Do expandable cage size and number of cages matter in transforaminal lumbar interbody fusion at L5-S1? A comparative biomechanical analysis using finite element modeling.

OBJECTIVE: Expandable transforaminal lumbar interbody fusion (TLIF) cages were designed to address the limitations of static cages. Bilateral cage insertion can potentially enhance stability, fusion rates, and segmental lordosis. However, the benefits of unilateral versus bilateral expandable cages with varying sizes in TLIF remain unclear. This study used a validated finite element spine model to compare the biomechanical properties of L5-S1 TLIF by using differently sized expandable cages inserted unilaterally or bilaterally. METHODS: A finite element model of X-PAC expandable lumbar cages was created and used at the L5-S1 level. This model had cage dimensions of 9 mm in height, 15° in lordosis, and varying widths and lengths. Various placements (unilateral vs bilateral) and sizes were examined under pure moment loading to evaluate range of motion, adjacent-segment motion, and endplate stress. RESULTS: Stability at the L5-S1 level decreased when smaller cages were used in both the unilateral and bilateral cage models. In the unilateral model, cage 1 (the smallest cage) resulted in 47.9% more motion at the L5-S1 level compared to cage 5 (the largest cage) in flexion, as well as 64.8% more motion in extension. Similarly, in the bilateral TLIF model, bilateral cage 1 led to 49.4% more motion at the L5-S1 level in flexion and 73.4% more motion in extension compared to bilateral cage 5. Unilateral insertion of cage 5 provided superior stability in flexion and surpassed cages 1-3 in extension when compared to cages inserted either unilaterally or bilaterally. Reduced motion at L5-S1 correlated with increased adjacent-segment motion at L4-5. Bilateral TLIF resulted in greater adjacent-segment motion compared to unilateral TLIF with the same-size cages. Inferior endplates experienced higher stress during flexion and extension than superior endplates, with this difference being more pronounced in the bilateral model. In bilateral cage placement, stress differences ranged from 46.3% to 60.0%, while they ranged from 1.1% to 9.6% in unilateral cages. Qualitative analysis revealed increased focal stress in unilateral cages versus bilateral cages. CONCLUSIONS: The authors' study shows that using a large unilateral TLIF cage may offer better stability than the bilateral insertion of smaller cages. While large bilateral cages increase adjacent-segment motion, they also provide a uniform stress distribution on the endplates. These findings deepen our understanding of the biomechanics of the available expandable TLIF cages.

Management of a recurrent spinal arachnoid cyst presenting as arachnoiditis in the setting of spontaneous spinal subarachnoid hemorrhage: illustrative case.

BACKGROUND: Spontaneous spinal subarachnoid hemorrhage is a rare pathological entity with a variety of presentations depending on the underlying etiology, which often remains cryptogenic. The literature is sparse regarding the most efficacious treatment or management option, and there is no consensus on follow-up time or modalities. Additionally, there are very few reports that include operative videos, which is provided herein. OBSERVATIONS: The authors present a case of spontaneous spinal subarachnoid hemorrhage without an underlying etiology in a patient with progressive myelopathy, back pain, and lower-extremity paresthesias. She presented to our institution, and because of progressive worsening of her symptoms and the development of compressive arachnoid cysts, she underwent thoracic laminectomies for evacuation of subdural fluid, fenestration of the arachnoid cysts, and lysis of significant arachnoid adhesions. Her clinical course was further complicated by the recurrence of worsening myelopathy and the development of a large compressive arachnoid cyst with further arachnoiditis. The patient underwent repeat surgical intervention for cyst decompression with an improvement in symptoms. LESSONS: This case highlights the importance of long-term follow-up for these complicated cases with an emphasis on repeat magnetic resonance imaging. Unfortunately, surgical intervention is associated with short-term relief of the symptoms and no significant nonoperative management is available for these patients.

What is the effect of preoperative depression on outcomes after minimally invasive surgery for adult spinal deformity? A prospective cohort analysis.

OBJECTIVE: Depression has been implicated with worse immediate postoperative outcomes in adult spinal deformity (ASD) correction, yet the specific impact of depression on those patients undergoing minimally invasive surgery (MIS) requires further clarity. This study aimed to evaluate the role of depression in the recovery of patients with ASD after undergoing MIS. METHODS: Patients who underwent MIS for ASD with a minimum postoperative follow-up of 1 year were included from a prospectively collected, multicenter registry. Two cohorts of patients were identified that consisted of either those affirming or denying depression on preoperative assessment. The patient-reported outcome measures (PROMs) compared included scores on the Oswestry Disability Index (ODI), numeric rating scale (NRS) for back and leg pain, Scoliosis Research Society Outcomes Questionnaire (SRS-22), SF-36 physical component summary, SF-36 mental component summary (MCS), EQ-5D, and EQ-5D visual analog scale. RESULTS: Twenty-seven of 147 (18.4%) patients screened positive for preoperative depression. The nondepressed cohort had an average of 4.83 levels fused, and the depressed cohort had 5.56 levels fused per patient (p = 0.267). At 1-year follow-up, 10 patients still reported depression, representing a 63% decrease. Postoperatively, both cohorts demonstrated improvement in their PROMs; however, at 1-year follow-up, those without depression had statistically better outcomes based on the EQ-5D, MCS, and SRS-22 scores (p < 0.05). Patients with depression continued to experience higher NRS leg scores at 1-year follow-up (3.63 vs 2.22, p = 0.018). After controlling for covariates, the authors found that depression significantly impacted only 1-year follow-up MCS scores (ß = 8.490, p < 0.05). CONCLUSIONS: Depressed and nondepressed patients reported similar improvements after MIS surgery, except MCS scores were more likely to improve in nondepressed patients.

Cervical spondylotic myelopathy and driving abilities: defining the prevalence and long-term postoperative outcomes using the Quality Outcomes Database.

OBJECTIVE: Cervical spondylotic myelopathy (CSM) can cause significant difficulty with driving and a subsequent reduction in an individual's quality of life due to neurological deterioration. The positive impact of surgery on postoperative patient-reported driving capabilities has been seldom explored. METHODS: The CSM module of the Quality Outcomes Database was utilized. Patient-reported driving ability was assessed via the driving section of the Neck Disability Index (NDI) questionnaire. This is an ordinal scale in which 0 represents the absence of symptoms while driving and 5 represents a complete inability to drive due to symptoms. Patients were considered to have an impairment in their driving ability if they reported an NDI driving score of 3 or higher (signifying impairment in driving duration due to symptoms). Multivariable logistic regression models were fitted to evaluate mediators of baseline impairment and improvement at 24 months after surgery, which was defined as an NDI driving score < 3. RESULTS: A total of 1128 patients who underwent surgical intervention for CSM were included, of whom 354 (31.4%) had baseline driving impairment due to CSM. Moderate (OR 2.3) and severe (OR 6.3) neck pain, severe arm pain (OR 1.6), mild-moderate (OR 2.1) and severe (OR 2.5) impairment in hand/arm dexterity, severe impairment in leg use/walking (OR 1.9), and severe impairment of urinary function (OR 1.8) were associated with impaired driving ability at baseline. Of the 291 patients with baseline impairment and available 24-month follow-up data, 209 (71.8%) reported postoperative improvement in their driving ability. This improvement seemed to be mediated particularly through the achievement of the minimal clinically important difference (MCID) in neck pain and improvement in leg function/walking. Patients with improved driving at 24 months noted higher postoperative satisfaction (88.5% vs 62.2%, p < 0.01) and were more likely to achieve a clinically significant improvement in their quality of life (50.7% vs 37.8%, p < 0.01). CONCLUSIONS: Nearly one-third of patients with CSM report impaired driving ability at presentation. Seventy-two percent of these patients reported improvements in their driving ability within 24 months of surgery. Surgical management of CSM can significantly improve patients' driving abilities at 24 months and hence patients' quality of life.

Impact of Educational Background on Preoperative Disease Severity and Postoperative Outcomes Among Patients With Cervical Spondylotic Myelopathy.

STUDY DESIGN: Retrospective review of a prospectively maintained database. OBJECTIVE: Assess differences in preoperative status and postoperative outcomes among patients of different educational backgrounds undergoing surgical management of cervical spondylotic myelopathy (CSM). SUMMARY OF BACKGROUND DATA: Patient education level (EL) has been suggested to correlate with health literacy, disease perception, socioeconomic status (SES), and access to health care. METHODS: The CSM data set of the Quality Outcomes Database (QOD) was queried for patients undergoing surgical management of CSM. EL was grouped as high school or below, graduate-level, and postgraduate level. The association of EL with baseline disease severity (per patient-reported outcome measures), symptoms >3 or ≤3 months, and 24-month patient-reported outcome measures were evaluated. RESULTS: Among 1141 patients with CSM, 509 (44.6%) had an EL of high school or below, 471 (41.3%) had a graduate degree, and 161 (14.1%) had obtained postgraduate education. Lower EL was statistically significantly associated with symptom duration of >3 months (odds ratio=1.68), higher arm pain numeric rating scale (NRS) (coefficient=0.5), and higher neck pain NRS (coefficient=0.79). Patients with postgraduate education had statistically significantly lower Neck Disability Index (NDI) scores (coefficient=-7.17), lower arm pain scores (coefficient=-1), and higher quality-adjusted life-years (QALY) scores (coefficient=0.06). Twenty-four months after surgery, patients of lower EL had higher NDI scores, higher pain NRS scores, and lower QALY scores ( P <0.05 in all analyses). CONCLUSIONS: Among patients undergoing surgical management for CSM, those reporting a lower educational level tended to present with longer symptom duration, more disease-inflicted disability and pain, and lower QALY scores. As such, patients of a lower EL are a potentially vulnerable subpopulation, and their health literacy and access to care should be prioritized.

Pelvis-Sacrum-Lumbar Spine Injury Characteristics From Underbody Blast Loading.

INTRODUCTION: Combat-related injuries from improvised explosive devices occur commonly to the lower extremity and spine. As the underbody blast impact loading traverses from the seat to pelvis to spine, energy transfer occurs through deformations of the combined pelvis-sacrum-lumbar spine complex, and the time factor plays a role in injury to any of these components. Previous studies have largely ignored the role of the time variable in injuries, injury mechanisms, and warfighter tolerance. The objective of this study is to relate the time or temporal factor using a multi-component, pelvis-sacrum-lumbar spinal column complex model. MATERIALS AND METHODS: Intact pelvis-sacrum-spine specimens from pre-screened unembalmed human cadavers were prepared by fixing at the superior end of the lumbar spine, pelvis and abdominal contents were simulated, and a weight was added to the cranial end of the fixation to account for torso effective mass. Prepared specimens were placed on the platform of a custom vertical accelerator device and aligned in a seated soldier posture. An accelerometer was attached to the seat platen of the device to record the time duration to peak velocity. Radiographs and computed tomography images were used to document and associate injuries with time duration. RESULTS: The mean age, stature, weight, body mass index, and bone density of 12 male specimens were as follows: 65 ± 11 years, 1.8 ± 0.01 m, 83 ± 13 kg, 27 ± 5.0 kg/m2, and 114 ± 21 mg/cc. They were equally divided into short, medium, and long time durations: 4.8 ± 0.5, 16.3 ± 7.3, and 34.5 ± 7.5 ms. Most severe injuries associated with the short time duration were to pelvis, although they were to spine for the long time duration. CONCLUSIONS: With adequate time for the underbody blast loading to traverse the pelvis-sacrum-spine complex, distal structures are spared while proximal/spine structures sustain severe/unstable injuries. The time factor may have implications in seat and/or seat structure design in future military vehicles to advance warfighter safety.

Resection of a large thoracolumbar intradural ependymoma: a 2D operative video.

In this video, the authors present the resection of a large thoracolumbar intradural ependymoma in a 33-year-old female. The patient underwent T9-L3 laminectomies, intradural tumor resection, and posterior instrumented fixation and fusion. The surgical procedure aimed to relieve the mass effect, obtain a diagnosis, prevent further neurological decline, and achieve a potential curative resection. The pathology confirmed a myxopapillary ependymoma, a rare tumor with a preference for the conus medullaris, cauda equina, or filum terminale. The video provides insights into the case, surgical steps, clinical outcomes, and background information on myxopapillary ependymomas and treatment options.

Robotic-Assisted Surgery and Navigation in Deformity Surgery.

Deformity surgery is advancing quickly with the use of three-dimensional navigation and robotics. In spinal fusion, the use of robotics improves screw placement accuracy and reduces radiation, complications, blood loss, and recovery time. Currently, there is limited evidence showing that robotics is better than traditional freehand techniques. Most studies favoring robotics are small and retrospective due to the novelty of the technology in deformity surgery. Using these systems can also be expensive and time-consuming. Surgeons should use these advancements as tools, but not rely on them to replace surgical experience, anatomy knowledge, and good judgment.

The Role of Magnetic Resonance Imaging and Computed Tomography in Spinal Cord Injury.

Traumatic injuries of the spine are associated with long-term morbidity and mortality. Timely diagnosis and appropriate management of mechanical instability and spinal cord injury are important to prevent further neurologic deterioration. Spine surgeons require an understanding of the essential imaging techniques concerning the diagnosis, management, and prognosis of spinal cord injury. We present a review in the role of computed tomography (CT) including advancements in multidetector CT (MDCT), dual energy CT (DECT), and photon counting CT, and how it relates to spinal trauma. We also review magnetic resonance imaging (MRI) and some of the developed MRI based classifications for prognosticating the severity and outcome of spinal cord injury, such as diffusion weighted imaging (DWI), diffusion tractography (DTI), functional MRI (fMRI), and perfusion MRI.

Cervical spine spondylodiscitis: Review of literature on current treatment strategies.

Infections of the spine are an ever-increasing health concern requiring an often complex and prolonged treatment that can lead to significant morbidity. Of particular interest is the cervical spine where there is an increase rate of post-infectious deformity, secondary neurological deficits and substantially higher rates of associated morbidity and mortality than the thoracic or lumbar spine. In this review, we explore the diagnosis and treatment of spondylodiscitis with particular focus on the cervical spine.

Does surgery for metastatic spinal tumors improve functional outcomes in patients without spinal cord compression but with potentially unstable spines (SINS 7-12)?

OBJECTIVE: In the absence of spinal cord compression, it is unclear if surgery is more effective than radiation treatment for improving functional outcomes in metastatic spinal tumor patients with potentially unstable spines. The authors compared functional status outcomes assessed with Karnofsky Performance Status (KPS) and Eastern Cooperative Oncology Group (ECOG) scores after surgery or radiation in patients without spinal cord compression with Spine Instability Neoplastic Score (SINS) values of 7-12 indicating possible instability (SINS 7-12). METHODS: A retrospective review was performed of patients with metastatic spinal tumor SINS values of 7-12 at a single institution between 2004 and 2014. Patients were divided into two different groups: 1) those treated with surgery and 2) those treated with radiation. Baseline clinical characteristics were measured, and KPS and ECOG scores were obtained pre- and postradiation or postsurgery. The paired, nonparametric Wilcoxon signed-rank test and ordinal logistic regression analysis were used for statistical analysis. RESULTS: A total of 162 patients met inclusion criteria; 63 patients were treated operatively and 99 patients were treated with radiation. The mean follow-up was 1.9 years, with a median of 1.1 years for the surgical cohort (ranging from 2.5 months to 13.8 years) and a mean of 2 years with a median of 0.8 years for the radiation cohort (ranging from 2 months to 9.3 years). After covariates were accounted for, the average posttreatment changes in KPS scores in the surgical cohort were 7.46 ± 17.3 and in the radiation cohort were -2 ± 13.6 (p = 0.045). No significant difference was observed in ECOG scores. KPS scores improved postoperatively in 60.3% of patients in the surgical group and postradiation in 32.3% of patients in the radiation cohort (p < 0.001). Subanalysis within the radiation cohort revealed no differences in fracture rates or local control between patients treated with external-beam radiation therapy versus stereotactic body radiation therapy. In patients initially treated with radiation, 21.2% eventually developed compression fractures at a treated level. Five of the 99 patients in the radiation cohort-all of whom had a fracture-eventually underwent either methyl methacrylate augmentation or instrumented fusion. CONCLUSIONS: Patients with SINS values of 7-12 who underwent surgery had greater improvement in KPS scores-but not in ECOG scores-than patients undergoing radiation alone. In patients treated with radiation, treatment was converted to a procedural intervention such as surgery only in patients who sustained fractures. Of the patients with fractures after radiation (21 of 99), 5 patients underwent an invasive procedure and 16 did not.

Sleep Disturbances in Cervical Spondylotic Myelopathy: Prevalence and Postoperative Outcomes-an Analysis From the Quality Outcomes Database.

STUDY DESIGN: Prospective observational study, level of evidence 1 for prognostic investigations. OBJECTIVES: To evaluate the prevalence of sleep impairment and predictors of improved sleep quality 24 months postoperatively in cervical spondylotic myelopathy (CSM) using the quality outcomes database. SUMMARY OF BACKGROUND DATA: Sleep disturbances are a common yet understudied symptom in CSM. MATERIALS AND METHODS: The quality outcomes database was queried for patients with CSM, and sleep quality was assessed through the neck disability index sleep component at baseline and 24 months postoperatively. Multivariable logistic regressions were performed to identify risk factors of failure to improve sleep impairment and symptoms causing lingering sleep dysfunction 24 months after surgery. RESULTS: Among 1135 patients with CSM, 904 (79.5%) had some degree of sleep dysfunction at baseline. At 24 months postoperatively, 72.8% of the patients with baseline sleep symptoms experienced improvement, with 42.5% reporting complete resolution. Patients who did not improve were more like to be smokers [adjusted odds ratio (aOR): 1.85], have osteoarthritis (aOR: 1.72), report baseline radicular paresthesia (aOR: 1.51), and have neck pain of ≥4/10 on a numeric rating scale. Patients with improved sleep noted higher satisfaction with surgery (88.8% vs 72.9%, aOR: 1.66) independent of improvement in other functional areas. In a multivariable analysis including pain scores and several myelopathy-related symptoms, lingering sleep dysfunction at 24 months was associated with neck pain (aOR: 1.47) and upper (aOR: 1.45) and lower (aOR: 1.52) extremity paresthesias. CONCLUSION: The majority of patients presenting with CSM have associated sleep disturbances. Most patients experience sustained improvement after surgery, with almost half reporting complete resolution. Smoking, osteoarthritis, radicular paresthesia, and neck pain ≥4/10 numeric rating scale score are baseline risk factors of failure to improve sleep dysfunction. Improvement in sleep symptoms is a major driver of patient-reported satisfaction. Incomplete resolution of sleep impairment is likely due to neck pain and extremity paresthesia.

Racial Differences in Postoperative Opioid Prescribing Practices in Spine Surgical Patients.

BACKGROUND: As the opioid epidemic accelerates in the United States, numerous sociodemographic factors have been implicated its development and are, furthermore, a driving factor of the disparities in postoperative pain management. Recent studies have suggested potential associations between the influence of race and ethnicity on pain perception but also the presence of unconscious biases in the treatment of pain in minority patients. OBJECTIVE: To characterize the perioperative opioid requirements across racial groups after spine surgery. METHODS: A retrospective, observational study of 1944 opioid-naive adult patients undergoing a neurosurgical spine procedure, from June 2012 to December 2019, was performed at a large, quaternary care institute. Postoperative inpatient and outpatient opioid usage was measured by oral morphine equivalents, across various racial groups. RESULTS: Case characteristics were similar between racial groups. In the postoperative period, White patients had shorter lengths of stay compared with Black and Asian patients ( P < .05). Asian patients used lower postoperative inpatient opioid doses in comparison with White patients ( P < .001). White patients were discharged with significantly higher doses of opioids compared with Black patients ( P < .01); however, they were less likely to be readmitted within 30 days of discharge ( P < .01). CONCLUSION: In a large cohort of opioid-naive postoperative neurosurgical patients, this study demonstrates higher inpatient and outpatient postoperative opioid usage among White patients. Increasing physician awareness to the effect of race on inpatient and outpatient pain management would allow for a modified opioid prescribing practice that ensures limited yet effective opioid dosages void of implicit biases.

Leveraging machine learning to ascertain the implications of preoperative body mass index on surgical outcomes for 282 patients with preoperative obesity and lumbar spondylolisthesis in the Quality Outcomes Database.

OBJECTIVE: Prior studies have revealed that a body mass index (BMI) ≥ 30 is associated with worse outcomes following surgical intervention in grade 1 lumbar spondylolisthesis. Using a machine learning approach, this study aimed to leverage the prospective Quality Outcomes Database (QOD) to identify a BMI threshold for patients undergoing surgical intervention for grade 1 lumbar spondylolisthesis and thus reliably identify optimal surgical candidates among obese patients. METHODS: Patients with grade 1 lumbar spondylolisthesis and preoperative BMI ≥ 30 from the prospectively collected QOD lumbar spondylolisthesis module were included in this study. A 12-month composite outcome was generated by performing principal components analysis and k-means clustering on four validated measures of surgical outcomes in patients with spondylolisthesis. Random forests were generated to determine the most important preoperative patient characteristics in predicting the composite outcome. Recursive partitioning was used to extract a BMI threshold associated with optimal outcomes. RESULTS: The average BMI was 35.7, with 282 (46.4%) of the 608 patients from the QOD data set having a BMI ≥ 30. Principal components analysis revealed that the first principal component accounted for 99.2% of the variance in the four outcome measures. Two clusters were identified corresponding to patients with suboptimal outcomes (severe back pain, increased disability, impaired quality of life, and low satisfaction) and to those with optimal outcomes. Recursive partitioning established a BMI threshold of 37.5 after pruning via cross-validation. CONCLUSIONS: In this multicenter study, the authors found that a BMI ≤ 37.5 was associated with improved patient outcomes following surgical intervention. These findings may help augment predictive analytics to deliver precision medicine and improve prehabilitation strategies.

Use of an exoscope for enhanced visualization of a Schwab grade 5 osteotomy to correct kyphotic deformity.

The development of the 3D exoscope has advanced intraoperative visualization by providing access to visual corridors that were previously difficult to obtain or maintain with traditional operating microscopes. Favorable ergonomics, maneuverability, and increased potential for instruction provide utility in a large range of procedures. Here, the authors demonstrate the exoscope system in a patient with progressive thoracolumbar junctional kyphosis with bony retropulsion of a T12-L1 fracture requiring a Schwab grade 5 osteotomy and fusion. The utilization of the exoscope provides visual access to the ventrolateral dura for the entire surgical team (surgeons, learners, and scrub nurse). The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21190.

Short segment rib resection to mitigate risk of pleural violation during retropleural lateral thoracic interbody fusion.

It can be difficult to avoid violating the pleura during the retropleural approach to the thoracolumbar spine. In this video, the authors resect a short segment of rib to allow more room for pleural dissection during a minimally invasive (MIS) lateral retropleural approach. After a lateral MIS skin incision, the rib is dissected and removed, clearly identifying the retropleural space. The curvature of the rib can then be followed, decreasing the risk of pleural violation. The pleura can then be mobilized ventrally until the spine is accessed. Managing the diaphragm is also illustrated by separating the fibers without a traditional cut through the muscle. The video can be found here: https://stream.cadmore.media/r10.3171/2022.3.FOCVID21138.