CT guided biopsy for osteodiscitis reduces cost of hospitalization in the landscape of increasing intravenous drug use: A single center retrospective analysis.

OBJECTIVE: Osteodiscitis has been demonstrated to show significant morbidity and mortality. Cultures and CT guided biopsy (CTB) are commonly used diagnosis of osteodiscitis. This study's purpose is to evaluate the cost burden of CTB and to evaluate how IVDU affects patient management in the setting of osteodiscitis. METHODS: Patients admitted for osteodiscitis from 2011-2021 were retrospectively reviewed and stratified into cohorts by CTB status. Additional cohorts were stratified by Intravenous Drug Use (IVDU). Patient demographics, total cost of hospitalization, length of hospitalization, time to biopsy, IVDU status, and other factors were recorded. T-Test, Chi-squared analysis, and ANOVA were used for statistical analysis. RESULTS: Total cost of hospitalization was recorded for 140 patients without CTB and 346 patients with CTB. Average cost of hospitalization for non-CTB was $227,317.86 compared to CTB at $119,799.20 (p < 0.001). Length of stay (LOS) was found to be 18.01 days for non-CTB and 14.07 days for CTB patients (0.00282). When stratified by days until biopsy, patients who had CTB sooner, had significantly reduced cost of hospitalization (p = 0.0003). Patients with IVDU history were significantly younger (p < 0.001) with lower BMI (p < 0.001) and a significantly different clinical profile. There was a significant difference in positive open biopsy when separated by IVDU status (p = 0.025). CONCLUSION: CTB was associated with significantly reduced cost of hospitalization and LOS compared to non-CTB. IVDU patients with osteodiscitis have significantly different clinical profiles than non-IVDU that may impact diagnosis and treatment. Further work is indicated to elucidate causes of these differences to provide high value care to patients with osteodiscitis.

Impact of obesity on adult spinal deformity (ASD) long-segment spinal fusion radiographic and clinical outcomes.

STUDY DESIGN: Retrospective chart review of patients receiving long-segment fusion during a five-year period. OBJECTIVE: To determine whether obese patients receive comparable benefits when receiving long-segment fusion compared to non-obese patients and to identify factors that may predict hardware failure and post-surgical complications among obese patients. METHODS: Demographic, spinopelvic radiographic, patient-reported outcome measures (PROMs), and complications data was retrospectively collected from 120 patients who underwent long-segment fusion during a five-year period at one tertiary care medical center. Radiographic measurements were pelvic incidence, pelvic tilt (PT), lumbar lordosis, L4-S1 lordosis, thoracic kyphosis, sagittal vertical axis, PI-LL mismatch, and proximal junction cobb angle at upper instrumented vertebrae + 2 (UIV+2). PROMs were Oswestry disability index, numeric rating scale (NRS) Back Pain, NRS Leg Pain, RAND SF-36 pain, and RAND SF-36 physical functioning. Included patients were adults and had at least 2-years of postoperative follow-up. Descriptive and multivariate statistical analysis was performed with α = 0.05. RESULTS: Patients with a BMI ≥ 30 (n=63) and patients with a BMI < 30 (n=57) demonstrated comparable improvements (P>0.05) for all spinopelvic radiographic measurements and PROMs. Each cohort demonstrated significant improvements from pre-assessment to post-assessment on nearly all spinopelvic radiographic measurements and PROMs (P<0.05), except PT and L4-S1 lordosis where neither group improved (p=0.95 and 0.58 for PT and P=0.23 and 0.11 for L4-S1 lordosis fornon-obese and obese cohorts respectively) and SF-36 physical functioning where the non-obese cohort not statistically improve (P=0.08). Patients with a BMI ≥ 30 demonstrated an increased incidence of cardiovascular complications (P=0.0293), acute kidney injury (P=0.0241), rod fractures (P=0.0293), and reoperations (P=0.0241) when compared to patients with a BMI < 30. CONCLUSION: This study adds to a growing body of evidence linking demographic factors with risks of hardware failure. Further, this data challenges the assumption that obese patients may not receive sufficient benefit to be long-segment surgical candidates. However, given their elevated risk for post-operative and delayed hardware complications, obese patients should be appropriately counseling before undergoing surgery.

Use of global sagittal flexibility to predict proximal junctional kyphosis after spinal deformity surgery.

OBJECTIVE: Sagittal alignment is an important predictor of functional outcomes after surgery for adult spinal deformity (ASD). A rigid spinal column may create a large lever arm that may impact the rate of proximal junctional kyphosis (PJK) after ASD surgery. In this study, the authors sought to determine whether relatively low preoperative global spinal flexibility (i.e., rigid spine) predicts increased incidence of PJK at 1 year after ASD surgery. METHODS: The authors retrospectively reviewed long-segment thoracolumbar fusions with pelvic fixation performed at a single tertiary care center between October 2015 and September 2020 in patients with a minimum of 1-year radiographic and clinical follow-up. Two cohorts were established on the basis of the optimal value for spinal flexibility, as defined by the absolute difference between the preoperative standing and supine C7 sagittal vertical axes, which the authors termed global sagittal flexibility (GSF). Demographic information, radiographs, various associated complications, and patient-reported outcome measures (PROMs) were analyzed. RESULTS: Eighty-five patients met the inclusion criteria. Receiver operating characteristic (ROC) analysis using GSF to predict an increase in the proximal junctional sagittal Cobb angle (PJCA) greater than or equal to 10° at 1-year follow-up provided an area under the curve of 0.64 and identified an optimal GSF threshold value of 3.7 cm. Patients with GSF > 3.7 cm were considered globally flexible (48 patients), and those with GSF ≤ 3.7 cm were classified as rigid (37 patients). Rigid patients were noted to have a significantly higher risk of ΔPJCA ≥ 10° at 1-year follow-up (51.4% vs 29.3%, p = 0.049). No changes in the reoperation rates or PROMs based on GSF were observed in the 1- or 2-year postoperative window. CONCLUSIONS: Based on these retrospective data, preoperative global spinal rigidity portends an independently elevated risk for the development of PJK after ASD surgery. No differences in other complication rates or PROMs data were observed between groups. Data collection was limited to a 2-year postoperative window; therefore, longer follow-up is required to further elucidate the relationship between rigidity and reoperation rates. Based on these retrospective data, flexibility may influence the outcomes of patients with ASD.

Predicting the Need for Surgery in Patients with Lumbar Disc Herniation: A New Internally Validated Scoring System.

STUDY DESIGN: Prospective study. PURPOSE: To propose a scoring system for predicting the need for surgery in patients with lumbar disc herniation (LDH). OVERVIEW OF LITERATURE: The indications for surgery in patients with LDH are well established. However, the exact timing of surgery is not. According to surgeons, patients with failed conservative treatment who underwent delayed surgery, often after 6 months postsymptom initiation, have poor functional recovery and outcome. METHODS: The current study included patients with symptomatic LDH. Patients with an indication for emergent surgery such as profound or progressive motor deficit, cauda equina syndrome, and diagnoses other than single-level LDH were excluded from the analysis. All patients followed a conservative treatment regimen (a combination of physical therapy, pain medications, and/or spinal epidural steroid injections). Surgery was indicated for patients who continuously experienced pain despite maximal conservative therapy. RESULTS: In total, 134 patients met the inclusion and exclusion criteria. Among them, 108 (80.6%) responded to conservative management, and 26 (19.4%) underwent unilateral laminotomy and microdiscectomy. The symptom duration, disc degeneration grade on magnetic resonance imaging (Pfirrmann disc grade), herniated disc location and type, fragment size, and thecal sac diameter significantly differed between patients who responded to conservative treatment and those requiring surgery. The area under the receiver operating characteristic curve of the scoring system based on the anteroposterior size of the herniated disc fragment and herniated disc location and type was 0.81. CONCLUSIONS: A scoring system based on herniated disc/fragment size, location, and type can be applied to predict the need for surgery in patients with LDH. In the future, this tool can be used to prevent unnecessarily prolonged conservative management (>4-8 weeks).

Delayed stenosis associated with sublaminar band placement in the thoracic spine for proximal junctional kyphosis.

Background: Proximal junctional thoracic kyphosis (PJK) is common following adult spinal deformity (ASD) surgery and may require revision operations. In this case series, we present delayed complications associated with the use of sublaminar banding (SLBs) for PJK prophylaxis. Case Description: Three patients underwent long-segment thoracolumbar decompression and fusions for ASD. All had undergone SLB placement for PJK prophylaxis. All three subsequently developed neurologic complications secondary to cephalad spinal cord compression/stenosis requiring urgent revision surgery. Conclusion: The placement of SLBs placed to prevent PJK may lead to sublaminar inflammation contributing to severe cephalad spinal canal stenosis and myelopathy following ASD surgery. Surgeons should be aware of this potential complication and may consider alternatives to SLB placement to avoid this complication.

Electronic versus paper patient-reported outcome measure compliance rates: A retrospective analysis.

OBJECTIVE: Patient-reported outcome measures (PROMs) are key tools used to inform clinical research and patient-centered care. Application of data collected from PROMs, however, may be limited by incomplete responses, and little is known regarding the efficacy of varied PROM delivery methods. The objective of this study was to compare PROMs compliance when delivered via paper and electronic formats. METHODS: Elective adult spinal deformity patients were screened for inclusion. Data collected included demographics, type of surgery, PROMs compliance, and discharge care. Descriptive statistics and multivariate analysis (MVA) were performed to compare pre- and postoperative compliance rates. RESULTS: Of the 474 included patients, 177 were administered paper PROMs, while 297 were electronic. Preoperatively, 101 patients (57.1%) had any portion of their paper PROMs available; 179 (60.3%) had any of their electronic PROMs available (p = 0.492). Among all patients, 76 (42.9%) and 170 (57.2%) had all of their completed preop PROMs available (p = 0.003). Among patients with any of their preop PROMs completed, 75.2% with paper and 95.0% with electronic were completed in their entirety (p < 0.001). Similar trends were observed among postoperative PROMs. MVA demonstrated electronic delivery as the only significant correlate with pre- and post-operative PROMs compliance (p < 0.001 and p = 0.003, respectively). CONCLUSIONS: No differences were observed across modalities when considering any available PROMs, yet electronic PROM delivery was associated with higher completion of PROMs. In order to improve the quality of patient-reported data, electronic delivery with alternative methods of quality improvement may be considered to increase PROMs retention rates.

Subsidence Rates Associated With Porous 3D-Printed Versus Solid Titanium Cages in Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective Cohort Study. OBJECTIVE: To determine whether 3D-printed porous titanium (3DPT) interbody cages offer any clinical or radiographic advantage over standard solid titanium (ST) interbody cages in transforaminal lumbar interbody fusions (TLIF). METHODS: A consecutive series of adult patients undergoing one- or two-level TLIF with either 3DPT or ST "banana" cages were analyzed for patient reported outcome measures (PROMs), radiographic complications, and clinical complications. Exclusion criteria included clinical or radiographic follow-up less than 1 year. RESULTS: The final cohort included 90 ST interbody levels from 74 patients, and 73 3DPT interbody levels from 50 patients for a total of 124 patients. Baseline demographic variables and comorbidity rates were similar between groups (P > .05). Subsidence of any grade occurred more frequently in the ST group compared with the 3DPT group (24.4% vs 5.5%, respectively, P = .001). Further, the ST group was more likely to have higher grades of subsidence than the 3DPT group (P = .009). All PROMs improved similarly after surgery and revision rates did not differ between groups (both P > .05). On multivariate analysis, significant positive correlators with increasing subsidence grade included greater age (P = .015), greater body mass index (P = .043), osteoporosis/osteopenia (P < .027), and ST cage type (P = .019). CONCLUSIONS: When considering interbody material for TLIF, both ST and 3DPT cages performed well; however, 3DPT cages were associated with lower rates of subsidence. The clinical relevance of these findings deserves further randomized, prospective investigation.

The Effects of Nicotine- and Cigarette-Related Products on Osteogenesis, Bone Formation, and Bone Mineralization: A Systematic Review.

BACKGROUND: Many clinicians associate nicotine as the causative agent in the negative and deleterious effects of smoking on bone growth and spine fusion. Although nicotine is the primary driver of physiological addiction in smoking, isolated and controlled use of nicotine is one of the most effective adjuncts to quitting smoking. OBJECTIVE: To explore the relationship between nicotine and noncombustion cigarette products on bone growth. METHODS: One thousand five studies were identified, of which 501 studies were excluded, leaving 504 studies available for review. Of note, 52 studies were deemed to be irrelevant. Four hundred fifty-two studies remained for eligibility assessment. Of the remaining 452, 218 failed to assess study outcomes, 169 failed to assess bone biology, 13 assessed 5 patients or fewer, and 12 were deemed to be ineligible of the study criteria. Forty studies remained for inclusion within this systematic review. RESULTS: Of the 40 studies identified for inclusion within the study, 30 studies were classified as "Animal Basic Science," whereas the remaining 10 were categorized as "Human Basic Science." Of the 40 studies, 11 noted decreased cell proliferation and boney growth, whereas 8 showed an increase. Four studies noted an increase in gene expression products, whereas 11 noted a significant decrease. CONCLUSION: The results of this study demonstrate that nicotine has a variety of complex interactions on osteoblast and osteoclastic activities. Nicotine demonstrates dose-dependent effects on osteoblast proliferation, boney growth, and gene expression. Further study is warranted to extrapolate the effects of solitary nicotine on clinical outcomes.

Endoscopic endonasal resection of craniovertebral junction osteomyelitis: illustrative cases.

BACKGROUND: Operative management of craniovertebral junction (CVJ) osteomyelitis has traditionally been extracranial and focused on debriding the infection. In select patients, the endoscopic endonasal approach (EEA) with a focus on additional resection versus debridement may be preferred. The goal of this study is to present the authors' experience with the EEA with gross or subtotal resection for the treatment of osteomyelitis at the CVJ and describe their technique in the context of the literature. OBSERVATIONS: Two patients of the authors' and 6 detailed case reports in the literature were identified with a mean age of 58.9 years. Most patients (n = 5; 62.5%) underwent skull base surgery and debridement (n = 5; 62.5%). Although more common, debridement was inferior to resection in terms of neurological improvement (66.7% vs. 100.0%) postoperatively. The majority (n = 7; 87.5%) of patients underwent occipitocervical fusion. LESSONS: Osteomyelitis is an exceedingly rare lesion of the CVJ. Despite the region's delicate biomechanical stability, resection of infected bone may be superior to debridement alone in terms of clinical outcome. Given how well established the safety of the EEA is to this region, further study of outcomes with resection is warranted.

Early Postural Stability Changes in Patients Undergoing Correction of Spinal Deformity: A Prospective, Controlled Pilot Study.

BACKGROUND CONTEXT: Adult spinal deformity (ASD) is a prevalent condition often requiring surgical intervention. Improved outcomes among ASD patients have been shown to correlate with postoperative spinopelvic parameters, yet little is currently known about the role of postural stability and balance assessment for ASD patients. PURPOSE: Explore early changes in postural stability following ASD correction. STUDY DESIGN: Prospective cohort study. PATIENT SAMPLE: Sixteen adult patients who underwent four-level or greater posterolateral fusion to address global spinal malalignment and 14 healthy controls with no known spinal deformity nor surgery. OUTCOME MEASURES: Postural stability parameters, spinopelvic parameters preoperatively and postoperatively. METHODS: Force plate balance assessment was completed where participants and healthy controls were instructed to stand with their hands at their sides, standing still, with eyes open. Center of pressure (COP), center of gravity (COG), and cone of economy (COE) parameters were analyzed with paired and unpaired t tests with an alpha of 0.05. RESULTS: Preoperatively, ASD patients demonstrated more COG (P=0.0244) and sagittal and coronal head (P<0.05) sway than healthy controls. Postoperatively, ASD patients exhibited less COP (P=0.0308), COG (P=0.0276) and head (P=0.0345) sway. Compared to healthy controls, ASD patients postoperatively exhibited similar postural stability, aside from COP and COG sway amplitudes (P<0.05), and coronal head sway (P=0.0309). Pelvic incidence-lumbar lordosis and sagittal vertical axis improved from 16.2° to 4.8° (P<0.01) and 82.2 to 22.5 mm (P<0.01), respectively. CONCLUSION: We report a novel early improvement in postural stability, comparable to healthy controls, following ASD correction that may be related to improved spinopelvic alignment. Force plate evaluation may be a useful tool for ASD patients postoperatively. Future clinical trials assessing the impact of postural stability on clinical and radiographic outcomes are warranted.

Spinal deformity correction in ankylosing spondylitis.

Background: Ankylosing spondylitis (AS) is a complex, debilitating disease with few available medical therapies in its later stages. Methods: We reviewed current clinical approaches for caring for AS patients with an emphasis on the risks and outcomes associated with surgical intervention. Results: It is critical to understand the natural history and surgical outcomes of patient with AS. Surgery is not without risks, as a vertebral body osteotomy is often required to re-establish spinopelvic equilibrium. However, surgery can lead to clinical improvements in pain, disability, cardiac function, respiration, digestion, and sexual activity. Conclusion: Deformity correction for AS should be carefully considered in symptomatic patients.

Baseline parameters and the prediction of treatment failure in patients with intravenous drug use-associated spinal epidural abscesses.

OBJECTIVE: Despite the increasing incidence of spinal epidural abscess (SEA), the baseline parameters potentially predictive of treatment failure remain poorly characterized. In this study, the authors identify the relevant baseline parameters that predict multimodal treatment failure in patients with either intravenous drug use (IVDU)-associated SEA or non-IVDU-associated SEA. METHODS: The authors reviewed the electronic medical records of a large institutional series of consecutive patients with diagnosed SEA between January 2011 and December 2017 to characterize epidemiological trends as well as the complement of baseline measures that are predictive of failure after multimodal treatment in patients with and without concomitant IVDU. The independent impact of clinical and imaging factors in detecting treatment failure was assessed by performing stepwise binary logistic regression analysis. RESULTS: A total of 324 consecutive patients with diagnosed SEA were identified. Overall, 226 patients (69.8%) had SEA related to other causes and 98 (30.2%) had a history of recent IVDU. While non-IVDU SEA admission rates remained constant, year-over-year admissions of patients with IVDU SEA nearly tripled. At baseline, patients with IVDU SEA were distinct in many respects including younger age, greater unemployment and disability, less frequent diabetes mellitus (DM), and more frequent methicillin-resistant Staphylococcus aureus infection. However, differences in length of stay, loss to follow-up, and treatment failure did not reach statistical significance between the groups. The authors constructed independent multivariate logistic regression models for treatment failure based on identified parameters in the two cohorts. For the non-IVDU cohort, the authors identified four variables as independent factors: DM, hepatitis B/C, osteomyelitis, and compression deformity severity. In contrast, for patients with IVDU, the authors identified three variables: albumin, endocarditis, and endplate destruction. Receiver operating characteristic and area under the curve (AUC) analyses were undertaken for the multivariate models predicting the likelihood of treatment failure in the two cohorts (AUC = 0.88 and 0.89, respectively), demonstrating that the derived models could adequately predict the risk of multimodal treatment failure. Treatment failure risk factor point scales were derived for the identified variables separately for both cohorts. CONCLUSIONS: Patients with IVDU SEA represent a unique population with a distinct set of baseline parameters that predict treatment failure. Identification of relevant prognosticating factors will allow for the design of tailored treatment and follow-up regimens.

Static Cage Morphology in Short-Segment Transforaminal Lumbar Interbody Fusions Is Associated With Alterations in Foraminal Height But Not Clinical Outcomes.

INTRODUCTION: Steerable "banana" cages have been posited to increase segmental lordosis in short-segment transforaminal lumbar interbody fusions (TLIF). The same is not necessarily true for straight "bullet" cages. Although increased lordosis is generally thought to be advantageous, a potential complication is decreased foraminal height. Here we evaluate for any association between cage type and change in foraminal height and clinical outcomes following short-segment TLIFs. METHODS: We retrospectively reviewed consecutive 1- and 2-level TLIFs with bilateral facetectomies with minimum 1-year clinical and radiographic follow-up. Two cohorts were based on cage morphology: steerable "banana" cage or straight "bullet" cage. Patient reported outcome measures (PROMs), radiographic measurements, and revision rates were compared. RESULTS: A total of 46 patients with 53 straight and 95 patients with 131 steerable cage levels were included. Steerable cages showed increased segmental lordosis (9.1° vs. 13.5°, P < 0.001) and decreased foraminal height (20.3 vs. 18.5 mm, P < 0.001) after surgery. Straight cages demonstrated similar segmental lordosis (8.7° vs 8.1°, P = 0.30) and foraminal height (19.4 vs 20.0 mm, P < 0.065). Both cohorts showed improved PROMs at last follow-up (P ≤ 0.005). Subanalysis comparing patients who had increased or decreased foraminal height revealed similarly improved PROMs between cohorts. Revision rates at 1 year were similar between cohorts (4.3% for straight and 3.2% for steerable group, P = 0.72). CONCLUSIONS: Although the increased segmental lordosis afforded by placement of steerable cages may decrease foraminal height after short segment TLIF, clinical outcomes are not negatively affected by this association.

Radiographic and clinical outcomes in one- and two-level transforaminal lumbar interbody fusions: a comparison of bullet versus banana cages.

OBJECTIVE: The aim of this study was to determine whether cage morphology influences clinical and radiographic outcomes following short-segment transforaminal lumbar interbody fusion (TLIF) procedures. METHODS: The authors retrospectively reviewed one- and two-level TLIFs at a single tertiary care center between August 2012 and November 2019 with a minimum 1-year radiographic and clinical follow-up. Two cohorts were compared based on interbody cage morphology: steerable "banana" cage or straight "bullet" cage. Patient-reported outcome measures (PROMs), radiographs, and complications were analyzed. RESULTS: A total of 135 patients with 177 interbody levels were identified; 45 patients had 52 straight cages and 90 patients had 125 steerable cages. Segmental lordosis increased with steerable cages, while it decreased with straight cages (+3.8 ± 4.6 vs -1.9 ± 4.3, p < 0.001). Conversely, the mean segmental lordosis of adjacent lumbar levels decreased in the former group, while it increased in the latter group (-0.52 ± 1.9 vs +0.52 ± 2.1, p = 0.004). This reciprocal relationship results in global sagittal parameters, including pelvic incidence minus lumbar lordosis and lumbar distribution index, which did not change after surgery with either cage morphology. Multivariate analysis confirmed that steerable cage morphology, anterior cage positioning, and less preoperative index-level segmental lordosis were associated with greater improvement in index-level segmental lordosis. PROMs were improved after surgery with both cage types, and the degree of improvement did not differ between cohorts (p > 0.05). Perioperative and radiographic complications were similar between cohorts (p > 0.05). Overall reoperation rates, as well as reoperation rates for adjacent-segment disease within 2 years of surgery, were not significantly different between cohorts. CONCLUSIONS: Steerable cages are more likely to lie within the anterior disc space, thus increasing index-level segmental lordosis, which is accompanied by a reciprocal change in segmental alignment at the adjacent lumbar levels. The converse relationship occurs for straight cages, with a kyphotic change at the index levels and reciprocal lordosis occurring at adjacent levels.

Unilateral atlantoaxial pseudoarticulation: A case report, literature review, and proposed mechanism.

BACKGROUND: Atlantoaxial pseudoarticulation rarely involves the cervical spine, and its etiology is unclear. In theory, pseudoarticulation is comparable to Bertolotti's syndrome in the lumbar spine or may be attributed to an aberrant focal fusion between C0-C1-C2 that occurs during the gastrulation of embryologic development. CASE DESCRIPTION: A 39-year-old female presented with neck pain and upper extremity weakness. Magnetic resonance/computed tomography studies documented a left-sided unilateral pseudoarticulation between the lamina of C1 and C2 causing compression of the dorsal spinal cord. Following resection of the accessory C1/C2 joint utilizing a C1 hemilaminectomy and partial C2 laminectomy, the patient's neck pain and weakness resolved. Histologically, the tissue showed benign osteocartilaginous tissue with no synovial capsule. CONCLUSION: Here, the authors present a case of occiput-C1-C2 pseudojoint formation, leading to clinical and radiographic findings of cord compression due to boney outgrowth.

A comprehensive finite element model of surgical treatment for cervical myelopathy.

BACKGROUND: Cervical myelopathy is a common and debilitating chronic spinal cord dysfunction. Treatment includes anterior and/or posterior surgical intervention to decompress the spinal cord and stabilize the spine, but no consensus has been made as to the preferable surgical intervention. The objective of this study was to develop an finite element model of the healthy and myelopathic C2-T1 cervical spine and common anterior and posterior decompression techniques to determine how spinal cord stress and strain is altered in healthy and diseased states. METHODS: A finite element model of the C2-T1 cervical spine, spinal cord, pia, dura, cerebral spinal fluid, and neural ligaments was developed and validated against in vivo human displacement data. To model cervical myelopathy, disc herniation and osteophytes were created at the C4-C6 levels. Three common surgical interventions were then incorporated at these levels. FINDINGS: The finite element model accurately predicted healthy and myelopathic spinal cord displacement compared to motions observed in vivo. Spinal cord strain increased during extension in the cervical myelopathy finite element model. All surgical techniques affected spinal cord stress and strain. Specifically, adjacent levels had increased stress and strain, especially in the anterior cervical discectomy and fusion case. INTERPRETATIONS: This model is the first biomechanically validated, finite element model of the healthy and myelopathic C2-T1 cervical spine and spinal cord which predicts spinal cord displacement, stress, and strain during physiologic motion. Our findings show surgical intervention can cause increased strain in the adjacent levels of the spinal cord which is particularly worse following anterior cervical discectomy and fusion.

Impact of the Inclusion of C2 in Posterior Cervical Fusions for Cervical Myelopathy on Sagittal Cervical Alignment.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To determine the impact of including C2 in posterior fusions on radiographic parameters of cervical alignment in cervical spondylotic myelopathy. SUMMARY OF BACKGROUND DATA: Despite the use of posterior instrumentation and arthrodesis after cervical laminectomy, loss of lordosis and the development of kyphosis are prevalent. Inadequate cervical lordosis and other measures of sagittal cervical alignment have been shown to correlate with disability, general health scores, and severity of myelopathy. The role of C2 in the posterior tension band, which maintains sagittal alignment, differs from the subaxial spine, as it is the insertion point for erector spinae muscles that play a critical role in maintaining posture. PATIENTS AND METHODS: This study compares the radiographic outcomes of sagittal balance between 2 cohorts of patients who underwent posterior cervical decompression and fusion for cervical myelopathy over a 12-year period at a single institution. Demographic and surgical characteristics were collected using the electronic medical record of patients undergoing posterior cervical fusions (PCF) which included the axis [axial fusion (AF)] and those that were subaxial fusions (SAF). Radiographic measurements included preopertaive and postoperative C2-C7 lordosis (CL), C2-C7 sagittal vertical axis (SVA), and T1 slope (T1S). RESULTS: After review of the electronic medical records, 229 patients were identified as having PCF and decompression for treatment of myelopathy. One hundred sixty-seven patients had AF, whereas 62 had SAF. PCF resulted in loss of CL in both cohorts. Although there was no statistical difference in postoperative CL, there was a significant increase in SVA (P<0.001) and T1S (P<0.001) with AF. CONCLUSIONS: PCF often result in loss of lordosis. When compared with SAF, inclusion of C2 into the fusion construct may result in worsened sagittal balance, increasing the SVA and T1S.