No abstract

OBJECTIVEThe subtraction of lumbar lordosis (LL) from the pelvic incidence (PI) offers an estimate of the LL required for a given PI value. Relative LL (RLL) and the lordosis distribution index (LDI) are PI-based individualized measures. RLL quantifies the magnitude of lordosis relative to the ideal lordosis as defined by the magnitude of PI. LDI defines the magnitude of lower arc lordosis in proportion to total lordosis. The aim of this study was to compare RLL and PI − LL for their ability to predict postoperative complications and their correlations with health-related quality of life (HRQOL) scores.METHODSInclusion criteria were ≥ 4 levels of fusion and ≥ 2 years of follow-up. Mechanical complications were proximal junctional kyphosis/proximal junctional failure, distal junctional kyphosis/distal junctional failure, rod breakage, and implant-related complications. Correlations between PI − LL, RLL, PI, and HRQOL were analyzed using the Pearson correlation coefficient. Mechanical complication rates in PI − LL, RLL, LDI, RLL, and LDI interpreted together, and RLL subgroups for each PI − LL category were compared using chi-square tests and the exact test. Predictive models for mechanical complications with RLL and PI − LL were analyzed using binomial logistic regressions.RESULTSTwo hundred twenty-two patients (168 women, 54 men) were included. The mean age was 52.2 ± 19.3 years (range 18–84 years). The mean follow-up was 28.8 ± 8.2 months (range 24–62 months). There was a significant correlation between PI − LL and PI (r = 0.441, p < 0.001), threatening the use of PI − LL to quantify spinopelvic mismatch for different PI values. RLL was not correlated with PI (r = −0.093, p > 0.05); therefore, it was able to quantify divergence from ideal lordosis for all PI values. Compared with PI − LL, RLL had stronger correlations with HRQOL scores (p < 0.05). Discrimination performance was better for the model with RLL than for PI − LL. The agreement between RLL and PI − LL was high (κ = 0.943, p < 0.001), moderate (κ = 0.455, p < 0.001), and poor (κ = −0.154, p = 0.343), respectively, for large, average, and small PI sizes. When analyzed by RLL, each PI − LL category was further divided into distinct groups of patients who had different mechanical complication rates (p < 0.001).CONCLUSIONSUsing the formula of PI − LL may be insufficient to quantify normolordosis for the whole spectrum of PI values when applied as an absolute numeric value in conjunction with previously reported population-based average thresholds of 10° and 20°. Schwab PI − LL groups were found to constitute an inhomogeneous group of patients. RLL offers an individualized quantification of LL for all PI sizes. Compared with PI − LL, RLL showed a greater association with both mechanical complications and HRQOL. The use of RLL and LDI together, instead of PI − LL, for surgical planning may result in lower mechanical complication rates and better long-term HRQOL.

The GAP score is a new pelvic-incidence-based proportional method of analyzing the sagittal plane that predicts mechanical complications in patients undergoing surgery for adult spinal deformity. Setting surgical goals according to the GAP score may decrease the prevalence of mechanical complications.

Study Design. Retrospective analysis of prospectively collected data. Objective. To report the follow-up curve behaviors in different Sanders staging groups. Summary of Background Data. Vertebral body tethering (VBT) is a growth modulation technique that allows gradual spontaneous follow-up curve correction as the patient grows. There is a lack of scientific evidence regarding appropriate patient selection and timing of implantation. Methods. Patients were grouped into five as: Sanders 1, 2, 3, 4–5, and 6–7. Data were collected preoperatively, at the day before discharge, and at each follow-up. Outcome measures were pulmonary and mechanical complications, readmission, and reoperation rates. Demographic, perioperative, clinical, radiographic, and complication data were compared using Fisher–Freeman–Halton exact tests for categorical variables and Kruskal-Wallis tests for the continuous variables. Results. Thirty-one (29 F, 2 M) consecutive patients with a minimum of 12 months of follow-up were included. The mean age at surgery was 12.1 (10–14). The mean follow-up was 27.1 (12–62) months. The mean preoperative main thoracic curve magnitude was 47° ± 7.6°. For all curves, preoperative and first erect curve magnitudes, bending flexibility, and operative correction percentages were similar between groups (for all comparisons, P > 0.05). The median height gained during follow-up was different between groups (P < 0.001), which was reflected into median curve correction during follow-up. Total curve correction percentage was different between groups (P = 0.009). Four (12.9%) patients had pulmonary and six (19.4%) had mechanical complications. One (3.2%) patient required readmission and two (6.5%) required reoperation. Occurrence of pulmonary complications was similar in Sanders groups (P = 0.804), while mechanical complications and overcorrection was significantly higher in Sanders 2 patients (P = 0.002 and P = 0.018). Conclusion. Follow-up curve behavior after VBT is different in patients having different Sanders stages. Sanders 2 patients experienced more overcorrection, thus timing and/or correction should be adjusted, since Sanders 3, 4, and 5 patients displayed a lesser risk of mechanical complications. Level of Evidence: 3.