title: Temporal delimitation of the healing phases via monitoring of fracture callus stiffness in rats.
abstract: The healing process consists of at least three phases: inflammatory, repair, and remodeling phase. Because callus stiffness correlates with the healing phases, it is suitable for evaluating the fracture healing process. Our aim was to develop a method which allows determination of callus stiffness in vivo, the healing time and the duration of the repair phase. The right femurs of 16 Wistar rats were osteotomized and stabilized with either more rigid or more flexible external fixation. Fixator deformation was measured using strain gauges during gait analysis. The strains were recalculated as the callus stiffness over the time course of healing, and the healing phases were identified based on stiffness thresholds. Our hypothesis was that stabilization with more flexible external fixation prolongs the repair phase, therefore resulting in an extended healing time. Confirming our hypothesis, the duration of the repair phase (rigid: approximately 15 days, flexible: approximately 41 days) and the healing time (rigid: approximately 27 days, flexible: approximately 62 days) were significantly longer for more flexible external fixation. Our method allows the quantitative detection of differences in the healing time and duration of the repair phase without multiple time-point sacrifices, which reduces the number of animals in experimental studies.
authors.affiliation: Institute of Orthopaedic Research and Biomechanics, Center of Musculoskeletal Research, Ulm University, Helmholtzstrasse 14, 89081, Ulm, Germany.
authors.forename: Tim
authors.initials: T
authors.lastname: Wehner
authors.forename: Katharina
authors.initials: K
authors.lastname: Gruchenberg
authors.forename: Ronny
authors.initials: R
authors.lastname: Bindl
authors.forename: Stefan
authors.initials: S
authors.lastname: Recknagel
authors.forename: Malte
authors.initials: M
authors.lastname: Steiner
authors.forename: Anita
authors.initials: A
authors.lastname: Ignatius
authors.forename: Lutz
authors.initials: L
authors.lastname: Claes
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D002146:Bony Callus / Q000502:physiology*; D017102:Fracture Healing / Q000502:physiology*; D008297:Male; D017208:Rats, Wistar; D013997:Time Factors
keywords: fixation stability; fracture healing; monitoring callus stiffness; rats; repair phase