Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: Spine
Abstract number: 24291
HOW MUCH APICAL DEROTATION OCCURS AS A RESULT OF CORONAL
CURVE CORRECTION IN AIS, ASSESSMENT USING THE FULCRUM BENDING
RADIOGRAPH
Keith D.K LUK, Wai Yuen CHEUNG, Kenneth M.C CHEUNG, Y.W. WONG
The University of Hong Kong, Hong Kong (HONG KONG)
Introduction: Various studies have reported vertebral derotational effects with
different implant constructs and surgical techniques. However none of them has
considered the spontaneous coupling effect on vertebral derotation produced by
correction of coronal deformity. Method: Patients aged between 10 to 20 years who
suffered from Lenke type 1 idiopathic scoliosis with Cobb angles more than 45° and
underwent posterior spinal fusion were prospectively included. Scoliosis Cobb angles
and apical vertebral rotations in standing, supine and fulcrum bending positions
before surgery, and in supine position after surgery, were measured on x-rays and
CT scans. They were compared using paired t-test. Results: Eighteen patients were
included. The mean age at surgery was 15.5yr. The Cobb angles and apical vertebral
rotations in standing, supine and fulcrum bending positions before surgery and in
supine position after surgery were 54°,26°; 40°,19° ; 17°,10°; and 14°,8° respectively.
The differences in Cobb angles and apical vertebral rotation between standing,
supine and fulcrum bending positions were statistically significant. The differences in
Cobb angle and apical vertebral rotation between fulcrum bending position and postoperation
were statistically insignificant. Discussion and Conclusion: Our study
demonstrated that spontaneous apical derotation occurred concomittently with
correction of the coronal deformity. The amount of vertebral derotation achievable
under fulcrum bending may predict the post-operative vertebral rotation correction.
Apical rotation was corrected by 27% on supine and 62% on fulcrum bending
positions. Such spontaneous derotation effect should be considered when assessing
the effects with different implants and surgical strategies.
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