Radiographic Predictors for Mechanical Failure After Adult Spinal Deformity Surgery: A Retrospective Cohort Study in 138 Patients

Spinopelvic fixation failure in the adult spinal deformity population: systematic review and meta-analysis

INTRODUCTION

Despite modern fixation techniques, spinopelvic fixation failure (SPFF) after adult spinal deformity (ASD) surgery ranges from 4.5 to 38.0%, with approximately 50% requiring reoperation. Compared to other well-studied complications after ASD surgery, less is known about the incidence and predictors of SPFF.

AIMS/OBJECTIVES

Given the high rates of SPFF and reoperation needed to treat it, the purpose of this systematic review and meta-analysis was to report the incidence and failure mechanisms of SPF after ASD surgery.

MATERIALS/METHODS

The literature search was executed across four databases: Medline via PubMed and Ovid, SPORTDiscus via EBSCO, Cochrane Library via Wiley, and Scopus. Study inclusion criteria were patients undergoing ASD surgery with spinopelvic instrumentation, report rates of SPFF and type of failure mechanism, patients over 18 years of age, minimum 1-year follow-up, and cohort or case-control studies. From each study, we collected general demographic information (age, gender, and body mass index), primary/revision, type of ASD, and mode of failure (screw loosening, rod breakage, pseudarthrosis, screw failure, SI joint pain, screw protrusion, set plug dislodgment, and sacral fracture) and recorded the overall rate of SPF as well as failure rate for each type. For the assessment of failure rate, we required a minimum of 12 months follow-up with radiographic assessment.

RESULTS

Of 206 studies queried, 14 met inclusion criteria comprising 3570 ASD patients who underwent ASD surgery with pelvic instrumentation (mean age 65.5 ± 3.6 years). The mean SPFF rate was 22.1% (range 3-41%). Stratification for type of failure resulted in a mean SPFF rate of 23.3% for the pseudarthrosis group; 16.5% for the rod fracture group; 13.5% for the iliac screw loosening group; 7.3% for the SIJ pain group; 6.1% for the iliac screw group; 3.6% for the set plug dislodgement group; 1.1% for the sacral fracture group; and 1% for the iliac screw prominence group.

CONCLUSION

The aggregate rate of SPFF after ASD surgery is 22.1%. The most common mechanisms of failure were pseudarthrosis, rod fracture, and iliac screw loosening. Studies of SPFF remain heterogeneous, and a consistent definition of what constitutes SPFF is needed. This study may enable surgeons to provide patient specific constructs with pelvic fixation constructs to minimize this risk of failure.

Anterior Column Realignment Through Open Pre-posterior Release-Anterior-Posterior Fusion Versus Hybrid Minimally Invasive-Anterior-Posterior Fusion for Dynamic Sagittal Imbalance of the Spine

STUDY DESIGN

Retrospective comparative study.

OBJECTIVES

To investigate the clinical and radiological outcomes after anterior column realignment (ACR) through pre-posterior release-anterior-posterior surgery (PAP) and minimally invasive surgery -lateral lumbar interbody fusion (MIS-LLIF) using hybrid anterior-posterior surgery (AP).

METHODS

A total of 91 patients who underwent ACR with long fusions from T10 vertebra to the sacropelvis with a follow-up period of at least 2 years after corrective surgery for adult spinal deformity were included and divided into two groups by surgical method: AP and PAP. AP was performed in 26 and PAP in 65 patients. Clinical outcomes and radiological parameters were investigated and compared. A further comparison was conducted after propensity score matching between the groups.

RESULTS

The more increase of LL and decrease of PI-LL mismatch were observed in the PAP group than in the AP group postoperatively. After propensity score matching, total operation time and intraoperative bleeding were greater, and intensive care unit care and rod fracture were more frequent in the PAP group than in the AP group with statistical significance. Reoperation rate was higher in PAP (29.2%) than in AP (16.7%) without statistical significance.

CONCLUSIONS

PAP provides a more powerful correction for severe sagittal malalignment than AP procedures. AP results in less intraoperative bleeding, operation time, and postoperative complications. Therefore, this study does not suggest that one treatment is superior to the other.

LEVEL OF EVIDENCE

III.

Does the interfacing angle between pedicle screws and support rods affect clinical outcomes after posterior thoracolumbar fusion? A retrospective clinical study

BACKGROUND CONTEXT

Proper alignment and tightening of the pedicle screw/rod assembly after instrumented posterior fusion of the lower spine is known to be crucial in order to achieve satisfactory clinical results. Such interfacing angle mismatches indicate stress overloading of the implant system.

PURPOSE

The objective of this study is to investigate the incidence of postoperative screw/rod interfacing angle mismatch and to analyze the impact of mismatches on clinical outcome in terms of (1) revision surgery, (2) adjacent segment degeneration (ASD), and (3) pain.

STUDY DESIGN

This is a monocentric retrospective observational study.

PATIENT SAMPLE

Patients underwent fusion surgery with pedicle screw/rod systems for predominantly degenerative pathologies.

OUTCOME MEASURES

Pedicle screw/rod interfacing angle mismatch (mismatch is the angular deviation from 90° formed by the rod axis and the pedicle screw head axis as an indicator for missing form-fit) revision rate, ASD at the immediately adjacent cranial segment and VAS pain.

METHODS

Revision refers to subsequent procedures in which all or part of the original implant configuration is changed or removed. Radiographic parameters are evaluated using a/p and lateral radiographs at final follow-up. The interfacing angle mismatch between pedicle screw and rod is measured as the angle between two parallel lines on either side of each pedicle screw head and a line laterally along the associated rod. Multiple comparisons are counteracted by Bonferroni correction, adjusted significance level is at *p<.01.

RESULTS

Pedicle screw and rod interfacing angle mismatch was found in 171/406 (42.1%) of patients undergoing fusion surgery, affecting 613/3016 (20.3%) screws. The overall revision incidence was 11.8% (48/406), and a new ASD occurred in 12.1% of all patients (49/406) with an average follow-up of 5 years. Mean VAS pain score at final follow-up was 2.0. Comparison of the two groups with and without mismatches revealed statistically significantly higher (1) numbers of revision procedures performed (26.9% vs 0.9%), (2) numbers of new ASD developed (27.5% vs 3.8%), and (3) higher VAS pain scores (2.8/10 vs 1.4/10) for cases with mismatch. When comparing patients who underwent intraoperative correction and/or reduction with those who did not, statistically significant more screw mismatches (63.4% vs 39.7%) and revision surgeries (29.3% vs 9.9%) were noted in patients who had these forceful maneuvers.

CONCLUSIONS

Pedicle screw/rod interfacing angle mismatch is a frequent occurrence after fusion surgery. Mismatches indicate that the construct was assembled under mechanical stress. All preventable mechanical stresses, for example, unintentional uncontrolled forces on the instrumentation, should be avoided as much as possible, as they can negatively influence the clinical outcome.

The lower Osteotomy Level is Associated With Decreased Revision Surgery Due to Mechanical Complications After Three-Column Osteotomy in Patients With Adult Spinal Deformity: A Multi-Institutional Retrospective Study

STUDY DESIGN

A multi-institutional retrospective study.

OBJECTIVES

To investigate risk factors of mechanical failure in three-column osteotomy (3COs) in patients with adult spinal deformity (ASD), focusing on the osteotomy level.

METHODS

We retrospectively reviewed 111 patients with ASD who underwent 3COs with at least 2 years of follow-up. Radiographic parameters, clinical data on early and late postoperative complications were collected. Surgical outcomes were compared between the low-level osteotomy group and the high-level osteotomy group: osteotomy level of L3 or lower group (LO group, n = 60) and osteotomy of L2 or higher group (HO group, n = 51).

RESULTS

Of the 111 patients, 25 needed revision surgery for mechanical complication (mechanical failure). A lower t-score (odds ratio [OR] .39 P = .002) and being in the HO group (OR 4.54, P = .03) were independently associated with mechanical failure. In the analysis divided by the osteotomy level (LO and HO), no difference in early complications or neurological complications was found between the two groups. The rates of overall mechanical complications, rod failure, and mechanical failure were significantly higher in the HO group than in the LO group. After propensity score matching, mechanical complications and failures were still significantly more observed in the HO group than in the LO group (P = .01 and .029, respectively).

CONCLUSIONS

A lower t-score and osteotomy of L2 or higher were associated with increased risks of mechanical failure. Lower osteotomy was associated with better correction of sagittal balance and a lower rate of mechanical complications.

Decompression Alone in the Setting of Adult Degenerative Lumbar Scoliosis and Stenosis: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic review and meta-analysis.OBJECTIVESSurgical decompression alone for patients with neurogenic leg pain in the setting of degenerative lumbar scoliosis (DLS) and stenosis is commonly performed, however, there is no summary of evidence for outcomes.

METHODS

A systematic search of English language medical literature databases was performed for studies describing outcomes of decompression alone in DLS, defined as Cobb angle >10˚, and 2-year minimum follow-up. Three outcomes were examined: 1) Cobb angle progression, 2) reoperation rate, and 3) ODI and overall satisfaction. Data were pooled and weighted averages were calculated to summarize available evidence.

RESULTS

Across 15 studies included in the final analysis, 586 patients were examined. Average preoperative and postoperative Cobb angles were 17.6˚ (Range: 12.7 - 25˚) and 18.0 (range 14.1 - 25˚), respectively. Average change in Cobb angle was an increase of 1.8˚. Overall rate of reoperation ranged from 3 to 33% with an average of 9.7%. Average ODI before surgery, after surgery, and change in scores were 56.4%, 27.2%, and an improvement of 29% respectively. Average from 8 studies that reported patient satisfaction was 71.2%.

CONCLUSIONS

Current literature on decompression alone in the setting of DLS is sparse and is not high quality, limited to patients with small magnitude of lumbar coronal Cobb angle, and heterogenous in the type of procedure performed. Based on available evidence, select patients with DLS who undergo decompression alone had minimal progression of Cobb angle, relatively low reoperation rate, and favorable patient-reported outcomes.

The Impact of Global Alignment and Proportion Score and Bracing on Proximal Junctional Kyphosis in Adult Spinal Deformity

STUDY DESIGN

Retrospective chart review.

OBJECTIVE

The goal of this study is to examine the relationship between global alignment and proportion (GAP) score and postoperative orthoses with likelihood of developing proximal junctional kyphosis (PJK).

METHODS

Patients who underwent thoracic or lumbar fusions of ≥4 levels for adult spinal deformity (ASD) with 1-year post-operative alignment x-rays were included. Chart review was conducted to determine spinopelvic alignment parameters, PJK, and reoperation.

RESULTS

A total of 81 patients were included; baseline and 1-year postoperative alignment did not differ between patients with and without PJK. There was no PJK in 53.1%, 29.6% had PJK from 10-20°, and 17.3% had severe PJK over 20° (sPJK). At baseline, 80% of patients had severely disproportioned GAP, 13.75% moderate, 6.25% proportioned. GAP improved across the population, but improved GAP was not associated with sPJK. Greater correction of the upper instrumented vertebra to pelvic angle (UIV-PA) was associated with a larger PJK angle (PJKA) change (R = -0.28) as was the 1 year T1-upper instrumented vertebra (T1-UIV) angle (R = 0.30), both P < .05. GAP change was not correlated with PJKA change. Postoperative orthoses were used in 46% of patients and did not impact sPJK.

CONCLUSIONS

There was no correlation between PJK and GAP or change in GAP. Greater correction of UIV-PA and larger postop T1-UIV was associated with greater PJKA change; suggesting that the greater alignment correction led to greater likelihood of failure. Postoperative orthoses had no impact on PJK.

Biomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery

Background: Posterior long spinal fusion was the common procedure for adult spinal deformity (ASD). Although the application of sacropelvic fixation (SPF), the incidence of pseudoarthrosis and implant failure is still high in long spinal fusion extending to lumbosacral junction (LSJ). To address these mechanical complications, advanced SPF technique by multiple pelvic screws or multirod construct has been recommended. This was the first study to compare the biomechanical performance of combining multiple pelvic screws and multirod construct to other advanced SPF constructs for the augmentation of LSJ in long spinal fusion surgery through finite element (FE) analysis.

Methods: An intact lumbopelvic FE model based on computed tomography images of a healthy adult male volunteer was constructed and validated. The intact model was modified to develop five instrumented models, all of which had bilateral pedicle screw (PS) fixation from L1 to S1 with posterior lumbar interbody fusion and different SPF constructs, including No-SPF, bilateral single S2-alar-iliac (S2AI) screw and single rod (SS-SR), bilateral multiple S2AI screws and single rod (MS-SR), bilateral single S2AI screw and multiple rods (SS-MR), and bilateral multiple S2AI screws and multiple rods (MS-MR). The range of motion (ROM) and stress on instrumentation, cages, sacrum, and S1 superior endplate (SEP) in flexion (FL), extension (EX), lateral bending (LB), and axial rotation (AR) were compared among models.

Results: Compared with intact model and No-SPF, the ROM of global lumbopelvis, LSJ, and sacroiliac joint (SIJ) was decreased in SS-SR, MS-SR, SS-MR, and MS-MR in all directions. Compared with SS-SR, the ROM of global lumbopelvis and LSJ of MS-SR, SS-MR, and MS-MR further decreased, while the ROM of SIJ was only decreased in MS-SR and MS-MR. The stress on instrumentation, cages, S1-SEP, and sacrum decreased in SS-SR, compared with no-SPF. Compared with SS-SR, the stress in EX and AR further decreased in SS-MR and MS-SR. The most significantly decreased ROM and stress were observed in MS-MR.

Conclusion: Both multiple pelvic screws and multirod construct could increase the mechanical stability of LSJ and reduce stress on instrumentation, cages, S1-SEP, and sacrum. The MS-MR construct was the most adequate to reduce the risk of lumbosacral pseudarthrosis, implant failure, and sacrum fracture. This study may provide surgeons with important evidence for the application of MS-MR construct in the clinical settings.

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.

Association between sagittal alignment and loads at the adjacent segment in the fused spine: a combined clinical and musculoskeletal modeling study of 205 patients with adult spinal deformity

PURPOSE

Sagittal malalignment is a risk factor for mechanical complications after surgery for adult spinal deformity (ASD). Spinal loads, modulated by sagittal alignment, may explain this relationship. The aims of this study were to investigate the relationships between: (1) postoperative changes in loads at the proximal segment and realignment, and (2) absolute postoperative loads and postoperative alignment measures.

METHODS

A previously validated musculoskeletal model of the whole spine was applied to study a clinical sample of 205 patients with ASD. Based on clinical and radiographic data, pre-and postoperative patient-specific alignments were simulated to predict loads at the proximal segment adjacent to the spinal fusion.

RESULTS

Weak-to-moderate associations were found between pre-to-postop changes in lumbar lordosis, LL (r =  - 0.23, r =  - 0.43; p < 0.001), global tilt, GT (r = 0.26, r = 0.38; p < 0.001) and the Global Alignment and Proportion score, GAP (r = 0.26, r = 0.37; p < 0.001), and changes in compressive and shear forces at the proximal segment. GAP score parameters, thoracic kyphosis measurements and the slope of upper instrumented vertebra were associated with changes in shear. In patients with T10-pelvis fusion, moderate-to-strong associations were found between postoperative sagittal alignment measures and compressive and shear loads, with GT showing the strongest correlations (r = 0.75, r = 0.73, p < 0.001).

CONCLUSIONS

Spinal loads were estimated for patient-specific full spinal alignment profiles in a large cohort of patients with ASD pre-and postoperatively. Loads on the proximal segments were greater in association with sagittal malalignment and malorientation of proximal vertebra. Future work should explore whether they provide a causative mechanism explaining the associated risk of proximal junction complications.

Is preoperative S-albumin associated to postoperative complications and readmission in patients with adult spinal deformity: a prospective analysis of 128 patients using the Spine AdVerse Event Severity (SAVES) system

PURPOSE

To assess the association between preoperative S-albumin and postoperative outcome following adult spinal deformity (ASD) surgery.

METHODS

All patients undergoing ASD surgery from February 1, 2017 and January 31, 2018 at a single quaternary referral center were prospectively included. Adverse events (AE) during admission were assessed using the Spine AdVerse Events Severity (SAVES) system. Based on preoperative S-albumin, patients were categorized as "normal" or "abnormal" and compared regarding postoperative outcome, adverse events (AEs), 30- and 90-day readmission, revision surgery, and mortality.

RESULTS

A total of 128 patients aged ≥ 18 years were included, and S-albumin was available in 88%. Of these, 73% (n = 93) were classified as "normal", 16% (n = 20) as "abnormal", and 12% (n = 15) as "missing". The "normal" albumin group had less comorbidity burden [ASA score 2 (2, 3) vs 3 (2, 3), p = 0.011], higher hemoglobin levels (8.4 (± 0.9) mmol/L vs 7.4 (± 1.1) mmol/L, p < 0.001), and higher S-albumin (38.9 (± 2.7) g/L vs 31.9 (± 4.4) g/L, < 0.001). The rate of 90-day readmission was significantly increased in the "abnormal" group (65% vs 36%), corresponding to a relative risk increase of 1.25 (95% CI 1.02-1.52, p = 0.029). Similar increased risks were found in subsequent logistic regression analyses, although results were not significant in multivariable analysis (p = 0.102). Comparing remaining outcome parameters, point estimates revealed increased AEs, 30-day readmission, and revision in the "abnormal" albumin group, although effects did not reach statistical significance.

CONCLUSIONS

In a prospective, consecutive, single-center cohort of 128 patients undergoing ASD surgery, we found a significant association between "abnormal" preoperative S-albumin and increased 90-day readmission. Furthermore, although the findings were not statistically significant, we did find that AEs, 30-day readmission, and revision were numerically more frequent in the "abnormal" group, suggesting an expected tendency that should be further investigated. We conclude that nutritional status prior to ASD surgery could be important to consider and suggest validation in larger prospective cohorts.

LEVEL OF EVIDENCE

Prognostic II.

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

STUDY DESIGN

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

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

Understanding "Kyphosis" and "Lordosis" for Sagittal Balancing in Two Common Standing Postures

STUDY DESIGN

Cross-sectional radiographic comparison study.

OBJECTIVE

The aim of this study was to understand whole-body balancing in directed and natural standing postures, through comparison of kypholordotic ratios on whole-body radiographs of young, healthy subjects.

SUMMARY OF BACKGROUND DATA

Recent studies highlighted the importance of understanding whole-body balancing, proposing the use of the more physiological natural standing posture, together with the conventional directed standing posture, for imaging.

METHODS

Sixty healthy, 21-year-old subjects (36 males, 24 females) were recruited. EOS whole-body radiographs of subjects in directed and natural standing postures were obtained. Radiographic parameters compared include C2-sagittal vertical axis (C2-SVA), C7-SVA, C2-7-SVA, global cervical angles (C0-T1 and C2-C7), regional cervical angles (C0-C2, C2-C4, C4-C7), T1-slope, global thoracic angles (T1-T12 and T1-inflection vertebra [Inf]), thoracolumbar angle (T11-L2), global lumbar angles (T12-S1 and Inf-S1), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), spinocoxa angle (SCA), and femoral alignment angle (FAA). Kypholordotic ratios of T1-12/T12-S1, T1-Inf/Inf-S1, Tl-Inf/SCA, and (T1-Inf + FAA)/(T1-slope + SCA) were calculated and compared.

RESULTS

Compared to directed standing, natural standing has greater C2-SVA and C7-SVA, more lordotic global and regional cervical angles (except C0-2 angle), higher T1-slope, larger T1- T12 and T1-Inf kyphotic angles, smaller T12-S1 and Inf-S1 lordotic angles, larger PT, more lordotic SCA, and smaller SS and FAA angles. T1-12/T12-S1 and T1-Inf/Inf-S1 ratios in natural standing, and (Tl-Inf + FAA)/(T1-slope + SCA) ratio in both postures approximate 1. There were significant differences between postures for Tl-l2/Tl2-Sl, Tl-Inf/Inf-Sl and Tl-Inf/SCA ratios.

CONCLUSION

Whole-body balancing requires understanding of the balance between kyphosis and lordosis, which varies with the posture of patients. Analysis of kypholordotic ratios obtained in this study allude to the importance of performing whole-body imaging in the directed standing posture, and whole-spine or whole-body imaging in the natural standing posture, so as to fully understand spinal and whole body balancing for spinal realignment surgeries.Level of Evidence: Level 3.

Which sagittal evaluation system can effectively predict mechanical complications in the treatment of elderly patients with adult degenerative scoliosis? Roussouly classification or Global Alignment and Proportion (GAP) Score

Background

To achieve the proper sagittal alignment, previous studies have developed different assessment systems for adult degenerative scoliosis (ADS) which could help the spine surgeon in making treatment strategies. The purpose of our study is to evaluate whether Roussouly classification or global alignment and proportion (GAP) score is more appropriate in the prediction of mechanical complications after surgical treatment of ADS.

Methods

ADS patients who received long segmental fusion in the treatment during the period from December 2016 to December 2018 were evaluated in this study. Basic information and radiologic measurements were collected for analysis. Patients were divided into two groups according to occurrence or absence of mechanical complications for comparison. Mechanical complications included proximal junctional kyphosis (PJK), proximal junctional failure (PJF). GAP categories divided GAP score into proportioned spinopelvic position, moderately disproportioned position, and severely disproportioned position according to the cut-off values. The correlation between evaluation systems and mechanical complications was analyzed through a logistic regression model via stepwise backward elimination based on the Wald statistics. Receiver operator characteristic (ROC) curve was used to determine the predictability of the evaluation systems in the occurrence of mechanical complications and calculate their cut-off value. Area under the curve (AUC) was used to evaluate the validity of the thresholds.

Results

A total of 80 patients were included in this study. There were 41 patients in mechanical complication group and 39 patients in no mechanical complication group. GAP score (P = 0.008) and GAP categories (P = 0.007) were positively correlated with mechanical complications; Roussouly score was negatively correlated with mechanical complications (P = 0.034); GAP score was positively correlated with PJK (P = 0.021); Roussouly score was negatively correlated with implant-related complications (P = 0.018); GAP categories were correlated with implant loosening (P = 0.023). Results of ROC showed that GAP score was more effective in predicting PJK (AUC = 0.863) and PJF (AUC = 0.724) than Roussouly score; GAP categories (AUC = 0.561) was more effective than GAP score (AUC = 0.555) in predicting implant-related complications.

Conclusions

Roussouly classification could only be a rough estimate of optimal spinopelvic alignment. Quantitative parameters in GAP score made it more effective in predicting mechanical complications, PJK and PJF than Roussouly classification.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-021-02786-8.

Lordosis Distribution Index in Short-Segment Lumbar Spine Fusion - Can Ideal Lordosis Reduce Revision Surgery and Iatrogenic Deformity?

OBJECTIVE

The demand for spinal fusion is increasing, with concurrent reports of iatrogenic adult spinal deformity (flatback deformity) possibly due to inappropriate lordosis distribution. This distribution is assessed using the lordosis distribution index (LDI) which describes the upper and lower arc lordosis ratio. Maldistributed LDI has been associated to adjacent segment disease following interbody fusion, although correlation to later-stage deformity is yet to be assessed. We therefore aimed to investigate if hypolordotic lordosis maldistribution was associated to radiographic deformity-surrogates or revision surgery following instrumented lumbar fusion.

METHODS

All patients undergoing fusion surgery ( ≤ 4 vertebra) for degenerative lumbar diseases were retrospectively included at a single center. Patients were categorized according to their postoperative LDI as: "normal" (LDI 50-80), "hypolordotic" (LDI < 50), or "hyperlordotic" (LDI > 80).

RESULTS

We included 149 patients who were followed for 21 ± 14 months. Most attained a normally distributed lordosis (62%). The hypolordotic group had increased postoperative pelvic tilt (PT) (p < 0.001), pelvic incidence minus lumbar lordosis (PI-LL) mismatch (p < 0.001) and decreased global lordosis (p = 0.007) compared to the normal group. Survival analyses revealed a significant difference in revision surgery (p = 0.03), and subsequent multivariable logistic regression showed increased odds of 1-year revision in the hypolordotic group (p = 0.04). There was also a negative, linear correlation between preoperative pelvic incidence (PI) and postoperative LDI (p < 0.001).

CONCLUSION

In patients undergoing instrumented lumbar fusion surgery, hypolordotic lordosis maldistribution (LDI < 50) was associated to increased risk of revision surgery, increased postoperative PT and PI-LL mismatch. Lordosis distribution should be considered prior to spinal fusion, especially in high PI patients.

Partial Intraoperative Global Alignment and Proportion Scores Do Not Reliably Predict Postoperative Mechanical Failure in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective radiographic review.

OBJECTIVES

The Global Alignment and Proportion (GAP) score allows sagittal plane analysis for deformity patients and may be predictive of mechanical complications. This study aims to assess the effectiveness of predicting mechanical failure based on partial intraoperative GAP (iGAP) scores.

METHODS

A retrospective radiographic review was performed on 48 deformity patients between July 2015 to January 2017 with a 2-year follow-up. Using the same methodology as the original GAP study, the partial iGAP score was calculated with the sum of the scores for age, relative lumbar lordosis (RLL), and lordosis distribution index (LDI). Therefore, the iGAP score (0-7) was grouped into proportional (0-2), mildly disproportionate (3-5), and severely disproportionate (6-7). Logistic regression was performed to assess the ability of the partial iGAP score to predict postoperative mechanical failure.

RESULTS

The mean iGAP for patients with a mechanical failure was 3.54, whereas the iGAP for those without a mechanical failure was 3.46 (P = .90). The overall mechanical failure rate was 27.1%. The mechanical failures included 8 proximal junctional kyphosis, 7 rod fractures, and 1 rod slippage from the distal end of the construct. Logistic regression analysis revealed that the partial iGAP score was not able to predict postoperative mechanical failure (χ2 = 1.4; P = .49).

CONCLUSION

The iGAP scores for RLL or LDI did not show any significant correlation to postoperative mechanical failure. Ultimately, the proposed partial iGAP score did not predict postoperative mechanical failure and thus, cannot be used as an intraoperative alignment assessment to avoid postoperative mechanical complications.

Fulcrum to Generate Maximum Extension of the Spine and Hip-Proposing A New Strategy using EOS Imaging for Patient-specific Assessment of Degenerated Lumbar Spines

STUDY DESIGN

A retrospective, radiographic comparative study conducted in a single academic institution.

OBJECTIVE

This study aims to compare fulcrum extension with conventional extension imaging to determine maximum "hip lordosis" (HL), an important novel patient-specific parameter in spinal realignment surgery, as well as understand the extension capabilities of the lower lumbar spine, which together, are key contributors to whole-body balancing.

SUMMARY OF BACKGROUND DATA

Recent literature recognizes the hip as an important contributor to whole-body lordosis beyond a compensator for spinal imbalance.

METHODS

Patients >45 years' old with mechanical low back pain due to degenerative spinal conditions were included and grouped based on the imaging performed-fulcrum or conventional extension. All imaging was performed using EOS under standardized instructions and visual aids. Radiographic parameters include global lumbar angle (GLA), inflexion-S1 (Inf-S1) angle, segmental lumbar angles, pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), femoral alignment angle (FAA), HL and spinocoxa angle (SCA). Unpaired t test was used to compare between radiographic parameters.

RESULTS

One hundred patients (40 males and 60 females, mean age 63.0 years) underwent either fulcrum or conventional extension EOS® imaging. Both groups had comparable baseline radiographic parameters. Fulcrum extension gave a larger mean GLA (-60.7° vs. -48.5°, P = 0.001), Inf-S1 angle (-58.8° vs. -48.8°, P = 0.003), SCA (-36.5° vs. -24.8°, P < 0.001), L4/5 and L5/S1 lordosis (-20.7° vs. -17.7°, P = 0.041, and -22.3° vs. -17.1°, P = 0.018, respectively), compared to conventional extension. PI, SS, PT, FAA, and HL were similar between both extension postures.

CONCLUSION

Fulcrum extension, compared to conventional extension, is better at generating lordosis in the lower lumbar spine, thus improving preoperative assessment of stiffness or instability of the lumbar spine. Both extension methods were equally effective at determining the patient-specific maximum HL to assess the flexibility and compensation occurring at the hip, potentially guiding surgical management of patients with degenerative spines.Level of Evidence: 3.

Surgical pathway proposal for severe paralytic scoliosis in adolescents with myelomeningocele

PURPOSE

The increased life expectancy of patients with myelomeningocele led to the necessity of new management for addressing complex spine deformities with severe pelvic obliquity. Tethered cord release (TCR) and spinal fusion were described as treatment options. However, nowadays, the surgical strategy is not well defined and high rates of mechanical failures and complications are reported. Our aim was to propose a new two-stage surgical pathway to treat a selected group of severe myelomeningocele scoliosis.

METHODS

This is a retrospective series of myelomeningocele scoliosis in paralytic adolescent patients treated with concurrent TCR and posterior spinal fusion (PSF), followed by delayed anterior fusion (ASF) through minimally invasive lateral approach. Inclusion criteria were as follows: evolutive scoliosis in tethered cord syndrome and paraplegia, main curve >70°, pelvic obliquity >20°, and age between 10 and 18 years. Clinical, surgical, and radiographic parameters were evaluated preoperatively and at a mean follow-up (FU) of 2.8 years.

RESULTS

Six patients out of 58 met the inclusion criteria and were included in the study (mean age 12.3 years old). The mean curve and pelvic obliquity correction were 68.8% and 82%, respectively. No loss of correction was recorded at FU. One case of cerebrospinal fluid leakage requiring revision surgery was recorded.

CONCLUSION

To the best of our knowledge, this is the first study proposing a two-stage surgical pathway for severe MMC spinopelvic deformity treatment. Concurrent TCR and PSF with delayed minimally invasive ASF permitted to minimize complications providing good fusion rates without loss of correction and implant failure.

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

STUDY DESIGN

Systematic review.

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Reducing revision rates following Pedicle Subtraction Osteotomy surgery: a single-center experience of trends over 7 years in patients with Adult Spinal Deformity

STUDY DESIGN

This is a single-center, retrospective study.

OBJECTIVE

To assess if implemented changes to clinical practice have reduced mechanical complications following pedicle subtraction osteotomy (PSO) surgery. Adult spinal deformity (ASD) is increasing in prevalence with concurrent increasing demands for surgical treatment. The most extensive technique, PSO, allows for major correction of rigid deformities. However, surgery-related complications have been reported in rates up to 77% and especially mechanical complications occur at unsatisfactory frequencies.

METHODS

We retrospectively included all patients undergoing PSO for ASD between 2010 and 2016. Changes to clinical practice were introduced continuously in the study period, including rigorous patient selection; inter-disciplinary conferences; implant-material; number of surgeons; surgeon experience; and perioperative standardized protocols for pain, neuromonitoring and blood-loss management. Postoperative complications were recorded in the 2-year follow-up period. Competing risk survival analysis was used to assess cumulative incidence of revision surgery due to mechanical complications. The Mann-Kendall test was used for analysis of trends.

RESULTS

We included 185 patients undergoing PSO. The level of PSO changed over the study period (P < 0.01) with L3 being the most common level in 2010 compared to L4 in 2016. Both preoperative and surgical corrections of sagittal vertical axis were larger towards the end of the study period. The 2-year revision rate due to mechanical failure steadily declined over the study period from 52% in 2010 to 14% for patients treated in 2016, although without statistically significant trend (P = 0.072). In addition, rates of mechanical complications steadily declined over the study period and significant decreasing trends were observed in time trend analyses of overall complications, major complications and rod breakage.

CONCLUSIONS

We observed decreased risks of revision surgery due to mechanical complications following PSO in patients with ASD over a 7-year period. We attribute these improvements to advancements in patient selection, surgical planning and techniques, surgeon experience and more standardized perioperative care.

LEVEL OF EVIDENCE

III.

Sagittal alignment changes and postoperative complications following surgery for adult spinal deformity in patients with Parkinson's disease: a multi-institutional retrospective cohort study

Background

Parkinson’s disease (PD) has been found to increase the risk of postoperative complications in patients with adult spinal deformity (ASD). However, few studies have investigated this by directly comparing patients with PD and those without PD.

Methods

In this multicenter retrospective cohort study, we reviewed all surgically treated ASD patients with at least 2 years of follow-up. Among them, 27 had PD (PD+ group). Clinical data were collected on early and late postoperative complications as well as any revision surgery. Radiographic parameters were evaluated before and immediately after surgery and at final follow-up, including sagittal vertical axis (SVA), thoracic kyphosis, lumbar lordosis, sacral slope, and pelvic tilt. We compared the surgical outcomes and radiographic parameters of PD patients with those of non-PD patients.

Results

For early complications, the PD+ group demonstrated a higher rate of delirium than the PD− group. In terms of late complications, the rate of non-union was significantly higher in the PD+ group. Rates of rod failure and revision surgery due to mechanical complications also tended to be higher, but not significantly, in the PD+ group (p = 0.17, p = 0.13, respectively). SVA at final follow-up and loss of correction in SVA were significantly higher in the PD+ group.

Conclusion

Extra attention should be paid to perioperative complications, especially delirium, in PD patients undergoing surgery for ASD. Furthermore, loss of correction and rate of non-union were greater in these patients.

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

STUDY DESIGN

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

OBJECTIVE

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

SUMMARY OF BACKGROUND DATA

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

METHODS

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

RESULTS

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

CONCLUSION

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

Comprehensive Evaluation of Accessory Rod Position, Rod Material and Diameter, Use of Cross-connectors, and Anterior Column Support in a Pedicle Subtraction Osteotomy Model: Part I: Effects on Apical Rod Strain: An In Vitro and In Silico Biomechanical Study

STUDY DESIGN

In silico finite element study.

OBJECTIVE

The aim of this study was to evaluate the effect of six construct factors on apical rod strain in an in silico pedicle subtraction osteotomy (PSO) model: traditional inline and alternative Ames-Deviren-Gupta (ADG) multi-rod techniques, number of accessory rods (three- vs. four-rod), rod material (cobalt-chrome [CoCr] or stainless steel [SS] vs. titanium [Ti]), rod diameter (5.5 vs. 6.35 mm), and use of cross-connectors (CC), or anterior column support (ACS).

SUMMARY OF BACKGROUND DATA

Rod fracture following lumbar PSO is frequently reported. Clinicians may modulate reconstructs with multiple rods, rod position, rod material and diameter, and with CC or ACS to reduce mechanical demand or rod contouring. A comprehensive evaluation of these features on rod strain is lacking.

METHODS

A finite element model (T12-S1) with intervertebral discs and ligaments was created and validated with cadaveric motion data. Apical rod strain of primary and accessory rods was collected for 96 constructs across all six construct factors, and normalized to the Ti two-rod control.

RESULTS

Regardless of construct features, CoCr and SS material reduced strain across all rods by 49.1% and 38.1%, respectively; increasing rod diameter from 5.5 mm to 6.35 mm rods reduced strain by 32.0%. Use of CC or lumbosacral ACS minimally affected apical rod strain (<2% difference from constructs without CC or ACS). Compared to the ADG technique, traditional inline reconstruction reduced primary rod strain by 32.2%; however, ADG primary rod required 14.2° less rod contouring. The inline technique produced asymmetrical loading between left and right rods, only when three rods were used.

CONCLUSION

The number of rods and position of accessory rods affected strain distribution on posterior fixation. Increasing rod diameter and using CoCr rods was most effective in reducing rod strain. Neither CC nor lumbosacral ACS affected apical rod strain.

LEVEL OF EVIDENCE

N/A.

Mechanical revision following pedicle subtraction osteotomy: a competing risk survival analysis in 171 consecutive adult spinal deformity patients

STUDY DESIGN

Retrospective study.

OBJECTIVE

To report the incidence of revision surgery due to mechanical failure following pedicle subtraction osteotomy (PSO) in adult spinal deformity (ASD) patients. PSO allow major surgical correction of ASD, although; the risk of mechanical complications remains considerable. Previous reports have been based on smaller cohorts or multicenter databases and none have utilized competing risk (CR) survival analysis.

METHODS

All ASD patients undergoing PSO surgery from 2010 to 2015 at a single, tertiary institution were included. Demographics, long standing radiographs as well as intra- and postoperative complications were registered for all. A CR-model was used to estimate the incidence of revision surgery due to mechanical failure and two predefined multivariable models were used to assess radiographic prediction of failure and reported as odds ratios (OR) with 95% confidence intervals (95% CI).

RESULTS

A total of 171 patients were included with 2-year follow-up available for 91% (mean [IQR]: 35 [24-50] months). Mechanical failure occurred in 111 cases (65%) at any time in follow-up, the most frequent being rod breakage affecting 81 patients (47%). Cumulative incidence of revision surgery due to mechanical failure was estimated to 34% at 2 years and 58% at 5 years. A multivariable proportional odds model with death as competing risk showed significantly increased odds of revision with fusion to the sacrum (OR: 5.42; 95% CI 1.89-15.49) and preoperative pelvic tilt (PT) > 20° (OR: 2.41; 95% CI 1.13-5.16). History of previous surgery, number of instrumented vertebra, as well as postoperative SRS-Schwab modifiers and Global Alignment and Proportion score were not associated with significant effects on odds of revision.

CONCLUSIONS

In a consecutive single-center cohort of patients undergoing PSO for ASD, we found an estimated incidence of revision surgery due to mechanical failure of 34% 2 years postoperatively. Fusion to the sacrum and preoperative PT > 20° were associated with elevated risks of revision.

LEVEL OF EVIDENCE

Prognostic III.

Revision surgery and mortality following complex spine surgery: 2-year follow-up in a prospective cohort of 679 patients using the Spine AdVerse Event Severity (SAVES) system

STUDY DESIGN

Prospective study.

OBJECTIVE

To determine the 2-year risk of revision surgery and all-cause mortality after complex spine surgery, and to assess if prospectively registered adverse events (AE) could predict either outcome. Revision surgery and mortality are serious complications to spine surgery. Previous studies of frequency have mainly been retrospective and few studies have employed competing risk survival analyses. In addition, assessment of predictors has focused on preoperative patient characteristics. The effect of perioperative AEs on revision and all-cause mortality risks are not fully understood.

METHODS

Between January 1 and December 31, 2013, we prospectively included all patients undergoing complex spine surgery at a single, tertiary institution. Complex spine surgery was defined as conditions deemed too complicated for surgery at a secondary institute, or patients with severe comorbidities requiring multidisciplinary observation and treatment. AEs were registered using the Spine Adverse Event Severity system and patients were followed for minimum 2 years regarding revision surgery and all-cause mortality. Incidences were estimated using competing risk survival analyses and correlation between AEs and either outcome was assessed using proportional odds models.

RESULTS

We included a complete and consecutive cohort of 679 adult and pediatric patients. Demographics, surgical data, AEs, and events of revision or all-cause mortality were registered. The cumulative incidence of 2-year all-cause revision was 19% (16-22%) and all-cause mortality was 15% (12-18%). Deformity surgery was the surgical category with highest incidence of revision and the highest incidence of all-cause mortality was seen in the tumor group. Across surgical categories, cumulative incidences of 2-year revision ranged between 11% (tumor) and 33% (deformity), whilst 2-year all-cause mortality ranged between 3% (deformity) and 33% (tumor). We found that major intraoperative AEs were associated to increased odds of revision. Deep wound infection was associated to increased odds of all-cause mortality.

CONCLUSIONS

We report the cumulative incidences of revision surgery and all-cause mortality following complex spine surgery. We found higher incidences of revision compared to previous retrospective studies. Prospectively registered AEs were correlated to increased odds of revision surgery and all-cause mortality. These results may serve as reference for future interventional studies and aid in identifying at-risk patients.

LEVEL OF EVIDENCE

I.

Surgical correction of Adult Spinal Deformity in accordance to the Roussouly classification: effect on postoperative mechanical complications

STUDY DESIGN

Single-center, retrospective.

OBJECTIVES

To assess the restoration of ideal sagittal spine shape in accordance to the Roussouly classification and the effect on postoperative mechanical complications. Surgical correction of Adult Spinal Deformity is both challenging and complex. The risk of postoperative complications is considerable, especially mechanical complications requiring revision surgery. Attention has been directed toward defining alignment targets in attempts to minimize these risks, and the Roussouly classification has been proposed as a potential surgical aim.

METHODS

All patients undergoing ASD surgery from 2013-2016 were included at a single, quaternary institute. Successful restoration of Roussouly spine shape was retrospectively assessed, and patients were classified as either "restored" or "non-restored". Cumulative incidence of revision surgery due to mechanical failure was estimated using the Aalen-Johansen estimator, with death as the competing risk. A multivariable proportional odds model was used to estimate the effect of the Roussouly algorithm on revision surgery due to mechanical failure.

RESULTS

We identified a complete and consecutive cohort of 233 patients who were followed for a mean period of 36 (± 14) months. The 2-year cumulative incidence of revision surgery was 28%. Comparing the "restored" to the "non-restored" group, the overall revision rates were high in both groups. However, when adjusting for known cofounders in a multivariable proportional odds analysis, there was an almost fivefold increased odds of revision due to mechanical failure in the "non-restored" group (p = 0.036).

CONCLUSION

Surgical correction of ASD in accordance to the ideal Roussouly spine shape was correlated to a marked and significant decrease in risk of revision surgery due to mechanical failure. Nonetheless, the overall revision risk was elevated in both groups.

LEVEL OF EVIDENCE

Therapeutic III.

Identification of Predictive Factors for Mechanical Complications After Adult Spinal Deformity Surgery: A Multi-Institutional Retrospective Study

STUDY DESIGN

A retrospective multicenter observational study.

OBJECTIVE

To investigate correction surgeries that were performed in relatively aged patients in terms of mechanical complications (MCs) and their predictive factors.

SUMMARY OF BACKGROUND DATA

The risk factors associated with MCs have not yet been well examined, especially in aged populations.

METHODS

We retrospectively reviewed 230 surgically treated ASD patients with an average age of 72.2 years. Twenty-eight patients with ASD caused by vertebral fractures were excluded. The minimum follow-up was 2 years. Postoperative MCs were defined as proximal junction kyphosis, distal junction kyphosis, pseudoarthrosis, rod breakage, and vertebral fractures. We divided all the ASD patients into two groups: patients with MC (the MC (+) group) and patients without MC (the MC (-) group). Radiographic parameters were evaluated before and immediately after surgery. The SRS-Schwab ASD classification and global alignment and proportion (GAP) score were also evaluated.

RESULTS

Of the 202 patients, 91 (45.0%) had MCs. The age at surgery was significantly higher in the MC (+) group than in the MC (-) group. Regarding radiographic parameters, postoperative global tilt (GT), pre- and postoperative thoracolumbar kyphosis (TLK), and postoperative thoracic kyphosis were significantly higher in the MC (+) group than in the MC (-) group. Other parameters, such as the proposed ideal alignment target of PI-LL<10, did not significantly affect MC rates. The GAP score was high in both groups and not significantly related to a higher rate of MC. Forward stepwise logistic regression indicated that the age at surgery, postoperative GT, and preoperative TLK were significant risk factors for MCs.

CONCLUSION

Older age, higher postoperative GT, and higher pre and postoperative TLK can be risk factors for MCs. The GAP score was high in both groups and not significantly related to a higher rate of MC.

LEVEL OF EVIDENCE

4.

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

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

Readmission following complex spine surgery in a prospective cohort of 679 patients - 2-years follow-up using the Spine AdVerse Event Severity (SAVES) system

BACKGROUND CONTEXT

Recent studies suggest that prospective registration more accurately reflects the true incidence of adverse events (AEs). To our knowledge, no previous study has investigated prospectively registered AEs' influence on hospital readmission following spine surgery.

PURPOSE

To determine the frequency and type of unplanned readmissions after complex spine surgery, and to investigate if prospectively registered AEs can predict readmissions.

DESIGN

This is a prospective, consecutive cohort study.

PATIENT SAMPLE

We conducted a single-center study of 679 consecutive patients who underwent complex spine surgery defined as conditions deemed too complicated for surgery at a secondary institute, or patients with severe comorbidities requiring multidisciplinary observation and treatment.

OUTCOME MEASURES

The outcomes in this study were (1) readmission to any hospital department within 30 days of discharge and (2) readmission to a surgical spine center at any time in follow-up.

METHODS

All patients undergoing complex spine surgery, at our tertiary referral center, were consecutively, and prospectively, included from January 1 to December 31, 2013. Demographics and perioperative AEs were registered using the Spine AdVerse Events Severity (SAVES) system. Patients were followed for a minimum of two years. A competing risk survival model was used to estimate rates of readmissions with death as a competing risk. Patient characteristics, surgical parameters and perioperative AEs were analyzed to identify factors associated with readmission. Analyses of 30-day readmission were performed using logistic regression models. A proportional odds model, with death as competing risk, was used for readmissions to a spine center at any time in follow-up. Results were reported as odds ratios with 95% confidence intervals (95% CI).

RESULTS

Within 2 years of index discharge, 443 (65%) were readmitted. Only 20% of readmissions were to a spine center. Cumulative incidence (95% CI) of readmission was estimated to 13% (10%-16%) at 30 days, 26% (23%-30%) at 90 days, 50% (46%-54%) at 1 year, and 59% (55%-63%) at 2 years following discharge. Rates were markedly lower for readmissions to a spine center. Increased odds of 30-day readmission were correlated to intraoperative hypotension (p=.02) and major intraoperative blood loss (p<.01). Readmission to a spine center was associated with the number of instrumented vertebrae (p=.047), major intraoperative AE (p=.01), and intraoperative hypotension (p<.01).

CONCLUSIONS

To the best of our knowledge, this is the first study to analyze prospectively registered AEs' association to readmission up to 2 years after complex spine surgery. We found that readmissions were more frequent than previously reported when including readmissions to any department or hospital. Factors related to major intraoperative blood loss were associated to increased odds of readmission. This should be considered during planning of postoperative observation and care.

Revision Risk After Primary Adult Spinal Deformity Surgery: A Nationwide Study With Two-Year Follow-up

STUDY DESIGN

Cohort study.

OBJECTIVES

To report the two-year revision risk following primary adult spinal deformity (ASD) surgery, describe reasons for revisions, and assess risk factors for revision surgery.

SUMMARY OF BACKGROUND DATA

Revision risk following primary ASD surgery has been reported to vary between 7% and 26%, but with loss to follow-up as a considerable challenge.

METHODS

Patients ≥18 years of age undergoing primary instrumented surgery for ASD in Denmark during 2006-2014 were identified by procedure and diagnosis codes in the Danish National Patient Registry (DNPR). Complete two-year follow-up on revision surgery for each patient was achieved. Medical records were reviewed to determine reasons for revisions. Overall comorbidity was summarized using the Charlson Comorbidity Index (CCI) based on DNPR data; low comorbidity (CCI 0); medium comorbidity (CCI 1-2); and high comorbidity (CCI ≥3). Risk factors for revision were assessed in a Cox regression model.

RESULTS

A total of 553 patients were identified. Of these, 19.9% were revised within the two-year follow-up and 7.2% of patients were revised more than once. Median time to revision was 308 days (interquartile range 105-508). The most common reason for revision was implant failure (38.2%) followed by infection (11.8%). Increased age (hazard ratio [HR] = 1.13, 95% confidence interval [CI] 1.01-1.26, per 10 years increment) and high comorbidity burden (HR = 2.10, 95% CI 1.16-3.79) were associated with increased revision risk. Risk of revision increased from 2006 to 2014; hence, year of primary surgery (with 2006 as reference) was associated with increased revision risk (HR = 1.09, 95% CI 1.01-1.18).

CONCLUSIONS

The revision risk within 2 years after primary ASD surgery was 19.9% nationwide in Denmark, and implant failure was the most common reason for revision. Increased comorbidity and age were separately associated with increased risk of revision.

LEVEL OF EVIDENCE

Level II.

Ability of the Global Alignment and Proportion Score to Predict Mechanical Failure Following Adult Spinal Deformity Surgery-Validation in 149 Patients With Two-Year Follow-up

STUDY DESIGN

Retrospective analysis of prospectively collected data.

OBJECTIVES

To validate the Global Alignment and Proportion (GAP) score in a single-center cohort of adult spinal deformity (ASD) patients.

SUMMARY OF BACKGROUND DATA

Surgical treatment for ASD is associated with a high risk of mechanical failure and consequent revision surgery. To improve prediction of mechanical complications, the GAP score was developed with promising results. Development was based on the assumption that not all patients would benefit from the same fixed radiographic targets as pelvic incidence is an individual, morphological parameter that greatly influences the sagittal curves of the spine.

METHODS

In a validation study of the GAP score, patients undergoing ASD surgery with four or more levels of instrumentation were consecutively included at a tertiary spine unit. Patients were followed for a minimum of two years. Pre- and postoperative GAP score and categories were calculated for all patients, and the association with mechanical failure and revision surgery was analyzed.

RESULTS

A total of 149 patients with a mean age of 57.4 years were included. Overall, the rates of mechanical failure and revision surgery were 51% and 35% respectively. The area under the curve (AUC) using receiver operating characteristic was classified as "no or low discriminatory power" for the GAP score in predicting either outcome (AUC = 0.50 and 0.49, respectively). Similarly, there were no significant associations between GAP categories and the occurrence of mechanical failure or revision surgery when using Cochran-Armitage test of trend (p = .28 for mechanical failure and p = .58 for revision surgery).

CONCLUSIONS

In a consecutive series of surgically treated ASD patients, we found no significant association between postoperative GAP score and mechanical failure or revision surgery. Despite minor limitations in similarities to the original study cohort, further validation studies or adjustments to the original scoring system are proposed.

LEVEL OF EVIDENCE

Level II.

Postoperative Disability After Long Corrective Fusion to the Pelvis in Elderly Patients With Spinal Deformity

STUDY DESIGN

A prospective case series analysis.

OBJECTIVE

The purpose of this study was to investigate the degree of difficulty in daily activities of adult spinal deformity (ASD) patients after corrective long fusion to the pelvis, with an emphasis on bend forward activities.

SUMMARY OF BACKGROUND DATA

No prospective studies have been reported regarding the postoperative impairments and their time course after long fusion in ASD patients.

METHODS

One-hundred three patients [26 men, 77 women; mean age 68 (50-82) years] who underwent corrective long fusion from the thoracic spine to the pelvis were included. As a control group, 578 volunteers [213 men, 365 women; mean age 72 (50-84)] who underwent musculoskeletal examination were included. Seven daily activities were assessed using Disability Scores (DS10), which ask patients to rate the difficulty of actions from 1 (very easy) to 10 (very difficult). The activities selected were a) gait, b) ability to trim toe nails, c) lie supine, d) perform personal hygiene, e) put on pants, f) pick up an item from the floor, and g) get down on all fours. Each of these activities were rated by all volunteers and patients at five assessment points in 2 years. Questionnaires (ODI, SRS-22, and DS10) were administered preoperatively, at discharge, 6 months, 1 year, and 2 years postoperatively. Radiographic parameters and clinical results of the control group were compared with those of the ASD patients and the patients with different upper instrumented vertebrae.

RESULTS

Although successful clinical results and deformity corrections were achieved, the ASD patients reported significant difficulty in b), d), e), f), and g) after the surgery (all P < 0.0001), regardless of the fusion length. The difficulty gradually improved toward 2 years but did not reach preoperative status.

CONCLUSION

Activities requiring patients to bend forward were more difficult for elderly ASD patients postoperatively.

LEVEL OF EVIDENCE

3.

Differences in primary and revision deformity surgeries: following 1,063 primary thoracolumbar adult spinal deformity fusions over time

Background

This study aims to describe properties of adult spinal deformity (ASD) revisions relative to primary surgeries and determine clinical variables that can predict revision. ASD is a common pathology that can lead to decreased quality of life, pain, physical limitations, and dissatisfaction with self-image. Durability of interventions for deformity treatment is of paramount concern to surgeons, as revision rates remain high.

Methods

Patients undergoing thoracolumbar fusion, five or more levels, for scoliosis (primary diagnosis ICD-9 737.x) were identified on a state-wide database. Primary and revision (returning for re-fusion procedure) surgeries were compared based on demographic, hospital stay, and clinical characteristics. Differences between primary and revision surgeries, and predictors of primary surgeries requiring revision, utilized binary logistic regression controlling for age, comorbidity burden, and levels fused.

Results

A total of 1,063 patients (average 7.4 levels fused, mean age: 47.6 years, 69.0% female) undergoing operative treatment for ASD were identified, of which 123 (average 7.1 levels fused, 11.6%, mean age 61.43, 80.5% female) had surgical revision. Primary surgeries were ~0.3 levels longer (P=0.013), used interbody ~11% more frequently (P=0.020), and used BMP ~12% less frequently (P=0.008). Revisions occurred 176.4 days after the primary on average. The most frequent causes of revisions were: 43.09% implant failure, 24.39% acquired kyphosis, and 14.63% enduring scoliosis. After controlling for age, comorbidities, and levels fused older, more comorbid, female, and white-race patients were more likely to be revised. Upon multivariate regression, after controlling for age and levels fused, overall complications remained non-different (OR: 0.8, 95% CI: 0.6-1.2). However, revision remained an independent predictor for infection (OR: 5.5, 95% CI: 2.8-10.5).

Conclusions

In a statewide database with individual patient follow up of up to 4 years 10% of ASD patients undergoing scoliosis correction required revision. Revision surgeries had higher infection incidence.