Functional nanoscale organization of signaling molecules downstream of the T cell antigen receptor.

Receptor-regulated cellular signaling often is mediated by formation of transient, heterogeneous protein complexes of undefined structure. We used single and two-color photoactivated localization microscopy to study complexes downstream of the T cell antigen receptor (TCR) in single-molecule detail at the plasma membrane of intact T cells. The kinase ZAP-70 distributed completely with the TCRζ chain and both partially mixed with the adaptor LAT in activated cells, thus showing localized activation of LAT by TCR-coupled ZAP-70. In resting and activated cells, LAT primarily resided in nanoscale clusters as small as dimers whose formation depended on protein-protein and protein-lipid interactions. Surprisingly, the adaptor SLP-76 localized to the periphery of LAT clusters. This nanoscale structure depended on polymerized actin and its disruption affected TCR-dependent cell function. These results extend our understanding of the mechanism of T cell activation and the formation and organization of TCR-mediated signaling complexes, findings also relevant to other receptor systems.

Identifying Risk Factors for 30-Day Readmissions After Triple Arthrodesis Surgery.

Rigid flatfoot deformity is a debilitating condition that can be managed by triple arthrodesis surgery. Triple arthrodesis has the potential to restore health-related quality of life, but it is also associated with several complications. Few studies have examined the 30-day readmission rates after triple arthrodesis. The objective of this study was to investigate risk factors for 30-day all-cause readmissions after triple arthrodesis. The nationwide readmission database was queried from 2013. By using International Classification of Disease, Ninth Revision, procedure codes, all triple arthrodesis procedures were identified. Demographic factors, comorbidities, insurance status, and hospital characteristics were statistically compared between patients who experienced a 30-day readmission and those who did not. Multivariable logistic regression was used to identify independent risk factors for 30-day readmission. Overall, 1916 triple arthrodesis cases were identified. The overall 30-day readmission rate after triple arthrodesis was 4.6%. Univariate analysis revealed a statistically higher proportion of patients with electrolyte abnormalities (13.8% vs 4.6%; p < .01) in the patients who were readmitted within 30 days compared with those who were not. Multivariable analysis demonstrated Medicaid insurance, relative to private insurance, as the only statistically significant predictor of 30-day readmission with an odds ratio of 4.43 (p < .05). These results suggest that patients of lower socioeconomic status may be at a greater risk for development of a short-term readmission after triple arthrodesis surgery. These findings are important for surgeon and patient communication, counseling, and postoperative care when choosing to pursue triple arthrodesis surgery.

Machine Learning Accurately Predicts Short-Term Outcomes Following Open Reduction and Internal Fixation of Ankle Fractures.

Ankle fractures are common orthopedic injuries with favorable outcomes when managed with open reduction and internal fixation (ORIF). Several patient-related risk factors may contribute to poor short-term outcomes, and machine learning may be a valuable tool for predicting outcomes. The objective of this study was to evaluate machine-learning algorithms for accurately predicting short-term outcomes after ORIF for ankle fractures. The Nationwide Inpatient Sample and Nationwide Readmissions Database were queried for adult patients ≥18 years old who underwent ORIF of an ankle fracture during 2013 or 2014. Morbidity and mortality, length of stay >3 days, and 30-day all-cause readmission were the outcomes of interest. Two machine-learning models were created to identify patient and hospital characteristics associated with the 3 outcomes. The machine learning models were evaluated using confusion matrices and receiver operating characteristic area under the curve values. A total of 16,501 cases were drawn from the Nationwide Inpatient Sample and used to assess morbidity and mortality and length of stay >3 days, and 33,504 cases were drawn from the Nationwide Readmissions Database to assess 30-day readmission. Older age, Medicaid, Medicare, deficiency anemia, congestive heart failure, chronic lung disease, diabetes, hypertension, and renal failure were the variables associated with a statistically significant increased risk of developing all 3 adverse events. Logistic regression and gradient boosting had similar area under the curve values for each outcome, but gradient boosting was more accurate and more specific for predicting each outcome. Our results suggest that several comorbidities may be associated with adverse short-term outcomes after ORIF of ankle fractures, and that machine learning can accurately predict these outcomes.

Comparing 30-day all-cause readmission rates between tibiotalar fusion and total ankle replacement.

BACKGROUND: End-stage ankle arthritis is a debilitating condition that negatively impacts patient quality of life. Tibiotalar fusion and total ankle replacement are treatment options for managing ankle arthritis. Few studies have examined short term readmission rates of these two procedures. The objective of this study was compare all-cause 30-day readmission rates between patients undergoing tibiotalar fusion vs. total ankle replacement. METHODS: This study queried the Nationwide Readmission Database (NRD) from 2013-2014 and used international classification of disease, 9th revision (ICD-9) procedure codes to identify all patients who underwent a tibiotalar fusion or a total ankle replacement. Comorbidities, insurance status, hospital characteristics, and readmission rates were statistically compared between the two cohorts. Risk factors were then identified for 30-day readmission. RESULTS: A total of 5660 patients were analyzed with 2667 in the tibiotalar fusion cohort and 2993 in the total ankle replacement cohort. Univariate analysis revealed that the readmission rate after tibiotalar fusion (4.4%) was statistically greater than after total ankle replacement (1.4%). Multivariable regression analysis indicated that deficiency anemia (OR 2.18), coagulopathy (OR 3.51), renal failure (OR 2.83), other insurance relative to private (OR 3.40), and tibiotalar fusion (OR 2.51) were all statistically significant independent risk factors for having a readmission within 30-days. CONCLUSIONS: These findings suggest that during the short-term period following discharge from the hospital, patients who received a tibiotalar fusion are more likely to experience a 30-day readmission. These findings are important for decision making when a surgeon encounters a patient with end stage ankle arthritis. LEVEL OF EVIDENCE: Level III, cohort study.

A phospholipase C-γ1-independent, RasGRP1-ERK-dependent pathway drives lymphoproliferative disease in linker for activation of T cells-Y136F mutant mice.

Mice expressing a germline mutation in the phospholipase C-γ1-binding site of linker for activation of T cells (LAT) show progressive lymphoproliferation and ultimately die at 4-6 mo age. The hyperactivated T cells in these mice show defective TCR-induced calcium flux but enhanced Ras/ERK activation, which is critical for disease progression. Despite the loss of LAT-dependent phospholipase C-γ1 binding and activation, genetic analysis revealed RasGRP1, and not Sos1 or Sos2, to be the major Ras guanine exchange factor responsible for ERK activation and the lymphoproliferative phenotype in these mice. Analysis of isolated CD4(+) T cells from LAT-Y136F mice showed altered proximal TCR-dependent kinase signaling, which activated a Zap70- and LAT-independent pathway. Moreover, LAT-Y136F T cells showed ERK activation that was dependent on Lck and/or Fyn, protein kinase C-θ, and RasGRP1. These data demonstrate a novel route to Ras activation in vivo in a pathological setting.

Opening Side of Unilateral Open-Door Laminoplasty Does Not Impact Improvement in Arm Pain or Space Available for the Spinal Cord.

Background/Objectives: There exists limited data guiding open-door laminoplasty. The objective of this study is to determine if open-door laminoplasty affects radiographic decompression or arm pain outcomes. Methods: Adult patients who underwent unilateral open-door laminoplasty cervical myelopathy were included. The side opened was dependent on surgeon discretion. We recorded preoperative side of symptoms, side of radiographic compression, arm pain scores, and canal diameter. Patients with open-side ipsilateral or contralateral to dominant symptoms or compression were compared to determine any effect on arm pain outcomes or spinal canal diameter. If the symptoms were equal bilaterally, patients were neutral. Results: A total of 167 patients were included, with an average age of 64 ± 11 years and average follow-up time of 64.5 ± 72 weeks. The average preoperative arm pain visual analog score (VAS) was 2.13 ± 2.86, and the average arm VAS after 6 months was 1.52 ± 2.68. For dominant symptoms, the ipsilateral, contralateral, and neutral groups had a significant improvement in arm VAS at >6 months postoperatively. For dominant compression, the ipsilateral and contralateral groups had a significant improvement in both arm VASs and canal diameter at >6 months postoperatively. No differences were seen between groups for either. We observed a significant correlation between size of plate and change in canal diameter; however, no differences were noted for arm pain. Conclusions: Laminoplasty may be effective in addressing radicular arm pain by increasing the spinal canal's diameter and space available for the cord. The laterality of open-door laminoplasty did not affect arm pain improvement or canal expansion.

Post-Operative Hyperextension Bracing Has the Potential to Reduce Proximal Junctional Kyphosis: A Propensity Matched Analysis of Braced versus Non-braced Cohorts.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: Determine effects of bracing on proximal junctional kyphosis (PJK) after adult deformity correction. METHODS: Patients were identified from a single-surgeon dataset of posterior-only fusions for ASD (pelvis to UIV of T9-12) with a minimum of 1-year follow up. Starting in 2021, all lower thoracic fusions were braced using a hyperextension brace. Patients wore the brace at all times (unless in bed) for the first 6 weeks after surgery. A 1:1 propensity-match was performed based on age, number of levels, 3 column osteotomies, and magnitude of correction to identify a comparative non-braced cohort. RESULTS: 141 patients (113 non-brace, 28 brace) were evaluated. After matching, 56 patients were identified to form similar cohorts. Non-matched and matched groups had no statistically significant differences in demographics, comorbid conditions, surgical characteristics (except shorter operative time and lower EBL in the braced group), and preoperative radiographic parameters. For the overall cohort, the change in proximal junctional angle at 1-year was higher in the non-braced group (7.6° vs 8.1°, P = .047), and non-braced patients had a higher incidence of PJK at 1-year in both the overall cohort (36% vs 14%, P = .045) and matched cohort (43% vs 14%, P = .038). There was no difference in proximal junctional failure between groups. CONCLUSION: This pilot study shows that our protocol for extension bracing may reduce rates of PJK. These findings can form the basis for future multi-center trials examining the effect of extension bracing on junctional complications.

Ninety Percent of Patients Are Satisfied With Their Decision to Undergo Spine Surgery for Degenerative Conditions.

STUDY DESIGN: Cross-sectional survey and retrospective review of prospectively collected data. OBJECTIVE: To explore how patients perceive their decision to pursue spine surgery for degenerative conditions and evaluate factors correlated with decisional regret. SUMMARY OF BACKGROUND DATA: Prior research shows that one-in-five older adults regret their decision to undergo spinal deformity surgery. However, no studies have investigated decisional regret in patients with degenerative conditions. METHODS: Patients who underwent cervical or lumbar spine surgery for degenerative conditions (decompression, fusion, or disk replacement) between April 2017 and December 2020 were included. The Ottawa Decisional Regret Questionnaire was implemented to assess prevalence of decisional regret. Questionnaire scores were used to categorize patients into low (<40) or medium/high (≥40) decisional regret cohorts. Patient-reported outcome measures (PROMs) included the Oswestry Disability Index, Patient-reported Outcomes Measurement Information System, Visual Analog Scale (VAS) Back/Leg/Arm, and Neck Disability Index at preoperative, early postoperative (<6 mo), and late postoperative (≥6 mo) timepoints. Differences in demographics, operative variables, and PROMs between low and medium/high decisional regret groups were evaluated. RESULTS: A total of 295 patients were included (mean follow-up: 18.2 mo). Overall, 92% of patients agreed that having surgery was the right decision, and 90% would make the same decision again. In contrast, 6% of patients regretted the decision to undergo surgery, and 7% noted that surgery caused them harm. In-hospital complications (P=0.02) and revision fusion (P=0.026) were significantly associated with higher regret. The medium/high decisional regret group also exhibited significantly worse PROMs at long-term follow-up for all metrics except VAS-Arm, and worse achievement of minimum clinically important difference for Oswestry Disability Index (P=0.007), Patient-Reported Outcomes Measurement Information System (P<0.0001), and VAS-Leg (P<0.0001). CONCLUSIONS: Higher decisional regret was encountered in the setting of need for revision fusion, increased in-hospital complications, and worse PROMs. However, 90% of patients overall were satisfied with their decision to undergo spine surgery for degenerative conditions. Current tools for assessing patient improvement postoperatively may not adequately capture the psychosocial values and patient expectations implicated in decisional regret.

Concepts and Techniques to Prevent Cervical Spine Deformity After Spine Surgery: A Narrative Review.

Adult cervical spine deformity is associated with decreased health-related quality of life, disability, and myelopathy. A number of radiographic parameters help to characterize cervical deformity and aid in the diagnosis and treatment. There are several etiologies for cervical spine deformity, the most common being iatrogenic. Additionally, spine surgery can accelerate adjacent segment degeneration which may lead to deformity. It is therefore important for all spine surgeons to be aware of the potential to cause iatrogenic cervical deformity. The aim of this review is to highlight concepts and techniques to prevent cervical deformity after spine surgery.

The Association of Lumbar Plexus Lengthening with Neurologic Deficit After Adult Spinal Deformity Surgery.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: This study aimed to evaluate the association between nerve lengthening after adult deformity correction and motor deficits dervied from the upper lumbar plexus or femoral nerve. SUMMARY OF BACKGROUND DATA: Adult spinal deformity (ASD) surgery is associated with high rates of neurological deficits. Certain postoperative deficits may be related to lengthening of the upper lumbar plexus (ULP) and/or femoral nerve (FN) after correction of lumbar deformity. METHODS: Patients with ASD who underwent posterior-only corrective surgery from the sacrum to L3 or above were included. The length of each lumbar nerve root (NR) was calculated geometrically using the distance from the foramen to the midpoint between the anterosuperior iliac crest and pubic symphysis on AP and lateral radiographs. The mean lengths of the L1-3 and L2-4 NRs were used to define the lengths of the ULP and FN, respectively. Pre- to postoperative changes in nerve length were calculated. Neurological examination was performed at discharge. Proximal weakness (PW) was defined as the presence of weakness compared to baseline in either hip flexors or knee extensors. Multiple linear regression analysis was used for estimating the postoperative lengthening according to the magnitude of preoperative curvature and postoperative correction angles. RESULTS: A total of 202 sides were analyzed in 101 patients, and PW was present on 15 (7.4%) sides in 10 patients. Excluding the 10 cases with three-column osteotomies, those with PW had a significantly higher rate of pure sagittal deformity (P<.001) and greater nerve lengthening than those without PW (ULP 24 vs 15 mm, P=0.02; FN 18 vs 11 mm, P=0.05). No patient had advanced imaging showing neural compression, and complete recovery of PW occurred in 8 patients at 1-year follow-up. CONCLUSIONS: After ASD surgery, lengthening of the ULP was associated with PW. In preoperative planning, surgeons must consider how the type of correction may influence the risk for nerve lengthening, which may contribute to postoperative neurologic deficit. LEVEL OF EVIDENCE: 3.

Postoperative Radiculitis After L5-S1 Anterior Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective chart review. OBJECTIVE: This study aimed to examine postoperative radiculitis after isolated L5-S1 anterior lumbar interbody fusion (ALIF), determine which factors contribute to its development, and investigate the comparative outcomes of patients with versus without postoperative radiculitis. SUMMARY OF BACKGROUND DATA: Both standalone and traditionalALIF are common and safe lumbar spine fusion techniques. Although optimal safety and effectiveness are achieved through appropriate patient selection, postoperative radiculitis after L5-S1 ALIF is a potential complication that seems to be the least predictable in the absence of iatrogenic injury. PATIENTS AND METHODS: All adult patients (18-80 yr) with preoperative radiculopathies who underwent L5-S1 ALIF by 9 board-certified spine surgeons at a single academic institution from January 2016 to December 2021 with a minimum of 3 months follow-up were included. Patient records were assessed for data on clinical characteristics and patient-reported outcome scores (patient-reported outcome measures). All patient records were evaluated to determine whether postoperative radiculitis developed. Radiographic measurements using x-rays were completed using all available pre and postoperative imaging. Multivariable logistic regressions were performed utilizing radiculitis as the dependent variable and various independent predictor variables. RESULTS: One hundred forty patients were included, 48 (34%) patients developed postoperative radiculitis, with symptom onset and resolution occurring at 14.5 and 83 days, respectively. The two groups had no differences in preoperative or postoperative radiographic parameters. Multivariable regression showed 3 independent predictors of postoperative radiculitis: methylprednisolone use [OR: 6.032; (95% CI: 1.670-25.568)], increased implant height [OR: 1.509; (95% CI: 1.189-1.960)], and no posterior fixation [OR: 2.973; (95% CI: 1.353-0.806)]. CONCLUSIONS: Of the 34% of patients who developed postoperative radiculitis after L5-S1 ALIF, it resolved on average within 3 months of surgery. These findings may help reduce the risk of undue short-term morbidity after isolated L5-S1 ALIF by informing preoperative counseling and intraoperative decision-making.

Predictors of Subsidence and its Clinical Impact After Expandable Cage Insertion in Minimally Invasive Transforaminal Interbody Fusion.

STUDY DESIGN: Retrospective review of prospectively collected multisurgeon data. OBJECTIVE: Examine the rate, clinical impact, and predictors of subsidence after expandable minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) cage. SUMMARY OF BACKGROUND DATA: Expandable cage technology has been adopted in MI-TLIF to reduce the risks and optimize outcomes. Although subsidence is of particular concern when using expandable technology as the force required to expand the cage can weaken the endplates, its rates, predictors, and outcomes lack evidence. MATERIALS AND METHODS: Patients who underwent 1 or 2-level MI-TLIF using expandable cages for degenerative lumbar conditions and had a follow-up of >1 year were included. Preoperative and immediate, early, and late postoperative radiographs were reviewed. Subsidence was determined if the average anterior/posterior disc height decreased by >25% compared with the immediate postoperative value. Patient-reported outcomes were collected and analyzed for differences at the early (<6 mo) and late (>6 mo) time points. Fusion was assessed by 1-year postoperative computed tomography. RESULTS: One hundred forty-eight patients were included (mean age, 61 yr, 86% 1-level, 14% 2-level). Twenty-two (14.9%) demonstrated subsidence. Although statistically not significant, patients with subsidence were older, had lower bone mineral density, and had higher body mass index and comorbidity burden. Operative time was significantly higher ( P = 0.02) and implant width was lower ( P < 0.01) for subsided patients. Visual analog scale-leg was significantly lower for subsided patients compared with nonsubsided patients at a >6 months time point. Long-term (>6 mo) patient-acceptable symptom state achievement rate was lower for subsided patients (53% vs . 77%), although statistically not significant ( P = 0.065). No differences existed in complication, reoperation, or fusion rates. CONCLUSIONS: Of the patients, 14.9% experienced subsidence predicted by narrower implants. Although subsidence did not have a significant impact on most patient-reported outcome measures and complication, reoperation, or fusion rates, patients had lower visual analog scale-leg and patient-acceptable symptom state achievement rates at the >6-month time point. LEVEL OF EVIDENCE: Level 4.

Severe Cervical Kyphosis and Spondyloptosis with Myelopathy in Larsen Syndrome: A Report of 2 Cases.

CASE: Two patients (ages 5 and 14 years) with Larsen syndrome and severe cervical kyphosis (patient 1) and spondyloptosis (patient 2), as well as complete anterior-posterior dissociation of the cervical spine, presented with severe, progressive myelopathy. Both patients underwent preoperative halo-gravity traction to slowly reduce the deformity followed by staged anterior-posterior decompression and fusion. Both patients demonstrated complete return of neurologic function. CONCLUSION: Patients with Larsen syndrome should be screened for cervical deformity at the time of diagnosis. Proper screening will facilitate early detection and treatment of significant deformities to prevent neurologic deterioration, which can be catastrophic in these patients.

Elevated and variable groundwater iron in rural northwestern Bangladesh.

Over the past 30 years, tubewells have become a ubiquitous source of potable groundwater in South Asia. Considered safer than surface water, groundwater naturally contains minerals that may impact human health; however, few data exist on tubewell water mineral content or its association with human nutritional or health conditions. We surveyed iron concentration in tubewell water across a 435 km2, contiguous, rural area in northwestern Bangladesh to map and quantify levels of iron in drinking water. One tubewell was randomly sampled from each of 948 adjacent grid cells 675 m2 in size. Water sampling was standardized and iron concentration measured using a field-based colorimetric kit. The median (interquartile range) concentration of iron in tubewell water was 7.6 (1.6, 17.6) mg l(-1). There was high geographic variation (range of 0-46.5 mg l(-1)), and iron in only 3% of surveyed tubewells fell below the WHO aesthetic cut-off of 0.3 mg l(-1) suggesting elevated levels of iron throughout the area. Villagers accurately perceived groundwater iron concentration, based on a 4-point ('none', 'a little', 'medium', 'a lot') scale (p<0.001). Water source iron content can be readily quantified in population settings offering the potential to evaluate the health relevance of groundwater iron exposure in rural communities.

Length of stay and 30-day readmissions after isolated humeral shaft fracture open reduction and internal fixation compared to intramedullary nailing.

INTRODUCTION: Open reduction with internal fixation (ORIF) and intramedullary nailing (IMN) have similar union rates for treating humerus shaft fractures, but IMN leads to increased incidence of shoulder impingement and reoperation. The difference in 30-day readmission rate and length of stay (LOS) between these procedures is unknown. The objective of the study was to compare 30-day unplanned readmissions and length of stay between humeral shaft fractures fixed with either ORIF or IMN. METHODS: The nationwide readmissions database (NRD) was queried for patients with humeral shaft fractures treated with ORIF or IMN between 2015-2016. IMN cases were propensity matched to ORIF cases based on demographic and co-morbid variables. Multivariable logistic regression determined if treatment modality was an independent risk factor for 30-day readmission or length of stay >3 days. RESULTS: There were 406 patients treated with IMN matched to 406 patients treated with ORIF. The 30-day readmission rate was 6.4% for IMN and 4.9% for ORIF (p = 0.45), and the median LOS was 3 days for each group (p = 0.45). Congestive heart failure (CHF)(OR=2.7, p = 0.04), depression (OR=3.3, p = 0.0008), and electrolyte abnormality (OR=3.6, p = 0.0003) were independent risk factors for readmission. Older age (OR=1.02, p = 0.03), CHF (OR=2.4, p = 0.03), electrolyte abnormality (OR=2.6, p = 0.0001), obesity (OR=2.8, p<0.0001), Medicaid (OR=2.1, p = 0.04), discharge to a facility (OR = 5.2, p<0.0001), discharge with home health services (OR=2.4, p = 0.0003), and open fracture (OR=2.3, p = 0.01) were independent risk factors for LOS >3 days. Procedure (ORIF vs. IMN) was not a predictor of 30-day readmission or LOS >3 days. CONCLUSION: Comorbid conditions are risk factors for 30-day readmission and increased LOS. Comorbidity, discharge disposition, and open fractures are risk factors for increased LOS. Treating humeral shaft fractures with either ORIF or IMN did not affect readmission or length of stay.

Analysis and Review of Automated Risk Calculators Used to Predict Postoperative Complications After Orthopedic Surgery.

PURPOSE OF REVIEW: To discuss the automated risk calculators that have been developed and evaluated in orthopedic surgery. RECENT FINDINGS: Identifying predictors of adverse outcomes following orthopedic surgery is vital in the decision-making process for surgeons and patients. Recently, automated risk calculators have been developed to quantify patient-specific preoperative risk associated with certain orthopedic procedures. Automated risk calculators may provide the orthopedic surgeon with a valuable tool for clinical decision-making, informed consent, and the shared decision-making process with the patient. Understanding how an automated risk calculator was developed is arguably as important as the performance of the calculator. Additionally, conveying and interpreting the results of these risk calculators with the patient and its influence on surgical decision-making are paramount. The most abundant research on automated risk calculators has been conducted in the spine, total hip and knee arthroplasty, and trauma literature. Currently, many risk calculators show promise, but much research is still needed to improve them. We recommend they be used only as adjuncts to clinical decision-making. Understanding how a calculator was developed, and accurate communication of results to the patient, is paramount.

Compression of the S1 Nerve Root by an Extradural Vascular Malformation: A Case Report and Discussion of Atypical Causes of Lumbar Radiculopathy.

We present a case of lumbar radiculopathy due to a vascular malformation in the lumbar spine and discuss various causes of atypical lumbar radiculopathy. Lumbar radiculopathy is a condition of neurologic deficits and painful symptoms of the lower extremities due to nerve root compression, most commonly at the L5 and S1 levels. Several factors contribute to lumbar radiculopathy, including intervertebral disc herniation, foraminal stenosis, and spinal instability. There are also a number of atypical causes, including medication side effects or metabolic disorders, which produce symptoms of radiculopathy but do not involve compression of the nerve root. Anatomic variations in the nerve roots or vascular supply surrounding the nerve root may also increase the risk of developing radiculopathy and serve as an obstacle to interpreting imaging during a preoperative workup. A 38-year-old woman presented with sudden onset radicular symptoms in her right lower extremity. Lumbar magnetic resonance imaging demonstrated a right-sided L5-S1 extruded nucleus pulposus. Her symptoms failed to improve after conservative management so she underwent surgical decompression of L4-S1. Intraoperatively, we discovered an extensive, extradural vascular malformation present at the L5-S1 level and believed this to be the true cause of her radiculopathy. This case represents an atypical cause of lumbar radiculopathy and demonstrates the importance of considering atypical causes during diagnostic workup and preoperative planning.

A Review of Techniques, Time Demand, Radiation Exposure, and Outcomes of Skin-anchored Intraoperative 3D Navigation in Minimally Invasive Lumbar Spinal Surgery.

STUDY DESIGN: Retrospective cohort. OBJECTIVE: To describe our technique for and evaluate the time demand, radiation exposure and outcomes of skin-anchored intraoperative three-dimensional navigation (ION) in minimally invasive (MIS) lumbar surgery, and to compare these parameters to 2D fluoroscopy for MI-TLIF. SUMMARY OF BACKGROUND DATA: Limited visualization of anatomic landmarks and narrow access corridor in MIS procedures result in greater reliance on image guidance. Although two-dimensional fluoroscopy has historically been used, ION is gaining traction. METHODS: Patients who underwent MIS lumbar microdiscectomy, laminectomy, or MI-TLIF using skin-anchored ION and MI-TLIF by the same surgeon using 2D fluoroscopy were selected. Operative variables, radiation exposure, and short-term outcomes of all procedures were summarized. Time-demand and radiation exposure of fluoroscopy and ION for MI-TLIF were compared. RESULTS: Of the 326 patients included, 232 were in the ION cohort (92 microdiscectomies, 65 laminectomies, and 75 MI-TLIFs) and 94 in the MI-TLIF using 2D fluoroscopy cohort. Time for ION setup and image acquisition was a median of 22 to 24 minutes. Total fluoroscopy time was a median of 10 seconds for microdiscectomy, 9 for laminectomy, and 26 for MI-TLIF. Radiation dose was a median of 15.2 mGy for microdiscectomy, 16.6 for laminectomy, and 44.6 for MI-TLIF, of this, 93%, 95%, and 37% for microdiscectomy, laminectomy, and MI-TLIF, respectively were for ION image acquisition, with the rest attributable to the procedure. There were no wrong-level surgeries. Compared with fluoroscopy, ION for MI-TLIF resulted in lower operative times (92 vs. 108 min, P < 0.0001), fluoroscopy time (26 vs. 144 s, P < 0.0001), and radiation dose (44.6 vs. 63.1 mGy, P = 0.002), with equivalent time-demand and length of stay. ION lowered the radiation dose by 29% for patients and 55% for operating room personnel. CONCLUSION: Skin-anchored ION does not increase time-demand compared with fluoroscopy, is feasible, safe and accurate, and results in low radiation exposure. LEVEL OF EVIDENCE: 3.

Radiation Exposure in Minimally Invasive Transforaminal Lumbar Interbody Fusion: The Effect of the Learning Curve.

BACKGROUND: Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) has comparable fusion rates and outcomes to the open approach, though many surgeons avoid the technique due to an initial learning curve. No current studies have examined the learning curve of MI-TLIF with respect to fluoroscopy time and exposure. Our objective with this retrospective review was to therefore use a repeatable mathematical model to evaluate the learning curve of MI-TLIF with a focus on fluoroscopy time and exposure. METHODS: We conducted a retrospective review of single level, primary fusions performed by a single surgeon during his initial experience with minimally invasive spine surgery. Chronologic case number was plotted against variables of interest, and learning was identified as the point at which the instantaneous rate of change of a curve fit to the data set equaled the average rate of change of the data set. RESULTS: One hundred nine cases were reviewed. Proficiency in operative time was achieved at 38 cases with the first 38 requiring a median of 137 minutes compared to 104 minutes for the latter 71 cases (P < .0001). Mastery of fluoroscopy use occurred at case 51. The median fluoroscopy time for the first 51 cases was 2.8 minutes, which dropped to 2.1 minutes for cases 52 to 109 (P < .0001). The complication rate plateaued after 43 cases, with 3 of 11 total complications occurring in the latter 76 cases. CONCLUSIONS: Our results demonstrate the most gradual learning occurred with respect to fluoroscopy time and exposure, and operative time improved the quickest. LEVEL OF EVIDENCE: IV. CLINICAL RELEVANCE: These findings may guide spine surgeon education and training in minimally invasive techniques, and help determine safe case loads for radiation exposure during the initial learning phase of the technique. The model used to identify the learning curve can also be applied to several fields and surgical techniques.

Predictive Factors and Rates of Fusion in Minimally Invasive Transforaminal Lumbar Interbody Fusion Utilizing rhBMP-2 or Mesenchymal Stem Cells.

BACKGROUND: Several fusion adjuncts exist to enhance fusion rates during minimally invasive transforaminal lumbar interbody fusion (MI-TLIF). The objective of this study was to compare fusion rates in patients undergoing MI-TLIF with either rhBMP-2 or cellularized bone matrix (CBM). METHODS: We conducted a single surgeon retrospective cohort study of patients who underwent MI-TLIF with either rhBMP-2 or CBM placed in an interbody cage. Single and multilevel procedures were included. Fusion was assessed on computed tomography scans at 12-month follow-up by an independent, blinded, board-certified neuroradiologist. Fusion rates and rate of revision surgery were compared with a Fisher exact test between the 2 groups. A multivariate regression analysis was performed to identify patient factors that were predictive of radiographic nonunion after MI-TLIF. RESULTS: A total of 93 fusion levels in 78 patients were reviewed. Thirty-nine patients received CBM, and 39 patients received rhBMP-2. The patients receiving rhBMP-2 were older on average (61.4 vs 55.6, P = .03). The overall fusion rate was 68% in the CBM group (32/47 levels) and 78% in the rhBMP-2 group (36/46) (P = .35). Only preoperative hypertension was predictive of radiographic nonunion (odds ratio = 3.5, P = .05). There were 3 smokers in the CBM group and 4 smokers in the BMP group, and 1 in each group experienced radiographic pseudarthrosis. A total of 4 patients, 3 in the CBM group and 1 in the BMP group (P = .61), required revision for symptomatic pseudarthrosis. All of these patients had a single-level index procedure. CONCLUSIONS: There were no differences in radiographic fusion and rate of revision surgery in patients who underwent MI-TLIF with either rhBMP-2 or CBM as fusion adjuncts. LEVEL OF EVIDENCE: 3. CLINICAL RELEVANCE: Both rhBMP-2 and CBMs can be used as effective fusion adjuncts without any clear advantage of one over the other.