Collagen Scaffold Bioaugmentation for ATFL Repair in Chronic Ankle Instability

Background. Ankle sprain is one of the most common musculoskeletal injuries, accounting for approximately 12% of emergency department visits and 30% of all sports-related injuries. Because the recurrence rate is high, about 30-40% of patients progress to chronic ankle instability (CAI), characterized by recurrent sprains, a subjective feeling of giving way, pain, reduced sports performance, functional limitations, and an increased risk of post-traumatic ankle osteoarthritis.

Arthroscopic ligament repair has become an important surgical option for chronic lateral ankle instability because it can simultaneously address intra-articular pathology such as synovitis, impingement, loose bodies, and osteochondral lesions. However, the strength of a conventional repair may reach only about 50% of the native ATFL, which is often insufficient in patients with scarred, thinned, or partially resorbed ligament remnants, in high-demand patients, or in revision cases.

The Internal Brace technique augments ATFL repair with a high-strength suture tape (FiberTape) anchored to the fibula and talus, providing immediate mechanical stability and protecting the repair during early healing. Its reinforcement is, however, mechanical rather than biological and does not by itself promote the regeneration of ligament-like tissue.

REGENETEN (Smith \& Nephew) is a highly purified, bioinductive, absorbable type I collagen scaffold with a porous microstructure and aligned fiber orientation. It supports host cell migration and tissue ingrowth, gradually degrades over approximately six months, and is gradually replaced by tendon-/ligament-like tissue. A randomized study of 124 patients with non-acute full-thickness rotator cuff tears reported a one-year re-tear rate of 8.3% with REGENETEN augmentation versus 25.8% in controls, and additional studies have shown improvements in pain and function scores.

Objective. To compare the clinical efficacy and safety of arthroscopic ATFL repair with Internal Brace augmentation alone versus Internal Brace augmentation combined with REGENETEN bioaugmentation in patients with chronic lateral ankle instability.

Study design. A prospective, multicenter, randomized, parallel-group, controlled, superiority trial. After written informed consent, eligible patients are randomized 1:1 to one of two groups, with stratification by study site and allocation concealed using a central computer-generated schedule. The study is investigator-initiated. The total study duration is 24 months from the date of ethics approval.

Population. Adults aged 18-65 with clinically and radiologically confirmed chronic lateral ankle instability refractory to standardized non-operative treatment, and with poor ATFL tissue quality (scarring, thinning, partial resorption, intra-operative assessment of insufficient repair tension, high BMI, or high sport demand), or with prior failed lateral ligament repair requiring revision.

Interventions. Both groups undergo standardized arthroscopic ATFL repair with Internal Brace augmentation, using the LassoLoop self-locking suture technique for the residual ligament and bioabsorbable suture anchors plus a 4.75 mm SwiveLock anchor with FiberTape to construct the Internal Brace. In the experimental group, a REGENETEN collagen scaffold braided onto a TigerTape suture is passed through fibular and talar bone tunnels and fixed with 4.75 mm SwiveLock anchors, completing the bioaugmented repair. Post-operative anterior drawer testing is performed under arthroscopy to confirm stability.

Primary endpoint. Change from baseline in the Karlsson-Peterson ankle function score at 12 months post-operatively.

Secondary endpoints (assessed at 3, 6, 12, and 24 months). FAOS subscales (Pain, Symptoms, ADL, Sport/Rec, QoL); FAAM-ADL and FAAM-Sports; Tegner activity score; NRS pain at rest and after activity; anterior drawer and talar tilt tests; MRI evaluation of ATFL continuity, thickness, signal intensity, and (in the experimental group) scaffold integration, absorption, and remodeling; subjective giving-way and fear of re-sprain; recurrent sprain rate; treatment failure and revision surgery rate; and safety (infection, wound healing problems, nerve injury, thromboembolism, joint stiffness, persistent pain, implant-related irritation or foreign-body reaction, and collagen-scaffold-related adverse events).