title: External fixator clamp reuse degrades clamp mechanical performance.
abstract: OBJECTIVE
  To determine the effects of clamp reuse for the Kirschner-Ehmer (KE); Securos; and the IMEX-SK clamp.
  
  
  METHODS
  Experimental bench test of mechanical properties.
  
  
  METHODS
  Specially designed fixtures were used to mechanically test 18 clamps of each type with respect to 6 mechanical variables: fixator pin slippage, connecting bar slippage, fixator pin rotation, connecting bar rotation, and clockwise and counterclockwise clamp-bolt axis pivot. Each clamp was tested 6 times for each variable at 7.68 Nm of clamp-bolt tightening torque.
  
  
  RESULTS
  were compared using repeated measures ANOVA. Results- For the IMEX-SK clamp, a significant degradation in the force required to cause slippage was found for connecting bar slippage and fixator pin rotation; however, this clamp also had a significant increase in the force to initiate slippage for clockwise clamp-bolt axis pivot with reuse. The Securos clamp had significant degradation in connecting bar slippage, connecting bar rotation, and fixator pin rotation whereas the KE clamp had significant degradation in connecting bar slippage only.
  
  
  CONCLUSIONS
  All 3 external fixator clamp types degraded in 1 or more movement variables in their ability to resist motion with reuse. The IMEX and Securos clamps were more subject to degradation than the KE clamp and this may have clinical importance for fixator composite rigidity.
  
  
  CONCLUSIONS
  Fracture-reduction stability is related to the ability to resist motion within a clamp. The unpredictable nature of degradation we found cautions against repeated use. Clinicians should consider reuse of external fixator clamps with the knowledge that repeated use degrades clamp mechanical performance.
authors.affiliation: Department of Clinical Studies, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA. rsgilley@vet.upenn.edu
authors.forename: Robert S
authors.initials: RS
authors.lastname: Gilley
authors.forename: David P
authors.initials: DP
authors.lastname: Beason
authors.forename: David M
authors.initials: DM
authors.lastname: Snyder
authors.forename: Raymond C
authors.initials: RC
authors.lastname: Boston
authors.forename: Alex
authors.initials: A
authors.lastname: Radin
authors.forename: Amy S
authors.initials: AS
authors.lastname: Kapatkin
authors.forename: Gail K
authors.initials: GK
authors.lastname: Smith
authors.forename: Louis J
authors.initials: LJ
authors.lastname: Soslowsky
mesh_terms: D000818:Animals; D004867:Equipment Design / Q000662:veterinary; D004868:Equipment Failure / Q000662:veterinary; D016267:External Fixators / Q000662:veterinary*; D005592:Fracture Fixation / Q000295:instrumentation* / Q000662:veterinary; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary; D013314:Stress, Mechanical