We compared the mechanical performance of the Orthofix pelvic external fixator 
with that of the Pittsburgh triangular frame (PTF) on eight fresh-frozen cadaver 
pelves with experimentally created Malgaigne (double-vertical) 
fracture/dislocations. The pelves were quasi-statically loaded in longitudinal 
compression and loss of reduction (i.e., failure) was defined as 1.5 cm of 
diastasis at either of the fracture/dislocation sites. The Orthofix frame-pelvis 
complex (four 6-mm half-pins) was comparable to the PTF-pelvis complex (eight 
5-mm half-pins) in terms of load to failure and overall stiffness, but was 4-7 
times stiffer at lower load levels. Both frame-and-pin complexes deformed 
moderately at the pin-bone interface, but, while the PTF also showed moderate 
displacement between frame components, the Orthofix had almost no frame 
intercomponent motion.