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

How to view the effectiveness of spinal deformity surgery for adult degenerative scoliosis in octogenarian population? A comprehensive analysis and judgment

This study aims to explore the connections between risk factors and clinical outcomes in octogenarian patients diagnosed with adult degenerative scoliosis (ADS). A total of 394 patients participated in this study, with 206 individuals in the younger group and 188 in the octogenarian group. We meticulously gathered patient demographics, including basic information, comorbidities, radiographic data, clinical scoring systems, and details on medical and surgical complications as well as revision surgeries. Univariable linear regression analysis revealed positive correlations between age and several postoperative outcomes: Sagittal vertical axis (SVA) (B = -0.572, P = 0.001), Oswestry Disability Index (ODI) (B = 0.145, P < 0.001), and Japanese Orthopaedic Association (JOA) score (B = 0.035, P < 0.001). Additionally, a positive relationship was observed between age and both proximal junctional kyphosis (PJK) (B = 0.055, P = 0.039) and internal fixation loosening (B = 0.253, P < 0.001). Receiver operator characteristic (ROC) curve analysis indicated that the age threshold values for predicting PJK and internal fixation loosening were 71.5 and 79.5, respectively. In octogenarian patients with ADS, the cost associated with spinal deformity surgery is accompanied by a greater incidence of surgical complications. Compared to younger patients, surgical intervention tends to be more effective at enhancing objective motor functions while having a lesser impact on the subjective experiences of octogenarian patients.

Revision Strategy for Proximal Junctional Failure: Combined Effect of Proximal Extension and Focal Correction

Study designRetrospective review of a prospectively-collected multicenter database.ObjectivesThe objective of this study was to determine optimal strategies in terms of focal angular correction and length of proximal extension during revision for PJF.Methods134 patients requiring proximal extension for PJF were analyzed in this study. The correlation between amount of proximal junctional angle (PJA) reduction and recurrence of proximal junctional kyphosis (PJK) and/or PJF was investigated. Following stratification by the degree of PJK correction and the numbers of levels extended proximally, rates of radiographic PJK (PJA >28° & ΔPJA >22°), and recurrent surgery for PJF were reported.ResultsBefore revision, mean PJA was 27.6° ± 14.6°. Mean number of levels extended was 6.0 ± 3.3. Average PJA reduction was 18.8° ± 18.9°. A correlation between the degree of PJA reduction and rate of recurrent PJK was observed (r = -.222). Recurrent radiographic PJK (0%) and clinical PJF (4.5%) were rare in patients undergoing extension ≥8 levels, regardless of angular correction. Patients with small reductions (<5°) and small extensions (<4 levels) experienced moderate rates of recurrent PJK (19.1%) and PJF (9.5%). Patients with large reductions (>30°) and extensions <8 levels had the highest rate of recurrent PJK (31.8%) and PJF (16.0%).ConclusionWhile the degree of focal PJK correction must be determined by the treating surgeon based upon clinical goals, recurrent PJK may be minimized by limiting reduction to <30°. If larger PJA correction is required, more extensive proximal fusion constructs may mitigate recurrent PJK/PJF rates.

Advantages of Combined Use of Claw Hooks and Sublaminar Wires as the Upper Foundation of Long Fixation from the Thoracic Spine to the Pelvis in Osteoporotic Cases: A Finite Element Analysis of Proximal Junction Stress

Introduction

This study aimed to compare the biomechanical stress at the proximal junctional aspect between the conventional pedicle screw (PS) fixation (PSF) and the low PS density fixation (LPF) method.

Methods

This study involved 10 patients, half of whom have non-osteoporosis and the other half have osteoporosis. We made two types of intact models (one is from the upper thoracic-to-pelvis model, and the other is from the lower thoracic-to-pelvis model). From the intact models, we constructed two kinds of fusion models: (1) PSF and (2) LPF. The LPF method was as follows: The claw hooks (the combination of the down-going transverse process hooks and facet hooks) were set at the upper instrumented vertebra (UIV) and sublaminar wires at the thoracic spine and PSs at the lumbo-pelvis.

Results

Upper thoracic to pelvis fixation model In non-osteoporosis, no significant difference between the PSF and LPF is found. In osteoporosis, the von Mises stresses of the vertebra body at UIV, UIV+1, and disc were significantly lower in LPF than in PSF. Lower thoracic-to-pelvis fixation model In non-osteoporosis, the average von Mises stress of the vertebral body at UIV+1 and the maximum stress at UIV were lower in LPF than in PSF; however, no significant difference was found in the others. In osteoporosis, the von Mises stress was significantly lower in LPF than in PSF.

Conclusions

The claw hooks stabilized the vertebra body at UIV firmly, and sublaminar wires reduced load translation from the fixed spine.

Short-Segment Fixation for Thoracolumbar Kyphosis Caused by Osteoporotic Vertebral Compression Fractures: A Case Series

OBJECTIVE

To evaluate short-segment fixation (SSF), with or without advanced osteotomy, for treating thoracolumbar kyphosis caused by osteoporotic vertebral compression fractures (OVCFs).

METHODS

This retrospective analysis included 28 patients with thoracolumbar kyphosis caused by OVCFs who underwent SSF at our hospital between 2017 and 2022. The change in the Cobb angle between standing and supine positions was measured to establish whether an advanced osteotomy was necessary. Bone mineral density (T-score) and related hematologic bone metabolism markers were recorded to assess the patient's osteoporosis status. The Cobb angle and sagittal plane parameters were measured before and after surgery to determine the orthopedic outcomes, and function was assessed using a visual analog scale and the Oswestry Disability Index.

RESULTS

A total of 28 patients successfully underwent SSF with or without advanced osteotomy, with no serious complications. The mean follow-up period was 29 ± 3 months. The Cobb angle decreased significantly, from 45° ± 6° before surgery to 11° ± 3° at the last follow-up (P < 0.05). The visual analog scale scores and Oswestry Disability Index at the last follow-up were significantly improved compared with those before surgery (P < 0.05). Five patients developed low back pain within 6 months of surgery (proximal junctional kyphosis in 4 patients and internal fixation fractures in 1 patient), and 2 of these patients underwent a second surgery. In the long-term follow-up, 2 patients had proximal junctional kyphosis/distal junctional kyphosis after the re-trauma. The 21 remaining patients maintained good internal fixation at the last follow-up, with no broken screws or rods, loosening, or displacement.

CONCLUSIONS

SSF, with or without advanced osteotomy, is an effective treatment for thoracolumbar kyphosis caused by OVCFs, achieving good orthopedic outcomes and improving the quality of life of patients. Continuous standardized anti-osteoporosis treatment is essential for long-term recovery.

Machine learning analysis of cervical balance in early-onset scoliosis post-growing rod surgery: a case-control study

We aimed to analyze the cervical sagittal alignment change following the growing rod treatment in early-onset scoliosis (EOS) and identify the risk factors of sagittal cervical imbalance after growing-rod surgery of machine learning. EOS patients from our centre between 2007 and 2019 were retrospectively reviewed. Radiographic parameters include the cervical lordosis (CL), T1 slope, C2-C7 sagittal vertical axis (C2-7 SVA), primary curve Cobb angle, thoracic kyphosis (TK), C7-S1 sagittal vertical axis (C7-S1 SVA) and proximal junctional angle (PJA) were evaluated preoperatively, postoperatively and at the final follow-up. The parameters were analyzed using a t-test and χ2 test. The machine learning methodology of a sparse additive machine (SAM) was applied to identify the risk factors that caused the cervical imbalance. 138 patients were enrolled in this study (96 male and 42 female). The mean thoracic curve Cobb angle was 67.00 ± 22.74°. The mean age at the first operation was 8.5 ± 2.6yrs. The mean follow-up was 38.48 ± 10.87 months. CL, T1 slope, and C2-7 SVA increased significantly in the final follow-up compared with the pre-operative data. (P < 0.05). The CL and T1 slope increased more significantly in the group of patients who had proximal junctional kyphosis (PJK) compared with the patients without PJK (P < 0.05). The location of the upper instrumented vertebrae (UIV) and single/dual growing rod had no significant influence on the sagittal cervical parameters (P > 0.05). According to the SAM analysis of machine learning algorithms, Postoperative PJK, more improvement of kyphosis, and T1 slope angle were identified as the risk factors of cervical sagittal imbalance during the treatment of growing rod surgery. The growing rod surgery in EOS significantly affected the cervical sagittal alignment. Postoperative PJK and more improvement of kyphosis and T1 slope angle would lead to a higher incidence of cervical sagittal imbalance.

Lower Incidence of ASP Requiring Surgery With Minimally Invasive TLIF Than With Open PLIF: A long-term Analysis of Adjacent Segment Survival

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To assess the incidence of and risk factors for adjacent segment pathology (ASP) requiring surgery among patients previously treated with spinal fusion. Survival of the adjacent segment was compared in patients undergoing open posterior lumbar interbody fusion (O-PLIF) versus minimally invasive transforaminal interbody fusion (MI-TLIF).

SUMMARY OF BACKGROUND DATA

Compared with O-PLIF, MI-TLIF may reduce ASP in the long term by preserving more of the paraspinal muscle and ligamentous structures connected to adjacent segments.

METHODS

The study population consisted of 740 consecutive patients who had undergone lumbar spinal fusion of 3 or fewer segments. O-PLIF was performed in 564 patients, and MI-TLIF in 176 patients. The incidence and prevalence of revision surgery for ASP were calculated using the Kaplan-Meier method. A risk factor analysis was performed using the log-rank test and a Cox regression analysis.

RESULTS

After index spinal fusion, 26 patients (3.5%) underwent additional surgery for ASP. Kaplan-Meier analysis predicted a disease-free survival rate of adjacent segments in 87.2% at 10 years after the index operation. The incidence of ASP requiring surgery within 10 years was 16.4% after O-PLIF and 6.1% after MI-TLIF (P=0.045). This result was supported by the Cox regression analysis, which showed a significant difference between MI-TLIF and O-PLIF (P=0.034). The hazard ratio of revision surgery was about 3 times higher with O-PLIF than with MI-TLIF. Patients 65 years or older at the time of the index operation were 2.9 times more likely to undergo revision surgery than those younger than 65 years (P=0.015).

CONCLUSIONS

MI-TLIF results in less ASP requiring surgery than O-PLIF. 65 years or older is an independent risk factor for ASP. By preserving the soft tissues, MI-TLIF may result in a lower incidence of ASP than the open technique.

LEVEL OF EVIDENCE

Level 3.

Long-term outcomes of spinal fusion in adolescent idiopathic scoliosis: a literature review

Adolescent idiopathic scoliosis (AIS) is the most common form of spinal deformity in the younger population. The surgical management for these patients improved constantly over the last year and might not be comparable to modern treatment strategies. However, under this aspect the present investigation updates and discusses current evidence regarding the long-term outcome of the surgical management of AIS. All the clinical studies which evaluated the long-term outcomes of spinal fusion were considered. Level of evidence, clinical and radiological data, results of health-related questionnaires and surgery-associated complications during long-term follow-up, e.g., proximal and distal junctional kyphosis (PJK/DJK), and adjacent segment degeneration (ASD), are presented. Data concerning the following patient-reported outcomes measures were collected: Oswestry Disability Index (ODI), Scoliosis Research Society (SRS) Outcome Questionnaire, visual analogue scale (VAS), and short form-12 and 36 (SF-12/SF-36). Overall, data from 1115 patients were included. Of them, 324 underwent anterior and 791 posterior spinal fusion. One study focuses on a combined anterior/posterior fusions. The mean follow-up was 22.6 years (posterior fusion: 24.6 years, anterior fusion: 18.31 years). Seven studies focus on the thoracic segments, while 12 focus on the lumbar spine. Data on imaging was reported in 13 studies and those on PROMs in 15 investigations. In conclusion, there is low quality and paucity of long-term data on AIS. However, the long-term results of the implicated studies on AIS patients in this review appear to be satisfactory, although there are limitations in the outcome compared to healthy comparison cohorts. Adjacent degenerations appear to be the most common mechanical complication after long-segment fusions, despite their influence on the outcome remains unclear. With regard to pregnancies, there are slightly increased cesarean section rates, which could be explained by deviations in the sagittal profile.

Proximal Junctional Degeneration and Failure Modes: A Novel Classification and Clinical Implications

STUDY DESIGN

Case-control study.

OBJECTIVE

To introduce a classification system that will include the major types of degenerative changes and failures related to the proximal junction, and to determine the clinical course and characteristics for the different types of proximal junctional degeneration.

BACKGROUND

Proximal junctional kyphosis and failures are well recognized after adult spinal fusion; however, a standardized classification is lacking.

MATERIALS AND METHODS

The proposed system identified 4 different patterns of proximal junctional degeneration: (1) Type 1 (multilevel symmetrical collapse), (2) Type 2 (single adjacent level collapse), (3) Type 3 (fracture), and (4) Type 4 (spondylolisthesis). A single-center database was reviewed from 2018 to 2021. Patients 18 years or older of age, who underwent posterior spinal fusion of ≥3 levels with an upper instrumented vertebral level between T8 and L2, and a follow-up of ≥2 years were included. Radiographic measurements, revision surgery, and time to revision were the primary outcomes.

RESULTS

One hundred fifty patients were included with a mean age of 65.1 (±9.8) years and a mean follow-up of 3.2 (±1) years. Sixty-nine patients (46%) developed significant degenerative changes in the proximal junction and were classified accordingly. Twenty (13%) were type 1, 17 (11%) were type 2, 22 (15%) were type 3, and 10 (7%) were type 4. Type 3 had a significantly shorter time to revision with a mean of 0.9 (±0.9) years. Types 3 and 4 had greater preoperative sagittal vertical axis, and types 1 and 3 had greater final follow-up lumbar lordosis. Bone density measured by Hounsfield units showed lower measurements for type 3. Types 1 and 4 had lower rates of developing proximal junctional kyphosis. Type 1 had the lowest revision rate with 40% (types 2, 3, and 4 were 77%, 73%, and 80%, respectively, P = 0.045).

CONCLUSION

This novel classification system defines different modes of degeneration and failures at the proximal junction, and future studies with larger sample sizes are needed for validation.

LEVEL OF EVIDENCE

Level III.

The Effect of Osteoporosis on Complications and Reoperation Rates After Surgical Management of Adult Thoracolumbar Spinal Deformity: A Systematic Review and Meta Analysis

STUDY DESIGN

Systematic Review.

OBJECTIVES

While substantial research has explored the impact of osteoporosis on patients undergoing adult spinal deformity (ASD) correction, the literature remains inconclusive. As such, the purpose of this study is to synthesize and analyze existing studies pertaining to osteoporosis as a predictor of postoperative outcomes in ASD surgery.

METHODS

We performed a systematic review and meta-analysis to determine the effect that a diagnosis of osteoporosis, based on ICD-10 coding, dual-energy X-ray absorptiometry (DEXA) or computed tomography, has on the incidence of adverse outcomes following surgical correction of ASD. Statistical analysis was performed using Comprehensive Meta-Analysis (Version 2) using a random effects model to account for heterogeneity between studies.

RESULTS

After application of inclusion and exclusion criteria, 36 and 28 articles were included in the systematic review and meta-analysis, respectively. The meta-analysis identified greater rates of screw loosening amongst osteoporotic patients (70.5% vs 31.9%, P = .009), and decreased bone mineral density in patients who developed proximal junctional kyphosis (PJK) (.69 vs .79 g/cm2, P = .001). The systematic review demonstrated significantly increased risk of any complication, reoperation, and proximal junctional failure (PJF) associated with reduced bone density. No statistical difference was observed between groups regarding fusion rates, readmission rates, and patient-reported and/or functional outcome scores.

CONCLUSION

This study demonstrates a higher incidence of screw loosening, PJK, and revision surgery amongst osteoporotic ASD patients. Future investigations should explore outcomes at various follow-up intervals in order to better characterize how risk changes with time and to tailor preoperative planning based on patient-specific characteristics.

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

BACKGROUND

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

PURPOSE

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

STUDY DESIGN

A computational biomechanical analysis.

METHODS

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

RESULTS

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

CONCLUSION

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

CLINICAL SIGNIFICANCE

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

Preoperative Planning of Lumbar Lordosis for Adult Degenerative Scoliosis Surgery in the Chinese Population

OBJECTIVE

Pelvic incidence minus lumbar lordosis mismatch (PI-LL) is directly related to poor quality of life in adult degenerative scoliosis (ADS) patients. The purpose of the study was to determine the most appropriate postoperative PI-LL value for patients with ADS.

METHODS

The medical records of patients with ADS in our department were retrospectively collected. The data included age, sex, body mass index, age-adjusted Charlson comorbidity index, osteopenia, length of hospital stay, operative duration, estimated blood loss, American Society of Anesthesiologists score, number of fusion levels, lumbar lordosis, sagittal vertical axis, pelvic incidence, PI-LL, Scoliosis Research Society-22 score, Oswestry Disability Index score, and mechanical complications.

RESULTS

A total of 316 patients were enrolled. PI-LL, lumbar lordosis, sagittal vertical axis, Scoliosis Research Society-22 score, Oswestry Disability Index score at the time of last follow-up were 20.7 ± 8.5°, 23.4 ± 14.1°, 4.0 ± 2.1 cm, 3.7 ± 0.9, and 18.1 ± 5.5, respectively. In terms of mechanical complications, 88 patients (27.8%), 34 patients (10.8%), and 19 patients (6.0%) had proximal junctional kyphosis, distal junctional kyphosis, and implant-related complications, respectively. In the fully adjusted model, compared with 0 grade PI-LL group and ++ grade PI-LL group, + grade PI-LL group had the best clinical outcomes and the fewest mechanical complications. The stability of these conclusions was verified in sensitivity analyses.

CONCLUSIONS

Optimal PI-LL value should be 10°-20° after corrective surgery in patients with ADS, which is associated with excellent clinical outcomes and lower complication rates. Previous criteria may be at risk of overcorrection, which may lead to proximal junctional kyphosis.

Long-term Outcomes After Adult Spinal Deformity Surgery Using Lateral Interbody Fusion: Short Versus Long Fusion

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To investigate long-term outcomes after short or long fusion for adult spinal deformity using lateral interbody fusion.

SUMMARY OF BACKGROUND DATA

Lateral interbody fusion is commonly used in adult spinal deformity surgery. Favorable short-term outcomes have been reported, but not long-term outcomes. Lateral interbody fusion with strong ability to correct deformity may allow the selection of short fusion techniques.

MATERIALS AND METHODS

We retrospectively reviewed adults who underwent this surgery with a minimum of 5 years of follow-up. Short fusion with the uppermost instrumented vertebra in the lumbar spine was performed in patients without degenerative changes at the thoracolumbar junction (S-group); others underwent long fusion with the uppermost instrumented vertebra in the thoracic spine (L-group). We assessed radiographic and clinical outcomes.

RESULTS

Short fusion was performed in 29 of 54 patients. One patient per group required revision surgery. Of the remainder, with similar preoperative characteristics and deformity correction between groups, correction loss (pelvic incidence-lumbar lordosis, P =0.003; pelvic tilt, P =0.005; sagittal vertical axis, P ˂0.001) occurred within 2 years postoperatively in the S-group, and sagittal vertical axis continued to increase until the 5-year follow-up ( P =0.021). Although there was a significant change in Oswestry disability index in the S-group ( P =0.031) and self-image of Scoliosis Research Society 22r score in both groups ( P =0.045 and 0.02) from 2- to 5-year follow-up, minimum clinically important differences were not reached. At 5-year follow-up, there was a significant difference in Oswestry Disability Index ( P =0.013) and Scoliosis Research Society 22r scores (function: P =0.028; pain: P =0.003; subtotal: P =0.006) between the groups, but satisfaction scores were comparable and Oswestry Disability Index score (29.8%) in the S-group indicated moderate disability.

CONCLUSIONS

Health-related quality of life was maintained between 2- and 5-year follow-up in both groups. Short fusion may be an option for patients without degenerative changes at the thoracolumbar junction.

LEVEL OF EVIDENCE

III.

The Effect of Transpedicular Injection of Recombinant Human Bone Morphogenetic Protein-2/Beta-Tricalcium Phosphate Carrier on the Prevention of Proximal Junctional Kyphosis in Adult Spinal Deformity Surgery: A Pilot Study

BACKGROUND AND OBJECTIVES

Several studies have explored strategies to prevent proximal junctional kyphosis (PJK) which is the unresolved issue in adult spinal deformity (ASD) surgery. This study aimed to investigate the preventive effects of upper instrumented vertebrae (UIV) recombinant human bone morphogenetic protein-2 (rhBMP-2) with beta-tricalcium phosphate (β-TCP) carrier injection on PJK.

METHODS

This study was conducted through a retrospective analysis of data collected both prospectively and retrospectively. In the rhBMP-2 group, consisting of 25 patients with ASD, rhBMP-2 along with β-TCP carrier was administered to the UIV through the pedicle. To minimize time-related bias, control-1 included 66 patients who had undergone ASD surgery by the same surgeon in the year preceding the commencement of the study. Control-2 consisted of 63 patients who had undergone ASD surgery by the same surgeon during the year after the end of the study. The primary outcome is the occurrence of PJK within one year postsurgery, and the secondary outcome is the change in Hounsfield unit of the UIV one year after the surgery.

RESULTS

When comparing baseline characteristics with control groups, a significant difference was observed only in body mass index, with control-1 (P = .006) and control-total (control-1 + control-2, P = .026) having a higher body mass index than the study group. In the rhBMP-2 group, there were 3 cases (PJK rate, 12.0%) of PJK, whereas control-1 and control-2 had 26 cases (PJK rate, 39.4%, P = .012) and 20 cases (PJK rate, 31.7%, P = .057), respectively. In the control-total, there were 46 cases (PJK rate, 35.7%, P = .020) of PJK. The UIV that received rhBMP-2 showed a statistically significant increase in Hounsfield unit measurements compared to preoperative values 1 year after surgery (P = .001).

CONCLUSION

The transpedicular injection of rhBMP-2/β-TCP carrier at the UIV significantly contributed to the prevention of PJK and effectively increased trabecular bone density at the UIV.

Spinopelvic Parameters in the Elderly: Does Inadequate Correction Portend Worse Outcomes?

Introduction

This study aimed to compare the outcomes of corrective fusion for adult spinal deformity (ASD) in older people using two different sagittal correction goals: the conventional formula of "pelvic incidence (PI)-lumbar lordosis (LL) mismatch <10°" and an undercorrection strategy based on the range of 10°≤PI-LL≤20°.

Methods

A total of 102 consecutive patients (11 male and 91 female patients; mean age, 72.0 years) aged above 65 years with scoliosis >20° or LL<20° who had undergone long-segment fusion from the lower thoracic spine to the pelvis for ASD and had been followed-up for a minimum of two years at our institution since March 2013 were included in this retrospective study. After excluding patients with PI-LL≤-10° on postoperative standing radiographs, the remaining patients were divided into two groups: 31 patients with 10°≤PI-LL≤20° (U group) and 63 patients with -10°

Results

The incidence of proximal junctional kyphosis and mechanical failure was not significantly different between the groups (p=0.659 and 1.000, respectively). After excluding patients who underwent reoperation due to mechanical failure, there were no differences in the Oswestry Disability Index (ODI) and each domain of the Visual Analog Scale score, Scoliosis Research Society-22r patient questionnaire (SRS-22r), or the short form 36 health survey questionnaire at the final observation between the U (n=27) and M (n=57) groups. In addition, the non-inferiority and equivalence of the U group to the M group were demonstrated in all domains of the SRS-22r and ODI. Furthermore, the superiority of the U group was demonstrated by the functional domain of SRS-22r.

Conclusions

For the sagittal correction goal in corrective fusion surgery for ASD in the elderly, strict adherence to "PI-LL mismatch <10°" is not necessary and "PI-LL≤20°" may be acceptable.

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Key Words

• Scoliosis Research Society-Schwab classification
• adult spinal deformity
• elderly patients with spinal deformity
• extensive corrective fusion
• pelvic incidence minus lumbar lordosis mismatch
• sagittal corrective goal
• undercorrection

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Affiliation(s)

Masanari Takami Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Shunji Tsutsui Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Keiji Nagata Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Hiroshi Iwasaki Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Akihito Minamide Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan Spine Center, Dokkyo Medical University Nikko Medical Center, Nikko, Japan
Yasutsugu Yukawa Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan Spine Center, Nagoya Kyoritsu Hospital, Nagoya, Japan
Motohiro Okada Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan Department of Orthopaedic Surgery, Sumiya Orthopaedic Hospital, Wakayama, Japan
Ryo Taiji Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Shizumasa Murata Department of Orthopaedic Surgery, Shingu Municipal Medical Center, Shingu, Japan
Takuhei Kozaki Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Hiroshi Hashizume Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan
Hiroshi Yamada Department of Orthopaedic Surgery, Wakayama Medical University, Wakayama, Japan

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Instrumentation Failure in Adult Spinal Deformity Patients

In recent years, advances in the surgical treatment of adult spinal deformity (ASD) have led to improved outcomes. Although these advances have helped drive the development of deformity surgery to meet the rising volume of patients seeking surgical treatment, many challenges have yet to be solved. Instrumentation failure remains one of the most common major complications following deformity surgery, associated with significant morbidity due to elevated re-operation rates among those experiencing mechanical complications. The two most frequently encountered subtypes of instrumentation failure are rod fracture (RF) and proximal junctional kyphosis/proximal junctional failure (PJK/PJF). While RF and PJK/PJF are both modes of instrumentation failure, they are two distinct entities with different clinical implications and treatment strategies. Considering that RF and PJK/PJF continue to represent a major challenge for patients with ASD and deformity surgeons alike, this review aims to discuss the incidence, risk factors, clinical impact, treatment strategies, preventive measures, and future research directions for each of these substantial complications.

The Shape of the Fused Spine is Associated With Acute Proximal Junctional Kyphosis in Adult Spinal Deformity: An Assessment Based on Vertebral Pelvic Angles

STUDY DESIGN

Retrospective review of prospective database.

OBJECTIVES

Vertebral pelvic angles (VPAs) account for complexity in spine shape by assessing the relative position of each vertebra with regard to the pelvis. This study uses VPAs to investigate the shape of the fused spine after T10-pelvis fusion, in patients with adult spinal deformity (ASD), and then explores its association with proximal junctional kyphosis (PJK).

METHODS

Included patients had radiographic evidence of ASD and underwent T10-pelvis realignment. VPAs were used to construct a virtual shape of the post-operative spine. VPA-predicted and actual shapes were then compared between patients with and without PJK. Logistic regression was used to identify components of the VPA-based model that were independent predictors of PJK occurrence and post-operative shape.

RESULTS

287 patients were included. VPA-predicted shape was representative of the true post-operative contour, with a mean point-to-point error of 1.6-2.9% of the T10-S1 spine length. At 6-weeks follow-up, 102 patients (35.5%) developed PJK. Comparison of the true post-operative shapes demonstrated that PJK patients had more posteriorly translated vertebrae from L3 to T7 (P < .001). Logistic regression demonstrated that L3PA (P = .047) and T11PA (P < .001) were the best independent predictors of PJK and were, in conjunction with pelvic incidence, sufficient to reproduce the actual spinal contour (error <3%).

CONCLUSIONS

VPAs are reliable in reproducing the true, post-operative spine shape in patients undergoing T10-pelvis fusion for ASD. Because VPAs are independent of patient position, L3PA, T11PA, and PI measurements can be used for both pre- and intra-operative planning to ensure optimal alignment.

The influence of osteoporosis on mechanical complications in lumbar fusion surgery: a systematic review

Background

Adults undergoing spine surgery often have underlying osteoporosis, which may be a risk factor for postoperative complications. Although these associations have been described, osteoporosis remains profoundly underdiagnosed and undertreated in the spine surgery population. A thorough, comprehensive systematic review summarizing the relationships between bone mineral density (BMD) and specific complications of lumbar fusion surgery could be a valuable resource for raising awareness and supporting clinical practice changes.

Methods

PubMed, Embase, and Web of Science databases were searched for original clinical research articles reporting on BMD, or surrogate measure, as a predictor of complications in adults undergoing elective lumbar fusion for degenerative disease or deformity. Endpoints included cage subsidence, screw loosening, pseudarthrosis, vertebral fracture, junctional complications, and reoperation.

Results

A total of 71 studies comprising 12,278 patients were included. Overall, considerable heterogeneity in study populations, methods of bone health assessment, and definition and evaluation of clinical endpoints precluded meta-analysis. Nevertheless, low BMD was associated with higher rates of implant failures like cage subsidence and screw loosening, which were often diagnosed with concomitant pseudarthrosis. Osteoporosis was also a significant risk factor for proximal junctional kyphosis, particularly due to fracture. Many studies found surgical site-specific BMD to best predict focal complications. Functional outcomes were inconsistently addressed.

Conclusions

Our findings suggest osteoporosis is a significant risk factor for mechanical complications of lumbar fusion. These results emphasize the importance of preoperative osteoporosis screening, which allows for medical and surgical optimization of high-risk patients. This review also highlights current practical challenges facing bone health evaluation in patients undergoing elective surgery. Future prospective studies using standardized methods are necessary to strengthen existing evidence, identify optimal predictive thresholds, and establish specialty-specific practice guidelines. In the meantime, an awareness of the surgical implications of osteoporosis and utility of preoperative screening can provide for more informed, effective patient care.

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

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

Incidence and risk factors of proximal junctional kyphosis in adolescent idiopathic scoliosis after correction surgery: a meta-analysis and systematic review

AIM

To analyze the risk factors of proximal junctional kyphosis (PJK) after correction surgery in patients with adolescent idiopathic scoliosis (AIS).

METHODS

PubMed, Medline, Embase, Cochrane Library, Web of Science, CNKI, and EMCC databases were searched for retrospective studies utilizing all AIS patients with PJK after corrective surgery to collect preoperative, postoperative, and follow-up imaging parameters, including thoracic kyphosis (TK), lumbar lordosis (LL), proximal junctional angle (PJA), the sagittal vertical axis (SVA), pelvic incidence (PI), pelvic tilt (PT), pelvic incidence-lumbar lordosis (PI-LL), sacral slope (SS), rod contour angle (RCA) and upper instrumented vertebra (UIV).

RESULTS

Nineteen retrospective studies were included in this meta-analysis, including 550 patients in the intervention group and 3456 patients in the control group. Overall, sex (OR 1.40, 95% CI (1.08, 1.83), P = 0.01), larger preoperative TK (WMD 6.82, 95% CI (5.48, 8.16), P < 0.00001), larger follow-up TK (WMD 8.96, 95% CI (5.62, 12.30), P < 0.00001), larger postoperative LL (WMD 2.31, 95% CI (0.91, 3.71), P = 0.001), larger follow-up LL (WMD 2.51, 95% CI (1.19, 3.84), P = 0.0002), great change in LL (WMD - 2.72, 95% CI (- 4.69, - 0.76), P = 0.006), larger postoperative PJA (WMD 4.94, 95% CI (3.62, 6.26), P < 0.00001), larger follow-up PJA (WMD 13.39, 95% CI (11.09, 15.69), P < 0.00001), larger postoperative PI-LL (WMD - 9.57, 95% CI (- 17.42, - 1.71), P = 0.02), larger follow-up PI-LL (WMD - 12.62, 95% CI (- 17.62, - 7.62), P < 0.00001), larger preoperative SVA (WMD 0.73, 95% CI (0.26, 1.19), P = 0.002), larger preoperative SS (WMD - 3.43, 95% CI (- 4.71, - 2.14), P < 0.00001), RCA (WMD 1.66, 95% CI (0.48, 2.84), P = 0.006) were identified as risk factors for PJK in patients with AIS. For patients with Lenke 5 AIS, larger preoperative TK (WMD 7.85, 95% CI (5.69, 10.00), P < 0.00001), larger postoperative TK (WMD 9.66, 95% CI (1.06, 18.26), P = 0.03, larger follow-up TK (WMD 11.92, 95% CI (6.99, 16.86), P < 0.00001, larger preoperative PJA (WMD 0.72, 95% CI (0.03, 1.41), P = 0.04, larger postoperative PJA (WMD 5.54, 95% CI (3.57, 7.52), P < 0.00001), larger follow-up PJA (WMD 12.42, 95% CI 9.24, 15.60), P < 0.00001, larger follow-up SVA (WMD 0.07, 95% CI (- 0.46, 0.60), P = 0.04), larger preoperative PT (WMD - 3.04, 95% CI (- 5.27, - 0.81), P = 0.008, larger follow-up PT (WMD - 3.69, 95% CI (- 6.66, - 0.72), P = 0.02) were identified as risk factors for PJK.

CONCLUSION

Following corrective surgery, 19% of AIS patients experienced PJK, with Lenke 5 contributing to 25%. Prior and post-op measurements play significant roles in predicting PJK occurrence; thus, meticulous, personalized preoperative planning is crucial. This includes considering individualized treatments based on the Lenke classification as our future evaluation standard.

Use of Dynamic Spinal Instruments (Dynesys) in Adult Spinal Deformities According to Silva-Lenke and Berjano-Lamartina Classifications

BACKGROUND

Adult spinal deformities (ASD) present complex challenges in spine surgery. The diverse nature of these deformities requires a comprehensive understanding of their classification and treatment options. Traditional approaches, such as fusion and rigid stabilization are associated with complications, including screw loosening, breakage, proximal junctional kyphosis (PJK), and pseudoarthrosis. Dynamic stabilization techniques have emerged as promising alternatives, to reduce these complications and preserve spinal motion.

OBJECTIVE

This study investigated the effectiveness of dynamic stabilization using the Dynesys system in the surgical treatment of adult degenerative spinal deformities, with a particular emphasis on their classification.

METHODS

ASDs were classified according to the Berjano-Lamartina (BL) and Silva-Lenke (SL) classifications. We analyzed the efficacy of the Dynesys system in enhancing sagittal balance, radiological parameters, and clinical outcomes in this context.

RESULTS

Dynamic stabilization of patients with ASDs using the Dynesys system significantly improved the visual analog scale and Oswestry Disability Index scores and decreased the complication rates. Patients with BL types 2, 3, and 4 experienced a significant improvement in sagittal balance followed by sagittal vertical axis measurements (p = 0.045, p = 0.015, and p < 0.0001, respectively).

CONCLUSION

The SL and BL classifications, which were originally developed for rigid spinal stabilization, can be applied in dynamic stabilization. Furthermore, dynamic stabilization using the Dynesys system can be used as an alternative to rigid stabilization in SL levels 2 and 3, and BL types 1, 2, and 3, and in some patients with type 4 ASDs.

Compensation from mild and severe cases of early proximal junctional kyphosis may manifest as progressive cervical deformity at two year follow-up

BACKGROUND

Postoperative reciprocal changes (RC) in the cervical spine associated with varying factors of proximal junctional kyphosis (PJK) following fusions of the thoracopelvic spine are poorly understood.

PURPOSE

Explore reciprocal changes in the cervical spine associated with varying factors (severity, progression, patient age) of PJK in patients undergoing adult spinal deformity (ASD) correction.

PATIENTS AND METHODS

Retrospective review of a multicenter ASD database.

INCLUSION

ASD patients > 18 y/o, undergoing fusions from the thoracic spine (UIV: T6-T12) to the pelvis with two-year radiographic data. ASD was defined as: Coronal Cobb angle ≥ 20°, Sagittal Vertical Axis ≥ 5 cm, Pelvic Tilt ≥ 25°, and/or Thoracic Kyphosis ≥ 60°. PJK was defined as a ≥ 10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV + 2. Patients were grouped by mild (M; 10°-20°) and severe (S; > 20°) PJK at one year. Propensity Score Matching (PSM) controlled for CCI, age, PI and UIV. Unpaired and paired t test analyses determined difference between RC parameters and change between time points. Pearson bi-variate correlations analyzed associations between RC parameters (T4-T12, TS-CL, cSVA, C2-Slope, and T1-Slope) and PJK descriptors.

RESULTS

284 ASD patients (UIV: T6: 1.1%; T7: 0.7%; T8: 4.6%; T9: 9.9%; T10: 58.8%; T11: 19.4%; T12: 5.6%) were studied. PJK analysis consisted of 182 patients (Mild = 91 and Severe = 91). Significant difference between M and S groups were observed in T4-T12 Δ1Y(- 16.8 v - 22.8, P = 0.001), TS-CLΔ1Y(- 0.6 v 2.8, P = 0.037), cSVAΔ1Y(- 1.8 v 1.9, P = 0.032), and C2 slopeΔ1Y(- 1.6 v 2.3, P = 0.022). By two years post-op, all changes in cervical alignment parameters were similar between mild and severe groups. Correlation between age and cSVAΔ1Y(R = 0.153, P = 0.034) was found. Incidence of severe PJK was found to correlate with TS-CLΔ1Y(R = 0.142, P = 0.049), cSVAΔ1Y(R = 0.171, P = 0.018), C2SΔ1Y(R = 0.148, P = 0.040), and T1SΔ2Y(R = 0.256, P = 0.003).

CONCLUSIONS

Compensation within the cervical spine differed between individuals with mild and severe PJK at one year postoperatively. However, similar levels of pathologic change in cervical alignment parameters were seen by two years, highlighting the progression of cervical compensation due to mild PJK over time. These findings provide greater evidence for the development of cervical deformity in individuals presenting with proximal junctional kyphosis.

Navigated Hybrid Open/Muscle-sparing Approach to 2-level Cement Augmentation of the UIV and UIV+1 for Prevention of Proximal Junctional Failure: Supplemental Manuscript to Operative Video

STUDY DESIGN

Operative video and supplemental manuscript.

OBJECTIVE

To present a cement augmentation technique of the upper instrumented vertebra (UIV) and UIV+1 for prevention of proximal junctional fractures (PJFs) in multi-level thoracolumbar posterior instrumented fusions.

SUMMARY OF BACKGROUND DATA

PJFs are unfortunately a common occurrence after multi-level thoracolumbar instrumented fusions to the pelvis for adult spinal deformity that can result in significant functional disability and often require costly revision operations. As such, their prevention is key.

METHODS

A surgical video illustrates the nuances of a 2-level cement augmentation technique, consisting of an open vertebroplasty of the UIV through fenestrated screws and a muscle-sparing kyphoplasty of the UIV+1.

RESULTS

Utility of performing an open vertebroplasty of the UIV through fenestrated screws and muscle-sparing kyphoplasty of the UIV+1 lies in its ability to minimize soft-tissue disruption at the adjacent segment while providing additional structural support to the anterior column at this high-risk zone.

CONCLUSIONS

Cement augmentation of the UIV and UIV+1 consisting of a hybrid open vertebroplasty and muscle-sparing kyphoplasty can be an effective strategy to decrease the incidence of PJF after multi-level posterior thoracolumbar instrumented fusions to the pelvis for adult spinal deformity.

Proximal Junctional Failure after Corrective Surgery: Focusing on Elderly Patients with Severe Sagittal Imbalance

Background

Previous reports with proximal junctional failure (PJF) included relatively young patients or deformity without sagittal imbalance. The present study focused on the two well-known risk factors for PJF, old age and severe sagittal imbalance. With these high-risk patients, the present study aimed to identify a strategy that could prevent PJF and to investigate whether the degree of correction would really affect the PJF occurrence.

Methods

Patients who were ≥ 60 years of age and underwent long fusion (≥ 4) to the sacrum for severe sagittal imbalance (defined as pelvic incidence minus lumbar lordosis [PI-LL] ≥ 30°) were included. PJF was defined as a vertebral fracture at the uppermost instrumented vertebra (UIV) or UIV+1, failure of UIV fixation, myelopathy, or any need for proximal extension of fusion. Presumed risk factors were compared between the patients with and without PJF.

Results

Total 146 patients (mean age, 68.4 years) with preoperative mean PI-LL of 46.8° were included. PJF developed in 39 patients (26.7%) at a mean of 18.1 months after surgery. Multivariate analysis showed that osteoporosis (odds ratio [OR], 2.812; p = 0.019) and UIV located below T10 (OR, 3.773; p = 0.010) were significant risk factors for developing PJF. However, the degree of correction did not affect PJF occurrence.

Conclusions

The present study indicates that osteoporosis should be well corrected preoperatively and extending the fusion above T10 should be considered for severe imbalance in old patients. However, the amount of correction was not associated with PJF development.

Biomechanical effects of osteoporosis severity on the occurrence of proximal junctional kyphosis following long-segment posterior thoracolumbar fusion

BACKGROUND

Proximal junctional kyphosis is a common long-term complication in adult spinal deformity surgery that involves long-segment posterior spinal fusion. However, the underlying biomechanical mechanisms of the impact of osteoporosis on proximal junctional kyphosis remain unclear. The present study was to evaluate adjacent segment degeneration and spine mechanical instability in osteoporotic patients who underwent long-segment posterior thoracolumbar fusion.

METHODS

Finite element models of the thoracolumbar spine T1-L5 with posterior long-segment T8-L5 fusion under different degrees of osteoporosis were constructed to analyze intervertebral disc stress characterization, vertebrae mechanical transfer, and pedicle screw system loads during various motions.

FINDINGS

Compared with normal bone mass, the maximum von Mises stresses of T7 and T8 were increased by 20.32%, 22.38%, 44.69%, 4.49% and 29.48%, 17.84%, 40.95%, 3.20% during flexion, extension, lateral bending, and axial rotation in the mild osteoporosis model, and by 21.21%, 18.32%, 88.28%, 2.94% and 37.76%, 15.09%, 61.47%, -0.04% in severe osteoporosis model. The peak stresses among T6/T7, T7/T8, and T8/T9 discs were 14.77 MPa, 11.55 MPa, and 2.39 MPa under lateral bending conditions for the severe osteoporosis model, respectively. As the severity of osteoporosis increased, stress levels on SCR8 and SCR9 intensified during various movements.

INTERPRETATION

Osteoporosis had an adverse effect on proximal junctional kyphosis. The stress levels in cortical bone, intervertebral discs and screws were increased with bone mass loss, which can easily lead to intervertebral disc degeneration, bone destruction as well as screw pullout. These factors have significantly affected or accelerated the occurrence of proximal junctional kyphosis.

Advances and Evolving Challenges in Spinal Deformity Surgery

BACKGROUND

Surgical intervention is a critical tool to address adult spinal deformity (ASD). Given the evolution of spinal surgical techniques, we sought to characterize developments in ASD correction and barriers impacting clinical outcomes.

METHODS

We conducted a literature review utilizing PubMed, Embase, Web of Science, and Google Scholar to examine advances in ASD surgical correction and ongoing challenges from patient and clinician perspectives. ASD procedures were examined across pre-, intra-, and post-operative phases.

RESULTS

Several factors influence the effectiveness of ASD correction. Standardized radiographic parameters and three-dimensional modeling have been used to guide operative planning. Complex minimally invasive procedures, targeted corrections, and staged procedures can tailor surgical approaches while minimizing operative time. Further, improvements in osteotomy technique, intraoperative navigation, and enhanced hardware have increased patient safety. However, challenges remain. Variability in patient selection and deformity undercorrection have resulted in heterogenous clinical responses. Surgical complications, including blood loss, infection, hardware failure, proximal junction kyphosis/failure, and pseudarthroses, pose barriers. Although minimally invasive approaches are being utilized more often, clinical validation is needed.

CONCLUSIONS

The growing prevalence of ASD requires surgical solutions that can lead to sustained symptom resolution. Leveraging computational and imaging advances will be necessary as we seek to provide comprehensive treatment plans for patients.

Risk Factors and Three Radiological Predictor Models for the Progression of Proximal Junctional Kyphosis in Adult Degenerative Scoliosis Following Posterior Corrective Surgery: 113 Cases With 2-years Minimum Follow-Up

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To identify risk factors and predictive models for proximal junctional kyphosis (PJK) in a long-term follow-up of patients with adult degenerative scoliosis (ADS) following posterior corrective surgeries.

MATERIALS AND METHODS

A consecutive 113 ADS patients undergoing posterior corrective surgery between January 2008 and April 2019 with minimum 2-year follow-up were included. All patients underwent preoperative, postoperative, and final follow-up by X-ray imaging. Multivariate logistic analysis was performed on various risk factors and radiological predictor models.

RESULTS

PJK was identified radiographically in 46.9% of patients. Potential risk factors for PJK included postoperative thoracic kyphosis (TK) (P < .05), final follow-up Pelvic Tilt (PT) (P < .05), PT changes at final follow-up (P < .05), age over 55 years old at the surgery (P < .05), theoretical thoracic kyphosis-actual thoracic kyphosis mismatch (TK mismatch) (P < .05) and theoretical lumbar lordosis-acutal lumbar lordosis mismatch (LL mismatch) (P < .05). As for the predictive models, PJK was predictive by the following indicators: preoperative global sagittal alignment ≥45° (Model 1), postoperative pelvic incidence-lumbar lordosis mismatch (PI-LL)≤10° and postoperative PI-LL overcorrection (Model 2), and TK+LL≥0° (Model 3) (P < .05). Postoperative TK mismatch (OR = 1.064) was independent as risk factors for PJK, with the cut-off values respectively set at -28.56° to predict occurrence of PJK.

CONCLUSION

The risk of radiographic PJK increases with an age over 55 years old and higher postoperative TK. In addition, postoperative TK mismatch is an independent risk factor for developing PJK. All three predictive models could effectively indicate the occurrence of PJK.

Which Bone Mineral Density Measure Offers a More Reliable Prediction of Mechanical Complications in Adult Spinal Deformity Surgery: Hounsfield Units or DEXA Scan?

OBJECTIVE

In patients undergoing adult spinal deformity (ASD) surgery, we sought to: (1) determine the relationship between dual-energy x-ray absorptiometry (DEXA)-measured bone mineral density (BMD), T-scores, and Hounsfield units (HU), and (2) compare the ability of DEXA-measured BMD, T-scores, and HU to predict mechanical complications and reoperations.

METHODS

A single-institution retrospective cohort study was undertaken for cases from 2013 to 2017.

INCLUSION CRITERIA

≥5-level-fusion, sagittal/coronal deformity, and 2-year follow-up. Multivariable regression controlled for age, body mass index, receiving anabolic medications, and postoperative sagittal vertical axis and pelvic-incidence lumbar-lordosis mismatch. A subanalysis was performed for osteopenic patients (-1 < T-score < -2).

RESULTS

Of 145 patients undergoing ASD surgery, 72 (49.6%) had both preoperative DEXA and computed tomography scans. Mean DEXA-measured BMD was 0.91 ± 0.52 g/cm2, mean T-score was -1.61 ± 1.03, and mean HU was 153.5 ± 52.8. While no correlation was found between DEXA-measured BMD and HU (r = 0.17, P = 0.144), T-score and HU had a weakly positive correlation (r = 0.31, P = 0.007). Mechanical complications occurred in 48 (66.7%) patients, including 27 (37.5%) proximal junctional kyphosis (PJK), 1 (1.4%) distal junctional kyphosis, 5 (6.9%) implant failure, 30 (41.7%) rod fracture/pseudarthrosis, 42 (58.3%) reoperations, and 16 (22.2%) reoperations due to PJK. No association was found between DEXA-measured BMD or T-scores with mechanical complications or reoperations. While univariate regression showed a significant association between lower HU and PJK (OR 0.98, 95%CI 0.97-0.99, P = 0.011), the significance was lost after multivariable analysis. When considering osteopenic patients (n = 37), only DEXA-measured BMD was an independent risk factor for PJK (OR 0.01, 95%CI 0.00-0.09, P = 0.017), with a threshold of 0.82 g/cm2 (AUC 0.70, 95%CI 0.53-0.84, P = 0.019).

CONCLUSIONS

Poor correlation was found between the 3 BMD modalities. DEXA-measured BMD may be superior to T-scores and HU in predicting PJK among patients with osteopenia with a threshold of BMD <0.82 g/cm2.

Proximal and distal mechanical repercussions of instrumentation by double rods and interbody grafts in adult scoliosis

INTRODUCTION

Correction of adult scoliosis by instrumentation with double rods and interbody grafts aims to reduce the risk of pseudarthrosis with rod fracture. An increase in instrumentation rigidity can lead to an increase in stresses at the proximal and distal ends of the construct. The aim of this study was to analyze the incidence and clinical repercussions of proximal junctional kyphosis (PJK), proximal junctional failure (PJF) and iliac screw loosening.

MATERIEL AND METHODS

An analysis of patients operated on for adult scoliosis with instrumentation to the pelvis using 4 rods and interbody cages was carried out from a prospective register. The Visual Analog Scale (VAS), Oswestry Disability Index (ODI), Scoliosis Research Society 22 (SRS-22) clinical scores and radiological parameters were collected preoperatively, postoperatively at 3 months, 1 year and 2 years. The appearance of PJK, PJF or distal screw loosening was sought; the clinical impact and the risk factors were analyzed by Bayesian inference.

RESULTS

Fifty-one patients with a mean age of 64.5 years were included. The clinical scores improved significantly (Pr>0.95) at 2 years: VAS back 6.9 versus 2.6, VAS leg 4.9 versus 2.5, ODI 48.2 versus 25.4, SRS-22 2.4 versus 3.5. The radiological parameters were corrected (Pr>0.95): Cobb angle 63.9° versus 22.8°, spinosacral angle (SSA) 112.4° versus 118.8°, T1-pelvic angle (TPA) 24, 8° versus 20.8°, lumbar lordosis 43.8° versus 51.0°, thoracic kyphosis 45.2° versus 53.6°. Thirteen patients (25.5%) presented with PJK and 11 (21.6%) with PJF. Seven patients (13.7%) presented with iliac screw loosening. None of these complications was associated with a significant deterioration in clinical scores. Cranial migration of the lumbar apex increased the risk of distal screw loosening: Odds-Ratio 10.31 (Pr>0.999). Two patients were re-operated on for PJF and one patient for iliac screw loosening (5.9%). No rod fracture with pseudarthrosis was found.

CONCLUSION

Instrumentation with double rods and interbody grafts was associated with a rate of 47.1% of mechanical repercussions at the extremity of the construct. However, these complications were not associated with a significant deterioration in clinical scores.

LEVEL OF EVIDENCE

III.

Comparative Analysis of Hounsfield Units and Vertebral Bone Quality Scores for Predicting Proximal Junctional Failure in Female Adult Spinal Deformity Patients Undergoing Planned 2-Stage Corrective Surgery with Lateral Lumbar Interbody Fusion

OBJECTIVE

This study aimed to evaluate the utility of computed tomography (CT)-based Hounsfield units (HUs) and magnetic resonance imaging-based Vertebral Bone Quality (VBQ) scores as alternatives to dual-energy x-ray absorptiometry for predicting the risk of proximal junctional failure (PJF) in female patients with adult spinal deformity (ASD) undergoing 2-stage corrective surgery with lateral lumbar interbody fusion (LLIF).

METHODS

The study included 53 female patients with ASD who underwent 2-stage corrective surgery with LLIF from January 2016 to April 2022 with a minimum follow-up of 1 year. CT and magnetic resonance imaging scans were evaluated for their correlation with PJF.

RESULTS

Of the 53 patients (mean age 70.2 years), 14 had PJF. Patients with PJF had significantly lower HU values at the upper instrumented vertebra (UIV) (113.0 ± 29.4 vs. 141.1 ± 41.5, P = 0.036) and L4 (113.4 ± 59.5 vs. 160.0 ± 64.9, P = 0.026) than those without PJF. However, there was no difference in VBQ scores between the 2 groups. PJF correlated with HU values at UIV and L4 but not with VBQ scores. Patients with PJF also had significantly different pre- and postoperative thoracic kyphosis, postoperative pelvic tilt, pelvic incidence minus lumbar lordosis, and proximal junctional angle compared to those without PJF.

CONCLUSIONS

The findings suggest that measuring HU values at UIV or L4 by CT may be useful for predicting the risk of PJF in female ASD patients undergoing 2-stage corrective surgery with LLIF. Therefore, CT-based HUs should be considered in ASD surgery planning to reduce the risk of PJF.

Influential literature regarding proximal junctional kyphosis: A bibliometric review

Study design

Retrospective review.

Objective

This bibliometric review summarizes the publication trends and critical information about the most cited Proximal Junction Kyphosis (PJK) articles.

Background

Data: Proximal junctional kyphosis is frequently diagnosed after spinal fusion surgery. However, there continues to be heavy debate regarding the definition, incidence, risk factors, and treatment of this disorder.

Methods

Nine hundred eleven articles were found when searching The Web of Science database with the keywords "Proximal junctional kyphosis" and "proximal junctional failure." The 200 top-cited articles were reviewed and screened to ensure PJK was discussed. The articles were filtered based on the highest to lowest number of citations, and the top 50 articles were chosen. Inclusion criteria included articles that contained a discussion of PJK and outcomes after surgery. Exclusion criteria included articles without mentioning PJK, or that studied non-human subjects. The 50 most cited articles were sorted by level of evidence and their classification for analysis.

Results

The 50 most cited articles in this study were published a total of 6056 times. These articles were cited 71-413 times in the literature, with publications from 1994 to 2018. Most of the top 50 articles (64%) were published in the USA. Specifically, HSS and Washington University are the institutions with the most contributions to the publication of the most cited articles on PJK (n = 16). Lenke was the author that contributed to most publications in the top 50 articles on PJK.

Conclusion

This study provides a framework for the most cited articles published on PJK. Most articles on this topic were in the category of clinical outcomes (36%) and were of a level of evidence III (46%). Most of the top-cited articles came from the journal Spine (68%) and were published in the USA (64%). These top-cited papers are essential to understanding this critical trending topic in spine surgery.

Level of evidence

III.

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

BACKGROUND AND OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSION

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

Patterns of Lumbar Spine Malalignment Leading to Revision Surgery for Proximal Junctional Kyphosis: A Cluster Analysis of Over- Versus Under-Correction

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Investigate the patterns of fused lumbar alignment in patients requiring revision surgery for proximal junctional kyphosis (PJK).

METHODS

Fifty patients (67.8 yo, 76% female) with existing thoraco-lumbar fusion (T10/12 to pelvis) and indicated for surgical correction for PJK were included. To investigate patterns of radiographic alignment prior to PJK revision, unsupervised 2-step cluster analysis was run on parameters describing the fused lumbar spine (PI-LL) to identify natural independent groups within the cohort. Clusters were compared in terms of demographics, pre-operative alignment, surgical parameters, and post-operative alignment. Associations between pre- and post-revision PJK angles were investigated using a Pearson correlation analysis.

RESULTS

Analysis identified 2 distinct patterns: Under-corrected (UC, n = 12, 32%) vs over-corrected (OC, n = 34, 68%) with a silhouette of .5. The comparison demonstrated similar pelvic incidence (PI) and PJK angle but significantly greater deformity for the UC vs OC group in terms of PI-LL, PI-LL offset, pelvic tilt, and sagittal vertebral axis. The surgical strategy for PJK correction did not differ between the 2 groups in terms of approach, American Society of Anesthesiologists grade, decompression, use of osteotomy, interbody fusion, or fusion length. The post-revision PJK angle significantly correlated with the amount of PJK correction within the OC group but not within the UC group.

CONCLUSIONS

This study identified 2 patterns of lumbar malalignment associated with severe PJK: over vs under corrected. Despite the difference in PJK etiology, both patterns underwent the same revision strategy. Future analysis should look at the effect of correcting focal deformity alone vs correcting focal deformity and underlying malalignment simultaneously on recurrent PJK rate.

The influence of ligament biomechanics on proximal junctional kyphosis and failure in patients with adult spinal deformity

Purpose

It is unknown whether the biomechanics of the posterior ligamentous complex (PLC) are impaired in individuals undergoing surgery for adult spinal deformity (ASD). Characterizing these properties may improve our understanding of proximal junctional kyphosis (PJK; defined as proximal junctional angle [PJA] of >10 deg from UIV-1 to UIV + 2), as well as proximal junctional failure (PJF; symptomatic PJK requiring revision). The purpose of this prospective observational study is to compare biomechanical properties of the PLC in individuals with ASD who do, and do not develop PJK or PJF within 1 year of spinal fusion surgery.

Methods

Intraoperative biopsies of PLC were obtained from 32 consecutive patients undergoing spinal fusions for ASD (>4 levels). Ligament peak force, tensile stress, tensile strain, and elastic modulus (EM) were measured with a materials testing system. Biomechanical properties and tissue dimensions were correlated with age, gender, BMI, vitamin D level, osteoporosis, sagittal alignment, PJA and change in PJA preoperatively, within 3 months, and at 1 year postoperatively.

Results

Longer ligaments were associated with greater PJA change at 3 months (p = 0.04), and thinner ligaments were associated with greater PJA change at 1 year (r = 0.57, p = 0.01). Greater EM was associated with greater PJA at both 3 months and 1 year (p = 0.03). Five participants had a change in PJA of >10 1 year postoperatively, and three participants demonstrated PJF. EM was significantly higher in individuals who required revision surgery (p = 0.003), and ligament length was greater (p = 0.03). Preoperative sagittal alignment was not related to incidence of revision surgery (p > 0.10).

Conclusions

The biomechanical properties of the PLC may be associated with higher risk for proximal failure. Ligaments that are longer, thinner, and less elastic are associated with higher postoperative PJA. Furthermore stiffer EM of the ligament is associated with the need for revision surgery.

Dynamic cord compression induced by proximal junctional failure and loose pedicle screws after thoracolumbar fusion surgery: a case report

BACKGROUND

One of the common mechanical complications following spinal fusion surgery is proximal junctional failure (PJF). The incidence of neurological deficit associated with PJF has been poorly described in the literature. Here, we report a case in which numbness in the lower extremities was recognized as the first symptom, but the discrepancy in the imaging findings made PJF difficult to diagnose.

METHODS

A 71-year-old female underwent corrective fusion surgery. Three weeks later, she complained of persistent right leg numbness. Standing X-ray showed the back-out of the pedicle screws (PSs) in the upper instrumented vertebra (UIV), but there was no obvious evidence of cord compression on computed tomography (CT), which caused the delay of diagnosis. Five weeks later, magnetic resonance image (MRI) did not show cord compression on an axial view, but there were signal changes in the spinal cord.

RESULTS

The first reason for the delayed diagnosis was the lack of awareness that leg numbness could occur as the first symptom of PJF. The second problem was the lack of evidence for spinal cord compression in various imaging tests. Loosened PSs were dislocated on standing, but were back to their original position on supine position. In our case, these contradictory images led to a delay in diagnosis.

CONCLUSION

Loosened PSs caused dynamic cord compression due to repeated deviation and reduction. Supine and standing radiographs may be an important tool in the diagnosis of PJF induced by dynamic cord compression.

Biomechanical evaluation of different semi-rigid junctional fixation techniques using finite element analysis

BACKGROUND

Proximal junctional failure is a common complication attributed to the rigidity of long pedicle screw fixation constructs used for surgical correction of adult spinal deformity. Semi-rigid junctional fixation achieves a gradual transition in range of motion at the ends of spinal instrumentation, which could lead to reduced junctional stresses, and ultimately reduce the incidence of proximal junctional failure. This study investigates the biomechanical effect of different semi-rigid junctional fixation techniques in a T8-L3 finite element spine segment model.

METHODS

First, degeneration of the intervertebral disc was successfully implemented by altering the height. Second, transverse process hooks, one- and two-level clamped tapes, and one- and two-level knotted tapes instrumented proximally to three-level pedicle screw fixation were validated against ex vivo range of motion data of a previous study. Finally, the posterior ligament complex forces and nucleus pulposus stresses were quantified.

FINDINGS

Simulated range of motions demonstrated the fidelity of the general model and modelling of semi-rigid junctional fixation techniques. All semi-rigid junctional fixation techniques reduced the posterior ligament complex forces at the junctional zone compared to pedicle screw fixation. Transverse process hooks and knotted tapes reduced nucleus pulposus stresses, whereas clamped tapes increased nucleus pulposus stresses at the junctional zone.

INTERPRETATION

The relationship between the range of motion transition and the reductions in posterior ligament complex and nucleus pulposus stresses was complex and dependent on the fixation techniques. Clinical trials are required to compare the effectiveness of semi-rigid junctional fixation techniques in terms of reducing proximal junctional failure incidence rates.

Chance Fracture Pattern Presenting in Proximal Junctional Failure

INTRODUCTION

We present a case series of proximal junctional failure due to a Chance-type fracture.

METHODS

This is a retrospective review of patients who developed proximal junctional kyphosis because of Chance-type proximal junctional failure after spinal fusion for adult spinal deformity.

RESULTS

Fifteen patients were identified (4M:11F). The average age was 61.4 years (range, 39 to 77). The mean time to fracture identification was 25.4 days (range, 3 to 65). The average number of levels instrumented was 6.7 (range, 2 to 17). No patients had antecedent trauma before fracture onset. In 67% of cases with a lumbar upper instrumented vertebra (UIV), there was overcorrection of lumbar lordosis (LL) and/or lower LL. The five cases with a lower thoracic UIV had undergone notable correction of preoperative thoracolumbar junction kyphosis. 14 of 15 patients were treated with extension of fusion. Pedicle screws at the fracture level were salvaged by changing to an anatomic trajectory.

CONCLUSION

Continued pain at 6 to 12 weeks with radiographs showing an increased proximal junctional angle and cephalocaudal pedicle widening at the UIV should raise suspicion for this unique fracture pattern. A CT scan is recommended. Low bone density, LL and/or lower LL overcorrection, and selection of lower thoracic UIV in the setting of notable thoracolumbar junction correction may contribute to fracture risk.

The Relationship between the Hounsfield Units Value of the Upper Instrumented Vertebra and the Severity of Proximal Junctional Fracture after Adult Spinal Deformity Surgery

Background and Objectives: In this retrospective cohort study, we investigate associations between the Hounsfield units (HU) value of upper instrumented vertebra (UIV) and proximal junctional kyphosis (PJK) after adult spinal deformity (ASD) surgery. Materials and Methods: The cohort consisted of 60 patients (mean age 71.7 years) who underwent long instrumented fusion surgery (≥6 vertebrae) for ASD with at least 1 year of follow-up. The preoperative bone mineral density (BMD) measured on DXA scans, the HU values at UIV and UIV+1, and the radiographic parameters were compared between the PJK and non-PJK groups. The severity of UIV fracture was assessed using a semiquantitative (SQ) grade. Results: PJK occurred in 43% of patients. No significant differences in patient age, sex, BMD, and preoperative radiographic parameters were observed between the PJK and non-PJK groups. The HU values of the UIV (103.4 vs. 149.0, p < 0.001) and UIV+1 (102.0 vs. 145.7, p < 0.001) were significantly lower in the PJK group. The cutoff values of HU at UIV and UIV+1 were 122.8 and 114.9, respectively. Lower HU values at UIV (Grade 1: 134.2, Grade 2: 109.6, Grade 3: 81.1, p < 0.001) and UIV+1 (Grade 1: 131.5, Grade 2: 107.1, Grade 3: 82.1, p < 0.001) were associated with severe SQ grade. Conclusions: Lower HU values at UIV and UIV+1 had a negative impact on signal incidence of PJK and were correlated with the severity of UIV fractures. Preoperative treatment of osteoporosis seems necessary for preoperative UIV HU values less than 120.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Hooks Versus Pedicle Screws at the Upper Instrumented Level: An In Vitro Biomechanical Comparison

STUDY DESIGN

Controlled laboratory study.

OBJECTIVE

The aim was to compare motions at the upper instrumented vertebra (UIV) and supra-adjacent level (UIV+1) between two fixation techniques in thoracic posterior spinal fusion constructs. We hypothesized there would be greater motion at UIV+1 after cyclic loading across all constructs and bilateral pedicle screws (BPSs) with posterior ligamentous compromise would demonstrate the greatest UIV+1 range of motion.

SUMMARY OF BACKGROUND DATA

Proximal junctional kyphosis is a well-recognized complication following long thoracolumbar posterior spinal fusion, however, its mechanism is poorly understood.

MATERIALS AND METHODS

Twenty-seven thoracic functional spine units were randomly divided into three UIV fixation groups (n=9): (1) BPS, (2) bilateral transverse process hooks (TPHs), and (3) BPS with compromise of the posterior elements between UIV and UIV+1 (BPS-C). Specimens were tested on a servohydraulic materials testing system in native state, following instrumentation, and after cyclic loading. functional spine units were loaded in flexion-extension (FE), lateral bending, and axial rotation.

RESULTS

After cyclic testing, the TPH group had a mean 29.4% increase in FE range of motion at UIV+1 versus 76.6% in the BPS group ( P <0.05). The BPS-C group showed an increased FE of 49.9% and 62.19% with sectioning of the facet joints and interspinous ligament respectively prior to cyclic testing.

CONCLUSION

BPSs at the UIV led to greater motion at UIV+1 compared to bilateral TPH after cyclic loading. This is likely due to the increased rigidity of BPS compared to TPH leading to a "softer" transition between the TPH construct and native anatomy at the supra-adjacent level. Facet capsule compromise led to a 49.9% increase in UIV+1 motion, underscoring the importance of preserving the posterior ligamentous complex. Clinical studies that account for fusion rates are warranted to determine if constructs with a "soft transition" result in less proximal junctional kyphosis in vivo .

Association of spinopelvic index with proximal junctional failure developing in adult spinal deformity after surgical treatment: an observational study

BACKGROUND

Those pelvic parameters of sacral slope (SS) and pelvic tilt (PT) correlated significantly to lumbar spine and hip joints respectively. We proposed the match between SS and PT, namely spinopelvic index (SPI), in order to investigate whether the SPI correlated to proximal junctional failure (PJF) in adult spinal deformity (ASD) after correction surgery.

METHODS

Ninety-nine ASD patients who had undergone long-fusion (≥ 5 vertebras) surgeries were reviewed retrospectively in two medical institutions from January 2018 to December 2019. Those SPI were calculated with the equation: SPI = SS/PT, and analyzed using the receiver operating characteristic curve (ROC) analysis. All participants were subdivided into the observational and control group. Comparisons of demographics, surgical and radiographic data between the two groups were performed. A Kaplan-Meier curve and log-rank test was used to analyze the differences in PJF-free survival time, and the 95% confidence intervals (CI) were recorded respectively.

RESULTS

Nineteen patients suffering from PJF had much smaller postoperative SPI (P = 0.015), but much larger TK postoperatively (P < 0.001). ROC analysis determined the best cutoff value of 0.82 for SPI (sensitivity = 88.5%, specificity = 57.9%; AUC = 0.719, 95%CI: 0.612-0.864; P = 0.003). There were 19 and 80 cases in the observational (SPI ≤ 0.82) and control group (SPI > 0.82) respectively. The incidence of PJF in the observational group was much higher (11/19 VS 8/80, P < 0.001); further logistic regression analysis showed that SPI ≤ 0.82 was associated with increased odds of PJF (odds ratio: 12.375; 95%CI: 3.851-39.771). PJF-free survival time in the observational group decreased significantly (P < 0.001, log-rank test), moreover, multivariate analysis demonstrated that a value of SPI ≤ 0.82 (HR 6.626, 95%CI: 1.981-12.165) was significantly associated with PJF.

CONCLUSIONS

For ASD patients underwent long-fusion surgeries, the SPI should be over 0.82. The incidence of PJF may increase by 12-fold in such individuals with the immediate SPI ≤ 0.82 postoperatively.

Pelvic incidence is a risk factor for lower instrumented vertebra failure in adult spinal deformity patients who underwent corrective fusion terminating at the L5 vertebra

BACKGROUND

Factors related to postoperative mechanical failure after long fusion with lower instrumented vertebra (LIV) at L5 have not been well investigated. Elucidating such factors may allow us to perform alternatives to spinopelvic fusion for adult spinal deformity (ASD) cases. We investigated the incidence and risk factors of LIV failure in patients with ASD who underwent surgical treatment of long corrective fusion until the L5 vertebrae.

METHODS

Between 2009 and 2018, 52 patients who underwent corrective fusions to L5 were followed-up for at least one-year. We evaluated the associated patient factors for LIV failure which include loosening of the pedicle screw of LIV, fracture of LIV, distal junctional kyphosis (DJK).

RESULTS

The mean age of the participants was 71.2 ± 7.59 (range, 44-84). LIV failure occurred in 20 patients (38.5%), and 6 patients (11.5%) underwent secondary surgery for caudal segments. The mean pelvic incidence (PI) was 52.5 ± 9.8 in the failure group versus 45.3 ± 11.4 in non-failure group (P = 0.02) and pelvic tilt (PT) was 39.1 ± 9.0 versus 32.4 ± 13.0. There were no significant differences in sex, age, body mass index, number of levels fused, and other radiographic data. Logistic regression analysis that included T1 pelvic angle, PT, PI - postoperative LL and PI also identified PI as the only significant determinant of LIV failure (OR = 1.07, P = 0.034). Receiver operating characteristic analysis demonstrated that a PI over 50.0° was associated with LIV failure (sensitivity 63%, specificity 70%, AUC 0.694).

CONCLUSION

LIV failure was frequently observed after long corrective fusion for patients with ASD. High PI was found to be a significant risk factor for the LIV failure.

Predicting the Magnitude of Distal Junctional Kyphosis Following Cervical Deformity Correction

STUDY DESIGN

Retrospective review of a cervical deformity database.

OBJECTIVE

This study aimed to develop a model that can predict the postoperative distal junctional kyphosis angle (DJKA) using preoperative and postoperative radiographic measurements.

SUMMARY OF BACKGROUND DATA

Distal junctional kyphosis (DJK) is a complication following cervical deformity correction that can reduce of patient quality of life and functional status. Although researchers have identified the risk factors for DJK, no model has been proposed to predict the magnitude of DJK.

MATERIALS AND METHODS

The DJKA was defined as the Cobb angle from the lower instrumented vertebra (LIV) to LIV-2 with traditional DJK having a DJKA change >10°. Models were trained using 66.6% of the randomly selected patients and validated in the remaining 33.3%. Preoperative and postoperative radiographic parameters associated with DJK were identified and ranked using a conditional variable importance table. Linear regression models were developed using the factors most strongly associated with postoperative DJKA.

RESULTS

A total of 131 patients were included with a mean follow-up duration of 14±8 months. The mean postoperative DJKA was 14.6±14° and occurred in 35% of the patients. No significant differences between the training and validation cohort were observed. The variables most associated with postoperative DJK were: preoperative DJKA (DJKApre), postoperative C2-LIV, and change in cervical lordosis (∆CL). The model identified the following equation as predictive of DJKA: DJKA=9.365+(0.123×∆CL)-(0.315×∆C2-LIV)-(0.054×DJKApre). The predicted and actual postoperative DJKA values were highly correlated ( R =0.871, R2 =0.759, P <0.001).

CONCLUSIONS

The variables that most increased the DJKA were the preoperative DJKA, postoperative alignment within the construct, and change in cervical lordosis. Future studies can build upon the model developed to be applied in a clinical setting when planning for cervical deformity correction.

An Analysis of Whether a New Formula Can Predict Proximal Junctional Failure in Adult Spinal Deformity Patients with Global Kyphosis

OBJECTIVE

A new formula containing terms for age and sagittal curvature reported by the International Spine Study Group is ideal lumbar lordosis (iLL) = pelvic incidence - 0.3 thoracic kyphosis - 0.5Age + 10. However, there are no reports of whether proximal junctional failure (PJF) can be predicted using this formula. We assessed the utility of this formula in PJF in patients with adult spinal deformity with global kyphosis using the Roussouly classification.

METHODS

Forty-four patients with adult spinal deformity global kyphosis (mean age 70.0 years) who underwent multiple levels of lateral lumbar interbody fusion combined with posterior instrumentation were included. Patients were divided into 2 groups: PJF and non-PJF. Demographic, surgical, and radiological parameters were compared. The iLL was calculated according to the new formula, and spinal parameters were compared preoperatively, immediately after, and at the final follow-up.

RESULTS

PJF occurred in 11 of 44 (25.0%) patients. Patients with PJF had a large preoperative and postoperative TK, but there was no statistically significant difference in iLL between PJF and non-PJF patients (33.4° vs. 30.2°, P = 0.357). In addition, there was no statistically significant difference in LL and iLL changes (ΔiLL) immediately after surgery (19.0° vs. 23.4°, P = 0.379). Furthermore, there was no correlation between ΔiLL immediately after surgery and at the final follow-up and the proximal junctional angle at the final follow-up.

CONCLUSIONS

The results of ΔiLL suggest that overcorrection needs to be addressed but that this new formula, including age adjustment, may not predict PJF.

Artificial intelligence in spine surgery

The continuous progress of research and clinical trials has offered a wide variety of information concerning the spine and the treatment of the different spinal pathologies that may occur. Planning the best therapy for each patient could be a very difficult and challenging task as it often requires thorough processing of the patient's history and individual characteristics by the clinician. Clinicians and researchers also face problems when it comes to data availability due to patients' personal information protection policies. Artificial intelligence refers to the reproduction of human intelligence via special programs and computers that are trained in a way that simulates human cognitive functions. Artificial intelligence implementations to daily clinical practice such as surgical robots that facilitate spine surgery and reduce radiation dosage to medical staff, special algorithms that can predict the possible outcomes of conservative versus surgical treatment in patients with low back pain and disk herniations, and systems that create artificial populations with great resemblance and similar characteristics to real patients are considered to be a novel breakthrough in modern medicine. To enhance the body of the related literature and inform the readers on the clinical applications of artificial intelligence, we performed this review to discuss the contribution of artificial intelligence in spine surgery and pathology.

Validation of Age-adjusted Ideal Sagittal Alignment in Terms of Proximal Junctional Failure and Clinical Outcomes in Adult Spinal Deformity

STUDY DESIGN

Retrospective study.

OBJECTIVE

To validate the age-adjusted ideal sagittal alignment in terms of proximal junctional failure (PJF) and clinical outcomes.

SUMMARY OF BACKGROUND

It is reported that optimal sagittal correction with regard to the age-adjusted ideal sagittal alignment reduces the risk of PJF development. However, few studies have validated this concept. The age-considered optimal correction is likely to be undercorrection in terms of conventional surgical target, such as pelvic incidence (PI)-lumbar lordosis (LL) within ±9°. Therefore, the clinical impact of age-adjusted sagittal alignment should be evaluated along with radiographic effect.

MATERIALS AND METHODS

Adult spinal deformity patients, aged 50 years and above, who underwent greater than or equal to four-level fusion to sacrum with a minimum of four years of follow-up data were included in this study. Radiographic risk factors for PJF (including age-adjusted ideal PI-LL) were evaluated with multivariate analyses. Three groups were created based on PI-LL offset between age-adjusted ideal PI-LL and actual actual PI-LL: undercorrection, ideal correction, and overcorrection. Clinical outcomes were compared among the three groups.

RESULTS

This study included 194 adult spinal deformity patients. The mean age was 68.5 years and there were 172 females (88.7%). PJF developed in 99 patients (51.0%) at a mean postoperative period of 14.9 months. Multivariate analysis for PJF revealed that only PI-LL offset group had statistical significance. The proportion of patients with PJF was greatest in the overcorrection group followed by the ideal correction and undercorrection groups. Overcorrected patients regard to the age-adjusted ideal alignment showed poorer clinical outcomes than the other patient groups.

CONCLUSIONS

Overcorrection relative to age-adjusted sagittal alignment increases the risk of PJF development and is associated with poor clinical outcomes. Older patients and those with small PI are likely to be overcorrected in terms of the age-adjusted PI-LL target. Therefore, the age-adjusted alignment should be considered more strictly in these patients.

Changes in health-related quality of life measures associated with degree of proximal junctional kyphosis

PURPOSE

To explore the changes in health-related quality of life parameters observed in patients experiencing varying degrees of proximal junctional kyphosis following corrective adult spinal deformity fusions.

METHODS

Inclusion: adult spinal deformity patients > 18 y/o, undergoing spinal fusion. PJK: ≥ 10° measure of the sagittal Cobb angle between the inferior endplate of the UIV and the superior endplate of the UIV + 2. Severe PJK: > 28° PJK. Mild PJK: ≥ 10^oand ≤ 28°. ANOVA, followed by ANCOVA, compared the change in HRQoLs between time points (BL, 1Y, 2Y) among PJK groups. Correlation-related change in PJK and change in HRQoL for mild and severe groups.

RESULTS

969 patients (age: 64.5 y/o,75% F, posterior levels fused:12.3) were studied. 59% no PJK, 32% mild PJK, 9% severe PJK. No differences in HRQoLs were seen between no PJK and PJK groups at baseline, one year, and 2 years. Adjusted analysis revealed Severe PJK patients improved less in SRS-22 Satisfaction (NoPJK: 1.6, MildPJK: 1.6, SeverePJK: 1.0; p = 0.022) scores at 2 years. Linear regression analysis only found clinical improvement in SRS-22 Satisfaction to correlate with the change of the PJK angle by 2 years (R = 0.176, P = 0.008). No other HRQoL metric correlated with either the incidence of PJK or the change in the PJK angle by one or 2 years.

CONCLUSIONS

These results maintain that patients presenting with and without proximal junctional kyphosis report similar health-related qualities of life following corrective adult spinal deformity surgery, and SRS-22 Satisfaction may be a clinical correlate to the degree of PJK. Rather than proving proximal junctional kyphosis to have a minimal clinical impact overall on HRQoL metrics, these data suggest that future analysis of this phenomenon requires different assessments.

LEVEL OF EVIDENCE

Level of evidence: III.

The Impact of Upper Instrumented Vertebra Orientation on Proximal Junctional Kyphosis: A Novel and Fixed Parameter, Fused Spinopelvic Angle

STUDY DESIGN

A retrospective study.

OBJECTIVES

To evaluate the impact of upper instrumented vertebra (UIV) orientation including the fused spinopelvic angle (FSPA) on proximal junctional kyphosis (PJK).

SUMMARY OF BACKGROUND DATA

PJK is a challenging complication after adult spinal deformity (ASD) surgery. Some studies proposed UIV orientation act as a risk factor of PJK, but there remain debates because UIV orientation is changed by position. Therefore, we investigated the relationship between the FSPA, a novel parameter for the relationship between UIV and pelvis which did not change by position, and PJK.

MATERIALS AND METHODS

ASD patients who underwent long-segment fusion to the pelvis and followed up for more than two years were included. Comparative analysis was performed on spinopelvic parameters including UIV orientation parameters (UIV slope angle and FSPA) between PJK and non-PJK group. Binary regression analysis was conducted to find out the risk factors for PJK. And correlation analysis was conducted to find out the parameters that affect the FSPA.

RESULTS

A total of 190 patients were included. PJK incidence was 13.2% (25/190). PJK group showed a significantly greater postoperative UIV slope (21.3° vs. 18.8°, P =0.041) and significantly lesser postoperative FSPA (-0.9° vs. 4.5°, P <0.001). In binary regression analysis, only FSPA acted as a risk factor of PJK (odds ratio=0.920, P =0.004). The FSPA has strong positive correlation with pelvic incidence (PI)-lumbar lordosis (LL) ( r =0.666, P <0.001) and negative correlation with lordosis distribution index (LDI) ( r =-0.228, P =0.004).

CONCLUSION

The FSPA is a fixed parameter which is not dependent on position. A reduction of the FSPA increases the risk for PJK. The FSPA can be adjusted through PI-LL and LDI. Thus, surgeons should increase the FSPA by adjusting the PI-LL and LDI during ASD surgery to prevent PJK.

The importance of thoracolumbar junctional orientation, change in thoracolumbar angle, and overcorrection of lumbar lordosis in development of proximal junctional kyphosis in adult spinal deformity surgery

OBJECTIVE

Changes in the thoracolumbar angle (TLA) would play a pivotal role in the reciprocal changes following spine realignment surgery, thereby leading to the development of proximal junctional kyphosis (PJK). This study aimed to investigate the association between TLA and the development of PJK following adult spinal deformity surgery.

METHODS

A total of 107 patients were divided into PJK+ and PJK- groups according to the development of PJK within 12 months after surgery. The TLA and spinopelvic radiological parameters were compared between the PJK+ and PJK- groups. A multivariate logistic regression model was used to identify the risk factors for PJK. The receiver operating characteristic curves of the regression models were used to investigate the cutoff values of significant parameters needed so that PJK would not occur.

RESULTS

The change in TLA (ΔTLA) in the PJK+ group was significantly larger than in the PJK- group (6.7° ± 7.9° and 2.2° ± 8.1°, respectively; p = 0.006). Multivariate logistic regression analysis demonstrated that age, postoperative pelvic incidence-lumbar lordosis, and ΔTLA were significant risk factors for PJK. The risk of developing PJK was higher when the postoperative pelvic incidence-lumbar lordosis was < 5.2 and the ΔTLA was > 3.58°.

CONCLUSIONS

The present study highlights the thinking that extensive correction of TLA and lumbar lordosis should be avoided in patients with adult spinal deformity. Overcorrection of TLA of > 3.58° could result in higher odds of PJK.

Paraspinal muscle degeneration and lower bone mineral density as predictors of proximal junctional kyphosis in elderly patients with degenerative spinal diseases: a propensity score matched case–control analysis

Study design

Retrospective case–control study.

Objectives

Proximal junctional kyphosis (PJK) is a postoperative complication involving the proximal segments which is commonly seen in patients with degenerative spine diseases (DSD). The purpose of the present study was to identify predictive factors for postoperative PJK in elderly patients with DSD.

Methods

We reviewed elderly patients with DSD who underwent thoracolumbar fusion involving no less than 3 levels. Patients who developed PJK were propensity score-matched with patients with DSD who received the same procedure but did not develop PJK. Demographic characteristics, sagittal vertical axis (SVA), computed tomography (CT) value (Hounsfield unit), and paraspinal muscle parameters were compared between PJK and non-PJK groups.

Results

Eighty-three PJK and non-PJK patients were selected by propensity score matching for age, sex, history of smoking, body mass index, number of fused segments, and upper instrumented vertebra (UIV) location. SVA showed no significant difference between the two groups. In PJK group, fatty infiltration (FI) in erector spinae and multifidus was significantly greater, while the relative cross-sectional area (rCSA) of erector spinae was significantly smaller than that in non-PJK group. CT value was significantly lower in PJK group. Lower erector spinae rCSA and CT value of the UIV, higher erector spinae FI and multifidus FI were identified as predictors of postoperative PJK.

Conclusions

PJK is a common complication in older patients with DSD. Paraspinal muscle degeneration and low bone mineral density of the UIV are predictors of PJK. Protective measures targeting paraspinal muscles and the UIV may help prevent postoperative PJK.