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PURPOSE: To evaluate proximal junctional biomechanics of a MLSS relative to traditional pedicle screw fixation at the proximal extent of T10-pelvis posterior instrumentation constructs (T10-p PSF). METHODS: A previously validated three-dimensional osseoligamentous spinopelvic finite element (FE) model was used to compare proximal junctional range-of-motion (ROM), vertebral body stresses, and discal biomechanics between two groups: (1) T10-p with a T10-11 MLSS (T10-11 MLSS) and (2) T10-p with a traditional T10 pedicle screw (Traditional T10-PS). RESULTS: The T10-11 MLSS had a 5% decrease in T9 cortical bone stress compared to Traditional T10-PS. Conversely, the T10 and T11 bone stresses increased by 46% and 98%, respectively, with T10-11 MLSS compared to Traditional T10-PS. Annular stresses and intradiscal pressures (IDP) were similar at T9-T10 between constructs. At the T10-11 disc, T10-11 MLSS decreased annular stresses by 29% and IDP by 48% compared to Traditional T10-PS. Adjacent ROM (T8-9 & T9-10) were similar between T10-11 MLSS and Traditional T10-PS. T10-11 MLSS had 39% greater ROM at T10-11 and 23% less ROM at T11-12 compared to Traditional T10-PS. CONCLUSIONS: In this FE analysis, a T10-11 MLSS at the proximal extent of T10-pelvis posterior instrumentation resulted in increased T10 and T11 cortical bone stresses, decreased discal annular stress and IDP and increased ROM at T10-11, and no change in ROM at the adjacent level. Given the complex and multifactorial nature of proximal junctional kyphosis, these results require additional biomechanical and clinical evaluations to determine the clinical utility of MLSS on the proximal junctions of thoracolumbar posterior instrumented fusions.

Background. The development of the adjacent level syndrome and, as a consequence, adjacent segment degenerative disease are currently the most common complications of decompression and stabilization surgery with the development of segmental instability.The aim of the study. To conduct a comprehensive neuroimaging assessment of the proximal adjacent segment after rigid fixation and dynamic stabilization in degenerative lumbar disease.Materials and methods. We conducted a prospective multicenter study of the results of surgical treatment of 274 patients with degenerative-dystrophic diseases of the lumbar spine, who underwent monosegmental decompression and stabilization surgery using the TLIF (transforaminal lumbar interbody fusion) technique and open transpedicular rigid fixation, as well as open hemilaminectomy with stabilization of the operated segments with nitinol rods. The study included radiography, diffusion-weighted magnetic resonance imaging and computed tomography (dualenergy mode) of intervertebral discs and isolated facet degeneration of the upper adjacent level.Results and discussion. Combination of the initial proximal segment degeneration in the form of facet joints degeneration (density of cartilaginous plate – 163.5 ± 14.2 HU, density of external facet – 709.35 ± 13.6 HU, density of internal facet – 578.1 ± 12.1 HU), Pfirrmann III, IV grade degeneration of intervertebral disc and a measured diffusion coefficient of less than 1300 mm2/s cause high risks of developing adjacent segment degenerative disease, which regulates the use of monosegmental dynamic fixation with nitinol rods, or preventive rigid fixation of the adjacent segment.Conclusion. Using complex neuroimaging in the preoperative period makes it possible to predict the results of surgical treatment, take timely measures to prevent degenerative diseases of the adjacent segment, and to carry out dynamic monitoring of processes in the structures of the spinal motion segment.

Objective: The objective of the study was to evaluate the extent of deterioration in nearby upper and lower segments in lumbar isthmic and degenerative spondylolisthesis using magnetic resonance imaging (MRI). Material and Methods: A retrospective evaluation was conducted on lumbar spine MRI scans of 51 individuals diagnosed with isthmic spondylolisthesis and 55 individuals diagnosed with degenerative spondylolisthesis. Adjacent intervertebral segments were evaluated for disc space height, thickness of ligamentum flavum, spinal dural sac transverse area, disc degeneration, facet hypertrophy, and disc contour. Results: In all patients, both the upper segment (p=0.003) and lower segment (p=0.024) showed statistically significant differences between the two types of spondylolisthesis. Additionally, at the L4-L5 level (between the fourth and fifth lumbar vertebrae), there was a significant difference for the upper segment (p=0.005). There were statistically significant differences between the two types in the spinal dural sac transverse area in all patients for the upper segment (p=0.004), disc degeneration in all patients for the upper segment (p=0.003), disc contour in all patients for the upper segment (p=0.014), and L4-L5 level spondylolisthesis for the upper segment (p=0.021). Conclusion: Disc space height measurements, spinal dual sac transverse area, disc degeneration, and disc contour were all worse in adjacent segments of degenerative spondylolisthesis compared with isthmic spondylolisthesis.

Abstract Objective There may be biomechanical changes in the adjacent hip joint after lumbosacral fusion. The literature has limited information on how these biomechanical changes may result in hip joint space. Material method Our retrospective study examined hip joint space narrowing in patients who underwent lumbosacral fusion between 2020 and 2022. In addition, spinopelvic parameters such as sacral slope, the sagittal vertical axis, pelvic incidence, lumbar lordosis, and pelvic tilt were compared in patients who underwent short-segment (up to three levels, S group) and long-segment (4 and higher levels, L group) fusions. Results Our study found no significant relationship between spinopelvic parameters and joint space narrowing in the S and L groups. In addition, it was determined that there was more narrowing in the hip joint space in the long-segment group, and there was a positive correlation between the segment length and the narrowing in the hip joint space. Conclusion After lumbosacral fusion, narrowing of the hip joint space was observed. Particularly patients with long-segment lumbosacral fusion should be followed closely regarding hip osteoarthritis risk.

Spinal fusion surgery leads to the restriction of mobility in the vertebral segments postoperatively, thereby causing stress to rise at the adjacent levels, resulting in early degeneration and a high risk of adjacent vertebral fractures. Thus, to address this issue, non-fusion surgery applies some pedicle screw-based dynamic stabilisation systems to provide stability and micromotion, thereby reducing stress in the fusion segments. Among these systems, the hybrid performance stabilisation system (HPSS) combines a rigid rod, transfer screw, and coupler design to offer a semi-rigid fixation method that preserves some mobility near the fusion site and reduces the adjacent segment compensatory effects. However, further research and confirmation are needed regarding the biomechanical effects of the dynamic coupler stiffness of the HPSS on the intrinsic degenerated adjacent segment. Therefore, this study utilised the finite element method to investigate the impact of the coupler stiffness of the HPSS on the mobility of the lumbar vertebral segments and the stress distribution in the intervertebral discs under flexion, extension, and lateral bending, as well as the clinical applicability of the HPSS on the discs with intrinsic moderate and severe degeneration at the adjacent level. The analytical results indicated that, regardless of the degree of disc degeneration, the use of a dynamic coupler stiffness of 57 N/mm in the HPSS may reduce the stress concentrations at the adjacent levels. However, for severely degenerated discs, the postoperative stress on the adjacent segments with the HPSS was still higher compared with that of the discs with moderate degeneration. We conclude that, when the discs had moderate degeneration, increasing the coupler stiffness led to a decrease in disc mobility. In the case of severe disc degeneration, the effect on disc mobility by coupler stiffness was less pronounced. Increasing the coupler stiffness ked to higher stress on intervertebral discs with moderate degeneration, while its effect on stress was less pronounced for discs with severe degeneration. It is recommended that patients with severe degeneration who undergo spinal dynamic stabilisation should remain mindful of the risk of accelerated adjacent segment degeneration. [ABSTRACT FROM AUTHOR]

Objective: The objective of the study was to evaluate the extent of deterioration in nearby upper and lower segments in lumbar isthmic and degenerative spondylolisthesis using magnetic resonance imaging (MRI). Material and Methods: A retrospective evaluation was conducted on lumbar spine MRI scans of 51 individuals diagnosed with isthmic spondylolisthesis and 55 individuals diagnosed with degenerative spondylolisthesis. Adjacent intervertebral segments were evaluated for disc space height, thickness of ligamentum flavum, spinal dural sac transverse area, disc degeneration, facet hypertrophy, and disc contour. Results: In all patients, both the upper segment (p=0.003) and lower segment (p=0.024) showed statistically significant differences between the two types of spondylolisthesis. Additionally, at the L4-L5 level (between the fourth and fifth lumbar vertebrae), there was a significant difference for the upper segment (p=0.005). There were statistically significant differences between the two types in the spinal dural sac transverse area in all patients for the upper segment (p=0.004), disc degeneration in all patients for the upper segment (p=0.003), disc contour in all patients for the upper segment (p=0.014), and L4-L5 level spondylolisthesis for the upper segment (p=0.021). Conclusion: Disc space height measurements, spinal dual sac transverse area, disc degeneration, and disc contour were all worse in adjacent segments of degenerative spondylolisthesis compared with isthmic spondylolisthesis. [ABSTRACT FROM AUTHOR]

Abstract Objective Posterior instrumented fusion is the most widely accepted surgical treatment for spinal stenosis and disc herniation. However, fusion can affect daily activities due to lumbar stiffness. In recent years, dynamic stabilization has been introduced to overcome the drawbacks of fusion, however, it is inconclusive whether dynamic stabilization requires the maintenance of a level of activity that is closer to the physiological state of activity for better clinical efficacy. The purpose of this study was to compare the effectiveness of dynamic stabilization with different levels of activity (Isobar EVO and TTL) in the treatment of spinal stenosis and disc herniation. Methods This study retrospectively reviewed 80 consecutive patients with lumbar degenerative diseases who were undergoing surgical treatment between March 2014 and July 2018. 41 patients (EVO group) and 39 patients (TTL group) underwent fenestrated decompression with Isobar EVO stabilization and Isobar TTL stabilization, respectively. Clinical outcomes, radiographic data, and postoperative complications were compared between the two groups. Results At an average follow-up of 52.23 ± 2.97 months, there were no significant differences in the oswestry disability index (ODI) (P > 0.05). The visual analog scale for back pain (VASback) and visual analog scale for the leg pain (VASleg) of the EVO group were lower compared with the TTL group (P 0.05). Conclusion Both Isobar EVO dynamic stabilization and TTL dynamic stabilization can improve clinical outcomes of patients with spinal stenosis and disc herniation. Isobar EVO has advantages over Isobar TTL in terms of improving low back and leg pain, maintaining mobility of the operated segment, and preventing further degeneration of the upper adjacent segment.

Objective: There may be biomechanical changes in the adjacent hip joint after lumbosacral fusion. The literature has limited information on how these biomechanical changes may result in hip joint space. Material: method: Our retrospective study examined hip joint space narrowing in patients who underwent lumbosacral fusion between 2020 and 2022. In addition, spinopelvic parameters such as sacral slope, the sagittal vertical axis, pelvic incidence, lumbar lordosis, and pelvic tilt were compared in patients who underwent short-segment (up to three levels, S group) and long-segment (4 and higher levels, L group) fusions. Results: Our study found no significant relationship between spinopelvic parameters and joint space narrowing in the S and L groups. In addition, it was determined that there was more narrowing in the hip joint space in the long-segment group, and there was a positive correlation between the segment length and the narrowing in the hip joint space. Conclusion: After lumbosacral fusion, narrowing of the hip joint space was observed. Particularly patients with long-segment lumbosacral fusion should be followed closely regarding hip osteoarthritis risk. [ABSTRACT FROM AUTHOR]

Rigid spinal fusion with instrumentation has been widely applied in treating degenerative spinal disorders and has shown excellent and stable surgical results. However, adjacent segment pathology or implants' loosening could be problematic due to the spine's segmental fusion. Therefore, this study verified a novel concept for posterior stabilization with polyethylene inserts inside a pedicle screw assembly using bone models. We observed that although the gripping capacity of the dynamic pedicle screw system using a tensile and compression tester was less than half that of the rigid pedicle screw system, the flexion‐extension moment of the dynamic pedicle screws was significantly lower than that of the rigid pedicle screws. Furthermore, while the bending force of the rigid pedicle screw assembly increased linearly with an increase in the bending angle throughout the test, that of the dynamic pedicle screw assembly also increased linearly until a bending angle of 2.5° was reached. However, this angle decreased at a bending angle of more than 2.5°. Additionally, the fatigue test of 1.0 × 106 cycles showed that the pull‐out force of the dynamic pedicle screws from two different polyurethane foam blocks was significantly higher than that of the rigid pedicle screws. Therefore, based on our results, we propose that the device can be applied in clinical cases to reduce screw loosening and adjacent segment pathology. [ABSTRACT FROM AUTHOR]

Introduction. According to the literature, the development of adjacent-level syndrome 10 years after posterior rigid stabilization is noted in 6.7–80 % of patients, of which 24 % require revision surgery.The aim: to conduct a comprehensive analysis of the results of surgical treatment of patients with degenerative diseases of the lumbar spine using rigid fixation systems.Materials and methods. A multicenter retrospective study of the results of surgical treatment of 268 patients with degenerative-dystrophic diseases of the lumbar spine, who underwent mono- or bisegmental decompression-stabilizing intervention with the implementation of the TLIF (Transforaminal Lumbar Interbody Fusion) technique and open transpedicular rigid fixation, was conducted. The study included radiography, MRI and CT (in 2-energy mode) of intervertebral discs and isolated facet degeneration of the upper adjacent level.Results and discussion. The combination of the initial degeneration of the adjacent spinal motion segment in the form of disc degeneration of grade III and higher according to Pfirrmann with threshold values of the density of the outer cartilaginous plate from 161.7 ± 18.8 to 164.8 ± 14.2 HU, the density of the outer facet – from 702.43 ± 12.3 to 713.65 ± 13.6 HU and the density of the inner facet – from 580.5 ± 11.6 to 582.1 ± 15.1 HU, as well as with signs of segmental instability of the adjacent segment can be considered as risk factors for the development of its degeneration. With the progression of degeneration of the upper intervertebral disc, revision interventions were performed within 12–60 months after surgery.Conclusion. Bisegmental stabilization with signs of initial degeneration in the intervertebral disc and facet joints in the upper segment has proven its clinical and instrumental effectiveness in the period of 36 months and reduces the risks of developing degenerative disease of the adjacent disc.

Purpose: Sagittal malalignment is a risk factor for mechanical complications after surgery for adult spinal deformity (ASD). Spinal loads, modulated by sagittal alignment, may explain this relationship. The aims of this study were to investigate the relationships between: (1) postoperative changes in loads at the proximal segment and realignment, and (2) absolute postoperative loads and postoperative alignment measures. Methods: A previously validated musculoskeletal model of the whole spine was applied to study a clinical sample of 205 patients with ASD. Based on clinical and radiographic data, pre-and postoperative patient-specific alignments were simulated to predict loads at the proximal segment adjacent to the spinal fusion. Results: Weak-to-moderate associations were found between pre-to-postop changes in lumbar lordosis, LL (r = − 0.23, r = − 0.43; p < 0.001), global tilt, GT (r = 0.26, r = 0.38; p < 0.001) and the Global Alignment and Proportion score, GAP (r = 0.26, r = 0.37; p < 0.001), and changes in compressive and shear forces at the proximal segment. GAP score parameters, thoracic kyphosis measurements and the slope of upper instrumented vertebra were associated with changes in shear. In patients with T10-pelvis fusion, moderate-to-strong associations were found between postoperative sagittal alignment measures and compressive and shear loads, with GT showing the strongest correlations (r = 0.75, r = 0.73, p < 0.001). Conclusions: Spinal loads were estimated for patient-specific full spinal alignment profiles in a large cohort of patients with ASD pre-and postoperatively. Loads on the proximal segments were greater in association with sagittal malalignment and malorientation of proximal vertebra. Future work should explore whether they provide a causative mechanism explaining the associated risk of proximal junction complications. [ABSTRACT FROM AUTHOR]

Introduction: The present study aimed to understand the characteristics of adjacent segment stenosis post-surgery by examining the status of adjacent segment stenosis in patients with long-term follow-up after muscle-preserving selective laminectomy (SL). Methods: We examined 43 patients who underwent muscle-preserving SL at a single academic institution and were followed up for >10 years. The C2-C7 angle, C2-C7 sagittal vertical axis, range of motion, and C7 slope were measured using an X-ray lateral view. The anterior-posterior diameter of the spinal cord (AP of SC) and anterior-posterior diameter of the dural tube (AP of dura) at adjacent segment were measured using magnetic resonance imaging T2-weighted sagittal section. Residual space for the spinal cord at the adjacent segment (SAC) was calculated as the difference between AP of SC and AP of dura. Results: Four cases had cephalad adjacent segment stenosis at the last follow-up (upper stenosis (US) group), 9 cases had caudal adjacent segment stenosis ( lower stenosis (LS) group), and 30 cases had no stenosis (none (N) group). AP of SC, AP of dura, and SAC at the upper adjacent segment were significantly lower in the US group. AP of dura and SAC at the lower adjacent segment were significantly lower in the LS group. Multivariate logistic regression analysis revealed that the small AP of dura in the upper adjacent segment and small SAC in the lower adjacent segment were risk factors for developing a new stenosis. Conclusions: Decompression should be considered beforehand in adjacent segments with small AP of SC and small AP of dura when performing cervical decompression.

Study Design: Prospective randomized placebo controlled animal trial.Objective: Determine the effect of daily subcutaneous abaloparatide injection on the intervertebral fusion rate in rabbits undergoing posterolateral fusion.Study Of Background Data: Despite the wide utilization of spine fusion, pseudarthrosis remains prevalent, and results in increased morbidity. Abaloparatide is a novel analog of parathyroid hormone-related peptide (1-34) and has shown efficacy in a rat posterolateral spine fusion model to increase fusion rates. The effect of abaloparatide on the fusion rate in a larger animal model remains unknown.Materials and Methods: A total of 24 skeletally mature New Zealand White male rabbits underwent bilateral posterolateral spine fusion. Following surgery, the rabbits were randomized to receive either saline as control or abaloparatide subcutaneous injection daily. Specimens underwent manual assessment of fusion, radiographic analysis with both x-ray and high-resolution peripheral quantitative computed tomography, and biomechanical assessment.Results: Rabbits that received abaloparatide had a 100% (10/10) fusion rate compared with 45% (5/11) for controls ( P <0.02) as assessed by manual palpation. Radiographic analysis determined an overall mean fusion score of 4.17±1.03 in the abaloparatide group versus 3.39±1.21 for controls ( P <0.001). The abaloparatide group also had a greater volume of bone formed with a bone volume of 1209±543 mm 3 compared with 551±152 mm 3 ( P <0.001) for controls. The abaloparatide group had significantly greater trabecular bone volume fraction and trabecular thickness and lower specific bone surface and connectivity density in the adjacent levels when compared with controls. Abaloparatide treatment did not impact trabecular number or separation. There were no differences in biomechanical testing in flexion, extension, or lateral bending ( P >0.05) between groups.Conclusions: Abaloparatide significantly increased the fusion rate in a rabbit posterolateral fusion model as assessed by manual palpation. In addition, there were marked increases in the radiographic evaluation of fusion. [ABSTRACT FROM AUTHOR]

To compare radiographic parameters at adjacent segments before and after minimally invasive transforaminal lumbar interbody fusion and assess relationships of radiographic changes between adjacent segments and fused level. Study participants included 44 patients who underwent minimally invasive transforaminal lumbar interbody fusion at L4-5 level. Radiographic parameters at adjacent segments (L3-4 and L5-S1) and clinical parameters were reviewed. Postoperative dural sac area significantly increased in upper (mean change 8.05 mm2, P < 0.001) and lower (14.08 mm2, P < 0.001) adjacent segments. Significant increases in SAPD were seen in upper (0.85 mm, P < 0.001) and lower (0.66 mm, P < 0.001) adjacent segments. Ligamentum flavum thickness significantly decreased in lower adjacent segments (−0.37 mm, P = 0.006). For every 1-mm increase in fused level disc height, lower SAPD increased 0.22 mm (P = 0.04), and lower segmental angle increased 0.91° (P = 0.04). For every 1° increase in fused level segmental angle, lower dural sac area increased 1.25 mm2 (P = 0.03), and lower SAPD increased 0.12 mm (P = 0.003). The 6- and 12-month postoperative visual analog scale back and leg scores significantly decreased compared with preoperatively (back: mean change −5.98 and −6.05, P < 0.001; leg: −6.86 and −6.89, P < 0.001). Performing minimally invasive transforaminal lumbar interbody fusion at the symptomatic index level does not worsen canal dimension of asymptomatic adjacent segments during short-term follow-up. It might be possible to improve canal dimension at adjacent segments by changing disc height or lordosis at the fused level via adjusting size and position of the interbody cage. [ABSTRACT FROM AUTHOR]

Spinal fusion surgery leads to the restriction of mobility in the vertebral segments postoperatively, thereby causing stress to rise at the adjacent levels, resulting in early degeneration and a high risk of adjacent vertebral fractures. Thus, to address this issue, non-fusion surgery applies some pedicle screw-based dynamic stabilisation systems to provide stability and micromotion, thereby reducing stress in the fusion segments. Among these systems, the hybrid performance stabilisation system (HPSS) combines a rigid rod, transfer screw, and coupler design to offer a semi-rigid fixation method that preserves some mobility near the fusion site and reduces the adjacent segment compensatory effects. However, further research and confirmation are needed regarding the biomechanical effects of the dynamic coupler stiffness of the HPSS on the intrinsic degenerated adjacent segment. Therefore, this study utilised the finite element method to investigate the impact of the coupler stiffness of the HPSS on the mobility of the lumbar vertebral segments and the stress distribution in the intervertebral discs under flexion, extension, and lateral bending, as well as the clinical applicability of the HPSS on the discs with intrinsic moderate and severe degeneration at the adjacent level. The analytical results indicated that, regardless of the degree of disc degeneration, the use of a dynamic coupler stiffness of 57 N/mm in the HPSS may reduce the stress concentrations at the adjacent levels. However, for severely degenerated discs, the postoperative stress on the adjacent segments with the HPSS was still higher compared with that of the discs with moderate degeneration. We conclude that, when the discs had moderate degeneration, increasing the coupler stiffness led to a decrease in disc mobility. In the case of severe disc degeneration, the effect on disc mobility by coupler stiffness was less pronounced. Increasing the coupler stiffness ked to higher stress on intervertebral discs with moderate degeneration, while its effect on stress was less pronounced for discs with severe degeneration. It is recommended that patients with severe degeneration who undergo spinal dynamic stabilisation should remain mindful of the risk of accelerated adjacent segment degeneration.

Purpose: Anterior cervical discectomy and fusion (ACDF) is a common surgical treatment for degenerative disease in the cervical spine. However, resultant biomechanical alterations may predispose to early-onset adjacent segment degeneration (EO-ASD), which may become symptomatic and require reoperation. This study aimed to develop and validate a machine learning (ML) model to predict EO-ASD following ACDF. Methods: Retrospective review of prospectively collected data of patients undergoing ACDF at a quaternary referral medical center was performed. Patients > 18 years of age with > 6 months of follow-up and complete pre- and postoperative X-ray and MRI imaging were included. An ML-based algorithm was developed to predict EO-ASD based on preoperative demographic, clinical, and radiographic parameters, and model performance was evaluated according to discrimination and overall performance. Results: In total, 366 ACDF patients were included (50.8% male, mean age 51.4 ± 11.1 years). Over 18.7 ± 20.9 months of follow-up, 97 (26.5%) patients developed EO-ASD. The model demonstrated good discrimination and overall performance according to precision (EO-ASD: 0.70, non-ASD: 0.88), recall (EO-ASD: 0.73, non-ASD: 0.87), accuracy (0.82), F1-score (0.79), Brier score (0.203), and AUC (0.794), with C4/C5 posterior disc bulge, C4/C5 anterior disc bulge, C6 posterior superior osteophyte, presence of osteophytes, and C6/C7 anterior disc bulge identified as the most important predictive features. Conclusions: Through an ML approach, the model identified risk factors and predicted development of EO-ASD following ACDF with good discrimination and overall performance. By addressing the shortcomings of traditional statistics, ML techniques can support discovery, clinical decision-making, and precision-based spine care. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this retrospective study was to evaluate radiological and clinical outcomes in patients undergoing cervical disc arthroplasty (CDA) for cervical degenerative disc disease. The results may assist in surgical decision-making and enable more effective and safer implementation of cervical arthroplasty. Materials and Methods: A total of 125 patients who were treated with CDA between 2006 and 2019 were assessed. Radiological measurements and clinical outcomes included the visual analogue scale (VAS), the Neck Disability Index (NDI), and the Japanese Orthopaedic Association (JOA) myelopathy score assessment preoperatively and at ≥2 years of follow-up. Results: The mean follow-up period was 38 months (range, 25-114 months). Radiographic data demonstrated mobility at both the index and adjacent levels, with no signs of hypermobility at an adjacent level. There was a non-significant loss of cervical global motion and range of motion (ROM) of the functional spinal unit at the operated level, as well as the upper and lower adjacent disc levels, compared to preoperative status. The cervical global and segmental angle significantly increased. Postoperative neck VAS, NDI, and JOA scores showed meaningful improvements after one- and two-level CDA. We experienced a 29.60% incidence of heterotrophic ossification and a 3.20% reoperation rate due to cervical instability, implant subsidence, or osteolysis. Conclusion: CDA is an effective surgical technique for optimizing clinical outcomes and radiological results. In particular, the preservation of cervical ROM with an artificial prosthesis at adjacent and index levels and improvement in cervical global alignment could reduce revision rates due to adjacent segment degeneration. [ABSTRACT FROM AUTHOR]

Abstract Purpose To compare the effect of conventional pedicle screw (CPS) and cement-augmented pedicle screw instrumentation (CAPSI) on adjacent segment degeneration (ASD). Methods A normal male volunteer without a history of spinal disease was selected, lumbar CT data was collected, an intact L3-S1 three-dimensional finite element model was created by software including Mimics, Geomagic, and SolidWorks, and the fixation methods were performed accordingly. A common pedicle screw model and a cement-augmented pedicle screw model of L4–L5 with fusion and internal fixation were constructed. With ANSYS Workbench 17.0, a 500 N load was applied to the upper surface of L3 to simulate the weight of a human body, and a 7.5 N m moment was applied at the neutral point to simulate flexion, extension, left/right bending, left/right rotation of the spine. The peak von Mises stress of intervertebral disc and the range of motion (ROM) on the adjacent segments (L3–4 and L5–S1) were compared. Results The validity of the intact model shows that the ROM of the model is similar to that of a cadaveric study. Compared with the intact model, CPS model and CAPSI model in all motion patterns increased the ROM of adjacent segments. The intervertebral disc stress and the ROM of adjacent segments were found to be higher in the CAPSI model than in the CPS model, especially in L3–4. Conclusion In general, the biomechanical analysis of an osteoporotic lumbar spine showed that both CPS and CAPSI can increase the ROM and disc stresses of osteoporotic lumbar models, and compared with CPS, CAPSI is more likely to increase the potential risk of adjacent segment degeneration.

Aims and Objectives: The human spine degenerates with age. Intervertebral disc degeneration occurs in the cervical spine. The objective of this study is to determine the effects of degenerative disc diseases on the range of motion (ROM) of the human cervical spinal column using a validated finite-element model. Materials and Methods: The validated intact and healthy C2–T1 finite-element model simulated the cortical shell, cancellous core, posterior elements of the vertebrae, and spinal ligaments (longitudinal, capsular, spinous and ligamentum flava, and nucleus and annulus of the discs). Three different stages of the disc disease, that is, mild, moderate, and severe, were simulated at the C5–C6, C6–C7, and C5–C6–C7 discs, respectively, and they were termed as upper single level, lower single level, and bi-level (BL) models, respectively. The material properties and geometry of the disc(s) were altered to simulate the different stages of degeneration. The external mechanical loading was applied in the sagittal mode, via flexion–extension motions and the magnitude was 2.0 Nm for each mode. They were applied to each of the healthy and disc degeneration models, and for each of the three severities of degeneration. The ROM at adjacent and index levels was extracted and normalized with respect to the healthy (baseline) spine. Results: A nonuniform distribution in the ROM was found for different disc degeneration states, segmental levels, and flexion–extension loading modes. The specific results for each and level are reported in the results section of the paper. Conclusion: Closer follow-up times may be necessary in symptomatic patients with progressive disease, especially with BL involvements.

Early onset adjacent segment degeneration (ASD) can be found within six months after anterior cervical discectomy and fusion (ACDF). Deficits in deep paraspinal neck muscles may be related to early onset ASD. This study aimed to determine whether the morphometry of preoperative deep neck muscles (multifidus and semispinalis cervicis) predicted early onset ASD in patients with ACDF. Thirty‐two cases of early onset ASD after a two‐level ACDF and 30 matched non‐ASD cases were identified from a large‐scale cohort. The preoperative total cross‐sectional area (CSA) of bilateral deep neck muscles and the lean muscle CSAs from C3 to C7 levels were measured manually on T2‐weighted magnetic resonance imaging. Paraspinal muscle CSA asymmetry at each level was calculated. A support vector machine (SVM) algorithm was used to identify demographic, radiographic, and/or muscle parameters that predicted proximal/distal ASD development. No significant between‐group differences in demographic or preoperative radiographic data were noted (mean age: 52.4 ± 10.9 years). ACDFs comprised C3 to C5 (n = 9), C4 to C6 (n = 20), and C5 to C7 (n = 32) cases. Eighteen, eight, and six patients had proximal, distal, or both ASD, respectively. The SVM model achieved high accuracy (96.7%) and an area under the curve (AUC = 0.97) for predicting early onset ASD. Asymmetry of fat at C5 (coefficient: 0.06), and standardized measures of C7 lean (coefficient: 0.05) and total CSA measures (coefficient: 0.05) were the strongest predictors of early onset ASD. This is the first study to show that preoperative deep neck muscle CSA, composition, and asymmetry at C5 to C7 independently predicted postoperative early onset ASD in patients with ACDF. Paraspinal muscle assessments are recommended to identify high‐risk patients for personalized intervention. [ABSTRACT FROM AUTHOR]

Abstract Objective To evaluate the short-term in vivo dynamic motion characteristics of the lower lumbar spine (L3–S1) after unilateral pedicle screw fixation (UPSF) or bilateral pedicle screw fixation (BPSF) combined with TLIF for treatment of L4–5 lumbar degenerative disc diseases (DDD). Methods Twenty-eight patients were recruited (13 UPSF, 15 BPSF). Each patient was CT-scanned to construct 3D models of the L3–S1 vertebrae. The dual fluoroscopic imaging system (DFIS) was then used to image the lumbar spine while the patient performed seven functional activities (upright standing, maximum extension, flexion, left–right twist, and left–right bend). The in vivo vertebral positions were reproduced using the 3D vertebral models and DFIS images. The ranges of motion (ROMs) of L3–4, L4–5, and L5–S1 segments were analyzed. Results At the index L4–5 segment, the primary ROM of left–right twist of the UPSF group (2.11 ± 0.52°) was significantly larger (p = 0.000) than the BPSF group (0.73 ± 0.32°). At the proximal adjacent L3–4 segment, the primary ROMs of left–right twist, and left–right bend of the UPSF group (2.16 ± 0.73°, 2.28 ± 1.03°) were significantly less (p = 0.003, 0.023) than the BPSF group (3.17 ± 0.88, 3.12 ± 1.04°), respectively. However, at distal adjacent L5–S1 segment, no significant difference was found between the two groups during all activities. Conclusions The ROM in left–right twisting of UPSF group was significantly larger compared with BPSF group at the index level in the short term. The UPSF has less impact on the cranial adjacent level (L3–4) in left–right twisting and bending activities compared to the BPSF. The data implied that the UPSE and BPSF combined with TLIF would result in different biomechanics in the index and cranial adjacent segment biomechanics. Long-term follow-up studies are necessary to compare the clinical outcomes of the two surgeries.

Aim: We aimed to determine the anatomical remodeling seen after lumbar spine stabilization in detail. Using magnetic resonance images, it is also aimed to reveal this remodeling is not only limited to the adjacent segment and also happens in the upper instrumented vertebra region. At the end of this study, it is suggested to develop new radiological parameters to predict the changes in the adjacent segment and upper instrumented vertebra regions. Materials and Methods: Twenty cases operated for degenerative lumbar stenosis were included in our study. Quantitative data were obtained by radiological measurements by a radiologist and neurosurgeon. On magnetic resonance images, the anatomical structures changed by remodeling were compared before and after the operation during (6-26 months) postoperative period. Unlike previous studies, anterior, middle and posterior disc heights; Cobb angle in the adjacent segment, spinal canal area, bilateral neural foramen, facet joint areas and flavum thicknesses were evaluated. Results: From the sixth month after lumbar fusion, it was observed that angles and anatomical structures were changed in adjacent segment. Also, it was observed that the areas with neural structures expanded in the upper instrumented vertebra region. The degeneration in adjacent segment and relaxation in the upper instrumented vertebra region were found to be statistically significant. A statistically strong positive correlation was found between the number of vertebrae included in the lumbar fusion and the mean height of the adjacent segment disc (r: 0.526, p: 0.017). Conclusion: After comparing the measurements in adjacent segment and upper instrumented vertebra regions before and after the operation, it was concluded that the remodeling was statistically significant. We suggest that the parameters in our study can be used as a scoring method for early detection of adjacent segment degeneration and/or disease. Thus, it will be possible to create follow-up indicators findings after fusion. [ABSTRACT FROM AUTHOR]

Introduction: A comparative clinical study has been conducted on patients involved using lateral intersomatic arthrodesis for the treatment of adjacent segment disease using titanium and PEEK intersomatic devices. Material and methods: Clinical (EVA and oswestry disability index ODI) and radiological (alignment and fusion), complications (major and minor) and quality of life (EQ5D) of 32 patients intervened from September 2015 to September 2018 have been analyzed and compared, with an average follow-up of 25 months (46-18). The average age in surgery was 66 years (39-89) and 68% of patients were women. Results: The most common segment involved was L3-L4 (62%) right retroperitoneal approach 86%. Lumbar EVA improved from 6.2 ± 2.12 to 4.1 ± 1.71 (p = 0.028). The LEG EVA descended from 5.3 ± 2.26 to 1.9 ± 1.58 (p = 0.02). The ODI scales improved from 50.2 ± 18.9 to 33.3 ± 10.2 (p = 0.025) and the EQ5D went from 0.52 to 0.73 (p = 0.039) with no statistically significant differences between the groups (ODI p = 0.18, EQ5D p = 0.293). Radiologically increased intervertebral height, lumbar and segmental lordosis, decreased Cobb's angle and the overall melting rate was 84.3% (88% Ti/82% PEEK), with no differences between the groups. Conclusion: Lateral lumbar interbody fusion is an effective method for treating adjacent segment disease with clinical-radiological results and literature-like complications. No differences have been found between Ti and PEEK implants. [ABSTRACT FROM AUTHOR]

Aims and Objectives: The human spine degenerates with age. Intervertebral disc degeneration occurs in the cervical spine. The objective of this study is to determine the effects of degenerative disc diseases on the range of motion (ROM) of the human cervical spinal column using a validated finite-element model. Materials and Methods: The validated intact and healthy C2–T1 finite-element model simulated the cortical shell, cancellous core, posterior elements of the vertebrae, and spinal ligaments (longitudinal, capsular, spinous and ligamentum flava, and nucleus and annulus of the discs). Three different stages of the disc disease, that is, mild, moderate, and severe, were simulated at the C5–C6, C6–C7, and C5–C6–C7 discs, respectively, and they were termed as upper single level, lower single level, and bi-level (BL) models, respectively. The material properties and geometry of the disc(s) were altered to simulate the different stages of degeneration. The external mechanical loading was applied in the sagittal mode, via flexion–extension motions and the magnitude was 2.0 Nm for each mode. They were applied to each of the healthy and disc degeneration models, and for each of the three severities of degeneration. The ROM at adjacent and index levels was extracted and normalized with respect to the healthy (baseline) spine. Results: A nonuniform distribution in the ROM was found for different disc degeneration states, segmental levels, and flexion–extension loading modes. The specific results for each and level are reported in the results section of the paper. Conclusion: Closer follow-up times may be necessary in symptomatic patients with progressive disease, especially with BL involvements. [ABSTRACT FROM AUTHOR]

Objective: The information available on the association between transforaminal lumbar interbody fusion (TLIF) surgery and adjacent segment degeneration (ASD) in lumbar spinal stenosis (LSS) patients is extremely limited. To explore the risk factors involved in the development of ASD after decompression and fusion surgery for LSS. Materials and Methods: This study subjects were patients who underwent lumbar posterior segmental instrumentation and spinal decompression surgery for degenerative LSS, in L4-5 or L5-S1, during 2010-2015. These patients were classified into two groups based on their stage of ASD development. The diagnosis of ASD was based on magnetic resonance imaging findings. The study groups were compared to determine the risk factors for ASD. Results: A total of 162 patients (68 men, 94 women) of a mean age 60.76±6.4 years (age range: 37-89 years) were evaluated. The mean followup period for these patients was 67.42±5.6 months. Decompression surgery with TLIF was applied to 67 patients, while decompression surgery without TLIF was applied to 95 patients. Overall, ASD developed in 40 patients (24.7%). The type of stenosis was found to be a risk factor for ASD. Conclusion: Our results suggested that, although instrumentation and fusion applied to the surgical area caused an increase in stress and degeneration in the adjacent segment owing to immobilisation and stiffness in this area, the rate of increase did not rise with TLIF cage. Furthermore, the type of stenosis was determined to be a risk factor for ASD in our study. [ABSTRACT FROM AUTHOR]

Objective To observe the long-term progress of paravertebral ossification (PO) of adjacent segments and normal segments following cervical artificial disc replacement (CADR) based on CT examination. Methods Forty-five patients who underwent CADR were included. The segments were divided into the following groups: operative level, ad 」acent level, or non-adjacent level groups (control group). Preoperative and final follow-up CT images (range 57-108 months) were collected. We took the center of each segment of the vertebral body as the center of a circle and divided each segment into four areas: left Luschka joint area (L), right Luschka」oint area (R), anterior area (A), posterior area (P). PO from the C2/3 to C7/T1 segments in each patient was graded based on CT images. Results The proportion of high-level PO (grades 2 and 3) in every areas in the operative level group, adjacent level group, and control group was higher than that before surgery (P < 0. 05). Progression of PO in Land R areas in the operative level group was significantly more severe than that in the control group (P < 0. 05). There was no significant difference in PO progression in the A and P areas between the operative level group and the control group, and there was no significant difference in PO progression between the adjacent level group and the control group (both P > 0. 05). C . Conclusions The incidence of PO after CADR is significantly higher in comparison with that in the preoperative status. Progression of PO with CADR at the operative level is concentrated in areas of the Luschka Jointsrather than A and P areas. CADR has little influence on the progression of PO development in the adjacent segments. [ABSTRACT FROM AUTHOR]

Background: Adjacent segment disease (ASDz) is a potential complication following lumbar spinal fusion. A common nomenclature based on etiology and ASDz type does not exist and is needed to assist with clinical prognostication, decision making, and management. Questions/Purposes: The objective of this study was to develop an etiology-based classification system for ASDz following lumbar fusion. Methods: We conducted a retrospective chart review of 65 consecutive patients who had undergone both a lumbar fusion performed by a single surgeon and a subsequent procedure for ASDz. We established an etiology-based classification system for lumbar ASDz with the following six categories: "degenerative" (degenerative disc disease or spondylosis), "neurologic" (disc herniation, stenosis), "instability" (spondylolisthesis, rotatory subluxation), "deformity" (scoliosis, kyphosis), "complex" (fracture, infection), or "combined." Based on this scheme, we determined the rate of ASDz in each etiologic category. Results: Of the 65 patients, 27 (41.5%) underwent surgery for neurogenic claudication or radiculopathy for adjacent-level stenosis or disc herniation and were classified as "neurologic." Ten patients (15.4%) had progressive degenerative disc pathology at the adjacent level and were classified as "degenerative." Ten patients (15.4%) had spondylolisthesis or instability and were classified as "instability," and three patients (4.6%) required revision surgery for adjacent-level kyphosis or scoliosis and were classified as "deformity." Fifteen patients (23.1%) had multiple diagnoses that included a combination of categories and were classified as "combined." Conclusion: This is the first study to propose an etiology-based classification scheme of ASDz following lumbar spine fusion. This simple classification system may allow for the grouping and standardization of patients with similar pathologies and thus for more specific pre-operative diagnoses, personalized treatments, and improved outcome analyses. [ABSTRACT FROM AUTHOR]

Vertebral osteomyelitis manifesting as a compression fracture misdiagnosed in the setting of steroid-induced or senile osteoporosis is very rare, although such patients are prone to infection or reactivation, as their immune system is exhausted. Spondylodiscitis occurring at adjacent levels following instrumented spinal fusion leading to pathologic fracture and proximal junctional failure, especially caused by tuberculosis, to our knowledge, has not been discussed in the literature. In case 1, a 61-year-old woman with osteoporotic T12 collapse was treated with corpectomy, anterior reconstruction, and posterior fixation from T9-L2. Initial biopsy and culture were normal. She presented 4 months later with compression fracture of T8; T8 corpectomy with anterior reconstruction and proximal extension of the construct was performed. In case 2, a 65-year-old woman with multiple comorbidities and osteoporotic L1 compression fracture was treated with L1 corpectomy, anterior reconstruction, and posterior instrumentation from T11-L3. She presented 4 months later with T10 vertebral body acute collapse; 2-stage anterior corpectomy and reconstruction was performed. In both cases, probing the affected vertebral body yielded pus. Pus and bone tissue samples sent for culture and histopathologic examination were positive for tuberculosis suggesting tuberculous spondylitis in both cases. In both patients, tuberculous spondylodiscitis at the proximal adjacent level was diagnosed <1 year after the initial spinal surgery. Neither patient had a previous history of pulmonary or extrapulmonary tuberculosis. They were successfully treated with antituberculous therapy and proximal extension of the construct with anterior reconstruction. Adjacent segment spondylodiscitis should be suspected and intraoperative biopsy must be considered for histopathologic and microbiologic examination to rule out subclinical infection in immunosuppressed patients with multiple comorbidities. Management should be individualized, considering the context of infection, causative organism, extent of bone destruction, and neurologic involvement. [ABSTRACT FROM AUTHOR]

Objective: This study aims to assess the impact of surgical approaches and other factors on the incidence of Adjacent Segment Degeneration (ASD) following Spinal Fusion for Adolescent Idiopathic Scoliosis (AIS)., Methods: We conducted a comprehensive search of four electronic databases from their inception until March 30, 2023. Two independent reviewers screened titles, abstracts, and full texts and evaluated the methodological quality of the studies. A random-effects model was used to calculate the incidence of ASD., Results: Our analysis included 14 studies involving 651 individuals. The overall incidence of ASD was 47% (95%CI: 0.37, 0.56). Subgroup analyses revealed that the prevalence of ASD increased with postoperative time (53% (95%CI: 0.31, 0.75) versus 48% (95%CI: 0.36, 0.60) versus 39% (95%CI: 0.22, 0.56)). For the number of fused segments, a group with more than 10 segments had a higher prevalence (49% (95%CI: 0.38, 0.60) versus 44% (95%CI: 0.21, 0.69)). In terms of regions, East Asia had the highest prevalence, followed by Occident and West Asia (52% (95%CI: 0.41, 0.62) versus 43% (95%CI: 0.20, 0.68) versus 37% (95%CI: 0.17, 0.59)). However, the surgical approach, male ratio, and the position of the lowest instrumented vertebra (LIV) did not show significant differences between groups. Funnel plots and Egger's test did not reveal any significant publication bias (Egger's test: t = 1.62, p -value = .1274)., Conclusion: This meta-analysis found that nearly half of AIS patients following spinal fusion surgery experienced ASD. Long-term follow-up, regular screening, and timely interventions are essential to reduce the prevalence of ASD., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

The effects of adjacent segment degeneration (ASD) after spinal fusion of vertebral fractures have previously not been demonstrated in patients with trauma-related paraplegia. The aim of this study was to evaluate the role of ASD in patients with paraplegia caused by vertebral fractures and to observe whether there is a difference between unilateral or combined spinal fusion in long-term results regarding the degeneration of cranial or caudal adjacent spinal segments. A total of 111 paraplegic patients with an average age of 45 years who underwent spinal fusion of vertebral fractures were observed in a retrospective longitudinal study with a follow-up period of 4 years. Conventional X‑ray images and magnetic resonance imaging (MRI) scans were used to assess the ASD in the adjacent free vertebral segments cranial and caudal to the spinal fusion using the following elements: ventral spondylophytes, intervertebral space, intervertebral disc signal in MRI, posterior spondylophytes, facet joint arthrosis, bone bridging and ossification of the anterior longitudinal ligament. Additionally, the classification by the American Spinal Injury Association (ASIA) impairment scale and spinal cord independence measure version 3 score were surveyed. The 4‑year incidence of radiographically detectable ASD was 3–12 % in this study. The majority of ASDs were observed in the cranial segments adjacent to the interbody fusion. The dorsoventral spinal fusion showed the least effects on the adjacent segments. In conclusion, a concept of prompt surgery using short dorsoventral segment fusion carried out by an interdisciplinary paralysis center is recommended. The role of natural degeneration processes and whether they are influenced by iatrogenic manipulation through the vertebral stabilization is unclear. For this reason it is important to further investigate strategies for ASD reduction in the future to ensure the best possible treatment success including the lowest degree of additional impairments for this special patient group. [ABSTRACT FROM AUTHOR]

Aim: The majority of studies about adjacent segment disease (ASD) in the literature concern adult patients who were operated on because of degenerative process-related diseases, such as lumbar instability or lumbar stenosis. Material and Methods: We retrospectively reviewed cases of AIS surgically treated in our institution between 2012 and 2015. Patients with an increase in the amount of disc degeneration at adjacent segment (AS) (the ASD group) were compared with those with no increase in degeneration at AS (the non-ASD group). Results:ASD was observed postoperatively in 24 patients (57.1%), and 18 patients (42.9%) had no increase in disc degeneration at the latest follow-up. The mean follow-up was 13 to 34 months, with an average of 22±7.1 months and the lowest instrumented vertebra for 10 of the patients was L2, and the other 32 patients had L3. The rate of ASD in patients with fusion at T4-L3 was significantly higher than for the other instrumentation levels (p < 0.05). All 24 patients in the ASD group had L3 as the lowest instrumented vertebra (LIV) (p < 0.05). Conclusion: We believe that ASD is present even in short-term follow-up in patients who undergo long-segment fusion at a young age due to AIS and leaving as many mobile segments as possible will protect from ASD. [ABSTRACT FROM AUTHOR]

Study DesignRetrospective case series.PurposeTo assess the effect of non-kyphotic aligned congenital C3-4 synostosis on the adjacent segment in 10 patients.Overview of LiteratureIn the cervical spine, fusion disease at the adjacent motion segments may be a risk factor for potential neurological compromise and death.MethodsRadiograms of 10 patients 13 to 69 years of age presenting with neck/shoulder discomfort or pain with or without trauma history were examined. C3-4 synostosis was found incidentally in all patients on routine examination radiographs of cervical spine.ResultsAdjacent segment disease (ASD) was not found in the three patients younger than 39 years of age. Five of the 10 (50%) patients, including a 67-year-old man, did not develop spondylosis in any of the cervical mobile segments. Spondylosis was observed only in the caudal 1-2 mobile segments in the remaining five patients. The youngest was a 40-year-old male who had spondylosis in the two caudal mobile segments (C4-5 and C5-6). Spondylosis was limited to the two close caudal mobile segments and was not in the cranial segments. Flaring of the lower part of synostotic vertebra associated with advanced narrowed degenerate disc was evident in five patients.ConclusionsMobile segment spondylosis in the individuals with congenital monosegment C3-4 synostosis over age of 40 years may be a natural manifestation of aging and is not solely an adjacent segment disease directly and fully related with congenital C3-4 synostosis.

Objective: To analyze the biomechanical effects of proximal iatrogenic muscle-ligaments complex (MLC) damage on adjacent segments following posterior lumbar interbody fusion (PLIF) by finite element (FE) analysis., Methods: The multifidus muscle force was loaded in the validated intact lumbosacral finite element model. Based on whether undergoing PLIF or the proximal MLC damage, three models were established. Range of motion (ROM) and the maximum von Mises (VM) stress of adjacent segments were analyzed, as well as the average muscle force and work capacity in four loading directions., Results: PLIF results in significant changes in ROM and stress. ROM changed significantly in the upper adjacent segment, the PLIF model changed the most in extension, and the largest change in the lower adjacent segment occurred after MLC damage. The VM stress of the upper adjacent segment occurred in extension of the PLIF model, and that of the lower adjacent segment occurred in rotation after MLC damage. In flexion, ROM, and stress of the damaged MLC fusion model were significantly increased compared with the normal and PLIF models, there was a stepwise amplification. The average muscle force comparison of three models was 5.8530, 12.3185, and 13.4670 N, respectively. The total work capacity comparison was close to that of muscle force., Conclusion: PLIF results in increased ROM and the VM stress of adjacent segments, the proximal MLC damage will aggravate this change. This may increase the risk of ASD and chronic low back pain. Preserving the proximal MLC reduces the biomechanical effects on adjacent segments., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Road alignments that combine horizontal and vertical curves on freeways have effects on drivers’ speed changes that can lead to safety problems. This study examines speed changes on four types of combined curves: downslope, upslope, crest and sag. From design blueprints for a mountainous freeway under construction in Hunan Province, a total of 70 combined curves were programmed into the Tongji University driving simulator. Study participants drove through the simulated freeway while vehicle operation data was continuously captured. Speed changes on the combined curves were determined by calculating the differences between minimum and maximum speed values, and were classified into three behaviors: substantial speed decrease, steady speed (minimal change), and substantial speed increase. Multinomial logit models were used and the marginal effects of each variable were calculated in order to examine the effects on speed change behavior of each combined curve type and their adjacent segments. Results show that: 1) the speed change behaviors on the four types of combined curves differ in frequency, 2) the significant effects of geometric design characteristics on speed change differed by type of combined curve, and 3) design characteristics of adjacent segments also have significant and varying effects on speed change. Combined curves should therefore be studied separately, and their adjacent segments should be considered when combined curves are planned. [ABSTRACT FROM AUTHOR]

Background Context Lumbar total disc replacement (TDR) operation represents an alternative to lumbar fusion for the treatment of symptomatic lumbar intervertebral disc degeneration and has gained increasing attention in recent years. Purpose This study aimed to assess clinical outcomes in a cohort of patients with TDR and the long-term survival rate of the prostheses. Study Design This is a retrospective, single-center clinical study. Patient Sample The sample comprised 30 patients, giving a total of 35 prostheses after an average follow-up (FU) of 15.2 years following TDR, which was performed for the treatment of lumbar degenerative disc disease. Outcome Measures Clinical evaluation included visual analog scale (VAS) and the Oswestry Disability Index (ODI). Radiological parameters of intervertebral disc height (IDH), range of motion (ROM), lumbar lordosis, lumbar scoliosis, and prosthesis position were evaluated in surgical and adjacent levels. Complications and re-operation rates were also assessed. Methods Clinical evaluation and radiological parameters were evaluated preoperatively and at final FU. All data were collected by members of our department, including research assistants and nurses who were not involved in the decision making of this study. Results Thirty of the 35 patients participated in the final FU. The cumulative survival rate of the prosthesis at a mean FU of 15.4 years was 100%. The clinical success rate was 93.3%. The VAS and ODI scores at final FU were significantly lower than preoperatively (p<.001). The average ROM of the operated and superior adjacent segment decreased significantly at the final FU, whereas the inferior adjacent segment was not affected. The IDH of all surgical and adjacent levels were well maintained at the final FU. Ten patients had a lumbar scoliosis >3° and the mean angle was 8.5°, of which 7 had left convex curvature. Three prostheses were offset more than 5 mm from the midline on the coronal plane. Four prostheses showed subsidence. Twenty-six operative segments and five adjacent segments showed heterotopic ossification. Two patients of the total 35-patient cohort underwent a secondary operation. Conclusions Satisfactory clinical results and good prosthesis survival can be achieved in the long term. Lumbar TDR surgeries also have the potential to reduce the incidence of adjacent segment disease. [ABSTRACT FROM AUTHOR]

Study Design: A prospective cohort study.Objective: This study evaluated the cumulative reoperation rate and indications for reoperation following instrumented lumbar spine fusion (LSF).Summary Of Background Data: LSF reduces disability and improves health-related quality of life for patients with several spinal disorders. The rate of instrumented LSF has drastically increased over the last few decades. The increased incidence of LSF, however, has led to increased reoperation rates.Methods: The data are based on the prospective LSF database of Tampere University Hospital that includes all elective indications for LSF surgery. A total of 433 consecutive patients (64% women, mean age 62 years) who underwent LSF in Tampere University Hospital between 2008 and 2011 were evaluated and indications for reoperations were rechecked from patient records and radiographs. The most common diagnosis for the primary surgery was degenerative spondylolisthesis and the mean follow-up time was 3.9 years. The cumulative incidence of reoperations and the "time to event" survival rate was calculated by Kaplan-Meier analysis.Results: By the end of 2013, 81 patients had undergone at least one reoperation. The cumulative reoperation rate at 2 years was 12.5% (95% confidence interval: 95% CI: 9.7-16.0) and at 4 years was 19.3% (95% CI: 15.6-23.8). The most common pathology leading to reoperation was adjacent segment pathology with a cumulative reoperation rate of 8.7% (95% CI: 6.1-12.5) at 4 years. The corresponding rates for early and late instrumentation failure were 4.4% (95% CI: 2.7-7.0) and 2.9% (95% CI: 1.9-7.1), respectively, and for acute complications, 2.5% (95% CI: 1.4-4.5).Conclusion: Although previous studies reported that early results of spinal fusion are promising, one in five patients required reoperation within 4 years after surgery. Patients and surgeons should be aware of the reoperation rates when planning fusion surgery.Level Of Evidence: 4. [ABSTRACT FROM AUTHOR]