Objective To determine the optimal targets of the L1 pelvic angle (L1PA) that minimize the risk of both proximal junctional kyphosis (PJK) and pelvic nonresponse (PNR) following adult spinal deformity (ASD) surgery.
Methods A retrospective study was conducted on 323 patients who underwent fusion surgery from the low thoracic spine (T9–12) to the pelvis and were followed up for 2 years. Risk factors for PJK and PNR were evaluated separately using multivariate logistic regression analysis. Receiver operating characteristic (ROC) curve analyses were performed to identify L1PA cutoff values predictive of PJK and PNR across 3 pelvic incidence (PI) categories: <45°, 45°–60°, and ≥60°. L1PA thresholds were defined to delineate “ideal” alignment.
Results Risk factor analyses revealed that low L1PA was an independent risk factor for PJK (odds ratio [OR], 0.927; p=0.019), while high PI–LL (OR, 1.101; p<0.001) and high L1PA (OR, 1.249; p<0.001) were significant risk factors for PNR. On ROC curve analyses, optimal L1PA ranges were 2.5°–4.5° for PI<45°, 8.7°–12.6° for PI 45°–60°, and 15.1°–17.3° for PI≥60°. Patients within these ideal L1PA ranges had significantly lower rates of both PJK and PNR compared to those exceeding ideal L1PA ranges.
Conclusion This study demonstrated that optimal correction based on these L1PA targets reduced the risk of both PJK and PNR. Therefore, these L1PA targets can serve as reliable alignment goals to optimize surgical outcomes in ASD surgery.
Objective To identify the risk factors for proximal junctional failure (PJF) after adult spinal deformity (ASD) surgery despite ideal sagittal correction according to age-adjusted alignment target.
Methods The study included patients who underwent low thoracic to pelvic fusion for ASD and obtained ideal correction according to age-adjusted pelvic incidence minus lumbar lordosis. PJF was defined either radiographically as a proximal junctional angle (PJA) of >28° plus a difference in PJA of >22° or clinically as revision surgery for proximal junctional complications. Clinical and radiographic variables were assessed to identify the risk factors for PJF.
Results The final study cohort consisted of 196 patients, of whom 170 were women (86.7%), with an average age of 68.3 years. During mean follow-up duration of 45.9 months, PJF occurred in 43 patients (21.9%). Multivariate logistic regression analysis revealed that old age (odds ratio [OR], 1.063; 95% confidence interval [CI], 1.001–1.129; p=0.046), large preoperative sagittal vertical axis (OR, 1.007; 95% CI, 1.001–1.013; p=0.024), nonuse of a transverse process (TP) hook (OR, 5.556; 95% CI, 1.205–19.621; p=0.028), and high lumbar distribution index (LDI) (OR, 1.136; 95% CI, 1.109–1.164; p<0.001) were significant risk factors for PJF development.
Conclusion A sizeable proportion of patients (21.9%) developed PJF despite achieving ideal sagittal correction. Using TP hooks with avoiding excessive LDI can be helpful to further mitigate the risk of PJF development in this patient group.
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Objective To determine the clinical impact of the baseline sagittal imbalance severity in patients with adult spinal deformity (ASD).
Methods We retrospectively reviewed patients who underwent ≥ 5-level fusion including the pelvis, for ASD with a ≥ 2-year follow-up. Using the Scoliosis Research Society-Schwab classification system, patients were classified into 3 groups according to the severity of the preoperative sagittal imbalance: mild, moderate, and severe. Postoperative clinical and radiographic results were compared among the 3 groups.
Results A total of 259 patients were finally included. There were 42, 62, and 155 patients in the mild, moderate, and severe groups, respectively. The perioperative surgical burden was greatest in the severe group. Postoperatively, this group also showed the largest pelvic incidence minus lumbar lordosis mismatch, suggesting a tendency towards undercorrection. No statistically significant differences were observed in proximal junctional kyphosis, proximal junctional failure, or rod fractures among the groups. Visual analogue scale for back pain and Scoliosis Research Society-22 scores were similar across groups. However, severe group’s last follow-up Oswestry Disability Index (ODI) scores significantly lower than those of the severe group.
Conclusion Patients with severe sagittal imbalance were treated with more invasive surgical methods along with increased the perioperative surgical burden. All patients exhibited significant radiological and clinical improvements after surgery. However, regarding ODI, the severe group demonstrated slightly worse clinical outcomes than the other groups, probably due to relatively higher proportion of undercorrection. Therefore, more rigorous correction is necessary to achieve optimal sagittal alignment specifically in patients with severe baseline sagittal imbalance.
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Objective To introduce a new sagittal parameter, uppermost instrumented vertebra-pelvic tilt angle (UIVPTA), and to determine the effects on the proximal junctional kyphosis (PJK) development in adult spinal deformity (ASD) surgery.
Methods Patients ≥ 60 years with ASD who underwent low thoracic spine to pelvis fusion with a minimum of 2-years of follow-up were included in this study. Two groups were created according to PJK development. Various clinical and radiographic factors were compared between PJK and non-PJK groups to identify the risk factors for PJK. Cutoff value of UIVPTA for PJK development was calculated using receiver operating characteristic curve according to different pelvic incidence groups. Linear regression analysis was performed to identify factors to affect UIVPTA.
Results One hundred fifity-one patients were included in this study. There were 135 female patients (89.4%). Mean age was 70.5 years. PJK developed in 65 patients (43.0%). Multivariate analysis showed that overcorrection relative to age-adjusted pelvic incidence (PI) minus lumbar lordosis (LL) (PI–LL) target and lower UIVPTA were independent risk factors for PJK. The cutoff value of UIVPTA for PJK development was calculated as 4.0° in patients with PI less than 45°, 9.5° in patients with PI between 45° and 60°, and 13.0° in patients with PI greater than 60°. Linear regression analysis showed that UIVPTA was positively affected by postoperative values of LL (coefficient = 0.505), PI–LL (coefficient = 0.674), and pelvic tilt (coefficient = 0.286).
Conclusion Optimal correction within the age-adjusted PI–LL combined with keeping UIVPTA within optimal range is suggested for the prevention of PJK.
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