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Quan-chang Tan, Jian-wei Wu, Fei Peng, Yuan Zang, Yang Li, Xiong Zhao, Wei Lei and Zi-xiang Wu

OBJECTIVE

This study investigated the optimum injection volume of polymethylmethacrylate (PMMA) to augment a novel fenestrated pedicle screw (FPS) with diameter-tapered perforations in the osteoporotic vertebral body, and how the distribution characteristics of PMMA affect the biomechanical performance of this screw.

METHODS

Two types of FPSs were designed (FPS-A, composed of 6 perforations with an equal diameter of 1.2 mm; and FPS-B, composed of 6 perforations each with a tapered diameter of 1.5 mm, 1.2 mm, and 0.9 mm from tip to head. Each of 28 human cadaveric osteoporotic vertebrae were randomly assigned to 1 of 7 groups: FPS-A1.0: FPS-A+1.0 ml PMMA; FPS-A1.5: FPS-A+1.5 ml PMMA; FPS-A2.0: FPS-A+2.0 ml PMMA; FPS-B1.0: FPS-B+1.0 ml PMMA; FPS-B1.5: FPS-B+1.5 ml PMMA; FPS-B2.0: FPS-B+2.0 ml PMMA; and conventional pedicle screws (CPSs) without PMMA. After the augmentation, 3D CT was performed to assess the cement distribution characteristics and the cement leakage rate. Axial pullout tests were performed to compare the maximum pullout force thereafter.

RESULTS

The CT construction images showed that PMMA bone cement formed a conical mass around FPS-A and a cylindrical mass around FPS-B. When the injection volume was increased from 1.0 ml to 2.0 ml, the distribution region of the PMMA cement was enlarged, the PMMA was distributed more posteriorly, and the risk of leakage was increased. When the injection volume reached 2.0 ml, the risk of cement leakage was lower for screws having diameter-tapered perforations. The pullout strengths of the augmented FPS-A groups and FPS-B groups were higher than that of the CPS group (p < 0.0001). All FPS-B groups had a higher pullout strength than the FPS-A groups.

CONCLUSIONS

The diameter of the perforations affects the distribution of PMMA cement. The diameter-tapered design enabled PMMA to form larger bone-PMMA interfaces and achieve a relatively higher pullout strength, although statistical significance was not reached. Study results indicated 1.5-ml of PMMA was a conservative volume for PMMA augmentation; more cement injection would significantly increase the risk of cement leakage.

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Peigen Xie, Feng Feng, Junyan Cao, Zihao Chen, Bingjun He, Zhuang Kang, Lei He, Wenbin Wu, Lei Tan, Kai Li, Rongqin Zheng and Limin Rong

OBJECTIVE

Percutaneous transforaminal endoscopic discectomy (PTED) is usually performed under fluoroscopic guidance and is associated with a large radiation dose. Ultrasonography (US)–MR image fusion navigation combines the advantages of US and MRI and requires significantly less radiation than fluoroscopy. The purpose of this study was to evaluate the safety and effectiveness of US-MR image fusion navigation for PTED.

METHODS

From January to September 2018, patients with L4–5 lumbar disc herniation requiring PTED were randomized to have the procedure conducted with US-MR image fusion navigation or fluoroscopy. The number of fluoroscopies, radiation dose, duration of imaging guidance, intraoperative visual analog scale (VAS) pain score, intraoperative complications, and clinical outcomes were compared between the groups.

RESULTS

There were 10 patients in the US-MR navigation group and 10 in the fluoroscopy group, and there were no significant differences in age, sex ratio, or BMI between the 2 groups (all p > 0.05). Intraoperatively, the total radiation dose, number of fluoroscopies performed, duration of image guidance, and VAS low-back and leg pain scores were all significantly lower in the US-MRI navigation group than in the fluoroscopy group (all p < 0.05). There were no intraoperative complications in either group. Postoperative improvements in Japanese Orthopaedic Association, Oswestry Disability Index, and VAS pain scale scores were similar between the 2 groups.

CONCLUSIONS

US-MR image fusion navigation is a promising technology for performing PTED and requires significantly less radiation than fluoroscopy.

Clinical trial registration no.: NCT03403244 (ClinicalTrials.gov).

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Hua-Qiao Tan, Ming-Hua Li, Pei-Lei Zhang, Yong-Dong Li, Jian-Bo Wang, Yue-Qi Zhu and Wu Wang

Object

Placement of covered stents has emerged as a promising therapeutic option for cerebrovascular diseases. However, the medium- and long-term efficacy and safety of covered stents in the treatment of these diseases remain unclear. The purpose of this study was to evaluate the medium-term clinical and angiographic outcomes of covered stent placement for the treatment of intracranial aneurysms.

Methods

The authors' institutional review board approved the study. Thirty-four patients (13 females and 21 males; mean age 41.9 years) with 38 intracranial aneurysms were treated with the Willis covered stent. Clinical and angiographic follow-up were performed at 3 months, at 6–12 months, and annually thereafter. The initial procedural and follow-up outcomes were collected and analyzed retrospectively.

Results

Forty-two covered stents were successfully implanted into the target artery in 33 patients with 37 aneurysms, and 1 covered stent navigation failed in 1 patient. A complete aneurysm exclusion was initially achieved in 24 patients with 28 aneurysms, and a minor endoleak occurred in 9 patients with 9 aneurysms. Postoperatively, 2 patients died of complications related to the procedure. Angiographic and clinical follow-up data are available in 30 patients. The angiographic follow-up (17.5 ± 9.4 months [mean ± SD]) exhibited complete occlusion in 28 patients with 31 aneurysms, and incomplete occlusion in 2 aneurysms, with an asymptomatic in-stent stenosis in 3 patients (10%). The clinical follow-up (26.7 ± 13 months [mean ± SD]) demonstrated that 16 patients (53.3%) experienced a full recovery, and 14 patients (46.7%) improved. No aneurysm rupture, thromboembolic events, or neurological deficits resulting from closure of a perforating vessel by covered stent placement occurred.

Conclusions

Endovascular reconstruction with the Willis covered stent represents a safe, durable, and curative treatment option for selected intracranial aneurysms, yielding an excellent medium-term patency of the parent artery and excellent clinical outcomes.