Postoperative Proximal Junctional Kyphosis Research Articles

Independent Risk Factors of Proximal Junctional Kyphosis with Vertebral Fracture After Spinal Long Fusion: Survivorship Analysis of Adult Spinal Deformity Surgery Patients

ObjectiveThis study aimed to identify risk factors for postoperative proximal junctional kyphosis (PJK) with vertebral fracture in adult spinal deformity (ASD) patients. We performed a survival analysis considering various factors, including osteoporosis. MethodsThis single-center retrospective study included 101 ASD patients (mean age: 67.2 years, mean follow-up: 8.1 years). We included patients aged ≥ 50 years with abnormal radiographic variables undergoing corrective long spinal fusion. The main outcome measure was PJK with vertebral fracture, analyzed based on patient data, radiographic measurements, sagittal parameters, bone mineral density, and osteoporosis medication. ResultsPJK occurred in 37.6% of patients, with vertebral fracture type 2 accounting for 65% of these cases. Kaplan-Meier analysis indicated a median PJK-free survival time of 60.7 months. Existing vertebral fracture (grade 1 or higher or grade 2 or higher) was a significant risk factor for PJK with vertebral fracture, with hazard ratios of 4.58 and 5.61, respectively. The onset time of PJK with vertebral fracture was 1.5 months postoperatively, with 44% of these cases occurring within 1 month and 64% within 2 months. ConclusionsPJK with vertebral fracture affected 25% of ASD patients, emphasizing the importance of osteoporosis evaluation. Existing vertebral fracture emerged as a significant independent risk factor, surpassing bone mineral density. This study provides valuable insights for spine surgeons, highlighting the need to provide osteoporosis treatment and emphasize potential postoperative complications during discussions with patients.

Predictive role of FRAX© for postoperative proximal junctional kyphosis with vertebral fracture after adult spinal deformity surgery.

To identify risk factors, including FRAX (a tool for assessing osteoporosis) scores, for development of proximal junctional kyphosis (PJK), defined as Type 2 in the Yagi-Boachie classification (bone failure), with vertebral fracture (VF) after surgery for symptomatic adult spinal deformity. This was a retrospective, single institution study of 127 adults who had undergone corrective long spinal fusion of six or more spinal segments for spinal deformity and been followed up for at least 2years. The main outcome was postoperative development of PJK with VF. Possible predictors of this outcome studied included age at surgery, BMI, selected radiographic measurements, bone mineral density, and 10-year probability of major osteoporotic fracture (MOF) as determined by FRAX. We also analyzed use of medications for osteoporosis. Associations between the selected variables and PJK with VF were assessed by the Mann-Whitney, Fishers exact, and Wilcoxon signed-rank tests, and Kaplan-Meier analysis, as indicated. Forty patients (31.5%) developed PJK with VF postoperatively,73% of them within 6months of surgery. Statistical analysis of the selected variables found that only a preoperative estimate by FRAX of a > 15% risk of MOF within 10years, pelvic tilt > 30° at first standing postoperatively and lower instrumented level (fusion terminating at the pelvis) were significantly associated with development of PJK with VF. Preoperative assessment of severity of osteoporosis using FRAX provides an accurate estimate of risk of postoperative PJK with VF after surgery for adult spinal deformity.

Spinopelvic morphology impacts on postoperative proximal junctional kyphosis in congenital scoliosis with thoracolumbar hemivertebrae.

It aims to investigate the lumbar and pelvic morphology in congenital scoliosis with thoracolumbar hemivertebrae and its impact on proximal junctional kyphosis (PJK) incidence after hemivertebra resection and short fusion. 23 congenital scoliosis patients with thoracolumbar hemivertebra aged between 10 and 18years were enrolled in the retrospective study. Spinopelvic sagittal parameters were analyzed on whole-spine standing lateral radiographs preoperatively, one-week postoperatively and at the final follow-up. Pearson correlations were calculated for local kyphosis (LK), lumbar and pelvic morphology parameters. Binary logistic regression and receiver operating characteristics (ROC) curve analysis were performed to identify the risk factors for PJK. Thoracolumbar hemivertebra caused LK of 29.2° ± 17.3°, an increased lumbar lordosis (LL) (-64.7° ± 16.3°), lower LL apex (52.2% at L5), and small pelvic incidence (PI) (36.8° ± 6.6°). LK was correlated with lumbar morphology parameters, including LL (r = -0.837), upper arc of LL (LLUA) (r = -0.879), thoracolumbar kyphosis (TLK) (r = 0.933), thoracic kyphosis (TK) (r = 0.762) and TK apex (TKA) (r = -0.749). Surgical treatment improved the lumbar morphology, but not pelvic morphology. At the final follow-up, LL had returned to its preoperative value (p = 0.158). PJK occurred in 30.4% of cases as a compensatory mechanism. Preoperatively, significant differences of parameters between non-PJK and PJK groups were observed in LK and TLK. Binary logistic regression identified three independent risk factors for PJK: preoperative LLA (OR = 0.005, 95%CI = 0.000-0.287, p = 0.011), preoperative TLK (OR = 1.134, 95%CI = 1.001-1.286, p = 0.048), and preoperative lumbar lordosis morphology type (OR = 5.507, 95%CI = 1.202-25.227, p = 0.028). However, residual LK after surgery was not correlated with PJK incidence. ROC curve analysis verified that preoperative TLK > 22.59° was associated with increased PJK incidence after surgery. Lumbar morphology changes as a compensatory mechanism beneath the thoracolumbar hemivertebra. However, a stable pelvis tends to allow the LL to return to its preoperative value. PJK occurred as a cranial compensatory mechanism for increasing LL and corrected TLK. A larger TLK (> 22.59°) was an independent risk factor for PJK incidence in patients with type 2 and 3A lumbar lordosis morphology.

Simplified S1 vertebral bone quality score independently predicts proximal junctional kyphosis after surgery for degenerative lumbar scoliosis

ObjectiveOur study aimed to assess the effectiveness of the simplified S1 vertebral bone quality (VBQ) score in predicting the incidence of proximal junctional kyphosis (PJK) after surgery for degenerative lumbar scoliosis (DLS).MethodsWe reviewed 122 patients with DLS who underwent posterior lumbar decompression and long-segment fusion surgery in our hospital from January 2016 to December 2020. The patients were classified into PJK group and non-PJK group. S1 VBQ scores are determined by signal intensity measurements taken from the mid-sagittal plane of T1-weighted non-contrast MRI. Logistic regression analysis was used to identify factors associated with PJK. Receiver-operating characteristic curve (ROC) analysis was used to evaluate the value of S1 VBQ score in predicting pedicle PJK after DLS.Results122 DLS patients (90 females and 32 males) met the inclusion criteria. In addition, 27 patients (22.13%) had PJK at the time of last follow-up. VBQ was higher in PJK patients than non-PJK patients (3.58 ± 0.67 vs. 3.08 ± 0.54, p < 0.001). Preoperatively, patients in the PJK group had a greater TLK than those in the non-PJK group (20.00 ± 6.22 vs. 16.86 ± 5.38, p = 0.011). After surgery, patients in the PJK group had greater TLK (p < 0.001) and PJA (p < 0.001) compared with the non-PJK group. At final FU, patients in the PJK group had greater TK (p = 0.002), TLK (p < 0.001), SVA (p < 0.001), and PJA (p < 0.001) than patients in the non-PJK group (Table 4). In multivariate logistic regression analysis, higher VBQ score (OR 4.565, 95% CI 1.43–14.568, p = 0.010), advanced age (OR 1.119, 95% CI 1.021–1.227, p = 0.016), and larger TLK (OR 1.191, 95% CI 1.041–1.362, p = 0.011) were significant predictors of postoperative PJK in patients with DLS (Table 6). A statistically significant positive correlation existed between VBQ score and PJA change (r = 0.370, p < 0.001). We created ROC curves for VBQ scores as predictors of PJK with a diagnostic accuracy of 72.1% (95% CI 60.15–82.9%.The ideal limit for the VBQ score was 3.205 (sensitivity: 77.8%, specificity: 81.4%).ConclusionTo the best of our knowledge, this is the first study to evaluate the effectiveness of the S1 VBQ score in predicting postoperative PJK in DLS. Our study included major risk factors and found that S1 VBQ score was a significant predictor of PJK in patients undergoing DLS surgery. The higher the S1 VBQ score, the higher the probability of PJK.

Erector Spinae Atrophy Correlates with Global Sagittal Imbalance and Postoperative Proximal Junctional Kyphosis Incidence in Lumbar Degenerative Kyphosis.

Retrospective cohort study. This study aimed to investigate the relationship between lumbar erector muscle atrophy and global sagittal imbalance in lumbar degenerative kyphosis (LDK) and with postoperative proximal junctional kyphosis. Lumbar erector muscle atrophy has been studied in LDK. However, its role in the compensatory mechanism is still under intense discussion, and the role of erector spinae (ES) muscle is always overlooked. This study enrolled 51 patients with LDK out of 382 patients with adult degenerative spinal deformity. Baseline information was reviewed including demographic data and complications. Sagittal spinopelvic alignments and global imbalance parameters were assessed on full-length X-ray images of the spine. Muscularity and the fatty infiltration area of the ES and multifidus (MF) were measured at the L4/5 level on preoperative magnetic resonance image to evaluate the lumbar erector muscle atrophy. Stratification by sagittal vertical axis (SVA) was performed: group 1 with SVA <100 mm and group 2 with SVA >100 mm, and these groups were compared. Spearman correlation and multivariable logistic regression analyses were performed to analyze and define risk factors of postoperative proximal junctional kyphosis (PJK). Group 2 had lower ES and MF muscularity than group 1. ES muscularity correlated with SVA (r=-0.510, p<0.003), lumbar lordosis (r=-0.415, p<0.018), and postoperative PJK (r=-0.508, p<0.022). MF muscularity did not correlate with the above parameters. Multivariable logistic regression analysis verified ES muscularity (odds ratio [OR], 0.001; p<0.039) and SVA (OR, 1.034; p<0.048) as the risk factors for postoperative PJK. ES atrophy, besides the MF, is an important predictor in distinguishing decompensated LDK from well-compensated ones. It plays an important role in compensatory mechanism, not only correlates with global sagittal imbalance but also ties to PJK after deformity corrective surgery.

Proximal junctional kyphosis in Lenke 5C adolescent idiopathic scoliosis after selective posterior thoracolumbar/lumbar fusion: risk factors and predictive index

BackgroundAlthough several studies have reported that selective posterior thoracolumbar/lumbar (TL/L) fusion can yield satisfactory results in Lenke 5C adolescent idiopathic scoliosis (AIS), the proximal junctional kyphosis (PJK) is still a common complication that occurs after surgery. The purpose of this study is to analyse the risk factors for postoperative proximal junctional kyphosis in Lenke 5C patients who underwent selective posterior TL/L fusion and explore whether PJK can be predicted.MethodsA total of 83 AIS patients with Lenke 5C curves who met the inclusion criteria were analysed. All patients were divided into two groups based on the occurrence of postoperative PJK. Univariate and multivariate analyses were used to identify independent factors significantly associated with PJK, and an PJK index was proposed and verified.ResultsPJK was observed in 27 of 83 (32.5%) patients in the study. Preoperative thoracic kyphosis (TK) and the immediate postoperative proximal junctional angle (PJA) were the primary factors identified by the binary logistic regression analysis. The PJK index was defined as 1.1× preoperative TK + 2.3× immediate postoperative PJA. The receiver operating characteristics curve indicated that the occurrence rate of PJK was 85% and non-occurrence rate was 82% when the PJK index was greater than 42.ConclusionLarge preoperative TK and a large immediate postoperative PJA play important roles in the development of PJK in Lenke 5C patients treated with selective posterior thoracolumbar/lumbar fusion. The PJK index can be used to predict the occurrence of PJK with high accuracy. To prevent the occurrence of PJK, we should pay attention to the TLK, and preserving more posterior proximal intervertebral elements at the upper instrumented vertebral level would be an important part of corrective surgery; however, moderate correction of the lumbar curve is recommended.

Analysis of factors associated with proximal junctional kyphosis after surgery for Lenke type 5 adolescent idiopathic scoliosis

Objective: To investigate the risk factors associated with the development of proximal junctional kyphosis (PJK) after posterior spinal fusion for in children with Lenke type 5 adolescent idiopathic scoliosis (AIS). Methods: It was a retrospective case-control study that included medical records of 98 children with Lenke type 5 AIS who underwent posterior orthopedic surgery under general anesthesia at the Honghui Hospital Affiliated to Xi'an Jiaotong University from January 2013 to December 2018. There were 23 males and 75 females with a mean age of (14.5±2.2) years (10-18 years). Patients were divided into PJK and non-PJK groups according to whether the posterior junctional angle (PJA) was greater than 10° and increased for more than 10° from the preoperative period at the the last follow-up. Univariate analysis was used to analyze the correlation of general data of the children with occurrence of PJK after the operation. Multivariate logistic regression analysis was used to analyze the risk factors of postoperative PJK. Results: There were 35 cases in the PJK group and 63 cases in the non-PJK group. The PJK and non-PJK groups were followed up for (35.6±7.3) months and (36.4±7.5) months, respectively, and the difference was not statistically significant (P=0.637). There was no statistically significant difference between the two groups in general data such as gender, age, and body mass index (all P>0.05), while there were statistically significant differences between the two groups in upper instrumented vertebrea (UIV) location and junctional area posterior ligamentous complex (PLC) injury (all P<0.05). The results of univariate analysis showed that UIV location at T10-T12, junctional area PLC injury, preoperative coronal thoracic curve (TC), preoperative and final follow-up PJA, and preoperative and final follow-up pelvic incidence-lumbarlordosis (PI-LL) were correlated with postoperative PJK (OR=2.50, 5.37, 0.92, 1.12, 1.32, 1.06, 3.35, all P<0.05). Multifactorial logistic regression analysis showed that UIV located at T10-T12 (OR=2.346, 95%CI: 1.582-3.481, P=0.001), junctional area PLC injury (OR=5.112, 95%CI: 1.283-20.418, P=0.023) and last follow-up PI-LL (OR=1.826, 95%CI: 1.558-24.745, P=0.012) were risk factors for the occurrence of postoperative PJK in children with Lenke type 5 AIS. Conclusions: Postoperative UIV fixation to the thoracolumbar segment, PLC injury in the junctional area and excessive postoperative PI-LL in children with Lenke type 5 AIS may be the risk factors for the occurrence of PJK after the operation. It is suggested that avoidance of UIV selection to the thoracolumbar segment, intraoperative protection of the PLC located near the UIV and restoration of a good PI-LL relationship may reduce the incidence of PJK.

The association between bone mineral density and proximal junctional kyphosis in adult spinal deformity: a systematic review and meta-analysis.

Proximal junctional kyphosis (PJK) is a complication of surgical management for adult spinal deformity (ASD) with a multifactorial etiology. Many risk factors are controversial, and their relative importance is not fully understood. The authors aimed to elucidate the association between bone mineral density (BMD) and PJK. A systematic literature search was performed using PubMed and Web of Science keywords of "Proximal Junctional Kyphosis [MeSH] OR Proximal Junctional Failure [MeSH]" AND "Bone Mineral Density [MeSH] OR Hounsfield Units [MeSH] OR DEXA [MeSH]" set to the date range of January 2002 to July 2022. Studies required a minimum of 10 patients and 12 months of follow-up. Articles were included if they were in the English language and presented a primary retrospective cohort that included a comparison of patients with and without PJK, as well as a radiographic biomarker for BMD, such as Hounsfield units (HU) or T-score. A total of 18 unique studies with 2185 patients who underwent ASD surgery were identified. Of these, 537 patients (24.6%) developed PJK. Eight studies provided T-scores that were amenable to comparison, which found that patients who developed PJK were found to have lower BMD T-scores by a mean of -0.69 (95% CI -0.88 to -0.50; I2 = 63.9%, p < 0.001). The HU at the UIV among patients with the PJK group (n = 101) compared with the non-PJK group (n = 156) was found to be significantly lower (mean difference -32.35, 95% CI -46.05 to -18.65; I2 = 28.7%, p < 0.001). This meta-analysis suggests that low preoperative BMD as measured by T-score and a diagnosis of osteoporosis were associated with higher postoperative PJK. Additionally, lower HU on CT at the UIV were found to be significant risk factors for postoperative PJK as well. These findings suggest that more attention to preoperative BMD is a risk factor for PJK among ASD patients is warranted.

Postoperative proximal junctional kyphosis correlated with thoracic inlet angle in Lenke 5c adolescent idiopathic scoliosis patients following posterior surgery

BackgroundProximal junctional kyphosis is a common complication after posterior fusion in patients with adolescent idiopathic scoliosis and is correlated with postoperative changes of thoracic kyphosis. In lenke 5c patients, higher postoperative LL and spontaneous change of TK may produce an effect on final PJK. However, no studies has been performed to evaluate the correlation of PJK with thoracocervical parameters in patients with AIS.MethodsData from 98 patients who underwent posterior fusion for Lenke 5C AIS with 2 years of follow-up were retrospectively reviewed. Patients in the extended fusion group underwent fusion at levels higher than upper-end vertebra + 2 (n = 38), and those in the thoracolumbar/lumbar (TL/L) fusion group underwent fusion at UEV + 2 or lower (n = 60).ResultsDuring an average follow-up of 38.1 months, 23 of 98 patients developed PJK. The extended fusion group had a higher incidence of PJK than the TL/L fusion group (14/38 vs. 9/60, respectively; P = 0.01) and a significantly greater decrease in thoracic kyphosis than the TL/L group (P < 0.01). Patients with PJK had a significantly larger preoperative thoracic inlet angle (TIA) than those without PJK (P < 0.01). Multivariate analysis showed that a greater preoperative TIA and extended fusion were associated with PJK. The Scoliosis Research Society 22-item questionnaire score did not significantly differ between the PJK and non-PJK groups.ConclusionsThe preoperative TIA could be a predictor of PJK. Among patients with Lenke 5C AIS, those with a TIA of > 71° are more likely to develop PJK. Additionally, extended fusion in patients with Lenke 5C may increase the risk of PJK.

Long spine fusions to the sacrum-pelvis are associated with greater post-operative proximal junctional kyphosis angle in sitting position.

A single-centre retrospective study. Although adult patients spend most of their time in sitting positions, the assessment of spinopelvic parameters in adult deformity surgery is commonly performed in standing X-rays. Our study compares the standing and sitting sagittal alignment parameters in subjects who underwent thoracolumbar fusion. Patients who underwent corrective surgery for adult scoliosis with at least five instrumented vertebra were stratified according to the upper instrumented vertebra (UIV) and pelvic fixation. Group A:UIV proximal to T6 with pelvis fixation. B:UIV lower than T6 and pelvic fixation. Group C: thoracolumbar fusion without pelvic fixation. Post-operative spinopelvic sagittal parameters were measured in both standing and sitting X-rays. A total of 51 patients were enrolled in the study (11:Males and 40:Females). The mean age was 52.3 ± 21.7y/o. The comparison of post-operative standing and sitting X-ray within the group A and B showed that a significant change was observed in terms of JA-Junctional Angle-(Group A 6.3 ± 4.3 vs. 8.1 ± 3.3, p value = 0.03) (Group B 8.5 ± 6.4 vs. 10.9 ± 6.4, p value = 0.02). Group C showed statistically significant difference in terms of PT (15.6 ± 11.2 vs. 19.3 ± 9.2, p value = 0.04), AVA-Acetabular Version Angle-(41.1 ± 5.9 vs. 48.3 ± 6.6, p value < 0.01) and LL (- 51.3 ± 16.0 vs. - 42.6 ± 10.7, p value < 0.01). In our series, the post-operative sagittal alignment showed peculiar behaviours and adaptations in sitting position, depending on the length and the site of the instrumented area. If the pelvis is included, the JA tends to significantly increase in sitting position. These findings can improve the knowledge of pathologies as proximal junctional kyphosis or specific cases of anterior hip impingement. IV.

Pelvic Nonresponse Following Treatment of Adult Spinal Deformity: Influence of Realignment Strategies on Occurrence.

Despite adequate correction, the pelvis may fail to readjust, deemed pelvic nonresponse (PNR). To assess alignment outcomes [PNR, proximal junctional kyphosis (PJK), postoperative cervical deformity (CD)] following adult spinal deformity (ASD) surgery utilizing different realignment strategies. ASD patients with two-year data were included. PNR defined as undercorrected in age-adjusted pelvic tilt (PT) at six weeks and maintained at two years. Patients classified by alignment utilities: (a) improvement in Scoliosis Research Society-Schwab sagittal vertical axis, (b) matching in age-adjusted pelvic incidence-lumbar lordosis, (c) matching in Roussouly, (d) aligning Global Alignment and Proportionality (GAP) score. Multivariable regression analyses, controlling for age, baseline deformity, and surgical factors, assessed rates of PNR, PJK, and CD development following realignment. A total of 686 patients met the inclusion criteria. Rates of postoperative PJK and CD were not significant in the PNR group (both P >0.15). PNR patients less often met substantial clinical benefit in Oswestry Disability Index by two years [odds ratio: 0.6 (0.4-0.98)]. Patients overcorrected in age-adjusted pelvic incidence-lumbar lordosis, matching Roussouly, or proportioned in GAP at six weeks had lower rates of PNR (all P <0.001). Incremental addition of classifications led to 0% occurrence of PNR, PJK, and CD. Stratifying by baseline PT severity, Low and moderate deformity demonstrated the least incidence of PNR (7.7%) when proportioning in GAP at six weeks, while severe PT benefited most from matching in Roussouly (all P <0.05). Following ASD corrective surgery, 24.9% of patients showed residual pelvic malalignment. This occurrence was often accompanied by undercorrection of lumbopelvic mismatch and less improvement of pain. However, overcorrection in any strategy incurred higher rates of PJK. We recommend surgeons identify a middle ground using one, or more, of the available classifications to inform correction goals in this regard. III.

A predictive scoring system for proximal junctional kyphosis after posterior internal fixation in elderly patients with chronic osteoporotic vertebral fracture: A single-center diagnostic study

ObjectiveTo establish a predictive scoring system for proximal junctional kyphosis (PJK) after posterior internal fixation in elderly patients with chronic osteoporotic vertebral fracture (COVF).Materials and methodsThe medical records of 88 patients who were diagnosed with COVF and underwent posterior internal fixation in our hospital from January 2013 to December 2017 were retrospectively analyzed. The included patients were divided into two groups according to whether they suffered PJK after surgery, namely, the PJK group (25 cases) and non-PJK group (63 cases). The following clinical characteristics were recorded and analyzed: age, gender, body mass index (BMI), bone mineral density (BMD), smoking history, fracture segment, proximal junction angle, sagittal vertebral axis, pelvic incidence (PI)–lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), posterior ligamentous complex (PLC) injury, upper instrumented vertebra, lower instrumented vertebra, and the number of fixed segments. The prevalence of these clinical characteristics in the PJK group was evaluated, and the scoring system was established using logistic regression analysis. The performance of the scoring system was also prospectively validated.ResultsThe predictive scoring system was established based on five clinical characteristics confirmed as significant predictors of PJK, namely, age > 70 years, BMI > 28 kg/m2, BMD < −3.5 SD, preoperative PI-LL > 20°, and PLC injury. PJK showed a significantly higher score than non-PJK (7.80 points vs. 2.83 points, t=9.556, P<0.001), and the optimal cutoff value for the scoring system was 5 points. The sensitivity and specificity of the scoring system for predicting postoperative PJK were 80.00% and 88.89%, respectively, in the derivation set and 75.00% and 80.00% in the validation set.ConclusionThe predictive scoring system was confirmed with satisfactory sensitivity and specificity in predicting PJK after posterior internal fixation in elderly COVF patients. The risk of postoperative PJK in patients with a score of 6–11 is high, while the score of 0–5 is low.

Relook into the Risk Factors of Proximal Junctional Kyphosis in Early Onset Scoliosis Patients: Does the Location of Upper Instrumented Vertebra in Relation to the Sagittal Apex Matter?

ObjectiveGrowing rods surgery is the mainstay of treatment for early‐onset scoliosis (EOS) while proximal junctional kyphosis (PJK) is one of the most commonly reported postoperative complications. We sought to investigate the impact of the location of upper instrumented vertebra (UIV) in relation to the sagittal apex on proximal junctional kyphosis in EOS after traditional growing rods (GRs) treatment.MethodsA total of 102 EOS patients who received traditional growing rods treatment with a follow‐up of at least 2 years between 2009 and 2020 were retrospectively reviewed. Radiographic measurements were performed before and after the index surgery and at the latest follow‐up. We investigated the coronal Cobb angle and spinopelvic parameters of the whole spine. The location of the UIV, apex, lower instrumented vertebra (LIV), inflection vertebra (IV), the number and distance of UIV‐apex, LIV‐apex and IV‐apex were also recorded. Risk factors for PJK were analyzed by logistic regression analysis.ResultsPJK was observed in 21 patients (20.6%) during the follow‐up period. The PJK group showed a younger age at the index surgery (5.9 vs. 7.1 years, P = 0.042), more lengthening procedure times (5.0 vs. 4.0, P = 0.032), larger preoperative coronal Cobb angle (82.0 vs. 75.6°, P = 0.038), higher correction rate (51.2% vs. 44.4%, P = 0.047) and larger postoperative proximal junctional angle (PJA) (13.9 vs. 5.5°, P < 0.001) than the non‐PJK group. The ratio of the number and distance from UIV‐apex to IV‐apex also differed significantly between the two groups. The logistic regression revealed that age at the index surgery ≤ 7 years, the ratio of the number from UIV‐ apex to IV‐ apex ≤ 0.6 and the ratio of the distance from UIV‐ apex to IV‐ apex ≤ 0.6 were independent risk factors for postoperative PJK.ConclusionBesides younger age, a closer location of UIV relative to the sagittal apex is identified to be an independent risk factor of postoperative PJK. Selection of UIV at a relatively farther location away from the sagittal apex might help prevent occurrence of PJK.

Impact of C2-femoral heads center and sacroiliac fixation on the occurrence of post-operative proximal junctional kyphosis in adults with spinal deformity

Objective: To analyze the relationship between post-operative proximal junctional kyphosis (PJK) and C2-femoral heads center (C2-FH), pelvic fixation in adult spinal deformity (ASD) patients, so as to provide a reference for the preoperative decision-making and the postoperative intervention timely. Methods: It was a retrospective study that analyzed 34 cases of ASD patients who underwent posterior pedicle screw fixation in Nanjing Drum Tower Hospital between January 2017 and May 2017. ASD patients were divided into two groups according to fixation options: the sacroiliac fixation group and the non-sacroiliac fixation group. The spine-pelvis parameters were evaluated on full-length X ray films of spine at preoperatively, 2 weeks postoperatively and the last follow-up, and the incidence of PJK was recorded. Results: A total of 34 ASD patients (3 males and 31 females) were included in this study, with an average age of (58±6) years. The mean follow-up period was (2.9±1.0) years (2.0-4.0 years). The age, follow-up time and various spine-pelvis parameters showed no significant differences between the two groups (all P>0.05). The immediate postoperative C2-FH in the sacroiliac fixation group was significantly lower than that in the non-sacroiliac fixation group [(-69.46±30.85) mm vs (-31.62±15.31) mm, P<0.001]. The incidence of PJK was as high as 50.0% (8/16) in patients with sacroiliac fixation, but it was only 22% (4/18) in patients without sacroiliac fixation (P=0.016). At the last follow-up, the C2-FH of both groups were both higher than -20 mm (both were approximately -15 mm, P=0.976), indicating that the C2-FH was compensated in both groups. Due to the loss of the distal compensation ability, the incidence of PJK in the sacroiliac fixation group was higher than that in the non-sacroiliac fixation group. Due to the fixation of pelvis and most of lumbar spine, no significant differences were found in lumbar lordosis (LL), pelvic tilt (PT) and sacral slope (SS) at the last follow-up in both groups when compared with those after the operation (all P>0.05); while the thoracic kyphosis (TK) and cervical lordosis (CL) increased significantly (both P<0.05) to compensate C2-FH at the last follow-up. Conclusion: It's demonstrated that C2-FH< -2 cm and pelvic fixation are high risk factors of PJK in ASD patients. It is suggested that both global sagittal balance and pelvic fixation should be considered in decision-making and corrective surgery, rather than only focusing on spine-pelvic parameters.

Risk factors for proximal junctional kyphosis after posterior long-segment internal fixation for chronic symptomatic osteoporotic thoracolumbar fractures with kyphosis

BackgroundThis study aimed to analyze the risk factors for proximal junctional kyphosis (PJK) for patients with chronic symptomatic osteoporotic thoracolumbar fractures (CSOTLF) and kyphosis who underwent long-segment internal fixation.MethodsWe retrospectively reviewed the records of patients with CSOTLF complicated with kyphosis who underwent posterior multilevel internal fixation in our hospital between January 2013 and January 2020. The patients’ age, sex, body mass index (BMI), bone mineral density (BMD), smoking status, cause of injury, comorbidities, injury segments, and American Spinal Injury Association (ASIA) grading non-surgical data; posterior ligament complex (PLC) injury, upper and lower instrumented vertebral position (UIV and LIV, respectively), number of fixed segments surgical data, proximal junctional angle (PJA), sagittal vertebral axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) surgical indicators were collected. Patients were divided into postoperative PJK and non-PJK groups.ResultsThis study included 90 patients; among them, 30 (31.58%) developed PJK postoperatively. All patients were followed up for > 24 months (mean 32.5 months). Univariate analysis showed significant differences in age, BMI, BMD, PLC injury, UIV, and LIV fixation position, number of fixation stages, and preoperative PJA, SVA, PI-LL, and SS between the two groups (P < 0.05). Additionally, no significant differences were observed in sex, smoking, cause of injury, complications, injury segment ASIA grade, and preoperative PT between the two groups (P > 0.05). Multifactorial logistic regression analysis showed that age > 70 years (OR = 32.279, P < 0.05), BMI > 28 kg/m2 (OR = 7.876, P < 0.05), BMD T value < − 3.5 SD (OR = 20.836, P < 0.05), PLC injury (OR = 13.981, P < 0.05), and preoperative PI-LL > 20° (OR = 13.301, P < 0.05) were risk factors for PJK after posterior long-segment internal fixation in elderly patients with CSOTLF complicated with kyphosis.ConclusionCSOTLF patients undergoing posterior long segment internal fixation are prone to PJK, and age > 70 years, BMI > 28 kg/m2, BMD T value < − 3.5 SD, preoperative PI-LL > 20° and PLC injury may increase their risk.

807 Peak Force of the Posterior Ligamentous Complex is Lower in Patients with Adult Spinal Deformity Requiring Revision Surgery

INTRODUCTION: Proximal Junctional Kyphosis (PJK) is observed in up to 40% of those undergoing fusion surgery for adult spinal deformity (ASD). Despite common use of surgical techniques reinforcing ligamentous integrity (e.g. tethering, augmentation), it is unknown whether ligamentous biomechanics are impaired in this population. METHODS: Sample: 23 consented individuals with a diagnosis of ASD undergoing primary (N=14) or revision (N=9) multilevel spinal fusions (&gt;4 levels). Intraoperative biopsies of the PLC were harvested 2 levels below the upper instrumented level (primary) or at the failed junctional segment (revision). Peak force (strength) and elastic modulus (stiffness) were compared between primary and revision groups using independent student t-tests, and relationships between biomechanical parameters and patient characteristics evaluated. RESULTS: Participants in the revision group were older (73.3(3.6) years) than the primary group (54.7(19.2)years), p=0.02, but did not differ in number of fused vertebrae (12.0(4.3); primary and (11.3(3.4); revision), p=0.71). Mean pre-operative Vitamin D levels were 40.6(11.5), spino-vertebral angle (SVA) was 54.4(56.8) degrees, Pelvic Tilt (PT) was 24.1(11.0) degrees, Pelvic Incidence-Lumbar Lordosis mismatch (PI-LL) was 15.3(22.4) degrees, and Proximal Junctional Kyphosis (PJK) was 9.4(8.1) degrees. Mean post-operative SVA was 8.3(28.2) degrees, PT was 20.6(6.9) degrees, PI-LL was 4.4(10.0) degrees, and PJK was 12.0 (10.5) degrees. Peak force was significantly lower in the revision group (143.1(72.5) N) compared to the primary group (238.5(109.8) N), p=0.03. There were no differences in ligament stiffness between the primary (5.9(2.0) MPa) and revision groups (5.3(3.1) MPa), p=0.92). There was a significant association between greater peak force and lower age (r=-0.56, p=0.003), larger ligament area (r=0.50, p=0.015), lower vitamin D levels (r=-0.63, p=0.015), and lower pre-operative PI-LL (r=-0.53, p=0.014). There was also a significant association between greater ligament stiffness and greater post-operative PJK (r=0.60, p=0.013). CONCLUSIONS: Peak force of the posterior ligamentous complex in individuals undergoing revision surgery was &lt;60% of those undergoing primary surgery, suggesting an important role of ligament in stabilization of the proximal junctional interface in patients with ASD, particularly in older individuals.

112 Global Sagittal Flexibility Predicts Proximal Junctional Kyphosis After Spine Deformity Surgery

INTRODUCTION: Adult spinal deformity (ASD) is a devastating disease with an estimated prevalence of 68%. Proximal junctional kyphosis (PJK) is a common complication of surgical intervention for ASD. With an incidence reported as high as 40%, PJK can lead to sagittal decompensation and necessitate reoperation. Few studies exist that examine the predictive utility of preoperative radiographic measurements in foreseeing postoperative PJK. METHODS: Demographic information, radiographs, complications, and patient-reported outcome measures (PROMs) were retrospectively analyzed from 109 patients who underwent long-segment thoraco-lumbar fusion at one midwest academic medical center. A Youden J-statistic was calculated based on ROC analysis of the difference between pre-operative standing and supine Sagittal Vertical Axis (ΔSVA), and the development of PJK at UIV + 2. Risk analysis was performed utilizing 2 × 2 contingency tables and Fisher’s exact test. RESULTS: ROC analysis revealed an optimal ΔSVA threshold value of 38.8 mm. Patients with a ΔSVA &gt; 38.8 were considered globally flexible, and those with ΔSVA ≤ 38.8 mm rigid. Rigid patients were noted to have a significantly higher change in their post-operative proximal junctional cobb angle (ΔPJCA p = 0.03) at the one-year time point, with a relative risk of 1.82 (Fisher's p = 0.0072). CONCLUSION: Based on this retrospective data, pre-operative global spinal rigidity portends an independently elevated risk (RR 1.82) for the development of PJK after ASD surgery. No differences in other complication rates or PROMs data was seen between groups. Our data collection is limited to a two year post-operative window. Future studies could look at longer timepoints to see if an increase in reoperation rates (extension of fusion surgery) is similarly seen.

111 Comparison of Hounsfield Units Versus T-Score in Predicting Postoperative Proximal Junctional Kyphosis

INTRODUCTION: Vertebral body (VB) bone quality is generally estimated indirectly via femoral neck dual-energy x-ray absorptiometry (DEXA) to counsel patients on their risk for development of proximal junctional kyphosis (PJK) after thoraco-lumbar fusion for adult spinal deformity. It is currently unknown whether direct measurement of VB bone quality through Hounsfield unit analysis (HUs) can successfully stratify patients on their risk of delayed complications. METHODS: 108 patients who underwent surgery for ASD were enrolled. Demographic characteristics, radiologic measurements, complication profile, and clinical outcomes were recorded both pre- and post-operatively. A Youden J-statistic was calculated based on an ROC analysis of the UIV Hounsfield unit data to give a single HU threshold to segregate patients into either a high or low HU group. Patient groups were then compared with respect to the mentioned clinical and radiographic outcome measures. RESULTS: Youden statistic revealed a HU threshold value of 126.8 for maximal group stratification. Significant change in proximal junctional cobb angle (PJCA) was observed between the low and high HU groups at one and two years (p &lt; 0.0001 and p = 0.0001 respectively). This was not similarly seen in hip or spine DEXA analysis (p &gt; 0.05). CONCLUSION: Assessment of bone quality via pre-operative measurement of the UIV VB HU can predict post-operative changes in PJCA. UIV HUs &lt; 126.8 are associated with 2.8x elevated risk of developing post-operative PJK. Current standard of care measurement of bone quality via femoral neck DEXA is of more limited utility compared to HU analysis.

Surgical Procedures Used for Correction of Scheuermann's Kyphosis: A Meta-Analysis.

Objectives Scheuermann's kyphosis can cause severe back pain and cosmetic disorders to patients. Previous studies on surgical procedure selection for correction of Scheuermann's kyphosis have drawn controversial conclusions. Here, a meta-analysis was performed to figure out a better way between anterior-posterior (AP) combined procedures and posterior-only (PO) procedures. Methods We searched PubMed database and Ovid database, as well as Cochrane Library (between January 2009 and December 2020, around recent ten years), for studies reporting Scheuermann's kyphosis correction in an anterior way or a posterior way. Random effects meta-analysis regarding correction degrees and incidence of proximal junctional kyphosis (PJK) was performed. Results Finally, 13 unique studies including 586 patients (AP: 300; PO: 286) were identified and included for this meta-analysis. Overall, 6 AP cohorts and 10 PO cohorts were pooled regarding the correction degrees of kyphosis in the analysis, respectively. Pooled correction degrees in AP cohorts were 33.31 (95% CI: 27.48–39.15; I2 = 86%, P < 0.001) and in PO cohorts were 31.16 (95% CI: 26.97–35.35; I2 = 81.1%, P < 0.001). Comparison of correction between AP and PO cohorts did not indicate any significant difference. Likewise, postoperative PJK incidence showed no difference. Back pain can be caused by both AP and PO procedures, but which causes less pain remains to be conclusive. The PO approach showed less blood loss and shorter surgical duration as compared to the AP approach. Conclusions In summary, this meta-analysis shows similar treatment effects between AP and PO procedures in correcting Scheuermann's kyphosis, suggesting the advantage of PO procedures due to less blood loss and surgical duration. However, the postoperative complications PJK and distal junctional kyphosis (DJK) cannot be well concluded due to the limitation of existing data.

140. C2 pelvic angle (C2PA) is a useful intraoperative radiographic parameter that correlates with the risk of developing proximal junctional kyphosis postoperatively

<h3>BACKGROUND CONTEXT</h3> We established the first intraoperative parameter that directly correlates with postoperative proximal junctional kyphosis (PJK). C2 pelvic angle (C2PA) is a novel, intraoperative radiographic parameter used to assess for potential development of PJK. Intraoperative C2PA >15° is a critical angle with 2.5 times the relative risk for developing PJK. No patient with intraoperative C2PA <15° developed PJK. <h3>PURPOSE</h3> PJK is a postoperative complication of adult spinal deformity surgery that leads to poorer patient clinical outcomes. There is no literature on intraoperative assessment of sagittal alignment to prevent PJK. Intraoperative C2PA is a novel, radiographic parameter derived from the difference between global spinal alignment and the alignment proximal to the uninstrumented spine. The goal of this study is to demonstrate a positive relationship between the intraoperative C2PA and PJK. <h3>STUDY DESIGN/SETTING</h3> Prospectively collected cohorts. <h3>PATIENT SAMPLE</h3> Sixty deformity patients from 2015- 2018 who had preop, intraop, immediate postop and 2-year postop full length spine films. <h3>OUTCOME MEASURES</h3> Logistic regression and Chi-square analyses evaluated the relationship between the postop PJA and intraop C2PA/PJA. <h3>Methods</h3> We performed radiographic analysis on 60 deformity patients from 2015- 2018. Of the 60 patients, 35 were fused to the sacrum/pelvis. C2PA is defined as the angle between the posterior superior sacrum, C2 centroid and upper instrumented vertebrae (UIV) centroid and measured in the pre-, intra-, and postop setting (immediate and 2 years or prior to return to OR). PJK was defined as postop PJA >15°. Logistic regression and Chi-square analyses evaluated the relationship between the postop PJA and intraop C2PA/PJA. <h3>Results</h3> Of the 60 patients, 20 had PJK at the 2-year postop X-ray or prior to return to OR films. The intraop C2PA for the non-PJK and PJK group were 12.5° and 21.2°, respectively (p < 0.0001). The intraop PJA for the non-PJK and PJK group were 5.6° and 7.4°, respectively (p=0.04). The relative risk ratio of developing PJK for patients with intraop C2PA >15° was 2.43, and no one with intraop C2PA <15° developed PJK in the 2-year follow-up. <h3>Conclusions</h3> This is the first intraoperative measurement that demonstrates a direct correlation with PJK. Intraoperative C2PA >15° is a critical angle with 2.5 times the relative risk for developing PJK. No patient with intraoperative C2PA <15° developed PJK. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.