Sustained Dynamic Compression Device Adaptively Compensates to Bone Resorption Following Arthrodesis in Ovine Hindlimb Model

• Published in: Foot & ankle orthopaedics 2024-12, Vol.9 (4)
• Main Authors: Safranski, David, Estrada, Erin, Johnson, James, Dupont, Ken, Griffis, Jack, Gadomski, Ben, Shibuya, Naohiro, Latt, Daniel, Easley, Jeremiah
• Format: Article
• Language: English
• ISSN: 2473-0114; 2473-0114
• DOI: 10.1177/2473011424S00514

Category: Midfoot/Forefoot; Basic Sciences/Biologics Introduction/Purpose: Charcot neuroarthropathy (CN) is a degenerative disease, which often impacts the midfoot and ankle, potentially leading to dislocations/fractures in the boney structures of the foot. The degenerative nature of this disease challenges the surgical intervention (beaming of the medial and lateral columns) for this condition by decelerating the fusion time, exposing the hardware to increased loading magnitude and duration, ultimately leading to increased hardware failure rate in these patients/procedures. To address this challenging patient population, a device was designed to apply sustained dynamic compression for use in midfoot fusion. While similar devices have been successfully implemented clinically in tibiotalocalcaneal fusion, this study sought to confirm mechanical durability via bench top testing and efficacy of this dynamic device in an ovine model of midfoot arthrodesis. Methods: A 7 x 100 mm dynamic device and an equivalent sized static device were used in this study. This 2x2 study divided the thirty-two mature Rambouillet Cross ewes into four groups based on bone quality (normal vs depleted) and device type (static vs dynamic) (CSU IACUC #1199). A pre-established model was utilized to reduce the bone quality of the target limb prior to arthrodesis via external fixation unloading, which has previously demonstrated a 29% decrease in bone mineral density. Multi-joint arthrodesis surgery was performed through the calcaneus-tarsus-metatarsal complex, followed by serial radiographic evaluations every four weeks. Sheep were euthanized 8-months postoperatively for biomechanical testing, micro-computed tomography analysis, and histology assessment of bone-device constructs. The study was conducted under strict ethical guidelines and approved by the Colorado State University Animal Care and Use Committee. Separate benchtop testing was conducted to confirm resorption capacity of both static and dynamic devices. Results: In vivo radiographic assessment revealed no significant differences in bone resorption/joint settling distances across bone quality at all timepoints (p≥.40), with ≥52.3% of total resorption/settling occurring within the first two months post-implantation. At the end of the 8-month study period, the normal and depleted bone quality samples exhibited 2.2 and 1.6mm of total resorption (4mm maximum device capability), respectively (p=.40). Four-point bending of treated