Prognostic Criteria for Post-Operative Success in Patients Undergoing Surgery for Adult Spinal Deformities

The current reported rate of revision after surgery for adult spinal deformities (ASDs) is up to 45%. The aim of this study was to analyze patients with ASD who underwent failed primary surgery and required revision surgeries, in order to identify the reasons for failure and revision, while assessing possible prognostic criteria. Materials and Methods: Thirty-two patients (27 women, 5 men) with a mean age of 69.8 years and follow-up period of 44.6 months were included. Before first revision, patients had a mean sagittal vertical axis (SVA) of 94.2 mm, lumbar lordosis (LL) of 33.3, thoracic kyphosis (TK) of 35.3, pelvic incidence (PI) of 56.9, pelvic tilt (PT) of 27.8, PI-LL of 24.9, and coronal Cobb angle of 22. Mean duration from the initial surgery until the first revision was 34.8 months. Fusion levels extended from T1 to S2. Twenty patients received transforaminal lumbar interbody fusion and 9 received anterior lumbar interbody fusion cages. Five patients underwent corpectomy combined with anterior cage. Three patients underwent ponte-, and 7 underwent pedicle subtraction osteotomies. Results: After the last revision surgery, patients' sagittal plane parameters were significantly corrected (p<0.001 for mean SVA, LL, PT, PI-LL mismatch and coronal Cobb). The most frequent reason for revision was found as advanced sagittal malalignment (ASM) in 29 patients (90.6%) followed by proximal junctional kyphosis (PJK) in 13 patients (40.6%). The most common surgical planning mistakes leading to revision were detected as proximal short fusion extending to thoracolumbar junction and not to T10, thus avoiding the stabilizing effect of the rib cage in 18 patients (56.3%); followed by no bone cement [polymethylmethacrylate (PMMA)] augmented screw application despite documented osteoporosis in 17 patients (53.1%).