title: Restrained Differential Growth: The Initiating Event of Adolescent Idiopathic Scoliosis?
abstract: METHODS
  An experimental model study and a short review of literature.
  
  
  OBJECTIVE
  The purpose of this study was to explore a new hypothesis suggesting that the curvatures seen in adolescent idiopathic scoliosis (AIS) originate from restrained differential growth between the vertebral column and the surrounding musculo-ligamentary structures.
  
  
  BACKGROUND
  Despite decades of research, there is no generally accepted theory on the physical origin of the severe spinal deformations seen in AIS. The prevailing theories tend to focus on left-right asymmetry, rotational instability, or the sagittal spinal profile in idiopathic scoliosis.
  
  
  METHODS
  We test our hypothesis with a physical model of the spine that simulates growth, counteracted by ligaments and muscles, modeled by tethers and springs. Growth of the spine is further restrained by an anterior band representing the thorax, the linea alba, and abdominal musculature. We also explore literature in search of molecular mechanisms that may induce differential growth.
  
  
  RESULTS
  Differential growth in the restrained spine model first induces hypokyphosis and mild lateral bending of the thoracic spine, but then suddenly escalates into a scoliotic deformity, consistent with clinical observations of AIS. The band simulating the ventral structures of the body had a pivotal effect on sagittal curvature and the initiation of lateral bending and rotation. In literature, several molecular mechanisms were found that may explain the occurrence of differential growth between the spine and the musculo-ligamentary structures.
  
  
  CONCLUSIONS
  While AIS is a three-dimensional deformation of the spine, it appears that restrained differential growth in the sagittal plane can result in lateral bending and rotation without a pre-existing left-right asymmetry. This supports the concept that AIS may result from a growth imbalance rather than a local anatomical defect.
  
  
  METHODS
  N/A.
authors: Department of Orthopedic Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors: Tom Joris
authors: TJ
authors: Crijns
authors: Department of Orthopedic Surgery, VU University Medical Center, Amsterdam, The Netherlands.
authors: Agnita
authors: A
authors: Stadhouder
authors: Department of Orthopedic Surgery, VU University Medical Center, Amsterdam, The Netherlands.|MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.|Department of Orthopedic Surgery, Academic Medical Center, Amsterdam, The Netherlands.
authors: Theodoor Henri
authors: TH
authors: Smit
mesh_terms: D000293:Adolescent; D006801:Humans; D008022:Ligaments / Q000254:growth & development; D008159:Lumbar Vertebrae / Q000254:growth & development* / Q000503:physiopathology; D008953:Models, Anatomic; D018482:Muscle, Skeletal / Q000254:growth & development; D012600:Scoliosis / Q000209:etiology* / Q000503:physiopathology; D013904:Thoracic Vertebrae / Q000254:growth & development* / Q000503:physiopathology