The Journal of bone and joint surgery. American volume
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J Bone Joint Surg Am · Jun 1987
Comparative StudyStability of ten configurations of the Hoffmann external-fixation frame.
The rigidity, load to yield, and load to failure of ten configurations of the Hoffmann external fixator were investigated using a model of wooden pylons with a simulated fracture that consisted of either a reduced transverse cut or a ten-millimeter gap. The axial compressive, torsional, anterior-posterior bending, and medial-lateral bending characteristics of four forms of the single half-frame (half-pinned), four double half-frame, and two full-frame (transfixion-pinned) configurations were examined. Of the single half-frame configurations, a system with a second stacked connecting-rod proved to be superior; however, the system yielded at a mean axial compressive load of only 199 newtons and failed totally at 355 newtons. ⋯ The two full-frame systems performed poorly in torsion and particularly poorly in anterior-posterior bending. The loads that caused a one-millimeter movement within the fracture gap in axial compression were notably low: for the stacked half-frames the load did not exceed a mean value of 174 newtons; for the double half-frame, 190 newtons; and for the quadrilateral frame, 412 newtons. We concluded that no frame had a good over-all performance with regard to rigidity.(ABSTRACT TRUNCATED AT 250 WORDS)