After Adult Spinal Deformity Surgery Research Articles

Hounsfield units and vertebral bone quality score for predicting mechanical complications after adult spinal deformity surgery: a systematic review and meta-analysis.

The purpose of this systematic review and meta-analysis is to assess existing literature and determine the association between the Hounsfield unit (HU) value and the vertebral body quality (VBQ) score with mechanical complications (MCs) after adult spinal deformity (ASD) surgery. Although bone quality is considered an increasingly important factor for MCs after ASD surgery, the utility of the HU value assessed by computed tomography and the VBQ score assessed by magnetic resonance imaging remains unknown. A systematic review of PubMed, Embase, and Cochrane Library databases was performed to find studies evaluating the association between the HU value and the VBQ score with MCs after ASD surgery. In the subsequent meta-analysis, MC outcomes were combined using a random-effects model, and the standardized mean difference and 95% confidence interval were calculated. The final analysis included a total of 20 studies. Nineteen studies reported HU values, and two studies reported VBQ scores. Proximal junctional kyphosis/failure (PJK/PJF) was reported as the MC in 16 studies, whereas other MCs were included in 6 studies. Six studies with a pool of 506 patients with ASD revealed that preoperative HU values at the upper instrumented vertebra (UIV) and UIV+1 were significantly lower in patients with PJK/PJF (standardized mean difference, -0.74; 95% confidence interval, -1.09 to -0.40). Three studies suggested an cutoff HU value of approximately ≤120, yielding a pooled sensitivity of 0.77, specificity of 0.67, and diagnostic odds ratio of 7.01. However, two studies reported conflicting results on the relationship between the VBQ score and PJK/PJF. Low HU values predicted the risk of certain MCs, particularly PJK/PJF, after ASD surgery. An HU value of <120 should alert surgeons to be cautious about the postoperative occurrence of PJK/PJF. Future studies are needed to validate the cutoff HU value and evaluate the utility of the VBQ score.

Characterization of Patients with Poor Clinical Outcome after Adult Spinal Deformity Surgery: A Multivariate Analysis of Mean 8-Year Follow-Up Data.

Background/Objective: Limited data exist regarding the long-term clinical outcomes and related factors after adult spinal deformity (ASD) surgery. This study aims to characterize patients who experienced poor clinical outcomes during long-term follow-up after ASD surgery. Methods: Patients who underwent ASD surgery with ≥5-vertebra fusion including the sacrum and ≥5-year follow-up were included. They were divided into two groups according to the Oswestry Disability Index (ODI) at the last follow-up: group P (poor outcome, ODI > 40) and group NP (non-poor outcome, ODI ≤ 40). Clinical variables, including patient factors, surgical factors, radiographic parameters, and mechanical complications (proximal junctional kyphosis [PJK] and rod fracture), were compared between the groups. Results: A total of 105 patients were evaluated, with a mean follow-up of 100.6 months. The mean age was 66.3 years, and 94 patients (89.5%) were women. There were 52 patients in group P and 53 patients in group NP. Univariate analysis showed that low T-score, postoperative correction relative to age-adjusted pelvic incidence-lumbar lordosis, T1 pelvic angle (TPA) at last follow-up, and PJK development were significant factors for poor clinical outcomes. Multivariate analysis identified PJK as the single independent risk factor (odds ratio [OR] = 3.957 for PJK development relative to no PJK, OR = 21.141 for revision surgery for PJK relative to no PJK). Conclusions: PJK development was the single independent factor affecting poor clinical outcomes in long-term follow-up. Therefore, PJK prevention appears crucial for achieving long-term success after ASD surgery.

Unintended readmissions and reoperations within 30 and 90 days following adult spinal deformity surgery.

This study investigated the rates and etiologies of unintended readmissions and reoperations within 30 and 90 days after adult spinal deformity (ASD) surgery. The authors aimed to identify the risk factors for readmission and reoperation by analyzing patient demographic and surgical characteristics. This retrospective cohort study included 307 consecutive patients who underwent surgery for ASD from 2012 to 2022 at a single academic institution. Data were collected on patient demographic characteristics, comorbidities, operative details, and postoperative complications. Chi-square and multivariable logistic regression models were used to identify the risk factors associated with 30- and 90-day readmissions and reoperations. The mean ± SD age at surgery was 66.6 ± 10.5 years, and the majority (80.8%) of patients were female. The 30-day and 90-day readmission rates were 11.7% and 15.3%, respectively. Multivariable regression for 30-day readmissions revealed that length of hospital stay (LOS) after index surgery of > 20 days (OR 2.48) and surgical factors such as vertebral column resection (VCR) (OR 4.26) and pelvic fixation (OR 4.38) were risk factors. Other factors such as the American Society of Anesthesiologists Physical Status Classification System (ASA) class, prior spine surgery, and age were not associated with 30-day readmissions. Ninety-day readmission was associated with high ASA class (OR 2.37) and LOS > 20 days (OR 2.82). The 30- and 90-day reoperation rates were 7.8% and 10.1%, respectively. The variables associated with 30-day reoperations were intraoperative VCR (OR 3.34) and LOS > 20 days (OR 9.38). Ninety-day reoperations were associated with dural tears (OR 3.33) and LOS > 20 days (OR 3.68). This study provides valuable insights into the incidence of unintended readmission and reoperation within 30 and 90 days after ASD surgery in an Asian population. By identifying the associated risk factors, healthcare providers can customize surgical strategies and optimize perioperative care to effectively mitigate these events.

Prediction of proximal junctional kyphosis and failure after corrective surgery for adult spinal deformity: an MRI-based model combining bone and paraspinal muscle quality metrics

BACKGROUNDProximal junctional kyphosis (PJK) and proximal junctional failure (PJF) are common complications observed after adult spinal deformity (ASD) surgery and major cause for unplanned reoperations. In addition to spinal alignment, osteoporosis and paraspinal muscle (PSM) degeneration are reportedly indispensable factors that account for PJK/PJF. PURPOSETo investigate the utility of the preoperative risk assessment model using MRI-based skeletomuscular metrics in predicting PJK and/or PJF(PJK/PJF) after ASD correction. STUDY DESIGNRetrospective case-control study. PATIENT SAMPLEConsecutive series of 149 patients at a single academic institution. OUTCOME MEASURESMRI-based measurements of vertebral bone quality at upper instrumented vertebra (VBQ-U) score and fat infiltration rate (FI%) of paraspinal muscle (PSM). METHODSWe performed a retrospective analysis of patients with ASD who underwent ≥5-segment fusion. The vertebral bone quality (VBQ) scoring system was used to assess the bone quality. The PSM quality including FI% and cross-sectional area (CSA) was evaluated. Multivariate logistic regression was performed to determine potential risk factors of PJK/PJF. RESULTSOf 149 patients who underwent ASD surgery, PJK/PJF was found in 45(30.2%). Mean VBQ-U scores were 3.45±0.64 and 3.00±0.56 for patients with and without PJK/PJF (p<.001). Mean FI% of PSM(L3/L4) was 27.9±12.8 and 20.7±13.3 for patients with and without PJK/PJF (p<.001). On multivariate analysis, the VBQ-U score and FI% of PSM were significant independent predictors of PJK/PJF. The AUC for the novel risk assessment model is 0.806, with a predictive accuracy of 86.7%. CONCLUSIONIn patients undergoing ASD correction, paraspinal muscle and vertebral bone quality significantly outweigh radiographic alignment parameters in predicting PJK/PJF. The MRI-based risk assessment model offers a valuable tool for early assessing individualized risk for PJK/PJF.

Return to sporting activities following long fusions to the pelvis in adult spinal deformity

Returning to recreational sporting activities after adult spinal deformity (ASD) correction may significantly impact the patient's perceived quality of life. This study sought to characterize participation in sporting activities before and after ASD surgery, and to identify factors associated with impaired return to sports. Cross-sectional survey and retrospective review of prospectively collected data. Patients who underwent posterior-only thoracolumbar ASD surgery between 2016 and 2021 with ≥1 year follow-up and ≥3 levels of fusion to the pelvis were included. Preoperative and postoperative participation in sports, timing of return to these activities, and reasons for limited sports participation postoperatively were assessed. A survey was used to evaluate outcome measures. Differences in demographic, surgical, and perioperative variables between patients who reported improved, unchanged, or worsened activity tolerance were evaluated. Ninety-five patients were included (mean age: 64.3±10.1 years; BMI: 27.3±6.1 kg/m2; median levels fused: 7). The survey was completed at an average of 43.5±15.9 months after surgery. Sixty-eight (72%) patients participated in sports preoperatively. The most common sports were swimming (n=33, 34.7%), yoga (n=23, 24.2%), weightlifting (n=20, 21.1%), elliptical (n=19, 20.0%), and golf (n=11, 11.6%). Fifty-seven (83.8%) returned to at least one sport postoperatively, most commonly 6-12 months after surgery (45%). Elliptical had the highest rate of equal or improved participation (53%). Patients generally returned below their preoperative level to all other sports. Reasons for reduced sporting activities included physical limitation (51.4%), fear (20.0%), pain (17.1%), and surgeon advice (8.6%). There were no differences in the demographic, surgical, or perioperative characteristics between those who returned to sports at the same or better level compared with those who returned at a lower level. About 84% of patients successfully resumed sporting activities after undergoing fusion to the sacrum/pelvis for ASD. However, this return is typically at a lower level of participation than their preoperative participation, particularly in higher demand sports. Understanding trends in sporting activity may be valuable for counseling patients and setting expectations.

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

Despite modern fixation techniques, spinopelvic fixation failure (SPFF) after adult spinal deformity (ASD) surgery ranges from 4.5 to 38.0%, with approximately 50% requiring reoperation. Compared to other well-studied complications after ASD surgery, less is known about the incidence and predictors of SPFF. Given the high rates of SPFF and reoperation needed to treat it, the purpose of this systematic review and meta-analysis was to report the incidence and failure mechanisms of SPF after ASD surgery. The literature search was executed across four databases: Medline via PubMed and Ovid, SPORTDiscus via EBSCO, Cochrane Library via Wiley, and Scopus. Study inclusion criteria were patients undergoing ASD surgery with spinopelvic instrumentation, report rates of SPFF and type of failure mechanism, patients over 18years of age, minimum 1-year follow-up, and cohort or case-control studies. From each study, we collected general demographic information (age, gender, and body mass index), primary/revision, type of ASD, and mode of failure (screw loosening, rod breakage, pseudarthrosis, screw failure, SI joint pain, screw protrusion, set plug dislodgment, and sacral fracture) and recorded the overall rate of SPF as well as failure rate for each type. For the assessment of failure rate, we required a minimum of 12months follow-up with radiographic assessment. Of 206 studies queried, 14 met inclusion criteria comprising 3570 ASD patients who underwent ASD surgery with pelvic instrumentation (mean age 65.5 ± 3.6years). The mean SPFF rate was 22.1% (range 3-41%). Stratification for type of failure resulted in a mean SPFF rate of 23.3% for the pseudarthrosis group; 16.5% for the rod fracture group; 13.5% for the iliac screw loosening group; 7.3% for the SIJ pain group; 6.1% for the iliac screw group; 3.6% for the set plug dislodgement group; 1.1% for the sacral fracture group; and 1% for the iliac screw prominence group. The aggregate rate of SPFF after ASD surgery is 22.1%. The most common mechanisms of failure were pseudarthrosis, rod fracture, and iliac screw loosening. Studies of SPFF remain heterogeneous, and a consistent definition of what constitutes SPFF is needed. This study may enable surgeons to provide patient specific constructs with pelvic fixation constructs to minimize this risk of failure.

Who Can Be Discharged Home after Adult Spinal Deformity Surgery?

Introduction: After adult spinal deformity (ASD) surgery, patients often require postoperative rehabilitation at an inpatient rehabilitation (IPR) center or a skilled nursing facility (SNF). However, home discharge is often preferred by patients and hsas been shown to decrease costs. In a cohort of patients undergoing ASD surgery, we sought to (1) report the incidence of discharge to home, (2) determine the factors significantly associated with discharge to home in the form of a simple scoring system, and (3) evaluate the impact of discharge disposition on patient-reported outcome measures (PROMs). Methods: A single-institution, retrospective cohort study was undertaken for patients undergoing ASD surgery from 2009 to 2021. Inclusion criteria were ≥ 5-level fusion, sagittal/coronal deformity, and at least 2-year follow-up. Exposure variables included preoperative, perioperative, and radiographic data. The primary outcome was discharge status (dichotomized as home vs. IPR/SNF). Secondary outcomes included PROMs, such as the numeric rating scales (NRSs) for back and leg pain, the Oswestry Disability Index (ODI), and EQ-5D. A subanalysis comparing IPR to SNF discharge was conducted. Univariate analysis was performed. Results: Of 221 patients undergoing ASD surgery with a mean age of 63.6 ± 17.6, 112 (50.6%) were discharged home, 71 (32.2%) were discharged to an IPR center, and 38 (17.2%) were discharged to an SNF. Patients discharged home were significantly younger (55.7 ± 20.1 vs. 71.8 ± 9.1, p < 0.001), had lower rate of 2+ comorbidities (38.4% vs. 45.0%, p = 0.001), and had less hypertension (57.1% vs. 75.2%, p = 0.005). Perioperatively, patients who were discharged home had significantly fewer levels instrumented (10.0 ± 3.0 vs. 11.0 ± 3.4 levels, p = 0.030), shorter operative times (381.4 ± 139.9 vs. 461.6 ± 149.8 mins, p < 0.001), less blood loss (1101.0 ± 977.8 vs. 1739.7 ± 1332.9 mL, p < 0.001), and shorter length of stay (5.4 ± 2.8 vs. 9.3 ± 13.9 days, p < 0.001). Radiographically, preoperative SVA (9.1 ± 6.5 vs. 5.2 ± 6.8 cm, p < 0.001), PT (27.5 ± 11.1° vs. 23.4 ± 10.8°, p = 0.031), and T1PA (28.9 ± 12.7° vs. 21.6 ± 13.6°, p < 0.001) were significantly higher in patients who were discharged to an IPR center/SNF. Additionally, the operating surgeon also significantly influenced the disposition status (p < 0.001). A scoring system of the listed factors was proposed and was validated using univariate logistic regression (OR = 1.55, 95%CI = 1.34-1.78, p < 0.001) and ROC analysis, which revealed a cutoff value of > 6 points as a predictor of non-home discharge (AUC = 0.75, 95%CI = 0.68-0.80, p < 0.001, sensitivity = 63.3%, specificity = 74.1%). The factors in the scoring system were age > 56, comorbidities ≥ 2, hypertension, TIL ≥ 10, operative time > 357 mins, EBL > 1200 mL, preop SVA > 6.6 cm, preop PT > 33.6°, and preop T1PA > 15°. When comparing IPR (n = 71) vs. SNF (n = 38), patients discharged to an SNF were significantly older (74.4 ± 8.6 vs. 70.4 ± 9.1, p = 0.029) and were more likely to be female (89.5% vs. 70.4%, p = 0.024). Conclusions: Approximately 50% of patients were discharged home after ASD surgery. A simple scoring system based on age > 56, comorbidities ≥ 2, hypertension, total instrumented levels ≥ 10, operative time > 357 mins, EBL > 1200 mL, preop SVA > 6.6 cm, preop PT > 33.6°, and preop T1PA > 15° was proposed to predict non-home discharge. These findings may help guide postoperative expectations and resource allocation after ASD surgery.

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

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

The Relationship between the Hounsfield Units Value of the Upper Instrumented Vertebra and the Severity of Proximal Junctional Fracture after Adult Spinal Deformity Surgery.

Background and Objectives: In this retrospective cohort study, we investigate associations between the Hounsfield units (HU) value of upper instrumented vertebra (UIV) and proximal junctional kyphosis (PJK) after adult spinal deformity (ASD) surgery. Materials and Methods: The cohort consisted of 60 patients (mean age 71.7 years) who underwent long instrumented fusion surgery (≥6 vertebrae) for ASD with at least 1 year of follow-up. The preoperative bone mineral density (BMD) measured on DXA scans, the HU values at UIV and UIV+1, and the radiographic parameters were compared between the PJK and non-PJK groups. The severity of UIV fracture was assessed using a semiquantitative (SQ) grade. Results: PJK occurred in 43% of patients. No significant differences in patient age, sex, BMD, and preoperative radiographic parameters were observed between the PJK and non-PJK groups. The HU values of the UIV (103.4 vs. 149.0, p < 0.001) and UIV+1 (102.0 vs. 145.7, p < 0.001) were significantly lower in the PJK group. The cutoff values of HU at UIV and UIV+1 were 122.8 and 114.9, respectively. Lower HU values at UIV (Grade 1: 134.2, Grade 2: 109.6, Grade 3: 81.1, p < 0.001) and UIV+1 (Grade 1: 131.5, Grade 2: 107.1, Grade 3: 82.1, p < 0.001) were associated with severe SQ grade. Conclusions: Lower HU values at UIV and UIV+1 had a negative impact on signal incidence of PJK and were correlated with the severity of UIV fractures. Preoperative treatment of osteoporosis seems necessary for preoperative UIV HU values less than 120.

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

An aberrant inflammatory response, which plays a role in the development of postoperative complications, is observed in autoimmune diseases, Yet, there is a paucity of literature regarding the effects of autoimmune diseases after adult spinal deformity (ASD) surgery. The goal of this study was to determine the effects of autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus) on postoperative medical complications, patient-reported outcome measures (PROMs), and radiographic alignment in patients who underwent ASD surgery. Propensity-score matching for age and sex was performed for patients with autoimmune disease (group A) and nonautoimmune patients (group NA1). Postoperative medical complications, preoperative and 2-year follow-up PROMs, and preoperative, immediate postoperative, and 2-year follow-up radiographic alignment were evaluated. Among 386 patients (27 in group A and 359 in group NA1), autoimmune patients had a higher incidence of respiratory complications (11.1% vs 2.2%, p = 0.036), gastrointestinal complications (14.8% vs 3.1%, p = 0.016), urinary tract infections (14.8% vs 3.1%, p = 0.016), cholecystitis (7.4% vs 0%, p = 0.005), and fever of unknown origin (14.8% vs 0%, p < 0.001). Autoimmune patients had worse preoperative ODI (54.2 vs 44.7, p = 0.004) and 2-year follow-up Scoliosis Research Society 22-item Questionnaire (SRS-22) scores (3.1 vs 3.5, p = 0.039), with higher preoperative sacral slope (23.4° vs 17.8°, p = 0.020). Propensity-score matching for age and sex yielded 27 pairs (group A and group NA2). Having at least one medical complication (group A 74.1% vs group NA2 22.2%, p < 0.001), total complications per person (1.3 vs 0.3, p = 0.010), prognostic nutrition index (44.8 vs 48.6, p = 0.034), steroid use (51.9% vs 0%, p < 0.001), immunosuppressant use (48.1% vs 0%, p < 0.001), length of hospital stay (38 vs 27 days, p = 0.018), and discharge to care facility (29.6% vs 7.4%, p = 0.036) were higher in group A. Preoperative ODI (54.2 vs 43.2, p = 0.011) and 2-year follow-up SRS-22 scores (3.1 vs 3.6 p = 0.019) were worse in group A. No differences were observed in radiographic alignment. Patients with autoimmune disease had higher complication rates and worse PROMs following ASD surgery in this study. There was no difference in spinal alignment compared with controls. Multidisciplinary planning and full disclosure of possible adverse effects should be completed prior to correction of ASD in patients with autoimmune disease.

Assessing the influence of modifiable patient-related factors on complication rates after adult spinal deformity surgery.

Postoperative complication rates remain relatively high after adult spinal deformity (ASD) surgery. The extent to which modifiable patient-related factors influence complication rates in patients with ASD has not been effectively evaluated. The aim of this retrospective cohort study was to evaluate the association between modifiable patient-related factors and complications after corrective surgery for ASD. ASD patients with two-year data were included. Complications were categorized as follows: any complication, major, medical, surgical, major mechanical, major radiological, and reoperation. Modifiable risk factors included smoking, obesity, osteoporosis, alcohol use, depression, psychiatric diagnosis, and hypertension. Patients were stratified by the degree of baseline deformity (low degree of deformity (LowDef)/high degree of deformity (HighDef): below or above 20°) and age (Older/Younger: above or below 65 years). Complication rates were compared for modifiable risk factors in each age/deformity group, using multivariable logistic regression analysis to adjust for confounders. A total of 480 ASD patients met the inclusion criteria. By two years, complication rates were 72% ≥ one complication, 28% major, 21% medical, 27% surgical, 11% major radiological, 8% major mechanical, and 22% required reoperation. Younger LowDef patients with osteoporosis were more likely to suffer either a major mechanical (odds ratio (OR) 5.9 (95% confidence interval (CI) 1.1 to 36.9); p = 0.048) or radiological complication (OR 7.0 (95% CI 1.9 to 25.9); p = 0.003). Younger HighDef patients were much more likely to develop complications if obese, especially major mechanical complications (OR 2.8 (95% CI 1.1 to 8.6); p = 0.044). Older HighDef patients developed more complications when diagnosed with depression, including major radiological complications (OR 3.5 (95% CI 1.1 to 10.6); p = 0.033). Overall, a diagnosis of depression proved to be a risk factor for the development of major radiological complications (OR 2.4 (95% CI 1.3 to 4.5); p = 0.005). Certain modifiable patient-related factors, especially osteoporosis, obesity, and mental health status, are associated with an increased risk of complications after surgery for spinal deformity. Surgeons should look for these conditions when assessing a patient for surgery, and optimize them to the fullest extent possible before proceeding to surgical correction so as to minimize the prospect of postoperative morbidity.Cite this article: Bone Joint J2022;104-B(11):1249-1255.

Sacroiliac Joint Pain Should Be Suspected in Early Buttock and Groin Pain after Adult Spinal Deformity Surgery: An Observational Study.

Sacroiliac joint pain (SIJP) is one of the pathological conditions of adjacent segment disorders occurring after adult spinal deformity (ASD) surgery. This study aimed to test the hypothesis that even in ASD surgery using S2 alar-iliac (S2AI) screws, SIJP can develop much earlier than reported previously and can be rescued by ultrasound-guided sacroiliac joint block. Overall, 94 patients with ASD treated with long spinal fusion using S2AI screws were prospectively investigated for SIJP postoperatively, and the effect of ultrasound-guided sacroiliac joint block was evaluated. Additionally, the relationship between the symptomatic side of the SIJP and the surgical procedure; the preoperative and postoperative whole-spine sagittal and coronal alignment, lumbar pelvis sagittal plane alignment, and pelvic incidence-lumbar lordosis were retrospectively compared between the groups with and without SIJP. Eleven of 94 cases (11.7%) developed SIJP. The average onset was 12.0 (±6.2) days after surgery. The "one-finger test," "Gaenslen test," and "tenderness of the posterosuperior iliac spine" had high positivity rates for SIJP. Night pain occurred in 81.8% of patients and was one of the diagnostic features. There were no significant relationships between the symptomatic side of SIJP and the approach-side of lumbar interbody fusion, donor site of the iliac bone graft, or malposition of the S2AI screw. There were no significant differences in preoperative characteristics and radiological parameters between the SIJP-positive and -negative groups preoperatively, postoperatively, or in postoperative changes. Two of the 11 cases required the SIJ block four times, but all patients eventually achieved >70% pain relief with no recurrence. For good pain control and physical therapy, the fact that early buttock-groin pain after spinal fusion surgery has a 12% likelihood of being due to SIJP and can be relieved with the ultrasound-guided SIJ block is clinically important for diagnosis and pain management.

Timing of inpatient medical complications after adult spinal deformity surgery: early ambulation matters

BACKGROUNDThe substantial risk for medical complication after adult spinal deformity (ASD) surgery is well known. However, the timing of medical complications during the inpatient stay have not been previously described. Accurate anticipation of complications and adverse events may improve patient counseling and postoperative management. PURPOSE(1) Describe the rate of medical complication and adverse events by postoperative day after ASD surgery and (2) determine whether early ambulation is protective for complications. STUDY DESIGN/SETTINGSingle institution retrospective cohort study. PATIENT SAMPLETwo hundred thirty-five patients with ASD who underwent posterior-only fusion of the lumbar spine (≥5 levels to the pelvis) between 2013 and 2020. OUTCOME MEASURESMedical complications, categorized per the International Spine Study Group-AO system (cardiopulmonary [CP], gastrointestinal [GI], central nervous system [CNS], infectious [nonsurgical site], and renal) and adverse events (postoperative blood transfusion, urinary retention, and electrolyte abnormalities). METHODSPatients were identified from an institutional ASD database. Outcome measures were classified by the first postoperative day the event was recognized. Demographics, year of surgery, surgical factors, radiographic parameters, surgical invasiveness (ASD-S Index), frailty (Modified Frailty Index-5 [mFI-5]), Charlson Comorbidity Index (CCI), obstructive sleep apnea (OSA), smoking, preoperative opioid use, depression, and post-operative day of ambulation were assessed as risk factors for inpatient medical complications. RESULTSAfter exclusions of patients with incomplete medical chart data, 191 patients were available for analysis, mean age 66±10 y, BMI 28±5 kg/m2, PI-LL 24±20°, T1PA 28±13°. Inpatient medical complications occurred in 55 (28.8%) patients; adverse events occurred in 137 (71.7%). Length of stay was higher in patients with medical complications (mean 8.5±3.8 vs. 5.8±2.3 days, p<.001). However, for patients who had an adverse event, but no medical complication, LOS was comparable (p>.05). Most medical complications occurred by POD3 (58% of all complications). Risk (defined as the proportion of patients with that complication out of all inpatients that day) of CNS, CP, and GI complication peaked early in the postoperative course (CNS on POD1 [2.1% risk]; GI on POD2 [3.7%]; CP on POD3 [2.7%]). Risk for infectious and renal complications (infectious POD8 [2.7%]; renal POD7 [0.9%]) peaked later (Figure 1). On univariate analysis, patients with medical complications had higher rates of OSA (9.1% vs. 2.2%, p=.045), ASD-S (45.9 vs. 40.8, p=.04), max coronal cobb (46.9 vs. 36.7°, p=.003), ASA class (2.5 vs. 2.3, p=.01), and POD of ambulation (1.9 vs. 1.3, p=.01). On multivariate logistic regression (c-statistic 0.78), larger coronal cobb and later POD of ambulation were independent risk factors for complications (OR 1.04, 95% CI 1.01–1.07 and OR 2.3, 95% CI 1.2–4.7, respectively). CONCLUSIONSOur data may inform peri-operative management and patient expectations for hospitalization after ASD surgery. Early ambulation may reduce the risk of complications.

The Impact of Upper Instrumented Vertebra Orientation on Proximal Junctional Kyphosis: A Novel and Fixed Parameter, Fused Spinopelvic Angle.

A retrospective study. To evaluate the impact of upper instrumented vertebra (UIV) orientation including the fused spinopelvic angle (FSPA) on proximal junctional kyphosis (PJK). PJK is a challenging complication after adult spinal deformity (ASD) surgery. Some studies proposed UIV orientation act as a risk factor of PJK, but there remain debates because UIV orientation is changed by position. Therefore, we investigated the relationship between the FSPA, a novel parameter for the relationship between UIV and pelvis which did not change by position, and PJK. ASD patients who underwent long-segment fusion to the pelvis and followed up for more than two years were included. Comparative analysis was performed on spinopelvic parameters including UIV orientation parameters (UIV slope angle and FSPA) between PJK and non-PJK group. Binary regression analysis was conducted to find out the risk factors for PJK. And correlation analysis was conducted to find out the parameters that affect the FSPA. A total of 190 patients were included. PJK incidence was 13.2% (25/190). PJK group showed a significantly greater postoperative UIV slope (21.3° vs. 18.8°, P =0.041) and significantly lesser postoperative FSPA (-0.9° vs. 4.5°, P <0.001). In binary regression analysis, only FSPA acted as a risk factor of PJK (odds ratio=0.920, P =0.004). The FSPA has strong positive correlation with pelvic incidence (PI)-lumbar lordosis (LL) ( r =0.666, P <0.001) and negative correlation with lordosis distribution index (LDI) ( r =-0.228, P =0.004). The FSPA is a fixed parameter which is not dependent on position. A reduction of the FSPA increases the risk for PJK. The FSPA can be adjusted through PI-LL and LDI. Thus, surgeons should increase the FSPA by adjusting the PI-LL and LDI during ASD surgery to prevent PJK.

Surgical site infection is a major risk factor of pseudarthrosis in adult spinal deformity surgery

BACKGROUND CONTEXTDespite the evidence in appendicular skeletal surgery, the effect of infection on spinal fusion remains unclear, particularly after Adult Spinal Deformity (ASD) surgery. PURPOSEThe purpose of this study was to determine the impact of surgical site infection (SSI) in ASD surgery fusion rates and its association with other risks factors of pseudarthrosis. STUDY DESIGNWe conducted an international multicenter retrospective study on a prospective cohort of patients operated for spinal deformity. PATIENT SAMPLEA total of 956 patients were included (762 females and 194 males). OUTCOME MEASURESPatient's preoperative characteristics, pre and postoperative spinopelvic parameters, surgical variables, postoperative complications and were recorded. Surgical site infections were asserted in case of clinical signs associated with positive surgical samples. Each case was treated with surgical reintervention for debridement and irrigation. Presence of pseudarthrosis was defined by the association of clinical symptoms and radiological signs of nonfusion (either direct evidence on CT-scan or indirect radiographic clues such as screw loosening, rod breakage, screw pull out or loss of correction). Each iterative surgical intervention was collected. METHODSUnivariate and multivariate analysis with logistic regression models were performed to evaluate the role of risk factors of pseudarthrosis. RESULTSNine hundred fifty-six surgical ASD patients with more than two years of follow-up were included in the study. 65 of these patients were treated for SSI (6.8%), 138 for pseudarthrosis (14.4%), and 28 patients for both SSI and pseudarthrosis.On multivariate analysis, SSI was found to be a major risk factor of pseudarthrosis (OR=4.4; 95% CI=2.4,7.9) as well as other known risks factors: BMI (OR=1.1; 95% CI=1.0,1.1), smoking (OR=1.6; 95% CI=1.1,2.9), performance of Smith-Petersen osteotomy (OR = 1.6; 95% CI 1.0,2.6), number of vertebrae instrumented (OR=1.1; 95% CI=1.1,1.2) and the caudal level of fusion, with a distal exponential increment of the risk (OR max for S1=6, 95% CI=1.9,18.6). CONCLUSIONSSI significantly increases the risk of pseudarthrosis with an OR of 4.4.

159. Impact of smoking status on early and late outcomes after adult spinal deformity surgery

159. Impact of smoking status on early and late outcomes after adult spinal deformity surgery

160. Survival analysis using fusion status after adult spinal deformity (ASD) surgery with minimum 4-year follow-up

BACKGROUND CONTEXT Prior reports have focused on grading fusion status after adult spinal deformity (ASD) surgery; however, few focused on fusion status after 4-years postop. PURPOSE To identify risk factors for nonunion in a prospective cohort of ASD patients with long-term follow-up (=4 years). STUDY DESIGN/SETTING Prospective multicenter observational series. PATIENT SAMPLE Database enrollment required age =18 years, scoliosis =20°, sagittal vertical axis (SVA) =5cm, pelvic tilt =25°, or thoracic kyphosis =60°. OUTCOME MEASURES Fusions were rated as bilaterally fused (A), unilaterally fused (B), partially fused (C), or not fused (D). Primary outcome was fusion (grade A or B) vs nonunion (grade C or D) at minimum 4-year follow-up. Secondary outcome measures included health-related quality of life (HRQL) (Oswestry Disability Index [ODI], Short Form-36 [SF-36] scores, Scoliosis Research Society-22 [SRS-22r] scores). METHODS Surgically treated ASD patients prospectively enrolled into a multicenter study (2008-2020) were assessed for fusion (grade A or B) vs nonunion (grade C or D). Inclusion required postop fusion grading at minimum 4-year follow-up. Demographics, frailty, comorbidities, alignment (baseline and initial correction), index surgery (total levels fused, iliac fixation, interbody fusion [IBF], use of bone morphogenetic protein [BMP] and/or demineralized bone matrix [DBM], 3-column osteotomy [3CO]) were assessed to identify potential predictors of nonunion (grade C or D), which were then analyzed using Kaplan-Meier survival curves and log-rank comparisons. RESULTS A total of 227 patients achieved minimum 4-year follow-up and were included (age 58±14y, 82% women, BMI 27±5kg/m2, 40% prior spine surgery, ASD-FI 0.31 [frail], 15% osteoporosis). Index operations had 12±4 posterior levels, 70% iliac fixation, 62% IBF, 76% had BMP, 33% had DBM (of which 52% also had BMP), and 15% had 3CO. At final follow-up, 61 patients (27%) demonstrated nonunion (grade C or D). Older age (61±14 vs 57±14, p=0.015), no BMP usage (p 60 years) had significantly higher probability of nonunion (log-rank test p=0.024), and BMP had protective effect (log-rank test p 0.05). CONCLUSIONS This study demonstrated that older age (>60 years) was associated with significantly higher rates of nonunion at long-term follow-up (4 years) after ASD surgery, and that use of BMP had significant protective effect against this complication. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs. Prior reports have focused on grading fusion status after adult spinal deformity (ASD) surgery; however, few focused on fusion status after 4-years postop. To identify risk factors for nonunion in a prospective cohort of ASD patients with long-term follow-up (=4 years). Prospective multicenter observational series. Database enrollment required age =18 years, scoliosis =20°, sagittal vertical axis (SVA) =5cm, pelvic tilt =25°, or thoracic kyphosis =60°. Fusions were rated as bilaterally fused (A), unilaterally fused (B), partially fused (C), or not fused (D). Primary outcome was fusion (grade A or B) vs nonunion (grade C or D) at minimum 4-year follow-up. Secondary outcome measures included health-related quality of life (HRQL) (Oswestry Disability Index [ODI], Short Form-36 [SF-36] scores, Scoliosis Research Society-22 [SRS-22r] scores). Surgically treated ASD patients prospectively enrolled into a multicenter study (2008-2020) were assessed for fusion (grade A or B) vs nonunion (grade C or D). Inclusion required postop fusion grading at minimum 4-year follow-up. Demographics, frailty, comorbidities, alignment (baseline and initial correction), index surgery (total levels fused, iliac fixation, interbody fusion [IBF], use of bone morphogenetic protein [BMP] and/or demineralized bone matrix [DBM], 3-column osteotomy [3CO]) were assessed to identify potential predictors of nonunion (grade C or D), which were then analyzed using Kaplan-Meier survival curves and log-rank comparisons. A total of 227 patients achieved minimum 4-year follow-up and were included (age 58±14y, 82% women, BMI 27±5kg/m2, 40% prior spine surgery, ASD-FI 0.31 [frail], 15% osteoporosis). Index operations had 12±4 posterior levels, 70% iliac fixation, 62% IBF, 76% had BMP, 33% had DBM (of which 52% also had BMP), and 15% had 3CO. At final follow-up, 61 patients (27%) demonstrated nonunion (grade C or D). Older age (61±14 vs 57±14, p=0.015), no BMP usage (p 60 years) had significantly higher probability of nonunion (log-rank test p=0.024), and BMP had protective effect (log-rank test p 0.05). This study demonstrated that older age (>60 years) was associated with significantly higher rates of nonunion at long-term follow-up (4 years) after ASD surgery, and that use of BMP had significant protective effect against this complication.

An Artificial Neural Network Model for the Prediction of Perioperative Blood Transfusion in Adult Spinal Deformity Surgery.

Prediction of blood transfusion after adult spinal deformity (ASD) surgery can identify at-risk patients and potentially reduce its utilization and the complications associated with it. The use of artificial neural networks (ANNs) offers the potential for high predictive capability. A total of 1173 patients who underwent surgery for ASD were identified in the 2017–2019 NSQIP databases. The data were split into 70% training and 30% testing cohorts. Eighteen patient and operative variables were used. The outcome variable was receiving RBC transfusion intraoperatively or within 72 h after surgery. The model was assessed by its sensitivity, positive predictive value, F1-score, accuracy (ACC), and area under the curve (AUROC). Average patient age was 56 years and 63% were female. Pelvic fixation was performed in 21.3% of patients and three-column osteotomies in 19.5% of cases. The transfusion rate was 50.0% (586/1173 patients). The best model showed an overall ACC of 81% and 77% on the training and testing data, respectively. On the testing data, the sensitivity was 80%, the positive predictive value 76%, and the F1-score was 78%. The AUROC was 0.84. ANNs may allow the identification of at-risk patients, potentially decrease the risk of transfusion via strategic planning, and improve resource allocation.

Patients With Coronal Malalignment Undergoing Adult Spinal Deformity Surgery: Does Coronal Alignment Change From Immediately Postoperative to 2-years?

Retrospective cohort study. The objectives were to: (1) characterize the changes in coronal vertical axis (CVA) after adult spinal deformity (ASD) surgery from immediate postoperative to 2-years postoperative, and (2) assess for predictors of CVA change from immediate postoperative to 2-years postoperative. It is unknown whether coronal correction obtained immediately postoperative accurately reflects long-term coronal alignment. A retrospective, single-institution registry was queried for patients undergoing ASD surgery from 2015-2019, including patients undergoing ≥6-level fusions with preoperative coronal malalignment (CM), defined as CVA≥3cm. A clinically significant change in CVA was defined a priori as ≥1cm. Radiographic variables were obtained preoperatively, immediately postoperative, and at 2-years postoperative. Of 368 patients undergoing ASD surgery, 124 (33.7%) had preoperative CM, and 64 (17.0%) completed 2-years follow-up. Among 64 patients, mean age was 53.6±15.4 years. Preoperatively, absolute mean CVA was 5.4±3.1cm, which improved to 2.3±2.0cm ( P <0.001) immediately postoperative and 2.2±1.6cm ( P <0.001) at 2-years. The mean change in CVA from preoperative to immediately postoperative was 2.2±1.9cm (0.3-14.4). During the immediate postoperative to 2-years interval, 29/64 (45.3%) patients experienced a significant change of CVA by ≥1cm, of which 22/29 (76%) improved by a mean of 1.7cm and 7/29 (24%) worsened by a mean of 3.5cm. No preoperative or surgical factors were associated with changed CVA from immediately postoperative to 2-years. Among 64 patients undergoing ASD surgery with preoperative CM, 45.3% experienced a significant (≥1cm) change in their CVA from immediately postoperative to 2-years postoperative. Of these 29 patients, 22/29 (76%) improved, whereas 7/29 (24%) worsened. Although no factors were associated with undergoing a change in CVA, this information is useful in understanding the evolution and spontaneous coronal alignment changes that take place after major ASD coronal plane correction.

A Novel Weave Tether Technique for Proximal Junctional Kyphosis Prevention in 71 Adult Spinal Deformity Patients: A Preliminary Case Series Assessing Early Complications and Efficacy.

Proximal junctional kyphosis (PJK) rates may be as high as 69.4% after adult spinal deformity (ASD) surgery. PJK is one of the greatest unsolved challenges in long-segment fusions for ASD and remains a common indication for costly and impactful revision surgery. Junctional tethers may help to reduce the occurrence of PJK by attenuating adjacent-segment stress. To report our experience and assess early safety associated with a novel "weave-tether technique" (WTT) for PJK prophylaxis in a large series of patients. This single-center retrospective study evaluated consecutive patients who underwent ASD surgery including WTT between 2017 and 2018. Patient demographics, operative details, standard radiographic measurements, and complications were analyzed. A total of 71 patients (mean age 66 ± 12 yr, 65% women) were identified. WTT included application to the upper-most instrumented vertebrae (UIV) + 1 and UIV+2 in 38(53.5%) and 33(46.5%) patients, respectively. No complications directly attributed to WTT usage were identified. For patients with radiographic follow-up (96%; mean duration 14 ± 12 mo), PJK occurred in 15% (mean 1.8±1.0 mo postoperatively). Proximal junctional angle increased an average 4° (10° to 14°, P=.004). Rates of symptomatic PJK and revision for PJK were 8.8% and 2.9%, respectively. Preliminary results support the safety of the WTT for PJK prophylaxis. Approximately 15% of patients developed radiographic PJK, no complications were directly attributed to WTT usage, and the revision rate for PJK was low. These early results warrant future research to assess longer-term efficacy of the WTT for PJK prophylaxis in ASD surgery.