Influence of the number of cortices on the stiffness of plate fixation of diaphyseal fractures.
OBJECTIVE
To determine the influence of the number of cortices of fixation on the stiffness of plate fixation of diaphyseal fractures.


METHODS
Canine experimental study.


METHODS
Tertiary referral and teaching hospital in Toronto, Canada.


METHODS
Paired radii from fourteen skeletally mature, cross-bred dogs.


METHODS
One member of each pair of radii was tested intact as a control, and the other had a transverse osteotomy plated sequentially with five to ten cortices of fixation on either side of the simulated fracture. Dynamic compression plates and limited contact dynamic compression plates were used in two groups with seven paired radii each. Normalized torsional stiffness and four-point bending stiffness were determined in the elastic range for the control and each of the plated constructs in both groups, using a materials testing machine.


RESULTS
The authors found no significant difference between the stiffness of the dynamic compression plates and limited contact dynamic compression plates. With either plate of a given length, significantly increased torsional stiffness is achieved with end bicortical screws. For bending stability with the plate at right angles to the bending plane, even short plated constructs have a stiffness exceeding that of intact bone.


CONCLUSIONS
For a transverse osteotomy with no fracture interdigitation, the bending rigidity with the plate at right angles to the bending plane is greater than the original stiffness of the bone for all constructs tested, with the exception of the limited contact dynamic compression plate with five cortices of fixation. The torsional rigidity of fixation only approaches the original rigidity of the bone for ten cortices of fixation with the dynamic compression plate and the limited contact dynamic compression plate.
ElMaraghy
A W
AW
Musculoskeletal Research Laboratory, Division of Orthopaedic Surgery, Department of Surgery, St. Michael's Hospital and the University of Toronto, Toronto, Ontario, M5C 1R6 Canada.
ElMaraghy
M W
MW
Nousiainen
M
M
Richards
R R
RR
Schemitsch
E H
EH
D000818:Animals; D001696:Biomechanical Phenomena; D001860:Bone Plates; D004195:Disease Models, Animal; D004285:Dogs; D004548:Elasticity; D004867:Equipment Design; D004869:Equipment Safety; D005260:Female; D005593:Fracture Fixation, Internal / Q000295:instrumentation* / Q000379:methods; D008297:Male; D008422:Materials Testing; D011885:Radius Fractures / Q000473:pathology / Q000601:surgery*; D012016:Reference Values; D012680:Sensitivity and Specificity