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Study Design: Multicentric, retrospective analysis of prospectively collected data., Objective: To utilize machine-learning (ML) for clustering and management prediction (conservative vs. operative) in surgically treated adult spine deformity (ASD) patients, and to compare the attainment of the Minimum Clinically Important Difference (MCID) between predicted surgical and conservative patients., Summary of Background Data: Management choice in ASD is complex. ML can identity patient clusters and predicted treatment, but it is unclear whether patients treated according to the prediction also show better clinical outcomes., Methods: ASD patients (2-year follow-up) were divided into groups using k-means clustering. Management choice was predicted among operated patients in each cluster. The MCID for the Oswestry Disability Index (ODI) and the Scoliosis Research Society-22 (SRS-22) was calculated and compared between patients with and without surgical prediction., Results: In Cluster 1 (idiopathic scoliosis, n=675, 150 surgeries), 57% of patients had a conservative prediction. Of these, 52% and 49% achieved MCID for ODI and SRS-22, respectively, compared to 68% and 75% for those with surgical predictions (OR=2 and 3.1, respectively).In Cluster 2 (moderate sagittal imbalance, n=561, 200 surgeries), 12% had a conservative prediction. Of these, 29% and 46% achieved MCID for ODI and SRS-22, respectively, compared to 47% and 56% for those with surgical predictions.In Cluster 3 (significant sagittal imbalance, n=537, 197 surgeries), 17% had a conservative prediction. Of these, 12% and 15% achieved MCID for ODI and SRS-22, respectively, compared to 37% and 45% for those with surgical predictions (OR=4.2 and 4.5, respectively)., Conclusion: Patients with a concordant surgical prediction and management had higher odds of achieving the MCID, indicating a good correlation between prediction and clinical outcomes. In Cluster 3, the low percentage of patients with conservative prediction achieving the MCID suggests that machine learning could well identify patients with poor clinical outcomes., Competing Interests: Conflict of interest: AlBa, DL, SH, CR, AnBu: none; LB Consultant: Spineart, Spinevision; IO: Royalties : Spineart, alphatec, Clariance, Consultant : Medtronic, Depuy, spinevision Research support : Medtronic, Depuy; JP Consultant: Medtronic, Grants: medtronic Depuy; FP: Research support: DePuySpine Synthes / Medtronic / Nuvasive / Orthofix / SpineArt Consultant: Medtronic / Nuvasive; AA: Consultancy: Globus, Zimvie, Research Grant: Depuy, Medtronic Royalty: Zimvie; FK: Depuy Spine Speakers Bureau and Research Grant; YPC: Consultant: Clariance, Stryker, Ceraver, Spinevision, Research Grants: Clariance, Stryker, Medtronic; CY: Consultant, Medtronic. All conflict of interest are not relevant to the present study., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective analysis of prospectively collected data., Objective: To identify the best definition of primary anteverted pelvis in the setting of adult spine deformity (ASD), and to investigate whether this is a pathologic setting that requires surgical correction., Summary of Background Data: While pelvic retroversion has been thoroughly investigated, pelvic anteversion (AP) is a far lesser discussed topic. Four different AP definitions have been proposed, and AP has been described as a normal or pathologic entity by different authors., Materials and Methods: All patients consulting for ASD at the five participating sites were included. First, the four definitions of AP were compared with descriptive statistics (anatomic method-Pelvic Tilt <0°; Relative Pelvic Version method-RPV >5°; Roussouly method-Pelvic Incidence (PI)<50° and Sacral Slope (SS)>35°); low PT method-PT/PI <25th percentile). Second a subgroup analysis among operated AP patients with a two-year follow-up was performed. Complication rate, radiographic parameters, and clinical scores (ODI, SF-36) were compared in a multivariate analysis between patients who did and did not maintain an AP at the 2-year follow-up., Results: A total of 1163 patients were available for the first analysis. The RPV method seemed to be the most appropriate to define AP in ASD patient. For the second analysis, data on 410 subjects were available, and most of them were young adults with idiopathic scoliosis that did not require pelvic fixation. AP patients who maintained an AP after ASD surgery presented comparable radiographic and clinical outcomes to the patients who presented a normoverted/retroverted pelvis after surgery., Conclusions: According to the results of the presented study, the RPV method is the most appropriate to define primary AP, which is not a pathologic condition and is most often observed in young adults with idiopathic scoliosis. Anteverted pelvis does not require direct surgical correction in this patient group., Competing Interests: LB Consultant: Spineart, Spinevision; I.O.: Royalties : Spineart, alphatec, Clariance, Consultant : Medtronic, Depuy, spinevision Research support : Medtronic, Depuy; JP Consultant: Medtronic, Grants: Medtronic Depuy; F.P.: Research support: DePuySpine Synthes/Medtronic/Nuvasive/Orthofix/SpineArt Consultant: Medtronic/Nuvasive; A.A.: Consultancy: Globus, Zimvie, Research Grant: Depuy, Medtronic Royalty: Zimvie; F.K.: Depuy Spine Speakers Bureau and Research Grant; YPC: Consultant: Clariance, Stryker, Ceraver, Spinevision, Research Grants: Clariance, Stryker, Medtronic; C.Y.: Consultant, Medtronic. The remaining authors report no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Advancements in non-ionizing methods for quantifying spinal deformities are crucial for assessing and monitoring scoliosis. In this study, we analyzed the observer variability of a newly developed digital tool for quantifying body asymmetry from clinical photographs. Methods: Prospective observational multicenter study. Initially, a digital tool was developed using image analysis software, calculating quantitative measures of body asymmetry. This tool was integrated into an online platform that exports data to a database. The tool calculated 10 parameters, including angles (shoulder height, axilla height, waist height, right and left waistline angles, and their difference) and surfaces of the left and right hemitrunks (shoulders, waists, pelvises, and total). Subsequently, an online training course on the tool was conducted for twelve observers not involved in its development (six research coordinators and six spine surgeons). Finally, 15 standardized back photographs of adolescent idiopathic scoliosis patients were selected from a multicenter image bank, representing various clinical scenarios (different age, gender, curve type, BMI, and pre- and postoperative images). The 12 observers measured the photographs at two different times with a three-week interval. For the second round, the images were randomly mixed. Inter- and intra-observer variabilities of the measurements were analyzed using intraclass correlation coefficients (ICCs), and reliability was measured by the standard error of measurement (SEM). Group comparisons were made using Student's t -test. Results: The mean inter-observer ICC for the ten measurements was 0.981, the mean intra-observer ICC was 0.937, and SEM was 0.3-1.3°. The parameter with the strongest inter- and intra-observer validity was the difference in waistline angles 0.994 and 0.974, respectively, while the highest variability was found with the waist height angle 0.963 and 0.845, respectively. No test-retest differences ( p > 0.05) were observed between researchers (0.948 ± 0.04) and surgeons (0.925 ± 0.05). Conclusion: We developed a new digital tool integrated into an online platform demonstrating excellent reliability and inter- and intra-observer variabilities for quantifying body asymmetry in scoliosis patients from a simple clinical photograph. The method could be used for assessing and monitoring scoliosis and body asymmetry without radiation.

Study Design: A retrospective study., Objective: Relationship between rod and spinal shape in the sagittal plane in adult spinal deformity (ASD) surgery., Background: Corrective surgery for adult spinal deformity (ASD) involves the use of contoured rods to correct and modify the spinal curvatures. Adequate rod bending is crucial for achieving optimal correction. The correlation between rods and spinal shape in long constructs has not been reported previously., Methods: We conducted a retrospective analysis of a prospective, multicenter database of patients who underwent surgery for ASD. The inclusion criteria were patients who underwent pelvic fixation and had an upper instrumented vertebra at or above T12. Pre- and post-operative standing radiographs were used to assess lumbar lordosis at the L4S1 and L1S1 levels. The angle between the tangents to the rod at the L1, L4, and S1 pedicles was calculated to determine the L4S1 and L1S1 rod lordosis. The difference between the lumbar lordosis (LL) and the rod lordosis (RL) was calculated as ΔL = LL-RL. The correlation between this difference (ΔL) and various characteristics was analyzed using descriptive and statistical methods., Results: Eighty-three patients were included in the study, resulting in 166 analyzed differences (ΔL) between the rod and spinal lordosis. The values for rod lordosis were found to be both greater and lesser than those of the spine but were mostly lower. The range for total ΔL was -24 °-30.9 °, with a mean absolute ΔL of 7.8 ° for L1S1 (standard deviation (SD) = 6.0) and 9.1 ° for L4S1 (SD = 6.8). In 46% of patients, both rods had a ΔL of over 5 °, and over 60% had at least one rod with a ΔL difference of over 5 °. Factors found to be related to a higher ΔL included postoperative higher lumbar lordosis, presence of osteotomies, higher corrected degrees, older age, and thinner rods. Multivariate analysis correlated only higher postoperative L1S1 lordosis with higher ΔL. No correlation was found between a higher ΔL and sagittal imbalance., Conclusions: Variations between spinal and rod curvatures were observed despite the linear regression correlation. The shape of the rod does not seem to be predictive of the shape of the spine in the sagittal plane in ASD long-construct surgeries. Several factors, other than rod contouring, are involved in explaining the postoperative shape of the spine. The observed variation calls into question the fundamentals of the ideal rod concept., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Coronal balance is a major factor impacting the surgical outcomes in adult spinal deformity (ASD). The Obeid coronal malalignment (O-CM) classification has been proposed to improve the coronal alignment in ASD surgery. Aim of this study was to investigate whether a postoperative CM < 20 mm and adherence to the O-CM classification could improve surgical outcomes and decrease the rate of mechanical failure in a cohort of ASD patients., Methods: Multicenter retrospective analysis of prospectively collected data on all ASD patients who underwent surgical management and had a preoperative CM > 20 mm and a 2-year follow-up. Patients were divided in two groups according to whether or not surgery had been performed in adherence to the guidelines of the O-CM classification and according to whether or not the residual CM was < 20 mm. The outcomes of interest were radiographic data, rate of mechanical complications and Patient-Reported Outcome Measures., Results: At 2 years, adherence to the O-CM classification led to a lower rate of mechanical complications (40 vs. 60%). A coronal correction of the CM < 20 mm allowed for a significant improvement in SRS-22 and SF-36 scores and was associated with a 3.5 times greater odd of achieving the minimal clinical important difference for the SRS-22., Conclusion: Adherence to the O-CM classification could reduce the risk of mechanic complications 2 years after ASD surgery. Patients with a residual CM < 20 mm showed better functional outcomes and a 3.5 times greater odd of achieving the MCID for the SRS-22 score., (© 2023. The Author(s).)

Background Context: There remains significant variability in the use of postoperative opioids. On one end, it is proven that appropriate pain control is a critical aspect of patient management; on the other end, past few decades have been associated with major increases in opioid-related overdoses and addiction treatment. We hypothesized that several pre- and postoperative risk factors affecting long-term opioid use could be identified., Purpose: Evaluation of factors associated with minimum 5-year postoperative opioid use following adult spinal deformity surgery., Study Design/setting: Prospectively followed study group database., Patient Sample: Adult spinal deformity patients who underwent elective spine surgery between 2009 and 2016 were included., Outcome Measures: Opioid usage or otherwise at minimum 5 years follow-up. Use of nonopioid analgesics, weak and strong opioids METHODS: Retrospective analysis of patients undergoing elective spinal deformity surgery. A total of 37 factors comprising patient characteristics, radiographic measurements, operative details, preoperative and early postoperative opioid use, and mechanical complications and revisions were analyzed. Details on identified factors were provided., Results: A total of 265 patients (215F, 50M) from five sites were included. The mean follow-up duration was 68.4±11.7 (60-102) months. On average, 10.6±3.5 levels were fused. Preoperatively, 64 (24.2%) patients were using opioids. The rate of opioid users increased to 33.6% at 6 weeks and decreased to 21.5% at 6 months. During follow-up, there were patients who discontinued opioids, while others have started and/or restarted using opioids. As a result, 59 (22.3%) patients were still on opioids at the latest follow-up. Multivariate analyses showed that factors independently affecting opioid use at an average of 68 months postoperatively, in order of significance, were opioid use at sixth weeks, preoperative opioid use and opioid use at sixth months with the odds ratios of 2.88, 2.51, and 2.38 respectively. At these time points, factors such as age, number of comorbidities, tobacco use, the time of the last prior spine surgery and postoperative sagittal plane alignment affected opioid usage rates., Conclusions: Opioid usage at 6 weeks was found to be more predictive of long-term opioid use compared to preoperative use. Patients should be well informed to have realistic expectations regarding opioid use when considering adult spinal deformity surgery., Competing Interests: Declarations of Competing Interests One or more of the authors declare financial or professional relationships on ICMJE-NASSJ disclosure forms., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Background: The objective of this study was to determine the effect of obesity on the functional outcomes and complication rates of patients with adult spinal deformity (ASD) undergoing multi-level thoracolumbar fusion., Methods: An age and sex matched comparison of functional outcomes [Numeric Rating Scale (NRS) back and leg scores, Core Outcome Measurement Index (COMI) back scores, Scoliosis Research Society 22 (SRS22) satisfaction and total scores, Short Form 36 (SF36) general health scores, Physical Component Score (PCS), Mental Component Score (MCS), Oswestry Disability Index (ODI) (including all domains)] at 6 months, 1, 2, 3 and 4 years and the complication rates at final follow-up between obese [body mass index (BMI) >30] and normal BMI (18.5-24.9) patients undergoing more than 3 levels of thoracolumbar fusion with a minimum 2-year follow-up. Patients who had undergone any previous spinal surgery were excluded., Results: Thirty patients were included in each arm of the study. Baseline demographics, including the number of levels fused, were similar between the groups. Estimated blood loss (EBL) was higher in obese patients (1,916 vs. 1,099 mL, P=0.001), but operative time was similar (282 vs. 320 min, P=0.351). The functional outcomes and satisfaction scores were consistently poorer in the obese group at all time-points, but their satisfaction scores were similar. Obese patients had a higher complication rate (OR 3.05, P=0.038) predominantly due to dural tears and nerve root injuries, but a similar reoperation rate., Conclusions: In patients with ASD undergoing multi-level thoracolumbar fusion, obesity results in a higher blood loss, poorer sagittal correction, poorer post-operative functional scores and higher complication rates than patients with a normal BMI. However, obesity does not affect operative times, length of hospital stay or reoperation rates. Furthermore, patients with obesity have similar post-operative satisfaction scores to patients with normal BMIs., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://aoj.amegroups.com/article/view/10.21037/aoj-22-14/coif). The authors have no conflicts of interest to declare., (2022 Annals of Joint. All rights reserved.)

Study Design: Retrospective cohort., Purpose: This study aims to evaluate the impact of anemia on functional outcomes, health-related quality of life (HRQoL), and early hospital readmission (EHR) rates after adult spinal deformity (ASD) surgery at the time of discharge from the hospital., Overview of Literature: Concerns with risks of transfusion, insufficient evidence for its benefits, and the possibility of associated adverse outcomes have led to restrictive transfusion practices. Therefore, patients are discharged according to patient blood management programs that are implemented in hospitals nationwide to reduce unnecessary blood transfusions. However, not many comprehensive kinds of studies exist on the effect of postoperative anemia on functional life and complications., Methods: Anemia severity was defined following the 2011 World Health Organization guidelines. All patients had HRQoL tests as well as complete blood counts pre- and postoperatively. EHR is the admission within 30 days of discharge and was used as the dependent parameter., Results: This study comprised 225 surgically treated ASD patients with a median age of 62.0 years, predominantly women (80%). Of the 225 patients, 82, 137, and six had mild, moderate, and severe anemia at the time of discharge, respectively. Seventeen of the patients (mild [11, 64.7%]; moderate [5, 29.4%]; severe [1, 5.9%]) were readmitted within 30 days. The mean hemoglobin values were higher in readmitted patients (p=0.071). Infection was the leading cause of readmission (n=12), but a low hemoglobin level was not observed in any of these patients at the time of discharge. Except for Scoliosis Research Society-22 questionnaire, HRQoL improvements did not reach statistical significance in early readmitted patients in the first year after surgery., Conclusions: The results of this study demonstrated that the occurrence and the severity of postoperative anemia are not associated with EHR in surgically treated patients with ASD. The findings of the current research suggested that clinical awareness of the parameters other than postoperative anemia may be crucial. Thus, improvements in HRQoL scores were poor in early readmitted patients 1 year after surgery.

Objective: To evaluate Obeid-coronal malalignment (O-CM) modifiers according to age, sagittal alignment, and patient-reported outcome measures (PROMs), in the mobile spine., Methods: Retrospective review of a prospective multicenter adult spinal deformity (ASD) database with 1,243 (402 nonoperative, 841 operative) patients with no prior fusion surgery. Patients were included if they were aged over 18 years and were affected by spinal deformity defined by one of: Cobb angle ≥ 20°, pelvic tilt ≥ 25°, sagittal vertical axis ≥ 5 cm, thoracic kyphosis ≥ 60°. Patients were classified according to the O-CM classification and compared to coronally aligned patients. Multivariate analysis was performed on the relationship between PROMs and age, global tilt (GT) and coronal malalignment (CM)., Results: Four hundred forty-three patients had CM of more than 2 cm compared to 800 who did not. The distribution of these modifiers was correlated to age. After multivariate analysis, using age and GT as confounding factors, we found that before the age of 50 years, 2A1 patients had worse sex life and greater satisfaction than patients without CM. After 50 years of age, patients with CM (1A1, 1A2) had worse self-image and those with 2A2, 2B had worse self-image, satisfaction, and 36-item Short Form Health Survey physical function. Self-image was the consistent determinant of patients opting for surgery for all ages., Conclusion: CM distribution according to O-CM modifiers is age dependent. A clear correlation between the coronal malalignment and PROMs exists when using the O-CM classification and in the mobile spine, this typically affects self-image and satisfaction. Thus, CM classified according to O-CM modifiers is correlated to PROMs and should be considered in ASD.

Background: Both adult spinal deformity (ASD) and obesity are growing concerns internationally. This study therefore aims to determine the effect of increasing body mass index (BMI) on the pain and function of patients with ASD., Methods: A retrospective review of prospectively collected data from a multicentre European database was undertaken. Initially a univariate analysis was performed on the effect of BMI on the initial presentation of functional scores in patients with ASD. The functional scores included the Numerical Rating Scale (NRS) back and leg score, Core Outcome Measures Index (COMI) back score, SRS22 total score, Short Form 36 (SF-36) [general health, physical component score (PCS) and mental component score (MCS)] and Oswestry Disability Index (ODI) score (including all domains). Subsequently a multivariate analysis controlling for age, sex, comorbidities, employment status, smoking status and radiological parameters [coronal cobb, coronal balance, sagittal balance, global tilt, and pelvic incidence minus lumbar lordosis (PI - LL) mismatch] was performed., Results: A total of 1,004 patients were included in this study (166 male, 838 female). On univariate analysis a statistically significant (P<0.05) moderate correlation between NRS leg pain, ODI (walking, standing, sex life, social life and total score), SF-36 (physical component), sagittal balance, global tilt and age were recognised (P<0.05). A statistically significant low correlation was identified for all other outcomes, except coronal balance (P=0.640). On multivariate analysis BMI remained significantly related to all functional outcomes except ODI-pain and ODI-travelling (P>0.05)., Conclusions: Increasing BMI has a significant adverse effect on the pain and functioning of patients with ASD. Clinicians should recognise this association and treat patients accordingly., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare., (2019 Journal of Spine Surgery. All rights reserved.)

Purpose: The aim of this study was to investigate the difference in patient-reported outcomes and surgical complication rates between lumbar procedures carried out either by experienced board-certified spine surgeons (BCS) or by supervised spine surgery residents (RES) in a large Swiss teaching hospital., Methods: This was a single-center retrospective analysis of data collected prospectively within the framework of the EUROSPINE Spine Tango Registry. It involved the data of 1415 patients undergoing first-time surgery in our institution between the years 2004 and 2016. Patients were divided into three groups based on the surgical procedure: lumbar single-level fusion (SLF), single-level decompression (SLD) for lumbar spinal stenosis and disc hernia procedures (DH). Patient-reported outcome measures (primary outcome) included the multidimensional Core Outcome Measures Index (COMI) preoperatively and 3 and 12 months postoperatively plus single items concerning satisfaction with care and global treatment outcome (GTO). Secondary outcomes included surgical variables such as blood loss, duration of surgery, complication rates and length of stay., Results: There were no significant differences between the RES and BCS patient groups for most of the demographic and baseline clinical variables with the exception of age in the SLD group (p = 0.012), BMI in the DH group (p = 0.02) and leg pain in the SLF group (p = 0.03). COMI scores improved significantly after all three types of procedure (p < 0.0001) without significant difference (p > 0.05) between the patients of RES and BCS. There was no significant difference (p > 0.05) between RES and BCS patients with regard to satisfaction and GTO. There were no significant differences between RES and BCS (p > 0.05) in the surgical or medical complication rates., Conclusion: In the given setting, surgical training of spine surgery residents under guided supervision by board-certified spine surgeons was shown to be safe, as it was not associated with greater morbidity or mortality. Furthermore, it had no detrimental influence on patient-reported outcomes. The findings can be used to give reassurance to prospective patients that are to be operated on by supervised spine surgery residents. These slides can be retrieved under Electronic Supplementary Material.

Purpose: We compared the value of different uni- and multimodal intraoperative neurophysiological monitoring (IONM) methods on the detection of neurological complications during spine surgery., Methods: IONM data derived from sensory spinal and cortical evoked potentials combined with continuous electromyography monitoring, motor evoked potentials and spinal recording were evaluated in relation to subsequent post-operative neurological changes. Patients were categorised based on their true-positive or true-negative post-operative neurological status., Results: In 2728 consecutive patients we had 909 (33.3%) IONM alerts. We had 8 false negatives (0.3%) with post-operative radicular deficit that completely recovered within 3 months, except for one. There was no false negative for spinal cord injury. 107 were true positives, and 23 were false positives. Multimodal IONM sensitivity and specificity were 93.0% and 99.1%, respectively. The frequency of neurological complications including minor deficits was 4.2% (n = 115), of which 0.37% (n = 10) were permanent. Analysis of the single IONM modalities varied between 13 and 81% to detect neurological complications compared with 93% when using all modalities., Conclusion: Multimodal IONM is more effective and accurate in assessing spinal cord and nerve root function during spine surgeries to reduce both neurological complications and false-negative findings compared to unimodal monitoring. We recommend multimodal IONM in all complex spine surgeries. These slides can be retrieved from Electronic Supplementary Material.

Study Design: Retrospective review of prospectively collected data from a multicentric database., Objectives: To determine the clinical impact of diagnosis, age, and gender on treatment outcomes in surgically treated adult spinal deformity (ASD) patients., Methods: A total of 199 surgical patients with a minimum follow-up of 1 year were included and analyzed for baseline characteristics. Patients were separated into 2 groups based on improvement in health-related quality of life (HRQOL) parameters by minimum clinically important difference. Statistics were used to analyze the effect of diagnosis, age, and gender on outcome measurements followed by a multivariate binary logistic regression model for these results with statistical significance., Results: Age was found to affect SF-36 PCS (Short From-36 Physical Component Summary) score significantly, with an odds ratio of 1.017 (unit by unit) of improving SF-36 PCS score on multivariate analysis ( P < .05). The breaking point in age for this effect was 37.5 years (AUC = 58.0, P = .05). A diagnosis of idiopathic deformity would increase the probability of improvement in Oswestry Disability Index (ODI) by a factor of 0.219 and in SF-36 PCS by 0.581 times ( P < .05). Gender was found not to have a significant effect on any of the HRQOL scores., Conclusions: Age, along with a diagnosis of degenerative deformity, may have positive effects on the likelihood of improvement in SF-36 PCS (for age) and ODI (for diagnosis) in surgically treated patients with ASD and the breaking point of this effect may be earlier than generally anticipated. Gender does not seem to affect results. These may be important in patient counseling for the anticipated outcomes of surgery., Competing Interests: Declaration of Conflicting Interests: The author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: Selim Ayhan: None. Selcen Yuksel: None. Vugar Nabiyev: None. Prashant Adhikari: Grants/research support: Medtronic. Alba Vila-Casademunt: Grants/research support: Depuy Synthes. Ferran Pellise: Grants/research support: Depuy Synthes, K2M; Consultant: Depuy Synthes. Francisco Sanchez Perez-Grueso: Grants/research support: Depuy Synthes; Consulting: Depuy Synthes Spine. Ahmet Alanay, Grants/research support: Depuy Synthes; Consulting: Depuy Synthes, Stryker, Medtronic. Ibrahim Obeid: Grants/research support: Depuy Synthes; Consulting: Depuy Synthes, Medtronic, Alphatec. Frank Kleinstuck: Grants/research support: Depuy Synthes. Emre Acaroglu: Grants/research support: DePuy Synthes, Medtronic, Stryker Spine; Speaker’s bureau: AO Spine, Medtronic, Stryker Spine, Zimmer Biomet; Advisory board or panel: AO Spine; Stock/shareholder: IncredX (self-managed).

Study Design: A retrospective evaluation of radiographs in patients with idiopathic scoliosis was undertaken to assess predictors of flexibility., Objective: To evaluate potential predictors of flexibility in patients with thoracolumbar and lumbar scoliosis., Summary of Background Data: Curve flexibility is an important consideration in the operative management of idiopathic scoliosis. Flexibility of the major curve is a useful predictor of expected surgical correction, and flexibility of compensatory curves determines whether they are structural or nonstructural. An accurate assessment of curve flexibility has important implications on surgical approaches and planning for deformity correction. The role of age and curve magnitude in predicting curve flexibility has not been well defined. A quantitative assessment of changes in curve flexibility with age and progression of deformity may yield important insight into the change in surgical management options over time., Methods: A retrospective review of 75 patients with idiopathic thoracolumbar and lumbar scoliosis (age range 13-78 years) was undertaken. Preoperative standing and side-bending radiographs of thoracolumbar and lumbar curves were evaluated. Cobb angles of structural and fractional curves, curve flexibility, presence of lateral listhesis, and axial and radicular pain were documented. Predictors of structural and fractional curve flexibility were evaluated with correlation and regression analysis. Correlation analysis was used to demonstrate an association between radiographic findings and the clinical presentation., Results: Seventy-five patients had an average major curve magnitude of 56 degrees (range 34-82 degrees ) with flexibility averaging 55% (range 20-93%). Structural curve flexibility was highly inversely correlated with both curve magnitude (r = -0.7; P< 0.001) and with age (r = -0.6; P< 0.001). Lumbar fractional curve (L4-S1) flexibility showed a high inverse correlation with age (r = -0.65; P< 0.001) but did not show correlation with Cobb angle. Thoracic compensatory curves showed a moderate correlation with Cobb angle (r = 0.53). Structural and fractional curve flexibility showed high correlation with each other (r = 0.5-0.66). Regression analysis yielded a formula to predict the flexibility of the structural curve (FSC): FSC = 130 - (Cobb + Age/2). Axial pain was correlated with age (r = 0.63); however, it was not correlated with curve magnitude., Conclusion: We have shown that curve magnitude and patient age are the main predictors of structural flexibility. Every 10 degrees increase in curve magnitude over 40 degrees results in a 10% decrease in flexibility; every 10-year increase in age decreases flexibility of the structural curve by 5% and the lumbosacral fractional curve by 10%. Curve magnitude and age of the patients are significant predictors of curve flexibility. The demonstration of this association offers useful information in estimating how surgical options for deformity correction may change over time.

Bone graft substitutes may be broadly classified as mineralized and demineralized preparations. This article reviews the basic science and biology underlying each preparation. A review of the clinical and experimental applications of each preparation follows. The text concludes with a review of growth factors as biological supplements.