Sagittal Balance Parameters and Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis.

Background: To review and evaluate multiple preoperative and postoperative sagittal parameters and their association with the risk of developing proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS) who undergo correction surgery. Methods: A systematic search was performed in December 2022 in PubMed, Embase and the Cochrane Library to retrieve all the studies relevant to our research. After the study selection and data extraction following PRISMA guidelines, RevMan 5.3 was used for statistical analysis. All the analyzed factors were evaluated by using odds ratios and weighted mean differences with 95% confidence intervals. Moreover, the meta-analysis of proportions via MedCalc was used for analyzing quantitative data from the studies. Results: A total of 22 studies were included in our meta-analysis. All the available values of sagittal parameters were evaluated. Among all the potential risk factors, higher preoperative thoracic kyphosis (Test for overall effect Z = 11.79, p < 0.00001), higher preoperative sagittal vertical axis (SVA) (test for overall effect Z = 11.19, p < 0.00001), greater thoracic kyphosis change post-op. compared to pre-op. (test for overall effect Z = 6.02, p < 0.00001), increased postoperative lumbar lordosis (test for overall effect Z = 3.65, p = 0.0003), higher post-op. SVA (test for overall effect Z = 24.93, p < 0.00001) and a larger pelvic incidence/lumbar lordosis (PI/LL) mismatch (test for overall effect Z = 20.50, p < 0.00001) were found to be the risk factors for PJK after AIS surgery. Moreover, a decreased rod contour angle (RCA) (test for overall effect Z = 3.79, p < 0.0002) and higher proximal junctional angle-rod contour angle (PJA-RCA) (test for overall effect Z = 39.18, p < 0.00001) play a significant role in the risk of developing PJK after AIS correction. Conclusions: Sagittal balance is of great importance when considering the surgical correction of AIS. Many factors in our meta-analysis were found to increase the incidence for PJK such as higher preoperative thoracic kyphosis and pre-op. SVA. Furthermore, increased thoracic kyphosis change, increased post-operative lumbar lordosis, SVA and PI/LL mismatch are also factors that influence the possibility of post-op. PJK. Lastly, RCA and PJA-RCA are two important factors that need attention during AIS, as over-contouring of the rod could lead to PJK in AIS patients.

Low radius of curvature growth-friendly rib-based implants increase the risk of developing clinically significant proximal junctional kyphosis.

BACKGROUND: Clinically significant proximal junctional kyphosis (PJK) occurs in 20% of children with scoliosis treated with posterior distraction-based growth-friendly surgery. In an effort to identify modifiable risk factors, it has been theorized biomechanically that low radius of curvature (ROC) implants (i.e., more curved rods) may increase post-operative thoracic kyphosis, and thus may pose a higher risk of developing PJK. We sought to test the hypothesis that early onset scoliosis (EOS) patients treated with low ROC distraction-based implants will have a greater risk of developing clinically significant PJK as compared to those treated with high ROC (straighter) implants. METHODS: We conducted a retrospective review of prospectively collected data obtained from a multi-centre EOS database on children treated with rib-based distraction with a minimum 2-year follow-up. Variables of interest included: implant ROC at index (220 mm or 500 mm), participant age, pre-operative scoliosis, pre-operative kyphosis, and scoliosis etiology. PJK was defined as clinically significant if revision surgery with a superior extension of the upper instrumented vertebrae was performed. RESULTS: In 148 participants with scoliosis, there was a higher risk of clinically significant PJK with low ROC (more curved) rods (OR: 2.6 (95% CI 1.09-5.99), χ2 (1, n = 148) = 4.8, p = 0.03). Participants had a mean pre-operative age of 5.3 years (4.6y 220 mm vs 6.2y 500 mm, p = 0.002). A logistic regression model was created with age as a confounding variable, but it was determined to be not significant (p = 0.6). Scoliosis etiologies included 52 neuromuscular, 52 congenital, 27 idiopathic, 17 syndromic with no significant differences in PJK risk between etiologies (p = 0.07). Overall, participants had pre-op scoliosis of 69° (67° 220 mm vs 72° 500 mm, p = 0.2), and kyphosis of 48° (45° 220 mm vs 51° 500 mm, p = 0.1). The change in thoracic kyphosis pre-operatively to final follow-up (mean 4.0 ± 0.2 years) was higher in participants treated with 220 mm implants compared to 500 mm implants (220 mm: 7.5 ± 2.6° vs 500 mm: - 4.0 ± 3.0°, p = 0.004). CONCLUSIONS: Use of low ROC (more curved) posterior distraction implants is associated with a significantly greater increase in thoracic kyphosis which likely led to a higher risk of developing clinically significant PJK in participants with EOS. LEVEL OF EVIDENCE: Level III - retrospective comparative study.

The importance of Hounsfield units in adult spinal deformity surgery: finding an optimal threshold to minimize the risk of mechanical complications.

Background: Low bone mineral density (BMD) is a well-established risk factor for mechanical complications following adult spinal deformity (ASD) surgery. Hounsfield units (HU) measured on computed tomography (CT) scans are a proxy of BMD. In ASD surgery, we sought to: (I) evaluate the association of HU with mechanical complications and reoperation, and (II) identify optimal HU threshold to predict the occurrence of mechanical complications. Methods: A single-institution retrospective cohort study was undertaken for patients undergoing ASD surgery from 2013-2017. Inclusion criteria were: ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. HU were measured on 3 axial slices of one vertebra, either at the upper instrumented vertebra (UIV) itself or UIV ±4 from CT scans. Multivariable regression controlled for age, body mass index (BMI), postoperative sagittal vertical axis (SVA), and postoperative pelvic-incidence lumbar-lordosis mismatch. Results: Of 145 patients undergoing ASD surgery, 121 (83.4%) had a preoperative CT from which HU were measured. Mean age was 64.4±10.7 years, mean total instrumented levels was 9.8±2.6, and mean HU was 153.5±52.8. Mean preoperative SVA and T1PA were 95.5±71.1 mm and 28.8°±12.8°, respectively. Postoperative SVA and T1PA significantly improved to 61.2±61.6 mm (P<0.001) and 23.0°±11.0° (P<0.001). Mechanical complications occurred in 74 (61.2%) patients, including 42 (34.7%) proximal junctional kyphosis (PJK), 3 (2.5%) distal junctional kyphosis (DJK), 9 (7.4%) implant failure, 48 (39.7%) rod fracture/pseudarthrosis, and 61 (52.2%) reoperations within 2 years. Univariate logistic regression showed a significant association between low HU and PJK [odds ratio (OR) =0.99; 95% confidence interval (CI): 0.98-0.99; P=0.023], but not on multivariable analysis. No association was found regarding other mechanical complications, overall reoperations, and reoperations due to PJK. HU below 163 were associated with increased PJK on receiver operating characteristic (ROC) curve analysis [area under the curve (AUC) =0.63; 95% CI: 0.53-0.73; P<0.001]. Conclusions: Though several factors contribute to PJK, it appears that 163 HU may serve as a preliminary threshold when planning ASD surgery to mitigate the risk of PJK.

Operative choices matter: the role of UIV and sagittal balance in the development of proximal junctional kyphosis following posterior instrumentation for Scheuermann's kyphosis.

PURPOSE: This study sought to investigate associations between upper instrumented vertebra (UIV) location and the risk of proximal junctional kyphosis (PJK) at 2 years following posterior spinal fusion (PSF) for Scheuermann's kyphosis (SK). METHODS: In this retrospective cohort study, SK patients who underwent PSF and reached 2 years postop were identified in a multicenter international registry, excluding those with anterior release, prior spine surgery, neuromuscular comorbidity, post-traumatic kyphosis, or kyphosis apex below T11-T12. Location of UIV as well as the number of levels between UIV and preoperative kyphosis apex was determined. Additionally, the degree of kyphosis correction was evaluated. PJK was defined as a proximal junctional angle ≥ 10° that is ≥ 10° greater than the preoperative measurement. RESULTS: 90 patients (16.5 ± 1.9 yo, 65.6% male) were included. Preoperative and 2-year postoperative major kyphosis was 74.6 ± 11.6° and 45.9 ± 10.5°, respectively. Twenty-two (24.4%) patients developed PJK at 2 years. Patients with UIV below T2 had a 2.09 times increased risk of PJK when compared to those with UIV at or above T2, adjusting for distance between UIV and preoperative kyphosis apex [95% Confidence Interval (CI) 0.94; 4.63, p = 0.070]. Patients with UIV ≤ 4.5 vertebrae from the apex had a 1.57 times increased risk of PJK, adjusting for UIV relative to T2 [95% CI 0.64; 3.87, p = 0.326]. CONCLUSION: SK patients with UIV below T2 had an increased risk of developing PJK at 2 years following PSF. This association supports consideration of UIV location during preoperative planning. LEVEL OF EVIDENCE: Prognostic Level II.

Biomechanics of adjacent segment after three-level lumbar fusion, hybrid single-level semi-rigid fixation with two-level lumbar fusion.

Multi-level spinal fusion has been reported in some cases to lead to adjacent segment disease (ASD) and proximal junctional kyphosis (PJK). The purpose of this study was to demonstrate a polyether-ether-ketone (PEEK) rod fixation system implanted adjacent to a two-level lumbar fusion would have a lower risk of PJK than three-level lumbar fusion, which was investigated by comparing the biomechanical effects on the adjacent level after surgical procedures. Four finite element (FE) models of the lumbar-sacral spine (intact model (INT), L4-S1 fusion model (L4-S1 FUS), L3-S1 fusion model (L3-S1 FUS), and single-level PEEK rod semi-rigid fixation adjacent to L4-S1 fusion model (FUSPRF)) were established. Displacement-controlled finite element (FE) analysis was used during the simulation. Compared with the two-level fusion model (L4-S1 FUS), both three-level implanted models (L3-S1 FUS and FUSPRF) showed an increase intersegmental rotation angle, and maximum von-Mises stress on the disc annulus. The results also showed that the intersegmental rotation, stress on the disc annulus and maximum stress on the rod were lower in the FUSPRF model than the L3-S1 FUS model. Though the maximum screw stress was higher in the FUSPRF model than the L3-S1 FUS model under all moments except for torsion, the maximum screw stress in the two models were far below the yield strength of titanium alloy. As the parameters above have been indicated as risk factors for PJK, it can be concluded that hybrid single-level PEEK rod semi-rigid fixation and two-level lumbar fusion have a lower risk of PJK than three-level lumbar fusion.

CT based bone mineral density as a predictor of proximal junctional fractures.

Background: Proximal junctional fractures (PJFr) can be a catastrophic complication associated with adult spinal deformity surgery. Osteoporosis can be a major risk factor for the cause of PJFr. Recent studies suggest using surrogate computed tomography (CT) scans in place of spinal dual-energy x-ray absorptiometry (DEXA) scores for bone mineral density (BMD). Investigate the feasibility of using preoperative CT based bone mineral density at upper instrumented vertebrae (UIV) and one level proximally (UIV+1) and distally (UIV-1) to predict the possibility of PJFr risk. Methods: Retrospective two-academic center case-controlled study, reviewed consecutive adult spinal deformity surgeries; included constructs encompassing at least five fusion levels and fusions to pelvis. Examined demographic, surgical, and radiographic data preoperatively, postoperatively, and final follow-up. Formed groups based on type of proximal junctional deformity (PJD): Control (no PJD), proximal junctional kyphosis (PJK) and PJFr. Preoperative CT BMD values measured in Hounsfield units (HU) for sagittal and axial planes at UIV, UIV+1, and UIV-1 and compared between groups. Results: N=92 patients. Preoperative CT scan BMD values were significantly lower in PJFr vs. control at: UIV+1 in sagittal (p=0.007), axial (p=0.02) planes; UIV sagittal (p=0.04) and axial (p=0.03) planes; and UIV-1 sagittal (p=0.05) plane. Similarly, lower CT scan BMD values noted in PJFr vs. PJK at: UIV+1 in sagittal (p=0.04) and axial (p=0.03) planes. Trend seen with lower CT scan BMD values at UIV+1 level in PJFr vs. PJK in sagittal (p=0.12) and axial (p=0.10) planes. Preoperative global sagittal imbalance measurements significantly lower in control, but comparable between PJK and PJFr. Conclusions: Higher preoperative global sagittal imbalance with lower preoperative CT BMD values at UIV and UIV+1 vertebral body may increase the risk of proximal junctional fractures after adult spine deformity surgery. Proximal junctional hooks may supplement the pathogenesis. Readers should note the small sample size.Level of Evidence: 3.

Proximal junctional kyphosis post tuberculous spine corrective surgery in paediatric patients.

STUDY DESIGN: Retrospective case series. Proximal junctional kyphosis (PJK) is a well-recognised post-operative complication of deformity correction surgery. Our local tuberculosis (TB) endemic is responsible for severe kyphotic deformities. The most challenging is in the paediatric environment where powerful instrumentation is used in immature spines with more flexible disco-ligamentous structures than adults. OBJECTIVE: To establish the incidence of PJK and management thereof in our paediatric TB spine patients undergoing corrective surgery. METHODS: Twenty-seven consecutive paediatric patients undergoing fusion surgery for TB spine with 2-year follow-up were identified from our prospectively maintained database. Age at surgery was 8.0 years (2.5-17 ± 3.98) with 14 under the age of 7. Only anterior surgery was performed in 1, posterior only in 13 and combined in 13 with a total of 5 (1-11) levels fused. RESULTS: Nine (33.3%) patients developed PJK (progression by > = 10°) with an average progression of 16.2°(11-26 ± 5.42) compared the overall cohorts change of 5.1°(- 26-15 ± 9.24). Although not reaching statistical significance, there was a trend to higher incidence of PJK when instrumented, 8/20 (40%) compared to 1/7 (14.3%), more so in posterior only surgery compared to combined, 6/13 (46.2%) compared to 3/13 (23.1%) and when the UIV was at T7 or above, 7/17 (41.2%) compared to 2/10 (20%). There was a higher PJK rate when the number of levels fused was > = 6, 7/12 (58.3%) compared to 2/10 (p = 0.014), when the kyphotic correction was more than 39º, 5/8 (62.5%) compared to 4/19 (21.1%) (p = 0.07) and when < = 7 years old, 7/14 (50%) compared to 2/13 (15.4%) (p = 0.05). Two of the nine PJK cases required revision for junctional failure. CONCLUSION: In paediatric TB kyphosis correction, there was a 33% incidence of PJK with 2/9 requiring revision surgery for proximal failure. Our data suggest that this incidence of PJK was related to the magnitude of correction, the number of levels fused with a trend of increase in higher UIVs, posterior approach and instrumentation.This suggests that in young children, one should be cautious of overzealous kyphosis correction due to the risk of catastrophic proximal junctional failure.

Soft Landing technique as a possible prevention strategy for proximal junctional failure following adult spinal deformity surgery.

BACKGROUND: This cross sectional study describes a "Soft Landing" strategy utilizing hooks for minimizing proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). The technique creates a gradual transition from a rigid segmental construct to unilateral hooks at the upper instrumented level and preservation of the soft tissue attachments on the contralateral side of the hooks. Authors devise a novel classification system for better grading of PJK severity. METHODS: Thirty-nine consecutive adult spinal deformity (ASD) patients at a single institution received the "Soft Landing" technique. The proximal junctional angle was measured preoperatively and at last follow-up using standing 36-inch spinal radiographs. Changes in proximal junctional angle and rates of PJK and PJF were measured and used to create a novel classification system for evaluating and categorizing ASD patients postoperatively. RESULTS: The mean age of the cohort was 61.4 years, and 90% of patients were women. Average follow up was 2.2 years. The mean change in proximal junctional angle was 8° (SD 7.4°) with the majority of patients (53%) experiencing less than 10° and only 1 patients with proximal junctional angle over 20°. Four patients (10%) needed additional surgery for proximal extension of the uppermost instrumented vertebra (UIV) secondary to PJF. CONCLUSIONS: Soft Landing technique is a possibly effective treatment strategy to prevent PJK and PJF following ASD that requires further evaluation. The described classification system provides management framework for better grading of PJK. The "Soft Landing" technique warrants further comparison to other techniques currently used to prevent both PJK and failure.

The prevalence of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) in patients undergoing circumferential minimally invasive surgical (cMIS) correction for adult spinal deformity: long-term 2- to 13-year follow-up.

OBJECTIVES: This aim of this study is to evaluate the prevalence of PJK and PJF in patients who underwent circumferential minimally invasive surgery (cMIS) for ASD. METHODS: A prospective database of patients who underwent cMIS correction of ASD from November 2006 to July 2018 was queried. PJK was defined as angle > 10° and at least 10° greater than the baseline when measuring UIV to UIV + 2. PJF was defined as any type of symptomatic PJK which required surgery. Pre-op, latest and delta SVA and PI-LL mismatch were compared between patients with PJK and without. Only patients instrumented at 4 or more levels with full length 36″ films and a minimum 2-year follow-up were included. RESULTS: A total of 184 patients met inclusion criteria for this study. Mean follow-up time was 85.2 months (24-158.9 months, SD 39.1). Mean age was 66 years (22-85 years). The mean number of operated levels was 6.9 levels (4-16 levels, SD 2.8). A total of 21 patients (10.8%) met PJK criteria. Only 10 (4.9%) were symptomatic (PJF) and underwent revision surgery. The other 11 patients remained asymptomatic. Comparing PJK to non-PJK patients, there was no statistically significant difference in the post-op SVA, delta SVA, post-op PI/LL and delta PI/LL between the two groups. CONCLUSION: Our study would suggest that in the appropriately selected and well-optimized patient, CMIS deformity correction is associated with a low prevalence of PJK and PJF.

Short-segment minimally disruptive anterior column release for focal sagittal deformity correction of the thoracolumbar spine.

BACKGROUND: Sagittal malalignment is associated with poor quality of life. Correction of lumbar lordosis through anterior column release (ACR) has been shown to improve overall sagittal alignment, however typically in combination with long posterior constructs and associated morbidity. The technical feasibility and radiographic outcomes of short-segment anterior or lateral minimally invasive surgery (MIS) ACR techniques in moderate to severe lumbar sagittal deformity were evaluated. METHODS: Consecutive patients treated with short-segment MIS ACR techniques for moderate to severe lumbar sagittal deformity correction were retrospectively analyzed from a prospectively collected database. Clinical outcomes included perioperative measures of invasiveness, including operative time, blood loss, complications, and average length of stay. Radiographic outcomes included measurement of preoperative, immediate postoperative, and long-term follow-up radiographic parameters including coronal Cobb angle, lumbar lordosis (LL), pelvic incidence (PI), PI-LL mismatch, pelvic tilt (PT), T1 pelvic angle (TPA), T1 spino-pelvic inclination (T1SPI), proximal junctional angle (PJA), and sagittal vertical axis (SVA). RESULTS: The cohort included 34 patients (mean age 63) who were treated at an average 2.5 interbody levels (range 1-4) through a lateral or anterior approach (LLIF or ALIF). Of 89 total interbody levels treated, 63 (71%) were ACR levels. Posterior fixation was across an average of 3.2 levels (range 1-5). Mean total operative time and blood loss were 362 minutes and 621 mL. Surgical complications occurred in 2 (5.9%). Average hospital stay was 5.5 days (including staging). At last follow-up (average 25.4 months; range 0.5-7 years), all patients (100%) demonstrated successful achievement of one or more alignment goal, with significant improvements in coronal Cobb, LL, PI-LL mismatch, PT, and TPA. No patient was revised for PJK. CONCLUSIONS: These data show that short-segment MIS ACR correction of moderate to severe lumbar sagittal deformity is feasible and effective at achieving overall alignment goals with low procedural morbidity and risk of proximal junctional issues.

Proximal junction kyphosis after posterior spinal fusion for early-onset scoliosis.

STUDY DESIGN: Retrospective study. OBJECTIVE: The aim of this study was to assess the presence of proximal junctional kyphosis (PJK) in our population of children with early-onset scoliosis (EOS) and to identify the predisposing factors for the development of PJK in the postoperative period after posterior spinal fusion (PSF). Few studies have been conducted to evaluate the incidence of proximal junction kyphosis (PJK) in children after early-onset scoliosis (EOS) after posterior spinal fusion (PSF). MATERIALS AND METHODS: Overall, 114 pediatric patients aged < 10 years who underwent surgery for scoliosis or kyphoscoliosis at a single center between 2013 and 2015 were evaluated. Forty-five patients submitted to PSF of five or more levels met the inclusion criteria. The sample included 12 female and 10 male patients. Mean age at surgery was 7 years and 8 months. RESULTS: PJK was observed in 22 patients (48.9%). Overall, the mean proximal junctional angle at 12 and 36 months was 17.1° and 22°, respectively. The uppermost instrumented vertebra (UIV) with the highest PJK rate was T6-T7. The lowest instrumented vertebra (LIV) with the highest PJK rate was L2. Etiology was idiopathic in 4, neuromuscular in 11, congenital in 14, and syndromic in 16. According to underlying disorder, prevalence of PJK was 78% in those with a congenital, 50% in those with a syndromic, 12% in those with idiopathic, and 9% in those with a neuromuscular EOS. Surgical revision rate was 4% (one patient). Mean postoperative follow-up was of 3 years and 4 months (range 3-4 years and 1 month). CONCLUSION: Congenital and syndromic etiology, but not age at PJK onset or sex of the patient, significantly affected the incidence rate of PJK. The UIV with the highest PJK rate was T6-T7 and the LIV with the highest PJK rate was L2. The patients had a low surgical revision rate. LEVEL OF EVIDENCE: Level IV.

Surgical, Radiographic, and Patient-Related Risk Factors for Proximal Junctional Kyphosis: A Meta-Analysis.

STUDY DESIGN: Meta-analysis. OBJECTIVE: Proximal junctional kyphosis (PJK) is a complication of surgical management for adult spinal deformity with a multifactorial etiology. Many risk factors are controversial and their relative importance are not fully understood. We aimed to identify the surgical, radiographic, and patient-related risk factors associated with PJK and proximal junctional failure (PJF). METHODS: A systematic literature search was performed using PubMed, Cochrane Database of Systematic Reviews, and EMBASE. The inclusion criteria included prospective randomized control trials and prospective/retrospective cohort studies of adult patients with radiographic evidence of PJK, which was defined as a proximal junctional sagittal Cobb angle ≥10° and at least 10° greater than the preoperative measurement. Studies required a minimum of 10 patients and 12 months of follow-up. RESULTS: A total of 14 unique studies, including 1908 patients were included. The pooled analysis showed significant differences between the PJK and non-PJK groups in age (weighted mean difference [WMD] -3.80; P = .03), prevalence of osteopenia/osteoporosis (odds ratio [OR] 1.99; P = .0004), preoperative sagittal vertical axis (SVA) (WMD -17.52; P = .02), preoperative lumbar lordosis (LL) (WMD -1.22; P = .002), pedicle screw instrumentation at the upper instrumented vertebra (UIV) (OR 1.67; P = .02), change in SVA (WMD -11.87; P = .01), fusion to sacrum/pelvis/ilium (OR 2.14; P < .00 001), change in LL (WMD -5.61; P = .01), and postoperative SVA (WMD -7.79; P = .008). CONCLUSIONS: Our meta-analysis suggests that age, osteopenia/osteoporosis, high preoperative SVA, high postoperative SVA, low preoperative LL, use of pedicle screws at the UIV, SVA change/correction, LL change/correction, and fusion to sacrum/pelvis/iliac region are risk factors for PJK.

Reciprocal Changes in Sagittal Alignment With Operative Treatment of Adolescent Scheuermann Kyphosis-Prospective Evaluation of 96 Patients.

INTRODUCTION: Sagittal alignment abnormalities in Scheuermann kyphosis (SK) strongly correlate with quality of life measures. The changes in spinopelvic parameters after posterior spinal fusion have not been adequately studied. This study is to evaluate the reciprocal changes in spinopelvic parameters following surgical correction for SK. METHODS: Ninety-six operative SK patients (65% male; age 16 years) with minimum 2-year follow-up were identified in the prospective multicenter study. Changes in spinopelvic parameters and the incidence of proximal (PJK) and distal (DJK) junctional kyphosis were assessed as were changes in Scoliosis Research Society-22 (SRS-22) questionnaire scores. RESULTS: Maximum kyphosis improved from 74.4° to 46.1° (p < .0001), and lumbar lordosis was reduced by 10° (-63.3° to -53.3°; p < .0001) at 2-year postoperation. Pelvic tilt, sacral slope, and sagittal vertical axis remained unchanged. PJK and DJK incidence were 24.2% and 0%, respectively. In patients with PI <45°, patients who developed PJK had greater postoperative T2-T12 (54.8° vs. 44.2°, p = .0019), and postoperative maximum kyphosis (56.4° vs. 44.6°, p = .0005) than those without PJK. In patients with PI ≥45°, patients with PJK had less postoperative T5-T12 than those without (23.6° vs. 32.9°, p = .019). Thoracic and lumbar apices migrated closer to the gravity line after surgery (-10.06 to -4.87 mm, p < .0001, and 2.28 to 2.10 mm, p = .001, respectively). Apex location was normalized to between T5-T8 in 68.5% of patients with a preoperative apex caudal to T8, whereas 90% of patients with a preoperative apex between T5 and T8 remained unchanged. Changes in thoracic apex location and lumbar apex translation were associated with improvements in the SRS function domain. CONCLUSION: PJK occurred in 1 in 4 patients, a lower incidence than previously reported perhaps because of improved techniques and planning. Both thoracic and lumbar apices migrated closer to the gravity line, and preoperative apices caudal to T8 normalized in more than two-thirds of patients, resulting in improved postoperative function. Individualizing kyphosis correction to prevent kyphosis and PI mismatch may be protective against PJK.

Proximal junctional kyphosis in adult spinal deformity with long spinal fusion from T9/T10 to the ilium.

BACKGROUND: Proximal junctional kyphosis (PJK) is a common complication after corrective long spinal fusion for adult spinal deformity. Although some reports evaluated PJK after corrective long spinal fusion, there is no report about analysis of PJK cases in the same fusion area. The purpose of this study to investigated the incidence of and risk factors for PJK in adults undergoing long spinal fusion from the distal thoracic vertebrae (T9/T10) to the ilium. METHODS: We enrolled 56 adult patients (>40 years of age) who underwent posterior corrective surgery with same fusion area from T9 or T10 to the ilium for spinal deformity. Pre- and postoperative radiographic measurements included the sagittal vertical axis (SVA), lumbar lordosis (LL), thoracic kyphosis (TK), pelvic tilt (PT), and pelvic incidence minus LL (PI-LL). The Oswestry disability index (ODI) was used to evaluate patient outcomes preoperatively and one year after surgery. We analyzed the incidence for PJK and compared PJK and non-PJK cases. RESULTS: PJK at the final follow-up occurred in 19 of 56 (33.9%) patients. The mean age and ODI were not significantly different between the PJK and non-PJK groups. Both two groups had good spinopelvic sagittal alignment after surgery in terms of SVA and PI-LL. Only three cases required revision surgery for symptomatic PJK. Three cases had history of rheumatoid arthritis and/or total hip arthroplasty surgery. CONCLUSIONS: The incidence of PJK was 33.9%, and ODI was not significantly different between the PJK and non-PJK groups. Symptomatic PJK was only three cases and all of them had lower extremity joint disorders. We should pay attention also lower extremity joint to prevent symptomatic PJK at the lower thoracic level.

Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis-The Pelvis and Other Considerations.

STUDY DESIGN: Prospective multicenter database study. OBJECTIVES: To assess the incidence of proximal junctional kyphosis (PJK) in operative adolescent idiopathic scoliosis (AIS) using contemporary surgical techniques and to identify risk factors for PJK. SUMMARY OF BACKGROUND DATA: The incidence of PJK has been reported as high as 46% in AIS. Factors associated with PJK have been incompletely explored. METHODS: Prospectively enrolled 851 AIS patients (2000-2011, 78.5% female, average 14.4 years) were evaluated 2 years postoperatively. Radiographic and sagittal spinopelvic parameters and rod contour angle (RCA), a new measure that reflects the proximal contouring of the rod, were independently evaluated for association with PJK based on Lenke type. Multivariate logistic regression with backward elimination was performed to identify risk factors for PJK. RESULTS: Overall PJK incidence was 7.05% and varies based on Lenke type (Lenke 1, 6.35%; Lenke 2 and 4, 4.39%; Lenke 3 and 6, 11.64%; and Lenke 5, 8.49%; p = .06). Among patients with Lenke 1 curves, risk factors for PJK were loss of kyphosis after surgery, and stopping caudal to the upper end vertebra (UEV). The risk of developing PJK increases by 7.1% with each lost degree of kyphosis compared with preoperation that occurs after the instrumentation is placed. For Lenke 2 and 4 curves, loss of kyphosis and more lordotic (negative) RCA were risk factors for PJK. For Lenke 3 and 6 curves, larger preoperative T5-T12 kyphosis was the only significant risk factor for PJK. Upper instrumented vertebra (UIV) at or cephalad to the UEV was associated with increased risk of PJK in Lenke 5 curves, which was contrary to the finding for Lenke 1 curves. No significant correlation was found between sagittal pelvic parameters and developing PJK. CONCLUSION: The incidence of PJK in patients after surgery for AIS is 7.05% and varies based on Lenke type. Loss of kyphosis, larger preoperative kyphosis, UIV caudal to the proximal UEV (Lenke 1), UIV at or cephalad to the UEV (Lenke 5), and decreased RCA were the major risk factors for PJK in AIS. LEVEL OF EVIDENCE: Level II.

Correlation between preoperative spinopelvic alignment and risk of proximal junctional kyphosis after posterior-only surgical correction of Scheuermann kyphosis.

BACKGROUND CONTEXT: Surgical correction of Scheuermann kyphosis (SK) is challenging and plagued by relatively high rates of proximal junctional kyphosis and failure (PJK and PJF). Normal sagittal alignment of the spine is determined by pelvic geometric parameters. How these parameters correlate with the risk of developing PJK in SK is not known. PURPOSE: The study aimed to investigate the relationship between preoperative and postoperative spinopelvic alignment and occurrence of PJK and PJF. STUDY DESIGN/SETTING: This is a retrospective observational cohort study. PATIENT SAMPLE: The sample included 37 patients who underwent posterior correction of SK from January 2006 to December 2012. OUTCOME MEASURES: The outcome measure was correlation analysis between preoperative and postoperative spinopelvic alignment parameters and the development of PJK over the course of the study period. METHODS: Whole spine x-rays obtained before surgery, 3 months after surgery, and at the latest follow-up were analyzed. The following parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), and sacral slope (SS). The development of PJK was considered the primary end point of the study. Patient population was split into a control and a PJK group; repeated-measures analysis of variance was used to assess group and time differences. RESULTS: Seven patients developed PJK over the study period. Although the severity of the preoperative deformity (TK) did not differ significantly between the two groups, preoperative PI was significantly higher in the PJK group (51.9°C±8.6°C vs. 42.7°C±8.8°C, p=.018). Postoperative correction of TK was similar between the two groups (39.3% and 41.2%, p=.678) and final LL did not differ as well (53.6°C±9.2°C vs. 51.3°C±11.5°C). However, because PJK patients had larger preoperative PI values, a significant deficit of LL was observed at final follow-up in this group compared with the control group (ΔLL -10.5°C±9.8°C vs. 0.6°C±10.5°C, p=.013). CONCLUSIONS: Scheuermann kyphosis patients who developed PJK appeared to have a significant postoperative deficit of LL (lumbopelvic mismatch). Lumbar lordosis decreases after surgery following correction of TK; therefore, TK correction should be planned according to preoperative PI values to avoid excessive reduction of LL in patients with higher PI values.