Effect of anal draw-out laparoscopic anterior resection of rectal cancer on gastrointestinal motility and prognosis in patients with low rectal cancer / 国际外科学杂志

Objective:To investigate the effect of rectal draw-out laparoscopic anterior resection on gastrointestinal motility and prognosis in patients with low rectal cancer.Methods:A total of 140 patients with low rectal cancer who received treatment in Chongqing Ninth People′s Hospital from May 2017 to May 2018 were selected, including 82 males and 58 females, aged from 35 to 78 years with an average age of (59.33±9.12) years.According to the operation methods, all patients were divided into observation group (transanal pullout laparoscopic anterior resection of rectal cancer, n=70) and the control group (laparoscopic assisted anterior rectal resection, n=70). Independent sample t test or χ2 test were used to compare operation-related indicators, occurrence of complications, changes of fluid gastric emptying, small intestinal transport capacity, gastrin and motilin in 2 groups. Kaplan-meier survival curve was plotted to compare tumor progression-free survival (PFS) and overall survival (OS) in two groups. The two groups of PFS and OS were compared by log-rank test. Results:The operative time, intraoperative blood loss, postoperative drainage volume, and postoperative recovery time of the observation group were lower than those of the control group, the ability of liquid gastric emptying 24 h after operation, small intestine transport function at 24 h and 48 h after operation, the capacity of liquid gastric emptation, intestinal transport function 24 h and 48 h postoperatively, gastrin and motilin levels at 24 h, 48 h and 72 h postoperatively were significantly higher than those of the control group, with statistically significant differences ( P<0.05). Two years PFS (85.71% vs. 81.43%) and OS (92.86% vs. 90.00%) after surgery between the observation group and the control group were not statistically significant ( P>0.05). Conclusion:The anterior resection of rectal cancer by draw-out laparoscope is safe and radical, without increasing postoperative complications. Moreover, the recovery of gastrointestinal function is earlier than traditional laparoscopic assisted rectal cancer resection, which is conducive to improving the postoperative quality of life of patients, and is worthy of clinical promotion.

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.

Influences from Implant Angle of Suture Anchors on the Maximum Pullout Force / 医用生物力学

Objective To make biomechanical evaluation on ultimate pullout strength of the suture anchors based on the angle of suture anchor (SA) implanted into the humerus during arthroscopic rotator cuff repair (RCR) surgery. Methods Polyurethane materials with densities of 0.16 g/cm3 and 0.32 g/cm3 were used to simulate osteoporosis and normal cancellous bone, and polyurethane materials with densities of 0.64 g/cm3 and 3 mm thickness were used to simulate human cortical bone. The two kinds of cancellous bone models were respectively adhered together with cortical bone model to construct human humerus model. Titanium metal suture anchors were inserted into humerus models at 45°, 60°, 75° and 90° angle, then the continuous tensile experiments were performed, and 45° pulling direction between the humerus model surface and suture anchor was used to simulate the supraspinatus physiological traction direction, and each group was continuously tested 8 times, recording the pullout strength and failure modes. ResultsThe pullout force of high-density bone models was significantly higher than that of low-density bone models (P＜0.001), and at the same density, compared with 45°, 60° and 75°, the implant angle of 90° has a larger pullout force (P＜0.01). Conclusions In the model of humerus, the 90° implantation of suture anchor showed better biomechanical properties, and the vertical implantation of anchor in the repair of rotator cuff was beneficial to the knotting during operation and postoperative recovery of the supraspinatus.

Dual pitch titanium-coated pedicle screws improve initial and early fixation in a polyetheretherketone rod semi-rigid fixation system in sheep / 中华医学杂志(英文版)

Background@#Reports on the efficacy of modifications to the thread design of pedicle screws are scarce. The aim of the study was to investigate initial and early fixation of pedicle screws with a plasma-sprayed titanium coating and dual pitch in the pedicle region (dual pitch titanium-coated pedicle screw [DPTCPS]) in a polyetheretherketone (PEEK) rod semi-rigid fixation system.@*Methods@#Fifty-four sheep spine specimens and 64 sheep were used to investigate initial ( "0-week" controls) and early (postoperative 6 months) fixation, respectively. Sheep were divided into dual pitch pedicle screw (DPPS), standard pitch pedicle screw (SPPS), DPTCPS, and standard pitch titanium-coated pedicle screw (SPTCPS) groups. Specimens/sheep were instrumented with four screws and two rods. Biomechanical evaluations were performed, and histology at the implant-bone interface was investigated.@*Results@#At 0-week, mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS (557.0 ± 25.2 vs. 459.1 ± 19.1 N, t = 3.61, P < 0.05; 622.6 ± 25.2 vs. 459.1 ± 19.1 N, t = 3.43, P < 0.05). On toggle-testing, the DPTCPS was significantly more resistant than the SPPS and SPTCPS (343.4 ± 16.5 vs. 237.5 ± 12.9 N, t = 3.52, P < 0.05; 343.4 ± 16.5 vs. 289.9 ± 12.8 N, t = 3.12, P < 0.05; 124.7 ± 13.5 vs. 41.9 ± 4.3 cycles, t = 2.18, P < 0.05; 124.7 ± 13.5 vs.79.5 ± 11.8 cycles, t = 2.76, P < 0.05). On cyclic loading, maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS (1.8 ± 0.13 vs. 3.76 ± 0.19 mm, t = 2.29, P < 0.05; 1.8 ± 0.13 vs. 2.46 ± 10.20 mm, t = 2.69, P < 0.05). At post-operative 6 months, mean axial pull-out strength was significantly higher for the DPTCPS and SPTCPS than the SPPS (908.4 ± 33.6 vs. 646.5 ± 59.4 N, t = 3.34, P < 0.05; 925.9 ± 53.9 vs. 646.5 ± 59.4 N, t = 3.37, P < 0.05). On toggle-testing, the DPTCPS was significantly more resistant than the SPPS and SPTCPS (496.9 ± 17.9 vs. 370.3 ± 16.4 N, t = 2.86, P < 0.05; 496.9 ± 17.9 vs. 414.1 ± 12.8 N, t = 2.74, P < 0.05; 249.1 ± 11.0 vs.149.9 ± 11.1 cycles, t = 2.54, P < 0.05; 249.1 ± 11.0 vs.199.8 ± 7.2 cycles, t = 2.61, P < 0.05). On cyclic loading, maximum displacement was significantly lower for the DPTCPS than the SPPS and SPTCPS (0.96 ± 0.11 vs. 2.39 ± 0.14 mm, t = 2.57, P < 0.05; 0.96 ± 0.11 vs. 1.82 ± 0.12 mm, t = 2.73, P < 0.05). Resistance to toggle testing (370.3 ± 16.4 vs. 414.1 ± 12.8 N, t = 3.29, P < 0.05; 149.9 ± 11.1 vs.199.8 ± 7.2 cycles, t = 2.97, P < 0.05) was significantly lower and maximum displacement in cyclic loading (2.39 ± 0.14 vs.1.82 ± 0.12 mm; t = 3.06, P < 0.05) was significantly higher for the SPTCPS than the DPTCPS. Bone-to-implant contact was significantly increased for the DPTCPS compared to the SPPS (58.3% ± 7.0% vs. 36.5% ± 4.4%, t = 2.74, P < 0.05); there was no inflammatory reaction or degradation of coated particles.@*Conclusion@#DPTCPSs might have stronger initial and early fixation in a PEEK rod semi-rigid fixation system.

Pullout Strength Predictor: A Machine Learning Approach

STUDY DESIGN: A biomechanical study. PURPOSE: To develop a predictive model for pullout strength. OVERVIEW OF LITERATURE: Spine fusion surgeries are performed to correct joint deformities by restricting motion between two or more unstable vertebrae. The pedicle screw provides a corrective force to the unstable spinal segment and arrests motions at the unit that are being fused. To determine the hold of a screw, surgeons depend on a subjective perioperative feeling of insertion torque. The objective of the paper was to develop a machine learning based model using density of foam, insertion angle, insertion depth, and reinsertion to predict the pullout strength of pedicle screw. METHODS: To predict the pullout strength of pedicle screw, an experimental dataset of 48 data points was used as training data to construct a model based on different machine learning algorithms. A total of five algorithms were tested in the Weka environment and the performance was evaluated based on correlation coefficient and error matrix. A sensitive study of various parameters for obtaining the best combination of parameters for predicting the pullout strength was also preformed using the L9 orthogonal array of Taguchi Design of Experiments. RESULTS: Random forest performed the best with a correlation coefficient of 0.96, relative absolute error of 0.28, and root relative squared error of 0.29. The difference between the experimental and predicted value for the six test cases was not significant (p >0.05). CONCLUSIONS: This model can be used clinically for understanding the failure of pedicle screw pullout and pre-surgical planning for spine surgeon.

Delayed Lateral Row Anchor Failure in Suture Bridge Rotator Cuff Repair: A Report of 3 Cases

Compared to single row repair, use of lateral row anchors in suture bridge rotator cuff repair enhances repair strength and increases footprint contact area. If a lateral knotless anchor (push-in design) is inserted into osteoporotic bone, pull-out of the lateral row anchor can developed. However, failures of lateral row anchors have been reported at several months after surgery. In our cases, even though complete cuff healing occurred, delayed pull-out of the lateral row anchor in the suture bridge repair occurred. In comparison to a conventional medial anchor, further biomechanical evaluation of the pull-out force, design, and insertion angle of the lateral anchor is needed in future studies. We report three cases with delayed pull-out of lateral row anchor in suture bridge rotator cuff repair with a literature review.

Avulsion Fracture of the Posterior Cruciate Ligament from Femoral Insertion Occurred in a Patient with Residual Poliomyelitis: A Case Report

Avulsion fracture of the posterior cruciate ligament from its femoral insertion is quite rare, particularly in adults, and the treatment guidelines have not been established. A 68-year-old female patient with residual poliomyelitis presented with an avulsion fracture of the femoral insertion of the posterior cruciate ligament after a falling accident and was treated with arthroscopic headless compression screw fixation and pull-out suture of the avulsed ligament. We report this case with a relevant discussion of this type of injury.

Research on screw stability in fracture internal fixation / 中华创伤骨科杂志

Internal fixation is one of the most important treatments for fractures.The stability of screws in internal fixation can be influenced by bone mineral density,quality of pilot holes,improper structure and surface characteristics of screws chosen,insertion torque,insertion angle,and screws unfit for the bone holes.Internal fixation of fractures can fail due to the instability of screws.This paper,on the basis of a comprehensive review of the studies on all the above factors influencing the screw stability,proposes effective methods to enhance screw stability so as to improve surgical outcomes of fracture internal fixation.

Effect on pedicle screw stability of polymethylmethacrylate volume and distribution in synthetic bone block for patients with osteoporosis / 解放军医学杂志

Objective To compare the stability of injectable pedicle screw with different lateral holes augmented with different volume of polymethylmethacrylate (PMMA) in synthetic bone block used for patients with osteoporosis,and analyze the relationship between screw stability and injected volume and distribution pattern of PMMA.Methods The synthetic bone blocks used for patients with osteoporosis were randomly divided into groups A,B,C and D according to the screw difference,and the blocks in each group were then randomly divided again into subgroups 0,1,2 and 3 according to the difference of PMMA volume.A pilot hole was prepared in advance using the same method in all samples.Pedicle screws of type A-C were directly inserted into vertebrae of groups A-C respectively,and then different volumes of PMMA (0,1.0,1.5 and 2.0ml) were injected through screw into the blocks of subgroups 0,1,2 and 3 respectively.The pilot hole was filled with different volumes of PMMA (0,1.0,1.5 and 2.0ml) followed by insertion of screw in groups D0,D1,D2 and D3 respectively.X-ray examination was performed to evaluate the screw position and PMMA distribution,and axial pull-out test was performed to measure the maximum axial pullout strength (Fmax).Results X-ray examination revealed that PMMA wrapt the anterior 1/3 part of screw in groups A1-A3,wrapt the middle 1/3 part of screw in groups B1-B3 and groups C1-C3,and evenly wrapt the full length of screw in groups D1-D3.Two factor ANOVA showed that both volume and distribution of PMMA significantly influenced Fmax (P＜0.05),but no marked interaction existed between the two factors (P=0.877).Among groups with the same screw,no significant difference of Fmax was found between the groups injected of 1.0ml and 1.5ml PMMA and those of 1.5ml and 2.0ml PMMA (P＞0.05),but the Fmax was significantly higher in groups with injection of 2.0ml PMMA than that in groups with injection of 1.0ml PMMA (P＜0.05).Among the groups injected with same volume of PMMA,no significant differences on Fmax were found among the groups A0-D0,A2-D2 and A3-D3 (P＞0.05).The Fmax was significantly lower in group A1 than in group DI (P=0.026),and no significant differences existed between the other two groups injected with the same volume of PMMA (P＞0.05).Conclusion PMMA can significantly enhance the stability of different injectable pedicle screws in synthetic bone block used for patients with osteoporosis,and the stability is significantly correlated with injected volume and distribution pattern of PMMA.

Comparative Analysis of Effect of Density, Insertion Angle and Reinsertion on Pull-Out Strength of Single and Two Pedicle Screw Constructs Using Synthetic Bone Model

STUDY DESIGN: Biomechanical study. PURPOSE: To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. OVERVIEW OF LITERATURE: Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the single screw construct may lead to using expensive implants or increasing the fusion levels specifically in osteoporotic bones. METHODS: Single screw and two screw pull-out strength tests were carried out according to American Society for Testing and Materials F 543-07 on foam models to test the effect of density, insertion angle and reinsertion using poly axial pedicle screws. RESULTS: Bone density was the most significant factor deciding the pull-out strength in both single and two screw constructs. The difference in pull-out strength between single screw and two screw configurations in extremely osteoporotic bone model (80 kg/m3) was 78%, whereas in the normal bone model it was 48%. Axial pull-out value was highest for the single screw configuration; in the two screw configuration the highest pull-out strength was at 10°-15°. There was an 18% reduction in pull-out strength due to reinsertion in single screw configuration. The reinsertion effect was insignificant in the two screw configuration. CONCLUSIONS: A significant difference in response of various factors on holding power of pedicle screw between single and two-screw configurations is evident. The percentage increase in pull-out strength between single and two screw constructs is higher for osteoporotic bone when compared to normal bone. Reinsertion has no significant effect on pull-out strength in the two screw rod configuration.

Comparative Analysis of Effect of Density, Insertion Angle and Reinsertion on Pull-Out Strength of Single and Two Pedicle Screw Constructs Using Synthetic Bone Model

STUDY DESIGN: Biomechanical study. PURPOSE: To determine the effect of density, insertion angle and reinsertion on pull-out strength of pedicle screw in single and two screw-rod configurations. OVERVIEW OF LITERATURE: Pedicle screw pull-out studies have involved single screw construct, whereas two screws and rod constructs are always used in spine fusions. Extrapolation of results using the single screw construct may lead to using expensive implants or increasing the fusion levels specifically in osteoporotic bones. METHODS: Single screw and two screw pull-out strength tests were carried out according to American Society for Testing and Materials F 543-07 on foam models to test the effect of density, insertion angle and reinsertion using poly axial pedicle screws. RESULTS: Bone density was the most significant factor deciding the pull-out strength in both single and two screw constructs. The difference in pull-out strength between single screw and two screw configurations in extremely osteoporotic bone model (80 kg/m3) was 78%, whereas in the normal bone model it was 48%. Axial pull-out value was highest for the single screw configuration; in the two screw configuration the highest pull-out strength was at 10°-15°. There was an 18% reduction in pull-out strength due to reinsertion in single screw configuration. The reinsertion effect was insignificant in the two screw configuration. CONCLUSIONS: A significant difference in response of various factors on holding power of pedicle screw between single and two-screw configurations is evident. The percentage increase in pull-out strength between single and two screw constructs is higher for osteoporotic bone when compared to normal bone. Reinsertion has no significant effect on pull-out strength in the two screw rod configuration.

A Surgical Method for Determining Proper Screw Length in ACDF

OBJECTIVE: We describe a surgical tool that uses the distractor pin as a reference for determining proper screw length in ACDF. It is critical that screw purchase depth be as deep as possible without violating or penetrating the posterior cortical wall, which ensures strong pull out strength. METHODS: We enrolled 81 adult patients who underwent ACDF using an anterior cervical plate from 2010 to 2012. Patients were categorized into Groups A (42 patients: retractor pin used as a reference for screw length) and B (39 patients: control group). Intraoperative lateral x-rays were taken after screwing the retractor pin to confirm the approaching vertebral level. The ratio of retractor pin length to body anteroposterior (A-P) diameter was measured as a reference. Proper screw length was determined by comparison to the reference. RESULTS: The average distance from screw tip to posterior wall was 3.0+/-1.4mm in Group A and 4.1+/-2.3mm in Group B. The ratio of screw length to body sagittal diameter was 86.2+/-5.7% in Group A and 80.8+/-9.0% in Group B. Screw length to body sagittal diameter ratios higher than 4/5 occurred in 33 patients (90%) in Group A and 23 patients (59%) in Group B. No cases violated the posterior cortical wall. CONCLUSION: We introduce a useful surgical method for determining proper screw length in ACDF using the ratio of retractor pin length to body A-P diameter as a reference. This method allows for deeper screw purchase depth without violation of the posterior cortical wall.

Modified Pull-out Suture in Posterior Root Tear of the Medial Meniscus: Using a Posteromedial Portal

In cases with root tear of the medial meniscus posterior horn, the meniscus usually can be repaired by a pull out suture technique. However, there is difficulty in manipulating a suture hook via the anteromedial portal and looking through the arthroscopic camera via anterolateral portal in the narrow medial joint space at the same time. This article describes a modified simple pull out suture technique for root tear of the medial meniscus posterior horn using a posteromedial portal that provides a safe and easy handling of the suture hook. Our indications of this technique used in patients with Outerbridge 1-2 arthritic change and minimal varus axis change. Benefits of this technique are simple, less invasive, and reduced operation time by simultaneous suture with a hook via posteromedial portal and pulling of a string with grasper. It may reduce the possibility of an additional chondral or meniscal injury.

Minimum 1 Year Results of Arthroscopic Pull-out Repair for Posterior Root Tear of Medial Meniscus / 대한스포츠의학회지

This study is to evaluate clinical and arthroscopic second-look results of arthroscopic repairs of posterior root tears of medial meniscus which may cause loss of circumferential hoop tension and extrusion of meniscus. From October 2006 to May 2009, fifty-eight patients (59 knees) underwent arthroscopic pull-out repairs. Clinical results were evaluated using Hospital for Special Surgery (HSS) score and International Knee Documentation Committee (IKDC) score for 12-month follow-up. Second-look arthroscopy was done to evaluate meniscal healing in 21 cases. Magnetic resonance imaging (MRI) was performed to assess status of repaired meniscus and tibial tunnel position in 9 patients. Average preoperative HSS score and IKDC score of 59 cases were 69.5 and 36.0, respectively. Average postoperative HSS score and IKDC score of 59 cases had been changed into 90.3 (p<0.001) and 66.8 (p<0.001), respectively. Second-look arthroscopies revealed complete or incomplete healing except one case. Two patients showed increased one grade according to the Kellgren-Lawrence radiologic classification system and others showed no change. Of 9 patients who performed MRI, six patients showed complete healing. The average position of tibial tunnel was 4.8 mm anterior and 5.7 mm medial to center of posterior cruciate ligament. Arthroscopic pull-out repair technique using transtibial tunnel seems to be simple and effective procedure for posterior root tear of medial meniscus. Further evaluation of arthroscopic repair of posterior root tear of medial meniscus should be needed to prove the effectiveness on the prevention of osteoarthritis of knee.

Repair of the Complete Radial Tear of the Anterior Horn of the Medial Meniscus in Rabbits: A Comparison between Simple Pullout Repair and Pullout Repair with Human Bone Marrow Stem Cell Implantation

PURPOSE: To evaluate the degree of biological healing response that occurs between the anterior horn of the medial meniscus (MM) and the tibial plateau and investigate the biological healing response after injection of human bone marrow stem cells (hBMSCs) in a rabbit model. MATERIALS AND METHODS: Twenty-five rabbits with a mean body weight of 2.5 kg were chosen for this study. On the left knee, a complete radial tear was made at the anterior tibial attachment site of MM and after removal of tibial cartilage, pullout repair of the torn MM was performed on the tibial plateau. On the right knee, the same procedure was performed, and a scaff old (matrix gel) that contained human bone marrow stem cell was implanted between MM and the tibial plateau. A biopsy was performed at 2 (group 1), 4 (group 2), and 8 (group 3) weeks postoperatively. The authors compared the differences in the degree of biological healing of each group and investigated the degree of biologic healing after hBMSC implantation by comparing the left knee with the right knee. RESULTS: On the biopsy of 40 knees of 20 rabbits that survived after operation, all groups did not show the healing response between the undersurface of MM and the tibial plateau. There was no significant difference in terms of the pathological criteria such as fibroblasts and fibrochondrocytes etc., with and without hBMSC implantation. CONCLUSIONS: There was no attachment between the repaired MM and the tibial plateau after complete radial tear on MM and the authors could not identify the effect of hBMSC.

Primary stability of orthodontic miniscrews inserted into femurs of osteopenic rats

Aim: To test the hypothesis that bone quality may affect the stability of anchorage devices implanted in a rat model. Methods: Twenty male Wistar rats were divided into 2 groups: Group 1 (rats treated with FK506) and Group 2(rats treated with saline solution vehicle). The immunosuppressant tacrolimus was used with the intention of causing a condition of osteopenia in Group 1. A total of 20 orthodontic mini-implants were used. One mini-implant was inserted in the right femur of each rat. After sacrificing the animals, blocks of bone tissue containing the mini-implants were removed for mechanical pull-out tests to be performed in a universal test machine at a crosshead speed of 0.5 mm/s. The maximum insertion force values and pull-out test were recorded and submitted the nonparametric analyses including the Kruskal-Wallis test and Mann-Whitney tests (p<0.05). The test for Pearson’s correlation was used to verify the correlation between bone mineral density and the pull-out test. The dose of FK506 was 2 mg/kg/day. Densitometric analysis was performed to observe the effect of FK506 on the bone mineral density. Results: The mean insertion force values were similar in both groups, with no statistically significant difference between them (P > 0.05). The mean pull-out force values were higher in Group 2 than in Group 1, with statistically significant difference between the groups (P < 0.05). Conclusions: Bone quality may affect the stability of mini-implants. Orthodontic mini-implants did not present good primary stability in a rat model with osteopenia.

Three dimensional finite element analysis of stress distribution on continuously varying of length of pedicle screw / 医用生物力学

Objective To study the stress distribution on different length of pedicle screws under the physiological load by using the three dimensional finite element analysis. Method A three dimension model of the pedicle screw and L1 vertebral body were constructed with the model meshed on the basis of the finite element method. The feature dimension of pedicle screw in the model was set in a specified varied range. Under the physiological load, the stress on every model with different diameter sizes of pedicle screw was analyzed. ResultsThe stress on every bone model decreased with the increase of stress on screw under the axially pullout force as the length of screw ranged from 30mm to 50mm. And the maximum Equivalent Stress (EQV Stress) in the pedicle screw appeared in the central area of the pedicle screw, the maximum Equivalent Stress (EQV Stress) in the cortical bone appeared in both sides of contact surface, the maximum Equivalent Stress (EQV Stress) of the cancellous bone appeared in both sides of contact surface of the top of pedicle screw and cancellous bone. In a certain external load, with the 50mm length of screw, the load that transfers to the cortical bone and cancellous bone is reduced by 43.1% and 42.3%, respectively, while the maximum Equivalent Stress (EQV Stress) of screw was increased 38%. When L≥45mm, the variable stress on all models become stable. Conclusions While the length of screw is in range of 4.0　mm to 6.5　mm, 30～50 mm ,the increase of pedicle screw length could improve the distribution of axial pullout stress on the screws, cortical bone and cancellous bone. As long as the bone mass allowed, the length of pedicle screws should be not less than 45mm in clinical choice.

Avaliação da estabilidade primária de mini-implantes ortodônticos em diferentes regiões da maxila e mandíbula de porcos / Evaluation the primary stability of orthodontic mini-implants inserted into different regions maxilla and mandible of minipigs

Objetivo: avaliar a estabilidade primária de mini-implantes ortodônticos inserido em diferentes regiões da maxila e mandíbula de porcos. Materiais e Métodos: foram utilizados 36 mini-implantes ortodônticos distribuídos em seis grupos (n=6). Os grupos foram nomeados de acordo com a região da cavidade bucal onde foram inseridos. Grupo incisivo superior (IS), molar superior (MS), sutura palatina (S), incisivo inferior (II), molar inferior (MI) e retromolar (RM). Utilizou-se 3 porcos (Susscrofa Piau), onde foram inseridos 12 mini-implantes em três áreas da mandíbula e três da maxila. Após a inserção, os animais foram eutanasiados e foram obtidos blocos ósseos com o mini-implante inserido, os quais foram utilizados para realização de ensaio mecânico de tração em máquina universal de ensaios universais (Emic, São José dos Pinhais, Brasil) operada a uma velocidade de 0,5 mm/s. Os valores de força máxima para inserção obtidos em N.cm foram anotados e submetidos à análise de variância (ANOVA) e ao teste de Tukey. Resultados: demonstraram maior estabilidade para os mini-implantes inseridos na região de molar superior (MS) seguido de molar inferior (MI) e retromolar (RM). Esses grupos não apresentaram diferenças estatísticas entre si (P>.05), entretanto foram estatisticamente superiores aos demais. Os mini-implantes inseridos na região de sutura palatina (S) apresentaram menor estabilidade, resultado este estatisticamente inferior aos demais (P<.05). Conclusão: as diversas regiões bucais diferem quanto à estabilidade primária que, por sua vez, está diretamente relacionada à espessura da cortical óssea a qual o mini-implante está inserido.

Objective: The objective of the present work is to assess the primary stability of orthodontic mini-implants inserted into different swine maxillary and mandibular regions. Materials and Methods: 36 mini-implants orthodontic were used distributed in six groups (n = 6). The groups were appointed in accordance with area of cavity mouth was inserted. Group upper incisor (IS), upper molar (MS), suture palate (S), lower incisor (II), lower molar (MI) and retromolar (RM). It was used 3 pigs (Susscrofa Piau), which was added 12 mini-implants in three areas of the jaw and three of the jaw. After insertion, the animals were sacrificed and osseous blocks containing the mini-implants were obtained for mechanical pull-out tests to be performed by a universal test machine (Emic, São José dos Pinhais, Brazil) at cross-head speed of 0.5 mm/s. Maximum force values (N/cm) for insertion were recorded and submitted to both analysis of variance (ANOVA) and Tukey’s test. Results: demonstrated more stability to the mini-implants inserted in the region of upper molar (MS) followed by lower molar (MI) and retromolar (RM), the groups showed no statistical differences between them (P> .05), have been statistical superior to the other. The mini-implants inserted in the region of suture palate (S) had less stability, this result statistically lower than the other (P <.05). Conclusion: the various regions differ in oral primary stability which in turn is directly related to the thickness of cortical bone which the mini-implant is inserted.

Evaluation of insertion of torque and pull-out strength of mini-screws according to different thickness of artificial cortical bone / 대한치과교정학회지

OBJECTIVE: The purpose of this study was to evaluate the mechanical performance of mini-screws during insertion into artificial bone with use of the driving torque tester (Biomaterials Korea, Seoul, Korea), as well as testing of Pull-out Strength (POS). METHODS: Experimental bone blocks with different cortical bone thickness were used as specimens. Three modules of commercially available drill-free type mini-screws (Type A; pure cylindrical type, Biomaterials Korea, Seoul, Korea, Type B; partially cylindrical type, Jeil Medical, Seoul, Korea, Type C; combination type of cylindrical and tapered portions, Ortholution, Seoul, Korea), were used. RESULTS: Difference in the cortical bone thickness had little effect on the maximum insertion torque (MIT) in Type A mini-screws. But in Type B and C, MIT increased as the cortical bone thickness increased. MIT of Type C was highest in all situations, then Type B and Type A in order. Type C showed lower POS than Type A or B in all situations. There were statistically significant correlations between cortical bone thickness and MIT, and POS for each type of the mini-screws. CONCLUSION: Since different screw designs showed different insertion torques with increases in cortical bone thickness, the best suitable screw design should be selected according to the different cortical thicknesses at the implant sites

The Treatment of Gynecomastia using Ultrasound-Assisted Liposuction with Pull-Out Method or Excision through Periareolar Incision

PURPOSE: Gynecomastia is an abnormal increase in the volume of the male breast. Patients affected by gynecomastia with significant glandular enlargement may respond to suction alone and/or sharp dissection and excision. The purpose of this report is to introduce the indications and results of authors' two techniques. METHODS: The diameter of parenchyme was determined by a pinch test after liposuction. For the parenchymal diameter less than 4cm, ultrasound-assisted liposuction was performed, in conjunction with the "pull- out technique" to effectively remove the fibrofatty tissue of the male breast through a single 5-7mm incision. For the parenchymal diameter more than 4cm, ultrasound-assisted liposuction and excision were applied through 2.5cm periareolar approach. RESULTS: A total of 94 patients (185 breasts) underwent the operation from October 2000 to October 2003 and mean follow-up period was 12 months. The volume of aspirates ranged from 50 to 450 cc per breast. There were no major complications such as skin flap necrosis. Five reoperations were performed for 1 hypertrophic scar, 2 under-resected and 2 hematoma cases. The patient's satisfaction was high and most of them were pleased with the shape of the breasts and scars. CONCLUSION: These procedures can minimize scars and reduce the incidence of contour problem such as saucer deformity, and provides consistent results. Patients can return to full activities in 48 hours. It can be offered as an option for the treatment of gynecomastia.