Department of Orthopedics and Physical Rehabilitation
Arthrodesis; Bone Nails
Orthopedics | Rehabilitation and Therapy
BACKGROUND: Knee or tibiotalocalcaneal arthrodesis is a salvage procedure, often with unacceptable rates of nonunion. Basic science of fracture healing suggests that compression across a fusion site may decrease nonunion. A novel ratcheting arthrodesis nail designed to improve dynamic compression is mechanically tested in comparison to existing nails.
METHODS: A novel ratcheting nail was designed and mechanically tested in comparison to a solid nail and a threaded nail using sawbones models (Pacific Research Laboratories, Inc.). Intramedullary nails (IM) were implanted with a load cell (Futek LTH 500) between fusion surfaces. Constructs were then placed into a servo-hydraulic test frame (Model 858 Mini-bionix, MTS Systems) for application of 3 mm and 6 mm dynamic axial displacement (n = 3/group). Load to failure was also measured.
RESULTS: Mean percent of initial load after 3-mm and 6-mm displacement was 190.4% and 186.0% for the solid nail, 80.7% and 63.0% for the threaded nail, and 286.4% and 829.0% for the ratcheting nail, respectively. Stress-shielding (as percentage of maximum load per test) after 3-mm and 6-mm displacement averaged 34.8% and 28.7% (solid nail), 40.3% and 40.9% (threaded nail), and 18.5% and 11.5% (ratcheting nail), respectively. In the 6-mm trials, statistically significant increase in initial load and decrease in stress-shielding for the ratcheting vs. solid nail (p = 0.029, p = 0.001) and vs. threaded nail (p = 0.012, p = 0.002) was observed. Load to failure for the ratcheting nail; 599.0 lbs, threaded nail; 508.8 lbs, and solid nail; 688.1 lbs.
CONCLUSION: With significantly increase of compressive load while decreasing stress-shielding at 6-mm of dynamic displacement, the ratcheting mechanism in IM nails may clinically improve rates of fusion.
Rights and Permissions
© 2010 McCormick et al; licensee BioMed Central Ltd.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
DOI of Published Version
J Orthop Surg Res. 2010 Oct 14;5:74. Link to article on publisher's site
Journal of orthopaedic surgery and research
McCormick JJ, Li X, Weiss DR, Billiar KL, Wixted JJ. (2010). Biomechanical investigation of a novel ratcheting arthrodesis nail. Orthopedics and Physical Rehabilitation Publications. https://doi.org/10.1186/1749-799X-5-74. Retrieved from https://escholarship.umassmed.edu/ortho_pp/13