title: Influence of size and stability of the osteotomy gap on the success of fracture healing.
abstract: Flexible fixation of fractures with minimally invasive surgical techniques has become increasingly popular. Such techniques can lead to relatively large fracture gaps (larger than 5 mm) and considerable interfragmentary movements (0.2-5 mm). We investigated the influence of the size of the fracture gap, interfragmentary movement, and interfragmentary strain on the quality of fracture healing. A simple diaphyseal long-bone fracture was modeled by means of a transverse osteotomy of the right metatarsus in sheep. In 42 sheep, the metatarsus was stabilized with a custom-made external ring fixator that was adjustable for gap size and axial interfragmentary movement. The sheep were randomly divided into six groups with three different gap sizes (1, 2, or 6 mm) and small or large interfragmentary strain (approximately 7 or 31%). The movement of the fracture gap was monitored telemetrically by a displacement transducer attached to the fixator. After 9 weeks of healing, the explanted metatarsus was evaluated mechanically in a three-point bending test to determine bending stiffness and was radiographed to measure the amount of periosteal callus formation. Increased size of the gap (from 1 to 6 mm) resulted in a significant reduction in the bending stiffness of the healed bones. Larger interfragmentary movements and strains (31 compared with 7%) stimulated larger callus formation for small gaps (1-2 mm) but not for larger gaps (approximately 6 mm). The treatment of simple diaphyseal fractures with flexible fixation can be improved by careful reduction of the fracture; this prevents large interfragmentary gaps. The experimental fracture model for the metatarsus showed that the healing process was inferior when the gap was larger than 2 mm.
authors.affiliation: Abteilung Unfallchirurgische Forschung und Biomechanik, Universität Ulm, Germany. claes@sirius.medizin.uni-ulm.de
authors.forename: L
authors.initials: L
authors.lastname: Claes
authors.forename: P
authors.initials: P
authors.lastname: Augat
authors.forename: G
authors.initials: G
authors.lastname: Suger
authors.forename: H J
authors.initials: HJ
authors.lastname: Wilke
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001858:Bone Nails; D002146:Bony Callus / Q000503:physiopathology*; D017102:Fracture Healing; D008297:Male; D008684:Metatarsus / Q000293:injuries* / Q000601:surgery; D010027:Osteotomy; D011183:Postoperative Complications; D012756:Sheep