Are Controversial Issues in Cervical Total Disc Replacement Resolved or Unresolved?: A Review of Literature and Recent Updates

Since the launch of cervical total disc replacement (CTDR) in the early 2000s, many clinical studies have reported better outcomes of CTDR compared to those of anterior cervical discectomy and fusion. However, CTDR is still a new and innovative procedure with limited indications for clinical application in spinal surgery, particularly, for young patients presenting with soft disc herniation with radiculopathy and/or myelopathy. In addition, some controversial issues related to the assessment of clinical outcomes of CTDR remain unresolved. These issues, including surgical outcomes, adjacent segment degeneration (ASD), heterotopic ossification (HO), wear debris and tissue reaction, and multilevel total disc replacement (TDR) and hybrid surgeries are a common concern of spine surgeons and need to be resolved. Among them, the effect of CTDR on patient outcomes and ASD is theoretically and clinically important; however, this issue remains disputable. Additionally, HO, wear debris, multilevel TDR, and hybrid surgery tend to favor CTDR in terms of their effects on outcomes, but the potential of these factors for jeopardizing patients' safety postoperatively and/or to exert harmful effects on surgical outcomes in longer-term follow-up cannot be ignored. Consequently, it is too early to determine the therapeutic efficacy and cost-effectiveness of CTDR and will require considerable time and studies to provide appropriate answers regarding the same. For these reasons, CTDR requires longer-term follow-up data

Lumbar Interbody Fusion using Low-dose of Recombinant Human Bone Morphogenetic Protein-2 (rh-BMP2); Minimum 1-year Follow-up Results at A Single Institute

Objective The authors evaluate clinical results of the lumbar interbody fusion surgery using low-dose of recombinant human bone morphogenetic protein type 2(rhBMP-2) to assess the safety and efficacy of rhBMP-2. Methods 199 patients who underwent lumbar interbody fusion surgery including posterior lumbar interbody fusion (PLIF) and oblique interbody fusion (OLIF) using rhBMP-2 (0.05 mg per disc) were selected. Fusion status at the operated segment was classified from grade 1 to 4, according follow-up CT scan. The occurrence of complications was observed including heterotopic ossification, postoperative radiculitis, and endplate osteolysis. Results There were 61 men and 138 women. Total surgical levels were 424 levels. According to the surgical method, 335 segments were operated with the PLIF and 89 segments with the OLIF. On follow up CT scan, fusion grade was distributed as 330 levels of grade 1 (77.8%), 66 of grade 2 (15.6%), 22 of grade 3 (5.2%), and 6 of grade 4 (1.4%). Overall fusion success rate was found to be 93.4%. According to fusion method, in PLIF group, it was distributed as 267 levels of grade 1 (79.7%), 45 of grade 2 (13.4%), 18 of grade 3 (5.4%), and 5 of grade 4 (1.5%), and in OLIF group, 63 levels of grade 1 (70.8%), 21 of grade 2 (23.6%), 4 of grade 3 (4.5%), and 1 of grade 4 (1.1%). No patient was suspected of having postoperative radiculitis related to the use of rh-BMP2. Two case showed ectopic bone formation without clinical symptom. There were 2 cases of endplate osteolysis. Conclusion The known complications is not common in the present study, which may be caused by using low-dose rhBMP-2. Further long term observations are needed to clarify these issues of such complications

Full-endoscopic Foraminotomy in Degenerative Spondylolisthesis: A “Module-based” Approach for Surgical Planning and Execution

Objective Degenerative Lumbar Spondylolisthesis (DSL) is a common spinal pathology characterized by the anterior slippage of one vertebral body on another. DSL is caused mainly by degeneration of the intervertebral disc in the first place, with subsequent degeneration of the facet joints that end causing the slippage. As the disease evolves, stability is restored as a result of advanced degeneration and disc collapse. But while this natural evolution takes place, DSL may produce radicular symptoms by different mechanisms. To present a “module-based” approach for the surgical planning and execution of full-endoscopic foraminotomy in DSL, combined with case examples of the most common surgical scenarios. Methods We propose a “module-based surgery” using the standard endoscopic foraminotomy technique as a baseline. According to the patient’s clinical and imaging characteristics, several “modules” can be added. The resulting endoscopic surgery is a summation of the basic endoscopic foraminotomy plus all the additional required modules. Results Surgical modules description and case examples are provided. Conclusion Transforaminal lumbar endoscopic foraminotomy represents a minimally invasive technique to treat foraminal and combined foraminal-lateral recess stenosis. DSL and its multiple scenarios represent a challenge to the endoscopic surgeon. Module-based approach can help systematize and execute these demanding endoscopic procedures

Structural and Physiological Exploration of Salmonella Typhi YfdX Uncovers Its Dual Function in Bacterial Antibiotic Stress and Virulence

YfdX is a prokaryotic protein encoded by several pathogenic bacteria including Salmonella enterica serovar Typhi, which causes one of the most fatal infectious diseases, typhoid fever. YfdX is a product of the yfdXWUVE operon and is known to be under the control of EvgA, a regulator protein controlling the expression of several proteins involved in response to environmental stress, in Escherichia coli. Nevertheless, unlike other proteins encoded by the same operon, the structural and physiological aspects of YfdX have been poorly characterized. Here, we identified a previously unknown pH-dependent stoichiometric conversion of S. Typhi YfdX between dimeric and tetrameric states; this conversion was further analyzed via determining its structure by X-ray crystallography at high resolution and by small-angle X-ray scattering in a solution state and via structure-based mutant studies. Biologically, YfdX was proven to be critically involved in Salmonella susceptibility to two β-lactam antibiotics, penicillin G and carbenicillin, as bacterial growth significantly impaired by its deficiency upon treatment with each of the two antibiotics was recovered by chromosomal complementation. Furthermore, by using Galleria mellonella larvae as an in vivo model of Salmonella infection, we demonstrated that Salmonella virulence was remarkably enhanced by YfdX deficiency, which was complemented by a transient expression of the wild-type or dimeric mutant but not by that of the monomeric mutant. The present study work provides direct evidence regarding the participation of YfdX in Salmonella antibiotic susceptibility and in the modulation of bacterial virulence, providing a new insight into this pathogen’s strategies for survival and growth

Numerical Investigation of Aerodynamic Drag and Pressure Waves in Hyperloop Systems

Hyperloop is a new, alternative, very high-speed mode of transport wherein Hyperloop pods (or capsules) transport cargo and passengers at very high speeds in a near-vacuum tube. Such high-speed operations, however, cause a large aerodynamic drag. This study investigates the effects of pod speed, blockage ratio (BR), tube pressure, and pod length on the drag and drag coefficient of a Hyperloop. To study the compressibility of air when the pod is operating in a tube, the effect of pressure waves in terms of propagation speed and magnitude are investigated based on normal shockwave theories. To represent the pod motion and propagation of pressure waves, unsteady simulation using the moving-mesh method was applied under the sheer stress transport k–ω turbulence model. Numerical simulations were performed for different pod speeds from 100 to 350 m/s. The results indicate that the drag coefficient increases with increase in BR, pod speed, and pod length. In the Hyperloop system, the compression wave propagation speed is much higher than the speed of sound and the expansion wave propagation speed that experiences values around the speed of sound