203. APICAL VERTEBRA PEDICLE MORPHOLOGY IN SCOLIOSIS

Abstract

Purpose: There is scant literature with respect to reproducibility in radiological measurements of vertebral morphology. The purpose was to determine the reliability of measurement of various parameters of vertebral morphology in idiopathic scoliosis.

Method: Ten patients with AIS were investigated with standardised low dose multi-slice helical CT. Axial reconstructions in the plane of the T8 (apical) vertebra were performed prone, as per Jamieson et al (2008). Antero-posterior (AP) canal diameter, left and right pedicle width, canal width, left and right mid-point to medial pedicle length, left and right pedicle length, and cord length, left and right transverse angles, and left and right canal area were measured by our spine surgeons and spine surgery fellow. Statistical analysis for intra-class coefficients (ICC) for intra and inter observer reliability was then performed.

Results: Intra-observer reliability was excellent, with a mean ICC score of 0.930 (range 0.608–0.996), across all fourteen variables. Inter-observer reliability was very good with a mean ICC score of 0.890 (range 0.360–0.987), across all variables. There was poor inter-observer reliability for measurement of the transverse pedicle angles (0.360 – 0.446). The intra-observer reliability for transverse pedicle angles, whilst good (0.608–0.861), was worse than any of the other intra-observer reliabilities.

Conclusion: We demonstrate excellent intra, and inter observer reliability for measurement of apical vertebrae morphology in AIS. This tool can be utilized in the further study of pedicle dysplasia. Measurement of transverse pedicle angle was less reliable than any of the other measurement variables. A standardised measurement of the morphology of vertebral canal, pedicles and vertebral body morphology is reliable both within individual observers, and across a group of observers. A standardised measure for further investigation has been validated which will enable study of the evolution of pedicle dysplasia over time. This will lead to a better understanding of the etiology of pedicle dysplasia in scoliosis.