Anterior controllable antidisplacement and fusion surgery for the treatment of extensive cervico-thoracic ossification of posterior longitudinal ligament with severe myelopathy: case report and literature review.

OPLL generally occurs in the cervical spine and involves no more than three vertebral segments, while extensive OPLL that involves the cervico-thoracic spine and spans over multiple segments is rare. Surgically it is difficult to achieve a satisfactory clinical outcome without surgical complications via the traditional anterior or posterior approaches. We report the first application of Anterior controllable antidisplacement and fusion (ACAF) in treating extensive cervico-thoracic OPLL. A 45-year old patient experienced severe walking disturbance, bladder and bowel dysfunction for 5 months after a fall. His preoperative Japanese Orthopedic Association (JOA) score was 8 of 17. Preoperative CT and MRI demonstrated a K-line (-) and mixed-type extensive OPLL from C2 to T2, causing significant cord compression. After ACAF surgery, neurological symptoms improved immediately without postoperative complications. Postoperative CT and MRI scanning showed restoration of spinal canal cross section and cord decompression. At 6 months he was able to stand and walk again without assistance and urinary bladder and bowel function returned to normal completely. At 15 months his JOA score was 14 of 17. ACAF surgery provides a promising alternative for the treatment of extensive cervico-thoracic OPLL.

ACVR1-knockout promotes osteogenic differentiation by activating the Wnt signaling pathway in mice.

Osteogenic differentiation refers to the process of bone formation and remodeling, which is controlled by complex molecular mechanisms. Activin A receptor type I (ACVR1) is reported to be associated with osteogenic differentiation. However, the underlying molecular mechanism remains elusive. Therefore, this study evaluates the function of ACVR1 in osteogenic differentiation through the Wnt signaling pathway. The expression of osteocalcin (Oc) and osterix together with osteogenic differentiation and mineralization was examined in ACVR1-knockout (KO) mouse. Furthermore, the Wnt signaling pathway was inhibited in bone marrow stromal cells (BMSCs) of mice to explore the role of the Wnt signaling pathway in osteogenic differentiation by means of alkaline phosphatase (ALP) activity detection and evaluation of mineralized nodules and calcium content. Subsequently, the effect of ACVR1 on the Wnt signaling pathway was assessed by determining the expression of ACVR1, ß-catenin, glycogen synthase kinase 3 ß (GSK3ß), dickkopf-related protein 1 (DKK1), and frizzled class receptor 1 (FZD1). Both their effects on osteogenic differentiation were further evaluated by determination of Oc, osterix, and Runx2 expression. AVCR1 KO mice exhibited increased Oc and osterix expression and promoted bone resorption and formation. ACVR1-knockout was observed to activate the Wnt signaling pathway with an increase of ß-catenin and reductions in GSK3ß, DKK1, and FZD1. With the inhibited Wnt signaling pathway expression of Oc, osterix, and Runx2 was decreased, and ALP activity, mineralized nodule, and calcium content in cellular matrix were decreased as well, indicating that inactivation of the Wnt signaling pathway reduced the differentiation of BMSCs into osteoclasts. These findings indicate that ACVR1-knockout promotes osteogenic differentiation by activating the Wnt signaling pathway in mice.

Computer-Based 3D Simulations to Formulate Preoperative Planning of Bridge Crane Technique for Thoracic Ossification of the Ligamentum Flavum.

BACKGROUND The bridge crane technique is a novel surgical technique for the treatment of thoracic ossification of the ligamentum flavum (TOLF), but its preoperative planning has not been studied well, which limits the safety and efficacy of surgery to some extent. The purpose of this study was to investigate the method of application and effect of computer-aided preoperative planning (CAPP) on the bridge crane technique for TOLF. MATERIAL AND METHODS This retrospective multi-center included 40 patients with TOLF who underwent the bridge crane technique from 2016 to 2018. According to the utilization of CAPP, patients were divided into Group A (with CAPP, n=21) and Group B (without CAPP, n=19). Comparisons of clinical and radiological outcomes were carried out between the 2 groups. RESULTS The patients in Group A had higher post-mJOA scores and IR of neurological function than those in Group B (p<0.05). Group A had shorter surgery time, fewer fluoroscopic images, and lower incidence of complications than Group B. In Group A, there was a high consistency of all the anatomical parameters between preoperative simulation and postoperative CT (p>0.05). In Group B, there were significant differences in 3 anatomical parameters between postoperative simulation and postoperative CT (p<0.05). In Group B, the patients with no complications had higher post-SVOR and lower SVRR and height of posterior suspension of LOC in postoperative CT than those in postoperative simulation (p<0.05). CONCLUSIONS CAPP can enable surgeons to control the decompression effect accurately and reduce the risk of related complications, which improves the safety and efficacy of surgery.

Risk assessment of vertebral artery injury in anterior controllable antedisplacement and fusion (ACAF) surgery: a cadaveric and radiologic study.

PURPOSE: We have introduced a novel surgery technique named anterior controllable antedisplacement and fusion (ACAF) for the treatment of ossification of the posterior longitudinal ligament. As reported, the satisfactory postoperative outcome can be attributed to the larger decompression width. However, it may associate with high prevalence of vertebral artery injury (VAI) theoretically. Thus, assessment of the vulnerability of vertebral artery in ACAF is of great importance. METHODS: Computed tomographic scan data of 28 patients were retrospectively studied. Seven radiographic parameters were evaluated: uncinate process (UP) tips distance, transverse foramen (TF)-UP tips distance, TF-LWL (the ipsilateral limited wedging line) distance, the limited distance of lateral decompression, the maximum oblique angle of LWL, TF-LWG (the lateral wall of groove) distance, and width of groove. Eleven fresh cadaveric spines undergoing ACAF surgery were also studied. Two anatomic parameters were evaluated: width of groove and LWG-TF distance. RESULTS: The UP tips distance increased from C3 to C6 and tended to be larger in males. The UP tip-TF distance and LWL-TF distance were smallest at C4, but both were larger than 2 mm. Maximum oblique angle decreased from C3 to C6. Postoperatively, both radiographic and cadaveric measurements showed the width of groove was larger than UP tips distance, but LWG-TF distance was larger than 2 mm in all levels. CONCLUSION: UP can be used as anatomical landmarks to avoid VAI during ACAF surgery. Radiographic and cadaveric measurements verified the safety of ACAF surgery, even for those cases with wedging and lateral slotting.

Protective effect of epigenetic silencing of CyclinD1 against spinal cord injury using bone marrow-derived mesenchymal stem cells in rats.

This study focuses on the protective effect of epigenetic silencing of CyclinD1 against spinal cord injury (SCI) using bone marrow-derived mesenchymal stem cells (BMSCs) in rats. Eighty-eight adult female Wistar rats were randomly assigned into the sham group, the control group, the si-CyclinD1 + BMSCs group and the BMSCs group. CyclinD1 protein and mRNA expressions after siRNA transfection were detected by Western blotting and qRT-PCR. The siRNA-CyclinD1 BMSCs were transplanted into rats in the si-CyclinD1 + BMSCs group using stereotaxic method 6 hr after SCI. Hindlimb locomotor performance was determined using inclined plane test and Basso-Beattie-Bresnahan (BBB) locomotor rating scale. Expressions of glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) were detected by immunohistochemistry. Inclined plane and BBB scores in the control, si-CyclinD1 + BMSCs, and BMSCs groups were significantly lower than the sham group, but these scores were evidently decreased in the control group and increased in the si-CyclinD1 + BMSCs group compared with the BMSCs group. The repair degree of spinal cord tissues of rats in the si-CyclinD1 + BMSCs group was obvious than the BMSCs group. GFAP and NGF protein expressions were markedly decreased in the control, si-CyclinD1 + BMSCs and BMSCs groups when compared with the sham group. GFAP- and NGF-positive cells were significantly increased in the si-CyclinD1 + BMSCs group while decreased in the control group. Our study provides evidence that epigenetic silencing of CyclinD1 using BMSCs might accelerate the repair of SCI in rats.

Effects of MicroRNA-494 on Astrocyte Proliferation and Synaptic Remodeling in the Spinal Cord of a Rat Model of Chronic Compressive Spinal Cord Injury by Regulating the Nogo/Ngr Signaling Pathway.

BACKGROUND/AIMS: Chronic compression of the spinal cord causes the loss of motor neurons in the anterior horn, but the precise and extensive mechanism for the loss is not completely determined. Therefore, this study aims to explore the role of microRNA-494 (miR-494) in the proliferation of astrocytes and in the synaptic remodeling in the spinal cord of a rat model of chronic spinal cord injury (SCI) by regulating the Nogo/NgR signaling pathway. METHODS: A rat model of chronic, compressive SCI was established, and the spinal cord state, blood supply changes, and astrocyte apoptosis were observed. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Western blotting were used to detect expression of miR-494 and the Nogo/NgR signaling pathway-related genes. Fluorescence in situ hybridization (FISH) was used for detecting miR-494 expression and distribution. RESULTS: Higher miR-494 expression was accompanied by the inhibition of astrocyte proliferation and synaptic remodeling. In addition, CDK6 could be regulated by miR-494 and was shown to be one of the target genes of miR-494. Positive expression of miR-494 detected by FISH was consistent with the results from RT-qPCR that miR-494 could downregulate CDK6 gene expression. Moreover, the direct miR-494 target CDK6 plays important inhibitory roles in chronic SCI by suppressing the Nogo/ NgR signaling pathway. CONCLUSIONS: The results demonstrated that miR-494 inhibition can promote astrocyte proliferation and synaptic remodeling by suppressing the Nogo/NgR signaling pathway in a rat model of chronic SCI.

Evaluating the Rotation Correction of the Main Thoracic Curve in Severe Adolescent Idiopathic Scoliosis: Bending and Traction vs. Fulcrum - A Preliminary Report.

BACKGROUND Flexibility evaluation methods were only used to assess the changes of coronal Cobb angle in patients with adolescent idiopathic scoliosis (AIS). Little attention was attached to the vertebral rotation in these methods. MATERIAL AND METHODS 21 patients with severe adolescent idiopathic scoliosis were enrolled in this study. Coronal flexibility and rotation correction were compared on the supine bending, traction and fulcrum bending radiographs. The apical vertebral body rib ratio (AVB-R), and Perdriolle rotation angles were used to measure the rotation of the main thoracic curve. Statistical analysis was performed with one-way Analysis of Variance(ANOVA). Correlations between postoperative AVB-R and AVB-R in supine bending, traction and fulcrum bending radiographs were assessed utilizing the Linear Regression. RESULTS There were trends towards increased coronal flexibility in fulcrum bending versus traction versus supine bending, but there were no significant differences due to the limited sample size. And all were significantly lower than postoperative correction. The correction of AVB-R at traction and supine bending radiographs were significantly better than fulcrum bending, however, all were significantly lower than postoperative correction. Correction of Perdriolle rotation angle at traction radiograph was best among these methods. A univariant linear regression analysis showed a strong linear correlation between the postoperative AVB-R and the AVB-R in the traction radiograph. CONCLUSIONS As to patients with severe AIS, the coronal plane flexibility evaluated at the fulcrum bending radiograph is superior to that at the traction radiograph. This may be explained by the measurement errors induced by the better derotation capacity at the traction radiograph. Rotation correction evaluated at the traction radiograph proves better than the fulcrum bending radiographs, showing a linear correlation with the postoperative correction.

A Novel "De-tension"-guided Anterior Decompression Strategy-Thoracic Anterior Controllable Antedisplacement Fusion (TACAF) for Multilevel Ossification of Posterior Longitudinal Ligament in Thoracic Spine: A Retrospective Study with at Least 2-Year Follow-Up.

OBJECTIVE: To propose a novel surgical strategy-thoracic anterior controllable antedisplacement fusion (TACAF) to treat multilevel thoracic ossification of the posterior longitudinal ligament (mT-OPLL), and investigate its safety and efficacy. METHODS: Between January 2019 and December 2021, a total of 49 patients with thoracic myelopathy due to mT-OPLL surgically treated with TACAF were retrospectively reviewed. Patients' demographic data, radiologic parameters, and surgery-related complications, modified Japanese Orthopedic Association (mJOA) and visual analog scale (VAS) scores, thoracic kyphosis (TK), kyphosis angle in fusion area (FSK), thoracic curvature, spinal cord curvature, and curvature of curved rod in surgical region, diameter, and area of the spinal cord at the most compressed level were included. RESULTS: All patients acquired satisfactory recovery of neurologic function and overall complication rate was low at the final follow up. The mean mJOA of the laminectomy+TACAF and Full Lamina Preservation +TACAF groups, respectively, was 3.74 ± 2.05, 3.67 ± 1.95 before surgery, and 9.97 ± 0.83, 9.80 ± 0.68 at the final followed up, with the recovery rate of 84.26% ± 14.20%, 82.79% ± 10.35%, as to VAS Scores. The mean FSK was 34.50 ± 4.46,35.33 ± 3.44 before surgery, and was restored to 20.97 ± 5.70, 22.93 ± 6.34 at the final followed up respectively, as to mean TK (P < 0.05). Spinal cord curvature was improved from 34.12 ± 3.59, 33.93 ± 3.45 before surgery to 19.47 ± 3.53, 18.80 ± 3.17 at the final follow-up respectively, as to thoracic curvature (P < 0.05). In addition, the area and diameter of the spinal cord was also significantly improved at the final follow up (all P < 0.05). The curvature of the thoracic pulp and thoracic vertebra is closely related to the curvature of the rod. There was no statistically significant difference in the incidence of the pelvis and the slope value of the sacrum. CONCLUSIONS: This strategy provides a novel solution for the treatment of mT-OPLL with favorable recovery of neurological function, the tension of spinal cord, and fewer complications.

Regulation of the osteogenesis of pre-osteoblasts by spatial arrangement of electrospun nanofibers in two- and three-dimensional environments.

Orientation of extracellular matrix (ECM) fibrils contributes to the anisotropy of bones, but little is known about how fibril orientation induces osteoblastic responses. Here, biomimetic polycaprolactone/type I collagen (PCL/COL-1) nanofibers with aligned and random fiber arrangements were used as models to study their effects on pre-osteoblasts. Elongated cell morphology, accelerated cell migration, elevated alkaline phosphatase activity and calcium content, up-regulated expression of osteogenic markers and differential expression of integrins were observed for cells cultured on two-dimensional (2D) aligned nanofibers. To emulate in vivo tissue structure, three-dimensional (3D) cell/nanofiber constructs with cells embedded among nanofiber layers were built via layer-by-layer assembly. These showed that aligned nanofibers in the 3D constructs continuously induced cell polarization and promoted osteogenesis. These findings revealed that nanofiber alignment favored osteogenic differentiation of pre-osteoblasts, and demonstrated the potential of 3D cell/nanofiber construct as a model to study specific cell-material interactions in a physiologically relevant environment. FROM THE CLINICAL EDITOR: In this novel study, biomimetic polycaprolactone/type I collagen nanofibers with aligned and random fiber arrangements were used to demonstrate their effects on pre-osteoblasts with an overall goal of improved orientation of extracellular matrix fibrils to optimize osteoblastic responses and improve osteogenesis for future therapeutic exploitation.

[Clinical observation and evaluation of reasons for pseudarthrosis after anterior cervical fusion].

OBJECTIVE: To explore the causes of pseudarthrosis and evaluate the clinical neurological function and neck subaxial symptoms after anterior cervical fusion. METHODS: A total of 412 patients were followed up with an average of 5.4 years. The bone mineral density, bone graft trimming and placement, management of endplate, smoking and neck support fixation time were observed. Japanese Orthopedic Association (JOA) score was used to evaluate the changes of neurological functions and clinical outcomes. Visual analog scale (VAS) score was used to evaluate the neck subaxial symptoms. And pseudarthrosis was examined by flexion-extension radiography. SPSS statistical software 13.0 was used to evaluate the differences of JOA and VAS scores between pseudarthrosis and control groups. RESULTS: Among them, 37 cases of pseudarthrosis were observed. There were osteoporosis (n = 30 vs n = 119), cartilage end-plate punctuate hemorrhage (n = 18 vs n = 340), 25 and 43 cases with ineffective cervical external fixation (n = 25 vs n = 43) and smoking (n = 26 vs n = 87) in pseudarthrosis and fusion groups respectively. Significant differences existed in the above-mentioned indices between two groups. However, no significant difference existed in bone graft shape between two groups. There were significant differences in JOA and VAS scores between two groups. CONCLUSION: The causes of pseudarthrosis included decreased bone density, osteoporosis, over-curette of endplate, shortness of neck support fixation time and smoking. And pseudarthrosis may influence the long-term recovery of neurological functions or it is correlated significantly with neck symptoms.

Three-dimensional imaging analysis for the diagnosis of dural ossification in thoracic ossification of the ligamentum flavum: a multicenter study.

Background: Unforeseen dural ossification (DO) increases the risk of complications in the surgical management of thoracic ossification of the ligamentum flavum (OLF). Several methods have been proposed to identify DO; however, these approaches either have low diagnostic accuracy or poor feasibility. Therefore, we aimed to determine the relationship between DO and the severity and range of thoracic OLF compression using a 3-dimensional (3D) imaging analysis and to evaluate its superiority in diagnosing DO over conventional measurement methods. Methods: A total of 114 consecutive patients who underwent decompressive laminectomy for thoracic OLF in 4 institutions were retrospectively enrolled and divided into DO and non-DO groups. Univariate analysis was performed to determine the relationship between OLF compression and DO. We measured the 3D occupying ratio (OR; 3D OR = OLF volume/normal canal volume × 100%), calculated its cutoff values, and compared its diagnostic value in DO with that of conventional 1D and 2D radiological parameters in the whole thoracic spine. Results: The 3D OR in the DO group (50.9%±7.9%) was significantly higher than that in the non-DO group (30.8%±7.5%; P<0.01). The overall reliability and reproducibility for measurements of the 3D OR (intra- and interobserver correlation coefficients 0.94 and 0.90, respectively) were excellent. Thus, the 3D OR could be used as an indicator to distinguish between DO and non-DO, with high diagnostic accuracy (91.2%). Moreover, a 3D OR of >43%, known as the "ossification zone", was indicative of DO in OLF, whereas a value of <37% was considered the "safe zone". Additionally, the 3D OR [area under the curve (AUC) =0.98, 95% confidence interval (CI): 0.93-0.99] showed a statistically higher diagnostic value for DO in the upper, middle, lower, and whole thoracic spine than did both 1D (AUC =0.81; 95% CI: 0.73-0.88) and 2D (AUC =0.87; 95% CI: 0.79-0.92) parameters (P<0.01). Conclusions: DO was significantly associated with the severity and range of OLF compression. The 3D OR could be used as a critical diagnostic indicator for identifying DO in the whole thoracic spine, owing to its superiority over conventional radiological parameters. Classification of the 3D OR could maximize the clinical feasibility and thus help surgeons to decrease the incidence of DO-related surgical complications.

The effect of K-line classification in different cervical dynamic position on surgical outcomes in patients with ossification of the posterior longitudinal ligament after anterior controllable antedisplacement and fusion.

Purpose: To investigate whether the K-line classification in different cervical dynamic position of patients with Ossification of the Posterior Longitudinal Ligament (OPLL) affects clinical outcome after Anterior Controllable Antedisplacement and Fusion (ACAF) surgery. Methods: A total of 93 patients who suffered from cervical spondylosis caused by OPLL underwent ACAF surgery between June 2015 and December 2017 in a single institution. Neutral, neck-flexed and neck-extended cervical radiographs were obtained from every patient. Subsequently they were classified into K-line (+) and K-line (-) with reference to the K-line classification criteria. Clinical outcomes were assessed by the JOA score, improvement rate (IR) and visual analogue scale (VAS). Radiological assessment included Cobb angle and occupation ratio (OR) of OPLL. Correlations between the long-term surgical outcomes and classification of K-line in different dynamic position were analyzed by one-way analysis of variance. Results: Significant improvements were shown in all postoperative clinical and radiographic assessments (P < 0.05). There were no differences in IR, Cobb angle and VAS among flexion K-line (-), flexion K-line (+), extension K-line (-) and extension K-line (+) at the 2-year follow-up (P > 0.05). However, the OR of extension K-line (-) (16.13% ± 11.58%) was higher than that of extension K-line (+) (9.00% ± 10.27%) and flexion K-line (+) subgroup (9.47% ± 9.97%) (P < 0.05). Conclusion: The ACAF procedure has shown satisfactory surgical outcomes in various K-line classifications in different dynamic position.

Metagenomic next-generation sequencing for the detection of pathogenic microorganisms in patients with pulmonary infection.

OBJECTIVE: To explore the clinical value of metagenomic next-generation sequencing (mNGS) in diagnosing pulmonary infectious diseases. METHODS: A retrospective analysis was performed on 82 patients with pulmonary infection who were admitted to the Eighth Affiliated Hospital of Guangxi Medical University & Guigang City People's Hospital from January 2020 to December 2021. The pathogens were detected by mNGS and conventional methods (culture and PCR). Then, the type and number of detected pathogens, as well as the specificity and sensitivity, were compared between the two methods. In addition, the positive rates of bacteria, fungi, tubercle bacillus, and mixed infection in bronchoalveolar lavage fluid, sputum, pleural effusion, and blood detected by mNGS, and the advantage in required test time were evaluated. RESULTS: More types and numbers of pathogens were detected by mNGS with a higher sensitivity but a lower specificity, as compared to the conventional detection methods (all P<0.05). The positive rates and integrity rates of bacteria, fungi, and tubercle bacillus detected by mNGS were higher than those by conventional methods (all P<0.05). Moreover, there was no difference in the overall sensitivity of mNGS among different sample types, but the sensitivities of mNGS in bronchoalveolar lavage fluid and sputum samples were significantly higher than those of conventional methods (both P<0.05). The average test time for mNGS was shorter than that of conventional methods. CONCLUSION: mNGS can detect more types and numbers of pathogenic microorganisms, improve the detection sensitivity, and reduce the detection time in patients with pulmonary infection.

Anterior controllable antedisplacement and fusion: quantitative analysis of a single surgeon's learning experience.

BACKGROUND CONTEXT: Anterior controllable antedisplacement and fusion (ACAF) is a novel surgical technique for the treatment of ossification of the posterior longitudinal ligament (OPLL) but the surgical learning curve for this technique has not been previously characterized. PURPOSE: The aim of this study was to quantify a surgeon's learning curve for ACAF and the effect of surgeon experience on postoperative outcomes. STUDY DESIGN: Prospective study of a single institution and single surgeon experience with ACAF surgery. PATIENT SAMPLE: A total of 70 consecutive patients with OPLL undergoing ACAF surgery by a single, non-ACAF trained surgeon between 2017 and 2020 were analyzed. OUTCOME MEASURES: Intraoperative and postoperative outcomes (blood loss, operative time, errors of surgical procedure, length of hospital stay, Japanese Orthopedic Association (JOA) scoring system, and surgical complications) were assessed. METHODS: We prospectively reviewed the first 70 ACAF procedures between 2017 and 2020 performed by a single, non-ACAF trained surgeon. The function relationship between the operative time and case number was fitted using a locally weighted scatterplot smoothing (LOESS) plot. Spearman's correlation analysis was performed to determine factors affecting the operative time. The operative time-related learning curve for ACAF was established and difficulty of each procedure was assessed using a cumulative sum (CUSUM) model. The association between the specific errors of surgical procedures and surgeon experience was further analyzed. A modified CUSUM model was also used to establish the surgical procedure-related learning curve, and thus whether these two learning curves matched with each other was observed. Postoperative outcomes in relation to surgeon experience was compared using a Wilcoxon rank sum test and Chi-squared test. RESULTS: Operative time presented a specific pattern of fewer patient-dependent changes as the case number increased. Spearman's correlation analysis showed the operative time was more affected by the case number (r=-0.73) than the complexity of condition and number of levels hoisted. The operative time-related CUSUM model identified the early (first 29 cases) and late phase (late 41 cases) of the learning process, which was also confirmed by a modified CUSUM model based on surgical procedure. The critical point of the CUSUM model for bilateral osteotomies was at case number 29, and time reduction after the early phase was approximately 34 minutes. Length of hospital stay and blood loss were less during the late phase than during the early phase (p<.05). Although no significant difference was observed in postoperative JOA scores between two phases, patients in the late phase obtained higher recovery rates of neurologic function than those in the early phase (p<.01). There was significant difference in the number of specific errors between the two phases (p=.02). There were no significant differences in overall complication rates between two phases, but a higher incidence of certain complications caused by specific errors was observed in the early phase (p=.02), including CSF leakage, C5 palsy and incomplete decompression. CONCLUSIONS: We described, for the first time, a detailed learning curve for ACAF surgery. About 29 cases were needed to achieve mastery of ACAF. Once mastered, the surgeon could deal with various OPLL presentations in a universal way regardless of condition complexity and number of surgical levels. Bilateral osteotomies were the most difficult part of ACAF and produced the greatest reduction in time after mastery. We found a close association between specific errors of surgical procedure for ACAF and surgeon experience. Furthermore, certain complications caused by these errors should be on the alert during the early phase of learning ACAF, including CSF leakage, C5 palsy and incomplete decompression.

New anterior controllable antedisplacement and fusion surgery for cervical ossification of the posterior longitudinal ligament: a biomechanical study.

OBJECTIVE: The traditional anterior approach for multilevel severe cervical ossification of the posterior longitudinal ligament (OPLL) is demanding and risky. Recently, a novel surgical procedure-anterior controllable antedisplacement and fusion (ACAF)-was introduced by the authors to deal with these problems and achieve better clinical outcomes. However, to the authors' knowledge, the immediate and long-term biomechanical stability obtained after this procedure has never been evaluated. Therefore, the authors compared the postoperative biomechanical stability of ACAF with those of more traditional approaches: anterior cervical discectomy and fusion (ACDF) and anterior cervical corpectomy and fusion (ACCF). METHODS: To determine and assess pre- and postsurgical range of motion (ROM) (2 Nm torque) in flexion-extension, lateral bending, and axial rotation in the cervical spine, the authors collected cervical areas (C1-T1) from 18 cadaveric spines. The cyclic fatigue loading test was set up with a 3-Nm cycled load (2 Hz, 3000 cycles). All samples used in this study were randomly divided into three groups according to surgical procedures: ACDF, ACAF, and ACCF. The spines were tested under the following conditions: 1) intact state flexibility test; 2) postoperative model (ACDF, ACAF, ACCF) flexibility test; 3) cyclic loading (n = 3000); and 4) fatigue model flexibility test. RESULTS: After operations were performed on the cadaveric spines, the segmental and total postoperative ROM values in all directions showed significant reductions for all groups. Then, the ROMs tended to increase during the fatigue test. No significant crossover effect was detected between evaluation time and operation method. Therefore, segmental and total ROM change trends were parallel among the three groups. However, the postoperative and fatigue ROMs in the ACCF group tended to be larger in all directions. No significant differences between these ROMs were detected in the ACDF and ACAF groups. CONCLUSIONS: This in vitro biomechanical study demonstrated that the biomechanical stability levels for ACAF and ACDF were similar and were both significantly greater than that of ACCF. The clinical superiority of ACAF combined with our current results showed that this procedure is likely to be an acceptable alternative method for multilevel cervical OPLL treatment.

Anatomical Evaluation of Spinal Nerve and Cervical Intervertebral Foramina in Anterior Controllable Antedisplacement and Fusion Surgery: A Cadaveric and Radiologic Study.

OBJECTIVE: To achieve the anatomical evaluation of spinal nerve and cervical intervertebral foramina in anterior controllable antedisplacement and fusion (ACAF) surgery, a novel surgical technique with the wider decompression, through a cadaveric and radiologic study. METHODS: Radiographic data of consecutive 47 patients (21 by ACAF and 26 by anterior cervical corpectomy and fusion [ACCF]) who have accepted surgery for treatment of cervical ossification of the posterior longitudinal ligament(OPLL) and stenosis from March 2017 to March 2018 were retrospectively reviewed and compared between an ACAF group and ACCF group. Three postoperative radiographic parameters were evaluated: the decompression width and the satisfaction rate of decompression at the entrance zone of intervertebral foramina on computed tomography (CT), and the transverse diameter of spinal cord in the decompression levels on magnetic resonance imaging (MRI). In the anatomic study, three fresh cadaveric spines (death within 3 months) undergoing ACAF surgery were also studied. Four anatomic parameters were evaluated: the width of groove, the distance between the bilateral origins of ventral rootlets, the length of ventral rootlet from their origin to the intervertebral foramina, the descending angle of ventral rootlet. RESULTS: The groove created in ACAF surgery included the bilateral origins of ventral rootlets. The rootlets tended to be vertical from the rostral to the caudal direction as their takeoff points from the central thecal sac became higher and farther away from their corresponding intervertebral foramina gradually. No differences were identified between left and right in terms of the length of ventral rootlet from the origin to the intervertebral foramina and the descending angle of ventral rootlet. The decompression width was significantly greater in ACAF group (19.2 ± 1.2 vs 14.7 ± 1.2, 21.3 ± 2.2 vs 15.4 ± 0.9, 21.5 ± 2.1 vs 15.7 ± 1.0, 21.9 ± 1.6 vs 15.9 ± 0.8, from C3 to C6 ). The satisfactory rate of decompression at the entrance zone of intervertebral foramina tended to be better in the left side in ACAF group (significant differences were identified in the left side at C3/4 , C4/5 , C6/7 level, and in the right side at C4/5 level when compared with ACCF). And decompression width was significantly greater than the transverse diameter of spinal cord in ACAF group. Comparatively, there existed no significant difference in the ACCF group besides the C5 level. CONCLUSION: ACAF can decompress the entrance zone of intervertebral foramina effectively and its decompression width includes the origins and massive running part of bilateral ventral rootlets. Due to its wider decompression range, ACAF can be used as a revision strategy for the patients with failed ACCF.

Anterior Controllable Antedisplacement and Fusion (ACAF) vs Posterior Laminoplasty for Multilevel Severe Cervical Ossification of the Posterior Longitudinal Ligament: Retrospective Study Based on a Two-Year Follow-up.

OBJECTIVES: To compare the clinical outcomes of anterior controllable antedisplacement fusion (ACAF), a new surgical technique, with laminoplasty for the treatment of multilevel severe cervical ossification of the posterior longitudinal ligament (OPLL) based on a 2-year follow-up. METHODS: Clinical data of 53 patients (21 by ACAF and 32 by laminoplasty) who have accepted surgery for treatment of cervical myelopathy caused by multilevel severe OPLL (occupying rate ≥ 50%) from March 2015 to March 2017 were retrospectively reviewed and compared between ACAF group and laminoplasty group. Operative time, blood loss, and complications of the two groups were recorded. Radiographic parameters were evaluated pre- and postoperatively: cervical lordosis on X-ray, space available for the cord (SAC) and the occupying ratio (OR) on computed tomography (CT), and the anteroposterior (AP) diameter of the spinal cord at the narrowest level and the spinal cord curvature on magnetic resonance imaging (MRI). Japanese Orthopaedic Association (JOA) scoring was used to evaluate neurologic recovery. Statistical analysis was conducted to analyze the differences between two groups. The Mann-Whitney U test and chi square test were used to compare categorical variables. unpaired t test was used to compare continuous data. RESULTS: All patients were followed up for at least 24 months. The operative time was longer in ACAF group (286.5 vs 178.2 min, P < 0.05). The blood loss showed no significant difference (291.6 vs 318.3 mL, P > 0.05). Less complications were observed in ACAF group than in laminoplasty group (one case [4.7%] of C5 palsy and one case [4.7%] of cerebrospinal fluid [CSF] leakage in ACAF group; four cases [12.5%] of C5 palsy, two cases [6.3%] of CSF leakage, and four cases [12.5%] of axial symptoms in laminoplasty group). The mean JOA score at last follow-up (14.6 vs 12.8, P < 0.05) and the improvement rate (IR) (63.8% vs 47.8%, P < 0.05) in ACAF group were superior to those in laminoplasty group significantly. The postoperative OR (16.7% vs 40.9%, P < 0.05), SAC (150.8 vs 110.5 mm2 , P < 0.05), AP spinal cord diameter (5.5 vs 4.2 mm, P < 0.05), and cervical lordosis (12.7° vs 4.7°, P < 0.05) were improved more considerably in ACAF group, with significant differences between two groups. Notably, the spinal cord on MRI showed a better curvature in ACAF group. CONCLUSIONS: This study showed that ACAF is considered superior to laminoplasty for the treatment of multilevel severe OPLL as anterior direct decompression and better curvature of the spinal cord led to satisfactory neurologic outcomes and low complication rate.

The clinical value of three-dimensional measurement in the diagnosis of thoracic myelopathy caused by ossification of the ligamentum flavum.

BACKGROUND: Thoracic ossification of the ligamentum flavum (OLF) is a major cause of thoracic myelopathy, which is often accompanied by multiple segmental stenosis or other degenerative spinal diseases. However, in the above situations, it is difficult to determine the exact segment responsible. The objective of this study was to analyze three-dimensional (3D) radiological parameters in order to establish a novel diagnostic method for discriminating the responsible segment in OLF-induced thoracic myelopathy, and to evaluate its superiority compared to the conventional diagnostic methods. METHODS: Eighty-one patients who underwent surgery for thoracic myelopathy caused by OLF from 2016 to 2020 were enrolled in this study as the myelopathy group, and 79 patients who had thoracic OLF but displayed no definite neurological signs from 2018 to 2020 were enrolled as the non-myelopathy group. We measured the one-dimensional (1D), two-dimensional (2D), and 3D radiological parameters, calculated their optimal cutoff values, and compared their diagnostic values. RESULTS: Significant differences were observed in the 1D, 2D, and 3D radiological parameters between the myelopathy and non-myelopathy groups (P<0.01). As a 3D radiological parameter, the OLF volume (OLFV) ratio (OLFV ratio = OLFV/normal canal volume × 100%) was the most accurate parameter for diagnosing OLF-induced thoracic myelopathy, with a diagnostic coincidence rate of 88.1%. We also found that an OLFV ratio of 26.3% could be used as the optimal cutoff value, with a sensitivity of 87.7% and a specificity of 88.6%. Moreover, the OLFV ratio [area under the curve (AUC): 0.92, 95% confidence interval (CI): 0.86-0.95] showed a statistically higher diagnostic value than the 1D and 2D parameters (AUC: 0.75, 95% CI: 0.67-0.81; AUC: 0.84, 95% CI: 0.77-0.89, respectively) (P<0.05). Pearson correlation analysis illustrated that the OLFV ratio was significantly negatively correlated with preoperative modified Japanese Orthopedic Association (mJOA) score (r=-0.73, 95% CI: -0.81 to -0.60, P<0.01). CONCLUSIONS: Our results demonstrate the superiority of the OLFV ratio over the conventional 1D and 2D computed tomography (CT)-based radiological parameters for the diagnosis of OLF-induced thoracic myelopathy. The novel diagnostic method based on the OLFV ratio will help to determine the responsible segment in multi-segmental thoracic OLF or when thoracic OLF coexists with other degenerative spinal diseases. The OLFV ratio also accurately reflects the clinical state of symptomatic patients with thoracic OLF.

Snake-Eye Screwing: A Novel Free-Hand Technique of Pedicle Screw Placement in Cervicothoracic Spine and Preliminary Clinical Results.

OBJECTIVE: To propose a novel technique of free-hand pedicle screw placement in cervicothoracic spine (snake-eye method) and evaluate the preliminary effects and safety in clinical practice. METHODS: This is a retrospective study and we defined the period of this study as from December 2017 to April 2019 in our institution. Forty patients were included in this study who underwent cervicothoracic internal fixation in our hospital, and all patients undergoing implantation of 200 pedicle screws were divided into two groups. Twenty-two patients (108 screws) had screw placement using traditional method, while 18 patients (92 screws) had screw placement using snake-eye method. To reduce the possible selection bias, the patients we recruited in this study was originally performed on by one radiological doctor who was blind to the objective of this study. Patient demographics, including patient age, sex, obesity, smoking, and hypertension, were evaluated to figure out baseline differences between groups. Medical information was recorded including time, accuracy, and immediate (within 30 days after surgery) postoperative complications of pedicle screw placement (including pulmonary embolism or other thromboembolic events, surgical site infection, neurovascular injury, and mortality). RESULTS: There were 24 males and 16 females, with an average age of 52.2 years (range, 24-77). Finally, a total of 200 screws were successfully inserted in these patients, including fifteen patients with four pedicle screws, four patients with six screws, three patients with eight screws in traditional method group, and 12 patients with four pedicle screws, two patients with six screws, four patients with eight screws in snake-eye method group. Patient demographic and comparison of two surgery methods are shown in Tables 1 and 2. The data baselines of the two groups were comparable because no impact of the two groups on population characteristics was demonstrated in the presented experiment. Also, we noticed that time and accuracy of the two groups were different with statistical significance at the level of P = 0.05. We observed that immediate (within 30 days after surgery) postoperative complications, including pulmonary embolism (PE), surgical site infection (SSI), neurovascular injury (NI), and mortality, in the two groups did not differ. CONCLUSION: This study highlights a safe and effective technique for pedicle screw placement in cervicothoracic spine named snake-eye method, and this technique may be particularly useful in emergency conditions with limited resources.

How much space of the spinal canal should be restored by hoisting the vertebrae-OPLL complex for sufficient decompression in anterior controllable antedisplacement and fusion? A multicenter clinical radiological study.

BACKGROUND CONTEXT: Anterior controllable antedisplacement and fusion (ACAF) is a novel surgical technique for the treatment of ossification of the posterior longitudinal ligament (OPLL). Its prognostic factors for decompression have not been well studied. Additionally, no detailed radiological standard has been set for hoisting the vertebrae-OPLL complex (VOC) in ACAF. PURPOSE: To identify the possible prognostic factors for decompression outcomes after ACAF for cervical OPLL, to determine the critical value of radiological parameters for predicting good outcomes, and to establish a radiological standard for hoisting the VOC in ACAF. STUDY DESIGN: This was a retrospective multicenter study. PATIENT SAMPLE: A total of 121 consecutive patients with OPLL who underwent ACAF at a point between January 2017 and June 2018 at any one of seven facilities and were monitored for at least 1 year afterward were enrolled in a multicenter study. OUTCOME MEASURES: Japanese Orthopedic Association (JOA) scores, recovery rate (RR) of neurologic function, and surgical complications were used to determine the effectiveness of ACAF. METHODS: Patients were divided into two groups according to their RR for neurologic function. Patients with an RR of ≥50% and an RR of <50% were designated as having good and poor decompression outcomes, respectively. The relationship between various possible prognostic factors and decompression outcomes was assessed by univariate and multivariate analysis. The receiver operating characteristic curve was used to determine the optimal cutoff value of the radiological parameters for prediction of good decompression outcomes. Next, the patients were redivided into three groups according to the cutoff value of the selected radiological parameter (postoperative anteroposterior canal diameter [APD] ratio). Patients with postoperative APD ratios of ≤80.7%, 80.7%-100%, and ≥100% were defined as members of the incomplete, optimal, and excessive antedisplacement groups, respectively. Differences in decompression outcomes among the three groups were compared to verify the reliability of the postoperative APD ratio and assess the necessity of excessive antedisplacement. RESULTS: Multivariate logistic regression analysis showed that patients' age at surgery (odds ratio [OR]=1.18; 95% confidence interval [CI]=1.08-1.29; p<.01) and postoperative APD ratio (OR=0.83; 95% CI=0.77-0.90; p<.01) were independently associated with decompression outcomes. The optimal cutoff point of the postoperative APD ratio was calculated at 80.7%, with 86.2% sensitivity and 73.5% specificity. There were no significant differences in the postoperative JOA scores and RRs between the excessive antedisplacement group and optimal antedisplacement group (p>.05). However, a lower incidence of cerebrospinal fluid leakage and screw slippage was observed in the optimal antedisplacement group (p<.05). CONCLUSIONS: Patients' age at surgery and their postoperative APD ratio are the two prognostic factors of decompression outcomes after ACAF. The postoperative APD ratio is also the most accurate radiological parameter for predicting good outcomes. Our findings suggest that it is essential for neurologic recovery to restore the spinal canal to more than 80.7% of its original size (postoperative APD ratio >80.7%), and restoration to less than its original size (postoperative APD ratio <100%) will help reduce the incidence of surgical complications. This may serve as a valuable reference for establishment of a radiological standard for hoisting the VOC in ACAF.