Short Posterior Fixation Research Articles

THORACOLOMBAR BURST FRACTURES: SHORT FIXATION, WITHOUT ARTHRODESIS AND WITHOUT REMOVAL OF THE IMPLANT.

To present the functional outcomes, through the first case series in our country, of patients with thoracolumbar burst fractures (A3,A4), submitted to short posterior fixation, without arthrodesis and without removal of the implants, until the end of the minimum follow-up of one year. Fifty five patients consecutively treated between January/2010 and January/2019 were evaluated through medical records and imaging exams. Radiographic analysis was performed by mea suring local and segmental kyphosis using the Cobb method. Functional assessment was analyzed using the non-specific SF-36 questionnaire and the 1983 Denis pain and work-specific questionnaire, applied after 12 months of follow-up. With a loss of five patients (9%), 22 (44%) patients reported having minimal and occasional pain and 8 (16%) patients reported having no pain. Three (6%) patients responded that they were completely incapacitated. Patients had a mean score of 73.16 points in the SF-36 domains. There was a significant reduction in kyphosis in 12 months (9.1±5.2 [min-max 0-22]) compared to the preoperative period (14.9±7.8 [min-max 0-32]) ( p≤0.01). One patient required implant removal due to the symptomatic prominence of the implant. This case series suggests that the technique leads to satisfactory functional results, without implant failure or significant kyphosis after a minimum follow-up of 12 months of treatment. Evidence Level IV; Case series.

Stent Screw−Assisted Internal Fixation (SAIF) of Severe Lytic Spinal Metastases: A Comparative Finite Element Analysis of the SAIF Technique

A new stent-screw-assisted internal fixation (SAIF) minimally invasive cement-augmentation technique has been introduced to treat patients with extreme osteolytic lesions of the vertebral body. The aim of the current finite element study, employing a spine model with an extreme osteolytic defect, was to assess the effect of the SAIF technique in reducing strains in the vertebral body in comparison with a standard surgical short posterior fixation. Different finite element models of a L1-S1 spine were developed, representing an intact condition (reference configuration), an extreme osteolysis condition, and its treatment, respectively with stand-alone SAIF, SAIF and posterior fixation, and with stand-alone posterior fixation. Each model was loaded to reproduce standing and upper body bending. Principal strains were calculated on the superior endplate, anterior and posterior cortical walls. A paired Wilcoxon test with a 0.05 significance level was performed to statistically analyze the results. Median strains on the bony structures increased in the osteolysis model compared with the intact model, and the SAIF technique was effective in reducing such strains under both standing and flexion conditions. Additional posterior fixation, combined with the SAIF technique, produced minimal further reduction of the median strains on the bony structures. Stand-alone posterior fixation only shielded the osteolytic vertebra avoiding excessive displacements but failed in restoring the axial stiffness to values typical of the intact vertebra. The new SAIF technique resulted effective in restoring the load-bearing capacity of the extensively osteolytic vertebra; additional posterior fixation provided only further minor advantages.

INEFFECTIVE ONE-STAGE SURGICAL TREATMENT OF DISSEMINATED TUBERCULOUS SPONDYLITIS: A CLINICAL CASE AND LITERATURE REVIEW

The paper presents a clinical case of ineffective one-stage surgical treatment of disseminated tuberculous spondylitis. Female patient with extensive destruction of the vertebrae was treated by simultaneously performed posterior decompression and drainage of the abscess and short posterior fixation using dynamic titanium nickelide implant. After 4 months, inadequate primary surgical sanitation of the inflammation focus through posterior approach resulted in the progression of tuberculosis lesions of the spine. After repeated staged surgical treatment, the patient achieved favorable outcome of the disease. A review of the literature on disseminated forms of tuberculosis spondylitis has shown that at present there are staged and singlestep approaches to the treatment of this disease. Most modern researchers of tuberculosis spondylitis tend to single-step combined operations.

REVIEW OF MCCORMACK CLASSIFICATION FOR THORACOLUMBAR SEGMENT FRACTURES

ABSTRACT Objective: The aim of this study was to evaluate the success and complications rates of thoracolumbar fractures with a score equal or superior to 7 according to the load sharing classification (McCormack), surgically treated with short posterior fixation at three points. Methods: We evaluated 40 patients with thoracolumbar fractures and score by the load sharing classification greater than or equal to 7, treated exclusively by surgery by short posterior fixation. We assessed epidemiological data, increased kyphosis, loss of vertebral body height and complications at 2-year follow-up. Results: Although there was a statistically significant increase in kyphosis and a decrease in vertebral height, there was no clinical repercussion. Conclusion: We conclude that the McCormack classification is not a fundamental predictor for indication of anterior approach complementary to the short posterior fixation.

RETROSPECTIVE COMPARATIVE ANALYSIS OF SURGICAL TREATMENT OF THORACOLUMBAR BURST FRACTURE: SHORT VERSUS LONG FIXATION

ABSTRACT Objective: The objective of this study is to compare short posterior fixation to long posterior fixation in thoracolumbar burst fractures. Methods: Fifty-three patients were divided into Group I (n=24) treated with short instrumentation (one level above and one below the fracture) and into Group II (n=29) treated with long instrumentation (two or more levels above and below the fracture). The load sharing classification was used to stratify cases. The evaluation of the sagittal index was performed using the Cobb method. Results: In subgroups with load sharing classification ≤ 6, Group I had loss of correction of 4.2 degrees and a procedure failure in 14.3% of cases, Group II showed loss of correction of 5.4 degrees and failure in 21.7% of cases. In subgroups with load sharing classification ≥7, Group I had a loss of correction of 11.2 degrees and procedure failure in 70% of cases, and Group II showed a loss of correction of 9 degrees and failure of 46.7%. Group I had a tendency to worse outcomes, especially in the subgroup of patients with load sharing classification ≥7. Conclusion: Despite the tendency for poorer results in the short fixation group in the cases with load sharing ≥7, in no sample was there statistically significant difference between the groups studied.

Pedicle Screw Configuration for Thoracolumbar Burst Fracture Treatment: Short versus Long Posterior Fixation Constructs with and without Anterior Column Augmentation

Study DesignAn in-vitro study.PurposeThe current study is aimed at investigating the differences in stability between short posterior fixation (SPF), hybrid posterior fixation (HPF), and long posterior fixation (LPF) with and without anterior column augmentation using calcium phosphate bone cement (CaP) for treating burst fractures (BFs).Overview of LiteratureThe ideal treatment for thoracolumbar BF is controversial regarding the use of short or LPF constructs.MethodsSeven human thoracolumbar spines (T9-L4) were tested on a six degree of freedom spine simulator in three physiologic planes, flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Tested surgical constructs included the following: intact, injury (BF), SPF (T12-L2), HPF (T11-L2), LPF (T11-L3), SPF+CaP, HPF+CaP, LPF+CaP, and CaP alone (CaP). Range of motion (ROM) was recorded at T12-L2 in FE, LB, and AR.ResultsThe reduction in mean ROM trended as follows: LPF>HPF>SPF. Only LPF constructs and HPF with anterior column augmentation significantly reduced mean ROM in FE and LB compared to the intact state. All instrumented constructs (SPF, HPF, and LPF) significantly reduced ROM in FE and LB compared to the injured condition. Furthermore, the instrumented constructs did not provide significant rotational stability. Injecting CaP provided minimal additional stability.ConclusionsFor the injury created, LPF and HPF provided better stability than SPF with and without anterior column augmentation. Therefore, highly unstable fractures may require extended, long or hybrid fusion constructs for optimum stability.

En bloc spondylectomy reconstructions in a biomechanical in-vitro study

Wide surgical margins make en bloc spondylectomy and stabilization a referred treatment for certain tumoral lesions. With a total resection of a vertebra, the removal of the segment's stabilizing structures is complete and the instrumentation guidelines derived from a thoracolumbar corpectomy may not apply. The influence of one or two adjacent segment instrumentation, adjunct anterior plate stabilization and vertebral body replacement (VBR) designs on post-implantational stability was investigated in an in-vitro en bloc spondylectomy model. Biomechanical in-vitro testing was performed in a six degrees of freedom spine simulator using six human thoracolumbar spinal specimens with an age at death of 64 (+/- 20) years. Following en bloc spondylectomy eight stabilization techniques were performed using long and short posterior instrumentation, two VBR systems [(1) an expandable titanium cage; (2) a connected long carbon fiber reinforced composite VBR pedicle screw system)] and an adjunct anterior plate. Test-sequences were loaded with pure moments (+/- 7.5 Nm) in the three planes of motion. Intersegmental motion was measured between Th12 and L2, using an ultrasound based analysis system. In flexion/extension, long posterior fixations showed significantly less range of motion (ROM) than the short posterior fixations. In axial rotation and extension, the ROM of short posterior fixation was equivalent or higher when compared to the intact state. There were only small, nonsignificant ROM differences between the long carbon fiber VBR and the expandable system. Antero-lateral plating stabilized short posterior fixations, but did not markedly effect long construct stability. Following thoracolumbar en bloc spondylectomy, it is the posterior fixation of more than one adjacent segment that determines stability. In contrast, short posterior fixation does not sufficiently restore stability, even with an antero-lateral plate. Expandable verses nonexpandable VBR system design does not markedly affect stability.

Three-dimensional stiffness in a thoracolumbar en-bloc spondylectomy model: A biomechanical in vitro study

In selected cases, en-bloc spondylectomy is the only option to reach wide resection margins for patients with malignant tumours of the thoracolumbar spine. These patients must be also provided a secure initial stabilization of the spine and this is the role of vertebral body replacements employed with posterior fixation systems. The aim of this study was to determine the postimplantation stiffness of a connected vertebral body replacement pedicle screw system in different implantation scenarios following an en-bloc spondylectomy. Reconstruction was varied by posterior fixation lengths and axial compression forces during implantation. Three-dimensional stiffness was assessed in 6 fresh frozen human spinal specimens (Th11-L3) using a six degree of freedom spine simulator. Following en-bloc spondylectomy reconstruction was performed using a carbon composite fibre vertebral body replacement connected to a posterior fixation system by two artificial pedicles. The spines were loaded with pure moments (7.5Nm) in the three main motion planes. The intersegmental rotations were measured between Th12 and L2. Reconstructions using long posterior fixation modes demonstrated significant (P<0.05) higher stiffness compared to short posterior fixations in all motion planes. In axial rotation short posterior fixation modes failed to reach the values of the intact state. Neither high nor low axial compression force during implantation showed a significant impact on postfusional stiffness. In this biomechanical model, the employed system should be implanted with a posterior fixation of two adjacent segments to the lesion in order to achieve a secure stabilization of the treated segment.