Locked plates reduce displacement of vertically unstable pelvic fractures in a Mechanical Testing Model.
BACKGROUND
The purpose of this study is to compare a locked screw construct to a single iliosacral screw for fixation of a vertically unstable pelvic ring injury in a transforaminal sacral fracture model.


METHODS
Orthopaedic Trauma Association type 61-C1.3a2c5 fractures were created in 10 fresh frozen cadaveric pelvis specimens. Specimens were divided into two groups of five. In both groups, the anterior ring was stabilized with a six-hole 3.5-mm reconstruction plate. In the locked plate (LP) group, the posterior injury was stabilized using a two-hole locking plate with one solid 5.0-mm locking iliosacral screw directed onto the S1 body and a second locking screw directed into the lateral sacral ala. In the iliosacral screw group, the posterior injury was stabilized using a single cannulated 7.3-mm screw. Testing was conducted on a Materials Testing System. Values for displacement and rotation were recorded. Each pelvis was axially loaded with a compressive sine wave from 175 N to 350 N for 10,000 cycles to simulate limited weight bearing, with data recorded at 1,000 cycle increments.


RESULTS
Two specimens in the iliosacral screw group displaced more than 1 cm during the first 1,000 cycles. These two specimens displayed gross fracture motion in all planes. All five specimens in the LP group completed 10,000 cycles of testing with less than 1 cm of displacement. A vector displacement calculation from the plane displacement data revealed that the LP group had significantly less displacement (median 1.9 mm) than the specimens in the iliosacral group (median 6.7 mm; p = 0.008) after 10,000 cycles.


CONCLUSIONS
A two-hole plate locked head screw construct resulted in less displacement than a single iliosacral screw in a transforaminal sacral fracture model.
Humphrey
Catherine A
CA
Department of Orthopaedics and Rehabilitation, University of Rochester, Rochester, New York, USA.
Liu
Qi
Q
Templeman
David C
DC
Ellis
Thomas J
TJ
D000328:Adult; D000368:Aged; D001696:Biomechanical Phenomena; D001860:Bone Plates; D002102:Cadaver; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D050723:Fractures, Bone / Q000601:surgery*; D006801:Humans; D008297:Male; D008422:Materials Testing / Q000379:methods*; D008875:Middle Aged; D010384:Pelvic Bones / Q000293:injuries* / Q000601:surgery; D011474:Prosthesis Design; D016474:Weight-Bearing