title: In vivo assessment of regenerate axial stiffness in distraction osteogenesis.
abstract: This paper presents an in vivo test for assessment of regenerate axial stiffness after the distraction phase of lengthening therapy. The test result supplements radiography in evaluating bone healing and assists in determining when the regenerate stiffness is sufficient for removal of the external fixator. The test is non-invasive and does not require fixator removal. The theoretical basis for the method is that an externally applied load is shared between the fixator and the regenerating bone. The amount of load carried by the regenerate depends on its axial stiffness, which increases with advanced mineralization. By measuring the force in the fixator while applying a known external load to the limb, the load-share ratio between fixator and limb can be assessed. A load-share ratio of 100% indicates that the entire load is carried by the fixator. The ratio decreases as the regenerate structure gradually stiffens. In a clinical trial of 22 individuals with tibial lengthening, the fixator was removed when the load-share ratio dropped below 10%. None of the patients experienced fracture after removal of the fixator.
authors.affiliation: National Hospital Orthopaedic Department, Rikshospitalet University Hospital, Oslo 0027, Norway.
authors.forename: Gudrun Trøite
authors.initials: GT
authors.lastname: Aarnes
authors.forename: Harald
authors.initials: H
authors.lastname: Steen
authors.forename: Per
authors.initials: P
authors.lastname: Ludvigsen
authors.forename: Nicholas A
authors.initials: NA
authors.lastname: Waanders
authors.forename: Rik
authors.initials: R
authors.lastname: Huiskes
authors.forename: Steven A
authors.initials: SA
authors.lastname: Goldstein
mesh_terms: D001696:Biomechanical Phenomena; D001861:Bone Regeneration; D006801:Humans; D008433:Mathematics; D008962:Models, Theoretical; D019857:Osteogenesis, Distraction