title: Biomechanical evaluation of a second generation headless compression screw for ankle arthrodesis in a cadaver model.
abstract: BACKGROUND
  Many types of screws, plates, and strut grafts have been utilized for ankle arthrodesis. Biomechanical testing has shown that these constructs can have variable stiffness. More recently, headless compression screws have emerged as an evolving method of achieving compression in various applications but there is limited literature regarding ankle arthrodesis. The aim of this study was to determine the biomechanical stability provided by a second generation fully threaded headless compression screw compared to a standard headed, partially threaded cancellous screw in a cadaveric ankle arthrodesis model.
  
  
  METHODS
  Twenty fresh frozen human cadaver specimens were subjected to simulated ankle arthrodesis with either three standard cancellous-bone screws (InFix 7.3mm) or with three headless compression screws (Acumed Acutrak 2 7.5mm). The specimens were subjected to cyclic loading and unloading at a rate of 1Hz, compression of 525 Newtons (N) and distraction of 20N for a total of 500 cycles using an electromechanical load frame (Instron). The amount of maximum distraction was recorded as well as the amount of motion that occurred through 1, 10, 50, 100, and 500 cycles.
  
  
  RESULTS
  No significant difference (p=0.412) was seen in the amount of distraction that occurred across the fusion site for either screw. The average maximum distraction after 500 cycles was 201.9μm for the Acutrak 2 screw and 235.4μm for the InFix screw. No difference was seen throughout each cycle over time for the Acutrak 2 screw (p-value=0.988) or the InFix screw (p-value=0.991).
  
  
  CONCLUSIONS
  Both the traditional InFix type screw and the second generation Acumed Acutrak headless compression screws provide adequate fixation during ankle arthrodesis under submaximal loads.
  
  
  CONCLUSIONS
  There is no demonstrable difference between traditional cannulated partially threaded screws and headless compression screws studied in this model.
authors: Andrews Research and Education Institute, 1040 Gulf Breeze Parkway, Gulf Breeze, FL 32561, USA.
authors: Andrew Max
authors: AM
authors: Somberg
authors: Andrews Research and Education Institute, 1040 Gulf Breeze Parkway, Gulf Breeze, FL 32561, USA. Electronic address: will.whiteside@yahoo.com.
authors: William K
authors: WK
authors: Whiteside
authors: Andrews Research and Education Institute, 1040 Gulf Breeze Parkway, Gulf Breeze, FL 32561, USA.
authors: Erik
authors: E
authors: Nilssen
authors: Andrews Research and Education Institute, 1040 Gulf Breeze Parkway, Gulf Breeze, FL 32561, USA.
authors: Daniel
authors: D
authors: Murawski
authors: Auburn University, 301 Wire Road, Auburn, AL 36849, USA.
authors: Wei
authors: W
authors: Liu
mesh_terms: D000843:Ankle Joint / Q000503:physiopathology / Q000601:surgery*; D001174:Arthrodesis / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005593:Fracture Fixation, Internal / Q000295:instrumentation; D006801:Humans
keywords: Ankle arthrodesis; Arthritis; Biomechanics; Cadaver model; Cannulated screws; Headless compression screws