Design Considerations for Nitinol Bone Staples

Abstract

The use of Nitinol in orthopedic staples has a long, successful history beginning with their first commercial introduction in the early 1980s. Nitinol bone staples are generally inserted through a process of being chilled, opened, and inserted into predrilled holes. Upon insertion, they recover their preprogrammed shape either through springing back after removal of a constraint (using superelasticity) or thermal triggering (using thermal shape memory). In general, Nitinol bone staples fall into one of three categories: (1) those which are superelastic at room temperature, (2) those which recover their shape upon heating to body temperature, or (3) those which recover their shape upon heating above body temperature with the application of an external heat source. These three different design approaches-room temperature superelastic, body temperature activated, and heat activated-each have different performance characteristics. A version of the heat activated staple that uses a controlled heat source appears to have the best combination of clinical forces and procedural control.

Assessing the performance characteristics and clinical forces in simulated shape memory bone staple surgical procedure: The significance of SMA material model

“…5b) measures 9.3 mm wide (matching the width of the base of the staple), 18.0 mm high, and 3.0 mm deep (thickness). In our simulation here, it is assumed that all the necessary clinical steps, such as bone surface preparation, regional anesthesia of the osteotomy site and appropriate realignment of the fragmented bone pieces, are already established [12], hence leaving us to focus on the mechanical and thermal activation aspects of this fixation operation.…”

“…Our decision to deform the staple at the martensite state (instead of deforming it at the austenite state) was guided by the experimental test results shown in Fig. 3, as well as the recent rise in the use of this methodology for deforming SMA medical devices before their subsequent deployment into the human body [10] in comparison to other possible alternative ways [12]. Fig.…”

“…2, our approach here is to carry out an engineering simulation using a nonlinear finite element procedure which incorporates an SMA constitutive framework model [11] to ascertain the crucial role played by a powder metallurgically processed nickel-rich NiTi (PM/NiTi-P) SMA material on the functional performance of an SMA bone staple. Among the other schemes of activating the SMA staple [12], the staple used for our current demonstration is designed to self-generate the compression force needed for the fixation once it gets heated to the body temperature.…”

Preparation and Characterization of Nitinol Bone Staples for Cranio-Maxillofacial Surgery

“…NiTi shape memory alloys with a chemical composition consistent with ASTM F2063-05 have been approved as metal biomaterials and are used in production of medical implants and devices (Ref [1][2][3]. Products of NiTi alloys exhibiting phenomena of shape memory and superelasticity are widespread in such applications as orthodontic archwires, staples for osteosynthesis, stents, endodontic and surgical instruments .…”

Caracterização parcial de liga Nitinol atuador através de pontos críticos de transformação de fases utilizando calorimetria diferencial de varredura

“…(Ryhänen, 1999). Do ponto de vista de aplicação em grampos para reabilitação de ossos, Russel (2009) classifica as ligas NiTi em 3 tipos: super-elásticas (SE), como sendo aquela liga que tem Af, logo abaixo da temperatura ambiente de 25ºC, body temperature (BT), temperatura corporal com Af, logo abaixo da temperatura do corpo 37ºC e a liga termo ativada (HÁ) que tem As logo acima da temperatura ambiente e Af, logo abaixo de 60ºC.…”