title: Stability of locking and non-locking plates in an osteoporotic calcaneal fracture model.
abstract: BACKGROUND
  The aim of this biomechanical cadaver study of calcaneal fractures was to investigate whether a locking calcaneal plate provides more stiffness in osteoporotic bone compared to a non-locking plate.
  
  
  METHODS
  Sixteen fresh frozen bone mineral density (BMD)-matched cadaver feet were tested in a four-part model of a Sanders Type IIB calcaneal fracture. The fractures were fixed either with a non-locking AO (Sanders) plate or an interlocking AO plate (Synthes, Paoli, PA) to the lateral calcaneal wall with six screws. Specimens were subjected to cyclic loading which was increased stepwise to full body weight. Displacement of the posterior facet fragment was measured with an optical tracking system in the sagittal and transverse planes.
  
  
  RESULTS
  No statistically significant differences were observed between the non-locking and the locking plates with respect to number of cycles to failure or 1-mm displacement of the posterior facet. The initial stiffness was significantly higher for non-locking plates.
  
  
  CONCLUSIONS
  In osteoporotic bone, the greater stiffness of the screw-locking-plate construct was offset by the smaller diameter of the screw threads and the lower friction between the plate and bone when a locking plate was used. In clinical practice, the plate should first be compressed to osteoporotic bone with cancellous screws and at least two screws should be placed in the anterior process and in the tuberosity of the calcaneus.
authors.affiliation: Department of Traumatology and Reconstructive Surgery, University Hospital Carl-Gustav-Carus, Fetscherstrasse 74, 01309 Dresden, Germany. illert@web.de
authors.forename: Till
authors.initials: T
authors.lastname: Illert
authors.forename: Stefan
authors.initials: S
authors.lastname: Rammelt
authors.forename: Tim
authors.initials: T
authors.lastname: Drewes
authors.forename: René
authors.initials: R
authors.lastname: Grass
authors.forename: Hans
authors.initials: H
authors.lastname: Zwipp
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D001860:Bone Plates; D002102:Cadaver; D002111:Calcaneus / Q000293:injuries / Q000601:surgery*; D005260:Female; D005593:Fracture Fixation, Internal; D050723:Fractures, Bone / Q000145:classification / Q000601:surgery*; D006801:Humans; D008297:Male; D010024:Osteoporosis / Q000150:complications; D011474:Prosthesis Design; D013314:Stress, Mechanical