Freedman, Brett A.

Abstract Background Current approaches to diagnosing suspected native vertebral osteomyelitis (NVO) rely on imaging and microbiological workup, including blood and CT-guided biopsy cultures. These existing diagnostic methods often result in ambiguity, necessitating additional tests to distinguish NVO from its mimics. Our study aims to validate pilot findings demonstrating that an elevated neutrophil differential (PMN) in vertebral bone biopsy/ disc space fluid aspirate is associated with NVO. This may allow stratification of patients with suspected NVO into those who can be monitored closely versus those who may benefit from further invasive testing or empiric antibiotic therapy (Fig 1). Figure 1: Proposed workup of patients with suspected native vertebral osteomyelitis guided by disc space/ vertebral body neutrophil (PMN) differential. Methods This analysis examines a subset of patients from a prospective cohort study, enrolling adults referred to Mayo Clinic's neuroradiology department for spine biopsy. After collecting routine clinical specimens, the needle is rinsed with saline into an EDTA tube for automated cell count and differential analysis. To evaluate the predictive capacity of neutrophil (PMN) differential for NVO, logistic regression models were employed, and receiver operating characteristic (ROC) curve analyses were conducted for various PMN percentage cutoff points. Results In this preliminary analysis, 39 patients were included, comprising 7 patients with NVO and 32 patients with alternative diagnoses. Baseline characteristics are presented in Table 1. All NVO patients received antibiotics within two weeks of the spine biopsy. The median biopsy sample PMN percentage for NVO patients was 83.0 (77.5-88.0), compared to 65.0 (56.5-69.5) for those without NVO (p=0.005) (Fig 2A). The estimated relationship between the probability of NVO and each measure across the full range of percentages is illustrated in Fig 2B. The optimal ROC curve point corresponds to a PMN differential of 72.5% (sensitivity=0.86, specificity=0.81) (Fig 3).Table 1:Baseline Characteristics of Patients Included in the Preliminary AnalysisFigure 2:A) Distribution of spine biopsy neutrophil percent by native vertebral osteomyelitis (NVO) status, B) Loess nonparametric smoother showing the relationship between the probability of NVO and biopsy sample neutrophil percentage.Figure 3:ROC curve analysis of neutrophil percent and NVO Conclusion This preliminary analysis indicates that an elevated PMN differential in spine biopsy samples may serve as a valuable diagnostic tool for NVO, with results seemingly unaffected by recent antibiotic intake. The PMN differential cutoff of 72.5% exhibited notable sensitivity and specificity. Investigations are ongoing to further validate these findings Disclosures Brett Freedman, MD, Clear Choice Therapeutics: Stocks/Bonds|Medtronic: Grant/Research Support|Neuroinnovations: Stocks/Bonds Aaron J. Tande, M.D., Musculoskeletal Infection Society: Board Member|Wolters Kluwer Health - Lippincott Williams & Wilkins: Publishing royalties, financial or material support

Study design. Retrospective observational study of consecutive patients. Objective. The purpose of the study is to determine if a surgeon’s qualitative assessment of bone intraoperatively correlates with radiologic parameters of bone strength. Summary of Background Data. Preoperative radiologic assessment of bone can include modalities such as computed tomography (CT) Hounsfield units (HUs), dual-energy x-ray absorptiometry (DXA) bone mineral density with trabecular bone score (TBS) and magnetic resonance imaging vertebral bone quality (VBQ). Quantitative analysis of bone with screw insertional torque and pull-out strength measurement has been performed in cadaveric models and has been correlated to these radiologic parameters. However, these quantitative measurements are not routinely available for use in surgery. Surgeons anecdotally judge bone strength, but the fidelity of the intraoperative judgment has not been investigated. Methods. All adult patients undergoing instrumented posterior thoracolumbar spine fusion by one of seven surgeons at a single center over a 3-month period were included. Surgeons evaluated the strength of bone based on intraoperative feedback and graded each patient’s bone on a 5-point Likert scale. Two independent reviewers measured preoperative CT HUs and magnetic resonance imaging VBQ. Bone mineral density, lowest T-score, and TBS were extracted from DXA within 2 years of surgery. Results. Eighty-nine patients were enrolled and 16, 28, 31, 13, and 1 patients had Likert grade 1 (strongest bone), 2, 3, 4, and 5 (weakest bone), respectively. The surgeon assessment of bone correlated with VBQ (τ=0.15, P=0.07), CT HU (τ=−0.31, P<0.01), lowest DXA T-score (τ=−0.47, P<0.01), and TBS (τ=−0.23, P=0.06). Conclusion. Spine surgeons’ qualitative intraoperative assessment of bone correlates with preoperative radiologic parameters, particularly in posterior thoracolumbar surgeries. This information is valuable to surgeons as this supports the idea that decisions based on feel in surgery have a statistical foundation.

OBJECTIVE Spine metastases are commonly treated with radiotherapy for local tumor control; pathologic fracture is a potential complication of spinal radiotherapy. Both Hounsfield units (HUs) on CT and vertebral bone quality (VBQ) on MRI have been argued to predict stability as measured by odds of pathologic fracture, although it is unclear if there is a difference in the predictive power between the two methodologies. The objective of the present study was to examine whether one methodology is a better predictor of pathologic fracture following radiotherapy for mobile spine metastases. METHODS Patients who underwent radiotherapy (conventional external-beam radiation therapy, stereotactic body radiation therapy, or intensity-modulated radiation therapy) for mobile spine (C1–L5) metastases at a tertiary care center were retrospectively identified. Details regarding underlying pathology, patient demographics, and tumor morphology were collected. Vertebral involvement was assessed using the Weinstein-Boriani-Biagini (WBB) system. Bone quality of the non–tumor-involved bone was assessed on both pretreatment CT and MRI. Univariable analyses were conducted to identify independent predictors of fracture, and Kaplan-Meier analyses were used to identify significant predictors of time to pathologic fracture. Stepwise Cox regression analysis was used to determine independent predictors of time to fracture. RESULTS One hundred patients were included (mean age 62.7 ± 11.9 years; 61% male), of whom 35 experienced postradiotherapy pathologic fractures. The most common histologies were lung (22%), prostate (21%), breast (14%), and renal cell (13%). On univariable analysis, the mean HUs of the vertebrae adjacent to the fractured vertebra were significantly lower among those experiencing fracture; VBQ was not significantly associated with fracture odds. Survival analysis showed that average HUs ≤ 132, nonprostate pathology, involvement of ≥ 3 vertebral body segments on the WBB system, Spine Instability Neoplastic Score (SINS) ≥ 7, and the presence of axial pain all predicted increased odds of fracture (all p < 0.001). Cox regression found that HUs ≤ 132 (OR 2.533, 95% CI 1.257–5.103; p = 0.009), ≥ 3 WBB vertebral body segments involved (OR 2.376, 95% CI 1.132–4.987; p = 0.022), and axial pain (OR 2.036, 95% CI 0.916–4.526; p = 0.081) predicted increased fracture odds, while prostate pathology predicted decreased odds (OR 0.076, 95% CI 0.009–0.613; p = 0.016). Sensitivity analysis suggested that an HU threshold of ≤ 132 and a SINS of ≥ 7 identified patients at increased risk of fracture. CONCLUSIONS The present results suggest that bone density surrogates as measured on CT, but not MRI, can be used to predict the risk of pathologic fracture following radiotherapy for mobile spine metastases. More extensive vertebral body involvement and the presence of mechanical axial pain additionally predict increased fracture odds.

Study Design. Retrospective cohort study. Objective. Hounsfield units (HUs) are known to correlate with clinical outcomes, but no study has evaluated how they correlate with biomechanical computed tomography (BCT) and dual-energy x-ray absorptiometry (DXA) measurements. Summary of Background. Low bone mineral density (BMD) represents a major risk factor for fracture and poor outcomes following spine surgery. DXA can provide regional BMD measurements but has limitations. Opportunistic HUs provide targeted BMD estimates; however, they are not formally accepted for diagnosing osteoporosis in current guidelines. More recently, BCT analysis has emerged as a new modality endorsed by the International Society for Clinical Densitometry for assessing bone strength. Methods. Consecutive cases from 2017 to 2022 at a single institution were reviewed for patients who underwent BCT in the thoracolumbar spine. BCT-measured vertebral strength, trabecular BMD, and the corresponding American College of Radiology Classification were recorded. DXA studies within three months of the BCT were reviewed. Pearson Correlation Coefficients were calculated, and receiver-operating characteristic curves were constructed to assess the predictive capacity of HUs. Threshold analysis was performed to identify optimal HU values for identifying osteoporosis and low BMD. Results. Correlation analysis of 114 cases revealed a strong relationship between HUs and BCT vertebral strength (r=0.69; P<0.0001; R 2=0.47) and trabecular BMD (r=0.76; P<0.0001; R 2=0.58). However, DXA poorly correlated with opportunistic HUs and BCT measurements. HUs accurately predicted osteoporosis and low BMD (Osteoporosis: C=0.95, 95% CI 0.89–1.00; Low BMD: C=0.87, 95% CI 0.79–0.96). Threshold analysis revealed that 106 and 122 HUs represent optimal thresholds for detecting osteoporosis and low BMD. Conclusion. Opportunistic HUs strongly correlated with BCT-based measures, while neither correlated strongly with DXA-based BMD measures in the thoracolumbar spine. HUs are easy to perform at no additional cost and provide accurate BMD estimates at noninstrumented vertebral levels across all American College of Radiology-designated BMD categories.

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

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.

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.

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.

OBJECTIVE Several growth-preserving surgical techniques are employed in the management of early-onset scoliosis (EOS). The authors’ objective was to compare the use of traditional growing rods (TGRs), magnetically controlled growing rods (MCGRs), Shilla growth guidance techniques, and vertically expanding prosthetic titanium ribs (VEPTRs) for the management of EOS. METHODS A systematic review of electronic databases, including Ovid MEDLINE and Cochrane, was performed. Outcomes of interest included correction of Cobb angle, T1–S1 distance, and complication rate, including alignment, hardware failure and infection, and planned and unplanned reoperation rates. The percent changes and 95% CIs were pooled across studies using random-effects meta-analysis. RESULTS A total of 67 studies were identified, which included 2021 patients. Of these, 1169 (57.8%) patients underwent operations with TGR, 178 (8.8%) Shilla growth guidance system, 448 (22.2%) MCGR, and 226 (11.1%) VEPTR system. The mean ± SD age of the cohort was 6.9 ± 1.2 years. The authors found that the Shilla technique provided the most significant improvement in coronal Cobb angle immediately after surgery (mean [95% CI] 64.3% [61.4%–67.2%]), whereas VEPTR (27.6% [22.7%–33.6%]) performed significantly worse. VEPTR also performed significantly worse than the other techniques at final follow-up. The techniques also provided comparable gains in T1–S1 height immediately postoperatively (mean [95% CI] 10.7% [8.4%–13.0%]); however, TGR performed better at final follow-up (21.4% [18.7%–24.1%]). Complications were not significantly different among the patients who underwent the Shilla, TGR, MCGR, and VEPTR techniques, except for the rate of infections. The TGR technique had the lowest rate of unplanned reoperations (mean [95% CI] 15% [10%–23%] vs 24% [19%–29%]) but the highest number of planned reoperations per patient (5.31 [4.83–5.82]). The overall certainty was also low, with a high risk of bias across studies. CONCLUSIONS This analysis suggested that the Shilla technique was associated with a greater early coronal Cobb angle correction, whereas use of VEPTR was associated with a lower correction rate at any time point. TGR offered the most significant height gain at final follow-up. The complication rates were comparable across all surgical techniques. The optimal surgical approach should be tailored to individual patients, taking into consideration the strengths and limitations of each option.

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