Less-invasive decompression procedures can reduce risk of reoperation for lumbar spinal stenosis with diffuse idiopathic skeletal hyperostosis extended to the lumbar segment: analysis of two retrospective cohorts.

PURPOSE: Clinical outcomes after decompression procedures are reportedly worse for lumbar spinal stenosis (LSS) with diffuse idiopathic skeletal hyperostosis (DISH), especially DISH extended to the lumbar segment (L-DISH). However, no studies have compared the effect of less-invasive surgery versus conventional decompression techniques for LSS with DISH. The purpose of this study was to compare the long-term risk of reoperation after decompression surgery focusing on LSS with L-DISH. METHODS: This study compared open procedure cohort (open conventional fenestration) and less-invasive procedure cohort (bilateral decompression via a unilateral approach) with ≥ 5 years of follow-up. After stratified analysis by L-DISH, patients with L-DISH were propensity score-matched by age and sex. RESULTS: There were 57 patients with L-DISH among 489 patients in the open procedure cohort and 41 patients with L-DISH among 297 patients in the less-invasive procedure cohort. The reoperation rates in L-DISH were higher in the open than less-invasive procedure cohort for overall reoperations (25% and 7%, p = 0.026) and reoperations at index levels (18% and 5%, p = 0.059). Propensity score-matched analysis in L-DISH demonstrated that open procedures were significantly associated with increased overall reoperations (hazard ratio [HR], 6.18; 95% confidence interval [CI], 1.37-27.93) and reoperations at index levels (HR, 4.80; 95% CI, 1.04-22.23); there was no difference in reoperation at other lumbar levels. CONCLUSIONS: Less-invasive procedures had a lower risk of reoperation, especially at index levels for LSS with L-DISH. Preserving midline-lumbar posterior elements could be desirable as a decompression procedure for LSS with L-DISH.

Evaluation of Surgical Indications for Full Endoscopic Discectomy at Lumbosacral Disc Levels Using Three-Dimensional Magnetic Resonance/Computed Tomography Fusion Images Created with Artificial Intelligence.

Background and Objectives: Although full endoscopic lumbar discectomy with the transforaminal approach (FED-TF) is a minimally invasive spinal surgery for lumbar disc herniation, the lumbosacral levels present anatomical challenges when performing FED-TF surgery due to the presence of the iliac bone. Materials and Methods: In this study, we simulated whether FED-TF surgery could be safely performed on a total of 52 consecutive cases with L5-S1 or L5-L6 disc herniation using fused three-dimensional (3D) images of the lumbar nerve root on magnetic resonance imaging (MRI) created with artificial intelligence and of the lumbosacral spine and iliac on computed tomography (CT) images. Results: Thirteen of the fifty-two cases were deemed operable according to simulated FED-TF surgery without foraminoplasty using the 3D MRI/CT fusion images. All 13 cases underwent FED-TF surgery without neurological complications, and their clinical symptoms significantly improved. Conclusions: Three-dimensional simulation may allow for the assessment from multiple angles of the endoscope entry and path, as well as the insertion angle. FED-TF surgery simulation using 3D MRI/CT fusion images could be useful in determining the indications for full endoscopic surgery for lumbosacral disc herniation.

Elucidation of the Mechanism of Occasional Anterior Longitudinal Ligament Rupture with Posterior Correction Procedure for Adult Spinal Deformity Using LLIF-Finite Element Analysis of the Impact of the Lordotic Angle of Intervertebral LLIF Cage.

Background and Objectives: There are several advantages of using lateral lumbar interbody fusion (LLIF) for correction surgeries for adult spinal deformity (ASD); however, we currently have unresolved new issues, including occasional anterior longitudinal ligament (ALL) rupture during the posterior correction procedure. When LLIF was initially introduced, only less lordotic cages were available and ALL rupture was more frequently experienced compared with later periods when more lordotic cages were available. We performed finite element analysis (FEA) regarding the mechanism of ALL rupture during a posterior correction procedure. Methods: A spring (which mimics ALL) was introduced at the location of ALL in the FEA and an LLIF cage with two different lordotic angles, 6 and 12 degrees (6DC/12DC), was employed. To assess the extent of burden on the ALL, the extension length of the spring during the correction procedure was measured and the location of the rotation center was examined. Results: We observed a significantly higher degree of length extension of the spring during the correction procedure in the FEA model with 6DC compared with that of 12DC. We also observed that the location of the rotation center was shifted posteriorly in the FEA model with 6DC compared with that of 12DC. Conclusions: It is considered that the posterior and rostral edge of the less lordotic angle cage became a hinge, and the longer lever arm increased the burden on ALL as the principle of leverage. It is important to use an LLIF cage with a sufficient lordotic angle, that is compatible with the degree of posterior osteotomy in ASD correction.

Morphological analysis of Kambin's triangle using 3D CT/MRI fusion imaging of lumbar nerve root created automatically with artificial intelligence.

PURPOSE: We developed a software program that automatically extracts a three-dimensional (3D) lumbar nerve root image from magnetic resonance imaging (MRI) lumbar nerve volume data using artificial intelligence. The aim of this study is to evaluate the morphology of Kambin's triangle in three dimensions based on an actual endoscopic transforaminal surgical approach using three-dimensional (3D) computed tomography (CT)/ magnetic resonance imaging (MRI) fusion images of the lumbar spine and nerve tissue. METHODS: Three-dimensional lumbar spine/nerve images of 100 patients (31 males and 69 females; mean age, 66.8 years) were used to evaluate the relationship between the superior articular process (SAP), exiting nerve root (ENR), and dural canal at the L2/3, L3/4, and L4/5 levels at 45° and 60° approach angles. RESULTS: The SAP-ENR distance at 60° was the greatest at L4/5 and was significantly greater at L2/3 and L4/5 than at L3/4 (P < 0.01, P < 0.01, respectively). The SAP-ENR distance at 45° was the greatest at L2/3, and it was larger in L2/3 and L4/5 than in L3/4 (P < 0.01, P < 0.01, respectively). The SAP-ENR distances at L4/5 were significantly greater at 60° than at 45° (P < 0.01). The dural canal was located within Kambin's triangle on the plane of the upper endplate of the lower vertebra at L2/3 in 41.5% of the cases and at L3/4 in 14% of the cases at 60° but not at L4/5. CONCLUSION: The 3D lumbar spine/nerve image enabled a combined assessment of the positional relationship between the SAP, ENR, and dural canal to quantify the safety zone of practical endoscopic spinal surgery using a transforaminal approach. Three-dimensional lumbar spine/nerve images could be useful for examining parameters, including bones and nerves, to ensure the safety of surgery.

Characterization of Push-Pull-Type Benzo[X]quinoline Derivatives (X = g or f): Environmentally Responsive Fluorescent Dyes with Multiple Functions.

Benzo[X]quinoline (X = g or f: BQX) derivatives bearing bis-trifluoromethyl and amine groups have been designed as push-pull-type fluorescent dyes. Through the synthesis of BQX derivatives from 2,7-diaminonaphthalene, linear-type (BQL) and angular-type (BQA) structural isomers were obtained. X-ray structures of single crystals from six given BQX derivatives revealed that the BQL and BQA series adopt planar- and bowl-shaped structures. In the fluorescence spectra, interestingly, the BQL series emitted in the near-infrared region over 700 nm in polar solvents. Based on the visible absorptions and base properties related to the amine moiety, the ammonia responsiveness was investigated using an ion-exchange reaction by the BQX-HCl salt. By exploiting the environmentally responsive fluorescence probe, cell imaging through confocal laser microscopy was conducted using HeLa and 3T3-L1 cells, emitting specific lipid droplets. The results indicate that BQX derivatives have multiple functions and may be applied in materials chemistry and biochemistry.

Accuracy of cortical bone trajectory screw placement using patient-specific template guide system.

Cortical bone trajectory (CBT) can facilitate both minimum invasiveness and strong screw fixation; however, ensuring the ideal cortical trajectory is challenging due to the narrow corridor, necessitating high-level surgical skill. A patient-specific template guide for CBT screw placement may be a promising solution to improve accuracy and safety. Little has been reported on the use of a CBT screw guide in clinical practice. The aim of the present study was to evaluate the accuracy of CBT screw placement using the template guide. This study was a retrospective clinical evaluation of prospectively collected patients. Forty-three consecutively enrolled patients who underwent posterior lumbar spinal fusion using the guide system were included. First, three-dimensional planning of CBT screw placement was performed using computer simulation software. The trajectory was directed in a more anterior position of the vertebral body, compared with the original CBT, and the standard size was set as 5-6 mm in diameter and 40-45 mm in length. Then, screw guides were created for each vertebra preoperatively and used. The safety and accuracy of a total of 198 inserted screws (L1 to L5) were analyzed using postoperative computed tomography by evaluation of pedicle perforation and measurement of screw deviations between the planned and actual screw positions. A total of 193 screws (97.5%) were placed completely inside the pedicle and there was no incidence of neurovascular injuries. The mean screw deviation from the planned trajectory on the coronal plane at the midpoint of the pedicle was 0.62 ± 0.42 mm, and the mean angular deviations in the sagittal and transverse planes were 1.68 ± 1.24° and 1.27 ± 0.77°, respectively. CBT screw placement using a patient-specific template guide was accurate enough for clinical application. This technique could be an effective solution to achieve both correct screw insertion and a reduction of complications.

Heating sensation in patients with and without spinal fixation devices during MRI examination at different magnetic field strengths.

BACKGROUND: Radiofrequency (RF) heating during MRI theoretically increases with magnetic field strength. In addition, implanted metallic devices are reported to further increase RF heating. However, a detailed evaluation of this type of heating remains scarce in clinical practice. PURPOSE: To assess possible risks and discomfort related to RF heating during MRI examinations of patients with and without metallic implantable devices. STUDY TYPE: A retrospective study of previous questionnaire results on the heating sensation during MRI examinations of the lumbar spine. SUBJECTS: In all, 715 patients, of whom 101 had implanted lumbar spine fixation devices. FIELD STRENGTH/SEQUENCE: 1T and 3T/T1 - and T2 -weighted imaging. ASSESSMENT: The number of patients who perceived heating around the lumbar spine or other regions during the MRI examination. STATISTICAL TESTS: A chi-square test with respect to static field strength B0 , presence of lumbar spine fixation devices, and duration of the MRI examination. RESULTS: The number of patients who perceived heating around the lumbar spine during the MRI examination significantly increased from 5.0% at 1T to 47.5% at 3T (P < 0.001), without a significant difference between patients with and without lumbar spine fixation devices (P = 0.23 at 1T, P = 0.48 at 3T), and regardless of the duration of the MRI examination (P = 0.88 at 1T, P = 0.15 at 3T). DATA CONCLUSION: Sensation of RF heating increased by around 10 times from 1T to 3T MRI examination, but the influence of implanted lumbar spine fixation devices on the RF heating sensation has not been observed. LEVEL OF EVIDENCE: 4 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:525-533.

Diffuse idiopathic skeletal hyperostosis is associated with lumbar spinal stenosis requiring surgery.

Factors related to the onset and progression of lumbar spinal stenosis (LSS) have not yet been identified. Diffuse idiopathic skeletal hyperostosis (DISH) increases mechanical loading on the non-fused lumbar levels and may therefore lead to LSS. This cross-sectional study aimed to identify associations between LSS and DISH. This study included 2363 consecutive patients undergoing surgery for LSS and 787 general inhabitants without symptoms of LSS as participants of the population-based cohort study, Research on Osteoarthritis/Osteoporosis Against Disability. Standing whole-spine radiographs were used to diagnose DISH based on the criteria proposed by Resnick and Niwayama. The prevalence of DISH showed a significant step-wise increase among asymptomatic inhabitants without radiographic LSS, asymptomatic inhabitants with radiographic LSS, and patients with LSS requiring surgery (14.4, 21.1, and 31.7%, respectively; p < 0.001). The distribution of DISH was similar between the groups, but the lower thoracic and upper-middle lumbar spine regions were more frequently involved in patients with LSS requiring surgery. Multivariate analysis indicated that DISH was an independent associated factor for LSS requiring surgery (adjusted odds ratio 1.65; 95% confidence interval 1.32-2.07) after adjustment for age, sex, body mass index, and diabetes mellitus. Among patients with LSS requiring surgery, a higher occurrence of stenosis at the upper lumbar levels and multi-level stenosis were observed in patients with DISH requiring surgery than in patients without DISH. In conclusion, DISH is independently associated with LSS requiring surgery. The decrease in the lower mobile segments by DISH may increase the onset or severity of LSS.

Regional Hounsfield unit measurement of screw trajectory for predicting pedicle screw fixation using cortical bone trajectory: a retrospective cohort study.

BACKGROUND: The sufficiency of screw anchoring is a critical factor for achieving successful spinal fusion; however, no reliable method for predicting pedicle screw fixation has been established. Recently, Hounsfield units (HU) obtained from computed tomography (CT) was developed as a new reliable tool to determine the bone quality. The purpose of the present study was to demonstrate the utility of regional HU measurement of the screw trajectory to predict the primary and long-term fixation strength of pedicle screws. METHOD: The insertional torque of pedicle screws using the cortical bone trajectory technique was measured intraoperatively in 92 consecutive patients who underwent single-level posterior lumbar interbody fusion. The cylindrical area of each screw was plotted on the preoperative CT image by precisely confirming the screw position, and the screw trajectory was measured in HU. First, three parameters: the bone mineral density (BMD) of the femoral neck and lumbar vertebrae, and regional HU values of the screw trajectory, were correlated with the insertional torque and compared among three groups. Next, pedicle screw loosening was evaluated by postoperative CT obtained 12 months after surgery, and clinical and imaging data were analyzed to assess whether regional HU values could be used as a predictor of screw loosening. RESULTS: Regional HU values of the screw trajectory (r = 0.75, p < 0.001) had stronger correlation with the insertional torque than the femoral BMD (r = 0.59, p < 0.001) and lumbar BMD (r = 0.55, p < 0.001). The incidence of screw loosening was 4.6% (16/351). Multivariate logistic regression analysis revealed that regional HU value (odds ratio = 0.70; 95% confidence interval = 0.56-0.84; p = 0.018) was an independent risk factor significantly affected screw loosening. CONCLUSIONS: Regional HU values of the screw trajectory could be a strong predictor of both primary and long-term screw fixation in vivo.

Cortical pedicle screw placement in lumbar spinal surgery with a patient-matched targeting guide: A cadaveric study.

BACKGROUND: Cortical pedicle screw placement is an attractive technique in terms of both fixation strength and less invasiveness. However, to insert the screw with penetrating cortical bone on the ideal trajectory is technically demanding. The use of three-dimensional (3D) patient-matched guides may facilitate the use of this technique. PURPOSE: To examine the accuracy of cortical screw placement using a patient-matched targeting guide with a cadaveric study assessing the accuracy. METHODS: The 3D planning of the pedicle screw placement, including the location at which the screw would pass through the center of the pedicle, sagittal/transverse trajectory (angle), length, and diameter, was developed using 3D CAD design software. Three-dimensional guides based on the preoperative planning were created for three cadaveric specimens (L1 to S1, 36 pedicles). Screws (n = 18) and pins (n = 18) were placed using K-wire or drill-based guides, without X-ray exposure. Actual positioning was compared to the preoperative plan by superimposing the inserted screws/pins based on postoperative CT. The placement accuracy was graded based on the degree of perforation of the pedicle by the pedicle screw or pin using an acceptance criterion (no perforation; Grade A, 0-2 mm; Grade B, 2-4 mm; and Grade C, >4 mm). The mean deviation between the planned and inserted screw positions on the coronal plane at the midpoint of the pedicle was compared to the accuracy of screw guide for traditional pedicle screw trajectory (0.70 mm). RESULTS: Of 35 evaluated screws and pins, 32 (91.4%) were inserted completely inside the pedicle. All pedicle perforation was within 2 mm. The mean deviation from the plan at the midpoint of pedicle was 0.66 mm; thus, the accuracy was within the predefined criteria. CONCLUSIONS: Cortical pedicle screw placement using 3D-patient matched guides is accurate. Further clinical studies are required to confirm the radiographic and clinical effects.

Surgical treatment of double thoracic adolescent idiopathic scoliosis with a rigid proximal thoracic curve.

PURPOSE: There is limited consensus on the optimal surgical strategy for double thoracic adolescent idiopathic scoliosis (AIS). Recent studies have reported that pedicle screw constructs to maximize scoliosis correction cause further thoracic spine lordosis. The objective of this study was to apply a new surgical technique for double thoracic AIS with rigid proximal thoracic (PT) curves and assess its clinical outcomes. METHODS: Twenty one consecutive patients with Lenke 2 AIS and a rigid PT curve (Cobb angle ≥30º on side-bending radiographs, flexibility ≤30 %) treated with the simultaneous double-rod rotation technique (SDRRT) were included. In this technique, a temporary rod is placed at the concave side of the PT curve. Then, distraction force is applied to correct the PT curve, which reforms a sigmoid double thoracic curve into an approximate single thoracic curve. As a result, the PT curve is typically converted from an apex left to an apex right curve before applying the correction rod for PT and main thoracic curve. RESULTS: All patients were followed for at least 2 years (average 2.7 years). The average main thoracic and PT Cobb angle correction rate at the final follow-up was 74.7 and 58.0 %, respectively. The average preoperative T5-T12 thoracic kyphosis was 9.3°, which improved significantly to 19.0° (p < 0.0001) at the final follow-up. Although 71 % patients had preoperative level shoulders or a positive radiographic shoulder height, all patients had mildly imbalanced or balanced shoulders at the final follow-up. The average preoperative main thoracic apical vertebral rotation angle of 20.7° improved significantly after surgery to 16.4° (p = 0.0046), while the average preoperative total SRS questionnaire score of 3.7 improved significantly to 4.4 (p = 0.0012) at the final follow-up. CONCLUSIONS: Radiographic findings and patient outcomes were satisfactory. Thoracic kyphosis can be maintained or improved, while coronal and axial deformities can be corrected using SDRRT for Lenke 2 AIS with a rigid PT curve.

Biomechanical evaluation of fixation strength among different sizes of pedicle screws using the cortical bone trajectory: what is the ideal screw size for optimal fixation?

BACKGROUND: The cortical bone trajectory (CBT) has attracted attention as a new minimally invasive technique for lumbar instrumentation by minimizing soft-tissue dissection. Biomechanical studies have demonstrated the superior fixation capacity of CBT; however, there is little consensus on the selection of screw size, and no biomechanical study has elucidated the most suitable screw size for CBT. The purpose of the present study was to evaluate the effect of screw size on fixation strength and to clarify the ideal size for optimal fixation using CBT. METHOD: A total of 720 analyses on CBT screws with various diameters (4.5-6.5 mm) and lengths (25-40 mm) in simulations of 20 different lumbar vertebrae (mean age: 62.1 ± 20.0 years, 8 males and 12 females) were performed using a finite element method. First, the fixation strength of a single screw was evaluated by measuring the axial pullout strength. Next, the vertebral fixation strength of a paired-screw construct was examined by applying forces simulating flexion, extension, lateral bending, and axial rotation to the vertebra. Lastly, the equivalent stress value of the bone-screw interface was calculated. RESULTS: Larger-diameter screws increased the pullout strength and vertebral fixation strength and decreased the equivalent stress around the screws; however, there were no statistically significant differences between 5.5-mm and 6.5-mm screws. The screw diameter was a factor more strongly affecting the fixation strength of CBT than the screw fit within the pedicle (%fill). Longer screws significantly increased the pullout strength and vertebral fixation strength in axial rotation. The amount of screw length within the vertebral body (%length) was more important than the actual screw length, contributing to the vertebral fixation strength and distribution of stress loaded to the vertebra. CONCLUSIONS: The fixation strength of CBT screws varied depending on screw size. The ideal screw size for CBT is a diameter larger than 5.5 mm and length longer than 35 mm, and the screw should be placed sufficiently deep into the vertebral body.

Percutaneous Endoscopic Transforaminal Lumbar Interbody Fusion (PETLIF): Current Techniques, Clinical Outcomes, and Narrative Review.

Full endoscopic techniques are becoming more popular for degenerative lumbar pathologies. Percutaneous endoscopic lumbar interbody fusion (PETLIF) is a minimally invasive surgical technique for spondylolisthesis and lumbar spinal canal stenosis with instability. Nagahama first introduced PETLIF in 2019. This study investigated the clinical outcomes and complications of 24 patients who underwent PETLIF in our facility and compared them with previous studies. Literature searches were conducted on PubMed and Web of Science. The PETLIF surgical technique involves three steps to acquire disc height under general anesthesia. The procedure includes bone harvesting, spondylolisthesis reduction, endoscopic foraminoplasty, disc height expansion using an oval dilator, and intervertebral disc curettage. A cage filled with autologous bone is inserted into the disc space and secured with posterior fixation. Patients underwent PETLIF with an average operation time of 130.8 min and a blood loss of 24.0 mL. Postoperative hospital stays were 9.5 days. Improvement in VAS, disc height, spinal canal area, and % slip was observed, while lumbar lordosis remained unchanged. Complications included end plate injury, subsidence, and exiting nerve root injury. The differences between PETLIF and the extracted literature were found in patients' age, direct decompression, epidural or local anesthesia, approach, order of PPS, and cage insertion. In conclusion, PETLIF surgery is a practical, minimally invasive surgical technique for patients with lumbar degenerative diseases suffering from back and leg pain, demonstrating significant improvements in pain scores. However, it is essential to carefully consider the potential complications and continue to refine the surgical technique further to enhance the safety and efficacy of this procedure.

Influence of Lateral Translation of Lowest Instrumented Vertebra on L4 Tilt and Coronal Balance for Thoracolumbar and Lumbar Curves in Adolescent Idiopathic Scoliosis.

This study aimed to evaluate the lowest instrumented vertebra translation (LIV-T) in the surgical treatment of thoracolumbar/lumbar adolescent idiopathic scoliosis and to analyze the radiographic parameters in relation to LIV-T and L4 tilt and global coronal balance. A total of 62 patients underwent posterior spinal fusion (PSF, n = 32) or anterior spinal fusion (ASF, n = 30) and were followed up for a minimum of 2 years. The mean preoperative LIV-T was significantly larger in the ASF group than the PSF (p < 0.01), while the final LIV-T was equivalent. LIV-T at the final follow-up was significantly correlated with L4 tilt and the global coronal balance (r = 0.69, p < 0.01, r = 0.38, p < 0.01, respectively). Receiver-operating characteristic analysis for good outcomes, with L4 tilt <8° and coronal balance <15 mm at the final follow-up, calculated the cutoff value of the final LIV-T as 12 mm. The cutoff value of preoperative LIV-T that would result in the LIV-T of ≤12 mm at the final follow-up was 32 mm in PSF, although no significant cutoff value was calculated in ASF. ASF can centralize the LIV better than PSF with a shorter segment fusion, and could be useful in obtaining a good curve correction and global balance without fixation to L4 in cases with large preoperative LIV-T.

Prediction of Cobb Angle Using Deep Learning Algorithm with Three-Dimensional Depth Sensor Considering the Influence of Garment in Idiopathic Scoliosis.

Adolescent idiopathic scoliosis (AIS) is the most common pediatric spinal deformity. Early detection of deformity and timely intervention, such as brace treatment, can help inhibit progressive changes. A three-dimensional (3D) depth-sensor imaging system with a convolutional neural network was previously developed to predict the Cobb angle. The purpose of the present study was to (1) evaluate the performance of the deep learning algorithm (DLA) in predicting the Cobb angle and (2) assess the predictive ability depending on the presence or absence of clothing in a prospective analysis. We included 100 subjects with suspected AIS. The correlation coefficient between the actual and predicted Cobb angles was 0.87, and the mean absolute error and root mean square error were 4.7° and 6.0°, respectively, for Adam's forward bending without underwear. There were no significant differences in the correlation coefficients between the groups with and without underwear in the forward-bending posture. The performance of the DLA with a 3D depth sensor was validated using an independent external validation dataset. Because the psychological burden of children and adolescents on naked body imaging is an unignorable problem, scoliosis examination with underwear is a valuable alternative in clinics or schools.

Development of Notch-Free, Pre-Bent Rod Applicable for Posterior Corrective Surgery of Thoracolumbar/Lumbar Adolescent Idiopathic Scoliosis.

Adolescent idiopathic scoliosis (AIS), the most common pediatric musculoskeletal disorder, causes a three-dimensional spine deformity. Lenke type 5 AIS is defined as a structural thoracolumbar/lumbar curve with nonstructural thoracic curves. Although a rod curvature will affect clinical outcomes, intraoperative contouring of the straight rod depends on the surgeon's knowledge and experience. This study aimed to determine the optimum rod geometries to provide a pre-bent rod system for posterior spinal surgery in patients with Lenke type 5 AIS. These pre-bent rods will be beneficial for achieving proper postoperative outcomes without rod contouring based on surgeon experience. We investigated 20 rod geometries traced in posterior spinal reconstruction in patients with Lenke type 5 AIS. The differences between the center point clouds in each cluster were evaluated using the iterative closest point (ICP) method with modification. Before the evaluation using the ICP method, the point clouds were divided into four clusters based on the rod length using a hierarchical cluster analysis. Because the differences in the values derived from the ICP method were <5 mm for each length-based cluster, four representative rod shapes were generated from the length-based clusters. We identified four optimized rod shapes that will reduce operation time, leading to a decreased patient and surgeon burden.

Crystal structures and emitting properties of trifluoromethylaminoquinoline derivatives: thermal single-crystal-to-single-crystal transformation of polymorphic crystals that emit different colors.

2,4-Trifluoromethylquinoline (TFMAQ) derivatives that have amine (1), methylamine (2), phenylamine (3), and dimethylamine (4) substituents at the 7-position of the quinoline ring were prepared and crystallized. Six crystals including the crystal polymorphs of 2 (crystal GB and YG) and 3 (crystal B and G) were obtained and characterized by X-ray crystallography. In solution, TFMAQ derivatives emitted relatively strong fluorescence (lambda(max)(f)=418-469 nm and Φ(f)(s)=0.23-0.60) depending on the solvent polarity. From Lippert-Mataga plots, Δµ values in the range of 7.8-14 D were obtained. In the crystalline state, TFMAQ derivatives emitted at longer wavelengths (lambda(max)(f)=464-530 nm) with lower intensity (Φ(f)(c)=0.01-0.28) than those in n-hexane solution. The polymorphous crystals of 2 and 3 emitted different colors: 2, lambda(max)(f)=470 and 530 nm with Φ(f)(c)=0.04 and approximately 0.01 for crystal GB and YG, respectively; and 3, lambda(max)(f)=464 and 506 nm with Φ(f)(c)=0.28 and approximately 0.28 for crystal B and G, respectively. In both crystal polymorphs of 2 and 3, crystals GB and G showed emission color changes by heating/melting/cooling cycles that were representative. By following the color changes in heating at the temperature below the melting point with X-ray diffraction measurements and X-ray crystallography, the single-crystal-to-single-crystal transformations from crystal GB to YG for 2 and from crystal B to G for 3 were revealed.

A simple method for in vivo measurement of implant rod three-dimensional geometry during scoliosis surgery.

Scoliosis is defined as a spinal pathology characterized as a three-dimensional deformity of the spine combined with vertebral rotation. Treatment for severe scoliosis is achieved when the scoliotic spine is surgically corrected and fixed using implanted rods and screws. Several studies performed biomechanical modeling and corrective forces measurements of scoliosis correction. These studies were able to predict the clinical outcome and measured the corrective forces acting on screws, however, they were not able to measure the intraoperative three-dimensional geometry of the spinal rod. In effect, the results of biomechanical modeling might not be so realistic and the corrective forces during the surgical correction procedure were intra-operatively difficult to measure. Projective geometry has been shown to be successful in the reconstruction of a three-dimensional structure using a series of images obtained from different views. In this study, we propose a new method to measure the three-dimensional geometry of an implant rod using two cameras. The reconstruction method requires only a few parameters, the included angle θ between the two cameras, the actual length of the rod in mm, and the location of points for curve fitting. The implant rod utilized in spine surgery was used to evaluate the accuracy of the current method. The three-dimensional geometry of the rod was measured from the image obtained by a scanner and compared to the proposed method using two cameras. The mean error in the reconstruction measurements ranged from 0.32 to 0.45 mm. The method presented here demonstrated the possibility of intra-operatively measuring the three-dimensional geometry of spinal rod. The proposed method could be used in surgical procedures to better understand the biomechanics of scoliosis correction through real-time measurement of three-dimensional implant rod geometry in vivo.

Mid-term clinical results of minimally invasive decompression and posterolateral fusion with percutaneous pedicle screws versus conventional approach for degenerative spondylolisthesis with spinal stenosis.

INTRODUCTION: In order to minimize perioperative invasiveness and improve the patients' functional capacity of daily living, we have performed minimally invasive lumbar decompression and posterolateral fusion (MIS-PLF) with percutaneous pedicle screw fixation for degenerative spondylolisthesis with spinal stenosis. Although several minimally invasive fusion procedures have been reported, no study has yet demonstrated the efficacy of MIS-PLF in degenerative spondylolisthesis of the lumbar spine. This study prospectively compared the mid-term clinical outcome of MIS-PLF with those of conventional PLF (open-PLF) focusing on perioperative invasiveness and patients' functional capacity of daily living. MATERIALS AND METHODS: A total of 80 patients received single-level PLF for lumbar degenerative spondylolisthesis with spinal stenosis. There were 43 cases of MIS-PLF and 37 cases of open-PLF. The surgical technique of MIS-PLF included making a main incision (4 cm), and neural decompression followed by percutaneous pedicle screwing and rod insertion. The posterolateral gutter including the medial transverse process was decorticated and iliac bone graft was performed. The parameters analyzed up to a 2-year period included the operation time, intra and postoperative blood loss, Oswestry-Disability Index (ODI), Roland-Morris Questionnaire (RMQ), the Japanese Orthopaedic Association score, and the visual analogue scale of low back pain. The fusion rate and complications were also reviewed. RESULTS: The average operation time was statistically equivalent between the two groups. The intraoperative blood loss was significantly less in the MIS-PLF group (181 ml) when compared to the open-PLF group (453 ml). The postoperative bleeding on day 1 was also less in the MIS-PLF group (210 ml) when compared to the open-PLF group (406 ml). The ODI and RMQ scores rapidly decreased during the initial postoperative 2 weeks in the MIS-PLF group, and consistently maintained lower values than those in the open-PLF group at 3, 6, 12, and 24 months postoperatively. The fusion rate was statistically equivalent between the two groups (98 vs. 100%), and no major complications occurred. CONCLUSION: The MIS-PLF utilizing a percutaneous pedicle screw system is less invasive compared to conventional open-PLF. The reduction in postoperative pain led to an increase in activity of daily living (ADL), demonstrating rapid improvement of several functional parameters. This superiority in the MIS-PLF group was maintained until 2 years postoperatively, suggesting that less invasive PLF offers better mid-term results in terms of reducing low back pain and improving patients' functional capacity of daily living. The MIS-PLF utilizing percutaneous pedicle screw fixation serves as an alternative technique, eliminating the need for conventional open approach.

Alterations in stress distribution patterns through the forearm joint surface of the elbow in baseball players assessed using computed tomography osteoabsorptiometry.

BACKGROUND: The distribution of subchondral bone density well reflects long-term resultant stress acting on an articular surface in living joints. Consequently, a measurement of the distribution pattern can determine the stress distribution across the elbow joint surface under long-term loading conditions of baseball pitching. Our purpose was to elucidate the characteristic alterations in the distribution pattern of subchondral bone density across the forearm bones of the elbow with pitching activities. The hypothesis is that pitching activities would change the stress distribution in living subjects. METHODS: The analysis was performed using computed tomography (CT) images obtained from the dominant elbow of ten nonthrowing athletes (control group), ten college baseball fielders (fielder group), and ten college baseball pitchers (pitcher group). The distribution pattern of subchondral bone density through the articular surface of the proximal radius and ulna bones was assessed using CT osteoabsorptiometry. RESULTS: The maximum density area was located in the posterior part of the trochlea notch in all study participants. This maximum density area was significantly increased in the baseball groups compared with that in the control group. The pitcher group also showed a significant distribution of the maximum density area in the anterior part of the radial head. CONCLUSION: Our analysis indicates that pitching activities increase actual stress on the articular surface not only in the posterior part of the trochlea notch but also in the anterior part of the radial head. The stress across the elbow may be expanded from the ulnohumeral to the radiohumeral joint by repetitive pitching activities in living subjects.