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Study Design: Multicenter case-control study., Objective: To identify imaging characteristics of the cervical spine in patients with retro-odontoid pseudotumor (ROP) without rheumatoid arthritis (RA) and determine the pathogenesis of ROP., Background: ROP results from proliferative changes in the soft tissue of the atlantoaxial junction surrounding the region of the transverse ligament, and is commonly seen in RA patients. However, the pathogenesis of ROP caused by mechanical instability of the upper cervical spine in patients without RA is yet to be explained., Materials and Methods: We collected imaging data [preoperative radiographs, magnetic resonance imaging (MRI), and computed tomography (CT)] of patients who underwent surgery between April 2011 and March 2022 at the three university hospitals for ROP (cases) and cervical spondylotic myelopathy (as age, sex, and institution matched controls). The two groups were compared for different parameters on cervical dynamic radiographs, MRI, and CT., Results: The ROP group consisted of 42 patients, and the control group comprised 168 patients. C2-C7 range of motion was significantly smaller in the ROP group (25.8 ± 2.6°) compared with the control group (33.0 ± 1.0°). C2-C7 sagittal vertical axis was significantly larger in the ROP group than the control group (39.3 ± 3.6 vs. 32.2 ± 1.3 mm). MRI and CT assessment showed progressive degeneration at all intervertebral levels in the ROP group. A significant positive correlation was observed between the thickness of the soft tissue posterior to the dental process and the atlantodental interval in the flexion position ( r = 0.501)., Conclusions: The development of ROP was associated with degeneration of facet joints and intervertebral disks in the middle and lower cervical spine. Our findings suggest that decreased mobility of the middle and lower cervical spine may cause instability in the upper cervical spine, leading to the formation of ROP., Competing Interests: The authors report no conflicts of interest., (Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc.)

Study Design: A prospective longitudinal magnetic resonance imaging (MRI) study., Objective: The objective of this study was to describe the progression of intervertebral disk (IVD) degeneration in patients who underwent posterior decompression surgery for lumbar spinal canal stenosis (LSS)., Summary of Background Data: IVD degeneration contributes to the pathogenesis of LSS; however, the long-term consequences of degenerative changes after decompression surgery remain unknown., Materials and Methods: Of 258 consecutive patients who underwent posterior lumbar decompression surgery for LSS, 62 who underwent MRI at their 10-year follow-up were included; 17 age-matched asymptomatic volunteers were analyzed as controls. Three MRI findings representing IVD degeneration were graded on their severity: decrease in signal intensity, posterior disk protrusion (PDP), and disk space narrowing (DSN). Clinical outcome was assessed using the low back pain (LBP) score from the Japanese Orthopaedic Association scoring system. We examined the association between the progression of degenerative changes on MRI and LBP/associated factors using logistic regression adjusting for age at baseline and sex., Results: The severity of IVD degeneration tended to be higher in patients with LSS than asymptomatic volunteers at both baseline and follow-up. IVD degeneration progressed in all patients during the 10-year follow-up period. Progression of decrease in signal intensity and PDP was observed at L1/2 in 73% and at L2/3 in 34%, respectively (the highest frequencies in the lumbar spine). Progression of DSN was highest at L4/5 in 42%. The rates of PDP and DSN progression during the 10-year follow-up period tended to be greater in patients with LSS than in asymptomatic volunteers. No significant difference in the proportion of LBP deterioration was evident for individuals with and without MRI findings of progression., Conclusions: Our study reveals a natural history of the long-term postoperative course of IVD degeneration after posterior decompression surgery for LSS. Compared with healthy controls, patients with LSS seemed to be predisposed to IVD degeneration. Lumbar decompression surgery may promote the progression of DSN; however, progression of IVD degeneration after lumbar decompression surgery was not associated with worsening LBP scores., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: A retrospective study of consecutive collected data., Objective: To investigate risk factors for postoperative distal adding-on (DA) in Lenke Type 1B and 1C curves using intraoperative radiographs., Summary of Background Data: In adolescent idiopathic scoliosis (AIS), DA radiographic complication can negatively affect postoperative clinical results. However, few studies have focused on assessing risk factors for DA using intraoperative radiographs., Methods: We retrospectively evaluated 69 AIS patients with Lenke Type 1B or 1C curves who underwent posterior selective thoracic fusion. We divided patients into DA and non-DA groups based on radiograph data at 2-year follow-up using Wang et al (Spine 2011) definition of DA. We compared coronal radiographic parameters, including relative positions of end vertebra (EV), stable vertebra (SV), neutral vertebra (NV), and last touching vertebra (LTV) to lowest instrumented vertebra (LIV), and intraoperative radiographic parameters, between the two groups., Results: DA was present in 13 patients (18.8%) at 2-year follow-up. The mean LIV-EV, LIV-NV, LIV-SV, and LIV-LTV relative positions were significantly smaller in the DA group than in the non-DA group. Multivariate analysis showed that LIV-LTV was significantly associated with DA (DA: -0.2 ± 0.7, non-DA: 0.6 ± 0.7). Intraoperative radiographs showed that the mean angulation of the first disc below the LIV after final adjustment was significantly larger in the DA group (2.3° ± 1.1°) than in the non-DA group (0.9° ± 0.7°). Patients whose angulation of the first disc below the LIV was more than 3° were significantly associated with DA., Conclusion: The LIV selected at more cranial to the LTV may be a risk factor for postoperative DA in Lenke Type 1B and 1C curves. Moreover, it was suggested that LIV extension might be considered when the first disc's angulation below the LIV is >3° in intraoperative radiographs.Level of Evidence: 3., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective review of 159 surgically treated consecutive adult symptomatic lumbar deformity (ASLD) (65 ± 9 years, female: 94%) from a multicenter database., Objective: The aim of this study was to provide a comprehensive analysis of the risk of a poor clinical outcome in ASLD surgery., Summary of Background Data: Poor-risk patients with ASLD remain poorly characterized., Methods: ASLD was defined as age >40 years with a lumbar curve ≥30° or C7SVA ≥5 cm and Scoliosis Research Society 22 (SRS22) pain or function <4. Poor outcome was defined as 2y SRS22 total <4 or pain, function or satisfaction ≤3. The outcomes of interest included age, sex, body mass index, bone mineral density, Schwab-SRS type, frailty, history of arthroplasty, upper-instrumented vertebral, lower-instrumented vertebral, levels involved, pedicle subtraction osteotomy, lumbar interbody fusion, sagittal alignment, global alignment and proportion (GAP) score, baseline SRS22r score, estimated blood loss, time of surgery, and severe adverse event (SAE). Poisson regression analyses were performed to identify the independent risks for poor clinical outcome. A patient was considered at poor risk if the number of risks was >4., Results: All SRS22 domains were significantly improved after surgery. In total, 21% (n = 34) reported satisfaction ≤3 and 29% (n = 46) reported pain or function ≤3. Poisson regression analysis revealed that frailty (odds ratio [OR]: 0.2 [0.1-0.8], P = .03), baseline mental-health (OR: 0.6 [0.4-0.9], P = .01) and function (OR: 1.9 [1.0-3.6], P < .01), GAP score (OR: 4.6 [1.1-18.7], P = .03), and SAE (OR: 3.0 [1.7-5.2], P < .01) were identified as independent risk for poor clinical outcome. Only 17% (n = 6) of the poor-risk patients reached SRS22 total score >4.0 at 2 years., Conclusion: The overall clinical outcome was favorable for ASLD surgery. Poor-risk patients continue to have inferior outcomes, and alternative treatment strategies are needed to help improve outcomes in this patient population. Recognition and optimization of modifiable risk factors, such as physical function and mental health, and reduced SAEs may improve overall clinical outcomes of ASLD surgery.Level of Evidence: 3., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Multicenter retrospective case series., Objective: To report the risks, recovery, and clinical impact of neurological complications (NCs) in adult spinal deformity (ASD) surgery., Summary of Background Data: Although recent studies have reported the incidence of NCs in ASD surgery, few have addressed the recovery from and clinical impacts of NC., Methods: We reviewed records from a multicenter database for 285 consecutive surgically treated ASD patients who had reached a 2-year follow-up. NCs were categorized as sensory only or motor deficit (MD). Recovery was noted as none, partial, or complete, during hospitalization and at every postoperation visit. Uni- and multivariate risk analyses were performed to identify risk factors for MD., Results: NC developed in 29 (10%) patients within 30 days of surgery, of which 11 were permanent deficits (seven no recovery, and four partial recovery). MD developed in 14 (5%) patients, including one spinal cord injury. Seven MD patients required physical assistance at the latest follow-up. While NC patients experienced significant improvements in health-related quality of life at the 2-year follow-up, the health-related quality of life was significantly worse for the NC versus no-NC group at this time point. Univariate analyses revealed that Schwab-SRS types N and L, pelvic tilt, modified frailty index physical function, and an inferior SRS22 function domain at baseline were risk factors for MD. Among them, modified frailty index physical function, which represented a preoperative decline in activities of daily living, was identified as an independent risk factor for MD (OR: 4.0, 95% CI: 1.2-13.5, P = 0.03)., Conclusions: NC developed in 10% of ASD surgery patients, with permanent deficits occurring in 4%. Half of the patients who developed MD required physical assistance, which contributed to the inferior clinical outcomes. Surgical intervention should be considered before severe activities of daily living decline to prevent NCs., Level of Evidence: 4.

Study Design: A retrospective review of 281 consecutive cases of adult spine deformity (ASD) surgery (age 55 ± 19 yrs, 91% female, follow-up 4.3 ± 1.9 yrs) from a multicenter database., Objective: To compare the value and predictive ability of the 5-item modified frailty index (mFI-5) to the conventional 11-item modified frailty index (mFI-11) for severe adverse events (SAEs)., Summary of Background Data: Several recent studies have described associations between frailty and surgical complications. However, the predictive power and usefulness of the mFI-5 have not been proven., Methods: SAEs were defined as: Clavien-Dindo grade >3, reoperation required, deterioration of motor function at discharge, or new motor deficit within 2 years. The patients' frailty was categorized by the mFI-5 and mFI-11 (robust, prefrail, or frail). Spearman's rho was used to assess correlation between the mFI-5 and mFI-11. Univariate and multivariate Poisson regression analyses were conducted to analyze the relative risk of mFI-5 and mFI-11 as a predictor for SAEs in ASD surgery. Age, sex, and baseline sagittal alignment (Schwab-SRS classification subcategories) were used to adjust the baseline variance of the patients., Results: Of the 281 patients, 63 (22%) had developed SAE at 2 years. The weighted Kappa ratio between the mFI-5 and mFI-11 was 0.87, indicating excellent concordance across ASD surgery. Frailty was associated with increased total complications, perioperative complications, implant-related complications, and SAEs. Adjusted and unadjusted models showed similar c-statistics for mFI-5 and mFI-11 and a strong predictive ability for SAEs in ASD surgery. As the mFI-5 increased from 0 to ≥2, the rate of SAEs increased from 17% to 63% (P < 0.01), and the relative risk was 2.2 (95% CI: 1.3-3.7)., Conclusion: The mFI-5 and the mFI-11 were equally effective predictors of SEA development in ASD surgery. The evaluation of patient frailty using mFI-5 may help surgeons optimize procedures and counsel patients., Level of Evidence: 4.

Study Design: A retrospective multicenter database review of 240 consecutive patients at least 21 years of age (mean 58 ± 17, range 22-79) who underwent surgery for adult spinal deformity (ASD) and were followed at least 2 years., Objective: To investigate how treatment for frailty affects complications in surgery for ASD., Summary of Background Data: Several recent studies have focused on associations between frailty and surgical complications. However, it is not clear whether treating frailty affects complication rates in surgery for ASD., Methods: Patients were categorized as robust (R group), prefrail, or frail based on the modified frailty index (mFI); prefrail and frail patients were divided by good control of frailty (G group), defined as treatment following the appropriate guidelines for each mFI factor, or poorly controlled frailty (PC group). We compared clinical outcomes and perioperative and 2-year complications between the three groups., Results: Of the 240 patients, 142 (59%) were robust, 81 (34%) were prefrail, and 17 (7%) were frail. Among the frail and prefrail patients, 71 (72%) were classified as G and 27 (28%) as PC. The perioperative complication rate was similar in the G and PC groups (32% vs. 37%) but was significantly lower in the R group (15%, P < 0.01). The age- and sex-adjusted odds ratio for 2-year complications was not different in the P group when the G group was referenced (odds ratio 1.3 [0.5-3.2], P = 0.63). In the G and PC groups, which had similar 2-year outcomes, the Scoliosis Research Society-22 function and total scores were significantly lower than in the R group (function: R 3.9 ± 0.7, G 3.5 ± 0.7, P 3.3 ± 0.6; total: R 3.9 ± 0.6, 3.7 ± 0.7, 3.4 ± 0.6; P < 0.01)., Conclusion: Regardless of its treatment status, frailty increases the risk of complications and inferior clinical outcomes in ASD surgery. Surgeons should routinely evaluate frailty and inform patients of frailty-related risks when considering surgery for ASD., Level of Evidence: 4.

Study Design: Single-center retrospective analysis of consecutively collected data., Objective: To determine the clinical characteristics of idiopathic spinal epidural lipomatosis (SEL)., Summary of Background Data: SEL is associated with the overt accumulation of nonencapsulated adipose tissue in the epidural space, leading to spinal cord or nerve root compression. The etiology of this condition is currently not completely understood., Methods: Data of 166 male patients who underwent primary surgery for lumbar spinal canal stenosis (LSS) from May 2013 to February 2016 were retrospectively reviewed. Participants were divided into three groups based on the degree of epidural lipomatous lesion. Patient data of age at surgery, body mass index, prevalence of common noncommunicable diseases, blood tests, arteriosclerotic index, and preoperative clinical scores (assessed using the Japanese Orthopedic Association Back Pain Evaluation Questionnaire) were evaluated. Multivariate analysis was performed to assess the potential associated factors for idiopathic SEL., Results: Patients with LSS with severe SEL had a significantly higher body mass index and elevated serum levels of total cholesterol and triglyceride compared with those without SEL. Analysis of preoperative clinical scores revealed that patients with SEL experienced pain more frequently and showed less walking ability than did those without SEL. Multivariate analysis revealed that hyperlipidemia was significantly associated with idiopathic SEL (odds ratio = 3.74, 95% confidence interval = 1.31-10.64)., Conclusion: Our data suggest that aberrant lipid metabolism is related to the pathogenesis of idiopathic SEL and that patients with LSS with idiopathic SEL have more severe pain than do those without SEL., Level of Evidence: 3.

Study Design: Questionnaire survey on leg cramps for patients with lumbar spinal canal stenosis (LCS)., Objective: To evaluate the prevalence of leg cramps in patients with LCS treated surgically and the relationship between leg cramps and the surgical outcomes., Summary of Background Data: Although it has been anecdotally reported that LCS patients have suffered from leg cramps, the true prevalence remains unknown., Methods: One hundred twenty LCS patients who underwent decompression surgery (men 85, women 35, mean age 73.5) and 370 elderly subjects from the general population (men 162, women 208, mean age 75.6) were enrolled in the study. The participants filled in a questionnaire regarding: (all participants) (1) experience of leg cramps, (2) frequency and time of the day of the cramp attacks; (for LCS patients only), (3) changes in cramps before and after surgery, (4) activities of daily living disturbance because of leg cramps, (5) satisfaction with surgery and walking ability, (6) the Roland-Morris Disability Questionnaire, and (7) the Oswestry Disability Index., Results: Eighty-five (70.8%) patients with LCS and 137 (37.2%) of the control population experienced leg cramps (age and sex adjusted odds ratio; 4.6, P < 0.01). Leg cramps occurred once or twice a week in 34.9% of the LCS group and once in several months in 44.5% of the control group, and occurred nocturnally in 73.3% of the LCS patients and in 91.6% of the control group. In LCS patients, leg cramps improved after surgery in 18.2%, remained unchanged in 45.5%, and worsened in 26.1%, and activities of daily living were disturbed in 47.6%. There was no significant difference in satisfaction with surgery, the Oswestry Disability Index, the Roland-Morris Disability Questionnaire scores, or walking ability between the LCS patients with or without leg cramps., Conclusion: LCS patients had significantly more frequent attacks of nocturnal leg cramps than the control population, and leg cramps disturbed the quality of the patients' life, and they rarely improved after decompression surgery. Leg cramps should be recognized as one of the symptoms of LCS, which disturb the patients' quality of life.