Lumbar Facet Arthroplasty Versus Fusion for Grade-I Degenerative Spondylolisthesis with Stenosis: A Prospective Randomized Controlled Trial.

BACKGROUND: The comparative effectiveness of decompression plus lumbar facet arthroplasty versus decompression plus instrumented lumbar spinal fusion in patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis is unknown. METHODS: In this randomized, controlled, Food and Drug Administration Investigational Device Exemption trial, we assigned patients who had single-level lumbar spinal stenosis and grade-I degenerative spondylolisthesis to undergo decompression plus lumbar facet arthroplasty (arthroplasty group) or decompression plus fusion (fusion group). The primary outcome was a predetermined composite clinical success score. Secondary outcomes included the Oswestry Disability Index (ODI), visual analog scale (VAS) back and leg pain, Zurich Claudication Questionnaire (ZCQ), Short Form (SF)-12, radiographic parameters, surgical variables, and complications. RESULTS: A total of 321 adult patients were randomized in a 2:1 fashion, with 219 patients assigned to undergo facet arthroplasty and 102 patients assigned to undergo fusion. Of these, 113 patients (51.6%) in the arthroplasty group and 47 (46.1%) in the fusion group who had either reached 24 months of postoperative follow-up or were deemed early clinical failures were included in the primary outcome analysis. The arthroplasty group had a higher proportion of patients who achieved composite clinical success than did the fusion group (73.5% versus 25.5%; p < 0.001), equating to a between-group difference of 47.9% (95% confidence interval, 33.0% to 62.8%). The arthroplasty group outperformed the fusion group in most patient-reported outcome measures (including the ODI, VAS back pain, and all ZCQ component scores) at 24 months postoperatively. There were no significant differences between groups in surgical variables or complications, except that the fusion group had a higher rate of developing symptomatic adjacent segment degeneration. CONCLUSIONS: Among patients with lumbar spinal stenosis and grade-I degenerative spondylolisthesis, lumbar facet arthroplasty was associated with a higher rate of composite clinical success than fusion was at 24 months postoperatively. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

MRI Vertebral Bone Quality Correlates With Interbody Cage Subsidence After Anterior Cervical Discectomy and Fusion.

STUDY DESIGN: Retrospective observational study of consecutive patients. OBJECTIVE: The purpose of the study was to evaluate VBQ as a predictor of interbody subsidence and to determine threshold values that portend increased risk of subsidence. SUMMARY OF BACKGROUND DATA: Many risk factors have been reported for the subsidence of interbody cages in anterior cervical discectomy and fusion (ACDF). MRI Vertebral Bone Quality (VQB) is a relatively new radiographic parameter that can be easily obtained from preoperative MRI and has been shown to correlate with measurements of bone density such as DXA and CT Hounsfield Units. METHODS: All patients who underwent 1- to 3-level ACDF using titanium interbodies with anterior plating between the years 2018 and 2020 at our tertiary referral center were included. Subsidence measurements were performed by 2 independent reviewers on CT scans obtained 6 months postoperatively. VBQ was measured on pre-operative sagittal T1 MRI by 2 independent reviewers, and values were averaged. RESULTS: Eight-five fusion levels in 44 patients were included in the study. There were 32 levels (38%) with moderate subsidence and 12 levels with severe subsidence (14%). The average VBQ score in those patients with severe subsidence was significantly higher than those without subsidence (3.80 vs. 2.40, P<0.01). A threshold value of 3.2 was determined to be optimal for predicting subsidence (AUC=0.99) and had a sensitivity of 100% and a specificity of 94.1% in predicting subsidence. CONCLUSIONS: VBQ strongly correlates with the subsidence of interbody grafts after ACDF. A threshold VBQ score value of 3.2 has excellent sensitivity and specificity for predicting subsidence. Spine surgeons can use VBQ as a readily available screening tool to identify patients at higher risk for subsidence. LEVEL OF EVIDENCE: Level-IV.

Bone Quality as Measured by Hounsfield Units More Accurately Predicts Proximal Junctional Kyphosis than Vertebral Bone Quality Following Long-Segment Thoracolumbar Fusion.

OBJECTIVE: To compare the prognostic power of Hounsfield units (HU) and Vertebral Bone Quality (VBQ) score for predicting proximal junctional kyphosis (PJK) following long-segment thoracolumbar fusion to the upper thoracic spine (T1-T6). METHODS: Vertebral bone quality around the upper instrumented vertebrae (UIV) was measured using HU on preoperative CT and VBQ on preoperative MRI. Spinopelvic parameters were also categorized according to the Scoliosis Research Society-Schwab classification. Univariable analysis to identify predictors of the occurrence of PJK and survival analyses with Kaplan-Meier method and Cox regression were performed to identify predictors of time to PJK (defined as ≥10° change in Cobb angle of UIV+2 and UIV). Sensitivity analyses showed thresholds of HU < 164 and VBQ > 2.7 to be most predictive for PJK. RESULTS: Seventy-six patients (mean age 66.0 ± 7.0 years; 27.6% male) were identified, of whom 15 suffered PJK. Significant predictors of PJK were high postoperative pelvic tilt (P = 0.038), high postoperative T1-pelvic angle (P = 0.041), and high postoperative PI-LL mismatch (P = 0.028). On survival analyses, bone quality, as assessed by the average HU of the UIV and UIV+1 was the only significant predictor of time to PJK (odds ratio [OR] 3.053; 95% CI 1.032-9.032; P = 0.044). VBQ measured using the UIV, UIV+1, UIV+2, and UIV-1 vertebrae approached, but did not reach significance (OR 2.913; 95% CI 0.797-10.646; P = 0.106). CONCLUSIONS: In larger cohorts, VBQ may prove to be a significant predictor of PJK following long-segment thoracolumbar fusion. However, Hounsfield units on CT have greater predictive power, suggesting preoperative workup for long-segment thoracolumbar fusion benefits from computed tomography versus magnetic resonance imaging alone to identify those at increased risk of PJK.

The Effect of C2 Muscular Exposure Technique on Radiographic and Clinical Outcomes After C2-T2 Posterior Cervical Fusion.

STUDY DESIGN: Retrospective cohort analysis. OBJECTIVE: To determine whether the C2 exposure technique was a predictor of change in cervical alignment and patient-reported outcomes measures (PROMs) after posterior cervical decompression and fusion (PCDF) for degenerative indications. BACKGROUND: In PCDF handling of the C2 posterior paraspinal musculature during the operative approach varies by surgeon technique. To date, no studies have investigated whether maintenance of the upper cervical semispinalis cervicis attachments as compared with complete reflection of upper cervical paraspinal musculature from the posterior bony elements is associated with superior radiographic and clinical outcomes after PCDF. PATIENTS AND METHODS: All adult patients who underwent C2-T2 PCDF for myelopathy or myeloradiculopathy at multi-institutional academic centers between 2013 and 2020 were retrospectively identified. Patients were dichotomized by the C2 exposure technique into semispinalis preservation or midline muscular reflection groups. Preoperative and short and long-term postoperative radiographic outcomes (upper cervical alignment, global alignment, and fusion status) and PROMs (Visual Analog Scale-Neck, Neck Disability Index, and Short Form-12) were collected. Univariate analysis compared patient factors, radiographic measures, and PROMs across C2 exposure groups. RESULTS: A total of 129 patients met the inclusion/exclusion criteria (73 muscle preservation and 56 muscle reflection). Patients in the muscular preservation group were on average younger (P= 0.005) and more likely to have bone morphogenic protein (P< 0.001) and C2 pars screws (P= 0.006) used during surgery. Preoperative to postoperative changes in C2 slope, C2 tilt, C2-C3 segmental lordosis, C2-C3 listhesis, C0-C2 Cobb angle, proximal junctional kyphosis, ADI, C1 lamina-occiput distance, C2 sagittal vertical axis, C2-C7 lordosis, and PROMs at all follow-up intervals did not vary significantly by C2 exposure technique. Likewise, there were no significant differences in fusion status, C2-C3 pseudoarthrosis, C2 screw loosening, and complication and revision rates between C2 exposure groups. CONCLUSIONS: Preservation of C2 semispinalis attachments versus muscular reflection did not significantly impact cervical alignment, clinical outcomes, or proximal junction complications in long-segment PCDF. LEVEL OF EVIDENCE: Level III.

The effect of C2 screw type on perioperative outcomes and long-term stability after C2-T2 posterior cervical decompression and fusion.

PURPOSE: To determine if C2 pedicle versus pars screw type predicts change in fusion status, C2 screw loosening, cervical alignment, and patient-reported outcomes measures (PROMs) after C2-T2 posterior cervical decompression and fusion (PDCF). METHODS: All adult patients who underwent C2-T2 PCDF for myelopathy or myeloradiculopathy between 2013-2020 were retrospectively identified. Patients were dichotomized by C2 screw type into bilateral C2 pedicle and bilateral C2 pars screw groups. Preoperative and short- and long-term postoperative radiographic outcomes and PROMs were collected. Univariate and multivariate analysis compared patient factors, fusion status, radiographic measures, and PROMs across groups. RESULTS: A total of 159 patients met the inclusion/exclusion criteria (76 bilateral pedicle screws, 83 bilateral pars screws). Patients in the C2 pars relative to C2 pedicle screw group were on average more likely to have bone morphogenic protein (p = 0.001) and four-millimeter diameter rods utilized intraoperatively (p = 0.033). There were no significant differences in total construct and C2-3 fusion rate, C2 screw loosening, or complication and revision rates between C2 screw groups in univariate and regression analysis. Changes in C2 tilt, C2-3 segmental lordosis, C0-2 Cobb angle, proximal junctional kyphosis, atlanto-dens interval, C1 lamina-occiput distance, C2 sagittal vertical axis, C2-7 lordosis, and PROMs at all follow-up intervals did not vary significantly by C2 screw type. CONCLUSION: There were no significant differences in fusion status, hardware complications, and radiographic and clinical outcomes based on C2 screw type following C2-T2 PCDF. Accordingly, intraoperative usage criteria can be flexible based on patient vertebral artery positioning and surgeon comfort level.

A Standardized Curriculum Improves Trainee Rod Bending Proficiency in Spinal Deformity Surgery. Results of a Prospective Randomized Controlled Educational Study.

INTRODUCTION: Surgical simulation is increasingly being accepted as a training platform to promote skill development and a safe surgical technique. Preliminary investigations in spine surgery show that simulation paired with educational intervention can markedly improve trainee performance. This study used a newly developed thoracolumbar fusion rod bending model to assess the effect of a novel educational curriculum and simulator training on surgical trainee rod bending speed and proficiency. METHODS: Junior (PGY1 to 2) and senior (PGY3-fellow) surgical trainees at a single academic institution were prospectively enrolled in a rod bending simulation using a T7-pelvis spinal fusion model. Participants completed two simulations, with 1 month between first and second attempts. Fifty percent of surgeons in each training level were randomized to receive an educational curriculum (rod bending technique videos and unlimited simulator practice) between simulation attempts. Rod bending simulation proficiency was determined by the percentage of participants who completed the task (conclusion at 20 minutes), time to task completion or conclusion, and number of incomplete set screws at task conclusion. Participants completed a preparticipation and postparticipation survey. Univariate analysis compared rod bending proficiency and survey results between education and control cohorts. RESULTS: Forty trainees (20 junior and 20 senior) were enrolled, with 20 participants randomized to the education and control cohorts. No notable differences were observed in the first simulation rod bending proficiency or preparticipation survey results between the education and control cohorts. In the second simulation, the education versus the control cohort demonstrated a significantly higher completion rate ( P = 0.01), shorter task time ( P = 0.009), fewer incomplete screws ( P = 0.003), and greater experience level ( P = 0.008) and comfort level ( P = 0.002) on postparticipation survey. DISCUSSION: Trainees who participated in a novel educational curriculum and simulator training relative to the control cohort improved markedly in rod bending proficiency and comfort level. Rod bending simulation could be incorporated in existing residency and fellowship surgical skills curricula. LEVEL OF EVIDENCE: I.

Automated measurements of interscrew angles in vertebral body tethering patients with deep learning.

BACKGROUND CONTEXT: Vertebral body tethering is the most popular nonfusion treatment for adolescent idiopathic scoliosis. The effect of the tether cord on the spine can be segmentally assessed by comparing the angle between two adjacent screws (interscrew angle) over time. Tether breakage has historically been assessed radiographically by a change in adjacent interscrew angle by greater than 5° between two sets of imaging. A threshold for growth modulation has not yet been established in the literature. These angle measurements are time consuming and prone to interobserver variability. PURPOSE: The purpose of this study was to develop an automated deep learning algorithm for measuring the interscrew angle following VBT surgery. STUDY DESIGN/SETTING: Single institution analysis of medical images. PATIENT SAMPLE: We analyzed 229 standing or bending AP or PA radiographs from 100 patients who had undergone VBT at our institution. OUTCOME MEASURES: Physiologic Measures: An image processing algorithm was used to measure interscrew angles. METHODS: A total of 229 standing or bending AP or PA radiographs from 100 VBT patients with vertebral body tethers were identified. Vertebral body screws were segmented by hand for all images and interscrew angles measured manually for 60 of the included images. A U-Net deep learning model was developed to automatically segment the vertebral body screws. Screw label maps were used to develop and tune an image processing algorithm which measures interscrew angles. Finally, the completed model and algorithm pipeline was tested on a 30-image test set. Dice score and absolute error were used to measure performance. RESULTS: Inter- and Intra-rater reliability for manual angle measurements were assessed with ICC and were both 0.99. The segmentation model Dice score against manually segmented ground truth across the 30-image test set was 0.96. The average interscrew angle absolute error between the algorithm and manually measured ground truth was 0.66° and ranged from 0° to 2.67° in non-overlapping screws (N=206). The primary modes of failure for the model were overlapping screws on a right thoracic/left lumbar construct with two screws in one vertebra and overexposed images. An algorithm step which determines whether an overlapping screw was present correctly identified all overlapping screws, with no false positives. CONCLUSION: We developed and validated an algorithm which measures interscrew angles for radiographs of vertebral body tether patients with an accuracy of within 1° for the majority of interscrew angles. The algorithm can process five images per second on a standard computer, leading to substantial time savings. This algorithm may be used for rapid processing of large radiographic databases of tether patients and could enable more rigorous definitions of growth modulation and cord breakage to be established.

Fractures in the ankylosed spine are associated with poor bone quality and lower hounsfield units.

STUDY DESIGN: Retrospective study INTRODUCTION: Patients with ankylosing spinal disorders have a higher risk of fractures, highlighting the need for bone health surveillance. Bone assessment by dual energy x-ray absorptiometry (DXA) is challenging due to abnormal bone formation but measurements by quantitative computed tomography (qCT) have demonstrated higher sensitivity and specificity. However, no studies have analyzed bone quality using qCT in the ankylosed spine population to assess three-column fracture characteristics and subsequent outcomes. METHODS: 106 patients with 115 three-column fractures were identified from 1999 to 2020. Patient demographics, Charlson comorbidity index, and injury severity score were extracted. Bone quality measured in Hounsfield units (HU), fracture characteristics, neurologic injury, and mortality were obtained. RESULTS: Most injuries occurred in the thoracic spine (70.4%) following a ground level fall (60.5%). HU adjacent to the fracture (127 HU) was significantly lower than the mobile segments (173 HU) (p < 0.001). Fracture adjacent HU was significantly lower in AS patients compared to DISH (109 vs 150 HU, p = 0.02, respectively) and were lower in fractures that resulted in a non-union or revision surgery (88 vs 137 HU, p = 0.04). Patients with longer fused segments were associated with multilevel and displaced fractures. CONCLUSIONS: Fracture adjacent HUs within the autofused segments were significantly lower than in the mobile segments, and longer fusion segments were associated with displaced, multilevel fractures. This study reinforces the importance of assessing patients for decreased HUs as well as better understand how the length of fused segments is associated with displaced, multilevel fractures. LEVEL OF EVIDENCE: Level III.

Paraspinal Sarcopenia is Associated With Worse Patient-Reported Outcomes Following Laminoplasty for Degenerative Cervical Myelopathy.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The present study is the first to assess the impact of paraspinal sarcopenia on patient-reported outcome measures (PROMs) following cervical laminoplasty. BACKGROUND: While the impact of sarcopenia on PROMs following lumbar spine surgery is well-established, the impact of sarcopenia on PROMs following laminoplasty has not been investigated. METHODS: We performed a retrospective review of patients undergoing laminoplasty from C4-6 at a single institution between 2010 and 2021. Two independent reviewers utilized axial cuts of T2-weighted magnetic resonance imaging sequences to assess fatty infiltration of the bilateral transversospinales muscle group at the C5-6 level and classify patients according to the Fuchs Modification of the Goutalier grading system. PROMs were then compared between subgroups. RESULTS: We identified 114 patients for inclusion in this study, including 35 patients with mild sarcopenia, 49 patients with moderate sarcopenia, and 30 patients with severe sarcopenia. There were no differences in preoperative PROMs between subgroups. Mean postoperative neck disability index scores were lower in the mild and moderate sarcopenia subgroups (6.2 and 9.1, respectively) than in the severe sarcopenia subgroup (12.9, P =0.01). Patients with mild sarcopenia were nearly twice as likely to achieve minimal clinically important difference (88.6 vs. 53.5%; P <0.001) and six times as likely to achieve SCB (82.9 vs. 13.3%; P =0.006) compared with patients with severe sarcopenia. A higher percentage of patients with severe sarcopenia reported postoperative worsening of their neck disability index (13 patients, 43.3%; P =0.002) and Visual Analog Scale Arm scores (10 patients, 33.3%; P =0.03). CONCLUSION: Patients with severe paraspinal sarcopenia demonstrate less improvement in neck disability and pain postoperatively and are more likely to report worsening PROMs following laminoplasty. LEVEL OF EVIDENCE: 3.

Is Severe Neck Pain a Contraindication to Performing Laminoplasty in Patients With Cervical Spondylotic Myelopathy?

STUDY DESIGN: Retrospective review. OBJECTIVE: The purpose of this study was to investigate the surgical outcomes in a cohort of patients with severe preoperative axial neck pain undergoing laminoplasty for cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: No study has investigated whether patients with severe axial symptoms may achieve satisfactory neck pain and disability outcomes after laminoplasty. METHODS: We performed a retrospective review of 91 patients undergoing C4-6 laminoplasty for CSM at a single academic institution between 2010 and 2021. Patient-reported outcome measures (PROMs), including Neck Disability Index (NDI), visual analog scale (VAS) Neck, and VAS Arm, were recorded preoperatively and at 6 months and 1 year postoperatively. Patients were stratified as having mild pain if VAS neck was 0-3, moderate pain if 4-6, and severe pain if 7-10. PROMs were then compared between subgroups at all the perioperative time points. RESULTS: Both the moderate and severe neck pain subgroups demonstrated a substantial improvement in VAS neck from preoperative to 6 months postoperatively (-3.1±2.2 vs. -5.6±2.8, respectively; P <0.001), and these improvements were maintained at 1 year postoperatively. There was no difference in VAS neck between subgroups at either the 6-month or 1-year postoperative time points. Despite the substantially higher mean NDI in the moderate and severe neck pain subgroups preoperatively, there was no difference in NDI at 6 months or 1 year postoperatively ( P =0.99). There were no differences between subgroups in the degree of cord compression, severity of multifidus sarcopenia, sagittal alignment, or complications. CONCLUSIONS: Patients with moderate and severe preoperative neck pain undergoing laminoplasty achieved equivalent PROMs at 6 months and 1 year as patients with mild preoperative neck pain. The results of this study highlight the multifactorial nature of neck pain in these patients and indicate that severe axial symptoms are not an absolute contraindication to performing laminoplasty in well-aligned patients with CSM.

Delayed open treatment of aortic penetration by a thoracic pedicle screw: illustrative case.

BACKGROUND: Iatrogenic aortic injury from pedicle screw malpositioning or anterior prominence in posterior spinal fusion represents a rare but potentially devasting complication. While intraoperative aortic injury is associated with hemodynamic instability, delayed presentations of pedicle screw aortic impingement or violation often present insidiously with pseudoaneurysm or vascular remodeling in clinically asymptomatic patients. Currently, there is a lack of guidance in the field for the recommended surveillance, urgency of operative intervention, and optimal surgical management of delayed pedicle screw aortic injuries. OBSERVATIONS: The following case study discusses the open treatment of delayed thoracic aortic penetration from an excessively long T12 pedicle screw in an asymptomatic adolescent patient with idiopathic scoliosis. The pedicle screw prominence anteriorly was corrected by burring the screw tip until it was flush with the vertebral body. The associated aortic injury was addressed with open vascular repair via primary anastomosis supplemented with a bovine pericardial patch. LESSONS: Complete aortic wall penetration from an excessively long thoracic pedicle screw with otherwise stable screw positioning may be addressed most effectively with a single anterior surgical approach for open aortic repair and screw tip burring.

Lower Hounsfield Units and Severe Multifidus Sarcopenia Are Independent Predictors of Increased Risk for Proximal Junctional Kyphosis and Failure Following Thoracolumbar Fusion.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: The purpose of the present study was to assess the impact of sarcopenia on the development of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following thoracolumbar spine fusion surgery using opportunistic evaluation of paraspinal fatty degeneration on preoperative magnetic resonance imaging. SUMMARY OF BACKGROUND DATA: While paraspinal sarcopenia has been shown to have detrimental consequences following posterior cervicothoracic fusions, the impact of paraspinal sarcopenia on PJK and PJF following thoracolumbar spine fusion surgery remains unknown. MATERIALS AND METHODS: We performed a retrospective review of patients who underwent posterior spine fusion surgery that extended caudally to the pelvis and terminated cranially between T10 and L2 between 2010 and 2017. The cohort was divided into three groups: (1) patients without PJK or PJF, (2) patients with PJK but no PJF, and (3) patients with PJF. Univariate and multivariate analyses were performed to determine risk factors for the development of proximal junctional complications. RESULTS: We identified 150 patients for inclusion in this study. Mean Hounsfield Units at the upper instrumented vertebra (UIV) was 148.3±34.5 in the cohort of patients without PJK or PJF, which was substantially higher than values recorded in the PJK (117.8±41.9) and PJF (118.8±41.8) subgroups (P<0.001). Severe multifidus sarcopenia was identified at a much higher rate in the subgroups of patients who developed PJK (76.0%) and PJF (78.9%) than in the subgroup of patients who developed neither PJK nor PJF (34.0%; P<0.001). Multivariate analysis demonstrated both low HU at the UIV and moderate-severe multifidus sarcopenia to be risk factors for the development of PJK and PJF. CONCLUSION: The results of this study suggest severe paraspinal sarcopenia and diminished bone density at the UIV impart an increased risk of developing PJK and PJF, while markers of systemic frailty such as modified Frailty Index and Charlson Comorbidity Index are not associated with an increased risk of these complications. LEVEL OF EVIDENCE: III.

Risk Factors for Allograft Subsidence Following Anterior Cervical Discectomy and Fusion.

OBJECTIVE: The purpose this study was to precisely characterize patterns of allograft subsidence following anterior cervical discectomy and fusion (ACDF) utilizing computed tomography scans, determine risk factors for cervical allograft subsidence, and investigate the impact of subsidence on pseudarthrosis rates. METHODS: We performed a retrospective review of patients undergoing 1-to 3-level ACDF utilizing allograft interbodies with anterior plating between 2011 and 2019. Subsidence measurements were performed by 2 independent reviewers on computed tomography scans obtained 6 months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplates were both ≤2 mm, moderate if the worst subsidence into the inferior- or superior endplate was between 2 and 4 mm, or severe if the worst subsidence into the inferior- or superior endplate was ≥4 mm. Multivariate analysis was performed to identify risk factors for the development of subsidence. RESULTS: We identified 98 patients (152 levels) for inclusion. A total of 73 levels demonstrated mild subsidence (≤2 mm), 61 demonstrated moderate subsidence (2-4 mm), and 18 demonstrated severe subsidence (≥4 mm). On multivariate analysis, risk factors for severe subsidence included excessive vertebral endplate resection and lower screw tip to vertebral body height ratio. Severe subsidence was associated with an increased rate of pseudarthrosis (94.1% vs. 13.6%) without an associated increase in reoperation rate. CONCLUSIONS: Following ACDF with allograft interbodies, 50% of interbodies will subside >2 mm and 10% of interbodies will subside >4 mm. Risk factors for severe subsidence should be mitigated to decrease the risk of pseudarthrosis.

Semispinalis Cervicis Sarcopenia is Associated With Worsening Cervical Sagittal Balance and Junctional Alignment Following Posterior Cervical Fusion for Myelopathy.

STUDY DESIGN: This was a retrospective cohort study. OBJECTIVE: The present study is the first to investigate whether cervical paraspinal sarcopenia is associated with cervicothoracic sagittal alignment parameters after posterior cervical fusion (PCF). SUMMARY OF BACKGROUND DATA: Few studies have investigated the association between sarcopenia and postoperative outcomes after cervical spine surgery. METHODS: We retrospectively reviewed patients undergoing PCF from C2-T2 at a single institution between the years 2017-2020. Two independent reviewers utilized axial cuts of T2-weighted magnetic resonance imaging sequences to perform Goutallier classification of the bilateral semispinalis cervicis (SSC) muscles. Cervical sagittal alignment parameters were compared between subgroups based upon severity of SSC sarcopenia. RESULTS: We identified 61 patients for inclusion in this study, including 19 patients with mild SSC sarcopenia and 42 patients with moderate or severe SSC sarcopenia. The moderate-severe sarcopenia subgroup demonstrated a significantly larger change in C2-C7 sagittal vertical axis (+6.8 mm) from the 3-month to 1-year postoperative follow-up in comparison to the mild sarcopenia subgroup (-2.0 mm; P =0.02). The subgroup of patients with moderate-severe sarcopenia also demonstrated an increase in T1-T4 kyphosis (10.9-14.2, P =0.007), T1 slope (28.2-32.4, P =0.003), and C2 slope (24.1-27.3, P =0.05) from 3-month to 1-year postoperatively and a significant decrease in C1-occiput distance (6.3-4.1, P =0.002) during this same interval. CONCLUSIONS: In a uniform cohort of patients undergoing PCF from C2-T2, SSC sarcopenia was associated with worsening cervicothoracic alignment from 3-month to 1-year postoperatively.

Titanium Cervical Cage Subsidence: Postoperative Computed Tomography Analysis Defining Incidence and Associated Risk Factors.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: Substantial variability in both the measurement and classification of subsidence limits the strength of conclusions that can be drawn from previous studies. The purpose of this study was to precisely characterize patterns of cervical cage subsidence utilizing computed tomography (CT) scans, determine risk factors for cervical cage subsidence, and investigate the impact of subsidence on pseudarthrosis rates. METHODS: We performed a retrospective review of patients who underwent one- to three-levels of anterior cervical discectomy and fusion (ACDF) utilizing titanium interbodies with anterior plating between the years 2018 and 2020. Subsidence measurements were performed by two independent reviewers on CT scans obtained 6 months postoperatively. Subsidence was then classified as mild if subsidence into the inferior and superior endplate were both ≤2 mm, moderate if the worst subsidence into the inferior or superior endplate was between 2 to 4 mm, or severe if the worst subsidence into the inferior or superior endplate was ≥4 mm. RESULTS: A total of 51 patients (100 levels) were included in this study. A total of 48 levels demonstrated mild subsidence (≤2 mm), 38 demonstrated moderate subsidence (2-4 mm), and 14 demonstrated severe subsidence (≥4 mm). Risk factors for severe subsidence included male gender, multilevel constructs, greater mean vertebral height loss, increased cage height, lower Taillard index, and lower screw tip to vertebral body height ratio. Severe subsidence was not associated with an increased rate of pseudarthrosis. CONCLUSION: Following ACDF with titanium cervical cages, subsidence is an anticipated postoperative occurrence and is not associated with an increased risk of pseudarthrosis.

Dynamic Radiographs Are Unreliable to Assess Arthrodesis Following Cervical Fusion: A Modeled Radiostereometric Analysis of Cervical Motion.

STUDY DESIGN: In vitro study. OBJECTIVE: The purpose of the present study was to utilize an idealized cervical spine model to determine whether the parallax effect or changes in the position of the spine relative to the x-ray generator influence intervertebral motion parameters on dynamic cervical spine radiographs. SUMMARY OF BACKGROUND DATA: The utility of flexion-extension radiographs in clinical practice remains in question due to poor reliability of the parameters utilized to measure motion. MATERIALS AND METHODS: A cervical spine model with tantalum beads inserted into the tip of each spinous process was utilized to measure interspinous process distance (IPD) on plain radiographs. The model was then manipulated to alter the generator angle and generator distance, and the IPD was measured. The impact of individual and combined changes in these parameters on IPD was assessed. Multivariate analysis was performed to identify independent drivers of variability in IPD measurements. RESULTS: Isolated changes in the generator distance and generator angle and combined changes in these parameters led to significant changes in the measured IPD at each intervertebral level in neutral, flexion, and extension, which, in many instances, exceeded an absolute change of >1 mm or >2 mm. Multivariate analysis revealed that generator distance and generator angle are both independent factors impacting IPD measurements that have an additive effect. CONCLUSIONS: In an idealized cervical spine model, small clinically feasible changes in spine position relative to the x-ray generator produced substantial variability in IPD measurements, with absolute changes that often exceeded established cutoffs for determining the presence of pathologic motion across a fused segment. This study further reinforces that motion assessment on dynamic radiographs is not a reliable method for determining the presence of an arthrodesis unless these sources of variability can be consistently eliminated. LEVEL OF EVIDENCE: 3.

Performing 2-Stage Circumferential Fusion in an Adolescent With High-Grade Spondylolisthesis: A Surgical Technique.

The surgical approach to high-grade spondylolisthesis at the lumbosacral junction remains controversial. Appropriate surgical techniques can be challenging with the potential for high complication rates, particularly with reduction. Multiple techniques have been described including posterior only reduction and instrumentation, posterior only instrumentation with in situ arthrodesis, and anterior-posterior reduction and instrumentation. Regardless of technique, the operative goals are to provide sufficient stability and biological support to promote bony fusion, maintain global balance, and decompress the neural elements while avoiding neurological complications. During instrumentation of a high-grade spondylolisthesis at the lumbosacral junction, it can be difficult to obtain access to the L5-S1 disc space for interbody insertion. We present a novel technique for improving access to the L5-S1 disc space through an osteotomy of the anterior-inferior aspect of the L5 vertebral body as part of a 2-stage circumferential fusion in the treatment of high-grade spondylolisthesis in an adolescent.

A Prospective Study of Lumbar Facet Arthroplasty in the Treatment of Degenerative Spondylolisthesis and Stenosis: Results from the Total Posterior Spine System (TOPS) IDE Study.

STUDY DESIGN: Prospective randomized Food and Drug Administration investigational device exemption clinical trial. OBJECTIVE: The purpose of the present study is to report the 1-year clinical and radiographic outcomes and safety profile of patients who underwent lumbar facet arthroplasty through implantation of the Total Posterior Spine System (TOPS) device. SUMMARY OF BACKGROUND DATA: Lumbar facet arthroplasty is one proposed method of dynamic stabilization to treat grade-1 spondylolisthesis with stenosis; however, there are currently no Food and Drug Administration-approved devices for facet arthroplasty. METHODS: Standard demographic information was collected for each patient. Radiographic parameters and patient-reported outcome measures were assessed preoperatively and at regular postoperative intervals. Complication and reoperation data were also collected for each patient. RESULTS: At the time of this study, 153 patients had undergone implantation of the TOPS device. The mean surgical time was 187.8 minutes and the mean estimated blood loss was 205.7cc. The mean length of hospital stay was 3.0 days. Mean Oswestry Disability Index, Visual Analog Score leg and back, and Zurich Claudication Questionnaire scores improved significantly at all postoperative time points ( P >0.001). There were no clinically significant changes in radiographic parameters, and all operative segments remained mobile at 1-year follow-up. Postoperative complications occurred in 11 patients out of the 153 patients (7.2%) who underwent implantation of the TOPS device. Nine patients (5.9%) underwent a total of 13 reoperations, 1 (0.6%) of which was for device-related failure owing to bilateral L5 pedicle screw loosening. CONCLUSIONS: Lumbar facet arthroplasty with the TOPS device demonstrated a statistically significant improvement in all patient-reported outcome measures and the ability to maintain motion at the index level while limiting sagittal translation with a low complication rate.

En bloc resection of a high cervical chordoma followed by reconstruction with a free vascularized fibular graft: illustrative case.

BACKGROUND: Wide excision of chordoma provides better local control than intralesional resection or definitive radiotherapy. The en bloc excision of high cervical chordomas is a challenging endeavor because of the complex anatomy of this region and limited reconstructive options. OBSERVATIONS: This is the first case report to describe reconstruction with a free vascularized fibular graft following the en bloc excision of a chordoma involving C1-3. LESSONS: This report demonstrates the durability of this construct at 10-year follow-up and is the first case report demonstrating satisfactory long-term oncological outcomes after a true margin-negative resection of a high cervical chordoma.