Biomechanical Comparison of the Trocar Tip Point and the Hollow Ground Tip Point for Smooth External Skeletal Fixation Pins

Abstract

Thermal and microstructural damage are reduced by the HG tip, but pin-bone interface stability is also compromised. The use of a tip with 0.254 mm reduction in the cutting edge may optimize the biological and mechanical factors at the pin-bone interface.

AnIn VitroComparison of Hollow Ground and Trocar Points on Threaded Positive‐Profile External Skeletal Fixation Pins in Canine Cadaveric Bone

“…The hollow‐ground (HG) tip, previously evaluated in our laboratory, is a modification of the traditional T‐tip, in which the facets are concave, providing some room for accumulation of bone debris generated by the cutting edges. Our in vitro study showed that the pin‐tip temperature and the energy associated with drilling smooth pins with HG tips were significantly reduced when compared to pins with T‐tips 11 …”

“…Although no difference was detected in drilling energy, type RT‐T showed significantly increased maximum pullout and end‐insertional torque values in cortical bone, suggesting that the T tip maximizes the radial preload onto the pin. HG‐tipped smooth pins inserted without predrilling showed significantly lower pullout force compared with T‐tipped pins in cortical and cancellous bone 11 . It was suggested that the efficient cutting action of the HG tip cut a hole of nearly equal diameter to that of the pin shank, thus reducing the friction at the pin‐bone interface along the threaded portion of the pin.…”

“…A modification of the HG tip in which the sharp edges of the concave facets are modified so that they do not extend to the full pin diameter has been shown to increase radial preload in smooth pins, 11 and may prove advantageous in threaded pins. It is hypothesized that this modified tip would produce a slightly smaller drill hole than the HG pin tip, and, therefore, the pin would be forced into the bone, increasing the radial preload and achieving a better circumferential fit along the threaded portion of the pin.…”

Biomechanical analysis of four external fixation pin insertion techniques

“…As the tip spins to cut the far cortex, the bone threads in the near cortex are stripped, thus diminishing mechanical integrity. 13 Concerns also exist in that a bicortical pin can damage neurovascular structures that lie beyond the far cortex if the pin penetrates too deeply. Unicortical fixation would prevent both of these pin insertion complications.…”

Comparison of pull-out resistance of Kirschner wires and Imex™ miniature interface fixation half pins in polyurethane foam

“…Weakening of the pin-bone interface can lead to complications such as pin loosening, pain, pin tract sepsis, and failure of the fixator (13,17). Biomechanical evaluations such as pull-out testing have been used to examine the influence of pin design and pin insertion techniques on the bone-holding power of pins (1,2,4,8,11,12,14,18).…”