Publications by authors named "Joon Y Lee"

94 Publications

Surgery Related Factors Do Not Affect Short-Term Adjacent Segment Kinematics After Anterior Cervical Arthrodesis.

Spine (Phila Pa 1976) 2021 Apr 23. Epub 2021 Apr 23.

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center Department of Neurosurgery, University of Pittsburgh Medical Center.

Study Design: Prospective cohort study.

Objective: To identify surgical factors that affect adjacent segment kinematics after anterior cervical discectomy and fusion (ACDF) as measured by biplane radiography.

Summary Of Background Data: Previous studies investigated the effect of surgical factors on spine kinematics as a potential etiology for adjacent segment disease (ASD). Those studies used static flexion-extension radiographs to evaluate range of motion. However, measurements from static radiographs are known to be unreliable. Furthermore, those studies were unable to evaluate the effect of ACDF on adjacent segment axial rotation.

Methods: Patients had continuous cervical spine flexion/extension and axial rotation movements captured at 30 images per second in a dynamic biplane radiography system preoperatively and 1 year after ACDF. Digitally reconstructed radiographs generated from subject-specific CT scans were matched to biplane radiographs using a previously validated tracking process. Dynamic kinematics, postoperative segmental kyphosis, and disc distraction were calculated from this tracking process. Plate-to-disc distance was measured on postoperative radiographs. Graft type was collected from the medical record. Multivariate linear regression was performed to identify surgical factors associated with 1-year post-surgery changes in adjacent segment kinematics. A secondary analysis was also performed to compare adjacent segment kinematics between each of the surgical factors and previously defined thresholds believed to be associated with adjacent segment degeneration.

Results: Fifty-nine patients completed preoperative and postoperative testing. No association was found between any of the surgical factors and change in adjacent segment flexion/extension or axial rotation range of motion (all p > 0.09). The secondary analysis also did not identify differences between adjacent segment kinematics and surgical factors (all p > 0.07).

Conclusions: Following ACDF for cervical spondylosis, factors related to surgical technique were not associated with short-term changes in adjacent segment kinematics that reflect the hypermobility hypothesized to lead to the development of ASD.Level of Evidence: 2.
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http://dx.doi.org/10.1097/BRS.0000000000004080DOI Listing
April 2021

Pre-Operative Bariatric Surgery Imparts An Increased Risk of Infection, Re-Admission and Operative Intervention Following Elective Instrumented Lumbar Fusion.

Global Spine J 2021 Apr 28:21925682211011601. Epub 2021 Apr 28.

Department of Orthopaedic Surgery, 6595University of Pittsburgh Medical Center, PA, USA.

Study Design: Retrospective cohort study.

Objectives: To evaluate the impact of bariatric surgery on patient outcomes following elective instrumented lumbar fusion.

Methods: A retrospective review of a prospectively collected database was performed. Patients who underwent a bariatric procedure prior to an elective instrumented lumbar fusion were evaluated. Lumbar procedures were performed at a large academic medical center from 1/1/2012 to 1/1/2018. The primary outcome was surgical site infection (SSI) requiring surgical debridement. Secondary outcomes were prolonged wound drainage requiring treatment, implant failure requiring revision, revision secondary to adjacent segment disease (ASD), and chronic pain states. A randomly selected, surgeon and comorbidity-matched group of 59 patients that underwent an elective lumbar fusion during that period was used as a control. Statistical analysis was performed using Student's two-way t-tests for continuous data, with significance defined as < .05.

Results: Twenty-five patients were identified who underwent bariatric surgery prior to elective lumbar fusion. Mean follow-up was 2.4 ± 1.9 years in the bariatric group vs. 1.5 ± 1.3 years in the control group. Patients with a history of bariatric surgery had an increased incidence of SSI that required operative debridement, revision surgery due to ASD, and a higher incidence of chronic pain. Prolonged wound drainage and implant failure were equivalent between groups.

Conclusion: In the present study, bariatric surgery prior to elective instrumented lumbar fusion was associated increased risk of surgical site infection, adjacent segment disease and chronic pain when compared to non-bariatric patients.
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http://dx.doi.org/10.1177/21925682211011601DOI Listing
April 2021

Correction to: ISSLS prize in basic science 2021: a novel inducible system to regulate transgene expression of TIMP1.

Eur Spine J 2021 Mar 7. Epub 2021 Mar 7.

Ferguson Laboratory for Orthopaedic and Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

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http://dx.doi.org/10.1007/s00586-021-06783-7DOI Listing
March 2021

ISSLS prize in basic science 2021: a novel inducible system to regulate transgene expression of TIMP1.

Eur Spine J 2021 Feb 1. Epub 2021 Feb 1.

Ferguson Laboratory for Orthopaedic and Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

Purpose: Inflammatory and oxidative stress upregulates matrix metalloproteinase (MMP) activity, leading to intervertebral disc degeneration (IDD). Gene therapy using human tissue inhibitor of metalloproteinase 1 (hTIMP1) has effectively treated IDD in animal models. However, persistent unregulated transgene expression may have negative side effects. We developed a recombinant adeno-associated viral (AAV) gene vector, AAV-NFκB-hTIMP1, that only expresses the hTIMP1 transgene under conditions of stress.

Methods: Rabbit disc cells were transfected or transduced with AAV-CMV-hTIMP1, which constitutively expresses hTIMP1, or AAV-NFκB-hTIMP1. Disc cells were selectively treated with IL-1β. NFκB activation was verified by nuclear translocation. hTIMP1 mRNA and protein expression were measured by RT-PCR and ELISA, respectively. MMP activity was measured by following cleavage of a fluorogenic substrate.

Results: IL-1β stimulation activated NFκB demonstrating that IL-1β was a surrogate for inflammatory stress. Stimulating AAV-NFκB-hTIMP1 cells with IL-1β increased hTIMP1 expression compared to unstimulated cells. AAV-CMV-hTIMP1 cells demonstrated high levels of hTIMP1 expression regardless of IL-1β stimulation. hTIMP1 expression was comparable between IL-1β stimulated AAV-NFκB-hTIMP1 cells and AAV-CMV-hTIMP1 cells. MMP activity was decreased in AAV-NFκB-hTIMP1 cells compared to baseline levels or cells exposed to IL-1β.

Conclusion: AAV-NFκB-hTIMP1 is a novel inducible transgene delivery system. NFκB regulatory elements ensure that hTIMP1 expression occurs only with inflammation, which is central to IDD development. Unlike previous inducible systems, the AAV-NFκB-hTIMP1 construct is dependent on endogenous factors, which minimizes potential side effects caused by constitutive transgene overexpression. It also prevents the unnecessary production of transgene products in cells that do not require therapy.
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http://dx.doi.org/10.1007/s00586-021-06728-0DOI Listing
February 2021

Chronic Subdural Hematoma as a Complication of Cerebrospinal Fluid Leak During Revision Lumbar Spine Surgery: A Case Report and Review of the Literature.

HSS J 2020 Dec 5;16(Suppl 2):482-484. Epub 2019 Aug 5.

Department of Orthopaedic Surgery, Ferguson Lab for Orthopaedic Research, University of Pittsburgh Medical Center, E1643 Biomedical Science Tower, 200 Lothrop Street, Pittsburgh, PA 15213 USA.

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http://dx.doi.org/10.1007/s11420-019-09709-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7749911PMC
December 2020

Use of Fondaparinux Following Elective Lumbar Spine Surgery Is Associated With a Reduction in Symptomatic Venous Thromboembolism.

Global Spine J 2020 Oct 30;10(7):844-850. Epub 2019 Sep 30.

6595University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Study Design: Retrospective cohort study.

Objective: To assess the impact of fondaparinux on venous thromboembolism (VTE) following elective lumbar spine surgery in high-risk patients.

Methods: Matched patient cohorts who did or did not receive inpatient fondaparinux starting postoperative day 2 following elective lumbar spine surgery were compared. All patients received 1 month of acetyl salicylic acid 325 mg following discharge. The primary outcome was a symptomatic DVT (deep vein thrombosis) or PE (pulmonary embolus) within 30 days of surgery. Secondary outcomes included prolonged wound drainage, epidural hematoma, and transfusion.

Results: A significantly higher number of DVTs were diagnosed in the group that did not receive inpatient VTE prophylaxis (3/102, 2.9%) compared with the fondaparinux group (0/275, 0%, = .02). Increased wound drainage was seen in 18.5% of patients administered fondaparinux, compared with 25.5% of untreated patients ( = .15). Deep infections were equivalent (2.2% with fondaparinux vs 4.9% control, = .18). No epidural hematomas were noted, and the number of transfusions after postoperative day 2 and 90-day return to operating room rates were equivalent.

Conclusions: Patients receiving fondaparinux had lower rates of symptomatic DVT and PE and a favorable complication profile when compared with matched controls. The retrospective nature of this work limits the safety and efficacy claims that can be made about the use of fondaparinux to prevent VTE in elective lumbar spine surgery patients. Importantly, this work highlights the potential safety of this regimen, permitting future high-quality trials.
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http://dx.doi.org/10.1177/2192568219878418DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7485070PMC
October 2020

Undisclosed Conflict of Interest Is Prevalent in Spine Literature.

Spine (Phila Pa 1976) 2020 Nov;45(21):1524-1529

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA.

Study Design: Cohort study.

Objective: The aim of this study was to determine the rate of accurate conflict of interest (COI) disclosure within three prominent subspecialty Spine journals during a 4-year period.

Summary Of Background Data: Industry-physician relationships are crucial for technological advancement in spine surgery but serve as a source of bias in biomedical research. The Open Payments Database (OPD) was established after 2010 to increase financial transparency.

Methods: All research articles published from 2014 to 2017 in Spine, The Spine Journal (TSJ), and the Journal of Neurosurgery: Spine (JNS) were reviewed in this study. In these articles, all author's COI statements were recorded. The OPD was queried for all author entries within the disclose period of the journal. Discrepancies between the author's self-reported COIs and the documented COIs from OPD were recorded.

Results: A total of 6816 articles meeting inclusion criteria between 2014 and 2017 in Spine, TSJ, and JNS with 39,869 contributing authors. Overall, 15.8% of all authors were found to have an OPD financial relationship. Of 2633 authors in Spine with financial disclosures, 77.1% had accurate financial disclosures; 42.5% and 41.0% of authors with financial relationships in the OPD had accurate financial disclosures in TSJ and JNS, respectively. The total value of undisclosed conflicts of interest between 2014 and 2017 was $421 million with $1.48 billion in accurate disclosures. Of undisclosed payments, 68.7% were <$1000 and only 7.2% were >$10,000. Undisclosed payments included $180 million in research funding and $188 million in royalties.

Conclusion: This study demonstrates that undisclosed COI is highly prevalent for authors in major Spine journals. This study indicates that there remains a need to standardize definitions and financial thresholds for significant COI as well as to shift the reporting burden for COI to journals who actively review potential COIs instead of relying on self-reporting.

Level Of Evidence: 3.
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http://dx.doi.org/10.1097/BRS.0000000000003589DOI Listing
November 2020

Assessing the biofidelity of in vitro biomechanical testing of the human cervical spine.

J Orthop Res 2020 Apr 25. Epub 2020 Apr 25.

Ferguson Lab for Orthopaedic Research, Department of Orthopaedic Surgery, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania.

In vitro biomechanical studies of the osteoligamentous spine are widely used to characterize normal biomechanics, identify injury mechanisms, and assess the effects of degeneration and surgical instrumentation on spine mechanics. The objective of this study was to determine how well four standards in vitro loading paradigms replicate in vivo kinematics with regards to the instantaneous center of rotation and arthrokinematics in relation to disc deformation. In vivo data were previously collected from 20 asymptomatic participants (45.5 ± 5.8 years) who performed full range of motion neck flexion-extension (FE) within a biplane x-ray system. Intervertebral kinematics were determined with sub-millimeter precision using a validated model-based tracking process. Ten cadaveric spines (51.8 ± 7.3 years) were tested in FE within a robotic testing system. Each specimen was tested under four loading conditions: pure moment, axial loading, follower loading, and combined loading. The in vivo and in vitro bone motion data were directly compared. The average in vitro instant center of rotation was significantly more anterior in all four loading paradigms for all levels. In general, the anterior and posterior disc heights were larger in the in vitro models than in vivo. However, after adjusting for gender, the observed differences in disc height were not statistically significant. This data suggests that in vitro biomechanical testing alone may fail to replicate in vivo conditions, with significant implications for novel motion preservation devices such as cervical disc arthroplasty implants.
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http://dx.doi.org/10.1002/jor.24702DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7606317PMC
April 2020

Rabbit Annulus Fibrosus Cells Express Neuropeptide Y, Which Is Influenced by Mechanical and Inflammatory Stress.

Neurospine 2020 Mar 31;17(1):69-76. Epub 2020 Mar 31.

Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh, Pittsburgh, PA, USA.

Objective: Rabbit annulus fibrosus (AF) cells were exposed to isolated or combined mechanical and inflammatory stress to examine the expression of neuropeptide Y (NPY). This study aims to explore the ability of AF cells to produce NPY in response to mechanical and inflammatory stress.

Methods: Lumbar AF cells of 6- to 8-month-old female New Zealand white rabbits were harvested and exposed to combinations of inflammatory (interleukin-1β) and mechanical (6% or 18%) tensile stress using the Flexcell System. NPY concentrations were measured in the media via enzyme-linked immunosorbent assay. The presence of NPY receptor-type 1 (NPY-1R) in AF cells of rabbit intervertebral discs was also analyzed via immunohistochemistry and immunofluorescence.

Results: Exposure to inflammatory stimuli showed a significant increase in the amount of NPY expression compared to control AF cells. Mechanical strain alone did not result in a significant difference in NPY expression. While combined inflammatory and mechanical stress did not demonstrate an increase in NPY expression at low (6%) levels of strain, at 18% strain, there was a large-though not statistically significant-increase in NPY expression under conditions of inflammatory stress. Lastly, immunofluorescence and immunohistochemistry of AF cells and tissue, respectively, demonstrated the presence of NPY-1R.

Conclusion: These findings demonstrate that rabbit AF cells are capable of expressing NPY, and expression is enhanced in response to inflammatory and mechanical stress. Because both inflammatory and mechanical stress contribute to intervertebral disc degeneration (IDD), this observation raises the potential of a mechanistic link between low back pain and IDD.
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http://dx.doi.org/10.14245/ns.2040046.023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7136102PMC
March 2020

The effects of age, pathology, and fusion on cervical neural foramen area.

J Orthop Res 2021 03 20;39(3):671-679. Epub 2020 Mar 20.

Department of Orthopedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania.

Cervical radiculopathy is a relatively common neurological disorder, often resulting from mechanical compression of the nerve root within the neural foramen. Anterior cervical discectomy and fusion (ACDF) is a common treatment for radicular symptoms that do not resolve after conservative treatment. One mechanism by which ACDF is believed to resolve symptoms is by replacing degenerated disc tissue with bone graft to increase the neural foramen area, however in vivo evidence demonstrating this is lacking. The aim of this study was to evaluate the effects of age, pathology, and fusion on bony neural foramen area. Participants included 30 young adult controls (<35 years old), 23 middle-aged controls (36 to 60 years old), and 36 cervical arthrodesis patients tested before and after ACDF surgery. Participants' cervical spines were imaged in the neutral, full flexion, and full extension positions while seated within a biplane radiography system. A validated model-based tracking technique determined three-dimensional vertebral position and orientation and automated software identified the neural foramen area in each head position. The neural foramen area decreased throughout the entire sub-axial cervical spine with age and pathology, however, no changes in neural foramen area were observed due solely to replacing degenerated disc tissue with bone graft. The neural foramen area was not associated with disc height in young adult controls, but moderate to strong associations were observed in middle-aged controls. The results provide evidence to inform the debate regarding localized versus systemic spinal degeneration and provide novel insight into the mechanism of pain relief after ACDF.
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http://dx.doi.org/10.1002/jor.24663DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7487021PMC
March 2021

In vivo changes in adjacent segment kinematics after lumbar decompression and fusion.

J Biomech 2020 03 14;102:109515. Epub 2019 Nov 14.

Department of Orthopaedic Surgery, Orthopaedic Biodynamics Laboratory, University of Pittsburgh, Pittsburgh, USA; EMPA (Swiss Federal Laboratories for Materials Science and Research), Mechanical Systems Engineering (Lab 304), Duebendorf, Switzerland.

The pathogenesis of lumbar adjacent segment disease is thought to be secondary to altered biomechanics resulting from fusion. Direct in vivo evidence for altered biomechanics following lumbar fusion is lacking. This study's aim was to describe in vivo kinematics of the superior adjacent segment relative to the fused segment before and after lumbar fusion. This study analyzed seven patients with symptomatic lumbar degenerative spondylolisthesis (5 M, 2F; age 65 ± 5.1 years) using a biplane radiographic imaging system. Each subject performed two to three trials of continuous flexion of their torso according to established protocols. Synchronized biplane radiographs were acquired at 20 images per second one month before and six months after single-level fusion at L4-L5 or L5-S1, or two-level fusion at L3-L5 or L4-S1. A previously validated volumetric model-based tracking process was used to track the position and orientation of vertebrae in the radiographic images. Intervertebral flexion/extension and AP translation (slip) at the superior adjacent segment were calculated over the entire dynamic flexion activity. Skin-mounted surface markers were tracked using conventional motion analysis and used to determine torso flexion. Change in adjacent segment kinematics after fusion was determined at corresponding angles of dynamic torso flexion. Changes in adjacent segment motion varied across patients, however, all patients maintained or increased the amount of adjacent segment slip or intervertebral flexion/extension. No patients demonstrated both decreased adjacent segment slip and decreased rotation. This study suggests that short-term changes in kinematics at the superior adjacent segment after lumbar fusion appear to be patient-specific.
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http://dx.doi.org/10.1016/j.jbiomech.2019.109515DOI Listing
March 2020

Research-Track Residency Programs in Orthopaedic Surgery: A Survey of Program Directors and Recent Graduates.

J Bone Joint Surg Am 2019 Aug;101(15):1420-1427

Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania.

Background: The importance of research in resident education has been emphasized in the orthopaedic surgery community, and a number of residency programs have incorporated a year or more of protected research time into their training. However, limited information exists as to what programs are looking for in applicants to research-track residency programs or the perceived benefits of completing such a program.

Methods: We identified orthopaedic surgery programs that have tracks involving at least 1 year of protected research time and sent surveys to their program directors and to the 2012 through 2016 research-track graduates.

Results: Twenty-three programs with research tracks were identified, and 19 program directors (83%) responded to the survey. The survey revealed that only 2 (11%) of these program directors were willing to accept lower scores and grades among applicants to their research track compared with their primary clinical (categorical) track. While most of the program directors (14 [74%]) preferred that applicants have an interest in academics, only a few (3 [16%]) considered it a failure if their research-track residents did not pursue academic careers. We obtained the e-mail addresses of 82 research-track graduates, and 66 (80%) responded to the survey. The survey revealed that those who went into academic careers were more likely than those who went into private practice to view completing a research track as beneficial for fellowship (73% versus 35%, respectively) and job (73% versus 22%, respectively) applications, believed that the income lost from the additional year of residency would be compensated for by opportunities gained from the research year (50% versus 17%, respectively), and said that they would pursue a research-track residency if they had to do it over again (81% versus 39%, respectively; all p values <0.05).

Conclusions: The majority of program directors preferred that applicants to their research-track program have an interest in academics, although most did not consider it a failure if their research-track residents entered nonacademic careers. Graduates of research-track residency programs who entered academics more frequently viewed the completion of a research track as being beneficial compared with those who went into private practice.
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http://dx.doi.org/10.2106/JBJS.18.00472DOI Listing
August 2019

Cervical Spine Fractures: Who Really Needs CT Angiography?

Spine (Phila Pa 1976) 2019 Dec;44(23):1661-1667

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA.

Study Design: Retrospective cohort study.

Objective: Compare a novel two-step algorithm for indicating a computed tomography angiography (CTA) in the setting of a cervical spine fracture with established gold standard criteria.

Summary Of Background Data: As CTA permits the rapid detection of blunt cerebrovascular injuries (BCVI), screening criteria for its use have broadened. However, more recent work warns of the potential for the overdiagnosis of BCVI, which must be considered with the adoption of broad criteria.

Methods: A novel two-step metric for indicating CTA screening was compared with the American College of Surgeons guidelines and the expanded Denver Criteria using patients who presented with cervical spine fractures to a tertiary-level 1 trauma center from January 1, 2012 to January 1, 2016. The ability for each metric to identify BCVI and posterior circulation strokes that occurred during this period was assessed.

Results: A total of 721 patients with cervical fractures were included, of whom 417 underwent CTAs (57.8%). Sixty-eight BCVIs and seven strokes were diagnosed in this cohort. All algorithms detected an equivalent number of BCVIs (52 with the novel metric, 54 with the ACS and Denver Criteria, P = 0.84) and strokes (7/7, 100% with the novel metric, 6/7, 85.7% with the ACS and Denver Criteria, P = 1.0). However, 63% fewer scans would have been needed with the proposed screening algorithm compared with the ACS or Denver Criteria (261/721, 36.2% of all patients with our criteria vs. 413/721, 57.3% with the ACS standard and 417/721, 57.8%) with the Denver Criteria, P < 0.0002 for each).

Conclusion: A two-step criterion based on mechanism of injury and patient factors is a potentially useful guide for identifying patients at risk of BCVI and stroke after cervical spine fractures. Further prospective analyses are required prior to widespread clinical adoption.

Level Of Evidence: 4.
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http://dx.doi.org/10.1097/BRS.0000000000003163DOI Listing
December 2019

Dynamic functional nucleus is a potential biomarker for structural degeneration in cervical spine discs.

J Orthop Res 2019 04 28;37(4):965-971. Epub 2019 Feb 28.

Department of Orthopedic Surgery, University of Pittsburgh, 3820 South Water Street, Pittsburgh, 15203, Pennsylvania.

If intervertebral disc degeneration can be identified early, preventative treatments may be initiated before symptoms become disabling and costly. Changes in disc mechanics, such as the decrease in the compressive modulus of the nucleus, are some of the earliest signs of degeneration. Therefore, in vivo changes in the disc response to compressive load may serve as a biomarker for pending or early disc degeneration. The aim of this study was to assess the potential for using in vivo dynamic disc deformation to identify pathologic structural degeneration of the intervertebral disc. A validated model-based tracking technique determined vertebral motion from biplane radiographs collected during dynamic flexion/extension and axial rotation of the cervical spine. A computational model of the subaxial intervertebral discs was developed to identify the dynamic functional nucleus of each disc, that is, the disc region that underwent little to no additional compression during dynamic movements. The size and location of the dynamic functional nucleus was determined for 10 C5/C6 spondylosis patients, 10 C5/C6/C7 spondylosis patients, and 10 asymptomatic controls. The dynamic functional nucleus size was sensitive (significantly smaller than controls in 5 of 6 measurements at the diseased disc) and specific (no difference from controls in 9 of 10 measurements at non-diseased discs) to pathologic disc degeneration. These results provide evidence to suggest that structural disc degeneration, manifested by changes in the disc response to functional loading, may be identified in vivo from dynamic imaging collected during functional movements. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:1-7, 2019.
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http://dx.doi.org/10.1002/jor.24252DOI Listing
April 2019

"Post-Decompressive Neuropathy": New-Onset Post-Laminectomy Lower Extremity Neuropathic Pain Different from the Preoperative Complaint.

Asian Spine J 2018 Dec 16;12(6):1043-1052. Epub 2018 Oct 16.

Division of Spine Surgery, Department of Orthopedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Study Design: Level III retrospective cross-sectional study.

Purpose: To define and characterize the presentation, symptom duration, and patient/surgical risk factors associated with 'postdecompressive neuropathy (PDN).'

Overview Of Literature: PDN is characterized by lower extremity radicular pain that is 'different' from pre-surgical radiculopathy or claudication pain. Although it is a common constellation of postoperative symptoms, PDN is incompletely characterized and poorly understood. We hypothesize that PDN is caused by an intraoperative neuropraxic event and may develop early (within 30 days following the procedure) or late (after 30 days following the procedure) within the postoperative period.

Methods: Patients who consented to undergo lumbar laminectomy with or without an instrumented fusion for degenerative lumbar spine disease were followed up prospectively from July 2013 to December 2014. Relevant data were extracted from the charts of the eligible patients. Patient demographics and surgical factors were identified. Patients completed postoperative questionnaires 3 weeks, 3 months, 6 months, and 1 year postoperatively. Questions were designed to characterize the postoperative pain that differed from preoperative pain. A diagnosis of PDN was established if the patient exhibited the following characteristics: pain different from preoperative pain, leg pain worse than back pain, a non-dermatomal pain pattern, and nocturnal pain that often disrupted sleep. A Visual Analog Scale was used to monitor the pain, and patients documented the effectiveness of the prescribed pain management modalities. Patients for whom more than one follow-up survey was missed were excluded from analysis.

Results: Of the 164 eligible patients, 118 (72.0%) completed at least one follow-up survey at each time interval. Of these eligible patients, 91 (77.1%) described symptoms consistent with PDN. Additionally, 75 patients (82.4%) described early-onset symptoms, whereas 16 reported symptoms consistent with late-onset PDN. Significantly more female patients reported PDN symptoms (87% vs. 69%, p=0.03). Patients with both early and late development of PDN described their leg pain as an intermittent, constant, burning, sharp/stabbing, or dull ache. Early PDN was categorized more commonly as a dull ache than late-onset PDN (60% vs. 31%, p=0.052); however, the difference did not reach statistical significance. Opioids were significantly more effective for patients with early-onset PDN than for those with late-onset PDN (85% vs. 44%, p=0.001). Gabapentin was most commonly prescribed to patients who cited no resolution of symptoms (70% vs. 31%, p=0.003). Time to symptom resolution ranged from within 1 month to 1 year. Patients' symptoms were considered unresolved if symptoms persisted for more than 1 year postoperatively. In total, 81% of the patients with earlyonset PDN reported complete symptom resolution 1 year postoperatively compared with 63% of patients with late-onset PDN (p=0.11).

Conclusions: PDN is a discrete postoperative pain phenomenon that occurred in 77% of the patients who underwent lumbar laminectomy with or without instrumented fusion. Attention must be paid to the constellation and natural history of symptoms unique to PDN to effectively manage a self-limiting postoperative issue.
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http://dx.doi.org/10.31616/asj.2018.12.6.1043DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6284122PMC
December 2018

Influence of follower load application on moment-rotation parameters and intradiscal pressure in the cervical spine.

J Biomech 2018 07 15;76:167-172. Epub 2018 Jun 15.

Ferguson Laboratory for Spine Research, Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, PA, United States.

The objective of this study was to implement a follower load (FL) device within a robotic (universal force-moment sensor) testing system and utilize the system to explore the effect of FL on multi-segment cervical spine moment-rotation parameters and intradiscal pressure (IDP) at C45 and C56. Twelve fresh-frozen human cervical specimens (C3-C7) were biomechanically tested in a robotic testing system to a pure moment target of 2.0 Nm for flexion and extension (FE) with no compression and with 100 N of FL. Application of FL was accomplished by loading the specimens with bilateral cables passing through cable guides inserted into the vertebral bodies and attached to load controlled linear actuators. FL significantly increased neutral zone (NZ) stiffness and NZ width but resulted in no change in the range of motion (ROM) or elastic zone stiffness. C45 and C56 IDP measured in the neutral position were significantly increased with application of FL. The change in IDP with increasing flexion rotation was not significantly affected by the application of FL, whereas the change in IDP with increasing extension rotation was significantly reduced by the application of FL. Application of FL did not appear to affect the specimen's quantity of motion (ROM) but did affect the quality (the shape of the curve). Regarding IDP, the effects of adding FL compression approximates the effect of the patient going from supine to a seated position (FL compression increased the IDP in the neutral position). The change in IDP with increasing flexion rotation was not affected by the application of FL, but the change in IDP with increasing extension rotation was, however, significantly reduced by the application of FL.
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http://dx.doi.org/10.1016/j.jbiomech.2018.05.031DOI Listing
July 2018

Prophylactic perioperative dexamethasone decreases the incidence of postoperative C5 palsies after a posterior cervical laminectomy and fusion.

Spine J 2019 02 22;19(2):253-260. Epub 2018 May 22.

Department of Orthopaedic Surgery, Ferguson Laboratory for Orthopaedic Research, University of Pittsburgh, E1643 Biomedical Science Tower, 200 Lothrop St, Pittsburgh, PA 15213, USA. Electronic address:

Background Context: Postoperative C5 palsy is a well-known complication of cervical decompression procedures. Studies have shown that posterior laminectomy and fusions confer the greatest risk of C5 palsy. Despite this, pharmacologic preventive measures remain unknown. We hypothesize that prophylactic perioperative dexamethasone (DEX) will decrease the rate of postoperative C5 palsy in patients undergoing a multilevel posterior cervical laminectomy and fusion.

Purpose: The purpose of this study was to assess the safety and efficacy of prophylactic perioperative DEX in decreasing the rate of postoperative C5 palsy.

Design: This is a retrospective, single-institution clinical study.

Patient Sample: The patient population included all patients undergoing multilevel posterior cervical laminectomy and instrumented fusion procedures for myeloradiculopathy or myelopathy, who also received a course of perioperative dexamethasone. Surgeries occurred between 2012 and 2017 at a single tertiary care center by a single surgeon with at least 1 year of follow-up. Patients who underwent decompression procedures other than multilevel posterior cervical laminectomy and instrumented fusions; had trauma, fracture; underwent decompression not including C5-level, insulin-dependent diabetes mellitus; and had documented adverse reactions to steroids were excluded.

Outcome Measures: Preoperative demographics and postoperative complications, including development of postoperative C5 palsy, were considered as outcome measures.

Materials And Methods: A total of 189 consecutive patients who underwent multilevel posterior cervical laminectomy and instrumented fusion and received prophylactic perioperative DEX were reviewed. The rate of C5 palsy was investigated and compared with our historical control rate of C5 palsy before the institutional implementation of perioperative DEX. Demographics were reviewed, and risk factor stratification was analyzed. The safety of using DEX was investigated by examining postoperative complications. The clinical course of patients who developed C5 palsy was then reported.

Results: Postoperative C5 palsy occurred in 5 of the 138 patients (3.6%) meeting the inclusion criteria. Patients receiving perioperative DEX had a significantly decreased rate of postoperative C5 palsy compared with those who did not (3.6% vs. 9.5%, p=.01). Age was the only risk factor that was significantly correlated with development of C5 palsy (72.71±7.76 vs. 61.07±10.59, p=.02). Infection, seroma, and wound complication rates were 2.8%, 2.17%, and 1.44%, respectively, in patients receiving prophylactic DEX. All five patients receiving DEX who developed C5 palsy recovered with no residual deficits at an average of 16.8 weeks postoperatively.

Conclusions: Perioperative prophylactic DEX therapy is a safe and effective way to decrease the incidence of C5 palsies in patients who undergo multilevel posterior laminectomy and fusion for myeloradiculopathy or myelopathy.
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http://dx.doi.org/10.1016/j.spinee.2018.05.031DOI Listing
February 2019

Cervical bracing practices after degenerative cervical surgery: a survey of Cervical Spine Research Society members.

Spine J 2018 10 21;18(10):1950-1955. Epub 2018 May 21.

Department of Orthopedic Surgery, Brigham and Women's Hospital, 75 Francis St, Boston, MA 02115, USA.

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http://dx.doi.org/10.1016/j.spinee.2018.05.014DOI Listing
October 2018

ISSLS PRIZE IN BIOENGINEERING SCIENCE 2018: dynamic imaging of degenerative spondylolisthesis reveals mid-range dynamic lumbar instability not evident on static clinical radiographs.

Eur Spine J 2018 04 22;27(4):752-762. Epub 2018 Feb 22.

Department of Orthopaedic Surgery, Orthopaedic Biodynamics Laboratory, University of Pittsburgh, 3820 South Water Street, Pittsburgh, PA, 15203, USA.

Purpose: Degenerative spondylolisthesis (DS) in the setting of symptomatic lumbar spinal stenosis is commonly treated with spinal fusion in addition to decompression with laminectomy. However, recent studies have shown similar clinical outcomes after decompression alone, suggesting that a subset of DS patients may not require spinal fusion. Identification of dynamic instability could prove useful for predicting which patients are at higher risk of post-laminectomy destabilization necessitating fusion. The goal of this study was to determine if static clinical radiographs adequately characterize dynamic instability in patients with lumbar degenerative spondylolisthesis (DS) and to compare the rotational and translational kinematics in vivo during continuous dynamic flexion activity in DS versus asymptomatic age-matched controls.

Methods: Seven patients with symptomatic single level lumbar DS (6 M, 1 F; 66 ± 5.0 years) and seven age-matched asymptomatic controls (5 M, 2 F age 63.9 ± 6.4 years) underwent biplane radiographic imaging during continuous torso flexion. A volumetric model-based tracking system was used to track each vertebra in the radiographic images using subject-specific 3D bone models from high-resolution computed tomography (CT). In vivo continuous dynamic sagittal rotation (flexion/extension) and AP translation (slip) were calculated and compared to clinical measures of intervertebral flexion/extension and AP translation obtained from standard lateral flexion/extension radiographs.

Results: Static clinical radiographs underestimate the degree of AP translation seen on dynamic in vivo imaging (1.0 vs 3.1 mm; p = 0.03). DS patients demonstrated three primary motion patterns compared to a single kinematic pattern in asymptomatic controls when analyzing continuous dynamic in vivo imaging. 3/7 (42%) of patients with DS demonstrated aberrant mid-range motion.

Conclusion: Continuous in vivo dynamic imaging in DS reveals a spectrum of aberrant motion with significantly greater kinematic heterogeneity than previously realized that is not readily seen on current clinical imaging.

Level Of Evidence: Level V data These slides can be retrieved under Electronic Supplementary Material.
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http://dx.doi.org/10.1007/s00586-018-5489-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6032516PMC
April 2018

Adaptation of a clinical fixation device for biomechanical testing of the lumbar spine.

J Biomech 2018 03 5;69:164-168. Epub 2018 Jan 5.

Ferguson Laboratory for Spine Research, Department of Orthopedic Surgery, University of Pittsburgh, Pittsburgh, PA, USA.

In-vitro biomechanical testing is widely performed for characterizing the load-displacement characteristics of intact, injured, degenerated, and surgically repaired osteoligamentous spine specimens. Traditional specimen fixture devices offer an unspecified rigidity of fixation, while varying in the associated amounts and reversibility of damage to and "coverage" of a specimen - factors that can limit surgical access to structures of interest during testing as well as preclude the possibility of testing certain segments of a specimen. Therefore, the objective of this study was to develop a specimen fixture system for spine biomechanical testing that uses components of clinically available spinal fixation hardware and determine whether the new system provides sufficient rigidity for spine biomechanical testing. Custom testing blocks were mounted into a robotic testing system and the angular deflection of the upper fixture was measured indirectly using linear variable differential transformers. The fixture system had an overall stiffness 37.0, 16.7 and 13.3 times greater than a typical human functional spine unit for the flexion/extension, axial rotation and lateral bending directions respectively - sufficient rigidity for biomechanical testing. Fixture motion when mounted to a lumbar spine specimen revealed average motion of 0.6, 0.6, and 1.5° in each direction. This specimen fixture method causes only minimal damage to a specimen, permits testing of all levels of a specimen, and provides for surgical access during testing.
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http://dx.doi.org/10.1016/j.jbiomech.2017.12.029DOI Listing
March 2018

Cervical spine bone density in young healthy adults as a function of sex, vertebral level and anatomic location.

Eur Spine J 2017 09 6;26(9):2281-2289. Epub 2017 May 6.

Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, USA.

Purpose: Bone mineral density (BMD) measured using quantitative computed tomography (QCT) has been shown to correlate with bone mechanical properties. Knowledge of BMD within specific anatomic regions of the spine is valuable to surgeons who must secure instrumentation to the vertebrae, to medical device developers who design screws and disc replacements, and to researchers who assign mechanical properties to computational models. The objective of this study was to comprehensively characterize BMD in the cervical spine of young healthy adults.

Methods: QCT was used to determine BMD in the cervical spines of 31 healthy adults (age 20-35). Subject-specific 3D models of each vertebra were created from CT scans, and anatomic regions of interest were identified in each bone (C1: 3 regions; C2: 9 regions, C3-C7: 13 regions). Statistical tests were performed to identify differences in BMD according to vertebral level, anatomic regions within vertebrae, and sex.

Results: BMD varied significantly among vertebral levels and among anatomic regions within each vertebra. Females had higher BMD than males (p = .041) primarily due to higher BMD in the posterior regions of each vertebra.

Conclusions: These data can serve as a baseline to identify BMD changes in older and symptomatic patients. This data set is also the first report of volumetric bone density within different anatomic regions of the atlas and axis of the cervical spine. The finding of higher BMD in females is in agreement with the previous QCT results but contradicts DEXA results that are known to be dependent upon bone size.
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http://dx.doi.org/10.1007/s00586-017-5119-2DOI Listing
September 2017

Longitudinal Study of the Six Degrees of Freedom Cervical Spine Range of Motion During Dynamic Flexion, Extension, and Rotation After Single-level Anterior Arthrodesis.

Spine (Phila Pa 1976) 2016 Nov;41(22):E1319-E1327

Department of Orthopaedic Surgery, Brigham and Women's Hospital, Boston, MA.

Study Design: A longitudinal study using biplane radiography to measure in vivo intervertebral range of motion (ROM) during dynamic flexion/extension, and rotation.

Objective: To longitudinally compare intervertebral maximal ROM and midrange motion in asymptomatic control subjects and single-level arthrodesis patients.

Summary Of Background Data: In vitro studies consistently report that adjacent segment maximal ROM increases superior and inferior to cervical arthrodesis. Previous in vivo results have been conflicting, indicating that maximal ROM may or may not increase superior and/or inferior to the arthrodesis. There are no previous reports of midrange motion in arthrodesis patients and similar-aged controls.

Methods: Eight single-level (C5/C6) anterior arthrodesis patients (tested 7 ± 1 months and 28 ± 6 months postsurgery) and six asymptomatic control subjects (tested twice, 58 ± 6 months apart) performed dynamic full ROM flexion/extension and axial rotation whereas biplane radiographs were collected at 30 images per second. A previously validated tracking process determined three-dimensional vertebral position from each pair of radiographs with submillimeter accuracy. The intervertebral maximal ROM and midrange motion in flexion/extension, rotation, lateral bending, and anterior-posterior translation were compared between test dates and between groups.

Results: Adjacent segment maximal ROM did not increase over time during flexion/extension, or rotation movements. Adjacent segment maximal rotational ROM was not significantly greater in arthrodesis patients than in corresponding motion segments of similar-aged controls. C4/C5 adjacent segment rotation during the midrange of head motion and maximal anterior-posterior translation were significantly greater in arthrodesis patients than in the corresponding motion segment in controls on the second test date.

Conclusion: C5/C6 arthrodesis appears to significantly affect midrange, but not end-range, adjacent segment motions. The effects of arthrodesis on adjacent segment motion may be best evaluated by longitudinal studies that compare maximal and midrange adjacent segment motion to corresponding motion segments of similar-aged controls to determine if the adjacent segment motion is truly excessive.

Level Of Evidence: 3.
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http://dx.doi.org/10.1097/BRS.0000000000001629DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5119762PMC
November 2016

A novel MRI classification system for congenital functional lumbar spinal stenosis predicts the risk for tandem cervical spinal stenosis.

Eur Spine J 2017 02 20;26(2):368-373. Epub 2016 Jun 20.

Department of Orthopaedic Surgery, University of Pittsburgh, Kaufman Building Suite 1011, 3471 Fifth Avenue, Pittsburgh, PA, 15213, USA.

Purpose: The purpose of this study was to develop a simple and clinically useful morphological classification system for congenital lumbar spinal stenosis using sagittal MRI, allowing clinicians to recognize patterns of lumbar congenital stenosis quickly and be able to screen these patients for tandem cervical stenosis.

Methods: Forty-four subjects with an MRI of both the cervical and lumbar spine were included. On the lumbar spine MRI, the sagittal canal morphology was classified as one of three types: Type I normal, Type II partially narrow, Type III globally narrow. For the cervical spine, the Torg-Pavlov ratio on X-ray and the cervical spinal canal width on MRI were measured. Kruskal-Wallis analysis was done to determine if there was a relationship between the sagittal morphology of the lumbar spinal canal and the presence of cervical spinal stenosis.

Results: Subjects with a type III globally narrow lumbar spinal canal had a significantly lower cervical Torg-Pavlov ratio and smaller cervical spinal canal width than those with a type I normal lumbar spinal canal.

Conclusion: A type III lumbar spinal canal is a globally narrow canal characterized by a lack of spinal fluid around the conus. This was defined as "functional lumbar spinal stenosis" and is associated with an increased incidence of tandem cervical spinal stenosis.
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http://dx.doi.org/10.1007/s00586-016-4657-3DOI Listing
February 2017

Mechanical role of the posterior column components in the cervical spine.

Eur Spine J 2016 07 6;25(7):2129-38. Epub 2016 Apr 6.

Department of Orthopaedic Surgery, University of Pittsburgh, 200 Lothrop Street, E1641 Biomedical Science Tower, Pittsburgh, PA, 15261, USA.

Purpose: To quantify the mechanical role of posterior column components in human cervical spine segments.

Methods: Twelve C6-7 segments were subjected to resection of (1) suprasinous/interspinous ligaments (SSL/ISL), (2) ligamenta flavum (LF), (3) facet capsules, and (4) facets. A robot-based testing system performed repeated flexibility testing of flexion-extension (FE), axial rotation (AR), and lateral bending (LB) to 2.5Nm and replayed kinematics from intact flexibility tests for each state. Range-of-motion, stiffness, moment resistance and resultant forces were calculated.

Results: The LF contributes largely to moment resistance, particularly in flexion. Facet joints were primary contributors to AR and LB mechanics. Moment/force responses were more sensitive and precise than kinematic outcomes.

Conclusions: The LF is mechanically important in the cervical spine; its injury could negatively impact load distribution. Damage to facets in a flexion injury could lead to AR or LB hypermobility. Quantifying the contribution of spinal structures to moment resistance is a sensitive, precise process for characterizing structural mechanics.
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http://dx.doi.org/10.1007/s00586-016-4541-1DOI Listing
July 2016

Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery.

Instr Course Lect 2016 ;65:281-90

Orthopaedic Spine Fellow, Department of Orthopaedics, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania.

The incidence of intraoperative complications during cervical spine surgery is low; however, if they do occur, intraoperative complications have the potential to cause considerable morbidity and mortality. Spine surgeons should be familiar with methods to minimize intraoperative complications. If they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.
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July 2016

Reliable Magnetic Resonance Imaging Based Grading System for Cervical Intervertebral Disc Degeneration.

Asian Spine J 2016 Feb 16;10(1):70-4. Epub 2016 Feb 16.

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA, USA.

Study Design: Observational.

Purpose: To develop a simple and comprehensive grading system for cervical discs that precisely, consistently and meaningfully presents radiologic and morphologic data.

Overview Of Literature: The Thompson grading system is commonly used to classify the severity of degenerative lumbar discs on magnetic resonance imaging (MRI). Inherent differences in the morphological and physiological characteristics of cervical discs have hindered development of precise classification systems. Other grading systems have been developed for degenerating cervical discs, but their versatility and feasibility in the clinical setting is suboptimal.

Methods: MRIs of 46 human cervical discs were de-identified and displayed in PowerPoint format. Each slide depicted a single disc with a normal (grade 0) disc displayed in the top right corner for reference. The presentation was given to 25 physicians comprising attending spine surgeons, spine fellows, orthopaedic residents, and two attending musculoskeletal radiologists. The grading system included Grade 0 (normal height compared to C2-3, mid cleft still visible), grade 1 (dark disc, normal height), grade 2 (collapsed disc, few osteophytes), and grade 3 (collapsed disc, many osteophytes). The ease of use of the system was gauged in the participants and the interobserver reliability was calculated.

Results: The intraclass correlation coefficient for interobserver reliability was 0.87, and 0.94 for intraobserver reliability, indicating excellent reliability. Ninety-five percent and 85 percent of the clinicians judged the grading system to be clinically feasible and useful in daily practice, respectively.

Conclusions: The grading system is easy to use, has excellent reliability, and can be used for precise and consistent clinician communication.
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http://dx.doi.org/10.4184/asj.2016.10.1.70DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4764544PMC
February 2016

Avoiding and Managing Intraoperative Complications During Cervical Spine Surgery.

J Am Acad Orthop Surg 2015 Dec 30;23(12):e81-90. Epub 2015 Oct 30.

The incidence of intraoperative complications in cervical spine surgery is low. However, when they do occur, such complications have the potential for causing considerable morbidity and mortality. Spine surgeons should be familiar with methods of minimizing such complications. Furthermore, if they do occur, surgeons must be prepared to immediately treat each potential complication to reduce any associated morbidity.
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http://dx.doi.org/10.5435/JAAOS-D-14-00446DOI Listing
December 2015

Cervical motion segment contributions to head motion during flexion\extension, lateral bending, and axial rotation.

Spine J 2015 Dec 31;15(12):2538-43. Epub 2015 Aug 31.

Department of Orthopaedic Surgery, University of Pittsburgh, 15213, USA.

Background Context: Cervical spine segmental contributions to motion may reveal movement abnormalities associated with whiplash, disc herniation, disc arthroplasty, or fusion.

Purpose: The objective of this study was to determine the cervical spine segmental contributions to head flexion\extension, lateral bending, and axial rotation during dynamic motion in young, healthy individuals.

Study Design: The study design was a descriptive control study.

Patient Sample: Twenty-nine young (20-35 years of age) healthy individuals comprised the patient sample.

Outcome Measures: Physiologic measures of contributions from each cervical motion segment to the primary head rotation were the outcome measures for this study.

Methods: Twenty-nine healthy participants performed full range of motion (ROM) flexion\extension, lateral bending, and axial rotation while biplane radiographs were collected at 30 images per second. Surface-based markers were used to determine head kinematics for each movement, and a validated volumetric model-based tracking technique was used to determine intervertebral kinematics. Contributions from each cervical motion segment to the primary head rotation were determined continuously during each of the three head movements. This study was funded by Synthes Spine (F).

Results: For each head movement, motion segments in the lower cervical spine increased their contributions to head motion near the end of the ROM. Cervical motion segment contributions to left and right lateral bending were mirror images of each other, as were contributions to left and right axial rotation. However, cervical motion segment contributions to flexion were not mirror images of the contributions to extension.

Conclusions: Cervical motion segment contributions to head motion change over the full ROM and cannot be accurately characterized solely from endpoint data. The continuously changing segmental contributions suggest that the compressive and shear loads applied to each motion segment also change over the ROM. The clinical implication of increased contributions from the inferior motions segments near the end ROM is that the clinician may advise the patient to avoid end ROM positions to lessen the demand on the discs of inferior motion segments.
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http://dx.doi.org/10.1016/j.spinee.2015.08.042DOI Listing
December 2015

Three-dimensional intervertebral kinematics in the healthy young adult cervical spine during dynamic functional loading.

J Biomech 2015 May 14;48(7):1286-93. Epub 2015 Mar 14.

University of Pittsburgh, Department of Orthopaedic Surgery, United States.

The objective of this study was to determine the intervertebral kinematics of the young, healthy cervical spine during dynamic, three-dimensional, functional loading. Intervertebral motion was characterized by the range of motion (ROM) and the helical axis of motion (HAM). Biplane radiographs of the cervical spine were collected at 30 images/s as 29 participants (20-35 yr) performed dynamic flexion\extension, axial rotation, and lateral bending. Vertebral motion (C1-T1 in flexion\extension, C3-T1 in lateral bending and axial rotation) was tracked with sub-millimeter accuracy using a validated volumetric model-based tracking process that matched subject-specific CT-based bone models to the radiographs. Flexion\extension ROM was smallest at the C2-C3 motion segment (12.7±2.6°) and largest at the C5-C6 motion segment (19.7±3.7°). During head lateral bending and axial rotation, the intervertebral bending ROM was greater than the rotation ROM at every motion segment. The HAM demonstrated differences among motion segments and among movements. During flexion\extension, the helical axis of motion was directed nearly perpendicular to the sagittal plane for the C2-C3 through C7-T1 motion segments. During lateral bending, the angle between the HAM and the transverse plane progressively increased from the C6-C7 motion segment (approximately ±22°) to the C3-C4 motion segment (approximately ±40°). During axial rotation, the angle between the transverse plane and the HAM was approximately ±42° at the C3-C4 through C5-C6 motion segments, and approximately ±32° at the C6-C7 motion segment. This study provides valuable reference data for evaluating the effects of age, degeneration, and surgical procedures on cervical spine kinematics during three-dimensional dynamic functional loading.
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http://dx.doi.org/10.1016/j.jbiomech.2015.02.049DOI Listing
May 2015

Traumatic brachial plexus root avulsion and cervical spine epidural hematoma in an 18-year-old man.

Spine J 2015 Feb 2;15(2):365-6. Epub 2014 Oct 2.

Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, 3471 Fifth Ave., Suite 911, Pittsburgh, PA 15213, USA.

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http://dx.doi.org/10.1016/j.spinee.2014.09.024DOI Listing
February 2015