title: Recovery of decreased bone mineral mass after lower-limb fractures in adolescents.
abstract: BACKGROUND
  Loss of bone mineral mass, muscle atrophy, and functional limitations are predictable consequences of immobilization and subsequent weight-bearing restriction due to leg or ankle fractures. The aim of this study was to prospectively determine whether decreased bone mineral mass following lower-limb fractures recovers at follow-up durations of six and eighteen months in adolescents.
  
  
  METHODS
  In the present study, we included fifty adolescents who underwent cast immobilization for a leg or ankle fracture. Dual x-ray absorptiometry scans of four different sites (total hip, femoral neck, entire lower limb, and calcaneus) were performed at the time of the fracture, at cast removal, and at follow-ups of six and eighteen months. Patients with fractures were paired with healthy controls according to sex, age, and ethnicity. Dual x-ray absorptiometry values were compared between groups and between injured and non-injured legs in adolescents with fractures.
  
  
  RESULTS
  Among those with fractures, lower-limb bone mineral variables were significantly lower at the injured side compared with the non-injured side at cast removal, with differences ranging from 6.2% to 31.7% (p &lt; 0.0001). Similarly, injured adolescents had significantly lower bone mineral values at the level of the injured lower limb compared with healthy controls (p &lt; 0.0001). At the six-month follow-up, there were still significant residual differences between injured and non-injured legs in adolescents with fractures (p &lt; 0.0001). However, a significant residual difference between healthy controls and injured adolescents was present only for femoral neck bone mineral density (p = 0.011). At the eighteen-month follow-up, no significant difference was observed at any lower-limb site.
  
  
  CONCLUSIONS
  Bone mineral loss following a fracture of the lower limb in adolescents is highly significant and affects the lower limb both proximal to and distal to the fracture site. In contrast to observations in adults, a rapid bone mass reversal occurs with full bone recovery by eighteen months.
  
  
  METHODS
  Prognostic Level I. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Pediatric Cardiology Unit, Department of Child and Adolescent, University Hospitals of Geneva, 6 Rue Willy Donzé, 1211 Geneva 14, Switzerland. dimitri.ceroni@hcuge.ch
authors.forename: Dimitri
authors.initials: D
authors.lastname: Ceroni
authors.forename: Xavier E
authors.initials: XE
authors.lastname: Martin
authors.forename: Cécile
authors.initials: C
authors.lastname: Delhumeau
authors.forename: Nathalie J
authors.initials: NJ
authors.lastname: Farpour-Lambert
authors.forename: Geraldo
authors.initials: G
authors.lastname: De Coulon
authors.forename: Victor
authors.initials: V
authors.lastname: Dubois-Ferrière
authors.forename: René
authors.initials: R
authors.lastname: Rizzoli
mesh_terms: D015502:Absorptiometry, Photon; D000293:Adolescent; D015519:Bone Density / Q000502:physiology*; D001861:Bone Regeneration; D016022:Case-Control Studies; D002370:Casts, Surgical / Q000009:adverse effects*; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D050723:Fractures, Bone / Q000503:physiopathology*; D006801:Humans; D007103:Immobilization / Q000009:adverse effects* / Q000379:methods; D008137:Longitudinal Studies; D035002:Lower Extremity / Q000293:injuries* / Q000502:physiology*; D008297:Male; D011446:Prospective Studies