title: Biomechanical performance of a new device for medial malleolar fractures.
abstract: BACKGROUND
  Displaced medial malleolus fractures require surgical repair because of the critical role the structure plays in normal joint function. Various approaches exist, but options are limited for small fragment fractures. This study compared repair with the Medial Malleolar Sled fixation system (Trimed, Inc, Valencia, CA) to lag screws in 2 modes of biomechanical loading in a cadaveric model.
  
  
  METHODS
  A Müller type B medial malleolus fracture was simulated on matched pairs of cadaveric lower extremities and repaired with the sled or 2 cancellous lag screws. Tibial distraction (tension, n = 10) or internal rotation (torsion, n = 11) was applied. Fragment movement was measured in the sagittal (tension and torsion) and transverse (torsion-only) planes. Fragment movement at 1 mm and 2 mm (clinical malunion) of gapping during tension and at 2, 4, 6, and 8 N-m during torsion was analyzed via paired t tests.
  
  
  RESULTS
  In tension, the load at the 2-mm gap was statistically lower for screws (P = .026). Opening angle was statistically larger for the sled at the 1-mm (P = .0004) and 2-mm (P = .008) gap. In torsion, gapping was statistically lower for the sled (ranging from P = .0013 at 4 N-m to P = .0187 at 8 N-m). No differences were detected for opening angle or transverse plane movement.
  
  
  CONCLUSIONS
  The sled appeared stronger in tension and as effective as lag screws in torsion. The sled may be a viable option for fractures too small for 4.0- or 3.5-mm lag screws.
  
  
  CONCLUSIONS
  The sled may be suitable in applications where a tension band would normally be considered and may provide stronger fixation in osteoporotic bone compared with lag screw fixation.
authors.affiliation: Virginia Commonwealth University, Richmond, VA, USA.
authors.forename: Tejas
authors.initials: T
authors.lastname: Patel
authors.forename: John R
authors.initials: JR
authors.lastname: Owen
authors.forename: William A
authors.initials: WA
authors.lastname: Byrd
authors.forename: Ryan B
authors.initials: RB
authors.lastname: Graves
authors.forename: Ruchi D
authors.initials: RD
authors.lastname: Chande
authors.forename: Varatharaj
authors.initials: V
authors.lastname: Mounasamy
authors.forename: Robert S
authors.initials: RS
authors.lastname: Adelaar
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Wayne
mesh_terms: D000328:Adult; D000368:Aged; D016512:Ankle Injuries / Q000601:surgery*; D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws; D001864:Bone Wires; D002102:Cadaver; D005260:Female; D005471:Fluoroscopy; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D008297:Male; D008875:Middle Aged; D013978:Tibial Fractures / Q000601:surgery*; D019415:Torque