title: Can DCP and LCP plates generate more compression? The effect of multiple eccentrically placed screws and their drill positioning guides.
abstract: OBJECTIVE
  The purpose of this biomechanical study was to assess the capacity of dynamic and locking compression plates (DCP and LCP) in improving fracture compression through the use of multiple compression screws, and the effect of alternating their placement between the two sides of the fracture compared with placing them all on one side. The study also compared fracture compression between DCP and LCP, and between the loading and universal drill guides in DCP.
  
  
  METHODS
  Fracture compression was measured using a customised load cell placed in a transverse osteotomy in synthetic bone models. The starting pressure across the osteotomy site was standardised to allow comparison. Large fragment DCP and LCP plates were used for fixation. The eccentrically placed compression screws were inserted in two sequences: all on the initial compression screw side, or alternating between the initial compression and neutral sides. In the DCP, the effect of using the universal guide for eccentric screw insertion point was compared with the loading guide.
  
  
  RESULTS
  In the DCP, the second eccentrically placed screw improved fracture compression in both sequences (p=0.002). A third eccentrically placed screw improved compression only when placed in alternating sequence (p=0.002), whereas the fourth screw had no significant effect (p=0.13). The universal guide generated higher compression than the loading guide (p=0.0001). In the LCP, fracture compression significantly improved following insertion of a second compression screw (p=0.002), but the initial neutral screw failed to re-engage completely into its hole due to lack of space for horizontal gliding towards the fracture. There was no significant difference in compression between the first two compression screws in DCP and LCP (p=0.64, 0.92).
  
  
  CONCLUSIONS
  Fracture compression can be improved either using multiple eccentrically placed screws alternated between the two sides of the plate in LCP and DCP, or by the use of a universal drill guide in DCP. Although the compression hole in the LCP is shorter, it generates compression comparable to the DCP.
authors: Orthopaedic Department, Sunderland Royal Hospital, Sunderland, SR4 7TP, UK. firasyaish2@hotmail.com
authors: Feras M M
authors: FM
authors: Ya'ish
authors: Ananda M
authors: AM
authors: Nanu
authors: Anthony T
authors: AT
authors: Cross
mesh_terms: D001696:Biomechanical Phenomena; D001860:Bone Plates; D001863:Bone Screws; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008422:Materials Testing; D008954:Models, Biological; D010027:Osteotomy; D011312:Pressure; D011474:Prosthesis Design; D019919:Prosthesis Implantation / Q000379:methods; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical