A common and difficult fracture scenario is that of the short fracture fragment where traditional linear fixation techniques are hard to use because the limited amount of bone prevents use of an optimum number of fixation pins. When forced to use less than optimal pin numbers to fully share the load of weight bearing, stronger pins have potential to protect the pin-bone interface by decreasing localized end shear and axial loads at the pin-bone interface and to better withstand cyclic loading over time.

When forced to use less than optimal pin numbers to fully share the load of weight bearing, stronger pins have potential to protect the pin-bone interface by decreasing localized end shear and axial loads at the pin-bone interface and to better withstand cyclic loading over time.

Fractures of the humerus and femur are always considered difficult when repaired with external fixation. One major reason for this is the thick layer of surrounding muscle that requires the fixation clamp and external bar to be placed further from the bone compared to fractures of the radius and tibia. Since pin stiffness is inversely proportional to working length (length of the pin from the bone to the clamp) to the third power, there is a significant reduction of pin stiffness when repairing humeral or femoral fractures. The same issues exist when using ESF for repair of spinal fractures and luxations. Unfortunately, increased pin stiffness can only be achieved by increasing the diameter of the pin when using currently marketed positive-profile pins. If pin diameter increases too much, fracture of the surrounding bone may occur. The increased stiffness of Duraface fixation half-pins minimizes the negative effects of long pin working lengths without a dangerous increase in bone-hole diameters that could result in iatrogenic fracture.

Highly comminuted fractures are typically considered non-load sharing scenarios. In non-load sharing scenarios, the hardware (fixation pins, clamps and connecting bars) are required to carry all the load of weight bearing until fracture callous begins to form. As a result, there is a greater tendency for elastic deformation of the pin and loosening at the pin-bone interface due to repetitive cyclic motion. Often, in the case of highly comminuted fractures, there is also considerable soft tissue damage which decreases blood supply to the fracture site and increases the potential for delay in fracture healing. Duraface ESF half-pins with increased stiffness can reduce end shear and axial loads at the pin-bone interface, prolonging the longevity of the fixator-bone composite until bone healing allows the load of weight bearing to be shared between bone and hardware. Increased fatigue life of Duraface fixation half-pins can provide additional safety during prolonged healing events related to soft tissue and blood supply damage, old age, and systemic diseases.

Even transverse fractures, which intuitively seem stable, can benefit from Duraface fixation half-pins. Transverse fractures are often considered an “easy” fracture repair, but in reality, the single, small fracture line concentrates all movement (strain) at the fracture site (as contrasted to the same amount of strain spread out over many fracture lines in a comminuted fracture). High local strains can lead to delayed union or non-union. Duraface fixation half-pins with their increased stiffness can facilitate strain reduction at the fracture gap and provide added longevity in potentially prolonged healing situations.

Obese patients with small bones represent another challenging fracture repair scenario because the animal’s extra weight calls for a larger pin diameter than the bone can accept without undue risk of fracture. In these scenarios, Duraface fixation half-pins may provide the stiffness needed to support fracture healing. A Duraface fixation half-pin approximates the stiffness of the next larger positive-profile fixation pin allowing the smaller Duraface pin to function well in mechanically challenging scenarios such as the obese patient above or even the overly active patient with a noncompliant owner.

Any orthopedic scenario involving multiple limb fractures or single limb fractures with other limbs suffering either acute or chronic injury are typically much more prone to orthopedic complications including pin loosening or mechanical failure of the fixation device. These complications occur because of the patient’s inability to protect the externally-fixated limb during daily use, leading to high levels of cyclic stress on the fixation device and bone over time. These high peak stresses create a greater likelihood of pin loosening or even pin failure. Duraface half-pins from IMEX offer greater longevity and durability in these challenging cases somewhat analogous to stacked plating or broad plates.

Surgeons performing limb lengthening report that small diameter wires used in circular external fixation frames (CESF) near the elbow and stifle create a significant amount of morbidity due to their irritation of high motion soft tissues near the joint. To avoid this complication, surgeons will create “linearized” CESF frames that use half-pins near the elbow or stifle joint in order to avoid wire placement through mobile soft tissues. When used in this fashion, half-pins are placed under significant load and subject to increased bending or failure of the pin-bone interface. Stiffer pins such as Duraface fixation half-pins support additional loads with less deformation and less potential for failure.