Stress Distribution of Different Pedicle Screw Insertion Techniques Following Single-Segment TLIF: A Finite Element Analysis Study.

OBJECTIVES: At present, a variety of posterior lumbar internal fixation implantation methods have been developed, which makes it difficult for spine surgeons to choose. The stress distribution of the internal fixation system is one of the important indexes to evaluate these technologies. Common insertion technologies include Roy Camille, Magerl, Krag, AO, and Weinstein insertion techniques. This study aimed to compare the distribution of von Mises stresses in different screw fixation systems established by these insertion technologies. METHODS: Here, the three-dimensional finite element (FE) method was selected to evaluate the postoperative stress distribution of internal fixation. Following different pedicle screw insertion techniques, five single-segment transforaminal lumbar interbody fusion (TLIF) models were established after modeling and validation of the L1-S1 vertebrae FE model. RESULTS: By analyzing the data, we found that stress concentration phenomenon was in all the models. Additionally, Roy-Camille, Krag, AO, and Weinstein insertion techniques led to the great stress on lumbar vertebra, intervertebral disc, and screw-rod fixation systems. Therefore, we hope that the results can provide ideas for clinical work and development of pedicle screws in the future. It is worth noting that flexion, unaffected side lateral bending, and affected side axial rotation should be limited for the patients with cages implanted. CONCLUSIONS: Overall, our method obtained the results that Magerl insertion technique was the relatively safe approach for pedicle screw implantation due to its relatively dispersive stress in TLIF models.

Unilateral pedicle screw fixation of lumber spine: A safe internal fixation method.

Background: Unilateral pedicle screw fixation several advantages, including reduced trauma and low cost. However, its stability and safety have not been widely recognized. In this study, the biomechanical differences in the vertebral body and screw-rod system after unilateral and bilateral pedicle screw fixation were compared using both the finite element model and calf lumbar model. Method: We used the verified finite element model to establish unilateral and bilateral posterior lumbar surgery models. The biomechanical data of different parts of the models were recorded under different working states. Then, three calf lumbar models were selected to simulate different working states with the help of a universal testing machine and other instruments. Finally, the biomechanical data of the screw-rod system were obtained from a static strain test and analysis system. Results: By analyzing and comparing biomechanical data obtained using two different methods, this study found that unilateral pedicle screw fixation does not bring excessive loads to the lumbar spine and screw-rod system. Conclusion: From the perspective of biomechanics, unilateral pedicle screw fixation is considered a safe and reliable implantation technique.

Protective effect of homogeneous polysaccharides of Wuguchong (HPW) on intestinal mucositis induced by 5-fluorouracil in mice.

BACKGROUND: In hospitalized patients, drug side effects usually trigger intestinal mucositis (IM), which in turn damages intestinal absorption and reduces the efficacy of treatment. It has been discovered that natural polysaccharides can relieve IM. In this study, we extracted and purified homogenous polysaccharides of Wuguchong (HPW), a traditional Chinese medicine, and explored the protective effect of HPW on 5-fluorouracil (5-FU)-induced IM. METHODS AND RESULTS: First, we identified the physical and chemical properties of the extracted homogeneous polysaccharides. The molecular weight of HPW was 616 kDa, and it was composed of 14 monosaccharides. Then, a model of small IM induced by 5-FU (50 mg/kg) was established in mice to explore the effect and mechanism of HPW. The results showed that HPW effectively increased histological indicators such as villus height, crypt depth and goblet cell count. Moreover, HPW relieved intestinal barrier indicators such as D-Lac and diamine oxidase (DAO). Subsequently, western blotting was used to measure the expression of Claudin-1, Occludin, proliferating cell nuclear antigen, and inflammatory proteins such as NF-κB (P65), tumour necrosis factor-α (TNF-α), and COX-2. The results also indicated that HPW could reduce inflammation and protect the barrier at the molecular level. Finally, we investigated the influence of HPW on the levels of short-chain fatty acids, a metabolite of intestinal flora, in the faeces of mice. CONCLUSIONS: HPW, which is a bioactive polysaccharide derived from insects, has protective effects on the intestinal mucosa, can relieve intestinal inflammation caused by drug side effects, and deserves further development and research.

Is Early or Delayed Weightbearing the Better Choice After Microfracture for Osteochondral Lesions of the Talus? A Meta-analysis and Systematic Review.

Osteochondral lesions of the talus (OLT) are common injuries requiring surgery. Arthroscopic microfracture treatment is effective and acceptable. Although the concept of postoperative rehabilitation is continuously being updated, the choice between early weightbearing (EWB) versus delayed weightbearing (DWB) following microfracture is still not settled. A meta-analysis and systematic review was performed to compare the rehabilitation effect of 2 different weightbearing protocols following microfracture. Five databases were searched for relevant studies, and full-text articles comparing EWB and DWB were reviewed. Review Manager 5.3 software was used to summarize the results of the included studies. Two reviewers independently filtered the studies, assessed quality, extracted data, and estimated the risk of bias. The pain score and functional assessment of the ankle were selected as the endpoints. The mean difference was calculated as the summary statistic for continuous data. Then, visual analog scale and American Orthopedic Foot and Ankle Society scale scores were collected and pooled. Five randomized controlled trials including 283 patients were identified for this study, revealing that there was no significant difference in pain scores between EWB and DWB following microfracture 3 months, 6 months, 12 months, and 24 months postoperatively. Function assessment showed similar results. Comprehensive analysis of current evidence still suggests that EWB and DWB after microfracture of OLT produce comparable clinical outcomes in terms of pain and functional activity. Therefore, EWB is recommended to shorten the length of time before returning to work or sports after microfracture of OLT.