Publications by authors named "David Polly"

247 Publications

Odontoid Fracture as Proximal Junctional Failure in Patients With Multilevel Spine Fusions.

Global Spine J 2021 May 11:21925682211008833. Epub 2021 May 11.

Department of Neurosurgery, University of Minnesota, Minneapolis, MN, USA.

Study Design: Retrospective study.

Objective: Proximal junctional failure (PJF) commonly occurs as a recognized potential outcome of fusion surgery. Here we describe a unique series of patients with multilevel spine fusion including the cervical spine, who developed PJF as an odontoid fracture.

Methods: We performed a single site retrospective review of patients with prior fusion that included a cervical component, who presented with an odontoid fracture between 2012 and 2019. Radiographic measurements included C2-C7 SVA, C2-C7 lordosis, T1 slope, Occiput-C2 angle, proximal junctional kyphosis, and cervical mismatch. Associated fractures, medical comorbidities, and treatments were determined via chart review after IRB approval.

Results: Nine patients met inclusion criteria. 5 reported trauma with subsequent onset of pain. All patients sustained a Type II odontoid fracture. 5 with associated C1/Jefferson fractures. In all patients, pre-injury Occiput-C2 angle was outside normative range; C2-C7 SVA was greater than 4 cm in 6 patients; T1-slope minus cervical lordosis was greater than 18.5 degrees in 6 patients. 7 patients were treated operatively with extension of fusion to C1 and 2 patients declined operative treatment.

Conclusion: In this series of 9 patients with multilevel fusion with type II odontoid fractures, all patients demonstrated abnormal pre-fracture sagittal alignment parameters and a greater than normal association of C1 fractures was noted. Further study is needed to establish the role of poor sagittal alignment with compensatory occiput-C2 angulation as a predisposing factor for odontoid fracture as a proximal junctional failure mechanism.
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http://dx.doi.org/10.1177/21925682211008833DOI Listing
May 2021

The Scoliosis Research Society adult spinal deformity standard outcome set.

Spine Deform 2021 Apr 6. Epub 2021 Apr 6.

Department of Orthopedic Surgery, Norton Leatherman Spine Center, University of Louisville, Louisville, KY, USA.

Purpose: Symptomatic adult spinal deformity (ASD) with an extremely variable presentation with pain, with and without neurogenic leg pain, and/or disturbed sagittal and coronal balance, causes a significant societal burden of disease. It is an important consequence of the aging adult population, generating a plethora of spine-related interventions with variable treatment efficacy and consistently high costs. Recent years have witnessed more than a threefold increase in the prevalence and treatment of ASD, and further increases over the coming decades are expected with the growing elderly population worldwide. The ability to monitor and assess clinical outcomes has not kept pace with these developments. This paper addresses the pressing need to provide a set of common outcome metrics for this growing group of patients with back pain and other disabilities due to an adult spinal deformity.

Methods: The standard outcome set was created by a panel with global representation, using a thorough modified Delphi procedure. The three-tiered outcome hierarchy (Porter) was used as a framework to capture full cycle of care. The standardized language of the International Classification of Functioning, Disability and Health (WHO-ICF) was used.

Results: Consensus was reached on a core set of 25 WHO-ICF outcome domains ('What to measure'); on the accompanying globally available clinician and patient reported measurement instruments and definitions ('How to measure'), and on the timing of the measurements ('When to measure'). The current work has brought to light domains not routinely reported in the spinal literature (such as pulmonary function, return to work, social participation), and domains for which no adequate instruments have yet been identified (such as how to clinically quantify in routine practice lumbar spinal stenosis, neurogenic claudication, radicular pain, and loss of lower extremity motor function).

Conclusion: A standard outcome set was developed for patients undergoing treatment for adult spinal deformity using globally available outcome metrics. The current framework can be considered a reference for further work, and may provide a starting point for routine methodical and systematic monitoring of outcomes. Post-COVID e-health may accelerate the routine capture of these types of data.
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http://dx.doi.org/10.1007/s43390-021-00334-2DOI Listing
April 2021

Cost-Utility Analysis of Anterior Vertebral Body Tethering versus Spinal Fusion in Idiopathic Scoliosis from a US Integrated Healthcare Delivery System Perspective.

Clinicoecon Outcomes Res 2021 15;13:175-190. Epub 2021 Mar 15.

Zimmer Biomet, Warsaw, IN, USA.

Purpose: Anterior vertebral body tethering (VBT) is a non-fusion, minimally invasive, growth-modulating procedure with some early positive clinical outcomes reported in pediatric patients with idiopathic scoliosis (IS). VBT offers potential health-related quality of life (HRQoL) benefits over spinal fusion in allowing patients to retain a greater range of motion after surgery. We conducted an early cost-utility analysis (CUA) to compare VBT with fusion as a first-choice surgical treatment for skeletally immature patients (age >10 years) with moderate to severe IS, who have failed nonoperative management, from a US integrated healthcare delivery system perspective.

Patients And Methods: The CUA uses a Markov state transition model, capturing a 15-year period following index surgery. Transition probabilities, including revision risk and subsequent fusion, were based on published surgical outcomes and an ongoing VBT observational study (NCT02897453). Patients were assigned utilities derived from published patient-reported outcomes (PROs; SRS-22r mapped to EQ-5D) following fusion and the above VBT study. Index and revision procedure costs were included. Probabilistic (PSA) and deterministic sensitivity analyses (DSA) were performed.

Results: VBT was associated with higher costs but also higher quality-adjusted life years (QALYs) than fusion (incremental costs: $45,546; QALYs gained: 0.54). The subsequent incremental cost-effectiveness ratio for VBT vs fusion was $84,391/QALY gained. Mean PSA results were similar to the base case, indicating that results were generally robust to uncertainty. The DSA indicated that results were most sensitive to variations in utility values.

Conclusion: This is the first CUA comparing VBT with fusion in pediatric patients with IS and suggests that VBT may be a cost-effective alternative to fusion in the US, given recommended willingness-to-pay thresholds ($100,000-$150,000). The results rely on HRQoL benefits for VBT compared with fusion. For improved model accuracy, further analyses with longer-term PROs for VBT, and comparative effectiveness studies, would be needed.
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http://dx.doi.org/10.2147/CEOR.S289459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7979350PMC
March 2021

2-Dimensional Long Film O-Arm Imaging, an Alternative When Intraoperative Fluoroscopy Is Inadequate.

World Neurosurg 2021 Mar 20;150:54-55. Epub 2021 Mar 20.

Department of Neurosurgery, University of Minnesota, Minneapolis, Minnesota, USA; Department of Orthopedic Surgery, University of Minnesota, Minneapolis, Minnesota, USA.

Obtaining intraoperative images of the spine in the obese patient and at the cervicothoracic junction have historically been technically difficult due to variable penetration and x-ray scatter. This is particularly true for spinal deformity cases, where clear visualization of the end plates is needed to determine if functional alignment has been restored to the spine. The novel "2D long film" functionality for the Medtronic O-arm is capable of capturing the x-ray backscatter, producing enhanced intraoperative images. Furthermore, images can be obtained along the gantry translation of the O-arm and combined into a single long image, optimizing the workflow of surgeons who use the O-arm for intraoperative navigation. The purpose of this report is to highlight 2 example spinal deformity cases that underscore the utility of this imaging technology. In both cases, standard intraoperative fluoroscopy visualization was unacceptable, so 2D long film images were obtained to assess postcorrection spinal alignment.
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http://dx.doi.org/10.1016/j.wneu.2021.03.078DOI Listing
March 2021

Intrawound vancomycin application after spinal surgery: a propensity score-matched cohort analysis.

J Neurosurg Spine 2021 Mar 5:1-11. Epub 2021 Mar 5.

1Department of Surgery.

Objective: Surgical site infection (SSI) following spine surgery is associated with increased morbidity and healthcare costs. In an effort to reduce SSI rates, the application of intrawound vancomycin powder has gained popularity. However, there is limited high-quality evidence to support the safety and efficacy of this practice. The authors sought to determine if intrawound application of vancomycin powder improves 90-day overall SSI rates.

Methods: The authors performed a retrospective, vancomycin exposure-matched cohort study at a single tertiary care hospital over 21 months. They included all patients undergoing elective spinal surgery and stratified the patients into two groups: those who received intrawound vancomycin powder application and those who received no application of vancomycin powder. The primary outcome of interest was the 90-day overall SSI rate. Secondary outcomes included rates of superficial SSI, deep SSI, wound disruption, and a post hoc analysis of the microbiology and minimum inhibitory concentrations. Baseline patient demographics, clinical presentation, comorbidities, perioperative factors, and 90-day postoperative outcomes were manually abstracted from patient charts. To mitigate bias, we performed 1:1 matching after calculating propensity scores and identified 1 patient from the no-vancomycin cohort for each patient in the vancomycin cohort.

Results: A total of 997 patients met our inclusion criteria (473 patients receiving vancomycin and 524 patients not receiving vancomycin). Propensity score matching produced 221 matched pairs. Risk-adjusted analysis demonstrated similar overall SSI rates between the groups (OR 1.9, p = 0.329). On unadjusted analysis, the overall 90-day SSI rate was greater in the vancomycin group (n = 10 [4.5%]) than in the no-vancomycin group (n = 5 [2.3%]) (p < 0.001), as were the superficial SSI rate (7 [3.2%] vs 4 [1.8%], p < 0.001), deep SSI rate (3 [1.4%] vs 1 [0.5%], p < 0.001), and wound disruption rate (5 [2.3%] vs 1 [0.5%], p < 0.001). No cultured isolate demonstrated vancomycin resistance.

Conclusions: The authors observed no difference in SSI rates after the intrawound application of vancomycin powder during spine surgery. Vancomycin use did not contribute to antimicrobial resistance; however, it may select out gram-negative bacteria and increase rates of wound disruption.
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http://dx.doi.org/10.3171/2020.8.SPINE201129DOI Listing
March 2021

Toward the Development of a Comprehensive Clinically Oriented Patient Profile: A Systematic Review of the Purpose, Characteristic, and Methodological Quality of Classification Systems of Adult Spinal Deformity.

Neurosurgery 2021 May;88(6):1065-1073

Department of Orthopaedic Surgery, Radboud University Medical Center, Nijmegen, The Netherlands.

Background: Existing adult spinal deformity (ASD) classification systems are based on radiological parameters but management of ASD patients requires a holistic approach. A comprehensive clinically oriented patient profile and classification of ASD that can guide decision-making and correlate with patient outcomes is lacking.

Objective: To perform a systematic review to determine the purpose, characteristic, and methodological quality of classification systems currently used in ASD.

Methods: A systematic literature search was conducted in MEDLINE, EMBASE, CINAHL, and Web of Science for literature published between January 2000 and October 2018. From the included studies, list of classification systems, their methodological measurement properties, and correlation with treatment outcomes were analyzed.

Results: Out of 4470 screened references, 163 were included, and 54 different classification systems for ASD were identified. The most commonly used was the Scoliosis Research Society-Schwab classification system. A total of 35 classifications were based on radiological parameters, and no correlation was found between any classification system levels with patient-related outcomes. Limited evidence of limited quality was available on methodological quality of the classification systems. For studies that reported the data, intraobserver and interobserver reliability were good (kappa = 0.8).

Conclusion: This systematic literature search revealed that current classification systems in clinical use neither include a comprehensive set of dimensions relevant to decision-making nor did they correlate with outcomes. A classification system comprising a core set of patient-related, radiological, and etiological characteristics relevant to the management of ASD is needed.
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http://dx.doi.org/10.1093/neuros/nyab023DOI Listing
May 2021

Change in pelvic incidence between the supine and standing positions in patients with bilateral sacroiliac joint vacuum signs.

J Neurosurg Spine 2021 Jan 15:1-6. Epub 2021 Jan 15.

Departments of1Neurological Surgery and.

Objective: Pelvic incidence (PI) is a commonly utilized spinopelvic parameter in the evaluation and treatment of patients with spinal deformity and is believed to be a fixed parameter. However, a fixed PI assumes that there is no motion across the sacroiliac (SI) joint, which has been disputed in recent literature. The objective of this study was to determine if patients with SI joint vacuum sign have a change in PI between the supine and standing positions.

Methods: A retrospective chart review identified patients with a standing radiograph, supine radiograph, and CT scan encompassing the SI joints within a 6-month period. Patients were grouped according to their SI joints having either no vacuum sign, unilateral vacuum sign, or bilateral vacuum sign. PI was measured by two independent reviewers.

Results: Seventy-three patients were identified with an average age of 66 years and a BMI of 30 kg/m2. Patients with bilateral SI joint vacuum sign (n = 27) had an average absolute change in PI of 7.2° (p < 0.0001) between the standing and supine positions compared to patients with unilateral SI joint vacuum sign (n = 20) who had a change of 5.2° (p = 0.0008), and patients without an SI joint vacuum sign (n = 26) who experienced a change of 4.1° (p = 0.74). ANOVA with post hoc Tukey test showed a statistically significant difference in the change in PI between patients with the bilateral SI joint vacuum sign and those without an SI joint vacuum sign (p = 0.023). The intraclass correlation coefficient between the two reviewers was 0.97 for standing PI and 0.96 for supine PI (p < 0.0001).

Conclusions: Patients with bilateral SI joint vacuum signs had a change in PI between the standing and supine positions, suggesting there may be increasing motion across the SI joint with significant joint degeneration.
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http://dx.doi.org/10.3171/2020.8.SPINE20742DOI Listing
January 2021

AN ADJUNCTIVE USE OF ASFOTASE ALFA AND ZOLEDRONIC ACID AFTER SPINAL SURGERY IN NEUROFIBROMATOSIS TYPE 1 RELATED DYSTROPHIC SCOLIOSIS.

AACE Clin Case Rep 2020 Nov-Dec;6(6):e305-e310. Epub 2020 Aug 6.

Objective: Dystrophic scoliosis is a serious skeletal manifestation of neurofibromatosis 1 (NF1). The condition requires surgical intervention that is frequently associated with poor outcome due to the high rate of impaired bone healing, pseudoarthrosis, and loosening of the spinal instrumentation. New therapeutic approaches are needed to improve surgical outcomes.

Methods: Clinical, laboratory, and radiographic data are presented.

Results: A 54-year-old woman with severe NF1 related dystrophic scoliosis and 3 prior surgical interventions underwent revision of lumbar fusion with intraoperative recombinant human bone morphogenetic protein (rhBMP-2) for loosening and a fracture of the left vertical rod at the L4 pedicle screw connection. Two days after surgery, a computed tomography (CT) scan revealed a left posterior iliac periscrew fracture. Given a high risk of mechanical failure, zoledronic acid and asfotase alfa were also administered at 3 and 7 months after surgery. At 14 months after surgery, back pain improved, and a CT scan showed stable spinal fusion and a healed left posterior iliac screw fracture.

Conclusion: Combination therapy including asfotase alfa with rhBMP-2 and bisphosphonate resulted in solid arthrodesis after spinal surgery in NF1-related dystrophic scoliosis.
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http://dx.doi.org/10.4158/ACCR-2020-0222DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7685405PMC
August 2020

Morphological integration and modularity in the hyperkinetic feeding system of aquatic-foraging snakes.

Evolution 2021 Jan 30;75(1):56-72. Epub 2020 Nov 30.

Department of Herpetology, American Museum of Natural History, New York, New York, 10024.

The kinetic skull is a key innovation that allowed snakes to capture, manipulate, and swallow prey exclusively using their heads using the coordinated movement of eight bones. Despite these unique feeding behaviors, patterns of evolutionary integration and modularity within the feeding bones of snakes in a phylogenetic framework have yet to be addressed. Here, we use a dataset of 60 μCT-scanned skulls and high-density geometric morphometric methods to address the origin and patterns of variation and integration in the feeding bones of aquatic-foraging snakes. By comparing alternate superimposition protocols allowing us to analyze the entire kinetic feeding system simultaneously, we find that the feeding bones are highly integrated, driven predominantly by functional selective pressures. The most supported pattern of modularity contains four modules, each associated with distinct functional roles: the mandible, the palatopterygoid arch, the maxilla, and the suspensorium. Further, the morphological disparity of each bone is not linked to its magnitude of integration, indicating that integration within the feeding system does not strongly constrain morphological evolution, and that adequate biomechanical solutions to a wide range of feeding ecologies and behaviors are readily evolvable within the constraint due to integration in the snake feeding system.
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http://dx.doi.org/10.1111/evo.14130DOI Listing
January 2021

Minimally Invasive Sacroiliac Joint Fusion: A Lateral Approach Using Triangular Titanium Implants and Navigation.

JBJS Essent Surg Tech 2020 Oct-Dec;10(4). Epub 2020 Oct 19.

Department of Orthopedic Surgery, University of Minnesota, Minneapolis, Minnesota.

Minimally invasive sacroiliac (SI) joint fusion is indicated for low back pain from the SI joint that is due to degenerative sacroiliitis and/or sacroiliac joint disruption. This technique is safe and effective in relieving pain uncontrolled by nonoperative management. There is some controversy, but there continues to be increasing evidence of effectiveness.

Description: This procedure is performed, with the patient under general anesthesia and in the prone position, using fluoroscopy or 3-dimensional (3D) navigation such as cone-beam computed tomographic (CT) imaging. After navigation setup, a navigated probe is used to approximate the desired location of each implant and trajectory. These positions are marked on the skin, and the skin is incised. A 3 to 5-cm lateral incision is made. The gluteal fascia is bluntly dissected to the outer table of the ilium. A guide pin is passed across the SI joint and into the center of the sacrum lateral to the neural foramina, which is confirmed with imaging. This is then drilled and broached. Triangular titanium rods are placed. Typically, 3 implants are placed, 2 in S1 and 1 in S2. Multiplanar postplacement imaging of the pelvis is obtained. The wound is irrigated and closed in layers.

Alternatives: Nonsurgical alternatives have been reported to include pharmacological therapies, such as nonsteroidal anti-inflammatory drugs, therapeutic SI joint blocks, and physical therapy, such as core stabilization, orthotics (SI belts), and radiofrequency ablation. The surgical alternative is an open anterior or posterior approach with SI joint arthrodesis. The anterior approach differs by the resection of the SI joint cartilage, the use of a plate or screws across the joint for stabilization, and the packing of bone graft to facilitate fusion. These are more morbid and have a much longer recovery.

Rationale: Conservative management for SI joint pain is inadequate for all patients. Having 3 of 5 positive physical examination maneuvers, having confirmatory diagnostic block(s), and ruling out the hip or spine as the pain generator provide a success rate of >80%. These patients have early and sustained clinically important and significantly improved outcomes across varying measures compared with conservative treatment.

Expected Outcomes: Patients can expect to experience decreased pain, reduced disability, increased daily function, and improved quality of life soon after the procedure is performed. These patients typically have an improvement of ≥50% in the Oswestry Disability Index score and a clinically significant decrease in visual analog pain scores. The procedure appears durable through at least 5 years. Complete pain relief is rare, but clinically important improvement is typical.

Important Tips: Proper setup of the navigation system or fluoroscopy is needed to ensure accurate starting points.For 3D navigation, use a reference pin in the contralateral posterior superior iliac spine.Although navigation is used, radiographic images are made periodically to confirm proper placement of guide pins and implants. Images provide the greatest benefit when establishing navigation, after guide-pin placement when an outlet view allows for evaluation of pin depth, and after implant placement to confirm proper placement.Blood loss is generally low, but care should be taken to avoid vascular injury. Although rare, improper placement has led to injury of the superior gluteal artery and iliac artery. This can be avoided by staying in bone.Proper placement of the implant is imperative in this procedure. There is the potential for nerve injury with improper placement of the implant: an L5 nerve injury if the implant is too ventral or an S1 or S2 nerve injury if the implant is too deep and into the foramen. Revision surgery is commonly due to nerve root impingement and/or malpositioning.Preoperative 3D imaging is indicated when it is necessary to rule out differential diagnoses that mimic SI joint pain. This enables the surgeon to rule out intrapelvic pathology, assess sacral bone density, and identify dysmorphic sacra or transitional vertebrae.
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http://dx.doi.org/10.2106/JBJS.ST.19.00067DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7665262PMC
October 2020

Surgeon Preference for Radiologist Interpretation of Deformity Radiographs-A Survey of Lumbar Spine Research Society Membership.

Int J Spine Surg 2020 Aug 31;14(4):527-533. Epub 2020 Jul 31.

The Department of Radiology, University of Minnesota, Minneapolis, Minnesota.

Background: The radiologist interpretation of scoliosis films is non-standardized, with some practitioners providing detailed measurements of the deformity whereas others defer the interpretation of the deformity to the ordering surgeon. For radiologists, the standard of care is not clear, and this creates confusion in terms of how much interpretation is required. However, detailed radiologist reports sometimes conflict with the surgeon's interpretation, which can create confusion for patients who receive the reports, or in extreme cases can lead to insurance denials. Thus, the purpose of this study was to help establish a standard for interpretation of these films by surveying the ordering surgeons and documenting expert opinion about the amount and type of radiologist interpretation that is requested.

Methods: We designed a SurveyMonkey survey which aimed to look at standard practice for radiologist dictation of scoliosis radiographs. Twelve questions were sent to Lumbar Spine Research Society membership via email with a description of the study. One follow-up email was also sent to non-responders.

Results: The rate of completed surveys was 46 out of 185 Lumbar Spine Research Society members (25%). Thirty-seven respondents (80%) worked in academic institutions, 33 were orthopedists (71%), and 13 were neurosurgeons (28%). Fifty percent reported that radiologists' level of detail in dictations was inconsistent at their institution. Detailed numeric reporting was rare (6.5%). When the radiologist did provide numeric measurements, surgeons reported that they often differed from the surgeon's own measurements, with only 4% reporting that the measurements "rarely" differed from the surgeon's; 49% reported that the radiologist's measurements that differed from the surgeon's had led to insurance denials for their patients. The majority of respondents (70%) did not want the radiologist to provide detailed numeric measurements of the deformity, and 91% reported that the radiologist's measurements had no impact on their clinical decision making.

Conclusions: Detailed deformity measurements are time consuming for the radiologist, and would seem to have low clinical utility for the responding surgeons in this survey, with significant potential for discrepancies in interpretation to lead to insurance denials.

Level Of Evidence: IV.
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http://dx.doi.org/10.14444/7069DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7478053PMC
August 2020

The effect of simulation training on resident proficiency in thoracolumbar pedicle screw placement using computer-assisted navigation.

J Neurosurg Spine 2020 Sep 4:1-8. Epub 2020 Sep 4.

1Departments of Neurosurgery and.

Objective: Residency work-hour restrictions necessitate efficient, reproducible training. Simulation training for spinal instrumentation placement shows significant benefit to learners' subjective and objective proficiency. Cadaveric laboratories are most effective but have high cost and low availability. The authors' goal was to create a low-cost, efficient, reproducible spinal instrumentation placement simulation curriculum for neurosurgery and orthopedic surgery residents using synthetic models and 3D computer-assisted navigation, assessing subjective and objective proficiency with placement of thoracolumbar pedicle screws.

Methods: Fifteen neurosurgery and orthopedic surgery residents participated in a standardized curriculum with lecture followed by two separate sessions of thoracolumbar pedicle screw placement in a synthetic spine model utilizing 3D computer-assisted navigation. Data were collected on premodule experience, time and accuracy of screw placement, and both subjective and objective ratings of proficiency.

Results: Fifteen of 15 residents demonstrated improvement in subjective (Physician Performance Diagnostic Inventory Scale [PPDIS]) and 14 in objective (Objective Structured Assessment of Technical Skills [OSATS]) measures of proficiency in navigated screw placement with utilization of this curriculum (p < 0.001 for both), regardless of the number of cases of previous experience using thoracolumbar spinal instrumentation. Fourteen of 15 residents demonstrated decreased time per screw placement from session 1 to session 2 (p = 0.006). There was no significant difference in pedicle screw accuracy between session 1 and session 2.

Conclusions: A standardized curriculum using synthetic simulation training for navigated thoracolumbar pedicle screw placement results in significantly improved resident subjective and objective proficiency. Development of a nationwide competency curriculum using simulation training for spinal instrumentation placement should be considered for safe, efficient resident training.
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http://dx.doi.org/10.3171/2020.5.SPINE2067DOI Listing
September 2020

Regional improvements in lumbosacropelvic Hounsfield units following teriparatide treatment.

Neurosurg Focus 2020 08;49(2):E11

Departments of1Neurologic Surgery.

Objective: Opportunistic Hounsfield unit (HU) determination from CT imaging has been increasingly used to estimate bone mineral density (BMD) in conjunction with assessments from dual energy x-ray absorptiometry (DXA). The authors sought to compare the effect of teriparatide on HUs across different regions in the pelvis, sacrum, and lumbar spine, as a surrogate measure for the effects of teriparatide on lumbosacropelvic instrumentation.

Methods: A single-institution retrospective review of patients who had been treated with at least 6 months of teriparatide was performed. All patients had at least baseline DXA as well as pre- and post-teriparatide CT imaging. HUs were measured in the pedicle, lamina, and vertebral body of the lumbar spine, in the sciatic notch, and at the S1 and S2 levels at three different points (ilium, sacral body, and sacral ala).

Results: Forty patients with an average age of 67 years underwent a mean of 20 months of teriparatide therapy. Mean HUs of the lumbar lamina, pedicles, and vertebral body were significantly different from each other before teriparatide treatment: 343 ± 114, 219 ± 89.2, and 111 ± 48.1, respectively (p < 0.001). Mean HUs at the S1 level for the ilium, sacral ala, and sacral body were also significantly different from each other: 124 ± 90.1, -10.7 ± 61.9, and 99.1 ± 72.1, respectively (p < 0.001). The mean HUs at the S2 level for the ilium and sacral body were not significantly different from each other, although the mean HU at the sacral ala (-11.9 ± 52.6) was significantly lower than those at the ilium and sacral body (p = 0.003 and 0.006, respectively). HU improvement occurred in most regions following teriparatide treatment. In the lumbar spine, the mean lamina HU increased from 343 to 400 (p < 0.001), the mean pedicle HU increased from 219 to 242 (p = 0.04), and the mean vertebral body HU increased from 111 to 134 (p < 0.001). There were also significant increases in the S1 sacral body (99.1 to 130, p < 0.05), S1 ilium (124 vs 165, p = 0.01), S1 sacral ala (-10.7 vs 3.68, p = 0.04), and S2 sacral body (168 vs 189, p < 0.05).

Conclusions: There was significant regional variation in lumbar and sacropelvic HUs, with most regions significantly increasing following teriparatide treatment. The sacropelvic area had lower HU values than the lumbar spine, more regional variation, and a higher degree of correlation with BMD as measured on DXA. While teriparatide treatment resulted in HUs > 110 in the majority of the lumbosacral spine, the HUs in the sacral ala remained suggestive of severe osteoporosis, which may limit the effectiveness of fixation in this region.
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http://dx.doi.org/10.3171/2020.5.FOCUS20273DOI Listing
August 2020

Functional Tradeoffs Carry Phenotypes Across the Valley of the Shadow of Death.

Authors:
P David Polly

Integr Comp Biol 2020 11;60(5):1268-1282

Departments of Earth & Atmospheric Science, Biology, and Anthropology, Indiana University, Bloomington, IN, 47405, USA.

Functional tradeoffs are often viewed as constraints on phenotypic evolution, but they can also facilitate evolution across the suboptimal valleys separating performance peaks. I explore this process by reviewing a previously published model of how disruptive selection from competing functional demands defines an intermediate performance optimum for morphological systems that cannot simultaneously be optimized for all of the functional roles they must play. Because of the inherent tradeoffs in such a system, its optimal morphology in any particular environmental context will usually be intermediate between the performance peaks of the competing functions. The proportional contribution of each functional demand can be estimated by maximum likelihood from empirically observed morphologies, including complex ones measured with multivariate geometric morphometrics, using this model. The resulting tradeoff weight can be mapped onto a phylogenetic tree to study how the performance optimum has shifted across a functional landscape circumscribed by the function-specific performance peaks. This model of tradeoff evolution is sharply different from one in which a multipeak Ornstein-Uhlenbeck (OU) model is applied to a set of morphologies and a phylogenetic tree to estimate how many separate performance optima exist. The multi-peak OU approach assumes that each branch is pushed toward one of two or more performance peaks that exist simultaneously and are separated by valleys of poor performance, whereas the model discussed here assumes that each branch tracks a single optimal performance peak that wanders through morphospace as the balance of functional demands shifts. That the movements of this net performance peak emerge from changing frequencies of selection events from opposing functional demands are illustrated using a series of computational simulations. These simulations show how functional tradeoffs can carry evolution across putative performance valleys: even though intermediate morphologies may not perform optimally for any one function, they may represent the optimal solution in any environment in which an organism experiences competing functional demands.
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http://dx.doi.org/10.1093/icb/icaa092DOI Listing
November 2020

Willingness to enroll in a surgical randomized controlled trial: patient and parent preferences regarding implant density for adolescent idiopathic scoliosis fusion.

Spine Deform 2020 10 3;8(5):957-963. Epub 2020 Jun 3.

University of Minnesota, Minneapolis, MN, USA.

Study Design: Prospective survey of adolescent idiopathic scoliosis (AIS) patients/parents with surgical magnitude curves.

Objective: We hypothesized that patients and families considering fusion surgery would be willing to enroll in a randomized controlled trial (RCT) evaluating the effect of number of implants on curve correction. Surgical RCTs are infrequently performed, particularly in a pediatric population. Parental willingness to enroll affects both study design and trial feasibility. The Minimize Implants Maximize Outcomes (MIMO) Clinical Trial proposes to randomize patients to more versus fewer screws (high or low density) for Lenke 1A curve patterns, but it is unclear whether families and patients are willing to enroll in such a trial.

Methods: This study was undertaken at 4 of the 14 sites participating in the MIMO Clinical Trial. AIS patients with Cobb > 45° were included. Implant density is defined as screws per level fused. Patients and families reviewed the MIMO education module describing proposed advantages and disadvantages of high (> 1.8) vs. low (< 1.4) density screw constructs and completed a custom survey regarding their preferences about the trial.

Results: 159 individuals were surveyed (78 families), including 82 parents/guardians, and 77 patients. Of those surveyed, 95% mostly or completely understood the trial (range 47-78%), and 63% agreed to enroll. Parents and patients who completely understood the trial were significantly more likely to enroll.

Conclusion: Randomization in the MIMO Trial was acceptable to the majority (63%) of patients and parents. Clear patient and parent education materials and access to the surgeon may facilitate enrollment in the trial. Parents afforded the child much autonomy when considering enrollment, although most families agree both child and parent should be in agreement before entering the trial.

Level Of Evidence: II.
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http://dx.doi.org/10.1007/s43390-020-00143-zDOI Listing
October 2020

Quantifying the effect of posterior spinal instrumentation on the MRI signal of adjacent intervertebral discs.

Spine Deform 2020 10 24;8(5):845-851. Epub 2020 May 24.

Division of Rehabilitation Science, Department of Rehabilitation Medicine, Medical School, University of Minnesota, Minneapolis, MN, USA.

Study Design: Ex vivo porcine imaging study.

Objectives: Quantitatively evaluate change in MRI signal at the discs caudal to spinal fusion instrumentation. Individuals who receive posterior spinal instrumentation are at risk of developing accelerated disc degeneration at adjacent levels. Degeneration is associated with a loss of biochemical composition and mechanical integrity of the disc, which can be noninvasively assessed through quantitative T2* (qT2*) MRI techniques. However, qT2* is sensitive to magnetic susceptibility introduced by metal.

Methods: Nine ex vivo porcine lumbar specimens were imaged with 3 T MRI. Fast spin-echo T2-weighted (T2w) images and gradient-echo qT2* maps were acquired, both without and with posterior spinal fusion instrumentation. Average T2* relaxation times of the nuclei pulposi (NP) were measured at the adjacent and sub-adjacent discs and measurements were compared using t tests before and after instrumentation. The size of the signal void and metal artifact were determined (modified ASTM F2119-07) within the vertebral body and spinal cord for both MRI sequences. The relationship between T2* signal loss and distance from the instrumentation was evaluated using Pearson's correlation.

Results: There was no significant difference between adjacent and sub-adjacent NP T2* relaxation time prior to instrumentation (p = 0.86). Following instrumentation, there was a significant decrease in the T2* relaxation time at the adjacent NP (average = 20%, p = 0.02), and no significant difference at the sub-adjacent NP (average = - 3%, p = 0.30). Furthermore, there was a significant negative correlation between signal loss and distance to disc (r = - 0.61, p < 0.01).

Conclusions: Spinal fusion instrumentation interferes with T2* relaxation time measurements at the adjacent disc but not at the sub-adjacent discs. However, there is sufficient signal at the adjacent disc to quantify changes in the T2* relaxation time following spinal fusion. Hence, baseline MRI scan following spinal fusion surgery are required to interpret and track changes in disc health at the caudal discs.

Level Of Evidence: N/A.
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http://dx.doi.org/10.1007/s43390-020-00139-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7541587PMC
October 2020

The effectiveness of a free-standing lead-shield in reducing spine surgeon radiation exposure during intraoperative 3-dimensional imaging.

Spine J 2020 10 20;20(10):1685-1691. Epub 2020 May 20.

Department of Orthopedic Surgery, University of Minnesota, 2512 South 7th St, Suite R200, Minneapolis, MN, USA. Electronic address:

Background: CONTEXT Intraoperative three-dimensional (3D) computed tomography (CT) imaging has become increasingly popular in spine surgery. Previous spine surgeon radiation exposure research has focused largely on procedures using fluoroscopy, however, few studies have been performed on the subject since the introduction of the 3D imaging systems. As a result, concerns have re-emerged over surgeon radiation exposure and the effectiveness of operating room (OR) protocols for decreasing workplace radiation. Current radiation safety guidelines require surgeons wear full body protective lead while any type of radiation is being administered during surgery. As a result, local institutions do not allow for the use of free-standing lead shields for sole radiation protection in the operating room. However, there is no data available to demonstrate whether the additional personal lead is required, or if in fact the lead shield alone is sufficient.

Purpose: This study investigated the effectiveness of a free-standing lead shield in reducing spine surgeon radiation exposure in the operating room during intraoperative imaging.

Study Design/setting: A prospective clinical research study at a large, tertiary care center.

Patient Sample: Twenty-seven patients undergoing instrumented spinal procedures between June and August 2019.

Outcome Measures: Fluoroscopy time, total fluoroscopy dose delivered, 3D dose delivered, total 3D spins, number of HD spins, number of standard spins, number of fluoroscopic images, number of spine levels operated on, patient size setting, shield distance from patient, radiation dose in front of shield, radiation dose behind shield.

Methods: Twenty-seven instrumented spinal procedures using the O-Arm Imaging System (Medtronic, Minneapolis, MN) were observed to determine radiation exposure to a spine surgeon standing behind a lead shield in the OR. Two thermoluminescent dosimeters were used to measure scatter radiation in front of and behind lead shields. Both fluoroscopy and intraoperative CT based radiation exposure was recorded. The dosimeter readings were compared to determine the degree of radiation attenuation by the lead shield. Regression analysis of the exposure values from behind the shield, shield distance from the patient, and radiation dose delivered by the imaging system was utilized to estimate the number of cases required to surpass annual exposure limits. Case numbers were calculated for the highest "worst case" and "average case" exposure values. The safe annual occupation exposure limit determined by the National Council on Radiation Protection is five roentgen equivalent man (rem) or 50,000 microsieverts (μSv).

Results: Average surgeon radiation exposure per case was 0.694 μSv (SD: 0.501, Range: 0.105-2.167) behind the lead shield compared to 14.577 μSv (SD: 9.864, Range: 2.185-44.492) in front of the lead shield. The average radiation dose reduction by the lead shield was 13.962 μSv (SD: 9.49, Range: 2.08-42.72) per case, which is equivalent to an average of 95.65% (SD: 1.71) radiation attenuation by lead shielding. If surgeons stand behind lead shields in the OR, the annual number of 3D image-guided spinal procedures required to surpass exposure limits is 15,479 and 67,060 based on "worst case" and "average case" analyses, respectively.

Conclusions: Our study demonstrates standing behind intraoperative lead shields is very effective at decreasing radiation exposure to surgeons. Additionally, surgeon radiation doses behind lead shielding fall far below annual exposure limits. Surgeons should not need additional protective equipment when a lead shield is used.
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http://dx.doi.org/10.1016/j.spinee.2020.05.099DOI Listing
October 2020

Team Approach: Safety and Value in the Practice of Complex Adult Spinal Surgery.

JBJS Rev 2020 04;8(4):e0145

Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota.

Surgical management of complex adult spinal deformities is of high risk, with a substantial risk of operative mortality. Current evidence shows that potential risk and morbidity resulting from surgery for complex spinal deformity may be minimized through risk-factor optimization. The multidisciplinary team care model includes neurosurgeons, orthopaedic surgeons, physiatrists, anesthesiologists, hospitalists, psychologists, physical therapists, specialized physician assistants, and nurses. The multidisciplinary care model mimics previously described integrated care pathways designed to offer a structured means of providing a comprehensive preoperative medical evaluation and evidence-based multimodal perioperative care. The role of each team member is illustrated in the case of a 66-year-old male patient with previous incomplete spinal cord injury, now presenting with Charcot spinal arthropathy and progressive vertebral-body destruction resulting in lumbar kyphosis.
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http://dx.doi.org/10.2106/JBJS.RVW.19.00145DOI Listing
April 2020

Is the middle cranial fossa a reliable predictor of temporal lobe volume in extant and fossil anthropoids?

Am J Phys Anthropol 2020 08 1;172(4):698-713. Epub 2020 Apr 1.

Department of Paleobiology, Centro Nacional de Investigación sobre la Evolución Humana, Burgos, Spain.

Objectives: We investigate the suitability of middle cranial fossa (MCF) size as a proxy for temporal lobe volume (TLV), examining the strength of the association between TLV and MCF metrics and assess the reliability predicting TLV in fossil anthropoids. The temporal lobe of the primate brain is a multimodal association cortex involved in long-term memory, auditory, and visual processing with unique specializations in modern humans for language comprehension. The MCF is the bony counterpart for the temporal lobe providing inferences for fossil hominin temporal lobe evolution. We now investigate whether the MCF is a suitable proxy for the temporal lobe.

Methods: A sample of 23 anthropoid species (n = 232, including 13 fossil species) from computed tomography (CT) scans of ex vivo crania and magnetic resonance imaging (MRI) of the in vivo brain were generated into three-dimensional (3D) virtual models. Seven linear metrics were digitally measured on the right MCF with right TLV calculated from in vivo MRI.

Results: Regression analyses produced statistically significant correlations between TLV and all MCF metrics (r ≥ 0.85; p ≤ 0.0009) with TLV predictions within ±1 standard error and three MCF metrics (posterior-width, mid-length, and mid-width) the most reliable predictors of TLV with only one metric weakly associated with TLV.

Discussion: These findings indicate a strong association between the MCF and TLV, provide reliable predictors of fossil TLV that were previously unattainable, allow the inclusion of fragmentary fossil material, and enable inferences into the emergence of modern human temporal lobe morphology.
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http://dx.doi.org/10.1002/ajpa.24053DOI Listing
August 2020

Minimally Invasive Sacroiliac Joint Fusion: The Current Evidence.

Int J Spine Surg 2020 Feb 10;14(Suppl 1):20-29. Epub 2020 Feb 10.

Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota.

Background: Fusion of the sacroiliac (SI) joint as a treatment for low back pain remains controversial. The purpose of this manuscript is to review the current literature and clinical outcomes of SI joint fusion surgery.

Methods: We conducted a literature review and included studies with the term "sacroiliac joint fusion" that had at least 12 months of clinical follow-up, reported on minimally invasive techniques, and included patient-reported outcome measures.

Results: Two approach types (dorsal and lateral) and numerous different implant manufacturers were identified. Most studies included level 4 data, with a small number of level 2 prospective cohort studies and 2 prospective level 1 studies. Every reviewed study reported clinical benefit in terms of improved pain scores or improvement in validated disability measures. Complication rates were low.

Conclusions: Minimally invasive SI joint fusion provides clinically significant improvement in pain scores and disability in most patients, across multiple studies and implant manufacturers.

Level Of Evidence: 5.

Clinical Relevance: Emerging evidence in support of SI joint fusion indicates that clinicians should examine the SI joint and include SI joint pain in their differential diagnosis for low back pain patients.
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http://dx.doi.org/10.14444/6072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7041666PMC
February 2020

Sacral Dysmorphism and Lumbosacral Transitional Vertebrae (LSTV) Review.

Int J Spine Surg 2020 Feb 10;14(Suppl 1):14-19. Epub 2020 Feb 10.

Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, Minnesota.

Background: Anatomic variation in the relationship between the lumbar spine and sacrum was first described in the literature nearly a century ago and continues to play an important role in spine deformity, low back pain (LBP), and pelvic trauma. This review will focus on the clinical and surgical implications of abnormal lumbosacral anatomy in the context of sacroiliac joint (SIJ) disease, spine deformity, and pelvic trauma.

Methods: A PubMed search using the keywords "lumbosacral transitional vertebrae," "LSTV," "transitional lumbosacral vertebrae," "TLSV," and "sacral dysmorphism" was performed. The articles presented here were evaluated by the authors.

Clinical Significance: The prevalence of LSTV varies widely in the literature from 3.9-% to 35.6% in the spine literature, and sacral dysmorphism is described in upwards of 50% of the population in the trauma literature. The relationship between LSTV and LBP is well established. While there is no agreed-on etiology, the source of pain is multifactorial and may be related to abnormal biomechanics and alignment, disc degeneration, and arthritic changes.

Surgical Implications: Understanding abnormal lumbosacral anatomy is crucial for preoperative planning of SIJ fusion, spine deformity, and pelvic trauma surgery. LSTV can alter spinopelvic parameters crucial in planning spine deformity correction. Traditional safe zones for sacroiliac screw placement do not apply in the first sacral segment in sacral dysmorphism and risk iatrogenic nerve injury.

Conclusions: LSTV and sacral dysmorphism are common anatomic variants found in the general population. Abnormal lumbosacral anatomy plays a significant role in clinical evaluation of LBP and surgical planning in SIJ fusion, spine deformity, and pelvic trauma. Further studies evaluating the influence of abnormal lumbosacral anatomy on LBP and surgical technique would help guide treatment for these patients.
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http://dx.doi.org/10.14444/6075DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7041668PMC
February 2020

Editor's Message: Understanding the Sacroiliac Joint.

Authors:
David W Polly

Int J Spine Surg 2020 Feb 10;14(Suppl 1). Epub 2020 Feb 10.

Professor and Chief of Spine Service, Department of Orthopedic Surgery, University of Minnesota Medical School, M Health Clinics and Surgery Center, Minneapolis, Minnesota.

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http://dx.doi.org/10.1444/6083DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7041663PMC
February 2020

Minimally invasive sacroiliac joint fusion conservative management for chronic sacroiliac joint pain.

Authors:
David W Polly

J Spine Surg 2019 Sep;5(3):381-383

Department of Orthopedic Surgery, University of Minnesota, Minneapolis, MN, USA.

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http://dx.doi.org/10.21037/jss.2019.06.10DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6787368PMC
September 2019

The Deformity TLIF: Bilateral Facetectomy and Osteotomy Closure with a Hinged Table.

Iowa Orthop J 2019 ;39(1):81-84

Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN.

Background: Increasing emphasis has been placed on segmental lordosis correction, even in short segment constructs. However, the majority of reports on TLIF indicate that lordosis correction is modest at best. TLIF with bilateral facetecomy has been described with better lordosis correction, but is usually performed with the spine in extension throughout the case. This report presents a new technique for lordosis correction during TLIF with the use of bilateral facetectomy and osteotomy closure using a mechanically hinged operative table.

Methods: A 78-year-old male presented with claudicatory back and leg pain due to foraminal stenosis and spondylolisthesis at L4-5 and L5-S1, and was operated on with bilateral facetectomies and TLIF while positioned on a motorized-hinged table, which started in flexion for the decompression and was brought into extension at the end of the case for osteotomy closure.

Results: Segmental lordosis from L4-S1 increased from 15° pre-operatively to 42° postoperatively.

Conclusions: A comparison of pre- and post-operative lateral radiographs showed 27° segmental lordosis correction, and intra-operative fluoroscopy showed correlation between extension of the table and segmental lordosis correction. Bilateral facetectomy and TLIF allows for segmental lordosis correction. Use of the hinged table allowed for ideal positioning during the decompression and controlled osteotomy closure with close correlation between table position and segmental alignment. V.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6604555PMC
February 2020

High-Density Morphometric Analysis of Shape and Integration: The Good, the Bad, and the Not-Really-a-Problem.

Integr Comp Biol 2019 09;59(3):669-683

Departments of Earth and Atmospheric Sciences, Biology, and Anthropology, Indiana University, 1001 E. 10th Street, Bloomington, IN 47405, USA.

The field of comparative morphology has entered a new phase with the rapid generation of high-resolution three-dimensional (3D) data. With freely available 3D data of thousands of species, methods for quantifying morphology that harness this rich phenotypic information are quickly emerging. Among these techniques, high-density geometric morphometric approaches provide a powerful and versatile framework to robustly characterize shape and phenotypic integration, the covariances among morphological traits. These methods are particularly useful for analyses of complex structures and across disparate taxa, which may share few landmarks of unambiguous homology. However, high-density geometric morphometrics also brings challenges, for example, with statistical, but not biological, covariances imposed by placement and sliding of semilandmarks and registration methods such as Procrustes superimposition. Here, we present simulations and case studies of high-density datasets for squamates, birds, and caecilians that exemplify the promise and challenges of high-dimensional analyses of phenotypic integration and modularity. We assess: (1) the relative merits of "big" high-density geometric morphometrics data over traditional shape data; (2) the impact of Procrustes superimposition on analyses of integration and modularity; and (3) differences in patterns of integration between analyses using high-density geometric morphometrics and those using discrete landmarks. We demonstrate that for many skull regions, 20-30 landmarks and/or semilandmarks are needed to accurately characterize their shape variation, and landmark-only analyses do a particularly poor job of capturing shape variation in vault and rostrum bones. Procrustes superimposition can mask modularity, especially when landmarks covary in parallel directions, but this effect decreases with more biologically complex covariance patterns. The directional effect of landmark variation on the position of the centroid affects recovery of covariance patterns more than landmark number does. Landmark-only and landmark-plus-sliding-semilandmark analyses of integration are generally congruent in overall pattern of integration, but landmark-only analyses tend to show higher integration between adjacent bones, especially when landmarks placed on the sutures between bones introduces a boundary bias. Allometry may be a stronger influence on patterns of integration in landmark-only analyses, which show stronger integration prior to removal of allometric effects compared to analyses including semilandmarks. High-density geometric morphometrics has its challenges and drawbacks, but our analyses of simulated and empirical datasets demonstrate that these potential issues are unlikely to obscure genuine biological signal. Rather, high-density geometric morphometric data exceed traditional landmark-based methods in characterization of morphology and allow more nuanced comparisons across disparate taxa. Combined with the rapid increases in 3D data availability, high-density morphometric approaches have immense potential to propel a new class of studies of comparative morphology and phenotypic integration.
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http://dx.doi.org/10.1093/icb/icz120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6754122PMC
September 2019

Sacroiliac Joint Fusion: Approaches and Recent Outcomes.

PM R 2019 08 22;11 Suppl 1:S114-S117. Epub 2019 Jul 22.

Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN.

The sacroiliac joint may be a primary source of pain in patients complaining of low back and/or buttock pain. Nonsurgical treatment of sacroiliac joint pain typically includes structured core and pelvic muscle flexibility and strengthening; pharmaceutical management through oral and injectable medication; and ablation procedures. For patients who do not improve with comprehensive, nonoperative treatment, surgical fusion of the sacroiliac joint is an option with overall good reported outcomes and high patient satisfaction. Minimally invasive surgery (MIS) approaches have been shown to have lower morbidity and earlier recovery than traditional open approaches. To date, the majority of published clinical studies on MIS sacroiliac joint fusion are industry-sponsored and predominantly using one system (ingrowth triangular titanium rods). These include two level 1 randomized controlled trials comparing MIS sacroiliac joint fusion to nonoperative management, with results favoring surgery.
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http://dx.doi.org/10.1002/pmrj.12198DOI Listing
August 2019

Responding to Intraoperative Neuromonitoring Changes During Pediatric Coronal Spinal Deformity Surgery.

Global Spine J 2019 May 8;9(1 Suppl):15S-21S. Epub 2019 May 8.

AOSpine Knowledge Forum Deformity, Davos, Switzerland.

Study Design: Retrospective case study on prospectively collected data.

Objectives: The purpose of this explorative study was: 1) to determine if patterns of spinal cord injury could be detected through intra-operative neuromonitoring (IONM) changes in pediatric patients undergoing spinal deformity corrections, 2) to identify if perfusion based or direct trauma causes of IONM changes could be distinguished, 3) to observe the effects of the interventions performed in response to these events, and 4) to attempt to identify different treatment algorithms for the different causes of IONM alerts.

Methods: Prospectively collected neuromonitoring data in pre-established forms on consecutive pediatric patients undergoing coronal spinal deformity surgery at a single center was reviewed. Real-time data was collected on IONM alerts with >50% loss in signal. Patients with alerts were divided into 2 groups: unilateral changes (direct cord trauma), and bilateral MEP changes (cord perfusion deficits).

Results: A total of 97 pediatric patients involving 71 females and 26 males with a mean age of 14.9 (11-18) years were included in this study. There were 39 alerts in 27 patients (27.8% overall incidence). All bilateral changes responded to a combination of transfusion, increasing blood pressure, and rod removal. Unilateral changes as a result of direct trauma, mainly during laminotomies for osteotomies, improved with removal of the causative agent. Following corrective actions in response to the alerts, all cases were completed as planned. Signal returned to near baseline in 20/27 patients at closure, with no new neurological deficits in this series.

Conclusion: A high incidence of alerts occurred in this series of cases. Dividing IONM changes into perfusion-based vs direct trauma directed treatment to the offending cause, allowing for safe corrections of the deformities. Patients did not need to recover IONM signal to baseline to have a normal neurological examination.
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http://dx.doi.org/10.1177/2192568219836993DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6512195PMC
May 2019

Cost-Effectiveness for Surgical Treatment of Degenerative Spondylolisthesis.

Neurosurg Clin N Am 2019 Jul 10;30(3):365-372. Epub 2019 Apr 10.

Department of Neurosurgery, University of Minnesota, Minneapolis, MN, USA; Department of Orthopaedic Surgery, University of Minnesota, 2450 Riverside Avenue Southeast, Suite R200, Minneapolis, MN 55454, USA.

Surgery for degenerative lumbar spondylolisthesis is significantly more cost-effective than nonsurgical management in patients who have failed to improve with a 6-week trial of nonsurgical management. Decompression plus fusion becomes more cost-effective compared with decompression alone at 2 years following surgery. Further study is needed to evaluate the most cost-effective fusion approach and augmentation strategy.
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http://dx.doi.org/10.1016/j.nec.2019.02.010DOI Listing
July 2019

Minimum 20-Year Health-Related Quality of Life and Surgical Rates After the Treatment of Adolescent Idiopathic Scoliosis.

Spine Deform 2019 05;7(3):417-427

Department of Orthopedic Surgery, Mayo Clinic, 200 First St. SW, Rochester, MN 55905, USA.

Study Design: Longitudinal cohort.

Objectives: To determine the patient-reported functional outcomes and need for related surgical procedures in a US cohort of adolescent idiopathic scoliosis (AIS) patients with minimum 20-year follow-up.

Summary Of Background Data: There is limited information regarding the long-term outcomes of scoliosis treatment in the US population.

Methods: A novel population of patients who underwent pediatric treatment for AIS with minimum 20-year follow-up was identified. Search of a single-center diagnostic registry generated 337 patients who fulfilled the inclusion criteria (AIS, curve magnitude >35°, and childhood treatment with bracing, surgery, or observation from 1975 to 1992). Any additional spine surgery as well as EQ5D, ODI, SRS 22, SAQ were determined. A total of 180 patients were included (mean of 30-year follow-up, range 20-37). Childhood treatment entailed bracing (41 patients), surgery (103 patients), and observation (36 patients).

Results: During the study period, only 1 of the 41 bracing patients underwent additional scoliosis-related spine surgery, whereas 5 of the 36 patients in the observation cohort underwent scoliosis surgery as adults. Seven of 103 childhood surgical patients required additional revision surgery as adults. Fifteen patients (4 braced, 7 fusion, and 4 observed) underwent chest wall surgery as adults. SRS scores were around 10% worse compared to population-based controls, with the exception of SRS mental health scores, which were similar to controls. Overall, 5.6% of patients were on disability, with no difference between operative and nonoperative groups.

Conclusion: We found a low rate of adult scoliosis surgery in the braced population, and a low rate of revision surgery at the 30-year follow-up in patients undergoing spine fusion for AIS between 1975 and 1992. No detected differences in patient-reported outcomes were found between the braced, surgical, and observed populations at a mean of 30 years' follow-up.

Level Of Evidence: Level III, therapeutic.
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http://dx.doi.org/10.1016/j.jspd.2018.09.003DOI Listing
May 2019