Cortical Endplate Bone Density Measured by Novel Phantomless Quantitative Computed Tomography May Predict Cage Subsidence more Conveniently and Accurately.

OBJECTIVE: Previous studies have shown that bone mineral density (BMD) is a predictor of cage subsidence. Phantom-less quantitative computed tomography (PL-QCT) can measure volumetric bone mineral density (vBMD) of lumbar trabecular and cortical bone. The study of endplate vBMD (EP-vBMD) is important in predicting cage settlement after extreme lateral interbody fusion (XLIF). This study aimed to determine the risk factors for postoperative cage subsidence after XLIF, particularly focusing on the relationship between vBMD measured by automatic PL-QCT and cage subsidence. METHODS: Patients who underwent XLIF surgery from January 2018 to October 2020 with a minimum of 6 months of follow-up were retrospectively included. Cage subsidence was defined as >2 mm cage sinking on the adjacent endplate in follow-up imaging evaluation. Outcome measures were localized vBMDs included EP-vBMDs with different region of interest (ROI) heights measured by PL-QCT based on a customized muscle-fat algorithm. Shapiro-Wilk test, one-way ANOVA, Mann-Whitney test, Fisher exact test, univariable and multivariable logistic regression and receiver operating characteristic (ROC) curve analysis were executed in this study. RESULTS: One hundred and thirteen levels of 78 patients were included in the analysis. The mean age was 65 ± 7.9 years for 11 males and 67 females. Cage subsidence occurred on 45 (39.8%) surgical levels. There was no significant difference in demographics, fused levels, or preoperative radiographic parameters. 1.25-mm EP-vBMD (0.991 [0.985,0.997], p = 0.004) and P-TB-vBMD (cage-positioned trabecular volumetric bone mineral density) (0.988 [0.977-0.999], p = 0.026) were cage-subsidence relevant according to univariate analysis. Low 1.25-mm EP-vBMD (0.992 [0.985, 0.999], p = 0.029) was an independent risk factor according to multifactorial analysis. CONCLUSION: Preoperative low EP-vBMD was an independent risk factor for postoperative cage subsidence after XLIF. EP-vBMD measured by most cortex-occupied ROI may be the optimal vBMD parameter for cage subsidence prediction.

Biomechanical effects of screws of different materials on vertebra-pediculoplasty: a finite element study.

Background: The effects of cannulated screws made of polyetheretherketone (PEEK) on the biomechanical properties of the vertebral body during vertebra-pediculoplasty remain unclear. This study aimed to investigate whether PEEK screws have the potential to replace titanium alloy screws. Methods: The surgical model of two different materials of screws was constructed using the finite element method. The biomechanical effects of the two models on the vertebral body under different working conditions were compared. Results: ① The peak von Mises stress of PEEK screws was significantly lower than that of titanium screws, with a reduction ranging from 52% to 80%. ② The von Mises stress values for the injured T12 spine were similar for both materials. Additionally, the segmental range of motion and intervertebral disc pressure showed no significant difference between the two materials. Conclusion: PEEK screws demonstrated advantages over titanium screws and may serve as a viable alternative for screw materials in vertebra-pediculoplasty.

Advances in Therapeutic Applications of Extracellular Vesicles.

Extracellular vesicles (EVs) are nanoscale bilayer phospholipid membrane vesicles released by cells. Contained large molecules such as nucleic acid, protein, and lipid, EVs are an integral part of cell communication. The contents of EVs vary based on the cell source and play an important role in both pathological and physiological conditions. EVs can be used as drugs or targets in disease treatment, and changes in the contents of EVs can indicate the progression of diseases. In recent years, with the continuous exploration of the structure, characteristics, and functions of EVs, the potential of engineered EVs for drug delivery and therapy being constantly explored. This review provides a brief overview of the structure, characteristics and functions of EVs, summarizes the advanced application of EVs and outlook on the prospect of it. It is our hope that this review will increase understanding of the current development of medical applications of EVs and help us overcome future challenges.

Extracellular matrix (ECM)-inspired high-strength gelatin-alginate based hydrogels for bone repair.

It has always been a huge challenge to construct high-strength hydrogels that are composed entirely of natural polymers. In this study, inspired by the structural characteristics of the extracellular matrix (ECM), gelatin and hydrazide alginate were employed to mimic the composition of collagen and glycosaminoglycans (GAGs) in the ECM, respectively, to develop natural polymer (NP) high-strength hydrogels crosslinked by physical and covalent interactions (Gelatin-HAlg-DN). First, HAlg and gelatin can form physically crosslinked hydrogels (Gelatin-HAlg) due to electrostatic and hydrogen bond interactions. Then, the Gelatin-HAlg hydrogels can be further covalently crosslinked in the presence of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to obtain Gelatin-HAlg-DN hydrogels. The obtained Gelatin-HAlg-DN hydrogels exhibit considerably enhanced mechanical properties (tensile strength: 0.9 MPa; elongation at break: 177%) with a maximum 16- and 3.2-fold increase in tensile strength and elongation at break, respectively, compared with gelatin methacrylate (GelMA) hydrogels. Importantly, the Gelatin-HAlg-DN hydrogels exhibit excellent biodegradability and swelling stability under physiological conditions, and the capability to support cell adhesion and proliferation. In a rat critical size bone defect model, Gelatin-HAlg-DN hydrogels loaded with psoralen could effectively promote bone regeneration, showing appealing potential as tissue engineering scaffolds.

Endplate volumetric bone mineral density biomechanically matched interbody cage.

Disc degenerative problems affect the aging population, globally, and interbody fusion is a crucial surgical treatment. The interbody cage is the critical implant in interbody fusion surgery; however, its subsidence risk becomes a remarkable clinical complication. Cage subsidence is caused due to a mismatch of material properties between the bone and implant, specifically, the higher elastic modulus of the cage relative to that of the spinal segments, inducing subsidence. Our recent observation has demonstrated that endplate volumetric bone mineral density (EP-vBMD) measured through the greatest cortex-occupied 1.25-mm height region of interest, using automatic phantomless quantitative computed tomography scanning, could be an independent cage subsidence predictor and a tool for cage selection instruction. Porous design on the metallic cage is a trend in interbody fusion devices as it provides a solution to the subsidence problem. Moreover, the superior osseointegration effect of the metallic cage, like the titanium alloy cage, is retained. Patient-specific customization of porous metallic cages based on the greatest subsidence-related EP-vBMD may be a good modification for the cage design as it can achieve biomechanical matching with the contacting bone tissue. We proposed a novel perspective on porous metallic cages by customizing the elastic modulus of porous metallic cages by modifying its porosity according to endplate elastic modulus calculated from EP-vBMD. A three-grade porosity customization strategy was introduced, and direct porosity-modulus customization was also available depending on the patient's or doctor's discretion.

Can the Full-Percutaneous Endoscopic Lumbar Discectomy in Day Surgery Mode Achieve Better Outcomes Following Enhanced Recovery after Surgery Protocol? A Retrospective Comparative Study.

Background: Full-percutaneous endoscopic lumbar discectomy (F-PELD) is a popular operation for the treatment of lumbar disc herniation (LDH). Some studies have reported that F-PELD in day surgery mode produced favorable outcomes for LDH. At the same time, minimally invasive spinal surgery following enhanced recovery after surgery (ERAS) presents a rising trend in recent years, but few studies reported whether F-PELD will produce better outcomes in the day surgery (DS) mode combined with ERAS. Objective: To analyze whether F-PELD in day surgery mode following ERAS can produce better clinical outcomes than in traditional surgery mode. Methods: The patients who underwent F-PELD between January 2019 and October 2020 were retrospectively analyzed, and the patients who met the inclusive criteria were followed up. The patients were divided into day surgery (DS) group (n = 152) that combined with ERAS and traditional surgery (TS) group (n = 123) without ERAS. The length of hospital stays (LOS), visual analogue scale (VAS), and Oswestry Disability Index (ODI) of two groups were compared before surgery, immediately after surgery, one month after surgery, and one year after surgery. Results: A total of 298 patients who underwent F-PELD were reviewed. 290 patients were included in the study and followed up, and 275 patients who had completed the follow-up were available for analysis. There were no statistically significant differences between the two groups in terms of age, gender, preoperative VAS, and ODI. There were significant statistical differences in the VAS and ODI immediately after surgery (VAS for back pain: DS group 1.4 ± 1.1, TS group 2.0 ± 1.2, p < 0.001; VAS for leg pain: DS group 0.8 ± 0.8, TS group 1.1 ± 1.1, p = 0.010; ODI: DS group 5.8 ± 4.3, TS group 7.6 ± 7.4, p = 0.010) and one month after surgery (VAS for back pain: DS group 0.8 ± 0.9, TS group 1.1 ± 1.0, p = 0.035; ODI: DS group 3.2 ± 3.5, TS group 4.5 ± 6.5, p = 0.036). At one year after surgery, the VAS (back pain: DS group 0.3 ± 0.6, TS group 0.3 ± 0.7, p = 0.798; leg pain: DS group 0.2 ± 0.4, TS group 0.1 ± 0.4, p = 0.485) and ODI (DS group 0.8 ± 1.2, TS group 0.7 ± 1.7, p = 0.729) were further improved, but no statistically significant difference was observed between two groups. LOS of DS group (1.38 ± 0.49 days) was significantly shorter than the TS group (5.83 ± 2.24 days, p < 0.001), and some postoperative complications occurred in the TS group, including throat discomfort (n = 5, 4.1%), discomfort after catheterization (n = 7, 5.7%), abdominal distention (n = 3, 2.4%), and nausea (n = 5, 4.1%). None of the above complications resulted in serious consequences. Conclusion: The F-PELD in day surgery mode following ERAS produced a better short-term clinical effect and reduced the LOS, which is worthy of promotion.