USE OF THE uCentum SYSTEM IN THE SURGICAL TREATMENT OF DISEASES OF THE VERTEBRAL SPINE

ABSTRACT Objectives: Evaluate the treatment outcome and the performance of the uCentum spinal fixation system in treating traumatic, degenerative, and tumoral diseases of the spine. Methods: This is a therapeutic study to investigate treatment outcomes and level of evidence III, including twenty-three adult patients of both sexes undergoing surgical treatment of degenerative (13 patients), traumatic (04 patients), or tumor diseases (06 patients). Patients were prospectively evaluated using clinical parameters: pain (visual analog scale), clinical and functional assessment questionnaires (SF-36, Oswestry and Roland-Morris), and radiological criteria (arthrodesis consolidation, loosening, breakage or deformation of the implants). Results: Twenty patients were followed for a period of 01 month to 12 month (mean 6,5±7,77). Three patients died due to complications unrelated to the primary disease (traumatic brain injury, septicemia, and lung tumor). Improvements were observed in clinical parameters and scores of the evaluation questionnaires used. No implant-related complications (breakage, loosening, deformation) were observed. Conclusion: the uCentum fixation system showed great versatility for performing the surgical treatment, allowing the performance of open, percutaneous procedures, the introduction of acrylic cement inside the implants, and conversion of polyaxial screws into monoaxial screws intraoperatively. Level of Evidence III; Therapeutic Studies - Investigating the Results of Treatment.


INTRODUCTION
Arthrodesis has been the most commonly used surgical procedure in the surgical treatment of spinal diseases, although new technologies have been developed to preserve the mobility of the vertebral segment. 1,27][8] The development of fixation systems that can meet the widest spectrum of procedures, from classic open procedures to the percutaneous ones that have been recently introduced, has been occurring in parallel so that the same fixation system can meet the widest spectrum of surgical procedures.The development of universal systems that can more broadly meet the technical needs of surgical procedures has technical, logistical, and economic advantages.
The uCentum system (Ulrich® -Ulm-Germany) was developed to meet the different requirements of open or percutaneous spine procedures so that large spectrums of procedures can be performed with the same spine fixation system.The uCentum system (Ulrich® -Ulm-Germany) is universal.Its versatility is characterized by its open or percutaneous use, complementation with acrylic cement for fixing the fenestrated screws, conversion of the polyaxial implant into a monoaxial one during surgery, and corrective maneuvers.(Figure 1) The study aimed to evaluate the versatility and results of treating the spine's degenerative, traumatic, and tumor diseases using the uCentum (Ulrich®-Ulm-Germany) spinal fixation system.

MATERIAL AND METHODS
The Ethics Committee of HCFMRP-USP approved the study under No. 16606/2012.Twenty-three patients underwent surgical treatment using the uCentum spinal fixation system (Ulrich).
The uCentum system is a method of titanium vertebral fixation consisting of screws and hooks.It is indicated for treating diseases of the thoracic and lumbar segments that require stabilization or correction.The screws are polyaxial, monoaxial, and polyaxial screws that can be converted to monoaxial screws at the time of fixation.The implants are low profile and can be used along the entire length of the thoracic, lumbar, and sacral spine.All the system's screws are cannulated and fenestrated, allowing percutaneous use, use of guide wire, and infusion of acrylic cement inside.The diameter of the screws varies from 4.5 mm to 10 mm, and the length from 25 mm to 60 mm.The connecting rods of the system has a diameter of 5.5 mm.The system requires classical technical conditions such as fluoroscopy or navigation, and the supporting instruments are used according to the selected technique (open, percutaneous, less invasive, acrylic cement infusion).
The patients were evaluated using clinical parameters: pain (visual analog scale), clinical and functional evaluation questionnaires (SF-36, Oswestry, and Roland-Morris), and radiological criteria (consolidation of arthrodesis, loosening, breakage, or deformity of the implants).Evaluations were performed preoperatively, immediately postoperatively, at two, six, and 12 months.
All participating patients read and signed the Informed Consent Form, printed in two copies, which the responsible researcher also signed.
Descriptive statistics (minimum value, maximum value, mean, standard deviation, and confidence interval) were performed.The normality of the sample was assessed using the Kolmogorv-Smirnov test.Mixed effects analysis was used to compare the means of the different evaluation periods, and the significance level was set at 5% (p < 0.05).
The complications observed were the death of three patients, which was related to the severity of the primary disease.One patient with a metastatic lung tumor progressed with postoperative pain improvement, and the cause of death during follow-up was associated with the primary disease.Another cause of death was sepsis in a patient with degenerative disease and chronic kidney disease undergoing kidney transplantation.The cause of death in the third patient was traumatic brain injury related to the primary trauma.

DISCUSSION
The uCentum fixation system has shown great versatility in the surgical treatment of degenerative, traumatic, and tumor diseases of the spine.It has allowed the performance of classically established open and less invasive or percutaneous procedures.The system also allowed the conversion of polyaxial to monoaxial screws intraoperatively and the introduction of acrylic cement inside the pedicle screws.Cannulated screws allow less invasive or percutaneous procedures and provide greater security for placing the implants inside the vertebral pedicle. 9,10he system's versatility for its use in open, less invasive, or percutaneous surgeries and its possibility to treat a wide spectrum of spinal diseases make the system universal with technical, logistical, and economic benefits.Different treatment techniques, such as the classic open, less invasive, or percutaneous, could be used in different diseases with the fixation system.
2][13] The treatment of unstable thoracolumbar spine fractures has received increasing acceptance and represents a major therapeutic advance, and the reports corroborating the advantages of this treatment modality have increased. 14Less invasive surgery for treating spine fractures has reduced the complications and shown safety and effectiveness. 14,15In the presence of associated lesions, as occurred in the group of patients studied who had an open fracture of the sacrum, percutaneous fixation of the fracture reduces the possibility of complications arising from the procedure.
][18] Percutaneous fixation of metastases associated with radiotherapy in lesions sensitive to this treatment modality has significantly reduced postoperative complications.This treatment modality also allows for early complementary treatments, such as radiotherapy.
Unilateral fixation using the less invasive technique we use for the treatment of degenerative diseases allows decompression of the nerve structures, the performance of inter somatic arthrodesis through the posterior approach, and fixation of the vertebral segment.0][21] We have used unilateral fixation using a less invasive approach associated with decompression and reconstruction of the anterior spine in patients with metastases.This treatment modality has been developed following the concept of unilateral fixation, and the preliminary results have been satisfactory.The group of patients in the study was composed of different diseases.Due to the group's heterogeneity, the evaluation was not performed considering the specific diseases but through the general evaluation questionnaires (visual analog scale, SF-36, Oswestry, and Roland Morris).This modality of evaluation has been prevalent, based on the patient's understanding of his or her clinical situation, and shows the surgeon the real value of the procedure performed. 22,23Radiographic findings are routinely used in evaluations despite their tenuous correlation with clinical results. 24,25Clinical evaluation using the study parameters showed improvement in the different parameters selected for the different diseases and treatment methods used by the fixation system.

CONCLUSION
The uCentum spinal fixation system has allowed the surgical treatment of different spinal diseases and the use of various techniques using a single system through the classical open approach, less invasive surgery, or percutaneous surgery.
The versatility and possibility of the application of the system in different disease modalities and treatment strategies cannot be measured, and the examples and results of the application of the system express this attribute of the attachment system.
The limitation of the study consists of the number of patients evaluated and the non-specific evaluation of the use of the fixation system in specific diseases or treatments.

Figure 1 .
Figure 1.Implantation of the uCentrum system and its adaptation for percutaneous use.

Figure 2 .
Figure 2. Pre-and post-operative radiographs and at 12-month follow-up, with the radiographic evolution of a patient with degenerative disease and root compression symptoms (pre-operative VAS 10 / post-operative 0).

Figure 3 .
Figure 3. Radiographs of a patient with degenerative disease and symptoms of radicular compression (preoperative VAS 8 / postoperative 0).

Figure 5 .
Figure 5. Preoperative tomography, radiography, postoperative clinical appearance, and radiography at 12 months postoperative and supplementary treatment with radiotherapy of a patient with thyroid tumor metastasis.

Figure 6 .
Figure 6.The average visual analog scale values on follow-up periods.

Figure 7 .
Figure 7.Comparison of the means and standard deviation on SF-36 questionnaire domains.(*): statistical difference.

Figure 4 .
Figure 4. CT scan, post-operative photo, and radiograph at 12 months post--operative of a victim of fall from height with T11 fracture and open fracture of the sacrum.

Figure 9 .
Figure 9. Evaluation using the Roland Morris questionnaire during the follow-up period.Pre op.Pos op. 2 m 6 m 12 m