The use of circular, or ring fixators requires patience and experience, but offers additional versatility over other systems.
By maintaining wire tension across a ring, similar construct stiffness can be achieved using smaller diameter wires than linear or free-form external fixation. Coupled with good flexibility over the direction of pin placement, circular ESF can be particularly useful when managing small fragments.
Frames are often constructed to allow adjustment of the spacing and angular relationship between the rings; this is very useful for adjusting bone length (capitalising on the phenomenon of distraction osteogenesis) and in the management of angular limb deformities.
In veterinary patients, true circular frames are reserved exclusively for the lower limb as full 360˚ access is required for positioning of the components. When frames are applied close to joints, full rings may restrict full joint movement and impinge on soft tissues. In these circumstances, part rings are normally substituted. Part rings are not as stiff as full rings.
Circular style frames are sometimes used in locations where anatomical constraints completely prevent the use of full rings. All rings in an assembly of this type will be part rings or ‘arches’. The same anatomical restrictions will often prevent the use of full wires and half pins of a slightly greater diameter will often be required to achieve a similar stiffness; application to the axial skeleton an infrequent, but perhaps the most obvious example.
Frames are often hybridised with linear components to improve their versatility. Posts holding KE Plus or SF clamps may be added to a circular ESF construct to achieve additional points of fixation or longer, hybrid rods may be used to leave a circular frame at one end of the bone and a linear frame at the other end of the bone. Most commonly this is used for the management of juxta-articular fractures.
Our standard M6 system can get a bit heavy for smaller patients.