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Study Design: Retrospective chart review. Objective: The goal of this study is to examine the relationship between global alignment and proportion (GAP) score and postoperative orthoses with likelihood of developing proximal junctional kyphosis (PJK). Methods: Patients who underwent thoracic or lumbar fusions of ≥4 levels for adult spinal deformity (ASD) with 1-year post-operative alignment x-rays were included. Chart review was conducted to determine spinopelvic alignment parameters, PJK, and reoperation. Results: A total of 81 patients were included; baseline and 1-year postoperative alignment did not differ between patients with and without PJK. There was no PJK in 53.1%, 29.6% had PJK from 10-20°, and 17.3% had severe PJK over 20° (sPJK). At baseline, 80% of patients had severely disproportioned GAP, 13.75% moderate, 6.25% proportioned. GAP improved across the population, but improved GAP was not associated with sPJK. Greater correction of the upper instrumented vertebra to pelvic angle (UIV-PA) was associated with a larger PJK angle (PJKA) change (R = -0.28) as was the 1 year T1-upper instrumented vertebra (T1-UIV) angle (R = 0.30), both P <.05. GAP change was not correlated with PJKA change. Postoperative orthoses were used in 46% of patients and did not impact sPJK. Conclusions: There was no correlation between PJK and GAP or change in GAP. Greater correction of UIV-PA and larger postop T1-UIV was associated with greater PJKA change; suggesting that the greater alignment correction led to greater likelihood of failure. Postoperative orthoses had no impact on PJK. [ABSTRACT FROM AUTHOR]

Background Current studies investigating surgical treatment of distal biceps tendon tears largely consist of small, retrospective case series. The purpose of this study was to investigate the current patient demographics, surgical trends, and postoperative complication rates associated with operative treatment of distal biceps tendon tears using a large database of privately insured, non-Medicare patients. Methods Patients who underwent surgical intervention for distal biceps tendon tears from 2007 to 2011 were identified using the PearlDiver database. Demographic and surgical data as well as postoperative complications were reviewed. Statistical analysis was performed using linear regression analysis and χ 2 tests, with statistical significance set at P  < .05. Results A total of 1443 patients underwent surgical treatment for distal biceps tendon tears. Men and patients aged 40 to 59 years accounted for 98% and 72% of the cohort, respectively. Regarding surgical technique, reinsertion to the radial tuberosity was preferred (95%) over tenodesis to the brachialis (5%) ( P  < .01). In total, revision surgery for tendon rerupture occurred in 5.4% of treated patients. The incidence of revision surgery for rerupture in acute and chronic distal biceps tears was 5.1% and 7.0%, respectively ( P  = .36). Postoperative infection and peripheral nerve injury rates were 1.1% and 0.6%, respectively. Conclusion Surgeons strongly preferred anatomic reinsertion to the radial tuberosity for treatment, regardless of the chronicity of the injury. Postoperative complication rates were similar to those found in prior studies, although the true rate of rerupture may be higher than previously thought. [ABSTRACT FROM AUTHOR]

Background: Pre- and postoperative rehabilitation are important to the management of patients with anterior cruciate ligament (ACL) reconstruction, but little attention has been given to the costs. This study evaluated the pre- and postoperative rehabilitation charges in patients with ACL reconstruction in the United States.Hypothesis: Patients receive preoperative rehabilitation less commonly than postoperative rehabilitation.Study Design: Retrospective database study.Level Of Evidence: Level 4.Methods: Using the PearlDiver database, we identified patients undergoing ACL reconstruction from 2007 through 2011 using Current Procedural Terminology codes. The associated rehabilitation charges billed to insurance providers for 90 days preoperatively and 6 months postoperatively were categorized as physical therapy or as durable medical equipment (DME). The charges were examined by year and geographic region and represented as per-patient average charges (PPACs).Results: A total of 92,179 patients were identified in the study period. The PPAC for rehabilitation was $241 during the 90-day preoperative period and $1876 for the 6-month postoperative period. Patients averaged 2 preoperative sessions for physical therapy, with 44% of patients receiving preoperative rehabilitation in contrast with an average of 17 postoperative sessions per patient in 93% of patients. Rehabilitation charges were greater postoperatively than preoperatively (P < 0.05). Preoperatively, 24% of patients received a DME, while 35% received a DME postoperatively. Preoperative rehabilitation PPACs were highest in the Northeast, followed by Midwest, South, and West (P < 0.05). There were no significant differences in postoperative rehabilitation PPACs for geographic region (P = 0.43).Conclusion: Preoperative rehabilitation charges were lower than postoperative charges. A patient undergoing ACL reconstruction typically received 9 times more sessions of postoperative physical therapy than preoperative.Clinical Relevance: This study found that preoperative supervised rehabilitation for patients with ACL reconstruction was infrequent across the United States. [ABSTRACT FROM AUTHOR]

The purpose of this study was to investigate the latest trends and demographics of surgical treatment of posterior cruciate ligament (PCL) insufficiency in the United States. Patients who underwent surgical treatment of PCL insufficiency from 2007 to 2011 were identified by searching the International Classification of Diseases, Ninth Revision, Clinical Modification codes and Current Procedural Terminology codes in the PearlDiver Patient Records Database (PearlDiver Technologies, Warsaw, Indiana), a publicly available national database of insurance records. The chronicity of injury, year of procedure, age, sex, region of the United States the surgery was performed, and other concomitant meniscus and ligamentous operations were elicited for each patient. In total, 701 cases of surgical PCL procedures (222 isolated and 479 combined) were identified. More PCL surgeries were completed for acute injuries (74%) than for chronic injuries (26%). Among associated procedures, meniscectomies and meniscus repairs were performed for 293 (41%) and 51 (7%) patients, respectively. Meniscectomies were completed in 77 (35%) isolated reconstructions vs 216 (45%) combined reconstructions (P=.01; odds ratio, 0.65). Of the combined PCL surgeries, anterior cruciate ligament (ACL)/PCL was the most common (62%), followed by ACL/ PC L/collateral ligament repair (11%) and PCL/other ligamentous reconstruction (9%). No specific trends were observed in the yearly number of PCL procedures performed. The peak number of isolated PCL surgeries was observed in a younger age group (20-29 years) than that of combined PCL surgeries (30-39 years) (P<.01). Surgical treatment for PCL insufficiency remains reserved for acute multiligamentous knee injuries, with ACL/PCL operations being the most common combined procedure. [ABSTRACT FROM AUTHOR]

Study Design. A kinematic magnetic resonance imaging study. Objective. To investigate the distribution of Schmorl nodes (SNs) in the lumbar spine in healthy adults, and determine the association with lumbar disk degeneration and lumbar spine motion. Summary of Background Data. SNs have been associated with several pathologies of the lumbar spine, although it has been demonstrated that they also occur in the healthy adult population without a clearly identified cause. A thorough understanding of SN distribution may help reveal reasons for their formation. How disk degeneration and lumbar spine motion relate to SNs is poorly understood. Methods. Kinematic magnetic resonance images (0.6 T) were available for 1179 healthy individuals from 15 to 85 years of age. Spine specialists performed computer-based measurements. All parameters were measured and calculated automatically using the eRAD PACS Viewer (eRAD Inc., version 6.2.1.1). Lumbar disk degeneration was documented according to the Pfirrmann classification system. Lumbar spine lordosis was quantified as the angle between the inferior endplate of L1 and superior endplate of S1 .The level of significance was defined as P≤ 0.05. The distribution of SNs along the lumbar spine and their relationship with age and sex was investigated using the single factor analysis of variance χ² test. The relationship between SNs, age group, disk location, and overall grades of lumbar disk degeneration were investigated by multiple logistic regression analysis. Lumbar spine motion was compared between patients with and without SNs via independent f test among 585 individuals with qualified kinematic images. Multiple logistic regression analysis was performed on associations of lumbar motion range among the SN population. Results. The prevalence of SNs in our study population was 28.4%, and SNs were observed to be present more frequently in males (34.6%) than in females (20.2%) (ρ < 0.01). There was no significant difference in the incidence of SNs between age groups (ρ = 0.18). SNs were more common at the L2 and L3 vertebral bodies (14.3% and 14.4%), whereas SNs were least common at S1 vertebral bodies (1.5%). The highest incidences of SNs presentation was on disks with degeneration grade III (41.9%) and grade IV (45.3%). SN occurrence, aging, and disk location were positively correlated with lumbar disk degeneration grade. The lumbar spine range of motion was significantly different between individuals with and without SNs (31.4° vs. 37.9°, ρ < 0.01). The frequency of SNs was associated with decreased lumbar range of motion in all age groups except 51 to 60 years and 61 to 70 years. Conclusion. SNs have a high incidence in individuals without persistent lumbar disorders and were found in disks at all degrees of degeneration. SNs occurrence were positively associated with lumbar disk degeneration In addition, the presence of SNs was correlated with decreased overall lumbar motion across all age groups. [ABSTRACT FROM AUTHOR]

Proximal junctional kyphosis (PJK) is a devastating complication of adult spinal deformity (ASD) surgery. Optimal alignment specifications to maximize quality of life while limiting PJK have yet to be defined. Previous studies have primarily examined sagittal vertical axis (SVA) to determine likelihood of PJK. More recently, other alignment parameters such as thoracic-pelvic angles (TPAs) and age-adjusted alignment have been examined. The goal of this study is to examine the relationship between GAP, TPAs, and bracing with likelihood of developing PJK. A retrospective chart review was conducted to identity ASD patients with at least 1 year of radiographic follow up. Patients who underwent fusions to the pelvis and >4 levels fused from 2013 to 2018 and have 1-year postoperative alignment x-rays were included. The rate of radiographic PJK (change of 10-20°) and severe PJK (change>20°) was determined for each group. Reoperation rates were also collected. Surgical records were reviewed to determine patient sample. Chart and X-ray review were conducted to determine spinopelvic alignment parameters, GAP scores, bracing, and reoperation. X-rays were reviewed up to one year postoperatively in order to determine PJK. A total of 81 patients were included (mean 64y 63%F); baseline and 1-year postoperative alignment did not differ between PJK and no PJK patients. There was no PJK in 53.1%, 30.9% had PJK from 10-20°, and 16% had sPJK. Of these, 7 patients had revision surgery: 1 for PJK and 1 for rod fracture. Postop bracing was used in 54% of patients. There was no difference in sPJK according to brace use. At baseline, 79% of patients had severely disproportioned GAP, 16% moderate, 5% proportioned. Of severely disproportioned, 63% had no change in GAP at 1 year. Improved GAP was not associated with sPJK (improved: 22% vs no change: 18%, p=.72). Greater correction of the UIV-PA was associated with a larger PJK angle change (R=.26) as was the 1 year T1-UIV angle (R=.30), both p<.05.GAP change was not correlated with PJKA change. The magnitude of T1PA correction was not associated with sPJK, p>.05. There was no correlation between PJK and GAP alone or change in GAP; it is notable that these patients tended to be disproportioned pre and postop. Greater correction of UIV-PA and larger postop T1-UIV was associated with greater PJKA change; suggesting that the greater alignment correction led to greater likelihood of it failing. Our data suggest bracing was not effective in preventing PJK. These parameters may help surgeons understand alignment targets in ASD. This abstract does not discuss or include any applicable devices or drugs. [ABSTRACT FROM AUTHOR]

Lateral interbody fusion (LLIF) is often performed with biologic adjuvants to promote fusion. Commercially available bone allograft containing allogeneic stem cells (ASC) and bone morphogenetic protein-2 (BMP) are designed to promote fusion while avoiding the morbidity of iliac crest autograft; however, no study to date has directly compared the two in LLIF. The ASC studied is Osteocel Pro (NuVasive, Inc). This non-industry funded study compares fusion rate, complications, and costs between LLIF with BMP and ASC. Single center retrospective comparative study. Patients with 1-3 lumbar levels treated with LLIF. Outcomes measures are fusion at 1 year postoperative, complication rates, length of stay, and costs. A retrospective chart review was conducted to identify patients treated with LLIF and ASC or BMP from February 2012 through September 2017. Patients were included who had from 1-3 lumbar levels treated with LLIF and at least 1 year of radiographic follow up. Interbody fusion was assessed on lumbar X-ray images using a validated scale. A total of 94 patients were included representing 162 levels fused. Of these, 74 patients and 133 levels were treated with BMP; 20 patients and 29 levels were treated with ASC. Comparing patients treated with BMP or ASC, there were no differences in age [61.6 vs 60.4, p=0.7], BMI [29.8 vs 28.3, p=0.3], gender [60.8% vs 55.0% female], smoking status [12.2% vs 10.0%, p=1], diabetes [28.4% vs 15.0%, p=0.2], Charleston Comorbidity Index [4.3 vs 3.5, p=0.2], revision status [47.3% vs 45.0%, p=0.9], intraoperative complications [4.1% vs 5.0%, p=1], postoperative complications [37.8% vs 30.0%, p=0.5], or blood loss [881 vs 528ml, p=0.2]. More levels were fused in the BMP group (1.8 vs 1.45, p=0.04) and the BMP group tended toward a longer length of stay [4.8 vs 3.8 days, p=0.06]. There was a nonsignificant trend toward a higher fusion rate with BMP vs ASC[98.5% vs 93.1%, p=0.1]. The average amount of rhBMP used per level was 2.0 cc compared to 5.9 cc of ASC. There was no difference in the cost of the BMP per level compared with ASC [4.45% vs 4.80%, p=0.33], but the BMP group tended toward a higher cost of total care [103.5% vs 87.6%, p=0.1]. ASC and BMP are both acceptable adjuvants in LLIF that demonstrate comparable fusion rates at 1 year with comparable cost in the setting of similar groups of patients. The radiographic fusion rate seen in our study compares to previous reports in the literature using ASC. Cost considerations are becoming ever more cogent in spine surgery; the results of this study can inform decision making regarding which biologic adjuvant to use in lumbar interbody fusion. Osteocel (Approved for this indication), rhBMP (Infuse) (Not approved for this indication) [ABSTRACT FROM AUTHOR]

C5 palsy is a common postoperative complication after cervical fusion and is associated with increased health care costs and diminished quality of life. Accurate prediction of C5 palsy may allow for appropriate preoperative counseling and risk stratification. We primarily aim to develop an algorithm for the prediction of C5 palsy after instrumented cervical fusion and identify novel features for risk prediction. Additionally, we aim to build a risk calculator to provide the risk of C5 palsy. We identified adult patients who underwent instrumented cervical fusion at a tertiary care medical center between 2013 and 2020. The primary outcome was postoperative C5 palsy. We developed ensemble machine learning, standard machine learning, and logistic regression models predicting the risk of C5 palsy–assessing discrimination and calibration. Additionally, a web-based risk calculator was built with the best-performing model. A total of 1024 patients were included, with 52 cases of C5 palsy. The ensemble model was well-calibrated and demonstrated excellent discrimination with an area under the receiver-operating characteristic curve of 0.773. The following features were the most important for ensemble model performance: diabetes mellitus, bipolar disorder, C5 or C4 level, surgical approach, preoperative non-motor neurologic symptoms, degenerative disease, number of fused levels, and age. We report a risk calculator that generates patient-specific C5 palsy risk after instrumented cervical fusion. Individualized risk prediction for patients may facilitate improved preoperative patient counseling and risk stratification as well as potential intraoperative mitigating measures. This tool may also aid in addressing potentially modifiable risk factors such as diabetes and obesity. [ABSTRACT FROM AUTHOR]

Ogilvie syndrome (OS) is a rare but serious condition seen in the postoperative period. This was an epidemiologic study using data from the National Inpatient Sample from 2005 to 2014 to look at incidence, risk factors, and outcomes associated with OS after primary spine fusion. International Classification of Diseases, Ninth Revision codes were used to identify patients who underwent spine fusion surgery. Patients were separated into 2 cohorts based on the diagnosis of OS. Outcome measures and risk factors for cohorts were analyzed using multivariate logistic regression and compared. Over the 10-year study period, 3,884,395 patients underwent primary spine fusion surgery. Among these, 0.04% developed OS during the index hospitalization. The greatest incidence seen in primary fusion involved the thoracic spine (0.15%). OS was more common after spine fusion for spine deformity (P < 0.001). Patients with OS were more likely to be men (P < 0.001), older (P < 0.0001), and have more comorbidities (P < 0.0001). Patients with OS were more likely to require postoperative blood transfusions (odds ratio [OR], 3.39; 95% confidence interval [CI], 2.51–4.59; P < 0.001) and sustain any complication (OR, 4.20; 95% CI, 3.17–5.57; P < 0.001). Patients with OS had a longer length of stay (15.7 vs. 3.9 days; P < 0.001) and increased average hospitalization cost ($63,037.03 vs. $26,792.19; P < 0.001). The development of OS was associated with fluid electrolyte disorder (OR, 4.06; 95% CI, 2.99–5.51; P < 0.001). OS is a rare but serious complication of primary spine fusion surgery. Identifying the specific risk factors, symptoms, and potential complications related to OS is critical to aid in decreasing the significant morbidity associated with its development. [ABSTRACT FROM AUTHOR]

As surgery is increasingly recommended for patients with neurologic deterioration secondary to central cord syndrome (CCS), it is important to investigate the relationship between time to surgery and patient outcomes. The merits of early vs delayed surgical treatment remain controversial in the literature. Investigate associations between time to surgical intervention and surgical outcomes for CCS patients Retrospective review of Healthcare Cost and Utilization Project's Nationwide Inpatient Sample (NIS) A total of 9,246 weighted inpatient discharges. Complication rates, discharge destination, length of hospital stay (LOS). CCS patients (ICD-9 codes 952.03, 952.08, 952.13, 952.18) were isolated in the NIS database 2005-2013. Operative patients were grouped by time to intervention: same day as admission, 1-day delay, 2-day, 3-day, 4-7 days, 8-14 days, and >14 days. As appropriate, analysis of variance and chi-squared tests compared demographics, Charlson Comorbidity Index (CCI) scores, surgical details, LOS, discharge status, periop complications and total charges across patient groups. Controlling for age, CCI and concurrent traumatic fractures, binary logistic regression assessed surgical timing associated with increased odds of perioperative complication, using same-day patients as a reference group (odds ratio [95% confidence interval]). Included: 6,734 CSS patients (59±16yrs, 26%F, mean CCI: 1.2±1.6). Overall rate of surgical treatment was 64.1%, with rates of surgery increasing from 2005 (50.0%) to 2013 (73.0%, p<0.001). The most common mechanisms of injury were falls (30.3%), pedestrian accidents (6.9%), assault (3.2%) and bicycle-related injury (2.7%). Of the patients that underwent surgery, 52.0% underwent fusion (62.4% 2-3 levels, 33.2% eight-levels, 0.5% 9+ levels), 30.1% discectomy, and 13.8% other exploration/decompression of the spinal canal. Breakdown by time to procedure was: 38.5% same day, 16.1% 1 day, 9.6% 2 days, 7.5% 3 days, 16.2% 4-7 days, 8.3% 8-14 days, and 2.7% >14 days. Timing groups did not differ in trauma status at admission (shock or hemorrhage, p=0.261); however, age differed between groups (min: 1 day [58±15 years], max: >14 days [63±13 years], p<0.001). Relative to other groups, same-day patients had the lowest LOS (7.7±9.8 days vs 9.4-37.3 days, p<0.001) highest rates of home discharge (42.09% vs 30.9%-14.4%, p<0.001). Same-day patients showed a trend of lower perioperative neurologic complications (0.4%) than 1-day (0.6%) and 2-day (1.0%) patients, while patients delayed 3+ days had the lowest (0.1%, p=0.144). Patients delayed >14 days to surgery had increased odds of periop cardiac (7.0 [1.6-30.0]) and infection (6.1 [2.2-16.3]) complications. All timing groups beyond 3 days showed increased odds of VTE: 4-7 days (3.0 [1.6-5.5]), 8-14 days (3.0 [1.4-6.3]), 14+ days (5.6 [2.3-13.6]). Same-day surgery was also associated with lower total hospital charges than delayed surgery ($87,741 vs $118,815-$272,901, p<0.001). Patients undergoing surgery for CCS on the same day as admission showed significantly lower odds of complication, hospital charges, and higher rates of discharge to home than patients that experienced a delay to operation. In contrast, patients delayed >14 days to surgery were associated with inferior outcomes, including increased odds of cardiac complication and infection. This abstract does not discuss or include any applicable devices or drugs. [ABSTRACT FROM AUTHOR]

Achieving fusion in spine surgery can be challenging because of patient factors such as smoking and diabetes. The consequences of pseudarthrosis can be severe, including pain, instability, and additional surgery. Autologous iliac crest bone graft is the historical standard for augmenting spine fusion, providing high rates of fusion throughout the cervical, thoracic, and lumbar spine. Harvest of autologous iliac crest bone can be associated with comorbidities and this has led to development of alternative biologic materials to enhance spine fusion. Substitutes include various forms of allograft products including decellularized allograft; demineralized bone matrix; synthetic materials including bioactive glass; and autologous and allograft mesenchymal stem cells. Bone morphogenetic proteins can be efficacious for fusion but have significant risks and are not suitable for all spine procedures. There is a wide variety of utilization of biologics for spine fusion that are influenced by spinal region, surgeon preference, surgical training, health system formulary, and cost.

Background: Intraoperative neuromonitoring (ION), such as motor-evoked potential (MEP), somatosensory evoked potentials (SSEP), and electromyography (EMG), is used to detect impending neurological injuries during spinal surgery. To date, little is known about the trends in the use of ION for scoliosis surgery in the United States., Methods: A retrospective review was performed using the PearlDiver Database to identify patients that had scoliosis surgery with and without ION from years 2005 to 2011. Demographic information (such as age, gender, region within the United States) and clinical information (such as type of ION and rates of neurological injury) were assessed., Results: There were 3618 patients who had scoliosis surgery during the study period. Intraoperative neuromonitoring was used in 1361 (37.6%) of these cases. The number of cases in which ION was used increased from 27% in 2005 to 46.9% in 2011 ( P < .0001). Multimodal ION was used more commonly than unimodal ION (64.6% versus 35.4%). The most commonly used modality was combined SSEP and EMG, while the least used modality was MEP only. Neurological injuries occurred in 1.8 and 2.0% of patients that had surgery with and without ION, respectively ( P = .561). Intraoperative neuromonitoring was used most commonly in patients <65 years of age and in the Northeastern part of the United States (age P = .006, region P < .0001)., Conclusions: The use of ION for scoliosis surgery gradually increased annually from 2005 to 2011. Age and regional differences were noted with neuromonitoring being most commonly used for scoliosis surgery in nonelderly patients and in the Northeastern part of the United States. No differences were noted in the risk of neurological injury in patients that had surgery with and without ION. Although the findings from this study may seem to suggest that ION may not influence the risk of neurologic injury, this result must be interpreted with caution as inherently riskier surgeries may utilize ION more, leading to an actual reduction in injuries more dramatic than observed in this study., Competing Interests: Disclosures and COI: No funds were received in support of this work. No relevant financial disclosures are associated with this work.

Background: Intraoperative neuromonitoring (ION) such as motor-evoked potential (MEP), somatosensory evoked potentials (SSEP) and electromyography (EMG) are used to detect impending neurological injuries during spinal surgery. To date, little is known on the trends in the use of ION for scoliosis surgery in the United States., Methods: A retrospective review was performed using the PearlDiver Database to identify patients that had scoliosis surgery with and without ION from years 2005 to 2011. Demographic information (such as age, gender, region within the United States) and clinical information (such as type of ION and rates of neurological injury) were assessed., Results: There were 3618 patients who had scoliosis surgery during the study period. ION was used in 1361 (37.6%) of these cases. The number of cases in which ION was used increased from 27% in 2005 to 46.9% in 2011 (p < 0.0001). Multimodal ION was used more commonly than unimodal ION (64.6% vs. 35.4%). The most commonly used modality was combined SSEP and EMG while the least used modality was MEP only. Neurological injuries occurred in 1.8% and 2.0% of patients that had surgery with and without ION, respectively (p = 0.561). ION was used most commonly in patients < 65 years of age and in the Northeastern part of the United States (age; p = 0.006, region; p < 0.0001)., Conclusions: The use of ION for scoliosis surgery gradually increased annually from 2005 to 2011. Age and regional differences were noted with neuromonitoring being most commonly used for scoliosis surgery in non-elderly patients and in the Northeastern part of the United States. No differences were noted in the risk of neurological injury in patients that had surgery with and without ION. Although the findings from this study may seem to suggest that ION may not influence the risk of neurologic injury, this result must be interpreted with caution as inherently riskier surgeries may utilize ION more, leading to an actual reduction in injuries more dramatic than observed in this study.

Study Design: This is a cross-sectional radiologic study., Objective: The purpose of this study was to assess radiologic features related to dynamic changes of dural sac diameter using kinematic magnetic resonance imaging., Summary of Background Data: It is well known that the cross-sectional area of the lumbar spinal canal decreases during movement from flexion to extension. However, the radiologic characteristics related to dynamic changes of the lumbar spinal canal have not been elucidated., Methods: A total of 453 consecutive patients with clinically symptomatic low back pain or radiculopathy were recruited to undergo lumbar kinematic magnetic resonance imaging. The study participants consisted of 271 males (60%) and 182 females (40%). The average age was 44.5±12.2 years old. We investigated the following measurements at each level from L3-L4 to L5-S1: dural sac diameter, ligamentum flavum thickness, disk bulge, disk degeneration, angular motion, translational motion, and posterior disk height. The odds ratios (ORs) for ≥2 mm change of dural sac diameter between flexion and extension were calculated., Results: The average dural sac diameter was 12.2 mm in neutral, 12.5 mm in flexion, and 11.7 mm in extension, with an average difference between flexion and extension of 0.83 mm. The OR of a ≥2 mm change in L5-S1 was 0.55 as compared with L3-L4. Significantly increased ORs were observed with ≥3 mm of ligamentum flavum in neutral (OR: 4.05), 3-3.9 and ≥4 mm of disk bulge in neutral (ORs: 1.62 and 1.81, respectively), grade IV and V disk degeneration (OR: 2.59 and 2.86, respectively), ≥8 degrees of angular motion (OR: 1.81), and ≥2 mm of posterior disk height change (OR: 1.84)., Conclusions: Several radiologic characteristics related to the dynamic change of dural sac diameter have been demonstrated.