Proximal kyphosis after posterior spinal fusion in patients with idiopathic scoliosis

Systematic review and meta-analysis for the proximal junctional kyphosis in adolescent idiopathic scoliosis

Objective

The risk factors of PJK (proximal junctional kyphosis) related to AIS (adolescent idiopathic scoliosis) are inconsistent due to heterogeneity in study design, diagnostic criteria, and population. Therefore, the meta-analysis was conducted to investigate the factors affecting PJK after posterior spinal fusion for AIS patients.

Methods

We implemented a systematic search to obtain potential literature relevant to PJK in AIS surgery. Then, a meta-analysis was performed to assess the incidence of PJK and its risk factors.

Results

We retrieved 542 articles, and 24 articles were included. The PJK incidence was 17.67%. The use of hooks at UIV (upper instrumented vertebrae) (p = 0.001) could prevent PJK. Before surgery, the larger TK (thoracic kyphosis) (p < 0.001), GTK (global thoracic kyphosis) (p < 0.001), and LL (lumbar lordosis) (p < 0.001) were presented in the PJK group. Immediately post-operatively, in the PJK group, the following parameters were higher: TK (p = 0.001), GTK (p < 0.001), LL (p = 0.04), PJA (proximal junctional angle) (p < 0.001), and PJA-RCA (rod contouring angle) (p = 0.001). At the final follow-up, the following parameters were higher in the PJK group: TK (p < 0.001), GTK (p < 0.001), LL (P < 0.001), and PJA (P < 0.001). Sub-group analysis detected that before surgery, the following parameters were larger in the PJK group: TK (p < 0.001), LL (p = 0.005), and PJA (p = 0.03) in Lenke type 5 AIS patients. Immediately post-operatively, in the PJK group, the following parameters were higher: TK (p < 0.001), LL (p = 0.005), and PJA (p < 0.001). At the final follow-up, the following parameters were higher in the PJK group: TK (p < 0.001), LL (p < 0.001), and PJA (p < 0.001).

Conclusion

The individuals with larger preoperative TK were more susceptible to PJK, and PJA was mainly influenced by the adjacent segments rather than the whole sagittal alignment. Using hooks or claws at UIV should prevent PJK.

Excessive posterior placement of upper instrumented vertebra relative to lower instrumented vertebra as a predictor of proximal junction kyphosis after selective spinal fusion for adolescent idiopathic scoliosis Lenke type 5C curves

PURPOSE

We defined sagittal S-line tilt (SSLT) as the tilt of the line connecting the upper instrumented vertebra and the lower instrumented vertebra. This study aimed to: (1) examine the correlation between SSLT and proximal junctional angle (PJA) change values, and (2) determine the cut-off value of SSLT with respect to proximal junctional kyphosis (PJK) occurrence.

METHODS

Eighty-six consecutive patients (81 female and 5 male; mean age: 15.8 years) with Lenke 5C AIS who underwent posterior selective spinal fusion. Pearson's correlation coefficients were used to examine the relationship between preoperative SSLT and changes in PJA from preoperative to 2 years postoperative. The impact of SSLT on PJK at 2 years after surgery was assessed using a receiver operating characteristic (ROC) curve.

RESULTS

We observed a moderate positive correlation between preoperative SSLT and change in PJA (R = 0.541, P < 0.001). We identified 18 patients (21%) with PJK at 2 years postoperative. Mean preoperative SSLT in the PJK group and the non-PJK group differed significantly at 23.3 ± 4.1° and 16.1 ± 5.0°, respectively (P < 0.001). The cut-off value of preoperative SSLT for PJK at 2 years postoperative was 18° in ROC curve analysis, with a sensitivity of 94%, specificity of 68%, and area under the ROC curve of 0.868.

CONCLUSION

In selective lumbar fusion for AIS Lenke type 5C curves, preoperative SSLT was significantly correlated with PJA change from preoperative to 2 years postoperative. SSLT was a predictor of PJK occurrence, with a cut-off value of 18°.

Evaluating the biomechanical effects of pedicle subtraction osteotomy at different lumbar levels: a finite element investigation

BACKGROUND

Pedicle subtraction osteotomy (PSO) is effective for correcting spinal malalignment but is associated with high complication rates. The biomechanical effect of different PSO levels remains unclear, and no finite element (FE) analysis has compared L2-, L3-, L4-, and L5-PSOs.

PURPOSE

To assess the effects of PSO level on the spine's global range of motion, stresses on posterior instrumentation, load sharing with the anterior column, and proximal junctional stresses.

STUDY DESIGN

A computational biomechanical analysis.

METHODS

A validated 3D spinopelvic FE model (T10-Pelvis) was used to perform PSOs at L2, L3, L4 and L5. Each model was instrumented with a 4-rod configuration (primary rods + in-line satellite rods) from T11-Pelvis. Simulation included a 2-step analysis; (1) applying 300 N to thoracic, 400 N to lumbar, and 400 N to sacrum, and (2) applying a 7.5 Nm moment to the top endplate of the T10 vertebral body. Acetabulum surfaces were fixed in all degrees of freedom. The range of motion, spinopelvic parameters (lumbar lordosis [LL], sacral slope [SS], pelvic incidence [PI], and pelvic tilt [PT]), PSO force, and von Mises stresses were measured. All models were compared with the L3-PSO model and percentage differences were captured.

RESULTS

Compared to the intact alignment: LL increased by 48%, 45%, 59%, and 56% in the L2-, L3-, L4-, and L5-PSO models; SS increased by 25%, 15%, and 11% while PT decreased by 76%, 53%, and 45% in L2-, L3-, and L4-PSOs (SS and PT approximated intact model in L5-PSO); Lumbar osteotomy did not affect the PI. Compared to L3-PSO: L2-, L4-, and L5-PSOs showed up to 32%, 34%, and 34% lower global ROM. The least T10-T11 ROM was observed in L5-PSO. The left and right SIJ ROM were approximately similar in each model. Amongst all, the L5-PSO model showed the least ROM at the SIJ. Compared to L3-PSO, the L2-, L4-, and L5-PSO models showed up to 67%, 61%, and 78% reduced stresses at the UIV, respectively. Minimum stress at UIV+ was observed in the L3-PSO model. The L2-and L3-PSOs showed the maximum PSO force. The L5-PSO model showed the lowest stresses on the primary rods in all motions.

CONCLUSION

Our FE investigation indicates that L5-PSO results in the greatest lumbar lordosis and lowest global, SIJ, and T10-T11 ROMs and stresses on the primary rods, suggesting potential mechanical benefits in reducing the risk of rod breakage. However, L4- and L5-PSOs led to the least force across the osteotomy site, which may increase the risk of pseudarthrosis. These findings provide biomechanical insights that may inform surgical planning, though further clinical investigation is essential to determine the optimal PSO level and validate these results.

CLINICAL SIGNIFICANCE

Understanding the biomechanical impact of PSO level is crucial for optimizing surgical outcomes and minimizing the risks of postoperative complications.

A comparison of idiopathic scoliosis surgery between teenage years and adulthood

PURPOSE

Idiopathic scoliosis is an evolutive deformity during patient's life. In case of moderate deformity in a well aligned adolescent, it's a big concern to decide when to do the surgery. Objective of this work was to evaluate and compare clinical, radiological and surgical data of patients with adolescent idiopathic scoliosis operated in childhood (before 20 years) and those operated adults (after 35 years).

METHODS

In this retrospective multicenter study, inclusion period extended from 2008 to 2018. Two groups were defined, those operated on before the age of 20 (YAIS), and those operated on after 35 years (OAIS). Demographic, radiographic and surgical data were collected. At follow-up, radiographic data and functional outcomes (VAS, SRS, SF12, Oswestry) were analyzed. Minimum FU was 5 years for young and 2 years for old patients.

RESULTS

YAIS group included 364 patients, and OAIS group, 131 patients. In both groups, deformity was important (mean Cobb 63°). Vertebral osteotomies were significantly more frequent, fusions and length of stays were longer for old than young patients. Main Cobb correction was better in young than old (37 ± 10° vs 2 ± 13°, p = 0.03). Functional outcomes were better for young, operated patients than for operated groups after 35 years (SF12 PCS 50 ± 7 vs 39 ± 6, p = 0.02). The same trends were observed at longer follow-up.

CONCLUSION

Surgery for idiopathic scoliosis seems to offer a better quality of life and deformity correction when it is performed at adolescence. After 35 years, surgery remains an acceptable therapeutic option, despite higher complication rate.

Can We Rely on Prophylactic Two-Level Vertebral Cement Augmentation in Long-Segment Adult Spinal Deformity Surgery to Reduce the Incidence of Proximal Junctional Complications?

Background and Objectives: Proximal junctional kyphosis (PJK) and failure (PJF), the most prevalent complications following long-segment thoracolumbar fusions for adult spinal deformity (ASD), remain lacking in defined preventive measures. We studied whether one of the previously reported strategies with successful results-a prophylactic augmentation of the uppermost instrumented vertebra (UIV) and supra-adjacent vertebra to the UIV (UIV + 1) with polymethylmethacrylate (PMMA)-could also serve as a preventive measure of PJK/PJF in minimally invasive surgery (MIS). Materials and Methods: The study included 29 ASD patients who underwent a combination of minimally invasive lateral lumbar interbody fusion (MIS-LLIF) at L1-2 through L4-5, all-pedicle-screw instrumentation from the lower thoracic spine to the sacrum, S2-alar-iliac fixation, and two-level balloon-assisted PMMA vertebroplasty at the UIV and UIV + 1. Results: With a minimum 3-year follow-up, non-PJK/PJF group accounted for fifteen patients (52%), PJK for eight patients (28%), and PJF requiring surgical revision for six patients (21%). We had a total of seven patients with proximal junctional fracture, even though no patients showed implant/bone interface failure with screw pullout, probably through the effect of PMMA. In contrast to the PJK cohort, six PJF patients all had varying degrees of neurologic deficits from modified Frankel grade C to D3, which recovered to grades D3 and to grade D2 in three patients each, after a revision operation of proximal extension of instrumented fusion with or without neural decompression. None of the possible demographic and radiologic risk factors showed statistical differences between the non-PJK/PJF, PJK, and PJF groups. Conclusions: Compared with the traditional open surgical approach used in the previous studies with a positive result for the prophylactic two-level cement augmentation, the MIS procedures with substantial benefits to patients in terms of less access-related morbidity and less blood loss also provide a greater segmental stability, which, however, may have a negative effect on the development of PJK/PJF.

Digital Phenotyping, Wearables, and Outcomes

There is a significant need for robust and objective outcome assessments in spine surgery. Constant monitoring via smartphones and wearable devices has the potential to fill this role by providing an in-depth picture of human well-being, creating an unprecedented amount of objective data to augment clinical decision-making. The metrics obtained from continuous patient monitoring increase the amount and ecological validity of data relevant to spine surgery. This can provide physicians with patient and disease-specific medical information, facilitating personalized patient care.

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.

Flexibility-tilt agreement best predicts shoulder balance following posterior spine fusion for adolescent idiopathic scoliosis

PURPOSE

We propose a novel concept, called flexibility-tilt agreement (FTA), which could be applied intra-operatively to improve shoulder balance following posterior spine fusion for Adolescent Idiopathic Scoliosis (AIS). We retrospectively applied this concept to a cohort with thoracic-only curves, seeking to: (1) evaluate the impact of FTA and other peri-operative variables on post-operative shoulder balance, and (2) evaluate deformity characteristics associated with achieving FTA.

METHODS

A single-institution registry was queried for patients undergoing PSF from 2000 to 2017 with main thoracic and double thoracic curves with at least 2-year follow-up. Flexibility was defined as the Cobb angle of the unfused proximal thoracic curve (cephalad to chosen UIV) on pre-operative bender. Tilt refers to post-operative UIV tilt angle. FTA means these values cancel (Flexibility + Tilt = 0 ± 5°). Logistic regression was performed to determine the association between peri-operative variables and shoulder balance.

RESULTS

One hundred and sixty-one patients were included, mean age 13.6 years old, and 47-month mean follow-up. FTA was achieved in 74 (46%) patients and was associated with post-operative (OR = 4.59) and final (OR = 6.98) medial shoulder balance with a threshold of 6° (AUC = 0.77, p = 0.038). FTA was the best predictor of shoulder balance of all tested variables.

CONCLUSION

Patients that showed flexibility-tilt agreement, or FTA, had vastly increased odds of medial and lateral shoulder balance at a minimum of 2-year follow-up for all thoracic curves. Future studies can evaluate whether applying FTA to determine intra-operative corrective maneuvers prospectively leads to improvements in shoulder balance.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

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

BACKGROUND

Although 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.

METHODS

A 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.

RESULTS

PJK 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.

CONCLUSION

Large 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.

Risk factors for proximal junctional kyphosis in a multicenter study of Lenke type 5 and 6 adolescent idiopathic scoliosis patients

PURPOSE

In Lenke type 5 and 6 curves, a major thoracolumbar or lumbar curve, the rates of PJK are reported as high as 50%. The purpose of this study was to confirm the rate of PJK, investigate possible risk factors, and evaluate surgical complications and the long-term effects of PJK on patient outcomes.

METHODS

A retrospective review of multicenter data identified 192 with patients with 2 year and 94 with 5-year follow-up. Included patients had a Lenke type 5 or 6 curve and underwent a selective thoracolumbar or lumbar curve fusion. All radiographs preoperatively and postoperatively (1 year, 2 years, and 5 years) were evaluated. Demographic and radiographic data was analyzed as risk factors for PJK using a multi-variate regression. Outcomes scores and complications were compared between groups.

RESULTS

17 patients (8.9%) developed radiographic PJK; 1 at 1 year, 7 at 2 years, and another 9 at 5 years. All 17 patients had an upper instrumented vertebra (UIV) within 3 levels or less caudal of the thoracic kyphosis apex (the most horizontal vertebra on the sagittal); no patient with a UIV 4 or more levels from the thoracic apex (n = 96) developed PJK (X2 = 13.03, p < 0.001). In addition, PJA > 8° was found to significantly increase the risk of PJK (p = 0.039). SRS scores were significantly worse for PJK patients at 5 years in the self-image and function (p < 0.01).

CONCLUSION

In Lenke 5/6 curves, no patient with a UIV 4 or more levels caudal to the thoracic kyphosis apex had PJK up to 5 years postoperatively. PJA greater than 8° was identified as a risk factor for PJK. Patients with radiographic PJK had worse SRS scores 5 years postoperatively.

Changes in sagittal balance and pre-existing junctional angle influence development of proximal junctional kyphosis in growth guidance systems for early-onset scoliosis

PURPOSE

Proximal junctional kyphosis (PJK) has been reported to occur at a rate of about 30% in traditional growing rods (GR) and magnetically controlled growing rods (MCGR). Growth guidance systems (GGS) have non-rigid, gliding fixation along rods, which may mitigate PJK. There have been no studies done in shilla around PJK, hence this study aimed to assess the occurrence, risk factors, and timeline of PJK.

METHODS

A prospective, multicenter database was queried for EOS patients who underwent surgery utilizing GGS.

INCLUSION CRITERIA

< 10 years at index surgery and > 2 year follow-up.

RESULTS

Sixty-five patients (thirty-six female) met inclusion criteria. Mean age at index surgery was 6.2 y/o (2-9); mean follow-up was 66 m. Most common etiologies were syndromic (n = 23). Mean thoracic kyphosis at pre-op was 41.8°, post-op was 35.5°, and final was 42.2°. Mean PJA at pre-op was 6.15°, post-op 1 was 4.2°, and final was 15.6°. Incidence of PJK at post-op was 35% and final was 43%. Pre-op sagittal balance and change in sagittal balance from pre-op to post-op were associated with post-op PJK (p = 0.05, 0.02). Change in spinal height from pre-op to post-op was associated with PJK at final (p = 0.04). Interestingly, increased PJA at pre-op was significantly associated with decreased PJK at post-op and final (p = 0.01, 0.03).

CONCLUSION

PJK was identified in 43% of patients post-operatively after GGS for EOS. Pre-op PJA was negatively correlated with an increased incidence of PJK. Changes in sagittal balance, in either direction, was the strongest predictor for development of PJK post-operatively.

Clinical and radiographic outcomes following correction of idiopathic scoliosis in adolescence vs young adulthood

PURPOSE

The natural history of adolescent idiopathic scoliosis (AIS) has been well documented, but the impact of age at the time of surgical correction is relatively understudied. In this study, we matched patients undergoing surgical correction of adult idiopathic scoliosis (AdIS) with a cohort of AIS patients to compare: (1) coronal and sagittal radiographic correction, (2) operative variables, and (3) postoperative complications.

METHODS

A single-institution scoliosis registry was queried for patients undergoing idiopathic scoliosis surgery from 2000-2017.

INCLUSION CRITERIA

patients with idiopathic scoliosis, no previous spine surgery, and 2-year follow-up. AdIS patients were matched 1:2 with AIS patients based on Lenke classification and curve characteristics. Independent sample t-test and Chi-square test was used to analyze the data.

RESULTS

31 adults underwent surgical correction of idiopathic scoliosis and were matched with 62 adolescents. Mean age of adults was 26.2 ± 11.05, mean BMI was 25.6 ± 6.0, and 22 (71.0%) were female. Mean age of adolescents was 14.2 ± 1.8, mean BMI was 22.7 ± 5.7, and 41(66.7%) were female. AdIS had significantly less postoperative major Cobb correction (63.9% vs 71.3%, p = 0.006) and final major Cobb correction (60.6% vs 67.9%, p = 0.025). AdIS also had significantly greater postoperative T1PA (11.8 vs 5.8, p = 0.002). AdIS had longer operative times (p = 0.003), higher amounts of pRBCs transfused (p = 0.005), longer LOS (p = 0.016), more ICU requirement (p = 0.013), higher overall complications (p < 0.001), higher rate of pseudarthrosis (p = 0.026), and more neurologic complications (p = 0.013).

CONCLUSION

Adult patients undergoing surgical correction of idiopathic scoliosis had significantly worse postoperative coronal and sagittal alignment when compared with adolescent patients. Adult patients also had higher rates of complications, longer operative times, and longer hospital stays.

LEVEL OF EVIDENCE

III.

Percutaneous Vertebroplasty and Upper Instrumented Vertebra Cement Augmentation Reducing Early Proximal Junctional Kyphosis and Failure Rate in Adult Spinal Deformity: Case Series and Literature Review

BACKGROUND AND OBJECTIVES

One of the risks involved after long-segment fusions includes proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). There are reported modalities to help prevent this, including 2-level prophylactic vertebroplasty. In this study, our goal was to report the largest series of prophylactic cement augmentation with upper instrumented vertebra (UIV) + 1 vertebroplasty and a literature review.

METHODS

We retrospectively reviewed our long-segment fusions for adult spinal deformity from 2018 to 2022. The primary outcome measures included the incidence of PJK and PJF. Secondary outcomes included preoperative and postoperative Oswestry Disability Index, visual analog scale back and leg scores, surgical site infection, and plastic surgery closure assistance. In addition, we performed a literature review searching PubMed with a combination of the following words: "cement augmentation," "UIV + 1 vertebroplasty," "adjacent segment disease," and "prophylactic vertebroplasty." We found a total of 8 articles including 4 retrospective reviews, 2 prospective reviews, and 2 systematic reviews. The largest cohort of these articles included 39 patients with a PJK/PJF incidence of 28%/5%.

RESULTS

Overall, we found 72 long-segment thoracolumbar fusion cases with prophylactic UIV cement augmentation with UIV + 1 vertebroplasty. The mean follow-up time was 17.25 months. Of these cases, 8 (11.1%) developed radiographic PJK and 3 (4.2%) required reoperation for PJF. Of the remaining 5 patients with radiographic PJK, 3 were clinically asymptomatic and treated conservatively and 2 had distal fractured rods that required only rod replacement.

CONCLUSION

In this study, we report the largest series of patients with prophylactic percutaneous vertebroplasty and UIV cement augmentation with a low PJK and PJF incidence of 11.1% and 4.2%, respectively, compared with previously reported literature. Surgeons who regularly perform long-segment fusions for adult spinal deformity can consider this in their armamentarium when using methods to prevent adjacent segment disease because it is an effective modality in reducing early PJK and PJF that can often result in revision surgery.

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.

Can placement of hook at the upper instrumented level decrease the proximal junctional kyphosis risk in adolescent idiopathic scoliosis?

OBJECTIVE

Proximal junctional kyphosis is a commonly encountered clinical and radiographic phenomenon after pediatric and adolescent spinal deformity surgery that may lead to postoperative deformity, pain, and dissatisfaction. The purpose of the study was to identify whether the placement of transverse process hooks is an effective way to prevent PJK.

METHODS

Adolescent idiopathic scoliosis patients who underwent posterior spinal fusion between November 2015 and May 2019 were retrospectively analyzed. A minimum 2-year follow-up was required. Demographic and surgical data included UIV level type of instrumentation (hook vs screw) were reported. Radiologic parameters included main curve Cobb angle, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), and proximal junctional angle (PJA) were assessed. Patients were divided into two groups based on the type of instrumentation at the UIV level whether placement of hook versus pedicle screw.

RESULTS

Three hundred and thirty-seven patients were included with the mean age 14.2 ± 1.9 years. Thirty patients (8.9%) were diagnosed with proximal junctional kyphosis radiographically. PJK incidence was found 3.2% (5/154) in the hook group and 13.3% (23/172) in the screw group and the difference found statistically significant. In the PJK group, preoperative thoracic kyphosis and the degree of kyphosis correction were also significantly higher than non-PJK patients.

CONCLUSION

Placement of transverse process hooks at the UIV level in posterior spinal fusion surgery for AIS patients was associated with decreased risk of PJK. A larger preoperative kyphosis and greater degree of kyphosis correction correlated with PJK.

Vertebral Bone Quality Score Independently Predicts Proximal Junctional Kyphosis and/or Failure After Adult Spinal Deformity Surgery

BACKGROUND

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) can be catastrophic complications associated with adult spinal deformity (ASD) surgery. These complications are markedly influenced by osteoporosis, leading to additional vertebral fracture and pedicle screw loosening. The MRI-based vertebral bone quality score (VBQ) is a newly developed tool that can be used to assess bone quality.

OBJECTIVE

To investigate the utility of the VBQ score in predicting PJK and/or PJF (PJF/PJK) after ASD correction.

METHODS

We conducted a retrospective chart review to identify patients age ≥50 years who had received ASD surgery of 5 or more thoracolumbar levels. Demographic, spinopelvic parameters, and procedure-related variables were collected. Each patient's VBQ score was calculated using preoperative T1-weighted MRI. Univariate analysis and multivariate logistic regression were performed to determine potential risk factors of PJK/PJF. Receiver operating characteristic analysis and area-under-the-curve values were generated for prediction of PJK/PJF.

RESULTS

A total of 116 patients were included (mean age, 64.1 ± 6.8 years). Among them, 34 patients (29.3%) developed PJK/PJF. Mean VBQ scores were 3.13 ± 0.46 for patients with PJK/PJF and 2.46 ± 0.49 for patients without, which was significantly different between the 2 groups ( P < .001). On multivariate analysis, VBQ score was the only significant predictor of PJK/PJF (odds ratio = 1.745, 95% CI = 1.558-1.953, P < .001), with a predictive accuracy of 94.3%.

CONCLUSION

In patients undergoing ASD correction, higher VBQ was independently associated with PJK/PJF occurrence. Measurement of VBQ score on preoperative MRI may be a useful adjunct to ASD surgery planning.

Paediatric Spinal Deformity Surgery: Complications and Their Management

Surgical correction of paediatric spinal deformity is associated with risks, adverse events, and complications that must be preoperatively discussed with patients and their families to inform treatment decisions, expectations, and long-term outcomes. The incidence of complications varies in relation to the underlying aetiology of spinal deformity and surgical procedure. Intraoperative complications include bleeding, neurological injury, and those related to positioning. Postoperative complications include persistent pain, surgical site infection, venous thromboembolism, pulmonary complications, superior mesenteric artery syndrome, and also pseudarthrosis and implant failure, proximal junctional kyphosis, crankshaft phenomenon, and adding-on deformity, which may necessitate revision surgery. Interventions included in enhanced recovery after surgery protocols may reduce the incidence of complications. Complications must be diagnosed, investigated and managed expeditiously to prevent further deterioration and to ensure optimal outcomes. This review summarises the complications associated with paediatric spinal deformity surgery and their management.

Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis-The Spinous Processes and Proximal Rod Contouring

Proximal junctional kyphosis (PJK), as one of the most discussed problems after corrective surgery in adolescent idiopathic scoliosis (AIS), is still not fully clarified and seems to be multifactorial. Biomechanical and a few clinical studies have shown the influence of destruction of posterior ligaments by resection of spinous processes and some parameters concerning rod contouring as risk factors for PJK. To verify these results, 192 patients with AIS and corrective surgery via a posterior approach between 2009 and 2017 were included. Radiographic parameters were analyzed preoperatively (preOP), postoperatively (postOP), and with a mean follow up (FU) of 27 months. The participants were divided into two groups (PJK group and non-PJK group). The incidence of PJK was 15.6%. Contrary to the results of biomechanical studies, we could not find any significant influence of the spinous process resection. However, the PJK group had significantly larger preOP T4-T12 kyphosis (31.1° ± 13.93° vs. 23.3° ± 14.93°, p = 0.016). Furthermore, the PJK group showed a significantly larger rod contour angle (RCA) (8.0° ± 4.44° vs. 5.9° ± 3.28°, p = 0.003) and mismatch of postOP proximal junctional angle (PJA) and RCA (3.5° ± 5.72° vs. 0.9° ± 4.86°, p = 0.010) compared to the non-PJK group. An increase in the mismatch of postOP PJA and RCA (OR = 1.14, p = 0.008) and a high RCA are risk factors for PJK and need to be focused on by surgeons.

Unmatched rod contouring at the proximal end predisposes to occurrence of junctional kyphosis in early-onset scoliosis patients undergoing traditional growing rods treatment

STUDY DESIGN

A retrospective case series.

OBJECTIVE

To investigate whether unmatched rod contouring at the proximal end predisposed to the occurrence of proximal junctional kyphosis (PJK) in early-onset scoliosis (EOS) patients after traditional growing rods (TGR) treatment. TGR treatment has become a mainstay of treatment for EOS patients. PJK is one of the most common alignment-related complications.

METHODS

A consecutive series of EOS patients who had undergone TGR treatment were retrospectively reviewed. They were divided into PJK and non-PJK groups according to the occurrence of PJK or not. Demographic data, surgical strategies, and radiographic parameters were recorded and compared between groups. Proximal junctional angle (PJA) was defined as the angle between the caudal endplate of the UIV and the cephalad endplate of the second supradjacent vertebra above the UIV, while proximal rod contouring angle (PRCA) was defined as the angle of proximal rod contouring, which was represented by the angle between the cephalad endplate of the UIV and the caudal endplate of the second vertebra caudal to the UIV. Unmatched proximal rod contouring was regarded if the postoperative PRCA-PJA difference was greater than 5°.

RESULTS

This study finally included 73 patients. The mean age at the index surgery was 6.5 ± 2.2 years (range, 2-10 years). Mean follow-up lasted 5.0 ± 1.7 years (range, 2-9 years). They received mean 4.6 ± 1.6 lengthening procedures. There were 13 patients who were observed with PJK (18%). In comparison with the non-PJK group, the PJK group showed a larger preoperative major curve (82 ± 21° vs 70 ± 17°, P = 0.041) and global kyphosis (57 ± 6° vs. 44 ± 15°, P = 0.044). In addition, the PJK group had significantly larger postoperative PJA (10 ± 3 vs. 5 ± 3, P<0.001) and greater postoperative PJA-PRCA (6 ± 3 vs. 3 ± 3, P = 0.031). The proportion of patients with unmatched proximal rod contouring in PJK group was significantly higher than that in the non-PJK group (69% vs. 25%). Multiple logistic regression showed that preoperative GK>50°, postoperative PJA>10 and postoperative unmatched proximal rod contouring were the risk factors in predicting PJK after TGR treatment.

CONCLUSION

Approximately 18% EOS patients experienced PJK after TGR treatment. Unmatched proximal rod contouring may be an independent risk factor of PJK occurrence, in addition to greater preoperative GK and larger postoperative PJA.

LEVEL OF EVIDENCE: 3

Trends in Intraoperative Assessment of Spinal Alignment: A Survey of Spine Surgeons in the United States

STUDY DESIGN

Survey.

OBJECTIVES

To characterize national practices of and shortcomings surrounding intraoperative assessments of spinal alignment.

METHODS

Spine surgeons in the US were surveyed to analyze their experience with assessing spinal alignment intraoperatively.

RESULTS

108 US spine surgeons from 77 surgical centers with an average of 19.2 + 8.8 years of surgical experience completed the survey. To assess alignment intraoperatively, 84% (91/108) use C-arm or spot radiographs, 40% (43/108) use full-length radiographs, and 20% utilize the T-bar (22/108). 88% of respondents' surgical centers (93/106) possessed a navigation camera and 63% of respondents (68/108) report using surgical navigation for 40% of their deformity cases on average. Reported deterrents for using current technology to assess alignment were workflow interruption (54%, 58/108), expense (33%, 36/108), and added radiation exposure (26%, 28/108). 87% of respondents (82/94) reported a need for improvement in current capabilities of making intraoperative assessments of spinal alignment.

CONCLUSIONS

Corrective surgery for spinal deformity is a complex procedure that requires a high level of expertise to perform safely. The majority of surveyed surgeons primarily rely on radiographs for intraoperative assessments of alignment. Despite the majority of surveyed surgical practices possessing navigation cameras, they are utilized only for a minority of spinal deformity cases. With the majority of surveyed surgeons reporting a need for improvement in technology to assess spinal alignment intraoperatively, 3 of the top design considerations should include workflow interruption, expense, and radiation exposure.

Proximal Junction Kyphosis in Adult Scoliosis: Best Postoperative Radiological Predictors-A Retrospective Cohort Study

Background

Proximal junction kyphosis (PJK) is the postsurgical radiographic event seen in the surgical plane after the fusion of a spinal deformity. Unfavorable health outcomes have been reported in symptomatic PJK patients compared to non-PJK patients.

Methods

The data for adult scoliosis patients who underwent curve correction were extracted from the hospital database. Pelvic and spinal parameters were measured and calculated to compare four predictive formulae for occurrences of PJK. Formula 1. Restoration of hypothetical values of lumbar lordosis (LL) and thoracic kyphosis (TK) according to pelvic incidence (PI). Formula 2. Evaluation of global sagittal alignment. Formula 3. Restoration of the apex of LL to its hypothetical position according to the spine shape. Formula 4. Evaluation of positive-sum and negative-sum of (LL + TK).

Results

A total number of cases were 52. There were 14 cases of PJK. The incidence of PJK was 26.9%, and the mean age for PJK cases was 63.2 ± 5.2. The excellent predictor for occurrences of PJK was formula 3. Postsurgical sagittal apexes of lumbar lordosis were located in their hypothetical position in 24 cases, and 12.5% of these cases developed PJK. While sagittal apexes were not located in their hypothetical position in 28 patients, PJK occurred in 39.3% of them (P=0.03, OR: 4.53, (95% CI: 1.09–18.9)). The second good predictor for occurrences of PJK was formula 2 (GSA >45° versus GSA <45° OR = 2.5, (95% CI: 0.67–9.38), P=0.17). The other two formulae (1 and 4) were not good predictors for occurrences of PJK.

Conclusion

Among the four proposed formulae for predicting occurrences of PJK, the position of the sagittal apex of lumbar lordosis is an excellent predictor of the development of PJK, followed by GSA. Hypothetical values of LL and TK, and positive or negative-sum of (LL + TK), are weak predictors for occurrences of PJK.

Risk factors for the development of DJK in AIS patients undergoing posterior spinal instrumentation and fusion

PURPOSE

Typically, selection of lowest instrumented vertebra (LIV) in Adolescent Idiopathic Scoliosis (AIS) is based on the coronal radiograph; however, increasing evidence suggests that fusions proximal to the stable sagittal vertebrae (SSV) on the lateral radiograph can result in distal junctional kyphosis (DJK). The purpose of this study is to compare rates of DJK in patients with AIS that have a discordance between the Lowest Touched Vertebra (LTV) and the SSV and to identify risk factors for developing DJK.

METHODS

Patients with AIS Lenke type 1, 2 and 3 curves treated with a posterior spinal fusion were separated into two groups. Group 1 had SSV that was proximal to the LTV whereas group 2 had SSV that was distal to the LTV. Comparisons were made for patients that were fused to the SSV(a), LTV(b) or between(c). Distal junctional angle (DJA) > 5° and increasing kyphosis at the end of the fusion construct were evaluated as risk factors for DJK.

RESULTS

The rate of DJK was 0.0% in group 1a, 1b, and 1c compared to 4.3%, 18.5% and 10.0% in groups 2a, 2b and 2c, respectively(p < 0.001). The rate of DJK was 22.9% when the distal junctional angle(DJA) > 5° versus 1.4% when the DJA < 5°(p < 0.001).

CONCLUSION

There was a low risk for progression of DJK when the SSV was proximal to the LTV, however, those with SSV distal to the LTV represent a high-risk group. Importantly, the development of DJK occurred almost exclusively in patients with LIV at the thoracolumbar junction which demonstrates that surgeons need to be cautious when ending fusions at T11, T12, and L1 in patients at high risk for DJK. Furthermore, having a distal junctional angle 5° or greater increased the risk of developing DJK by roughly 16-fold. At a minimum of 5-year follow-up, the development of DJK did not appear to adversely impact SRS outcomes or revision rates.

The impact of segmental spinal alignment on the development of proximal junctional kyphosis after instrumented posterior spinal fusions for idiopathic scoliosis

PURPOSE

To assess if the preservation of preoperative kyphosis within the cephalad two motion segments of instrumented posterior spinal fusions (PSF), for idiopathic scoliosis (IS), would be associated with lower frequency of proximal junctional kyphosis (PJK) at 2 years postoperatively. Previous studies on PJK in IS have reported conflicting findings; none has evaluated the relationship between segmental kyphosis within the cephalad instrumented construct and PJK.

METHODS

One hundred consecutive patients undergoing PSF for IS by a single surgeon with minimum 2-year follow-up were evaluated. Radiographic evaluation focused on sagittal alignment of the upper instrumented vertebrae (UIV), the 1 and 2 vertebrae cephalad (UIV + 1, UIV + 2) and caudal (UIV - 1, UIV - 2). This was measured between the inferior endplate of the UIV and the superior endplate of the UIV + 1 and UIV + 2 or between the superior endplate of the UIV and the inferior endplate of the UIV - 1 and UIV - 2. PJK was defined as present if the final UIV + 2 ≥ 10° and final UIV + 2-preop UIV + 2 ≥ 10°.

RESULTS

There were 78 females and 22 males whose mean age was 14.6 (± 2.1) years at surgery; mean follow-up was 3.9 (2-9.3) years. The overall frequency of PJK was 25% (25/100) at final follow-up. Preoperative mean coronal curve measured 63° (40°-107°) with a mean 66% correction at final follow-up. UIV was T2 (n = 15), T3 (n = 47) or T4 (n = 38). More caudal UIVs were associated with PJK development (p = 0.04): T2 (13%), T3 (21%) and T4 (34%). Greater preoperative T5-T12 thoracic kyphosis and UIV - 2, and lower major curve apex (below T12) were more likely to develop PJK (p = 0.019, p = 0.004 and p = 0.007, respectively). Post-operatively, larger values for UIV - 1 (p ≤ 0.001) and UIV - 2 (p = 0.002) were associated with PJK at final follow-up. Longer fusion lengths (10-13 vs. 6-9 segments, p = 0.02) and the presence of thoracolumbar/lumbar structural curves (Lenke 3-6 vs. 1-2, p = 0.032) had higher rates of PJK (32% vs 10% and 37% vs 18%, respectively). Changes in UIV - 1 and UIV - 2 (preoperatively to immediately post-op) did not influence the development of PJK. At final follow-up, no patient required revision surgery for symptomatic proximal junctional kyphosis.

CONCLUSIONS

In this study, changes in UIV - 1 and UIV - 2 at surgery were not related to PJK. Greater preoperative T5-T12 thoracic kyphosis and UIV - 2, lower major curve apex (T12 and below), and greater post-operative UIV - 1 and UIV - 2 were associated with higher frequencies of PJK. Higher UIV (T2 vs. T4) and LIV levels had a protective effect against PJK. Based on this study, the preservation of segmental kyphosis within the instrumented cephalad two levels of the PSF did not minimize the occurrence of radiographic PJK.

LEVEL OF EVIDENCE

Level IV.

Proximal junctional kyphosis in pediatric spinal deformity surgery: a systematic review and critical analysis

PURPOSE

Proximal junctional kyphosis (PJK) is a commonly encountered clinical and radiographic phenomenon after pediatric and adolescent spinal deformity surgery that may lead to post-operative deformity, pain, and dissatisfaction. Understanding the risk factors of PJK can be useful for pre-operative informed consent as well as to identify any potential preventative strategies.

METHODS

We performed a systematic review and critical analysis following the PRISMA statement in July 2019 by searching the PubMed, Scopus, and Embase databases, including all prior published studies. We included articles with data on PJK in patients with operative pediatric and adolescent scoliosis and those that detailed risk factors and/or preventative strategies for PJK. Levels of evidence were determined based on consensus. Findings were summarized and grades of recommendation were assigned by consensus. This study was registered in the PROSPERO database; 202,457.

RESULTS

Six hundred and thirty five studies were identified. Thirty-seven studies met criteria for inclusion into the analysis. No studies including neuromuscular scoliosis met inclusion criteria. No findings had Grade A evidence. There were 4 findings found to contribute to PJK with Grade B evidence in EOS: higher number of distractions, disruption of posterior elements, greater sagittal plane correction. There was no difference in incidence noted between etiology of the curvature. Five findings with Grade B evidence were found to contribute to PJK in AIS populations: higher pre-operative thoracic kyphosis, higher pre-operative lumbar lordosis, longer fusion constructs, greater sagittal plane correction, and posterior versus anterior fusion constructs.

CONCLUSION

Greater sagittal plane correction has Grade B evidence as a risk factor for PJK in both EOS and AIS populations. In EOS patients, an increased number of distractions and posterior element disruption are Grade B risk factors. In AIS patients, longer fusion constructs, higher pre-operative thoracic kyphosis and lumbar lordosis, and posterior (as opposed to anterior) constructs also contributed to PJK with Grade B evidence. These findings can guide informed consent and surgical management, and provide the foundation for future studies.

Reduced proximal junctional failure with ligament augmentation in adult spinal deformity: a series of 242 cases with a minimum 1-year follow-up

OBJECTIVE

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are well-recognized complications of long-segment spinal fusion. Previous studies have suggested that ligament augmentation can decrease rates of PJF by reducing junctional stress and strengthening upper instrumented vertebrae (UIVs) and adjacent segments. However, there is a paucity of long-term data on the efficacy of ligament augmentation in preventing PJF. In this study, the authors sought to determine the effect of ligament augmentation on rates of PJF in a cohort of adult spinal deformity patients with at least 1 year of follow-up.

METHODS

They conducted a retrospective analysis of ligament augmentation in a consecutive series of surgical patients with adult spinal deformity. Data on patient demographics, surgical characteristics, and surgery for PJF were collected. The minimum follow-up was 12 months. Univariate and multivariate analyses were performed to identify factors associated with reoperation for PJF.

RESULTS

The authors identified a total of 242 patients (166 women [68.6%]) with ligament augmentation whose mean age was 66 years. The mean number of fused levels was 10, with a UIV distribution as follows: 90 upper thoracic UIVs (37.2%) and 152 lower thoracic UIVs (62.8%). Compared to a historical cohort of 77 patients treated before implementation of ligament augmentation, reoperation for PJF was significantly lower with ligament augmentation (15.6% vs 3.3%, p < 0.001). In a multivariate model, only ligament augmentation (OR 0.184, 95% CI 0.071-0.478, p = 0.001) and number of fused levels (OR 0.762, 95% CI 0.620-0.937, p = 0.010) were associated with reductions in reoperation for PJF.

CONCLUSIONS

Ligament augmentation was associated with significant reductions in the rate of reoperation for PJF at 12 months in a cohort of adult spinal deformity patients. The most dramatic reduction was seen among patients with lower thoracic UIV. These data suggest that in appropriately selected patients, ligament augmentation may be a valuable adjunct for PJF reduction; however, long-term follow-up is needed.

Incidence and Radiological Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw Instrumentation with Rod Derotation and Direct Vertebral Rotation: A Minimum 5-Year Follow-Up Study

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group (n = 62) and PJK group (n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively (p = 0.027), postoperatively (p = 0.001), and at last follow-up (p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

The impact of the lower instrumented level on outcomes in cervical deformity surgery

Background:

The lower instrumented vertebrae (LIVs) in cervical deformity (CD) constructs may have varying effects on patient outcomes that are still poorly understood.

Objective:

The objective of the study is to compare outcomes in CD patients undergoing instrumented correction according to the relation of LIV with primary driver (PD).

Methods:

Patients who met radiographic criteria for CD were included in the study. Patients were stratified by PD of deformity: cervical (C) through AMES classification (TS-CL >20 or cervical sagittal vertical axis >40) and thoracic (T) through hyper/hypokyphosis (TK) from T4-T12 (60 < TK < 40). Patients were further stratified by LIV in relation to curve apex (above/below). Univariate and multivariate analyses identified group differences in postoperative health-related quality-of-life and distal junctional kyphosis (DJK) (>10° LIV and LIV + 2) rate up to 1 year.

Results:

Sixty-two patients were analyzed. Twenty-one patients had a C-PD and 41 had a T-PD by definition. 100% of C-PDs had LIVs below CL apex, while 9.2% of T-PDs had LIVs below (caudal) to TK apex and 90.8% had LIVs above TK apex. By 1 year, C patients trended lower Neck Disability Index (NDI) (21.9 vs. 29.0, P = 0.245), lower numeric rating scales neck pain (4.2 vs. 5.1, P = 0.358), and significantly higher EuroQol five-dimensional questionnaire Visual Analog Scale (69.2 vs. 52.4, P = 0.040). When T patients with LIVs below TK apex were excluded, remaining T patients with LIV above apex had significantly higher 1-year NDI than C patients (37.5 vs. 21.9, P = .05). T patients also trended higher rates of postoperative DJK than C (19.5% vs. 4.8%, P = 0.119).

Conclusions:

Stopping before apex was more common in patients with a primary thoracic driver (T) and associated with deleterious effects. Primary cervical driver (C) tended to have LIVs inclusive of CL apex with lower rates of DJK.

Incidence of Proximal Junctional Kyphosis With Pedicle Screws at Upper Instrumented Vertebrae in Posterior Spinal Fusion for Adolescent Idiopathic Scoliosis

STUDY DESIGN

Longitudinal cohort.

OBJECTIVES

Posterior spinal fusion (PSF) using all-pedicle screw constructs has become the standard procedure in the treatment of adolescent idiopathic scoliosis (AIS). However, there have been several reports that all-pedicle screw constructs or the use of pedicle screws at the upper instrumented vertebrae (UIV) increases the incidence of proximal junctional kyphosis (PJK). We aimed to evaluate the impact of instrumentation type on the incidence of PJK following PSF for AIS.

METHODS

We performed a stratified random sampling from 3654 patients enrolled in a multicenter database of surgically treated AIS to obtain a representative sample from all Lenke types. Patients were then allocated into 3 groups based on the instrumentation type: all-pedicle screw (PS), hook at UIV with pedicle screws distally (HT), and hybrid constructs (HB). We measured proximal junctional angle (PJA) and defined PJK as PJA ≥ 10° and PJA progression of >10° at the final follow-up.

RESULTS

Fifteen (4.3%) of 345 cases had PJK. PJK was significantly more common in PS (11%) compared with HB (1%) and HT (0%) (P < .001). PJK patients were similar to non-PJK patients regarding age, sex, curve type, UIV, and preoperative coronal Cobb angle. Thoracic kyphosis was significantly higher in the PJK group before surgery. Patients who developed PJK had a statistically significantly larger negative sagittal balance compared with the non-PJK group.

CONCLUSION

The incidence of PJK was 4.3% and was more common in all-pedicle screw constructs. Using hooks at UIV might be a treatment strategy to limit PJK.

Complications in ambulatory pediatric patients with nonidiopathic spinal deformity undergoing fusion to the pelvis using the sacral-alar-iliac technique within 2 years of surgery

OBJECTIVE

Significant investigation in the adult population has generated a body of research regarding proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following long fusions to the sacrum and pelvis. However, much less is known regarding early complications, including PJK and PJF, in the ambulatory pediatric patient. As such, the objective of this study was to address the minimal literature on early complications after ambulatory pediatric patients underwent fusion to the sacrum with instrumentation to the pelvis in the era of sacral-alar-iliac (S2AI) instrumentation.

METHODS

The authors performed a retrospective review of pediatric patients with nonidiopathic spinal deformity < 18 years of age with ambulatory capacity who underwent fusion to the pelvis at a multisurgeon pediatric academic spine practice from 2016 to 2018. All surgeries were posterior-only approaches with S2AI screws as the primary technique for sacropelvic fixation. Descriptive, outcome, and radiographic data were obtained. The definition of PJF included symptomatic PJK presenting as fracture, screw pullout, or disruption of the posterior osseoligamentous complex.

RESULTS

Twenty-five patients were included in this study. Nine patients (36.0%) had 15 complications for an overall complication rate of 60.0%. Unplanned return to the operating room occurred 8 times in 6 patients (24.0%). Four patients (16.0%) had wound issues (3 with deep wound infection and 1 with wound breakdown) requiring reoperation. Three patients (12.0%) had PJF, all requiring reoperation. A 16-year-old female patient with syndromic scoliosis underwent extension of fusion due to posterior tension band failure at 6 months. A 17-year-old male patient with neuromuscular scoliosis underwent extension of fusion due to proximal screw pullout at 5 months. A 10-year-old female patient with congenital scoliosis underwent extension for PJF at 5 months following posterior tension band failure. One patient had pseudarthrosis requiring reoperation 20 months postoperatively.

CONCLUSIONS

Fixation to the pelvis enables significant deformity correction, but with rather high rates of complications and unexpected returns to the operating room. Considerations of sagittal plane dynamics for PJK and PJF should be strongly analyzed when performing fixation to the pelvis in ambulatory pediatric patients.

Proximal junctional kyphosis is a rebalancing spinal phenomenon due to insufficient postoperative thoracic kyphosis after adolescent idiopathic scoliosis surgery

PURPOSE

Many authors tried to explain proximal junctional kyphosis (PJK) after adolescent idiopathic scoliosis (AIS) surgery by looking for risk factors. Latest publications focus on sagittal alignment. Each healthy adolescent has a specific thoracic kyphosis (TK) depending on their pelvic parameters and lumbar lordosis (LL). The objective of this work is to determine if the difference between TK at follow-up (TKFU) and the patient-specific TK (PSTK) plays a role in PJK occurrence after AIS surgery. The secondary objective was to find other risk factors.

METHODS

We analyzed retrospectively 570 thoracic AIS who underwent a posterior thoracic fusion from nine centers. The series was separated in two groups: with and without PJK. PSTK was calculated with the formula PSTK = 2(PT + LL-PI). TK Gap was the difference between TKFU and PSTK. Logistic regression was utilized to test the impact of TK Gap and other known risk factors on PJK occurrence.

RESULTS

Univariate analysis showed 15 factors significantly different between the groups. In a multivariate analysis, three factors had a strong significant influence on PJK: TKFU, TK Gain and TK Gap. Four additional factors affected the rate of PJK: Posterior translation on two rods, preoperative TK, preoperative LL and number of instrumented vertebrae.

CONCLUSION

PJK is related to the insufficient TK at follow-up, compared to the specific TK that every patient should have according to their pelvic parameters. PJK incidence is significantly reduced by a strong gain in TK and a thoracic selective fusion which leaves the proximal lumbar vertebrae free.

LEVEL OF EVIDENCE I

Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Posterior Polyethylene Tethers Reduce Occurrence of Proximal Junctional Kyphosis After Multilevel Spinal Instrumentation for Adult Spinal Deformity: A Retrospective Analysis

BACKGROUND

Proximal junctional kyphosis (PJK) is a common postoperative complication after adult spinal deformity (ASD) surgery and may manifest with neurological decline, worsening spinal deformity, and spinal instability, which warrant reoperation. Rates of PJK may be as high as 69.4% after ASD surgery.

OBJECTIVE

To evaluate the efficacy of junctional tethers for PJK prophylaxis after multilevel instrumented surgery for ASD with minimum 2-yr follow-up.

METHODS

Single-center retrospective analysis of adult patients (age ≥18 yr) who underwent ASD surgery with index operations performed between November 2010 and June 2016 and achieved minimum 2-yr follow-up. Patients with ASD were subdivided into 3 treatment cohorts based on institutional protocol: no tether (NT), polyethylene tether-only (TO), and tether with crosslink (TC). PJK was defined as a proximal junctional angle (PJA) >10° and 10° greater than the corresponding preoperative measurement. Patient demographics, operative details, standard radiographic scoliosis measurements (including PJA and assessment of PJK), and complications were analyzed.

RESULTS

Of 184 patients, 146 (79.3%) achieved minimum 2-yr follow-up (mean = 45 mo; mean age = 67 yr; 67.8% women). PJK rates reported for the NT, TO, and TC cohorts were 60.7% (37/61), 35.7% (15/42), and 23.3% (10/43), respectively. PJK rates among TC patients were significantly lower than NT (P = .01601).

CONCLUSION

Junctional tethers with crosslink significantly reduced the incidence of PJK and revisions for PJK among ASD patients treated with long-segment posterior instrumented fusions who achieved minimum 2-yr follow-up.

Proximal Junctional Kyphosis According to the Type of Lumbar Degenerative Kyphosis Following Lumbosacral Long Fusion

STUDY DESIGN

A retrospective study.

OBJECTIVE

The aim of this study was to investigate proximal junctional kyphosis (PJK) after lumbosacral long fusion according to preoperative Roussouly and lumbar degenerative kyphosis (LDK) types.

SUMMARY OF BACKGROUND DATA

Although previous studies have suggested some risk factors for PJK, the effects of preoperative grade of sagittal imbalance and paraspinal muscles degeneration on PJK remain unclear.

METHODS

Eighty-seven patients who had undergone lumbosacral fusion more than five levels with available clinical and radiological data were enrolled. The presence of PJK defined as sagittal Cobb angle ≥20° between the uppermost instrumented vertebra (UIV) and two supra-adjacent vertebrae at postoperative 2-year radiographs was recorded. Its occurrence was compared according to preoperative Roussouly and LDK types (Takemistu type) and the degree of paraspinal muscle degeneration at the upper level of UIV. Other sagittal radiographic parameters were also measured.

RESULTS

In this series, 28 patients (group I, 32.2%) showed radiological PJK, whereas 59 patients did not show radiological PJK (non-PJK patients, group II, 67.8%) at postoperative 2 years. PJK presented more prevalence in type III and type IV of LDK types (26/27, 96.3%). However, Roussouly types did not show any significant difference in PJK prevalence. In radiological parameters, a larger preoperative SVA (P = 0.018) and PI-LL (P = 0.015) were associated with PJK. Also, smaller quantity and lower quality of paraspinal muscles at T12-L1 level showed significant (P < 0.001) relationship with PJK. On multivariate logistic regression, higher LDK type (odds ratio [OR]: 2.11, 95% confidence interval [CI]: 1.24-3.56), smaller quantity (OR: 1.03, 95% CI: 1.00-1.07), and higher degree of paraspinal muscle degeneration (OR: 1.46, 95% CI: 0.92-2.31) were independent predictors of postoperative PJK.

CONCLUSION

Although various factors are related to PJK following long segment fusion, preoperative conditions such as LDK types and degree of paraspinal muscle degeneration might be related to the development of PJK.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.

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.

Risk and Predictive Factors for Proximal Junctional Kyphosis in Patients Treated by Lenke Type 5 Adolescent Idiopathic Scoliosis Correction

OBJECTIVE

Proximal junctional kyphosis (PJK) is a common sagittal complication of adolescent idiopathic scoliosis (AIS) after corrective surgery, leading to new deformities, pain, and, even, revision surgery. In the present study, we investigated the risk and predictive factors for PJK in patients who had undergone Lenke type 5 AIS correction to identify the parameters relevant to intraoperative guidance.

METHODS

A total of 35 patients with Lenke type 5 AIS who had undergone corrective surgery at our hospital from January 2008 to February 2016 were divided into the PJK (n = 15) and non-PJK (n = 20) groups. Correlation and receiver operating characteristic curve analyses were performed to screen the parameters for significance and calculate the thresholds. A survival analysis was performed to examine the differences between the 2 groups.

RESULTS

Independent t tests revealed significant differences between the 2 groups in the preoperative pelvic incidence, preoperative pelvic tilt, postoperative proximal junctional angle (PJA), and postoperative thoracic kyphosis (TK). The postoperative PJA, postoperative TK, and other parameters correlated significantly with changes in the PJA at the final follow-up. The receiver operating characteristic curves revealed that the postoperative PJA and postoperative TK effectively predicted for the occurrence of PJK, with a threshold of 9.45° and 25.25°, respectively. The estimated survival times were 14.7 months for a PJA >9.45° and TK >25.25°, 19.2 months for a PJA >9.45°, and 33.9 months for TK >25.25°.

CONCLUSIONS

The results of the present study have shown that the postoperative PJA and postoperative TK can be used to effectively predict for the occurrence of PJK in patients with Lenke type 5 AIS after corrective surgery, with a threshold of 9.45° and 25.25°, respectively.

Comparison of Proximal Junctional Failure and Functional Outcomes Across Varying Definitions of Proximal Junctional Kyphosis

BACKGROUND

Proximal junctional kyphosis (PJK) is a well-recognized complication following surgery for adult spinal deformity (ASD); however, definitions for PJK and its clinical implications can significantly vary by study. This study compares multiple definitions of PJK and describes incidence and clinical significance by definition.

METHODS

From 2014 to 2019, patients with ASD who underwent spinal fusion were identified. Nine definitions of PJK were created based on previously established definitions using the following upper instrumented vertebra +2 (UIV+2) sagittal Cobb measurements: A= ≥10 postoperative AND preoperative, B = ≥10 postoperative, C = ≥10 preoperative, D = ≥15 postoperative AND preoperative, E = ≥15 postoperative, F = ≥15 preoperative, G = ≥20 postoperative AND preoperative, H = ≥20 postoperative, I = >20 preoperative. Incidence of PJK was calculated by definition. Area under the curve (AUC) was calculated based on a receiver operating characteristic to assess ability to predict proximal junctional failure (PJF). Univariate analysis was performed to assess association with postoperative Oswestry Disability Index (ODI) scores.

RESULTS

Across 82 patients, the incidence of PJK and AUC by definition was as follows: A = 47%, 0.47; B = 72%, 0.65; C = 49%, 0.45; D = 27%, 0.46; E = 57%, 0.62; F = 27%, 0.46; G = 10%, 0.55; H = 40%, 0.71; I = 10%, 0.55. No definition was associated with postoperative ODI scores (P < 0.05).

CONCLUSIONS

The incidence of PJK significantly decreased with stricter definitions. Definitions utilizing only postoperative UIV+2 values had higher incidences but were more likely to capture patients who developed PJF. No definition was associated with postoperative ODI scores. UIV+2 ≥20 was best in distinguishing patients who developed PJF.

Surgical Design Optimization of Proximal Junctional Kyphosis

Purpose

The objective of this study was to construct a procedural planning tool to optimize the proximal junction angle (PJA) to prevent postoperative proximal junctional kyphosis (PJK) for each scoliosis patient.

Methods

Twelve patients (9 patients without PJK and 3 patients with PJK) who have been followed up for at least 2 years after surgery were included. After calculating the loading force on the cephalad intervertebral disc of upper instrumented vertebra of each patient, the finite-element method (FEM) was performed to calculate the stress of each element. The stress information was summarized into the difference value before and after operation in different regions of interest. A two-layer fully connected neural network method was applied to model the relationship between the stress information and the risk of PJK. Leave-one-out cross-validation and sensitivity analysis were implemented to assess the accuracy and stability of the trained model. The optimal PJA was predicted based on the learned model by optimization algorithm.

Results

The mean prediction accuracy was 83.3% for all these cases, and the area under the curve (AUC) of prediction was 0.889. And the output variance of this model was less than 5% when the important factor values were perturbed in a range of 5%.

Conclusion

Our approach integrated biomechanics and machine learning to support the surgical decision. For a new individual, the risk of PJK and optimal PJA can be simultaneously predicted based on the learned model.

Adjacent segment disk degeneration three decades after fusion without attempted reduction for high-grade isthmic spondylolisthesis

STUDY DESIGN

Observational study.

OBJECTIVES

To evaluate adjacent segment disk degeneration (ASD) after fusion without attempted reduction at a young age for high-grade isthmic spondylolisthesis. The clinical relevance of ASD remains unclear. Previous studies have shown that spinal fusion is associated with increased ASD but without influence on clinical outcome. Since high-grade spondylolisthesis is a severe kyphotic deformity, one could hypothesize that fusion without attempted reduction in young patients leads to accelerated adjacent segment disk degeneration in adult life.

METHODS

Anterior and posterior disk heights were evaluated on supine radiographs of the spine 8 years and 29 years after fusion without attempted reduction for high-grade spondylolisthesis and also on standing radiographs 8 years and 33 years after surgery. Pelvic parameters were evaluated on standing radiographs obtained 33 years after surgery. Health-related quality of life was evaluated with the Scoliosis Research Society (SRS)-22r questionnaire.

RESULTS

One segment above fusion the anterior disk height significantly decreased on standing radiographs. Two segments above the fusion, the anterior disk height significantly decreased on supine as well as on standing radiographs. The largest reduction was found two segments above the fusion where the disk height was reduced from 33 to 28% of anterior vertebral height between the measurements at mean 8 years and mean 33 years after surgery. There were no statistically significant decreases in posterior disk heights in any measurement. The disk height showed a moderate negative correlation to PT. There was no correlation between disk height reduction and SRS-22r outcome.

CONCLUSIONS

In our long-term follow-up of fusion without attempted reduction for high-grade spondylolisthesis in young patients, we found only a minor but statistically significant reduction in adjacent segment disk height which had no apparent impact on clinical outcome.

LEVEL OF EVIDENCE

Level IV.

PREVALENCE OF PJK AFTER ARTHRODESIS IN PATIENTS WITH NEUROMUSCULAR SCOLIOSIS IN THE SECOND POSTOPERATIVE YEAR

ABSTRACT Objective The primary objective of this study was to analyze the prevalence of PJK in patients with neuromuscular scoliosis submitted to posterior spinal arthrodesis with instrumentation. Proximal junctional kyphosis (PJK) is a frequent phenomenon that, due to its importance, began to be studied by several authors, who laid the foundations for the radiographic definition and possible risk factors for its occurrence after long spinal arthrodesis with instrumentation. Despite the large number of PJK studies, most were related to the occurrence of adolescent idiopathic scoliosis, adult deformity and early-onset scoliosis, with few being targeted to patients with congenital and neuromuscular scoliosis. Methods In this study, data from electronic medical records of patients with neuromuscular scoliosis who underwent posterior arthrodesis with instrumentation between the years 2014 and 2016 were analyzed. Information on age, gender, pathology and radiographic measurements were extracted from this sample at the 2nd and 24th postoperative months. Results A total of 39 patients with neuromuscular scoliosis were analyzed. The sample was predominantly male (58.87%) and the mean age was 14.05 years. PJK occurred in 18 patients during the two years following surgery, with a prevalence of 46.15%. The incidence of PJK in the 2nd and 24th postoperative months was 23.1% and 30%, respectively. Conclusions A prevalence of PJK of 46.15% was found in patients with neuromuscular scoliosis treated surgically with posterior instrumentation after two years of follow-up, as compared to previous results . Level of Evidence III; Cross-sectional observational study.

The Effect of Spinopelvic Parameters on the Development of Proximal Junctional Kyphosis in Early Onset: Mean 4.5-Year Follow-up

BACKGROUND

Proximal junctional kyphosis (PJK) is a major complication after posterior spinal surgery. It is diagnosed radiographically based on a proximal junctional angle (PJA) and clinically when proximal extension is required. We hypothesized that abnormal spinopelvic alignment will increase the risk of PJK in children with early-onset scoliosis (EOS).

METHODS

A retrospective study of 135 children with EOS from 2 registries, who were treated with distraction-based implants. Etiologies included 54 congenital, 10 neuromuscular, 37 syndromic, 32 idiopathic, and 2 unknown. A total of 89 rib-based and 46 spine-based surgeries were performed at a mean age of 5.3±2.83 years. On sagittal radiographs, spinopelvic parameters were measured preoperatively and at last follow-up: scoliosis angle (Cobb method, CA), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope and PJA. Radiographic PJK was defined as PJA≥10 degrees and PJA≥10 degrees greater than preoperative measurement. The requirement for the proximal extension of the upper instrumented vertebrae was considered a proximal junctional failure (PJF). Analysis of risk factors for the development of PJK and PJF was performed.

RESULTS

At final follow-up (mean: 4.5±2.6 y), CA decreased (P<0.005), LL (P=0.029), and PI (P<0.005) increased, whereas PI-LL (pelvic incidence minus lumbar lordosis) did not change (P=0.706). Overall, 38% of children developed radiographic PJK and 18% developed PJF. Preoperative TK>50 degrees was a risk factor for the development of radiographic PJK (relative risk: 1.67, P=0.04). Children with high postoperative CA [hazard ratio (HR): 1.03, P=0.015], postoperative PT≥30 degrees (HR: 2.77, P=0.043), PI-LL>20 degrees (HR: 2.92, P=0.034), as well as greater preoperative to postoperative changes in PT (HR: 1.05, P=0.004), PI (HR: 1.06, P=0.0004) and PI-LL (HR: 1.03, P=0.013) were more likely to develop PJF. Children with rib-based constructs were less likely to develop radiographic PJK compared with children with spine-based distraction constructs (31% vs. 54%, respectively, P=0.038).

CONCLUSIONS

In EOS patients undergoing growth-friendly surgery for EOS, preoperative TK>50 degrees was associated with increased risk for radiographic PJK. Postoperative PI-LL>20 degrees, PT≥30 degrees, and overcorrection of PT and PI-LL increased risk for PJF. Rib-based distraction construct decreased the risk for radiographic PJK in contrast with the spine-based constructs.

LEVEL OF EVIDENCE

Level III.

Incidence and risk factors of reoperation in patients with adjacent segment disease: A meta-analysis

Study Design:

This was a systematic review of the literature and meta-analysis.

Objective:

The objective of this study was to evaluate the current literature regarding the risk factors contributing to reoperation due to adjacent segment disease (ASD).

Summary of Background Data:

ASD is a broad term referring to a variety of complications which might require reoperation. Revision spine surgery is known to be associated with poor clinical outcomes and high rate of complications. Unplanned reoperation has been suggested as a quality marker for the hospitals.

Materials and Methods:

An electronic search was conducted using PubMed. A total of 2467 articles were reviewed. Of these, 55 studies met our inclusion criteria and included an aggregate of 1940 patients. Data were collected pertaining to risk factors including age, sex, fusion length, lumbar lordosis, body mass index, pelvic incidence, sacral slope, pelvis tilt, initial pathology, type of fusion procedure, floating versus sacral or pelvic fusion, presence of preoperative facet or disc degeneration at the junctional segment, and sagittal orientation of the facets at the junctional segment. Analysis of the data was performed using Comprehensive Meta-Analysis software (Biostat, Inc.).

Results:

The overall pooled incidence rate of reoperation due to ASD from all included studies was 0.08 (confidence interval: 0.065–0.098). Meta-regression analysis demonstrated no significant interaction between age and reoperation rate (P = 0.48). A comparison of the event rates between males and females demonstrated no significant difference between male and female reoperation rates (P = 0.58). There was a significantly higher rate of ASD in patients with longer fusion constructs (P = 0.0001).

Conclusions:

We found that 8% of patients in our included studies required reoperation due to ASD. Our analysis also revealed that longer fusion constructs correlated with a higher rate of subsequent revision surgery. Therefore, the surgeon should limit the number of fusion levels if possible to reduce the risk of future reoperation due to ASD.

Level of evidence:

IV

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.

Effective Prevention of Proximal Junctional Failure in Adult Spinal Deformity Surgery Requires a Combination of Surgical Implant Prophylaxis and Avoidance of Sagittal Alignment Overcorrection

STUDY DESIGN

Propensity score matched analysis of a multi-center prospective adult spinal deformity (ASD) database.

OBJECTIVE

Evaluate if surgical implant prophylaxis combined with avoidance of sagittal overcorrection more effectively prevents proximal junctional failure (PJF) than use of surgical implants alone.

SUMMARY OF BACKGROUND DATA

PJF is a severe form of proximal junctional kyphosis (PJK). Efforts to prevent PJF have focused on use of surgical implants. Less information exists on avoidance of overcorrection of age-adjusted sagittal alignment to prevent PJF.

METHODS

Surgically treated ASD patients (age ≥18 yrs; ≥5 levels fused, ≥1 year follow-up) enrolled into a prospective multi-center ASD database were propensity score matched (PSM) to control for risk factors for PJF. Patients evaluated for use of surgical implants to prevent PJF (IMPLANT) versus no implant prophylaxis (NONE), and categorized by the type of implant used (CEMENT, HOOK, TETHER). Postoperative sagittal alignment was evaluated for overcorrection of age-adjusted sagittal alignment (OVER) versus within sagittal parameters (ALIGN). Incidence of PJF was evaluated at minimum 1 year postop.

RESULTS

Six hundred twenty five of 834 eligible for study inclusion were evaluated. Following PSM to control for confounding variables, analysis demonstrated the incidence of PJF was lower for IMPLANT (n = 235; 10.6%) versus NONE (n = 390: 20.3%; P < 0.05). Use of transverse process hooks at the upper instrumented vertebra (HOOK; n = 115) had the lowest rate of PJF (7.0%) versus NONE (20.3%; P < 0.05). ALIGN (n = 246) had lower incidence of PJF than OVER (n = 379; 12.0% vs. 19.2%, respectively; P < 0.05). The combination of ALIGN-IMPLANT further reduced PJF rates (n = 81; 9.9%), while OVER-NONE had the highest rate of PJF (n = 225; 24.2%; P < 0.05).

CONCLUSION

Propensity score matched analysis of 625 ASD patients demonstrated use of surgical implants alone to prevent PJF was less effective than combining implants with avoidance of sagittal overcorrection. Patients that received no PJF implant prophylaxis and had sagittal overcorrection had the highest incidence of PJF.

LEVEL OF EVIDENCE

3.

Proximal junctional kyphosis and rates of fusion following posterior instrumentation and spinal fusion for adolescent idiopathic scoliosis

BACKGROUND

Proximal junctional kyphosis (PJK) can cause significant functional impairment and neural compression. Varying rates of PJK and pseudoarthrosis following posterior instrumentation and fusion for adolescent idiopathic scoliosis (AIS) are described with multiple biologic and biomechanical correlations attributed. This retrospective study aims to determine our rate of pseudoarthrosis and PJK in posterior spinal fusion for AIS, along with analysing the influence of autograft and allograft bone volume.

METHODS

Immediate and 12-month post-operative radiographs of 78 patients treated for AIS were analysed along with late complications to a minimum of 2 years. Proximal kyphosis was determined by measuring and comparing the angle between the upper instrumented vertebra and upper instrumented vertebra + 2 for both immediate and 12-month post-operative radiographs. Spinal fusion was determined using an accepted grading scale on the 12-month radiograph. These findings were correlated with known surgical variables in bone grafting technique.

RESULTS

There was one case of PJK and no cases of pseudoarthrosis. Three patients showed a defect in the fusion mass but were still suggestive of fusion. The rates of fusion and PJK were not significantly different when using different allograft volumes or incorporating autograft.

CONCLUSION

Relatively low rates of PJK following AIS correction were observed compared to the literature. Rates were not increased with the use of proximal autograft. The amount of allograft used did not affect fusion rates either.

Revision surgery in proximal junctional kyphosis

INTRODUCTION

Proximal junctional kyphosis (PJK) is a relatively common complication following spinal deformity surgery that may require reoperation. Although isolating the incidence is highly variable, in part due to the inconsistency in how PJK is defined, previous studies have reported the incidence to be as high as 39% with revision surgery performed in up to 47% of those with PJK. Despite the discordance in reported incidence, PJK remains a constant challenge that can result in undesirable outcomes following adult spine deformity surgery.

METHODS

A comprehensive literature review using Medline and PubMed was performed. Keywords included "proximal junctional kyphosis," "postoperative complications," "spine deformity surgery," "instrumentation failure," and "proximal junctional failure" used separately or in conjunction.

RESULTS

While the characterization of PJK is variable, a postoperative proximal junction sagittal Cobb angle at least 10°, 15°, or 20° greater than the measurement preoperatively, it is a consistent radiographic phenomenon that is well defined in the literature. While particular studies in the current literature may ascertain certain variables as significantly associated with the development of proximal junctional kyphosis where other studies do not, it is imperative to note that they are not all one in the same. Different patient populations, outcome variables assessed, statistical methodology, surgeon/surgical characteristics, etc. often make these analyses not completely comparable nor generalizable.

CONCLUSIONS

The goal of adult spine deformity surgery is to optimize patient outcomes and mitigate postoperative complications whenever possible. Due to the multifactorial nature of this complication, further research is required to enhance our understanding and eradicate the pathology. Patient optimization is the principal guideline in not only PJK prevention, but overall postoperative complication prevention. These slides can be retrieved under Electronic Supplementary Material.

Bivertebral autostable claws for the proximal fixation in thoracic adolescent idiopathic scoliosis surgery

STUDY DESIGN

Retrospective monocentric study.

OBJECTIVES

To report radiologic outcomes of a consecutive series of AIS patients, operated with a bivertebral autostable claw for the upper instrumentation over a 5-year period. The upper fixation represents the weakest part of long constructs because of local anatomy and the high pull-out forces. Various implants have been proposed, but proximal junctional failures (PJF) and shoulder imbalance still occur with variable incidence. The autostable claw is a new implant, safe, and low profile, combining the mechanical strength of hooks with the initial stability of pedicle screws.

METHODS

All AIS patients operated between January 2010 and July 2015 for a Lenke 1 or 2 curve with the bivertebral autostable claw were included. A minimum 2-year follow-up was required. Full-spine biplanar stereoradiographs were performed preoperatively, within 8 weeks postoperative and at latest examination. Local and global sagittal and coronal parameters were analyzed and complications were reported.

RESULTS

237 patients (191 Lenke 1 and 46 Lenke 2) were included, with a mean follow-up of 4.1 ± 0.6 years. PJF occurred in 2 patients (0.8%), and radiologic PJKs were observed in 8.4% of the series. Shoulder balance was efficiently restored or maintained in 88.2%.

CONCLUSIONS

The bivertebral autostable claw is a safe and robust alternative to pedicle screws for proximal fixation in AIS long constructs. Compression and/or distraction can be applied to level shoulders, and mechanical failures remain rare at 4-year follow-up.

LEVEL OF EVIDENCE

IV.

Large Difference Between Proximal Junctional Angle and Rod Contouring Angle is a Risk Factor for Proximal Junctional Kyphosis

OBJECTIVE

To assess the role of the difference between the proximal junctional angle (PJA) and rod contouring angle (RCA) (PJA-RCA) in the development of postoperative proximal junctional angle (PJK) in Lenke I and II adolescent idiopathic scoliosis (AIS) patients.

METHODS

We performed a retrospective analysis of 84 Lenke I and II AIS patients who underwent posterior segmental spinal instrumentation and fusion between 2012 and 2018 (minimum follow-up of 1.5 years and an average follow-up of 2 years) at a single institution. The full-spine x-ray films taken at the preoperative, postoperative, and final follow-ups were measured for each patient. The radiographic parameters were compared between the PJK and non-PJK groups, and binary logistic regression with forward elimination (conditional) was also performed to identify the risk factors for the occurrence of PJK.

RESULTS

Among the 84 patients (mean age: 14.63 ± 1.33 years), the overall incidence of PJK was 23.81%. The PJK group showed a larger preoperative pelvic incidence (55.66° ± 8.66° vs. 50.29°±8.27°, P = 0.045), thoracic kyphosis (TK) (32.44° ± 5.60° vs. 27.19° ± 5.14°, P = 0.007) and sagittal vertical axis (SVA) (40.99 ± 21.82 mm vs. 18.13 ± 28.64 mm, P = 0.013) than the non-PJK group. Postoperatively, the PJK group showed a larger decrease in the TK (-10.62° ± 3.19° vs. -5.56° ± 1.17°, P < 0.001) and SVA (-24.28 ± 18.22 mm vs. -10.83 ± 15.02 mm, P = 0.007). In addition, the PJK group had significantly larger postoperative PJA (9.83° ± 2.64° vs. 5.77° ± 3.06°, P < 0.001) and postoperative PJA-RCA (6.56° ± 3.69° vs. 1.55° ±3.32°, P < 0.001). The proportion of patients with a PJA-RCA value greater than 5° was significantly larger in the PJK group (65.00% vs. 18.75%, P < 0.001). At the last follow-up, the PJK patients had significantly larger TK (35.11° ± 5.51° vs. 26.53° ± 4.71°, P < 0.001) and SVA (22.83 ±23.12 mm vs. 3.46 ±26.24 mm, P = 0.038). Binary logistic regression analysis showed that decreases in TK and postoperative PJA-RCA were the primary contributors to PJK in patients with AIS.

CONCLUSIONS

Large postoperative PJA-RCA and decreased TK are risk factors for PJK in Lenke I and II AIS patients, especially those with PJA-RCA greater than 5°, and the occurrence of PJK should be highly considered.

Mechanical complications in adult spinal deformity and the effect of restoring the spinal shapes according to the Roussouly classification: a multicentric study

PURPOSE

To evaluate the incidence of mechanical complications in patients with adult spine deformity (ASD) treated by restoring the normal shape according to the Roussouly classification.

METHODS

This is a retrospective multicentric study with a minimum follow-up of 2 years. Patients operated on with fusion for ASD (minimum performed fusion: L2 to sacrum) were included. Patients with a history of previous spinal fusion of more than three levels were excluded. Spinal and pelvic parameters were measured on the preoperative and the immediate postoperative follow-up. All mechanical complications were recorded.

RESULTS

A total of 290 patients met the criteria of inclusion with a minimum follow-up of 2 years. Mechanical complications occurred in 30.4% of the cohort. The most common complication was PJK with an incidence of 18% while nonunion or instrumentation failure (rod breakage, implant failure) occurred in 12.4%. 66% of the patients were restored to the normal shape according to the Roussouly classification based on their PI and had a mechanical complication rate of 22.5%, whereas the remaining 34% of patients had a complication rate of 46.8% (p < 0.001). The relative risk for developing a mechanical complication if the algorithm was not met was 3 (CI 1.5-4.3; p < 0.001) CONCLUSION: In the recent literature, there are no clear guidelines for ASD correction. Restoring the sagittal spinal contour to the normal shapes of Roussouly according to the PI could serve as a guideline for ASD treatment. Ignoring this algorithm has a threefold risk of increased mechanical complications. We recommend this algorithm for treatment of ASD.

LEVEL OF EVIDENCE

IV cross-sectional observational study. These slides can be retrieved under Electronic Supplementary Material.

Effectiveness of posterior structures in the development of proximal junctional kyphosis following posterior instrumentation: A biomechanical study in a sheep spine model

Introduction

Proximal junctional kyphosis – PJK has been defined by a 10 or greater increase in kyphosis at the proximal junction as measured by the Cobb angle from the caudal endplate of the uppermost instrumented vertebrae (UIV) to the cephalad endplate of the vertebrae 1 segments cranial to the UIV. In this biomechanical study, it is aimed to evaluate effects of interspinosus ligament complex distruption and facet joint degeneration on PJK development.

Materials and methods

Posterior instrumentation applied between T2 – T7 vertebrae using pedicle screws to randomly selected 21 sheeps, divided into 3 groups. First group selected as control group (CG), of which posterior soft tissue and facet joints are protected. In second group (spinosus group, SG) interspinosus ligament complex which 1 segment cranial to UIV has been transected, and third group (faset group-FG) was applied facet joint excision. 25 N, 50 N, 100 N, 150 N and 200 N forces applied at frequency of 5 Hertz as 100 cycles axial to the samples. Then, 250 N, 275 N and 300 N forces applied static axially. Interspinosus distance, kyphosis angle and discus heights was measured in radiological evaluation. Abnormal PJK was defined by a proximal junctional angle greater than 10⁰ and at least 10⁰ greater than the corresponding preoperative measurement.

Results

In CG group, average interspinosus distance was 6,6 ± 1.54 mm and kyphosis angle was 2,2 ± 0.46° before biomechanical testing, and they were measured as 9,4 ± 1.21 mm and 3,3 ±0.44° respectively after forces applied to samples. In SG group, average interspinosus distance was 6,2 ± 1.72 mm and kyphosis angle was 2,7 ± 1.01° before experiment, and they were measured as 20,8 ± 5.66 mm and 15,1 ± 2.34° respectively after forces applied to samples. In FG group, average interspinosus distance was 4,8 ± 1.15 mm and kyphosis angle was −1 ± 4.14° before experiment, and they were measured as 11,1 ±1.96mm and 11 ± 2.87° respectively after forces applied to samples. In comparison to group CG, statistically significant junctional kyphosis was seen on both FG and SG group after statistical analysis. (p < 0.05). PJK was seen statistically significant more on SG group than FG group. (p < 0.05). Not any statistically significant difference was seen on measurement of disk distances among three groups. (p > 0.05)

Conclusions

Protecting interspinosus ligament complex and facet joint unity during posterior surgical treatment for spine deformation is vital to prevent PJK development. Based on our literature review, this is the first biomechanical study that reveals interspinosus ligament complex are more effective on preventing PJK development than facet joints.