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.

Intraoperative electrical stimulation of the human dorsal spinal cord reveals a map of arm and hand muscle responses.

Although epidural stimulation of the lumbar spinal cord has emerged as a powerful modality for recovery of movement, how it should be targeted to the cervical spinal cord to activate arm and hand muscles is not well understood, particularly in humans. We sought to map muscle responses to posterior epidural cervical spinal cord stimulation in humans. We hypothesized that lateral stimulation over the dorsal root entry zone would be most effective and responses would be strongest in the muscles innervated by the stimulated segment. Twenty-six people undergoing clinically indicated cervical spine surgery consented to mapping of motor responses. During surgery, stimulation was performed in midline and lateral positions at multiple exposed segments; six arm and three leg muscles were recorded on each side of the body. Across all segments and muscles tested, lateral stimulation produced stronger muscle responses than midline despite similar latency and shape of responses. Muscles innervated at a cervical segment had the largest responses from stimulation at that segment, but responses were also observed in muscles innervated at other cervical segments and in leg muscles. The cervical responses were clustered in rostral (C4-C6) and caudal (C7-T1) cervical segments. Strong responses to lateral stimulation are likely due to the proximity of stimulation to afferent axons. Small changes in response sizes to stimulation of adjacent cervical segments argue for local circuit integration, and distant muscle responses suggest activation of long propriospinal connections. This map can help guide cervical stimulation to improve arm and hand function.NEW & NOTEWORTHY A map of muscle responses to cervical epidural stimulation during clinically indicated surgery revealed strongest activation when stimulating laterally compared to midline and revealed differences to be weaker than expected across different segments. In contrast, waveform shapes and latencies were most similar when stimulating midline and laterally, indicating activation of overlapping circuitry. Thus, a map of the cervical spinal cord reveals organization and may help guide stimulation to activate arm and hand muscles strongly and selectively.

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.

A national analysis on complications and readmissions for adult cerebral palsy patients undergoing primary spinal fusion surgery.

STUDY DESIGN: Retrospective National Database Study. OBJECTIVE: Surgical intervention with spinal fusion is often indicated in cerebral palsy (CP) patients with progressive scoliosis. The purpose of this study was to utilize the National Readmission Database to determine the national estimates of complication rates, 90-day readmission rates, and costs associated with spinal fusion in adult patients with CP. METHODS: The 2012-2015 NRD databases were queried for all adult (age ≥ 19 years) patients diagnosed with CP (ICD-9: 333.71, 343.0-4, and 343.8-9) undergoing spinal fusion (ICD-9: 81.00-08). RESULTS: 1166 adult patients with CP (42.7% female) underwent spinal fusion surgery between 2012 and 2015. 153 (13.1%) were readmitted within 90 days following the primary surgery, with a mean 33.8 ± 26.5 days. Mean hospital charge of the primary admission was $141,416 ± $157,359 and $167,081 ± $145,416 for the non-readmitted and readmitted patients, respectively (p = 0.06). The mean 90-day readmission charge was $72,479 ± $104,100. Most common complications with the primary admission included UTIs (no readmission vs. readmission: 7.6% vs. 4.8%; p = 0.18), respiratory (6.9% vs. 5.6%; p = 0.62), implant (3.8% vs. 6.0%; p = 0.21), and paralytic ileus (3.6% vs. 3.2%; p = 0.858). Multivariate analyses demonstrated the following as independent predictors for 90-day readmission: comorbid anemia (OR: 2.8; 95% CI: 1.6-4.9; p < 0.001), coagulopathy (2.9, 1.1-8.0, 0.037), perioperative blood transfusion (2.0, 1.1-3.8, 0.026), wound complication (6.4, 1.3-31.6, 0.023), and transfer to short-term hospital versus routine disposition (4.9, 1.0-23.3, 0.045). CONCLUSION: Quality improvement efforts should be aimed at reducing rates of infection related complications as this was the most common reason for short-term complications and unplanned readmission following surgery.

Correlation analysis of the PI-LL mismatch according to the pelvic incidence from a database of 468 asymptomatic volunteers.

PURPOSE: Previous studies on adults with degenerative scoliosis (ADS) have been fixed the threshold of PI-LL mismatch less than 10° for achieving good clinical outcomes. Recent studies discussed that PI-LL mismatch should consider individual pelvic incidence (PI) and should be set first in a normal population. The purpose of this study is to assess the variability of PI-LL mismatch according to PI in an asymptomatic population. METHODS: Full-body low dose stereoradiographic evaluation was done in a multi-ethnic cohort of 468 asymptomatic adult volunteers. Patients were clustered in three groups depending on individual PI values: PI < 45°, 45° < PI < 60° and PI > 60°. 3D measurements were performed using a commercially available 2D/3D modeling software to establish a correlation of PI with other spinopelvic parameters. ANOVA and Tukey's HSD for post-hoc analysis were used to determine the differences between the three groups. RESULTS: In our asymptomatic population, the mean value of PI-LL mismatch is - 5.4° ± 10.7°. Clusterization of the population reveals significant differences in the distribution of L1S1 lordosis, pelvic tilt and PI-LL with positive linear correlation according to PI values. As an interestingly result, PI-LL mismatch is equal to 0° when PI is around 64°. CONCLUSIONS: The present study demonstrated that PI-LL mismatch is negative in an asymptomatic population (- 5.4° ± 10.7°) and the value should be customized to each patient to be able to restore the appropriate lordosis in ADS. The PI-LL mismatch is given by the formula PI-LL = - 28.5 + 0.44 × PI.

Spinal fusion in pediatric patients with marfan syndrome: a nationwide assessment on short-term outcomes and readmission risk.

PURPOSE: The purpose of this study was to utilize the National Readmission Database (NRD) to determine estimates for complication rates, 90-day readmission rates, and hospital costs associated with spinal fusion in pediatric patients with Marfan syndrome. METHODS: The 2012-2015 NRD databases were queried for all pediatric (< 19 years old) patients diagnosed with Marfan syndrome undergoing spinal fusion surgery. The primary outcome variables in this study were index admission complications and 90-day readmissions. RESULTS: A total of 249 patients with Marfan syndrome underwent spinal fusion surgery between 2012 and 2015 (mean age ± standard deviation at the time of surgery: 14 ± 2.0, 132 (53%) female). 25 (10.1%) were readmitted within 90 days of the index hospital discharge date. Overall, 59.7% of patients experienced at least one complication during the index admission. Unplanned 90-day readmission could be predicted by older age (odds ratio 2.3, 95% confidence interval 1.3-4.2, p = 0.006), Medicaid insurance status (56.0, 3.8-820.0, p = 0.003), and experiencing an inpatient medical complication (42.9, 4.6-398.7, p = 0.001). Patients were readmitted for wound dehiscence (8 patients, 3.2%), nervous system related complications (3 patients, 1.2%), and postoperative infectious related complications (4 patients, 1.6%). CONCLUSION: This study is the first to demonstrate on a national level the complications and potential risk factors for 90-day hospital readmission for patients with Marfan syndrome undergoing spinal fusion. Patients with Marfan syndrome undergoing spinal fusion often present with multiple medical comorbidities that must be managed carefully perioperatively to reduce inpatient complications and early hospital readmissions.

The odontoid-CSVL distance in a global population of asymptomatic volunteers: normative values and implications for spinal coronal alignment.

PURPOSE: In a population of asymptomatic volunteers across 5 countries, we sought to: (a) establish normative values of the Odontoid-Central Sacral Vertical Line (OD-CSVL) across patient factors, and (b) assess correlations of OD-CSVL with other radiographic parameters. METHODS: A prospective, cross-sectional study of asymptomatic adult volunteers, ages 18-80 years, were enrolled across 5 countries (France, Japan, Singapore, Tunisia, United States) forming the Multi-Ethnic Alignment Normative Study (MEANS) cohort. Included volunteers had no known spinal disorder(s), no significant neck/back pain (VAS ≤ 2; ODI ≤ 20), and no significant scoliosis (Cobb ≤ 20°). Radiographic measurements included commonly used coronal alignment parameters (mm) and angles (°). OD-CSVL was defined as the difference between the odontoid plumb line (line from the tip of the odontoid vertically down) and the CSVL (vertical line from the center of the sacrum). Chi-square, student's t tests, Kruskal-Wallis, Wilcoxon rank-sum, linear regression, and Pearson's correlation were used with significance at p < 0.05. RESULTS: 467 volunteers were included with normative OD-CSVL values by age decade, gender, BMI, and country. Mean ± SD OD-CSVL was 8.3 mm ± 6.5 mm and 31 (6.6%) volunteers were almost perfectly aligned (OD-CSVL < 1 mm). A linear relationship was seen between OD-CSVL with both age (p < 0.001) and BMI (p = 0.015). Significant variation was seen between OD-CSVL and 5 different ethnicities (p = 0.004). OD-CSVL correlated best with other coronal radiographic parameters, C7-CSVL (r = 0.743, p < 0.001), OD-knee (r = 0.230, p < 0.001), CAM-knee (r = 0.612, p < 0.001), and regional TL cobb angle (r = 0.4214, p = 0.005). CONCLUSION: Among asymptomatic volunteers, increased OD-CSVL was significantly associated with increased age, increased BMI, and ethnicity, but not gender. OD-CSVL correlated strongest with C7-CSVL, TL cobb angle, OD-knee, and CAM-knee. OD-CSVL. These results support further study of OD-CSVL in symptomatic adult spine deformity patients.

Mechanical properties of bioresorbable self-reinforced posterior cervical rods.

STUDY DESIGN: A biomechanical study. OBJECTIVE: To test the mechanical and physical properties of self-reinforced copolymer bioresorbable posterior cervical rods and compare their mechanical properties to commonly used Irene titanium alloy rods. SUMMARY OF BACKGROUND DATA: Bioresorbable instrumentation is becoming increasingly common in surgical spine procedures. Compared with metallic implants, bioresorbable implants are gradually reabsorbed as the bone heals, transferring the load from the instrumentation to bone, eliminating the need for hardware removal. In addition, bioresorbable implants produce less stress shielding due to a more physiological modulus of elasticity. METHODS: Three types of rods were used: (1) 5.5 mm copolymer rods and (2) 3.5 mm and (3) 5.5 mm titanium alloy rods. Four tests were used on each rod: (1) 3-point bending test, (2) 4-point bending test, (3) shear test, and (4) differential scanning calorimeter test. The outcomes were recorded: Young modulus (E), stiffness, maximum load, deflection at maximum load, load at 1.0% strain of the rod's outer surface, and maximum bending stress. RESULTS: The Young modulus (E) for the copolymer rods (mean range, 6.4-6.8 GPa) was significantly lower than the 3.5 mm titanium rods (106 GPa) and the 5.5 mm titanium rods (95 GPa). The stiffness of the copolymer rods (mean range, 16.6-21.4 N/mm) was also significantly lower than the 3.5 mm titanium alloy rods (43.6 N/mm) and the 5.5 mm titanium alloy rods (239.6 N/mm). The mean maximum shear load of the copolymer rods was 2735 N and they had significantly lower mean maximum loads than the titanium rods. CONCLUSIONS: Copolymer rods have adequate shear resistance, but less load resistance and stiffness compared with titanium rods. Their stiffness is closer to that of bone, causing less stress shielding and better gradual dynamic loading. Their use in semirigid posterior stabilization of the cervical spine may be considered.

Risk factors for proximal junctional kyphosis in a multicenter study of Lenke type 5 and 6 adolescent idiopathic scoliosis patients.

PURPOSE: In Lenke type 5 and 6 curves, a major thoracolumbar or lumbar curve, the rates of PJK are reported as high as 50%. The purpose of this study was to confirm the rate of PJK, investigate possible risk factors, and evaluate surgical complications and the long-term effects of PJK on patient outcomes. METHODS: A retrospective review of multicenter data identified 192 with patients with 2 year and 94 with 5-year follow-up. Included patients had a Lenke type 5 or 6 curve and underwent a selective thoracolumbar or lumbar curve fusion. All radiographs preoperatively and postoperatively (1 year, 2 years, and 5 years) were evaluated. Demographic and radiographic data was analyzed as risk factors for PJK using a multi-variate regression. Outcomes scores and complications were compared between groups. RESULTS: 17 patients (8.9%) developed radiographic PJK; 1 at 1 year, 7 at 2 years, and another 9 at 5 years. All 17 patients had an upper instrumented vertebra (UIV) within 3 levels or less caudal of the thoracic kyphosis apex (the most horizontal vertebra on the sagittal); no patient with a UIV 4 or more levels from the thoracic apex (n = 96) developed PJK (X2 = 13.03, p < 0.001). In addition, PJA > 8° was found to significantly increase the risk of PJK (p = 0.039). SRS scores were significantly worse for PJK patients at 5 years in the self-image and function (p < 0.01). CONCLUSION: In Lenke 5/6 curves, no patient with a UIV 4 or more levels caudal to the thoracic kyphosis apex had PJK up to 5 years postoperatively. PJA greater than 8° was identified as a risk factor for PJK. Patients with radiographic PJK had worse SRS scores 5 years postoperatively.

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.

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.

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.

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.

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.

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.

Patient-Specific Rods in Adolescent and Adult Spinal Deformity Surgery: A Narrative Review.

Spinal deformity surgery often requires complex surgical interventions that can have a drastic effect on both patient quality of life and functional capacity. Modern-day corrective solutions for these deformities include spinal osteotomies, pedicle screw instrumentation, and dual/multirod constructs. These solutions are efficacious and are currently considered standard practice for spinal surgeons, but they lack individualization. Patient-specific rods (PSRs) are a novel technology that attempts to offer a personalized approach to spinal deformity correction based on preoperative computerized tomography scans. Moreover, PSRs may offer several advantages to conventional rods, which include achievement of desired rod contour angles according to surgical planning alignment goals, reduced operative time, and reduced blood loss. In adolescent idiopathic scoliosis, those instrumented with PSR have observed coronal Cobb reductions up to 74%. In adult spinal deformity, PSRs have offered superior correction in radiographic parameters such as sagittal vertical axis and pelvic incidence minus lumbar lordosis. However, there still remains a paucity of research in this area, mainly in health care expenditure, cost-effectiveness, and longitudinal clinical outcomes. The purpose of this article is to survey the current body of knowledge of PSR instrumentation in both adolescent and adult spinal deformity populations. The current strength, limitations, and future directions of PSRs are highlighted throughout this article.

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.

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.

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.

Cranial sagittal vertical axis to the hip as the best sagittal alignment predictor of patient-reported outcomes at 2 years postoperatively in adult spinal deformity surgery.

OBJECTIVE: The objective was to discern whether the cranial sagittal vertical axis (CrSVA) can best predict the trajectory of patient-reported outcome measures (PROMs) at 2 years postoperatively. METHODS: This was a retrospective cohort study of prospectively collected adult spinal deformity patient data. CrSVA relative to the sacrum, hip (CrSVA-H), knee, and ankle was measured as the horizontal distance to the vertical plumb line from the nasion-inion midpoint, with positive values indicating an anterior cranium. Standard sagittal alignment parameters were also collected. Outcome variables were PROMs as measured by Scoliosis Research Society-22r questionnaire (SRS-22r) total and subdomain scores and the Oswestry Disability Index. Pearson's correlation coefficients and univariate regressions were performed to investigate associations between predictors and PROMs. Two conceptual multivariable linear regression models for each 2-year outcome measure were built after adjusting for the impact of preoperative SRS-22r scores. Model 1 assessed pre- and postoperative alignment only relative to C2 and C7, while model 2 assessed alignment relative to C2 and C7 as well as the cranium. RESULTS: There was a total of 363 patients with 2 years of radiographic and PROM follow-up (68.0% female, mean [standard error of the mean] age 60.8 [0.78] years, BMI 27.5 [0.29], and total number of instrumented levels 12.8 [0.22]). CrSVA measures were significantly associated with the 2-year SRS-22r total and subdomain scores. In univariate regression, revision surgery, number of prior surgeries, frailty, BMI, total number of osteotomies, and lower baseline total SRS-22r score as well as postoperative sagittal alignment were significantly associated with worse 2-year SRS-22r scores. In multivariable regression, after adjusting for baseline SRS-22r scores, greater preoperative C2 to sacrum sagittal vertical axis (SVA) and C7 SVA were found to be the only independent predictors of 2-year total SRS-22r score (ß = -0.011 [p = 0.0026] and ß = 0.009 [p = 0.0211], respectively) when alignment was considered only relative to C2. However, in the subsequent model, CrSVA-H replaced C7 SVA as the independent factor driving postoperative SRS-22r total scores (ß = -0.006, p < 0.0001). That is, when the model included alignment relative to the cranium, C2, and C7, greater or more anterior CrSVA-H resulted in worse SRS-22r scores, while smaller or more posterior CrSVA-H resulted in better scores. Similar models for subdomains again found CrSVA-H to be the best predictor of function (ß = -0.0095, p < 0.0001), pain (ß = -0.0091, p < 0.0001), self-image (ß = -0.0084, p = 0.0004), and mental health (ß = -0.0059, p = 0.0026). CONCLUSIONS: In multivariable regression, C7 SVA was supplanted by CrSVA-H alignment as a significant, independent predictor of 2-year SRS-22r scores in patients with adult spinal deformity and should be considered as one of the standard postoperative sagittal alignment target goals.