Pedicle Screws and Facet Violation - The importance of the Angle between the Facet and the Screw / Parafusos pediculares e violação facetária - A importância do ângulo entre a faceta e o parafuso

Abstract Objective To verify whether, regardless of the screw placement technique, there is a safe distance or angle in relation to the facets that can prevent violation of the facet joint when the screws are placed. Methods Retrospective, single, comparative, non-randomized center. We evaluated by axial computed tomography: the angle of the screw/rod in relation to the midline, the angle of the center of the facets in relation to the midline, the distance between the head of the screw/rod to the midline, and the distance from the center of the facets to the midline; the violation of the facet joint will be evaluated in a gradation of 0 to 2. Also will be measured the difference between the angle os the facets and the angle of the screws (Δ Angle) and, the difference between the facet distance and the screw distance (Δ Distance). Results A total of 212 patients and 397 facets were analyzed (196 on the left and 201 on the right). Of these, 303 were not violated (grade 0), corresponding to 76,32%, and 94 suffered some type of violation (grade 1 and 2), corresponding to 23,68%. The mean of Δ angle was 9.87° +/− 4.66° (grade 0), and of 3.77° +/− 4.93° in facets (grade 1 and 2) (p< 0.001), and the Δ mean distance in cases in which there was no violation was 0.94 arbitrary units (a.u.) +/− 0.39 a.u., while the Δ distance in G1 and G2 cases was 0.56 a.u. +/− 0.25 a.u. (p< 0.001). Conclusion The measurements of angle and distance between facet and screw can help in the placement of screws. These parameters can be used as safety measures with the most frequent use of surgical navigation techniques.

Resumo Objetivo Verificar se, independente da técnica de colocação do parafuso, há uma distância ou angulação segura em relação as facetas para que os parafusos sejam colocados de modo a evitar a violação da articulação facetária. Métodos Estudo retrospectivo, comparativo, não randomizado, em centro único. Foram avaliados em tomografia computadorizada axial: o ângulo do parafuso/barra em relação a linha média, o ângulo do centro das facetas em relação a linha média, a distância entre a cabeça do parafuso/barra até a linha média, e a distância do centro das facetas até a linha média; a violação da articulação facetária será avaliada em uma gradação de 0 a 2. Serão também calculados a diferença entre o ângulo do parafuso e ângulo da faceta (Δ Ångulo) e também a diferença entre a distância da faceta e a distância do parafuso (Δ Distância). Resultados Um total de 212 pacientes e 397 facetas foram analisados (196 do lado esquerdo e 201 do lado direito). Destes, 303 foram não violados (grau 0), correspondendo a 76,32%, e 94 sofreram algum tipo de violação (grau 1 e 2), correspondendo a 23,68%. A média do Δ ângulo foi de 9,87° +/− 4,66° (grau 0) e de 3,77° +/− 4,93° em facetas (grau 1 e 2) (p< 0.001), e o Δ distância médio nos casos em que não houve violação foi de 0,94 unidades aleatórias (u.a.) +/− 0,39 u.a., enquanto o Δ distância de casos G1 e G2 foi de 0,56 u.a. +/− 0,25 u.a. (p< 0.001). Conclusão As medidas de ângulo e distância entre faceta e parafuso, podem auxiliar na colocação de parafusos. Esses parâmetros podem ser utilizados como medidas de segurança com o uso mais frequentes das técnicas de navegação cirúrgica.

Quantifying the ranges of relative motions of the intervertebral discs and facet joints in the normal cervical spine.

Functional neck motion is achieved by the cervical segments with each composed of an intervertebral disc (IVD) and two facet joints (FJs). Using biplane fluoroscopic imaging, we investigated the ranges of motion (ROMs) of the three joints in the cervical spines (from C3 to C7) of eighteen asymptomatic subjects. Three functional neck motions were examined, including flexion-extension (FE), lateral bending (LB) and axial twisting (AT). Our measurements showed that the translations of both IVD and FJs primarily occurred in the sagittal plane during all neck motions, and the anteroposterior translations of IVDs were significantly smaller than those of the corresponding FJs (p < 0.05) at all segments. For example, the ranges of IVD and FJ anteroposterior translations at C3/4 were 2.7 ± 0.7 mm vs. 3.5 ± 1.1 mm in FE, 0.9 ± 0.5 mm vs. 4.6 ± 1.1 mm in LB, and 1.0 ± 0.5 mm vs. 3.1 ± 1.0 mm in AT. Furthermore, we introduced an IVD-FJ translation ratio, which represents the ratio of the IVD to FJ translational ROMs. In FE neck motion, the IVD-FJ anteroposterior translation ratios decreased from 0.81 ± 0.18 at C3 to 0.52 ± 0.19 at C3, indicating gradually increasing resistances of IVDs compared to FJs from the proximal to distal levels. In LB neck motion, the smallest IVD-FJ translation ratios (0.14 ± 0.09 and 0.43 ± 0.30) occurred at C4/5 for both anteroposterior and left-right translations. In AT neck motion, the largest IVD-FJ anteroposterior translation ratio (0.42 ± 0.21) occurred at C3/4, and was significantly different from those at C4/5 and C5/6 (p < 0.05). These data could be used as references for improving motion-preserving cervical treatment methods that aimed to achieve the normal ranges of translational motions of both IVD and FJs.

Improving Fluoroscopic Visualization for Lower Cervical Medial Branch Blocks with a Modified Swimmer's View: A Technical Report.

BACKGROUND: Neural blockade of the cervical medial branches is a validated procedure in the diagnosis and treatment of cervical zygapophyseal joint pain. Fluoroscopic visualization of the lower cervical medial branch target zones (CMBTZs) in lateral view is sometimes challenging or not possible due to the patient's shoulders obscuring the target. Large shoulders and short necks often exacerbate the problem. Clear visualization is critical to accuracy and safety. OBJECTIVE: We aim to describe a method for optimal fluoroscopic visualization of the lower CMBTZs using a modified swimmer's view. STUDY DESIGN: A technical report. SETTING: A private practice. METHODS: Discussion with accompanying fluoroscopic images of the cervical spine, focusing on the lateral aspects of the lower cervical articular pillars in both the traditional lateral view and modified swimmer's view. Four authors served as volunteers for undergoing fluoroscopic x-rays in both views. Visualization of each lower CMBTZ was attempted and stored. The most caudal, clearly visualized levels were compared in both views for each participant. RESULTS: Visualization of the lower CMBTZs can be successfully obtained with the modified swimmer's view and in select patients is superior to a lateral view. LIMITATIONS: A limitation to this study is the design as a technical report. A future prospective study is warranted. CONCLUSIONS: Modified swimmer's view can serve as a primary method of visualizing the lower CMBTZs or an alternate view when a lateral view is unable to clearly demonstrate target landmarks. This can improve the ease, accuracy, and safety of performing diagnostic cervical medial branch blocks (CMBBs). KEY WORDS: Swimmer's view, cervical medial branch block, facet joint, fluoroscopy.

Controlled medial branch anesthetic block in the diagnosis of chronic lumbar facet joint pain: the value of a three-month follow-up.

OBJECTIVES: To verify the incidence of facetary and low back pain after a controlled medial branch anesthetic block in a three-month follow-up and to verify the correlation between the positive results and the demographic variables. METHODS: Patients with chronic lumbar pain underwent a sham blockade (with a saline injection) and then a controlled medial branch block. Their symptoms were evaluated before and after the sham injection and after the real controlled medial branch block; the symptoms were reevaluated after one day and one week, as well as after one, two and three months using the visual analog scale. We searched for an association between the positive results and the demographic characteristics of the patients. RESULTS: A total of 104 controlled medial branch blocks were performed and 54 patients (52%) demonstrated >50% improvements in pain after the blockade. After three months, lumbar pain returned in only 18 individuals, with visual analogue scale scores >4. Therefore, these patients were diagnosed with chronic facet low back pain. The three-months of follow-up after the controlled medial branch block excluded 36 patients (67%) with false positive results. The results of the controlled medial branch block were not correlated to sex, age, pain duration or work disability but were correlated with patient age (p<0.05). CONCLUSION: Patient diagnosis with a controlled medial branch block proved to be effective but was not associated with any demographic variables. A three-month follow-up is required to avoid a high number of false positives.

Comparison of computed tomography and magnetic resonance imaging in the evaluation of facet tropism and facet arthrosis in degenerative cervical spondylolisthesis.

The aim of this study was to determine the reliability of magnetic resonance imaging (MRI) in the assessment of facet tropism and facet arthrosis of spondylolisthesis levels in degenerative cervical spondylolisthesis as compared to computed tomography (CT). The discrepancies in the interpretation of CT and MRI data in the evaluation of facet tropism and arthrosis have given rise to questions regarding the reliability of comparisons of the two techniques. Using a 4-point scale, 3 blinded readers independently graded the severity of facet tropism and facet arthrosis of 79 cervical facet joints on axial T2-weighted and sagittal T1 and T2-weighted turbo spin echo images as well as the corresponding axial CT scans. All results were subjected to the kappa coefficient statistic for strength of agreement. In the assessment of the severity of facet arthrosis, intermethod agreement (weighted κ) between CT scanning with a moderate inter-rater reliability (range κ = 0.43-0.57) and MRI with fair inter-rater reliability (range κ = 0.23-0.38) was 0.76 and 0.43 for the severity of facet tropism and facet arthrosis, respectively. Intra-rater reliability for the severity of facet arthrosis was moderate to substantial for CT and was moderate for MRI scans. Intra-rater reliability for the severity of facet tropism was substantial to very good for CT and substantial for MRI scans. MRI can reliably determine the presence or degree of facet tropism but not facet arthrosis. Therefore, for a comprehensive assessment of cervical facet joint degeneration, both a CT and an MRI scan should be performed.

In vivo cervical facet joint capsule deformation during flexion-extension.

STUDY DESIGN: Nonrandomized controlled cohort. OBJECTIVE: To characterize subaxial cervical facet joint kinematics and facet joint capsule (FJC) deformation during in vivo, dynamic flexion-extension. To assess the effect of single-level anterior arthrodesis on adjacent segment FJC deformation. SUMMARY OF BACKGROUND DATA: The cervical facet joint has been identified as the most common source of neck pain, and it is thought to play a role in chronic neck pain related to whiplash injury. Our current knowledge of cervical facet joint kinematics is based on cadaveric mechanical testing. METHODS: Fourteen asymptomatic controls and 9 C5-C6 arthrodesis patients performed full range of motion flexion-extension while biplane radiographs were collected at 30 Hz. A volumetric model-based tracking process determined 3-dimensional vertebral position with submillimeter accuracy. FJC fibers were modeled and grouped into anterior, lateral, posterior-lateral, posterior, and posterior-medial regions. FJC fiber deformations (total, shear, and compression-distraction) relative to the static position were determined for each cervical motion segment (C2-C3 through C6-C7) during flexion-extension. RESULTS: No significant differences in the rate of fiber deformation in flexion were identified among motion segments (P = 0.159); however, significant differences were observed among fiber regions (P < 0.001). Significant differences in the rate of fiber deformation in extension were identified among motion segments (P < 0.001) and among fiber regions (P = 0.001). The rate of FJC deformation in extension adjacent to the arthrodesis was 45% less than that in corresponding motion segments in control subjects (P = 0.001). CONCLUSION: In control subjects, FJC deformations are significantly different among vertebral levels and capsule regions when vertebrae are in an extended orientation. In a flexed orientation, FJC deformations are different only among capsule regions. Single-level anterior arthrodesis is associated with significantly less FJC deformation adjacent to the arthrodesis when the spine is in an extended orientation. LEVEL OF EVIDENCE: 4.

Comparative analysis of assessment of the craniocervical equilibrium through two methods: cephalometry of Rocabado and cervical range of motion.

UNLABELLED: There are several instruments of evaluation of the craniocervical equilibrium; the most reliable are the radiographies. This study used the cephalometric analysis of Rocabado to measure the sensibility and specificity of the Cervical Range of Motion (CROM), a goniometer designed to assess cervical movements in degrees, and measure the forward head position in centimeters. This instrument frequently used, has been tested as a reliable instrument to evaluate the cervical movements but not the forward head. The sample consisted of 30 volunteers, 18 females, 12 males, mean age of 24.63 years. All participants were evaluated with CROM and radiographies in the resting head position and in erect head position. The values considered by the cephalometry consisted in the angle made between the McGregor plane and the vertical line formed by the base of the odontoid process to its apex; the posterior space between C0-C1 and C1-C2 and the hyoid triangle. RESULTS: 30% of the subjects had forward head posture, according to de cephalometry of Rocabado (decreased space between C0-C1, C1-C2) and 43,3% according to CROM. 16,6% had decreased posterior-inferior angle, and 13% had the hyoid triangle facing up. ROC curve of identifying forward head posture yielded area under the curve of 0,778 (95% confidence interval 0,596-0,960). The sensibility of CROM was: 77%. The specificity 71%. CONCLUSION: This study suggests that CROM has a moderate sensibility and specificity, useful for clinic use, but not for research.