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

Influence of configuration and anchor in ligamentous augmentation to prevent proximal junctional kyphosis: A finite element study

Ligament augmentation has been applied during spinal surgery to prevent proximal junctional kyphosis (PJK), but the configuration and distal anchor strategies are diverse and inconsistent. The biomechanics of different ligament augmentation strategies are, therefore, unclear. We aimed to create a finite element model of the spine for segments T6–S1. Model Intact was the native form, and Model IF was instrumented with a pedicle screw from segments T10 to S1. The remaining models were based on Model IF, with ligament augmentation configurations as common (CM), chained (CH), common and chained (CHM); and distal anchors to the spinous process (SP), crosslink (CL), and pedicle screw (PS), creating SP-CH, PS-CHM, PS-CH, PS-CM, CL-CHM, CL-CH, and CL-CM models. The range of motion (ROM) and maximum stress on the intervertebral disc (IVD), PS, and interspinous and supraspinous ligaments (ISL/SSL) was measured. In the PS-CH model, the ROM for segments T9–T10 was 73% (of Model Intact). In the CL-CHM, CL-CH, CL-CM, PS-CM, and PS-CHM models, the ROM was 8%, 17%, 7%, 13%, and 30%, respectively. The PS-CH method had the highest maximum stress on IVD and ISL/SSL, at 80% and 72%, respectively. The crosslink was more preferable as the distal anchor. In the uppermost instrumented vertebrae (UIV) + 1/UIV segment, the CM was the most effective configuration. The PS-CH model had the highest flexion load on the UIV + 1/UIV segment and the CL-CM model provided the greatest reduction. The CL-CM model should be verified in a clinical trial. The influence of configuration and anchor in ligament augmentation is important for the choice of surgical strategy and improvement of technique.

"Reasonable threshold" of spinopelvic parameters after fixation on distal stenosis in patients with degenerative thoracolumbar kyphosis: A STROBE-compliant article

The short-segment instrument for precision treatment of lumbar stenosis syndrome (LSS) combined with degenerative thoracolumbar kyphosis (DTLK) receives more attention and the reasonable range of sagittal parameters is debatable in these elderly patients. This study aimed to include LSS patients combined with DTLK performed short-segmental fixation on LSS, to evaluate the efficacy of this procedure, and to determine the reasonable threshold of sagittal parameters. Overall 138 patients (female, 62.3%) were eligible (mean age of 68.8 ± 7.7 years) with a follow-up time of 24.6 ± 11.1 months. Spinopelvic sagittal parameters containing TLK, lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), and sagittal vertical axis were obtained at baseline and final visit, where |PI-LL|, PT, and sagittal vertical axis were seen as the main parameters. Quality of life was evaluated by the Oswestry Disability Index (ODI), which were divided into 4 quarters orderly. The reasonable threshold of parameters corresponding to ODI was determined by both linear regression and logistic regression. For all participants, TLK decreased by a mean of 8.3° and cases got TLK correction occupied 40.4%. ODI got improvement by the change of 29.9 ± 9.9. At baseline, ODI was correlated to |PI-LL|, while at final, ODI was correlated to |PI-LL| and PT. The independent factor affecting preoperative ODI was |PI-LL|, with ODI = 0.19 × |PI-LL| + 36.9 and the mean threshold of preoperative |PI-LL| was 10.7°. At final, PT was the influencing factor with ODI = 0.21 × PT + 3.16 and PT = 0.60 × |PI-LL| + 12.22. The mean threshold of postoperative |PI-LL| was 16.0° and PT was 23.1° by both linear regression and logistic regression. With short-segment fixation on LSS, >40% of patients with DTLK acquired TLK correction. |PI-LL| = 16.0° and PT = 23.1° was the "reasonable threshold" of sagittal parameters with the procedure for this population.

Fusion Extension Leads to Spontaneous Resolution of Symptomatic Disc Herniations Associated With Proximal Junctional Kyphosis: A Report of 3 Cases

CASES

A retrospective chart and radiographic review was performed of 3 patients presenting with neurological deficits secondary to soft thoracic disc herniation associated with proximal junctional kyphosis. The patients were treated with proximal extension of the construct, correction of the focal sagittal malalignment, and posterior decompressive laminectomy without excision of the herniated disc. All 3 patients made complete neurological recovery and subsequent magnetic resonance imaging showed resolution of the herniated discs.

CONCLUSIONS

Laminectomy in conjunction with proximal extension of the construct without formal thoracic discectomy was associated with complete neurological recovery and spontaneous resolution of soft thoracic disc herniations associated with junctional failures.

The application of finite element analysis to determine the optimal UIV of growing-rod treatment in early-onset scoliosis

Objectives: To analyze the stress distribution in the proximal vertebral body and soft tissue of dual growing-rod (GR) with different upper instrumented vertebra (UIV) to determine the optimal UIV.

Methods: A ten-year-old male EOS case treated with GR was selected. Based on spiral computed tomography (CT) scanning performed in 0.6 mm thick slices, a finite element model (FEM) of the preoperative state (M0, the original spine state) of the patient was created. Subsequently, four models with different UIV fixations were numerically analyzed by FEM, including M1 (UIV = T1, i.e., the upper-end vertebrae (UEV) of the upper thoracic curve), M2 (UIV = T2), M3 (UIV = T3) and M4 (UIV = T4, i.e., the lower end vertebrae (LEV) of the upper thoracic curve). Displacement and maximum stress in the proximal vertebral body and soft tissue were measured and compared among the five models.

Results: The spine model was fixed with the sacrum, and the gravity conditions were imposed on each vertebral body according to the research of Clin and Pearsall. The results are as follows:M4 model has the largest overall displacement, while M1 has the least displacement among the four models. Except M2, the maximum normalized stress of UIV increases with the downward movement of UIV. M1 has the lowerest annulus fibrosus stress and highest joint capsule stress, which is characterized by the vertebrae backward leaning, while M4 is the opposite. The supraspinous ligament stress of M3 and M4 is significantly higher than that of M1 and M2. This suggests that UIV downshift increases the tendency of the proximal vertebral bodies to bend forward, thereby increasing the tension of the posterior ligaments (PL).

Conclusion: The UIV of the GR is recommended to be close to the UEV of the upper thoracic curve, which can reduce the stress of the proximal PL, thereby reducing the occurrence of proximal junctional kyphosis (PJK).

Characteristics of patients undergoing revision surgery for proximal junctional failure after adult spinal deformity surgery: revalidation of the Hart-International Spine Study Group proximal junctional kyphosis severity scale

OBJECTIVE

Score on the proximal junctional kyphosis severity scale (PJKSS) has been validated to show good correlations with likelihood of revision surgery for proximal junctional failure (PJF) after surgical treatment of adult spinal deformity (ASD). However, if the patient has progressive neurological deterioration, revision surgery should be considered regardless of severity based on PJKSS score. This study aimed to revalidate the correlation of PJKSS score with likelihood of revision surgery in patients with PJF but without neurological deficit. In addition, the authors provide the cutoff score on PJKSS that indicates need for revision surgery.

METHODS

A retrospective study was performed. Among 360 patients who underwent fusion of more than 4 segments including the sacrum, 83 patients who developed PJF without acute neurological deficit were included. Thirty patients underwent revision surgery (R group) and 53 patients did not undergo revision surgery (NR group). All components of PJKSS and variables other than those included in PJKSS were compared between groups. The cutoff score on PJKSS that indicated need for revision surgery was calculated with receiver operating characteristic curve analysis. Multivariate analysis with logistic regression was performed to identify which variables were most predictive of revision surgery.

RESULTS

The mean patient age at the time of index surgery was 69.4 years, and the mean fusion length was 6.1 segments. All components of PJKSS, such as focal pain, instrumentation problem, change in kyphosis, fracture at the uppermost instrumented vertebra (UIV)/UIV+1, and level of UIV, were significantly different between groups. The average total PJKSS score was significantly greater in the R group than in the NR group (6.0 vs 3.9, p < 0.001). The calculated cutoff score was 4.5, with 70% sensitivity and specificity. There were no significant between-group differences in patient, surgical, and radiographic factors (other than the PJKSS components). Three factors were significantly associated with revision surgery on multivariate analysis: instrumentation problem (OR 8.160, p = 0.004), change in kyphosis (OR 4.809, p = 0.026), and UIV/UIV+1 fracture (OR 6.462, p = 0.002).

CONCLUSIONS

PJKSS score positively predicted need for revision surgery in patients with PJF who were neurologically intact. The calculated cutoff score on PJKSS that indicated need for revision surgery was 4.5, with 70% sensitivity and specificity. The factor most responsible for revision surgery was bony failure with > 20° focal kyphotic deformity. Therefore, early revision surgery should be considered for these patients even in the absence of neurological deficit.

Cost-utility Analysis of Neoadjuvant Teriparatide Therapy in Osteopenic Patients Undergoing Adult Spinal Deformity Surgery

STUDY DESIGN

A cost-utility analysis study.

OBJECTIVE

This study aims to evaluate the cost-utility of neoadjuvant teriparatide therapy in osteopenic patients undergoing adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

There is increasing evidence supporting preoperative use of anabolic agents such as teriparatide for preoperative optimization of ASD patients with poor bone density. However, such treatments are associated with added costs. To our knowledge, the cost-utility of teriparatide in osteopenic patients undergoing ASD surgery has not been established.

MATERIALS AND METHODS

A decision-analysis model was developed for a hypothetical 68-year-old female patient with osteopenia ( T score <-1.0) undergoing a T11 to pelvis instrumented spinal fusion for ASD. A comprehensive literature review was conducted to create estimates for event probabilities, costs, and quality adjusted life years at each node. Key model assumptions were that administration of a 4-month preoperative teriparatide course reduced 2-year postoperative reoperation rates [for pseudarthrosis from 5% to 2.5% and for proximal junctional failure (PJF) from 15% to 5%]. Monte Carlo simulations were used to calculate the mean incremental cost utility ratio and incremental net monetary benefits. One-way sensitivity analysis was used to estimate the contribution of individual parameters to uncertainty in the model.

RESULTS

Teriparatide was the favored strategy in 82% of the iterations. The mean incremental cost utility ratio for the teriparatide strategy was negative (higher net benefit, lower net cost), and lower than the willingness-to-pay threshold of $50,000 per quality adjusted life year. Teriparatide use was associated with a mean incremental net monetary benefit of $3,948. One-way sensitivity analysis demonstrated that the factors with the greatest impact on the model were the incidence of PJF in the no teriparatide group, the duration and monthly cost of treatment, and the cost of reoperation due to PJF.

CONCLUSIONS

Neoadjuvant teriparatide is a cost-effective strategy to reduce postoperative complications in patients with osteopenia undergoing ASD surgery.

Instrumentation Techniques to Prevent Proximal Junctional Kyphosis and Proximal Junctional Failure in Adult Spinal Deformity Correction: A Systematic Review of Clinical Studies

STUDY DESIGN

Systematic review.

OBJECTIVES

To summarize the results of clinical studies investigating spinal instrumentation techniques aiming to reduce the postoperative incidence of proximal junctional kyphosis (PJK) and/or failure (PJF) in adult spinal deformity (ASD) patients.

METHODS

EMBASE and Medline® were searched for articles dating from January 2000 onward. Data was extracted by 2 independent authors and methodological quality was assessed using ROBINS-I.

RESULTS

18 retrospective- and prospective cohort studies with a severe or critical risk of bias were included. Different techniques were applied at the upper instrumented vertebra (UIV): tethers in various configurations, 2-level prophylactic vertebroplasty (2-PVP), transverse process hooks (TPH), flexible rods (FR), sublaminar tapes (ST) and multilevel stabilization screws (MLSS). Compared to a pedicle screw (PS) group, significant differences in PJK incidence were found using tethers in various configurations (18% versus 45%, P = 0.001, 15% versus 38%, P = 0.045), 2-PVP (24% vs 36%, P = 0.020), TPH (0% vs. 30%, P = 0.023) and FR (15% versus 38%, P = 0.045). Differences in revision rates for PJK were found in studies concerning tethers (4% versus 18%, P = 0.002), 2-PVP (0% vs 13%, P = 0.031) and TPH (0% vs 7%, P = n.a.).

CONCLUSION

Although the studies are of low quality, the most frequently studied techniques, namely 2-PVP as anterior reinforcement and (tensioned) tethers or TPH as posterior semi-rigid fixation, show promising results. To provide a reliable comparison, more controlled studies need to be performed, including the use of clinical outcome measures and a uniform definition of PJF.

Evolution of Proximal Junctional Kyphosis and Proximal Junctional Failure Rates Over 10 Years of Enrollment in a Prospective Multicenter Adult Spinal Deformity Database

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The aim of this study was to investigate the evolution of proximal junctional kyphosis (PJK) rate over 10-year enrollment period within a prospective database.

SUMMARY OF BACKGROUND DATA

PJK is a common complication following adult spinal deformity (ASD) surgery and has been intensively studied over the last decade.

METHODS

Patients with instrumentation extended to the pelvis and minimum 2-year follow-up were included. To investigate evolution of PJK/proximal junctional failure (PJF) rate, a moving average of 321 patients was calculated across the enrollment period. Logistic regression was used to investigate the association between the date of surgery (DOS) and PJK and/or PJF. Comparison of PJK/PJF rates, demographics, and surgical strategies was performed between the first and second half of the cohort.

RESULTS

A total of 641 patients met inclusion criteria (age: 64±10 years, 78.2% female, body mass index: 28.3±5.7). The overall rate of radiographic PJK at 2 years was 47.9%; 12.9% of the patients developed PJF, with 31.3% being revised within 2-year follow-up. Stratification by DOS produced two halves. Between these two periods, rate of PJK and PJF demonstrated nonsignificant decrease (50.3%-45.5%, P =0.22) and (15.0%-10.9%, P =0.12), respectively. Linear interpolation suggested a decrease of 1.2% PJK per year and 1.0% for PJF. Patients enrolled later in the study were older and more likely to be classified as pure sagittal deformity ( P <0.001). There was a significant reduction in the use of three-column osteotomies ( P <0.001), an increase in anterior longitudinal ligament release ( P <0.001), and an increase in the use of PJK prophylaxis (31.3% vs 55.1%). Logistical regression demonstrated no significant association between DOS and radiographic PJK ( P =0.19) or PJF ( P =0.39).

CONCLUSION

Despite extensive research examining risk factors for PJK/PJF and increasing utilization of intraoperative PJK prophylaxis techniques, the rate of radiographic PJK and/or PJF did not significantly decrease across the 10-year enrollment period of this ASD database.

Alignment Targets, Curve Proportion and Mechanical Loading: Preliminary Analysis of an Ideal Shape Toward Reducing Proximal Junctional Kyphosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Investigate risk factors for PJK including theoretical kyphosis, mechanical loading at the UIV and age adjusted offset alignment.

METHODS

373 ASD patients (62.7 yrs ± 9.9; 81%F) with 2-year follow up and UIV of at least L1 and LIV of sacrum were included. Images of patients without PJK, with PJK and with PJF were compared using standard spinopelvic parameters before and after the application of the validated virtual alignment method which corrects for the compensatory mechanisms of PJK. Age-adjusted offset, theoretical thoracic kyphosis and mechanical loading at the UIV were then calculated and compared between groups. A subanalysis was performed based on the location of the UIV (upper thoracic (UT) vs. Lower thoracic (LT)).

RESULTS

At 2-years 172 (46.1%) had PJK, and 21 (5.6%) developed PJF. As PJK severity increased, the post-operative global alignment became more posterior secondary to increased over-correction of PT, PI-LL, and SVA (all P < 0.005). Also, a larger under correction of the theoretical TK (flattening) and a smaller bending moment at the UIV (underloading of UIV) was found. Multivariate analysis demonstrated that PI-LL and bending moment offsets from normative values were independent predictors of PJK/PJF in UT group; PT and bending moment difference were independent predictors for LT group.

CONCLUSIONS

Spinopelvic over correction, under correction of TK (flattening), and under loading of the UIV (decreased bending moment) were associated with PJK and PJF. These differences are often missed when compensation for PJK is not accounted for in post-operative radiographs.

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

STUDY DESIGN

A retrospective case series.

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE: 3

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

OBJECTIVE

Growing rods surgery is the mainstay of treatment for early-onset scoliosis (EOS) while proximal junctional kyphosis (PJK) is one of the most commonly reported postoperative complications. We sought to investigate the impact of the location of upper instrumented vertebra (UIV) in relation to the sagittal apex on proximal junctional kyphosis in EOS after traditional growing rods (GRs) treatment.

METHODS

A total of 102 EOS patients who received traditional growing rods treatment with a follow-up of at least 2 years between 2009 and 2020 were retrospectively reviewed. Radiographic measurements were performed before and after the index surgery and at the latest follow-up. We investigated the coronal Cobb angle and spinopelvic parameters of the whole spine. The location of the UIV, apex, lower instrumented vertebra (LIV), inflection vertebra (IV), the number and distance of UIV-apex, LIV-apex and IV-apex were also recorded. Risk factors for PJK were analyzed by logistic regression analysis.

RESULTS

PJK was observed in 21 patients (20.6%) during the follow-up period. The PJK group showed a younger age at the index surgery (5.9 vs. 7.1 years, P = 0.042), more lengthening procedure times (5.0 vs. 4.0, P = 0.032), larger preoperative coronal Cobb angle (82.0 vs. 75.6°, P = 0.038), higher correction rate (51.2% vs. 44.4%, P = 0.047) and larger postoperative proximal junctional angle (PJA) (13.9 vs. 5.5°, P < 0.001) than the non-PJK group. The ratio of the number and distance from UIV-apex to IV-apex also differed significantly between the two groups. The logistic regression revealed that age at the index surgery ≤ 7 years, the ratio of the number from UIV- apex to IV- apex ≤ 0.6 and the ratio of the distance from UIV- apex to IV- apex ≤ 0.6 were independent risk factors for postoperative PJK.

CONCLUSION

Besides younger age, a closer location of UIV relative to the sagittal apex is identified to be an independent risk factor of postoperative PJK. Selection of UIV at a relatively farther location away from the sagittal apex might help prevent occurrence of PJK.

Sublaminar Tethers Significantly Reduce the Risk of Proximal Junctional Failure in Surgery for Severe Adult Spinal Deformity: A Propensity Score-matched Analysis

STUDY DESIGN

This was a retrospective case series of prospectively collected data.

OBJECTIVE

The present study first described the effect of sublaminar tethering (SLT) on proximal junctional failure (PJF) in adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

PJF is a devastating complication following ASD surgery. Teriparatide administration and spinous process tethering have been reported as alternatives for the prevention of PJF, but a clinically effective prevention strategy is still a matter of debate.

MATERIALS AND METHODS

We used data from an ASD database that included 381 patients with ASD (minimum 2-y follow-up). Among them, the data of patients who had a severe sagittal deformity and had surgery from the lower thoracic spine (T9-T11) to the pelvis were extracted and propensity score matched by age, sex, body mass index, bone mineral density, curve type, sagittal alignment, and fused level to clarify whether SLT prevented the development of PJF [SLT vs. control (CTR); age: 67±7 vs. 66±8 y, T-score: -1.4±0.7 vs. -1.3±0.6, body mass index: 22±4 vs. 22±5 kg/m2, C7 sagittal vertical axis (C7SVA): 12±7 vs. 11±5 cm, pelvic incidence-lumbar lordosis (PI-LL): 51±22 vs. 49±21 degrees, pelvic tilt (PT): 36±10 vs. 34±10 degrees, level fused: 11±2 vs. 11±2]. Sixty-four patients were matched into 32 pairs and compared in terms of the postoperative alignment and frequency of PJF.

RESULTS

Two years postoperatively, C7SVA and PT were significantly larger in the CTR group, while no significant difference in PI-LL was found (C7SVA: 3±3 vs. 6±4 cm, P<0.01, PT: 16±6 vs. 24±9 degrees, P<0.01, PI-LL: 7±9 vs. 11±11 degrees, P=0.22). The proximal junctional angle was significantly greater in the CTR group (proximal junctional kyphosis: 8±8 vs. 17±13 degrees, P<0.01). The incidence of PJF was significantly lower in the SLT group (3% vs. 25%, P=0.03), with an odds ratio of 0.1 (95% confidence interval: 0.0-0.8, P=0.03).

CONCLUSION

In the propensity score-matched cohort, the incidence of PJF was significantly lower in the SLT group. SLT is a promising procedure that may reduce the risk of PJF in severe ASD surgery.

Long-term Outcomes of Minimally Invasive Lateral Lumbar Interbody Fusion in the Treatment of Adult Scoliosis

The literature has shown the importance of long-term follow-up for adults with scoliosis treated surgically because complication and revision rates are high. The goal of this study was to determine long-term outcomes and complications of lateral lumbar interbody fusion (LLIF) with posterior instrumentation for adult patients with scoliosis. A retrospective review of our institution's database was performed to identify adult patients with scoliosis treated with LLIF between 2008 and 2013 with a minimum follow-up of 4 years. Medical records were reviewed for complications and revisions. Pre- and postoperative deformity Cobb angle measurements were taken as well as pelvic incidence (PI) and lumbar lordosis (LL). Functional outcome scores, including Oswestry Disability Index and visual analog scale score for back and leg pain, were assessed preoperatively and at follow-up. Standard binomial and categorical comparative analysis was performed. The 26 patients included had a mean age of 62 years, mean follow-up of 89 months, and mean of 1.8 levels per operation. Four patients (15.4%) required revisions. Mean deformity Cobb angle was 26° preoperatively and 14° postoperatively. Mean PI-LL mismatch was 11.7° preoperatively and 5.9° postoperatively. Nineteen (73%) patients had a PI-LL mismatch greater than 10° preoperatively, whereas only 2 (7.7%) had a mismatch postoperatively. Improvement was seen in all functional outcome scores. Long-term clinical results of LLIF for adults with deformity showed a low proportion of revision in the treatment of a condition with an established high rate of revision. The ability to reduce pelvic mismatch may further reduce the rate of revision. In this study, LLIF resulted in improved functional outcomes and patient satisfaction. [Orthopedics. 2022;45(3):e134-e139.].

Relationship Between Hounsfield Units of Upper Instrumented Vertebrae, Proximal Junctional Failure, and Global Alignment and Proportion Score in Female Patients with Adult Spinal Deformity

STUDY DESIGN

This was a retrospective observational study.

OBJECTIVES

The purpose of this study was to evaluate bone mineral density using Hounsfield unit (HU) values at the upper instrumented vertebrae (UIV), UIV+1, and UIV+2 and to investigate the association with proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD). We also evaluated the relationship between the global alignment and proportion (GAP) score and the HU value of patients after ASD surgery.

METHODS

Fifty-two patients (52 females, mean age =70.2 years) who underwent multiple-level lateral lumbar interbody fusion combined with posterior instrumentation for ASD were included. The patients were divided into 2 groups, PJF and non-PJF. The demographics, surgical characteristics, and radiographic parameters were compared. Vertebral HU values at UIV, UIV+1, and UIV+2 using preoperative computed tomography scans and immediate postoperative GAP scores were also compared.

RESULTS

PJF was found in 13 of 52 patients (25.0%). Preoperative and postoperative thoracic kyphosis was large in PJF patients. Based on the total GAP score, there was no significant difference among the categories of GAP scores (P = 0.514). The statistically significant difference in mean HU values (116.6 ± 28.1 vs. 141.8 ± 41.8, P = 0.049) between the two groups at UIV. Further correlation analysis showed that the mean HU values in UIV and UIV+1 showed a significantly negative correlation coefficient with the total GAP score.

CONCLUSIONS

Our study suggests that preoperative HU values at UIV may affect the development of PJF for female ASD patients. HU evaluation by preoperative computed tomography may help reduce the incidence of PJF.

Biomechanical Evaluation of Semi-rigid Junctional Fixation Using a Novel Cable Anchor System to Prevent Proximal Junctional Failure in Adult Spinal Deformity Surgery

STUDY DESIGN

A porcine cadaveric biomechanical study.

OBJECTIVE

To biomechanically evaluate a novel Cable Anchor System as semi-rigid junctional fixation technique for the prevention of proximal junctional failure after adult spinal deformity surgery and to make a comparison to alternative promising prophylactic techniques.

SUMMARY OF BACKGROUND DATA

The abrupt change of stiffness at the proximal end of a pedicle screw construct is a major risk factor for the development of proximal junctional failure after adult spinal deformity surgery. A number of techniques that aim to provide a gradual transition zone in range of motion (ROM) at the proximal junction have previously been studied. In this study, the design of a novel Cable Anchor System, which comprises a polyethylene cable for rod fixation, is assessed.

METHODS

Ten T6-T13 porcine spine segments were subjected to cyclic 4 Nm pure-moment loading. The following conditions were tested: uninstrumented, 3 level pedicle screw fixation (PSF), and PSF with supplementary Cable Anchors applied proximally at 1-level (Anchor1) or 2-levels (Anchor2), transverse process hooks (TPH), and 2-level sublaminar tapes (Tape2). The normalized segmental range of motion in the junctional zone was compared using one-way analysis of variance and linear regression.

RESULTS

Statistical comparison at the level proximal to PSF showed significantly lower ROMs for all techniques compared to PSF fixation alone in all movement directions. Linear regression demonstrated a higher linearity for Anchor1 (0.820) and Anchor2 (0.923) in the junctional zone in comparison to PSF (1-level: 0.529 and 2-level: 0.421). This linearity was similar to the compared techniques (TPH and Tape2).

CONCLUSION

The Cable Anchor System presented in this study demonstrated a gradual ROM transition zone at the proximal end of a rigid pedicle screw construct similar to TPH and 2-level sublaminar tape semi-rigid junctional fixation constructs, while providing the benefit of preserving the posterior ligament complex.Level of Evidence: 5.

Improvement and International Validation of the Predictive Probability of the Patient Demographics, Radiographic Index, and Surgical Invasiveness for Mechanical Failure (PRISM) Model for Preventive Procedures in Adult Spinal Deformity Surgery

STUDY DESIGN

This is an international multicenter retrospective review of 219 surgically treated consecutive adult spinal deformity (ASD) patients who had a minimum of five fused segments, completed a 2-year follow-up.

OBJECTIVE

The purpose of this study was to add the indices of preventive procedures to improve and to validate the predictive probability of the PRISM (patient demographics, radiographic index, and surgical invasiveness for mechanical failure) for mechanical failure (MF) following ASD surgery.

SUMMARY OF BACKGROUND DATA

The PRISM was developed from the data of 321 ASD patients, which stratified the risk of MF from six types of risk.

METHODS

Data from 136 Japanese ASD patients (age 49 ± 21 yr, 88% female) were used to develop PRISM2, and data from 83 US ASD patients (age 58 ± 12 yr, 86% female) were used for the external validation. We analyzed the associations between three preventive procedures (UIV+1 tethering [TH], teriparatide [TP], and multirod [MR]) and MF by multivariate logistic regression analysis (MRA). The values for the nearest integer of the β of the procedures were added to the six indices of the original PRISM to establish the PRISM2. The discriminative ability of the PRISM/ PRISM2 for MF was evaluated using the area under the receiver operating characteristic curve (AUC) and the precision-recall (PR) curve. The Cochran-Armitage test was used to analyze the trend between PRISM/PRISM2 scores and MF.

RESULTS

MF developed in 25% (34 cases). The β values for the preventive procedures calculated by MRA were TH: -2.5, TP: -3.0, and MR: -2.1. The Cochran-Armitage test showed an excellent trend between MF and PRISM/2. The diagnostic ability was superior for the PRISM2 compared with the PRISM (PRISM2; AUC = 0.94 [0.90-0.98], PRISM; AUC = 0.87 [0.81-0.93], difference = -0.07 [-0.11 to -0.03], P  < 0.01). The AUC of the PRISM2 was 0.70 [0.59-0.81, P < 0.01] in the US patient cohort.

CONCLUSION

We refined the PRISM by adding preventive procedures to the risk indices. Further validation and adjustment in a large different patient cohorts may improve the predictive probability of PRISM2.Level of Evidence: 3.

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

Background

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

Methods

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

Results

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

Conclusion

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

Low-Density Pedicle Screw Constructs Are Associated with Lower Incidence of Proximal Junctional Failure in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Determine whether screws per level and rod material/diameter are associated with incidence of proximal junctional kyphosis (PJF).

SUMMARY OF BACKGROUND DATA

PJF is a common and particularly adverse complication of adult spinal deformity (ASD) surgery. There is evidence that the rigidity of posterior spinal constructs may impact risk of PJF.

METHODS

Patients with ASD and 2-year minimum follow-up were included. Only patients undergoing primary fusion of more than or equal to five levels with lower instrumented vertebrae (LIV) at the sacro-pelvis were included. Screws per level fused was analyzed with a cutoff of 1.8 (determined by receiver operating characteristic curve (ROC) analysis). Multivariable logistic regression was utilized, controlling for age, body mass index (BMI), 6-week postoperative change from baseline in lumbar lordosis, number of posterior levels fused, sex, Charlson comorbidity index, approach, osteotomy, upper instrumented vertebra (UIV), osteoporosis, preoperative TPA, and pedicle screw at the UIV (as opposed to hook, wire, etc.).

RESULTS

In total, 504 patients were included. PJF occurred in 12.7%. The mean screws per level was 1.7, and 56.8% of patients had less than 1.8 screws per level. No differences were observed between low versus high screw density groups for T1-pelvic angle or magnitude of lordosis correction (both P > 0.15). PJF occurred in 17.0% versus 9.4% of patients with more than or equal to 1.8 versus less than 1.8 screws per level, respectively (P < 0.05). In multivariable analysis, patients with less than 1.8 screws per level exhibited lower odds of PJF (odds ratio (OR) 0.48, P < 0.05), and a continuous variable for screw density was significantly associated with PJF (OR 3.87 per 0.5 screws per level, P < 0.05). Rod material and diameter were not significantly associated with PJF (both P > 0.1).

CONCLUSION

Among ASD patients undergoing long-segment primary fusion to the pelvis, the risk of PJF was lower among patients with less than 1.8 screws per level. This finding may be related to construct rigidity. Residual confounding by other patient and surgeon-specific characteristics may exist. Further biomechanical and clinical studies exploring this relationship are warranted.Level of Evidence: 3.

Conditions for Achieving Postoperative Pelvic Incidence-Lumbar Lordosis < 10° in Circumferential Minimally Invasive Surgery for Adult Spinal Deformity

This retrospective study aimed to evaluate the clinical outcomes of circumferential minimally invasive surgery (CMIS) using lateral lumbar interbody fusion (LLIF) and percutaneous pedicle screw (PPS) in adult spinal deformity (ASD) patients, and to clarify the conditions for achieving postoperative pelvic incidence-lumbar lordosis (PI-LL) < 10°. Demographics and other parameters of ASD patients who underwent CMIS and who were divided into groups G (achieved postoperative PI-LL < 10°) and P (PI-LL ≥ 10°) were compared. Of the 145 included ASD patients who underwent CMIS, the average fused level, bleeding volume, operative time, and number of intervertebral discs that underwent LLIF were 10.3 ± 0.5 segments, 723 ± 375 mL, 366 ± 70 min, and 4.0 segments, respectively. The rod material was titanium alloy in all the cases. The PI-LL significantly improved from 37.3 ± 17.9° to 1.2 ± 12.2° postoperatively. Pre- and postoperative PI, postoperative LL, preoperative PI-LL, PI-LL after LLIF, and postoperative PI-LL were significantly larger in group P. PI-LL after LLIF was identified as a significant risk factor of postoperative PI-LL < 10° by logistic regression, and the cut-off value on receiver operating characteristic curve analysis was 20°. Sufficient correction was achieved by CMIS. If PI-LL after LLIF was ≤20°, it was corrected to the ideal alignment by the PPS procedure.

Analysis of measurement changes in pelvic incidence according to pelvic rotation using a three-dimensional model

Background

Pelvic incidence (PI) is used as a key parameter in surgical correction of adult spinal deformity (ASD). However, reflecting the exact center or inclination of the three-dimensional anatomical structures on the two-dimensional (2D) sagittal radiographs is limited, resulting in measurement errors. Therefore, we evaluated whether there is a change in PI measurement according to the actual rotation of the pelvis, and conducted a study on a more accurate method for PI measurement using 2D sagittal radiographs.

Methods

From 2014 to 2015, the data of 30 patients who visited our outpatient clinic were analyzed retrospectively. CT scans including those of the lower lumbar spine, pelvis, and both femurs in the DICOM format were imported to Mimics Research 17.0 (Materialise NV, Belgium), SolidWorks (Dassault systems, France), and AutoCAD 2014 (AUTODESK, US). The changes in PI according to vertical and horizontal pelvic rotations were evaluated.

Results

The average PIs according to the horizontal pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 48.7°, 48.3°, 47.8°, 46.9°, 45.6°, 44.0°, 42.2°, and 39.9°, respectively. The PI with an acceptable error of 6° on radiographs was 35° in the horizontal pelvic rotation. The average PIs according to the vertical pelvic rotations measured on AutoCAD with 0°, 5°, 10°, 15°, 20°, 25°, 30°, 35°, and 40° were 48.8°, 49.0°, 49.5°, 50.2°, 51.3°, 52.7°, 54.4°, 56.6°, and 59.4°, respectively. The PI with an acceptable error of 6° on radiographs was 30° in the vertical pelvic rotation.

Conclusions

This study revealed that the PI value could differ from the actual anatomical value due to the horizontal and vertical rotation of the pelvis while acquiring the radiograph. Regarding whole-spine lateral radiographs, errors in PI measurement may occur due to pelvic rotation or nonvertical projection of X-rays. In the standing pelvic lateral radiographs, ensuring superposition of the femoral heads at the center and obtaining the straight sacral endplate by referring to CT or magnetic resonance imaging would be a more accurate measurement method to define PI.

Optimal Anchor at the Uppermost Instrumented Vertebra in Long Fusion From the Pelvis to the Lower Thoracic Spine in Elderly Patients With Degenerative Spinal Deformity: Hook Versus Pedicle Screw

STUDY DESIGN

This was a retrospective cohort study.

OBJECTIVE

The objective of this study was to compare pedicle screws (PSs) and transverse process hooks (TPHs) as anchors at the uppermost instrumented vertebra (UIV) in the lower thoracic spine in elderly patients with adult spinal deformity.

SUMMARY OF BACKGROUND DATA

Less-rigid fixation using hooks at the UIV are thought to best prevent proximal junctional kyphosis (PJK) in long spinal fusion surgery. Although adult spinal deformity is commonly treated via spinal fusion from the pelvis to the lower thoracic spine, few studies have focused on UIV anchors in the lower thoracic spine.

MATERIALS AND METHODS

We retrospectively reviewed 53 patients aged 65 years and above who underwent spinal fusion from the pelvis to T9 or T10, with a minimum follow-up of 1 year. Radiographic outcomes including the incidence of PJK and implant failure were compared between 28 patients with TPHs and 25 patients PSs at the UIV.

RESULTS

The TPH and PS groups had similar radiographic values for pelvic incidence-lumbar lordosis (preoperative: 42.8 vs. 49.0 degrees, postoperative: 9.9 vs. 7.3 degrees) and the sagittal vertical axis (preoperative: 109.3 vs. 106.8 mm; postoperative: 21.9 vs. 11.2 mm). However, the incidence of PJK was significantly higher in the TPH group (35.7%) than that in the PS group (8.0%) at the 1-year follow-up (P=0.012). PJK in the TPH group was associated with UIV or UIV±1 fracture accompanied by posterior dislodgement of the TPH.

CONCLUSION

Rigid fixation using PSs at the UIV in the lower thoracic spine produced better radiographic outcomes than did TPHs in elderly patients undergoing spinopelvic fusion.

LEVEL OF EVIDENCE

Level III.

Upper instrumented vertebra-femoral angle and correlation with proximal junctional kyphosis in adult spinal deformity

INTRODUCTION

Although matching lumbar lordosis (LL) with pelvic incidence (PI) is an important surgical goal for adult spinal deformity (ASD), there is concern that overcorrection may lead to proximal junctional kyphosis (PJK). We introduce the upper instrumented vertebra-femoral angle (UIVFA) as a measure of appropriate postoperative position in the setting of lower thoracic to pelvis surgical correction for patients with sagittal imbalance. We hypothesize that a more posterior UIV position in relation to the center of the femoral head is associated with an increased risk of PJK given compensatory hyperkyphosis above the UIV.

METHODS

In this retrospective cohort study, adult patients undergoing lower thoracic (T9-T12) to pelvis correction of ASD with a minimum of 2-year follow-up were included. UIVFA was measured as the angle subtended by a line from the UIV centroid to the femoral head center to the vertical axis. Patients who developed PJK and those who did not were compared with preoperative and postoperative UIVFA as well as change between postoperative and preoperative UIVFA (deltaUIVFA).

RESULTS

Of 119 patients included with an average 3.6-year follow-up, 51 (42.9%) had PJK and 24 (20.2%) had PJF. Patients with PJK had significantly higher postoperative UIVFA (12.6 ± 4.8° vs. 9.4 ± 6.6°, p = 0.04), deltaUIVFA (6.1 ± 7.6° vs. 2.1 ± 5.6°, p < 0.01), postoperative pelvic tilt (27.3 ± 9.2 vs. 23.3 ± 11, p = 0.04), postoperative lumbar lordosis (47.7 ± 13.9° vs. 42.4 ± 13.1, p = 0.04) and postoperative thoracic kyphosis (44.9 ± 13.2 vs. 31.6 ± 18.8) than patients without PJK. With multivariate logistic regression, postoperative UIVFA and deltaUIVFA were found to be independent risk factors for PJK (p < 0.05). DeltaUIVFA was found to be an independent risk factor for PJF (p < 0.05). A receiver operating characteristic (ROC) curve for UIVFA as a predictor for PJK was established with an area under the curve of 0.67 (95% CI 0.59-0.76). Per the Youden index, the optimal UIVFA cut-off value is 11.5 degrees.

CONCLUSION

The more posterior the UIV is from the femoral head center after lower thoracic to pelvis surgical correction for ASD, the more patients are at risk for PJK. The greater the magnitude of posterior translation of the UIV from the femoral head center from preop to postop, the greater the likelihood for PJF.

A Retrospective Analysis of the L3-4 Disc and Spinopelvic Parameters on Outcomes in Thoracolumbar Fusion: Was Art Steffee Right?

OBJECTIVE

To determine if the L3-4 disc angle may be a surrogate marker for global lumbar alignment in thoracolumbar fusion surgery. To explore the relationship between radiographic and patient-reported outcomes (PROs) after thoracolumbar fusion surgery.

METHODS

Retrospective chart review was conducted on patients who had undergone a lumbar fusion involving levels from T9 to pelvis. EuroQol-Five Dimension (EQ-5D) scores and adverse events including adjacent segment disease and degeneration, pseudoarthrosis, proximal junctional kyphosis, stenosis, and reoperation were collected. Pre- and postoperative spinopelvic parameters were measured on weight-bearing radiographs, with the L3-4 disc angle of novel interest. Univariate logistic and linear regression were performed to assess the associations of radiographic parameters with adverse event incidence and improvement in EQ-5D, respectively.

RESULTS

182 patients met inclusion criteria. Univariable analysis revealed that increased magnitude of L3-4 disc angle, anterior pelvic tilt, and pelvic incidence measures are associated with increased likelihood of developing postoperative adverse events. Conversely, increased lumbar lordosis demonstrated a decreased incidence of developing a postoperative adverse event. Linear regression showed that radiographic parameters did not significantly correlate with postoperative EQ-5D scores although scores were significantly improved post-fusion in all dimensions except Self-care (P = 0.51).

CONCLUSIONS

L3-4 disc angle magnitude may serve as a surrogate marker of global lumbar alignment. Degree of spinopelvic alignment did not correlate to improvement in EQ-5D score in the present study, suggesting that quality of life metric change may not be a sensitive or specific marker of post-fusion alignment.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Health insurance policy on surgical treatment of adult spinal deformity

Background: Recent burgeoning research on adult spinal deformity (ASD) has unveiled the benefits of surgical treatment and how to gain the benefits although these have only been around for 10 years.Current Concepts: During the last decade, the significance of pelvic incidence in the global spinal sagittal alignment and introductions of the Scoliosis Research Society-Schwab classification for ASD have been the guidelines of surgical treatment for ASD and the milestones for promising surgical results. However, one of the unsolved problems for the surgical treatment of ASD is the proximal junctional kyphosis, for which multifactorial causative factors have been suggested. Recent studies have focused on dynamic natures in patients with ASD during daily activities, which might be a clue for both prevention of proximal junctional kyphosis and a better level of surgical results. Even though a recent remarkable advancement for surgical treatment for ASD is present, the national guideline for reimbursement is still following the surgical indication for lumbar degenerative kyphosis published in 1988.Discussion and Conclusion: A significant gap exists between the national reimbursement guideline and generally held surgical indication for ASD surgery. Consequently, this huge gap raises trouble in both patients and surgeons. The patients with ASD cannot take an appropriate surgery for ASD, while the spine surgeons experience unreasonable adjustment of the cost by the Health Insurance Review and Assessment Service.

The standing T1-L1 pelvic angle: a useful radiographic predictor of proximal junctional kyphosis in adult spinal deformity

OBJECTIVE

Proximal junctional kyphosis (PJK), which can worsen a patient's quality of life, is a common complication following the surgical treatment of adult spinal deformity (ASD). Although various radiographic parameters have been proposed to predict the occurrence of PJK, the optimal method has not been established. The present study aimed to investigate the usefulness of the T1-L1 pelvic angle in the standing position (standing TLPA) for predicting the occurrence of PJK.

METHODS

The authors retrospectively extracted data for patients with ASD who underwent minimum 5-level fusion to the pelvis with upper instrumented vertebra between T8 and L1. In the present study, PJK was defined as ≥ 10° progression of the proximal junctional angle or reoperation due to progressive kyphosis during 1 year of follow-up. The following parameters were analyzed on whole-spine standing radiographs: the T1-pelvic angle, conventional thoracic kyphosis (TK; T4-12), whole-thoracic TK (T1-12), and the standing TLPA (defined as the angle formed by lines extending from the center of T1 and L1 to the femoral head axis). A logistic regression analysis and a receiver operating characteristic curve analysis were performed.

RESULTS

A total of 50 patients with ASD were enrolled (84% female; mean age 74.4 years). PJK occurred in 19 (38%) patients. Preoperatively, the PJK group showed significantly greater T1-pelvic angle (49.2° vs 34.4°), conventional TK (26.6° vs 17.6°), and standing-TLPA (30.0° vs 14.9°) values in comparison to the non-PJK group. There was no significant difference in the whole-thoracic TK between the two groups. A multivariate analysis showed that the standing TLPA and whole-thoracic TK were independent predictors of PJK. The standing TLPA had better accuracy than whole-thoracic TK (AUC 0.86 vs 0.64, p = 0.03). The optimal cutoff value of the standing TLPA was 23.0° (sensitivity 0.79, specificity 0.74). Using this cutoff value, the standing TLPA was the best predictor of PJK (OR 8.4, 95% CI 1.8-39, p = 0.007).

CONCLUSIONS

The preoperative standing TLPA was more closely associated with the occurrence of PJK than other radiographic parameters. These results suggest that this easily measured parameter is useful for the prediction of PJK.

Correlation of Acetabular Anteversion and Thoracic Kyphosis Postoperatively with Proximal Junctional Failure in Adult Spinal Deformity Fused to Pelvis

Objectives

To investigate whether the immediate thoracic kyphosis (TK) and acetabular anteversion (AA) postoperatively are correlated with proximal junctional failure (PJF) in adult spinal deformity (ASD) patients underwent surgical treatment.

Methods

This is a retrospective study. Following institutional ethics approval, a total of 57 patients (49 Female, eight Male) with ASD underwent surgery fused to sacroiliac bone (S1, S2, or ilium) from March 2014 to January 2019 were included. All of those patients were followed up for at least 2 years. Demographic, radiographic and surgical data were recorded. The maximum range of flexion motion (F‐ROM) and extension motion (E‐ROM) actively of hip joints was measured and recorded at pre‐ and postoperation. The sum of F‐ROM and E‐ROM was defined as the range of hip motion (H‐ROM). Receiver operating characteristic (ROC) curve analysis was used to obtain the cut off value of parameters for PJF. A Kaplan–Meier curve and log‐rank test were used to analyze the differences in PJF‐free survival.

Results

In all, 14 patients developed PJF during follow‐up. Comparisons between patients with and without PJF showed significant differences in immediate TK (P < 0.001) and AA (P = 0.027) postoperatively. ROC curve analysis determined an optimal threshold of 13° for immediate AA postoperatively (sensitivity = 74.3%, specificity = 85.7%, area under the ROC curve [AUC] = 0.806, 95% CI [0.686–0.926]). Nineteen patients with post‐AA ≤13° were assigned into the observational group, and 38 patients with post‐AA >13° were being as the control group. Patients in the observational group had smaller H‐ROM (P = 0.016) and F‐ROM (P < 0.001), but much larger E‐ROM (P < 0.001). There were 10 patients showing PJF in the observational group and four in the control group (10/9 vs 4/34, P < 0.001). PJF‐free survival time significantly decreased in the observational group (P = 0.001, log‐rank test). Furthermore, patients in the observational group had much larger TK (post‐TK, P = 0.015). The optimal threshold for post‐TK (sensitivity = 85.7%, specificity = 76.7%; AUC = 0.823, 95% CI [0.672–0.974]) was 28.1° after the ROC curve was analyzed. In the observational group, those patients with post‐TK ≥28.1° had significantly higher incidence of PJF (9/2 vs 1/7, P < 0.001) than those with post‐TK < 28.1°. Moreover, PJF‐free survival time in those patients significantly decreased (P = 0.001, log‐rank test).

Conclusions

ASD patients with acetabular anteversion of ≤13° at early postoperation may suffer significantly restricted hip motion and much higher incidence of PJF during follow‐up, moreover, in those patients, postoperative TK ≥28.1° would be a significant risk factor for PJF developing.

The Long-term Fate of Asymptomatic Proximal Junctional Kyphosis Following Long Instrumented Fusion in Elderly Patients with Sagittal Imbalance

STUDY DESIGN

Retrospective study.

OBJECTIVE

The aim of this study was to investigate the long-term fate of asymptomatic PJK focusing on the elderly patients with sagittal imbalance by comparing the patients with and without PJK.

SUMMARY OF BACKGROUND DATA

Most of previous studies demonstrated that PJK does not negatively affect the clinical outcome compared to that of the patients without PJK. The question "will the asymptomatic PJK remain asymptomatic even in long-term follow-up?" has not been answered yet because the previous results were based on the short follow-up duration.

METHODS

Patients >60 years who underwent four or more level fusions to the sacrum for sagittal imbalance were followed up for >5 years. The radiographic and clinical outcomes were compared between PJK (n = 30) and non-PJK groups (n = 43). PJK was defined by proximal junctional angle (PJA) >10°. Only patients with >3 years of follow-up duration after PJK development were included in PJK group. The clinical outcome measures included visual analog scale (VAS) for the back and leg, Oswestry disability index (ODI), and Scoliosis Research Society (SRS)-22 scores.

RESULTS

The mean age was 69.2 years. Total follow-up duration was 92.4 months. Time between PJK development and the last follow-up was 67.4 months in PJK group. Although there were no differences between the two groups in terms of pelvic incidence-lumbar lordosis mismatch, pelvic tilt, or sacral vertical axis, PJA significantly increased from 6.5° postoperatively to 21.2° at the final follow-up in the PJK group. The clinical outcomes were worse (such as VAS for the back, ODI, and SRS-22 scores) in the PJK group than in non-PJK group, except for the satisfaction domain. Three (10%) of 30 patients underwent a revision surgery for PJK progression.

CONCLUSION

Even if PJK was asymptomatic at initial development, it progressed radiographically with time and eventually gave a negative impact on the clinical outcomes in long-term follow-up.Level of Evidence: 3.

Which Is More Predictive Value for Mechanical Complications: Fixed Thoracolumbar Alignment (T1 Pelvic Angle) Versus Dynamic Global Balance Parameter (Odontoid-Hip Axis Angle)

Objective

In this study, we investigate about relationship between postoperative global sagittal imbalance and occurrence of mechanical complications after adult spinal deformity (ASD) surgery. In global sagittal balance parameters, odontoid-hip axis (OD-HA) angle and T1 pelvic angle (TPA) were analyzed.

Methods

Between January 2009 and December 2016, 199 consecutive patients (26 males and 173 females) with ASD underwent corrective fusion of more than 4 levels and were followed up for more than 2 years. Immediate postoperative and postoperative 2 years whole spine x-rays were checked for evaluating immediate postoperative OD-HA, TPA, and other parameters. In clinical outcomes, back and leg pain visual analogue scale, Scoliosis Research Society-22 spinal deformity questionnaire (SRS-22), Oswestry Disability Index (ODI), 36-item Short Form Health Survey (SF-36) were evaluated.

Results

Based on the occurrence of mechanical complications, a comparative analysis was performed for each parameter. In univariable analysis, mechanical complications were significantly much more occurred in OD-HA abnormal group (odds ratio [OR], 3.296; p<0.001; area under the curve [AUC]=0.645). In multivariable analysis, the result was much more related (OR, 2.924; p=0.001; AUC=0.727). In contrast, there was no significant difference between normal and the occurrence of mechanical complications in TPA. In clinical outcomes (normal vs. abnormal), the differences of SRS-22 (0.88±0.73 vs. 0.68±0.64, p=0.042), ODI (-24.72±20.16 vs. -19.01±19.95, p=0.046), SF-36 physical composite score (19.33±18.55 vs. 12.90±16.73, p=0.011) were significantly improved in OD-HA normal group.

Conclusion

The goal of ASD surgery is to improve patient life quality through correction. In our study, TPA was associated with spinopelvic parameter and OD-HA angle was associated with health-related quality of life and complications. OD-HA angle is predictable factor for mechanical complications after ASD surgery.

Thoracic Reciprocal Change Can Be Predicted Before Surgery in Adult Spinal Deformity

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Analysis of postoperative sagittal alignment of the unfused spine is lacking in patients with adult spinal deformity (ASD). The present study aims to evaluate the efficacy of the whole spine full-flexion lateral radiograph to predict the reciprocal change of the unfused spine after correction surgery. We hypothesized that the novel parameter (T1-UIV angle: angle between the upper vertebral endplate of the T1 and the upper vertebral endplate of the upper instrumented vertebra) of the preoperative whole spine full-flexion lateral radiograph is similar to that of the postoperative lateral radiograph if the patient has the ideal sagittal alignment.

METHODS

Twenty-six ASD patients who underwent correction surgery with a minimum 2-year follow-up were enrolled and separated into the Ideal and Non-Ideal groups according to the Scoliosis Research Society (SRS)-Schwab classification of the final follow-up radiograph. Radiographic parameters, including T1-UIV of the preoperative whole spine full-flexion lateral radiograph, were obtained.

RESULTS

Thirteen patients were included in the Ideal group and 13 were in Non-Ideal group. Preoperative T1-UIV of the whole spine full-flexion lateral radiograph exhibited significant correlations with the T1-UIV angles of the postoperative and final follow-up radiographs (r = 0.64, P < .01, y = 0.800x + 8.012, and r = 0.69, P < .01, y = 0.857x + 2.960, respectively). Interestingly, this correlation was stronger for the Ideal group (r = 0.77, P < .01, y = 1.207x - 1.517, and r = 0.89, P < .01, y = 0.986x + 0.694, respectively).

CONCLUSION

A novel radiographic strategy (T1-UIV of preoperative the whole spine full-flexion lateral radiograph) could estimate the postoperative alignment of the unfused spine correctly.

The compensatory mechanisms for global sagittal balance in degenerative spinal kyphosis patients: a radiological analysis of muscle-skeletal associations

BACKGROUND

The position of the head relative to the spine can be used to evaluate the true global balance in patients with degenerative spinal kyphosis (DSK). However, it is still not clear how the position of the head is related to the spinal-pelvic parameters and lumbar muscles, which are most commonly considered.

METHODS

Sixty-seven patients with DSK admitted in the hospital from January 2017 to January 2019 were retrospectively analyzed. All patients had whole spine X-ray and lumbar MRI. The head position parameters include: the angles of both lines joining the center of acoustic meati (CAM) to the center of the bi-coxofemoral axis (BA) (CAM-BA) and the most superior point of dentiform apophyse of C2 odontoid (OD) to BA (OD-BA) with the vertical line; the distance between the vertical line passing CAM and the posterior upper edge of the S1 (CAM-SVA). The spinal parameters include: C7 sagittal vertical axis (C7-SVA), thoracic kyphosis (TK), thoracolumbar kyphosis (TLK), and lumbar lordosis (LL). The pelvic parameters include: pelvic incidence (PI), pelvic tilt (PT) and sacral slope (SS). The relative cross-sectional area (RCSA) of bilateral multifidus, erector spinae and psoas muscle at L3/4 and L4/5 segments were measured. The correlations between head position parameters and the spinal-pelvic parameters and RCSA of lumbar muscles were analyzed, respectively.

RESULTS

Significant positive correlations were found between each two of CAM-SVA, C7-SVA, CAM-BA and OD-BA (p < 0.001). SS was found to be significantly positively correlated with CAM-BA (r = 0.377, p = 0.034) and OD-BA (r = 0.402, p = 0.023). CAM-BA was found to be significantly negatively correlated with TK (r = - 0.367, p = 0.039). Significant positive correlations were found between RCSA of multifidus at L3/4 level and CAM-SVA (r = 0.413, p = 0.021), CAM-BA (r = 0.412, p = 0.019) and OD-BA (r = 0.366, p = 0.04).

CONCLUSIONS

Our study showed that the head position relative to the spine were significantly correlated to some spinal-pelvic parameters, and the lower lumbar multifidus muscle. The compensatory mechanisms of the global sagittal balance status should also involve the head position area.

Transiency of postoperative cervical kyphosis seen after surgical correction of sagittal malalignment in adult spinal deformity patients

Objective

In this study, we evaluated factors affecting changes in cervical lordosis after deformity correction and during follow-up period in adult spinal deformity (ASD) patients with severe sagittal imbalance.

Methods

Seventy-nine patients, with an average age of 71.6 years, who underwent long-segment fixation from T10 to S1 with sacropelvic fixation were included. We performed a comparative analysis of the radiographic parameters after surgery (Post) and at the last follow-up (Last). We calculated the Pearson’s correlation coefficient and performed multilinear regression analysis to predict independent parameters for Post and Last cervical lordosis (CL), T1 slope (T1S), and thoracic kyphosis (TK).

Results

Hyperlordotic changes of -23.3° in CL before surgery was reduced to -7° after surgery, and Last CL had increased to -15.3°. T1S was reduced from 27° before surgery to 14.4° after surgery and had increased to 18.8° at the last follow-up. Through multilinear regression analysis, we found that Post CL and T1S were more significantly affected by the amount of LL correction (p = .045 and .049). The effect of Last T1S was significantly associated with the Last CL; the effect of Last TK, with the Last T1S; and the effect of Post PI-LL, with the Last TK (p < .05).

Conclusion

The postoperative kyphotic change in CL in ASD patients with preoperative cervical hyperlordosis is not permanent and is affected by drastic LL correction and SVA restoration. To achieve spinopelvic harmony proportional to the difference in LL relative to PI, TK becomes modified over time to increase T1S and CL, in an effort to achieve optimal spine curvature.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

A Systematic Review of Treatment Strategies for the Prevention of Junctional Complications After Long-Segment Fusions in the Osteoporotic Spine

STUDY DESIGN

Systematic review.

OBJECTIVES

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are well-known complications after long-segment fusions in the thoracolumbar spine of osteoporotic patients. Recent advances in anti-resorptive and anabolic medications, instrumentation, surgical technique, and cement augmentation have all aided in the avoidance of junctional kyphosis. In this article, current literature on the prevention of PJK and PJF in the osteoporotic spine is reviewed.

METHODS

A systematic literature review was conducted using the PubMed/MEDLINE and Embase databases in order to search for the current preventive treatment methods for PJK and PJF published in the literature (1985 to present). Inclusion criteria included (1) published in English, (2) at least 1-year mean and median follow-up, (3) preoperative diagnosis of osteoporosis, (4) at least 3 levels instrumented, and (5) studies of medical treatment or surgical techniques for prevention of junctional kyphosis.

RESULTS

The review of the literature yielded 7 studies with low levels of evidence ranging from level II to IV. Treatment strategies reviewed addressed prophylaxis against ligamentous failure, adjacent vertebral compression fracture, and/or bone-implant interface failure. This includes studies on the effect of osteoporosis medication, cement augmentation, multi-rod constructs, and posterior-tension band supplementation. The role of perioperative teriparatide therapy maintains the highest level of evidence.

CONCLUSIONS

Perioperative teriparatide therapy represents the strongest evidence for preventive treatment, and further clinical trials are warranted. Use of cement augmentation, sublaminar tethers, and multi-rod constructs have low or insufficient evidence for recommendations. Future guidelines for adult spinal deformity correction may consider bone mineral density-adjusted alignment goals.

Posterior Displacement of L1 May be a Risk Factor for Proximal Junctional Kyphosis After Adult Spinal Deformity Correction

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Overcorrection in adult spinal deformity (ASD) surgery may lead to proximal junctional kyphosis (PJK) because of posterior spinal displacement. The aim of this paper is to determine if the L1 position relative to the gravity line (GL) is associated with PJK.

METHODS

ASD patients fused from the lower thoracic spine to sacrum by 4 spine surgeons at our hospital were retrospectively studied. Lumbar-only and upper thoracic spine fusions were excluded. Spinopelvic parameters, the L1 plumb line (L1PL), L1 distance to the GL (L1-GL), and Roussouly type were measured.

RESULTS

One hundred fourteen patients met inclusion criteria (63 patients with PJK, 51 without). Mean age and follow up was 65.51 and 3.39 years, respectively. There was no difference between the PJK and the non-PJK groups in baseline demographics, pre-operative and immediate post-operative pelvic incidence-lumbar lordosis mismatch, sagittal vertical axis, or coronal Cobb. The immediate postoperative L1-GL was -7.24 cm in PJK and -3.45 cm in non-PJK (P < 0.001), L1PL was 1.71 cm in PJK and 3.07 cm in non-PJK (P = 0.004), and PT (23.76° vs 18.90°, P = 0.026) and TK (40.56° vs 31.39°, P < 0.001) were larger in PJK than in non-PJK. After univariate and multivariate analyses, immediate postoperative TK and immediate postoperative L1-GL were independent risk factors for PJK without collinearity.

CONCLUSIONS

A dorsally displaced L1 relative to the GL was associated with an increased risk of PJK after ASD surgery. The postoperative L1-GL distance may be a factor to consider during ASD surgery.

Comparison of degenerative lumbar scoliosis correction and risk for mechanical failure using posterior 2-rod instrumentation versus 4-rod instrumentation and interbody fusion

PURPOSE

Four-rod instrumentation and interbody fusion may reduce mechanical complications in degenerative scoliosis surgery compared to 2-rod instrumentation. The purpose was to compare clinical results, sagittal alignment and mechanical complications with both techniques.

METHODS

Full spine radiographs were analysed in 97 patients instrumented to the pelvis: 58 2-rod constructs (2R) and 39 4-rod constructs (4R). Clinical scores (VAS, ODI, SRS-22, EQ-5D-3L) were assessed preoperatively, at 3 months, 1 year and last follow-up (average 4.2 years). Radiographic measurements were: thoracic kyphosis, lumbar lordosis, spinopelvic parameters, segmental lordosis distribution. The incidence of non-union and PJK were investigated.

RESULTS

All clinical scores improved significantly in both groups between preoperative and last follow-up. In the 2R-group, lumbar lordosis increased to 52.8° postoperatively and decreased to 47.0° at follow-up (p = 0.008). In the 4R-group, lumbar lordosis increased from 46.4 to 52.5° postoperatively and remained at 53.4° at follow-up. There were 8 (13.8%) PJK in the 2R-group versus 6 (15.4%) in the 4R-group, with a mismatch between lumbar apex and theoretic lumbar shape according to pelvic incidence. Non-union requiring revision surgery occurred on average at 26.9 months in 28 patients (48.3%) of the 2R-group. No rod fracture was diagnosed in the 4R-group.

CONCLUSION

Multi-level interbody fusion combined with 4-rod instrumentation decreased risk for non-union and revision surgery compared to select interbody fusion and 2-rod instrumentation. The role of additional rods on load sharing still needs to be determined when multiple cages are used. Despite revision surgery in the 2R group, final clinical outcomes were similar in both groups.

LEVEL OF EVIDENCE

III.

State of the art: proximal junctional kyphosis-diagnosis, management and prevention

Proximal junctional kyphosis (PJK) is a common problem that may occur following the surgical treatment of adult patients with spinal deformity. It is defined as the proximal junctional sagittal angle from the UIV and UVI + 2 of at least 10° AND at least 10° greater than the preop measurement. The reported incidence of radiographic PJK in the literature varies between 17 and 46%. A smaller subset of these patients may need revision surgery and are defined as proximal junctional failure (PJF), which can be associated with vertebral fracture, vertebral subluxation, failure of instrumentation, and neurological deficits. Several risk factors for development of PJK have been proposed. However, large-scale prospective studies are needed to better identify strategies to reduce the incidence of PJK.

Strategies for prevention of rod fracture in adult spinal deformity: cobalt chrome rod, accessory rod technique, and lateral lumbar interbody fusion

OBJECTIVE

Restoring the proper sagittal alignment in adult spinal deformity (ASD) can improve radiological and clinical outcomes, but pseudarthrosis including rod fracture (RF) is a common problematic complication. The purpose of this study was to analyze the methods for reducing the incidence of RF in deformity correction of ASD.

METHODS

The authors retrospectively selected 178 consecutive patients (mean age 70.8 years) with lumbar degenerative kyphosis (LDK) who underwent deformity correction with a minimum 2-year follow-up. Patients were classified into the non-RF group (n = 131) and the RF group (n = 47). For predicting the crucial factors of RF, patient factors, radiographic parameters, and surgical factors were analyzed.

RESULTS

The overall incidence of RF was 26% (47/178 cases), occurring in 42% (42/100 cases) of pedicle subtraction osteotomy (PSO), 7% (5/67 cases) of lateral lumbar interbody fusion (LLIF) with posterior column osteotomy, 18% (23/129 cases) of cobalt chrome rods, 49% (24/49 cases) of titanium alloy rods, 6% (2/36 cases) placed with the accessory rod technique, and 32% (45/142 cases) placed with the 2-rod technique. There were no significant differences in the incidence of RF regarding patient factors between two groups. While both groups showed severe sagittal imbalance before operation, lumbar lordosis (LL) was more kyphotic and pelvic incidence (PI) minus LL (PI-LL) mismatch was greater in the RF group (p < 0.05). Postoperatively, while LL and PI-LL did not show significant differences between the two groups, LL and sagittal vertical axis correction were greater in the RF group (p < 0.05). Nonetheless, at the last follow-up, the two groups did not show significant differences in radiographic parameters except thoracolumbar junctional angles. As for surgical factors, use of the cobalt chrome rod and the accessory rod technique was significantly greater in the non-RF group (p < 0.05). As for the correction method, PSO was associated with more RFs than the other correction methods, including LLIF (p < 0.05). By logistic regression analysis, PSO, preoperative PI-LL mismatch, and the accessory rod technique were crucial factors for RF.

CONCLUSIONS

Greater preoperative sagittal spinopelvic malalignment including preoperative PI-LL mismatch was the crucial risk factor for RF in LDK patients 65 years or older. For restoring and maintaining sagittal alignment, use of the cobalt chrome rod, accessory rod technique, or LLIF was shown to be effective for reducing RF in ASD surgery.

Proximal junctional fracture and kyphosis after long spinopelvic corrective fixation for adult spinal deformity

BACKGROUND

Proximal junctional fractures (PJFx) are the main cause for proximal junctional kyphosis (PJK), a complication of adult spinal deformity surgery. This study investigated risk factors for PJFx when performing long spinopelvic corrective fixation with lateral interbody fusion from T9 to ilium.

METHODS

This was a retrospective study of 43 patients with a minimum follow-up of 2 years. Radiographic measurements including thoracic kyphosis (TK), sagittal vertical axis (SVA), T1 pelvic angle (TPA), proximal junctional angle (PJA), lumbar lordosis (LL), lower LL, and pelvic tilt were measured preoperatively, one-month postoperatively, and at final follow up. TK and LL were also measured in a fulcrum backward-bending position preoperatively.

RESULTS

At final follow-up, PJK was found in 30/43 patients (69.8%); 20.9% of the cases had PJFx (9 patients). TPA (preoperative, and one-month postoperative) was significantly higher in the PJFx group than in the other groups. The differences in TPA, TK, and PJA between preoperative and one-month postoperative measurements in the PJFx group were significantly higher than those in the other groups. At final follow up, SVA was significantly higher in the PJFx group than in the "PJK without PJFx" group. TPA and TK were significantly higher in the PJFx group than in the other groups. PJA was significantly different between all groups.

CONCLUSION

Preoperative large TPA was the only risk factor for PJFx. Preoperative flexibility of the thoracolumbar spine and overcorrection of sagittal deformity were not related to PJFx or PJK.

Lowest Instrumented Vertebra Selection to S1 or Ilium Versus L4 or L5 in Adult Spinal Deformity: Factors for Consideration in 349 Patients With a Mean 46-Month Follow-Up

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To compare the outcomes of patients with adult spinal deformity (ASD) following spinal fusion with the lowest instrumented vertebra (LIV) at L4/L5 versus S1/ilium.

METHODS

A multicenter ASD database was evaluated. Patients were categorized into 2 groups based on LIV levels-groups L (fusion to L4/L5) and S (fusion to S1/ilium). Both groups were propensity matched by age and preoperative radiographic alignments. Patient demographics, operative details, radiographic parameters, revision rates, and health-related quality of life (HRQOL) scores were compared.

RESULTS

Overall, 349 patients had complete data, with a mean follow-up of 46 months. Patients in group S (n = 311) were older and had larger sagittal and coronal plane deformities than those in group L (n = 38). After matching, 28 patients were allocated to each group with similar demographic, radiographic, and clinical parameters. Sagittal alignment restoration at postoperative week 6 was significantly better in group S than in group L, but it was similar in both groups at the 2-year follow-up. Fusion to S1/ilium involved a longer operating time, higher PJK rates, and greater PJK angles than that to L4/L5. There were no significant differences in the complication and revision rates between the groups. Both groups showed significant improvements in HRQOL scores.

CONCLUSIONS

Fusion to S1/ilium had better sagittal alignment restoration at postoperative week 6 and involved higher PJK rates and greater PJK angles than that to L4/L5. The clinical outcomes and rates of revision surgery and complications were similar between the groups.

Who Will Require Revision Surgery Among Neurologically Intact Patients with Proximal Junctional Failure After Surgical Correction of Adult Spinal Deformity?

STUDY DESIGN

Retrospective study.

OBJECTIVE

To identify the risk factors for revision surgery among neurologically intact patients with proximal junctional failure (PJF) after adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

PJF following long fusion for ASD is a well-recognized complication that negatively affects clinical outcomes. However, revision surgery is not required for every patient with PJF especially if the patient does not present with neurologic deficit. Identifying the risk factors of revision surgery is necessary to determine who will need revision surgery as well as when is the right time for the revision surgery.

METHODS

Sixty-nine neurologically intact patients with PJF following ASD surgery were followed up with more than 2 years after PJF development or until undergoing revision surgery. PJF was divided into ligamentous failure (proximal junctional angle [PJA] of more than 20°) and bony failure. According to the conduct of revision surgery, two groups (revision and no revision) were created. Risk factors for revision surgery were analyzed in univariate and multivariate analysis with regard to patient, surgical and radiographic variables.

RESULTS

The mean age at the time of PJF development was 70.9 years. There were 45 patients with bony failure and 24 with ligamentous failure. Revision surgery was performed for 23 patients (33.3%). Multivariate analysis revealed that bony failure (odds ratio: 10.465) and PJA (odds ratio: 1.131) were significant risk factors. For those with bony failure, the cutoff value of PJA for performing revision surgery was calculated as 22°. The revision rate was significantly highest in patients (63.6%) with bony failure + PJA 22° or higher followed by patients (26.1%) with bony failure + PJA less than 22° and patients (12.5%) with ligamentous failure (P = 0.002).

CONCLUSION

Bony failure with PJA of greater than 22° increased the likelihood for revision surgery. Therefore, early surgical intervention should be considered in these patients.Level of Evidence: 4.

A single institution experience with proximal junctional kyphosis in the context of existing classification schemes - Systematic review

BACKGROUND

Proximal junctional kyphosis is a kyphotic deformity following spine instrumentation, predominantly seen in scoliosis patients. There have been previous attempts to develop classification schema of PJK. We analyzed the factors contributing to PJK based upon our own clinical experience with the goal of developing a clinical guidance tool which took into account both etiology and mechanism of failure.

METHODS

We performed a retrospective analysis of all re-operation thoracolumbar surgeries at a single institution over a 14-year period. Patients with PJK were identified and categorized based upon the etiology, mechanism of failure, and an indication of revision. Next, we conducted a systematic review on articles emphasizing a classification system for PJK.

RESULTS

Fourteen PJK patients were identified out of 121 patients who required revision spine surgery. The average age was 64.9 ± 10.2 years, with 10 males (71%) and 4 females (29%). Three primary etiologies were identified: 6/14 (47%) overcorrection, 6/14 (47%) osteopenia, and 2/14 (14%) ligamentous disruption. The mechanism of failure was likewise divided into three categories: 9/14 (64%) compression fracture, 1/14 (7%) hardware failure, and 4/14 (29%) disc degeneration. The relationship between osteopenia and the development of a compression fracture leading to PJK was statistically significant (p = 0.031).

CONCLUSION

There are multiple current classification systems for PJK. Our study findings were in line with previously published literature and suggest the need for a future classification system combining both etiology, mechanism of failure, and severity of disease.

Risk factors for acute proximal junctional kyphosis after adult spinal deformity surgery in preoperative motion analysis

OBJECTIVE

This study aimed to examine which motion analysis parameters regarding the dynamic aspects and/or balance affect the development acute proximal junctional kyphosis (PJK) following adult spinal deformity (ASD) surgery.

METHODS

A total of 90 consecutive patients were recruited prospectively, who underwent a corrective surgery for ASD with sagittal imbalance. According to the development of acute PJK within 6 months after surgery, the patients were divided into the PJK+ and PJK- groups. Before surgery, three-dimensional gait analyses were performed using a motion analysis system. The preoperative continuous and categorical variables were compared between the PJK+ and PJK- groups using independent t tests and chi-square tests, respectively. Finally, a multivariate logistic regression model was used to identify the risk factors and calculate the odds ratio (OR) for acute PJK.

RESULTS

A total of 20 and 70 patients were classified into the PJK+ and PJK- groups, respectively. There were no differences in the spinopelvic radiologic parameters pre- and postoperatively between the PJK+ and PJK- groups. The PJK+ group showed a significantly higher mean anterior pelvic tilt (Ant-PT) angle in preoperative motion analysis than the PJK- group (P = 0.001 for both sides). Multivariate analysis identified the mean Ant-PT angle (P = 0.047; OR 1.127; 95% CI 1.002-1.267) as a significant risk factor for acute PJK.

CONCLUSION

Preoperative Ant-PT angle during walking was associated with a higher OR in acute PJK after surgery.

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

Background

This cross sectional study describes a "Soft Landing" strategy utilizing hooks for minimizing proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). The technique creates a gradual transition from a rigid segmental construct to unilateral hooks at the upper instrumented level and preservation of the soft tissue attachments on the contralateral side of the hooks. Authors devise a novel classification system for better grading of PJK severity.

Methods

Thirty-nine consecutive adult spinal deformity (ASD) patients at a single institution received the "Soft Landing" technique. The proximal junctional angle was measured preoperatively and at last follow-up using standing 36-inch spinal radiographs. Changes in proximal junctional angle and rates of PJK and PJF were measured and used to create a novel classification system for evaluating and categorizing ASD patients postoperatively.

Results

The mean age of the cohort was 61.4 years, and 90% of patients were women. Average follow up was 2.2 years. The mean change in proximal junctional angle was 8° (SD 7.4°) with the majority of patients (53%) experiencing less than 10° and only 1 patients with proximal junctional angle over 20°. Four patients (10%) needed additional surgery for proximal extension of the uppermost instrumented vertebra (UIV) secondary to PJF.

Conclusions

Soft Landing technique is a possibly effective treatment strategy to prevent PJK and PJF following ASD that requires further evaluation. The described classification system provides management framework for better grading of PJK. The "Soft Landing" technique warrants further comparison to other techniques currently used to prevent both PJK and failure.

Rod contour and overcorrection are risk factors of proximal junctional kyphosis after adult spinal deformity correction surgery

PURPOSE

To examine the risk factors of proximal junctional kyphosis (PJK) after surgery for adult spinal deformity (ASD) focusing on rod contour.

METHODS

Sixty-three patients with ASD who underwent surgery using lateral lumbar interbody fusion and percutaneous pedicle screws were analyzed. Fixation range was from the lower thoracic spine to the pelvis in all cases. Patients were divided into two groups. The PJK group consisted of 16 patients with PJK. The non-PJK group had 47 patients without PJK. We examined various spinopelvic parameters and parameters related to rod contour.

RESULTS

Among the various spinal and pelvic parameters, those in the PJK group were significantly larger in terms of preoperative SVA and were significantly smaller in terms of postoperative "PI-LL." For parameters related to rod contour, the rod kyphotic curve at the thoracic spine in the PJK group was significantly less than that in the non-PJK group. The inclination of the pedicle screw at the upper instrumented vertebra (UIV) was significantly more cranial in the PJK group than in the non-PJK group. The kyphotic curve of the rod at the UIV was more parallel in the PJK group than in the non-PJK group. On logistic regression analysis, insufficient kyphotic curve at the thoracic spine along with UIV and overcorrection of the lumbar spine were identified as significant risk factors.

CONCLUSIONS

Insufficient kyphotic curve of the rod in the thoracic spine along with UIV and overcorrection of the lumbar spine were noted as significant risk factors of PJK.