title: Biomechanics of Internal Fixation Modalities for Middle Phalangeal Base Fracture Dislocation.
abstract: BACKGROUND
  Internal fixation modalities of unstable (>50 percent articular involvement) middle phalangeal volar lip fracture-dislocations include interfragmentary screw and volar buttress plating. This study investigates the mechanical properties (yield strength, ultimate tensile strength, and stiffness) of interfragmentary screw (IS), simple buttress plating (BP) and buttress plating with subchondral screw (BP+S).
  
  
  METHODS
  Fifteen cadaveric digits (5 index, 5 middle, and 5 ring) were prepared by excising its skin envelope and flexor tendons while preserving the structures around the proximal interphalangeal joint. An oblique osteotomy involving 50 percent of the articular surface was performed, and this was fixed with based on its study group: interfragmentary screw (IS), simple buttress plating (BP) and buttress plating with subchondral screw (BP+S). These specimens were then loaded to failure.
  
  
  RESULTS
  Yield strength was as follows: BP+S (33.5±9.76 N), IS (13.6±5.46 N), and BP (8.1±3.84 N). Ultimate tensile strength was as follows: BP+S (49.1±21.4 N), IS (15.6±5.19 N), and BP (8.86±3.99 N). Stiffness was as follows: BP+S (4.77±1.32 N/mm), IS (2.44±0.86 N/mm), and BP (1.84±0.71 N/mm).
  
  
  CONCLUSIONS
  A buttress plate and screw construct confers significantly more stability than either interfragmentary screw or buttress plate only fixation in an experimental model.
authors.affiliation: * Department of Hand & Reconstructive Microsurgery, National University Health System, Singapore.
authors.forename: Gen-Lin
authors.initials: GL
authors.lastname: Foo
authors.affiliation: † Department of Orthopedic Surgery, National University of Singapore, Singapore.
authors.forename: Amit K
authors.initials: AK
authors.lastname: Ramruttun
authors.affiliation: * Department of Hand & Reconstructive Microsurgery, National University Health System, Singapore.
authors.forename: Andre Eujin
authors.initials: AE
authors.lastname: Cheah
authors.affiliation: * Department of Hand & Reconstructive Microsurgery, National University Health System, Singapore.
authors.forename: Alphonsus Kin-Sze
authors.initials: AK
authors.lastname: Chong
authors.affiliation: * Department of Hand & Reconstructive Microsurgery, National University Health System, Singapore.
authors.forename: Tun-Lin
authors.initials: TL
authors.lastname: Foo
mesh_terms: D001860:Bone Plates; D001863:Bone Screws; D002102:Cadaver; D050278:Finger Phalanges / Q000293:injuries / Q000601:surgery*; D000072039:Fracture Dislocation / Q000601:surgery*; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D006801:Humans; D008422:Materials Testing; D013314:Stress, Mechanical; D013718:Tensile Strength
keywords: Dislocations; Finger injury; Interphalangeal joint; Intra-articular fractures