Structural stiffness and reducibility of external fixators placed in malalignment and malrotation.

OBJECTIVE: To determine the structural stiffness and reducibility of various external fixators placed in malalignment and malrotation. DESIGN: Uniform testing of all external fixator configurations. SETTING: Orthopaedic biomechanical laboratory. METHODS: Thirteen external fixators from different manufacturers, in a total of fifteen configurations, were studied. All external fixators were applied to a malreduction jig initially, and a subsequent anatomic reduction was then attempted. If an anatomic reduction was possible, the structural stiffness of those fixators was determined. If anatomic reduction was not possible, the external fixator was removed and reapplied to an anatomically reduced model, and then structural stiffness was determined. RESULTS: Six of the thirteen external fixator configurations allowed an anatomic reduction after placement on a malreduction model. The other nine external fixator configurations would not allow for an anatomic reduction. All the external fixator configurations were biomechanically tested in anteroposterior bending, lateral bending, axial load, and torsion. Each fixator had its own structural stiffness and is reported. CONCLUSIONS: Some external fixators will not allow for an anatomic reduction once placed in malalignment and malrotation without repositioning of the fixator pins. External fixator configurations (i.e., single-pin, dual-pin, and multipin barclamps) affect structural stiffness. Structural stiffness widely varied among the external fixators. Proper external fixator selection will enable early fracture immobilization in malalignment and malrotation in suboptimal conditions (e.g., wartime conditions or a civilian disaster), with subsequent external fixator adjustment for an anatomic reduction.

Traumatic spondylopelvic dissociation. A case report and literature review.

STUDY DESIGN: A case of traumatic spondylopelvic dissociation and a method of fixation are described. OBJECTIVES: The treatment of this rare injury pattern required differentiation from less severe lumbosacral fracture-dislocations or bilateral sacroiliac joint dislocations. SUMMARY OF BACKGROUND DATA: Several case reports have described less severe fracture patterns, but only a handful have illustrated true spondylopelvic dissociation in which there is complete displacement of the lumbar spine into the pelvis. METHODS: After initial stabilization at an outside hospital, the patient was transferred to the authors' institution for definitive care. After computed tomography imaging with three-dimensional multiplanar reconstruction, the fracture was stabilized with a pedicle screw construct attached to the pelvis by means of the Galveston technique. Bilateral iliosacral screws were used to increase stability. RESULTS: At a 2-year follow-up, the patient was pain-free and ambulating in an ankle-foot orthosis. He had a persistent deficit involving the right L5 and S1 nerve roots but was continent of stool. CONCLUSIONS: The unique fracture pattern described in this patient is presented to offer better insight into management of this complex injury and to delineate it from simpler patterns of injury to the lumbosacral junction.