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OBJECTIVE Achieving solid fusion of the lumbosacral junction continues to be a challenge in long-segment instrumentation to the sacrum. The purpose of this study was to test the condition of adding sacral anchors through an S1 alar screw (S1AS) and multirod construct relative to using S1 pedicle screws (S1PSs) alone with sacroiliac fixation in lumbosacral junction augmentation. METHODS Seven fresh-frozen human lumbar-pelvic spine cadaveric specimens were tested under nondestructive moments (7.5 Nm). The ranges of motion (ROMs) in extension, flexion, left and right lateral bending (LB), and axial rotation (AR) of instrumented segments (L3–S1); the lumbosacral region (L5–S1); and the adjacent segment (L2–3) were measured, and the axial construct stiffness (ACS) was recorded. The testing conditions were 1) intact; 2) bilateral pedicle screw (BPS) fixation at L3–S1 (S1PS alone); 3) BPS and unilateral S2 alar iliac screw (U-S2AIS) fixation; 4) BPS and unilateral S1AS (U-S1AS) fixation; 5) BPS and bilateral S2AIS (B-S2AIS) fixation; and 6) BPS and bilateral S1AS (B-S1AS) fixation. Accessory rods were used in testing conditions 3–6. RESULTS In all directions, the ROMs of L5–S1 and L3–S1 were significantly reduced in B-S1AS and B-S2AIS conditions, compared with intact and S1PS alone. There was no significant difference in reduction of the ROMs of L5–S1 between B-S1ASs and B-S2AISs. Greater decreased ROMs of L3–S1 in extension and AR were detected with B-S2AISs than with B-S1ASs. Both B-S1ASs and B-S2AISs significantly increased the ACS compared with S1PSs alone. The ACS of B-S2AISs was significantly greater than that of B-S1ASs, but with greater increased ROMs of L2–3 in extension. CONCLUSIONS Adding sacral anchors through S1ASs and a multirod construct was as effective as sacropelvic fixation in lumbosacral junction augmentation. The ACS was less than the sacropelvic fixation but with lower ROMs of the adjacent segment. The biomechanical effects of using S1ASs in the control of long-instrumented segments were moderate (better than S1PSs alone but worse than sacropelvic fixation). This strategy is appropriate for patients requiring advanced lumbosacral fixation, and the risk of sacroiliac joint violation can be avoided.

Hongtao Ding, Yong Hai, Yuzeng Liu, Li Guan, Aixing Pan, Xinuo Zhang, Bo Han, Yue Li, Peng Yin Department of Spine Surgery, Beijing Chao-Yang Hospital, Capital Medical University of China, Beijing, People’s Republic of ChinaCorrespondence: Yong Hai; Yuzeng Liu, Department of Spine Surgery, Beijing Chao-Yang Hospital, Capital Medical University of China, Beijing, People’s Republic of China, Tel +86 10-85231229 ; +86 13801221889 ; +86 13811552832, Email prof.haiyong@yahoo.com; yong.hai@ccmu.edu.cn; beijingspine2010@163.comStudy Design: This was a prospective randomized controlled trial study.Objective: To elucidate clinical and radiographic outcomes and complications of cortical bone trajectory (CBT)-screw fixation in patients with osteoporosis at 24-month follow-up and to compare the results with those after transforaminal lumbar interbody fusion (TLIF) using traditional pedicle screw (PS) fixation.Methods: We enrolled 124 patients and randomly assigned them to two groups (each group had 62 participants). The primary outcome was fusion rate. Secondary outcomes were VAS, Oswestry Disability Index (ODI), and Japanese Orthopaedic Association (JOA) scores, operation duration, incision length, estimated blood loss, drainage volume, radiological outcomes, and complications.Results: At the 6- and 12-month follow-up points, similar fusion rates were observed based on CT scans in both groups (P=0.583 and 0.583). CBT provided significantly better short-term functional status at 3 months postoperation on ODI and JOA scores (P=0.012 and 0) and similar improvements in pain intensity and functional status at other follow-up points. In addition, CBT resulted in significantly better surgical characteristics. Notably, CBT fixation led to lower incidence of screw loosening (P=0.006).Conclusion: CBT-screw fixation for single-level lumbar fusion in patients with osteoporosis provided improvement in clinical symptoms comparable to that of TLIF using PS fixation. Significantly better lumbar stability was found in the CBT group. We suggest that CBT-screw fixation is a reasonable and superior alternative to PS in TLIF in osteoporosis.Trial Registration Number: ChiCTR1900022658.Date of Registration: April 20, 2019.Keywords: cortical bone-trajectory screw, pedicle screw, lumbar fusion, osteoporosis, randomized controlled trial

To evaluate the validity of the Roussouly classification system for assessing distal junctional problems (DJP) after long instrumented spinal fusion in degenerative scoliosis.Sixty-four patients with degenerative scoliosis and long-segment fixation receiving treatment at our hospital between December 2012 and December 2018 were retrospectively analyzed. Patients were classified preoperatively and postoperatively (Roussouly classification) and divided into DJP and control groups. We observed whether patients restored to their preoperative Roussouly classification (based on pelvic incidence [PI]) postoperatively.The incidences of DJP were 11.11% and 50% in patients who did and did not match their sagittal Roussouly classification immediately postoperatively, respectively. The adjusted Chi-square test that showed whether the sagittal profile matched the Roussouly classification immediately after surgery was statistically significant (P = 0.012). PIs were 55.83 ± 4.94 and 47.21 ± 10.81 in the DJP and non-DJP groups, respectively (t' = 4.367, P 0.001). Distal junctional kyphosis angles were 6.33 ± 4.19° and 11.56 ± 5.02° in the DJP and non-DJP groups, respectively (t = - 2.595, P = 0.015). Preoperative PI-lumbar lordosis values were 29.14 ± 13.82 and 16.67 ± 11.39 in the DJP and non-DJP groups, respectively (t = - 2.626, P = 0.013). The logistic regression model showed that patients whose Roussouly classification did not match the postoperative PI value were more likely to have DJP (odds ratio [OR] = 4.01, 95% confidence interval [CI]: 0.51-31.61) and preoperative distal junctional kyphotic changes.If the postoperative sagittal profile can be restored to match the patient's own PI value, use of the Roussouly classification can greatly reduce the possibility of postoperative DJP.

Objective To compare the safety and accuracy of cortical bone trajectory screw placement between the robot-assisted and fluoroscopy-assisted approaches. Methods This retrospective study was conducted between November 2018 and June 2020, including 81 patients who underwent cortical bone trajectory (CBT) surgery for degenerative lumbar spine disease. CBT was performed by the same team of experienced surgeons. The patients were randomly divided into two groups—the fluoroscopy-assisted group (FA, 44 patients) and the robot-assisted group (RA, 37 patients). Robots for orthopedic surgery were used in the robot-assisted group, whereas conventional fluoroscopy-guided screw placement was used in the fluoroscopy-assisted group. The accuracy of screw placement and rate of superior facet joint violation were assessed using postoperative computed tomography (CT). The time of single screw placement, intraoperative blood loss, and radiation exposure to the surgical team were also recorded. The χ2 test and Student’s t-test were used to analyze the significance of the variables (P Results A total of 376 screws were inserted in 81 patients, including 172 screws in the robot-assisted group and 204 pedicle screws in the fluoroscopy-assisted group. Screw placement accuracy was higher in the RA group (160, 93%) than in the FA group (169, 83%) (P = 0.003). The RA group had a lower violation of the superior facet joint than the FA group. The number of screws reaching grade 0 in the RA group (58, 78%) was more than that in the FA group (56, 64%) (P = 0.041). Screw placement time was longer in the FA group (7.25 ± 0.84 min) than in the RA group (5.58 ± 1.22 min, P P = 0.313). The radiation time of the FA group (0.43 ± 0.07 min) was longer than the RA group (0.37 ± 0.10 min, P = 0.001). Furthermore, the overall learning curve tended to decrease. Conclusions Robot-assisted screw placement improves screw placement accuracy, shortens screw placement time, effectively improves surgical safety and efficiency, and reduces radiation exposure to the surgical team. In addition, the learning curve of robot-assisted screw placement is smooth and easy to operate.

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This paper presents a fabrication method for glassy carbon neural electrode arrays that combines 3D printing and chemical pyrolysis technology. The carbon electrodes have excellent biological compatibility and can be used in neural signal recording. A pretreated Si wafer is used as the substrate for 3D printing, and then, stereolithography 3D printing technology is employed to print photosensitive resin into a cone shape. Next, chemical pyrolysis is applied to convert the 3D prints into glassy carbon electrodes and modify the electrochemical performance of the carbon electrodes. Finally, the glassy carbon electrodes are packed with conductive wires and PDMS. The proposed fabrication method simplifies the manufacturing process of carbon materials, and electrodes can be fabricated without the need of deep reactive ion etching (DRIE). The height of the carbon electrodes is 1.5 mm, and the exposure area of the tips is 0.78 mm2, which is convenient for the implantation procedure. The specific capacitance of the glassy carbon arrays is higher than that of a platinum electrode (9.18 mF/cm2 vs 3.32 mF/cm2, respectively), and the impedance at 1 kHz is lower (7.1 kΩ vs 8.8 kΩ). The carbon electrodes were tested in vivo, and they showed excellent performance in neural signal recording. The signal-to-noise ratio of the carbon electrodes is 50.73 ± 6.11, which is higher than that of the Pt electrode (20.15 ± 5.32) under the same testing conditions. The proposed fabrication method of glassy carbon electrodes provides a novel approach to manufacture penetrating electrodes for nerve interfaces in biomedical engineering and microelectromechanical systems.

The mesenchymal stem cell (MSC) shows potential in degenerative disc disease (DDD) treatment. However, little is known about the function of heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) in modulating the chondrogenic differentiation of MSCs. This study aimed to investigate the role of hnRNPA1 in the chondrogenic differentiation of MSCs and potential mechanisms. Mouse MSCs C3H10 and chondrogenic ATDC5 cells were used to quantify hnRNPA1 expression. The hnRNPA1 overexpression vectors were transfected into C3H10 cells, cell viability and chondrogenic factors expressions were assessed by MTT assay, qPCR and Western blot, respectively. After microRNA-34a (miR-34a) inhibitor transfection, expressions of chondrogenic factors and the Wnt signaling were detected. RNA-binding protein immunoprecipitation (RIP) was performed to reveal the interaction between hnRNPA1 and miR-34a. Results showed that hnRNPA1 was significantly down-regulated in C3H10 compared to ATDC5.Overexpression of hnRNPA1 markedly promoted C3H10 cell viability and expressions of chondrogenic factors SRY-box 9 (SOX9), collagen II, hyaluronan synthase 2 (HAS2) and aggrecan, without significant influence on adipogenic factors. miR-34a inhibitor suppressed chondrogenic factors expressions. RIP results showed the interaction between miR-34a and hnRNPA1. Besides, hnRNPA1 promoted expressions of Wnt family member 3A (WNT3A), WNT5A and β-catenin, and these effects were abrogated by miR-34a inhibitor. We fund the promotive effect of hnRNPA1 on chondrogenic factors, which might require the interaction with miR-34a and the regulation of the Wnt signaling. Thus hnRNPA1 might induce the chondrogenic differentiation of MSCs that facilitate the MSC therapy for DDD.