RESUMO
Basilar invagination (BI) is a common deformity. This study aimed to quantitatively evaluate the height of clivus and atlanto-occipital lateral mass (LM) in patients with BI with or without atlas occipitalization (AOZ). We evaluated 166 images of patients with BI and of controls. Seventy-one participants were control subjects (group A), 68 had BI with AOZ (group B), and 27 had BI without AOZ (group C). Parameters were defined and measured for comparisons across the groups. Multiple linear regression analysis was used to test the relationship between Chamberlain's line violation (CLV) and the clivus height ratio or atlanto-occipital LM height. Based on the degree of AOZ, the lateral masses in group B were classified as follows: segmentation, incomplete AOZ, complete AOZ. From groups A to C, there was a decreasing trend in the clivus height and clivus height ratio. There was a linear negative correlation between the clivus height ratio and CLV in the three groups. Generally, the atlanto-occipital LM height followed the order of group B < group C < group A. The atlanto-occipital LM height was included only in the equations of groups B. There were no cases of atlantoaxial dislocation (AAD) in group C. There was a decreasing trend in LM height from the segmentation type to the complete AOZ type in group B. BI can be divided into three categories: AOZ causes LM height loss; Clivus height loss; Both clivus and LM height loss. The clivus height ratio was found to play a decisive role in both controls and BI group, while the atlanto-occipital LM height loss caused by AOZ could be a secondary factor in patients with BI and AOZ. AOZ may be a necessary factor for AAD in patients with congenital BI. The degree of AOZ is associated with LM height in group B.
Assuntos
Articulação Atlantoccipital , Fossa Craniana Posterior , Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Adulto Jovem , Adolescente , Atlas Cervical/diagnóstico por imagem , Imageamento por Ressonância Magnética , Idoso , Criança , Tomografia Computadorizada por Raios XRESUMO
BACKGROUND: Basilar invagination (BI) combined with atlantoaxial dislocation (AAD) leads to foramen magnum stenosis and medullary spinal cord compression, causing nerve dysfunction. The purpose of the surgery is to remove the bony compression at brainstem ventral side and fix the unstable spinal segment and make it fused stably. Occipital cervical internal fixation system that simultaneously reduces atlantoaxial horizontal and vertical dislocation are established. We propose here a new compression-distraction reduction (CDR) technique. We aimed to construct a congenital BI-AAD preoperative finite element model (FEM) to simulate the CDR technique for AAD reduction surgery. METHODS: Based on computed tomographic scans of patients' cervical vertebrae, a three-dimensional (3D) geometric model of the cervical spine (C0-C4) of congenital BI-AAD patients was established using Mimics13.1, Geomagic2012, and Space Claim14.0 softwares. The mechanical parameters of the tissues were assigned according to their material characteristics using ANSYS Workbench 14.0 software. A 3D FEM was established using the tetrahedral mesh method. The bending moment was loaded on C0. Physiological conditions-anteflexion, retroflexion, left and right flexion, left and right rotation-were simulated for preoperative verification. The occipital cervical fixation system FEM was established. The CDR technique was simulated to perform AAD reduction surgery. Data were obtained when the atlantoaxial horizontal and vertical dislocation reductions were verified postoperatively. Stress data for the two surgical schemes were analyzed, as was the reduction surgery optimization scheme for congenital BI-AAD patients with abnormal lateral atlantoaxial articulation ossification. RESULTS: Cervical spine (C0-C4) FEM of congenital BI-AAD patients was established. The CDR technique was simulated for AAD reduction. We obtained the mechanical data when the atlantoaxial horizontal and vertical dislocation reductions were satisfied for the two surgical schemes. CONCLUSIONS: The CDR technique for AAD reduction was feasible and effective. We propose this reduction optimization scheme for patients with lateral atlantoaxial articulation due to abnormal ossification of congenital BI-AAD. We also provide a biomechanically theoretical basis for improving the reliability of pure posterior reduction surgery and simplifying surgery for complicated BI-AAD disease.
Assuntos
Articulação Atlantoaxial/fisiopatologia , Vértebras Cervicais/fisiopatologia , Luxações Articulares/fisiopatologia , Força Compressiva , Simulação por Computador , Desenho de Equipamento , Análise de Elementos Finitos , Humanos , Imageamento Tridimensional , Reprodutibilidade dos Testes , Software , Fusão Vertebral/métodos , Tomografia Computadorizada por Raios XRESUMO
OBJECTIVE: Congenital basilar invagination (BI) is a craniocervical deformity marked by odontoid prolapse into the skull base. The foramen magnum angle (FMA), which is formed by the Chamberlain's line and McRae's line, has not been fully studied. The study aimed to investigate the FMA and its relationship with other craniocervical parameters. METHODS: Participants were divided into control, type A BI, and type B BI groups. Parameters included Chamberlain line violation, atlantodental interval, clivus height, clivus anteroposterior dimension, FMA, basal angle, clivo-axial angle, head and neck flexion angle, Boogard's angle, and subaxial cervical spine lordosis angle. A comparison of these parameters among the 3 groups and correlation analysis between FMA and other parameters were performed. The significance level was set at P < 0.05. RESULTS: A total of 111 controls, 111 type A BI patients, and 62 type B BI patients were enrolled. The FMAs in the control, type A BI, and type B BI groups were 6.21° (3.67°, 8.71°), 22.16° ± 6.61°, and 22.39° (17.27°, 31.08°), respectively. Correlation analysis revealed correlations between the FMA and other variables. In the 2 BI subgroups, FMA was significantly correlated with Chamberlain line violation, clivus height, clivus anteroposterior dimension, basal angle, clivo-axial angle, and Boogard's angle. CONCLUSIONS: The FMA in patients with BI was approximately 22° and approximately 6° in controls, indicating that the foramen magnum in BI had a greater tilt. As a pathological condition, FMA can reflect the degree of BI. Clivus hypogenesis is a reason for the excessive tilt of the FM.
Assuntos
Lordose , Platibasia , Vértebras Cervicais/patologia , Fossa Craniana Posterior/diagnóstico por imagem , Fossa Craniana Posterior/patologia , Forame Magno/diagnóstico por imagem , Forame Magno/patologia , Humanos , Lordose/patologia , Platibasia/diagnóstico por imagem , Platibasia/patologia , Platibasia/cirurgiaRESUMO
Pathologies of the lateral masses could lead to bone destruction of the cervical spine. Their treatment includes lesion resection and fixation. However, the resulting bone defect of a lateral mass is often neglected, resulting in difficulty in bone fusion. Therefore, we designed a subaxial lateral mass prosthesis to achieve lateral mass joint fusion. This study aims to evaluate the role of a new subaxial lateral mass prosthesis using finite element analysis. Five finite element models (intact, lateral mass resection, screw-rod fixation, prosthesis implantation, and prosthesis fusion groups) were compared in terms of the range of motion (ROM), prosthesis von Mises stress, and screw-rod von Mises stress during flexion, extension, lateral bending, and rotation. The ROM of the model increased significantly after lateral mass resection, and was significantly reduced after fixation with screws and rods. Screw-rod fixation combined with prosthesis implantation further reduced the ROM. After bone fusion in the prosthesis, the ROM can also be reduced slightly. The von Mises stress of the bilateral screws and rods significantly decreased after prosthesis implantation. The von Mises stress of the prosthesis further decreased during the right bending after bone fusion was achieved. Subaxial lateral mass prosthesis can help restore the stability of the cervical spine after lateral mass resection and can reduce the stress on the bilateral screws and rods. Reconstruction of a lateral mass is more consistent with the mechanical transmission of the three-column spine and contributes to interfacet fusion of the lateral mass joint.
Assuntos
Parafusos Pediculares , Fusão Vertebral , Análise de Elementos Finitos , Fusão Vertebral/métodos , Fenômenos Biomecânicos , Parafusos Ósseos , Vértebras Cervicais/diagnóstico por imagem , Vértebras Cervicais/cirurgia , Amplitude de Movimento ArticularRESUMO
BACKGROUND: The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks. OBJECTIVE: To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach. METHODS: A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements. RESULTS: The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion. CONCLUSION: Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.
Assuntos
Articulação Atlantoaxial , Luxações Articulares , Platibasia , Fusão Vertebral , Articulação Atlantoaxial/diagnóstico por imagem , Articulação Atlantoaxial/cirurgia , Humanos , Luxações Articulares/diagnóstico por imagem , Luxações Articulares/cirurgia , Platibasia/complicações , Platibasia/diagnóstico por imagem , Platibasia/cirurgia , Estudos RetrospectivosRESUMO
OBJECTIVE: This study evaluated the feasibility and efficacy of quantitative reduction and fixation to treat basilar invagination (BI) with atlantoaxial dislocation (AAD). METHODS: Posterior occipitocervical angle (POCA), occiput-C2 angle (Oc-C2A), clivusaxial angle (CAA), and C2-7 angle (C2-7A) were considered for quantitative reduction. Twelve patients with BI complicated with AAD received posterior interarticular release and individualized cage implantation to restore vertical dislocation. The POCA was adjusted using cantilever technology to further reduce the horizontal dislocation and adjust lower cervical vertebral angle. All patients received a radiological follow-up for ≥12 months. Improvements in spinal cord function were evaluated using Japanese Orthopedic Association (JOA) score. RESULTS: All the patients received successful quantitative reduction for BI-AAD, and bony fusion was achieved without spinal cord injury after surgery for 12 months. The JOA score was improved significantly to 15.2 ± 0.9 twelve months after surgery (p < 0.01). Radiological follow-up revealed that individualized cage and POCA play vital roles in quantitative correction: (1) distance of the dens above McRae's line and atlantodens interval were restored to normal level, respectively; (2) changes in Oc-C2 angle (ΔOc-C2A), C2-7 angle (ΔC2-7A), clivus-axial angle (ΔCAA), and POCA (ΔPOCA) were all caused by changes in axis tilt. Based on the changes of radiological parameter we deduced the formula for quantitative reduction by linear regression analysis: -ΔPOCA = ΔOc-C2A = -ΔC2-7A = ΔCAA. CONCLUSION: Quantitative posterior reduction by individualized cage and adjusting ΔPOCA is feasible for treating BI with AAD.
RESUMO
Three-dimensional visualization is opening new worlds for more precise diagnosis and higher-quality treatment. 3D reconstruction from medical images is widely used in diagnosis and medical research. This paper focuses on 3D surface reconstruction of the pelvis from CT images on a personal computer. We measure and analyze large numbers of interrelated parameters in order to help doctor in diagnosis, operation planning and the actual surgery.