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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. [ABSTRACT FROM AUTHOR]

Little is known regarding the incidence of the shoulder instability in Japan. The aim of this study was to evaluate the incidence of traumatic shoulder instability among Japanese military cadets. A prospective cohort study was performed to capture all traumatic shoulder instability events between 2009 and 2012 among cadets in a military educational academy of the Japan Self Defense Forces. The total number of cadets in the cohort was 5,402 (average age 20.6 years). The incidence of instability events, including dislocation or subluxation, was calculated. Chronicity, demographics of participants, mechanism of injury, and athletic events were also evaluated. The incidence of traumatic dislocation was 4.1/1,000 person-years and that of subluxation was 6.1/1,000 person-years. The incidence of primary dislocation or subluxation was 5.4/1,000 person-years and that of recurrent dislocation or subluxation was 4.7/1,000 person-years. Of first dislocations or subluxations, 92% occurred during sports activities, including after-school sports activities, military training, and gym classes. In conclusion, the overall incidence of shoulder instability events among Japanese military cadets was 10.3/1,000 person-years, and was extremely high. Most shoulder instability events occurred during sports activities, and a program to prevent such injuries during sports activities is necessary for young participants. [ABSTRACT FROM AUTHOR]

Objective: When using the cortical bone trajectory (CBT) technique, two technical countermeasures are recommended to promote bone fusion: taking a long CBT screw path directed more anteriorly and improving the stability of the spinal construct by facet joint preservation, cross-link augmentation, and rigid anterior interbody reconstruction. However, there has been no report on how these surgical procedures, which are heavily dependent on the surgeon's preference, contribute to successful bone fusion. The aim of the present study was to investigate the progression of lumbar spinal fusion using the long CBT technique and identify factors contributing to the time taken to achieve bone fusion, with a particular focus on the involvement of surgical procedures., Methods: A total of 167 consecutive patients with L4 degenerative spondylolisthesis who underwent single-level posterior lumbar interbody fusion at L4-5 using the long CBT technique were included (mean follow-up 42.8 months). Bone fusion was assessed to identify factors contributing to the time to achieve bone fusion. Investigated factors were 1) age, 2) sex, 3) BMI, 4) bone mineral density, 5) intervertebral mobility, 6) screw depth in the vertebra, 7) extent of facetectomy, 8) cross-link augmentation, 9) cage material, 10) cage design, 11) number of cages, and 12) contact area of cages with the vertebral endplate., Results: The bone fusion rate was 89.2% at 2 years postoperatively and 95.8% at the last follow-up, with a mean period to bone fusion of 16.6 ± 9.6 months. Multivariate regression analysis revealed that age (standardized regression coefficient [β] = 0.25, p = 0.002), female sex (β = -0.22, p = 0.004), and BMI (β = 0.15, p = 0.045) were significant independent factors affecting the time to achieve bone fusion. There was no significant effect of surgical procedures (p ≥ 0.364)., Conclusions: This is the first study to investigate the progression of lumbar spinal fusion using the long CBT technique and identify factors contributing to the time taken to achieve bone fusion. Patient factors such as age, sex, and BMI affected the progression of bone fusion, and surgical factors had only weak effects.

Background : This study aims to investigate the postoperative improvement of paralysis, fusion rate and risk factors for kyphosis progression in adults affected with spinal caries. Methods : Overall, 134 patients with spinal caries from the thoracic to lumbar spine from 1992 to 2021 were included in this study. Data concerning the affected level (thoracic, thoracolumbar, lumbar, and lumbosacral), bone fusion rate, and progression of the postoperative local kyphosis angle were collected. The risk factors for the progression of local kyphosis angle after anterior spinal fixation (ASF) were determined using linear regression analysis. Results : Preoperatively, the degree of spinal cord paralysis was D and E on Frankel classification. Improvement of paralysis was good with surgery, especially from C, D. The overall bone fusion rate was 83.2%. The only factor influencing the progression of local kyphosis angle after ASF was the level of the affected vertebra. Progression of kyphosis angle after ASF was very advanced in the thoracolumbar transition area. Conclusions : Surgical improvement in paraplegia and the fusion rate of ASF with only grafted bone was good. However, in patients affected in the thoracolumbar spine region, posterior instrumentation is desirable because of local kyphosis progression risk after surgery.

Study Design: This study adopted a cross-sectional study design., Purpose: This study was designed to investigate the effects of bone cross-link bridging on fracture mechanism and surgical outcomes in vertebral fractures using the maximum number of vertebral bodies with bony bridges between adjacent vertebrae without interruption (maxVB)., Overview of Literature: The complex interplay of bone density and bone bridging in the elderly can complicate vertebral fractures, necessitating a better understanding of fracture mechanics., Methods: We examined 242 patients (age >60 years) who underwent surgery for thoracic to lumbar spine fractures from 2010 to 2020. Subsequently, the maxVB was classified into three groups: maxVB (0), maxVB (2-8), and maxVB (9-18), and parameters, including fracture morphology (new Association of Osteosynthesis classification), fracture level, and neurological deficits were compared. In a sub-analysis, 146 patients with thoracolumbar spine fractures were classified into the three aforementioned groups based on the maxVB and compared to determine the optimal operative technique and evaluate surgical outcomes., Results: Regarding the fracture morphology, the maxVB (0) group had more A3 and A4 fractures, whereas the maxVB (2-8) group had less A4 and more B1 and B2 fractures. The maxVB (9-18) group exhibited an increased frequency of B3 and C fractures. Regarding the fracture level, the maxVB (0) group tended to have more fractures in the thoracolumbar transition region. Furthermore, the maxVB (2-8) group had a higher fracture frequency in the lumbar spine area, whereas the maxVB (9-18) group had a higher fracture frequency in the thoracic spine area than the maxVB (0) group. The maxVB (9-18) group had fewer preoperative neurological deficits but a higher reoperation rate and postoperative mortality than the other groups., Conclusions: The maxVB was identified as a factor influencing fracture level, fracture type, and preoperative neurological deficits. Thus, understanding the maxVB could help elucidate fracture mechanics and assist in perioperative patient management.

Introduction: An anterior surgical approach for severe infectious spondylodiscitis in the lumbar region is optimal but not always atraumatic. The aim of this study was to evaluate the efficacy and safety of a minimal anterior-lateral retroperitoneal approach, also known as a surgical approach for oblique lumbar interbody fusion, for cases with severe infectious spondylodiscitis with osseous defects., Methods: Twenty-four consecutive patients who underwent anterior debridement and spinal fusion with an autologous strut bone graft for infectious spondylodiscitis with osseous defects were reviewed retrospectively. Eleven patients underwent the minimal retroperitoneal approach (Group M), and 13 underwent the conventional open approach (Group C). Peri- and postoperative clinical outcomes, that is, estimated blood loss (EBL), operative time (OT), creatine kinase (CK) level, visual analog scale (VAS), and rates of bone union and additional posterior instrumentation, were evaluated, and the differences between both groups were assessed statistically., Results: Mean EBL, serum CK on the 1 st postoperative day, and VAS on the 14 th postoperative day were 202.1 mL, 390.9 IU/L, and 9.5 mm in Group M and 648.3 mL, 925.5 IU/L, and 22.3 mm in Group C, respectively, with statistically significant differences between the groups. There were no statistically significant intergroup differences in OT and rates of bone union and additional posterior instrumentation., Conclusions: Anterior debridement and spinal fusion using the minimal retroperitoneal approach is a useful and safe surgical technique. Although a preponderance of the minimal approach regarding early bone union is not validated, this technique has the advantages of conventional open surgery, but reduces blood loss, muscle injury, and pain postoperatively., Competing Interests: Conflicts of Interest: The authors declare that there are no relevant conflicts of interest., (Copyright © 2021 by The Japanese Society for Spine Surgery and Related Research.)

Objective: Most surgeons are forced to turn their heads away from the surgical field to see various intraoperative support monitors. These movements may result in inconvenience to surgeons and lead to technical difficulties and potential errors. Wearable devices that can be attached to smart glasses or any glasses are novel visualization tools providing an alternative screen in front of the user's eyes, allowing surgeons to keep their attention focused on the operative task without taking their eyes off the surgical field. The aim of the present study was to examine the feasibility of using glasses equipped with a wearable display device that transmits display monitor data during fluoroscopically guided minimally invasive spinal instrumentation surgery., Methods: In this pilot prospective randomized study, 20 consecutively enrolled patients who underwent single-segment posterior lumbar interbody fusion (PLIF) at L5-S1 performed using the percutaneous pedicle screw technique were randomly divided into two groups, a group for which the surgeon used a wearable display device attached to regular glasses while performing surgery (smart glasses group) and a group for which the surgeon did not use such a device (nonglasses group). Real-time intraoperative fluoroscopic images were wirelessly transmitted to the display device attached to the surgeon's glasses. The number of head turns performed by the surgeon to view the standard fluoroscopic monitor during procedures and the operative time, estimated blood loss, radiation exposure time, screw placement accuracy, and intraoperative complication rate were evaluated for comparison between the two groups., Results: The number of surgeon head turns to view the fluoroscopic monitor in the smart glasses group was 0.10 ± 0.31 times, which was significantly fewer than the head turns in the nonglasses group (82.4 ± 32.5 times; p < 0.001). The operative and radiation exposure times in the smart glasses group were shorter than those in the nonglasses group (operative time 100.2 ± 10.4 vs 105.5 ± 14.6 minutes, radiation exposure time 38.6 ± 6.6 vs 41.8 ± 16.1 seconds, respectively), although the differences were not significant. Postoperative CT showed one screw perforation in the nonglasses group, and no intraoperative complications were observed in either group., Conclusions: This is, to the authors' knowledge, the first report on the feasibility of using this wearable display device attached to glasses for fluoroscopically guided minimally invasive spinal instrumentation surgery. Smart glasses display devices such as this one may be a valid option to facilitate better concentration on operative tasks by improving ergonomic efficiency during surgery.

Study Design: A retrospective observational study., Objective: This study examined the role of skeletal muscles in the spinal alignment of lumbar degenerative kyphosis (LDK)., Summary of Background Data: Adult spinal deformity (ASD) may present as LDK, which is unusual in that it typically lacks any coronal deformity., Methods: This retrospective study included 367 female patients with ASD. Demographic and radiographic data from LDKs were compared with those with other ASD. The LDK multifidus was also subjected to histological analysis. The muscle volume and strength were analyzed using whole-body dual x-ray absorptiometry and pulmonary function tests. Magnetic resonance images were used to determine the cross-sectional area (CSA) and fatty infiltration area (FIA) of the psoas and multifidus., Results: A total of 52 patients (15%) were classified as LDK. Compared with other ASDs, those with LDK had a significantly larger sagittal vertical axis (16.3 ± 5.0 cm), and pelvic incidence minus lumbar lordosis (52.8° ± 9.2°). The LDK had significantly lower CSA and higher FIA of the multifidus, but not in the psoas (multifidus CSA 223 ± 96 vs. 477 ± 129 mm, P < 0.001; FIA 82% vs. 31%, P < 0.001). Eighty-six percent of LDK had a multifidus CSA of less than 300 mm, and 82% had an FIA of more than 80%. Whole-body dual x-ray absorptiometry showed no significant difference in the other body sections between LDK and other ASDs. The percent-predicted peak expiratory flow was within normal range in 82% of the LDK. LDK multifidus specimens revealed diffuse, nonuniform muscular fibers and growth of the interstitium and adipose tissue, with no muscular inflammation. We redefined LDK as drop body syndrome, a distinct form of ASD., Conclusion: Significantly decreased CSA and increased FIA of the multifidus were observed in LDK, whereas the muscle strength and volume of the other body sections were normal. These findings strongly suggest the presence of isolated lumbar extensor myopathy in LDK., Level of Evidence: 4.