title: Effect of interfragmentary gap on compression force in a headless compression screw used for scaphoid fixation.
abstract: We investigated the effect of an interfragmentary gap on the final compression force using the Acutrak 2 Mini headless compression screw (length 26 mm) (Acumed, Hillsboro, OR, USA). Two blocks of solid rigid polyurethane foam in a custom jig were separated by spacers of varying thickness (1.0, 1.5, 2.0 and 2.5 mm) to simulate an interfragmentary gap. The spacers were removed before full insertion of the screw and the compression force was measured when the screw was buried 2 mm below the surface of the upper block. Gaps of 1.5 mm and 2.0 mm resulted in significantly decreased compression forces, whereas there was no significant decrease in compression force with a gap of 1 mm. An interfragmentary gap of 2.5 mm did not result in any contact between blocks. We conclude that an increased interfragmentary gap leads to decreased compression force with this screw, which may have implications on fracture healing.
authors.affiliation: 1 Department of Hand Surgery, Singapore General Hospital, Singapore.
authors.forename: E S
authors.initials: ES
authors.lastname: Tan
authors.affiliation: 2 Biomechanics Laboratory, Singapore General Hospital, Singapore.|3 Wrist Analysis Research Laboratory, Singapore General Hospital, Singapore.
authors.forename: I S
authors.initials: IS
authors.lastname: Mat Jais
authors.affiliation: 2 Biomechanics Laboratory, Singapore General Hospital, Singapore.
authors.forename: S
authors.initials: S
authors.lastname: Abdul Rahim
authors.affiliation: 1 Department of Hand Surgery, Singapore General Hospital, Singapore.|2 Biomechanics Laboratory, Singapore General Hospital, Singapore.|3 Wrist Analysis Research Laboratory, Singapore General Hospital, Singapore.|4 Adjunct Associate Professor, Duke-NUS Medical School, Singapore.
authors.forename: S C
authors.initials: SC
authors.lastname: Tay
mesh_terms: D001863:Bone Screws; D004867:Equipment Design; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008422:Materials Testing; D008953:Models, Anatomic; D021361:Scaphoid Bone / Q000293:injuries*; D016474:Weight-Bearing
keywords: Interfragmentary gap; compression force; fully threaded headless compression screw; percutaneous fixation; scaphoid fracture