Radiographic Alignment Parameters for Lumbosacral Reconstruction in Patients With Altered S1 Morphology.

STUDY DESIGN: Retrospective quantitative analysis study. OBJECTIVES: Pelvic incidence has been established as central radiographic marker which determines patient-specific correction goals during surgery for adult spinal deformity. In cases with sacral doming or sacral osteotomy where the PI cannot be calculated, reliable radiographic parameters need to be established to determine surgical goals. We aim to determine multiple radiographic parameters and formulas that can be utilized when the S1 superior endplate is obscured. METHODS: Retrospective analysis was performed on 68 healthy volunteers without prior spine surgery with full-length radiographs. Pelvic incidence, sacral slope, and pelvic tilt were calculated for each patient. Additional measurements such as L4, L5, and S2 incidence, tilt, and slope were collected. A new radiographic parameter defined as the L4-Sciatic notch angle was measured. Regression analysis was performed on each value to determine its relationship with S1 based incidence, tilt, and slope. RESULTS: Mean values for L5 incidence, L4 incidence, and L4 sciatic notch angle were 21.8° ± 8.9, 4.4° ± 8.1, and 44.4° ± 12, respectively. The linear regression analysis produced the following formulas which can be utilized to determine deformity correction goals when pelvic incidence can be calculated pre-operatively: L5i = .65*S1i-11.4, L4i = .44*S1i-18.6, and L4SNA = -.34*S1i + 66.5. In settings where pelvic incidence cannot be calculated, the following formulas can be utilized: L5i = .66*S2i-32.3 and L4SNA = -.02*S2i2 + 1.1*S2i + 63.5. P-values for all regression analyses were <.001. CONCLUSION: This study provides target radiographic alignment values that can be utilized for patients with either pre-operative altered S1 endplates or in cases with intraoperative alteration of S1 (sacral osteotomy).

Low-Density Lipoprotein Cholesterol and Statin Usage Are Associated With Rates of Pseudarthrosis Following Single-Level Posterior Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To investigate the relationships of low-density lipoprotein cholesterol and statin usage with pseudarthrosis following single-level posterior or transforaminal lumbar interbody fusion (PLIF/TLIF). SUMMARY OF BACKGROUND DATA: Hypercholesterolemia can lead to atherosclerosis of the segmental arteries, which branch into vertebral bone through intervertebral foramina. According to the vascular hypothesis of disc disease, this can lead to ischemia of the lumbar discs and contribute to lumbar degenerative disease. Yet, little has been reported regarding the effects of cholesterol and statins on the outcomes of lumbar fusion surgery. MATERIALS AND METHODS: TriNetX, a global federated research network, was retrospectively queried to identify 52,140 PLIF/TLIF patients between 2002 and 2021. Of these patients, 2137 had high cholesterol (≥130 mg/dL) and 906 had low cholesterol (≤55 mg/dL). Perioperatively, 18,275 patients used statins, while 33,415 patients did not. One-to-one propensity score matching for age, sex, race, and comorbidities was conducted to balance the analyzed cohorts. The incidence of pseudarthrosis was then assessed in the matched cohorts within the six-month, one-year, and two-year postoperative periods. RESULTS: After propensity score matching, high-cholesterol patients had greater odds of developing pseudarthrosis six months [odds ratio (OR): 1.73, 95% confidence interval (CI): 1.28-2.33], one year (OR: 1.59, 95% confidence interval (CI): 1.20-2.10), and two years (OR: 1.57, 95% CI: 1.20-2.05) following a PLIF/TLIF procedure. Patients with statin usage had significantly lower odds of developing pseudarthrosis six months (OR: 0.74, 95% CI: 0.69-0.79), one year (OR: 0.76, 95% CI: 0.71-0.81), and two years (OR: 0.77, 95% CI: 0.72-0.81) following single-level PLIF/TLIF. CONCLUSIONS: The findings suggest that patients with hypercholesterolemia have an increased risk of developing pseudarthrosis following PLIF/TLIF while statin use is associated with a decreased risk. The data presented may underscore an overlooked opportunity for perioperative optimization in lumbar fusion patients, warranting further investigation in this area.

Single-level posterior cervical foraminotomy associated with increased incidence of early postoperative wound infection rates relative to anterior cervical discectomy with fusion and cervical disc arthroplasty.

Background: To date, there are no studies comparing perioperative outcomes of cervical radiculopathy patients managed by anterior cervical discectomy with fusion (ACDF), cervical disc arthroplasty (CDA), or posterior cervical foraminotomy (PCF). To assess if there were differences in perioperative outcomes between cervical radiculopathy patients who can be appropriately treated with ACDF, CDA, or PCF. Methods: Patients diagnosed with cervical radiculopathy who underwent a single-level ACDF, CDA, or PCF between 2012 and 2019 were retrospectively identified from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database using current procedural terminology (CPT) codes. Patients were subsequently stratified into those who underwent ACDF, CDA, or PCF, and propensity score-matched to adjust for differences in patient demographics/characteristics. Differences were assessed in terms of operative time, healthcare utilization metrics (reoperations, readmissions, lengths-of-stay), as well as medical and surgical complications. Results: A total of 18,614 cervical radiculopathy patients undergoing surgery were identified (ACDF: n=15,862; CDA: n=1,731; PCF: n=1,021). After 1:1 propensity score matching (n=535 each), there were no differences in characteristics in patients undergoing ACDF, CDA, or PCF (P>0.05). PCF patients had statistically higher rates of reoperation (2.1%) than ACDF (0.4%), CDA (0.6%) patients (P=0.010). PCF patients also experienced higher rates of superficial infection (P=0.001), and deep infection (P=0.007), relative to ACDF and CDA patients. There were no other significant differences in medical/surgical complications between the ACDF, CDA, or PCF patients. Conclusions: Cervical radiculopathy patients undergoing PCF are associated with higher rates of perioperative infection and overall reoperation than ACDF or CDA. Further research is required to elucidate the mechanism behind this association.

Opioid and Sedative NarxCare Scores Greater Than 300 Are Associated With Adverse Outcomes After Nonemergent Spine Surgery.

STUDY DESIGN: This was a prospectively captured cohort study. OBJECTIVE: To explore associations between the preoperative opioid-specific NarxCare Scores (NCS) (NCS-opioids) as well as sedative-specific NCS (NCS-sedatives) as measures of patients' prescription drug use and (1) 90-day postoperative readmission; (2) ED visits; (3) reoperation; (4) prolonged (>2 d) hospital length of stay (LOS); and (5) nonhome discharge. In addition, we sought to evaluate the previously suggested 300+ threshold as a cutoff for moderate/high-risk designation. BACKGROUND: The association between preoperative opioids and sedative use and healthcare utilization after nonemergent spine surgery is not well quantified. The NCS is a weighted scalar measure of opioids and sedatives that accounts for the number of prescribing providers, dispensing pharmacies, milligram equivalence doses, and overlapping prescription days. METHODS: A total of 4680 nonemergent spine surgery cases were included. Preoperative NCS-opioids/sedatives were captured. Bivariate and multivariable regression models were constructed to analyze associations between NCS-opioids/sedatives ranges and outcomes while accounting for baseline differences. Spline regression and propensity score matching (PSM) analyses were also implemented. RESULTS: For NCS-opioid, multivariable regression demonstrated higher odds of prolonged LOS starting in the 400 to 499 NCS-opioids category [odds ratio (OR): 1.44; 95% confidence interval (CI): 1.05-1.97; P =0.026] going into the 500+ category (OR: 1.94; 95% CI: 1.29-2.93; P =0.002]. The 500+ categories exhibited higher odds of 90-day readmission (OR: 1.77; 95% CI: 1.01-3.09; P =0.045). PSM comparison demonstrated that patients within the 300+ category had higher incidence of prolonged LOS [n=455 (44%) vs . n=537 (52%); P <0.001], 90-day readmission [n=118 (11%) vs . n=155 (15%); P =0.019] and 90-day reoperation [n=51 (4.9%) vs . n=74 (7.2%); P =0.042]. For NCS-sedative; there was higher odds of prolonged LOS (OR: 1.73; 95% CI: 1.14-2.63; P =0.010) and nonhome discharge(OR: 2.09; 95%CI: 1.22-3.63; P =0.008) within the 400 to 499 NCS-sedatives category. PSM comparison demonstrated significantly higher rates of prolonged LOS within the 300+ NCS-sedative cohort ( vs . scores <300), [n=277 (44%) vs. 319 (50%); P =0.021]. CONCLUSION: Spine surgery continues to advance toward patient-specific care. Higher NCS-opioids/sedatives values may predict up to a twofold increase in postoperative healthcare utilization. High values should prompt an interdisciplinary approach to mitigate deleterious prescription drug use.

Perioperative outcomes of cervical disc arthroplasty: no difference between orthopaedic and neurologic surgeons.

Background: Given differences in residency training background, there has been increasing interest in characterizing differential outcomes between orthopaedic surgeons (OS) and neurosurgeons (NS) with regards to outcomes after cervical disc arthroplasty (CDA). This study aimed to assess if there were differences in perioperative outcomes of CDA between OS and NS. Methods: Patients who underwent a single-level CDA between 2012 and 2019 were identified from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database using current procedural terminology codes. The patients were subsequently stratified into those who underwent CDA with OS versus NS, and propensity score-matched to adjust for differences in patient characteristics. Differences were assessed in medical and surgical complications, as well as operative time and healthcare utilization parameters [reoperations, readmissions, and lengths-of-stay (LOS)]. Results: A total of 2,148 patients were identified (NS: n=1,395; OS: n=753). After 1:1 propensity score matching (n=741 each), there were no differences in characteristics between patients who underwent CDA by OS versus NS (P>0.05). There were no significant differences in any of the medical or surgical complications between the two groups (P>0.05 for each). There was a significant difference in the operative time between NS and OS (103.7±36.18 vs. 98.75±36.69 minutes; P=0.009). There were no significant differences in readmissions, reoperations, or LOS between the two groups (P>0.05 for each). Conclusions: There were no differences in medical or surgical complications, as well as in reoperations, readmissions, and LOS in patients who underwent a single-level CDA between OS and NS. There was a statistically significant shorter operative time of four minutes for OS as compared to NS, which is unlikely to have clinical relevance.

New Imaging Modalities for Degenerative Cervical Myelopathy.

INTRODUCTION: Degenerative cervical myelopathy (DCM) is defined as dysfunction of the spinal cord as a result of compression from degenerative changes to surrounding joints, intervertebral disks, or ligaments. Symptoms can include upper extremity numbness and diminished dexterity, difficulty with fine manipulation of objects, gait imbalance, and incoordination, and compromised bowel and bladder function. Accurate diagnosis and evaluation of the degree of impairment due to degenerative cervical myelopathy remain a challenging clinical endeavor requiring a thorough and accurate history, physical examination, and assessment of imaging findings. METHODS: A narrative review is presented summarizing the current landscape of imaging modalities utilized in DCM diagnostics and the future direction of research for spinal cord imaging. RESULTS AND DISCUSSION: Current imaging modalities, particularly magnetic resonance imaging and, to a lesser extent, radiographs/CT, offer important information to aid in decision making but are not ideal as stand-alone tools. Newer imaging modalities currently being studied in the literature include diffusion tensor imaging, MR spectroscopy, functional magnetic resonance imaging, perfusion imaging, and positron emission tomography. These newer imaging modalities attempt to more accurately evaluate the physical structure, intrinsic connectivity, biochemical and metabolic function, and perfusion of the spinal cord in DCM. Although there are still substantial limitations to implementation, future clinical practice will likely be revolutionized by these new imaging modalities to diagnose, localize, surgically plan and manage, and follow patients with DCM.

The change in postoperative opioid prescribing after lumbar decompression surgery following state-level opioid prescribing reform.

OBJECTIVE: On August 31, 2017, the state of Ohio implemented legislation limiting the dosage and duration of opioid prescriptions. Despite the widespread adoption of such restrictions, few studies have investigated the effects of these reforms on opioid prescribing and patient outcomes. In the present study, the authors aimed to evaluate the effect of recent state-level reform on opioid prescribing, patient-reported outcomes (PROs), and postoperative emergency department (ED) visits and hospital readmissions after elective lumbar decompression surgery. METHODS: This study was a retrospective cohort study of patients who underwent elective lumbar laminectomy for degenerative disease at one of 5 hospitals within a single health system in the years prior to and after the implementation of the statewide reform (September 1, 2016-August 31, 2018). Patients were classified according to the timing of their surgery relative to implementation of the prescribing reform: before reform (September 1, 2016-August 31, 2017) or after reform (September 1, 2017- August 31, 2018). The outcomes of interest included total outpatient opioids prescribed in the 90 days following discharge from surgery as measured in morphine-equivalent doses (MEDs), total number of opioid refill prescriptions written, patient-reported pain at the first postoperative outpatient visit as measured by the Numeric Pain Rating Scale, improvement in patient-reported health-related quality of life as measured by the Patient-Reported Outcomes Measurement Information System-Global Health (PROMIS-GH) questionnaire, and ED visits or hospital readmissions within 90 days of surgery. RESULTS: A total of 1031 patients met the inclusion criteria for the study, with 469 and 562 in the before- and after-reform groups, respectively. After-reform patients received 26% (95% CI 19%-32%) fewer MEDs in the 90 days following discharge compared with the before-reform patients. No significant differences were observed in the overall number of opioid prescriptions written, PROs, or postoperative ED or hospital readmissions within 90 days in the year after the implementation of the prescribing reform. CONCLUSIONS: Patients undergoing surgery in the year after the implementation of a state-level opioid prescribing reform received significantly fewer MEDs while reporting no change in the total number of opioid prescriptions, PROs, or postoperative ED visits or hospital readmissions. These results demonstrate that state-level reforms placing reasonable limits on opioid prescriptions written for acute pain may decrease patient opioid exposure without negatively impacting patient outcomes after lumbar decompression surgery.

Longer operative time associated with prolonged length of stay, non-home discharge and transfusion requirement after anterior cervical discectomy and fusion: an analysis of 24,593 cases.

BACKGROUND: Prolonged operative time of single-level ACDF has been associated with adverse postoperative outcomes. The current literature does not contain a comprehensive quantitative description of these associations PURPOSE: This study characterized the associations between single-level anterior cervical discectomy and fusion(ACDF) operative time and (1)30-day postoperative healthcare utilization, and (2)the incidence of local wound complications, need for transfusion and mechanical ventilation. DESIGN/SETTING: Retrospective database analysis PATIENT SAMPLE: The American College of Surgeons National Surgical Quality Improvement Program(ACS-NSQIP) database was queried for single-level ACDF cases(2012-2018) using current procedural terminology codes. A total of 24,593 cases were included. OUTCOME MEASURES: Primary outcomes included healthcare utilization(lengths of stay[LOS], discharge dispositions, 30-day readmissions, and reoperations) per operative time category. The secondary outcome was the incidence of wound complications, blood transfusion and need for ventilation per operative time category. METHODS: Multivariate regression determined operative time categories associated with increased risk while adjusting for patient demographics and comorbidities. Predictive spline regression models visualized the associations. RESULTS: Compared to the reference operative time of 81-100-minutes, the 101-120-minute category was associated with higher odds of LOS >2 days(OR:1.36,95%CI(1.18-1.568);p<.001) and non-home discharge(OR:1.341,95%CI(1.081-1.664);p=.008). Three-times greater odds of LOS >2 days(OR:3.367,95%CI(2.719-4.169); p<.001) and twice the odds of non-home discharge(OR:2.174,95%CI(1.563-3.022);p<.001) were detected at 181-200-minutes. The highest operative time category(≥221 minutes) was associated with the highest odds of LOS>2 days(OR:4.838,95%CI(4.032-5.804);p<.001), non-home discharge(OR:2.687,95%CI(2.045-3.531);p<.001) and reoperation(OR:1.794,95%CI(1.094-2.943);p=.021). Patients within the 201-220 and the ≥221-minute categories exhibited a significant association with greater odds of transfusion(OR:8.57,95%CI(2.321-31.639);p<.001, and OR:11.699, 95%CI(4.179-32.749);p=.001, respectively). Spline regression demonstrated that the odds of LOS >2 days, non-home discharge disposition, reoperation and bleeding requiring transfusion events began to rise, starting at 94, 91.6, 91.6, and 93.3 minutes of operative time, respectively. CONCLUSION: This study demonstrated that prolonged operative time is associated with increased odds of healthcare utilization and transfusion after single-level ACDF. Operative times greater than 91 minutes may carry higher odds of postoperative complications.

Can a machine learning model accurately predict patient resource utilization following lumbar spinal fusion?

BACKGROUND CONTEXT: With the increasing emphasis on value-based healthcare in Centers for Medicare and Medicaid Services reimbursement structures, bundled payment models have been adopted for many orthopedic procedures. Immense variability of patients across hospitals and providers makes these models potentially less viable in spine surgery. Machine-learning models have been shown reliable at predicting patient-specific outcomes following lumbar spine surgery and could, therefore, be applied to developing stratified bundled payment schemes. PURPOSE: (1) Can a Naïve Bayes machine-learning model accurately predict inpatient payments, length of stay (LOS), and discharge disposition, following dorsal and lumbar fusion? (2) Can such a model then be used to develop a risk-stratified payment scheme? STUDY DESIGN: A Naïve Bayes machine-learning model was constructed using an administrative database. PATIENT SAMPLE: Patients undergoing dorsal and lumbar fusion for nondeformity indications from 2009 through 2016 were included. Preoperative inputs included age group, gender, ethnicity, race, type of admission, All Patients Refined (APR) risk of mortality, APR severity of illness, and Clinical Classifications Software diagnosis code. OUTCOME MEASURES: Predicted resource utilization outcomes included LOS, discharge disposition, and total inpatient payments. Model validation was addressed via reliability, model output quality, and decision speed, based on application of training and validation sets. Risk-stratified payment models were developed according to APR risk of mortality and severity of illness. RESULTS: A Naïve Bayes machine-learning algorithm with adaptive boosting demonstrated high reliability and area under the receiver-operating characteristics curve of 0.880, 0.941, and 0.906 for cost, LOS, and discharge disposition, respectively. Patients with increased risk of mortality or severity of illness incurred costs resulting in greater inpatient payments in a patient-specific tiered bundled payment, reflecting increased risk on institutions caring for these patients. We found that a large range in expected payments due to individuals' preoperative comorbidities indicating an individualized risk-based model is warranted. CONCLUSIONS: A Naïve Bayes machine-learning model was shown to have good-to-excellent reliability and responsiveness for cost, LOS, and discharge disposition. Based on APR risk of mortality and APR severity of illness, there was a significant difference in episode costs from lowest to highest risk strata. After using normalized model error to develop a risk-adjusted proposed payment plan, it was found that institutions incur significantly more financial risk in flat bundled payment models for patients with higher rates of comorbidities.

The efficacy of intraoperative multimodal monitoring in pedicle subtraction osteotomies of the lumbar spine.

OBJECTIVE: Iatrogenic spine injury remains one of the most dreaded complications of pedicle subtraction osteotomies (PSOs) and spine deformity surgeries. Thus, intraoperative multimodal monitoring (IOM), which has the potential to provide real-time feedback on spinal cord signal transmission, has become the gold standard in such operations. However, while the benefits of IOM are well established in PSOs of the thoracic spine and scoliosis surgery, its utility in PSOs of the lumbar spine has not been robustly documented. The authors' aim was to determine the impact of IOM on outcomes in patients undergoing PSO of the lumbar spine. METHODS: All patients older than 18 years who underwent lumbar PSOs at the authors' institution from 2007 to 2017 were analyzed via retrospective chart review and categorized into one of two groups: those who had IOM guidance and those who did not. Perioperative complications were designated as the primary outcome measure and postoperative quality of life (QOL) scores, specifically the Parkinson's Disease Questionnaire-39 (PDQ-39) and Patient Health Questionnaire-9 (PHQ-9), were designated as secondary outcome measures. Data on patient demographics, surgical and monitoring parameters, and outcomes were gathered, and statistical analysis was performed to compare the development of perioperative complications and QOL scores between the two cohorts. In addition, the proportion of patients who reached minimal clinically important difference (MCID), defined as an increase of 4.72 points in the PDQ-39 score or a decrease of 5 points in the PHQ-9 score, in the two cohorts was also determined. RESULTS: A total of 95 patients were included in the final analysis. IOM was not found to significantly impact the development of new postoperative deficits (p = 0.107). However, the presence of preoperative neurological comorbidities was found to significantly correlate with postoperative neurological complications (p = 0.009). Univariate analysis showed that age was positively correlated with MCID achievement 3 months after surgery (p = 0.018), but this significance disappeared at the 12-month postoperative time point (p = 0.858). IOM was not found to significantly impact MCID achievement at either the 3- or 12-month postoperative period as measured by PDQ-39 (p = 0.398 and p = 0.156, respectively). Similarly, IOM was not found to significantly impact MCID achievement at either the 3- or 12-month postoperative period, as measured by PHQ-9 (p = 0.230 and p = 0.542, respectively). Multivariate analysis showed that female sex was significantly correlated with MCID achievement (p = 0.024), but this significance disappeared at the 12-month postoperative time point (p = 0.064). IOM was not found to independently correlate with MCID achievement in PDQ-39 scores at either the 3- or 12-month postoperative time points (p = 0.220 and p = 0.097, respectively). CONCLUSIONS: In this particular cohort, IOM did not lead to statistically significant improvement in outcomes in patients undergoing PSOs of the lumbar spine (p = 0.220). The existing clinical equipoise, however, indicates that future studies in this arena are necessary to achieve systematic guidelines on IOM usage in PSOs of the lumbar spine.

DRG-based bundled reimbursement for lumbar fusion: implications for patient selection.

OBJECTIVE: Under the Bundled Payments for Care Improvement (BPCI) initiative, Medicare reimburses for lumbar fusion without adjusting for underlying pathology. However, lumbar fusion is a widely used technique that can treat both degenerative and traumatic pathologies. In other surgical cohorts, significant heterogeneity exists in resource use when comparing procedures for traumatic versus degenerative pathologies. If the same were true for lumbar fusion, BPCI would create a financial disincentive to treat specific patient populations. The goal of this study was to compare hospital resource use for lumbar fusion between 2 patient populations: patients with spondylolisthesis and patients with lumbar vertebral fracture. METHODS: The authors compared the hospital resource use of two lumbar fusion cohorts that BPCI groups into the same payment bundle for lumbar fusion: patients with spondylolisthesis and patients with lumbar vertebral fracture. National Inpatient Sample data from 2013 were queried for patients who underwent lumbar fusion for lumbar vertebral fracture or spondylolisthesis. Hospital resource use was measured using length of stay (LOS), direct hospital costs, and odds of discharge to a post-acute care facility and compared using multivariable linear and logistic regression. All models adjusted for patient demographics, 29 comorbidities, and hospital characteristics. RESULTS: After adjusting for patient demographics, insurance status, hospital characteristics, and 29 comorbidities, spondylolisthesis patients had a mean LOS that was 36% shorter (95% CI 26%-44%, p < 0.0001), a mean cost that was 13% less (95% CI 3.7%-21%, p < 0.0001), and 3.2 times greater odds of being discharged home (95% CI 2.5-5.4, p < 0.0001) than lumbar vertebral fracture patients. CONCLUSIONS: Under the proposed DRG (diagnosis-related group)-based BPCI, hospitals would be reimbursed the same amount for lumbar fusion regardless of the diagnosis. However, compared with fusion for spondylolisthesis, fusion for lumbar vertebral fracture was associated with longer LOS, greater direct hospital costs, and increased likelihood of being discharged to a post-acute care facility. These findings suggest that the BPCI episode of care for lumbar fusion dis-incentivizes treatment of trauma patients.

Mechanics of the eukaryotic flagellar axoneme: Evidence for structural distortion during bending.

The sliding doublet mechanism is the established explanation that allows us to understand the process of ciliary and flagellar bending. In this study, we apply the principles of the sliding doublet mechanism to analyze the mechanics of the counterbend phenomenon in sea urchin sperm flagella. When a passive, vanadate-treated, flagellum is forced into a bend with a glass microprobe, the portion of the flagellum distal to the probe exhibits a bend of opposite curvature (counterbend) to the imposed bend. This phenomenon was shown to be caused by the induction of inter-doublet shear and is dependent on the presence of an inter-doublet shear resistance. Here we report that in sea urchin flagella there is systematically less shear induced in the distal flagellum than is predicted by the sliding doublet mechanism, if we follow the assumption that the diameter of the flagellum is uniform. To account for the reduced shear that is observed, the likeliest and most direct interpretation is that the portion of the axoneme that is forced to bend undergoes substantial compression of the axoneme in the bending plane. A compression of 30-50 nm would be sufficient to account for the shear reduction from a bend of 2 radians. A compression of this magnitude would require considerable flexibility in the axoneme structure. This would necessitate that the radial spokes and/or the central pair apparatus are easily compressed by transverse stress. © 2016 Wiley Periodicals, Inc.

Genetic and functional studies of the intervertebral disc: a novel murine intervertebral disc model.

Intervertebral disc (IVD) homeostasis is mediated through a combination of micro-environmental and biomechanical factors, all of which are subject to genetic influences. The aim of this study is to develop and characterize a genetically tractable, ex vivo organ culture model that can be used to further elucidate mechanisms of intervertebral disc disease. Specifically, we demonstrate that IVD disc explants (1) maintain their native phenotype in prolonged culture, (2) are responsive to exogenous stimuli, and (3) that relevant homeostatic regulatory mechanisms can be modulated through ex-vivo genetic recombination. We present a novel technique for isolation of murine IVD explants with demonstration of explant viability (CMFDA/propidium iodide staining), disc anatomy (H&E), maintenance of extracellular matrix (ECM) (Alcian Blue staining), and native expression profile (qRT-PCR) as well as ex vivo genetic recombination (mT/mG reporter mice; AdCre) following 14 days of culture in DMEM media containing 10% fetal bovine serum, 1% L-glutamine, and 1% penicillin/streptomycin. IVD explants maintained their micro-anatomic integrity, ECM proteoglycan content, viability, and gene expression profile consistent with a homeostatic drive in culture. Treatment of genetically engineered explants with cre-expressing adenovirus efficaciously induced ex vivo genetic recombination in a variety of genetically engineered mouse models. Exogenous administration of IL-1ß and TGF-ß3 resulted in predicted catabolic and anabolic responses, respectively. Genetic recombination of TGFBR1fl/fl explants resulted in constitutively active TGF-ß signaling that matched that of exogenously administered TGF-ß3. Our results illustrate the utility of the murine intervertebral disc explant to investigate mechanisms of intervertebral disc degeneration.

Down regulation of Wnt signaling mitigates hypoxia-induced chemoresistance in human osteosarcoma cells.

Osteosarcoma (OS) is the most common type of solid bone cancer and remains the second leading cause of cancer-related death for children and young adults. Hypoxia is an element intrinsic to most solid-tumor microenvironments, including that of OS, and is associated with resistance to therapy, poor survival, and a malignant phenotype. Cells respond to hypoxia through alterations in gene expression, mediated most notably through the hypoxia-inducible factor (HIF) class of transcription factors. Here we investigate hypoxia-induced changes in the Wnt/ß-catenin signaling pathway, a key signaling cascade involved in OS pathogenesis. We show that hypoxia results in increased expression and signaling activation of HIF proteins in human osteosarcoma cells. Wnt/ß-catenin signaling is down-regulated by hypoxia in human OS cells, as demonstrated by decreased active ß-catenin protein levels and axin2 mRNA expression (p<0.05). This down-regulation appears to rely on both HIF-independent and HIF-dependent mechanisms, with HIF-1α standing out as an important regulator. Finally, we show that hypoxia results in resistance of human OS cells to doxorubicin-mediated toxicity (6-13 fold increase, p<0.01). These hypoxic OS cells can be sensitized to doxorubicin treatment by further inhibition of the Wnt/ß-catenin signaling pathway (p<0.05). These data support the conclusion that Wnt/ß-catenin signaling is down-regulated in human OS cells under hypoxia and that this signaling alteration may represent a viable target to combat chemoresistant OS subpopulations in a hypoxic niche.

Targeting receptor-activator of nuclear kappaB ligand in aneurysmal bone cysts: verification of target and therapeutic response.

Aneurysmal bone cyst (ABC) is a benign tumor of bone presenting as a cystic, expansile lesion in both the axial and appendicular skeleton. Axial lesions demand special consideration, because treatment-related morbidity can be devastating. In similar lesions, such as giant cell tumor of bone (GCTB), the receptor-activator of nuclear kappaB ligand (RANKL)-receptor-activator of nuclear kappaB (RANK) signaling axis is essential to tumor progression. Although ABC and GCTB are distinct entities, they both contain abundant multinucleated giant cells and are osteolytic characteristically. We hypothesize that ABCs express both RANKL and RANK similarly in a cell-type specific manner, and that targeted RANKL therapy will mitigate ABC tumor progression. Cellular expression of RANKL and RANK was determined in freshly harvested ABC samples using laser confocal microscopy. A consistent cell-type-specific pattern was observed: fibroblastlike stromal cells expressed RANKL strongly whereas monocyte/macrophage precursor and multinucleated giant cells expressed RANK. Relative RANKL expression was determined by quantitative real-time polymerase chain reaction in ABC and GCTB tissue samples; no difference in relative expression was observed (P > 0.05). In addition, we review the case of a 5-year-old boy with a large, aggressive sacral ABC. After 3 months of targeted RANKL inhibition with denosumab, magnetic resonance imaging demonstrated tumor shrinkage, bone reconstitution, and healing of a pathologic fracture. Ambulation, and bowel and bladder function were restored at 6 months. Denosumab treatment was well tolerated. Post hoc analysis demonstrated strong RANKL expression in the pretreatment tumor sample. These findings demonstrate that RANKL-RANK signal activation is essential to ABC tumor progression. RANKL-targeted therapy may be an effective alternative to surgery in select ABC presentations.

Mechanical properties of the passive sea urchin sperm flagellum.

In this study we used Triton X-100 extracted sea urchin spermatozoa to investigate the mechanical behavior of the basic 9+2 axoneme. The dynein motors were disabled by vanadate so that the flagellum is rendered a passive structure. We find that when a proximal portion of the flagellum is bent with a glass microprobe, the remainder of the flagellum distal to the probe exhibits a bend in the opposite direction (a counterbend). The counterbend can be understood from the prevailing sliding doublet model of axoneme mechanics, but does require the existence of elastic linkages between the outer doublets. Analysis of the shapes of counterbends provides a consensus value of 0.03-0.08/microm(2) for the ratio of the interdoublet shear resistance (E(S)) to the bending resistance (E(B)) and we find that the ratio E(S)/E(B) is relatively conserved for both passive flagella and transiently quiescent live flagella. This ratio expresses a fundamental mechanical property of the eukaryotic axoneme. It defines the contributions to total bending resistance derived from bending the microtubules and from stretching the interdoublet linkages, respectively. Using this ratio, and computer simulations of earlier experiments that measured the total stiffness of the flagellum, we obtain estimates of approximately 1 x 10(8) pN nm(2)/rad for E(B) and 6 pN/rad for E(S), assuming that both elasticities are linear. Our results indicate that the behavior of the flagellum is close to that predicted by a linear model for shear elasticity.

Insights into the mechanism of ADP action on flagellar motility derived from studies on bull sperm.

Adenosine diphosphate (ADP) is known to have interesting effects on flagellar motility. Permeabilized and reactivated bull sperm exhibit a marked reduction in beating frequency and a greatly increased beat amplitude in the presence of 1-4 mM ADP. In this study we examined the force production of sperm reactivated with 0.1 mM ATP with and without 1 mM ADP and found that there is little or no resulting change in the stalling force produced by a bull sperm flagella in response to ADP. Because bull sperm bend to a higher curvature after ADP treatment we explored the possibility that ADP-treated sperm flagella are more flexible. We measured the stiffness of 50 muM sodium vanadate treated bull sperm in the presence of 4 mM ADP, but found no change in the passive flagellar stiffness. When we analyzed the torque that develops in ADP-treated sperm at the point of beat reversal we found that the torque developed by the flagellum is significantly increased. Our torque estimates also allow us to calculate the transverse force (t-force) acting on the flagellum at the point of beat direction reversal. We find that the t-force at the switch-point of the beat is increased significantly in the ADP treated condition, averaging 0.7 +/- 0.29 nN/microm in 0.1 mM ATP and increasing to 2.9 +/- 1.2 nN/microm in 0.1 mM ATP plus 4 mM ADP. This suggests that ADP is exerting its effect on the beat by increasing the tenacity of dynein attachment at the B-subtubule. This could be a direct result of a regulatory effect of ADP on the binding affinity of dynein for the B-subtubule of the outer doublets. This result could also help to explain a number of previous experimental observations, as discussed.