title: Impact of Different Screw Designs on Durability of Fracture Fixation: In Vitro Study with Cyclic Loading of Scaphoid Bones.
abstract: OBJECTIVE
  The use of new headless compression screws (HCSs) for scaphoid fixation is growing, but the nonunion rate has remained constant. The aim of this study was to compare the stability of fixation resulting from four modern HCSs using a simulated fracture model to determine the optimal screw design(s).
  
  
  METHODS
  We tested 40 fresh-frozen cadaver scaphoids treated with the Acumed Acutrak 2 mini (AA), the KLS Martin HBS2 midi (MH), the Stryker TwinFix (ST) and the Synthes HCS 3.0 with a long thread (SH). The bones with simulated fractures and implanted screws were loaded uniaxially into flexion for 2000 cycles with a constant bending moment of 800 Nmm. The angulation of the fracture fragments was measured continuously. Data were assessed statistically using the univariate ANOVA test and linear regression analysis, and the significance level was set at p < 0.05.
  
  
  RESULTS
  The median angulation of bone fragments φ allowed by each screw was 0.89° for AA, 1.12° for ST, 1.44° for SH and 2.36° for MH. With regards to linear regression, the most reliable curve was achieved by MH, with a coefficient of determination of R2 = 0.827. This was followed by AA (R2 = 0.354), SH (R2 = 0.247) and ST (R2 = 0.019). Data assessed using an adapted ANOVA model showed no statistically significant difference (p = 0.291) between the screws.
  
  
  CONCLUSIONS
  The continuous development of HCSs has resulted in very comparable implants, and thus, at this time, other factors, such as surgeons' experience, ease of handling and price, should be taken into consideration.
authors.affiliation: Department of Orthopaedics and Traumatology, University Medical Center of Johannes Gutenberg University, Mainz, Germany.
authors.forename: Dominik
authors.initials: D
authors.lastname: Gruszka
authors.affiliation: Department of Orthopaedics and Traumatology, University Medical Center of Johannes Gutenberg University, Mainz, Germany.
authors.forename: Robert
authors.initials: R
authors.lastname: Herr
authors.affiliation: Physics Division, RheinMain University of Applied Sciences, Wiesbaden, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Hely
authors.affiliation: Physics Division, RheinMain University of Applied Sciences, Wiesbaden, Germany.
authors.forename: Peer
authors.initials: P
authors.lastname: Hofmann
authors.affiliation: Department of Orthopaedics and Traumatology, University Medical Center of Johannes Gutenberg University, Mainz, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Klitscher
authors.affiliation: Department of Orthopaedics and Traumatology, University Medical Center of Johannes Gutenberg University, Mainz, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Hofmann
authors.affiliation: Department of Orthopaedics and Traumatology, University Medical Center of Johannes Gutenberg University, Mainz, Germany.
authors.forename: Pol Maria
authors.initials: PM
authors.lastname: Rommens
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D019245:Compressive Strength; D015925:Cryopreservation; D004867:Equipment Design; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D050723:Fractures, Bone / Q000473:pathology / Q000601:surgery*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011312:Pressure; D021361:Scaphoid Bone / Q000293:injuries / Q000601:surgery*