Dynamic change of pelvic incidence after long fusion to pelvis with S2-alar-iliac screw: a 2-year follow-up study.

INTRODUCTION: Pelvic incidence (PI) is a key morphological parameter that reflects the relation between the sacrum and iliac wings. It is well accepted that PI remains constant after reaching maturity. However, recent studies indicated that PI might be altered after lumbosacral fusion. Additionally, it remains uncertain on the long-term influence of long fusion to pelvis with S2-alar-iliac screw on PI in patients with adult spinal deformity (ASD). STUDY DESIGN: A retrospective study. OBJECTIVE: To investigate whether and how PI would change during the follow-up in ASD patients who underwent S2AI fixation and to identify factors associated with the change in PI. METHODS: We retrospectively reviewed all ASD patients who underwent spinal surgery using S2AI screws between November 2014 and January 2017 at our institution. Patients with minimum follow-up of two years were included. The following sagittal radiographic parameters were measured: PI, Lumbar lordosis (LL), pelvic tilt (PT), PI-LL, sagittal vertical axis (SVA) at pre-op, post-op and 2-year follow-up. According to the changes in PI at immediate post-operation, patients were classified into two groups; Group A: Changes of PI less than or equal 5° and Group B: Changes of PI greater than 5°. RESULTS: A total of 82 ASD patients (Group A: 32, Group B: 50; mean age of 53.5 ± 12.6 years) with a mean follow-up period of 30.2 ± 9.2 months were included in this study. At immediate post-operation, Group A showed no significant change in PI (45.7° ± 11.4° to 45.3° ± 11.2°, p = 0.749); while Group B had a significant decrease in PI (51.6° ± 14.5° to 40.9° ± 14.0°, p < 0.001). At the last follow-up, 48% patients (24/50) in Group B had a significant increase in PI (32.8° ± 6.4° to 45.8° ± 11.2°, p < 0.001). Intergroup analysis showed that ΔPI, post-op PI, post-op PT and age were significantly different between both groups. In addition, pre-op PI, post-op PI, post-op PT, post-op PI-LL were significantly correlated with ΔPI at last follow-up. Also, logistic regression analysis showed that post-op PI was the associated risk factor (OR = 0.865, p = 0.024) for PI-LL mismatch. CONCLUSION: Our study showed that PI decreased in more than half of ASD patients immediately after spinal surgery using S2AI screws. Approximately 48% of them were able to recover during the 2-year follow-up. Lower pre-op PI, post-op PI and PT were found to be strongly associated with the return of PI. Thus, these current findings indicated that patients with a high PI at pre-operation should not be over-corrected to avoid PI-LL mismatch postoperatively.

Prediction of respiratory function in patients with severe scoliosis on the basis of the novel individualized spino-pelvic index.

OBJECTIVE: Our study aimed to evaluate the pulmonary function of patients with severe scoliosis after correcting standing height with spino-pelvic index (SPI). METHODS: Inclusion criteria: (1) with a coronal Cobb angle of more than 90°; (2) diagnosed as congenital (CS) or idiopathic scoliosis (IS); (3) aged between ten and 20 years; (4) with pulmonary function test (PFT) at the primary consultation. Patients with previous surgical intervention, with angular kyphosis, and with neuromuscular disease were excluded. Length of spine (LOS), height of spine (HOS), and height of pelvis (HOP) were measured on coronal films. SPI was defined as the ratio between LOS and HOP. The corrected body height was calculated: corrected body height = body height + (SPI × HOP - HOS). The PFTs included the following parameters: VCmax, FVC, FVC% predicted, FEV1, FEV1% predicted, PEF, and MVV. PFT results were recalculated using the corrected body height. RESULTS: Thirty patients were diagnosed as IS and 27 as CS with average Cobb angles of 99.88° ± 11.83 and 98.06° ± 14.27, respectively. Significant differences were observed in VCmax and FVC between IS and CS patients (P < 0.05). All the corrected PFT parameters were significantly lower than the original PFT parameters (P < 0.05). CONCLUSION: For the first time, this study proposed a method to predict pulmonary function of patients with severe scoliosis using SPI, as an age-independent parameter in normal adolescents. After body height correction, pulmonary function of patients with severe scoliosis was found to be significantly decreased, indicating that pulmonary function impairment was underestimated in patients with severe scoliosis when evaluating pulmonary function with arm span.

Comparison of Clinical and Radiologic Outcome of Three-Dimensional Correction in Lenke 5C Curve: Uniplanar Versus Polyaxial Pedicle Screws.

OBJECTIVE: To evaluate radiologic and clinical outcome of three-dimensional correction using the uniplanar pedicle screw (UPS) combined with vertebral body derotation technique for treatment of Lenke 5C adolescent idiopathic scoliosis. METHODS: Fifty patients treated with posterior selective fusion by UPS or polyaxial pedicle screw (PPS) were enrolled. Radiologic parameters, including degree of main curve, thoracic kyphosis, lumbar lordosis, and apical vertebral rotation, were evaluated preoperatively, postoperatively, and at a minimum 2-year follow-up. Scoliosis Research Society Version 22 questionnaire was assessed preoperatively and at 2-year follow-up. RESULTS: Preoperative lumbar Cobb angle was 48.9° in the UPS group and 49.1° in the PPS group (P = 0.59). Postoperatively, no difference in the correction of the main curve magnitude between the 2 groups was observed (74.4% vs. 73.9%, P = 0.74). Correction rate of apical vertebral rotation in the UPS group was significantly higher compared with the PPS group. No difference in average thoracic kyphosis and lumbar lordosis was observed between the 2 groups. At last follow-up, Scoliosis Research Society Version 22 scores were improved in both groups, of which the self-image score in the UPS group was significantly higher compared with the PPS group. CONCLUSIONS: The application of UPS combined with vertebral body derotation technique can reduce vertebral rotation and obtain better patient self-image score when favorable coronal and sagittal realignment is achieved. This improvement remains superior during 2-year follow-up. This combined application is a promising option to achieve spinal three-dimensional correction in treating Lenke 5C curve.