Identifying sources of variability in scoliosis classification using a rule-based automated algorithm.
METHODS
Use of a rule-based automated algorithm to determine sources of variability in radiographic classification.


OBJECTIVE
To determine whether unambiguous rules encoded in a computer program would ensure reliable classification.


BACKGROUND
Reliability problems have been identified in classifications used in surgical planning for patients with thoracic idiopathic scoliosis, but the sources of unreliability are not understood.


METHODS
Objective classification methodology was tested on the King et al (1983) scheme. There were two novel components: 1) positions of the corners of vertebrae in radiographs were digitized relative to a defined axis system and used in automated evaluation of spinal shape parameters required for classification; and 2) the assignment of a classification was done with a rule-based algorithm. The algorithm was implemented after some ambiguities and absence of precise definitions in the King et al classification scheme had been resolved. The algorithm was tested with radiographs of patients having adolescent idiopathic scoliosis.


RESULTS
The automated procedure could encounter reliability problems in cases in which a lumbar curve was very close to crossing the midline, thoracic and lumbar curves were of approximately equal value, when the apex level in the thoracolumbar region was ambiguous, when a Cobb angle was close to 10 degrees, or when the flexibility index was close to unity.


CONCLUSIONS
Objective measurements and rule-based algorithms can eliminate some sources of interobserver and intraobserver errors in classification of spinal deformity. When classification parameters fall close to the boundaries for classification, reliability problems will persist.
Stokes
Ian A F
IA
Department of Orthopaedics and Rehabilitation, University of Vermont, Burlington, Vermont 05405, USA. Ian.Stokes@uvm.edu
Aronsson
David D
DD
D000465:Algorithms; D006801:Humans; D008159:Lumbar Vertebrae / Q000002:abnormalities / Q000000981:diagnostic imaging; D011859:Radiography; D015203:Reproducibility of Results; D012600:Scoliosis / Q000145:classification / Q000175:diagnosis / Q000000981:diagnostic imaging*; D013904:Thoracic Vertebrae / Q000002:abnormalities / Q000000981:diagnostic imaging