Achilles Tendon Allografts With and Without InternalBrace Augmentation for Anterior Cruciate Ligament Revision Surgery: A Randomized Controlled Pilot Trial

Anterior cruciate ligament revision surgery remains challenging and may have less predictable outcomes than primary ACL reconstruction. In revision cases, prior bone tunnels and bone defects can complicate graft fixation. Achilles tendon allografts with calcaneal bone blocks provide a reliable graft configuration and may help fill pre-existing bone defects during a one-stage revision procedure. InternalBrace augmentation is intended to provide additional support to the reconstructed ligament during the healing period, but clinical evidence for its use with allograft ACL revision surgery is limited.

This prospective, randomized controlled pilot study enrolled patients from February 2017 to September 2020 at the Medical University of Graz. Eligible participants had MRI-confirmed re-tear of the ACL graft and clinical and patient-reported knee instability. Patients with advanced associated lesions requiring reconstruction or prolonged restricted weight bearing, signs of infection, advanced osteoarthritis, or neuromuscular disease were excluded. For all included participants, the procedure was the first revision surgery on the affected knee. The study was approved by the Ethics Committee of the Medical University of Graz, and written informed consent was obtained before participation.

All participants underwent revision ACL reconstruction using an Achilles tendon allograft with a calcaneal bone block. Participants were randomized in a 1:1 ratio to receive either additional InternalBrace augmentation or no InternalBrace augmentation. The InternalBrace group received a non-resorbable polyethylene FiberTape fixed separately and independently from the ACL graft. Apart from the additional InternalBrace fixation in one group, the surgical technique and postoperative rehabilitation protocol were the same for all participants.

Clinical and patient-reported outcomes were assessed preoperatively and at 6 weeks, 12 weeks, 6 months, and 13 months after surgery. Outcome measures included the International Knee Documentation Committee score, Lysholm Knee Questionnaire, Tegner Activity Scale, Knee Injury and Osteoarthritis Outcome Score, and Short Form-36. MRI scans were performed before surgery and 13 months after surgery to assess graft appearance, graft tightness, graft signal, ligament signs at the femoral and tibial tunnel insertions, and tunnel size.

The final analyzed study population included 30 participants, with 16 participants in the InternalBrace group and 14 participants in the non-InternalBrace group. Overall, clinical and patient-reported outcomes improved during follow-up. At the final 13-month follow-up, there were no clinically relevant differences between the InternalBrace and non-InternalBrace groups. Postoperative MRI showed elongated or insufficient ACL allografts in 15 of 30 participants, without significant differences between groups. The study concluded that ACL revision surgery using Achilles tendon allografts with bone blocks resulted in improved clinical outcomes at 13 months, but additional InternalBrace augmentation did not improve objective or subjective outcomes in this pilot trial.