Biomechanical evaluation of the pedicle screw insertion depth and role of cross-link in thoracolumbar junction fracture surgery: a finite element study under compressive loads

Introduction. The thoracolumbar junction is one of the most frequently damaged parts of the human spine when exposed to a traumatic factor. Corpectomy in combination with posterior decompression and restoration of the spinal support function is often performed using an interbody implant and posterior transpedicular stabilization to achieve adequate decompression and stabilization in severe traumatic injuries of this level. The surgery of this type is characterized by significant instability of the operated segment and determines increased requirements for the rigidity and reliability of posterior fixation. We have modeled the situation of a two-level corpectomy with subsequent replacement of bodies with a mesh implant and posterior transpedicular stabilization with 8 screws. Objective. To study the stress-strain state of the thoracolumbar spine model after resection of the Th12-L1 vertebrae with different variants of transpedicular fixation under the influence of a compressive load. Materials and methods. A mathematical finite element model of the human thoracolumbar spine has been developed, the components of which are the Th9 ‒ Th11 and L2-L5 vertebrae (vertebrae Th12-L1 are removed), as well as elements of hardware - interbody support and transpedicular system. Four variants of transpedicular fixation were modeled: using short screws and long screws passing through the cortical layer of anterior wall of vertebral body, as well as two cross links and without them. The stress-strain state of the models was studied under the influence of a vertical compressive distributed load, which was applied to the body of the Th9 vertebra and its articular surfaces. The load value was 350 N, corresponding to the weight of the upper body. Results. d It was found that transpedicular fixation of the thoracolumbar vertebrae with the use of long screws reduces the level of tension in the bone elements of the models. In the area of screw entry into the pedicle of the T10, T11, L2 and L3 vertebral arch, the load when using short screws was 3.1, 1.7, 3.9 and 12.1 MPa, respectively, when using bicortically installed screws - 2.9, 1.8, 3.8 and 10.6 MPa. The addition of two cross-links also reduces the maximum load values in critical areas of the model to a certain extent. In case of short screws combination and two cross-links, the load in these areas was 2.8, 1.7, 3.6 and 11.5 MPa, when using bicortical screws and cross-links - 2.8, 1.6, 3.3 and 9.3 MPa. The study of the stress-strain state of other parts of the model revealed a similar trend. Conclusions. The use of long screws with fixation in the cortical bone of anterior part of the vertebral bodies reduces the level of tension in the bone elements of the models. The use of cross links provides greater rigidity to the transpedicular system, that also reduces the tension in the bone tissue.

Decompression and Dynamic Transpedicular Stabilization Using Polyetheretherketone Rods and Pedicle Screws vs. Decompression Alone for Single-Level Spinal Canal Stenosis with Listhesis: A Retrospective Case-Control Study

Background Spinal stenosis is frequently caused by spondylolisthesis, and surgical treatment may be indicated. However, whether decompression alone or decompression with dynamic stabilization offers better surgical outcomes remains unclear. We compared the clinical and radiologic results of patients with single-level lumbar spinal stenosis and grade 1 spondylolisthesis undergoing microsurgical decompression alone or decompression with transpedicular dorsal dynamic stabilization. Methods We retrospectively analyzed 20 patients undergoing microsurgical decompression and dorsal dynamic transpedicular stabilization using polyetheretherketone (PEEK) rods in one center from 2011 to 2017. Twenty patients with the same diagnosis undergoing microsurgical decompression alone were used as controls. Reoperation of the index and neighboring segments, back/leg pain, neurologic deficits, and the use of pain medication were assessed. For stabilization patients, radiographic progression of degeneration in the neighboring segments, listhesis degree in the index segment, and implant failure were assessed. Results All patients had good clinical outcomes at 3 and 12 months postoperatively. In stabilization patients, the visual analog scale (VAS) score for leg pain decreased from 5 points (median) to 1.6 at 3 months and 0.6 at 1 year postoperatively. In controls, the VAS score improved from 4.8 points to 1.1 at 3 months and 0.3 at 1 year postoperatively. The VAS score for back pain in stabilization patients decreased from 7.6 points (median) to 1.7 at 3 months and 0.1 at 1 year postoperatively. In controls, it decreased from 7.7 points to 1.1 at 3 months and 0.2 at 1 year postoperatively. In patients with additional dynamic stabilization, a longer hospital stay (stabilization group: 8.7 ± 4.1; control: 6.2 ± 1.6 days), longer operative time (stabilization group: 132.7 ± 41.3; control: 83.2 ± 31.7 minutes), and higher complication rates (revision surgery performed in two stabilization patients) were found. Conclusion No indications in our study showed that additional dynamic stabilization with PEEK rods offers any advantage over decompression alone.

Iatrogenic lumbar artery pseudoaneurysm after lumbar transpedicular fixation: Case report

Only a few cases of iatrogenic lumbar injury have been reported in the literature. A 58-year-old male with severe back pain was admitted to our department. The patient was qualified for the transpedicular stabilization with interbody fixation at L4/L5 and L5/S1 levels. On the first day after surgery, the patient was mobile and reported significant pain relief. He was discharged the same day. After 2 weeks, the patient returned with severe right lower abdominal pain and radicular pain in his right leg. He was administered to the Neurology Department where the presence of a lumbar muscle hematoma and lumbar artery pseudoaneurysm were discovered. He was transferred to the Vascular Surgery Department where aortography was performed and the pseudoaneurysm was embolized. After few days, the patient’s overall condition improved significantly. Eight weeks after surgery, he was pain-free. Our case shows how initially innocuous symptoms may be the result of serious complications.

Interrelation of tropism and angulation parameters of facet joints and results of stabilization surgeries for degenerative diseases of the lumbar spine

Objective. To clarify indications for dynamic and rigid stabilization based on the analysis of correlation between neuroimaging parameters of facet joints (FJ) and clinical outcomes of surgical treatment of patients with degenerative diseases of the lumbar spine. Material and Methods. A total of 141 patients with degenerative diseases of the lumbar spine were surgically treated. Patients were divided into three groups: patients of Group I (n = 48) underwent surgical intervention with artificial intervertebral disc prosthesis; those of Group II (n = 42) – with interbody fusion and combined transpedicular and transfacetal stabilization; and those of Group III (n = 51) – with interbody fusion and bilateral transpedicular stabilization. The correlation between long-term clinical outcomes (pain syndrome according to VAS, functional state according to ODI, and satisfaction with surgical result according to MacNab scale) and preoperative neuroimaging parameters of FJ (degenerative changes according to Fujiwara, facet angle magnitudes, and the presence of tropism) was analyzed. Results. A direct significant nonparametric correlation of neuroimaging parameters of facet angles and FJ tropism with long-term clinical outcomes of surgical treatment according to VAS and ODI was revealed. It was established that good clinical outcomes were achieved with the following preoperative parameters: in Group I, the facet angle was less than 60°, while the presence of tropism had no correlation dependence; in Group II, the facet angle – more than 60°, in the absence of FJ tropism; and in Group III, the facet angle – more than 60°, in the presence of FJ tropism. Conclusion. Objective neuroimaging parameters of the facet angle magnitude of less than 60°, regardless of the presence of tropism, allow performing total arthroplasty. If the facet angle is more than 60°, the rigid stabilization of the operated segment is indicated; in the absence of tropism, a contralateral transfacetal fixation is possible, and in its presence – a bilateral transpedicular stabilization is reasonable.

RELATIONSHIP BETWEEN PARAMETERS OF THE LUMBAR FACET JOINTS IN A LONG-TERM POSTOPERATIVE OUTCOME

ABSTRACT Objective: To analyze the impact of the relationship between tropism and angulation of the lower lumbar facet joints on a remote clinical outcome after dynamic and rigid surgical interventions. Methods: Patients with degenerative diseases of the lower lumbar spine were subdivided into three groups, according to the method of surgical treatment: 1) (n=48) the use of an artificial prosthesis intervertebral disc (IVD); 2) (n=42) the use of interbody fusion combined with transpedicular and transfacet stabilization; 3) (n=51) the use of interbody fusion and bilateral transpedicular stabilization. Analysis was performed of the remote clinical parameters and neuroimaging characteristics before the operation was performed. Results: When analyzing clinical and instrumental parameters, a significant correlation was found between the long-term outcomes of surgical treatment on the VAS and Oswestry scales and the neuroimaging data on angulation and tropism of the facet joints (FJ). Conclusions: The data obtained testify to the importance of preoperative diagnosis of tropism and angulation of the lower lumbar facet joint, which enables differentiated surgical tactics to be selected, and remote clinical outcomes to be optimized. In the presence of neuroimaging parameters of Facet Joint angulation of less than 600, regardless of the presence of tropism, it is possible to perform total arthroplasty of IVD. When neuroimaging parameters of Facet Joint angulation of more than 600 are detected, rigid stabilization of the operated segment is recommended, while in the absence of tropism of Facet Joints, a contralateral transfacetal fixation is possible; in the presence of tropism, it is expedient to perform bilateral transpedicular stabilization. Level of Evidence II; Prognostic Studies—Investigating the Effect of a Patient Characteristic on the Outcome of Disease.

Minimally invasive surgical management of a fracture-dislocation at the thoracolumbar junction

Introduction: The surgical approach to treat thoracolumbar fractures is controversial. Case Report: The authors report the case of an L1 fracture-dislocation treated through posterior approach to perform spinal canal decompression, interbody fusion, transpedicular stabilization, posterolateral fusion, and reduction of kyphotic deformity. Conclusion: Minimally invasive surgical procedure with circumferential arthrodesis through the posterior approach could be considered an option to manage selected L1 fracture-dislocation.