title: Tissue response during monofocal and bifocal leg lengthening in patients.
abstract: The purpose of this investigation was to compare the tissue response during mono- and bifocal limb lengthening. The study includes four patients undergoing leg lengthening. All patients started out bifocally with a total diurnal distraction of 1.75 mm, but proceeded monofocally with a rate of 1 mm a day when the distal distraction was terminated due to contractures or pain. The tissue response was monitored by registration of axial force in the distraction rods. The force increased linearly during bifocal lengthening, but culminated or decreased in the period of monofocal lengthening. Average tissue stiffness, defined as the immediate force increase due to each 0.25 mm distraction increment, was significantly higher in the bifocal lengthening phase. The force decay between each distraction was significantly lower during bifocal lengthening, thus indicating decreased tissue accommodation. Details in the force registrations indicated that the soft tissue, not the regenerate, was the main contributor to the tensile force. Conclusively, the tissues at the two osteotomy sites do not lengthen independently. Bifocal lengthening exposes the entire soft tissue to large loads, resulting in increased tissue stiffness and reduced ability to adapt to the increased length. Accordingly, bifocal leg lengthening requires special attention to soft tissue adaptation.
authors.affiliation: National Hospital Orthopaedic Department, Biomechanics Laboratory, Oslo Orthopaedic University, Norway.
authors.forename: Gudrun Trøite
authors.initials: GT
authors.lastname: Aarnes
authors.forename: Harald
authors.initials: H
authors.lastname: Steen
authors.forename: Leif Pål
authors.initials: LP
authors.lastname: Kristiansen
authors.forename: Per
authors.initials: P
authors.lastname: Ludvigsen
authors.forename: Olav
authors.initials: O
authors.lastname: Reikerås
mesh_terms: D017102:Fracture Healing / Q000502:physiology; D006801:Humans; D018889:Ilizarov Technique; D007870:Leg Length Inequality / Q000503:physiopathology* / Q000601:surgery*; D010012:Osteogenesis / Q000502:physiology*; D013718:Tensile Strength