A New Objective Radiographic Criteria for Diagnosis of Adult Idiopathic Scoliosis: Apical Pedicle Diameter Asymmetry.

OBJECTIVES: To test the hypothesis that a difference of 1mm or greater in pedicle diameter between the convex and concave pedicles at the apex of a lumbar curve is a sensitive and/or specific criteria for adult idiopathic scoliosis (AdIS).

METHODS: 39 operative patients with adult deformity and lumbar major curves were identified. Chart review was performed. Radiographic measurements included lumbar Cobb, curve apex, and Cobb levels involved. Apical pedicle diameter at the concavity and convexity of the curve apex were measured.

RESULTS: Among 39 patients, the average cobb angle was 48.3 degrees. Curve apex averaged at L1/2 (range L1 - L3). The curves spanned 4.7 levels (range 3-7). 25 curves had the apex to the left, while 14 had apex to the right. The average pedicle diameter at the apex was 6.1mm. 14 patients had apical pedicle diameter asymmetry (APDA) >1mm. 7 of 8 (87.5%) patients with history of AIS had APDA>1mm. 7/31 (22.5%) patients without known history of AIS had APDA>1mm (p<0.01).

CONCLUSIONS: Apical pedicle diameter asymmetry is a sensitive diagnostic criteria for AdIS and may be useful for differentiating lumbar major AdIS from degenerative lumbar scoliosis (DLS). The sensitivity of APDA>1mm is 87.5%, with specificity of 77.4%.