Measurement of Nitinol Recovery Distance Using Pseudoelastic Intramedullary Nails for Tibiotalocalcaneal Arthrodesis Beau J. Kildow, MD 1 Christopher E. Gross, MD 1 Samuel D. Adams, MD 1 Mark E. Easley, MD 1 Selene G. Parekh, MD, MBA 1 * 1 Department of Orthopaedic Surgery Duke University Medical Center Durham, NC. *North Carolina Orthopaedic Clinic Department of Orthopaedic Surgery Fuqua Business School, Duke University
Disclosure Dr. Adams and Dr. Parekh report personal fees from Medshape Inc., outside the submitted work Dr. Easley reports grants and personal fees from Medshape Inc., during the conduct of the study
Background Compression across the fusion sites in tibiotalocalcaneal arthrodesis is necessary to obtain fusion Up to 90% of the initial compression achieved intra-operatively is lost over time with just 1mm of bone resorption using standard intramedullary nails 4. Current methods to dynamize across fusion sites include: ring external fixators: cumbersome, pin site infections dynamized nails: require invasive manipulation of proximal screw
Nitinol Nickel Titanium Discovered by US Naval Ordinance Labratory 2 Yakacki et al. Pseudoelastic property: Nitinol element stretched across fusion site Nitinol material responds by conforming back to original length while applying constant force across fusion site in response to bone resorption 5
Pseudoelastic IMN Yakacki et al.
Methods Purpose: to measure the in vivo movement of the Nitinol element over time. Methods: 15 patients Inclusion: All patients indicated for TTC fusion Exclusion: Active infection, non-ambulatory Serial Radiographs at 0,2, 6, 12, 24, 52 weeks to measure distance of Nitinol element migration proximally males females overall Age 63.29 47.25 54.7 Mass (kg) 99.14 96.81 97.9 Prior surgery (% yes) 57 62 60 Smoker (% yes) 28 25 27 Diabetes (% yes) 28 25 27 Nitinol element stretched outside titanium rod Nitinol element migrating proximally in response to bone resorption
Procedure The nail was inserted in retrograde fashion until the distal screw holes were centered in the calcaneus Two distal calcaneal screws placed The Nitinol element was stretched 6mm 3 millimeters of external compression was applied Two proximal tibial screws were placed. https://www.youtube.com/watch?v=wevz5 MbZ160 (Dr. Selene Parekh)
Results All 15 subjects who had TTC arthrodesis using MedShape Inc. Dynanail at least 2.38mm of Nitinol element migration proximally with mean 5.58 (+/- 1.38), (range, 2.38-8.11) mm Average follow up time to date of 195 (+/- 106.3), (range: 89 to 490) days. On average, 86% of the total recovered distance took place within the first 39.7 (+ 10.03) days
Results: Proximal Nitinol Migration The Nitinol element recovers distance when stretched intraoperatively and maintains moderate compression in response to bone resorption.
Discussion In a systematic review by Jehan et al., out of 641 TTC arthrodesis procedures using IMN, 556 obtained union (86.7%) 3 complication rate was 55.7% of which 23.8% were due to direct non-union. To date there is no data correlating loss of compression to bony non-union. Our study did not analyze fusion rates No fusion rates reported for Medshape Inc. Dynanail
References 1. Easley ME, Montijo HE, Wilson JB, Fitch RD, Nunley JA, 2nd. Revision tibiotalar arthrodesis. J Bone Joint Surg Am. 2008;90(6):1212-1223. 10.2106/jbjs.g.00506. 2. Machado LG, Savi MA. Medical applications of shape memory alloys. Braz J Med Biol Res. 2003;36(6):683-691. 3. Jehan S, Shakeel M, Bing AJ, Hill SO. The success of tibiotalocalcaneal arthrodesis with intramedullary nailing--a systematic review of the literature. Acta Orthop Belg. 2011;77(5):644-651. 4. Thomas RL, Sathe V, Habib SI. The use of intramedullary nails in tibiotalocalcaneal arthrodesis. J Am Acad Orthop Surg. 2012;20(1):1-7. 10.5435/jaaos-20-01-001. 5. Yakacki CM, Gall K, Dirschl DR, Pacaccio DJ. Pseudoelastic intramedullary nailing for tibiotalo-calcaneal arthrodesis. Expert Rev Med Devices. 2011;8(2):159-166. 10.1586/erd.10.93. 6. Yakacki CM, Khalil HF, Dixon SA, Gall K, Pacaccio DJ. Compression forces of internal and external ankle fixation devices with simulated bone resorption. Foot Ankle Int. 2010;31(1):76-85. 10.3113/fai.2010.0076. 7. http://www.medshape.com/our-products/dynanail.html?id=73&itemid=185