title: In vitro biomechanical comparison of a 4.5 mm narrow locking compression plate construct versus a 4.5 mm limited contact dynamic compression plate construct for arthrodesis of the equine proximal interphalangeal joint.
abstract: OBJECTIVE
  To compare the in vitro biomechanical properties of a 4.5 mm narrow locking compression plate (PIP-LCP) with 2 abaxially located transarticular screws and a 4.5 mm limited contact dynamic compression plate (LC-DCP) with 2 abaxially located transarticular screws using equine pasterns.
  
  
  METHODS
  Experimental. Paired in vitro biomechanical testing of 2 methods for stabilizing adult equine forelimb PIP joints.
  
  
  METHODS
  Adult equine forelimbs (n = 8 pairs).
  
  
  METHODS
  Each pair of PIP joints were randomly instrumented with either a PIP-LCP or LC-DCP plate axially and 2 parasagitally positioned 5.5 mm transarticular screws. The proximal aspect of the proximal phalanx (P1) and the distal aspect of the middle phalanx (P2) were embedded to allow for mounting on a mechanical testing machine. Each construct was tested in both cyclic and subsequently single cycle to failure in 4-point bending. The displacement required to maintain a target load of 1 kN over 3600 cycles at 1 Hz was recorded. Maximum bending moment at failure and construct stiffness was calculated from the single cycle to failure testing.
  
  
  RESULTS
  In cyclic testing, significantly more displacement occurred in the LC-DCP (0.46 ± 0.10 mm) than for the PIP-LCP (0.17 ± 0.11 mm) constructs (P = .016). During single cycle testing there was no significant difference in the bending moment between the LC-DCP (148.7 ± 19.4 N m) and the PIP-LCP (164.6 ± 17.6 N m) constructs (P = .553) and the stiffness of the LC-DCP (183.9 ± 26.9 N mm) was significantly lower than for the PIP-LCP (279.8 ± 15.9 N/mm) constructs (P = .011). All constructs failed by fracture of the bone associated with the transarticular screws and subsequently bending of the plates at the middle hole.
  
  
  CONCLUSIONS
  Use of the PIP-LCP resulted in a stiffer construct of the same strength as the LC-DCP in vitro using this 4-point bending model.
authors: Department of Clinical Studies, New Bolton Center, School of Veterinary Medicine, University of Pennsylvania, Kennett Square, PA, USA. ahernvet@gmail.com
authors: Benjamin J
authors: BJ
authors: Ahern
authors: Brent L
authors: BL
authors: Showalter
authors: Dawn M
authors: DM
authors: Elliott
authors: Dean W
authors: DW
authors: Richardson
authors: Liberty M
authors: LM
authors: Getman
mesh_terms: D000818:Animals; D001174:Arthrodesis / Q000379:methods / Q000662:veterinary*; D001696:Biomechanical Phenomena; D001860:Bone Plates / Q000592:standards / Q000662:veterinary*; D005552:Forelimb; D006736:Horses / Q000601:surgery*; D066298:In Vitro Techniques; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D014033:Toe Joint / Q000503:physiopathology / Q000601:surgery*