title: In vitro evaluation of the torsional strength reduction of neonate calf metatarsal bones with Bicortical defects resulting from the removal of external fixation implants.
abstract: OBJECTIVE
  To compare the torsional strength of calf metatarsal bones with defects produced by removal of 2 different implants.
  
  
  METHODS
  In vitro mechanical comparison of paired bones with bicortical defects resulting from the implantation of 2 different external fixation systems: the transfixation pin (TP) and the pin sleeve system (PS).
  
  
  METHODS
  Neonatal calf metatarsal bones (n = 6 pairs).
  
  
  METHODS
  From each pair, 1 bone was surgically instrumented with 2 PS implants and the contralateral bone with 2 TP implants. Implants were removed immediately leaving bicortical defects at identical locations between paired metatarsi. Each bone was tested in torque until failure. The mechanical variables statistically compared were the torsional stiffness, the torque and angle at failure, and work to failure.
  
  
  RESULTS
  For TP and PS constructs, respectively, there were no significant differences between construct types for any of the variables tested. Mean ± SD torsional stiffness: 5.50 ± 2.68 and 5.35 ± 1.79 (Nm/°), P = .75; torque: 57.42 ± 14.84 and 53.43 ± 10.16 (Nm); P = .34; angle at failure: 14.76 ± 4.33 and 15.45 ± 4.84 (°), P = .69; and work to failure 7.45 ± 3.19 and 8.89 ± 3.79 (J), P = .17).
  
  
  CONCLUSIONS
  Bicortical defects resulting from the removal of PS and TP implants equally affect the investigated mechanical properties of neonate calf metatarsal bones.
authors.affiliation: AO Research Institute, Davos Platz, Switzerland. stefano.brianza@aofoundation.org
authors.forename: Stefano
authors.initials: S
authors.lastname: Brianza
authors.forename: Susan
authors.initials: S
authors.lastname: Vogel
authors.forename: Stephan
authors.initials: S
authors.lastname: Rothstock
authors.forename: Andrè
authors.initials: A
authors.lastname: Desrochers
authors.forename: Ludovic
authors.initials: L
authors.lastname: Boure
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001696:Biomechanical Phenomena; D001858:Bone Nails / Q000662:veterinary*; D002102:Cadaver; D002417:Cattle; D004868:Equipment Failure / Q000662:veterinary; D016267:External Fixators / Q000662:veterinary*; D005260:Female; D005552:Forelimb / Q000601:surgery; D008297:Male; D054159:Torsion, Mechanical