Flexibility assessment of the unfused thoracic segments above the ‘potential upper instrumented vertebra’ using the supine side bending radiographs in lenke 5 and 6 curves for adolescent idiopathic scoliosis patients.

Publication date: Available online 24 July 2017
Source:The Spine Journal
Author(s): Mun Keong Kwan, Chee Kidd Chiu, Teik Seng Chan, Siti Mariam Abd Gani, Tan Shurn Heng, Chris Yin Wei Chan
Background contextSelection of UIV for Lenke 5 and 6 curves remains debatable, and several authors had described different selection strategies.ObjectiveThis study analyzed the flexibility of the unfused thoracic segments above the 'potential upper instrumented vertebrae (UIV)' (T1 to T12) and its compensatory ability in Lenke 5 and 6 curves using supine side bending (SSB) radiographs.Study DesignRetrospective studyPatient sample100 patientsOutcome measuresThe ability of the unfused thoracic segments above the 'potential upper instrumented vertebrae (UIV)' i.e. T1 to T12 to compensate back to normal in Lenke 5 and 6 curves. We also analysed post-operative radiological outcome of this cohort of patients with a minimum follow up of 12 months.MethodsRight and leftSSB were obtained. RSB and LSB angles were measured from T1 to T12. Compensatory ability of thoracic segments was the ability to return to neutral (CSVL) with the assumption of maximal correction of lumbar curve with a horizontal UIV. The Lenke 5 curves were classified to: 1) Lenke 5-ve (Mobile): main thoracic Cobb angle < 15° and 2) Lenke 5+ve (Stiff): main thoracic Cobb angle 15.0°to 24.9°.This study was self-funded with no conflict of interest.ResultsThere were 43 Lenke 5-ve, 31 Lenke 5 +ve, and 26 Lenke 6 curves analyzed. For Lenke 5-ve, >70% of thoracic segments were able to compensate when UIV were at T1 to T8 and T12 and >50%at T9 to T11. For Lenke 5+ve, >70% at T1 to T6 and T12, 61.3% at T7, 38.7% at T8, 3.2% at T9, 6.5% at T10 and 22.6% at T11. For Lenke 6 curve, >70% at T1 to T6, 69.2% at T7, 19.2% at T8, 7.7% at T9, 0% at T10, 3.8% at T11 and 34.6% at T12. There was a significant difference between Lenke 5-ve vs. Lenke 5+ve and Lenke 5-ve vs. Lenke 6 from T8 to T11. There were no significance differences between Lenke 5+ve and Lenke 6 curves from T1 to T11.ConclusionsThe compensatory ability unfused thoracic segment of Lenke 5+ve curves was different from the Lenke 5-ve curves and it demonstrated characteristics similar to the Lenke 6 curves.



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