title: Expansion thoracoplasty improves respiratory function in a rabbit model of postnatal pulmonary hypoplasia: a pilot study.
abstract: METHODS
  Using a rabbit model of postnatal pulmonary hypoplasia, we investigated how expansion thoracoplasty affected growth of the spine and lungs.
  
  
  OBJECTIVE
  By constricting the hemithorax in a growing rabbit to create postnatal pulmonary hypoplasia, we quantified how expansion thoracoplasty affects lung volume, respiratory function, alveolar morphology, and spine growth.
  
  
  BACKGROUND
  In children with thoracic insufficiency syndrome, expansion thoracoplasty of the constricted hemithorax improves respiratory function and controls scoliosis. We hypothesize that expansion thoracoplasty of the constricted hemithorax improves pulmonary hypoplasia by allowing the lung to expand, improving respiratory function and stimulating lung growth.
  
  
  METHODS
  Postnatal pulmonary hypoplasia and scoliosis were induced in 5-week old rabbits by constricting left ribs 3 to 8. Expansion thoracoplasty through the fused ribs was performed at 10 weeks. These were compared with Disease rabbits allowed to grow with a constricted left hemithorax and Normal rabbits. Spine and thoracic deformity, right and left lung volumes were measured on reconstructed 3-dimensional computed tomography images and functional residual capacity measured by plethysmography. At maturity, lungs were excised and quantitative histology performed to measure alveolar air fraction and surface density.
  
  
  RESULTS
  Expansion thoracoplasty of the constricted left hemithorax improved scoliosis but increased left lung volumes only moderately compared with Disease rabbits. For Disease and Thoracoplasty Treated rabbits, a compensatory increase in the volume of the right lung maintained total lung volumes equivalent to Normal. Alveolar air space fraction was greater in Disease rabbits, suggestive of emphysema improved by expansion thoracoplasty. Capillaries adjacent to the alveoli were prominent in Thoracoplasty Treated rabbits.
  
  
  CONCLUSIONS
  Expansion thoracoplasty reduces scoliosis and increases the volume of the constricted hemithorax, but the relative increase in the ipsilateral lung volume is small since compensatory hypertrophy of the contralateral lung also occurred. Expansion thoracoplasty may improve respiratory function by increasing alveolar capillaries and preventing emphysematous changes.
authors.affiliation: Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Hemal P
authors.initials: HP
authors.lastname: Mehta
authors.forename: Brian D
authors.initials: BD
authors.lastname: Snyder
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Baldassarri
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Hayward
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Giuffrida
authors.forename: Vahid
authors.initials: V
authors.lastname: Entezari
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Jackson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D005652:Functional Residual Capacity; D008168:Lung / Q000002:abnormalities* / Q000503:physiopathology / Q000601:surgery; D009929:Organ Size; D010865:Pilot Projects; D011650:Pulmonary Alveoli / Q000503:physiopathology; D011817:Rabbits; D012120:Respiration Disorders / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D012129:Respiratory Function Tests; D012272:Ribs / Q000601:surgery; D012600:Scoliosis / Q000150:complications / Q000503:physiopathology / Q000601:surgery*; D013131:Spine / Q000002:abnormalities* / Q000601:surgery; D013905:Thoracoplasty / Q000379:methods*; D013909:Thorax / Q000002:abnormalities* / Q000503:physiopathology; D016896:Treatment Outcome