Stability of ten configurations of the Hoffmann external-fixation frame.

Effects of Construct Stiffness on Healing of Fractures Stabilized with Locking Plates

“…On the basis of actuator displacement, construct stiffness of femoral locking plates has been reported to range from 63 N/mm 21 to 159 N/mm 22 . This stiffness is comparable with that of external fixators (50 to 400 N/mm [23][24][25] ), which are known to promote fracture-healing by callus formation. However, investigators who have measured the actual fracture-site motion at the far cortex (opposite the plate) have reported a more than tenfold higher stiffness (833 N/mm 26 to 2100 N/mm 27 ) for locked femoral bridge-plate constructs.…”

“…The 19% of the femoral fractures that became nonunions exhibited less callus formation, while stable implant alignment was maintained. This suggests that callus inhibition, rather a: Conventional (CP) and locked-plate (LP) constructs were comparably stiff and were approximately one order of magnitude stiffer than external fixators (ExFix) [23][24][25] . b: Axial loading caused plate bending and asymmetric gap closure, whereby interfragmentary motion (IFM) at the near cortex was minimal.…”

Far Cortical Locking Can Reduce Stiffness of Locked Plating Constructs While Retaining Construct Strength

“…The axial stiffness of the locked plating construct (2.9 kN/mm) was comparable with that reported for broad 4.5-mm conventional plating constructs (2.6 to 3.2 kN/mm) and locked plating constructs (2.1 to 2.7 kN/mm) tested under similar loading conditions and bridge plating configurations 15 . In contrast, the initial axial stiffness of the far cortical locking construct was 0.36 kN/mm, 88% lower than that of the locked plating construct and comparable with that of an external monolateral fixator, reported to be in the range of 0.05 to 0.4 kN/mm [30][31][32] . The stiffness reduction provided by far cortical locking may be desirable for bridge plating osteosynthesis, which relies on secondary, not primary, bone healing 6,33 .…”

A new device for external fixation

“…Therefore, it seems logical that the overall rigidity of an external fixation device should neutralize the principle forces acting on an injured limb during the early period of bone and soft-tissue consolidation. In addition, the construction of the frame should allow for reduction of the rigidity during the healing process (De Bastiani et al 1984, Burgess et al 1986, Gotzen et al 1986, Hammer and Helland 1987, Finlay et al 1987. Stabilization of tibial shaft fractures with a unilateral single-bar Hoffman frame, as an elastic or flexible external fixation, has been advocated (Bumy 1979).…”

“…Stabilization of tibial shaft fractures with a unilateral single-bar Hoffman frame, as an elastic or flexible external fixation, has been advocated (Bumy 1979). However, the low rotational rigidity of this simple frame (Finlay et al 1987) limits its use. In a series of 34 tibial fractures (Schmidt and Rorabeck 1983), stabilized by a single Hoffmann halfframe, the initial reduction was lost in 5.…”