Metagenomic analysis of the microbial communities and associated network of nitrogen metabolism genes in the Ryukyu limestone aquifer.

While microbial biogeochemical activities such as those involving denitrification and sulfate reduction have been considered to play important roles in material cycling in various aquatic ecosystems, our current understanding of the microbial community in groundwater ecosystems is remarkably insufficient. To assess the groundwater in the Ryukyu limestone aquifer of Okinawa Island, which is located in the southernmost region of Japan, we performed metagenomic analysis on the microbial communities at the three sites and screened for functional genes associated with nitrogen metabolism. 16S rRNA amplicon analysis showed that bacteria accounted for 94-98% of the microbial communities, which included archaea at all three sites. The bacterial communities associated with nitrogen metabolism shifted by month at each site, indicating that this metabolism was accomplished by the bacterial community as a whole. Interestingly, site 3 contained much higher levels of the denitrification genes such as narG and napA than the other two sites. This site was thought to have undergone denitrification that was driven by high quantities of dissolved organic carbon (DOC). In contrast, site 2 was characterized by a high nitrate-nitrogen (NO3-N) content and a low amount of DOC, and this site yielded a moderate amount of denitrification genes. Site 1 showed markedly low amounts of all nitrogen metabolism genes. Overall, nitrogen metabolism in the Ryukyu limestone aquifer was found to change based on environmental factors.

Mechanism of denitrification in subsurface-dammed Ryukyu limestone aquifer, southern Okinawa Island, Japan.

Denitrification crucially regulates the attenuation of groundwater nitrate and is unlikely to occur in a fast-flowing aquifer such as the Ryukyu limestone aquifer in southern Okinawa Island, Japan. However, evidences of denitrification have been observed in several wells within this region. This study analyzed environmental isotopes (δ15NNO3 and ẟ18ONO3) to derive the rationale for denitrification at this site. Additionally, the presence of two subsurface dams in the study area may influence the processes involved in nitrate attenuation. Herein, we analyzed 150 groundwater samples collected spatially and seasonally to characterize the variations in the groundwater chemistry and stable isotopes during denitrification. The values of δ15NNO3 and δ18ONO3 displayed a progressive trend up to +59.7 ‰ and + 21 ‰, respectively, whereas the concentrations of NO3--N decreased to 0.1 mg L-1. In several wells, the enrichment factors of δ15NNO3 ranged from -6.6 to -2.1, indicating rapid denitrification, and the δ15NNO3 to δ18ONO3 ratios varied from 1.3:1 to 2:1, confirming the occurrence of denitrification. Denitrification intensively proceeds under conditions of depleted dissolved oxygen concentrations (<2 mg L-1), sluggish groundwater flow with longer residence times, high concentrations of dissolved organic carbon (>1.2 mg L-1), and low groundwater levels during the dry season with precipitation rates of <100 mm per month (Jun-Sep). SF6 analysis indicated the exclusive occurrence of denitrification in specific wells with groundwater residence times exceeding 30 years. These wells are located in close proximity to the major NE-SW fault system in the Komesu area, where the hydraulic gradient was below 0.005. Detailed geological and lithological investigations based on borehole data revealed that subsurface dams did not cause denitrification while the major NE-SW fault system uplifted the impermeable basement rock of the Shimajiri Group, creating a lithological gap at an equivalent depth that ultimately formed a sluggish groundwater area, promoting denitrification.

Clinical Outcomes of Condoliase Injection Therapy for Lateral Lumbar Disc Herniation.

Introduction: This study aimed to evaluate the efficacy of condoliase injection therapy (CIT) for lateral lumbar disc herniation (LLDH). Methods: This retrospective study included 157 of 180 enrolled patients (70 males, 87 females; mean age: 52.6±16.9 years). These patients were divided into two groups (group L: LLDH, group M: medial LDH [subligamentous and transligamentous]). From baseline to 1 year after injection (final follow-up), leg pain was assessed using the visual analog scale (VAS) and the Japanese Orthopedic Association (JOA) scoring for CIT's clinical efficacy of CIT. Radiography and magnetic resonance imaging conducted before and 3 months after the injection were assessed. Patients with a VAS improvement of ≥50% at the final follow-up were defined as responders. The responder and nonresponder LLDH groups were also compared. Results: Groups L and M showed comparable responder rates (75.0% and 77.4%, respectively) (P=0.80). VAS and JOA scores at 1 year showed no significant differences between the groups (P=0.82 and 0.80, respectively). VAS score at 1 month after injection reduced considerably in the responder group compared with that in the nonresponder group (19.7 vs. 66.0, P<0.01) and continued to decrease at the last follow-up (3.5 vs. 52.0, P<0.001). Nonresponders had significantly lower disc heights after 3 months. However, intervertebral instability, alignment, and disc degeneration did not differ between the responders and nonresponders. Conclusions: The response rate of CIT for LLDH was comparable to that for medial LDH. Therefore, CIT is an effective treatment for LLDH.

Trabecular Bone Remodeling After Posterior Lumbar Interbody Fusion: Comparison of Three-Dimensional Porous Tantalum and Titanium-Coated Polyetheretherketone Interbody Cages.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: The criteria for determining completion of intervertebral stability after posterior lumbar interbody fusion (PLIF) remain controversial. Several new radiological indicators of bone growth and osteointegration have been established. We compared computed tomography (CT) findings related to osteointegration after PLIF with interbody cages of two different materials and designs. METHODS: We retrospectively analyzed data from 103 patients who underwent PLIF with three-dimensional porous tantalum (Tn) cages or titanium-coated polyetheretherketone (TiP) cages. CT images obtained 3 months and 1 year after surgery were examined for trabecular bone remodeling (TBR), cancellous condensation (CC), and vertebral endplate cyst (VEC) formation. The incidences of each finding were compared by cage type, and rates of instrument failure and pseudarthrosis were determined. RESULTS: Three months postoperatively, 87% of the levels with Tn cages exhibited TBR, whereas 96% of those with TiP cages did not (P < .001). Most levels with Tn cages levels exhibited TBR and no CC 3 months (81%) and 1 year (94%) after surgery. Although 78% of levels with TiP cages exhibited CC and no TBR 3 months after surgery, 59% exhibited both CC and TBR 1 year after surgery. Significantly fewer VECs formed around the Tn cages than around the TiP cages both 3 months (P = .002) and 1 year (P < .001) after surgery. Implant-related problems occurred at levels that exhibited neither TBR nor CC. CONCLUSIONS: The porous tantalum cage may enable intervertebral stability that is comparable to bony fusion soon after surgery.

Vertebral Endplate Concavity in Lateral Lumbar Interbody Fusion: Tapered 3D-Printed Porous Titanium Cage versus Squared PEEK Cage.

Background and Objectives: To prevent postoperative problems in extreme lateral interbody fusion (XLIF), it is critical that the vertebral endplate not be injured. Unintentional endplate injuries may depend on the cage. A novel porous titanium cage for XLIF has improved geometry with a tapered tip and smooth surface. We hypothesized that this new cage should lead to fewer endplate injuries. Materials and Methods: This retrospective study included 32 patients (mean 74.1 ± 6.7 years, 22 females) who underwent anterior and posterior combined surgery with XLIF for lumbar degenerative disease or adult spinal deformity from January 2018 to June 2022. A tapered 3D porous titanium cage (3DTi; 11 patients) and a squared PEEK cage (sPEEK; 21 patients) were used. Spinal alignment values were measured on X-ray images. Vertebral endplate concavity (VEC) was defined as concavity ≥ 1 mm of the endplate on computed tomography (CT) images, which were evaluated preoperatively and at 1 week and 3 months postoperatively. Results: There were no significant differences in the patient demographic data and preoperative and 3-month postoperative spinal alignments between the groups. A 3DTi was used for 25 levels and an sPEEK was used for 38 levels. Preoperative local lordotic angles were 4.3° for 3DTi vs. 4.7° for sPEEK (p = 0.90), which were corrected to 12.3° and 9.1° (p = 0.029), respectively. At 3 months postoperatively, the angles were 11.6° for 3DTi and 8.2° for sPEEK (p = 0.013). VEC was present in 2 levels (8.0%) for 3DTi vs. 17 levels (45%) for sPEEK (p = 0.002). After 3 months postoperatively, none of the 3DTi had VEC progression; however, eight (21%) levels in sPEEK showed VEC progression (p = 0.019). Conclusions: The novel 3DTi cage reduced endplate injuries by reducing the endplate load during cage insertion.

Effect of groundwater residence time on geogenic fluoride release into groundwater in the Mt. Meru slope area, Tanzania, the Great Rift Valley, East Africa.

People living in the Great Rift Valley in East Africa suffer from fluorosis resulting from their consumption of groundwater. This paper shows that geogenic fluoride contamination in a natural water system has changed in the last two decades in the Mt. Meru slope area of northern Tanzania based on water quality, dating of the residence time, and stable isotopes of groundwater. The results demonstrate that 1) the average recharge altitude of groundwater with a high geogenic fluoride concentration is estimated to range from 1900 m to 3000 m on the southern slope of Mt. Meru, and the fluoride concentration tends to increase with an increase in the recharge altitude, 2) the fluoride concentration increases with increasing groundwater residence time for groundwater with a residence time of 20 years or longer, suggesting that water-rock interaction processes (weathering, dissolution, and ion exchange), which depend on the contact time between the volcanic aquifer and groundwater, have predominated for approximately 20 years or longer, and 3) the mixing of aerobic young water and old groundwater has been active for approximately 20 years, and the fluoride concentration is increasing in some shallower well waters. The mixing of fluoride-contaminated groundwater with aerobic water infiltrating the aquifer through pumping groundwater in the last two decades may increase the spread of groundwater contaminated with fluoride due to increased water demand caused by rapid population growth, and urbanization, industrial growth, and the expansion of irrigated agriculture.

Laterality of lumbar disc herniation.

BACKGROUND: Lumbar disc herniation (LDH) is most common in men aged 20-40 at the L4/5 level; however, left-right differences have not been reported. Improving our understanding of left- and right-side LDH may facilitate the estimation of mechanical load on intervertebral discs. Here, we assessed left-right differences in LDH via a retrospective analysis of LDH cases. METHODS: Among 10,972 surgical cases of LDH identified in the Nagoya Spine Group database, 2899 in which right- and left-LDH sides were observable in a single vertebral segment were identified (mean age 46.3 ± 16.6 years, 2028 males). The following characteristics of patients with right- and left-LDH were compared: age, LDH level, surgical technique, operative time, blood loss, length of hospital stay, preoperative Japan Orthopaedic Association (JOA) score, and JOA recovery rate. RESULTS: LDH occurred on the right and left sides in 1358 and 1541 patients, respectively, with patients with right-side LDH significantly older than those with left (47.9 ± 16.6 versus 45.0 ± 16.5, respectively; p < 0.001). No between-group differences in sex, age, LDH level, surgical technique, operative time, blood loss, length of hospital stay, preoperative JOA score, or JOA recovery rate were observed. The occurrence of right-side LDH increased with age, occurring in 42.7%, 45.1%, 49.9%, and 54.7% of patients aged 10-29, 30-49, 50-69, and 70-89 years, respectively. CONCLUSION: Left-side LDH was observed more frequently than right; however, right-side LDH incidence increased with age. No significant between-group differences regarding symptoms, treatments, or outcomes were observed.

Trends in the numbers of spine surgeries and spine surgeons over the past 15 years.

The purpose of this study is to examine trends in spine surgeries at ten facilities over 15 years, and to analyze relationships with the number of spine surgeons at these facilities. The subjects were patients who underwent spine surgery at the ten facilities from 2003 to 2017. Data were collected every year via a questionnaire designed to obtain clinicopathological and surgical information. There were 37,601 spine surgeries (60.2% male) recorded in the registry at 9 facilities in the Nagoya Spine Group (NSG) between 2003 and 2017, with an increase in the annual number of surgeries by 2.4 times over 15 years. On the other hand, the number of spine surgeons has increased by just under 1.5 times. Instrumentation surgeries increased from 959 in 2003 to 2,276 in 2017 (2.3 times). There was a particularly marked increase in surgeries for spinal degenerative disease from 1,075 in 2003 to 2,821 in 2017 (2.6 times). The number of surgeries performed per surgeon increased from 61.4 in 2003 to 102.8 in 2017, while the average number of spine surgeons per hospital increased from 2.6 in 2003 to 3.7 in 2017. In conclusion, with heavier burden on spine surgeons and the major changes in the spine surgery environment, training and increasing surgeons with advanced expertise and skills will become increasingly important.

Last glacial temperature reconstructions using coupled isotopic analyses of fossil snails and stalagmites from archaeological caves in Okinawa, Japan.

We applied a new geoarchaeological method with two carbonate archives, which are fossil snails from Sakitari Cave and stalagmites from Gyokusen Cave, on Okinawa Island, Japan, to reconstruct surface air temperature changes over the northwestern Pacific since the last glacial period. Oxygen isotope ratios (δ18O) of modern and fossil freshwater snail shells were determined to infer seasonal temperature variations. The observational and analytical data confirm that δ18O values of fluid inclusion waters in the stalagmite can be regarded as those of spring waters at the sites where snails lived. Our results indicate that the annual mean, summer, and winter air temperatures were lower by 6-7 °C at ca. 23 thousand years ago (ka) and 4-5 °C at ca. 16-13 ka than those of the present day. Our reconstruction implies that surface air cooling was possibly two times greater than that of seawater around the Ryukyu Islands during the Last Glacial Maximum, which potentially enhanced the development of the East Asian summer monsoon during the last deglaciation. Considering the potential uncertainties in the temperature estimations, the climatic interpretations of this study are not necessarily definitive due to the limited number of samples. Nevertheless, our new geoarchaeological approach using coupled δ18O determinations of fossil snails and stalagmite fluid inclusion waters will be useful for reconstructing snapshots of seasonally resolved time series of air temperatures during the Quaternary.

Risk factors of non-union in Anderson-D'Alonzo type III odontoid fractures with conservative treatment.

OBJECTIVE: The purpose of this study was retrospectively to analyze the risk factors for non-union in Anderson-D'Alonzo type III odontoid fractures with conservative treatment. METHODS: 25 patients with type III fractures were analyzed. Coronal and sagittal tilt as well as sagittal and lateral mass gaps were measured by using computed tomography. RESULTS: The non-union group had significantly higher age, greater coronal tilt and lateral mass gap. Especially, the lateral mass gap was >2 mm in all cases with non-union. CONCLUSIONS: Higher age, coronal tilt, and lateral mass gap were significant risk factors for non-union.

Seasonal variation in incidence and causal organism of surgical site infection after PLIF/TLIF surgery: A multicenter study.

BACKGROUND: Postoperative SSI is a common and potentially serious complication in spine surgery. Seasonal variation occurs in rates of nosocomial infection, with higher rates found in the summer, during which hot, humid conditions may be optimal for proliferation of bacteria. This might also influence the rate of SSI. The purpose of the study was to examine seasonal variation in SSI after PLIF/TLIF surgery, including relationships with experience of surgeons and causal organisms. METHODS: Cases with SSI after PLIF/TLIF surgery at 10 facilities between January 1, 2012, and December 31, 2014 were retrieved from a database. Infection was defined based on CDC guidelines for SSIs. Patients were followed for at least two years after surgery. Surgeries were examined in spring (April-June), summer (July-September), autumn (October-December), and winter (January-March). Seasonal variation and other factors with a potential association with SSIs were evaluated. RESULTS: A total of 1174 patients (607 males, 567 females) who underwent PLIF/TLIF surgery were identified. The operations were PLIF (n = 667), TLIF (n = 443), MIS-PLIF (n = 27), and MIS-TLIF (n = 37). The total SSI rate for the 2-year period was 2.5% (29/1174), and the 2-year average SSI rates for surgeries in each season were spring, 2.6% (7/266); summer, 3.9% (13/335); fall, 1.3% (4/302); winter, 1.8% (5/271). The SSI rate was significantly higher in summer than non-summer (3.9% vs. 1.9%, p < 0.05). SSIs were caused by a variety of pathogens, including Gram-positive cocci, and Staphylococcus aureus was the most common pathogenic organism to cause SSI. CONCLUSION: Seasonality should be taken into account in strategies for SSI prevention, with particular attention on mitigation of increased temperature and humidity in the summer and on infection caused by Gram-positive cocci and S. aureus.

Postoperative iatrogenic spinal cord herniation: three case reports with a literature review.

Although a majority of spinal cord herniation reportedly occurs idiopathically, postoperative iatrogenic spinal cord herniation is rare. Therefore, the incidence rate, pathogenic mechanism, and clinical outcomes are not clear. We present three cases of postoperative iatrogenic spinal cord herniation and present a literature review. Our data base included 32253 patients who underwent spinal surgery, and among these patients, 3 showed postoperative spinal cord herniation. Postoperative spinal cord herniation was observed in a 55-year-old man and a 60-year-old man. Both these patients underwent cervical laminoplasty for degenerative cervical myelopathy; however, intraoperative dural tear was reported. They presented with severe quadriplegia and sensory disorders at 8 years and 2 months after initial surgery. The third case of postoperative spinal cord herniation was of a 47-year-old woman who underwent Th11/12 schwannoma resection. Her neurological symptoms did not improve after tumor resection, and MRI at 2 months after surgery revealed spinal cord herniation. All the 3 patients underwent spinal cord reduction surgery; one patient showed sufficient neurological improvement while 2 patients with cervical spinal cord herniation showed limited neurological improvement due to preoperative severe quadriplegia. Although postoperative iatrogenic spinal cord herniation is a relatively rare pathology, careful observation with postoperative MRI is required in cases of patients with new neurological symptoms after dural injury and durotomy.

Trends in Reoperation for Surgical Site Infection After Spinal Surgery With Instrumentation in a Multicenter Study.

STUDY DESIGN: A multicenter retrospective analysis of a prospectively maintained database. OBJECTIVE: To examine the characteristics of reoperation for surgical site infection (SSI) after spinal instrumentation surgery, including the efficacy of treatment for SSI and instrumentation retention. SUMMARY OF BACKGROUND DATA: Aging of the population and advances in surgical techniques have increased the demand for spinal surgery in elderly patients. Treatment of SSI after this surgery has the main goals of eliminating infection and retaining instrumentation. METHODS: The subjects were 16,707 patients who underwent spine surgery with instrumentation in 11 hospitals affiliated with the Nagoya Spine Group from 2004 to 2015. Details of those requiring reoperations for SSI were obtained from surgical records at each hospital. RESULTS: There were significant increases in the mean age at the time of surgery (54.6-63.7 years) and the number of instrumentation surgeries (726-1977) from 2004 to 2015. The incidence of reoperation for SSI varied from 0.9% to 1.8%, with a decreasing trend over time. Reoperation for SSI was performed in 206 cases (115 men, 91 women; mean age 63.2 years). The average number of reoperations (1.4 vs. 2.3, P < 0.05), time from SSI to first reoperation (4.3 vs. 9.5 days, P < 0.05), and the methicillin-resistant Staphylococcus identification rate (20% vs. 37%, P < 0.01) were all significantly lower in cases with instrumentation retention (n = 145) compared to those with instrumentation removal (n = 61). CONCLUSION: There were marked trends of aging of patients and an increase in operations over the study period; however, the incidences of reoperation and instrumentation removal due to SSI significantly decreased over the same period. Rapid debridement after SSI diagnosis may have contributed to instrumentation retention. These results can serve as a guide for developing strategies for SSI treatment and for improved planning of spine surgery in an aging society. LEVEL OF EVIDENCE: 3.

Predictors of Prolonged Length of Stay After Lumbar Interbody Fusion: A Multicenter Study.

STUDY DESIGN: Retrospective analysis of a prospectively database. OBJECTIVES: To identify factors associated with prolonged length of stay (LOS) in posterior /transforaminal lumbar interbody fusion (PLIF/TLIF). METHODS: The subjects were patients who underwent PLIF/TLIF at 10 facilities from 2012 to 2014. A total of 1168 such patients with a mean age of 65.9 ± 12.5 years (range 18-87 years) were identified in the database. Operations were PLIF (n = 675), TLIF (n = 443), minimally invasive surgery (MIS)-PLIF (n = 22), and MIS-TLIF (n = 32). Age, gender, body mass index, ambulatory status, comorbidities, perioperative American Society of Anesthesiologists (ASA) grade, operative factors, and complications were examined. LOS was defined as the number of calendar days from the operation to hospital discharge. LOS was categorized as normal (<75th percentile) or prolonged (≥75th percentile). RESULTS: The average LOS was 20.8 ± 9.8 days (range 7-77 days). There was a significant correlation between LOS and age (P < .05). Reoperation during hospitalization was performed in 20 cases for surgical site infection (n = 12), epidural hematoma (n = 5), and screw misplacement (n = 3). In multivariate analysis, prolonged LOS was associated with preoperative variables of age ≥70 years (odds ratio [OR] 1.87, 95% CI 1.38-2.54), and ASA class ≥III (OR 1.52, 95% CI 1.04-2.25); surgical variables of open procedures (OR 5.84, 95% CI 1.74-19.63), fused levels ≥3 (OR 5.17, 95% CI 3.17-8.43), operative time ≥300 minutes (OR 1.88, 95% CI 1.15-3.07), and estimated blood loss ≥500 mL (OR 1.71, 95% 1.07-2.75). CONCLUSIONS: The factors identified in this study should help with obtaining informed consent, surgical planning and complication prevention to reduce health care costs associated with prolonged LOS.

Trends of postoperative length of stay in spine surgery over 10 years in Japan based on a prospective multicenter database.

OBJECTIVES: To identify factors associated with prolonged length of stay (LOS) in spine surgery, with the goal of establishing details of LOS for multiple diseases and surgical procedures. PATIENTS AND METHODS: The subjects were patients who underwent spine surgery at 10 facilities in the Nagoya Spine Group from January 2005 to December 2015. Data were collected for patient background, primary spinal pathology, anatomical location of the lesion, and surgical methods. The primary outcome was LOS, which was defined as the calendar days from surgery to hospital discharge. RESULTS: A total of 10,829 patients (5953 males, 4876 females; age 5-93 years, mean 60.2 ± 28.8 years) were identified in the database. Average follow-up was 61 months (range: 13-120 months). Average LOS was 22.3 ± 21.3 days, and there was a gradual decrease in LOS over the study period. LOS was significantly correlated with age, and prolonged LOS was significantly associated with thoracic spine surgery and significantly longer after surgery with instrumentation. Average LOS was >30 days for intramedullary tumor resection and posterior cervical fusion, but only 10.2 days for microendoscopic discectomy. Reoperation was performed in 210 patients (1.9%) and these patients had a significantly higher average LOS of 43.1 days. CONCLUSION: These results will assist quality improvement in spine surgery. The identified risk factors for prolonged LOS will also assist in planning of surgery, postoperative care, and discharge, with the goal of reducing health care costs.

Postoperative Complications Associated With Spine Surgery in Patients Older Than 90 Years: A Multicenter Retrospective Study.

STUDY DESIGN: A review of a prospective database. OBJECTIVES: Surgery for elderly patients is increasing yearly due to aging of society and the desire for higher quality of life. The goal of the study was to examine perioperative complications in spine surgery in such patients. METHODS: A multicenter study of surgical details and perioperative complications was performed in 35 patients aged older than 90 years who underwent spinal surgery, based on a review of a prospective database. The frequency and severity of complications were assessed, and the effects of patient-specific and surgical factors were examined. Major complications were defined as those that were life threatening, required reoperation in the perioperative period or left a permanent injury. Ambulatory function before and after surgery was also analyzed. RESULTS: Perioperative complications occurred in 19 of the 35 cases (54%), and included 11 cases of postoperative delirium, most of which occurred after cervical spine surgery. There were 8 major complications (23%), including cerebral infarction (n = 3), coronary heart disease (n = 3), pulmonary embolism (n = 1), and angina (n = 1). Preoperative motor deficit, operative time, estimated blood loss, and instrumented fusion were significantly associated with major complications. An improved postoperative ambulatory status occurred in 61% of cases, with no change in 33%, and worsening in 2 cases (6%). CONCLUSIONS: Timing of surgery before paralysis progression and reduced surgical invasiveness are important considerations in treatment of the very elderly. Improved outcomes can be obtained with better management of spine surgery for patients aged 90 years or older.

Evaluation of a Combination of Waveform Amplitude and Peak Latency in Intraoperative Spinal Cord Monitoring.

STUDY DESIGN: Retrospective study. OBJECTIVE: The goal of the study was to investigate the significance of a change in latency in monitoring of transcranial muscle-action potential (Tc-MsEP) waveforms. SUMMARY OF BACKGROUND DATA: Tc-MsEP has become a common approach in spine surgery due to its sensitivity and importance in motor function. Many reports have defined the alarm point of Tc-MsEP waveform as a particular decrease in amplitude, but evaluation of the waveform latency has not attracted as much attention. METHODS: The subjects were 70 patients who underwent spine surgery using intraoperative Tc-MsEP monitoring. The peak latency was defined as the period from stimulation until the waveform amplitude reached its peak. Relationships with postoperative paralysis were examined separately for latency delays of 5% or more and 10% or more, and in combination with a decrease in amplitude of 70% or more from baseline. RESULTS: Acceptable baseline Tc-MsEP responses were obtained from 1225 of 1372 muscles in the extremities (89.3%). Seven of the 70 patients (10%) had postoperative paralysis. A decrease in intraoperative amplitude of 70% or more from baseline occurred in 25 cases, with sensitivity 100%, specificity 71%, false positive rate 29%, and positive predictive value (PPV) 28% for prediction of postoperative paralysis. Compared to baseline, 15 cases had a latency delay of 5% or more, which gave a sensitivity of 100%, specificity of 87%, false positive rate of 0%, and PPV 47%, and 8 cases had a delay of 10% or more, which gave a sensitivity of 86%, specificity of 97%, false positive rate of 3%, and PPV 75%. A combination of a decrease in amplitude of 70% or more from baseline and a delay in latency of 10% or more from baseline had a sensitivity of 86%, specificity of 98%, and a false positive rate of 2%, and PPV 86%. CONCLUSION: Combined use of latency and amplitude could lead to reduction of false positives and increase of PPV in Br(E)-MsEP monitoring. LEVEL OF EVIDENCE: 3.

A new criterion for the alarm point using a combination of waveform amplitude and onset latency in Br(E)-MsEP monitoring in spine surgery.

OBJECTIVE: Monitoring of brain evoked muscle-action potentials (Br[E]-MsEPs) is a sensitive method that provides accurate periodic assessment of neurological status. However, occasionally this method gives a relatively high rate of false-positives, and thus hinders surgery. The alarm point is often defined based on a particular decrease in amplitude of a Br(E)-MsEP waveform, but waveform latency has not been widely examined. The purpose of this study was to evaluate onset latency in Br(E)-MsEP monitoring in spinal surgery and to examine the efficacy of an alarm point using a combination of amplitude and latency. METHODS: A single-center, retrospective study was performed in 83 patients who underwent spine surgery using intraoperative Br(E)-MsEP monitoring. A total of 1726 muscles in extremities were chosen for monitoring, and acceptable baseline Br(E)-MsEP responses were obtained from 1640 (95%). Onset latency was defined as the period from stimulation until the waveform was detected. Relationships of postoperative motor deficit with onset latency alone and in combination with a decrease in amplitude of ≥ 70% from baseline were examined. RESULTS: Nine of the 83 patients had postoperative motor deficits. The delay of onset latency compared to the control waveform differed significantly between patients with and without these deficits (1.09% ± 0.06% vs 1.31% ± 0.14%, p < 0.01). In ROC analysis, an intraoperative 15% delay in latency from baseline had a sensitivity of 78% and a specificity of 96% for prediction of postoperative motor deficit. In further ROC analysis, a combination of a decrease in amplitude of ≥ 70% and delay of onset latency of ≥ 10% from baseline had sensitivity of 100%, specificity of 93%, a false positive rate of 7%, a false negative rate of 0%, a positive predictive value of 64%, and a negative predictive value of 100% for this prediction. CONCLUSIONS: In spinal cord monitoring with intraoperative Br(E)-MsEP, an alarm point using a decrease in amplitude of ≥ 70% and delay in onset latency of ≥ 10% from baseline has high specificity that reduces false positive results.

Reoperation within 2 years after lumbar interbody fusion: a multicenter study.

PURPOSE: Posterior lumbar interbody fusion (PLIF)/transforaminal lumbar interbody fusion (TLIF) can have complications that require reoperation. The goal of the study was to identify risk factors for reoperation within 2 years after PLIF/TLIF. METHODS: A retrospective analysis of a prospective multicenter database was performed for patients who underwent PLIF/TLIF. A total of 1363 patients (689 males and 674 females) were identified, with an average age of 65.9 years old. Comorbidities, perioperative ASA grade, and operative factors were compared between patients with and without reoperation. Risk factors for reoperation were identified in multivariate logistic analysis. RESULTS: There were 38 reoperations within 2 years after PLIF/TLIF (2.8%). The original surgical procedures were open PLIF (n = 26), open TLIF (n = 10), and minimally invasive surgery (n = 2). Reoperation was due to adjacent segment degeneration (ASD) (n = 10), surgical site infection (SSI) (n = 9), screw misplacement (n = 6), postoperative epidural hematoma (n = 6), pseudoarthrosis (n = 4), and cage protrusion (n = 3). Number of levels fused and dural tear were significantly associated with reoperation. In analysis of complications requiring reoperation, SSI was related to diabetes mellitus and dural tear, and postoperative epidural hematoma was related to fusion of two or more levels, EBL, and operation time. In multivariate logistic regression, fusion of two or more levels (HR 2.19) was significantly associated with reoperation. CONCLUSION: Surgical invasiveness, as reflected by number of fused levels, operation time, EBL and dural tear, was associated with reoperation. Fusion of two or more levels is a strong risk factor for reoperation within 2 years after initial PLIF/TLIF. These slides can be retrieved under Electronic Supplementary Material.