Biomechanical effects of polyaxial pedicle screw fixation on the lumbosacral segments with an anterior interbody cage support

BACKGROUND: Lumbosacral fusion is a relatively common procedure that is used in the management of an unstable spine. The anterior interbody cage has been involved to enhance the stability of a pedicle screw construct used at the lumbosacral junction. Biomechanical differences between polyaxial and monoaxial pedicle screws linked with various rod contours were investigated to analyze the respective effects on overall construct stiffness, cage strain, rod strain, and contact ratios at the vertebra-cage junction. METHODS: A synthetic model composed of two ultrahigh molecular weight polyethylene blocks was used with four titanium pedicle screws (two in each block) and two rods fixation to build the spinal construct along with an anterior interbody cage support. For each pair of the construct fixed with polyaxial or monoaxial screws, the linked rods were set at four configurations to simulate 0°, 7°, 14°, and 21° lordosis on the sagittal plane, and a compressive load of 300 N was applied. Strain gauges were attached to the posterior surface of the cage and to the central area of the left connecting rod. Also, the contact area between the block and the cage was measured using prescale Fuji super low pressure film for compression, flexion, lateral bending and torsion tests. RESULTS: Our main findings in the experiments with an anterior interbody cage support are as follows: 1) large segmental lordosis can decrease the stiffness of monoaxial pedicle screws constructs; 2) polyaxial screws rather than monoaxial screws combined with the cage fixation provide higher compression and flexion stiffness in 21° segmental lordosis; 3) polyaxial screws enhance the contact surface of the cage in 21° segmental lordosis. CONCLUSION: Polyaxial screws system used in conjunction with anterior cage support yields higher contact ratio, compression and flexion stiffness of spinal constructs than monoaxial screws system does in the same model when the spinal segment is set at large lordotic angles. Polyaxial pedicle screw fixation performs nearly equal percentages of vertebra-cage contact among all constructs with different sagittal alignments, therefore enhances the stabilization effect of interbody cages in the lumbosacral area

Evaluation of the function and quality of life of patients submitted to girdlestone's resection arthroplasty

OBJECTIVES: To evaluate function and quality of life of patients submitted to Girdlestone's arthroplasty, and to compare outcomes between unilateral Girdlestone's group with the group with contralateral total hip prosthesis. METHODS: Cross-sectional study where 9 patients were evaluated with unilateral Girdlestone's and 3 with Girdlestone's in one hip and contralateral total hip prosthesis. The evaluation consisted in filling in a generic questionnaire on quality of life SF-36 and a specific questionnaire for hip function Harris Hip Score (HHS). The comparison between groups was made by using the Student's t-test and the Fisher's test. RESULTS: The patients of the unilateral Girdlestone's group presented a higher number of SF-36 domains classified as high, although 77.8% of these showed poor results on the HHS. All patients had a leg-length discrepancy and positive Trendelenburg's test, which led to limping gait in 11 of 12 patients evaluated. Of these, only 6 underwent physiotherapy after surgery. CONCLUSION: Girdlestone's postoperative quality of life and function in a Brazilian population still requires further studies, because these outcomes are indicative of study variables' behavior and cannot be regarded as definite.OBJETIVOS: Avaliar a função e a qualidade de vida dos pacientes pós-artroplastia de Girdlestone e comparar os resultados entre os grupos Girdlestone unilateral e o grupo com prótese total de quadril contralateral. MÉTODOS: estudo transversal no qual foram avaliados 9 pacientes com Girdlestone unilateral e 3 com Girdlestone em um quadril e prótese total no quadril contralateral. A avaliação constitui-se em aplicar o questionário genérico de qualidade de vida SF-36 e um questionário funcional específico para o quadril, Harris Hip Score (HHS). A comparação dos grupos foi realizada usando-se o teste t- Student e o teste de Fisher. RESULTADOS: Os pacientes do grupo Girdlestone unilateral apresentaram maior quantidade de domínios do SF-36 classificados como elevados, embora 77,8% destes tenham obtido resultados ruins no HHS. Todos os pacientes apresentaram o teste de Trendelenburg positivo e discrepância de membros, o que levou à marcha claudicante em 11 dos 12 pacientes avaliados. Destes, apenas 6 submeteram-se a fisioterapia pós-operatória. CONCLUSÃO: A qualidade de vida e a função pós-operatória de Girdlestone, na população brasileira, ainda necessita ser mais pesquisada, pois estes resultados são indicações do comportamento das variáveis de estudo e não podem ser consideradas encerradas.Universidade Federal de São Paulo (UNIFESP) Escola Paulista de Medicina Departamento de Ortopedia e TraumatologiaUNIFESP-EPM DOTUNIFESP, EPM, Depto. de Ortopedia e TraumatologiaUNIFESP, EPM DOTSciEL

Critical Early Roles for col27a1a and col27a1b in Zebrafish Notochord Morphogenesis, Vertebral Mineralization and Post-embryonic Axial Growth

Fibrillar collagens are well known for their links to human diseases, with which all have been associated except for the two most recently identified fibrillar collagens, type XXIV collagen and type XXVII collagen. To assess functions and potential disease phenotypes of type XXVII collagen, we examined its roles in zebrafish embryonic and post-embryonic development.We identified two type XXVII collagen genes in zebrafish, col27a1a and col27a1b. Both col27a1a and col27a1b were expressed in notochord and cartilage in the embryo and early larva. To determine sites of type XXVII collagen function, col27a1a and col27a1b were knocked down using morpholino antisense oligonucleotides. Knockdown of col27a1a singly or in conjunction with col27a1b resulted in curvature of the notochord at early stages and formation of scoliotic curves as well as dysmorphic vertebrae at later stages. These defects were accompanied by abnormal distributions of cells and protein localization in the notochord, as visualized by transmission electron microscopy, as well as delayed vertebral mineralization as detected histologically.Together, our findings indicate a key role for type XXVII collagen in notochord morphogenesis and axial skeletogenesis and suggest a possible human disease phenotype

Metastatic epidural spinal cord compression: current concepts and treatment

Metastatic epidural spinal cord compression (MESCC) is a medical emergency complicating the course of 5–10% of patients with cancer [1]. When diagnosis and treatment is early with the patient ambulatory prognosis for continued ambulation is good [2]. If the patient is nonambulatory or paraplegic, prognosis for meaningful recovery of motor and bladder function is markedly decreased. In the last decade, significant advances in the understanding, management and treatment of metastatic epidural spinal cord compression have occurred.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45378/1/11060_2005_Article_BF01051052.pd