Parker P. Duncan, MD1 Clayton C. Bettin, MD1 James T. Reagan, MD2 Denis J. DiAngelo, PhD1 PJ Johnson, BS1 1
University of Tennessee-Campbell Clinic Department of Orthopaedic Surgery & Biomedical Engineering Memphis, Tennessee
2
Tennessee Orthopaedic Clinics Knoxville, Tennessee
A Biomechanical Investigation of Shape Memory Staples Purpose The use of shape memory alloys, specifically nitinol staples, has gained popularity in orthopedic osteosynthesis applications secondary to their inherent simplicity and ease of use as well as their biomechanical compressive ability. The key objectives of this pilot study were to determine the effect on staple leg and bridge length and unicortical versus bicortical fixation on compression, bending stiffness, and torsional rigidity as well as to investigate how staple position and construct configuration would altered these values.
Methods Transverse osteotomies were made using a sagittal saw in identical bicortical sawbones blocks to simulate an osteosynthesis site. This site was fixed with a single staple of varying bridge and leg length with unicortical or bicortical purchase. Tekscan sensors were used to determine compressive force before and after cyclic loading with a four-point bender and biaxial mechanical testing frame to determine bending stiffness and torsional rigidity of each construct. Also tested were anatomic sawbones 1st metatarsal and metacarpal models which were fixed with different staple products and constructs from multiple different manufacturers including: orthogonal and parallel placed two staple constructs, multiple four-leg staples, and a staple plate.
Results This study is currently underway at the UTHSC Orthopedic Biomechanics Lab (DiAngelo). All materials have been obtained, but await final protocol testing prior to formal testing runs.
Conclusions We hypothesize that staples placed with bicortical technique, perpendicular to a potential osteosynthesis site will produce the most compression, bending stiffness, and torsional rigidity. Also, we hypothesize that orthogonally placed staples will produce the most bending stiffness and torsional rigidity among staple constructs with each producing similar compressive ability.
Corresponding Author Clayton C. Bettin, MD 1211 Union Avenue, Suite 500 Memphis, TN 38104 P: 901-759-5422 F: 901-435-5639 cbettin@campbellclinic.com
34
CAMPBELL ORTHOPAEDIC JOURNAL • VOLUME 7, 2021
