BIOMECHANICAL ASSESSMENT OF SPINE DEFORMITIES IN BEKHTEREV’S DISEASE

Objective. To analyze the dependence of the spine shape and orientation in a sagittal plane on localization of a flexion deformity associated with Bekhterev’s disease, and the outcomes of surgical deformity correction. Material and Methods. The kinematic analysis of sagittal plane spondylograms of 44 patients (43 men and 1 woman, aged 21 to 49 years) with Bekhterev’s disease before and after surgery was performed basing on author’s classification of kyphotic deformities. Illness duration was 7 to 22 years. Results. One-level correction vertebrectomy caused the increase of lordosis at two or three levels in 50 % of cases. Correction vertebrectomy for flat lumbar kyphosis resulted in normalization of all biomechanical spine parameters characterizing its shape and sagittal orientation in 100 % of cases. Lumbar vertebrectomy for flexion deformity in the thoracic spine normalized sagittal position of vertebrae only in isolated segments. Cosmetic hyperkyphosis remained, though the trunk orthostatic position had been restored. Similar results were recorded in the group with multilevel deformities. Lost of correction at vertebrectomy level and progression of flexible deformity above vertebrectomy were not revealed. Kyphotic deformity formation (ranged 16.0° to 32.0°) at the segments caudal to vertebrectomy was observed in 10 % of cases. Conclusion. Flexion deformity localization in the spine determines the condition of its further progression in many respects. Correction lumbar vertebrectomy while reconstructing orthostatic trunk position does not always result in complete normalization of vertebra sagittal position in anchylosis spine.