Publications by authors named "Dean Chou"

244 Publications

Does transforaminal lumbar interbody fusion induce lordosis or kyphosis? Radiographic evaluation with a minimum 2-year follow-up.

J Neurosurg Spine 2021 Jul 9:1-8. Epub 2021 Jul 9.

1Department of Neurological Surgery, University of California, San Francisco, California; and.

Objective: Conflicting reports exist about whether transforaminal lumbar interbody fusion (TLIF) induces lordosis or kyphosis, ranging from decreasing lordosis by 3.71° to increasing it by 18.8°. In this study, the authors' aim was to identify factors that result in kyphosis or lordosis after TLIF.

Methods: A single-center, retrospective study of open TLIF without osteotomy for spondylolisthesis with a minimum 2-year follow-up was undertaken. Preoperative and postoperative clinical and radiographic parameters and cage specifics were collected. TLIFs were considered to be "lordosing" if postoperative induction of lordosis was > 0° and "kyphosing" if postoperative induction of lordosis was ≤ 0°.

Results: A total of 137 patients with an average follow-up of 52.5 months (range 24-130 months) were included. The overall postoperative disc angle (DA) and segmental lordosis (SL) increased by 1.96° and 1.88° (p = 0.003 and p = 0.038), respectively, whereas overall lumbar lordosis remained unchanged (p = 0.133). Seventy-nine patients had lordosing TLIFs with a mean SL increase of 5.72° ± 3.97°, and 58 patients had kyphosing TLIFs with a mean decrease of 3.02° ± 2.98°. Multivariate analysis showed that a lower preoperative DA, lower preoperative SL, and anterior cage placement were correlated with the greatest increase in postoperative SL (p = 0.040, p < 0.001, and p = 0.035, respectively). There was no difference in demographics, cage type or height, or spinopelvic parameters between the groups (p > 0.05). Linear regression showed that the preoperative DA and SL correlated with SL after TLIF (R2 = 0.198, p < 0.001; and R2 = 0.2931, p < 0.001, respectively).

Conclusions: Whether a TLIF induces kyphosis or lordosis depends on the preoperative DA, preoperative SL, and cage position. Less-lordotic segments became more lordotic postoperatively, and highly lordotic segments may lose lordosis after TLIF. Cages placed more anteriorly were associated with more lordosis.
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http://dx.doi.org/10.3171/2020.12.SPINE201665DOI Listing
July 2021

Telemedicine in Neurosurgery: Standardizing the Spinal Physical Examination Using A Modified Delphi Method.

Neurospine 2021 Jun 30;18(2):292-302. Epub 2021 Jun 30.

Department of Neurological Surgery, University of California, San Francisco, CA, USA.

Objective: The use of telemedicine has dramatically increased due to the coronavirus disease 2019 pandemic. Many neurosurgeons are now using telemedicine technologies for preoperative evaluations and routine outpatient visits. Our goal was to standardize the telemedicine motor neurologic examination, summarize the evidence surrounding clinical use of telehealth technologies, and discuss financial and legal considerations.

Methods: We identified a 12-member panel composed of spine surgeons, fellows, and senior residents at a single institution. We created an initial telehealth strength examination protocol based on published data and developed 10 agree/disagree statements summarizing the protocol. A blinded Delphi method was utilized to build consensus for each statement, defined as > 80% agreement and no significant disagreement using a 2-way binomial test (significance threshold of p < 0.05). Any statement that did not meet consensus was edited and iteratively resubmitted to the panel until consensus was achieved. In the final round, the panel was unblinded and the protocol was finalized.

Results: After the first round, 4/10 statements failed to meet consensus ( < 80% agreement, and p = 0.031, p = 0.031, p = 0.003, and p = 0.031 statistical disagreement, respectively). The disagreement pertained to grading of strength of the upper (3/10 statements) and lower extremities (1/10 statement). The amended statements clarified strength grading, achieved consensus ( > 80% agreement, p > 0.05 disagreement), and were used to create the final telehealth strength examination protocol.

Conclusion: The resulting protocol was used in our clinic to standardize the telehealth strength examination. This protocol, as well as our summary of telehealth clinical practice, should aid neurosurgical clinics in integrating telemedicine modalities into their practice.
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http://dx.doi.org/10.14245/ns.2040684.342DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8255762PMC
June 2021

Commentary: Disruptive Technology in Spine Surgery and Education: Virtual and Augmented Reality.

Authors:
Dean Chou

Oper Neurosurg (Hagerstown) 2021 Jul;21(2):E161-E162

Department of Neurosurgery, University of California San Francisco, San Francisco, California, USA.

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http://dx.doi.org/10.1093/ons/opab167DOI Listing
July 2021

Present and Future Spinal Robotic and Enabling Technologies.

Oper Neurosurg (Hagerstown) 2021 06;21(Suppl 1):S48-S56

Department of Neurosurgery, University of Michigan, Ann Arbor, Michigan, USA.

Enabling technologies include surgical planning software, computer-assisted navigation, intraoperative three-dimensional (3D) imaging, and robotic systems. Presently, these technologies are in various stages of refinement. Spinal robots in particular are currently limited to the positioning of an alignment guide for pedicle screw placement. Current generation spinal robots, therefore, play a more limited role in spinal surgery. In contrast to spinal robots, intraoperative imaging technology has been developed further, to a stage that allows accurate 3D spinal image acquisition that can be readily utilized for spinal navigation. The integration of these various technologies has the potential to maximize the safety, consistency, reliability, and efficacy of surgical procedures. To that end, the trend for manufacturers is to incorporate various enabling technologies into the spinal robotic systems. In the near-term, it is expected that integration of more advanced planning software and navigation will result in wider applicability and value. In the long-term, there are a variety of enabling technologies such as augmented reality that may be a component of spinal robots. This article reviews the features of currently available spinal robots and discusses the likely future advancements of robotic platforms in the near- and long-term.
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http://dx.doi.org/10.1093/ons/opaa338DOI Listing
June 2021

Commentary: Expandable Cage Technology-Transforaminal, Anterior, and Lateral Lumbar Interbody Fusion.

Authors:
Dean Chou

Oper Neurosurg (Hagerstown) 2021 06;21(Suppl 1):S83-S84

Department of Neurosurgery, University of California, San Francisco, San Francisco, California, USA.

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http://dx.doi.org/10.1093/ons/opaa351DOI Listing
June 2021

Commentary: Impact of Opioid Prescribing Guidelines on Postoperative Opioid Prescriptions Following Elective Spine Surgery: Results From an Institutional Quality Improvement Initiative.

Authors:
Dean Chou

Neurosurgery 2021 Jun 10. Epub 2021 Jun 10.

Department of Neurosurgery, University of California, San Francisco, San Francisco, California, USA.

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http://dx.doi.org/10.1093/neuros/nyab211DOI Listing
June 2021

Oncology and Spinal Neurosurgeons Performing Resections of Intramedullary Ependymomas Compared with Single Neurosurgeons: A 13-Year Experience at a Single Institution.

World Neurosurg 2021 May 28. Epub 2021 May 28.

Department of Neurological Surgery, University of California, San Francisco, San Francisco, California, USA.

Objective: Resection of intramedullary spinal ependymomas carries great risk of postoperative neurological deficits. The objective of this study was to describe our experience using co-neurosurgeon teams to address intramedullary ependymomas to determine if the use of 2 experienced attending neurosurgeons with expertise in both neurosurgical oncology and spine pathology can improve outcomes for intramedullary ependymoma resections.

Methods: We retrospectively compared surgical and disease control outcomes in intramedullary ependymoma cases performed by co-neurosurgeon (one neurosurgical oncologist and one neurosurgeon trained in spinal surgery) and single-neurosurgeon teams over a 13-year period at a single institution.

Results: Co-neurosurgeons performed resections in 34 (47.9%) patients, and a single neurosurgeon performed resections in 37 (52.1%) patients. There were no significant differences in the frequency of gross total resection in the co-neurosurgeon versus single-neurosurgeon group (85.7% vs. 78.4%, P = 0.45). Posterior spinal fusion was more common in the co-neurosurgeon group (35.3%) compared with the single-neurosurgeon group (8.1%) (P = 0.01). Two (5.9%) patients in the co-neurosurgeon group and 5 (13.5%) patients in the single-neurosurgeon group had complications requiring surgical revision (P = 0.28). Recurrence rates were similar in both groups (5.9% vs. 10.8%, P = 0.50). At last follow-up, 76% of patients who presented with mild or no deficits remained functionally independent.

Conclusions: Resection of intramedullary ependymomas by co-neurosurgeon teams resulted in similar rates of gross total resection, postoperative complications, and recurrence compared with surgeries performed by a single neurosurgeon. Functional neurological outcomes were not impacted by co-neurosurgeons performing ependymoma resections.
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http://dx.doi.org/10.1016/j.wneu.2021.05.082DOI Listing
May 2021

The Preoperative Cross-sectional Area of the Deep Cervical Extensor Muscles Does Not Predict Loss of Lordosis After Cervical Laminoplasty.

Clin Spine Surg 2021 May 24. Epub 2021 May 24.

Department of Neurological Surgery, University of California San Francisco, San Francisco, CA Department of Neurosurgery, Sichuan Academy of Medical Sciences and Sichuan Provincial People's Hospital, School of Medicine, University of Electronic Science and Technology of China, Chengdu, Sichuan, China.

Study Design: This was a retrospective, single center.

Objectives: The objective of this study was to investigate the association between the cross-sectional area (CSA) of the deep extensor muscles (DEM) and postlaminoplasty alignment.

Summary Of Background Data: The preoperative CSA of the semispinalis cervicis (SC) has been reported to correlate with loss of lordosis (LL) after laminoplasty, with a CSA <154.5 mm2 associated with a 10 degrees LL.

Methods: Laminoplasty patients at the University of California San Francisco between 2009 and 2018 by 2 spine surgeons were retrospectively studied. Patients with previous cervical surgery or nondegenerative diagnoses were excluded. Measurements included the C2-C7 Cobb, T1 slope, and cervical sagittal vertical axis. Preoperative DEM CSA was measured on magnetic resonance imaging. Variables associated with lordosis were analyzed with univariate analysis and multivariate logistic regression, and association between postoperative cervical alignment and the musculature was evaluated.

Results: Seventy-six patients with a mean age of 64 years were included. The average follow-up was 22.53 months. The overall average CSA of the DEM was 2274.55 mm2 and that of the SC was 275.64 mm2. Means of both CSAs were higher in men (P<0.001). Linear regression showed no correlation between LL with CSA of the DEM or the SC (r=0.005, P=0.119; r=0.001, P=0.095). Univariate and multivariate regression showed no differences in the CSA of the DEM and SC between groups with and without LL (P=0.092, 0.117 and 0.163, 0.292). There was no correlation in LL with sex or body mass index (P>0.05).

Conclusions: Preoperative CSA of the deep cervical extensor muscles may not predict LL after cervical laminoplasty. The correlation between the preoperative SC CSA and postoperative cervical alignment may not be as strong as previously reported.
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http://dx.doi.org/10.1097/BSD.0000000000001199DOI Listing
May 2021

Posterior Displacement of L1 May be a Risk Factor for Proximal Junctional Kyphosis After Adult Spinal Deformity Correction.

Global Spine J 2021 May 17:21925682211015651. Epub 2021 May 17.

Department of Neurosurgery, University of California San Francisco, USA.

Study Design: Retrospective cohort study.

Objective: Overcorrection in adult spinal deformity (ASD) surgery may lead to proximal junctional kyphosis (PJK) because of posterior spinal displacement. The aim of this paper is to determine if the L1 position relative to the gravity line (GL) is associated with PJK.

Methods: ASD patients fused from the lower thoracic spine to sacrum by 4 spine surgeons at our hospital were retrospectively studied. Lumbar-only and upper thoracic spine fusions were excluded. Spinopelvic parameters, the L1 plumb line (L1PL), L1 distance to the GL (L1-GL), and Roussouly type were measured.

Results: One hundred fourteen patients met inclusion criteria (63 patients with PJK, 51 without). Mean age and follow up was 65.51 and 3.39 years, respectively. There was no difference between the PJK and the non-PJK groups in baseline demographics, pre-operative and immediate post-operative pelvic incidence-lumbar lordosis mismatch, sagittal vertical axis, or coronal Cobb. The immediate postoperative L1-GL was -7.24 cm in PJK and -3.45 cm in non-PJK ( < 0.001), L1PL was 1.71 cm in PJK and 3.07 cm in non-PJK ( = 0.004), and PT (23.76° vs 18.90°, = 0.026) and TK (40.56° vs 31.39°, < 0.001) were larger in PJK than in non-PJK. After univariate and multivariate analyses, immediate postoperative TK and immediate postoperative L1-GL were independent risk factors for PJK without collinearity.

Conclusions: A dorsally displaced L1 relative to the GL was associated with an increased risk of PJK after ASD surgery. The postoperative L1-GL distance may be a factor to consider during ASD surgery.
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http://dx.doi.org/10.1177/21925682211015651DOI Listing
May 2021

An analysis of tumor-related potential spinal column instability (Spine Instability Neoplastic Scores 7-12) eventually requiring surgery with a 1-year follow-up.

Neurosurg Focus 2021 05;50(5):E6

Departments of1Neurosurgery.

Objective: Within the Spine Instability Neoplastic Score (SINS) classification, tumor-related potential spinal instability (SINS 7-12) may not have a clear treatment approach. The authors aimed to examine the proportion of patients in this indeterminate zone who later required surgical stabilization after initial nonoperative management. By studying this patient population, they sought to determine if a clear SINS cutoff existed whereby the spine is potentially unstable due to a lesion and would be more likely to require stabilization.

Methods: Records from patients treated at the University of California, San Francisco, for metastatic spine disease from 2005 to 2019 were retrospectively reviewed. Seventy-five patients with tumor-related potential spinal instability (SINS 7-12) who were initially treated nonoperatively were included. All patients had at least a 1-year follow-up with complete medical records. A univariate chi-square test and Student t-test were used to compare categorical and continuous outcomes, respectively, between patients who ultimately underwent surgery and those who did not. A backward likelihood multivariate binary logistic regression model was used to investigate the relationship between clinical characteristics and surgical intervention. Recursive partitioning analysis (RPA) and single-variable logistic regression were performed as a function of SINS.

Results: Seventy-five patients with a total of 292 spinal metastatic sites were included in this study; 26 (34.7%) patients underwent surgical intervention, and 49 (65.3%) did not. There was no difference in age, sex, comorbidities, or lesion location between the groups. However, there were more patients with a SINS of 12 in the surgery group (55.2%) than in the no surgery group (44.8%) (p = 0.003). On multivariate analysis, SINS > 11 (OR 8.09, CI 1.96-33.4, p = 0.004) and Karnofsky Performance Scale (KPS) score < 60 (OR 0.94, CI 0.89-0.98, p = 0.008) were associated with an increased risk of surgery. KPS score was not correlated with SINS (p = 0.4). RPA by each spinal lesion identified an optimal cutoff value of SINS > 10, which were associated with an increased risk of surgical intervention. Patients with a surgical intervention had a higher incidence of complications on multivariable analysis (OR 2.96, CI 1.01-8.71, p = 0.048).

Conclusions: Patients with a mean SINS of 11 or greater may be at increased risk of mechanical instability requiring surgery after initial nonoperative management. RPA showed that patients with a KPS score of 60 or lower and a SINS of greater than 10 had increased surgery rates.
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http://dx.doi.org/10.3171/2021.2.FOCUS201098DOI Listing
May 2021

Feasibility of achieving planned surgical margins in primary spine tumor: a PTRON study.

Neurosurg Focus 2021 05;50(5):E16

1Combined Neurosurgical and Orthopaedic Spine Program, University of British Columbia, Vancouver, British Columbia, Canada.

Objective: Oncological resection of primary spine tumors is associated with lower recurrence rates. However, even in the most experienced hands, the execution of a meticulously drafted plan sometimes fails. The objectives of this study were to determine how successful surgical teams are at achieving planned surgical margins and how successful surgeons are in intraoperatively assessing tumor margins. The secondary objective was to identify factors associated with successful execution of planned resection.

Methods: The Primary Tumor Research and Outcomes Network (PTRON) is a multicenter international prospective registry for the management of primary tumors of the spine. Using this registry, the authors compared 1) the planned surgical margin and 2) the intraoperative assessment of the margin by the surgeon with the postoperative assessment of the margin by the pathologist. Univariate analysis was used to assess whether factors such as histology, size, location, previous radiotherapy, and revision surgery were associated with successful execution of the planned margins.

Results: Three hundred patients were included. The surgical plan was successfully achieved in 224 (74.7%) patients. The surgeon correctly assessed the intraoperative margins, as reported in the final assessment by the pathologist, in 239 (79.7%) patients. On univariate analysis, no factor had a statistically significant influence on successful achievement of planned margins.

Conclusions: In high-volume cancer centers around the world, planned surgical margins can be achieved in approximately 75% of cases. The morbidity of the proposed intervention must be balanced with the expected success rate in order to optimize patient management and surgical decision-making.
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http://dx.doi.org/10.3171/2021.2.FOCUS201091DOI Listing
May 2021

Efficacy of computed tomography-assisted limited decompression in the surgical management of thoracolumbar fractures with neurological deficit.

J Orthop Surg Res 2021 Apr 14;16(1):263. Epub 2021 Apr 14.

Department of the Orthopaedic Surgery, The First Affiliated Hospital of Zhengzhou University, No.1 Jianshe East Road, Zhengzhou, China.

Objective: To investigate the effect of CT-assisted limited decompression in managing single segment A3 lumbar burst fracture.

Method: A retrospective study (January 2015-June, 2019). One hundred six cases with single-level Magerl type A3 lumbar burst fractures treated with short-segment posterior internal fixation and limited decompression. Patients were divided into two groups: CT-assisted group and non-CT-assisted group. Perioperative factors, clinical outcomes, post-operative complications, imaging parameters, and health-related quality of life (HRQoL) were evaluated.

Results: Kyphosis, loss of anterior and posterior vertebral body heights, operative time, and post-operative complications were not significantly different between the two groups. The visual analog score (VAS) and spinal canal encroachment in the CT-assisted group were lower compared with the non-CT-assisted group (p < 0.05). The Japanese Orthopaedic Association (JOA) score, the simplified HRQoL scale, and the American Spinal Injury Association (ASIA) Spinal Cord Injury Grade in the CT-assisted group were significantly higher compared with the non-CT-assisted group (p < 0.05).

Conclusion: CT-assisted limited decompression in the treatment of single-segment A3 lumbar burst fracture can achieve better fracture reduction and surgical results and improve the long-term recovery of the patients' neurological function and quality of life.
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http://dx.doi.org/10.1186/s13018-021-02388-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8048249PMC
April 2021

The Effect of Anterior Cervical Discectomy and Fusion on Cervical Sagittal Vertical Axis and Lordosis with Minimum 2-Year Follow-Up.

World Neurosurg 2021 Jun 30;150:e727-e734. Epub 2021 Mar 30.

Department of Neurological Surgery, University of California San Francisco, San Francisco, California, USA.

Background: Anterior cervical discectomy and fusion (ACDF) can induce lordosis and improve cervical sagittal vertical axis (SVA), but multilevel ACDF may inadvertently increase cervical SVA because of insufficient lordosis induction.

Methods: Patients who underwent 1-, 2-, or ≥3-level ACDF in the subaxial spine with minimum 2-year follow up were retrospectively studied. C2-C7 Cobb angle (lordosis), cervical SVA, and T1 slope were measured preoperatively, immediately postoperatively, and at last follow-up.

Results: Inclusion criteria were met by 127 patients. There were no differences in baseline demographics among 1-, 2-, and ≥3-level ACDF groups. Mean follow-up was 43.7 months (range, 24-142 months). Increase of cervical SVA immediately postoperatively was 1.94 mm, -1.44 mm, and 7.25 mm for 1-, 2-, and ≥3-level ACDF (P = 0.041) and at last follow-up was 2.97 mm, 0.70 mm, and 9.32 mm for 1-, 2-, and ≥3-level ACDF (P = 0.026). At last follow-up, 2-level ACDF patients had the greatest decrease in T1 slope (-0.43°) compared with increase of 2.71° for 1-level and 2.84° for ≥3-level patients (P = 0.028). In all 3 groups, segmental (ACDF levels) lordosis, cervical SVA, and T1 slope did not decrease from immediate postoperative to last follow-up. Only 2-level ACDF maintained C2-7 lordosis (2.16°) compared with loss of lordosis in 1-level (-0.84°) and ≥3-level (-2.00°) ACDF (P = 0.008) at last follow-up. Linear regression analysis showed that T1 slope had no relationship with correction of cervical SVA (P = 0.5310) but had a significant correlation with Cobb angle loss of C2-C7 lordosis (P = 0.0016).

Conclusions: Compared with 1- and 2-level ACDF, ≥3-level ACDF resulted in significant increase of cervical SVA and loss of overall lordosis. Compared with 1- and ≥3-level ACDF, 2-level ACDF had the greatest ability to maintain lordosis. T1 slope had a significant correlation with loss of C2-C7 lordosis after ACDF.
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http://dx.doi.org/10.1016/j.wneu.2021.03.117DOI Listing
June 2021

Commentary: Safety of Early Mobilization in Patients With Intraoperative Cerebrospinal Fluid Leak in Minimally Invasive Spine Surgery: A Case Series.

Authors:
Dean Chou

Oper Neurosurg (Hagerstown) 2021 06;21(1):E1-E2

Department of Neurosurgery, University of California San Francisco, San Francisco, California, USA.

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http://dx.doi.org/10.1093/ons/opab068DOI Listing
June 2021

The minimally invasive interbody selection algorithm for spinal deformity.

J Neurosurg Spine 2021 Mar 12:1-8. Epub 2021 Mar 12.

13Department of Neurological Surgery, Weill Cornell Medical College, New York, New York.

Objective: Minimally invasive surgery (MIS) for spinal deformity uses interbody techniques for correction, indirect decompression, and arthrodesis. Selection criteria for choosing a particular interbody approach are lacking. The authors created the minimally invasive interbody selection algorithm (MIISA) to provide a framework for rational decision-making in MIS for deformity.

Methods: A retrospective data set of circumferential MIS (cMIS) for adult spinal deformity (ASD) collected over a 5-year period was analyzed by level in the lumbar spine to identify surgeon preferences and evaluate segmental lordosis outcomes. These data were used to inform a Delphi session of minimally invasive deformity surgeons from which the algorithm was created. The algorithm leads to 1 of 4 interbody approaches: anterior lumbar interbody fusion (ALIF), anterior column release (ACR), lateral lumbar interbody fusion (LLIF), and transforaminal lumbar interbody fusion (TLIF). Preoperative and 2-year postoperative radiographic parameters and clinical outcomes were compared.

Results: Eleven surgeons completed 100 cMISs for ASD with 338 interbody devices, with a minimum 2-year follow-up. The type of interbody approach used at each level from L1 to S1 was recorded. The MIISA was then created with substantial agreement. The surgeons generally preferred LLIF for L1-2 (91.7%), L2-3 (85.2%), and L3-4 (80.7%). ACR was most commonly performed at L3-4 (8.4%) and L2-3 (6.2%). At L4-5, LLIF (69.5%), TLIF (15.9%), and ALIF (9.8%) were most commonly utilized. TLIF and ALIF were the most selected approaches at L5-S1 (61.4% and 38.6%, respectively). Segmental lordosis at each level varied based on the approach, with greater increases reported using ALIF, especially at L4-5 (9.2°) and L5-S1 (5.3°). A substantial increase in lordosis was achieved with ACR at L2-3 (10.9°) and L3-4 (10.4°). Lateral interbody arthrodesis without the use of an ACR did not generally result in significant lordosis restoration. There were statistically significant improvements in lumbar lordosis (LL), pelvic incidence-LL mismatch, coronal Cobb angle, and Oswestry Disability Index at the 2-year follow-up.

Conclusions: The use of the MIISA provides consistent guidance for surgeons who plan to perform MIS for deformity. For L1-4, the surgeons preferred lateral approaches to TLIF and reserved ACR for patients who needed the greatest increase in segmental lordosis. For L4-5, the surgeons' order of preference was LLIF, TLIF, and ALIF, but TLIF failed to demonstrate any significant lordosis restoration. At L5-S1, the surgical team typically preferred an ALIF when segmental lordosis was desired and preferred a TLIF if preoperative segmental lordosis was adequate.
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http://dx.doi.org/10.3171/2020.9.SPINE20230DOI Listing
March 2021

En bloc excision of sacroiliac chondrosarcoma aided by 3D laser printed modeling and stereotactic navigation.

J Clin Neurosci 2021 Mar 15;85:64-66. Epub 2021 Jan 15.

Department of Neurosurgery, University of California San Francisco, United States.

The surgical management of sacro-iliac chondrosarcomas is challenging given their intimate relationship to the nerves and vessels of the pelvis. Osteotomies for en bloc excision can be challenging because of lack of visualization and high risk of injury to pelvic structures. The use of three-dimensional (3D) printed models helps conceptualize the tumor relative to the patient's anatomy. Coupled with stereotactic navigation, safe osteotomy planning and execution can be performed with avoidance of vital nerves and vessels. Very few cases have been reported demonstrating the successful use of these 2 modern technologies for en bloc excision of difficult tumors. We present our technique of using a 3D printed model and navigation for en bloc excision of a large sacro-iliac chondrosarcoma, supplemented with an intraoperative video.
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http://dx.doi.org/10.1016/j.jocn.2020.12.007DOI Listing
March 2021

Smoking Is an Independent Risk Factor for 90-Day Readmission and Reoperation Following Posterior Cervical Decompression and Fusion.

Neurosurgery 2021 05;88(6):1088-1094

Department of Neurological Surgery, University of California, San Francisco, California.

Background: Posterior cervical decompression and fusion (PCF) is a common procedure used to treat various cervical spine pathologies, but the 90-d outcomes following PCF surgery continue to be incompletely defined.

Objective: To identify risk factors associated with 90-d readmission and reoperation following PCF surgery.

Methods: Adults undergoing PCF from 2012 to 2020 were identified. Demographic and radiographic data, surgical characteristics, and 90-d outcomes were collected. Univariate analysis was performed using Student's t-test, chi square, and Fisher exact tests as appropriate. Multivariable logistic regression models with lasso penalty were used to analyze various risk factors.

Results: A total of 259 patients were included. The 90-d readmission and reoperation rates were 9.3% and 4.6%, respectively. The most common reason for readmission was surgical site infection (SSI) (33.3%) followed by new neurological deficits (16.7%). Patients who smoked tobacco had 3-fold greater odds of readmission compared to nonsmokers (odds ratio [OR]: 3.48; 95% CI 1.87-6.67; P = .0001). Likewise, the most common reason for reoperation was SSI (33.3%) followed by seroma and implant failure (25.0% each). Smoking was also an independent risk factor for reoperation, associated with nearly 4-fold greater odds of return to the operating room (OR: 3.53; 95% CI 1.53-8.57; P = .003).

Conclusion: Smoking is a significant predictor of 90-d readmission and reoperation in patients undergoing PCF surgery. Smoking cessation should be strongly considered preoperatively in elective PCF cases to minimize the risk of 90-d readmission and reoperation.
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http://dx.doi.org/10.1093/neuros/nyaa593DOI Listing
May 2021

Revision Surgery Rates After Minimally Invasive Adult Spinal Deformity Surgery: Correlation with Roussouly Spine Type at 2-Year Follow-Up?

World Neurosurg 2021 04 11;148:e482-e487. Epub 2021 Jan 11.

Department of Neurosurgery University of California, San Francisco, San Francisco, California, USA.

Background: Spinopelvic parameters have hitherto dictated much of adult spinal deformity (ASD) correction. The Roussouly classification is used for the normal adult spine. We evaluated whether a correlation would be found between the Roussouly type and the rate of revision surgery in patients with ASD undergoing circumferential minimally invasive spinal (cMIS) correction.

Methods: A multicenter retrospective review of patients who had undergone cMIS surgery for ASD was performed. The inclusion criteria were age ≥18 years and 1 of the following: coronal Cobb angle >20°, sagittal vertical axis >5 cm, pelvic tilt >20°, pelvic incidence (PI) to lumbar lordosis (LL) mismatch >10°, cMIS surgery, and a minimum of 2 years of follow-up data available. The patients were classified by Roussouly type, and the clinical and radiographic outcomes were evaluated.

Results: A total of 104 patients were included in the present analysis. Of the 104 patients, 41 had Roussouly type 1, 32 had type 2, 23 had type 3, and 8 had type 4. Preoperatively, the patients with type 4 had the highest PI (P = 0.002) and LL (P < 0.001). Postoperatively, the PI-LL mismatch, Cobb angle, and sagittal vertical axis were not different among the 4 groups. However, the patients with type 2 had had the highest rate of complications (type 1, 29.3%; type 2, 61.3%; type 3, 34.8%; type 4, 25.0%; P = 0.031). The reoperation rates were comparable (type 1, 19.5%; type 2, 38.7%; type 3, 13.0%; type 4, 12.5%; P = 0.097). The reoperation rates for adjacent segment degeneration or proximal junctional kyphosis were also comparable (P = 0.204 and P = 0.060, respectively).

Conclusions: We did not find a clear correlation between Roussouly type and the rate of revision surgery for adjacent segment disease or proximal junctional kyphosis in patients who had undergone cMIS surgery for ASD.
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http://dx.doi.org/10.1016/j.wneu.2021.01.011DOI Listing
April 2021

A Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances.

Oper Neurosurg (Hagerstown) 2021 03;20(4):334-342

Department of Neurosurgery, Xuanwu Hospital, Capital Medical Universiy. Beijing, China.

Background: The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks.

Objective: To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach.

Methods: A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements.

Results: The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion.

Conclusion: Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.
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http://dx.doi.org/10.1093/ons/opaa391DOI Listing
March 2021

Microsurgical Anterior Controllable Antedisplacement Fusion to Treat Cervical Ossified Posterior Longitudinal Ligament: 2-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2021 02;20(3):E221

Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing, China.

The anterior decompression technique, including vertebral body sliding osteotomy1 and anterior controllable antedisplacement fusion (ACAF),2 treats ossified posterior longitudinal ligament (OPLL) without actual excision of the OPLL.3 The fundamental strategy is to separate the mid-portion of the vertebral body along with the OPLL using bilateral anterior osteotomies followed by controllable antedisplacement. These techniques restore the space of the spinal canal anteriorly by anterior translation of the OPLL, avoiding excision and dural manipulation.4 We illustrate the case of a patient who had failed laminoplasty and the surgical decision making for ACAF. We discuss the other surgical options regarding patient selection, present preoperative and postoperative imaging, to demonstrate the efficacy of ACAF and show strategies of ACAF to make it a safe and effective procedure. We demonstrate our technique of ACAF using the intraoperative microscope and models in this video to illustrate the steps of ACAF. A written consent to the procedure was obtained from the patient.
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http://dx.doi.org/10.1093/ons/opaa376DOI Listing
February 2021

Anterior Cervical Discectomy With Fusion and Plating for Correction of Degenerative Cervical Kyphosis: 2-Dimensional Operative Video.

Oper Neurosurg (Hagerstown) 2021 02;20(3):E214

This surgical video demonstrates the technique for correcting degenerative cervical kyphosis using an anterior cervical discectomy and fusion (ACDF). Degenerative cervical kyphosis can cause radiculopathy, myelopathy, and difficulty holding up one's head. The goal of surgical intervention is to alleviate pain, improve the ability for upright gaze, and decompress the spinal cord or nerve roots. Posterior-only approaches and anterior corpectomies are alternative treatments to address cervical kyphosis. However, an ACDF allows for sequential induction of lordosis via distraction over multiple segments and for further lordosis induction by sequential screw tightening, pulling the spine towards a lordotic cervical plate.1 This video shows 2 cases demonstrating a technique of correcting severe cervical degenerative kyphosis. The video illustrates our initial kyphotic Caspar pin placement coupled with sequential anterior distraction to correct kyphosis. The technique is most useful in patients who have good bone density, nonankylosed facets, and degenerative cervical kyphosis. We have received informed consent of this patient to submit this video.
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http://dx.doi.org/10.1093/ons/opaa339DOI Listing
February 2021

Supine anterior lumbar interbody fusion versus lateral position oblique lumbar interbody fusion at L5-S1: A comparison of two approaches to the lumbosacral junction.

J Clin Neurosci 2020 Dec 7;82(Pt A):134-140. Epub 2020 Nov 7.

Department of Neurosurgery, University of California San Francisco, USA.

Introduction: At L5-S1, anterior access can be performed with a supine anterior lumbar interbody fusion (ALIF) or lateral position oblique lumbar interbody fusion (LOLIF). We compared clinical and radiographic features of both approaches.

Methods: A retrospective study of L5-S1 ALIF and LOLIF patients (2013-2018) by 3 spine surgeons and a vascular surgeon at our hospital was performed. Inclusion criteria were patients undergoing L5-S1 anterior surgery only without other anterior or lateral fusion levels, and data collected were patient demographics, cage parameters, perioperative variables, and radiographic parameters. 58 patients were included (33 ALIF and 25 LOLIF).

Results: The average surgical time was 211.94 min for ALIF and 154.86 min for LOLIF (p < 0.001). The average blood loss was 214 ml for ALIF and 74 ml for LOLIF (p < 0.001). The average number of days to solid food was 2.55 for ALIF and 0.8 for LOLIF (p < 0.001). The average anterior L5-S1 disc height increase was 8.52 mm for ALIF and 5.02 mm LOLIF (p = 0.018), and the average posterior L5-S1 disc height increase was 3.34 mm for ALIF and 1.30 mm for LOLIF (p = 0.034). The average L5-S1 segmental lordosis increase was 6.82 degrees for ALIF and 7.63 degrees for LOLIF (p = 0.638).

Conclusion: The LOLIF is a feasible option for L5-S1 anterior access compared to ALIF. However, supine ALIF afforded larger cages to be placed, resulting in greater postoperative disc height. There did not appear to be a significant difference in postoperative L5-S1 segmental lordosis between the two approaches.
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http://dx.doi.org/10.1016/j.jocn.2020.10.043DOI Listing
December 2020

High Frequency Ultrasound Elastography for Estimating the Viscoelastic Properties of the Cornea Using Lamb Wave Model.

IEEE Trans Biomed Eng 2020 Dec 11;PP. Epub 2020 Dec 11.

Objective: Estimating the elasticity distribution in the cornea is important because corneal elasticity is usually influenced by corneal pathologies and surgical treatments, especially for early corneal sclerosis. Because the thickness of the cornea is typically less than 1 mm, high-resolution ultrasound elastography as well as the Lamb wave model is required for viscoelastic property estimation. In the present study, an array high-frequency ultrasound (HFUS) elastography method based on ultrafast ultrasound imaging was proposed for estimating the viscoelastic properties of porcine cornea.

Methods: The elastic wave was generated by an external vibrator, after which the wave propagation image was obtained using a 40-MHz array transducer. Viscoelasticity estimation was performed by fitting the phase velocity curve using the Lamb wave model. The performance of the proposed HFUS elastography system was verified using 2-mm-thick thin-layer gelatin phantoms with gelatin concentrations of 7% and 12%. Ex vivo experiments were carried out using fresh porcine cornea with artificial sclerosing.

Results: Experimental results showed that the estimated elasticity was close to the standard value obtained in the phantom study when the Lamb wave model was used for elasticity measurement. However, the error between the standard elasticity values and the elasticity values estimated using group shear wave velocity was large. In the ex vivo eyeball experiments, the estimated elasticities and viscosities were respectively 9.1 ± 1.3 kPa and 0.5 ± 0.10 Pas for a healthy cornea and respectively 15.9 ± 2.1 kPa and 1.1 ± 0.12 Pas for a cornea with artificial sclerosis. A 3D HFUS elastography was also obtained for distinguishing the region of sclerosis in the cornea. Conclusion The experimental results demonstrated that the proposed HFUS elastography method has high potential for the clinical diagnosis of corneal diseases compared with other HFUS single-element transducer elastography systems.
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http://dx.doi.org/10.1109/TBME.2020.3044066DOI Listing
December 2020

Commentary: Emerging Technologies in Spinal Surgery: Ultra-Low Radiation Imaging Platforms.

Authors:
Dean Chou

Oper Neurosurg (Hagerstown) 2021 06;21(Suppl 1):S46-S47

Department of Neurosurgery, University of California San Francisco, San Francisco, California.

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http://dx.doi.org/10.1093/ons/opaa352DOI Listing
June 2021

Characterizing the fusion order and level-specific rates of arthrodesis in 3-level anterior cervical discectomy and fusion: A radiographic study.

J Clin Neurosci 2020 Nov 22;81:328-333. Epub 2020 Oct 22.

Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave., Room 779 M, San Francisco, CA 94143-0112, USA. Electronic address:

Pseudarthrosis is a well-recognized complication following multi-level ACDF. We aim to characterize the fusion order and level-specific rates of arthrodesis across four time points following 3-level ACDF. Patients who underwent 3-level ACDF by three UCSF spine surgeons from August 2012 to December 2019 were identified. Fusion status at each level was determined by measuring the interspinous motion on flexion and extension radiographs and assessing for evidence of bridging bone. Measurements were performed post-operatively at 6 weeks, 6 months, 12 months, and 18-24 months. A total of 77 patients with 3-level ACDF were identified and included in this study. Specific ACDF levels include C3-C6 (17 patients), C4-C7 (57 patients), and C5-T1 (3 patients). At 6 months, the cranial, middle, and caudal level fusion rates were 17.0%, 34.0%, and 3.8%, respectively. By 24 months, fusion rates were 61.1%, 88.9%, and 27.8% at the cranial, middle, and caudal level, respectively. PEEK cages were associated with lower odds of multi-level arthrodesis. Arthrodesis occurred the quickest at the middle level with an 88.9% fusion rate by 24 months after surgery. The caudal level had the slowest rate of arthrodesis with only a 27.8% fusion rate at 24 months, likely due to increased biomechanical stress at the most caudal level. Allograft was associated with higher odds of multi-level arthrodesis compared to PEEK cages.
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http://dx.doi.org/10.1016/j.jocn.2020.10.024DOI Listing
November 2020

Long-term radiographic outcomes of expandable versus static cages in transforaminal lumbar interbody fusion.

J Neurosurg Spine 2020 Nov 13:1-10. Epub 2020 Nov 13.

Departments of1Neurosurgery and.

Objective: Potential advantages of using expandable versus static cages during transforaminal lumbar interbody fusion (TLIF) are not fully established. The authors aimed to compare the long-term radiographic outcomes of expandable versus static TLIF cages.

Methods: A retrospective review of 1- and 2-level TLIFs over a 10-year period with expandable and static cages was performed at the University of California, San Francisco. Patients with posterior column osteotomy (PCO) were subdivided. Fusion assessment, cage subsidence, anterior and posterior disc height, foraminal dimensions, pelvic incidence (PI), segmental lordosis (SL), lumbar lordosis (LL), pelvic incidence-lumbar lordosis mismatch (PI-LL), pelvic tilt (PT), sacral slope (SS), and sagittal vertical axis (SVA) were assessed.

Results: A consecutive series of 178 patients (with a total of 210 levels) who underwent TLIF using either static (148 levels) or expandable cages (62 levels) was reviewed. The mean patient age was 60.3 ± 11.5 years and 62.8 ± 14.1 years for the static and expandable cage groups, respectively. The mean follow-up was 42.9 ± 29.4 months for the static cage group and 27.6 ± 14.1 months for the expandable cage group. Within the 1-level TLIF group, the SL and PI-LL improved with statistical significance regardless of whether PCO was performed; however, the static group with PCOs also had statistically significant improvement in LL and SVA. The expandable cage with PCO subgroup had significant improvement in SL only. All of the foraminal parameters improved with statistical significance, regardless of the type of cages used; however, the expandable cage group had greater improvement in disc height restoration. The incidence of cage subsidence was higher in the expandable group (19.7% vs 5.4%, p = 0.0017). Within the expandable group, the unilateral facetectomy-only subgroup had a 5.6 times higher subsidence rate than the PCO subgroup (26.8% vs 4.8%, p = 0.04). Four expandable cages collapsed over time.

Conclusions: Expandable TLIF cages may initially restore disc height better than static cages, but they also have higher rates of subsidence. Unilateral facetectomy alone may result in more subsidence with expandable cages than using bilateral PCO, potentially because of insufficient facet release. Although expandable cages may have more power to induce lordosis and restore disc height than static cages, subsidence and endplate violation may negate any significant gains compared to static cages.
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http://dx.doi.org/10.3171/2020.6.SPINE191378DOI Listing
November 2020

The impact of increasing interbody fusion levels at the fractional curve on lordosis, curve correction, and complications in adult patients with scoliosis.

J Neurosurg Spine 2020 Nov 13:1-10. Epub 2020 Nov 13.

Departments of1Neurosurgery and.

Objective: Radiculopathy from the fractional curve, usually from L3 to S1, can create severe disability. However, treatment methods of the curve vary. The authors evaluated the effect of adding more levels of interbody fusion during treatment of the fractional curve.

Methods: A single-institution retrospective review of adult patients treated for scoliosis between 2006 and 2016 was performed. Inclusion criteria were as follows: fractional curves from L3 to S1 > 10°, ipsilateral radicular symptoms concordant on the fractional curve concavity side, patients who underwent at least 1 interbody fusion at the level of the fractional curve, and a minimum 1-year follow-up. Primary outcomes included changes in fractional curve correction, lumbar lordosis change, pelvic incidence - lumbar lordosis mismatch change, scoliosis major curve correction, and rates of revision surgery and postoperative complications. Secondary analysis compared the same outcomes among patients undergoing posterior, anterior, and lateral approaches for their interbody fusion.

Results: A total of 78 patients were included. There were no significant differences in age, sex, BMI, prior surgery, fractional curve degree, pelvic tilt, pelvic incidence, pelvic incidence - lumbar lordosis mismatch, sagittal vertical axis, coronal balance, scoliotic curve magnitude, proportion of patients undergoing an osteotomy, or average number of levels fused among the groups. The mean follow-up was 35.8 months (range 12-150 months). Patients undergoing more levels of interbody fusion had more fractional curve correction (7.4° vs 12.3° vs 12.1° for 1, 2, and 3 levels; p = 0.009); greater increase in lumbar lordosis (-1.8° vs 6.2° vs 13.7°, p = 0.003); and more scoliosis major curve correction (13.0° vs 13.7° vs 24.4°, p = 0.01). There were no statistically significant differences among the groups with regard to postoperative complications (overall rate 47.4%, p = 0.85) or need for revision surgery (overall rate 30.7%, p = 0.25). In the secondary analysis, patients undergoing anterior lumbar interbody fusion (ALIF) had a greater increase in lumbar lordosis (9.1° vs -0.87° for ALIF vs transforaminal lumbar interbody fusion [TLIF], p = 0.028), but also higher revision surgery rates unrelated to adjacent-segment pathology (25% vs 4.3%, p = 0.046). Higher ALIF revision surgery rates were driven by rod fracture in the majority (55%) of cases.

Conclusions: More levels of interbody fusion resulted in increased lordosis, scoliosis curve correction, and fractional curve correction. However, additional levels of interbody fusion up to 3 levels did not result in more postoperative complications or morbidity. ALIF resulted in a greater lumbar lordosis increase than TLIF, but ALIF had higher revision surgery rates.
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http://dx.doi.org/10.3171/2020.6.SPINE20256DOI Listing
November 2020

Does state malpractice environment affect outcomes following spinal fusions? A robust statistical and machine learning analysis of 549,775 discharges following spinal fusion surgery in the United States.

Neurosurg Focus 2020 11;49(5):E18

1Department of Neurological Surgery, University of California, San Francisco, California.

Objective: Spine surgery is especially susceptible to malpractice claims. Critics of the US medical liability system argue that it drives up costs, whereas proponents argue it deters negligence. Here, the authors study the relationship between malpractice claim density and outcomes.

Methods: The following methods were used: 1) the National Practitioner Data Bank was used to determine the number of malpractice claims per 100 physicians, by state, between 2005 and 2010; 2) the Nationwide Inpatient Sample was queried for spinal fusion patients; and 3) the Area Resource File was queried to determine the density of physicians, by state. States were categorized into 4 quartiles regarding the frequency of malpractice claims per 100 physicians. To evaluate the association between malpractice claims and death, discharge disposition, length of stay (LOS), and total costs, an inverse-probability-weighted regression-adjustment estimator was used. The authors controlled for patient and hospital characteristics. Covariates were used to train machine learning models to predict death, discharge disposition not to home, LOS, and total costs.

Results: Overall, 549,775 discharges following spinal fusions were identified, with 495,640 yielding state-level information about medical malpractice claim frequency per 100 physicians. Of these, 124,425 (25.1%), 132,613 (26.8%), 130,929 (26.4%), and 107,673 (21.7%) were from the lowest, second-lowest, second-highest, and highest quartile states, respectively, for malpractice claims per 100 physicians. Compared to the states with the fewest claims (lowest quartile), surgeries in states with the most claims (highest quartile) showed a statistically significantly higher odds of a nonhome discharge (OR 1.169, 95% CI 1.139-1.200), longer LOS (mean difference 0.304, 95% CI 0.256-0.352), and higher total charges (mean difference [log scale] 0.288, 95% CI 0.281-0.295) with no significant associations for mortality. For the machine learning models-which included medical malpractice claim density as a covariate-the areas under the curve for death and discharge disposition were 0.94 and 0.87, and the R2 values for LOS and total charge were 0.55 and 0.60, respectively.

Conclusions: Spinal fusion procedures from states with a higher frequency of malpractice claims were associated with an increased odds of nonhome discharge, longer LOS, and higher total charges. This suggests that medicolegal climate may potentially alter practice patterns for a given spine surgeon and may have important implications for medical liability reform. Machine learning models that included medical malpractice claim density as a feature were satisfactory in prediction and may be helpful for patients, surgeons, hospitals, and payers.
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http://dx.doi.org/10.3171/2020.8.FOCUS20610DOI Listing
November 2020

Is the Goutallier grade of multifidus fat infiltration associated with adjacent-segment degeneration after lumbar spinal fusion?

J Neurosurg Spine 2020 Oct 30:1-6. Epub 2020 Oct 30.

Departments of1Neurological Surgery and.

Objective: The aim of this study was to investigate whether fat infiltration of the lumbar multifidus (LM) muscle affects revision surgery rates for adjacent-segment degeneration (ASD) after L4-5 transforaminal lumbar interbody fusion (TLIF) for degenerative spondylolisthesis.

Methods: A total of 178 patients undergoing single-level L4-5 TLIF for spondylolisthesis (2006 to 2016) were retrospectively analyzed. Inclusion criteria were a minimum 2-year follow-up, preoperative MR images and radiographs, and single-level L4-5 TLIF for degenerative spondylolisthesis. Twenty-three patients underwent revision surgery for ASD during the follow-up. Another 23 patients without ASD were matched with the patients with ASD. Demographic data, Roussouly curvature type, and spinopelvic parameter data were collected. The fat infiltration of the LM muscle (L3, L4, and L5) was evaluated on preoperative MRI using the Goutallier classification system.

Results: A total of 46 patients were evaluated. There were no differences in age, sex, BMI, or spinopelvic parameters with regard to patients with and those without ASD (p > 0.05). Fat infiltration of the LM was significantly greater in the patients with ASD than in those without ASD (p = 0.029). Fat infiltration was most significant at L3 in patients with ASD than in patients without ASD (p = 0.017). At L4 and L5, there was an increasing trend of fat infiltration in the patients with ASD than in those without ASD, but the difference was not statistically significant (p = 0.354 for L4 and p = 0.077 for L5).

Conclusions: Fat infiltration of the LM may be associated with ASD after L4-5 TLIF for spondylolisthesis. Fat infiltration at L3 may also be associated with ASD at L3-4 after L4-5 TLIF.
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http://dx.doi.org/10.3171/2020.6.SPINE20238DOI Listing
October 2020

Exploring neurodegenerative disorders using a novel integrated model of cerebral transport: Initial results.

Proc Inst Mech Eng H 2020 Nov 20;234(11):1223-1234. Epub 2020 Oct 20.

Department of Mechanical Engineering, University College London, London, UK.

The (NVU) underlines the complex and symbiotic relationship between brain cells and the cerebral vasculature, and dictates the need to consider both neurodegenerative and cerebrovascular diseases under the same mechanistic umbrella. Importantly, unlike peripheral organs, the brain was thought not to contain a dedicated lymphatics system. The concept (a portmanteau of glia and lymphatic) has further emphasized the importance of cerebrospinal fluid transport and emphasized its role as a mechanism for waste removal from the central nervous system. In this work, we outline a novel multiporoelastic solver which is embedded within a high precision, subject specific workflow that allows for the co-existence of a multitude of interconnected compartments with varying properties (multiple-network poroelastic theory, or MPET), that allow for the physiologically accurate representation of perfused brain tissue. This novel numerical template is based on a six-compartment MPET system (6-MPET) and is implemented through an in-house finite element code. The latter utilises the specificity of a high throughput imaging pipeline (which has been extended to incorporate the regional variation of mechanical properties) and blood flow variability model developed as part of the [email protected] research platform. To exemplify the capability of this large-scale consolidated pipeline, a cognitively healthy subject is used to acquire novel, biomechanistically inspired biomarkers relating to primary and derivative variables of the 6-MPET system. These biomarkers are shown to capture the sophisticated nature of the NVU and the glymphatic system, paving the way for a potential route in deconvoluting the complexity associated with the likely interdependence of neurodegenerative and cerebrovascular diseases. The present study is the first, to the best of our knowledge, that casts and implements the 6-MPET equations in a 3D anatomically accurate brain geometry.
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http://dx.doi.org/10.1177/0954411920964630DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7675777PMC
November 2020