The influence of the number of cortices of screw purchase and ankle position in Weber C ankle fracture fixation.
OBJECTIVE
Biomechanical and clinical studies have shown that syndesmosis screws may be indicated in repairing Weber C ankle fractures. This study sought to determine the effect of the number of cortices of screw purchase and ankle position on syndesmosis width and tibiotalar rotation in Weber C ankle fracture fixation.


METHODS
Nine pairs of human cadaver legs were mechanically tested to determine syndesmosis width and tibiotalar rotation. This was done for intact specimens and after a Weber C injury was created and repaired with 3 and 4 cortices of purchase. Tests were performed for no axial load and for axial loads of 700 N with and without external torques of 1 and 5 Nm on the ankle. Torque-to-failure tests were also done for 4 cortices of fixation.


RESULTS
In comparison to baseline, the syndesmosis width was significantly decreased when the syndesmosis screw was inserted in plantarflexion with either 0 or 1 Nm of torque. Syndesmosis width significantly increased when the screw was inserted in dorsiflexion for 5 Nm of torque. For tibiotalar rotation, no statistical differences were detected for either plantarflexion or dorsiflexion when compared to baseline, except with axial load. Syndesmosis width was not affected by the number of cortices purchased by the syndesmosis screw. Failure torque and failure angle were also measured.


CONCLUSIONS
Because no difference was seen between 3 or 4 cortices, it is the surgeon's choice in determining how many cortices of fixation are achieved.
Nousiainen
Markku T
MT
Division of Orthopaedic Surgery, University of Toronto, Toronto, ON, Canada.
McConnell
Alison J
AJ
Zdero
Rad
R
McKee
Michael D
MD
Bhandari
Mohit
M
Schemitsch
Emil H
EH
D016512:Ankle Injuries / Q000503:physiopathology* / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D019544:Equipment Failure Analysis; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D017102:Fracture Healing; D050723:Fractures, Bone / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D011187:Posture; D019919:Prosthesis Implantation / Q000295:instrumentation* / Q000379:methods; D016059:Range of Motion, Articular; D016896:Treatment Outcome