Characteristics and risk factors for proximal junctional kyphosis in adult spinal deformity after correction surgery: a systematic review and meta-analysis

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.

Does Vertebral Cement Augmentation Reduce Postoperative Proximal Junction Complications in Spinal Deformity Corrective Surgery: A Systematic Review and Meta-analysis

OBJECTIVE

To assess the effectiveness of vertebral cement augmentation (VCA) at upper instrumented vertebra (UIV) and UIV+1 in preventing proximal junction complications in correction surgery for adult spinal deformity patients.

METHODS

A literature search was conducted on Web of Science, PubMed, and Cochrane Library databases for comparative studies published before December 30th, 2024. Two reviewers independently screened eligible articles based on the inclusion and exclusion criteria, assessed study quality with Newcastle-Ottawa scale, and extracted data like study characteristics, surgical details, primary and secondary outcomes. Data analysis was performed using Review Manager 5.4 and Stata software.

RESULTS

Of all 513 papers screened, a meta-analysis was conducted on 7 articles, which included 333 cases in the VCA group and 827 cases in the control group. Patients in the VCA group had significantly older age and lower T score than patients in the control group. Although there was no statistically significant difference in the incidence of proximal junctional failure between the 2 groups, the results of the meta-analysis showed that the incidence of proximal junctional failure and the need for revision surgery were reduced by 36% and 71%, respectively, in the VCA group. One study reported 2 clinically silent pulmonary cement embolism and 1 patient requiring surgical decompression for cement leak into the spinal canal.

CONCLUSION

This meta-analysis supported the use of VCA in corrective surgery for spinal deformities patients, especially in patients with advanced age and osteoporosis.

Proximal junctional kyphosis above long spinal fusions

INTRODUCTION

Spinal deformity in adults is a major public health problem. After failure of conservative treatment, correction and fusion surgery leads to clinical and radiological improvement. However, mechanical complications and more particularly - proximal junctional kyphosis (PJK) - are common with an incidence of 10%-40% depending on the studies.

ANALYSIS

Several risk factors have been identified and can be grouped into three categories. Among the patient-related factors, advanced age, comorbidities, osteoporosis and sarcopenia play a determining role. Among the radiological factors, changes in sagittal alignment (cranial migration of thoracolumbar inflection point, over-correction of lumbar hyperlordosis, preoperative thoracolumbar kyphosis) play a key role. Finally, the fusion technique itself may increase the risk of PJK (use of screws instead of hooks) as a surgical factor.

PREVENTION

Prevention happens at each phase of treatment. A patient assessment is done preoperatively to identify those at risk of PJK. Treating osteoporosis is beneficial. The surgical strategy must also be adapted: the choice of transitional implants such as sublaminar links or hooks and the use of ligament reinforcement techniques can help minimize the risk of PJK. Finally, methodical clinical and radiological follow-up will help to detect early signs of PJK and allow a surgeon to reoperate right away.

TREATMENT

Not all PJK requires surgical revision. Radiological monitoring and functional treatment is sometimes sufficient. However, if the patient develops pain, neurological complications or instability detected by imaging (unstable fracture, spondylolisthesis, spinal cord compression), revision surgery is necessary. It may consist of proximal extension of the fusion combined with decompression of the stenosis levels at a minimum.

CONCLUSION

PJK is a major challenge for surgeons. The best treatment is prevention, with a thorough analysis of risk factors leading to a well-planned and personalized surgery. Regular postoperative follow-up is essential.

LEVEL OF EVIDENCE

Expert opinion.

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.

Osteoporosis Treatment and Outcomes in Patients Undergoing Adult Spinal Deformity Surgery

BACKGROUND

This study aims to evaluate the prevalence and treatment of osteoporosis in patients undergoing long spinal fusion for adult spinal deformity (ASD) and compare the impact of osteoporosis treatment on surgical and radiographic outcomes.

METHODS

We conducted a retrospective study of adult patients aged ≥40 years who underwent thoracolumbar ASD surgery at a single academic center between 2015 and 2021. We recorded demographic information, procedural details, and pharmacologic treatments. Primary outcomes included preoperative and postoperative sagittal vertical axis, pelvic incidence-lumbar lordosis mismatch, and postoperative complications such as surgical site infection, pseudarthrosis, proximal junctional kyphosis (PJK), and proximal junctional failure. Patients with osteoporosis were compared to those without.

RESULTS

Among 168 patients, the prevalence of osteoporosis was 28.6%. Osteoporotic patients were older and predominantly female. At the time of surgery, 70.8% of osteoporotic patients were receiving pharmacologic treatment. Preoperative pelvic incidence-lumbar lordosis mismatch and sagittal vertical axis did not differ significantly between osteoporotic and nonosteoporotic cohorts. Both cohorts showed similar postoperative improvements. The osteoporotic cohort had a higher rate of PJK (35.4% vs. 17.5%, p=0.01), but no significant difference in proximal junctional failure rates. No significant differences were found between monotherapy and combination therapy outcomes for osteoporotic patients.

CONCLUSIONS

Osteoporotic patients undergoing ASD surgery exhibited similar surgical outcomes and alignment improvements compared to nonosteoporotic patients, despite a higher rate of PJK. Pharmacological treatment appears beneficial in managing osteoporosis-related surgical risks. These findings highlight the importance of identifying and treating osteoporosis in ASD patients to minimize complications.

Analysis of Risk Factors Associated with Proximal Junctional Kyphosis Following Long Instrumented Fusion from L1 to Sacrum: Age Itself Does Not Independently Increase the Risk

Background and Objectives: This study is a retrospective analysis aimed at understanding the incidence and risk factors of proximal junctional kyphosis (PJK) following long-instrumented spinal fusion from L1 to the sacrum in patients with mild to moderate sagittal imbalance. Materials and Methods: It recruited consecutive patients undergoing instrumented fusion from L1 to the sacrum for degenerative lumbar disease between June 2006 and November 2019 in a single institution. The patients' preoperative clinical data, muscle status at T12-L1 on magnetic resonance images, and sagittal spinopelvic parameters were analyzed. Univariate analysis was used to compare clinical and radiographic data between PJK and non-PJK patients. Logistic regression analysis was used to investigate the independent risk factors for PJK. Results: A total of 56 patients were included in this study. The mean age at surgery was 67.3 years and mean follow-up period was 37.3 months. In total, 10 were male and 46 were female. PJK developed in 23 (41.1%) out of 56; of these patients, 20 (87.0%) developed PJK within 1 year postoperatively. In the univariate analysis between PJK and non-PJK patients, the PJK group showed more frequent osteoporosis, lower body mass index, smaller cross-sectional area (CSA) and more fat infiltration (FI) in erector spinae muscle at T12-L1 and larger preoperative TLK and PT with statistical significance (p < 0.05). In the logistic regression analysis, severe (>50%) FI in erector spinae muscle (OR = 43.60, CI 4.10-463.06, R2N = 0.730, p = 0.002) and osteoporosis (OR = 20.49, CI 1.58-264.99, R2N = 0.730, p = 0.021) were statistically significant. Conclusions: Preexisting severe (>50%) fat infiltration in the erector spinae muscle and osteoporosis were independent risk factors associated with PJK following instrumented fusion from L1 to the sacrum, but age was not a risk factor.

The L3 Flexion Angle Predicts Failure of Non-Operative Management in Patients with Tandem Spondylolithesis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Determine impact of standard/novel spinopelvic parameters on global sagittal imbalance, health-related quality of life (HRQoL) scores, and clinical outcomes in patients with multi-level, tandem degenerative spondylolisthesis (TDS).

METHODS

Single institution analysis; 49 patients with TDS. Demographics, PROMIS and ODI scores collected. Radiographic measurements-sagittal vertical axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), PI-LL mismatch, sagittal L3 flexion angle (L3FA) and L3 sagittal distance (L3SD). Stepwise linear multivariate regression performed using full length cassettes to identify demographic and radiographic factors predictive of aberrant SVA (≥5 cm). Receiver operative curve (ROC) analysis used to identify cutoffs for lumbar radiographic values independently predictive of SVA ≥5 cm. Univariate comparisons of patient demographics, (HRQoL) scores and surgical indication were performed around this cutoff using two-way Student's t-tests and Fisher's exact test for continuous and categorical variables, respectively.

RESULTS

Patients with increased L3FA had worse ODI (P = .006) and increased rate of failing non-operative management (P = .02). L3FA (OR 1.4, 95% CI) independently predicted of SVA ≥5 cm (sensitivity and specifity of 93% and 92%). Patients with SVA ≥5 cm had lower LL (48.7 ± 19.5 vs 63.3 ± 6.9 mm, P < .021), higher L3SD (49.3 ± 12.9 vs 28.8 ± 9.2, P < .001) and L3FA (11.6 ± 7.9 vs -3.2 ± 6.1, P < .001) compared to patients with SVA ≤5 cm.

CONCLUSIONS

Increased flexion of L3, which is easily measured by the novel lumbar parameter L3FA, predicts global sagittal imbalance in TDS patients. Increased L3FA is associated with worse performance on ODI, and failure of non-operative management in patients with TDS.

Lumbar pedicle subtraction osteotomy: techniques and outcomes

Pedicle subtraction osteotomy has been thoroughly described and studied over the past 2 decades, being applied mainly in the lumbar spine, followed by the thoracic spine. Our better understanding of alignment biomechanics, and the progressive refinements of the surgical technique over time made it a very efficient procedure for the management of fixed sagittal malalignment. However, a long learning curve is mandatory to mitigate the associated risks particularly neurological deficits and achieve satisfactory clinical and radiological outcomes with an acceptable rate of complications.

Lumbar Lordosis Redistribution and Segmental Correction in Adult Spinal Deformity: Does it Matter?

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVE

Evaluate the impact of correcting normative segmental lordosis values on postoperative outcomes.

BACKGROUND

Restoring lumbar lordosis magnitude is crucial in adult spinal deformity surgery, but the optimal location and segmental distribution remain unclear.

PATIENTS AND METHODS

Patients were grouped based on offset to normative segmental lordosis values, extracted from recent publications. Matched patients were within 10% of the cohort's mean offset, less than or over 10% were undercorrected and overcorrected. Surgical technique, patient-reported outcome measures, and surgical complications were compared across groups at baseline and two years.

RESULTS

In total, 510 patients with a mean age of 64.6, a mean Charlson comorbidity index 2.08, and a mean follow-up of 25 months. L4-5 was least likely to be matched (19.1%), while L4-S1 was the most likely (24.3%). More patients were overcorrected at proximal levels (T10-L2; undercorrected, U: 32.2% vs. matched, M: 21.7% vs. overcorrected, O: 46.1%) and undercorrected at distal levels (L4-S1: U: 39.0% vs. M: 24.3% vs. O: 36.8%). Postoperative Oswestry disability index was comparable across correction groups at all spinal levels except at L4-S1 and T10-L2/L4-S1, where overcorrected patients and matched were better than undercorrected (U: 32.1 vs. M: 25.4 vs. O: 26.5, P =0.005; U: 36.2 vs. M: 24.2 vs. O: 26.8, P =0.001; respectively). Patients overcorrected at T10-L2 experienced higher rates of proximal junctional failure (U: 16.0% vs. M: 15.6% vs. O: 32.8%, P <0.001) and had greater posterior inclination of the upper instrumented vertebrae (U: -9.2±9.4° vs. M: -9.6±9.1° vs. O: -12.2±10.0°, P <0.001), whereas undercorrection at these levels led to higher rates of revision for implant failure (U: 14.2% vs. M: 7.3% vs. O: 6.4%, P =0.025).

CONCLUSIONS

Patients undergoing fusion for adult spinal deformity suffer higher rates of proximal junctional failure with overcorrection and increased rates of implant failure with undercorrection based on normative segmental lordosis.

LEVEL OF EVIDENCE

Level IV.

Proximal junctional kyphosis after adult spinal deformity operated patients with long fusion to the pelvis. Does the type of proximal anchor matter?

PURPOSE

To assess, in a large population of Adult Spinal Deformity (ASD) patients, the true interest of varying the upper anchors as a protective measure against Proximal Junctional Kyphosis (PJK), by analyzing and comparing 2 groups of patients defined according to their proximal construct. Another objective of the study is to look for any other factors, radiological or clinical, that would affect the occurrence of the proximal failure.

METHODS

Retrospective review of a prospective ASD database collected from 5 centers. Inclusion criteria were age of at least 18 years, presence of a spinal deformity with instrumentation from T12 or above to the pelvis, with minimum 2 years of follow-up. Demographic data, spinopelvic parameters, functional outcomes and complications were collected. Multiple logistic regression analysis was performed to identify the risk factors that would affect the occurrence of PJK.

RESULTS

254 patients were included. 166 in the group "screws proximally" (SP) and 88 in the group "hooks proximally" (HP). There was no difference between both groups for PJK (p = 0.967). The occurrence of PJK was rather associated with greater age and BMI, higher preoperative kyphosis, worst preoperative SRS22 and SF36 scores, greater postoperative Sagittal Vertical Axis (SVA), coronal malalignment and kyphosis.

CONCLUSION

The use of proximal hooks was not effective to prevent PJK after ASD surgery, when compared to proximal screws. Worse preoperative functional outcomes and worse postoperative sagittal and also coronal malalignment were the main drivers for the occurrence of PJK regardless the type of proximal implant.

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.

Simplified S1 vertebral bone quality score independently predicts proximal junctional kyphosis after surgery for degenerative lumbar scoliosis

OBJECTIVE

Our study aimed to assess the effectiveness of the simplified S1 vertebral bone quality (VBQ) score in predicting the incidence of proximal junctional kyphosis (PJK) after surgery for degenerative lumbar scoliosis (DLS).

METHODS

We reviewed 122 patients with DLS who underwent posterior lumbar decompression and long-segment fusion surgery in our hospital from January 2016 to December 2020. The patients were classified into PJK group and non-PJK group. S1 VBQ scores are determined by signal intensity measurements taken from the mid-sagittal plane of T1-weighted non-contrast MRI. Logistic regression analysis was used to identify factors associated with PJK. Receiver-operating characteristic curve (ROC) analysis was used to evaluate the value of S1 VBQ score in predicting pedicle PJK after DLS.

RESULTS

122 DLS patients (90 females and 32 males) met the inclusion criteria. In addition, 27 patients (22.13%) had PJK at the time of last follow-up. VBQ was higher in PJK patients than non-PJK patients (3.58 ± 0.67 vs. 3.08 ± 0.54, p < 0.001). Preoperatively, patients in the PJK group had a greater TLK than those in the non-PJK group (20.00 ± 6.22 vs. 16.86 ± 5.38, p = 0.011). After surgery, patients in the PJK group had greater TLK (p < 0.001) and PJA (p < 0.001) compared with the non-PJK group. At final FU, patients in the PJK group had greater TK (p = 0.002), TLK (p < 0.001), SVA (p < 0.001), and PJA (p < 0.001) than patients in the non-PJK group (Table 4). In multivariate logistic regression analysis, higher VBQ score (OR 4.565, 95% CI 1.43-14.568, p = 0.010), advanced age (OR 1.119, 95% CI 1.021-1.227, p = 0.016), and larger TLK (OR 1.191, 95% CI 1.041-1.362, p = 0.011) were significant predictors of postoperative PJK in patients with DLS (Table 6). A statistically significant positive correlation existed between VBQ score and PJA change (r = 0.370, p < 0.001). We created ROC curves for VBQ scores as predictors of PJK with a diagnostic accuracy of 72.1% (95% CI 60.15-82.9%.The ideal limit for the VBQ score was 3.205 (sensitivity: 77.8%, specificity: 81.4%).

CONCLUSION

To the best of our knowledge, this is the first study to evaluate the effectiveness of the S1 VBQ score in predicting postoperative PJK in DLS. Our study included major risk factors and found that S1 VBQ score was a significant predictor of PJK in patients undergoing DLS surgery. The higher the S1 VBQ score, the higher the probability of PJK.

Sagittal Balance Parameters and Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis

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

Biomechanical analysis of complications following T10-Pelvis spinal fusion: A population based computational study

Proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are challenging complications of long fusion constructs for the treatment of adult spinal deformity. The objective of this study is to understand the biomechanical stresses proximal to the upper instrumentation of a T10-pelvis fusion in a large patient cohort. The pre-fusion models were subject-specific thoracolumbar spine models that incorporate the height, weight, spine curvature, and muscle morphology of 250 individuals from the Framingham Heart Study Multidetector CT Study. To create post-fusion models, the subject-specific models were further modified to eliminate motion between the intervertebral joints from T10 to the pelvis. OpenSim analysis tools were used to calculate the medial lateral shear force, anterior posterior shear force, and compressive force on the T9 vertebra during the static postures. Differences between pre-fusion and post-fusion T9 biomechanics were consistent between increased segmental mobility and unchanged segmental mobility conditions. For all static postures, compression decreased (p < 0. 0005). Anterior-posterior shear force significantly increased (p < 0. 0005) during axial twist and significantly increased (p < 0. 0005) during trunk flexion. Medial lateral shear force significantly increased (p < 0. 0005) during axial twist. This computational study provided the first use of subject-specific models to investigate the biomechanics of long spinal fusions. Patients undergoing T10-Pelvis fusion were predicted to have increased shear forces and decreased compressive force at the T9 vertebra, independent of change in segmental mobility. The computational model shows potential for the investigation of spinal fusion biomechanics to reduce the risk of PJK or PJF.

PreOperative Planning for Adult Spinal Deformity Goals: Level Selection and Alignment Goals

Adult Spinal Deformity (ASD) is a complex pathologic condition with significant impact on quality of life, including pain, loss of function, and fatigue. Achieving realignment goals is crucial for long-term results. Reliable preoperative planning strategies, including nomograms, measurement tools, and level selection, are key to maximizing the likelihood of achieving a good outcome following ASD corrective surgery. This review covers recent literature on such strategies, including review of the different targets for realignment and their association with outcomes (both patients-reported outcomes and complications), selection of upper and lower instrumented vertebrae, and the latest innovation in preoperative planning for deformity surgery.

Sarcopenia at the upper instrumented vertebra is more significantly associated with proximal junctional kyphosis after long fusion for adult spinal deformity surgery than osteopenia

Proximal junctional kyphosis (PJK) is a major mechanical complication after adult spinal deformity (ASD) surgery, and is multifactorial. Osteopenia and sarcopenia are patient risk factors, but it has not yet been well-documented which of them is the more significant risk factor. We retrospectively studied patients older than 50 years who underwent ASD surgery from the lower thoracic spine to the pelvis. In addition to patient demographic data and pre- and post-operative radiographic sagittal parameters (PI: pelvic incidence; LL: lumbar lordosis; SVA: sagittal vertical axis; PT: pelvic tilt), Hounsfield unit (HU) values on preoperative computed tomography and cross sectional area (CSA) and fatty infiltration ratio (FI%) of the paraspinal musculature (PSM) on preoperative magnetic resonance image were measured from the upper-instrumented vertebra (UIV) to UIV + 2 and averaged. PJK was observed in 11 of 29 patients. There was no statistical difference between the patients with and without PJK in age at surgery, sex, body mass index, bone mineral density, preoperative PI-LL, SVA, PT, postoperative PI-LL, SVA, PT, HU, and CSA. FI% in patients with PJK (25.0) was significantly higher than that (15.3) in patients without PJK (P = 0.001). Logistic regression analysis identified FI% of PSM as a significant independent factor of PJK (odds ratio, 1.973; 95% confidence interval, 1.290-5.554; P < 0.0001). After successful elimination of possible factors related to PJK other than sarcopenia and osteopenia, sarcopenia assessed by fatty degeneration of the PSM at the UIV was shown to be a more important factor than osteopenia for PJK after long fusion for ASD.

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.

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.

Risk factors of early complications after thoracic and lumbar spinal deformity surgery: a systematic review and meta-analysis

PURPOSE

To determine risk factors increasing susceptibility to early complications (intraoperative and postoperative within 6 weeks) associated with surgery to correct thoracic and lumbar spinal deformity.

METHODS

We systematically searched the PubMed and EMBASE databases for studies published between January 1990 and September 2021. Observational studies evaluating predictors of early complications of thoracic and lumbar spinal deformity surgery were included. Pooled odds ratio (OR) or standardized mean difference (SMD) with 95% confidence intervals (CI) was calculated via the random effects model.

RESULTS

Fifty-two studies representing 102,432 patients met the inclusion criteria. Statistically significant patient-related risk factors for early complications included neurological comorbidity (OR = 3.45, 95% CI 1.83-6.50), non-ambulatory status (OR = 3.37, 95% CI 1.96-5.77), kidney disease (OR = 2.80, 95% CI 1.80-4.36), American Society of Anesthesiologists score > 2 (OR = 2.23, 95% CI 1.76-2.84), previous spine surgery (OR = 1.98, 95% CI 1.41-2.77), pulmonary comorbidity (OR = 1.94, 95% CI 1.21-3.09), osteoporosis (OR = 1.60, 95% CI 1.17-2.20), cardiovascular diseases (OR = 1.46, 95% CI 1.20-1.78), hypertension (OR = 1.37, 95% CI 1.23-1.52), diabetes mellitus (OR = 1.84, 95% CI 1.30-2.60), preoperative Cobb angle (SMD = 0.43, 95% CI 0.29, 0.57), number of comorbidities (SMD = 0.41, 95% CI 0.12, 0.70), and preoperative lumbar lordotic angle (SMD = - 0.20, 95% CI - 0.35, - 0.06). Statistically significant procedure-related factors were fusion extending to the sacrum or pelvis (OR = 2.53, 95% CI 1.53-4.16), use of osteotomy (OR = 1.60, 95% CI 1.12-2.29), longer operation duration (SMD = 0.72, 95% CI 0.05, 1.40), estimated blood loss (SMD = 0.46, 95% CI 0.07, 0.85), and number of levels fused (SMD = 0.37, 95% CI 0.03, 0.70).

CONCLUSION

These data may contribute to development of a systematic approach aimed at improving quality-of-life and reducing complications in high-risk patients.

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.

The top 100 most-cited articles on adult spinal deformity: The most popular topics are still sagittal plane parameters and complications

Purpose

This study aimed to summarize the characteristics of the 100 most-cited articles on adult spinal deformity (ASD) and to analyze past and current research hotspots and trends.

Methods

Literature searches (from inception to 28 April 2022) using Web of Science databases were conducted to identify ASD-related articles. The top 100 most-cited articles were collected for further analysis. Meanwhile, author keywords from articles published in the last 5 years were selected for further analysis.

Results

The top 100 most-cited articles on ASD were selected from 3,354 papers. The publication year ranged from 1979 to 2017, and all papers were written in English. The citation count among them ranged from 100 to 1,145, and the mean citation number was 215.2. The foremost productive first author was Schwab F. University of Washington had the largest number of publications. The United States of America had the largest number of published articles (n = 84) in this field. Spine was the most popular journal. Complications were the most studied themes. The visualization analysis of author keywords from the literature in the recent 5 years showed that complications, sagittal plane parameters, and surgical techniques are still the research hotspots, and minimally invasive surgery will continue to develop rapidly.

Conclusion

Based on a comparative analysis of the results of bibliometric and visualization, complications and sagittal plane parameters are still the major topics of research at present and even later, and minimally invasive surgery has a growth trend in this field of ASD.

Risk factors for proximal junctional kyphosis after posterior long-segment internal fixation for chronic symptomatic osteoporotic thoracolumbar fractures with kyphosis

Background

This study aimed to analyze the risk factors for proximal junctional kyphosis (PJK) for patients with chronic symptomatic osteoporotic thoracolumbar fractures (CSOTLF) and kyphosis who underwent long-segment internal fixation.

Methods

We retrospectively reviewed the records of patients with CSOTLF complicated with kyphosis who underwent posterior multilevel internal fixation in our hospital between January 2013 and January 2020. The patients’ age, sex, body mass index (BMI), bone mineral density (BMD), smoking status, cause of injury, comorbidities, injury segments, and American Spinal Injury Association (ASIA) grading non-surgical data; posterior ligament complex (PLC) injury, upper and lower instrumented vertebral position (UIV and LIV, respectively), number of fixed segments surgical data, proximal junctional angle (PJA), sagittal vertebral axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) surgical indicators were collected. Patients were divided into postoperative PJK and non-PJK groups.

Results

This study included 90 patients; among them, 30 (31.58%) developed PJK postoperatively. All patients were followed up for > 24 months (mean 32.5 months). Univariate analysis showed significant differences in age, BMI, BMD, PLC injury, UIV, and LIV fixation position, number of fixation stages, and preoperative PJA, SVA, PI-LL, and SS between the two groups (P < 0.05). Additionally, no significant differences were observed in sex, smoking, cause of injury, complications, injury segment ASIA grade, and preoperative PT between the two groups (P > 0.05). Multifactorial logistic regression analysis showed that age > 70 years (OR = 32.279, P < 0.05), BMI > 28 kg/m² (OR = 7.876, P < 0.05), BMD T value < − 3.5 SD (OR = 20.836, P < 0.05), PLC injury (OR = 13.981, P < 0.05), and preoperative PI-LL > 20° (OR = 13.301, P < 0.05) were risk factors for PJK after posterior long-segment internal fixation in elderly patients with CSOTLF complicated with kyphosis.

Conclusion

CSOTLF patients undergoing posterior long segment internal fixation are prone to PJK, and age > 70 years, BMI > 28 kg/m2, BMD T value < − 3.5 SD, preoperative PI-LL > 20° and PLC injury may increase their risk.

Restoring Theoretically Optimal Lumbar Lordosis Deduced from Pelvic Incidence and Thoracic Kyphosis has Advantages to Decrease the Risk of Postoperative Mechanical Complications in Adult Spinal Deformity

Objective

To establish a regression formula for LL based on individual PI and TK in asymptomatic population aged over 50 years and evaluate its predictive power for the occurrence of postoperative mechanical complications in patients with adult spinal deformity (ASD).

Methods

A total of 178 asymptomatic adults were recruited for the study. The association between LL and PI, LL and TK, was investigated to establish a predictive formula for ideal LL based on PI and TK. Additionally, 93 ASD patients undergoing posterior correction surgery were retrospectively analyzed. The absolute value of the gap between postoperative actual LL and theoretical LL was defined as ΔLL. Patients were classified into two groups depending on the presence or absence of mechanical complications. The demographic and radiological data of patients were compared between the two groups.

Results

A significant association was found between LL and PI (r = 0.599, P &lt; 0.001), LL and TK (r = 0.523, P &lt; 0.001). A novel formula was developed as follows: LL = 0.7*PI + 0.4*TK + 1 (R2 = 0.524). In the validation cohort, 29 patients developed mechanical complications. Postoperative ΔLL (12.5 ± 7.6° vs. 7.0 ± 5.4°, P = 0.001) significantly increased the incidence of mechanical complications. The most appropriate threshold of ΔLL for predicting mechanical complications was 9.8°. For patients whose ΔLL were &lt;9.8° and &gt;9.8°, the incidence of mechanical complications was 19.4% and 54.8%, respectively.

Conclusion

Ideal lumbar lordosis should be matched for PI and TK. The developed prediction formula for LL based on PI and TK in asymptomatic adults may help surgeons to understand the mechanisms of lumbar alignment generation and predict occurrence of mechanical complications after ASD surgery.

Paraspinal muscle characteristics on MRI in degenerative lumbar spine with normal bone density, osteopenia and osteoporosis: a case-control study

Background

To investigate the difference of paraspinal muscles in patients with normal bone density, osteopenia and osteoporosis.

Methods

Patients undergoing surgery for lumbar spinal stenosis were included. Thirty-eight patients with osteoporosis were matched to patients with osteopenia and patients with normal bone density in a 1:1 manner according to WHO criteria. Dual-energy X-ray absorptiometry (DXA) scans and lumbar CT were performed preoperatively to measure the BMD of lumbar, femur and hip and HU values of L1-L4 respectively. The relative total cross-sectional area (rTCSA) and fat infiltration (FI) of multifidus (MF) and erector spinae (ES), and the relative functional CSA (rFCSA) of psoas major (PS) were measured at L4–5 and L5-S level on preoperative MRI.

Results

Osteoporotic patients showed lower BMI, higher MF FI and higher ES FI when compared with normal bone density group (25.57 ± 3.71 vs 27.46 ± 3.11; 0.38 ± 0.1 vs 0.32 ± 0.08; 0.33 ± 0.1 vs 0.28 ± 0.08; all adjusted p < 0.05). Both the MF FI and ES FI were significantly correlated with lumbar T-score (r = − 0.223, p < 0.05; r = − 0.208, p < 0.05) and the averaged lumbar HU value (r = − 0.305, p < 0.01; r = − 0.239, p < 0.05).

Conclusions

Osteoporosis and paraspinal muscle degeneration might interact with each other and coexist in patients with degenerative lumbar diseases. It is recommended that the paraspinal muscle degeneration should be considered simultaneously when finding a patient with low bone mass before surgery.

Radiographic outcomes and complications after L4 or L5 pedicle subtraction osteotomy for fixed sagittal malalignment in 102 adult spinal deformity patients with a minimum 2-year follow-up

PURPOSE

The objective of this retrospective study was to provide the radiographic outcomes and complications for pedicle subtraction osteotomy (PSO) performed at the low lumbar spine, i.e., L4 or L5 for ASD patients with fixed sagittal malalignment.

METHODS

ASD patients who underwent L4 or L5 PSO with a minimum 2-year follow-up were included. Preoperative and postoperative radiographs, and complications were collected. Radiographic analysis included lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), thoracic kyphosis (TK), sagittal vertical axis (SVA), spinal lordosis (SL) ratio and global tilt (GT) on standing long-cassette radiographs.

RESULTS

A total of 102 patients from 2 spinal centers were analyzed. 66 patients underwent PSO at L4 and 36 patients at L5. From preoperatively to the final follow-up, significant improvements occurred in LL (from - 31° to - 52°), SVA (from 13 to 5 cm), and GT (from 44° to 27°) (all, p < 0.05). 12 patients had transient neurological deficits, and 8 patients had persistent neurological deficit. 23 patients underwent revision for PJK (2), pseudarthrosis (10), neurological deficit (2), epidural hematoma (1), or deep surgical site infection (8). No PJK was observed in any of the patients with L5 PSO.

CONCLUSIONS

PSO at the level of L4 or L5 remains a challenging technique but with an acceptable rate of complications and revisions. It enables correction of fixed sagittal malalignment in ASD patients with a globally satisfactory outcome. In comparison with L4 PSO, L5 PSO patients did not show PJK as a mechanical complication. Distal lumbar PSO at the level of L5 may represent one of the factors that may help preventing the proximal junctional kyphosis complication.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

LEVEL OF EVIDENCE

III.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Factors influencing upper-most instrumented vertebrae selection in adult spinal deformity patients: qualitative case-based survey of deformity surgeons

Background

The decision upper-most instrumented vertebrae (UIV) in a multi-level fusion procedure can dramatically influence outcomes of corrective spine surgery. We aimed to create an algorithm for selection of UIV based on surgeon selection/reasoning of sample cases.

Methods

The clinical/imaging data for 11 adult spinal deformity (ASD) patients were presented to 14 spine deformity surgeons who selected the UIV and provided reasons for avoidance of adjacent levels. The UIV chosen was grouped into either upper thoracic (UT, T1-T6), lower thoracic (LT, T7-T12), lumbar or cervical. Disagreement between surgeons was defined as ≥3 not agreeing. We performed a descriptive analysis of responses and created an algorithm for choosing UIV then applied this to a large database of ASD patients.

Results

Surgeons agreed in 8/11 cases on regional choice of UIV. T10 was the most common UIV in the LT region (58%) and T3 was the most common UIV in the UT region (44%). The most common determinant of UIV in the UT region was proximal thoracic kyphosis and presence of coronal deformity. The most common determinant of UIV in the LT region was small proximal thoracic kyphosis. Within the ASD database (236 patients), when the algorithm called for UT fusion, patients fused to TL region were more likely to develop proximal junctional kyphosis (PJK) at 1 year post-operatively (76.9% vs. 38.9%, P=0.025).

Conclusions

Our algorithm for selection of UIV emphasizes the role of proximal and regional thoracic kyphosis. Failure to follow this consensus for UT fusion was associated with twice the rate of PJK.

Correlation of vertebral trabecular attenuation in Hounsfield units and the upper instrumented vertebra with proximal junctional failure after surgical treatment of degenerative lumbar disease

OBJECTIVE

The aim of this study was to investigate whether bone mineral density (BMD) measured in Hounsfield units (HUs) is correlated with proximal junctional failure (PJF).

METHODS

A retrospective study of 104 patients with adult degenerative lumbar disease was performed. All patients underwent posterior instrumented fusion of 4 or more segments and were followed up for at least 2 years. Patients were divided into two groups on the basis of whether they had mechanical complications of PJF. Age, sex ratio, BMI, follow-up time, upper instrumented vertebra (UIV), lower instrumented vertebra, and vertebral body osteotomy were recorded. The spinopelvic parameters were measured on early postoperative radiographs. The HU value of L1 trabecular attenuation was measured on axial and sagittal CT scans. Statistical analysis was performed to compare the difference of continuous and categorical variables. Receiver operating characteristic (ROC) curve analysis was used to obtain attenuation thresholds. A Kaplan-Meier curve and log-rank test were used to analyze the differences in PJF-free survival. Multivariate analysis via a Cox proportional hazards model was used to analyze the risk factors.

RESULTS

The HU value of L1 trabecular attenuation in the PJF group was lower than that in the control group (p < 0.001). The spinopelvic parameter L4-S1 lordosis was significantly different between the groups (p = 0.033). ROC curve analysis determined an optimal threshold of 89.25 HUs (sensitivity = 78.3%, specificity = 80.2%, area under the ROC curve = 0.799). PJF-free survival significantly decreased in patients with L1 attenuation ≤ 89.25 HUs (p < 0.001, log-rank test). When L1 trabecular attenuation was ≤ 89.25 HUs, PJF-free survival in patients with the UIV at L2 was the lowest, compared with patients with their UIV at the thoracolumbar junction or above (p = 0.028, log-rank test).

CONCLUSIONS

HUs could provide important information for surgeons to make a treatment plan to prevent PJF. L1 trabecular attenuation ≤ 89.25 HUs measured by spinal CT scanning could predict the incidence of PJF. Under this condition, the UIV at L2 significantly increases the incidence of PJF.

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

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

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

OBJECTIVES

This aim of this study is to evaluate the prevalence of PJK and PJF in patients who underwent circumferential minimally invasive surgery (cMIS) for ASD.

METHODS

A prospective database of patients who underwent cMIS correction of ASD from November 2006 to July 2018 was queried. PJK was defined as angle > 10° and at least 10° greater than the baseline when measuring UIV to UIV + 2. PJF was defined as any type of symptomatic PJK which required surgery. Pre-op, latest and delta SVA and PI-LL mismatch were compared between patients with PJK and without. Only patients instrumented at 4 or more levels with full length 36″ films and a minimum 2-year follow-up were included.

RESULTS

A total of 184 patients met inclusion criteria for this study. Mean follow-up time was 85.2 months (24-158.9 months, SD 39.1). Mean age was 66 years (22-85 years). The mean number of operated levels was 6.9 levels (4-16 levels, SD 2.8). A total of 21 patients (10.8%) met PJK criteria. Only 10 (4.9%) were symptomatic (PJF) and underwent revision surgery. The other 11 patients remained asymptomatic. Comparing PJK to non-PJK patients, there was no statistically significant difference in the post-op SVA, delta SVA, post-op PI/LL and delta PI/LL between the two groups.

CONCLUSION

Our study would suggest that in the appropriately selected and well-optimized patient, CMIS deformity correction is associated with a low prevalence of PJK and PJF.

Effects of Restoration of Sagittal Alignment on Adjacent Segment Degeneration in Instrumented Lumbar Fusions

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

To investigate the effects of postoperative sagittal alignment on radiographic adjacent segment degeneration (ASD) after lumbar fusion surgery.

SUMMARY OF BACKGROUND DATA

ASD is one of inherent problems with fusion surgery. Many confounding factors are related to the development of ASD. Recently, sagittal alignment has been emphasized for its significance on ASD.

METHODS

Seventy-three patients who underwent four-level lumbar fusion surgery (L2-S1) were divided into two groups according to postoperative sagittal alignment (pelvic incidence-lumbar lordosis [PI-LL] ≥ or <9°): 44 patients (matched group, including 10 patients who underwent pedicle subtraction osteotomy [PSO] at L4) and 29 patients (mismatched group). The general demographics, radiographic parameters, and clinical outcomes were recorded. Preoperative disc degeneration at L1-2 was evaluated by Pfirrmann grade and Kellgren-Lawrence (K-L) grade. Disc degeneration at L1-2 was evaluated by the K-L grade on 2-year postoperative X-rays.

RESULTS

The incidence of radiographic ASD (11 [25%] vs. 16 patients [55%], P = 0.02) and Oswestry Disability Index (ODI) scores (36.9 ± 19.9 vs. 49.4 ± 20.7, P = 0.015) at postoperative 2 years were significantly higher in the mismatched group. There were no significant differences in other demographic and radiographic parameters between the two groups. On subgroup analysis between 10 PSO patients and the mismatched group, the mismatched group showed a higher incidence of radiographic ASD (16 [55%] vs. 1 patient [10%], P = 0.041) and worse ODI scores (49.7 ± 20.5 vs. 39.0 ± 20.7, P = 0.040). Preoperative Pfirrmann grade at L1-2 (odds ratio [OR] = 4.191, 95% confidence interval [CI]: 1.754-10.013, P = 0.001) and postoperative PI-LL mismatch (OR = 4.890, 95% CI: 1.550-15.427, P = 0.007) showed significant relationships with the development of radiographic ASD at postoperative 2 years.

CONCLUSION

The restoration of optimal sagittal alignment, even with PSO, may provide a protective effect on the development of radiographic ASD, although the preoperative disc degeneration grade was a risk factor for radiographic ASD.

LEVEL OF EVIDENCE

3.

Ideal sagittal profile restoration and ideal lumbar apex positioning play an important role in postoperative mechanical complications after a lumbar PSO

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVE

To determine the influence of postoperative ideal lordosis distribution and ideal sagittal harmony on mechanical complications in patients undergoing one-level lumbar pedicle subtraction osteotomy (L-PSO). Many variables have been associated with mechanical complications after L-PSO. However, the impact of restoring the ideal inflexion point, lumbar apex, and sagittal shape is still underexplored.

METHODS

Analyzed risk factors were: age and patient-related variables, PSO level, interbody cages, rod material/diameter, number of rods, upper instrumented vertebra, lower instrumented vertebra, PI-LL mismatch, global tilt (GT), postoperative level of lumbar apex (LApex), postoperative level of inflexion point (InfxP), and postoperative type of Roussouly sagittal profile (R-type). These last variables were compared to ideal (based on pelvic incidence). Univariate and multivariate analyses were performed to identify risks for mechanical complications with a minimum 2-year follow-up.

RESULTS

A total of 87 patients were included. Mean follow-up was 4.5 ± 1.7 years. 40.2% of the patients suffered postoperative mechanical complications (7 PJK, 4 PJF, 18 pseudoarthrosis/rod breakage, 6 screw pullout). Mean time for complications was 584 ± 416 days from surgery. Univariate analysis showed that age (63 vs 57 years; P = 0.04), BMI (28.1 vs 25.9; P = 0.024), preoperative-GT (50.7° vs 38.7°; P < 0.001), postoperative-GT (28.9° vs 23.4°; P = 0.018), postoperative LApex location mismatched from ideal (77.8% vs 22.2%; P = 0.036), and postoperative R-type mismatched from ideal (67.6% vs 22.6%; P < 0.001) were significantly related to mechanical complications. The independent factors selected by multivariate analysis were: postoperative R-type mismatched from ideal OR 11.3 (95% CI   3.9-32.6; P < 0.001), age OR 1.05 (95% CI 1-1.1; P = 0.03), and LApex matching OR 0.5 (95% CI 0.27-0.97; P = 0.04). The further the LApex was from its ideal position, the higher the risk of mechanical complications (P = 0.036).

CONCLUSIONS

Over other multiple suspected risk factors, proper lumbar apex position and ideal sagittal shape restoration played an important role in postoperative mechanical complications after L-PSO.

LEVEL OF EVIDENCE

III.

Local Mechanical Environment and Spinal Trabecular Volumetric Bone Mineral Density Measured by Quantitative Computed Tomography: A Study on Lumbar Lordosis

OBJECTIVE

There have been some reports on the association between spinal balance parameters and regional bone mineral density (BMD), but the results are controversial. The purpose of this study is to evaluate the relationship between spinopelvic parameters and regional volumetric BMDs (vBMDs) measured by quantitative computed tomography (QCT) in the lumbosacral region of patients undergoing lumbar fusion surgery.

METHODS

The data of consecutive patients undergoing posterior lumbar spinal fusion with preoperative computed tomography was reviewed. QCT measurements were conducted in L1-S1 vertebral trabecular bone. The associations between spinopelvic sagittal parameters and vBMDs were evaluated. Multivariate analyses adjusted with age, gender, race, and body mass index were conducted with vBMD as the response variable.

RESULTS

A total of 144 patients were included in the final analyses. Mean age (± standard deviation) was 65.4 ± 11.8 years. Mean vBMD in L1 (± standard deviation) was 118.3 ± 37.4 mg/cm³. After adjusting by cofactors, lumbar lordosis was negatively associated with vBMDs in all levels from L1 to L5 (% regression coefficients and adjusted R² values: L1, -0.438, 0.268; L2, -0.556, 0.296; L3, -0.608, 0.362; L4, -0.554, 0.228; L5, -0.424, 0.194), but not in S1. Sacral slope was negatively associated with vBMD only at L4 (% coefficient, -0.588; R², 0.208). Other parameters were not significantly associated with vBMDs at any levels.

CONCLUSIONS

Higher lumbar lordosis was associated with lower vBMDs in all lumbar spine levels. Our results suggest that BMD is affected not only by metabolic factors but also by the mechanical environment. Further longitudinal studies are needed to elucidate this effect of vBMD on clinical outcomes.