Biomecánica de la interfaz hueso-tornillo en instrumentación transpedicular de columna / Biomechanics of the bone-screw interface in transpedicular spinal instrumentation

Resumen: El aflojamiento de los implantes, la falla catastrófica de la interfaz hueso-tornillo, la migración de material y la pérdida de estabilidad de los componentes del ensamble de la fijación constituyen una seria complicación en la cirugía de columna de adultos. La contribución de la biomecánica se basa en la medición experimental y la simulación de las fijaciones transpediculares de columna. La trayectoria de inserción cortical mostró un incremento en la resistencia de la interfase tornillo-hueso respecto a la inserción pedicular tanto para fuerzas de tracción axiales al tornillo como en distribución de esfuerzos en la vértebra. Los tornillos de doble rosca tuvieron una resistencia similar a los pediculares estándar. Los tornillos de rosca parcial de cuatro filetes mostraron mejor resistencia a la fatiga en cuanto a mayor carga de rotura y número de ciclos para la falla. Los tornillos aumentados, ya sea con cemento o hidroxiapatita mejoraron también la resistencia a la fatiga en vértebras osteoporóticas. Las simulaciones de segmentos rígidos confirmaron la presencia de esfuerzos superiores en los discos intervertebrales que provocan el daño de los segmentos adyacentes. La parte posterior de las vértebras puede estar sometida a mayores esfuerzos, fundamentalmente en la superficie de la interfaz hueso-tornillo, por lo que son más susceptibles a la falla en esta región.

Abstract: Implant loosening, catastrophic failure of the bone-screw interface, material migration, and loss of stability of the fixation component assembly constitute a serious complication in adult spinal surgery. The contribution of biomechanics is based on experimental measurement and simulation of transpedicular spinal fixations. The cortical insertion trajectory showed an increase in the resistance of the screw-bone interface with respect to the pedicle insertion trajectory, both for axial traction forces to the screw and for stress distribution in the vertebra. The double-threaded screws and standard pedicle screws had similar strength. Partially threaded screws with four-thread showed better resistance to fatigue in terms of a higher failure load and number of cycles to fail. Cement or hydroxyapatite augmented screws with also showed a better fatigue resistance in osteoporotic vertebrae. Rigid segment simulations confirmed the presence of higher stresses on the intervertebral discs causing damage to adjacent segments. The posterior body of the vertebra may be subjected to high stresses, in the bone-screw interface, being this bone region more susceptible to failure.

Research on Self-tapping Performance Test of Self-tapping Bone Screws / 中国医疗器械杂志

OBJECTIVE@#To study the self-tapping performance test method of self-tapping bone screws based on the YY/T 1505 standard.@*METHODS@#With reference to the method of YY/T 1505, various factors affecting the self-tapping force test was optimised, and the self-tapping force judgment method was improved.@*RESULTS@#The experimental results showed that the self-tapping force obtained by the improved self-tapping force judgment method has good repeatability and high stability of the experimental data. At the same time, the test results of other influencing factors indicated that the manufacturer should fully consider the test material and the size of the pre-drilled hole.@*CONCLUSIONS@#An improved method for judging the self-tapping force is helpful for the repeatability and stability of the test data. This study has certain significance referring to the self-tapping performance test of self-tapping bone screws.

Long-term follow-up of ais treated surgically with pedicular screws / Seguimiento a largo plazo de eia intervenida quirúrgicamente con tornillos pediculares / Acompanhamento a longo prazo de eia tratada cirurgicamente com parafusos peduculares

ABSTRACT Objective: In the last three decades, there have been great advances in the surgical treatment of adolescent idiopathic scoliosis. There are few studies that focus on the long-term clinical and radiographic results of AIS operated on with pedicle screws that also consider psychological repercussions. Methods: We conducted an observational longitudinal study. We reviewed the AIS cases that were operated on with pedicle screws in our center between January 2009 and December 2010. We conducted follow-up until July 2019. A short questionnaire was administered to assess patient satisfaction and the long-term impact from both psychological and functional points of view. Results: A total of 19 patients met the inclusion criteria. The mean preoperative Cobb was 58°, the postoperative was 23° and at the end of follow-up it was 26°. No major complications were reported. Ninety percent were very satisfied with the overall results of the surgery. Ninety-five percent had no limitation for sports or daily activities and 90% were satisfied with the cosmetic results. Conclusion: The short- and long-term radiographic evolution in patients treated with third generation material presented good clinical results. In 3 cases (16%) loss of correction greater than 10% was reported. The overall satisfaction index and cosmetic results were very good at the end of follow-up despite the low correction rate (60%). There were no major complications and the incidence of functional limitation and pain at the end of the follow-up was very low. Level of evidence IV; Review article.

RESUMO Objetivo: Nas últimas três décadas houve grandes avanços no tratamento cirúrgico da escoliose idiopática do adolescente. Existem poucos trabalhos que estudam os resultados clínicos e radiográficos a longo prazo de EIA, tratados cirurgicamente com parafusos pediculares que também considerem a repercussão psicológica. Métodos: Realizamos um estudo longitudinal observacional. Analisamos a EIA de pacientes operados entre janeiro de 2009 e dezembro de 2010 que receberam parafusos pediculares em nosso centro. Realizamos o acompanhamento até julho de 2019. Foi realizado um breve questionário para avaliar a satisfação dos pacientes e a repercussão a longo prazo do ponto de vista psicológico e funcional. Resultados: Um total de 19 pacientes satisfizeram os critérios de inclusão. A média de Cobb pré-operatório foi de 58° e o pós-operatório foi de 23° e ao final do acompanhamento, de 26°. Não foram registradas complicações relevantes. Quanto à satisfação, 90% estão muito satisfeitos com o resultado geral da cirurgia, 95% não têm limitações para esportes ou atividades diárias e 90% estão satisfeitos com os resultados estéticos. Conclusões: A evolução radiográfica a curto e longo prazo nos pacientes tratados com material de terceira geração apresentou bons resultados clínicos. Em 3 casos (16%), registrou-se perda de correção superior a 10%. O índice geral de satisfação e resultado estético é muito bom no final do acompanhamento, apesar da baixa taxa de correção (60%). Não se constataram complicações importantes e a incidência de limitação funcional e dor ao final do acompanhamento foi muito baixa. Nível de evidência IV; Artigo de revisão.

RESUMEN Objetivo: En las últimas tres décadas han habido grandes avances en el tratamiento quirúrgico de las escoliosis idiopática del adolescente. Existen pocos trabajos que estudien el resultado clínico y radiográfico a largo plazo en las EIA intervenidas con tornillos pediculares que además contemplen repercusión psicológica. Métodos: Realizamos un estudio longitudinal observacional. Revisamos las EIA intervenidas entre enero de 2009 y diciembre de 2010 con tornillos pediculares en nuestro centro. Realizamos seguimiento hasta julio de 2019. Se realizó un breve cuestionario para evaluar satisfacción de los pacientes y la repercusión a largo plazo de punto de vista psicológico y funcional. Resultados: Un total de 19 pacientes cumplieron los criterios de inclusión. La media del Cobb pre operatorio fue de 58° y el post operatorio de 23° y al final del seguimiento, de 26°. No se registraron complicaciones mayores. El 90% está muy satisfecho con el resultado global de la cirugía. El 95% no presenta limitación para el deporte o actividad cotidiana y el 90% está conforme con resultado cosmético. Conclusiones: La evolución radiográfica a corto y largo plazo en pacientes tratados con material de tercera generación presentó buenos resultados clínicos. En 3 casos (16%) se registró perdida de corrección mayor a 10%. El índice de satisfacción global y resultado cosmético es muy bueno al final del seguimiento a pesar de la baja tasa de corrección (60%). No se constataron complicaciones mayores y la incidencia de limitación funcional y dolor al final del seguimiento fue muy baja. Nivel de evidencia IV; Estudio de revisión.

Mechanical Equation Verification and Mechanical Property Analysis of the TC4 Self-Tapping Bone Screw / 医用生物力学

Objective To test the validity for mechanical equation of the TC4 self-tapping bone screw and analyze the influence of bone screw parameters on its mechanical properties. Methods In order to derive the equation of self-tapping and pull-out for bone screw, the physical model of bone screw-polyurethane foam block was built. By reference of ASTMF543-07 standard specification and test method for metallic medical bone screw, the mechanical verification tests of selected conical head shallow thread locking bone screw (HAZ) and conical head deep thread locking bone screw (HBZ) with different diameters were performed on Instron E3000 mechanical testing machine, and the data of self-tapping force, self-tapping torque and pull-out force from 5 groups of bone screws were tested respectively. Results The calculated and measured values were basically the same, except for a few points with large individual errors. The average error of the two values was 11.02%, so the theoretical calculation formula was highly credible. The bone screw with a larger diameter or a higher tooth height would require greater self-tapping force and pull-out force. Conclusions The research results provide the calculation basis for mechanical properties of bone screw and the research direction for optimization and improvement of bone screw in future.

How Many Screws Are Needed for Reliable Stability of Extra-articular Nonosteoporotic Distal Radius Fractures Fixed with Volar Locking Plates?

BACKGROUND: We hypothesized that volar locking pate fixation using a minimum number of screws—four in the distal row and two in the shaft of the plate—will provide sufficient stability for unstable extra-articular fractures of the distal radius. We aimed to compare the biomechanical properties of different numbers and locations of screws in volar locking plate fixation and describe the clinical and radiological outcome of plate fixation using a minimum number of screws for distal radius fractures.METHODS: We divided 48 artificial radius fracture bones into four groups (group A–D) based on the number and location of screws used for fixation with volar locking plates. The artificial bone models were subjected to axial compression and volar bending load with a force of 250 N and 80 N, respectively, for 1,000 cycles at a frequency of 1 Hz. We also retrospectively reviewed 42 patients with unstable, extra-articular, distal radius fractures who were treated with volar locking plate fixation using a minimum number of screws.RESULTS: Group A (seven distal screws and three proximal screws) had the highest mean stiffness: 303.7 N/mm under axial compression and 61.1 N/mm under volar bending. Compared with group A, group D (four screws in the distal part and two screws in the shaft) showed significantly lower stiffness; therefore, group D was considered inferior in terms of stability. However, in the fatigue test, neither deformation of the metal plate nor detachment or breakage of the metal screws was observed in all groups. In the clinical study, all fractures united without displacement and satisfactory clinical outcome was obtained.CONCLUSIONS: In the dorsally comminuted, extra-articular, nonosteoporotic distal radius fractures, the minimum number of screws—four in the distal row and two in the shaft—in volar locking plate fixation can provide sufficient stability. Further biomechanical studies involving osteoporotic bone will be necessary to confirm the results because volar plate fixation is most commonly used in patients with osteoporosis.

Experimental Study of Stress Effects on the Degradation Rate in vitro of Novel Magnesium Alloy Bone Screws / 医用生物力学

Objective To study the effect of stress on the degradation rate in vitro of novel magnesium alloy bone screw. Methods A three-dimensional （3D） model of the tibia fracture was established using the reverse engineering method. Then, based on the FE model, the in vitro degradation experimental device for bone screws was designed. The stress distribution of the screw by finite element calculation was used as the in vitro experimental load, which effectively improved the accuracy and efficiency of the experiment. The experimental samples were divided into four groups. Group A was treated as control group without force application, while Groups B, C and D were subjected to 150, 250 and 350 N axial forces. The influence of different mechanical environment on the degradation rate in vitro of bone screws was investigated. Finally, combining the stress distributions with the degradation experiment results in vitro, the curve between the stress and the degradation rate in vitro of novel magnesium alloy bone screws was obtained. Results Degradation experiments in vitro showed that Group A had the lowest weight loss and hydrogen production, and the average degradation rate was (0.315±0.005) mm/a. While in the stress groups, the weight loss and hydrogen production increased gradually with the axial force increasing. The average degradation rates of Groups B, C and D were (0.379±0.006), (0.469±0.007) and (0.547±0.009) mm/a, respectively. Conclusions When the novel magnesium alloy bone screw was degraded in mechanical environment, the greater stress on the screw would cause the faster degradation rate in vitro. The obtained relationship between the maximum stress and the average degradation rate in vitro of the novel megnesium alloy bone screw provided data support and theoretical guidance for material selection, design and clinical application of magnesium alloy bone screws.

Distalization of the entire maxillary arch with mini-implants in the posterior palatal alveolus- A case report / Distalização de todo o arco maxilar com mini-implantes na região alveolar posterior palatina - Relato de caso

A 22 year old male patient reported to the hospital with a chief complaint of forwardly placed teeth. On examination patient had Angle's Class I malocclusion and proclination of the anterior teeth. There were signs of frictional keratosis on the buccal mucosa. Treatment plan was to extract the third molars alone and distalize the entire maxillary arch with palatal mini-implants. 0.022 MBT brackets were bonded on the buccal aspect. 0.019" x 0.025" stainless steel wire was placed sequentially. Mini-implants were placed on the posterior alveolus on the palatal surface of maxilla. Retractive force was applied from an attachment bonded on the palatal aspect of the maxillary canine. Patient was reviewed periodically. Comparison of pre-treatment and post-treatment results revealed that the entire maxillary arch intruded and translated distally with a counter-clockwise rotation of the mandible with reduction in LAFH. There was a mild reduction in inter-canine with marginal expansion in the premolar and molar region. An improvement in facial profile was noted with no sign of root resorption. Thus, the posterior alveolus may be considered as a new and appropriate site for placement of mini-implant to bring about distal movement of the entire maxillary dentition (AU)

Um Paciente do sexo masculino, 22 anos, foi encaminhado ao hospital com queixa principal de dentes posicionados para a frente. Ao exame clínico o paciente apresentava má oclusão de Classe I de Angle e inclinação vestibular dos dentes anteriores. Havia sinais de queratose friccional na mucosa bucal. O plano de tratamento foi extrair os terceiros molares e distalizar todo o arco maxilar com mini-implantes por palatino. Bráquetes MBT 0,022 foram colados por vestibular. Fio de aço inoxidável 0,019 "x 0,025" foi colocado seqüencialmente. Mini-implantes foram instalados na região alveolar posterior da superfície palatina da maxila. A força de retração foi aplicada a partir de acessórios colados nas faces palatinas dos caninos superiores. O paciente foi reavaliado periodicamente. Os resultados da comparação pré-tratamento e pós-tratamento revelaram que todo o arco maxilar intruiu e transladou distalmente com rotação da mandíbula no sentido anti-horário com redução da AFAI. Houve uma ligeira redução na distância intercanina com expansão marginal nas regiões de pré-molar e molar. Foi percebida melhora no perfil facial sem sinal de reabsorção radicular. Assim, a região alveolar posterior pode ser considerada como um novo e apropriado local para instalação de mini-implante para promover movimento distal de toda a dentição maxilar. (AU)

3D printed navigation template assists pedicle lag-screw placement for atypical Hangman's fracture / 中华创伤骨科杂志

Objectives To evaluate the 3D printed navigation template used to assist axis pedicle lag-screw placement in the treatment of atypical Hangman's fracture(AHF).Methods From May 2015 to January 2017,12 patients with AHF were treated at Department of Orthopedics,The Fourth Peopled Hospital of Zigong.In their operation,the axis pedicle lag-screw placement was assisted by a 3D printed navigation template.They were 8 men and 4 women,aged from 27 to 53 years(average,45.6 years).There were 7 cases of type Ⅰ,4 cases type Ⅱ and one case of type HA according to the Levine-Edwards classification.There were 2 cases of grade D and 12 cases of grade E according to the assessment of America Spinal Injury Association(ASIA).Their preoperative and postoperative neck pain was evaluated by visual analogue scale(VAS);their preoperative and postoperative ranges of cervical motion were recorded and compared.To evaluate the postoperative safety of screws,the insertion point,position within the pedicle,axial angle and sagittal angle of the screws and maximum fracture displacement were compared between actual operation and simulative operation.Results A total of 12 guide plates were designed and printed;a total of 24 lag-screws were placed.All patients underwent surgery uneventfully.They were followed up for 12 to 20 months,with an average of 14.7 months.Two patients with ASIA grade D recovered to ASIA grade E at the last follow-up.All patients showed a significant improvement in neck pain.Their VAS score at 5 days after surgery(5.86±2.02) was significantly lower than their preoperative score(8.29±1.88)(P<0.05) and their VAS score at the last follow-up(1.73±0.87) was also significantly lower than that at 5 days after surgery(P<0.05).Their range of cervical motion at 6 months after surgery was significantly larger than that at 3 months after surgery(P<0.05);their range of cervical motion returned to normal roughly at the last follow-up,showing no significant difference from that at 6 months(P>0.05).Their postoperative X-ray and CT images showed that the dislocation was all corrected.The last follow-up showed no obvious vertebral instability,screw breakage or loosening.Postoperative CT showed that the 24 screws had been located completely in the pedicle(grade 0),indicating that the screw placement was 100% accurate.The postoperative deviation at insertion point(0.70±0.78 mm),deviation within the pedicle(1.3±0.82 mm),axial angle(8.26°±0.88°) and sagittal angle(22.62°±0.86°) of the screws showed no significant differences from the preoperative simulative data(P>0.05).There was a significant difference in the maximum fracture displacement between the preoperative data(3.94±0.38 mm) and the postoperative data(2.21±0.39 mm)(P<0.05).Conclusion The 3D printed navigation template can be used to better assist axis pedicle lag-screw placement in the treatment of AHF,because it ensures safe screw placement,leading to good reduction and fixation and precise match with the preoperative plan.

Bone Microstructual Changes Around the Magnesium Based-Implant after Implantation in Rabbit Femur / 医用生物力学

Objective To study the change patterns of bone microstructural parameters around the magnesium based- implants after implantation in rabbit femur at different implantation time points. Methods The threaded and non-threaded high-purity magnesium (HP Mg, 99.99 wt.%) screws, with a 2 mm diameter and a 7 mm length, were implanted into the femoral condyle of the rabbits. The control group was the drilled and healthy group. Micro-CT scanning and analysis were performed at 8th, 12th and 16th week after operation. The obtained microstructural parameters included bone mineral density (BMD), bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N), trabecular separation (Tb.Sp). Results At 8th week, BMD and BV/TV in non-threaded magnesium screw group were significantly higher than those in healthy group, Tb.N was significantly higher than that in drilled and healthy group, and Tb.Sp was significantly lower than that in healthy group. At 12th week, BMD, BV/TV and Tb.N in threaded magnesium screw group were significantly higher than those in drilled and healthy group, Tb.Th was significantly higher than that in healthy group, and Tb.Sp was significantly lower than that in drilled and healthy group. At 16th week, BMD, BV/TV and Tb.N in non-threaded magnesium screw group were significantly higher than those in drilled and healthy group, and Tb.Sp was significantly lower than that in drilled and healthy group. Conclusions The magnesium based-implant promoted higher BMD, BV/TV, Tb.Th, Tb.N and lower Tb.Sp of surrounding implant, indicating that osseointegration and bone growth were in good condition. Magnesium based-implant could effectively promote the regeneration of bone. The results provide a theoretical basis for the orthopedic application of magnesium based-implants in clinic.

Bone cement-augmented pedicle screw fixation versus bone filling vertebroplasty for stable osteoporotic thoracolumbar burst fracture / 中华创伤骨科杂志

Objective To compare the clinical efficacy between bone cement-augmented pedicle screw fixation and bone filling vertebroplasty for stable osteoporotic thoracolumbar burst fracture (TBF).Methods From August 2014 to August 2017,48 patients with stable osteoporotic TBF but no neurological symptoms were treated at Department of Orthopedics,The First Affiliated Hospital to Chongqing Medical University.Those undergoing bone cement-augmented pedicle screw fixation were assigned into Group A while those undergoing bone filling vertebroplasty into Group B.The clinical efficacy was evaluated by comparing visual analogue scale (VAS) for pain assessment,Oswestry disability index (ODI),compression ratio of anterior vertebral height,and cobb kyphotic angle between preoperation and postoperation.The 2 groups were compared in terms of operation time,bone cement consumption,blood loss,hospital stay and relative medical costs.Results Of the 48 patients included in this study,27 were in Group A and 21 in Group B.The 2 groups were comparable as their baseline characteristics were insignificantly different (P ＞ 0.05).At 3 days after operation,the VAS (2.8 ± 1.0) and ODI (26.0 ±3.5) scores for group B were significantly lower than those for group A (4.6 ± 1.3 and 34.3 ± 2.9) (P ＜ 0.05).In group A at 3 months after operation and final follow-up,the VAS (2.9 ±0.9 and 2.3 ±0.7) and ODI (24.7 ±3.1 and 23.1 ±4.6) scores were significantly lower than those at 3 days after operation (4.6 ± 1.3 and 34.3 ± 2.9) (P ＜ 0.05).In group B at 3 months after operation and final follow-up,the VAS (2.8 ±0.9 and 2.3 ± 1.0) and ODI (23.8 ±3.7 and 22.8 ± 5.6) scores were insignificantly better than those at 3 days after operation (2.8 ± 1.0 and 26.0 ± 3.5) (P ＞ 0.05).At 3 days and 3 months after operation and final follow-up,group B had significantly smaller compression ratios of anterior vertebral height (81.1％ ± 3.7％,81.1％ ± 3.4％ and 75.6％ ± 5.8％) than group A did (91.4％ ±4.4％,90.1％ ±2.9％ and 83.5％ ±4.4％) but significantly larger cobb kyphotic angles (17.0° ± 4.0°,18.0° ± 3.5 ° and 22.1 ° ± 3.6°) than group A (14.0° ± 3.2°,14.3° ± 5.5° and 19.2° ± 3.2°) (P ＜ 0.05).The compression ratio of anterior vertebral height and cobb kyphotic angle at the final follow-up in all the patients were significantly improved compared with those at 3 days and 3 months after operation (P ＜ 0.05).Group B had significantly less operation time (51.5 ±7.3 min),blood loss (16.0 ± 8.2 mL),hospital stay (3.4 ±0.9 d) and medical costs per person (34,000 ±4,000 RMB yuan) than group A (91.5 ± 9.8 min,77.4 ± 16.5 mL,8.7 ± 2.2 d and 55,000 ± 9,000 RMB yuan),but significantly larger bone cement consumption (5.1 ± 0.7 mL) than group A (1.9 ± 0.7 mL) (P ＜ 0.05).Conclusion For patients with stable osteoporotic TBF,both bone cement-augmented pedicle screw fixation and bone filling vertebroplasty can lead to similar clinical outcomes,but the latter may have advantages of less invasion,faster recovery and lower medical costs.

Evaluation of miniscrew angulation in the posterior maxilla using cone-beam computed tomographic image

ABSTRACT Objective: This study aimed at evaluating whether changes in the insertion angle is a determining factor in the positioning of the miniscrews body in a region with larger interradicular space in the posterior maxilla. Methods: Analysis of 60 posterior maxillary quadrants were made using images obtained by means of cone-beam computed tomographic image (CBCT), with 0.076-mm voxel, which presented a real miniscrew inserted in the mesial region of the maxillary first molars, serving as reference point for the placement of the virtual miniscrews. Measurements of the distances between roots were made in three points on the body of the virtual miniscrews (A, B and C), at four different angulations, 70o, 60o, 50o and 40o (T1 to T4), in relation to the long axis of the second premolar. This evaluation was made in four groups, selected in accordance with the disposition of the roots of the second premolars and first molars: Group 1 (all types of roots), Group 2 (convergent roots), Group 3 (divergent roots) and Group 4 (parallel roots). Results: There were no statistically significant differences in the measurements of points A, B and C, at the different angles (70o, 60o, 50o and 40o) and in the different groups (p > 0.05). Conclusions: Changes in the insertion angle is not a determinant factor in the positioning of miniscrews body in regions with larger interradicular space in posterior maxilla.

RESUMO Objetivo: o presente estudo objetivou avaliar se alterações no ângulo de inserção do miniparafuso são um fator decisivo para a adaptação do corpo do parafuso em áreas com espaço inter-radicular aumentado, na região posterior da maxila. Métodos: foram realizadas análises em 60 quadrantes maxilares posteriores, a partir de imagens obtidas por tomografia computadorizada de feixe cônico (TCFC), com voxel de 0,076 mm, as quais apresentavam um miniparafuso real inserido na região mesial dos primeiros molares superiores, utilizado como ponto de referência para a inserção de miniparafusos virtuais. As distâncias inter-radiculares foram mensuradas utilizando-se três pontos marcados no corpo dos miniparafusos virtuais (A, B e C), inseridos com quatro angulações diferentes (70°, 60°, 50° e 40°) (T1 a T4) em relação ao longo eixo do segundo pré-molar. A avaliação foi realizada em quatro grupos, selecionados de acordo com a disposição das raízes dos segundos pré-molares e primeiros molares: Grupo 1 - contendo todos os tipos de raízes; Grupo 2 - raízes convergentes; Grupo 3 - raízes divergentes; e Grupo 4 - raízes paralelas. Resultados: não houve diferença estatisticamente significativa entre as medidas dos pontos A, B e C nas diferentes angulações (70°, 60°, 50° e 40°) ou entre os grupos (p > 0,05). Conclusões: alterações no ângulo de inserção dos miniparafusos não são um fator decisivo para a adaptação do corpo do parafuso, em áreas com espaço inter-radicular aumentado entre primeiro molar e segundo pré-molar superiores.

Failure Analysis and Strength Testing of Bone Screws / 医用生物力学

As an effective implant for bone fracture, bone screws are widely used in clinic. Based on the clinical application of bone screws, this study summarized different kinds of bone screws according to their structures and materials, analyzed 3 kinds of common screw failure (loosening, breaking, corrosion) and the influencing factors. The common testing methods of screws were summarized, especially the key points and difficulties during the testing process for bone screws were analyzed, which was important for improving the design of product, selection of materials and development of in vitro testing technology. The development trend for testing method of bone screws was prospected as well.

Treatment of Secondary Soft Tissue Compromised Calcaneus Fractures Using a Cannulated Screw and Simple Cerclage Wiring: A Report of Two Cases / 대한족부족관절학회지

Secondary soft tissue injuries can occur from the pressure of the displaced fragment of posterior calcaneal tuberosity in calcaneal tongue-type fractures and calcaneal tuberosity avulsion fractures. The soft tissue injury can be prevented by immediate reduction of the displaced fragments. Various techniques can be used to fix the fracture fragments, but the stability of fixation and minimal invasiveness to soft tissue should be considered. This paper reports the successful outcomes of patients with soft tissue compromises in calcaneal tongue-type fractures and calcaneal tuberosity avulsion fractures. The fixation technique of a large cannulated screw and simple cerclage wiring is believed to be a useful surgical option for the treatment of secondary soft tissue compromised calcaneal fractures.

Positioning of pedicle screws in adolescent idiopathic scoliosis using electromyography / Posição de parafusos pediculares na escoliose idiopática do adolescente com uso da eletromiografia / Posición de tornillos pediculares en escoliosis idiopática del adolescente con electromiografía

To analyze the occurrence of poor positioning of pedicle screws inserted with the aid of intraoperative electromyographic stimulation in the treatment of Adolescent Idiopathic Scoliosis (AIS).

Analisar a ocorrência do mau posicionamento de parafusos pediculares inseridos com auxílio de estimulação eletromiográfica intraoperatória, no tratamento de escoliose idiopática do adolescente (EIA).

Analizar la incidencia de la mala colocación de tornillos pediculares insertados con la ayuda de la estimulación electromiográfica intraoperatoria para el tratamiento de la Escoliosis Idiopática del Adolescente (EIA).

Fracture and Dislocation of Lisfranc Joint: Treatment with Screw and Kirschner Wire / 대한족부족관절학회지

PURPOSE: The purpose of this study is to retrospectively analyze the clinical results of screws and Kirschner wire (K-wire) fixation in patients with fracture dislocation of Lisfranc joint and the consequence of screw breakage. MATERIALS AND METHODS: Sixty patients underwent Lisfranc joint open reduction and removal of internal fixators from January 2007 to December 2011. Forty-nine cases (81.7%) underwent operations with screw alone, and 11 cases (18.3%) underwent operations with both screws and K-wires. Type of internal fixators, duration of internal fixator removal, breakage of internal fixators and satisfaction with reduction were investigated. Additionally, American Orthopaedic Foot and Ankle Society (AOFAS) midfoot scales were analyzed. RESULTS: The internal fixator was broken in 5 cases (8.3%). The average duration of instrument removal was 154 days in the non-broken screw group and 268.6 days in the broken screw group (p<0.05). The average AOFAS midfoot scale was 77.4 in the non-broken screw group and 74.2 in the broken screw group. The most commonly damaged portion was the first tarsometatarsal (Lisfranc) joint. CONCLUSION: Treatment with screws and K-wires was effective in patients with fracture dislocation of Lisfranc joint. The appropriate time for screw removal should be considered.

Outcome comparison of lisfranc injuries treated through dorsal plate fixation versus screw fixation

O objetivo deste estudo prospectivo foi testar se o tratamentode lesões de Lisfranc com redução aberta e fixação da placadorsal teria os mesmos resultados funcionais, ou melhores, do quetratamento padrão com fixação com parafuso transarticular. Métodos:Sessenta pacientes com lesão articular de Lisfranc foram tratadospor redução aberta e fixação da placa dorsal ou pelo método padrãopor fixação de parafusos. Os pacientes foram acompanhados por,em média, 31 meses. A avaliação foi realizada com base na queixaprincipal dos pacientes, exame clínico, radiografia, e escala AOFAS.Resultados: Trinta e dois pacientes foram tratados com redução abertae fixação da placa dorsal, e vinte e oito pacientes foram tratadoscom redução aberta e fixação com parafuso. Depois de dois anos deacompanhamento, a média do escore AOFAS foi de 83,1 pontos nogrupo de fixação da placa dorsal e 78,5 pontos no grupo de fixaçãocom parafusos (p <0,01). Do grupo de fixação com placa dorsal, aanálise radiográfica revelou redução anatômica em vinte e nove pacientes(90,6%, 29/32) e redução não anatômica em três pacientes.Do grupo de fixação com parafuso, a análise radiográfica revelou reduçãoanatômica em vinte e três pacientes e redução não anatômicaem cinco pacientes (82,1%, 23/28). Conclusões: A redução abertae fixação com placa dorsal para lesão de Lisfranc deslocada têmmelhor resultado a curto e médio prazo e uma taxa de reoperaçãoinferior do que a técnica padrão de redução aberta e fixação interna(RAFI) com parafuso. Em nossa experiência, recomendamos o usode placa dorsal em RAFI nas lesões de Lisfranc deslocadas. Nívelde Evidência II, Estudo Prospectivo Comparativo...

The objective of this prospective study was to testwhether the treatment of Lisfranc injuries with open reductionand dorsal plate fixation would have the same or better functionaloutcomes as treatment with standard trans-articular screwfixation. Methods: Sixty patients with primarily isolated Lisfrancjoint injury were treated by open reduction and dorsal platefixation or standard screw fixation. The patients were followedon average for 31 months. Evaluation was performed with patients’chief complaint, clinical examination, radiography, andAOFAS Midfoot Scale. Results: Thirty two patients were treatedwith open reduction and dorsal plate fixation, and twenty eightpatients were treated with open reduction and screw fixation.After two years follow-up, the mean AOFAS Midfoot score was83.1 points in the dorsal plate fixation group and 78.5 points inthe screw fixation group (p<0.01). Of the dorsal plate fixationgroup, radiographic analysis revealed anatomic reduction intwenty-nine patients (90.6%, 29/32) and nonanatomic reductionin three patients. Of the screw fixation group, radiographicanalysis revealed anatomic reduction in twenty-three patientsand nonanatomic reduction in five patients (82.1%, 23/28).Conclusions: Open reduction and dorsal plate fixation for adislocated Lisfranc injury do have better short and median termoutcome and a lower reoperation rate than standard screw ORIF.In our experience, we recommend using dorsal plate in ORIF ondislocated Lisfranc injuries. Level of Evidence II, ProspectiveComparative Study...

Pre-tibial synovial cyst after reconstruction of the anterior cruciate ligament: case report / Cisto sinovial pré-tibial após reconstrução do LCA – Relato de caso

Arthroscopic reconstruction of the anterior cruciate ligament has been modernized through new surgical techniques and new materials. When tibial fixation is performed using an absorbable screw, complications may occur, such as formation of a pre-tibial cyst. The case described here is about a patient who presented an anteromedial synovial cyst in his right knee, three years after having undergone ACL reconstruction. The patient did not present any pain nor any complaints other than a mass that progressively increased in size, worsened after physical activities. Imaging examinations were requested: simple radiography of the knee and magnetic resonance. Anteromedial imaging of the knee showed a mass with well-delimited borders and internal fluid content, suggestive of a synovial cyst, with communication with the joint cavity through the tibial tunnel, without presenting enlargement or absorption of the bone tunnel. The cyst was surgically resected and the tibial tunnel occlusion was performed using a bone plug. The diagnosis of a synovial cyst was subsequently confirmed through the results from the anatomopathological examination. The patient presented good clinical evolution, with disappearance of the symptoms and a return to physical activities...

A reconstrução do ligamento cruzado anterior (LCA) por via artroscópica vem sendo modernizada por novas técnicas cirúrgicas e novos materiais. Quando feita a fixação tibial com parafuso absorvível podem ocorrer complicações, como a formação de um cisto pré-tibial. O caso em questão é de um paciente que apresentou um cisto sinovial anteromedial em joelho direito três anos após ter sido submetido a reconstrução do LCA. O paciente não apresentava dor ou outras queixas, apenas massa de aumento progressivo, com pioria após atividades físicas. Foram solicitados exames de imagem: radiografias simples do joelho que não apresentavam alterações; e ressonância magnética com imagem anteromedial em joelho sugestiva de cisto sinovial. Apresentava bordas bem delimitadas e conteúdo líquido interno, com comunicação com a cavidade articular através do túnel tibial, sem apresentar alargamento ou absorção do túnel ósseo. Foram feitas ressecção cirúrgica do cisto e oclusão do túnel tibial com tampão ósseo, com posterior confirmação do diagnóstico de cisto sinovial após resultado do exame anatomopatológico. O paciente apresentou boa evolução clínica, com desaparecimento dos sintomas e retorno às atividades físicas...

A Novel Blasted and Grooved Low Profile Pedicle Screw Able to Resist High Compression Bending Loads

OBJECTIVE: Polyaxial pedicle screws are a safe, useful adjunct to transpedicular fixation. However, the large screw head size can cause soft tissue irritation, high rod positioning, and facet joint injury. However, the mechanical resistance provided by small and low profile pedicle screws is very limited. We therefore developed a novel, low profile pedicle screw using grooving and blasting treatment that is able to resist a high compression bending load. METHODS: We evaluated the compression bending force to displacement and yield loads for seven different screw head types that differed with regard to their groove intervals and whether or not they had been blasted. RESULTS: The rank order of screw types that had the greatest compression bending force to displacement was as follows: (1) universal polyaxial, (2) low polyaxial with 0.1mm grooves and blasting, (3) low polyaxial with blasting, (4) low polyaxial with 0.15mm grooves and blasting, (5) low polyaxial with 0.05mm grooves and blasting, (6) low polyaxial with 0.05mm grooves, (7) and low polyaxial. Low polyaxial screws with 0.1mm grooves and blasting had the maximum yield load and highest compression bending force to displacement of all seven polyaxial screw head systems evaluated. CONCLUSION: Blasting and grooving treatment of pedicle screw heads resulted in screw heads with a high yield load and compression bending force relative to displacement because of increased friction. Low polyaxial pedicle screws with 0.1 mm grooves treated by blasting have mechanical characteristics similar to those of universal polyaxial pedicle screws.

A Novel Blasted and Grooved Low Profile Pedicle Screw Able to Resist High Compression Bending Loads

OBJECTIVE: Polyaxial pedicle screws are a safe, useful adjunct to transpedicular fixation. However, the large screw head size can cause soft tissue irritation, high rod positioning, and facet joint injury. However, the mechanical resistance provided by small and low profile pedicle screws is very limited. We therefore developed a novel, low profile pedicle screw using grooving and blasting treatment that is able to resist a high compression bending load. METHODS: We evaluated the compression bending force to displacement and yield loads for seven different screw head types that differed with regard to their groove intervals and whether or not they had been blasted. RESULTS: The rank order of screw types that had the greatest compression bending force to displacement was as follows: (1) universal polyaxial, (2) low polyaxial with 0.1mm grooves and blasting, (3) low polyaxial with blasting, (4) low polyaxial with 0.15mm grooves and blasting, (5) low polyaxial with 0.05mm grooves and blasting, (6) low polyaxial with 0.05mm grooves, (7) and low polyaxial. Low polyaxial screws with 0.1mm grooves and blasting had the maximum yield load and highest compression bending force to displacement of all seven polyaxial screw head systems evaluated. CONCLUSION: Blasting and grooving treatment of pedicle screw heads resulted in screw heads with a high yield load and compression bending force relative to displacement because of increased friction. Low polyaxial pedicle screws with 0.1 mm grooves treated by blasting have mechanical characteristics similar to those of universal polyaxial pedicle screws.

Minimally Invasive Multilevel Percutaneous Pedicle Screw Fixation for Lumbar Spinal Diseases

OBJECTIVE: There are rare reports on the result of multilevel (> or =3 levels) percutaneous pedicle screw fixation (PPF). The purpose of this study was to report the clinical experiences for multilevel PPF of the lumbar spine. METHODS: A total of 17 patients of lumbar spinal disease (7 degenerative diseases, 6 infectious diseases, and 4 traumatic instabilities) underwent neural decompression and multilevel PPF. There were 8 men and 9 women with a mean age of 61.4 years (range, 25-84) and a mean follow-up period of 23.2 months (range, 13-48). The average PPF level was 3.7. A retrospective review of clinical, radiological, and surgical data was conducted. RESULTS: "Excellent" or "good" clinical results were obtained in 15 patients (88.2%) according to the Odom's criteria. The average improvement of visual analogue scale was 5.2 points (from 9.3 to 4.1), and the average improvement of Oswestry Disability Index was 36.2 (from 71.2 to 35.0) at the last visit (p<0.05). The fusion rate was 88.2%, but, screw loosening was occurred in 2 patients, and adjacent segmental degeneration was occurred in 2 patients. There was no statistical significance in the change of total lumbar lordotic angle. The average operation time was 5.9 hours, with an estimated blood loss of 550 ml and bed rest duration of 2.0 days. CONCLUSION: Although the current study examined a small sample with relatively short term follow up periods, our study results demonstrate that multilevel PPF is feasible and safe for selective lumbar spinal diseases.