Thoracolumbar Junction Orientation: A Novel Guide for Sagittal Correction and Proximal Junctional Kyphosis Prediction in Adult Spinal Deformity Patients

BACKGROUND

Novel radiographic sagittal parameters of the thoracolumbar junction orientation (TLJO, thoracolumbar slope [TLS] and thoracolumbar tilt [TLT]) have been introduced and correlated with lumbopelvic parameters and thoracic kyphosis.

OBJECTIVE

To determine a predictive model for reciprocal thoracic kyphosis and proximal junctional kyphosis (PJK) based on the TLJO.

METHODS

A total of 127 patients who had fusion from sacrum to T10-L2 from 2004 to 2014 were reviewed. TK (T5-T12), PI, SS, PT, LL, and proximal junctional angle (PJA) were measured preoperatively, 6 wk postoperatively, and at final follow-up. TLJO was measured by TLS and TLT. Changes between time points were determined (preop-6 wk = ΔParameterPre6wk and preop-final follow/up = ΔParameterPreFinal). Scoliosis Research Society (SRS) and Oswestry Disability Index (ODI) questionnaires were evaluated at final follow-up. Patients were divided into 2 groups based on the presence of PJK (ΔPJAPreFinal >15°). Independent t-tests and receiver operating characteristic (ROC) curves were used to investigate the significance of differences and cut-off values. Pearson correlations and linear regressions were used to analyze the entire cohort to determine the relationship between the changes in parameters.

RESULTS

Compared to patients without PJK (n = 100), those with PJK (n = 27) had significantly lower SRS scores and significantly greater ΔTKPreFinal, ΔLLPre6wk, and ΔTLSPre6wk. To maintain in the nonPJK group, ROC curves demonstrated a cut-off value of -9.4° for ΔTLSPre6wk. PJK was significantly correlated with ΔTKPreFinal and ΔTLSPre6wk. The linear correlation revealed that ΔTLSPre6wk < -25.3° is the risk factor of PJK > 15°.

CONCLUSION

As change of TLS reflects lumbopelvic realignment and influences reciprocal TK, reducing the change of TLS may be a sagittal realignment guideline to reduce the risk of PJK.

Thoracolumbar Slope Is Useful Parameter for Evaluating HealthRelated Quality of Life and Sagittal Imbalance Aggravation in Adult Spinal Deformity: A Prospective Observational Cohort Study

Objective

The purpose of the present study was to evaluate the natural course of primary degenerative sagittal imbalance (PDSI), its aggravating factors, and health-related quality of life (HRQoL) associated with various spinal alignment parameters (SAPs) in patients with PDSI who have not undergone surgery.

Methods

One hundred three participants volunteered to participate. The SAPs, including T1 pelvic angle (T1PA), thoracolumbar tilt, and thoracolumbar slope (TLS), were measured on whole-spine standing radiographs. The back and lumbar muscle volumes were measured. To determine HRQoL at baseline and at 2-year follow-up, face-to-face questionnaires were administered, which included visual analogue scale of the back and leg, physical component summary/mental component summary of 36-item Short Form Health Survey, Oswestry Disability Index (ODI), and Mini-Mental State Examination.

Results

Overall HRQoL measures had improved after 2 years of follow-up compared to baseline. PDSI aggravation was observed in 18 participants (26.1%). TLS, sagittal vertical axis (SVA), and T1PA were strongly correlated with each other. TLS, SVA, and T1PA were correlated with ODI score. Among them, TLS was most highly correlated with ODI score. TLS greater than -3.5° was a predicting factor for PDSI aggravation (p=0.034; 95% confidence interval, 1.173–63.61; odds ratio, 8.636).

Conclusion

The present study implied that PDSI does not necessarily worsen with aging. TLS is an appropriate parameter for assessing the clinical situation in patients with PDSI. Furthermore, a TLS greater than -3.5° predicts PDSI aggravation; thus, TLS may be a useful parameter for predicting prognosis in PDSI.

Novel radiological predictors for the progression of proximal junctional kyphosis in osteoporotic vertebral compression fracture with kyphosis following posterior corrective surgery

OBJECTIVE

This study aimed to identify the effect of some novel risk factors associated with L1 vertebrae and parameters closely related to the sagittal alignment for the occurrence of proximal junctional kyphosis (PJK) following surgery for patients with osteoporotic vertebral compression fractures (OVCF) kyphosis.

METHODS

74 OVCF patients undergoing posterior corrective surgery between January 2008 and June 2021 with a minimum 2-year follow-up were included. These patients were divided into PJK and non-PJK groups. Spinopelvic parameters, including thoracolumbar slope (TLS) and the L1 plumb line (L1PL) were measured preoperatively, postoperatively, and at follow-up. Multivariate logistic analysis was performed on various risk factors and Global Alignment and Proportion (GAP) scores. Associations between novel parameters and PJK were analyzed using receiver operating characteristic (ROC) analysis.

RESULTS

PJK was identified in 28.4% of patients. The mean age and follow-up were 63.45 years and 38.17 months, respectively. There was no difference between the PJK and the non-PJK groups in baseline demographics, pre-operative and immediate post-operative pelvic incidence-lumbar lordosis mismatch. Multiple comparisons showed that the proportion of PJK in the severely disproportioned group(the group with the highest GAP scores) and that of the other two groups with lower GAP scores were statistically different (P < 0.001). Potential risk factors for PJK included preoperative thoracic kyphosis (TK) (P < 0.001), TLS (P = 0.016), postoperative TLS (P < 0.001), and L1PL (P < 0.001). Postoperative TLS and L1PL were respectively independent risk factors for PJK, with the cut-off values set at 8.6° and 10.4 mm to predict the occurrence of PJK.

CONCLUSIONS

TLS and L1PL can be used to predict the occurrence of PJK in patients undergoing surgery for OVCF and are crucial for preventing the progression of PJK. Achieving a proportionate GAP Score postoperatively seems to be a viable option as higher GAP scores were associated with higher rates of PJK.

Normal Functional Local Alignment and Segmental Motion at the Thoracolumbar Junction: A Cross-Sectional Study of Healthy Subjects

OBJECTIVE

Several studies have investigated the mechanical behavior of the thoracolumbar spine. However, finding an accurate reference for the normal functional local alignment and segmental motion (SM) at the thoracolumbar junction (TLJ) is challenging. Therefore, this study aimed to assess age- and sex-related changes and differences in local alignment and SM at the TLJ.

METHODS

The study recruited healthy subjects aged 20 to 79 without complaints of back pain. Healthy subjects (60 males and 60 females) with appropriate imaging results were enrolled in the study. The subjects were divided into age groups (20-29, 30-39, 40-49, 50-59, 60-69, and 70-79 years); each group included 10 subjects of each sex.

RESULTS

The SM at the TLJ was small but noticeable, and the motion gradually increased toward the lower level of the TLJ, closer to the lumbar region. No significant differences were observed between male and female subjects in any SM measurements at the TLJ. The SM at the TLJ gradually decreased with age, while local kyphosis of TLJ progressed. The results also showed that the thoracolumbar slope value did not change with age and remained at a mean of -12.8 ± 7.2° (P = 0.893).

CONCLUSIONS

This study's results provide valuable guidance for appropriate surgical planning and rehabilitation of patients with spinal diseases or trauma. Furthermore, the results can be the basis for categorizing accurate criteria to evaluate the degree of disability after treatment.