title: Measurement of the tensile forces during bone lengthening.
abstract: BACKGROUND
  The purpose of this study was to investigate the effects of lengthening frequency on mechanical environment in limb lengthening.
  
  
  METHODS
  Tensile forces were continuously monitored using a load sensor attached to a unilateral external fixator. Twenty patients were monitored. Ten patients were with acquired femoral shortening, and five of them underwent quasi-continuous lengthening of 1440 steps per day, and the other five received step lengthening twice a day. The other 10 patients were with achondropalsia. Five of them underwent the same quasi-continuous lengthening, and the other five received the same step lengthening. The circadian change and the daily course of the tensile forces were assessed and compared between quasi-continuous lengthening and step lengthening.
  
  
  RESULTS
  As for circadian change, an acute increase in the force took place simultaneously with each step of lengthening in the step-lengthening group, but very little change of the baseline force level was seen during quasi-continuous lengthening. As for daily course of the tensile force, it increased almost linearly in both lengthening frequency groups in the initial stage of lengthening. No significant difference of the average force increment rate in this phase was recognized between the quasi-continuous and step lengthening groups irrespective of the etiologies.
  
  
  CONCLUSIONS
  The lengthening frequency greatly affected the circadian change of the tensile force, but did not affect the increment rate of the force in the linear phase.
authors.affiliation: Faculty of Medicine, Department of Orthopaedic Surgery, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku Tokyo, 113-0033, Japan. ohnishii-dis@h.u-tokyo.ac.jp
authors.forename: Isao
authors.initials: I
authors.lastname: Ohnishi
authors.forename: Takahide
authors.initials: T
authors.lastname: Kurokawa
authors.forename: Wakyo
authors.initials: W
authors.lastname: Sato
authors.forename: Kozo
authors.initials: K
authors.lastname: Nakamura
mesh_terms: D000293:Adolescent; D000328:Adult; D001852:Bone Lengthening / Q000295:instrumentation* / Q000379:methods*; D002940:Circadian Rhythm; D004867:Equipment Design; D005269:Femur / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D020127:Recovery of Function / Q000502:physiology*; D013314:Stress, Mechanical; D013718:Tensile Strength; D014159:Transducers; D016896:Treatment Outcome