• M C MacAvoy, R T McClellan, S B Goodman, C R Chien, W A Allen, and M C van der Meulen.
• Division of Orthopaedic Surgery, School of Medicine, Stanford University, California, USA.
• J Orthop Trauma. 1997 Nov 1; 11 (8): 590-3.

ObjectiveA new biomechanical model of single-limb stance was developed to test the stability of intact, injured, and internally fixed pelves.DesignSingle-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.InterventionTwo 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 MeasurementsWe 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.ResultsThe 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.ConclusionThis 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.

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