Effect of overcorrection on proximal junctional kyphosis in adult spinal deformity: analysis by age-adjusted ideal sagittal alignment

Revision surgery for proximal junctional failure: A single-center analysis

BACKGROUND

Proximal junctional kyphosis (PJK) is a radiographic complication following adult spinal deformity (ASD) surgery due to degeneration of mobile segments adjacent to fused spine. Proximal junctional failure (PJF) represents PJK with structural failure, neurologic deficit, or mechanical instability warranting revision with extension of fusion above the uppermost instrumented vertebra (UIV). This study investigates the clinical presentation, mechanisms of failure, revision strategies, and outcomes for ASD patients who develop PJF after instrumented fusion to the pelvis.

METHODS

Fifty-four ASD patients who developed PJF after a posterior instrumented fusion to the pelvis at a single institution from 2009 to 2021 were analyzed. PJF was defined by radiographic PJK with (1) UIV or UIV+1 fracture, UIV screw pullout, or soft-tissue posterior ligamentous disruption, and (2) neurological deficit at presentation.

RESULTS

The cohort was stratified into upper thoracic (UT, 10 patients, T2-T6), lower thoracic (LT, 35 patients, T8-T11), and lumbar (L, 9 patients, L1-L3) spine UIV groups based on index surgery. Patients developed PJF at a median of 14 months (mean 18 ± 16, range: 1-78) after their index surgery. Neurological deficits at presentation included radiculopathy (61 %), myelopathy (48 %), motor deficits (33 %), and bowel or bladder incontinence (9 %). Mechanisms of PJF were vertebral fracture and screw pullout (UT: 50 %, LT: 80 %, L: 89 %, P < 0.001) or soft-tissue disruption (UT: 50 %, LT: 20 %, L: 11 %, P = 0.089) at the UIV. Revision surgery commonly involved posterior column osteotomies (63 %) rather than three-column osteotomies (9 %). Of patients in the UT group, 40 % were extended above the cervicothoracic junction. In the LT and L groups, 91 % and 89 % of patients were extended to the UT and LT spine, respectively. Median follow-up for the cohort after revision for PJF was 24 months (range: 2-89). A total of 26 patients (48 %) required a second revision surgery (median 14 months, range: 1-50), 16 of whom (28 %) were revised for recurrent PJF. Patient-specific and radiographic risk factors for recurrent PJF could not be elucidated.

CONCLUSION

In this series of ASD patients, after revision for PJF, recurrent PJF was the most common complication requiring another revision. Junctional failures tended to be vertebral body fracture and screw pullout in the LT and L spine and soft tissue disruption in the UT spine. Most revisions involved posterior column osteotomies with proximal extension across the thoracolumbar junction or apex of thoracic kyphosis (e.g., L to LT, LT to UT); notably, nearly half of UT failures were not extended to the cervical spine. Future research is warranted to elucidate risk factors for recurrent PJF and potential preventative strategies.

Ideal Lumbar Lordosis Correction in Patients With Adult Spinal Deformity Without Adversely Impacting Pelvic Tilt and Pelvic Incidence Minus Lumbar Lordosis: A Study of 426 Cases

STUDY DESIGN

Retrospective study.

OBJECTIVES

To determine the ideal pelvic incidence (PI)-lumbar lordosis (LL) range to prevent pelvic tilt (PT) undercorrection while avoiding PI-LL overcorrection following adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND

PI-LL and PT are the important sagittal parameters to be restored to an adequate range by surgery. Ideal PI-LL target without causing PI-LL overcorrection and PT undercorrection has not been documented.

METHODS

We included patients with ASD undergoing ≥5-level fusion, including the sacrum. Receiver operating characteristic (ROC) curve analysis was performed to calculate the lower limit of the ideal PI-LL without causing PI-LL overcorrection and the upper limit of the ideal PI-LL without causing PT undercorrection. The calculated ideal PI-LL was validated in terms of proximal junctional kyphosis and failure (PJK and PJF) rates and clinical outcomes. Analyses were performed according to age subgroups (below 70 and 70 yr or above).

RESULTS

In total, 426 patients were included in the study. Female patients were predominant (85.4%), with a mean age of 69.8 years. The lower limits of PI-LL were calculated as 4.9° for all patients, 2.3° for patients aged below 70 years, and 7.9° for patients aged 70 years or above. Meanwhile, the upper limits of PI-LL were calculated as 12.7° for all patients, 12.5° for patients aged below 70 years, and 13.3° for patients aged 70 years or above. There were no significant differences in the PJK and PJF rates among the new three PI-LL groups. Clinical outcomes were significantly better in patients with the ideal PI-LL group than those in patients with overcorrection or undercorrection groups for all age groups.

CONCLUSIONS

The ideal PI-LL correction target without adversely impacting PT and PI-LL was calculated at 2.3° to 12.5° for patients aged below 70 years and 7.9° to 13.3° for patients aged 70 years or above. These guideline parameters may help ensure optimal clinical outcomes without increasing the risk of PJK/F.

Iatrogenic posterior translation of the construct at the uppermost instrumented vertebrae is associated with proximal junctional kyphosis

PURPOSE

To determine if iatrogenic posterior translation (UIV SPi) at the upper instrumented vertebrae (UIV) is associated with increased mechanical complications and secondarily to generate and validate a UIV SPi threshold for increased complications.

METHODS

Two patient databases were utilized: one for generating a UIV SPi threshold and another for validation. Patients with a UIV between T8-L1 and a LIV at ilium were included. A receiver operating curve (ROC) curve analyses was performed to generate a threshold that predicted proximal junctional complications. This UIV SPi angle (-16.0°) was rounded to -15.0° for practical clinical use and validated in a separate cohort. Patients were stratified as above (most translated, MT) or below (least translated, LT) the threshold for comparative demographic and outcomes analyses.

RESULTS

Generation of the threshold on 192 patients (122 LT, 70 MT) revealed that the MT group had higher absolute postoperative UIV SVA (MT=-56.1 ± 23.1 mm vs. LT=-10.4 ± 31.8 mm, p < 0.001), higher PT (25.7° vs. 19.3°, p < 0.001), and 2.8-5.8 times greater odds of postoperative proximal junctional complications at 2-years (p < 0.05). Validation on 135 patients (95 LT, 40 MT) revealed that the MT group had 11.7 times greater odds of radiographic PJK and had 4.5 times greater odds of all-cause reoperations (p < 0.05).

CONCLUSION

Patients with UIV posterior translation, despite similar PI-LL and T1PA, exhibit a high PT and experience higher odds of proximal junctional complications. Our findings support limiting the UIV SPi to < 15° of posterior translation to mitigate postoperative mechanical complications.

LEVEL OF EVIDENCE

IV.

Are Surgical Outcomes Different According to Baseline Balance Status in Elderly Patients with Degenerative Sagittal Imbalance?

STUDY DESIGN

This is a retrospective study.

OBJECTIVE

We sought to compare surgical outcomes according to baseline balance statuses in elderly patients with degenerative sagittal imbalance (DSI).

SUMMARY OF BACKGROUND

Although optimal sagittal correction has been emphasized for good surgical outcomes, the effect of the state of preoperative balance on surgical outcomes has been adequately described at present.

METHODS

Patients aged 60 years and above with DSI who underwent ≥5-level fusion to the sacrum were included. Among them, only those who postoperatively achieved the optimal age-adjusted pelvic incidence (PI) - lumbar lordosis (LL) target were included in this study. Study participants were divided into two groups according to their preoperative sagittal vertical axis (SVA): compensatory balance (SVA <5 cm, group CB) and decompensation (SVA ≥5 cm, group D). Comparisons between the two groups were performed using the χ 2 test or Fisher exact test for categorical variables and the independent t -test or Wilcoxon rank-sum test for continuous variables.

RESULTS

A total of 156 patients whose postoperative sagittal alignment matched the age-adjusted PI-LL target constituted the study cohort. There were 59 patients in group CB and 97 patients in group D. Mean follow-up duration was 50.0 months after surgery. Immediate postoperatively, sacral slope and SVA were significantly greater in group D than in group CB. At the last follow-up, the SVA was significantly greater in group D than in group CB (43.6 vs. 22.7 mm), while no significant differences were found in other sagittal parameters. The Oswestry disability index and Scoliosis Research Society -22 scores at the last follow-up were significantly worse in group D than in group CB.

CONCLUSION

The SVA tended to experience less correction postoperatively, with evidence of further deterioration during follow-up in group D than in group CB. This suboptimal correction of SVA may contribute to the inferior clinical outcomes encountered in group D relative to group CB. Therefore, we recommend correction of PI-LL as close as possible to the lower limit of the suggested PI-LL target range in patients with evidence of preoperative decompensation.

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.

Impact of Adjacent Muscular Anatomic Preservation on Proximal Junctional Kyphosis and Failure

BACKGROUND

Surgical intervention is a cornerstone of adult spinal deformity (ASD) management. However, there remain burdens from complications, including proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). Posterior anatomic preservation at the uppermost instrumented vertebra has emerged as an accessible approach to potentially reduce PJK/PJF risk.

METHODS

We assembled an institutional cohort of patients with ASD evaluated between 2017 and 2022 who had spinal fusion performed with a modified subperiosteal dissection at and immediately below the uppermost instrumented vertebra. Through a meta-analysis with a random-effects model, we compared our incidence of PJK/PJF against other prophylactic interventions.

RESULTS

Ninety patients were identified, (median age, 64 years; average follow-up, 19 months). Most had scoliosis and/or spinal stenosis with a median of 8 levels fused (40% revision cases). 6.7% and 3.3% of patients developed PJK and PJF, respectively, with the most common clinical correlate being a minor neurologic deficit such as numbness (37.8%). PJK/PJF and non-PJK/PJF patients had similar postoperative complication profiles. Radiographic parameters varied: the PJK/PJF cohort had greater preoperative pelvic incidence/pelvic tilt and postoperative pelvic incidence-lumbar lordosis mismatch as well as smaller operative correction of the thoracolumbar Cobb angle. In the literature, prophylactic interventions broadly reduced the incidence of PJK/PJF, with a pooled estimate of 19% compared with 36% in patients who did not receive any additional intervention.

CONCLUSIONS

Preservation of posterior anatomic structures likely has a role in reducing the rate of PJK/PJF. Linking radiographic parameters to PJK/PJF and studying techniques that keep posterior structures intact may be steps toward improving ASD correction outcomes.

Hook Fixation at Uppermost Instrumented Vertebra +1 Reduced Proximal Junctional Failure in Adult Patients With Spinal Deformity Having Achieved Optimal Deformity Correction by Sagittal Age-Adjusted Score

BACKGROUND AND OBJECTIVES

Appropriate correction relative to the age-adjusted sagittal alignment target reduces the proximal junctional failure (PJF) risk. Nonetheless, a considerable number of patients suffer from PJF despite optimal correction. The aim of this study was to identify the risk factors of PJF that occurs despite optimal correction relative to the sagittal age-adjusted score (SAAS) in adult spinal deformity surgery.

METHODS

Patients aged 60 years or older with adult spinal deformity who underwent ≥5-level fusion to the sacrum were initially screened. Among them, only patients who achieved optimal sagittal correction relative to the SAAS were included in the study. Optimal correction was defined as the SAAS point between -1 and +1. Various clinical and radiographic factors were compared between the PJF and no PJF groups and were further evaluated using multivariate analysis.

RESULTS

The final study cohort comprised 127 patients. The mean age was 67 years, and there were 111 women (87.4%). A mean of total fusion length was 7.2. PJF occurred in 42 patients (33.1%), while 85 patients (66.9%) did not develop PJF. Multivariate analysis showed that a high body mass index (odds ratio [OR] = 1.153, 95% CI = 1.027-1.295, P = .016), a higher lordosis distribution index (LDI) (OR = 1.024, 95% CI = 1.003-1.045, P = .022), and no use of hook fixation (OR = 9.708, 95% CI = 1.121-76.923, P = .032) were significant risk factors of PJF development. In the receiver operating characteristic curve analysis, the cutoff value for the LDI was calculated as 61.0% (area under the curve = 0.790, P < .001).

CONCLUSION

PJF developed in a considerable portion of patients despite optimal correction relative to the age-adjusted alignment. The risk factors of PJF in this patient group were high body mass index, high LDI exceeding 61%, and no use of hook fixation. PJF could be further decreased by properly managing these risk factors along with optimal sagittal correction.

Postsurgical outcomes differ according to baseline sagittal alignment status even in patients achieving adequate correction relative to age-adjusted alignment target for adult spinal deformity

BACKGROUND CONTEXT

Baseline severities of sagittal malalignment and degrees of pelvic compensation may affect postsurgical outcomes differently after adult spinal deformity (ASD) surgery, even if the patients achieved optimal correction of sagittal malalignment.

PURPOSE

To investigate whether postsurgical outcomes vary according to baseline sagittal alignment and pelvic compensation status in patients achieving adequate correction relative to age-adjusted alignment target in ASD surgery.

STUDY DESIGN/SETTING

Retrospective study PATIENT SAMPLE: Patients who underwent ≥ 5-level fusion to the pelvis for ASD; achieved matched correction relative to age-adjusted pelvic incidence (PI)-lumbar lordosis (LL); and completed ≥ 2-year follow-up.

OUTCOME MEASURES

Radiographic results, mechanical failures, and clinical outcomes METHODS: Patients were divided into three groups based on baseline sagittal vertical axis (SVA) and pelvic tilt (PT)/PI ratio (median value of PT/PI ratio = 0.61): Group A (SVA < 5 cm), Group B (SVA ≥ 5 cm and PT/PI ratio <0.61, and Group C (SVA ≥ 5 cm and PT/PI ratio ≥ 0.61). Radiographic results, mechanical failures, and clinical outcomes were compared among the three groups.

RESULTS

A total of 153 patients were included in the study. They were predominantly female (89.5%), with a mean age of 68.3 years. The mean follow-up duration was 49.0 months. There were 50 patients in group A (SVA < 5cm), 53 in group B (SVA ≥ 5cm and low PT/PI), and 50 in group C (SVA ≥ 5cm and high PT/PI). No significant differences were observed in all radiographic parameters at six weeks. At the last follow-up, the PI-LL was comparable among the three groups; however, the SVA was significantly greater in groups B and C than in group A (46.5mm and 46.9mm vs. 31.5mm, p=.039). The PT at the last follow-up was significantly lower in group B than in group A and C (22.4° vs. 26.0° and 28.2°, respectively, p=.001). The rates of mechanical failure and subsequent revision surgery and did not differ among the groups. The final clinical outcomes were comparable among the three groups.

CONCLUSIONS

This study revealed that patients in groups B and C were likely to have a suboptimal sagittal alignment status at the last follow-up compared with those in group A. Tailored approaches considering patient's baseline alignment and compensatory status are recommended to optimize the final sagittal alignment status.

Incidence and Risk Factors of Recurrent Proximal Junctional Failure in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

This study aimed to examine the incidence and risk factors for recurrent proximal junctional failure (R-PJF) in adult spinal deformity (ASD) surgery.

METHODS

Among 482 patients receiving ≥ five-level fusion to the pelvis for ASD, 60 patients who underwent fusion extension surgery for PJF were included in the study cohort. R-PJF was defined as the performance of re-revision surgery after revision surgery for PJF. Various clinical and radiographic variables were compared between no R-PJF and R-PJF groups. Stepwise multivariate logistic analysis was performed to identify the risk factors for R-PJF.

RESULTS

Of the 60 patients, there were 51 women (85.0%) and 9 men (15.0%) with a mean age of 72.4 ± 6.7 years. The mean fusion length at the index surgery was 7.3 ± 1.6 levels and an average of 4.1 ± 1.3 levels was extended during the revision surgery. Among them, R-PJF developed in 17 patients (28.3%). Multivariate analysis revealed that overcorrection relative to age-adjusted pelvic incidence (PI) - lumbar lordosis (LL) at the index surgery and high total sum of proximal junctional kyphosis severity scale (PJKSS) at the revision surgery were significant risk factors for R-PJF development. The cutoff value for the PJKSS sum was calculated as 8.5 points.

CONCLUSIONS

R-PJF was developed in 17 patients (28.3%). PI-LL overcorrection should be avoided during the index surgery to mitigate the R-PJF. In addition, timely surgical intervention is required in patients with PJF, considering that the PJF severity tends to increase over time.

Proximal Junctional Failure Development Despite Achieving Ideal Sagittal Correction According to Age-Adjusted Alignment Target in Patients With Adult Spinal Deformity: Risk Factor Analysis of 196 Cases Undergoing Low Thoracic to Pelvic Fusion

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.

The Role of Pelvic Compensation in Sagittal Balance and Imbalance: The Impact of Pelvic Compensation on Spinal Alignment and Clinical Outcomes Following Adult Spinal Deformity Surgery

BACKGROUND AND OBJECTIVES

The Scoliosis Research Society (SRS)-Schwab system does not include a pelvic compensation (PC) subtype, potentially contributing to gaps in clinical characteristics and treatment strategy for deformity correction. It also remains uncertain as to whether PC has differing roles in sagittal balance (SB) or imbalance (SI) status. To compare radiological parameters and SRS-22r domains between patients with failed pelvic compensation (FPC) and successful pelvic compensation (SPC) based on preoperative SB and SI.

METHODS

A total of 145 adult spinal deformity patients who received deformity correction were analyzed. Radiographic and clinical outcomes were collected for statistical analysis. Patients were classified into 4 groups based on the median value of PT/PI ratio (PTr) and the cutoff value of SB. Patients with low PTr and high PTr were defined as FPC and SPC, respectively. Radiographic and clinical characteristics of different groups were compared.

RESULTS

Patients with SPC exhibited significantly greater improvements in lumbar lordosis, pelvic tilt, PTr, and T1 pelvic angle as compared to patients with FPC, irrespective of SB or SI. No apparent differences in any of SRS-22r domains were observed at follow-up when comparing the SB-FPC and SB-SPC patients. However, patients with SI-SPC exhibited significantly better function, self-image, satisfaction, and subtotal domains at follow-up relative to those with SI-FPC. When SI-FPC and SI-SPC patients were subdivided further based on the degree of PI-LL by adjusting for age, the postoperative function and self-image domains were significantly better in the group with overcorrection of PI-LL than undercorrection of PI-LL in SI-FPC patients. However, no differences in these SRS-22r scores were observed when comparing the subgroups in SI-SPC patients.

CONCLUSION

Flexible pelvic rotation is associated with benefits to the correction of sagittal parameters, irrespective of preoperative SB or SI status. However, PC is only significantly associated with clinical outcomes under SI. Patients with SI-FPC exhibit poorer postoperative clinical outcomes, which should be recommended to minimize PI-LL.

Characterization of Patients with Poor Clinical Outcome after Adult Spinal Deformity Surgery: A Multivariate Analysis of Mean 8-Year Follow-Up Data

Background/Objective: Limited data exist regarding the long-term clinical outcomes and related factors after adult spinal deformity (ASD) surgery. This study aims to characterize patients who experienced poor clinical outcomes during long-term follow-up after ASD surgery. Methods: Patients who underwent ASD surgery with ≥5-vertebra fusion including the sacrum and ≥5-year follow-up were included. They were divided into two groups according to the Oswestry Disability Index (ODI) at the last follow-up: group P (poor outcome, ODI > 40) and group NP (non-poor outcome, ODI ≤ 40). Clinical variables, including patient factors, surgical factors, radiographic parameters, and mechanical complications (proximal junctional kyphosis [PJK] and rod fracture), were compared between the groups. Results: A total of 105 patients were evaluated, with a mean follow-up of 100.6 months. The mean age was 66.3 years, and 94 patients (89.5%) were women. There were 52 patients in group P and 53 patients in group NP. Univariate analysis showed that low T-score, postoperative correction relative to age-adjusted pelvic incidence-lumbar lordosis, T1 pelvic angle (TPA) at last follow-up, and PJK development were significant factors for poor clinical outcomes. Multivariate analysis identified PJK as the single independent risk factor (odds ratio [OR] = 3.957 for PJK development relative to no PJK, OR = 21.141 for revision surgery for PJK relative to no PJK). Conclusions: PJK development was the single independent factor affecting poor clinical outcomes in long-term follow-up. Therefore, PJK prevention appears crucial for achieving long-term success after ASD surgery.

Preoperative Planning of Lumbar Lordosis for Adult Degenerative Scoliosis Surgery in the Chinese Population

OBJECTIVE

Pelvic incidence minus lumbar lordosis mismatch (PI-LL) is directly related to poor quality of life in adult degenerative scoliosis (ADS) patients. The purpose of the study was to determine the most appropriate postoperative PI-LL value for patients with ADS.

METHODS

The medical records of patients with ADS in our department were retrospectively collected. The data included age, sex, body mass index, age-adjusted Charlson comorbidity index, osteopenia, length of hospital stay, operative duration, estimated blood loss, American Society of Anesthesiologists score, number of fusion levels, lumbar lordosis, sagittal vertical axis, pelvic incidence, PI-LL, Scoliosis Research Society-22 score, Oswestry Disability Index score, and mechanical complications.

RESULTS

A total of 316 patients were enrolled. PI-LL, lumbar lordosis, sagittal vertical axis, Scoliosis Research Society-22 score, Oswestry Disability Index score at the time of last follow-up were 20.7 ± 8.5°, 23.4 ± 14.1°, 4.0 ± 2.1 cm, 3.7 ± 0.9, and 18.1 ± 5.5, respectively. In terms of mechanical complications, 88 patients (27.8%), 34 patients (10.8%), and 19 patients (6.0%) had proximal junctional kyphosis, distal junctional kyphosis, and implant-related complications, respectively. In the fully adjusted model, compared with 0 grade PI-LL group and ++ grade PI-LL group, + grade PI-LL group had the best clinical outcomes and the fewest mechanical complications. The stability of these conclusions was verified in sensitivity analyses.

CONCLUSIONS

Optimal PI-LL value should be 10°-20° after corrective surgery in patients with ADS, which is associated with excellent clinical outcomes and lower complication rates. Previous criteria may be at risk of overcorrection, which may lead to proximal junctional kyphosis.

Analysis of Risk Factors Associated with Proximal Junctional Kyphosis Following Long Instrumented Fusion from L1 to Sacrum: Age Itself Does Not Independently Increase the Risk

Background and Objectives: This study is a retrospective analysis aimed at understanding the incidence and risk factors of proximal junctional kyphosis (PJK) following long-instrumented spinal fusion from L1 to the sacrum in patients with mild to moderate sagittal imbalance. Materials and Methods: It recruited consecutive patients undergoing instrumented fusion from L1 to the sacrum for degenerative lumbar disease between June 2006 and November 2019 in a single institution. The patients' preoperative clinical data, muscle status at T12-L1 on magnetic resonance images, and sagittal spinopelvic parameters were analyzed. Univariate analysis was used to compare clinical and radiographic data between PJK and non-PJK patients. Logistic regression analysis was used to investigate the independent risk factors for PJK. Results: A total of 56 patients were included in this study. The mean age at surgery was 67.3 years and mean follow-up period was 37.3 months. In total, 10 were male and 46 were female. PJK developed in 23 (41.1%) out of 56; of these patients, 20 (87.0%) developed PJK within 1 year postoperatively. In the univariate analysis between PJK and non-PJK patients, the PJK group showed more frequent osteoporosis, lower body mass index, smaller cross-sectional area (CSA) and more fat infiltration (FI) in erector spinae muscle at T12-L1 and larger preoperative TLK and PT with statistical significance (p < 0.05). In the logistic regression analysis, severe (>50%) FI in erector spinae muscle (OR = 43.60, CI 4.10-463.06, R2N = 0.730, p = 0.002) and osteoporosis (OR = 20.49, CI 1.58-264.99, R2N = 0.730, p = 0.021) were statistically significant. Conclusions: Preexisting severe (>50%) fat infiltration in the erector spinae muscle and osteoporosis were independent risk factors associated with PJK following instrumented fusion from L1 to the sacrum, but age was not a risk factor.

Transforaminal lumbar interbody fusion with or without release of the anterior longitudinal ligament: A single-center, retrospective observational cohort study

Background

Transforaminal anterior release (TFAR) is a technical extension of the transforaminal lumbar interbody fusion (TLIF) procedure with deliberate release of the anterior longitudinal ligament (ALL).

Methods

In a retrospective, single-center observational cohort study, consecutive adult patients undergoing TLIF surgery at L4/L5 and/or L5/S1 between 01/2018 and 12/2022 for degenerative disc disease or deformity were considered. The TFAR group (with ALL release) was compared to a standard TLIF group (without ALL release), matched in a 1:3 ratio. Uni- and multivariable logistic regression models were built to estimate the likelihood of any adverse event (AE), reoperation, and excellent/good clinical outcome at 12 months.

Results

Of 438 patients, 18 undergoing TFAR were matched to 53 undergoing standard TLIF. TFAR procedures were frequently part of extensive, anterior-posterior or multilevel fusion procedures with longer surgery time and higher blood loss. The rates of intraoperative surgical AEs were similar (16.7 vs. 11.3%, p=.789). The rates and severities of surgical AEs, as well as reoperation rates and clinical outcomes were similar at time of discharge, 90 days, and 12 months postoperatively (all p>.05). TFAR allowed for an increase in total lumbar lordosis of 16.1° and in lumbar lordosis between L4 and S1 of 16.3° at discharge, which was maintained during follow-up. In both the uni- and multivariable models, patients undergoing TFAR were as likely as patients undergoing standard TLIF to experience any AE (adjusted OR 0.78, 95% CI 0.21-2.94), any reoperation (aOR 0.46, 95% CI 0.11-1.90) or excellent/good clinical outcome at 12 months (aOR 2.01, 95% CI 0.52-7.74).

Conclusions

The TFAR technique has a safety profile which is comparable to the standard TLIF procedure, but it allows for a greater restoration of lumbar lordosis at L4-S1. We suggest considering the TFAR technique in selected patients with sagittal imbalance and mobile segments for restoration of lumbar lordosis.

Lumbar Lordosis Redistribution and Segmental Correction in Adult Spinal Deformity: Does it Matter?

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVE

Evaluate the impact of correcting normative segmental lordosis values on postoperative outcomes.

BACKGROUND

Restoring lumbar lordosis magnitude is crucial in adult spinal deformity surgery, but the optimal location and segmental distribution remain unclear.

PATIENTS AND METHODS

Patients were grouped based on offset to normative segmental lordosis values, extracted from recent publications. Matched patients were within 10% of the cohort's mean offset, less than or over 10% were undercorrected and overcorrected. Surgical technique, patient-reported outcome measures, and surgical complications were compared across groups at baseline and two years.

RESULTS

In total, 510 patients with a mean age of 64.6, a mean Charlson comorbidity index 2.08, and a mean follow-up of 25 months. L4-5 was least likely to be matched (19.1%), while L4-S1 was the most likely (24.3%). More patients were overcorrected at proximal levels (T10-L2; undercorrected, U: 32.2% vs. matched, M: 21.7% vs. overcorrected, O: 46.1%) and undercorrected at distal levels (L4-S1: U: 39.0% vs. M: 24.3% vs. O: 36.8%). Postoperative Oswestry disability index was comparable across correction groups at all spinal levels except at L4-S1 and T10-L2/L4-S1, where overcorrected patients and matched were better than undercorrected (U: 32.1 vs. M: 25.4 vs. O: 26.5, P =0.005; U: 36.2 vs. M: 24.2 vs. O: 26.8, P =0.001; respectively). Patients overcorrected at T10-L2 experienced higher rates of proximal junctional failure (U: 16.0% vs. M: 15.6% vs. O: 32.8%, P <0.001) and had greater posterior inclination of the upper instrumented vertebrae (U: -9.2±9.4° vs. M: -9.6±9.1° vs. O: -12.2±10.0°, P <0.001), whereas undercorrection at these levels led to higher rates of revision for implant failure (U: 14.2% vs. M: 7.3% vs. O: 6.4%, P =0.025).

CONCLUSIONS

Patients undergoing fusion for adult spinal deformity suffer higher rates of proximal junctional failure with overcorrection and increased rates of implant failure with undercorrection based on normative segmental lordosis.

LEVEL OF EVIDENCE

Level IV.

Different characteristics between acute and delayed proximal junctional failure in elderly patients undergoing corrective surgery for adult spinal deformity: comparative analysis of risk factor, failure mode, and clinical consequences

BACKGROUND CONTEXT

While numerous studies have been conducted on proximal junctional failure (PJF), the clinical significance of acute and delayed PJF remains poorly understood.

PURPOSE

The primary object of this study is to investigate the risk factors separately for acute and delayed PJF. Secondly, we aim to assess the incidence of each failure mode and their clinical consequences in relation to acute and delayed PJF.

STUDY DESIGN/SETTING

Retrospective comparative study.

PATIENT SAMPLE

Patients aged ≥60 years who underwent deformity correction with ≥5-level fusion to sacrum.

OUTCOME MEASURES

Risk factor, failure modes, and patient-reported outcome measure (PROM).

METHODS

Acute PJF is defined as PJF occurring within 6 months, while delayed PJF occurring after 6 months. Risk factors were analyzed by comparing various clinical and radiographic parameters among 3 groups: no, acute, and delayed PJF groups. The failure modes, including soft tissue failure, vertebral fracture, fixation failure, and myelopathy, were compared among these groups. The clinical subsequences after PJF development were evaluated by assessing the change in proximal junctional angle (PJA), revision rate, and patient-reported outcome measure (PROM).

RESULTS

A study cohort of 363 patients was included in the analysis. Among them, 156 patients experienced PJF, with 87 patients (55.8%) in the acute PJF group and 69 patients (44.2%) in the delayed PJF group. Multivariate analyses showed that older age (Odds ratio [OR] = 1.057, 95% confidence interval [CI] = 1.002-1.118), osteoporosis (OR=2.149, 95% CI = 1.074-4.300), high American Society of Anesthesiology ASA score (OR=2.150, 95% CI = 1.089-4.245), and overcorrection relative to the age-adjusted pelvic incidence - lumbar lordosis target (OR=4.031, 95% CI = 1.962-8.280) were identified as risk factors for the development of acute PJF. On the other hand, a high body mass index (OR=1.150, 95% CI = 1.049-1.251) and an uppermost instrumented vertebra located at ≤T10 (OR=2.267, 95% CI = 1.205-4.268) were found to be associated with delayed occurrence of PJF. No radiographic parameters were found to be related to the development of delayed PJF. In terms of failure modes, vertebral fracture and fixation failure were more commonly observed in acute PJF, while soft tissue failure and myelopathy were more predominant in delayed PJF. The clinical course was more aggressive in the acute PJF group compared to the delayed PJF group, as evidenced by a greater increase in PJA, a higher revision rate, and worse PROM.

CONCLUSIONS

This study demonstrated different risk factors between the acute and delayed PJF. It was found that overcorrection relative to the age-adjusted PI-LL target increased the risk of acute PJF, but had no impact on the development of delayed PJF. Therefore, a different surgical strategy needs to be established to mitigate both acute and delayed PJF.

Defining Age-Adjusted PI-LL Targets for Surgical Realignment in Adult Degenerative Scoliosis: A Retrospective Cohort Study

Objectives: The purpose of this study was to investigate postoperative pelvic incidence minus lumbar lordosis mismatch (PI-LL) and health-related quality of life (HRQOL) outcomes to determine age-adjusted PI-LL targets. Method: The dataset encompassed a range of variables, including age, sex, body mass index, Charlson comorbidity index, presence of osteopenia, hospital stay, operative duration, blood loss, American Society of Anesthesiologists score, number of fusion levels, lumbar lordosis, sagittal vertical axis, pelvic incidence, and PI-LL. The non-linear relationship between PI-LL and clinical outcomes was examined using a curve analysis, with adjustments made for potential confounding variables. Upon identification of a non-linear relationship, a two-piecewise regression model was employed to determine the threshold effect. Results: A total of 280 patients were enrolled. In the fully adjusted model, the optimal PI-LL target for patients aged 45-54 years old was PI-LL < 10°, the optimal target for patients aged 55-74 was 10-20°, and the optimal target for patients older than 75 years was more suitable for PI-LL > 20°. In the curve-fitting graph, it could be seen that the relationship between PI-LL and HRQOL outcomes was not linear in each age group. The peaks of the curves within each group occurred at different locations. Higher and lower thresholds for optimal surgical goals were determined using the two-piecewise regression model from the SRS-22 score and the ODI score. Conclusions: This study showed that the optimal PI-LL after corrective surgery in adult degenerative scoliosis patients should be adjusted according to age.

Sagittal Section Hounsfield Units of the Upper Instrumented Vertebrae as a Predictor of Proximal Junctional Vertebral Fractures Following Adult Spinal Deformity Surgery

STUDY DESIGN

A retrospective observational study.

PURPOSE

This study aimed to determine an accurate and convenient screening method for predicting proximal junctional fractures (PJFr) following surgery for adult spinal deformity (ASD) using computed tomography (CT)-based measurement of Hounsfield units (HUs).

OVERVIEW OF LITERATURE

CT-based measurement of HUs is an alternative tool for assessing bone mineral density. However, the optimal method for predicting adjacent vertebral fractures following spinal fusion using HUs remains unclear.

METHODS

This retrospective observational study included 42 patients who underwent reconstructive surgery for ASD. Elliptical regions of interest (ROIs) on the axial section and rectangular ROIs on the sagittal section were placed at the upper instrumented vertebrae (UIV), UIV+1, and UIV+2. In addition, the HU value of the L2 vertebra was used as the representative.

RESULTS

PJFr occurred in 28.6% of patients within 2 years following surgery. The HU values obtained from the axial sections of L2, UIV, UIV+1, and UIV+2 were not significantly associated with the incidence of PJFr within 2 years, except for the ROI set in the lower region of the L2 vertebra. However, the HU value of the anterior third of the UIV in the sagittal section was significantly lower in the PJFr group than in the nonPJFr group (87.0 vs. 160.3, p =0.001). A UIV HU value of <100 was associated with a higher incidence of PJFr than an HU vaue of >100 (p <0.05).

CONCLUSIONS

Measurements of HU in the anterior one-third of the UIV in the sagittal section demonstrated predictive ability for PJFr following ASD surgery. A UIV HU value of <100 emerged as a risk factor for PJFr.

Clinical Significance of Lordosis Orientation on Proximal Junctional Kyphosis Development in Long-Segment Fusion Surgery for Adult Spinal Deformity

OBJECTIVE

We sought to evaluate the clinical impact of lordosis orientation (LO) on proximal junctional kyphosis (PJK) development in adult spinal deformity surgery.

METHODS

This study included 152 patients who underwent low thoracic (T9-T12) to pelvis fusion and were followed up for ≥2 years. In the literature, 6 radiographic parameters representing LO were introduced, such as uppermost instrumented vertebra (UIV) slope, UIV inclination, UIV-femoral angle (UIVFA), thoracolumbar tilt, thoracolumbar slope, and lordosis tilt. Various clinical and radiographic factors including 6 LO parameters were investigated using logistic regression analysis to identify risk factors for PJK.

RESULTS

The mean age was 69.4 years, and 136 patients were females (89.5%). PJK developed in 65 patients (42.8%). Multivariate logistic regression analysis revealed that only small postoperative pelvic incidence (PI)-lumbar lordosis (LL) (odds ratio [OR] = 0.962, 95% confidence interval: 0.929-0.996, P = 0.030) and large UIVFA (OR = 1.089, 95% confidence interval: 1.028-1.154, P = 0.004) were significant for PJK development. UIVFA showed significantly positive correlation with pelvic tilt (CC = 0.509), thoracic kyphosis (CC = 0.384), and lordosis distribution index (CC = 0.223). UIVFA was also negatively correlated with sagittal vertical axis (CC = -0.371). However, UIVFA did not correlate with LL, PI-LL, or T1 pelvic angle.

CONCLUSIONS

LO significantly increases the risk of PJK development in ASD surgery. Multivariate analysis revealed that smaller postoperative PI-LL and greater UIVFA were significant risk factors for PJK. Surgeons should avoid undercorrection and overcorrection to prevent PJK development.

Adult spinal deformity correction surgery using age-adjusted alignment thresholds: clinical outcomes and mechanical complication rates. A systematic review of the literature

PURPOSE

Adult spinal deformity (ASD) surgery gives good clinical outcomes but has a high rate of mechanical complications (MC). In 2016, Lafage described the age-adjusted alignment thresholds (AAAT) to adapt the correction in relation to patient's age proposing less aggressive corrections for the elderly population. The aim of this review was to clarify the effectiveness of AAAT to achieve good health-related quality of life (HRQoL) and their relationship with post-operative MC.

MATERIALS AND METHODS

We performed a review of the literature, including articles reporting data on post-operative HRQoL and MC rates in relation to the AAAT. Data were stratified according to whether they matched the AAAT, dividing the population in undercorrected (U), matched (M) and overcorrected (O). The quality of the included studies was assessed using the GRADE and MINORS systems.

RESULTS

Six articles reporting data from 1,825 patients were included. The different categories (U, M and O) had homogeneous pre-operative sagittal parameters (p > 0.05) that became statistically different after surgeries (p < 0.05). Proximal junctional kyphosis (PJK) was more frequent in the O group compared to U (p = 0.05). Post-operative HRQoL parameters were similar in the 3 groups (p > 0.05). The quality of the included studies was generally low with a high bias risk.

CONCLUSION

The results extrapolated from this review are interesting, as for the same HRQoL the U group had a lower MC rate. Unfortunately, the results are inconsistent, mainly because of the low quality of the included studies and the lack of reporting of some important patient- and surgery-related factors.

Fusion Length Requiring Spinopelvic Fixation in Lumbosacral Fusion with Anterior Column Support at L5-S1: Assessment of Fusion Status Using Computed Tomography

Background

The lumbosacral (LS) junction has a higher nonunion rate than other lumbar segments, especially in long-level fusion. Nonunion at L5-S1 would result in low back pain, spinal imbalance, and poor surgical outcomes. Although anterior column support at L5-S1 has been recommended to prevent nonunion in long-level LS fusion, fusion length requiring additional spinopelvic fixation (SPF) in LS fusion with anterior column support at L5-S1 has not been evaluated thoroughly. This study aimed to determine the number of fused levels requiring SPF in LS fusion with anterior column support at L5-S1 by assessing the interbody fusion status using computed tomography (CT) depending on the fusion length.

Methods

Patients who underwent instrumented LS fusion with L5-S1 interbody fusion without additional augmentation and CT > 1 year postoperatively were included. The fusion rates were assessed based on the number of fused segments. Patients were divided into two groups depending on the L5-S1 interbody fusion status: those with union vs. those with nonunion. Binary logistic regression analyses were performed to identify risk factors for LS junctional nonunion.

Results

Fusion rates of L5-S1 interbody fusion were 94.9%, 90.3%, 80.0%, 50.0%, 52.6%, and 43.5% for fusion of 1, 2, 3, 4, 5, and ≥ 6 levels, respectively. The number of spinal levels fused ≥ 4 (p < 0.001), low preoperative bone mineral density (BMD; adjusted odds ratio [aOR], 0.667; p = 0.035), and postoperative pelvic incidence (PI) - lumbar lordosis (LL) mismatch (aOR, 1.034; p = 0.040) were identified as significant risk factors for nonunion of L5-S1 interbody fusion according to the multivariate logistic regression analysis.

Conclusions

Exhibiting ≥ 4 fused spinal levels, low preoperative BMD, and large postoperative PI-LL mismatch were identified as independent risk factors for nonunion of anterior column support at L5-S1 in LS fusion without additional fixation. Therefore, SPF should be considered in LS fusion extending to or above L2 to prevent LS junctional nonunion.

A Standardized Curriculum Improves Trainee Rod Bending Proficiency in Spinal Deformity Surgery. Results of a Prospective Randomized Controlled Educational Study

INTRODUCTION

Surgical simulation is increasingly being accepted as a training platform to promote skill development and a safe surgical technique. Preliminary investigations in spine surgery show that simulation paired with educational intervention can markedly improve trainee performance. This study used a newly developed thoracolumbar fusion rod bending model to assess the effect of a novel educational curriculum and simulator training on surgical trainee rod bending speed and proficiency.

METHODS

Junior (PGY1 to 2) and senior (PGY3-fellow) surgical trainees at a single academic institution were prospectively enrolled in a rod bending simulation using a T7-pelvis spinal fusion model. Participants completed two simulations, with 1 month between first and second attempts. Fifty percent of surgeons in each training level were randomized to receive an educational curriculum (rod bending technique videos and unlimited simulator practice) between simulation attempts. Rod bending simulation proficiency was determined by the percentage of participants who completed the task (conclusion at 20 minutes), time to task completion or conclusion, and number of incomplete set screws at task conclusion. Participants completed a preparticipation and postparticipation survey. Univariate analysis compared rod bending proficiency and survey results between education and control cohorts.

RESULTS

Forty trainees (20 junior and 20 senior) were enrolled, with 20 participants randomized to the education and control cohorts. No notable differences were observed in the first simulation rod bending proficiency or preparticipation survey results between the education and control cohorts. In the second simulation, the education versus the control cohort demonstrated a significantly higher completion rate ( P = 0.01), shorter task time ( P = 0.009), fewer incomplete screws ( P = 0.003), and greater experience level ( P = 0.008) and comfort level ( P = 0.002) on postparticipation survey.

DISCUSSION

Trainees who participated in a novel educational curriculum and simulator training relative to the control cohort improved markedly in rod bending proficiency and comfort level. Rod bending simulation could be incorporated in existing residency and fellowship surgical skills curricula.

LEVEL OF EVIDENCE

I.

Morphological description of sagittal lumbar spinal alignment using curve magnitude, span, and apex-the multiethnic alignment normative study (MEANS)

BACKGROUND CONTEXT

Current definition of lumbar lordosis uses the L1-S1 angle. Prevailing classification of sagittal spinal morphology, derived from a young adult population, classifies the spine into four subtypes defined by their sacral slope (SS) and curve morphology.

PURPOSE

To describe physiological sagittal alignment of the lumbar spine across age groups using three main parameters that dictate the lumbar curve: angular magnitude, span, and apex.

STUDY DESIGN

A large, multicenter, cross-sectional radiographic comparison study.

PATIENT SAMPLE

Four hundred sixty-eight healthy, asymptomatic subjects aged 18 to 80 years from five countries (184 males, 284 females; 98 France, 119 Japan, 79 Singapore, 80 Tunisia, 92 USA, mean age 40.61±14.99 years).

OUTCOME MEASURES

Sagittal lumbar profile subtypes clustered based on lumbar curve angular magnitude (ie, Cobb angle of the lumbar lordosis), span, and apex, and described by sagittal radiographic parameters.

METHODS

Subjects underwent whole-body low-dose EOS stereoradiographs. Comparisons between conventional L1-S1 lumbar lordosis (cLL) and true lumbar lordosis (tLL, defined by the inflection-S1 angle) were conducted. Using the K-means clustering algorithm, lumbar curve angular magnitude, span and apex were used to classify sagittal spinal morphology into subtypes, stratified across age groups. Further univariate and multivariate analyses were conducted to compare radiographic parameters across subtypes, and identify predictors for the lumbar curve's angular magnitude, span and apex.

RESULTS

Mean cLL was -57.27±11.37°, and tLL was -62.62±10.76°. Using tLL, instead of cLL, to describe sagittal spinal morphology, we found significant differences in terms of angular magnitude of the lumbar curve, the median thoracolumbar inflection vertebral level and pelvic incidence-lumbar lordosis mismatch Multivariate analysis found a larger SS, more positive T9 tilt, and more kyphotic T4-T12 predictive for a more lordotic tLL, while a larger overhang distance predicted for a less lordotic tLL (p-values<.001). In addition, a larger T9 tilt, less lordotic L1-L5 and smaller PT were predictors of a more caudal thoracolumbar inflection and lumbar apical vertebral levels (p-values<.001). Sagittal lumbar profiles of subjects age<30 years, 30≤age<60 years and age≥60 years, could be classified into 4, 6, and 3 subtypes, respectively.

CONCLUSIONS

Sagittal lumbar profile subtypes vary across age groups, with more homogenous morphologies at the extremes of ages. Improved understanding of the morphological evolution of sagittal spinal profiles with age in asymptomatic individuals will help guide future individualized surgical treatment.

PreOperative Planning for Adult Spinal Deformity Goals: Level Selection and Alignment Goals

Adult Spinal Deformity (ASD) is a complex pathologic condition with significant impact on quality of life, including pain, loss of function, and fatigue. Achieving realignment goals is crucial for long-term results. Reliable preoperative planning strategies, including nomograms, measurement tools, and level selection, are key to maximizing the likelihood of achieving a good outcome following ASD corrective surgery. This review covers recent literature on such strategies, including review of the different targets for realignment and their association with outcomes (both patients-reported outcomes and complications), selection of upper and lower instrumented vertebrae, and the latest innovation in preoperative planning for deformity surgery.

Does the Amount of Correction of Sagittal Deformity Really Promote Proximal Junctional Kyphosis? Multivariate Analyses According to Uppermost Instrumented Vertebra Levels

BACKGROUND

The present study assumed that the effects of deformity correction amounts on proximal junctional kyphosis (PJK) development after long deformity surgery would vary according to uppermost instrumented vertebrae (UIV) levels. Our study was to reveal the association between the amount of correction and PJK according to UIV levels.

METHODS

Adult spinal deformity patients aged >50 years who underwent thoracolumbar fusion (≥4 levels) were included. PJK was defined by proximal junctional angles ≥15°. Presumed demographic and radiographic risk factors for PJK were evaluated including parameters regarding the correction amount such as postoperative change in lumbar lordosis and postoperative offset grouping, the value associated with age-adjusted pelvic incidence-lumbar lordosis mismatch. The patients were divided according to UIV levels of T10 or above (group A) and T11 or below (group B). Multivariate analyses were performed separately for both groups.

RESULTS

The present study included 241 patients (74 for group A and 167 for group B). PJK developed in approximately half of all patients within an average of 5 years of follow-up. For group A, only body mass index (P = 0.002) was associated with PJK. No radiographic parameters were correlated. For group B, postoperative change in lumbar lordosis (P = 0.009) and offset value (P = 0.030) were significant risk factors for PJK development.

CONCLUSIONS

The correction amount of sagittal deformity increased the risk of PJK only in patients with UIV at or below T11. However, it was not associated with PJK development in patients with UIV at or above T10.

Introduction of a New Radiographic Parameter to Predict Proximal Junctional Kyphosis in Adult Spinal Deformity: UIVPTA (Uppermost Instrumented Vertebra-Pelvic Tilt Angle)

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.

External Validation of the Global Alignment and Proportion Score as Prognostic Tool for Corrective Surgery in Adult Spinal Deformity: A Systematic Review and Meta-Analysis

BACKGROUND

Since its proposal, the Global Alignment and Proportion (GAP) score has been the topic of several external validation studies, which have yielded conflicting results. Given the lack of consensus regarding this prognostic tool, the authors aim to assess the accuracy of GAP scores for predicting mechanical complications following adult spinal deformity correction surgery.

METHODS

A systematic search was performed using PubMed, Embase, and Cochrane Library for the purpose of identifying all studies evaluating the GAP score as a predictive tool for mechanical complications. GAP scores were pooled using a random-effects model to compare patients reporting mechanical complications after surgery versus those reporting no complications. Where receiver operator curves were provided, the area under the curve (AUC) was pooled.

RESULTS

A total of 15 studies featuring 2092 patients were selected for inclusion. Qualitative analysis using Newcastle-Ottawa criteria revealed moderate quality among all included studies (5.99/9). With respect to sex, the cohort was predominantly female (82%). The pooled mean age among all patients in the cohort was 58.55 years, with a mean follow-up of 33.86 months after surgery. Upon pooled analysis, we found that mechanical complications were associated with higher mean GAP scores, albeit minimal (mean difference = 0.571 [ 95% confidence interval: 0.163-0.979]; P = 0.006, n = 864). Additionally, age (P = 0.136, n = 202), fusion levels (P = 0.207, n = 358), and body mass index (P = 0.616, n = 350) were unassociated with mechanical complications. Pooled AUC revealed poor discrimination overall (AUC = 0.69; n = 1206).

CONCLUSIONS

GAP scores may have a minimal-to-moderate predictive capability for mechanical complications associated with adult spinal deformity correction.

Proximal Junctional Kyphosis or Failure After Adult Spinal Deformity Surgery - Review of Risk Factors and Its Prevention

Proximal junction kyphosis (PJK) is a common imaging finding after long-level fusion, and proximal junctional failure (PJF) is an aggravated form of the progressive disease spectrum of PJK. This includes vertebral fracture of upper instrumented vertebra (UIV) or UIV+1, instability between UIV and UIV+1, neurological deterioration requiring surgery. Many studies have reported on PJK and PJF after long segment instrumentation for adult spinal deformity (ASD). In particular, for spine deformity surgeons, risk factors and prevention strategies of PJK and PJF are very important to minimize reoperation. Therefore, this review aims to help reduce the occurrence of PJK and PJF by updating the latest contents of PJK and PJF by 2023, focusing on the risk factors and prevention strategies of PJK and PJF. We conducted a search on multiple database for articles published until February 2023 using the search keywords "proximal junctional kyphosis," "proximal junctional failure," "proximal junctional disease," and "adult spinal deformity." Finally, 103 papers were included in this study. Numerous factors have been suggested as potential risks for the development of PJK and PJF, including a high body mass index, inadequate postoperative sagittal balance and overcorrection, advanced age, pelvic instrumentation, and osteoporosis. Recently, with the increasing elderly population, sarcopenia has been emphasized. The quality and quantity of muscle in the surgical site have been suggested as new risk factor. Therefore, spine surgeon should understand the pathophysiology of PJK and PJF, as well as individual risk factors, in order to develop appropriate prevention strategies for each patient.

A Validation Study of Four Preoperative Surgical Planning Tools for Adult Spinal Deformity Surgery in Proximal Junctional Kyphosis and Clinical Outcomes

BACKGROUND

Four guidelines have been suggested for optimal correction in adult spinal deformity surgery: Scoliosis Research Society (SRS)-Schwab classification, age-adjusted sagittal alignment goals, Global Alignment and Proportion (GAP) score, and the Roussouly algorithm. Whether these goals provide benefit in both proximal junctional kyphosis (PJK) reduction and clinical outcome improvement remains unclear.

OBJECTIVE

To validate 4 preoperative surgical planning tools in PJK development and clinical outcomes.

METHODS

We retrospectively reviewed patients who underwent ≥5-segment fusion including the sacrum for adult spinal deformity with a follow-up of ≥2-year. PJK development and clinical outcomes were compared among the groups separately using 4 surgical guidelines: SRS-Schwab pelvic incidence (PI)-lumbar lordosis (LL) modifier (Group 0, +, ++), age-adjusted PI-LL goal (undercorrection, matched correction, and overcorrection), GAP score (proportioned, moderately disproportioned, and severely disproportioned groups), and the Roussouly algorithm (restored and nonrestored groups).

RESULTS

A total of 189 patients were included in this study. The mean age was 68.3 years, and there were 162 women (85.7%). There were no differences in the rate of PJK development and clinical outcomes among SRS-Schwab PI-LL modifier and GAP score groups. With the age-adjusted PI-LL goal, PJK developed significantly less frequently in the matched group compared with the under- and overcorrection groups. Clinical outcomes were significantly better in the matched group compared with the under- and overcorrection groups. With the Roussouly algorithm, PJK developed significantly less frequently in the restored group than in the nonrestored group. However, there were no differences in clinical outcomes between the 2 Roussouly groups.

CONCLUSION

Correction according to the age-adjusted PI-LL goal and the restored Roussouly type was associated with reduced PJK development. However, differences in clinical outcomes were only observed in the age-adjusted PI-LL groups.