Concentric Placement of Tibia Half Pins Reduces Risk of Stress Fractures With External Fixation
in People With Peripheral Neuropathy
Historically, surgeons have avoided using tibial half pins in circular external fixation for the fear of tibial stress fracture, a potentially devastating complication.
This is in spite of numerous studies demonstrating half pin ease of implementation, superior rigidity, and an overall risk of lower secondary complications, including superficial pin-site infection and loosening. The benefits of which are magnified when tibial half pins are combined with smooth Kirschner wires for circular external fixation.
Concentric versus eccentric half pin placement
In a first of its kind retrospective comparative study published in the Journal of Foot & Ankle Surgery, Wynes et al.assessed the incidence of tibia stress fracture was compared between patients who underwent bi-cortical placement of 6mm conical hydroxyapatite coated pins concentrically using a rancho-cube for “perfect circle” technique versus pins placed eccentrically. The pins were placed following placement of smooth Kirschner wires, and cortices of the tibia were avoided to lessen the incidence of stress fracture.
Overall, the rate of tibia stress fracture was significantly reduced to approximately 2% when the “perfect-circle” technique was used, compared to >18% when eccentric placement was performed.
Perhaps tibial stress fractures with half pin placement have less to do with the pins themselves and more to do with intra-operative placement.