Avoiding iatrogenic vascular injury in tibial external fixation with half pins. An in-vivo study based on CT...

External fixation is an important tool in the management of variety of tibial fractures. Appropriate half pin insertion is important, to provide stable fixation without compromising the surgical field for definitive surgical procedures, and avoiding further damage to the important structures of the traumatized limb. There is paucity of literature about the optimal trajectories and safe corridors for half pins insertion based on in vivo studies. The available studies are based on anatomic atlases, cadaveric studies or half pin related complications.The aim of the current study is to present the findings of CT angiograms, in patients with external fixation of tibia, to enhance our understanding of optimal trajectories in safe corridors for half pins insertion.

We performed a retrospective study of patients with external fixators on the tibia, who had undergone CT angiogram as part of pre-operative planning for orthoplastic reconstructive procedures. The relationship between the tips of the fixator half pins and named vessels of the leg were analyzed, pins within 5 mm of a named vessel were considered to be a risk of causing iatrogenic injury.

A total 51 patients, with in situ temporizing external fixators, with 134 half pins in different segments of the tibia were analyzed. More than 5 mm of penetration beyond the far cortex was noted in 47%, while in another 16% of pins penetration was more than 10 mm beyond the cortex. A tip to vessel distance (TVD) of 5 mm or less was noted in 28/134 (21%) of the pins, which highlights potential risk to the neurovascular bundles of the leg.

Risk of iatrogenic injury to neurovascular structures from half pin insertion can be reduced by meticulous use of fluoroscopy, by avoiding penetration beyond the far cortex, and avoiding exiting with half pins on the lateral surface in the distal 1/3rd of segment II of tibia. Moreover observing optimal trajectories and safe corridors for pin insertion, and selection of appropriate type of half pin can mitigate the risk to these structures.