The Journal of Bone and Joint Surgery, Vol 75, Issue 7 1019-1025, Copyright © 1993 by Journal of Bone and Joint Surgery, Inc
Control of motion of tibial fractures with use of a functional brace or an external fixator. A study of cadavera with use of a magnetic motion sensor
H McKellop, R Hoffmann, A Sarmiento and E Ebramzadeh
Orthopaedic Hospital, Los Angeles, California 90007.
A computer-linked magnetic motion transducer was used to monitor and record
the six components of motion of the bone fragments in eight cadaveric
tibiae in which a simulated, oblique fracture of the middle of the shaft
had been stabilized with a functional brace. The limbs were mounted in a
servo-hydraulic testing frame, and a cyclic load of 150 newtons was applied
along the axis of the tibia. Motion sensors, attached to each side of the
fracture, measured and displayed the values of the three translations
(axial, anterior-posterior, and medial-lateral), the axial rotation, and
the two angulations (anterior-posterior and varus-valgus) as they occurred.
Although only an axial load was applied, the off-axis motions were
comparable in magnitude with the motion along the axis. The elastic
(recoverable) translations of the fragments ranged from 0.5 to 1.9
millimeters, about four to ten times larger than the corresponding motions
that were recorded in an earlier study of such fractures that had been
stabilized with two types of external fixators. The recoverable rotation
and angulations of the fragments of the limbs in the functional brace
ranged from 0.7 to 1.2 degrees, about ten times those recorded when the
external fixators were used.
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