The anatomical positioning change of retroperitoneal organs in prone and lateral position: an assessment for single-prone position lateral lumbar surgery.

PURPOSE: There are reports that performing lateral lumbar interbody fusion (LLIF) in a prone, single position (single-prone LLIF) can be done safely in the prone position because the retroperitoneal organs reflect anteriorly with gravity. However, only a few study has investigated the safety of single-prone LLIF and retroperitoneal organ positioning in the prone position. We aimed to investigate the positioning of retroperitoneal organs in the prone position and evaluate the safety of single-prone LLIF surgery. METHODS: A total of 94 patients were retrospectively reviewed. The anatomical positioning of the retroperitoneal organs was evaluated by CT in the preoperative supine and intraoperative prone position. The distances from the centre line of the intervertebral body to the organs including aorta, inferior vena cava, ascending and descending colons, and bilateral kidneys were measured for the lumbar spine. An "at risk" zone was defined as distance less than 10 mm anterior from the centre line of the intervertebral body. RESULTS: Compared to supine preoperative CTs, bilateral kidneys at the L2/3 level as well as the bilateral colons at the L3/4 level had statistically significant ventral shift with prone positioning. The proportion of retroperitoneal organs within the at-risk zone ranged from 29.6 to 88.6% in the prone position. CONCLUSIONS: The retroperitoneal organs shifted ventrally with prone positioning. However, the amount of shift was not large enough to avoid risk for organ injuries and substantial proportion of patients had organs within the cage insertion corridor. Careful preoperative planning is warranted when considering single-prone LLIF.

Dermal ultrasound measurements for bone quality assessment : An investigation of advanced glycation endproducts derived from confocal fluorescence microscopy.

Bone quality is increasingly being recognized in the assessment of fracture risk. Nonenzymatic collagen cross-linking with the accumulation of advanced glycation end products stiffens and embrittles collagen fibers thus increasing bone fragility. Echogenicity is an ultrasound (US) parameter that provides information regarding the skin collagen structure. We hypothesized that both skin and bone collagen degrade in parallel fashion. Prospectively collected data of 110 patients undergoing posterior lumbar fusion was analyzed. Preoperative skin US measurements were performed in the lumbar region to assess dermal thickness and echogenicity. Intraoperative bone biopsies from the posterior superior iliac spine were obtained and analyzed with confocal fluorescence microscopy for fluorescent advanced glycation endproducts (fAGEs). Pearson's correlation was calculated to examine relationships between  (1) US and fAGEs, and (2) age and fAGEs stratified by sex. Multivariable linear regression analysis with adjustments for age, sex, body mass index (BMI), diabetes mellitus, and hemoglobin A1c (HbA1c) was used to investigate associations between US and fAGEs. One hundred and ten patients (51.9% female, 61.6 years, BMI 29.8 kg/m2 ) were included in the analysis. In the univariate analysis cortical and trabecular fAGEs decreased with age, but only in women (cortical: r = -0.32, p = 0.031; trabecular: r = -0.32; p = 0.031). After adjusting for age, sex, BMI, diabetes mellitus, and HbA1c, lower dermal (ß = 1.01; p = 0.012) and subcutaneous (ß = 1.01; p = 0.021) echogenicity increased with increasing cortical fAGEs and lower dermal echogenicity increased with increasing trabecular fAGEs (ß = 1.01; p = 0.021). This is the first study demonstrating significant associations between skin US measurements and in vivo bone quality parameters in lumbar fusion patients. As a noninvasive assessment tool, skin US measurements might be incorporated into future practice to investigate bone quality in spine surgery patients.

Fusion assessment in standalone lateral lumbar interbody fusion: 3D-printed titanium versus polyetheretherketone (PEEK) cages.

Background: Compare fusion at two independent timepoints (early and late) between 3D-printed titanium (Ti) and polyetheretherketone (PEEK) cages in patients undergoing standalone lateral lumbar interbody fusion (SA-LLIF). We hypothesized that 3D-printed Ti cages show higher fusion rates at an early timepoint compared to PEEK. Methods: A retrospective study of patients undergoing SA-LLIF with 3D-printed Ti cages and PEEK cages between 11/2016 and 01/2020 at a single academic institution was done. Fusion was assessed for each treated level using multiplanar reconstructed computed tomography (CT) scans. Presence of fully bridged interbody trabecular bone or continuous bone centered in the cage was considered as fusion. Results: In total, 91 patients (136 levels) were included in the final analysis, 49 patients (72 levels) in the early group and 42 patients (64 levels) in the late group. CT scans were performed on average 8.2±1.8 months postoperatively for the early group and 18.9±7.7 months for the late group. In the early group, fusion was significantly higher for 3D-printed Ti cages compared to PEEK cages (95.8% versus 62.5%; P=0.002), whereas in the late group no significant difference was seen (94.7% versus 80.0%; P=0.258). Conclusions: In SA-LLIF, porous 3D-printed Ti cages showed significantly higher fusion rates at an early timepoint compared to PEEK. However, the difference in fusion rates between 3D-printed Ti cages and PEEK cages was found not to be significantly different at a later timepoint in another patient group. This might support the assumption that 3D-printed Ti cages with a porous architecture are more osteoconductive compared to PEEK and tend to fuse earlier.

The predictive value of a novel site-specific MRI-based bone quality assessment, endplate bone quality (EBQ), for severe cage subsidence among patients undergoing standalone lateral lumbar interbody fusion.

BACKGROUND CONTEXT: Studies have shown that site-specific bone density measurements had more predictive value for complications than standard whole-region measurements. Recently, MRI-based assessments of vertebral bone quality (VBQ) were introduced. However, there have been few studies that investigate the association between site-specific MRI bone assessment and osteoporosis-related complications in patients undergoing lumbar interbody fusion. In this work, we created a novel site-specific MRI-based assessment of the endplate bone quality (EBQ) and assessed its predictive value for severe cage subsidence following standalone lateral lumbar interbody fusion (SA-LLIF). PURPOSE: To investigate the predictive value of a novel MRI-based bone assessment for severe cage subsidence after SA-LLIF. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: Patients who underwent SA-LLIF from 2008 to 2019 at a single, academic institution with available preoperative lumbar CT and T1-weighted MRIs. OUTCOME MEASURES: Association between EBQ and severe subsidence after SA-LLIF. METHODS: We retrospectively reviewed the records of SA-LLIF patients treated between 2008 and 2019. EBQ was measured using preoperative non-contrast T1-weighted MRIs of the lumbar spine. EBQ was defined as the average value of signal intensity of both endplates divided by that of the cerebrospinal fluid space at the level of L3. Bivariate and multivariable analyses with generalized linear mixed models were performed and set binary severe subsidence as the outcome. RESULTS: Two hundred five levels in 89 patients were included. Fifty levels (24.4%) demonstrated severe subsidence. Bone mineral density measured by quantitative computed tomography was significantly lower in the subsidence group. Both VBQ and EBQ were significantly higher in the subsidence group. The EBQ plus Modic change (MC) model demonstrated that the effect of EBQ was independent of MC. In multivariate analyses adjusted with QCT-vBMD, EBQ showed a significant association with cage subsidence whereas VBQ only showed a marginal trend. The EBQ-based prediction model for severe subsidence showed better goodness of fit compared to the VBQ-based model. CONCLUSIONS: High EBQ was an independent factor for severe cage subsidence after SA-LLIF and the EBQ-based model showed better goodness of fit compared to VBQ- or MC-based models. EBQ assessment before SA-LLIF may provide insight into a patient's risk for severe subsidence.

Preoperative MRI-based vertebral bone quality (VBQ) score assessment in patients undergoing lumbar spinal fusion.

BACKGROUND CONTEXT: The importance of bone status assessment in spine surgery is well recognized. The current gold standard for assessing bone mineral density is dual-energy X-ray absorptiometry (DEXA). However, DEXA has been shown to overestimate BMD in patients with spinal degenerative disease and obesity. Consequently, alternative radiographic measurements using data routinely gathered during preoperative evaluation have been explored for the evaluation of bone quality and fracture risk. Opportunistic quantitative computed tomography (QCT) and more recently, the MRI-based vertebral bone quality (VBQ) score, have both been shown to correlate with DEXA T-scores and predict osteoporotic fractures. However, to date the direct association between VBQ and QCT has not been studied. PURPOSE: The objective of this study was to evaluate the correlation between VBQ and spine QCT BMD measurements and assess whether the recently described novel VBQ score can predict the presence of osteopenia/osteoporosis diagnosed with QCT. STUDY DESIGN/SETTING: Cross-sectional study using retrospectively collected data. PATIENT SAMPLE: Patients undergoing lumbar fusion from 2014-2019 at a single, academic institution with available preoperative lumbar CT and T1-weighted MRIs were included. OUTCOME MEASURES: Correlation of the VBQ score with BMD measured by QCT, and association between VBQ score and presence of osteopenia/osteoporosis. METHODS: Asynchronous QCT measurements were performed. The average L1-L2 BMD was calculated and patients were categorized as either normal BMD (>120 mg/cm3) or osteopenic/osteoporotic (≤120 mg/cm3). The VBQ score was calculated by dividing the median signal intensity of the L1-L4 vertebral bodies by the signal intensity of the cerebrospinal fluid on midsagittal T1-weighted MRI images. Inter-observer reliability testing of the VBQ measurements was performed. Demographic data and the VBQ score were compared between the normal and osteopenic/osteoporotic group. To determine the area-under-curve (AUC) of the VBQ score as a predictor of osteopenia/osteoporosis receiver operating characteristic (ROC) analysis was performed. VBQ scores were compared with QCT BMD using the Pearson's correlation. RESULTS: A total of 198 patients (53% female) were included. The mean age was 62 years and the mean BMI was 28.2 kg/m2. The inter-observer reliability of the VBQ measurements was excellent (ICC of 0.90). When comparing the patients with normal QCT BMD to those with osteopenia/osteoporosis, the patients with osteopenia/osteoporosis were significantly older (64.9 vs. 56.7 years, p<.0001). The osteopenic/osteoporotic group had significantly higher VBQ scores (2.6 vs. 2.2, p<.0001). The VBQ score showed a statistically significant negative correlation with QCT BMD (correlation coefficient = -0.358, 95% CI -0.473 - -0.23, p<.001). Using a VBQ score cutoff value of 2.388, the categorical VBQ score yielded a sensitivity of 74.3% and a specificity of 57.0% with an AUC of 0.7079 to differentiate patients with osteopenia/osteoporosis and with normal BMD. CONCLUSIONS: We found that the VBQ score showed moderate diagnostic ability to differentiate patients with normal BMD versus osteopenic/osteoporotic BMD based on QCT. VBQ may be an interesting adjunct to clinically performed bone density measurements in the future.

Workers' Compensation Status in Association with a High NDI Score Negatively Impacts Post-Operative Dysphagia and Dysphonia Following Anterior Cervical Fusion.

BACKGROUND: Anterior cervical discectomy and fusion (ACDF) is a safe and effective procedure but has approach-related complications like postoperative dysphagia and dysphonia (PDD). Patient-reported outcome measures including the Hospital for Special Surgery Dysphagia and Dysphonia Inventory (HSS-DDI) have been used for the assessment of PDD. Various factors have been described that affect ACDF outcomes, and our aim was to investigate the effect of workers' compensation (WC) status. METHODS: We included patients who underwent ACDF from 2015 to 2018 stratified according to insurance status: WC/non-WC. PDDs were assessed using the HSS-DDI score. We conducted logistic regression analyses. Statistical significance was set at P < 0.05. RESULTS: We included 287 patients, 44 (15.33%) WC and 243 (84.67%) non-WC. A statistical comparison revealed a clinically relevant difference in the HSS-DDI total score and both subdomains (P = 0.015; dysphagia P = 0.021; dysphonia P = 0.002). Additional logistic regression analysis adjusting for preoperative Neck Disability Index scores resulted in no clinically relevant differences in the HSS-DDI total score and both subdomains (total score P = 0.420; dysphagia P = 0.531; dysphonia 0.315). CONCLUSIONS: WC status was associated with a worse HSS-DDI score but could not be shown to be an independent risk factor for PDD. The preoperative NDI score was a strong predictor for PDD with a clinically relevant difference in the HSS DDI score (P < 0.0001). Surgeon awareness of risk factors for PDD such as WC status, even if it could not be shown as independent, is important as it may influence surgical decision making and managing patient expectations.

C2 Pedicle Sclerosis Grading, More Than Diameter, Predicts Surgeons' Preoperative Assessment of Safe Screw Placement: A Novel Classification System.

BACKGROUND: The preoperative assessment of C2 morphology is important for safe instrumentation. Sclerotic changes are often seen in C2 pedicles. Evaluating the diameter measurements solely might not accurately assess the safety of screw insertion. We have proposed a novel grading system of the C2 pedicle that includes sclerosis and evaluated the predictive value of this grading system with the surgeon's safety evaluation. METHODS: We reviewed and measured the dimensional values in 220 cervical computed tomography angiograms. Additionally, we used a grading system that divides the findings into 5 grades according to the width measurement and degree of sclerosis in the C2 pedicle. Two spine surgeons independently classified the pedicles as follows: safe (minimal risk of pedicle violation), caution needed (caution to minimize pedicle violation), or dangerous (a high risk of pedicle violation). Finally, we compared the measurements and the surgeons' safety assessments. RESULTS: A total of 411 pedicles of 203 patients (mean age, 69.5 years; 49.5% women) were included. Of the 411 C2 pedicles, 170 were classified as high risk by ≥1 surgeon. Between the dimensional measurements and grading system, the sclerotic grade showed the best predictive value. CONCLUSIONS: We have introduced a novel tool to evaluate the safety of C2 pedicle screw placement. Our results suggest that our pedicle width-sclerosis grading system is reproducible and predicts the surgeon's assessment of safe screw placement better than C2 pedicle diametrical measurements alone.

Does the Addition of Either a Lateral or Posterior Interbody Device to Posterior Instrumented Lumbar Fusion Decrease Cost Over a 6-Year Period?

STUDY DESIGN: Retrospective case-control study. OBJECTIVES: Few studies have compared the costs of single-level (1) posterior instrumented fusion alone (PSF), (2) posterior interbody fusion with PSF (PLIF), and (3) lateral interbody fusion with PSF (circumferential LLIF). The purpose of this study was to compare costs associated with these procedures. METHODS: Charts were reviewed and patients followed-up with a telephone questionnaire. Medicare reimbursement data was used for cost estimation from the payer's perspective. Multivariate survival analysis was performed to assess time to elevated resource use (greater than 90% of study patients or $68 672). RESULTS: A total of 337 patients (PSF, 45; PLIF, 222; circumferential LLIF, 70) were included (63% follow-up at 6 years). PSF and circumferential LLIF patients were 3 times more likely to reach the cutoff value compared with PLIF patients (P = .017). CONCLUSIONS: Circumferential LLIF and PSF patients were more likely to have higher resource use than PLIF patients and thus incur greater costs at 6-year follow-up.

Cervical Spinal Fusion: 16-Year Trends in Epidemiology, Indications, and In-Hospital Outcomes by Surgical Approach.

BACKGROUND: The rate of cervical spinal fusion has been increasing significantly. However, there is a paucity of literature describing trends based on surgical approach using complete population databases. We investigated the approach-based trends in epidemiology, indications, and in-hospital outcomes of cervical spinal fusion. METHODS: New York's Statewide Planning and Research Cooperative System database was queried to identify patients who underwent primary subaxial cervical fusion from 1997 to 2012. Demographic and clinical information was obtained. Subgroup analyses were performed based on surgical approach: anterior (A), posterior (P), and circumferential (C). RESULTS: A total of 87,045 cervical fusions were included. Over the study period, the population-adjusted annual fusion rate increased from 23.7 to 50.6 per 100,000 population (P < 0.001). A fusion was most common (85.2%), followed by P (12.3%), and C (2.5%). Mean ages were 49.8 ± 11.9, 59.9 ± 15.2, and 55.1 ± 14.5 years (P < 0.001), respectively. Although rates remained steady among younger patients, they increased for older patients. Overall, degenerative conditions were the predominant indications for surgery and increased in rate over time. The mean length of stay was: A, 3.1 ± 10.5; P, 9.1 ± 14.1; and C, 14.1 ± 22.5 days (P < 0.001). Rates of in-hospital complications were A, 3.0%; P, 10.5%; and C, 18.9% (P < 0.001), and mortality was A, 0.3%, P, 1.8%, and C, 2.5% (P < 0.001). CONCLUSIONS: The rate of subaxial spinal fusions increased 114% from 1997 to 2012 in New York State. Rates remained stable in younger patients but increased in the older population. Preoperative indications and postoperative courses differed significantly among the various approaches, with patients undergoing anterior fusion having better short-term outcomes.

Shared decision-making in orthopaedic surgery.

BACKGROUND: The process of clinical decision-making and the patient-physician relationship continue to evolve. Increasing patient involvement in clinical decision-making is embodied in the concept of "shared decision-making" (SDM), in which the patient and physician share responsibility in the clinical decision-making process. Various patients' decision aid tools have been developed to enhance this process. QUESTIONS/PURPOSES: We therefore (1) describe decision-making models; (2) discuss the different types of patients' decision aids available to practice SDM; and (3) describe the practice and early impact of SDM on clinical orthopaedic surgery. METHODS: We performed a search of the literature using PubMed/MEDLINE and Cochrane Library. We identified studies related to shared decision-making and the use of patients' decision aids in orthopaedics. The search resulted in 113 titles, of which 21 were included with seven studies on patients' decision aid use specifically in orthopaedics. RESULTS: Although limited studies suggest the use of patients' decision aids may enhance decision-making, conclusions about the use of these aids in orthopaedic clinical practice cannot be made and further research examining the best type, timing, and content of patients' decision aids that will lead to maximum patient involvement and knowledge gains with minimal clinical workflow interruption are needed. CONCLUSION: In clinical practice today, patients are increasingly involved in clinical decision-making. Further research on SDM in orthopaedic surgery examining the feasibility and impact on practice, on patients' willingness and ability to actively participate in shared decision-making, and the timing and type of patients' decision aids appropriate for use is still needed.