title: Finite element analysis of a novel pin-sleeve system for external fixation of distal limb fractures in horses.
abstract: The transfixation pin cast (TPC) is an external skeletal fixation technique used to treat horses with distal limb fractures, but its use is often associated with pin-loosening and an increased risk of treatment failure. To address implant loosening, the pin sleeve cast system (PSC) was recently designed and consists of a pin-sleeve unit inserted into the bone. Each pin runs through a sleeve placed in the bone, making contact at two fixed points only within the sleeve. Each pin is attached to a ring embedded in a resin cast. In this report, the mechanical performance of a traditional TPC pin arrangement was compared with that of the PSC using validated finite element models of bone substitutes previously tested in vitro. The PSC resulted in a marked reduction in peak strain magnitude around the pins and a more even distribution of strain across the bone cortex. The two systems resulted in comparable proximal fragment displacement and had a similar stress concentration around bone defects during implant removal. The findings suggest that the PSC load transfer mechanism is effective even in geometrically complex structures like equine bones.
authors.affiliation: AO Foundation Research Institute, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland. Electronic address: stefano.brianza@aofoundation.org.
authors.forename: Stefano
authors.initials: S
authors.lastname: Brianza
authors.affiliation: AO Foundation Research Institute, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland.
authors.forename: Vittoria
authors.initials: V
authors.lastname: Brighenti
authors.affiliation: AO Foundation Research Institute, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Lansdowne
authors.affiliation: AO Foundation Research Institute, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland.
authors.forename: Karsten
authors.initials: K
authors.lastname: Schwieger
authors.affiliation: AO Foundation Research Institute, Clavadelerstrasse 8, 7270 Davos Platz, Switzerland.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Bouré
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails / Q000662:veterinary*; D018483:Diaphyses / Q000293:injuries / Q000601:surgery; D016267:External Fixators / Q000662:veterinary*; D020342:Finite Element Analysis; D005592:Fracture Fixation / Q000295:instrumentation / Q000379:methods / Q000662:veterinary*; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary*; D006736:Horses / Q000293:injuries*; D050279:Metacarpal Bones / Q000293:injuries* / Q000601:surgery; D008953:Models, Anatomic; D013314:Stress, Mechanical; D016474:Weight-Bearing