The Journal of Bone and Joint Surgery, Vol 76, Issue 6 839-847, Copyright © 1994 by Journal of Bone and Joint Surgery, Inc
A biomechanical analysis of prophylactic fixation for pathological fractures of the distal third of the humerus
TA Damron, JP Heiner, EM Freund, LA Damron, R McCabe and R Vanderby
Division of Orthopedic Surgery, University of Wisconsin School of Medicine, Madison 53792-3228.
Twenty-four matched pairs of fresh-frozen humeri from human cadavera were
divided randomly into four groups, in order to determine the most
biomechanically desirable construct for the prophylactic fixation of
impending fractures of the distal third of the humerus. Group I comprised
intact humeri and matched humeri in which a 50 per cent lateral,
semicylindrical cortical defect of the distal third had been created,
resulting in a reproducible model of an impending fracture due to a lytic
defect involving 50 per cent cortical disruption at the distal end of the
humeral medullary canal. In Group II, such a lateral defect was created in
both the right and the left, matched humeri. Group III was composed of
humeri in which the defect had been fixed prophylactically with a single
plate and the contralateral humeri, which had been treated with
double-plating. Group IV comprised specimens in which the defect had been
fixed with double-plating as well as those fixed with Rush rods. The
fixation of each specimen in Groups III and IV was supplemented with bone
cement. Each specimen was tested in torsion to failure, and the resulting
peak torque, torsional stiffness, and total energy absorbed were analyzed
for each group. The Group-I specimens that had a defect had a significantly
lower (p < 0.05) peak torque, torsional stiffness, and total energy
absorbed than the intact specimens; all of the specimens with a defect
failed at the defect, and all of the intact specimens failed proximally. In
Group II, there was a high side-to-side association with respect to peak
torque, torsional stiffness, and total energy absorbed.(ABSTRACT TRUNCATED
AT 250 WORDS)
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