title: Early motion following 4-corner arthrodesis using cannulated compression screws: a biomechanical study.
abstract: OBJECTIVE
  To assess the ability of headless compression screws to maintain immobile bony contact throughout wrist cycling following simulated 4-corner arthrodesis. Our hypothesis was that the screw constructs would not permit displacement of the carpal bones and, therefore, could tolerate early postoperative range of motion in vivo.
  
  
  METHODS
  Using 6 matched-paired cadaveric arms, 4-corner arthrodesis was performed using an all-cannulated compression screw construct (capitolunate, lunotriquetral, and triquetrohamate screws) or a partial compression screw combined with partial K-wire construct (2 crossing capitolunate screws with the lunotriquetral and triquetrohamate interfaces immobilized with 2 K-wires). Wrists were mounted and cycled 5,000 times. Intercarpal distances were measured at 0, 100, 1,000, and 5,000 cycles at fixed points of passive flexion. Because previously published studies considered intercarpal distances of greater than 1 mm as significant, we defined fixation failure as greater than 0.5 mm gapping.
  
  
  RESULTS
  Neither screw construct showed any significant intercarpal gapping at any point during the experimental cycling (largest average intercarpal gapping was 0.2 mm). There were no significant differences between the constructs regarding gapping at any point.
  
  
  CONCLUSIONS
  In this biomechanical model, cannulated compression screws effectively resist significant intercarpal gapping during early motion after 4-corner arthrodesis. This may allow for immediate postoperative range of motion.
  
  
  CONCLUSIONS
  Early gentle range of motion may be possible immediately following 4-corner arthrodesis using a construct consisting of headless compression screws.
authors.affiliation: New York University Hospital for Joint Diseases, New York, New York.
authors.forename: Andrew
authors.initials: A
authors.lastname: Greenberg
authors.forename: Mark
authors.initials: M
authors.lastname: Shreve
authors.forename: Daniel
authors.initials: D
authors.lastname: Bazylewicz
authors.forename: Rachel
authors.initials: R
authors.lastname: Goldstein
authors.forename: Anthony
authors.initials: A
authors.lastname: Sapienza
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001174:Arthrodesis / Q000295:instrumentation*; D001863:Bone Screws; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011184:Postoperative Period; D016059:Range of Motion, Articular; D014955:Wrist Joint / Q000503:physiopathology* / Q000601:surgery*
keywords: 4-Corner fusion; headless compression screws; scaphoid nonunion advanced collapse; scapholunate advanced collapse