Incidence, risk factors and classification of proximal junctional kyphosis: surgical outcomes review of adult idiopathic scoliosis

Semitendinosus Tendon Augmentation for Prevention of Proximal Junctional Failure

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to compare the incidence of proximal junctional kyphosis (PJK), proximal junctional failure (PJF), and clinical outcomes of patients who did and did not receive posterior ligament complex (PLC) augmentation using a semitendinosus allograft when undergoing long-segment posterior spinal fusion for adult spinal deformity.

SUMMARY OF BACKGROUND DATA

Clinical research on the augmentation of the PLC to prevent PJK and PJF has been limited to small case series without a comparable control group.

METHODS

From 2014 to 2019, a consecutive series of patients with adult spinal deformity who underwent posterior long-segment spinal fusion with semitendinosus allograft to augment the PLC (allograft) or without PLC augmentation (control) were identified. Preoperative and postoperative spinopelvic parameters were measured. PJK, PJF, and Oswestry Disability Index (ODI) scores were recorded and compared between the two groups. Univariate and multivariate analysis was performed. P ≤ 0.05 was considered significant.

RESULTS

Forty-nine patients in the allograft group and 34 patients in the control group were identified. There were no significant differences in demographic variables or operative characteristics between the allograft and control group. Preoperative and postoperative spinopelvic parameters were also similar between the two groups. PJK was present in 33% of patients in the allograft group and 32% of patients in the control group (P = 0.31). PJF did not occur in the allograft group, whereas six patients (18%) in the control group developed PJF (P = 0.01). Postoperative absolute ODI was significantly better in the allograft group (P = 0.007).

CONCLUSION

The utilization of semitendinosus allograft tendon to augment the PLC at the upper instrumented vertebrae in patients undergoing long-segment posterior spinal fusion for adult deformity resulted in a significant decrease in PJF incidence and improved functional outcomes when compared to a cohort with similar risk of developing PJK and PJFLevel of Evidence: 3.

Patients with abnormal microarchitecture have an increased risk of early complications after spinal fusion surgery

Spine fusion is one of the most common orthopedic surgeries, with more than 400,000 cases performed annually. While these procedures correct debilitating pain and deformities, complications occur in up to 45%. As successful fusion rests upon early stability of hardware in bone, patients with structural skeletal deficits may be at particular risk for complications. Few studies have investigated this relationship, and none have used higher order imaging to evaluate microstructural mechanisms for complications. Standard DXA measurements are subject to artifact in patients with spinal disease and therefore provide limited information. The goal of this prospective study was to investigate pre-operative bone quality as a risk factor for early post-operative complications using high resolution peripheral QCT (HR-pQCT) measurements of volumetric BMD (vBMD) and microarchitecture. We hypothesized that patients with low vBMD and abnormal microarchitecture at baseline would have more skeletal complications post-operatively. Conversely, we hypothesized that pre-operative DXA measurements would not be predictive of complications. Fifty-four subjects (mean age 63 years, BMI 27 kg/m²) were enrolled pre-operatively and followed for 6 months after multi-level lumbar spine fusion. Skeletal complications occurred in 14 patients. Patients who developed complications were of similar age and BMI to those who did not. Baseline areal BMD and Trabecular Bone Score by DXA did not differ. In contrast, HR-pQCT revealed that patients who developed complications had lower trabecular vBMD, fewer and thinner trabeculae at both the radius and tibia, and thinner tibial cortices. In summary, abnormalities of both trabecular and cortical microarchitecture were associated the development of complications within the first six months following spine fusion surgery. Our results suggest a mechanism for early skeletal complications after fusion. Given the burgeoning number of fusion surgeries, further studies are necessary to investigate strategies that may improve bone quality and lower the risk of post-operative complications.

Preoperative Hounsfield Units at the Planned Upper Instrumented Vertebrae May Predict Proximal Junctional Kyphosis in Adult Spinal Deformity

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To investigate the association between Hounsfield units (HU) measured at the planned upper instrumented vertebra (UIV) and UIV+1 and proximal junctional kyphosis (PJK) in patients with adult spinal deformity (ASD).

SUMMARY OF BACKGROUND DATA

PJK is a common complication following surgery for ASD and poor bone quality is noted to be one of the risk factors. HUs from standard computed tomography (CT) scans can be used for evaluating regional bone quality.

METHODS

Sixty-three patients were included from a single institution. The demographic characteristics and radiographic parameters were recorded. Local vertebral HUs at the planned UIV and UIV+ 1 were measured using preoperative CT scans. The patients were divided into three groups: no PJK, non-bony PJK, and bony PJK. The risk factors between the three groups and the correlation between the mean HU and increase in the PJK angle were analyzed.

RESULTS

The incidence of PJK was 36.5%. The mean HU was significantly lower in the bony PJK group (HU: 109.0) than in the no PJK group (HU: 168.7, P = 0.038), and the mean HU in the non-bony PJK group (HU: 141.7) was not different compared to the other two groups. There was a significant negative correlation between the mean HU values and the increase in the PJK angles (r = -0.475, P < 0.01). The cutoff value for the mean HU used to predict bony PJK was 120 and a HU value less than 120 was a significant risk factor for bony PJK (OR: 5.74, 95% CI [1.01-32.54], P = 0.04).

CONCLUSIONS

We noted a significant inverse relationship between the mean HUs at the UIV and UIV+ 1 and increase in the PJK angles postoperatively. In ASD patients, the HUs may be used preoperatively to identify patients with a higher risk of bony PJK.Level of Evidence: 3.

Predictive Probability of the Global Alignment and Proportion Score for the Development of Mechanical Failure Following Adult Spinal Deformity Surgery in Asian Patients

STUDY DESIGN

This is a multicenter retrospective review of 257 surgically treated consecutive ASD patients who had a minimum of five fused segments, completed a 2-year follow-up (53 ± 19 yrs, females: 236 [92%]).

OBJECTIVE

This study aimed to validate the predictive probability of the GAP score in an Asian ASD patient cohort.

SUMMARY OF BACKGROUND DATA

The GAP score is a recently established risk stratification model for MF following ASD surgery. However, the predictive ability of the GAP score is not well studied. This study aimed to validate the predictive probability of the GAP score in an Asian ASD patient cohort.

METHODS

Comparisons of the immediate postoperative GAP scores between MF the and MF-free groups were performed. We evaluated the discriminative ability of the GAP score based on the area under the receiver operating characteristic curve (AUROC). The Cuzick test was performed to determine whether there is a trend between the GAP score and the incidence of MF or revision surgery. Univariate logistic regression analyses were performed to explore the associations between the GAP score and the incidence of MF or revision surgery.

RESULTS

No difference was observed in the GAP score between the MF and MF-free groups (MF vs. MF-free; GAP: 5.9 ± 3.3 vs. 5.2 ± 2.7, P = 0.07). The Cuzick analysis showed no trend between the GAP score and the risk for MF or revision surgery. Likewise, the MF rate was not correlated with the GAP score, as shown by the ROC curve (AUC of 0.56 [95% CI 0.48-0.63], P = 0.124). Univariate logistic regression confirmed no associations between the GAP score and the incidence of MF or revision surgery (MF; moderately disproportioned [MD]: OR: 0.6 [95% CI: 0.3-1.2], P = 0.17, severely disproportioned [SD]: OR: 1.2 [95% CI: 0.6-2.3], P = 0.69, revision surgery; MD: OR: 0.8 [95% CI: 0.2-2.8], P = 0.71, SD: OR: 1.2 [95% CI: 0.9-8.7], P = 0.08).

CONCLUSION

In this multicenter study, in an Asian ASD patient cohort, the GAP score was not associated with the incidence of MF or revision surgery. Additional studies on the predictive ability of the GAP score in different patient cohorts are warranted.Level of Evidence: 3.

Recurrence of proximal junctional kyphosis after revision surgery for symptomatic proximal junctional kyphosis in patients with adult spinal deformity: incidence, risk factors, and outcomes

PURPOSE

Although proximal junctional kyphosis (PJK) is common after long spinal fusion, the outcomes of revision surgery for symptomatic PJK are unclear. Our aim was to assess the outcomes of revision surgery for symptomatic PJK in patients with adult spinal deformity and elucidate the incidence and risk factors for recurrent PJK (rePJK).

METHODS

We evaluated standing radiographs and health-related quality of life (HRQOL) in patients who underwent revision surgery for symptomatic PJK with at least 2-year follow-up. Patients were assigned to the non-rePJK or rePJK group according to PJK recurrence.

RESULTS

Thirty-nine consecutive patients (mean age, 63 ± 11 years; 24 women) met the inclusion criteria. RePJK occurred in 12 patients (31%). There were significant differences in the following parameters between groups (non-rePJK vs. rePJK): initial proximal junctional sagittal Cobb angle (PJA) (26.6° vs. 35.6°), thoracic kyphosis (TK) (38.6° vs. 52.8°), and sagittal vertical axis (SVA) (9.3 vs. 15.9 cm), and pre- to postoperative SVA decrease (6.1 vs. 12.2 cm). Significant risk factors for rePJK were initial PJA > 40°, preoperative TK > 60°, preoperative SVA > 10.0 cm, correction of TK > 15°, and correction of SVA > 5.0 cm. HRQOL scores improved significantly; however, postoperative SRS-22r activity scores were significantly worse in the rePJK group vs the non-rePJK group.

CONCLUSION

The incidence of rePJK was 31%. Risk factors for rePJK were large initial PJA, high preoperative TK and SVA, and greater correction of TK and SVA. HRQOL did not differ significantly between patients with vs without rePJK, except immediate postoperative SRS-22r activity scores.

LEVEL OF EVIDENCE

III.

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.

Effect of sagittal shape on proximal junctional kyphosis following thoracopelvic corrective fusion for adult spinal deformity: postoperative inflection vertebra cranial to T12 is a significant risk factor

STUDY DESIGN

This was a retrospective analysis of a prospectively collected consecutive case series of patients with adult spinal deformity (ASD).

OBJECTIVE

This study aimed to investigate the impact of the geometrical sagittal shape of the corrected spine on the development of proximal junctional kyphosis (PJK). Several studies have documented risk factors for PJK in ASD surgery. Geometrical assessment is vital for evaluating sagittal spinal deformity. It is essential to assess the postoperative geometrical shape of the spine and the location of the correction in the spine to decrease postoperative junctional stress and PJK.

METHODS

Consecutive patients with ASD who underwent corrective fusion with long constructs to the pelvis were included. Patients with neuromuscular disease, congenital and adolescent scoliosis, infection, and spinal tumor were excluded. We investigated the spinopelvic and geometrical parameters of the whole spine. The locations of the thoracic and lumbar apical vertebrae and the inflection vertebrae (IV), where the curvature of the associated adjacent vertebral bodies changes from kyphosis to lordosis, were investigated. The subjects were divided into PJK included patients who underwent revision surgery for junctional failure or with a change in proximal junctional angle ≥ 20°, and non-PJK groups.

RESULTS

A total of 139 patients (mean age, 69.6 years; range 18-82 years) were included. There were 47 and 92 patients in the PJK and non-PJK groups, respectively. The IV were located significantly cranial and posterior, the lumbar apex were located significantly posterior in the PJK group at the immediate postoperative time points. The significant risk factors for PJK on binary logistic regression were cranial IV and posterior lumbar apical vertebrae. The incidence of PJK in patients with IV at T12 or cranial tends PJK significantly higher (69%) than at L1 or caudal (26%).

CONCLUSIONS

Geometrical spinal shape should be taken into account to reduce the rate of postoperative mechanical complications.

LEVEL OF EVIDENCE

Level of evidence III.

Junctional kyphosis and junctional failure after multi-segmental posterior cervicothoracic fusion - A retrospective analysis of 64 patients

Introduction

Junctional kyphosis (JK) and junctional failure (JF) are known complications after thoracolumbar spinal deformity surgery. This study aims to define the incidence and possible risk factors for JK/JF following multi-segmental cervicothoracic fusion.

Methods

This is a retrospective analysis of 64 consecutive patients undergoing cervicothoracic fusion surgery, including at least five segments. Clinical and radiographic outcome measures were analyzed. A univariate analysis was performed to determine the effect of the level of upper instrumented vertebra (UIV) and lower instrumented vertebra (LIV), fusion status, C2 sagittal vertical axis (SVA), C2-C7 lordotic angle and T1 slope angle on the occurrence of JK/JF.

Results

A total of 46 patients were followed up for a median of 1.1 years (range 0.3-4) with a median age of 65.5 years (range 42.2-84.5). Indication for surgery was spinal stenosis in 87%, trauma in 7%, and tumor in 6% of cases. The median number of levels fused was 7; the most frequent UIV was C2, and the most frequent LIV was T2. Solid fusion was achieved in 78% at the last follow-up. Postoperatively, the median C2 SVA was 32 mm (range - 7-75), median T1 slope angle was 33° (range 2°-57°), C2-C7 sagittal cobb angle was 4° (-29°-12°). JK developed in 4% of cases, no case of JF was observed. No statistically significant impact of bone density, level of UIV, level of LIV or postoperative sagittal parameters on the occurrence of JK/JF was observed, even though fusion status and pathologic T1 slope angle showed a trend toward significance.

Conclusion

In this cohort of patients with mildly pathologic sagittal balance, JK was a rare event after multi-segmental fusion, observed in only 4% of cases. Neither level of UIV nor LIV had an influence on its occurrence; however, nonunion and pathologic sagittal alignment showed a nonsignificant trend.

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.

Prediction of Proximal Junctional Kyphosis After Posterior Scoliosis Surgery With Machine Learning in the Lenke 5 Adolescent Idiopathic Scoliosis Patient

Objective

To build a model for proximal junctional kyphosis (PJK) prognostication in Lenke 5 adolescent idiopathic scoliosis (AIS) patients undergoing long posterior instrumentation and fusion surgery by machine learning and analyze the risk factors for PJK.

Materials and Methods

In total, 44 AIS patients (female/male: 34/10; PJK/non-PJK: 34/10) who met the inclusion criteria between January 2013 and December 2018 were retrospectively recruited from West China Hospital. Thirty-seven clinical and radiological features were acquired by two independent investigators. Univariate analyses between PJK and non-PJK groups were carried out. Twelve models were built by using four types of machine learning algorithms in conjunction with two oversampling methods [the synthetic minority technique (SMOTE) and random oversampling]. Area under the receiver operating characteristic curve (AUC) was used for model discrimination, and the clinical utility was evaluated by using F1 score and accuracy. The risk factors were simultaneously analyzed by a Cox regression and machine learning.

Results

Statistical differences between PJK and non-PJK groups were as follows: gender (p = 0.001), preoperative factors [thoracic kyphosis (p = 0.03), T1 slope angle (T1S, p = 0.078)], and postoperative factors [T1S (p = 0.097), proximal junctional angle (p = 0.003), upper instrumented vertebra (UIV) – UIV + 1 (p = 0.001)]. Random forest using SMOTE achieved the best prediction performance with AUC = 0.944, accuracy = 0.909, and F1 score = 0.667 on independent testing dataset. Cox model revealed that male gender and larger preoperative T1S were independent prognostic factors of PJK (odds ratio = 10.701 and 57.074, respectively). Gender was also at the first place in the importance ranking of the model with best performance.

Conclusion

The random forest using SMOTE model has the great value for predicting the individual risk of developing PJK after long instrumentation and fusion surgery in Lenke 5 AIS patients. Moreover, the combination of the outcomes of a Cox model and the feature ranking extracted by machine learning is more valuable than any one alone, especially in the interpretation of risk factors.

Biomechanics of prophylactic tethering for proximal junctional kyphosis: effects of cyclic loading on tether strength and failure properties

STUDY DESIGN

Biomechanical evaluation of woven polyester tethers.

OBJECTIVES

To quantify changes in tether elongation, stiffness, and failure characteristics after cyclic loading. Ligamentous augmentation is gaining interest as a technique to prevent proximal junctional kyphosis (PJK) in adult spinal fusions. There are a lack of data regarding the effects of cyclic loading on polyester tether mechanical properties. Tether stretch may lead to loss of stabilization and increased risk of tether failure. Biomechanical data are needed to determine the effects of cyclic loading on tether integrity.

METHODS

Testing was done in two materials: (1) a synthetic cortical bone composite to determine baseline mechanical properties, and (2) nine cadaveric L1 spinous processes. 5 mm woven polyester tethers were looped through 2.5 mm holes drilled in each material. First, five tethers were tested directly to failure in the synthetic bone to establish baseline failure properties. Next, tethers were tested at one of the three cyclic load ranges [5%, 25%, and 50% (n = 5 each) of baseline failure] for 1000 cycles and then loaded to failure. Cadaveric tests were done at the 25% range and compared to synthetic bone tests at the same range. Cadaveric failure tests were classified as either tether failure or spinous process bone failure.

RESULTS

Greater cyclic loading range had a significant effect on tether loop elongation, increased stiffness, and decreased ultimate tensile force. Among the cadaveric failure tests, 56% resulted in tether failure and the remaining 44% resulted in bone failure.

CONCLUSIONS

Polyester tethers stretch significantly when loaded to physiological ranges. Anticipation of tether stretch may be an important consideration for a tethering strategy to prevent PJK. Improved understanding of tether material properties can provide guidance for the evaluation of clinical outcomes associated with techniques to reduce the risk of PJK caused by ligamentous laxity.

LEVEL OF EVIDENCE

Biomechanical study.

Spino-Pelvic Thresholds for Prevention of Proximal Junctional Kyphosis Following Combined Anterior Column Realignment and Short Posterior Spinal Fusion in Degenerative Lumbar Kyphosis

Objective

To analyze ideal indication for combined anterior column realignment (ACR) with short posterior spinal fusion (PSF) and posterior column osteotomy (PCO) for preventing proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients with lower lumbar kyphosis and compensatory thoracolumbar lordosis.

Methods

A retrospective study was conducted. This study included 27 ASD patients (average age of 66.6 years; one male and 26 females) with lower lumbar kyphosis and compensated thoracolumbar lordosis who underwent short PSF with PCO following ACR from 2006 to 2010. The minimum follow‐up period was 5 years. The patients were divided into two groups based on the sagittal vertical axis (SVA) of the last follow‐up radiographs, and a comparative analysis was performed evaluating spino‐pelvic parameters and clinical outcomes including the Oswestry Disability Index (ODI), Visual Analog Scale (VAS), and complications.

Results

The mean follow‐up time of included patients was 109.7 months, and the mean number of fused segments was 3.7. The uppermost instrumented vertebra was L₂ in 18 patients or L₃ in nine patients, and lowermost instrumented vertebra was sacrum in all patients. The mean lumbar lordosis (LL) values in the optimal SVA and suboptimal SVA groups were 4.4° and 4.2° preoperatively (P = 0.639), −48.1° and −35° postoperatively (P = 0.007), and −45.2° and −20.7° at the last follow‐up (P < 0.05). Overcorrection was seen in seven patients in the optimal SVA group, whereas all of the patients of the suboptimal SVA group were in the category of undercorrection (P = 0.021). Pelvic incidence (PI) of optimal SVA group (<50 mm, n = 16) and suboptimal SVA group (≥50 mm, n = 11) was 44.1° and 53.8° (P = 0.009). The prevalence of PJK was significantly higher in the suboptimal SVA group (P = 0.008), and last follow‐up VAS for back pain (P < 0.05), and postoperative and last follow‐up ODI (P = 0.002 and P < 0.05) were statistically larger for the suboptimal group than the optimal group.

Conclusions

Combined ACR with short PSF and PCO could effectively prevent sagittal decompensation of PJK and help achieve sagittal balance in the treatment of ASD patients with lower lumbar kyphosis, compensatory thoracolumbar lordosis, and especially low PI (<50°).

Incidence, Risk Factors, and Prevention Strategy for Proximal Junctional Kyphosis in Adult Spinal Deformity Surgery

Introduction

Proximal junctional kyphosis (PJK) is an acute complication of adult spinal deformity (ASD) surgery and may require re-operation because of proximal junctional failure (PJF). PJK causes and prevention strategies remain unknown. This study aimed to investigate the differences in the backgrounds of patients with PJK, compared to those without PJK, in ASD surgery.

Methods

We included data from 86 patients who underwent ASD surgery between 2012 and 2018. There were 40 patients (46.5%) with PJK; 46 patients did not have PJK until the last follow-up. We evaluated patient demographics, clinical outcomes, and radiographic parameters, such as Cobb angle and spinopelvic parameters on standing X-ray films, in each group.

Results

There was no significant difference in patient demographics, clinical outcomes, or preoperative radiographic parameters. Postoperative pelvic incidence minus lumbar lordosis (PI-LL) and pelvic tilt (PT) were significantly lower in the PJK group, and thoracic kyphosis (TK) was higher. The cutoff values were 34.5° for TK, 0.5° for PI-LL, and 15.5° for PT. Other radiographic parameters were not significantly different. PJF developed in seven patients (17.5%) in the PJK group. PJF patients had significantly older age, higher postoperative TK, higher postoperative proximal junctional Cobb angle (PJA), more changes between pre- and postoperative PJA, and lower satisfaction scores on the Scoliosis Research Society Outcomes Questionnaire (SRS-22 satisfaction) than non-PJF patients in the PJK group.

Conclusions

One risk factor for PJK was lower postoperative PI-LL that was 0° or less. In ASD surgery, the most critical factor in a PJK prevention strategy is to obtain a postoperative LL adjusted by PI, which is >0°.

The association between lower Hounsfield units of the upper instrumented vertebra and proximal junctional kyphosis in adult spinal deformity surgery with a minimum 2-year follow-up

OBJECTIVE

Patients undergoing long-segment fusions from the lower thoracic (LT) spine to the sacrum for adult spinal deformity (ASD) correction are at risk for proximal junctional kyphosis (PJK). One mechanism of PJK is fracture of the upper instrumented vertebra (UIV) or higher (UIV+1), which may be related to bone mineral density (BMD). Because Hounsfield units (HUs) on CT correlate with BMD, the authors evaluated whether HU values were correlated with PJK after long fusions for ASD.

METHODS

The authors performed a retrospective study of patients older than 50 years who had undergone ASD correction from the LT spine to the sacrum in the period from October 2007 to January 2018 and had a minimum 2-year follow-up. Demographic and spinopelvic parameters were measured. HU values were measured on preoperative CT at the UIV, UIV+1, and UIV+2 (2 levels above the UIV) levels and were assessed for correlations with PJK.

RESULTS

The records of 127 patients were reviewed. Fifty-four patients (19 males and 35 females) with a mean age of 64.91 years and mean follow-up of 3.19 years met the study inclusion criteria; there were 29 patients with PJK and 25 patients without. There was no statistically significant difference in demographics or follow-up between these two groups. Neither was there a difference between the groups with regard to postoperative pelvic incidence (PI), sacral slope (SS), lumbar lordosis (LL), PI minus LL (PI-LL), thoracic kyphosis (TK), or sagittal vertical axis (SVA; all p > 0.05). Postoperative pelvic tilt (p = 0.003) and T1 pelvic angle (p = 0.014) were significantly higher in patients with PJK than in those without. Preoperative HUs at UIV, UIV+1, and UIV+2 were 120.41, 124.52, and 129.28 in the patients with PJK, respectively, and 152.80, 155.96, and 160.00 in the patients without PJK, respectively (p = 0.011, 0.02, and 0.018). Three receiver operating characteristic (ROC) curves for preoperative HU values at the UIV, UIV+1, and UIV+2 as a predictor for PJK were established, with areas under the ROC curve of 0.710 (95% CI 0.574–0.847), 0.679 (95% CI 0.536–0.821), and 0.681 (95% CI 0.539–0.824), respectively. The optimal HU value by Youden index was 104 HU at the UIV (sensitivity 0.840, specificity 0.517), 113 HU at the UIV+1 (sensitivity 0.720, specificity 0.517), and 110 HU at the UIV+2 (sensitivity 0.880, specificity 0.448).

CONCLUSIONS

In patients undergoing long-segment fusions from the LT spine to the sacrum for ASD, PJK was associated with lower HU values on CT at the UIV, UIV+1, and UIV+2. The measurement of HU values on preoperative CTs may be a useful adjunct for ASD surgery planning.

Proximal Junctional Kyphosis in Degenerative Sagittal Deformity After Under- and Overcorrection of Lumbar Lordosis: Does Overcorrection of Lumbar Lordosis Instigate PJK?

STUDY DESIGN

Retrospective study.

OBJECTIVE

To analyze proximal junctional kyphosis (PJK) occurrence and surgical outcomes according to degree of lumbar lordosis (LL) correction relative to pelvic incidence (PI). In addition, risk factors of PJK including LL and sagittal vertical axis (SVA) correction were investigated.

SUMMARY OF BACKGROUND DATA

PJK is a common complication after adult spinal deformity surgery, and many factors are known to be associated with PJK. However, the effect of degree of LL correction on PJK occurrence is not fully understood.

METHODS

Eighty-three degenerative sagittal imbalance patients treated with deformity correction and long instrumented fusion to the sacrum with a minimum follow-up of 2 years were studied. Patients were divided into three groups according to their postoperative LL angle relative to PI using the SRS-Schwab classification: Group A (undercorrection, PI-LL> 10°), Group B (ideal correction, -10°

RESULTS

Overall PJK prevalence was 36.1% (30/83), and ratio of optimal SVA at postoperative and last follow-up were significantly higher in Group C (P < 0.001, P < 0.001). Nevertheless, there was no significant difference in PJK prevalence among three groups (40% vs. 37.5% vs. 34.1%; P = 0.907). Group C had better clinical outcomes (last follow-up ODI, VAS of LBP) than Group A (10.0 vs. 18.4; P < 0.001 and 1.5 vs. 4.0; P < 0.001). The increases in LL or SVA correction degree were not associated with PJK occurrence (P = 0.304, P = 0.201).

CONCLUSION

Overcorrection showed good surgical outcomes without increasing PJK prevalence. Degrees of LL and SVA correction do not act as risk factors for PJK. Therefore, in adult spinal deformity patients, LL correction greater than PI may be a good choice that can result in better clinical outcomes without increasing risk of PJK.

LEVEL OF EVIDENCE

4.

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Key Words Collapse

MESH Headings

• Adult
• Aged
• Animals
• Female
• Humans
• Kyphosis/diagnostic imaging
• Kyphosis/etiology
• Lordosis/diagnostic imaging
• Lordosis/surgery
• Lumbar Vertebrae/diagnostic imaging
• Lumbar Vertebrae/surgery
• Male
• Middle Aged
• Neurodegenerative Diseases/diagnostic imaging
• Neurodegenerative Diseases/etiology
• Neurosurgical Procedures/adverse effects
• Neurosurgical Procedures/trends
• Retrospective Studies
• Risk Factors

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Grants Collapse

Affiliation(s)

Sang-Kyu Im Department of Orthopedic Surgery, Graduate School, College of Medicine, Kyung Hee University, Seoul, Korea
Jung-Hee Lee
Kyung-Chung Kang
Sung Joon Shin
Ki Young Lee
Jong Jun Park
Man Ho Kim

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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.

Global Trends of Researches on Sacral Fracture Surgery: A Bibliometric Study Based on VOSviewer

STUDY DESIGN

Bibliometric analysis.

OBJECTIVE

This study aims to identify and summarize the articles related to sacral fracture surgery, to compare the papers from different countries and journals, to show the trends of researches on sacral fracture surgery.

SUMMARY OF BACKGROUND DATA

In recent years, studies on sacral fracture are growing rapidly, but there were no bibliometric studies regarding sacral fracture surgery.

METHODS

Excel 2016 and VOSviewer were used to identify and summarize the articles from Web of Science between 1900 and 2018. Publication number, publication year, publication country, publication organization, publication source, author, sum of times cited, H-index, and journal's impact factors were recorded and analyzed. Bibliometric maps of co-citations and maps of co-occurrence of keywords are drawn.

RESULTS

A total of 611 publications were extracted. United States published most articles (227, 37.2%), both total citations (3536) and H-index (32) of United States ranked first of all the countries. The most productive organization on sacral fracture surgery is Johns Hopkins University (14). Spine (43) published the most articles on sacral fracture surgery. The latest keyword "patterns" appeared in 2017 in 5 articles. Other relatively new keywords include "proximal junctional kyphosis," "spondylopelvic dissociation," "fragility fracture," "lumbopelvic fixation" that appeared in 2017 in eight, six, six, and 25 articles, respectively.

CONCLUSION

This bibliometric study showed that there is a growing trend both in published articles related to sacral fracture surgery and relative research interest in the last 30 years. United States dominates the research regarding sacral fracture surgery. Johns Hopkins University, Johannes Gutenberg University of Mainz, and Harborview Medical Center are the best institutions related to sacral fracture surgery research. Spine, J Orthop Trauma, and Injury are the top three productive journals on sacral fracture surgery. Sacral fracture patterns, proximal junctional kyphosis, spondylopelvic dissociation, fragility fracture, and lumbopelvic fixation may be the new research hotspot in this field.

LEVEL OF EVIDENCE

5.

Risk Factor Analysis of Proximal Junctional Kyphosis after Surgical Treatment of Adult Spinal Deformity with Oblique Lateral Interbody Fusion

Study Design

A single-center retrospective study.

Purpose

To investigate the prevalence of proximal junctional kyphosis (PJK) and its risk factors after surgical treatment of adult spinal deformity (ASD) with oblique lateral interbody fusion (OLIF).

Overview of Literature

Correction of ASD using OLIF has been developed because it is less invasive, and enables correction of severe deformities. Although PJK is a well-recognized complication after the correction of spinal deformity, few studies have evaluated the prevalence and risk factors for PJK after OLIF for ASD.

Methods

We reviewed 74 patients who underwent surgery for ASD. PJK was defined as a proximal junction sagittal Cobb angle exceeding 10°, and at least 10° greater than the preoperative measurement. We investigated the following as risk factors: age, sex, body mass index, medical history, number of fused segments, number of interbody fusions, number of OLIFs, number of osteotomies, level of upper instrumented vertebrae, lowest instrumented vertebrae, and radiographic parameters.

Results

The mean follow-up duration was 22.4 months and the mean age of the patients was 73.6 years. PJK was present in 19/74 patients (25.7%) and absent in 55/74 (74.3%). In the univariate analysis, those with PJK had a significantly higher proportion of patients with a history of vertebral compression fracture (7/19 patients [36.8%] vs. 6/55 patients [10.9%], p=0.027). Those with PJK had a significantly higher proportion of patients with fusion to the pelvis (18/19 patients [94.7%] vs. 34/55 patients [61.8%], p=0.016). According to the multivariate analysis, fusion to the pelvis was a significant risk factor for PJK.

Conclusions

Fusion to the pelvis was the most important risk factor for PJK. A history of vertebral compression fracture served as an additional risk factor for PJK. Clinicians should consider these factors before treating ASD patients with OLIF.

The patient demographics, radiographic index and surgical invasiveness for mechanical failure (PRISM) model established for adult spinal deformity surgery

Mechanical failure (MF) following adult spinal deformity (ASD) surgery is a severe complication and often requires revision surgery. Predicting a patient’s risk of MF is difficult, despite several potential risk factors that have been reported. The purpose of this study was to establish risk stratification model for predicting the MF based on demographic, and radiographic data. This is a multicenter retrospective review of the risk stratification for MF and included 321 surgically treated ASD patients (55 ± 19 yr, female: 91%). The analyzed variables were recorded for at least 2 yr and included age, gender, BMI, BMD, smoking status, frailty, fusion level, revision surgery, PSO, LIF, previous surgery, spinal alignment, GAP score, Schwab-SRS type, and rod materials. Multivariate logistic regression analyses were performed to identify the independent risk factors for MF. Each risk factor was assigned a value based on its regression coefficient, and the values of all risk factors were summed to obtain the PRISM score (range 0–12). We used an 8:2 ratio to split the data into a training and a testing cohort to establish and validate the model. MF developed in 41% (n = 104) of the training subjects. Multivariate analysis revealed that BMI, BMD, PT, and frailty were independent risk factors for MF (BMI: OR 1.7 [1.0–2.9], BMD: OR 3.8 [1.9–7.7], PT: OR 2.6 [1.8–3.9], frailty: OR 1.9 [1.1–3.2]). The MF rate increased with and correlated well with the risk grade as shown by ROC curve (AUC of 0.81 [95% CI 0.76–0.86]). The discriminative ability of the score in the testing cohort was also good (AUC of 0.86 ([95% CI 0.77–0.95]). We successfully developed an MF-predicting model from individual baseline parameters. This model can predict a patient’s risk of MF and will help surgeons adjust treatment strategies to mitigate the risk of MF.

Artificial Intelligence Models Predict Operative Versus Nonoperative Management of Patients with Adult Spinal Deformity with 86% Accuracy

OBJECTIVE

Patients with ASD show complex and highly variable disease. The decision to manage patients operatively is largely subjective and varies based on surgeon training and experience. We sought to develop models capable of accurately discriminating between patients receiving operative versus nonoperative treatment based only on baseline radiographic and clinical data at enrollment.

METHODS

This study was a retrospective analysis of a multicenter consecutive cohort of patients with ASD. A total of 1503 patients were included, divided in a 70:30 split for training and testing. Patients receiving operative treatment were defined as those undergoing surgery up to 1 year after their baseline visit. Potential predictors included available demographics, past medical history, patient-reported outcome measures, and premeasured radiographic parameters from anteroposterior and lateral films. In total, 321 potential predictors were included. Random forest, elastic net regression, logistic regression, and support vector machines (SVMs) with radial and linear kernels were trained.

RESULTS

Of patients in the training and testing sets, 69.0% (n = 727) and 69.1% (n = 311), respectively, received operative management. On evaluation with the testing dataset, performance for SVM linear (area under the curve =0.910), elastic net (0.913), and SVM radial (0.914) models was excellent, and the logistic regression (0.896) and random forest (0.830) models performed very well for predicting operative management of patients with ASD. The SVM linear model showed 86% accuracy.

CONCLUSIONS

This study developed models showing excellent discrimination (area under the curve >0.9) between patients receiving operative versus nonoperative management, based solely on baseline study enrollment values. Future investigations may evaluate the implementation of such models for decision support in the clinical setting.

Incidence and risk factors of proximal junctional kyphosis after internal fixation for adult spinal deformity: a systematic evaluation and meta-analysis

To investigate the factors associated with proximal junctional kyphosis (PJK). A systematic search was performed. The weighted mean difference (WMD) was pooled for continuous variables, and the odds ratio (OR) was calculated for dichotomous variables. The PJK group had higher values for age (WMD = 2.53, 95%CI = 1.38 ~ 3.68, P < 0.001), female gender (OR = 1.56, 95%CI = 1.29 ~ 1.87, P < 0.001), and diagnosed osteoporosis (OR = 1.58, 95%CI = 1.11 ~ 2.26, P = 0.01). Preoperatively, significant differences were detected in sagittal vertical axis (SVA) (WMD = 19.29, 95%CI = 16.60 ~ 21.98, P < 0.001), pelvic incidence minus lumbar lordosis (PI-LL) (WMD = 2.71, 95%CI = 0.25 ~ 5.18, P = 0.03), pelvic tilt (PT) (WMD = 2.64, 95%CI = 1.38 ~ 3.90, P < 0.001), lumbar lordosis (LL) (WMD = - 1.76, 95%CI = - 2.73 ~ -0.79, P < 0.001), and sacral slope (SS) (WMD = - 2.80, 95%CI = - 5.57 ~ -0.04, P = 0.001). At follow-up, the following were higher in the PJK group: thoracic kyphosis (TK) (WMD = 5.51, 95%CI = 2.23 ~ 8.80, P < 0.001), proximal junctional angle (PJA) (WMD = 9.07, 95%CI = 4.21 ~ 13.92, P < 0.001), and PT (WMD = 1.51, 95%CI = 0.31 ~ 2.72, P = 0.01). However, there was no significant difference in SS (P = 0.49), and SVA (P = 0.11) between groups. Fusion to S1 or pelvis significantly increased the risk of PJK (OR = 2.08, P < 0.001). Ligament augmentation reduced the risk of PJK (OR = 0.34, 95%CI = 0.21 ~ 0.53, P < 0.001) better than the use of laminar hook (OR = 0.46, P < 0.001). Although no difference was detected for preoperative SRS-22 score (P = 0.056), a lower score (WMD = - 0.24, 95%CI = - 0.35 ~ -0.14, P < 0.001) was detected in PJK group at follow-up. The elderly female ASD patients were more susceptible to PJK, especially for those with osteoporosis, high preoperative SVA, low LL, large PT, and LIV extended to pelvis. The use of laminar hook and ligament reinforcement at the proximal end might prevent PJK.

Should Thoracolumbar Junction Be Always Avoided as Upper Instrumented Vertebra in Long Instrumented Fusion for Adult Spinal Deformity?: Risk Factor Analysis for Proximal Junctional Failure

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of this study was to investigate the risk factors for proximal junctional failure (PJF) following long instrumented fusion stopping at thoracolumbar junction (TLJ) in adult spinal deformity (ASD) and to determine which cases are suitable for TLJ stop without increasing the risk for PJF.

SUMMARY OF BACKGROUND DATA

PJF following long fusion for ASD is a well-recognized complication that negatively affects clinical outcomes. Generally, the uppermost instrumented vertebra (UIV) at the TLJ is associated with the risk of PJF. Little is known about the risk factors for PJF in case with the UIV at TLJ.

METHODS

Radiographic and clinical data of 63 consecutive patients who underwent instrumented fusion from sacrum to TLJ (T11, T12, and L1) for the treatment of ASD with a minimum 2-year follow-up were analyzed to identify the risk factors for PJF, which was defined as proximal junctional angle (PJA) ≥20°, fracture at UIV or UIV+1, failure of UIV fixation, myelopathy, or 'need for proximal extension of fusion.

RESULTS

During the average follow-up duration of 51.7 months, PJF developed in 23 patients (36.5%) at a mean of 9.3 months after surgery. Multivariate analysis revealed that age >70 years (odds ratio [OR]: 1.119), osteoporosis (OR: 4.459), and preoperative kyphotic PJA (OR: 1.138) were significant risk factors for the development of PJF. No PJF occurred in 14 patients lacking any risk factors. The last follow-up clinical results were significantly inferior in the PJF group than in the non-PJF group in terms of Oswestry Disability Index and Scoliosis Research Society-22 score.

CONCLUSION

Age >70 years, osteoporosis, and PJA greater 0° were identified as significant risk factors for PJF. Therefore, the TLJ level can be considered as UIV selectively for patients younger than 70 years without osteoporosis and with lordotic preoperative PJA.

LEVEL OF EVIDENCE

3.

Assessment of Patient Outcomes and Proximal Junctional Failure Rate of Patients with Adult Spinal Deformity Undergoing Caudal Extension of Previous Spinal Fusion

OBJECTIVE

This case series examined patients undergoing caudal extension of prior fusion without alteration of the prior upper instrumented vertebra (UIV) to assess patient outcomes and rates of proximal junctional kyphosis (PJK)/proximal junctional failure (PJF).

METHODS

Patients eligible for 2-year minimum follow-up undergoing caudal extension of prior fusion with unchanged UIVs were identified. These patients were evaluated for PJK/PJF, and patient reported outcomes were recorded.

RESULTS

In total, 40 patients were included. Mean follow-up duration was 2.2 ± 0.3 years. Patients in this cohort had poor preoperative sagittal alignment (pelvic incidence minus lumbar lordosis [PI-LL] 26.7°, T1 pelvic angle [TPA] 29.0°, sagittal vertical axis [SVA] 93.4 mm) and achieved substantial sagittal correction (ΔSVA -62.2 mm, ΔPI-LL -19.8°, ΔTPA -11.1°) after caudal extension surgery. At final follow-up, there was a 0% rate of PJF among patients undergoing caudal extension of previous fusion without creation of a new UIV, but 27.5% of patients experienced PJK. Patients experienced significant improvement in both the Oswestry Disability Index and Scoliosis Research Society-22r total score at 2 years postoperatively (P < 0.05). In total, 7.5% (n = 3) of patients underwent further revision, at an average of 1.1 ± 0.54 years after the surgery with unaltered UIV. All 3 of these patients underwent revision for rod fracture with no revisions for PJK/PJF.

CONCLUSIONS

Patients undergoing caudal extension of previous fusions for sagittal alignment correction have high rates of clinical success, low revision surgery rates, and very low rates of PJF. Minimizing repetitive tissue trauma at the UIV may result in decreased PJF risk because the PJF rate in this cohort of patients with unaltered UIV is below historical PJF rates of patients undergoing sagittal balance correction.

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.

The effect of posterior tethers on the biomechanics of proximal junctional kyphosis: The whole human finite element model analysis

Little is known about the effects of posterior tethers on the development of proximal junctional kyphosis (PJK). We evaluated the ability of posterior tethers to the proximal motion segment stiffness in long instrumented spinal instrumentation and fusion using a whole body human FE model. A series of finite element (FE) analysis of long segmental spinal fusion (SF) from the upper thoracic vertebra (T1) or lower thoracic vertebra (T9) to the sacrum with pedicle screws and rods were performed using an entire human body FE model (includes 234,910 elements), and compressive stresses (CS) on the anterior column, and tensile stresses (TS) on the posterior ligamentous complex (PLC) in the upper-instrumented vertebra (UIV) and the vertebra adjacent to the UIV (UIV + 1) were evaluated with posterior tethers or without posterior tethers. The models were tested at three T1 tilts (0, 20, 40 deg.), with 20% muscle contraction. Deformable material models were assigned to all body parts. Muscle-tendon complexes were modeled by truss elements with a Hill-type muscle material model. The CS of anterior column decreased with increasing T1 slope with tethers in both models, while the CS remained relatively large in T9 model compared with T1 model (T1 UIV; 0.96 to 1.56 MPa, T9 UIV; 4.79 to 5.61 MPa). The TS of the supraspinous ligament was markedly reduced in both T1 and T9 models with posterior tethers (11-35%). High vertebral CS on UIV and UIV + 1 were seen in the T9 UIV model, and the TS on the PLC were increased in both UIV models. Posterior tethers may decrease PJK development after SF with a proximal thoracic UIV, while both posterior tethers and vertebral augmentation may be necessary to reduce PJK development with a lower thoracic UIV.

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.

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.

Thoracic pedicle subtraction osteotomy for correction of proximal junctional kyphosis after surgery for adolescent idiopathic scoliosis: A case report

•

Proximal junctional kyphosis in adolescent idiopathic scoliosis is frequent.

•

Poor visualization of the sagittal plane leads to incorrect identification of curve type.

•

Residual or progressive symptomatic kyphosis may require surgical treatment.

•

Pedicle subtraction osteotomy may be an effective corrective technique.

Introduction

Complications in the upper thoracic spine are not uncommon after corrective surgery for deformities in adults and adolescents. Proximal junctional failure has been linked to structural osseous or ligamentous failure and proximal junctional kyphosis has been described as an increase in preoperative proximal kyphosis.

Case description

A 20-year-old male patient intervened after atypical development of idiopathic scoliosis, with rapid progression nearing skeletal maturity. While an increase in the magnitude of the main thoracic curve in the coronal plane was observed, the progression of structural sagittal plane deformity of the proximal thoracic curve was not identified due to poor visualization. This resulted in improper identification of curve type and choice of fusion levels, with progressive residual kyphosis across follow-up. At the age of 27, the patient was re-intervened by means of pedicle subtraction osteotomy in the apical area of the proximal thoracic deformity. Although an adequate correction was achieved, the remaining deformity of 50° and the proximal failure required extending the instrumentation and fusion to the cervical spine. This has shown itself to be an effective technique for correction of proximal residual or progressive symptomatic fixed kyphosis, thereby avoiding the morbidity of the anterior or combined approaches.

Conclusions

In adolescent deformity, an adequate preoperative planning including clinical and radiological study must be carried out, paying special attention to the sagittal plane to identify major and minor structural curves.

The pedicle subtraction osteotomy, despite being a demanding technique and not entirely risk-free, has shown itself to be an effective corrective technique.

Effectiveness of percutaneous cement injection on proximal junctional failure after posterior lumbar interbody fusion: Preliminary study

Proximal junctional failure (PJF) is the greatest challenge after posterior lumbar interbody fusion (PLIF). The aim of this study was to evaluate the effectiveness of percutaneous cement injection (PCI) for PJF after PLIF patients requiring surgical revision.In this retrospective clinical study, we reviewed 7 patients requiring surgical revision for PJF after PLIF with 18 months follow-up. They received PCI at the collapsed vertebral body and supra-adjacent vertebra, with or without intervertebral disc intervention. The outcome measures were radiographic findings and revision surgery. Two different radiographic parameters (wedging rate (%) of the fractured vertebral body and local kyphosis angle) were used, and were performed before and immediately after PCI, and 18 month after the PCI.In our study, we showed that 5 of 7 patients who experienced PJF after PLIF did not receive any revision surgery after PCI. Immediately after cement injection, the anterior wedging rate (%) and the local kyphosis angle were significantly improved (P = .018, P = .028). The anterior wedging rates (%) and local kyphosis angle, at pre-PCI, immediate after PCI, and at final follow-up, were not significantly different between the non-revision surgery and revision surgery groups.Five of 7 patients who experienced PJF after PLIF did not receive revision surgery after PCI. Considering that general anesthesia and open surgery are high-risk procedures for geriatric patients, our results suggest that non-surgical PCI could be a viable alternative treatment option for PJF.SMC2017-01-011-001. Retrospectively registered 18 January 2017.

Scoliosis surgery in adulthood: what challenges for what outcome?

Adolescent idiopathic scoliosis that has progressed over time, de novo scoliosis, and degenerative scoliosis represent different types of adult spinal deformity (ASD). Functional impairment and muscular fatigue are due to sagittal and coronal imbalance of the trunk. Surgical treatment can provide a significant improvement of three-dimensional (3D) thoracolumbar alignment, function, and health-related quality of life (QoL). A patient-specific benefit-risk assessment, including clinical expectations, comorbidities, and the spinal deformity itself, has to be done preoperatively since the risk for mechanical complications is relatively high. Minimal invasive techniques combine posterior percutaneous instrumentation and lateral interbody fusion cages which enables vertebral realignment and indirect foraminal stenosis decompression. This strategy seems appropriate in mild and moderate ASD with a limited number of degenerated segments in the lumbar spine and remaining curve flexibility. Severe ASD needs to be addressed by open surgery, which combines posterior instrumentation, interbody fusion, and osteotomies in stiff deformities. Longer posterior instrumentation of the thoracolumbar spine, the sacrum, and the pelvis carries a risk for mechanical complications such as non-union and proximal junctional kyphosis (PJK). Modern surgical techniques including circumferential lumbosacral fusion and double rods might lower the risk for non-union. Accurate sagittal alignment planning, setting the lumbar sagittal apex according to pelvic incidence, and segmental lordosis distribution, are mandatory for minimizing the risk of PJK.

Development of Proximal Junctional Kyphosis After Minimally Invasive Lateral Anterior Column Realignment for Adult Spinal Deformity

BACKGROUND

Development of proximal junctional kyphosis (PJK) after correction of adult spinal deformity (ASD) undermines sagittal alignment. Minimally invasive anterior column realignment (ACR) is a powerful tool for correction of ASD; however, long-term PJK rates are unknown.

OBJECTIVE

To characterize PJK after utilization of ACR in ASD correction.

METHODS

A retrospective multi-institution cohort analysis per STROBE criteria was conducted of all patients who underwent lateral lumbar interbody fusion (LLIF) or ACR for ASD from 2010 to 2015. All patients obtained preoperative and follow-up upright radiographs, assessing spinal alignment and development of PJK. Patients without proper imaging or minimum 1-yr follow-up were excluded.

RESULTS

A total of 73 of 112 patients who underwent either LLIF or ACR for ASD met inclusion criteria. Mean follow-up was 22.8 mo. There was significant improvement of all spinopelvic parameters. Overall, PJK and proximal junctional failure (PJF) rates were 20.5% and 11%, respectively. The incidence of PJK increased with greater corrective surgery (0% LLIF, 30% ACR, 42.9% ACR + posterior column osteotomy (PCO); P < .001). PJF rates increased (0% LLIF, 11% ACR, 40% ACR + PCO; P = .005). Risk factors included location of the upper-instrumented vertebra at T10-L1 vs L2-L4 (P = .007), age (P = .029), severity of ASD, and overcorrection of sagittal imbalance.

CONCLUSION

The incidence of PJK after minimally invasive ACR is slightly lower than reported after open surgery but greater than in LLIF only and increases with PCO utilization. The PJK rate increases when crossing the TL junction, sagittal imbalance severity, and overcorrection. Elderly patients are at an increased risk, suggesting need for age appropriate correction goals.

Adjacent Level Tuberculous Spondylodiscitis Leading to Proximal Junctional Kyphosis: Rare and Unusual Presentation

BACKGROUND

Vertebral osteomyelitis manifesting as a compression fracture misdiagnosed in the setting of steroid-induced or senile osteoporosis is very rare, although such patients are prone to infection or reactivation, as their immune system is exhausted. Spondylodiscitis occurring at adjacent levels following instrumented spinal fusion leading to pathologic fracture and proximal junctional failure, especially caused by tuberculosis, to our knowledge, has not been discussed in the literature.

METHODS

In case 1, a 61-year-old woman with osteoporotic T12 collapse was treated with corpectomy, anterior reconstruction, and posterior fixation from T9-L2. Initial biopsy and culture were normal. She presented 4 months later with compression fracture of T8; T8 corpectomy with anterior reconstruction and proximal extension of the construct was performed. In case 2, a 65-year-old woman with multiple comorbidities and osteoporotic L1 compression fracture was treated with L1 corpectomy, anterior reconstruction, and posterior instrumentation from T11-L3. She presented 4 months later with T10 vertebral body acute collapse; 2-stage anterior corpectomy and reconstruction was performed. In both cases, probing the affected vertebral body yielded pus. Pus and bone tissue samples sent for culture and histopathologic examination were positive for tuberculosis suggesting tuberculous spondylitis in both cases.

RESULTS

In both patients, tuberculous spondylodiscitis at the proximal adjacent level was diagnosed <1 year after the initial spinal surgery. Neither patient had a previous history of pulmonary or extrapulmonary tuberculosis. They were successfully treated with antituberculous therapy and proximal extension of the construct with anterior reconstruction.

CONCLUSIONS

Adjacent segment spondylodiscitis should be suspected and intraoperative biopsy must be considered for histopathologic and microbiologic examination to rule out subclinical infection in immunosuppressed patients with multiple comorbidities. Management should be individualized, considering the context of infection, causative organism, extent of bone destruction, and neurologic involvement.

Is Sacral Extension a Risk Factor for Early Proximal Junctional Kyphosis in Adult Spinal Deformity Surgery?

Study Design

Retrospective cohort study.

Purpose

To investigate the role of sacral extension (SE) for the development of proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) surgery.

Overview of Literature

The development of PJK is multifactorial and different risk factors have been identified. Of these, there is some evidence that SE also affects the development of PJK, but data are insufficient.

Methods

Using a combined database comprising two propensity-matched groups of fusions following ASD surgery, one with fixation to S1 or S1 and the ilium (SE) and one without SE but with a lower instrumented vertebra of L5 or higher (lumbar fixation, LF), PJK and the role of further parameters were analyzed. The propensity-matched variables included age, the upper-most instrumented vertebra (UIV), preoperative sagittal alignment, and the baseline to 1 year change of the sagittal alignment.

Results

Propensity matching led to two groups of 89 patients each. The UIV, pelvic incidence minus lumbar lordosis, sagittal vertical axis, pelvic tilt, age, and body mass index were similar in both groups (p >0.05). The incidence of PJK at postoperative 1 year was similar for SE (30.3%) and LF (22.5%) groups (p =0.207). The PJK angle was comparable (p =0.963) with a change of −8.2° (SE) and −8.3° (LF) from the preoperative measures (p =0.954). A higher rate of PJK after SE (p =0.026) was found only in the subgroup of patients with UIV levels between T9 and T12.

Conclusions

Instrumentation to the sacrum with or without iliac extension did not increase the overall risk of PJK. However, an increased risk for PJK was found after SE with UIV levels between T9 and T12.

Preliminary report on the flexible rod technique for prevention of proximal junctional kyphosis following long-segment fusion to the sacrum in adult spinal deformity

OBJECTIVE

The incidence of proximal junctional kyphosis (PJK) after long-segment fixation in patients with adult spinal deformity (ASD) has been reported to range from 17% to 61.7%. Recent studies have reported using "hybrid" techniques in which semirigid fixation is introduced between the fused and flexible segments at the proximal level to allow a more gradual transition. The authors used these hybrid techniques in a clinical setting and analyzed PJK to evaluate the usefulness of the flexible rod (FR) technique.

METHODS

The authors retrospectively selected 77 patients with lumbar degenerative kyphosis (LDK) who underwent sagittal correction and long-segment fixation and had follow-up for > 1 year. An FR was used in 30 of the 77 patients. PJK development and spinal sagittal changes were analyzed in the FR and non-FR groups, and the predictive factors of PJK between a PJK group and a non-PJK group were compared.

RESULTS

The patient population comprised 77 patients (75 females and 2 males) with a mean (± SD) follow-up of 32.0 ± 12.7 months (36.7 ± 9.8 months in the non-FR group and 16.8 ± 4.7 months in the FR group) and mean (± SD) age of 71.7 ± 5.1 years. Sagittal balance was well maintained at final follow-up (10.5 and 1.5 mm) in the non-FR and FR groups, respectively. Thoracic kyphosis (TK) and lumbar lordosis (LL) were improved in both groups, without significant differences between the two (p > 0.05). PJK occurred in 28 cases (36.4%) in total, 3 (10%) in the FR and 25 (53.2%) in the non-FR group (p < 0.001). Postoperatively, PJK was observed at an average of 8.9 months in the non-FR group and 1 month in the FR group. No significant differences in the incidence of PJK regarding patient factors or radiological parameters were found between the PJK group and non-PJK group (p > 0.05). However, FR (vs non-FR) and interbody fusion except L5-S1 using oblique lumbar interbody fusion (vs non-oblique lumbar interbody fusion), demonstrated a significantly lower PJK prevalence (p < 0.001 and p = 0.044) among the surgical factors.

CONCLUSIONS

PJK was reduced after surgical treatment with the FR in the patients with LDK. Solid long-segment fixation and the use of the FR may become another surgical option for spine surgeons who plan and make decisions regarding spine reconstruction surgery for patients with ASD.

Comparison of long fusion terminating at L5 versus the sacrum in treating adult spinal deformity: a meta-analysis

Purpose

Choosing an optimal distal fusion level for adult spinal deformity (ASD) is still controversial. To compare the radiographic and clinical outcomes of distal fusion to L5 versus the sacrum in ASD, we conducted a meta-analysis.

Methods

Relevant studies on long fusion terminating at L5 or the sacrum in ASD were retrieved from the PubMed, Embase, Cochrane, and Google Scholar databases. Then, studies were manually selected for inclusion based on predefined criteria. The meta-analysis was performed by RevMan 5.3.

Results

Eleven retrospective studies with 1211 patients were included in meta-analysis. No significant difference was found in overall complication rate (95% CI 0.60 to 1.30) and revision rate (95% CI 0.59 to 1.99) between fusion to L5 group (L group) and fusion to the sacrum group (S group). Significant lower rate of pseudarthrosis and implant-related complications (95% CI 0.29 to 0.64) as well as proximal adjacent segment disease (95% CI 0.35 to 0.92) was found in L group. Patients in S group obtained a better correction of lumbar lordosis (95% CI − 7.85 to − 0.38) and less loss of sagittal balance (95% CI − 1.80 to − 0.50).

Conclusion

Our meta-analysis suggested that long fusion terminating at L5 or the sacrum was similar in scoliosis correction, overall complication rate, revision rate, and improvement in pain and disability. However, fusion to L5 had advantages in lower rate of pseudarthrosis, implant-related complications, and proximal adjacent segment disease, while fusion to the sacrum had advantages in the restoration of lumbar lordosis, maintenance of sagittal balance, and absence of distal adjacent segment disease.

Graphic abstract

These slides can be retrieved under Electronic Supplementary Material.

Cervical Alignment Changes in Patients Developing Proximal Junctional Kyphosis Following Surgical Correction of Adult Spinal Deformity

BACKGROUND

Proximal junctional kyphosis (PJK) following adult spinal deformity (ASD) surgery is a well-documented complication, but associations between radiographic PJK and cervical malalignment onset remain unexplored.

OBJECTIVE

To study cervical malalignment in ASD surgical patients that develop PJK.

METHODS

Retrospective review of prospective multicenter database. Inclusion: primary ASD patients (≥5 levels fused, upper instrumented vertebra [UIV] at T2 or above, and 1-yr minimum follow-up) without baseline cervical deformity (CD), defined as ≥2 of the following criteria: T1 slope minus cervical lordosis < 20°, cervical sagittal vertical axis < 4 cm, C2-C7 cervical lordosis < 10°. PJK presence (<10° change in UIV and UIV + 2 kyphosis) and angle were identified 1 yr postoperative. Propensity score matching between PJK and nonPJK groups controlled for baseline alignment. Preoperative and 1-yr postoperative cervical alignment were compared between PJK and nonPJK patients.

RESULTS

One hundred sixty-three patients without baseline CD (54.9 yr, 83.9% female) were included. PJK developed in 60 (36.8%) patients, with 27 (45%) having UIV above T7. PJK patients had significantly greater baseline T1 slope in unmatched and propensity score matching comparisons (P < .05). At 1 yr postoperative, PJK patients had significantly higher T1 slope (P < .001), C2-T3 Cobb (P = .04), and C2-T3 sagittal vertical axis (P = .02). New-onset CD rate in PJK patients was 15%, and 16.5% in nonPJK patients (P > .05). Increased PJK magnitude was associated with increasing T1 slope and C2-T3 SVA (P < .05).

CONCLUSION

Patients who develop PJK following surgical correction of ASD have a 15% incidence of development of new-onset CD. Patients developing PJK following surgical correction of ASD tend to have an increased preoperative T1 slope. Increased progression of C2-T3 Cobb angle and C2-T3 SVA are associated with development of PJK following surgical correction of thoracolumbar deformity.

The Risk of Proximal Junctional Kyphosis Decreases in Patients With Optimal Thoracic Kyphosis

STUDY DESIGN

A retrospective study of surgical outcomes.

OBJECTIVE

This study aimed to investigate the preoperative risk factors for proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

The cause of PJK is still unclear, although some risk factors have been reported in ASD surgery.

METHODS

A total of 185 patients who were followed up for more than two years and underwent ASD surgery were recruited. PJK was defined as a proximal junctional angle ≥20° or reoperation due to PJK within two years after surgery. These patients were divided into PJK and non-PJK groups. Whole-spine standing radiography was performed before and immediately, one year, and two years after the surgery.

RESULTS

The PJK and non-PJK groups comprised 58 and 127 cases, respectively. The incidence of PJK demonstrated significant differences according to preoperative thoracic kyphosis (TK): 37% (TK ≤19°), 33% (TK 20°-29°), 9% (TK 30°-39°), 32% (TK 40°-49°), and 41% (TK ≥50°) (p < .05). Logistic regression analysis suggested that the amount of change in TK before and just after the surgery (ΔTK) was a significant risk factor for PJK (p < .001; odds ratio 1.062, 95% confidence interval 1.029-1.097).

CONCLUSION

ΔTK was less in the TK group of 30°-39° because the TK of patients who underwent ASD surgery converged to 34.5° just after surgery. Consequently, a lower or higher TK was likely to result in a large ΔTK just after surgery. Therefore, patients who had an optimal TK (30°-39°) had a lower risk of PJK.

LEVEL OF EVIDENCE

Level IV.

Sacropelvic Fixation With S2 Alar Iliac Screws May Prevent Sacroiliac Joint Pain After Multisegment Spinal Fusion

STUDY DESIGN

A retrospective study.

OBJECTIVE

To examine the postoperative incidence of sacroiliac joint pain (SIJP) at the lower fusion level following multisegment fusion.

SUMMARY OF BACKGROUND DATA

Recently, multisegment fusion is being increasingly performed. While proximal junctional kyphosis (PJK) commonly develops following multisegment fusion, SIJP also commonly occurs following this surgery. In surgery for adult spinal deformity, fixation is often extended to the pelvis to include the sacroiliac joint. Therefore, the question of whether SIJP occurs in such cases is interesting. Here, we examined postoperative incidence of SIJP at the lower fusion level, including the incidence of PJK, and postoperative lumbopelvic alignment.

METHODS

Participants included 77 patients who underwent corrective fusion (≥3 segments). Patients were divided into three groups based on the lower fixation end: L5 (L5), S (sacrum), and P (pelvis). In the P group, an S2 alar iliac screw was used. Postoperative incidence of SIJP and PJK in each group was examined along with lumbopelvic parameters.

RESULTS

SIJP incidence was 16.7%, 26.1%, and 4.2% in the L5, S, and P groups, respectively, indicating the highest value in the S group and a significantly lower value in the P group. PJK incidence was 23.3%, 30.4%, and 29.2% in the L5, P, and S groups, respectively, with no significant differences. Regarding postoperative lumbopelvic parameters, there was no significant difference between the groups; however, lumbar lordosis tended to be better in the P group.

CONCLUSION

SIJP incidence was extremely high with fixation to the sacrum, and in the group with fixation to the pelvis, there was hardly any SIJP. Sacropelvic fixation using S2 alar iliac screws could prevent SIJP onset following multisegment fusion.

LEVEL OF EVIDENCE

3.

The Role of Potentially Modifiable Factors in a Standard Work Protocol to Decrease Complications in Adult Spinal Deformity Surgery: A Systematic Review, Part 1

STUDY DESIGN

Structured Literature Review.

OBJECTIVES

We sought to evaluate the peer-reviewed literature for potentially modifiable patient and surgical factors that could be incorporated into a Standard Work protocol to decrease complications in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

Lean Methodology uses Standard Work to improve efficiency and decrease waste and error. ASD is known to have a high surgical complication rate. Several patient and surgical potentially modifiable factors have been suggested to affect complications, including preoperative hemoglobin, bone density, body mass index (BMI), age-appropriate realignment, preoperative albumin/prealbumin, and smoking status. We sought to evaluate the literature for evidence supporting these factors to include in a Standard Work protocol to decrease complications.

METHODS

Each of these six factors was developed into an appropriate clinical question that included the patient population, surgical intervention, a comparison group, and outcomes measure (PICO question). A comprehensive literature search was then performed. The authors reviewed abstracts and analyzed data from included studies. From 456 initial citations with abstract, 173 articles underwent full-text review. The best available evidence for clinical questions regarding the influence of these factors was provided by 93 included studies.

RESULTS

We found fair evidence supporting a low preoperative hemoglobin level associated with increased transfusion rates and decreased BMD and increased BMI associated with increased complication rates. Fair evidence supported low albumin/prealbumin associated with increased complications. There was fair evidence associating smoking exposure to increased reoperations, but conflicting evidence associating it with increased complications. There was no evidence in the literature evaluating age-appropriate realignment and complications.

CONCLUSION

Preoperative hemoglobin, bone density, body mass index, preoperative albumin/prealbumin, and smoking status all are potentially modifiable risk factors that are associated with increased complications in the adult spine surgery population. Developing a Standard Work Protocol for patient evaluation and optimization should include these factors.

LEVEL OF EVIDENCE

Level II.

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.

Paraspinal muscle size as an independent risk factor for proximal junctional kyphosis in patients undergoing thoracolumbar fusion

OBJECTIVE

Proximal junctional kyphosis (PJK) is a structural complication of spinal fusion in 5%-61% of patients treated for adult spinal deformity. In nearly one-third of these cases, PJK is progressive and requires costly surgical revision. Previous studies have suggested that patient body habitus may predict risk for PJK. Here, the authors sought to investigate abdominal girth and paraspinal muscle size as risk factors for PJK.

METHODS

All patients undergoing thoracolumbosacral fusion greater than 2 levels at a single institution over a 5-year period with ≥ 6 months of radiographic follow-up were considered for inclusion. PJK was defined as kyphosis ≥ 20° between the upper instrumented vertebra (UIV) and two supra-adjacent vertebrae. Operative and radiographic parameters were recorded, including pre- and postoperative sagittal vertical axis (SVA), sacral slope (SS), lumbar lordosis (LL), pelvic tilt, pelvic incidence (PI), and absolute value of the pelvic incidence-lumbar lordosis mismatch (|PI-LL|), as well as changes in LL, |PI-LL|, and SVA. The authors also considered relative abdominal girth and the size of the paraspinal muscles at the UIV.

RESULTS

One hundred sixty-nine patients met inclusion criteria. On univariate analysis, PJK was associated with a larger preoperative SVA (p < 0.001) and |PI-LL| (p = 0.01), and smaller SS (p = 0.004) and LL (p = 0.001). PJK was also associated with more positive postoperative SVA (p = 0.01), ΔSVA (p = 0.01), Δ|PI-LL| (p < 0.001), and ΔLL (p < 0.001); longer construct length (p = 0.005); larger abdominal girth-to-muscle ratio (p = 0.007); and smaller paraspinal muscles at the UIV (p < 0.001). Higher postoperative SVA (OR 1.1 per cm), smaller paraspinal muscles at the UIV (OR 2.11), and more aggressive reduction in |PI-LL| (OR 1.03) were independent predictors of radiographic PJK on multivariate logistic regression.

CONCLUSIONS

A more positive postoperative global sagittal alignment and smaller paraspinal musculature at the UIV most strongly predicted PJK following thoracolumbosacral fusion.

Management of Catastrophic Proximal Junctional Failure Following Spinal Deformity Correction in an Adult with Osteogenesis Imperfecta: Case Report and Technical Note

BACKGROUND

Proximal junctional failure (PJF) is a major and sometimes devastating problem following adult spinal deformity (ASD) correction surgery. Common consensus still lags on guidelines for preventing and managing these complications. Surgical treatment of scoliosis in the presence of osteogenesis imperfecta (OI) in the pediatric population is well described. The complication rates are unusually higher in this special subset of patients owing to poor quality of bone. There is a paucity of literature focusing on surgical techniques, strategies, and problems involved in the management of ASD associated with OI.

CASE DESCRIPTION

We report a 59-year-old female with type 1 OI and adult scoliosis who underwent T10-to-pelvis fusion for ASD according to the principles of adult deformity correction. At a 1-year follow-up, she presented with asymptomatic proximal junctional kyphosis of 45° and 2 weeks later had PJF along with spinal cord injury after a fall. On computed tomography scan, kyphosis was increased to 60° at T9-T10. She underwent decompression and revision deformity correction using quadruple rods, with extension of instrumentation to T2 with soft landing using rib bands. At a 4-year follow-up, she had a good functional outcome after revision surgery.

CONCLUSIONS

This is the first report of successful management of PJF following ASD correction in the presence of OI using this technique. Suboptimal hold of implants due to poor bone quality must be at the focus of any surgical planning for these patients. All possible strategies to prevent PJF must be considered when planning the deformity correction in adults with OI.

Recovery kinetics following spinal deformity correction: a comparison of isolated cervical, thoracolumbar, and combined deformity morphometries

BACKGROUND CONTEXT

The postoperative recovery patterns of cervical deformity patients, thoracolumbar deformity patients, and patients with combined cervical and thoracolumbar deformities, all relative to one another, is not well understood. Clear objective benchmarks are needed to quantitatively define a "good" versus a "bad" postoperative recovery across multiple follow-up visits, varying deformity types, and guide expectations.

PURPOSE

To objectively define and compare the complete 2-year postoperative recovery process among operative cervical only, thoracolumbar only, and combined deformity patients using area-under-the-curve (AUC) methodology.

STUDY DESIGN/SETTING

Retrospective review of 2 prospective, multicenter adult cervical and spinal deformity databases.

PATIENT SAMPLE

One hundred seventy spinal deformity patients.

OUTCOME MEASURES

Common health-related quality of life (HRQOL) assessments across both databases included the EuroQol 5-Dimension Questionnaire and Numeric Rating Scale (NRS) back pain assessment. In order to compare disability improvements, the Neck Disability Index (NDI) and the Oswestry Disability Index (ODI) were merged into one outcome variable, the ODI-NDI. Both assessments are gauged on the same scale, with minimal question deviation. Sagittal Radiographic Alignment was also assessed at pre- and all postoperative time points.

METHODS

Operative deformity patients >18 years old with baseline (BL) to 2-year HRQOLs were included. Patients were stratified by cervical only (C), thoracolumbar only (T), and combined deformities (CT). HRQOL and radiographic outcomes were compared within and between deformity groups. AUC normalization generated normalized HRQOL scores at BL and all follow-up intervals (6 weeks, 3 months, 1 year, and 2 year). Normalized scores were plotted against follow-up time interval. AUC was calculated for each follow-up interval, and total area was divided by cumulative follow-up length, determining overall, time-adjusted HRQOL recovery (Integrated Health State, IHS). Multiple linear regression models determined significant predictors of HRQOL discrepancies among deformity groups.

RESULTS

One hundred seventy patients were included (27 C, 27 T, and 116 CT). Age, BMI, sex, smoking status, osteoporosis, depression, and BL HRQOL scores were similar among groups (p >. 05). T and CT patients had higher comorbidity severities (CCI: C 0.696, T 1.815, CT 1.699, p = .020). Posterior surgical approaches were most common (62.9%) followed by combined (28.8%) and anterior (6.5%). Standard HRQOL analysis found no significant differences among groups until 1-year follow-up, where C patients exhibited comparatively greater NRS back pain (4.88 vs. 3.65 vs. 3.28, p = .028). NRS Back pain differences between groups subsided by 2-years (p>.05). Despite C patients exhibiting significantly faster ODI-NDI minimal clinically important difference (MCID) achievement (33.3% vs. 0% vs. 23.0%, p < .001), all deformity groups exhibited similar ODI-NDI MCID achievement by 2-years (51.9% vs. 59.3% vs. 62.9%, p = 0.563). After HRQOL normalization, similar results were observed relative to the standard analysis (1-year NRS Back: C 1.17 vs. T 0.50 vs. CT 0.51, p < .001; 2-year NRS Back: 1.20 vs. 0.51 vs. 0.69, p = .060). C patients exhibited a worse NRS back normalized IHS (C 1.18 vs. T 0.58 vs. CT 0.63, p = .004), indicating C patients were in a greater state of postoperative back pain for a longer amount of time. Linear regression models determined postoperative distal junctional kyphosis (adjusted beta: 0.207, p = .039) and osteoporosis (adjusted beta: 0.269, p = .007) as the strongest predictors of a poor NRS back IHS (model summary: R² = 0.177, p = .039).

CONCLUSIONS

Despite C patients exhibiting a quicker rate of MCID disability (ODI-NDI) improvement, they exhibited a poorer overall recovery of back pain with worse NRS back scores compared with BL status and other deformity groups. Postoperative distal junctional kyphosis and osteoporosis were identified as primary drivers of a poor postoperative NRS back IHS. Utilization of the IHS, a single number adjusting for all postoperative HRQOL visits, in conjunction with predictive modelling may pose as an improved method of gauging the effect of surgical details and complications on a patient's entire recovery process.