title: Subtalar arthrodesis stabilisation with screws in an angulated configuration is superior to the parallel disposition: a biomechanical study.
abstract: OBJECTIVE
  The purpose of this study was to compare the stability of two established screw configurations (SC) for subtalar arthrodesis using a cyclic loading model.
  
  
  METHODS
  Eight paired human cadaver hindfoot specimens underwent subtalar arthrodesis with either parallel or angulated SC. The instrumented specimens were subjected to a cyclic loading protocol (1000 cycles: ±5 Nm rotation moment, 50 N axial force). The joint range of motion (ROM) was quantified before and after cyclic loading, in the three principal motion planes of the subtalar joint using pure bending moments of ±3 Nm.
  
  
  RESULTS
  After instrumentation, the angulated SC showed significantly less mean ROM compared to the parallel SC in internal/external rotation (1.4° ± 2.2° vs. 3.3° ± 2.8°, P = 0.006) and in inversion/eversion (0.9° ± 1.4° vs. 1.5° ± 1.1°, P = 0.049). After cyclic loading, the angulated SC resulted in significantly less mean ROM compared to the parallel SC in internal/external rotation (3.3° ± 4.6° vs. 8.8° ± 8.0°, P = 0.006) and in inversion/eversion (1.9° ± 2.3° vs. 3.9° ± 3.9°, P = 0.017). No significant differences in the mean ROM were found between the angulated and parallel SC in dorsal extension/plantar flexion.
  
  
  CONCLUSIONS
  The angulated SC resulted in decreased ROM in the subtalar arthrodesis construct after instrumentation and after cyclic loading compared to the parallel SC. The data from our study suggest that the clinical use of the angulated SC for subtalar arthrodesis might be superior to the parallel SC.
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Martin
authors.initials: M
authors.lastname: Eichinger
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Werner
authors.initials: W
authors.lastname: Schmölz
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Alexander
authors.initials: A
authors.lastname: Brunner
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria.
authors.forename: Raul
authors.initials: R
authors.lastname: Mayr
authors.affiliation: Department of Trauma Surgery, Medical University of Innsbruck, Anichstrasse 35, 6020, Innsbruck, Austria. andreas.boelderl@i-med.ac.at.
authors.forename: Andreas
authors.initials: A
authors.lastname: Bölderl
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001174:Arthrodesis / Q000379:methods*; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012399:Rotation; D013380:Subtalar Joint / Q000503:physiopathology / Q000601:surgery*
keywords: Arthrodesis; Biomechanics; Hindfoot; Screw fixation; Subtalar