Induce XT™ Bone Graft in Foot and Ankle Fusion

Clinical Background Ankle and hindfoot arthrodesis (fusion) is a well-established treatment for various foot and ankle conditions. These surgeries require supplemental graft material. Autogenous bone graft (ABG), typically harvested from sites like the iliac crest bone graft (ICBG), is considered the gold standard for bone grafting. However, the use of ABG presents several challenges, such as increased surgical time, blood loss, and the risk of infection and pain at the donor site. Additionally, the supply of autogenous bone is limited (Boone 2003, Baumhauer, Glazebrook et al. 2020).

Augment® Bone Graft is a substitute used to enhance bone healing in foot and ankle surgeries. It contains recombinant human platelet-derived growth factor BB (rhPDGF-BB) and a beta-tricalcium phosphate (β-TCP) matrix. The β-TCP matrix provides a structure that supports new bone growth, while rhPDGF-BB stimulates the recruitment and proliferation of cells involved in bone formation and promotes both angiogenesis and bone healing. Studies have demonstrated that Augment Bone Graft can be an alternative to ABG in foot and ankle fusion procedures (DiGiovanni, Lin et al. 2013). However, Augment is costly, must be stored at 2 to 8°C, and may handle poorly. It should also not be used in patients with cancer, near resected tumors, or in those who are pregnant or may become pregnant. Additionally, the radiopaque nature of β-TCP can obscure radiographic images, making it difficult to assess bone healing (FDA 2015, FDA 2018).

Demineralized bone matrix (DBM) is another option, used alone or in combination with ABG to support bone fusion. DBM provides a scaffold for new bone growth (osteoconduction) and has osteoinductive properties due to the presence of bone morphogenetic proteins (BMPs), including BMP-2. DBM also contains growth factors that promote angiogenesis and bone formation. However, its clinical effectiveness is limited due to the low amount and bioavailability of growth factors (Gruskin, Doll et al. 2012).

Study Rationale Induce XT is a new bone matrix product combining Natural Matrix Protein® (NMP®) derived from demineralized human cortical bone allograft with mineralized cancellous bone allograft. NMP has demonstrated higher bioavailability of BMP-2 and BMP-7 and enhanced osteoinductive activity compared to DBM in various studies (Kohen, Shivanna, and Peel 2022, Peel 2023). The mineralized cancellous bone component provides additional compression resistance and allows the graft to be seen on radiographs immediately after implantation. Induce XT is clinically used as a bone void filler.

Since its market release in January 2022, NMP bone grafts have been used in over 7,500 surgeries, including spine and foot/ankle fusions, with no reported adverse events. A retrospective study also showed a high fusion rate in lumbar spine procedures using NMP fibers (Nunley 2024).

This prospective clinical trial will enroll 60 patients at one clinical site in Canada to evaluate the safety and efficacy of Induce XT in hindfoot or ankle fusion surgeries. The study will assess radiographic, clinical, functional, and quality-of-life outcomes over a 52-week postoperative period.

Inclusion criteria

• Patients meeting all of the following criteria will be considered eligible for study participation:

• Patient has a bone defect in the hindfoot or ankle; and
• Is requiring fusion using an open surgical technique with supplemental bone graft/substitute; and
• Fusion site is able to be rigidly stabilized with no more than 3 screws across the fusion site; and
• Patient is requiring one of the following procedures:

• Ankle joint fusion
• Subtalar fusion
• Calcaneocuboid fusion
• Talonavicular fusion
• Triple arthrodesis (subtalar, talonavicular and calcaneocuboid joints)
• Double fusions (talonavicular and calcaneocuboid joints).

Exclusion criteria

• Patient meeting any of the following criteria will be excluded from study participation:

• Patient is under 18 years of age at the time of consent;
• Patient has an active (local or systemic) infection or is undergoing adjunctive treatment for infection;
• Patient has previous fusion surgery of the proposed fusion site;
• Patient has cognitive disorders or is unable to complete questionnaires or provide consent.