Implicit Dynamic Analysis on Tightening Procedure of Cancellous Lag Screw Placement / 医用生物力学

Objective To simulate the tightening procedure of a cancellous lag screw by using the implicit dynamic analysis method, and to evaluate the stress distributions on the screw-bone interface. Methods Finite element models of a lag screw with the surrounding bone were developed, and the implicit solver was set up for implicit dynamic analysis on the tightening procedure of the lag screw. The mechanical properties of the screw-bone interface were also analyzed according to strain and stress distributions on the screw and the surrounding bone. Results The stress of the lag screw was mainly distributed in the proximal portion of the screw thread rod. The high-stress region of the bone around the screw was located outside the outer edge of the screw, and it was approximately equal to the depth of the thread. The area of high-stress distributions on the bone was the main region that resisted screw stripping. Conclusions The method of implicit dynamic analysis can accurately simulate the mechanical properties of the screw-bone interface during screw tightening. The discovery of high-stress distributions on the surrounding bone can help researchers to further understand and improve the stability of screw insertion.

Epidemiological Features of Patients with Subdural Hygroma in a Prospective Case Series

Purpose To compare the efficacy and safety of the percutaneous screw fixation (PSF) and the open pedicle screw fixation (OPSF) on thoracolumbar (TL) fracture. Methods Sixty-four adult patients with TL vertebral fractures who underwent open or percutaneous posterior short-segment transpedicular screw fixation between January of 2013 and September of 2015 were retrospectively reviewed. All patients underwent clinical, radiological and quality of life follow-up for at least 18 months. Results There was no significant difference in age, gender, time between injury and surgery, and preoperative percentage of anterior column height, preoperative sagittal regional Cobb angle, or kyphotic angle of fractured vertebra between these two groups (p > 0.05). There was significantly less intraoperative blood loss in the PSF (87.6 24.6 mL) than in the OPSF group (271.4 142.6 mL) (p < 0.05). The mean surgery time was 62 minutes (range 42­130 minutes) for open and 58 minutes (range 35 to 128 minutes) for percutaneous screw fixation. The surgery time was shorter in the PSF group, but with no statistical significance (p > 0.05). The mean Oswestry disability index (ODI) scores after 18-months were 23.12 8.2 for the PSF and 24.12 9.2 for the OPSF group, without any statistical significance (p > 0.05). Conclusion Both open and percutaneous screw fixations are safe and effective. The percutaneous techniques significantly reduced the intraoperative blood loss compared with the open techniques.

Objetivo Comparar a eficácia e segurança das técnicas de fixação convencional e percutânea para fraturas toracolombares. Métodos Sessenta e quatro pacientes adultos com fraturas da transição toracolombar que foram submetidos a fixação pedicular curta por técnicas aberta convencional e percutânea entre janeiro de 2013 e setembro de 2015 foram retrospectivamente avaliados. Todos foram submetidos a avaliação clínica, radiológica e de qualidade de vida com no mínimo 18 meses do seguimento. Resultados Não houve diferença significativa na idade, sexo, tempo entre o trauma e o tratamento, porcentagem da redução da altura do corpo vertebral pré-operatório, angulo de Cob sagital na região da fratura, ou ângulo de de cifose da vértebra fraturada entre os dois grupos (p > 0,05). Houve uma menor perda sanguínea no grupo percutâneo (87,6 24,6 mL) em comparação com a técnica convencional (271,4 142,6 mL) (p < 0,05). O tempo médio da cirurgia foi 62 minutos (42 - 130 minutos) para a técnica convencional e 58 minutos (35 - 128 minutos) para a percutânea. Apesar de mais curto na técnica percutânea, não houve diferença estatisticamente significante no tempo cirúrgico entre os dois grupos (p > 0,05). Em relação ao índice de incapacidade de Oswestry após 18 meses do tratamento cirúrgico, também não houve diferença significante do ponto de vista estatístico entre os dois grupos, sendo 23,12 8,2 para a técnica percutânea e 24,12 9,2 para o grupo da técnica convencional (p > 0,05). Conclusão Ambas as técnicas mostraram-se eficazes e seguras para o tratamento de fraturas da transição toracolombar. A técnica percutânea apresentou uma taxa de perda sanguínea significativamente menor em comparação à técnica aberta convencional.

Open vs. Percutaneous Pedicle Screw Insertion for Thoracolumbar Traumatic A3 and A4 AO Fractures - 18-Months Follow-Up

Purpose To compare the efficacy and safety of the percutaneous screw fixation (PSF) and the open pedicle screw fixation (OPSF) on thoracolumbar (TL) fracture. Methods Sixty-four adult patients with TL vertebral fractures who underwent open or percutaneous posterior short-segment transpedicular screw fixation between January of 2013 and September of 2015 were retrospectively reviewed. All patients underwent clinical, radiological and quality of life follow-up for at least 18 months. Results There was no significant difference in age, gender, time between injury and surgery, and preoperative percentage of anterior column height, preoperative sagittal regional Cobb angle, or kyphotic angle of fractured vertebra between these two groups (p > 0.05). There was significantly less intraoperative blood loss in the PSF (87.6 24.6 mL) than in the OPSF group (271.4 142.6 mL) (p < 0.05). The mean surgery time was 62 minutes (range 42­130 minutes) for open and 58 minutes (range 35 to 128 minutes) for percutaneous screw fixation. The surgery time was shorter in the PSF group, but with no statistical significance (p > 0.05). The mean Oswestry disability index (ODI) scores after 18-months were 23.12 8.2 for the PSF and 24.12 9.2 for the OPSF group, without any statistical significance (p > 0.05). Conclusion Both open and percutaneous screw fixations are safe and effective. The percutaneous techniques significantly reduced the intraoperative blood loss compared with the open techniques.

Objetivo Comparar a eficácia e segurança das técnicas de fixação convencional e percutânea para fraturas toracolombares. Métodos Sessenta e quatro pacientes adultos com fraturas da transição toracolombar que foram submetidos a fixação pedicular curta por técnicas aberta convencional e percutânea entre janeiro de 2013 e setembro de 2015 foram retrospectivamente avaliados. Todos foram submetidos a avaliação clínica, radiológica e de qualidade de vida com no mínimo 18 meses do seguimento. Resultados Não houve diferença significativa na idade, sexo, tempo entre o trauma e o tratamento, porcentagem da redução da altura do corpo vertebral pré-operatório, angulo de Cob sagital na região da fratura, ou ângulo de de cifose da vértebra fraturada entre os dois grupos (p > 0,05). Houve uma menor perda sanguínea no grupo percutâneo (87,6 24,6 mL) em comparação com a técnica convencional (271,4 142,6 mL) (p < 0,05). O tempo médio da cirurgia foi 62 minutos (42 - 130 minutos) para a técnica convencional e 58 minutos (35 - 128 minutos) para a percutânea. Apesar de mais curto na técnica percutânea, não houve diferença estatisticamente significante no tempo cirúrgico entre os dois grupos (p > 0,05). Em relação ao índice de incapacidade de Oswestry após 18 meses do tratamento cirúrgico, também não houve diferença significante do ponto de vista estatístico entre os dois grupos, sendo 23,12 8,2 para a técnica percutânea e 24,12 9,2 para o grupo da técnica convencional (p > 0,05). Conclusão Ambas as técnicas mostraram-se eficazes e seguras para o tratamento de fraturas da transição toracolombar. A técnica percutânea apresentou uma taxa de perda sanguínea significativamente menor em comparação à técnica aberta convencional.

Pedicle Screw Instrumentation for Adolescent Idiopathic Scoliosis: The Insertion Technique, the Fusion Levels and Direct Vertebral Rotation

The pedicle is a power nucleus of the vertebra and offers a secure grip of all 3 columns. Pedicle screw instrumentation has advantages of rigid fixation with improved three-dimensional (3D) correction and it is accepted as a reliable method with a high margin of safety. Accurate placement of the pedicle screws is important to reduce possible irreversible complications. Many methods of screw insertion have been reported. The author has been using the K-wire method coupled with the intraoperative single posteroanterior and lateral radiographs, which is the most safe, accurate and fast method. Identification of the curve patterns and determining the fusion levels are very important. The ideal classification of adolescent idiopathic scoliosis should address the all patterns, predict the extent of accurate fusion and have good inter/intraobserver reliability. My classification system matches with the ideal classification system, and it is simple and easy to learn; and my classification system has only 4 structural curve patterns and each curve has 2 types. Scoliosis is a 3D deformity; the coronal and sagittal curves can be corrected with rod rotation, and rotational deformity has to be corrected with direct vertebral rotation (DVR). Rod derotation and DVR are true methods of 3D deformity correction with shorter fusion and improved correction of both the fused and unfused curves, and this is accomplished using pedicle screw fixation. The direction of DVR is very important and it should be opposite to the direction of the rotational deformity of the vertebra. A rigid rod has to be used to prevent rod bend-out during the derotation and DVR.

Computed Tomographical Evaluation of C1-2 for Transarticular Posterior Screw Fixation / 대한정형외과학회잡지

PURPOSE: To avoid neurovascular injuries and to establish the ideal trajectory of screw insertion, a computed tomographical evaluation was conducted. MATERIALS AND METHODS: Twenty volunteers without cervical disease were employed for this study. Axial and oblique CT scans were selected for evaluation. Oblique CT scans were obtained in the direction of provisional screw insertion, starting from the junction of the lamina and the inferior articular facet of the axis and extending to the center of anterior tubercle of the atlas. In the axial and oblique reconstructed views, the screw length, the diameters of the medial and lateral cortexes of the isthmus, the vertical distance, and the angle of C1 were measured. RESULTS: The screw lengths averaged 37.6 mm (35.1-40.5 mm) in males and 37.2 mm (33.6-43.4 mm) in females. The diameters of the medial cortex of the isthmus were 4.3 mm (3.3-5.2 mm) in males and 4.0 mm (2.8-5.6 mm) in females. No measurement was statistically different between males and females. CONCLUSION: Due to individual variations of atlantoaxial anatomy, especially in terms of the size of cortical diameter of the isthmus, 3-D reconstruction CT is a useful tool for planning transarticular C1-2 screw insertion.