Does an improvement in cord-level intraoperative neuromonitoring data lead to a reduced risk for postoperative neurologic deficit in spine deformity surgery?

PURPOSE: To determine if an improvement in cord-level intraoperative neuromonitoring (IONM) data following data loss results in a reduced risk for new postoperative motor deficit in pediatric and adult spinal deformity surgery. METHODS: A consecutive series of 1106 patients underwent spine surgery from 2015 to 2023 by a single surgeon. Cord alerts were defined by Somatosensory-Evoked Potentials (SSEP; warning criteria: 10% increase in latency or > 50% loss in amplitude) and Motor-Evoked Potentials (MEP; warning criteria: 75% loss in amplitude without return to acceptable limits after stimulation up 100 V above baseline level). Timing of IONM loss and recovery, interventions, and baseline/postoperative day 1 (POD1) lower extremity motor scores were analyzed. RESULTS: IONM Cord loss was noted in 4.8% (53/11,06) of patients and 34% (18/53) with cord alerts had a POD1 deficit compared to preoperative motor exam. MEP and SSEP loss attributed to 98.1% (52/53) and 39.6% (21/53) of cord alerts, respectively. Abnormal descending neurogenic-evoked potential (DNEP) was seen in 85.7% (12/14) and detected 91.7% (11/12) with POD1 deficit. Abnormal wake-up test (WUT) was seen in 38.5% (5/13) and detected 100% (5/5) with POD1 deficit. Most cord alerts occurred during a three-column osteotomy (N = 23/53, 43%); decompression (N = 12), compression (N = 7), exposure (N = 4), and rod placement (N = 14). Interventions were performed in all 53 patients with cord loss and included removing rods/less correction (N = 11), increasing mean arterial pressure alone (N = 10), and further decompression with three-column osteotomy (N = 9). After intervention, IONM data improved in 45(84.9%) patients (Full improvement: N = 28; Partial improvement: 17). For those with full and partial IONM improvement, the POD1 deficit was 10.7% (3/28) and 41.2% (7/17), respectively. For those without any IONM improvement (15.1%, 8/53), 100% (8/8) had a POD1 deficit, P < 0.001. CONCLUSION: A full or partial improvement in IONM data loss after intraoperative intervention was significantly associated with a lower risk for POD1 deficit with an absolute risk reduction of 89.3% and 58.8%, respectively. All patients without IONM improvement had a POD1 neurologic deficit.

Timing-dependent synergies between motor cortex and posterior spinal stimulation in humans.

Volitional movement requires descending input from the motor cortex and sensory feedback through the spinal cord. We previously developed a paired brain and spinal electrical stimulation approach in rats that relies on convergence of the descending motor and spinal sensory stimuli in the cervical cord. This approach strengthened sensorimotor circuits and improved volitional movement through associative plasticity. In humans, it is not known whether posterior epidural spinal cord stimulation targeted at the sensorimotor interface or anterior epidural spinal cord stimulation targeted within the motor system is effective at facilitating brain evoked responses. In 59 individuals undergoing elective cervical spine decompression surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord was stimulated with epidural electrodes, with muscle responses being recorded in arm and leg muscles. Spinal electrodes were placed either posteriorly or anteriorly, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and spinal sensory (posterior) but not spinal motor (anterior) stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred only when descending motor and spinal afferent stimuli were timed to converge in the spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, clinical signs suggest that facilitation was observed in both injured and uninjured segments of the spinal cord. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation. KEY POINTS: Pairs of stimuli designed to alter nervous system function typically target the motor system, or one targets the sensory system and the other targets the motor system for convergence in cortex. In humans undergoing clinically indicated surgery, we tested paired brain and spinal cord stimulation that we developed in rats aiming to target sensorimotor convergence in the cervical cord. Arm and hand muscle responses to paired sensorimotor stimulation were more than five times larger than brain or spinal cord stimulation alone when applied to the posterior but not anterior spinal cord. Arm and hand muscle responses to paired stimulation were more selective for targeted muscles than the brain- or spinal-only conditions, especially at latencies that produced the strongest effects of paired stimulation. Measures of clinical evidence of compression were only weakly related to the paired stimulation effect, suggesting that it could be applied as therapy in people affected by disorders of the central nervous system.

Preoperative rehabilitation optimization for spinal surgery: a narrative review of assessment, interventions, and feasibility.

PURPOSE: Postoperative physical therapy (PT) is a cornerstone of orthopedic and musculoskeletal rehabilitation, proven to provide various positive clinical benefits. However, there is a paucity of literature evaluating the utility of preoperative rehabilitation specific to spine surgery. Thus, this review article aims to provide an overview of previously published studies discussing the efficacy of preoperative rehabilitation programs and its role in spinal surgery. Special emphasis was given to preoperative frailty assessments, physical performance tests, interventional strategies, feasibility, and future directions. METHODS: We performed a literature review using PubMed, Google Scholar, EMBASE, and PubMed Central (PMC) using directed search terms. Articles that examined preoperative rehabilitation in adult spine surgery were compiled for this review. Prehabilitation programs focused on exercise, flexibility, and behavioral modifications have been shown to significantly improve pain levels and functional strength assessments in patients undergoing elective spine surgery. In addition, studies suggest that these programs may also decrease hospital stays, return to work time, and overall direct health care expenditure costs. Screening tools such as the FRAIL scale can be used to assess frailty while physical function tests like the timed-up-and go (TUGT), 5 repetition sit-to-stand test (5R-STST), and hand grip strength (HGS) can help identify patients who would most benefit from prehabilitation. CONCLUSIONS: This review illustrates that prehabilitation programs have the potential to increase quality of life, improve physical function and activity levels, and decrease pain, hospital stays, return to work time, and overall direct costs. However, there is a paucity of literature in this field that requires further study and investigation.

Innovative technologies in thoracolumbar and lumbar spine surgery failing to reach standard of care: state-of-art review.

PURPOSE: To evaluate previously popular technologies in the field of spine surgery, and to better understand their advantages and limitations to the current standards of care. Spine surgery is an ever-evolving field that serves to resolve various spinal pathologies in patients of all ages. While there are established treatments for various conditions, such as lumbar spinal stenosis, idiopathic scoliosis, and degenerative lumbar disease, there is always further research and development in these areas to produce innovative technologies that can lead to better outcomes. As this process progresses, we must remind ourselves of previously tried and tested inventions and their outcomes that have fallen short of becoming a standard to ensure we are able to learn lessons from the past. METHODS: A thorough literature review was conducted with the aim of compiling literature of previously utilized technologies in spine surgery. Biomedical databases were utilized to gather relevant articles including PubMed, MEDLINE, and EMBASE. Emphasis was placed on gathering articles with technologies or therapeutics aimed at treating common spinal pathologies including lumbar spinal stenosis (LSS), adolescent idiopathic scoliosis (AIS), and other degenerative lumbar spine diseases. The keywords used were: "failed technologies", "historical technologies", "spine surgery", "spinal stenosis", "adolescent idiopathic scoliosis", and "degenerative lumbar spine disease". A total of 47 articles were gathered after initial review. RESULTS: Different technologies pertaining to spine surgery were identified and critically evaluated. Some of these technologies included X-STOP, Vertiflex, Vertebral Body Stapling, and Dynesys. These technologies were evaluated for their strengths and limitations across their spinal pathology applications. While each type of technology had their benefits, the data tended to be mixed with various limitations across studies. CONCLUSION: These technologies have been trialed in the field of spine surgery across various spinal pathologies, but still prove of limited efficacy and shortcomings to the current standards of care.

Revision of Harrington rod constructs: a single-center's experience with this homogenous adult spinal deformity population at a minimum 2-year follow-up.

PURPOSE: To evaluate radiographic and clinical outcomes following revision surgery after HRC fusions. METHODS: Single-institution, retrospective study of patients revised following HRC with minimum 2-year follow-up post-revision. Demographics, perioperative information, radiographic parameters, complications, and Oswestry disability index (ODI) scores were collected. Radiographic parameters included global alignment, coronal and sagittal measurements pre and postoperatively, as well as final follow-up time points. RESULTS: 26 patients were included with a mean follow-up of 3.3 ± 1.1 years. Mean age was 55.5 ± 7.8 years, BMI 25.2 ± 5.8, and 22 (85%) were females. Instrumented levels increased from 9.7 ± 2.8 to 16.0 ± 2.2. Five (19.2%) patients underwent lumbar pedicle subtraction osteotomies, and 23 (88.4%) had interbody fusions. Patients significantly improved in all radiographic parameters at immediate and final follow-up (p < 0.005), except for thoracic kyphosis and pelvic incidence (p > 0.05). Correction was maintained from immediate postop to final follow-up (p > 0.05). 20 (76.9%) of patients experienced a complication at some point within the follow-up period with the most common being a lumbar nerve root deficit (n = 7). However, only one patient had a nerve root deficit at final follow-up, that being a 4/5 unilateral anterior tibialis function. 5 (19.2%) patients required further revision within a mean of 1.8 ± 1.1 years. On average, patients had an improvement in ODI score by final follow-up (35.6 ± 16.8 vs 25.4 ± 19.8, p = 0.035). CONCLUSION: Patients revised for HRCs significantly improve, both clinically and radiographically by final follow-up. This group did have a propensity for distal lumbar root neurological issues, which were common but all patients except for one, recovered to full strength by two-year follow-up.

Knee flexion compensation in postoperative adult spinal deformity patients: implications for sagittal balance and clinical outcomes.

PURPOSE: To determine whether maintaining good sagittal balance with significant knee flexion (KF) constitutes a suboptimal outcome after adult spinal deformity (ASD) correction. METHODS: This single-center, single-surgeon retrospective study, assessed ASD patients who underwent posterior spinal fusion between 2014 and 2020. Inclusion criteria included meeting at least one of the following: PI-LL ≥ 25°, T1PA ≥ 20°, or CrSVA-H ≥ 2 cm. Those with lower-extremity contractures were excluded. Patients were classified into four groups based on their 6-week postoperative cranio-hip balance and KF angle, and followed for at least 2 years: Malaligned with Knee Flexion (MKF+) (CrSVA-H > 20 mm + KFA > 10), Malaligned without Knee Flexion (MKF-) (CrSVA-H > 20 mm + KFA < 10), Aligned without Knee Flexion (AKF-) (CrSVA-H < 20 mm + KFA < 10), and Aligned with Knee Flexion (AKF+) (CrSVA-H < 20 mm + KFA > 10). The primary outcomes of this study included one and two year reoperation rates. Secondy outcomes included clinical and patient reported outcomes. RESULTS: 263 patients (mean age 60.0 ± 0.9 years, 74.5% female, and mean Edmonton Frailty Score 3.3 ± 0.2) were included. 60.8% (160/263 patients) exhibited good sagittal alignment at 6-week postop without KF. Significant differences were observed in 1-year (p = 0.0482) and 2-year reoperation rates (p = 0.0374) across sub-cohorts, with the lowest and highest rates in the AKF- cohort (5%, n = 8) and MKF + cohort (16.7%, n = 4), respectively. Multivariable Cox regression demonstrated the AKF- cohort exhibited significantly better reoperation outcomes compared to other groups: AKF + (HR: 5.24, p = 0.025), MKF + (HR: 31.7, p < 0.0001), and MKF- (HR: 11.8, p < 0.0001). CONCLUSION: Our findings demonstrate that patients relying on knee flexion compensation in the early postoperative period have inferior outcomes compared to those achieving sagittal balance without knee flexion. When compared to malaligned patients, those with CrSVA-H < 20 mm and KFA > 10 degrees experience fewer early reoperations but similar delayed reoperation rates. This insight emphasizes the importance of considering knee compensation perioperatively when managing sagittal imbalance in clinical practice.

The Importance of Pelvic Obliquity in Assessing Spinal Coronal Alignment: Normative Values, Demographic, and Radiographic Correlations.

STUDY DESIGN: Prospective, cross-sectional study. OBJECTIVE: In a geographically diverse population of asymptomatic volunteers, we sought to report the incidence of pelvic obliquity (PO), establish normative values of PO across patient factors, and assess the correlation of PO with radiographic parameters. SUMMARY OF BACKGROUND DATA: PO is defined as the misalignment of the pelvis and can be assessed through several anatomic landmarks. Significant PO, whether caused by leg-length discrepancy or not, can lead to coronal malalignment which causes severe pain and disability. Significant emphasis has been placed on achieving appropriate sagittal alignment in recent decades; however, a greater understanding of coronal alignment is needed, and PO is a crucial aspect of evaluating the coronal plane in adult spinal deformity patients. METHODS: Asymptomatic adult volunteers, ages 18-80 years, enrolled patients from 5 countries (France, Japan, Singapore, Tunisia, and the United States) in the "multiethnic alignment normative study" cohort (IRB 201812144). The included volunteers had no known spinal disorder(s), no significant neck or back pain (Visual Analog Scale: ≤2; Oswestry Disability Index: ≤20), and no abnormal alignment (Cobb ≤20°). PO was measured in the frontal plane as the distance between the highest points of each acetabulum, calculated along the vertical axis in millimeters (mm). The incidence of PO was defined as PO ≥10 mm. Kruskal-Wallis, Wilcoxon rank-sum, Pearson correlation, and linear regression were used. RESULTS: A total of 467 patients were included, and PO values by age, sex, body mass index, and country were provided. The overall incidence of PO ≥10 mm was 4.3%, and a nonsignificant trend toward increased PO with age was seen ( P = 0.077). No significant differences were seen in PO between sex, ethnicity, or body mass index groups. No significant correlation existed between PO and other commonly used coronal radiographic measurements. CONCLUSION: PO ≥10 mm occurred in 4.3% of asymptomatic volunteers. Despite the importance of recognizing PO in preventing coronal malalignment, PO did not seem to be associated with other radiographic and demographic information, which underscores the importance of intentionally assessing for any PO before surgery. These results in an asymptomatic population provide a foundation for studying PO in patients with spinal pathology.

Do adult spinal deformity patients who achieve and maintain PI-LL < 10 have better patient-reported and clinical outcomes compared to patients with PI-LL ≥ 10? A propensity score-matched analysis.

PURPOSE: To investigate whether patients with spinopelvic mismatch (PI-LL ≥ 10) report worse patient-reported outcomes (PROs) compared to patients who achieve PI-LL < 10 at 2-year postop. METHODS: In this retrospective study, propensity score matching (PSM) was used to analyze patients who underwent posterior spinal fusion due to deformity, as defined by one or more of the following criteria: PI-LL ≥ 25°, T1 pelvic angle ≥ 30°, sagittal vertical axis ≥ 15 cm, thoracic scoliosis ≥ 70°, thoracolumbar scoliosis ≥ 50°, coronal malalignment ≥ 7 cm, or those who underwent a three-column osteotomy or fusion with ≥ 12 levels. Key outcomes were total Scoliosis Research Society-22r, Oswestry Disability Index (PROs), and reoperation at 1- and 2-year postop. Patients were dichotomized based on their 2-year alignment: PI-LL ≥ 10° and PI-LL < 10°. A multivariable logistic regression model identified factors associated with achieving PI-LL < 10°, and independent predictors were matched using propensity score matching. Binary outcomes within matched cohorts were analyzed using the McNemar test, while continuous outcomes were analyzed using the Wilcoxon rank-sum test. RESULTS: One hundred sixty-four patients with 2-year follow-up were included; mean age was 50.5 (standard error mean (SEM): 1.4) years, body mass index was 24.1(SEM 1.0), and number of operative levels was 13.5 (SEM 0.3). 84 (51.2%) and 80 (48.8%) patients achieved PI-LL < 10 and PI-LL ≥ 10 at 2-year follow-up, respectively. Baseline pelvic incidence [odds ratio (OR): 0.96 (95% CI 0.92-0.99)] and baseline PI-LL [OR: 0.95 (95% CI 0.9-0.99)] were independent predictors of achieving PI-LL < 10 at 2 years. When comparing propensity matched pairs, no significant differences were found in baseline PROs. At both 1- and 2-year follow-up, outcomes on the SRS-22r scale were nearly identical for both groups (function [4.1(0.1) vs 4.0 (0.1), P = 0.75] ,Pain [3.9 (0.2) vs 3.9 (0.2), P = 0.86], appearance [4.2 (0.2) vs 3.8 (0.2), P = 0.08], mental health [4.1 (0.2) vs 4.1 (0.1), P = 0.96], satisfaction [4.4 (0.2) vs 4.4 (0.2), P = 0.72], and total [90.2 (2.5) vs 88.1 (2.5), P = 0.57]). Additionally, ODI scores at 2 years were comparable [18.1 (2.9) vs 22.4 (2.9), P = 0.30]. The 90-day reoperation rate was 2.6% (one patient) in both matched cohorts (P > 0.99). There was no significant difference in 1-year (P > 0.9999) or 2-year (P = 0.2207) reoperation rates between the groups. CONCLUSION: Patients who achieve and maintain PI-LL < 10 2-years postop following adult spinal deformity surgery have nearly identical SRS-22r and ODI outcomes, and comparable 2-year reoperation rates as compared to patients who have PI-LL ≥ 10.

Preoperative nutritional optimization for adult spinal deformity: Review.

PURPOSE: The main objective of this review article is to examine the role that nutrition has on adult spinal deformity. The information presented in this review aims to provide spine surgeons with a broad overview of screening, assessment, and interventional strategies that may be used for presurgical nutritional optimization. METHODS: A comprehensive literature review utilizing three biomedical databases was performed to generate articles of interest. Published articles related to nutrition, adult spinal deformity, spine surgery and orthopaedics were reviewed for the composition of this article. Nutrition may play a role in optimizing postoperative outcomes following adult spinal deformity surgeries, such as limiting delirium, length of stay, blood transfusion, and other medical complications. The use of screening tools, such as the PNI and CONUT score can assess preoperative nutritional status and may provide some utility in evaluating nutrition status in patients undergoing deformity surgery. Balancing both macronutrients and micronutrients, notably, carbohydrates, protein, albumin, and vitamin D can play a role in preoperative optimization. CONCLUSION: Adult spinal deformity patients are at an increased risk for malnutrition. These patients should be assessed for nutrition status to prime them for surgery, minimize complications, and maximize their outcomes. However, further studies are needed to determine how nutrition ultimately affects adult spinal deformity patients in the postoperative period and to establish specific nutritional recommendations for this unique population.

Impact of Teriparatide on Complications and Patient-Reported Outcomes of Patients Undergoing Long Spinal Fusion According to Bone Density.

BACKGROUND: Surgery for adult spinal deformity (ASD) poses substantial risks, including the development of symptomatic pseudarthrosis, which is twice as prevalent among patients with osteoporosis compared with those with normal bone mineral density (BMD). Limited data exist on the impact of teriparatide, an osteoanabolic compound, in limiting the rates of reoperation and pseudarthrosis after treatment of spinal deformity in patients with osteoporosis. METHODS: Osteoporotic patients on teriparatide (OP-T group) were compared with patients with osteopenia (OPE group) and those with normal BMD. OP-T patients were matched with OPE patients and patients with normal BMD at a 1:2:2 ratio. All patients had a minimum 2-year follow-up and underwent posterior spinal fusion (PSF) involving >7 instrumented levels. The primary outcome was the 2-year reoperation rate. Secondary outcomes included pseudarthrosis with or without implant failure, proximal junctional kyphosis (PJK), and changes in patient-reported outcomes (PROs). Clinical outcomes were analyzed using conditional logistic regression. Changes in PROs were analyzed using a mixed-effects model. RESULTS: Five hundred and forty patients (52.6% normal BMD, 32.9% OPE, 14.4% OP-T) were included. In the unmatched cohort, 2-year reoperation rates (odds ratio [OR] = 0.45 [95% confidence interval (CI): 0.20 to 0.91]) and pseudarthrosis rates (OR = 0.25 [95% CI: 0.08 to 0.61]) were significantly lower in the OP-T group than the OPE group. Seventy-eight patients in the OP-T group were matched to 156 patients in the OPE group. Among these matched patients, at 2 years, 23.1% (36) in the OPE group versus 11.5% (9) in the OP-T group had a reoperation (OR = 0.45, p = 0.0188), 21.8% (34) versus 6.4% (5) had pseudarthrosis with or without implant failure (OR = 0.25, p = 0.0048), and 6.4% (10) versus 7.7% (6) had PJK (OR = 1.18, p = 0.7547), respectively. At 2 years postoperatively, PROs were better among OP-T patients than OPE patients. Subsequently, 78 patients in the OP-T group were matched to 156 patients in the normal BMD group. Among these matched patients, there was no significant difference in 2-year reoperation (OR = 0.85 [95% CI: 0.37 to 1.98]), pseudarthrosis (OR = 0.51 [95% CI: 0.181 to 1.44]), and PJK rates (OR = 0.77 [95% CI: 0.28 to 2.06). CONCLUSIONS: Osteoporotic patients on teriparatide demonstrated lower reoperation and symptomatic pseudarthrosis rates 2 years postoperatively compared with osteopenic patients. Moreover, patient-reported and clinical outcomes for osteoporotic patients on teriparatide were not different from those for patients with normal BMD. LEVEL OF EVIDENCE: Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

Practical Methods of Assessing Coronal Alignment and Outcomes in Adult Spinal Deformity Surgery: A Comparative Analysis.

STUDY DESIGN: Asymptomatic cohort: prospective, cross-sectional, multicenter. Symptomatic: retrospective, multisurgeon, single-center. OBJECTIVE: To assess the association between cranial coronal alignment and adult spinal deformity (ASD) surgical risk and outcomes. SUMMARY OF BACKGROUND DATA: ASD leads to decreased quality of life. Studies have shown that coronal malignment (CM) is associated with worse surgical outcomes. MATERIALS AND METHODS: A total of 468 adult participants were prospectively enrolled in the asymptomatic cohort. Totally, 172 symptomatic ASD patients with 2-year follow-ups were retrospectively enrolled in the symptomatic cohort. Three cranial plumb line parameters: the positions of the plumb lines from the midpoint between the medial orbital rims (ORB-L5), the odontoid (OD-L5), and the C7 centroid (C7-L5) relative to the L5 pedicle, were measured. Each subject had plumb line medial (M), touching (T), or lateral (L) to either pedicle. The association between each group of patients and radiographic parameters, intraoperative variables, patient-reported outcomes, and clinical outcomes were analyzed. RESULTS: In the asymptomatic cohort, OD-L5 was medial to or touching the L5 pedicle in 98.3% of volunteers. In the symptomatic patients, preoperative OD-L5-L exhibited higher mean age (56.2±14.0), odontoid-coronal vertical axis (OD-CVA) (5.5±3.3 cm), Oswestry disability index (ODI) score (40.6±18.4), pelvic fixation rate (56/62, 90.3%), OR time (528.4±144.6 min), median estimated blood loss (1300 ml), and durotomy rate (24/62, 38.7%). A similar pattern of higher CVA, preoperative ODI, intraoperative pelvic fixation rate, OR time, estimated blood loss, and durotomy rate was observed in ORB-L5-L and C7-L5-L patients. Final follow-up postoperative OD-L5-L was associated with higher rates of proximal junctional kyphosis (13.0%) and pseudarthrosis (17.4%). CONCLUSION: Preoperative OD-L5, ORB-L5, and C7-L5 lateral to pedicles were associated with worse preoperative ODI and higher intraoperative complexity. Postoperative OD-L5-L was associated with higher rates of proximal junctional kyphosis and pseudarthrosis. Postoperative CM, approximated by the cranial plumb line lateral to the L5 pedicles, was associated with sagittal plane complications.

Optimizing Preoperative Chronic Pain Management in Elective Spine Surgery Patients: A Narrative Review of Outcomes with Opioid and Adjuvant Pain Therapies.

¼ Chronic preoperative opioid use negatively affects outcomes after spine surgery, with increased complications and reoperations, longer hospital stays, decreased return-to-work rates, worse patient-reported outcomes, and a higher risk of continued opioid use postoperatively.¼ The definition of chronic opioid use is not consistent across studies, and a more specific and consistent definition will aid in stratifying patients and understanding their risk of inferior outcomes.¼ Preoperative weaning periods and maximum dose thresholds are being established, which may increase the likelihood of achieving a meaningful improvement after surgery, although higher level evidence studies are needed.¼ Spinal cord stimulators and intrathecal drug delivery devices are increasingly used to manage chronic back pain and are equivalent or perhaps even superior to opioid treatment, although few studies exist examining how patients with these devices do after subsequent spine surgery.¼ Further investigation is needed to determine whether a true mechanistic explanation exists for spine-related analgesia related to spinal cord stimulators and intrathecal drug delivery devices.

Comparison of the Odontoid and Orbital-Coronal Vertical Axis Lines in Evaluating Coronal Alignment and Outcomes in Adult Spinal Deformity Surgery.

STUDY DESIGN: Asymptomatic Multi-Ethnic Alignment Normative Study (MEANS) cohort: cross-sectional, multi-center. Symptomatic cohort: retrospective, multi-surgeon, single-center. OBJECTIVE: To assess the association of odontoid-coronal vertical axis (OD-CVA) and orbital-coronal vertical axis (ORB-CVA) with radiographic parameters, patient-reported outcomes (PROs), and clinical outcomes. SUMMARY OF BACKGROUND DATA: Previous literature studied the OD-CVA in an asymptomatic cohort and ORB-CVA in a symptomatic cohort, demonstrating their correlations with radiographic parameters and ORB-CVA with outcomes. METHODS: 468 asymptomatic adult participants were prospectively enrolled in the MEANS cohort. 174 symptomatic ASD patients with 6 fused levels and 2-year follow-ups were retrospectively enrolled in the symptomatic cohort. The association between OD-CVA and ORB-CVA, and radiographic parameters, perioperative variables, PROs, and outcomes were analyzed. Pearson's correlation was used to assess correlation and logistic regression odds of outcomes. RESULTS: In the MEANS cohort, the ORB-CVA correlated with C7-CVA (r=0.58) and OD-CVA (r=0.74). In the symptomatic cohort, preoperative ORB-CVA correlated better with leg length discrepancy (LLD) (r=0.17, P=0.029) while preoperative OD-CVA correlated better with C7-CVA (r=0.90, P<0.001). Postoperative ORB-CVA correlated with postoperative C7-CVA (r=0.66, P<0.001) and postoperative OD-CVA correlated stronger with postoperative C7-CVA (r=0.81, P<0.001). Both preoperative OD-CVA (r=0.199) and ORB-CVA (r=0.208) correlated with preoperative Oswestry Disability Index (ODI). ORB-CVA correlated better than OD-CVA in the preoperative SRS-22r pain category but worse in total and other subcategories. Preoperative ORB-CVA was associated with increased odds of intraoperative complication (OR=1.28, 1.01-1.22), like OD-CVA (OR=1.30, 1.12-1.53). Neither preoperative ORB-CVA nor OD-CVA was associated with reoperations and readmissions after multivariate analysis. Preoperative OD-ORB mismatch >1.5 cm was not associated with increased odds of intraoperative and postoperative complications, reoperations, or readmissions. CONCLUSION: ORB-CVA and OD-CVA correlated with radiographic parameters, PROs, and intraoperative complications. ORB-CVA and OD-CVA can be used interchangeably as cranial coronal parameters in ASD surgery.

Timing dependent synergies between motor cortex and posterior spinal stimulation in humans.

Volitional movement requires descending input from motor cortex and sensory feedback through the spinal cord. We previously developed a paired brain and spinal electrical stimulation approach in rats that relies on convergence of the descending motor and spinal sensory stimuli in the cervical cord. This approach strengthened sensorimotor circuits and improved volitional movement through associative plasticity. In humans it is not known whether dorsal epidural SCS targeted at the sensorimotor interface or anterior epidural SCS targeted within the motor system is effective at facilitating brain evoked responses. In 59 individuals undergoing elective cervical spine decompression surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord with epidural electrodes while muscle responses were recorded in arm and leg muscles. Spinal electrodes were placed either posteriorly or anteriorly, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and spinal sensory (posterior) but not spinal motor (anterior) stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred only when descending motor and spinal afferent stimuli were timed to converge in the spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, paired stimulation effects were present regardless of the severity of myelopathy as measured by clinical signs or spinal cord imaging. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation.

Adult spinal deformity patients revised for pseudarthrosis have comparable two-year outcomes to those not undergoing any revision surgery.

PURPOSE: This study aimed to evaluate whether adult spinal deformity patients undergoing revision for symptomatic pseudarthrosis have comparable two-year outcomes as patients who do not experience pseudarthrosis. METHODS: Patients whose indexed procedure was revision for pseudarthrosis (pseudo) were compared with patients who underwent a primary procedure and did not have pseudarthrosis by 2Y post-op (non-pseudo). Patients were propensity-matched (PSM) based on baseline (BL) sagittal alignment, specifically C7SVA and CrSVA-Hip. Key outcomes were 2Y PROs (SRS and ODI) and reoperation. All patients had a minimum follow-up period of two years. RESULTS: A total of 224 patients with min 2-year FU were included (pseudo = 42, non-pseudo = 182). Compared to non-pseudo, pseudo-patients were more often female (P = 0.0018) and had worse BL sagittal alignment, including T1PA (P = 0.02], C2-C7 SVA [P = 0.0002], and CrSVA-Hip [P = 0.004]. After 37 PSM pairs were generated, there was no significant difference in demographics, BL and 2Y alignment, or operative/procedural variables. PSM pairs did not report any significantly different PROs at BL. Consistently, at 2Y, there were no significant differences in PROs, including SRS function [3.9(0.2) vs 3.7(0.2), P = 0.44], pain [4.0 (0.2) vs. 3.57 (0.2), P = 0.12], and ODI [25.7 (5.2) vs 27.7 (3.7), P = 0.76]. There were no differences in 1Y (10.8% vs 10.8%, P > 0.99) and 2Y (13.2% vs 15.8%, P = 0.64) reoperation, PJK rate (2.6% vs 10.5%, P = 0.62), or implant failure (2.6% vs 10.5%, P = 0.37). Notably, only 2 patients (5.4%) had recurrent pseudarthrosis following revision. Kaplan-Meier curves indicated that patients undergoing intervention for pseudarthrosis had comparable overall reoperation-free survival (log-rank test, χ2 = 0.1975 and P = 0.66). CONCLUSIONS: Patients undergoing revision for pseudarthrosis have comparable PROs and clinical outcomes as patients who never experienced pseudarthrosis. Recurrence of symptomatic pseudarthrosis was infrequent.

Using Machine Learning (ML) Models to Predict Risk of Venous Thromboembolism (VTE) Following Spine Surgery.

STUDY DESIGN: A retrospective cohort study. OBJECTIVES: Venous thromboembolism (VTE) is a potentially high-risk complication for patients undergoing spine surgery. Although guidelines for assessing VTE risk in this population have been established, development of new techniques that target different aspects of the medical history may prove to be of further utility. The goal of this study was to develop a predictive machine learning (ML) model to identify nontraditional risk factors for predicting VTE in spine surgery patients. SUMMARY OF BACKGROUND DATA: A cohort of 63 patients was identified who had undergone spine surgery at a single center from 2015 to 2021. Thirty-one patients had a confirmed VTE, while 32 had no VTE. A total of 113 attributes were defined and collected via chart review. Attribute categories included demographics, medications, labs, past medical history, operative history, and VTE diagnosis. METHODS: The Waikato Environment for Knowledge Analysis (WEKA) software was used in creating and evaluating the ML models. Six classifier models were tested with 10-fold cross-validation and statistically evaluated using t tests. RESULTS: Comparing the predictive ML models to the control model (ZeroR), all predictive models were significantly better than the control model at predicting VTE risk, based on the 113 attributes ( P <0.001). The Random Forest model had the highest accuracy of 88.89% with a positive predictive value of 93.75%. The Simple Logistic algorithm had an accuracy of 84.13% and defined risk attributes to include calcium and phosphate laboratory values, history of cardiac comorbidity, history of previous VTE, anesthesia time, selective serotonin reuptake inhibitor use, antibiotic use, and antihistamine use. The J48 model had an accuracy of 80.95% and it defined hemoglobin laboratory values, anesthesia time, beta-blocker use, dopamine agonist use, history of cancer, and Medicare use as potential VTE risk factors. CONCLUSION: Further development of these tools may provide high diagnostic value and may guide chemoprophylaxis treatment in this setting of high-risk patients.

Morphological description of sagittal lumbar spinal alignment using curve magnitude, span, and apex-the multiethnic alignment normative study (MEANS).

BACKGROUND CONTEXT: Current definition of lumbar lordosis uses the L1-S1 angle. Prevailing classification of sagittal spinal morphology, derived from a young adult population, classifies the spine into four subtypes defined by their sacral slope (SS) and curve morphology. PURPOSE: To describe physiological sagittal alignment of the lumbar spine across age groups using three main parameters that dictate the lumbar curve: angular magnitude, span, and apex. STUDY DESIGN: A large, multicenter, cross-sectional radiographic comparison study. PATIENT SAMPLE: Four hundred sixty-eight healthy, asymptomatic subjects aged 18 to 80 years from five countries (184 males, 284 females; 98 France, 119 Japan, 79 Singapore, 80 Tunisia, 92 USA, mean age 40.61±14.99 years). OUTCOME MEASURES: Sagittal lumbar profile subtypes clustered based on lumbar curve angular magnitude (ie, Cobb angle of the lumbar lordosis), span, and apex, and described by sagittal radiographic parameters. METHODS: Subjects underwent whole-body low-dose EOS stereoradiographs. Comparisons between conventional L1-S1 lumbar lordosis (cLL) and true lumbar lordosis (tLL, defined by the inflection-S1 angle) were conducted. Using the K-means clustering algorithm, lumbar curve angular magnitude, span and apex were used to classify sagittal spinal morphology into subtypes, stratified across age groups. Further univariate and multivariate analyses were conducted to compare radiographic parameters across subtypes, and identify predictors for the lumbar curve's angular magnitude, span and apex. RESULTS: Mean cLL was -57.27±11.37°, and tLL was -62.62±10.76°. Using tLL, instead of cLL, to describe sagittal spinal morphology, we found significant differences in terms of angular magnitude of the lumbar curve, the median thoracolumbar inflection vertebral level and pelvic incidence-lumbar lordosis mismatch Multivariate analysis found a larger SS, more positive T9 tilt, and more kyphotic T4-T12 predictive for a more lordotic tLL, while a larger overhang distance predicted for a less lordotic tLL (p-values<.001). In addition, a larger T9 tilt, less lordotic L1-L5 and smaller PT were predictors of a more caudal thoracolumbar inflection and lumbar apical vertebral levels (p-values<.001). Sagittal lumbar profiles of subjects age<30 years, 30≤age<60 years and age≥60 years, could be classified into 4, 6, and 3 subtypes, respectively. CONCLUSIONS: Sagittal lumbar profile subtypes vary across age groups, with more homogenous morphologies at the extremes of ages. Improved understanding of the morphological evolution of sagittal spinal profiles with age in asymptomatic individuals will help guide future individualized surgical treatment.

High Cell Saver Autotransfusion is Associated With Perioperative Medical Complications in Adult Spinal Deformity Patients.

STUDY DESIGN: A retrospective, propensity-matched observational study. OBJECTIVE: To assess the impact of cell saver (CS) homologous transfusion on perioperative medical complications in adult patients undergoing spinal deformity surgery. SUMMARY OF BACKGROUND DATA: Despite many endorsing its use, many analyses still refute the efficacy of CS on decreasing total perioperative allogenic red blood cell transfusions, cost efficiency, and its effect on perioperative complications. METHODS: Adult patients who underwent spinal deformity surgery at a single center between 2015 and 2021 were retrospectively reviewed. Patient-specific, operative, radiographic, and 30-day complications/readmission data were collected for further analysis. Two methods were utilized to test our hypothesis: (1) absolute threshold model: two cohorts created among patients who received ≥550 mL of CS intraoperatively and those who received less; (2) adjusted ratio model: two cohorts created dependent on the ratio of CS to estimated blood loss (EBL). Propensity-score matching and various statistical tests were utilized to test the association between CS and perioperative medical complications. RESULTS: Two hundred seventy-eight patients were included in this analysis with a mean age of 61.3±15.7yrs and 67.6% being female. Using the first method, 73 patients received ≥550 mL of CS, and 205 received less. Propensity-score matching resulted in 28 pairs of patients. 39.3% of patients with ≥550 mL CS required readmission within 30 days compared with 3.57% of patients in the <550 mL cohort ( P =0.016), despite a nearly identical proportion of patients requiring intraoperative blood transfusions ( P >0.9999). Using the second method, 155 patients had CS/EBL<0.33 and 123 with CS/EBL ≥0.33. 5.16% and 21.9% among patients with CS/EBL<0.33 and CS/EBL≥0.33, respectively, were readmitted by the 30-day marker ( P <0.0001). CONCLUSIONS: Our findings indicate that greater CS volumes transfused are associated with higher rates of 30-day readmissions. Thus, surgeons should consider limiting CS volume intraoperatively to 550 mL and when greater volumes are required or preferred, ensuring that the ratio of CS:EBL remains under 0.33.

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.

Predicting postoperative coronal alignment for adult spinal deformity: do lower-extremity factors matter?

OBJECTIVE: The objective was to describe an intraoperative method that accurately predicts postoperative coronal alignment for up to 2 years of follow-up. The authors hypothesized that the intraoperative coronal target for adult spinal deformity (ASD) surgery should account for lower-extremity parameters, including pelvic obliquity (PO), leg length discrepancy (LLD), lower-extremity mechanical axis difference (MAD), and asymmetrical knee bending. METHODS: Two lines were drawn on intraoperative prone radiographs: the central sacral pelvic line (CSPL) (the line bisecting the sacrum and perpendicular to the line touching the acetabular sourcil of both hips) and the intraoperative central sacral vertical line (iCSVL) (which is drawn relative to CSPL based on the preoperative erect PO). The distance from the C7 spinous process to CSPL (C7-CSPL) and the distance from the C7 spinous process to iCSVL (iCVA) were compared with immediate and 2-year postoperative CVA. To account for LLD and preoperative lower-extremity compensation, patients were categorized into four preoperative groups: type 1, no LLD (< 1 cm) and no lower-extremity compensation; type 2, no LLD with lower-extremity compensation (PO > 1°, asymmetrical knee bending, and MAD > 2°); type 3, LLD and no lower-extremity compensation; and type 4, LLD with lower-extremity compensation (asymmetrical knee bending and MAD > 4°). A retrospective review of a consecutively collected cohort with ASD who underwent minimum 6-level fusion with pelvic fixation was performed for validation. RESULTS: In total, 108 patients (mean ± SD age 57.7 ± 13.7 years, 14.0 ± 3.9 levels fused) were reviewed. Mean preoperative/2-year postoperative CVA was 5.0 ± 2.0/2.2 ± 1.8 cm. For patients with type 1, both C7-CSPL and iCVA had similar error margins for immediate postoperative CVA (0.5 ± 0.6 vs 0.5 ± 0.6 cm, p = 0.900) and 2-year postoperative CVA (0.3 ± 0.4 vs 0.4 ± 0.5 cm, p = 0.185). For patients with type 2, C7-CSPL was more accurate for immediate postoperative CVA (0.8 ± 1.2 vs 1.7 ± 1.8 cm, p = 0.006) and 2-year postoperative CVA (0.7 ± 1.1 vs 2.1 ± 2.2 cm, p < 0.001). For patients with type 3, iCVA was more accurate for immediate postoperative CVA (0.3 ± 0.4 vs 1.7 ± 0.8 cm, p < 0.001) and 2-year postoperative CVA (0.3 ± 0.2 vs 1.9 ± 0.8 cm, p < 0.001). For patients with type 4, iCVA was more accurate for immediate postoperative CVA (0.6 ± 0.7 vs 3.0 ± 1.3 cm, p < 0.001) and 2-year postoperative CVA (0.5 ± 0.6 vs 3.0 ± 1.6 cm, p < 0.001). CONCLUSIONS: This system, which accounted for lower-extremity factors, provided an intraoperative guide to determine both immediate and 2-year postoperative CVA with high accuracy. For patients with type 1 and 2 (no LLD, with or without lower-extremity compensation), C7-intraoperative CSPL accurately predicted postoperative CVA up to 2-year follow-up (mean error 0.5 cm). For patients with type 3 and 4 (LLD, with or without lower-extremity compensation), iCVA accurately predicted postoperative CVA up to 2-year follow-up (mean error 0.4 cm).