Connecting the S2 alar-iliac screw head to the satellite rod for surgical correction of degenerative sagittal imbalance.

PURPOSE: The S2AI screw technique has several advantages over the conventional iliac screw fixation technique. However, connecting the S2AI screw head to the main rod is difficult due to its medial entry point. We introduce a new technique for connecting the S2AI screw head to a satellite rod and compare it with the conventional method of connecting the S2AI screw to the main rod. METHODS: Seventy-four patients who underwent S2AI fixation for degenerative sagittal imbalance and were followed up for ≥ 2 years were included. All the patients underwent long fusion from T9 or T10 to the pelvis. The S2AI screw head was connected to the satellite rod (SS group) in 43 patients and the main rod (SM group) in 31 patients. In the SS group, the satellite rod was placed medial to the main rod and connected by the S2AI screw and domino connectors. In the SM group, the main rod was connected directly to the S2AI screw head and supported by accessory rods. Radiographic and clinical outcomes were evaluated in both groups. RESULTS: There were no significant differences in postoperative complications, including proximal junctional failure, proximal junctional kyphosis, rod breakage, screw loosening, wound problems, and infection between the two groups. Furthermore, the correction power of sagittal deformity and clinical results in the SS group were comparable to those in the SM group. CONCLUSION: Connecting the S2AI screw to the satellite rod is a convenient method comparable to the conventional S2AI connection method in terms of radiological and clinical outcomes.

Risk factors for postoperative complaints in patients following lumbar decompression and fusion: Analyses focusing on preoperative symptoms.

BACKGROUND: Several patients complained of residual symptoms following lumbar decompressive surgery for lumbar degenerative disease (LDD). However, few studies analyze this dissatisfaction by focusing on preoperative patients' symptoms. This study was conduct to determine the factors that could predict the patients' postoperative complaints by focusing on their preoperative symptoms. METHODS: Four hundred and seventeen consecutive patients who underwent lumbar decompression and fusion surgery for LDD were included. Postoperative complaint was defined by at least twice same complaint during the outpatient follow-up of 6,12, 18 and 24 months after surgery. A comparative analysis was performed between complaint group (group C, N = 168) and non-complaint group (group NC, N = 249). Demographic, operative, symptomatic, and clinical factors were compared between the groups by univariate and multivariate analyses. RESULTS: The main preoperative chief complaints were radiating pain (318/417, 76.2%). However, most common postoperative complaint was residual radiating pain (60/168, 35.7%) followed by tingling sensation (43/168, 25.6%). The presence of psychiatric disease (adjusted odds ratio [aOR], 4.666; P = 0.017), longer pain duration (aOR, 1.021; P < 0.001), pain to below the knee (aOR, 2.326; P = 0.001), preoperative tingling sensation (aOR, 2.631; P < 0.001), preoperative sensory and motor power decrease (aOR, 2.152 and 1.678; P = 0,047 and 0.011, respectively) were significantly correlated with postoperative patients' complaints in multivariate analysis. CONCLUSIONS: The postoperative patients' complaints could be predicted and explained in advance by checking the preoperative characteristics of patients' symptoms, including the duration and site carefully. This could be helpful to enhance the understanding of the surgical results preoperatively, which could control the anticipation of the patients.

The medial window technique as a salvage method to insert C2 pedicle screw in the case of a high-riding vertebral artery or narrow pedicle: a technical note and case series.

PURPOSE: To describe the safety and feasibility of C2 medial window screw (C2MWS) as an alternative salvage method for C2 pedicle screws in cases of high-riding vertebral artery (HRVA) or narrow pedicle. METHODS: The C2MWS technique involves screw insertion by intentionally breaching the medial cortex of the pedicle to avoid vertebral artery injury. Twelve patients who underwent C2 screw insertion via the C2MWS were retrospectively reviewed. C2MWS was indicated in cases of high-riding vertebral artery (HRVA) or narrow pedicle (pedicle width ≤ 4 mm). The width of the canal breach by screw, vertebral artery groove (VAG) breach, solid fusion, neck pain visual analogue scale (VAS) score, and Japanese Orthopedic Association (JOA) score were assessed as outcome measurements. RESULTS: C2MWS was indicated due to both HRVA and narrow pedicle for 11 screws, narrow pedicle for one screw, and HRVA for two screws. No screw VAG breach or vertebral artery injury was noted postoperatively. The mean width of canal breach was 2.9 ± 1.3 mm. There were no cases demonstrating neurologic deterioration, and 11 patients (91.7%) demonstrated solid fusion at 1-year follow-up. Furthermore, neck pain VAS and JOA scores significantly improved after the surgery. CONCLUSIONS: The C2MWS technique can provide 3-column fixation while reliably avoiding VA injury. C2MWS could be considered as a salvage alternative method when the insertion of C2 pedicle screw is complicated by HRVA or a narrow pedicle, while there is a need to provide firmer fixation strength than that provided by pars or translaminar screws.

Cut-out risk factor analysis after intramedullary nailing for the treatment of extracapsular fractures of the proximal femur: a retrospective study.

BACKGROUNDS: The basic method of surgical treatment for extracapsular hip fractures (ECFs), including intertrochanteric fracture and basicervical fracture (BCF), is osteosynthesis. Intramedullary nails are among the most commonly used fixation devices for these fractures. Our study aimed to report the clinical outcomes of ECF treatment with two different nail devices and to analyze the risk factors associated with screw cut-out. METHODS: We retrospectively reviewed the medical records of 273 patients (300 cases) from a single institution who underwent surgical treatment for ECF between January 2013 and October 2018. Overall, 138 patients were eligible for the study and were divided into two groups according to the osteosynthesis device used. We evaluated the clinical outcomes of fracture surgery and performed univariate and multivariate regression analyses to identify risk factors associated with screw cut-out in each group. RESULTS: We used proximal femoral nails (group 1) to treat 83 patients and cephalomedullary nails (group 2) to treat 55 patients. Nine cut-outs (group 1, 6 cases; group 2, 3 cases) occurred during follow-up. The patients' high body mass index (BMI) (p = 0.019), BCFs (p = 0.007), non-extramedullary reduction in the anteroposterior and lateral planes (p = 0.032 and p = 0.043, respectively), and anti-rotation screw pull-outs (p = 0.041) showed a positive correlation to screw cut-out in the univariate analysis of group 1. In group 2, only BCFs was positively correlated (p = 0.020). In the multivariate analysis of group 1, the patients' BMIs (p = 0.024) and BCFs (p = 0.024) showed a positive correlation with cut-out. Meanwhile, the multivariate analysis of group 2 did not identify any factors associated with cut-out. CONCLUSIONS: The cut-out risk was significantly higher in the BCF cases, regardless of the nail design used. Considerable attention should be paid to treating such unstable fractures. We expect that new-generation nails using a helical blade, or interlocking derotation and interlocking screws may improve surgical outcomes.

Factors affecting the prognosis of recovery of motor power and ambulatory function after surgery for metastatic epidural spinal cord compression.

OBJECTIVE: Metastatic epidural spinal cord compression (MESCC) causes neurological deficits that may hinder ambulation. Understanding the prognostic factors associated with increased neurological recovery and regaining ambulatory functions is important for surgical planning in MESCC patients with neurological deficits. The present study was conducted to elucidate prognostic factors of neurological recovery in MESCC patients. METHODS: A total of 192 patients who had surgery for MESCC due to preoperative neurological deficits were reviewed. A motor recovery rate ≥ 50% and ambulatory function restoration were defined as the primary favorable endpoints. Factors associated with a motor recovery rate ≥ 50%, regaining ambulatory function, and patient survival were analyzed. RESULTS: About one-half (48.4%) of the patients had a motor recovery rate ≥ 50%, and 24.4% of patients who were not able to walk due to MESCC before the surgery were able to walk after the operation. The factors "involvement of the thoracic spine" (p = 0.015) and "delayed operation" (p = 0.041) were associated with poor neurological recovery. Low preoperative muscle function grade was associated with a low likelihood of regaining ambulatory functions (p = 0.002). Furthermore, performing the operation ≥ 72 hours after the onset of the neurological deficit significantly decreased the likelihood of regaining ambulatory functions (p = 0.020). Postoperative ambulatory function significantly improved patient survival (p = 0.048). CONCLUSIONS: Delayed operation and the involvement of the thoracic spine were poor prognostic factors for neurological recovery after MESCC surgery. Furthermore, a more severe preoperative neurological deficit was associated with a lesser likelihood of regaining ambulatory functions postoperatively. Earlier detection of motor weaknesses and expeditious surgical interventions are necessary, not only to improve patient functional status and quality of life but also to enhance survival.

Is the Combination of Convex Compression for the Proximal Thoracic Curve and Concave Distraction for the Main Thoracic Curve Using Separate-rod Derotation Effective for Correcting Shoulder Balance and Thoracic Kyphosis?

BACKGROUND: Posterior correction of the proximal thoracic curve in patients with adolescent idiopathic scoliosis has been recommended to achieve shoulder balance. However, finding a good surgical method is challenging because of the small pedicle diameters on the concave side of the proximal thoracic curve. If the shoulder height can be corrected using screws on the convex side, this would appear to be a more feasible approach. QUESTIONS/PURPOSES: In patients with adolescent idiopathic scoliosis, we asked: (1) Is convex compression with separate-rod derotation effective for correcting the proximal thoracic curve, shoulder balance, and thoracic kyphosis? (2) Which vertebrum is most appropriate to serve as the uppermost-instrumented vertebra? (3) Is correction of the proximal thoracic curve related to the postoperative shoulder balance? METHODS: Between 2015 and 2017, we treated 672 patients with scoliosis. Of those, we considered patients with elevated left shoulder, Lenke Type 2 or 4, or King Type V idiopathic scoliosis as potentially eligible. Based on that, 17% (111 of 672) were eligible; 5% (6 of 111) were excluded because of other previous operations and left-side main thoracic curve, 22% (24 of 111) were excluded because they did not undergo surgery for the proximal thoracic curve with only pedicle screws, 21% (23 of 111) were excluded because the proximal thoracic curve was not corrected by convex compression and separate rod derotation, and another 3% (3 of 111) were lost before the minimum study follow-up of 2 years, leaving 50% (55 of 111) for analysis. During the study period, we generally chose T2 as the uppermost level instrumented when the apex was above T4, or T3 when the apex was T5. Apart from the uppermost-instrumented level, the groups did not differ in measurable ways such as age, sex, Cobb angles of proximal and main thoracic curves, and T1 tilt. However, shoulder balance was better in the T3 group preoperatively. The median (range) age at the time of surgery was 15 years (12 to 19 years). The median follow-up duration was 26 months (24 to 52 months). Whole-spine standing posteroanterior and lateral views were used to evaluate the improvement of radiologic parameters at the most recent follow-up and to compare the radiologic parameters between the uppermost-instrumented T2 (37 patients) and T3 (18 patients) vertebra groups. Finally, we analyzed radiologic factors related to shoulder balance, defined as the difference between the horizontal lines passing both superolateral tips of the clavicles (right-shoulder-up was positive), at the most recent follow-up. RESULTS: Convex compression with separate-rod derotation effectively corrected the proximal thoracic curve (41° ± 11° versus 17° ± 10°, mean difference 25° [95% CI 22° to 27°]; p < 0.001), and the most recent shoulder balance changed to right-shoulder-down compared with preoperative right-shoulder-up (8 ± 11 mm versus -8 ± 10 mm, mean difference 16 mm [95% CI 12 to 19]; p < 0.001). Proximal thoracic kyphosis decreased (13° ± 7° versus 11° ± 6°, mean difference 2° [95% CI 0° to 3°]; p = 0.02), while mid-thoracic kyphosis increased (12° ± 8° versus 18° ± 6°, mean difference -7° [95% CI -9° to -4°]; p < 0.001). Preoperative radiographic parameters did not differ between the groups, except for shoulder balance, which tended to be more right-shoulder-up in the T2 group (11 ± 10 mm versus 1 ± 11 mm, mean difference 10 mm [95% CI 4 to 16]; p = 0.002). At the most recent follow-up, the correction proportion of the proximal thoracic curve was better in the T2 group than the T3 group (67% ± 10% versus 49% ± 22%, mean difference 19% [95% CI 8% to 30%]; p < 0.001). In the T2 group, T1 tilt (6° ± 4° versus 6° ± 4°, mean difference 1° [95% CI 0° to 2°]; p = 0.045) and shoulder balance (-14 ± 11 mm versus -7 ± 9 mm, mean difference -7 mm [95% CI -11 to -3]; p = 0.002) at the most recent follow-up improved compared with those at the first erect radiograph. The most recent shoulder balance was correlated with the correction proportion of the proximal thoracic curve (r = 0.29 [95% CI 0.02 to 0.34]; p = 0.03) and change in T1 tilt (r = 0.35 [95% CI 0.20 to 1.31]; p = 0.009). CONCLUSION: Using the combination of convex compression and concave distraction with separate-rod derotation is an effective method to correct proximal and main thoracic curves, with reliable achievement of postoperative thoracic kyphosis and shoulder balance. T2 was a more appropriate uppermost-instrumented vertebra than T3, providing better correction of the proximal thoracic curve and T1 tilt. Additionally, spontaneous improvement in T1 tilt and shoulder balance is expected with upper-instrumented T2 vertebrae. Preoperatively, surgeons should evaluate shoulder balance because right-shoulder-down can occur after surgery in patients with a proximal thoracic curve. LEVEL OF EVIDENCE: Level III, therapeutic study.

Non-Cryogenic Structure and Dynamics of HIV-1 Integrase Catalytic Core Domain by X-ray Free-Electron Lasers.

HIV-1 integrase (HIV-1 IN) is an enzyme produced by the HIV-1 virus that integrates genetic material of the virus into the DNA of infected human cells. HIV-1 IN acts as a key component of the Retroviral Pre-Integration Complex (PIC). Protein dynamics could play an important role during the catalysis of HIV-1 IN; however, this process has not yet been fully elucidated. X-ray free electron laser (XFEL) together with nuclear magnetic resonance (NMR) could provide information regarding the dynamics during this catalysis reaction. Here, we report the non-cryogenic crystal structure of HIV-1 IN catalytic core domain at 2.5 Å using microcrystals in XFELs. Compared to the cryogenic structure at 2.1 Å using conventional synchrotron crystallography, there was a good agreement between the two structures, except for a catalytic triad formed by Asp64, Asp116, and Glu152 (DDE) and the lens epithelium-derived growth factor binding sites. The helix III region of the 140-153 residues near the active site and the DDE triad show a higher dynamic profile in the non-cryogenic structure, which is comparable to dynamics data obtained from NMR spectroscopy in solution state.

Does Preoperative Radiation Therapy Performed for Metastatic Spine Cancer at the Cervical Spine Increase Perioperative Complications of Anterior Cervical Surgery?

Background: Radiation therapy (RT) performed before anterior cervical spine surgery (ACSS) may cause fascial plane fibrosis, decreased soft-tissue vascularity, and vertebral body weakness, which could increase the risk of esophageal and major vessel injuries, wound complications, and construct subsidence. Therefore, this study aimed to evaluate whether preoperative RT performed for metastatic spine cancer (MSC) at the cervical spine increases perioperative morbidity for ACSS. Methods: Forty-nine patients who underwent ACSS for treatment of MSC at the cervical spine were retrospectively reviewed. All the patients underwent anterior cervical corpectomy via the anterior approach. Patient demographics, surgical factors, operative factors, and complications were recorded. Results of patients who were initially treated with RT before ACSS (RT group) were compared with those who did not receive RT before ACSS (non-RT group). Results: Eighteen patients (36.7%) were included in the RT group, while the remaining 31 (63.3%) were included in the non-RT group. Surgery-related factors, including operation time (p = 0.109), estimated blood loss (p = 0.246), amount of postoperative drainage (p = 0.604), number of levels operated (p = 0.207), and number of patients who underwent combined posterior fusion (p = 0.768), did not significantly differ between the 2 groups. Complication rates, including esophageal injury, dural tear, infection, wound dehiscence, and mechanical failure, did not significantly differ between the RT and non-RT groups. Early subsidence was significantly greater in the non-RT group compared to that in the RT group (p = 0.012). Conclusions: RT performed before surgery for MSC does not increase the risk of wound complication, mechanical failure, or vital structure injury during ACSS. The surgical procedural approach was not complicated by previous RT history. Therefore, surgeons can safely choose the anterior approach when the number of levels or location of MSC favors anterior surgery, and performing a posterior surgery is unnecessary due to a concern that previous RT may increase complication rates of ACSS.

Reoperation Rates According to Surgical Approach After Operation for Degenerative Cervical Pathology in Patients With Athetoid Cerebral Palsy: A Nationwide Cohort Study.

STUDY DESIGN: National population-based cohort study. OBJECTIVE: The overall complication rate for patients with athetoid cerebral palsy (CP) undergoing cervical surgery is significantly higher than that of patients without CP. The study was conducted to compare the reoperation and complication rates of anterior fusion, posterior fusion, combined fusion, and laminoplasty for degenerative cervical myelopathy/radiculopathy in patients with athetoid cerebral palsy. METHODS: The Korean Health Insurance Review and Assessment Service national database was used for analysis. Data from patients diagnosed with athetoid CP who underwent cervical spine operations for degenerative causes between 2002 and 2020 were reviewed. Patients were categorized into four groups for comparison: anterior fusion, posterior fusion, combined fusion, and laminoplasty. RESULTS: A total of 672 patients were included in the study. The overall revision rate was 21.0% (141/672). The revision rate was highest in the anterior fusion group (42.7%). The revision rates of combined fusion (11.1%; hazard ratio [HR], .335; P = .002), posterior fusion (13.8%; HR, .533; P = .030) were significantly lower than that of anterior fusion. Revision rate of laminoplasty (13.1%; HR, .541; P = .240) was also lower than anterior fusion although the result did not demonstrate statistical significance. CONCLUSION: Anterior fusion presented the highest reoperation risk after cervical spine surgery reaching 42.7% in patients with athetoid CP. Therefore, anterior-only fusion in patients with athetoid CP should be avoided or reserved for strictly selected patients. Combined fusion, with the lowest revision risk at 11.1%, could be safely applied to patients with athetoid CP.

Detection of Cervical Foraminal Stenosis from Oblique Radiograph Using Convolutional Neural Network Algorithm.

PURPOSE: This study was conducted to develop a convolutional neural network (CNN) algorithm that can diagnose cervical foraminal stenosis using oblique radiographs and evaluate its accuracy. MATERIALS AND METHODS: A total of 997 patients who underwent cervical MRI and cervical oblique radiographs within a 3-month interval were included. Oblique radiographs were labeled as "foraminal stenosis" or "no foraminal stenosis" according to whether foraminal stenosis was present in the C2-T1 levels based on MRI evaluation as ground truth. The CNN model involved data augmentation, image preprocessing, and transfer learning using DenseNet161. Visualization of the location of the CNN model was performed using gradient-weight class activation mapping (Grad-CAM). RESULTS: The area under the curve (AUC) of the receiver operating characteristic curve based on DenseNet161 was 0.889 (95% confidence interval, 0.851-0.927). The F1 score, accuracy, precision, and recall were 88.5%, 84.6%, 88.1%, and 88.5%, respectively. The accuracy of the proposed CNN model was significantly higher than that of two orthopedic surgeons (64.0%, p<0.001; 58.0%, p<0.001). Grad-CAM analysis demonstrated that the CNN model most frequently focused on the foramen location for the determination of foraminal stenosis, although disc space was also frequently taken into consideration. CONCLUSION: A CNN algorithm that can detect neural foraminal stenosis in cervical oblique radiographs was developed. The AUC, F1 score, and accuracy were 0.889, 88.5%, and 84.6%, respectively. With the current CNN model, cervical oblique radiography could be a more effective screening tool for neural foraminal stenosis.

XFEL structure of carbonic anhydrase II: a comparative study of XFEL, NMR, X-ray and neutron structures.

The combination of X-ray free-electron lasers (XFELs) with serial femtosecond crystallography represents cutting-edge technology in structural biology, allowing the study of enzyme reactions and dynamics in real time through the generation of `molecular movies'. This technology combines short and precise high-energy X-ray exposure to a stream of protein microcrystals. Here, the XFEL structure of carbonic anhydrase II, a ubiquitous enzyme responsible for the interconversion of CO2 and bicarbonate, is reported, and is compared with previously reported NMR and synchrotron X-ray and neutron single-crystal structures.

The Perioperative Effects of Preoperative Radiotherapy in Metastatic Spinal Tumor Patients.

OBJECTIVE: Radiotherapy is one of the important treatment options for metastatic spinal tumors but is not the definite intervention in all cases, as there are patients who still require surgical treatment because of severe pain or neurologic events after this treatment. We evaluated the perioperative effects of preoperative radiotherapy in these cases as a future guide for surgeons on critical considerations in this period. METHODS: We included 328 patients in this study who had undergone decompression and fusion surgery for metastatic spinal tumors. Patients who underwent surgery with preoperative radiotherapy were designated as the radiotherapy group (group RT, n = 81), and cases of surgery without preoperative radiotherapy were assigned to the non-radiotherapy group (group nRT, n = 247). We compared the demographic, intraoperative, and postoperative factors between these 2 groups. RESULTS: In terms of intraoperative factors, statistically significant differences were evident in operation time, estimated blood loss, and transfusion (RT vs. nRT: 188.1 ± 80.7 minutes vs. 231.2 ± 106.1 minutes, 607.2 ± 532.7 mL vs. 830.1 ± 1324.7 mL, and 30.9% vs. 43.3%, P < 0.001, P < 0.031, and P < 0.048, respectively). With regard to postoperative factors, the incidence of infection, wound problems, and local recurrence were statistically higher in group RT (RT vs. nRT: 6.2% vs. 0.8%, 12.3% vs. 0.8%, 23.4% vs. 13.7%, P = 0.004, P < 0.001, and P = 0.038, respectively). CONCLUSIONS: Preoperative radiotherapy has the intraoperative advantages of reducing bleeding and shortening the operating time, but postoperative caution is needed because of the possibility of infection, wound problems, and local recurrence increases.

Risk factors of revision operation and early revision for adjacent segment degeneration after lumbar fusion surgery: a case-control study.

BACKGROUND CONTEXT: Adjacent segment degeneration (ASD) following lumbar fusion operation is common and can occur at varying timepoints after index surgery. An early revision operation for ASD, however, signifies a short symptom-free period and might increase the risk of successive surgeries. PURPOSE: We aimed to elucidate the overall risk factors associated with revision surgeries for ASD with distinct attention to early revisions. STUDY DESIGN/SETTING: Retrospective, case-control study. PATIENT SAMPLE: The study included 86 patients who underwent revision operations for ASD after lumbar fusion in the revision group and 166 patients who did not for at least 5 years after index surgery. OUTCOME MEASURES: Sagittal parameters, Pfirrmann grading, facet degeneration grading, and disc space height (DSH) of adjacent segments were assessed. METHODS: Revision operations within 5 years postsurgery were defined as early revision. We compared the revision and no-revision groups as well as the early- and late-revision groups. RESULTS: The revision group demonstrated a significantly greater preoperative C7-S1 sagittal vertical axis (SVA) (p=.001), postoperative C7-S1 SVA (p<.001), and postoperative pelvic incidence (PI)-lumbar lordosis (LL) (p<.001) than those in the no-revision group. Preoperative DSH of the proximal adjunct segment (p=.001), postoperative PI-LL (p=.014), and postoperative C7-S1 SVA (p=.037) exhibited significant association with ASD in logistic regression analysis. The early-revision group had a significantly higher patient age (p=.001) and a greater number of levels fused (p=.030) than those in the late-revision group. Multivariate Cox regression analysis demonstrated that old age (p=.045), a significant number of levels fused (p=.047), and a narrow preoperative DSH of the proximal adjacent level (p=.011) were risk factors for early revision. CONCLUSIONS: Postoperative sagittal imbalance, including significant PI-LL and C7-S1 SVA were risk factors for revision operation for ASD but not for early revision. These factors are likely to affect the long-term risk of revision operation due to ASD and thus are not considered risk factors for early revision. Narrow DSH of the proximal adjacent level increased the risks of both revision and early revision surgeries. Moreover, old age and a significant number of levels fused further increased the risk for early revision for ASD.

Which Radiographic Parameter Can Aid in Deciding Optimal Allograft Height for Anterior Cervical Discectomy and Fusion?

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To identify preoperative radiographic parameters that can guide optimal allograft height selection for anterior cervical discectomy and fusion (ACDF). SUMMARY OF BACKGROUND DATA: Allograft height selection for ACDF depends on intraoperative assessment supported by trials; however, there is currently no radiographic reference parameter that could aid in allograft height selection for improved outcomes. METHODS: A total of 148 patients who underwent ACDF using allografts and were followed up for more than 1 year were retrospectively reviewed. Fusion rates, subsidence, segmental lordosis, and foraminal height were assessed. Segments were divided into 2 groups according to whether the inserted allograft height was within 1 mm from the following 3 reference radiographic parameters: (1) uncinate process height, (2) adjacent disc height, and (3) preoperative disc height +2 mm. RESULTS: This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤1 mm had a significantly higher fusion rate at 1-year follow-up compared with segments with allograft-uncinate height difference of >1 mm [85/107 (79.4%) vs. 35/56 (62.5%); P =0.025]. Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤1 mm and allograft failure were factors associated with fusion. CONCLUSIONS: The uncinate process height can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used in conjunction with intraoperative assessment when selecting allograft height.

Comparison of Fusion, Subsidence, and Clinical Results Between 3D-Printed Porous Titanium Cage and Polyetheretherketone Cage in Posterior Lumbar Interbody Fusion: A Minimum of 2 Years Follow-Up.

OBJECTIVE: The occurrence of early osteointegration and reduced modulus of elasticity have been proved with 3-dimensinally (3D) printed porous titanium (3DP-titanium) cages used for posterior lumbar interbody fusion (PLIF). The present study was conducted to demonstrate the fusion rate, subsidence, and clinical outcomes for the 3DP-titanium cage in PLIF and to compare its results with those of the polyetheretherketone (PEEK) cage. METHODS: A total of 150 patients who underwent 1-2-level PLIF and were followed up for >2 years were retrospectively reviewed. The fusion rates, subsidence, segmental lordosis, visual analog scale (VAS) score for back pain, VAS score for leg pain, and Oswestry disability index were assessed. RESULTS: A higher 1-year (3DP-titanium, 86.9%; PEEK, 67.7%; P = 0.002) and 2-year (3DP-titanium, 92.9%; PEEK, 82.3%; P = 0.037) fusion rate could be achieved with 3DP-titanium cages for PLIF than with PEEK cages. The amount of subsidence (3DP-titanium, 1.4 ± 1.6 mm; PEEK, 1.9 ± 1.8 mm; P = 0.092) and incidence of significant subsidence (3DP-titanium, 17.9%; PEEK, 23.4%; P = 0.389) was not significantly different between the 2 materials. Furthermore, the VAS score for back pain and leg pain and Oswestry disability index were not significantly different between the 2 groups. On logistic regression analysis, cage material (P = 0.027) showed a significant association with fusion, and the number of levels fused (P = 0.012) was associated with subsidence. CONCLUSIONS: The 3DP-titanium cage resulted in a higher fusion rate than the PEEK cage when used for PLIF. The subsidence rate did not differ significantly between the 2 cage materials. Therefore, the 3DP-titanium cage can be safely used for PLIF, considering its stable construct.

Preoperative Radiographic Simulation for Partial Uncinate Process Resection during Anterior Cervical Discectomy and Fusion to Achieve Adequate Foraminal Decompression and Prevention of Vertebral Artery Injury.

STUDY DESIGN: Retrospective radiographic study. PURPOSE: This study aims to demonstrate the proper resection trajectory of a partial posterior uncinate process resection combined with anterior cervical discectomy and fusion (ACDF) and evaluate whether foraminal stenosis or uncinate process degeneration increases the risk of vertebral artery (VA) injury. OVERVIEW OF LITERATURE: Appropriate resection trajectory that could result in sufficient decompression and avoid vertebral artery injury is yet unknown. METHODS: We retrospectively reviewed patients who underwent cervical magnetic resonance imaging and computed tomography angiography for preoperative ACDF evaluation. The segments were classified according to the presence of foraminal stenosis. The height, thickness, anteroposterior length, horizontal distance from the uncinate process to the VA, and vertical distance from the uncinate process baseline to the VA of the uncinate process were measured. The distance between the uncinate anterior margin and the resection trajectory (UAM-to-RT) was measured. RESULTS: There were no VA injuries or root injuries among the 101 patients who underwent ACDF (163 segments, mean age of 56.3±12.2). Uncinate anteroposterior length was considerably longer in foramens with foraminal stenosis, whereas uncinate process height, thickness, and distance between the uncinate process and VA were not significantly associated with foraminal stenosis. There were no significant differences in radiographic parameters based on uncinate degeneration. The UAM-to-RT distances for adequate decompression were 1.6±1.4 mm (range, 0-4.8 mm), 3.4±1.7 mm (range, 0-7.1 mm), 4.0±1.7 mm (range, 0-9.0 mm), and 4.5±1.2 mm (range, 2.5-7.5 mm) for C3-C4, C4-C5, C5-C6, and C6-C7, respectively. CONCLUSIONS: More than half of the uncinate process in the anteroposterior plane should be removed for adequate neural foramen decompression. Foraminal stenosis or uncinate degeneration did not alter the relative anatomy of the uncinate process and the VA and did not impact VA injury risk.

Risk Factors and Exit Strategy of Intraoperative Neurophysiological Monitoring Alert During Deformity Correction for Adolescent Idiopathic Scoliosis.

STUDY DESIGN: Retrospective cohort study. OBJECTIVE: To elucidate the risk factors of intraoperative neurophysiological monitoring (IONM) alert during deformity correction surgery for adolescent idiopathic scoliosis (AIS) and to describe the outcomes of patients who underwent staged correction surgery due to IONM alert during the initial procedure. METHODS: We reviewed 1 024 patients with idiopathic scoliosis who underwent deformity correction and were followed-up for ≥1 year. The pre-and postoperative Cobb angle of the major structural curve, operative time, estimated blood loss (EBL), number of levels fused, event that caused the IONM alert, and intervention required for the recovery of the signal were recorded. Patients who received IONM alerts (alert group) and those who did not (non-alert group) during the operation were compared. RESULTS: Compared to the non-alert group, the alert group had a significantly greater preoperative Cobb angle of the major structural curve (P < .001), number of levels fused (P = .003), operative time (P < .001), and EBL (P < .001). The percentage of correction did not significantly differ between the 2 groups (P = .348). Eight patients (.8%) underwent a staged operation because the IONM signal alert hindered correction of the deformity. The percentage of correction of patients who underwent staged operation was 64.9 ± 15.1%, and no permanent neurologic deficits occurred. CONCLUSIONS: A greater magnitude of preoperative deformity and surgical extent increases the risk of cord injury identified by IONM alerts during correction of deformities in patients with AIS. However, in patients in whom the IONM alert cannot be recovered or reproduced by proceeding with deformity correction, surgeons can minimize the risk by aborting the initial procedure and completing the correction using staged operations.

Relationship Between C2 Semispinalis Cervicis Preservation and C2 Spinous Process Morphology During Cervical Laminoplasty Involving C3.

STUDY DESIGN: Retrospective study. OBJECTIVES: Due to anatomical variations in the semispinalis cervicis insertion in the C2 spinous process, complete preservation is not always possible when the C3 level is included in a cervical laminoplasty. Three-dimensional computed tomography was used to evaluate the relationship between the incidence of semispinalis cervicis injury and the C2 inter-spinous angle. METHODS: We included 95 patients who underwent a cervical laminoplasty that included a C3 laminectomy for cervical myelopathy. Patients with a C2 inter-spinous angle above and below 60° were classified into wide- and narrow-angled groups, respectively (n = 48 and n = 47). Whether the C2 semispinalis cervicis insertion was preserved, or detached and reattached was reviewed from surgical records. The pre and postoperative C2-C7 lordosis and range of motion (ROM) were measured, and clinical outcomes were obtained from the patient charts. RESULTS: The C2 semispinalis cervicis was preserved in 47 patients (97.9%) in the wide-angled group but only in 14 patients (29.8%) in the narrow-angled group (P < .001). The postoperative C2-C7 lordosis extension and ROM were significantly greater in the wide-angled (P = .048 and .036). Postoperative neck pain was significantly greater in the narrow-angled (P = .018). CONCLUSIONS: The morphology of the C2 spinous process indicates that a C2 semispinalis cervicis insertion preservation is possible during a cervical laminoplasty that includes a C3 laminectomy. A careful surgical procedure should be conducted when the C2 inter-spinous angle is above 60° to increase the likelihood of achieving this preservation and thereby obtaining a more favorable clinical outcomes.

Foraminal Restenosis After Posterior Cervical Foraminotomy for the Treatment of Cervical Radiculopathy.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To elucidate incidence, risk factor, and clinical effect of bone regrowth after posterior cervical foraminotomy (PCF). METHODS: Ninety-eight patients who underwent PCF for the treatment of cervical radiculopathy and were followed up for >2 years were retrospectively reviewed. Foraminal dimension, sagittal gap at resected area, facet thickness, lamina length, and cervical range of motion (ROM) were measured. Neck pain visual analogue scale (VAS), arm pain VAS, and neck disability index (NDI) were recorded. Radiographic measures were compared between segments with foraminal narrowing of ≥20% at the 2-years follow-up (restenosis segments) and foraminal narrowing of <20% (patent segments). RESULTS: Sixty-nine patients with 109 segments were included. 73.4% (80/109) of foramens demonstrated foraminal narrowing and decrease of foraminal dimension of ≥20% occurred in 30.3% (30/109). Foraminal dimension at postoperative 2-days was significantly higher in the restenosis segments (P = .047). Furthermore, increase of foraminal dimension was significantly associated with foraminal restenosis of ≥20% (P = .018). Facet thickness was significantly higher in the restenosis segments compared to patent segments at postoperative 2-years follow-up (P = .038). Neck pain VAS was significantly aggravated only in the restenosis group at postoperative 2-years follow-up (P < .001). CONCLUSIONS: Foraminal narrowing commonly occurs after PCF due to bone healing. Bone growth occurs in all directions while medial facet growth contributes more to foraminal restenosis. Greater widening of foramen during PCF is a risk factor for postoperative foramen restenosis. Therefore, amount of bone resection should be kept optimal and excessive resection should be avoided to prevent foramen restenosis.

Vertebral Body Sliding Osteotomy as a Surgical Strategy for the Treatment of Cervical Myelopathy: Outcomes at Minimum Five years Follow-up.

STUDY DESIGN: A retrospective cohort study. OBJECTIVE: To evaluate the outcomes of vertebral body sliding osteotomy (VBSO) with a minimum follow-up of five years and compare the results with those of anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF). SUMMARY OF BACKGROUND DATA: VBSO reportedly results in fewer complications, better lordosis restoration, and faster bone union than corpectomy. Although previous studies demonstrate the outcomes of VBSO with follow-up of two years or longer, results in longer term surveillance remain unknown. METHODS: This study included 128 patients who underwent VBSO (n=38), ACDF (n=62), or ACCF (n=28) as a treatment for cervical myelopathy and was followed up for five years or more. Fusion, subsidence, C0-2 lordosis, C2-7 lordosis, segmental lordosis, C2-7 sagittal vertical axis, surgical complications, and neck pain visual analog scale, Neck Disability Index, and Japanese Orthopedic Association (JOA) scores were assessed. Comparisons between continuous variables in each group were made using independent sample t tests. For nominal variables, the Fisher exact test or the χ 2 test was used. Paired t test was used to analyze the changes in postoperative values compared with preoperative values. RESULTS: The reoperation rate (0.0%) after VBSO was significantly lower than that after ACCF (14.3%; P =0.028). VBSO had a higher fusion rate at six-month and one-year follow-up, but the fusion rate at five years (97.4%) was not significantly different from that of ACDF (85.5%; P =0.054) and ACCF (85.7%; P =0.077). Segmental lordosis at the five-year follow-up was significantly higher in the VBSO group (16.1°) than in the ACDF (11.9°; P =0.002) and ACCF (6.5°; P <0.001) groups. C2-7 lordosis at five-year follow-up was significantly higher in the VBSO group than in the ACCF group ( P =0.017). Neck pain visual analog scale, Neck Disability Index, and JOA scores and the JOA recovery rate did not show significant intergroup differences during the five-year study period. CONCLUSIONS: VBSO showed promising long-term results in terms of low revision rate, fast solid union, and effective segmental lordosis restoration when compared with other anterior reconstruction techniques.