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Stability of open-book pelvic fractures using a new biomechanical model of single-limb stance
M C MacAvoy1, R T McClellan, S B Goodman
1Division of Orthopaedic Surgery, School of Medicine, Stanford University, California, USA.
Objective:
A new biomechanical model of single-limb stance was developed to test the stability of intact, injured, and internally fixed pelves.
Design:
Single-limb stance was simulated by applying muscle forces and body mass loading to cadaver pelves. We created a rotationally unstable "open-book" pelvic injury in nine embalmed pelves by dividing the ligaments of the pubic symphysis, pelvic floor, and anterior and interosseus sacroiliac joint. All pelves were devoid of gross structural abnormalities.
Intervention:
Two methods of internal fixation of the pubis symphysis were compared: (a) a curved six-hole 3.5-millimeter reconstruction plate across the superior pubic symphysis, and (b) the same six-hole 3.5-millimeter reconstruction plate plus a perpendicularly oriented four-hole 3.5-millimeter reconstruction plate placed across the anterior symphysis.
Main Outcome Measurements:
We measured vertical shear displacement at the public symphysis and horizontal displacement at the anterior sacroiliac joint. The results for the injured and fixed specimens were compared with each other and with the results for the intact specimens.
Results:
The injured unfixed specimens showed marked instability that was prevented by both methods of fixation of the pubic symphysis. No significant differences could be demonstrated between single and double plating of the disrupted pubic symphysis when using this single-limb stance model.
Conclusion:
This model of single-limb stance suggests that a single symphyseal plate across the pubic symphysis can stabilize the open-book injury under short-term quasi-static loads.