title: Insertion force measurement of cervical traction tongs: a biomechanical study.
abstract: OBJECTIVE
  To measure the insertion forces for various cervical traction tong pins and the force required to penetrate cadaveric skull specimens.
  
  
  METHODS
  Cadaveric study testing tong pin forces.
  
  
  METHODS
  Insertion force and pin indicator displacement were measured in three tongs from each of three manufacturers (PMT, Depuy Ace, Gardner-Wells) after tightening pins per the manufacturer's recommendations and beyond. The force required for skull penetration was measured by driving each pin into cadaveric temporal specimens until the specimen failed or was penetrated.
  
  
  RESULTS
  Forces generated at the recommended pin settings were: PMT, 141 +/- 12 newtons; Ace, 0 +/- 0 newtons; Gardner-Wells, 132 +/- 9 newtons. The Ace tong required 1.0-millimeter indicator protrusion beyond manufacturer's recommended setting before generating clinically significant forces (120 +/- 8 newtons). Unlike the PMT and Ace pins, overtightening of the Gardner-Wells pins (by as little as 0.3 mm beyond recommended indicator displacement) resulted in substantially larger pin force (>448 newtons). Average failure loads of the temporal bone specimens were: PMT, 721 +/- 298 newtons; Ace, 636 +/- 351 newtons; Gardner-Wells, 965 +/- 227 newtons.
  
  
  CONCLUSIONS
  Although pin forces generated at the recommended end point for PMT and Gardner-Wells tongs appear safe, insufficient force was generated for Ace tongs. Furthermore, overtightening of the Gardner-Wells pins generated loads in excess of those that may be required to penetrate the skull.
authors.affiliation: Department of Orthopaedic Surgery, University of Maryland Hospital, Baltimore, USA.
authors.forename: K
authors.initials: K
authors.lastname: Littleton
authors.forename: A
authors.initials: A
authors.lastname: Curcin
authors.forename: V P
authors.initials: VP
authors.lastname: Novak
authors.forename: S M
authors.initials: SM
authors.lastname: Belkoff
mesh_terms: D001696:Biomechanical Phenomena; D002102:Cadaver; D019245:Compressive Strength; D006801:Humans; D008297:Male; D008875:Middle Aged; D012886:Skull; D013701:Temporal Bone; D014143:Traction / Q000295:instrumentation*