COMPARISON OF MONO AND POLY-AXIAL PEDICLE SCREW FIXATION IN THORACOLUMBAR A3/A4 FRACTURESABSTRACT
Objective: This study aims to compare the use of mono-axial and poly-axial screws in AOSpine type A3 and A4 thoracolumbar fractures.
Methods: Prospective case-control study involving patients treated surgically with short fixation using mono-axial or poly-axial screws. The type of treatment was chosen according to the surgeons’ preference and implant availability. The qualitative variables used were the type of implant (mono-axial or poly-axial), type of fracture (A3 or A4), neurological deficit, use of an additional screw in the fractured vertebra, and need for reoperation. The quantitative variables were preoperative Cobb (CobbPre); immediate postoperative Cobb (CobbPOI); late postoperative Cobb (CobbPOL); Delta (∆) kyphosis; preoperative anterior vertebral body collapse (AVBC%); postoperative AVBC%; ∆ AVBC%. For quantitative variables, the Student’s T Test was used.
Results: 35 patients were included, 22 in the mono-axial group (eight patients A3 and 14 A4) and 13 in the poly-axial group (two patients A3 and 11 A4). The postoperative AVBC% was statistically superior for the mono-axial group (mean of 0.60±0.09 in the pre-operative AVBC% to 0.77±0.11 in the post-operative), compared to the poly-axial group (0.60±0.12 to 0.69± 0.13), p=0.04. ∆ AVBC% was also statistically different (0.17±0.10 in the mono-axial group and 0.08±0.12 in the poly-axial group), p=0.01. The other quantitative variables had no significant differences.
Conclusion: Surgical treatment using mono-axial screws was statistically superior in recovering anterior vertebral body height. Level of Evidence III; Prospective Case-Control Study.
Keywords:
Spinal Fractures; Spinal Injuries; Pedicle Screws; Kyphosis
RESUMO
Objetivo: Este estudo tem como objetivo comparar o uso de parafusos monoaxiais e poliaxiais nas Fraturas toracolombares AOSpine tipo A3 e A4.
Métodos: Estudo prospectivo de caso-controle, envolvendo pacientes tratados cirurgicamente com fixação curta com parafusos monoaxiais ou poliaxiais. O tipo de tratamento foi escolhido de acordo com a preferência dos cirurgiões e a disponibilidade do implante. As variáveis qualitativas utilizadas foram tipo de implante (monoaxial ou poliaxial), tipo de fratura (A3 ou A4), déficit neurológico, uso de parafuso adicional na vértebra fraturada, necessidade de reoperação. As variáveis quantitativas foram Cobb pré-operatória (CobbPre); Cobb pós-operatório imediato (CobbPOI); Cobb pós-operatório tardio (CobbPOL); Delta (∆) cifose; colapso pré-operatório do corpo vertebral anterior (AVBC%); AVBC pós-operatório; ∆ AVBC%. Para as variáveis quantitativas, foi utilizado o Teste T de Student.
Resultados: Foram incluídos 35 pacientes, sendo 22 no grupo monoaxial (oito pacientes A3 e 14 A4) e 13 no grupo poliaxial (dois pacientes A3 e 11 A4). O AVBC% pós-operatório foi estatisticamente superior para o grupo monoaxial (média de 0,60±0,09 no AVBC% pré-operatório para 0,77±0,11 no pós-operatório), em comparação com o grupo poliaxial (0,60±0,12 para 0,69± 0,13), p=0,04. O ∆% AVBC% também foi estatisticamente diferente (0,17±0,10 no grupo monoaxial e 0,08±0,12 no grupo poliaxial), p=0,01. As demais variáveis quantitativas não apresentaram diferenças significativas.
Conclusão: O tratamento cirúrgico com parafusos monoaxiais foi estatisticamente superior na recuperação da altura do corpo vertebral anterior. Nível de Evidência III; Estudo Prospectivo Comparativo.
Descritores:
Fraturas da Coluna Vertebral; Traumatismos da Coluna Vertebral; Parafusos Pediculares; Cifose
RESUMEN
Objetivos: Este estudio tiene como objetivo comparar el uso de tornillos monoaxiales y poliaxiales en fracturas toracolumbares tipo A3 y A4 de AOSpine.
Métodos: Estudio prospectivo de casos y controles, con pacientes tratados quirúrgicamente con fijación corta mediante tornillos monoaxiales o poliaxiales. El tipo de tratamiento se eligió de acuerdo con la preferencia de los cirujanos y la disponibilidad de implantes. Las variables cualitativas utilizadas fueron: tipo de implante (monoaxial o poliaxial), tipo de fractura (A3 o A4), déficit neurológico, uso de tornillo adicional en la vértebra fracturada, necesidad de reintervención. Las variables cuantitativas fueron: Cobb preoperatorio (CobbPre); Cobb postoperatorio inmediato (CobbPOI); Cobb postoperatorio tardío (CobbPOL); Cifosis delta (∆); colapso preoperatorio del cuerpo vertebral anterior (AVBC%); AVBC% postoperatorio; ∆ AVBC%. Para las variables cuantitativas se utilizó la Prueba T de Student.
Resultados: Se incluyeron 35 pacientes, 22 en el grupo monoaxial (ocho pacientes A3 y 14 A4) y 13 en el grupo poliaxial (dos pacientes A3 y 11 A4). El AVBC% postoperatorio fue estadísticamente superior para el grupo monoaxial (media de 0,60±0,09 en el AVBC% preoperatorio a 0,77±0,11 en el postoperatorio), en comparación con el grupo poliaxial (0,60±0,12 a 0,69± 0,13), p=0,04. ∆ AVBC% también fue estadísticamente diferente (0,17±0,10 en el grupo monoaxial y 0,08±0,12 en el grupo poliaxial), p=0,01. Las demás variables cuantitativas no presentaron diferencias significativas.
Conclusión: El tratamiento quirúrgico con tornillos monoaxiales fue estadísticamente superior en la recuperación de la altura del cuerpo vertebral anterior. Nivel de Evidencia III; Estudio Prospectivo Comparativo.
Descriptores:
Fracturas de la Columna Vertebral; Traumatismos Vertebrales; Tornillos Pediculares; Cifosis
INTRODUCTION
The thoracolumbar region (T11-L3) is commonly affected by fractures, accounting for 60-90% of all spinal fractures, and there is controversy on the treatment of A3 and A4 (AOSpine) thoracolumbar fractures surgically or conservatively (previously named as “burst fractures’’).1-4 Despite its stability, it can further collapse the bone structure, causing persistent discomfort and/or segmental anomalies that can progress with increasing severity. In such instances, surgical intervention appears to be the most effective therapeutic approach,5 with a tendency favoring short-segment fixation over longer constructs and anterior instrumentation3. As several types of pedicle instrumentation systems are available, some authors have raised the debate regarding the need for mono-axial fixation.6-15 Those proposing the use of poly-axial screws state that they allow a greater variation in screw insertion and easier adjustment of the rod on the screw head, with less stress on both rod-to-screw and screw-to-bone interface.9-15 Those favoring mono-axial systems claim better kyphosis correction and maintenance of vertebral body height after surgery.6,7,10 The disadvantages include the possibility of malpositioning in the axial plane, the greater difficulty of inserting this type of screw,6,11 it’s greater rigidity and less flexibility, which can be a hurdle for bones damaged by fracture or degenerative conditions like osteoporosis.7
Even though some comparisons are described in the literature, few studies in thoracolumbar A3 and A4 fractures compare such instrumentation types. The goal of the present study is to evaluate and compare the effectiveness of mono-axial and poly-axial pedicle screws in restoring and maintaining alignment after surgical fixation of thoracolumbar fractures.
METHODS
A prospective case-control study included 35 patients with A3 and A4 thoracolumbar fractures treated by posterior fixation by mono-axial (internal fixator) or poly-axial screws between January 2017 and December 2021. Data was extracted from a prospective, multicenter study on A3/A4 TL fractures,3 and the inclusion criteria for this study were fractures between T10 and L3, AOSpine type A3 or A4, age between 18 and 70 years old, and time between fracture and definitive treatment not longer than 10 days. Pathological fractures, clinically evident osteoporosis, severe systemic disease, Type B/C injuries, pregnant patients, and injuries secondary to gunshot wounds were excluded from the study.
The choice of the screw was based on the availability of the implant at the hospital and the surgeon’s preference/personal experience. All patients with A3/A4 thoracolumbar fractures with or without neurological deficit who underwent short fixation (one vertebra above and one below the fractured level) were included. Cases of osteoporotic and pathological fractures were excluded, as well as cases with long fixation or a history of previous spine surgery.
This study was approved by the institution’s Ethics Committee (22675413.3.0000.0020), and all patients signed informed consent to participate.
Variables and Statistical Analysis
The qualitative variables used were the type of material (monoor poly-axial), type of fracture (A3 or A4), neurological deficit, screw fixation in the fractured vertebra, and need for reoperation. The quantitative variables were preoperative Cobb angle (CobbPre) (Figure 1); immediate postoperative Cobb angle (CobbPOI); late postoperative Cobb angle (CobbPOL), obtained at the sixth postoperative month; delta (∆) kyphosis; preoperative anterior wall height (AVBC%Pre); postoperative anterior wall height (AVBC%Pos); ∆ anterior vertebral height (AVH) (measurement detailed on Figure 2). The Student’s T-Test was used for quantitative variables with statistical significance determined as p<0.05.
The Cobb angle is the measurement between the superior endplate of the vertebra one level above the fracture and the inferior endplate of the vertebra one below the fracture.
The Anterior Vertebral Body Compression Percentage (AVBC%) = (V2/[V1+V3/2]) X 100%. The anterior vertebral body height of the fractured vertebra (V2) is divided by the average height of the adjacent vertebral bodies (V1+V3/2) and converted into a percentage.
Radiographic analysis
All admitted patients underwent computed tomography (CT) of the total spine and anteroposterior (AP) and lateral (lat) radiographs centered on the fracture in the initial evaluation and lateral radiographs in the immediate postoperative period and during outpatient follow-up. DICOM images were obtained, and measurements were performed using Surgimap software.
To analyze the kyphosis of the fractured segment, the Cobb method was employed (Figure 1), which consists of the angle formed by a tangent line to the upper plateau of the vertebra above the fracture and a tangent to the lower plateau of the vertebra below.7,16 To analyze the anterior wall height of the fractured segment, the anterior vertebral body compression percentage (AVBC%) was employed. (Figure 2)16
Surgical procedure
All patients underwent surgery through a conventional midline posterior approach, performed by one of the institution’s spine surgeons. All patients were positioned on a four-post frame, in the same manner, to regain a part of the lordosis by positioning.
Regardless of the implant used, patients received bipedicular instrumentation on the vertebra above and below the fracture (short-segment posterior fixation) and may or may not receive unipedicular instrumentation on the fractured level, depending on the condition of the pedicle and the surgeon’s intraoperative judgment.
After pedicle instrumentation, the fracture was reduced by ligamentotaxis through lordosis and distraction maneuvers, with the correction checked under the aid of fluoroscopy. In cases of neurological deficit, the patient underwent laminectomy and impaction of the vertebral body fragment.
No patient used orthosis after the procedure, and early ambulation was encouraged depending on the patient’s condition. Patients were followed clinically and radiographically until radiographic fusion was identified. The clinical data has been published previously,3 and radiographic measurements were performed using preoperative, immediate postoperative and six-month follow-up images.
RESULTS
There were 22 patients (18 men and four women) in the mono-axial group (62.8%) and 13 (nine men and four women) in the poly-axial group (37.2%). The average age was 51.1±13.9 years (range, 19-78) in all the samples; 52.2 ±13.5 (range, 29-78) to the mono-axial and 49.1±14.9 (range 19-70) to the poly-axial (p=0,2). (Table 1)
The most injured vertebrae were L1 (43%) for both groups (50% in mono-axial and 30.7% in poly-axial). There were 10 “A3” (28.5%) fractures and 25 “A4” (71.5%); in the mono-axial group there were eight “A3” (36.3%) and 14 “A4” (63.7%); in the poly-axial, two “A3” (15.3%) and 11 “A4” (84.7%). There were neurologic deficits before surgery in seven patients, five in the mono-axial group and two in the poly-axial group. The surgeons opted to insert a screw in the fractured vertebra in 21 patients, 12 in the mono-axial group and 9 in the poly-axial group. There was a 20% reoperation rate, three cases in the mono-axial and four in the poly-axial group. (Table 1)
The data for quantitative results are shown in Table 2. We have not found statistically significant differences among the groups regarding kyphosis. On the other hand, the groups had statistical differences among the AVBC%. The mono-axial group had a 17% improvement in the AVBC% (C.I. 95% of 0,747 to 0,793) after surgery, and the poly-axial group improved by 9% (C.I. 95% of 0,654 to 0,726). The p-values were 0.4139 to the AVBC%Pre, 0.04005 to the AVBC%Pos, and 0.01440 to the ∆ AVBC% (the difference between 77% and 69% is illustrated in Figure 3).
Radiographic analysis and results. In bold, the results with a statistically significant difference.
On the left, the mono-axial (AVBC%Pos 71%). On the right, the poly-axial (AVBC%Pos 63%) - a difference of eight percentage points.
DISCUSSION
The results show that the use of mono-axial systems is advantageous in comparison to poly-axial screws in thoracolumbar trauma. The mono-axial fixation group had a better AVH recovery, although no significant difference in lordosis existed. Including L3 in our study, a typically lordotic segment, could reduce the differences in kyphosis, but a sub-analysis removing L3 fractures did not show a change in the results.
Chung et al. described a comparison of 21 patients using mono-axial and poly-axial screws in the reduction of thoracolumbar A3 and A4 fractures using minimally invasive techniques (MIS) in both methods, with better results in the mono-axial group, not only in the anterior vertebral body height but also in the correction of local and regional kyphotic angles.6 Although this study’s technique was open surgery, the literature shows no differences between open and MIS techniques in vertebral body height and local kyphotic angle correction.8,17-18
Shim et al. compared 98 patients with A3 fractures in the thoracolumbar spine. The mono-axial group had better results in reducing and maintaining AVH. In addition to the regional kyphosis angle, they had a better correction rate and less correction loss in the mono-axial group.7 Yin et al. also found that the mono-axial group was significantly better than the poly-axial group in the AVH ratio and kyphosis Cobb angle in late follow-up.15 Both Shim and Yin’s studies used short-segment posterior fixation (one level above and one below), while Chung used long-segment posterior fixation (two levels above and two below).6-7,15 Guven et al. wrote that short-segment fixation with pedicle screw fixation at the fractured vertebra is the best choice when the spinal surgeon wants to provide AVH restoration and kyphosis correction.19 In the present study, short-segment posterior fixation was used; in 54% of the mono-axial group, the screw was used in the fractured vertebra, and in 70% of the poly group.
The study of Arbash et al. had 178 patients, comparing MIS and open surgery with a short-segment posterior fixation. In the mono-axial group, they used only open surgery; in the poly-axial group, they used MIS in 68%. They found that the mono-axial group was statistically better in surgical correction of the vertebral body height, but no statistical difference in loss of this correction.8 They found statistical differences in surgical correction of the local kyphotic angle preoperative and immediate post-operative (mono-axial group better). However, similarly to our study, the difference between both in late follow-up was insignificant.8 Differently from our sample, they did not use only type A (AOSpine) fractures.
Yao et al. evaluated 63 patients with open surgery and short-segment posterior fixation. They also used other types of fractures rather than type A (AOSpine) and found statistical differences in improving vertebral height and no difference in the correction of local kyphotic angle.10 Our sample is smaller (35 patients), but it is important to emphasize that we analyzed only A3 and A4 fractures. The studies that used open surgery had results that were most similar to the current study.8,10 We did not find another study with the same characteristics as ours (open surgery, short-segment posterior fixation, exclusively A3 and A4 fracture types).
Other authors studied different comparisons, such as Qin et al., who compared the exclusive use of poly-axial screws vs. the use of mono-axial screws in the adjacent vertebrae and poly-axial screws in the fractured vertebra, using the MIS technique. They found the monoaxial group statistically better than the polyaxial group in recovery of AVH ratio and restoration of Cobb angle.9 Liu et al. compared the efficiency of different pedicle screws designed in biomechanical studies. Poly-axial screws were found to have lower pedicle strain than mono-axial groups.14 Wang et al. did computer simulations showing that poly-axial screws are not as effective as mono-axial screws in the transmission of distraction to the anterior spine,13 in concordance with the findings of the current study.
Our analysis showed a higher reoperation rate in the poly-axial group (30%) vs. the mono-axial group (13.5%). The literature is variable regarding the reoperation rate.7,15
One limitation of this study is that the pre-operative Cobb angle between mono and poly groups was statistically different, which may have interfered with the results of local kyphotic angle correction. However, other studies with open surgery had similar results.8,10
Most of the studies do not mention a crucial part of surgical treatment: surgical positioning. If the patient is positioned on a bolster or lumbar frame, ligamentotaxis is limited. All our patients were positioned on a four-post (Hall type) frame, which allows for most of the correction regarding kyphosis and anterior vertebral body height. We hypothesize that our differences in comparing the use of mono-axial and poly-axial screws were relatively small because the surgical positioning as well as the reduction technique were similar for both groups.
The differences in anterior body height are due to the better lever arm of mono-axial systems and possible settling of the poly-axial screws at the stem-head junction, thus favoring the use of mono-axial screws, if possible and available, in thoracolumbar injuries amenable to ligamentotaxis (type A3 and A4 injuries).20
CONCLUSION
In the present study, surgical treatment using mono-axial screws was statistically superior in maintaining/recovering the height of the anterior wall. There were no statistically significant differences in other variable studies.
Data Availability Statement
Data generated or analyzed during this study are included in this article. Further inquiries can be directed to the corresponding author.
Statement of Ethics
The study was conducted ethically according to the World Medical Association Declaration of Helsinki and followed the ICMJE Recommendations for the Protection of Research Participants. The Ethics Committee of Hospital Universitário Cajuru approved this study (approval CAAE=02583312420010066). All patients’ identifications were removed to preserve anonymity.
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Study conducted by the Hospital Universitário Cajuru, PUC-PR, Curitiba, Brazil.
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Funding SourcesThis research received technical support from AOSpine Latin America for data storage and statistical analysis.
REFERENCES
-
1 Wood KB, Li W, Lebl DR, Ploumis A. Management of thoracolumbar spine fractures. Spine J. 2014;14(1):145-64. doi: 10.1016/j.spinee.2012.10.041.
» https://doi.org/10.1016/j.spinee.2012.10.041. -
2 Jansson K A, Blomqvist P, Svedmark P. Thoracolumbar vertebral fractures in Sweden: an analysis of 13,496 patients admitted to hospital. Eur J Epidemiol. 2010;25(6):431-7. doi: 10.1007/s10654-010-9461-5.
» https://doi.org/10.1007/s10654-010-9461-5. -
3 Vialle EN, Falavigna A, Arruda AO, Guasque JBCR, Pinto BMO, Finger G, et al. “Treatment for AOSpine Type A3 and A4 thoracolumbar fractures without neurological deficit: Prospective Observational Cohort Study. Rev Bras Ortop. 2023;58(1):42-7. doi: 10.1055/s-0042-1749622.
» https://doi.org/10.1055/s-0042-1749622. -
4 Siebenga J, Leferink VJ, Segers MJ, Elzinga MJ, Bakker FC, Haarman HJTM, et al. Treatment of traumatic thoracolumbar spine fractures: a multicenter prospective randomized study of operative versus nonsurgical treatment. Spine. 2006;31(25):2881-90. doi: 10.1097/01.brs.0000247804.91869.1e.
» https://doi.org/10.1097/01.brs.0000247804.91869.1e. -
5 Joaquim AF, Patel AA, Schroeder GD, Vaccaro AR. A simplified treatment algorithm for treating thoracic and lumbar spine trauma. J Spinal Cord Med. 2019;42(4):416-22. doi: 10.1080/10790268.2018.1433267.
» https://doi.org/10.1080/10790268.2018.1433267. -
6 Chung WH, Eu WC, Chiu CK, Chan CYW, Kwan MK. Minimally invasive reduction of thoracolumbar burst fracture using mono-axial percutaneous pedicle screws: Surgical technique and report of radiological outcome. J Orthop Surg. 2019;28(1):2309499019888977. doi: 10.1177/2309499019888977.
» https://doi.org/10.1177/2309499019888977. -
7 Shim JH, Seo EM. Efficacy and Radiographic Analysis of Minimally Invasive Posterior Mono-Axial Pedicle Screw Fixation in Treating Thoracolumbar Burst Fractures. J Clin Med. 2022;11(3):516. doi: 10.3390/jcm11030516.
» https://doi.org/10.3390/jcm11030516. -
8 Arbash MA, Parambathkandi AM, Baco AM, Alhammoud A. Impact of Screw Type on Kyphotic Deformity Correction after Spine Fracture Fixation: Cannulated versus Solid Pedicle Screw. Asian Spine J. 2018;12(6):1053-9. doi: 10.31616/asj.2018.12.6.1053.
» https://doi.org/10.31616/asj.2018.12.6.1053. -
9 Qin W, Chen K, Chen H, Yang P, Yang H, Mao H. Comparison of Poly-axial or Poly/Mono-axial Mixed Screw Fixation for Treatment of Thoracolumbar Fractures with O-Arm Navigation: A Case-Control Study. World Neurosurg. 2020;138:e10-6. doi: 10.1016/j.wneu.2020.01.123.
» https://doi.org/10.1016/j.wneu.2020.01.123. -
10 Yao W, Zhou T, Huang K, Dai M, Mo F, Xu J, et al. A comparison of mono-axial pedicle screw versus poly-axial pedicle screw in short-segment posterior fixation for the treatment of thoracolumbar fractured vertebra. Ann Transl Med. 2021;9(8):669. doi: 10.21037/atm-21-881.
» https://doi.org/10.21037/atm-21-881. -
11 Liu PY, Lai PL, Lin CL. A biomechanical investigation of different screw head designs for vertebral derotation in scoliosis surgery. Spine J. 2017;17(8):1171-9. doi: 10.1016/j.spinee.2017.04.010.
» https://doi.org/10.1016/j.spinee.2017.04.010. -
12 Fitschen-Oestern S, Scheuerlein F, Weuster M, Klueter T, Menzdorf L, Varoga D, et al. Reduction and retention of thoracolumbar fractures by minimally invasive stabilization versus open posterior instrumentation. Injury. 2015;46(Suppl 4):S63-70. doi: 10.1016/S0020-1383(15)30020-6.
» https://doi.org/10.1016/S0020-1383(15)30020-6. -
13 Wang H, Li C, Liu T, Zhao WD, Zhou Y. Biomechanical efficacy of mono-axial or poly-axial pedicle screw and additional screw insertion at the level of fracture, in lumbar burst fracture: An experimental study. Indian J Orthop. 2012;46(4):395-401. doi: 10.4103/0019-5413.98827.
» https://doi.org/10.4103/0019-5413.98827. -
14 Liu H, Wang H, Liu J, Li C, Zhou Y, Xiang L. Biomechanical comparison of posterior intermediate screw fixation techniques with hybrid mono-axial and poly-axial pedicle screws in the treatment of thoracolumbar burst fracture: a finite element study. J Orthop Surg Res. 2019;14(1):122. doi: 10.1186/s13018-019-1149.
» https://doi.org/10.1186/s13018-019-1149. -
15 Yin N, Du L, Pan M, Xue F, Shen Y, Ding L. Minimally invasive technique of mono-axial percutaneous screws and instrumentation maneuvers in thoracolumbar and lumbar fractures. Injury. 2022;53(12):4028-32. doi: 10.1016/j.injury.2022.09.019.
» https://doi.org/10.1016/j.injury.2022.09.019. -
16 Kuklo RT, Bono CM, Dimar JR, Rauschning WE, Vaccaro AR, Spine Trauma Study Group. Radiographic Measurement Manual, Medtronic Sofamor Danek USA, Inc. 2006. Available at: https://www.srs.org/Files/Research/Manuals-and-Publications/sdsg-radiographic-measuremnt-manual.pdf
» https://www.srs.org/Files/Research/Manuals-and-Publications/sdsg-radiographic-measuremnt-manual.pdf -
17 Wang H, Zhou Y, Li C, Liu J, Xiang L. Comparison of open versus percutaneous pedicle screw fixation using the sextant system in the treatment of traumatic thoracolumbar fractures. Clin Spine Surg. 2017;30(3):e239-6. doi: 10.1097/BSD.0000000000000135.
» https://doi.org/10.1097/BSD.0000000000000135. -
18 McAnany SJ, Overley SC, Kim JS, Baird EO, Qureshi SA, Anderson PA. Open versus minimally invasive fixation techniques for thoracolumbar trauma: a meta-analysis. Global Spine J. 2016;6(2):186-94. doi: 10.1055/s-0035-1554777.
» https://doi.org/10.1055/s-0035-1554777. -
19 Guven O, Kocaoglu B, Bezer M, Aydin N, Nalbantoglu U. The use of screw at the fracture level in the treatment of thoracolumbar burst fractures. J Spinal Disord Tech. 2009;22(6):417-21. doi: 10.1097/BSD.0b013e3181870385.
» https://doi.org/10.1097/BSD.0b013e3181870385. -
20 Whang PG, Vaccaro AR. Thoracolumbar fracture: posterior instrumentation using distraction and ligamentotaxis reduction. J Am Acad Orthop Surg. 2007;15(11):695-701. doi: 10.5435/00124635-200711000-00008.
» https://doi.org/10.5435/00124635-200711000-00008.
