study visit,” said Lyle J. Micheli, MD, director of the Boston Children’s Division of Sports Medicine and lead surgeon on the trial. “There were no graft or repair failures and recovery was similar for both groups, providing us with encouraging outcomes and an exciting road ahead.”

Since completion of the Phase I study, the researchers have moved forward with a randomized, blinded trial that included 100 patients, again comparing the BEAR procedure with standard ACL reconstruction. A third study will look further at the effects of age the outcomes of this novel technique


Murray MM, Fleming BC, Flutie BM, Thurber L, Freiberger C, Henderson R, Perrone G, Proffen B, Kramer DE, Yen Y-M, Micheli LJ. Bridge-enhanced ACL Repair: Two-year Results of the First Human Study (Paper 7). Presented at the Arthroscopy Association of North America/American Orthopaedic Society for Sports Medicine 2019 Specialty Day, March 16, 2019, Las Vegas, Nevada.

Murray MM, Kalish LA, Fleming BC, et al. Bridge-enhanced anterior cruciate ligament repair: two-year results of a first-in-human study. Orthop J Sports Med. 2019 Mar 22;7(3):2325967118824356. doi: 10.1177/2325967118824356. eCollection 2019 Mar.

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