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Hua Zhou, Shanshan Liu, Zhehuang Li, Xiaoguang Liu, Lei Dang, Yan Li, Zihe Li, Panpan Hu, Ben Wang, Feng Wei, and Zhongjun Liu

OBJECTIVE

A 3D-printed vertebral prosthesis can be used to reconstruct a bone defect more precisely because of its tailored shape, with its innermost porous structure inducing bone ingrowth. The aim of this study was to evaluate the clinical outcomes of using a 3D-printed artificial vertebral body for spinal reconstruction after en bloc resection of thoracolumbar tumors.

METHODS

This was a retrospective analysis of 23 consecutive patients who underwent surgical treatment for thoracolumbar tumors at our hospital. En bloc resection was performed in all cases, based on the Weinstein-Boriani-Biagini surgical staging system, and anterior reconstruction was performed using a 3D-printed artificial vertebral body. Prosthesis subsidence, fusion status, and instrumentation-related complications were evaluated. Stability of the anterior reconstruction method was evaluated by CT, and CT Hounsfield unit (HU) values were measured to evaluate fusion status.

RESULTS

The median follow-up was 37 (range 24–58) months. A customized 3D-printed artificial vertebral body was used in 10 patients, with an off-the-shelf 3D-printed artificial vertebral body used in the other 13 patients. The artificial vertebral body was implanted anteriorly in 5 patients and posteriorly in 18 patients. The overall fusion rate was 87.0%. The average prosthesis subsidence at the final follow-up was 1.60 ± 1.79 mm. Instrument failure occurred in 2 patients, both of whom had substantial subsidence (8.47 and 3.69 mm, respectively). At 3 months, 6 months, and 1 year postoperatively, the mean CT HU values within the artificial vertebral body were 1930 ± 294, 1997 ± 336, and 1994 ± 257, respectively, with each of these values being significantly higher than the immediate postoperative value of 1744 ± 321 (p < 0.05).

CONCLUSIONS

The use of a 3D-printed artificial vertebral body for anterior reconstruction after en bloc resection of the thoracolumbar spinal tumor may be a feasible and reliable option. The low incidence of prosthesis subsidence of 3D-printed endoprostheses can provide good stability instantly. Measurement of HU values with CT is a valuable method to evaluate the osseointegration at the bone-metal interface of a 3D-printed vertebral prosthesis.

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Xiaoguang Han, Wei Tian, Yajun Liu, Bo Liu, Da He, Yuqing Sun, Xiao Han, Mingxing Fan, Jingwei Zhao, Yunfeng Xu, and Qi Zhang

OBJECTIVE

The object of this study was to compare the safety and accuracy of pedicle screw placement using the TiRobot system versus conventional fluoroscopy in thoracolumbar spinal surgery.

METHODS

Patients with degenerative or traumatic thoracolumbar spinal disorders requiring spinal instrumentation were randomly assigned to either the TiRobot-assisted group (RG) or the freehand fluoroscopy-assisted group (FG) at a 1:1 ratio. The primary outcome measure was the accuracy of screw placement according to the Gertzbein-Robbins scale; grades A and B (pedicle breach < 2 mm) were considered clinically acceptable. In the RG, discrepancies between the planned and actual screw placements were measured by merging postoperative CT images with the trajectory planning images. Secondary outcome parameters included proximal facet joint violation, duration of surgery, intraoperative blood loss, conversion to freehand approach in the RG, postoperative hospital stay, and radiation exposure.

RESULTS

A total of 1116 pedicle screws were implanted in 234 patients (119 in the FG, and 115 in the RG). In the RG, 95.3% of the screws were perfectly positioned (grade A); the remaining screws were graded B (3.4%), C (0.9%), and D (0.4%). In the FG, 86.1% screws were perfectly positioned (grade A); the remaining screws were graded B (7.4%), C (4.6%), D (1.4%), and E (0.5%). The proportion of clinically acceptable screws was significantly greater in the RG than in the FG (p < 0.01). In the RG, the mean deviation was 1.5 ± 0.8 mm for each screw. The most common direction of screw deviation was lateral in the RG and medial in the FG. Two misplaced screws in the FG required revision surgery, whereas no revision was required in the RG. None of the screws in the RG violated the proximal facet joint, whereas 12 screws (2.1%) in the FG violated the proximal facet joint (p < 0.01). The RG had significantly less blood loss (186.0 ± 255.3 ml) than the FG (217.0 ± 174.3 ml; p < 0.05). There were no significant differences between the two groups in terms of surgical time and postoperative hospital stay. The mean cumulative radiation time was 81.5 ± 38.6 seconds in the RG and 71.5 ± 44.2 seconds in the FG (p = 0.07). Surgeon radiation exposure was significantly less in the RG (21.7 ± 11.5 μSv) than in the FG (70.5 ± 42.0 μSv; p < 0.01).

CONCLUSIONS

TiRobot-guided pedicle screw placement is safe and useful in thoracolumbar spinal surgery.

Clinical trial registration no.: NCT02890043 (clinicaltrials.gov)