A Less Invasive Technique for Correction of Thoracolumbar Sagittal Deformity in Ankylosing Spondylitis

Abstract

Background Data: Ankylosing spondylitis (AS) is a chronic inflammatory disease that can severely alter the normal spinal sagittal balance resulting in functional and social disability. Although the traditional open corrective techniques have provided a great radiographic improvement, they are associated with relatively high morbidity and mortality in an already vulnerable patient with several medical comorbidities. Therefore, a new less invasive technique has been developed in an attempt to achieve both radiographic and clinical improvement while minimizing the possible surgical risks of conventional open approaches. Purpose: To present an innovative less invasive technique for management of thoracic and/or lumbar sagittal imbalance in AS and to evaluate the morbidity, clinical results and radiographic correction following the use of this technique. Study design: Retrospective analysis of prospectively collected data. Methods: Between September 2008 and September 2013, 51 patients (43 males and 8 females) with thoracic and/or lumbar sagittal imbalance due to AS were operated upon. Those patients underwent minimally invasive dorso-ventral osteotomy and reconstruction plus posterior percutaneous instrumentation in the same prone position. Sagittal vertical axis (SVA), T1 pelvic angle (TPA), angle of fusion levels (AFL) and chin-brow vertical angle (CBVA) were used to evaluate radiographic outcomes and degree of correction. Clinical outcomes were assessed by Oswestry Disability Index (ODI) and visual analogue scale (VAS). Results: The mean age at operation was 49.02 years. The mean operative time was 419.31 min with a mean blood loss of 698.24 ml. One third of the patients underwent more than one single dorso-ventral osteotomy. All clinical and radiographic parameters (except for PI) showed a statistically significant improvement after surgery (P< 0.0001). The mean correction of AFL was 32.23±10.16° while the mean loss of correction was 2.00±2.89°. In the present study, not only the mean ODI improved significantly from 48.67±7.86 preoperatively to 19.25±10.22 at the latest follow up (P< 0.0001), but also 94% of the patients showed >30% improvement from the baseline ODI. Moreover, the changes in ODI were significantly related to