Determining a Cutoff Value for Hand Grip Strength to Predict Favorable Outcomes of Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective review.

OBJECTIVES

To establish a cutoff value for hand grip strength and predict the favorable outcomes of adult spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

Hand grip strength (HGS) has been suggested to predict surgical outcomes in various fields, including adult spinal deformity (ASD). However, to the best of our knowledge, no study has established a cutoff value for HGS in patients with ASD.

METHODS

This study included 115 female patients who underwent reconstructive spinal surgery for ASD between September 2016 and September 2020. HGS was measured preoperatively. The Oswestry Disability Index (ODI), EuroQOL-5-dimension (EQ-5D), and visual analog scale (VAS) scores for back pain were all recorded both before and after surgery. Patients were dichotomized either into favorable or unfavorable outcome groups using an ODI cutoff score of 22 at 1 year after surgery. Multivariate logistic regression analysis was done to identify significant factors leading to favorable outcomes. A receiver operating characteristic (ROC) curve was drawn to define the cutoff value of HGS for favorable outcomes.

RESULTS

Multivariate logistic regression analysis showed that HGS is significantly associated with favorable surgical outcomes in ASD (P = .031). The ROC curve suggested a cutoff value of 14.20 kg for HGS (area under the curve (AUC) = .678, P = .013) to predict favorable surgical outcomes in ASD. The surgical complications were not significantly affected by HGS.

CONCLUSION

The HGS of patients with ASD can be interpreted with a cutoff value of 14.20 kg. Patients with HGS above this cutoff value showed superior surgical outcomes at 1 year after surgery compared to those below this cutoff value.

Revision Surgery for Proximal Junctional Kyphosis and the Role for Addressing Residual Deformity

Proximal junctional kyphosis (PJK) is a common complication of adult spinal deformity surgery. Initially described in Scheuermann kyphosis and adolescent scoliosis, PJK now represents a wide spectrum of diagnoses and severities. Proximal junctional failure (PJF) is the most severe form of PJK. Revision surgery for PJK may improve outcomes in the setting of intractable pain, neurological deficits, and/or progressive deformity. Accurate diagnosis of the driver(s) of PJK and a surgical strategy that addresses these factors are required to optimize outcomes for revision surgery and to avoid recurrent PJK. One such factor is residual deformity. Recent investigations on recurrent PJK have identified radiographic parameters that may be useful in revision surgery to minimize the risk of recurrent PJK. In this review, we discuss classification systems used to guide sagittal plane correction and literature investigating their utility in predicting and preventing PJK/PJF, we review the literature on revision surgery for PJK and addressing residual deformity, and we present illustrative cases.

A Comparative Analysis of Frailty, Disability, and Sarcopenia With Patient Characteristics and Outcomes in Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective case series study.

OBJECTIVES

This study aims to compare preoperative indices, including the modified frailty index-11 (mFI-11), modified frailty index-5 (mFI-5), Oswestry Disability Index (ODI), and psoas muscle index (PMI), as they relate to outcomes in adult spinal deformity (ASD) surgery.

METHODS

We identified 235 patients who underwent thoracolumbar ASD surgery (≥4 levels). The mFI-11, mFI-5, ODI, and PMI were determined from preoperative visits and correlated to outcome measures, including perioperative transfusion, duration of anesthesia, hospital and ICU length of stay (LOS), discharge disposition, readmission, change in ODI at last follow-up, revision surgery, and mortality.

RESULTS

Our cohort had a mean age of 69.6 years and a male:female ratio of 1:2 with 177 undergoing an index surgery and 58 patients presenting after a failed multilevel fusion. The average number of levels fused was 9.3. The mFI-11 and mFI-5 were similar in predicting the need for intraoperative and postoperative transfusion. However, the mFI-11 was able to predict longer ICU and hospital LOS and mortality. The average preoperative ODI was 44.9% with an average decrease of 10.1% at the last follow-up. Preoperative ODI was the most significant predictor of postoperative change of ODI. Sarcopenia, defined as the lowest quartile of PMI values measured at L3 and L4, was not associated with any meaningful outcomes.

CONCLUSION

The mFI-11 better correlated with outcomes, indicating its increased prognostic value compared to other preoperative indices in ASD surgery. Preoperative ODI remains a significant predictor of postoperative change in ODI when evaluating ASD patients.

Use of Tethers for Proximal Junctional Kyphosis Prophylaxis in Adult Spinal Deformity Surgery: A Review of Current Clinical Evidence

BACKGROUND

Surgery for adult spinal deformity (ASD) often involves long-segment posterior instrumentation that introduces stress at the proximal junction that can result in proximal junctional kyphosis (PJK) or proximal junctional failure (PJF). Recently, the use of tethers at the proximal junction has been proposed as a means of buffering the transitional stresses and reducing the risk of PJK/PJF. Our objectives are to summarize the clinical literature on proximal junctional tethers for PJK/PJF prophylaxis.

METHODS

Articles published between 1 January 2000 and 10 November 2022 were identified via a PubMed search using combinations of the search terms "spine surgery," "ASD," "complication," "surgery," "PJK," "PJF," "tether," "sublaminar band," and "prophylaxis." No restrictions were placed on the number of patients, surgical indications, or surgical procedures. Relevant articles were reviewed and summarized.

RESULTS

Fifteen articles were identified, including 2 prospective cohorts (Level II), 10 retrospective cohorts (Level III), and 3 retrospective case series (Level IV). All studies were published between 2016 and 2022, and all focused on ASD patient populations. The mean age in each study ranged from 55 to 69 years, and most studies had a mean follow-up of at least 12 months (range, 5.5-45.4 months). Eleven studies used a polyethylene tether, 2 used soft sublaminar cables, and 2 used semitendinous allograft. The tether extended to the UIV+1 or UIV+2, passing either through or around the spinous processes, in 13 studies. In the remaining 2 studies, the tether was passed sublaminar at the UIV+1. Fourteen studies favored the use of tethers with regard to reduction of PJK/PJF rates, and one demonstrated similar rates of PJK between the tether and no-tether groups.

CONCLUSIONS

PJK/PJF remain major challenges in ASD surgery. Most early studies suggest that the use of tethers for ligamentous augmentation may help to mitigate the development of PJK/PJF. However, the multifactorial etiology of PJK/PJF makes it unlikely that any single technique will solve this complex problem. Further study is needed to address not only the effectiveness of junctional tethers but also to clarify whether there are optimal tether configurations, tether materials, and tether tension.

LEVEL EVIDENCE

3.

Analysis of Mechanical Failure Using the GAP Score After Surgery With Lateral and Posterior Fusion for Adult Spinal Deformity

STUDY DESIGN

A retrospective observational study.

OBJECTIVE

The purpose of this study was to evaluate the Global Alignment and Proportion (GAP) score and mechanical failure (MF) following corrective fusion surgery with planned 2-stage surgery using lateral lumbar interbody fusion in patients with adult spinal deformity (ASD).

METHODS

Fifty-four patients (2 men, 52 females, aged 70.3 years) were included. MF, proximal junctional failure (PJF), and rod breakage (RB) occurred in 46.3% (25/54), 22.2% (12/54), and 29.6% (16/54) of patients, respectively. The immediate postoperative GAP scores were compared between patients with MF and without MF (MF+ and MF-, respectively). GAP scores in groups with and without PJF or RB were also compared.

RESULTS

Patients were grouped according to the GAP score for spinopelvic alignment: 23 (42.6%) as proportioned, 22 (40.7%) as moderately disproportioned, and 9 (16.7%) as severely disproportioned. The pre- and postoperative spinopelvic parameters did not differ significantly between the MF- and MF+ groups except pelvic incidence. Postoperatively, the mean pelvic incidence-lumbar lordosis changed to <10° in both groups. The GAP score and 3 categories of GAP scores did not differ significantly between the PJF- and PJF+ groups or between the RB+ and RB- groups.

CONCLUSION

Multiple factors can cause PJF and RB, and the patient's background may affect the ability to use the GAP score to predict MF. Further research may be needed in the future using modified GAP scores with additional factors in ASD patients.

The ISSG-AO Complication Intervention Score, but Not Major/Minor Designation, is Correlated With Length of Stay Following Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective review.

OBJECTIVES

The International Spine Study Group-AO (ISSG-AO) Adult Spinal Deformity (ASD) Complication Classification System was developed to improve classification, reporting, and study of complications among patients undergoing ASD surgery. The ISSG-AO system classifies interventions to address complications by level of invasiveness: grade zero (none); grade 1, mild (e.g., medication change); grade 2, moderate (e.g., ICU admission); grade 3, severe (e.g., reoperation related to surgery of interest). To evaluate the efficacy of the ISSG-AO ASD Complication Classification System, we aimed to compare correlations between postoperative length of stay (LOS) and complication severity as classified by the ISSG-AO ASD and traditional major/minor complication classification systems.

METHODS

Patients age ≥18 in a multicenter ASD database who sustained in-hospital complications were identified. Complications were classified with the major/minor and ISSG-AO systems and correlated with LOS using an ensemble-based machine learning algorithm (conditional random forest) and a generalized linear mixed model.

RESULTS

490 patients at 19 sites were included. 64.9% of complications were major, and 35.1% were minor. By ISSG-AO classification, 20.4%, 66.1%, 6.7%, and 6.7% were grades 0-3, respectively. ISSG-AO complication grading demonstrated significant correlation with LOS, whereas major/minor complication classification demonstrated inverse correlation with LOS. In conditional random forest analysis, ISSG-AO classification had the greatest relative importance when assessing correlations across multiple variables with LOS.

CONCLUSIONS

The ISSG-AO system may help identify specific complications associated with prolonged LOS. Targeted interventions to avoid or reduce these complications may improve ASD surgical quality and resource utilization.

Circumferential Bone Fusion in Adult Spinal Deformity via Combination of Oblique Lateral Interbody Fusion and Grade 2 Posterior Column Osteotomy

STUDY DESIGN

Retrospective study.

OBJECTIVES

The combination of oblique lateral interbody fusion (OLIF) with grade 2 posterior column osteotomy (PCO) is an effective treatment for adult spinal deformity. However, grade 2 PCO may lead to pseudoarthrosis because it involves complete removal of the bilateral posterior facet joints. The main study objective was to determine the achievement rate of anterior and posterolateral fusion resulting in circumferential fusion in patients who underwent combined OLIF and grade 2 PCO.

METHODS

This retrospective study included consecutive patients who underwent OLIF and grade 2 PCO. The group comprised a long fusion group, with fusion from the thoracic level to the ilium, and a short fusion group, with fusion within the lumbar region. The OLIF with percutaneous pedicle screw insertion group was also used for reference. The Brantigan-Steffee-Fraser classification was used to assess interbody fusion and Lenke classification for assessment of posterolateral fusion.

RESULTS

Sixty-six patients with 109 lumbar levels were included in the study. We observed 100% anterior fusion in all 3 groups. The fusion rate for posterolateral fusion between the OLIF-grade 2 PCO group was 97%, with very low (3%) non-circumferential fusion (pseudoarthrosis only at the osteotomy site). In most cases, solid posterolateral fusions (Lenke A) occurred within 24 months.

CONCLUSIONS

The combination of OLIF and grade 2 PCO resulted in circumferential fusion for most (97%) of the cases within 24 months. OLIF and grade 2 PCO are considered a good combination treatment to achieve sufficient lumbar lordosis and solid bone fusion.

Use of multiple rods and proximal junctional kyphosis in adult spinal deformity surgery

OBJECTIVE

Multiple rods are utilized in adult spinal deformity (ASD) surgery to increase construct stiffness. However, the impact of multiple rods on proximal junctional kyphosis (PJK) is not well established. This study aimed to investigate the impact of multiple rods on PJK incidence in ASD patients.

METHODS

ASD patients from a prospective multicenter database with a minimum follow-up of 1 year were retrospectively reviewed. Clinical and radiographic data were collected preoperatively, at 6 weeks postoperatively, at 6 months postoperatively, at 1 year postoperatively, and at every subsequent year postoperatively. PJK was defined as a kyphotic increase of > 10° in the Cobb angle from the upper instrumented vertebra (UIV) to UIV+2 as compared with preoperative values. Demographic data, radiographic parameters, and PJK incidence were compared between the multirod and dual-rod patient cohorts. PJK-free survival analysis was performed using Cox regression to control for demographic characteristics, comorbidities, level of fusion, and radiographic parameters.

RESULTS

Overall, 307/1300 (23.62%) cases utilized multiple rods. Cases with multiple rods were more likely to be revisions (68.4% vs 46.5%, p < 0.001), to be posterior only (80.7% vs 61.5%, p < 0.001), involve more levels of fusion (mean 11.73 vs 10.60, p < 0.001), and include 3-column osteotomy (42.9% vs 17.1%, p < 0.001). Patients with multiple rods also had greater preoperative pelvic retroversion (mean pelvic tilt 27.95° vs 23.58°, p < 0.001), greater thoracolumbar junction kyphosis (-15.9° vs -11.9°, p = 0.001), and more severe sagittal malalignment (C7-S1 sagittal vertical axis 99.76 mm vs 62.23 mm, p < 0.001), all of which corrected postoperatively. Patients with multiple rods had similar incidence rates of PJK (58.6% vs 58.1%) and revision surgery (13.0% vs 17.7%). The PJK-free survival analysis demonstrated equivalent PJK-free survival durations among the patients with multiple rods (HR 0.889, 95% CI 0.745-1.062, p = 0.195) after controlling for demographic and radiographic parameters. Further stratification based on implant metal type demonstrated noninferior PJK incidence rates with multiple rods in the titanium (57.1% vs 54.6%, p = 0.858), cobalt chrome (60.5% vs 58.7%, p = 0.646), and stainless steel (20% vs 63.7%, p = 0.008) cohorts.

CONCLUSIONS

Multirod constructs for ASD are most frequently utilized in revision, long-level reconstructions with 3-column osteotomy. The use of multiple rods in ASD surgery does not result in an increased incidence of PJK and is not affected by rod metal type.

Outcomes and reoperation rates of adult spinal deformity patients with baseline sagittal malalignment based on the cranial axis to the hip at 2 years postoperatively

OBJECTIVE

The aim of this study was to discern whether patients with a cranial sagittal vertical axis to the hip (CrSVA-H) > 2 cm at 2 years postoperatively exhibit significantly worse patient-reported outcomes (PROs) and clinical outcomes compared with patients with CrSVA-H < 2 cm.

METHODS

This was a retrospective, 1:1 propensity score-matched (PSM) study of patients who underwent posterior spinal fusion for adult spinal deformity. All patients had a baseline sagittal imbalance of CrSVA-H > 30 mm. Two-year patient-reported and clinical outcomes were assessed in unmatched and PSM cohorts, including Scoliosis Research Society-22r (SRS-22r) and Oswestry Disability Index scores as well as reoperation rates. The study compared two cohorts based on 2-year alignment: CrSVA-H < 20 mm (aligned cohort) vs CrSVA-H > 20 mm (malaligned cohort). For the matched cohorts, binary outcome comparisons were carried out using the McNemar test, while continuous outcomes used the Wilcoxon rank-sum test. For unmatched cohorts, categorical variables were compared using chi-square/Fisher's tests, while continuous outcomes were compared using Welch's t-test.

RESULTS

A total of 156 patients with mean age of 63.7 (SEM 1.09) years underwent posterior spinal fusion spanning a mean of 13.5 (0.32) levels. At baseline, the mean pelvic incidence minus lumbar lordosis mismatch was 19.1° (2.01°), the T1 pelvic angle was 26.6° (1.20°), and the CrSVA-H was 74.9 (4.33) mm. The mean CrSVA-H improved from 74.9 mm to 29.2 mm (p < 0.0001). At the 2-year follow-up, 129 (78%) of 164 patients achieved CrSVA-H < 2 cm (aligned cohort). Patients who had CrSVA-H > 2 cm (malaligned cohort) at the 2-year follow-up had worse preoperative CrSVA-H (p < 0.0001). After performing PSM, 27 matched pairs were generated. In the PSM cohort, the aligned and malaligned cohorts demonstrated comparable preoperative patient-reported outcomes (PROs). However, at the 2-year postoperative follow-up, the malaligned cohort reported worse outcomes in SRS-22r function (p = 0.0275), pain (p = 0.0012), and mean total score (p = 0.0109). Moreover, when patients were stratified based on their magnitude of improvement in CrSVA-H (< 50% vs > 50%), patients with > 50% improvement in CrSVA-H had superior outcomes in SRS-22r function (p = 0.0336), pain (p = 0.0446), and mean total score (p = 0.0416). Finally, patients in the malaligned cohort had a higher 2-year reoperation rate (22% vs 7%; p = 0.0412) compared with patients in the aligned cohort.

CONCLUSIONS

Among patients who present with forward sagittal imbalance (CrSVA-H > 30 mm), patients with CrSVA-H exceeding 20 mm at the 2-year postoperative follow-up have inferior PROs and higher reoperation rates.

Calibration of a comprehensive predictive model for the development of proximal junctional kyphosis and failure in adult spinal deformity patients with consideration of contemporary goals and techniques

OBJECTIVE

The objective of this study was to calibrate an updated predictive model incorporating novel clinical, radiographic, and prophylactic measures to assess the risk of proximal junctional kyphosis (PJK) and failure (PJF).

METHODS

Operative patients with adult spinal deformity (ASD) and baseline and 2-year postoperative data were included. PJK was defined as ≥ 10° in sagittal Cobb angle between the inferior uppermost instrumented vertebra (UIV) endplate and superior endplate of the UIV + 2 vertebrae. PJF was radiographically defined as a proximal junctional sagittal Cobb angle ≥ 15° with the presence of structural failure and/or mechanical instability, or PJK with reoperation. Backstep conditional binary supervised learning models assessed baseline demographic, clinical, and surgical information to predict the occurrence of PJK and PJF. Internal cross validation of the model was performed via a 70%/30% cohort split. Conditional inference tree analysis determined thresholds at an alpha level of 0.05.

RESULTS

Seven hundred seventy-nine patients with ASD (mean 59.87 ± 14.24 years, 78% female, mean BMI 27.78 ± 6.02 kg/m2, mean Charlson Comorbidity Index 1.74 ± 1.71) were included. PJK developed in 50.2% of patients, and 10.5% developed PJF by their last recorded visit. The six most significant demographic, radiographic, surgical, and postoperative predictors of PJK/PJF were baseline age ≥ 74 years, baseline sagittal age-adjusted score (SAAS) T1 pelvic angle modifier > 1, baseline SAAS pelvic tilt modifier > 0, levels fused > 10, nonuse of prophylaxis measures, and 6-week SAAS pelvic incidence minus lumbar lordosis modifier > 1 (all p < 0.015). Overall, the model was deemed significant (p < 0.001), and internally validated receiver operating characteristic analysis returned an area under the curve of 0.923, indicating robust model fit.

CONCLUSIONS

PJK and PJF remain critical concerns in ASD surgery, and efforts to reduce the occurrence of PJK and PJF have resulted in the development of novel prophylactic techniques and enhanced clinical and radiographic selection criteria. This study demonstrates a validated model incorporating such techniques that may allow for the prediction of clinically significant PJK and PJF, and thus assist in optimizing patient selection, enhancing intraoperative decision making, and reducing postoperative complications in ASD surgery.

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

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

Purpose

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

Methods

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

Results

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

Conclusions

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

New Effective Intraoperative Techniques for the Prevention of Coronal Imbalance after Circumferential Minimally Invasive Correction Surgery for Adult Spinal Deformity

This study aimed to devise measures and investigate their effect on coronal imbalance (CI) after circumferential minimally invasive correction surgery (CMIS) with lateral lumbar interbody fusion and percutaneous pedicle screw for adult spinal deformity (ASD). A total of 115 patients with ASD who underwent CMIS from the lower thoracic spine to the ilium were included. Patients were stratified based on the distance between the spinous process of the upper instrumented vertebra and central sacrum vertical line (UIV-CSVL) after the first intraoperative rod application into groups P (UIV-CSVL > 10 mm, n = 50) and G (UIV-CSVL < 10 mm, n = 65). Measures to correct postoperative CI introduced during surgery, preoperative and postoperative UIV-CSVL, and changes in UIV-CSVL after various measures (ΔUIV-CSVL) were investigated in group P. Rod rotation (RR), S2 alar-iliac screw distraction (SD), and kickstand-rod (KR) technique were performed in group P. Group P was further divided into group RR (n = 38), group SD (RR and SD) (n = 7), and group KR (RR and KR) (n = 5); the ΔUIV-CSVLs were 13.9 mm, 20.1 mm, and 24.4 mm in these three groups, respectively. Postoperative C7-CSVL < 10 mm was achieved in all three correction groups. In conclusion, our measures enabled sufficient correction of the UIV-CSVL and are useful for preventing CI after CMIS for ASD.

Elucidation of the Mechanism of Occasional Anterior Longitudinal Ligament Rupture with Posterior Correction Procedure for Adult Spinal Deformity Using LLIF-Finite Element Analysis of the Impact of the Lordotic Angle of Intervertebral LLIF Cage

Background and Objectives: There are several advantages of using lateral lumbar interbody fusion (LLIF) for correction surgeries for adult spinal deformity (ASD); however, we currently have unresolved new issues, including occasional anterior longitudinal ligament (ALL) rupture during the posterior correction procedure. When LLIF was initially introduced, only less lordotic cages were available and ALL rupture was more frequently experienced compared with later periods when more lordotic cages were available. We performed finite element analysis (FEA) regarding the mechanism of ALL rupture during a posterior correction procedure. Methods: A spring (which mimics ALL) was introduced at the location of ALL in the FEA and an LLIF cage with two different lordotic angles, 6 and 12 degrees (6DC/12DC), was employed. To assess the extent of burden on the ALL, the extension length of the spring during the correction procedure was measured and the location of the rotation center was examined. Results: We observed a significantly higher degree of length extension of the spring during the correction procedure in the FEA model with 6DC compared with that of 12DC. We also observed that the location of the rotation center was shifted posteriorly in the FEA model with 6DC compared with that of 12DC. Conclusions: It is considered that the posterior and rostral edge of the less lordotic angle cage became a hinge, and the longer lever arm increased the burden on ALL as the principle of leverage. It is important to use an LLIF cage with a sufficient lordotic angle, that is compatible with the degree of posterior osteotomy in ASD correction.

Are We Focused on the Wrong Early Postoperative Quality Metrics? Optimal Realignment Outweighs Perioperative Risk in Adult Spinal Deformity Surgery

BACKGROUND

While reimbursement is centered on 90-day outcomes, many patients may still achieve optimal, long-term outcomes following adult spinal deformity (ASD) surgery despite transient short-term complications.

OBJECTIVE

Compare long-term clinical success and cost-utility between patients achieving optimal realignment and suboptimally aligned peers.

STUDY DESIGN/SETTING

Retrospective cohort study of a prospectively collected multicenter database.

METHODS

ASD patients with two-year (2Y) data included. Groups were propensity score matched (PSM) for age, frailty, body mass index (BMI), Charlson Comorbidity Index (CCI), and baseline deformity. Optimal radiographic criteria are defined as meeting low deformity in all three (Scoliosis Research Society) SRS-Schwab parameters or being proportioned in Global Alignment and Proportionality (GAP). Cost-per-QALY was calculated for each time point. Multivariable logistic regression analysis and ANCOVA (analysis of covariance) adjusting for baseline disability and deformity (pelvic incidence (PI), pelvic incidence minus lumbar lordosis (PI-LL)) were used to determine the significance of surgical details, complications, clinical outcomes, and cost-utility.

RESULTS

A total of 930 patients were considered. Following PSM, 253 "optimal" (O) and 253 "not optimal" (NO) patients were assessed. The O group underwent more invasive procedures and had more levels fused. Analysis of complications by two years showed that the O group suffered less overall major (38% vs. 52%, p = 0.021) and major mechanical complications (12% vs. 22%, p = 0.002), and less reoperations (23% vs. 33%, p = 0.008). Adjusted analysis revealed O patients more often met MCID (minimal clinically important difference) in SF-36 PCS, SRS-22 Pain, and Appearance. Cost-utility-adjusted analysis determined that the O group generated better cost-utility by one year and maintained lower overall cost and costs per QALY (both p < 0.001) at two years.

CONCLUSIONS

Fewer late complications (mechanical and reoperations) are seen in optimally aligned patients, leading to better long-term cost-utility overall. Therefore, the current focus on avoiding short-term complications may be counterproductive, as achieving optimal surgical correction is critical for long-term success.

Why Didn't You Walk Yesterday? Factors Associated With Slow Early Recovery After Adult Spinal Deformity Surgery

STUDY DESIGN

This is a retrospective case-control study.

OBJECTIVES

The objectives of this study are to identify (1) risk factors for delayed ambulation following adult spinal deformity (ASD) surgery and (2) complications associated with delayed ambulation.

METHODS

One-hundred and ninety-one patients with ASD who underwent posterior-only fusion (≥5 levels, LIV pelvis) were reviewed. Patients who ambulated with physical therapy (PT) on POD2 or later (LateAmb, n = 49) were propensity matched 1:1 to patients who ambulated on POD0-1 (NmlAmb, n = 49) based on the extent of fusion and surgical invasiveness score (ASD-S). Risk factors, as well as inpatient medical complications were compared. Logistic regressions were used to identify risk factors for late ambulation.

RESULTS

Of the patients who did not ambulate on POD0-1, 32% declined participation secondary to pain or dizziness/fatigue, while 68% were restricted from participation by PT/nursing due to fatigue, inability to follow commands, nausea/dizziness, pain, or hypotension. Logistic regression showed that intraoperative estimated blood loss (EBL) >2L (OR = 5.57 [1.51-20.55], P = .010) was independently associated with an increased risk of delayed ambulation, with a 1.25 times higher risk for every 250 mL increase in EBL (P = .014). Modified 5-Item Frailty Index (mFI-5) was also independently associated with delayed ambulation (OR = 2.53 [1.14-5.63], P = .023). LateAmb demonstrated a higher hospital LOS (8.4 ± 4.0 vs 6.2 ± 2.6, P < .001). The LateAmb group trended toward an increase in medical complications on POD3+ (14.3% vs 26.5%, P = .210).

CONCLUSIONS

EBL demonstrates a dose-response relationship with risk for delayed ambulation. Delayed ambulation increases LOS and may impact medical complications.

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.

Daily Physical Training Improved Coronal Imbalance of Adult Degenerative Scoliosis: A Case Report

Background and Objectives: Adult (de novo) degenerative scoliosis (ADS) develops through degenerative changes in the lumbar spine, leading to spinal malalignment, which usually progresses with age. Strong evidence for non-operative care in patients with ADS is lacking, and whether physical exercise can improve the scoliosis curve remains unknown. Materials and Methods: We present a case of early stage ADS in which the coronal imbalance was improved by daily training. A 65-year-old female patient complained of lower back pain (LBP) and bilateral leg pain. She was diagnosed with early stage ADS with lumbar degenerative spondylolisthesis by imaging. She completed six months of daily physical training, including swimming, aerobic bikes, stretching, yoga, and Taijiquan. Results: Her LBP and neurological symptoms improved, and coronal-spinal balance was restored, which was maintained for four years by continued daily physical training. Conclusions: This is the first case of a 65-year-old ADS patient whose coronal balance was significantly restored through daily physical training. Substantial physical training focused on trunk muscle strength is important for spinal stabilization and for improving spinal malalignment in patients with early stage ADS.

Fragility of L5 Vertebral Fracture After Rod Fracture at the Lumbosacral Junction Following Long-Segment Spinal Fusion Surgery for Adult Spine Deformity

We report a case of vertebral fracture in a patient with rod fractures after adult spinal deformity surgery, which occurred at the same level as the rod fractures, even though intervertebral bone fusion in the fusion range had been achieved. A 77-year-old female underwent corrective spinal surgery for adult spinal deformity from T12 to the pelvis but had a subsequent uppermost instrumented vertebral fracture, resulting in pseudarthrosis and severe kyphosis. The patient underwent proximal fusion extension to the T4, which improved alignment. A right-sided rod fracture at the lumbosacral junction occurred after 18 months; however, it showed no symptoms. After a month, the patient experienced severe low back pain with left leg pain and was diagnosed with bilateral rod fractures associated with L5 hyperextension vertebral fracture. The patient underwent revision surgery to repair the fractured rods with a multiple-rod construct. Rod fractures can occur even when bone fusion is achieved within the fusion range. When rod fractures are detected at the lumbosacral junction even if the interbody fusion was achieved, a hyperextension vertebral fracture may occur.

Identifying Subsets of Patients With Adult Spinal Deformity Who Maintained a Positive Response to Nonoperative Management

BACKGROUND

Adult spinal deformity (ASD) represents a major cause of disability in the elderly population in the United States. Surgical intervention has been shown to reduce disability and pain in properly indicated patients. However, there is a small subset of patients in whom nonoperative treatment is also able to durably maintain or improve symptoms.

OBJECTIVE

To examine the factors associated with successful nonoperative management in patients with ASD.

METHODS

We retrospectively evaluated a cohort of 207 patients with nonoperative ASD, stratified into 3 groups: (1) success, (2) no change, and (3) failure. Success was defined as a gain in minimal clinically importance difference in both Oswestry Disability Index and Scoliosis Research Society-Pain. Logistic regression model and conditional inference decision trees established cutoffs for success according to baseline (BL) frailty and sagittal vertical axis.

RESULTS

In our cohort, 44.9% of patients experienced successful nonoperative treatment, 22.7% exhibited no change, and 32.4% failed. Successful nonoperative patients at BL were significantly younger, had a lower body mass index, decreased Charlson Comorbidity Index, lower frailty scores, lower rates of hypertension, obesity, depression, and neurological dysfunction (all P < .05) and significantly higher rates of grade 0 deformity for all Schwab modifiers (all P < .05). Conditional inference decision tree analysis determined that patients with a BL ASD-frailty index ≤ 1.579 (odds ratio: 8.3 [4.0-17.5], P < .001) were significantly more likely to achieve nonoperative success.

CONCLUSION

Success of nonoperative treatment was more frequent among younger patients and those with less severe deformity and frailty at BL, with BL frailty the most important determinant factor. The factors presented here may be useful in informing preoperative discussion and clinical decision-making regarding treatment strategies.

Pelvic Fixation With a Quad-Rod Technique Using S2 Alar Iliac and Medialized Entry Iliac Screws for Long Fusion Constructs

PURPOSE

Patients with adult spinal deformity (ASD) may have risk factors for nonunion and subsequent instrumentation failure. This study reviews a novel surgical technique for a quad-rod construct to the pelvis using both S2 alar iliac (S2AI) screw fixation and medialized entry iliac screw fixation as described through three separate cases and a review of the literature.

METHODS

This technique facilitates alignment of the construct and rod insertion into the tulip heads. The medialized iliac screw technique also avoids the potential soft-tissue complications of the conventional iliac screw bolt given that it is deeper and has more soft-tissue coverage.

RESULTS

Three cases performed by the most senior author (V.A.) in which this novel technique was used are presented in this report along with clinical and radiographic images to educate the reader on appropriate execution of this technique. A review of the existing literature regarding pelvic fixation techniques for ASD was also done.

CONCLUSION

Quad-rod augmentation of long thoracolumbar spinal constructs with two independent SI anchoring points is potentially an effective technique to increase lumbar sacral construct rigidity, thereby promoting fusion rates and decreasing revision rates. The described technique provides spine surgeons with an additional tool in their armamentarium to treat patients with complex ASD.

The Association Between Corrective Surgery for Adult Spinal Deformity and Serum Levels of Hepatobiliary Enzymes

Background and objective The surgery to correct adult spinal deformity (ASD) is associated with a rare, but life-threatening complication called acute celiac artery compression syndrome (ACACS). To our knowledge, there is currently no study in the literature regarding the abnormal elevation of serum levels of hepatobiliary enzymes after surgery to correct the deformity. In light of this, the purpose of this study was to investigate this potential association. Materials and methods We collected data on 74 patients with ASD who underwent correction surgery at our institution. A Spearman's rank-order correlation was used to assess the association between serum levels of hepatobiliary enzymes and spinal parameters. Factors showing a correlation coefficient of 0.2 or more were combined in a stepwise multiple regression analysis. Results The mean age of the patients was 68.4 ± 7.7 years; the study comprised six men and 68 women. In our stepwise multiple regression analysis, there were two valid models that included spinal parameters as independent variables: changes in lactate dehydrogenase (LDH) - changes in thoracolumbar kyphosis (TLK) (B -0.0025 ± 0.0007, p<0.01), and changes in LDH - preoperative T12-L1 kyphosis (B 0.0031 ± 0.001, p<0.01). Additionally, both valid models contained median arcuate ligament (MAL) overlap defined as MAL crossing the base of the celiac artery (CA) as a significant independent variable. Conclusions Greater sagittal correction of TLK, larger preoperative T12-L1 kyphosis, and MAL overlap were factors associated with an elevated serum level of LDH. Although few patients were reported to have clinically severe symptoms, "potential" ACACS due to a temporary blood flow disturbance can occur in this patient population.

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

STUDY DESIGN

Retrospective observational study.

OBJECTIVES

This study aimed to evaluate the utility of CT-based Hounsfield units (HUs) and MRI-based vertebral bone quality (VBQ) scores as alternatives to DXA for predicting the risk of proximal junctional failure (PJF) in female adult spinal deformity (ASD) patients undergoing two-stage corrective surgery with lateral lumbar interbody fusion (LLIF).

METHODS

The study included 53 female ASD patients who underwent two-stage corrective surgery with lateral lumbar interbody fusion from January 2016 to April 2022 with a minimum follow-up of one year. CT and MRI 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 two 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, PI-LL, and proximal junctional angle compared to those without PJF.

CONCLUSION

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 two-stage corrective surgery with LLIF. Therefore, CT-based HUs should be considered in ASD surgery planning to reduce the risk of PJF.

Cervical Spinal Cord Compression in Adult Scoliosis

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

The aim was to examine cervical spinal cord compression (SCC) in adult scoliosis and clarify the prevalence of and risk factors for cervical SCC.

METHODS

This study included 270 adult scoliosis patients and 1211 healthy volunteers. Cervical SCC was evaluated on cervical magnetic resonance imaging (MRI). The rates of SCC for those with adult scoliosis and the healthy volunteers were compared. Logistic regression analysis was conducted to examine the factors associated with cervical SCC on MRI.

RESULTS

In cases with adult scoliosis, preoperative major scoliosis curve was 56.0° ± 18.8°, and cervical SCC was detected in 25 patients (9.3%). Among the healthy volunteers, 64 cases with cervical SCC were detected. Only in cases with adult scoliosis, logistic regression analysis revealed higher age (OR 1.09, 95% CI 1.04-1.14, P < .001), narrow canal diameter (OR 2.27, 95% CI 1.35-3.85, P = .002), and inferior sagittal balance (OR 2.45, 95% CI 1.02-5.89, P = .04) as significant risk factors. In the logistic regression analysis in all subjects (including adult scoliosis and healthy volunteers), higher age (OR 1.08, 95% CI 1.06-1.10, P < .001) and narrow canal diameter (OR 1.62, 95% CI 1.37-1.92, P < .001) were also found to be significant risk factors, but the presence of scoliosis was not a significant factor.

CONCLUSIONS

Adult scoliosis itself was not significantly associated with cervical SCC. Inferior sagittal balance in addition to scoliosis constituted a significant risk factor for cervical SCC.

Medical complications following adult spinal deformity correction in patients with autoimmune disease

OBJECTIVE

An aberrant inflammatory response, which plays a role in the development of postoperative complications, is observed in autoimmune diseases, Yet, there is a paucity of literature regarding the effects of autoimmune diseases after adult spinal deformity (ASD) surgery. The goal of this study was to determine the effects of autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus) on postoperative medical complications, patient-reported outcome measures (PROMs), and radiographic alignment in patients who underwent ASD surgery.

METHODS

Propensity-score matching for age and sex was performed for patients with autoimmune disease (group A) and nonautoimmune patients (group NA1). Postoperative medical complications, preoperative and 2-year follow-up PROMs, and preoperative, immediate postoperative, and 2-year follow-up radiographic alignment were evaluated.

RESULTS

Among 386 patients (27 in group A and 359 in group NA1), autoimmune patients had a higher incidence of respiratory complications (11.1% vs 2.2%, p = 0.036), gastrointestinal complications (14.8% vs 3.1%, p = 0.016), urinary tract infections (14.8% vs 3.1%, p = 0.016), cholecystitis (7.4% vs 0%, p = 0.005), and fever of unknown origin (14.8% vs 0%, p < 0.001). Autoimmune patients had worse preoperative ODI (54.2 vs 44.7, p = 0.004) and 2-year follow-up Scoliosis Research Society 22-item Questionnaire (SRS-22) scores (3.1 vs 3.5, p = 0.039), with higher preoperative sacral slope (23.4° vs 17.8°, p = 0.020). Propensity-score matching for age and sex yielded 27 pairs (group A and group NA2). Having at least one medical complication (group A 74.1% vs group NA2 22.2%, p < 0.001), total complications per person (1.3 vs 0.3, p = 0.010), prognostic nutrition index (44.8 vs 48.6, p = 0.034), steroid use (51.9% vs 0%, p < 0.001), immunosuppressant use (48.1% vs 0%, p < 0.001), length of hospital stay (38 vs 27 days, p = 0.018), and discharge to care facility (29.6% vs 7.4%, p = 0.036) were higher in group A. Preoperative ODI (54.2 vs 43.2, p = 0.011) and 2-year follow-up SRS-22 scores (3.1 vs 3.6 p = 0.019) were worse in group A. No differences were observed in radiographic alignment.

CONCLUSIONS

Patients with autoimmune disease had higher complication rates and worse PROMs following ASD surgery in this study. There was no difference in spinal alignment compared with controls. Multidisciplinary planning and full disclosure of possible adverse effects should be completed prior to correction of ASD in patients with autoimmune disease.