Page 350 - WSAVA2018
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 25-28 September, 2018 | Singapore
core diameter of the pin. This thread profile offers secure pin-to-bone fixation without having a breakage prone stress-concentrator. These pins were technically difficult to apply with older KE devices, but application is greatly simplified with the clamp design of the IMEX SKÔdevice. The disadvantage of these pins is their large “footprint” in available bone stock; this can be problematic in small bones or where ESF is used in combination with an intramedullary pin. Most recently, IMEX has introduced its DuraFaceÔpins that have a negative thread profile with a tapered thread run-out design at the thread-nonthreaded transition zone. This design feature eliminates the stress- concentrator issue of conventional negative-thread profile pins while adding pin stiffness when compared to a positive-profile pin of equivalent thread-diameter.
Cortical versus Cancellous thread form. A cortical thread form is used in most locations. The cortical thread
form has a finer thread pattern and a greater number
of threads per unit of pin length when compared to cancellous pins. Cancellous pins use their relatively coarse thread pattern and few threads per unit length
to maximize purchase of very soft cancellous bone in locations where there is little cortical bone for purchase (proximal tibial metaphysis, proximal humeral metaphysis, and, in some instances, distal femoral condyle, pelvis and vertebral body). The notion that all metaphyseal bone is soft is not true; cancellous pins should notbe used in the humeral condyle, distal tibia or in the radius.
Regular versus Extended Length Pins.Extended length pins are available in end-threaded designs (for use as half-pins) and centrally-threaded designs (for use as full-pins). Extended length pins have both an increased overall pin length and increased span of threads.
These pins are useful when standard thread length is insufficient to span the full diameter of bone or the soft tissue envelope is so extensive that standard length pins will not protrude sufficiently from the limb.
Linkage Devices (ExFix Pin Clamps)
The SKÔclamp offers a significant improvement over
the KE clamp in terms of both mechanical performance and “user-friendliness”. The mechanical performance
is enhanced by its adaptation to use of relatively large diameter connecting rods as compared to the old KE clamp. The connecting rods are made of carbon fiber composite or titanium instead of stainless steel to reduce their weight. The SKÔclamp design also allows simplified introduction of a variety of pin sizes and designs including positive profile pins.
SKÔclamps have a two-piece aluminum body, a pin- gripping bolt (also known as the primary bolt) with a slotted washer and tightening nut, and a secondary
bolt. The rod-gripping channel is formed by the hemi- circular cut-out shape of each half of the aluminum body. Tightening of the primary and secondary bolts allows
the SK clamp to tightly grip the connecting rod without deforming the shape of the clamp body. The clamps can either be pre-positioned on the connecting rod or can be assembled (or disassembled) on the rod at any desired location during surgical application. The gliding washer upon the primary bolt has a meniscus (slot) that enables the bolt to effectively grip a range of different pin diameters; the curvature of the meniscus corresponds
to the smallest diameter pin shank that can be securely gripped by the clamp (Table 1). The back of the slotted washer has serrated teeth that engage the outer surface of the aluminum clamp body when the primary bolt is tightened. This provides a rigid lock between the fixation pin and the connecting rod. Finger tightening of the secondary bolt allows the clamp to be stabilized on the connecting rod during pre-drilling and pin insertion, but still permits the clamp to swivel slightly as the primary bolt is tightened so that the orientation of the clamp can “self-correct” to the fixation pin.

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