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.

Spine stabilization in patients with the thoracic and lumbar vertebrae fractures in reduced bone mineral density

Objective To compare the clinical effectiveness of various technical and tactical options for surgical treatment of patients with thoracic and lumbar vertebrae fractures with reduced bone mineral density.Material and Methods The study included 238 patients with the thoracic and lumbar vertebrae fractures with reduced bone mineral density (BMD). The patients were aged between 48 and 85 with T-score –1.5 to –3.5. The study did not include the patients with recurrent or multiple vertebral fractures, with absence of the clear date and fact of fracture in the case history, with neurological complications or polytrauma. The patients had fractures А1.2, А1.3, В1.2, В2.3 according to the classification of Magerl (1992). All patients underwent bisegmental transpedicular fixation (TPF). Group 1 included 68 patients who underwent non-cement augmented transpedicular screw fixation. Group 2 included 170 patients who underwent cement augmented transpedicular fixation. Both groups were divided into 2 subgroups. Subgroups 1.1 and 2.1 included patients operated in two stages. The first stage was TPF and the second stage was anterior corporodesis. Subgroups 1.2 и 2.2 included patients who underwent only TPF. Outcomes and complications were studied. The observation period lasted for not less than 2 years. Correlation analysis was performed between the technique of performing operations and surgical tactics in four subgroups and treatment outcomes.Conclusion 1. In the treatment of patients with fractures in the thoracic or lumbar spine with reduced BMD, isolated TPF with cemented screw implantation is clinically equivalent to two-stage surgical treatment - TPF with cementless or cemented implantation and anterior corprodesis of injured FPS. 2. In cementless TPF in patients with decreased BMD, anterior corprodesis of the injured VMS is necessary because its failure leads to the loss of anatomical relationship correction achieved during surgery, increase in local kyphosis, and functional maladaptation of patients.

Comparative analysis of single-level anterior and posterior spinal fusion in degenerative disease of the lumbosacral spine

Transpedicular fixation (TPF) as a method of posterior fusion is currently the most common, reliable and economically justified option of spinal fusion in various diseases and injuries of the lumbar spine, having more than half a century of history. As a result of the search for less invasive and more effective methods of fixation of the spinal segments to improve the results of surgical treatment, shorten the hospitalization, and reduce the number of perioperative complications, an approach involving fusion with rigid implant from the anterior (ALIF) was developed. Objective. To analyze the immediate and long-term results of treatment of single-level herniated discs by total removal of the intervertebral disc using anterior access with a rigid spondylodesis (ALIF) and the method of posterior discectomy, spondylodesis and transpedicular fixation (TPF). Materials and methods. A prospective cohort study was conducted. The study included patients after total intervertebral disc removal by the ALIF method and patients after discectomy and TPF. The achieved result was evaluated using radiological tests, as well as using standardized questionnaires and surveys. Results. After the surgery, patients in both groups showed a significant reduction in pain on the NRS scale. Patients from the first group had 4 to 0 for back and 8 to 0 for leg, patients from the second group had 6 to 4 for back and 8 to 0 for leg. The quality-of-life assessment by ODI scale also showed a positive trend from 36 to 4 in the first group and from 22 to 12 in the second group. Clinically, the result of surgical treatment was rated as excellent 5 in the ALIF group and as good in the TPF group 4 on the modified subjective assessment scale Macnab. Conclusion. The ALIF method as a decompression-stabilizing surgical aid is less traumatic. The less invasive nature of the technique was confirmed by significantly shorter surgical intervention time, smaller volume of intraoperative blood loss, and a shorter period of hospitalization. In the long-term period, statistically significant differences were obtained indicating that the ALIF method is more effective than TPF.

Evaluation of the role of ventral interventions in the surgery of idiopathic scoliosis in patients with active bone growth

BACKGROUND: Today, the question of the tactics of surgical treatment of patients with idiopathic scoliosis during active bone growth, namely, the need for ventral interventions due to the emergence of modern dorsal instruments, remains open. AIM: This study aims to evaluate the role of ventral interventions in the surgical treatment of patients with progressive idiopathic scoliosis Lenke type 1, 2, 3 during the period of active bone growth. MATERIALS AND METHODS: The long-term results of operational correction 352 patients with thoracic idiopathic scoliosis aged from 10 to 14 years old operated in Novosibirsk Research Institute of Traumatology and Orthopedics n.a. Ya.L. Tsivyan from 1998 to 2018 using various methods and different instrumentation types. RESULTS: Among patients (352 people) aged 10 to 14 years with idiopathic thoracic scoliosis (Lenke type 1, 2, 3), statistically significant postoperative progression was observed in patients who underwent surgical deformity correction using laminar (hook) fixation. At the same time, additional ventral stage conduction could not prevent deformity progression in the postoperative period. In those groups where hybrid fixation was used combined with the ventral stage and total transpedicular fixation, no significant progression was observed in the postoperative period. CONCLUSION: Modern dorsal systems for transpedicular fixation narrow the indications for using additional mobilizing and stabilizing ventral interventions in the surgical treatment of progressive idiopathic scoliosis in patients with active bone growth. Total transpedicular fixation provides excellent main curve and anti-curvature arch correction in the absence of scoliotic deformity progression in the postoperative long-term follow-up.

Surgical options for traumatic fractures of the thoracic and lumbar spine

Background context. Thoracolumbar fractures represent a large number of spine injuries in adults. Such fractures are a result of traumatic accidents with high-energy impacts, such as falls from height or following motor vehicle accidents, often resulting in some degree of neurological deficit. Purpose. To report a total of 20 cases of thoracolumbar fractures in young adults with various neurological manifestations. The majority had indications for transpedicular fixation. Study Design. Series of 20 cases and review of the literature. Patient Sample. A series of 20 patients with a history of falling from a height or after motor vehicle accidents (RTA) with complicated fractures at the level of the thoracolumbar vertebrae which present with neurological deficits. Methods. We report here on a total of 20 patients with a history of falls from height or following RTA. Patients presented to the hospital complaining of back and abdominal pain. Fractures at the thoracolumbar vertebral level were confirmed with imaging studies revealing post-traumatic spinal deformities. All cases were initially considered for conservative medical treatment. However, unstable complicated cases with bone fragment migration as well as spinal canal compression were deemed candidates for surgical intervention via posterior spinal fusion with transpedicular screw fixation. Written informed consent was gathered from all patients. Detailed history, clinical examination, as well as X-ray, computed tomography and magnetic resonance imaging of the dorsolumbar spine were obtained in all cases. Neurological status was assessed using the Frankel grading for spinal cord injury. Results. The patients tolerated the operations without complications and remained in stable postoperative condition. Conclusion. Surgical treatments via transpedicular fixation are extremely efficient for treating unstable and complicated thoracolumbar spinal fractures. Nevertheless, conservative medical treatment is still of high value and should be considered as the first treatment option, especially in stable cases. The patients who underwent surgery showed excellent outcomes and improvement of neurological deficits. The surgical procedure preferred in the present study was the posterior spinal fusion with pedicle screw fixation.

The Effect of Smith-Peterson Osteotomy on Blood Loss during Surgical Correction of Adolescent Idiopathic Scoliosis

Introduction: Surgical correction of adolescent idiopathic scoliosis is inevitably accompanied by blood loss. About 37–85% of patients undergo allogeneic transfusions associated with a risk of serious complications. Prediction of the expected blood loss volume remains a topical problem. In this regard, there is a need to clarify predictors of increased blood loss. Aim: To assess the effect of vertebrectomy on the intraoperative blood loss volume during surgical correction of adolescent idiopathic scoliosis. Materials and methods: A retrospective study included 511 adolescents who underwent posterior correction of spinal deformity. Two groups were allocated: Group I consisted of 303 patients who underwent multilevel transpedicular fixation; Group II included 208 patients who underwent multilevel transpedicular fixation combined with Smith-Peterson osteotomy. Results: Intergroup comparisons revealed significant differences in the number of transpedicular fixation levels and the volume of blood loss, which were higher in Group II. After aligning the groups by the number of transpedicular fixation levels using the Propensity Score Matching method, no statistically significant difference was observed. We derived formulas for calculating the expected blood loss volume in Groups I and II. Comparison of the formulas revealed that the formula for Group II predicted a significantly lower volume of blood loss, by 2.51%, while the formula for Group I predicted a significantly higher volume of blood loss, by 3.27%. In our opinion, application of the formula that overestimates expected intraoperative blood loss is most reasonable due to a possibility of the worst case scenario during surgery; therefore, the formula for Group I approaches a universal model for use. Conclusion: Smith-Peterson osteotomy did not affect the amount of blood loss during surgical correction of adolescent idiopathic scoliosis, considering the number of transpedicular fixation levels.