A Preliminary Study on the Morphological Changes of an NiTi-Shaped Memory Alloy Stent in the Vertebral Body.

OBJECTIVE: At present, the most commonly used filler polymethyl methacrylate (PMMA) has the disadvantages of monomer toxicity, heat and leakage, and cannot be applied in young people. Therefore, finding a minimally invasive and good tissue-compatible alternative material has been a research hotspot in spine surgery in recent years. The aim of this study is to explore whether the memory alloy stent can avoid the complications of bone cement or not. METHODS: Four non-adjacent vertebral bodies of the thoracic and lumbar spine in the 18 10-month-old pigs were selected as the surgical site and were randomly divided into the scaffold group and the bone cement group. The memory alloy scaffold and PMMA (polymethyl methacrylate) bone cement were placed via percutaneous puncture, and intraoperative fluoroscopy and micro-CT were used to observe the changes in the height of scaffolds and bone cement in the vertebral body immediately, 6 weeks, and 12 weeks after operation, the microstructural parameters of the bone trabeculae (bone volume fraction, bone surface volume ratio, bone trabeculae number) were also measured. RESULTS: The memory alloy stent could expand in the vertebral body, and its height gradually increased with time; additionally, the height of the bone cement mass did not change with time (p = 0.00). New bone trabeculae could grow into the scaffold along the gap, and the volume fraction of bone, the volume ratio of bone surface area, and the number of bone trabeculae increased gradually (p = 0.00). However, the volume fraction of bone, the volume ratio of bone surface area, and the number of trabeculae in the cement block decreased gradually (p = 0.00). CONCLUSIONS: Memory alloy scaffolds have dynamic expansion characteristics in vivo, which can effectively avoid the complications of bone cement. Thus, it is beneficial to explore this minimally invasive treatment for vertebral compression fractures.

Comparison of the effects of Wiltse approach and minimally invasive percutaneous approach in the treatment of thoracolumbar fracture patients without neurological deficit / 西安交通大学学报(医学版)

【Objective】 To compare the clinical efficacy of minimally invasive percutaneous approach with Wiltse approach in the treatment of thoracolumbar fracture without neurological deficit in young and middle-aged patients. 【Methods】 A prospective study was conducted in 108 patients with thoracolumbar fracture without neurological symptoms treated in Department of Orthopedics， The First Affiliated Hospital of Xi’an Jiaotong University from March 2015 to March 2018. We randomly assigned 54 patients to minimally invasive percutaneous approach group （Group A） and 54 ones to Wiltse approach group （Group B）. We compared the operation time， intraoperative blood loss， incision length， the number of intraoperative fluoroscopy times， and postoperative hospital stay of Group A and Group B. We also compared the VAS scores of the two groups before and 3 days after surgery and at each review， the vertebral frontal height compression ratio and Cobb Angle before and immediately after surgery， 3 months 1 year and 3 years after surgery， and ODI index before surgery and 3 months， 1 year and 3 years after surgery. 【Results】 All the 108 patients were followed up. There were no significant differences in operation time， intraoperative blood loss or postoperative hospital stay between the two groups （P>0.05）. The number of intraoperative fluoroscopy times was significantly smaller in Group B than in Group A （P0.05）， after operation， or at follow-up， while the anterior vertebral body height ratio and Cobb angle were significantly lower in Group B than in Group A （P<0.0125）. 【Conclusion】 Minimally invasive percutaneous approach and Wiltse approach are both safe and effective in the treatment of thoracolumbar fracture without neurological deficit. However， the number of intraoperative fluoroscopy times of Wiltse approach was significantly reduced， the incision length was smaller than that of the percutaneous pedicle group， and the postoperative anterior vertebral compression rate and Cobb Angle were lower than those of the percutaneous group， indicating better clinical efficacy.