Biomechanics of artificial pedicle fixation in a 3D-printed prosthesis after total en bloc spondylectomy: a finite element analysis

Background This study compared the biomechanics of artificial pedicle fixation in spine reconstruction with a 3-dimensional (3D)-printed prosthesis after total en bloc spondylectomy (TES) by finite element analysis. Methods A thoracolumbar (T10–L2) finite element model was developed and validated. Two models of T12 TES were established in combination with different fixation methods: Model A consisted of long-segment posterior fixation (T10/11, L1/2) + 3D-printed prosthesis; and Model B consisted of Model A + two artificial pedicle fixation screws. The models were evaluated with an applied of 7.5 N·m and axial force of 200 N. We recorded and analyzed the following: (1) stiffness of the two fixation systems, (2) hardware stress in the two fixation systems, and (3) stress on the endplate adjacent to the 3D-printed prosthesis. Results The fixation strength of Model B was enhanced by the screws in the artificial pedicle, which was mainly manifested as an improvement in rotational stability. The stress transmission of the artificial pedicle fixation screws reduced the stress on the posterior rods and endplate adjacent to the 3D-printed prosthesis in all directions of motion, especially in rotation. Conclusions After TES, the posterior long-segment fixation combined with the anterior 3D printed prosthesis could maintain postoperative spinal stability, but adding artificial pedicle fixation increased the stability of the fixation system and reduced the risk of prosthesis subsidence and instrumentation failure.

Biomechanics of artificial pedicle fixation in a 3D-printed prosthesis after total en bloc spondylectomy: A finite element analysis

Background: This study compared the biomechanics of artificial pedicle fixation in spine reconstruction with a 3-dimensional (3D)-printed prosthesis after total en bloc spondylectomy (TES) by finite element analysis.Methods: A thoracolumbar (T10–L2) finite element model was developed and validated. Two models of T12 TES were established in combination with different fixation methods: Model A consisted of long-segment posterior fixation (T10/11, L1/2) + 3D-printed prosthesis; and Model B consisted of Model A + two artificial pedicle fixation screws. The models were evaluated with an applied of 7.5 N·m and axial force of 200 N. We recorded and analyzed the following: 1) stiffness of the two fixation systems; 2) hardware stress in the two fixation systems; and 3) stress on the endplate adjacent to the 3D-printed prosthesis.Results: The fixation strength of Model B was enhanced by the screws in the artificial pedicle, which was mainly manifested as an improvement in rotational stability. The stress transmission of the artificial pedicle fixation screws reduced the stress on the posterior rods and endplate adjacent to the 3D-printed prosthesis in all directions of motion, especially in rotation.Conclusions: After TES, the posterior long-segment fixation combined with the anterior 3D printed prosthesis could maintain postoperative spinal stability, but adding artificial pedicle fixation increased the stability of the fixation system and reduced the risk of prosthesis subsidence and instrumentation failure.

Spondylectomy in the Treatment of Neoplastic Spinal Lesions – A Retrospective Outcome Analysis of 582 Patients Using a Patient-Level Meta-Analysis

Background: En-bloc spondylectomy in the treatment of spinal tumors is a complex procedure with potential complications. This study aims at identifying predictors of postoperative complications, lesion recurrence and overall survival. Methods: A systematic review of the literature was conducted, and patient-level data extracted from the included studies. Multiple linear-regression models were calculated to predict the occurrence of postoperative complications, lesion recurrence and overall survival based on age, tumor etiology, surgical approach, mode of resection (en-bloc versus intralesional), tumor extension based on Weinstein-BorianiBiagini classification system and number of levels treated. Results: Data of 582 individual adult and pediatric patients were extracted from the literature; Patient characteristics are: 45% female, median age of 46 years (range 5-78); most common etiologies were: sarcoma (46%), metastases (31%) and chordoma (11%). The surgical technique was: anterior (2.5%), combined (45%) and posterior approach (52.4%); 68.5% underwent en-bloc spondylectomy; average levels resected were 1.6 (1-6); 65% of patients had neurologic deficits at presentation, average survival was 2.6 years; Direct procedure-related complications were observed in 17.7%, with the most prevalent being CSF leaks, wound infections and neural injury. For postoperative complications, recurrence and 5-year survival significant regression equations were found (F(7,90)=2.57, p=0.018) with an R2 of 0.1; (F(5,147)=2.35, p=0.044) with an R2 of 0.07 and (F(4,101)=7.2, p=0.01) with an R2 of 0.38. Odds ratio for predicted complications was 1.35 for en-bloc resection and 1.25 for more than one level treated. The odds ratio for tumor recurrence was 0.78 for en-bloc resection; odds ratio for 5-year survival were 0.79 for increased patient age, 0.65 for increasing tumor grade, 0.79 for tumor dissemination at diagnosis and 1.68 for en-bloc resection. Conclusion: En-bloc spondylectomy provides improved survival and lower recurrence rates but also higher operative complication rates when compared to intralesional resections. Interestingly the complication rate was not influenced by tumor stage (WBB scale) and tumor etiology.

Total en bloc spondylectomy combined with the satellite rod technique for spinal tumors

Background Instrumentation failure (IF) is a common complication after total en bloc spondylectomy (TES) in spinal tumors. This study aims to evaluate the clinical outcomes of TES combined with the satellite rod technique for the treatment of primary and metastatic spinal tumors. Methods The clinical data of 15 consecutively treated patients with spinal tumors who underwent TES combined with the satellite rod technique by a single posterior approach from June 2015 to September 2018 were analyzed retrospectively. Radiographic parameters including the local kyphotic angle (LKA), anterior vertebral height (AVH), posterior vertebral height (PVH), and intervertebral titanium mesh cage height (ITMCH) were assessed preoperatively, postoperatively, and at the final follow-up. The visual analog scale (VAS), Oswestry Disability Index (ODI), and American Spinal Injury Association (ASIA) scale were used to assess quality of life and neurological function. The operative duration, volume of blood loss, and complications were also recorded. Results The mean operation time and volume of blood loss were 361.7 min and 2816.7 mL, respectively. During an average follow-up of 31.1 months, 2 patients died of tumor recurrence and multiple organ metastases, while recurrence was not found in any other patients. Solid fusion was achieved in all but one patient, and no implant-related complications occurred during the follow-up. The VAS, ODI, and ASIA scores significantly improved from before to after surgery (P < 0.05). The LKA, AVH, and PVH significantly improved from before to immediately after surgery and to the final follow-up (P < 0.05), and the postoperative and final follow-up values did not significantly differ (P > 0.05). Conclusions TES combined with the satellite rod technique can yield strong three-dimensional fixation and reduce the occurrence of rod breakage, thereby improving the long-term quality of life of patients with spinal tumors.

Biomechanics of Artificial Pedicle Fixation in a 3d-printed Prosthesis After Total en Bloc Spondylectomy: A Finite Element Analysis

Background: This study compared the biomechanics of artificial pedicle fixation in spine reconstruction with a 3-dimensional (3D)-printed prosthesis after total en bloc spondylectomy (TES) by finite element analysis.Methods: A thoracolumbar (T10–L2) finite element model was developed and validated. Two models of T12 TES were established in combination with different fixation methods: Model A consisted of long-segment posterior fixation (T10/11, L1/2) + 3D-printed prosthesis; and Model B consisted of Model A + two artificial pedicle fixation screws. The models were evaluated with an applied of 7.5 N·m and axial force of 200 N. We recorded and analyzed the following: 1) stiffness of the two fixation systems; 2) hardware stress in the two fixation systems; and 3) stress on the endplate adjacent to the 3D-printed prosthesis.Results: The fixation strength of Model B was enhanced by the screws in the artificial pedicle, which was mainly manifested as an improvement in rotational stability. The stress transmission of the artificial pedicle fixation screws reduced the stress on the posterior rods and endplate adjacent to the 3D-printed prosthesis in all directions of motion, especially in rotation.Conclusions: After TES, the posterior long-segment fixation combined with the anterior 3D printed prosthesis could maintain postoperative spinal stability, but adding artificial pedicle fixation increased the stability of the fixation system and reduced the risk of prosthesis subsidence and instrumentation failure.