Issue: January 2014
January 01, 2014
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Bio-enhanced extracellular scaffolds used in repair healed torn ACLs

Issue: January 2014
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The results of an award-winning study indicate that ACL repair using a bio-enhanced scaffold results in less cartilage damage than traditional ACL reconstruction at 12 months and may be chondroprotective.

“With the bio-enhanced repairs, the cartilage was much cleaner and well preserved,” Martha M. Murray, MD, said. “If we place the bioactive scaffold into the wound site, we can stimulate repair.” Murray presented the results of the study, which won the Cabaud Memorial Award, at the American Orthopaedic Society for Sports Medicine Annual Meeting.

The researchers decided to study the possibility of using a scaffold to stimulate healing of the ACL after noting differences in the injury response of the medial collateral ligament (MCL) and ACL.

“When the MCL tears, blood forms a clot in the gap and immobilizes the two torn ends,” Murray said. “Cells then crawl into that provisional scaffold and remodel it into a healing tissue. In contrast, when the ACL tears, the ends bleed, but the synovial fluid does not allow a blood clot to form that encases the two ends.”

She added, “We found that platelets and plasma are both important in stimulating ACL cells [to heal], red blood cells help facilitate collagen production in the wound cells and white blood cells also release anabolic factors.”

Sutures (purple) are anchored to the femur at the ACL origin and then passed through the scaffold (white cylinder). The scaffold is then slid along the sutures up into the notch and against the femoral origin of the ACL. The tibia side of the torn ACL (green sutures) is maintained in an anterior position while the scaffold is put into the notch.

Sutures (purple) are anchored to the femur at the ACL origin and then passed through the scaffold (white cylinder). The scaffold is then slid along the sutures up into the notch and against the femoral origin of the ACL. The tibia side of the torn ACL (green sutures) is maintained in an anterior position while the scaffold is put into the notch.

Images: Murray MM

Based on these conclusions, the researchers designed a bio-enhanced scaffold (MIACH; Boston Children’s Hospital, Boston), which can be placed between the torn tissue ends and loaded with a few teaspoons of the patient’s own blood. The scaffold absorbs the blood and keeps it in the wound site.

Murray and Braden C. Fleming, PhD, of Brown University, tested the scaffolds in 62 adolescent pigs with transected ACLs who were randomized to receive one of the following treatments: ACL suture repair with the bio-enhanced scaffolds; ACL reconstruction using the bio-enhanced scaffolds; ACL reconstruction alone; or no treatment. The researchers assessed the biomechanical properties of the ligament and macroscopic damage of the knee cartilage at 6 months and 12 months.

The investigators discovered no significant differences for the structural properties of the ligaments when comparing the three treatment groups at 1 year, but found greater healing in these groups compared to the non-treatment group. They also found less macroscopic cartilage damage in the ACL suture repair and scaffold group than in the ACL reconstruction and scaffold group, ACL reconstruction-alone group and no treatment group.

Once the scaffold is in the notch, the sutures on the ACL (green) are used to pull the tibial side of the torn ACL up into the soft scaffold so the scaffold fills any gap between the two torn ends of the ligament. Autologous blood can be added to the scaffold during this step to provide the biologic components required for healing.

Once the scaffold is in the notch, the sutures on the ACL (green) are used to pull the tibial side of the torn ACL up into the soft scaffold so the scaffold fills any gap between the two torn ends of the ligament. Autologous blood can be added to the scaffold during this step to provide the biologic components required for healing.

The researchers have been accepted into the FDA’s Early Feasibility Device program and are finalizing mandated preclinical testing with the FDA, according to Murray.

“The bio-enhanced repair may help minimize post-traumatic osteoarthritis after ACL injury,” Murray said. – by Renee Blisard Buddle

Reference:
Murray M M. Use of a bioactive scaffold to stimulate ACL healing also minimizes post-traumatic osteoarthritis after surgery. Presented at: American Orthopaedic Society for Sports Medicine Annual Meeting; July 11-14, 2013; Chicago.
For more information:
Martha M. Murray, MD, can be reached at the Department of Orthopaedic Surgery, Children’s Hospital Boston, 300 Longwood Ave., Boston, MA 02115; email: martha.murray@childrens.harvard.edu.
Disclosure: Murray has no relevant financial disclosures. This work was funded by the NIH through NIAMS.