BACKGROUND Bioabsorbable interference screws are a widely used option for graft fixation in anterior cruciate ligament(ACL)reconstruction.Their ability to degrade over time and avoid secondary hardware removal makes t...BACKGROUND Bioabsorbable interference screws are a widely used option for graft fixation in anterior cruciate ligament(ACL)reconstruction.Their ability to degrade over time and avoid secondary hardware removal makes them advantageous.However,complications such as breakage and intra-articular migration of screws can cause significant clinical issues,including joint pain,swelling,and cartilage damage.Early diagnosis and management are critical in such cases.CASE SUMMARY A 26-year-old male presented with knee pain and swelling one year after ACL reconstruction using a hamstring graft and bioabsorbable tibial interference screw.The patient had been engaged in rigorous physical activity as part of military training.Clinical examination revealed mild effusion without instability,and imaging showed screw breakage with intra-articular migration.Therapeutic arthroscopy confirmed intact graft tension,and broken screw fragments were removed successfully.The patient resumed normal activity two weeks after surgery.CONCLUSION This case highlights the potential complications associated with bioabsorbable screws,emphasizing the need for meticulous surgical technique,postoperative monitoring,and timely intervention.A comprehensive review of the literature illustrates the mechanisms,risk factors,and preventive strategies associated with screw-related complications.展开更多
BACKGROUND Pedicle screw instrumentation is a critical technique in spinal surgery,offering effective stabilization for various spinal conditions.However,the impact of intraoperative imaging quality—specifically the ...BACKGROUND Pedicle screw instrumentation is a critical technique in spinal surgery,offering effective stabilization for various spinal conditions.However,the impact of intraoperative imaging quality—specifically the use of both anteroposterior(AP)and lateral views—on surgical outcomes remains insufficiently studied.Evaluating whether the adequacy of these imaging modalities affects the risk of unplanned returns to theatre(URTT)within 90 days due to screw malplacement is essential for refining surgical practices and improving patient care.AIM To evaluate how intraoperative imaging adequacy influences unplanned returnto-theatre rates,focusing on AP and lateral fluoroscopic views.METHODS This retrospective cohort study analyzed 1335 patients who underwent thoracolumbar and sacral pedicle screw instrumentation between January 2013 and December 2022.Data on intraoperative imaging adequacy,screw placement,and URTT events were collected and statistically analyzed using IBM SPSS v23.Imaging adequacy was assessed based on the presence of both AP and lateral views,and outcomes were compared between imaging groups.RESULTS A total of 9016 pedicle screws were inserted,with 82 screws identified as malplaced in 52 patients.Of these,46 patients required URTT due to screw malplacement,with 37 returning within 90 days(URTT90).Patients with both AP and lateral imaging saved intraoperatively had significantly lower URTT90 rates compared to those with only lateral imaging saved,demonstrating the critical role of imaging adequacy in improving surgical outcomes.CONCLUSION This study underscores that comprehensive intraoperative imaging with both AP and lateral views reduces unplanned returns,improves outcomes,enhances precision,and offers a cost-effective approach for better spinal surgery results.展开更多
Objective The aim of this study was to explore the influence of working length(determined by the screw position)on the stiffness and interfragmentary strain(IFS)of femoral locking compression plate(LCP)external fixato...Objective The aim of this study was to explore the influence of working length(determined by the screw position)on the stiffness and interfragmentary strain(IFS)of femoral locking compression plate(LCP)external fixators for lower tibial fractures under full weight-bearing conditions,with the goal of providing a reference basis for clinical applications.Methods Finite element analysis software was used to construct a model of a lower tibial fracture with external femoral LCP fixation.The models were divided into four groups according to the different working lengths(external femoral locking plate fixation 1[EF1],EF2,EF3,and EF4).Stress distribution clouds,fracture end displacements,stiffness and IFS were tested for each model group at different loads.Results Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 28%,31%,and 37%,respectively,under axial compression loading.Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 19%,33%,and 35%,respectively,under axial torsion loading.Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 32%,33%,and 35%,respectively,under a three-point bending load.The IFS of the four finite element models increased with the working length of the plate,with EF1(76%)<EF2(107%)<EF3(110%)<EF4(122%).Finite element analysis revealed that under full weight-bearing conditions,the structural stiffness of the femoral LCP external fixator decreased with increasing working length,leading to an increase in the IFS,which resulted in an IFS that exceeded the ideal range required for secondary healing.Conclusion For unstable lower tibial fractures,screws in the femoral LCP external fixator should be placed as close to the fracture end as possible to increase stability and promote fracture healing.展开更多
BACKGROUND Retrograde pubic ramus screw placement is an effective technique but requires substantial surgical expertise and specialized equipment.The management of osteoporotic anterior pelvic ring injuries remains ch...BACKGROUND Retrograde pubic ramus screw placement is an effective technique but requires substantial surgical expertise and specialized equipment.The management of osteoporotic anterior pelvic ring injuries remains challenging due to technical difficulties and a high risk of complications.AIM To introduce a novel and simplified surgical approach that utilizes a custom-designed handheld pelvic alignment guide(HPAG)in combination with a 6.0 mm hollow screw,aiming to enhance the accuracy,efficiency,and safety of retrograde pubic ramus screw fixation in osteoporotic pelvic fragility fractures.METHODS The HPAG and 6.0 mm hollow screw were employed during surgical treatment.A 2.0-3.0 cm incision was made to expose the optimal screw entry point.Intraop-erative pelvic inlet and obturator oblique views were used to monitor fracture reduction and guide screw insertion.Clinical outcomes and fracture reduction quality were evaluated using Matta,visual analog scale,and Majeed scores during follow-ups.A representative case is presented to demonstrate the surgical procedure in detail.RESULTS No perioperative complications were observed.The mean operative time was 35.2±6.97 minutes,with a screw insertion time of 7.25±1.86 minutes,an average incision length of 2.8±0.67 cm,and mean blood loss of 43.25±15.64 mL.At one-year follow-up,seven patients achieved excellent Majeed scores and three achieved good scores.CONCLUSION No perioperative complications were observed.The mean operative time was 35.2±6.97 minutes,with a screw insertion time of 7.25±1.86 minutes,an average incision length of 2.8±0.67 cm,and mean blood loss of 43.25±15.64 mL.At one-year follow-up,seven patients achieved excellent Majeed scores and three achieved good scores.展开更多
Pedicle screw fixation remains the gold standard for stabilizing unstable thoracolumbar fractures.However,ensuring long-term instrumentation stability continues to challenge both surgeons and implant designers.The stu...Pedicle screw fixation remains the gold standard for stabilizing unstable thoracolumbar fractures.However,ensuring long-term instrumentation stability continues to challenge both surgeons and implant designers.The study by Bokov et al contributes significantly to this discussion,identifying predictors of pedicle screw loosening such as low bone radiodensity,longer fixation constructs,and extensive decompression.Adjunctive strategies-auxiliary posterior fusion,anterior column reconstruction,and intermediate screw usage-support an individualized,biomechanically sound surgical plan.In this article,we explore the clinical relevance of these findings within spinal trauma care.We emphasize the role of preoperative bone quality assessment,including computed tomography-based Hounsfield unit analysis and magnetic resonance imaging-derived vertebral bone quality score,as modifiable predictors of long-term outcomes.We also discuss innovations in screw design,surface coatings,and patient-specific planning to reduce failure risk.Furthermore,emerging technologies such as finite element modeling and 3D-printed instrumentation may refine patient-specific strategies.By integrating biomechanical principles with personalized surgical planning,future approaches may enhance fixation durability.Ultimately,aligning mechanical stability with biological sustainability is critical to reducing implant failure in complex thoracolumbar trauma cases.展开更多
In pedicle screw fixation,surgical robot and preoperative planning are enabling technologies to improve the accuracy and safety of pedicle screw placement.In this study,an automatic segmentation method for the pedicle...In pedicle screw fixation,surgical robot and preoperative planning are enabling technologies to improve the accuracy and safety of pedicle screw placement.In this study,an automatic segmentation method for the pedicle and vertebral body is proposed based on the 3D anatomical features of vertebrae.Further,an optimal insertion path is obtained to balance the safety of pedicle screw placement and the vertebral-screw interface strength.The pedicle screw radius is then determined based on the pedicle radius.A classification method is proposed to assess the accuracy of path planning.Finally,the surgical robot’s path can be updated based on the actual positions of the surgical robot and the patient.The CT data of 12 human vertebrae(T6−L5),10 porcine vertebrae(L1−L5)and 5 ovine vertebrae(L1−L5)are used to validate the effectiveness of the proposed method.All pedicle screw placement paths are successfully generated,achieving an excellence or good rate of 98%.Ex vivo pedicle screw placement experiments are conducted on human spine phantom,porcine and ovine spines,and in vivo experiment is conducted on a Bama miniature pig.In the proposed method,both safety and accuracy of pedicle screw placement are improved.According to the widely recognized Gertzbein-Robbins classification,93.18%of the outcomes achieve Grade A,showing promising potential in clinics.展开更多
BACKGROUND Comminuted calcaneal fractures present significant treatment challenges.Open reduction and internal fixation carries risks such as infection and skin necrosis,while minimally invasive techniques may comprom...BACKGROUND Comminuted calcaneal fractures present significant treatment challenges.Open reduction and internal fixation carries risks such as infection and skin necrosis,while minimally invasive techniques may compromise reduction stability.Conservative management is generally limited to minimally displaced fractures.Traditional Chinese manual bone-setting has a long history in fracture treatment and is renowned globally for achieving functional reduction.It offers distinct advantages including lower cost,minimal soft tissue trauma,and the avoidance of expensive reduction equipment or internal fixation materials.CASE SUMMARY A 60-year-old female presented with left foot pain and limited mobility following a fall.Computed tomography scan revealed a Sanders type IV calcaneal fracture with a Böhler angle of 0°.A standardized,stepwise Traditional Chinese manual bone-setting was initially performed,followed by percutaneous screw fixation through several mini-incisions after satisfactory alignment was confirmed under fluoroscopy.The Visual Analog Scale score decreased from 5 on postoperative day 1 to 3 by day 3.The American Orthopaedic Foot and Ankle Society score improved from 73 at 6 weeks to 90 at 3 months,indicating rapid functional recovery and high patient satisfaction.At 7 months postoperatively,the American Orthopaedic Foot and Ankle Society score reached 95,prompting removal of internal fixation.At the 6-year follow-up,reduction remained well maintained,with the Böhler angle preserved at 22°.CONCLUSION The combination of Traditional Chinese manual bone-setting and percutaneous screw fixation achieved satisfactory functional reduction for comminuted calcaneal fractures.展开更多
The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers wer...The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers were divided into the AR navigation group using surgical guides and the free-hand group.Each group consisted of a novice and an experienced spine surgeon.A total of 80 pedicle screws were implanted.First,the AR group reconstructed the 3D model and planned the screw insertion route according to the computed tomography data of L2 lumbar vertebrae.Then,the Microsoft HoloLens™2 was used to identify the vertebral model,and the planned virtual path was superimposed on the real cone model.Next,the screw was placed according to the projected trajectory.Finally,Micron Tracker was used to measure the deviation of screws from the preoperatively planned trajectory,and pedicle screws were evaluated using the Gertzbein-Robbins scale.In the AR group,the linear deviations of the experienced doctor and the novice were(1.59±0.39)mm and(1.73±0.52)mm respectively,and the angle deviations were 2.72°±0.61°and 2.87°±0.63°respectively.In the free-hand group,the linear deviations of the experienced doctor and the novice were(2.88±0.58)mm and(5.25±0.62)mm respectively,and the angle deviations were 4.41°±1.18°and 7.15°±1.45°respectively.Both kinds of deviations between the two groups were significantly different(P<0.05).The screw accuracy rate was 95%in the AR navigation group and 77.5%in the free-hand group.The results of this study indicate that the integration of surgical guides and AR is an innovative technique that can substantially enhance the safety and precision of spinal surgery and assist inexperienced doctors in completing the surgery.展开更多
Objective To compare the clinical outcomes of retrograde pubic ramus intramedullary nail(RPRIN)and percutaneous cannulated screw(PCS)in the treatment of anterior pelvic ring fractures(APRFs).Methods This retrospective...Objective To compare the clinical outcomes of retrograde pubic ramus intramedullary nail(RPRIN)and percutaneous cannulated screw(PCS)in the treatment of anterior pelvic ring fractures(APRFs).Methods This retrospective cohort study included 45 patients with APRFs treated between February 2019 and October 2022 in our trauma center.Patients were divided into two groups based on the surgical method:20 received RPRIN fixation,and 25 received PCS fixation.Key variables including operation time,fluoroscopic time,blood loss,and postoperative complications were analyzed.Fracture reduction quality was assessed using the Matta score system,and pelvic functional recovery was evaluated using the Majeed score system at the final follow-up.Quantitative variables were compared using the independent sample t test,while categorical variables were analyzed using Chisquare and Fisher’s exact tests.Results The RPRIN group had significantly shorter operation time(36.3±5.6 min vs.49.5±6.9 min,P<0.01),fluoroscopic time(32.0±2.8 s vs.48.4±3.6 s,P<0.01),and less blood loss(20.4±7.6 mL vs.34.0±5.7 mL,P<0.01)than the PCS group.Fracture reduction quality(Matta outcome)and pelvic functional recovery(Majeed outcome)were comparable between the two groups(P>0.05).No significant complications were reported in either group.Conclusions Both RPRIN and PCS are effective for treating APRFs.However,RPRIN offers distinct advantages by reducing operation time,fluoroscopic time,and blood loss,making it a more efficient and less invasive option.Further multicenter studies and biomechanical analyses are warranted to confirm these findings.展开更多
Objective:To observe and study the actual effects of percutaneous pedicle screw minimally invasive surgery in the treatment of spinal fractures and its impact on spinal function.Methods:This study included 48 patients...Objective:To observe and study the actual effects of percutaneous pedicle screw minimally invasive surgery in the treatment of spinal fractures and its impact on spinal function.Methods:This study included 48 patients with spinal fractures admitted between May 2023 and May 2024.The patients were divided into a control group and an experimental group based on treatment differences,with 24 patients in each group.The control group underwent open internal fixation surgery,while the experimental group received percutaneous pedicle screw minimally invasive surgery.Clinical index improvements,cervical dysfunction index,Japanese Orthopaedic Association scores,and pain level improvements were compared between the two groups.Results:The intraoperative blood loss,incision length,operation time,and hospitalization duration in the experimental group were(88.63±18.85),(6.32±1.05),(73.42±4.05),and(12.58±2.56),respectively,compared to(279.95±17.32),(12.89±1.36),(89.93±4.79),and(22.41±2.87)in the control group.Significant differences were observed between the groups,with the experimental group showing superior improvements across all metrics(P<0.05).Conclusion:Percutaneous pedicle screw minimally invasive surgery shows more significant effects in treating spinal fractures,particularly in improving cervical and lumbar spine function,enhancing treatment efficacy and safety,reducing pain levels,and shortening recovery time.Clinical application and promotion are recommended.展开更多
Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for bot...Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors’ previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non?redundant screws in quasi?vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two?translational and three?rotational(2T3R)5?axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthe?sized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.展开更多
The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the fl...The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the flow domain are presented by using a fluid dynamics analysis package (Polyflow). The numerical results show that the temperatures are high in the intermeshing region and on the screw surface, the maximum pressure and the minimum pressure occur in the intermeshing region, and the flow rate is almost proportional to the screw speed.展开更多
COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress di...COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress distribution,abrasive wear of screws,and energy consumption during the operation of SF.Therefore,a three-dimensional semi-cylindrical model of actual size of COREX-3000 SF was established based on discrete element method to investigate the influences of screw casing structure.The results show that the increase in the gap between the outside of screw flight and screw casing is beneficial for the smooth operation of SF,resulting in uniform descending velocity along the radius of SF in the lower part,decreasing the size of recirculation region,and alleviating stress concentration in the screw casing.Moreover,raising the gap appropriately is also beneficial to weaken screw abrasive wear,decrease energy consumption,and then prolong the service life of the screws.However,enlarging the gap also leads to more undesired high temperature reduction gas into the SF from melter gasifier,thereby deteriorating the operation of SF.Thus,an ideal distance exists between the outside of the screw flight and the screw casing,which is suggested to be equal to the average of particle diameter.展开更多
BACKGROUND Whether it’s better to adopt unilateral pedicle screw(UPS)fixation or to use bilateral pedicle screw(BPS)one for lumbar degenerative diseases is still controversially undetermined.AIM To make a comparison ...BACKGROUND Whether it’s better to adopt unilateral pedicle screw(UPS)fixation or to use bilateral pedicle screw(BPS)one for lumbar degenerative diseases is still controversially undetermined.AIM To make a comparison between UPS and BPS fixation as to how they work efficaciously and safely in patients suffering from lumbar degenerative diseases.METHODS We have searched a lot in the databases through 2020 with index terms such as“unilateral pedicle screw fixation”and“bilateral pedicle screw fixation.”Only randomized controlled trials and some prospective cohort studies could be found,yielding 15 studies.The intervention was unilateral pedicle screw fixation;Primarily We’ve got outcomes of complications and fusion rates.Secondarily,we’ve achieved outcomes regarding total blood loss,operative time,as well as length of stay.Softwares were installed and utilized for subgroup analysis,analyzing forest plots,sensitivity,heterogeneity,forest plots,publication bias,and risk of bias.RESULTS Fifteen previous cases of study including 992 participants have been involved in our meta-analysis.UPS had slightly lower effects on fusion rate[relative risk(RR)=0.949,95%CI:0.910 to 0.990,P=0.015],which contributed mostly to this metaanalysis,and similar complication rates(RR=1.140,95%CI:0.792 to 1.640,P=0.481),Δvisual analog scale[standard mean difference(SMD)=0.178,95%CI:-0.021 to 0.378,P=0.080],andΔOswestry disability index(SMD=-0.254,95%CI:-0.820 to 0.329,P=0.402).In contrast,an obvious difference has been observed inΔJapanese Orthopedic Association(JOA)score(SMD=0.305,95%CI:0.046 to 0.563,P=0.021),total blood loss(SMD=-1.586,95%CI:-2.182 to-0.990,P=0.000),operation time(SMD=-2.831,95%CI:-3.753 to-1.909,P=0.000),and length of hospital stay(SMD=-0.614,95%CI:-1.050 to-0.179,P=0.006).CONCLUSION Bilateral fixation is more effective than unilateral fixation regarding fusion rate after lumbar interbody fusion.However,JOA,operation time,total blood loss,as well as length of stay were improved for unilateral fixation.展开更多
BACKGROUND Intertrochanteric(IT)fracture is one of the most common fractures seen in an orthopaedic practice.Proximal femoral nailing(PFN)is a common modality of fixing IT femur fracture.We retrospectively studied whe...BACKGROUND Intertrochanteric(IT)fracture is one of the most common fractures seen in an orthopaedic practice.Proximal femoral nailing(PFN)is a common modality of fixing IT femur fracture.We retrospectively studied whether a PFN with two proximal lag screws can be done without distal interlocking screws in the 31-A1 and 31-A2 fracture patterns according to the Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association(AO/OTA)guidelines for IT femur fractures.AIM To compare the outcomes of IT fractures(AO/OTA 31-A1 and 31-A2)treated by PFN with and without distal interlocking screws.METHODS We carried out a retrospective study of 140 patients in a tertiary care centre who had AO/OTA type 31-A1 and 31-A2 IT fractures.We divided the patients into two groups,in which one of the groups received distal interlocking screws(group 1)and the other group did not(group 2).The subjects were followed up for a mean period of 14 mo and assessed for radiological union time,fracture site collapse,mechanical stability of implant,and complications associated with the PFN with distal interlocking and without distal interlocking.Then,the results were compared.RESULTS PFN without distal interlocking screws has several advantages and gives better results over PFN with distal interlocking screws in the AO/OTA 31-A2 fracture pattern.However,similar results were observed in both groups with the fracture pattern AO/OTA 31-A1.In patients with fracture pattern AO/OTA 31-A2 treated by PFN without distal interlocking screws,there were minimal proximal lockrelated complications and no risk of distal interlock-related complications.The operative time,IITV radiation time and time to radiological union were reduced.These patients also had better rotational alignment of the proximal femur,and the anatomy of the proximal femur was well maintained.It was also noted that in the cases where distal interlocking was performed,there was a gradual decrease in neck shaft angle,which led to varus collapse and failure of bone-implant construct in 21.40%.CONCLUSION In fracture pattern AO/OTA 31-A2,PFN without distal interlocking had better results and less complications than PFN with distal interlocking.展开更多
The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element m...The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element method. Three dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing per forulance was characterized by the resident time distribution. The results indicate that the counter rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co rotating TSE has better performance in dispersive and distributive mixing.展开更多
BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stabi...BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stability have been insufficiently studied.AIM To estimate the contribution of screw design to rate of pedicle screw loosening in patients with degenerative diseases of the lumbar spine.METHODS This study is a prospective evaluation of 175 patients with degenerative diseases and instability of the lumbar spine segments.Participants underwent spinal instrumentation employing pedicle screws with posterior only or transforaminal interbody fusion.Follow-up was for 18 mo.Patients with signs of pedicle screw loosening on computed tomography were registered;logistic regression analysis was used to identify the factors that influenced the rate of loosening.RESULTS Parameters included in the analysis were screw geometry,type of thread,external and internal screw diameter and helical pitch,bone density in Hounsfield units,number of levels fused,instrumentation without anterior support,laminectomy,and unilateral and bilateral total facet joint resection.The rate of screw loosening decreased with the increment in outer diameter,decrease in core diameter and helical pitch.The rate of screw loosening correlated positively with the number of fused levels and decreasing bone density.Bilateral facet joint removal significantly favored pedicle screw loosening.The influence of other factors was insignificant.CONCLUSION Screw parameters had a significant impact on the loosening rate along with bone quality characteristics,the number of levels fused and the extensiveness of decompression.The significance of the influence of screw parameters was comparable to those of patient-and surgery-related factors.Pedicle screw loosening was influenced by helical pitch,inner and outer diameter,but screw geometry and thread type were insignificant factors.展开更多
BACKGROUND The incidence of lumbar tuberculosis is high worldwide,and effective treatment is a continuing problem.AIM To study the safety and efficacy of the multitrack and multianchor point screw technique combined w...BACKGROUND The incidence of lumbar tuberculosis is high worldwide,and effective treatment is a continuing problem.AIM To study the safety and efficacy of the multitrack and multianchor point screw technique combined with the contralateral Wiltse approach for lesion debridement to treat lumbar tuberculosis.METHODS The C-reactive protein(CRP)level,erythrocyte sedimentation rate(ESR),visual analogue scale(VAS)score,oswestry disability index(ODI)and American Spinal Injury Association(ASIA)grade were recorded and analysed pre-and postoperatively.RESULTS The CRP level and ESR returned to normal,and the VAS score and ODI were decreased at 3 mo postoperatively,with significant differences compared with the preoperative values(P<0.01).Neurological dysfunction was relieved,and the ASIA grade increased,with no adverse events.CONCLUSION The multitrack,multianchor point screw fixation technique combined with the contralateral Wiltse approach for debridement is an effective and safe method for the treatment of lumbar tuberculosis.展开更多
In the light of screw addition, the distribution of instantaneous axes along the common perpendicular of the two screws is determined and all possible sorts of axodes are derived cinematically with the pitch of the re...In the light of screw addition, the distribution of instantaneous axes along the common perpendicular of the two screws is determined and all possible sorts of axodes are derived cinematically with the pitch of the relative motion screw in the gear pair as the basis and the transmission ratio i as an independent variable.展开更多
文摘BACKGROUND Bioabsorbable interference screws are a widely used option for graft fixation in anterior cruciate ligament(ACL)reconstruction.Their ability to degrade over time and avoid secondary hardware removal makes them advantageous.However,complications such as breakage and intra-articular migration of screws can cause significant clinical issues,including joint pain,swelling,and cartilage damage.Early diagnosis and management are critical in such cases.CASE SUMMARY A 26-year-old male presented with knee pain and swelling one year after ACL reconstruction using a hamstring graft and bioabsorbable tibial interference screw.The patient had been engaged in rigorous physical activity as part of military training.Clinical examination revealed mild effusion without instability,and imaging showed screw breakage with intra-articular migration.Therapeutic arthroscopy confirmed intact graft tension,and broken screw fragments were removed successfully.The patient resumed normal activity two weeks after surgery.CONCLUSION This case highlights the potential complications associated with bioabsorbable screws,emphasizing the need for meticulous surgical technique,postoperative monitoring,and timely intervention.A comprehensive review of the literature illustrates the mechanisms,risk factors,and preventive strategies associated with screw-related complications.
文摘BACKGROUND Pedicle screw instrumentation is a critical technique in spinal surgery,offering effective stabilization for various spinal conditions.However,the impact of intraoperative imaging quality—specifically the use of both anteroposterior(AP)and lateral views—on surgical outcomes remains insufficiently studied.Evaluating whether the adequacy of these imaging modalities affects the risk of unplanned returns to theatre(URTT)within 90 days due to screw malplacement is essential for refining surgical practices and improving patient care.AIM To evaluate how intraoperative imaging adequacy influences unplanned returnto-theatre rates,focusing on AP and lateral fluoroscopic views.METHODS This retrospective cohort study analyzed 1335 patients who underwent thoracolumbar and sacral pedicle screw instrumentation between January 2013 and December 2022.Data on intraoperative imaging adequacy,screw placement,and URTT events were collected and statistically analyzed using IBM SPSS v23.Imaging adequacy was assessed based on the presence of both AP and lateral views,and outcomes were compared between imaging groups.RESULTS A total of 9016 pedicle screws were inserted,with 82 screws identified as malplaced in 52 patients.Of these,46 patients required URTT due to screw malplacement,with 37 returning within 90 days(URTT90).Patients with both AP and lateral imaging saved intraoperatively had significantly lower URTT90 rates compared to those with only lateral imaging saved,demonstrating the critical role of imaging adequacy in improving surgical outcomes.CONCLUSION This study underscores that comprehensive intraoperative imaging with both AP and lateral views reduces unplanned returns,improves outcomes,enhances precision,and offers a cost-effective approach for better spinal surgery results.
基金supported by the Health Commission of Guizhou Province(No.gzwkj2024-400)the“Open Competition Project”of Bijie Science and Technology Bureau(BST Major Project No.1,2022).
文摘Objective The aim of this study was to explore the influence of working length(determined by the screw position)on the stiffness and interfragmentary strain(IFS)of femoral locking compression plate(LCP)external fixators for lower tibial fractures under full weight-bearing conditions,with the goal of providing a reference basis for clinical applications.Methods Finite element analysis software was used to construct a model of a lower tibial fracture with external femoral LCP fixation.The models were divided into four groups according to the different working lengths(external femoral locking plate fixation 1[EF1],EF2,EF3,and EF4).Stress distribution clouds,fracture end displacements,stiffness and IFS were tested for each model group at different loads.Results Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 28%,31%,and 37%,respectively,under axial compression loading.Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 19%,33%,and 35%,respectively,under axial torsion loading.Compared with those in the EF1 group,the stiffnesses in the EF2,EF3,and EF4 groups decreased by 32%,33%,and 35%,respectively,under a three-point bending load.The IFS of the four finite element models increased with the working length of the plate,with EF1(76%)<EF2(107%)<EF3(110%)<EF4(122%).Finite element analysis revealed that under full weight-bearing conditions,the structural stiffness of the femoral LCP external fixator decreased with increasing working length,leading to an increase in the IFS,which resulted in an IFS that exceeded the ideal range required for secondary healing.Conclusion For unstable lower tibial fractures,screws in the femoral LCP external fixator should be placed as close to the fracture end as possible to increase stability and promote fracture healing.
基金Supported by Shanghai Tongren Hospital,Shanghai Jiaotong University School of Medicine,No.TRYJ2024 LC16the National Natural Science Foundation of China,No.82102577the Laboratory Open Fund of Key Technology and Materials in Minimally Invasive Spine Surgery,No.2024JZWC-YBA05.
文摘BACKGROUND Retrograde pubic ramus screw placement is an effective technique but requires substantial surgical expertise and specialized equipment.The management of osteoporotic anterior pelvic ring injuries remains challenging due to technical difficulties and a high risk of complications.AIM To introduce a novel and simplified surgical approach that utilizes a custom-designed handheld pelvic alignment guide(HPAG)in combination with a 6.0 mm hollow screw,aiming to enhance the accuracy,efficiency,and safety of retrograde pubic ramus screw fixation in osteoporotic pelvic fragility fractures.METHODS The HPAG and 6.0 mm hollow screw were employed during surgical treatment.A 2.0-3.0 cm incision was made to expose the optimal screw entry point.Intraop-erative pelvic inlet and obturator oblique views were used to monitor fracture reduction and guide screw insertion.Clinical outcomes and fracture reduction quality were evaluated using Matta,visual analog scale,and Majeed scores during follow-ups.A representative case is presented to demonstrate the surgical procedure in detail.RESULTS No perioperative complications were observed.The mean operative time was 35.2±6.97 minutes,with a screw insertion time of 7.25±1.86 minutes,an average incision length of 2.8±0.67 cm,and mean blood loss of 43.25±15.64 mL.At one-year follow-up,seven patients achieved excellent Majeed scores and three achieved good scores.CONCLUSION No perioperative complications were observed.The mean operative time was 35.2±6.97 minutes,with a screw insertion time of 7.25±1.86 minutes,an average incision length of 2.8±0.67 cm,and mean blood loss of 43.25±15.64 mL.At one-year follow-up,seven patients achieved excellent Majeed scores and three achieved good scores.
文摘Pedicle screw fixation remains the gold standard for stabilizing unstable thoracolumbar fractures.However,ensuring long-term instrumentation stability continues to challenge both surgeons and implant designers.The study by Bokov et al contributes significantly to this discussion,identifying predictors of pedicle screw loosening such as low bone radiodensity,longer fixation constructs,and extensive decompression.Adjunctive strategies-auxiliary posterior fusion,anterior column reconstruction,and intermediate screw usage-support an individualized,biomechanically sound surgical plan.In this article,we explore the clinical relevance of these findings within spinal trauma care.We emphasize the role of preoperative bone quality assessment,including computed tomography-based Hounsfield unit analysis and magnetic resonance imaging-derived vertebral bone quality score,as modifiable predictors of long-term outcomes.We also discuss innovations in screw design,surface coatings,and patient-specific planning to reduce failure risk.Furthermore,emerging technologies such as finite element modeling and 3D-printed instrumentation may refine patient-specific strategies.By integrating biomechanical principles with personalized surgical planning,future approaches may enhance fixation durability.Ultimately,aligning mechanical stability with biological sustainability is critical to reducing implant failure in complex thoracolumbar trauma cases.
基金Supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2024A1515011897)Shenzhen Science and Technology Program(Grant No.KQTD20210811090143060)+1 种基金Sustainable Development Science and Technology Special Project of Shenzhen(Grant No.KCXFZ20230731100900002)Tianjin Municipal Science and Technology Program(Grant No.22JCYBJC01240).
文摘In pedicle screw fixation,surgical robot and preoperative planning are enabling technologies to improve the accuracy and safety of pedicle screw placement.In this study,an automatic segmentation method for the pedicle and vertebral body is proposed based on the 3D anatomical features of vertebrae.Further,an optimal insertion path is obtained to balance the safety of pedicle screw placement and the vertebral-screw interface strength.The pedicle screw radius is then determined based on the pedicle radius.A classification method is proposed to assess the accuracy of path planning.Finally,the surgical robot’s path can be updated based on the actual positions of the surgical robot and the patient.The CT data of 12 human vertebrae(T6−L5),10 porcine vertebrae(L1−L5)and 5 ovine vertebrae(L1−L5)are used to validate the effectiveness of the proposed method.All pedicle screw placement paths are successfully generated,achieving an excellence or good rate of 98%.Ex vivo pedicle screw placement experiments are conducted on human spine phantom,porcine and ovine spines,and in vivo experiment is conducted on a Bama miniature pig.In the proposed method,both safety and accuracy of pedicle screw placement are improved.According to the widely recognized Gertzbein-Robbins classification,93.18%of the outcomes achieve Grade A,showing promising potential in clinics.
基金Supported by Jin-Wen Liu Academic Experience Heritage Studio Special Fund of National Famous Traditional Chinese Medicine,No.75.
文摘BACKGROUND Comminuted calcaneal fractures present significant treatment challenges.Open reduction and internal fixation carries risks such as infection and skin necrosis,while minimally invasive techniques may compromise reduction stability.Conservative management is generally limited to minimally displaced fractures.Traditional Chinese manual bone-setting has a long history in fracture treatment and is renowned globally for achieving functional reduction.It offers distinct advantages including lower cost,minimal soft tissue trauma,and the avoidance of expensive reduction equipment or internal fixation materials.CASE SUMMARY A 60-year-old female presented with left foot pain and limited mobility following a fall.Computed tomography scan revealed a Sanders type IV calcaneal fracture with a Böhler angle of 0°.A standardized,stepwise Traditional Chinese manual bone-setting was initially performed,followed by percutaneous screw fixation through several mini-incisions after satisfactory alignment was confirmed under fluoroscopy.The Visual Analog Scale score decreased from 5 on postoperative day 1 to 3 by day 3.The American Orthopaedic Foot and Ankle Society score improved from 73 at 6 weeks to 90 at 3 months,indicating rapid functional recovery and high patient satisfaction.At 7 months postoperatively,the American Orthopaedic Foot and Ankle Society score reached 95,prompting removal of internal fixation.At the 6-year follow-up,reduction remained well maintained,with the Böhler angle preserved at 22°.CONCLUSION The combination of Traditional Chinese manual bone-setting and percutaneous screw fixation achieved satisfactory functional reduction for comminuted calcaneal fractures.
基金the National Natural Science Foundation of China(No.11502146)the 1 Batch of 2021 MOE of PRC Industry University Collaborative Education Program(No.202101042008)。
文摘The aim of this study was to assess the potential of surgical guides as a complementary tool to augmented reality(AR)in enhancing the safety and precision of pedicle screw placement in spinal surgery.Four trainers were divided into the AR navigation group using surgical guides and the free-hand group.Each group consisted of a novice and an experienced spine surgeon.A total of 80 pedicle screws were implanted.First,the AR group reconstructed the 3D model and planned the screw insertion route according to the computed tomography data of L2 lumbar vertebrae.Then,the Microsoft HoloLens™2 was used to identify the vertebral model,and the planned virtual path was superimposed on the real cone model.Next,the screw was placed according to the projected trajectory.Finally,Micron Tracker was used to measure the deviation of screws from the preoperatively planned trajectory,and pedicle screws were evaluated using the Gertzbein-Robbins scale.In the AR group,the linear deviations of the experienced doctor and the novice were(1.59±0.39)mm and(1.73±0.52)mm respectively,and the angle deviations were 2.72°±0.61°and 2.87°±0.63°respectively.In the free-hand group,the linear deviations of the experienced doctor and the novice were(2.88±0.58)mm and(5.25±0.62)mm respectively,and the angle deviations were 4.41°±1.18°and 7.15°±1.45°respectively.Both kinds of deviations between the two groups were significantly different(P<0.05).The screw accuracy rate was 95%in the AR navigation group and 77.5%in the free-hand group.The results of this study indicate that the integration of surgical guides and AR is an innovative technique that can substantially enhance the safety and precision of spinal surgery and assist inexperienced doctors in completing the surgery.
基金supported by Clinical Application-oriented Medical Innovation Foundation from National Clinical Research Center for Orthopedics,Sports Medicine&Rehabilitation and Jiangsu China-Israel Industrial Technical Research Institute Foundation(No.2021-NCRC-CXJJ-ZH-24)National Key R&D Plan of the 14th Five-Year Plan(No.2022YFC2504303).
文摘Objective To compare the clinical outcomes of retrograde pubic ramus intramedullary nail(RPRIN)and percutaneous cannulated screw(PCS)in the treatment of anterior pelvic ring fractures(APRFs).Methods This retrospective cohort study included 45 patients with APRFs treated between February 2019 and October 2022 in our trauma center.Patients were divided into two groups based on the surgical method:20 received RPRIN fixation,and 25 received PCS fixation.Key variables including operation time,fluoroscopic time,blood loss,and postoperative complications were analyzed.Fracture reduction quality was assessed using the Matta score system,and pelvic functional recovery was evaluated using the Majeed score system at the final follow-up.Quantitative variables were compared using the independent sample t test,while categorical variables were analyzed using Chisquare and Fisher’s exact tests.Results The RPRIN group had significantly shorter operation time(36.3±5.6 min vs.49.5±6.9 min,P<0.01),fluoroscopic time(32.0±2.8 s vs.48.4±3.6 s,P<0.01),and less blood loss(20.4±7.6 mL vs.34.0±5.7 mL,P<0.01)than the PCS group.Fracture reduction quality(Matta outcome)and pelvic functional recovery(Majeed outcome)were comparable between the two groups(P>0.05).No significant complications were reported in either group.Conclusions Both RPRIN and PCS are effective for treating APRFs.However,RPRIN offers distinct advantages by reducing operation time,fluoroscopic time,and blood loss,making it a more efficient and less invasive option.Further multicenter studies and biomechanical analyses are warranted to confirm these findings.
文摘Objective:To observe and study the actual effects of percutaneous pedicle screw minimally invasive surgery in the treatment of spinal fractures and its impact on spinal function.Methods:This study included 48 patients with spinal fractures admitted between May 2023 and May 2024.The patients were divided into a control group and an experimental group based on treatment differences,with 24 patients in each group.The control group underwent open internal fixation surgery,while the experimental group received percutaneous pedicle screw minimally invasive surgery.Clinical index improvements,cervical dysfunction index,Japanese Orthopaedic Association scores,and pain level improvements were compared between the two groups.Results:The intraoperative blood loss,incision length,operation time,and hospitalization duration in the experimental group were(88.63±18.85),(6.32±1.05),(73.42±4.05),and(12.58±2.56),respectively,compared to(279.95±17.32),(12.89±1.36),(89.93±4.79),and(22.41±2.87)in the control group.Significant differences were observed between the groups,with the experimental group showing superior improvements across all metrics(P<0.05).Conclusion:Percutaneous pedicle screw minimally invasive surgery shows more significant effects in treating spinal fractures,particularly in improving cervical and lumbar spine function,enhancing treatment efficacy and safety,reducing pain levels,and shortening recovery time.Clinical application and promotion are recommended.
基金Supported by National Natural Science Foundation of China(Grant No.51675366)Tianjin Research Program of Application Foundation and Advanced Technology(Grant Nos.16JCYBJC19300,15JCZDJC38900)
文摘Unifying the models for topology design and kinematic analysis has long been a desire for the research of parallel kinematic machines(PKMs). This requires that analytical description, formulation and operation for both finite and instantaneous motions are performed by the same mathematical tool. Based upon finite and instantaneous screw theory, a unified and systematic approach for topology design and kinematic analysis of PKMs is proposed in this paper. Using the derivative mapping between finite and instantaneous screws built in the authors’ previous work, the finite and instantaneous motions of PKMs are analytically described by the simple and non?redundant screws in quasi?vector and vector forms. And topological and parametric models of PKMs are algebraically formulated and related. These related topological and parametric models are ready to do type synthesis and kinematic analysis of PKMs under the unified framework of screw theory. In order to show the validity of the proposed approach, a kind of two?translational and three?rotational(2T3R)5?axis PKMs is taken as example. Numerous new structures of the 2T3R PKMs are synthe?sized as the results of topology design, and their Jacobian matrix is obtained easily for parameter optimization and performance evaluation. Some of the synthesized PKMs have outstanding capabilities in terms of large workspaces and flexible orientations, and have great potential for industrial applications of machining and manufacture. Among them, METROM PKM is a typical example which has attracted a lot of attention from global companies and already been developed as commercial products. The approach is a general and unified approach that can be used in the innovative design of different kinds of PKMs.
文摘The 3 D non isothermal flow of non Newtonian viscous polymer melt in a co rotating twin screw extruder is modeled. The distributions of the velocity, temperature, pressure and the viscous dissipation in the flow domain are presented by using a fluid dynamics analysis package (Polyflow). The numerical results show that the temperatures are high in the intermeshing region and on the screw surface, the maximum pressure and the minimum pressure occur in the intermeshing region, and the flow rate is almost proportional to the screw speed.
基金supported by the National Key Technology Research and Development Program of China (Grant No.2011BAE04B02)National Natural Science Foundation of China(Grant No.51174053)
文摘COREX shaft furnace（SF）is a typical screw feeder with a storage container coupled with eight screw casings and screws.The structure of screw casing plays an important role in the moving behavior of burdens,stress distribution,abrasive wear of screws,and energy consumption during the operation of SF.Therefore,a three-dimensional semi-cylindrical model of actual size of COREX-3000 SF was established based on discrete element method to investigate the influences of screw casing structure.The results show that the increase in the gap between the outside of screw flight and screw casing is beneficial for the smooth operation of SF,resulting in uniform descending velocity along the radius of SF in the lower part,decreasing the size of recirculation region,and alleviating stress concentration in the screw casing.Moreover,raising the gap appropriately is also beneficial to weaken screw abrasive wear,decrease energy consumption,and then prolong the service life of the screws.However,enlarging the gap also leads to more undesired high temperature reduction gas into the SF from melter gasifier,thereby deteriorating the operation of SF.Thus,an ideal distance exists between the outside of the screw flight and the screw casing,which is suggested to be equal to the average of particle diameter.
基金Supported by the Health Science and Technology of Tianjin Municipality,No.RC20204Tianjin Institute of Orthopedics,No.2019TJGYSKY03the National Natural Science Foundation of China,No.818717771177226。
文摘BACKGROUND Whether it’s better to adopt unilateral pedicle screw(UPS)fixation or to use bilateral pedicle screw(BPS)one for lumbar degenerative diseases is still controversially undetermined.AIM To make a comparison between UPS and BPS fixation as to how they work efficaciously and safely in patients suffering from lumbar degenerative diseases.METHODS We have searched a lot in the databases through 2020 with index terms such as“unilateral pedicle screw fixation”and“bilateral pedicle screw fixation.”Only randomized controlled trials and some prospective cohort studies could be found,yielding 15 studies.The intervention was unilateral pedicle screw fixation;Primarily We’ve got outcomes of complications and fusion rates.Secondarily,we’ve achieved outcomes regarding total blood loss,operative time,as well as length of stay.Softwares were installed and utilized for subgroup analysis,analyzing forest plots,sensitivity,heterogeneity,forest plots,publication bias,and risk of bias.RESULTS Fifteen previous cases of study including 992 participants have been involved in our meta-analysis.UPS had slightly lower effects on fusion rate[relative risk(RR)=0.949,95%CI:0.910 to 0.990,P=0.015],which contributed mostly to this metaanalysis,and similar complication rates(RR=1.140,95%CI:0.792 to 1.640,P=0.481),Δvisual analog scale[standard mean difference(SMD)=0.178,95%CI:-0.021 to 0.378,P=0.080],andΔOswestry disability index(SMD=-0.254,95%CI:-0.820 to 0.329,P=0.402).In contrast,an obvious difference has been observed inΔJapanese Orthopedic Association(JOA)score(SMD=0.305,95%CI:0.046 to 0.563,P=0.021),total blood loss(SMD=-1.586,95%CI:-2.182 to-0.990,P=0.000),operation time(SMD=-2.831,95%CI:-3.753 to-1.909,P=0.000),and length of hospital stay(SMD=-0.614,95%CI:-1.050 to-0.179,P=0.006).CONCLUSION Bilateral fixation is more effective than unilateral fixation regarding fusion rate after lumbar interbody fusion.However,JOA,operation time,total blood loss,as well as length of stay were improved for unilateral fixation.
文摘BACKGROUND Intertrochanteric(IT)fracture is one of the most common fractures seen in an orthopaedic practice.Proximal femoral nailing(PFN)is a common modality of fixing IT femur fracture.We retrospectively studied whether a PFN with two proximal lag screws can be done without distal interlocking screws in the 31-A1 and 31-A2 fracture patterns according to the Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association(AO/OTA)guidelines for IT femur fractures.AIM To compare the outcomes of IT fractures(AO/OTA 31-A1 and 31-A2)treated by PFN with and without distal interlocking screws.METHODS We carried out a retrospective study of 140 patients in a tertiary care centre who had AO/OTA type 31-A1 and 31-A2 IT fractures.We divided the patients into two groups,in which one of the groups received distal interlocking screws(group 1)and the other group did not(group 2).The subjects were followed up for a mean period of 14 mo and assessed for radiological union time,fracture site collapse,mechanical stability of implant,and complications associated with the PFN with distal interlocking and without distal interlocking.Then,the results were compared.RESULTS PFN without distal interlocking screws has several advantages and gives better results over PFN with distal interlocking screws in the AO/OTA 31-A2 fracture pattern.However,similar results were observed in both groups with the fracture pattern AO/OTA 31-A1.In patients with fracture pattern AO/OTA 31-A2 treated by PFN without distal interlocking screws,there were minimal proximal lockrelated complications and no risk of distal interlock-related complications.The operative time,IITV radiation time and time to radiological union were reduced.These patients also had better rotational alignment of the proximal femur,and the anatomy of the proximal femur was well maintained.It was also noted that in the cases where distal interlocking was performed,there was a gradual decrease in neck shaft angle,which led to varus collapse and failure of bone-implant construct in 21.40%.CONCLUSION In fracture pattern AO/OTA 31-A2,PFN without distal interlocking had better results and less complications than PFN with distal interlocking.
基金Supported by the Industrial Foundation(20091041038)
文摘The flow process of unplasticized polyvinyl chloride （U PVC） through the mixing zone of intermeshing counter rotating and co rotating twin screw extruders （TSEs） were numerically simula ted by the finite element method. Three dimensional isothermal flow field of U-PVC in two kinds of TSE was calculated. The mixing performance of the screw elements of the extruders was statistically analyzed by particle tracking method. The dispersive mixing performance was characterized by the mixing index, the logarithm of stretching, and the segregation scale. The distributive mixing per forulance was characterized by the resident time distribution. The results indicate that the counter rotating TSE can build higher pressure and generate higher axial velocity and shear rate, whereas the co rotating TSE has better performance in dispersive and distributive mixing.
文摘BACKGROUND The majority of published data report the results of biomechanical tests of various design pedicle screw performance.The clinical relevance and relative contribution of screw design to instrumentation stability have been insufficiently studied.AIM To estimate the contribution of screw design to rate of pedicle screw loosening in patients with degenerative diseases of the lumbar spine.METHODS This study is a prospective evaluation of 175 patients with degenerative diseases and instability of the lumbar spine segments.Participants underwent spinal instrumentation employing pedicle screws with posterior only or transforaminal interbody fusion.Follow-up was for 18 mo.Patients with signs of pedicle screw loosening on computed tomography were registered;logistic regression analysis was used to identify the factors that influenced the rate of loosening.RESULTS Parameters included in the analysis were screw geometry,type of thread,external and internal screw diameter and helical pitch,bone density in Hounsfield units,number of levels fused,instrumentation without anterior support,laminectomy,and unilateral and bilateral total facet joint resection.The rate of screw loosening decreased with the increment in outer diameter,decrease in core diameter and helical pitch.The rate of screw loosening correlated positively with the number of fused levels and decreasing bone density.Bilateral facet joint removal significantly favored pedicle screw loosening.The influence of other factors was insignificant.CONCLUSION Screw parameters had a significant impact on the loosening rate along with bone quality characteristics,the number of levels fused and the extensiveness of decompression.The significance of the influence of screw parameters was comparable to those of patient-and surgery-related factors.Pedicle screw loosening was influenced by helical pitch,inner and outer diameter,but screw geometry and thread type were insignificant factors.
基金Supported by 2023 Hebei Province Medical Science Research Project Plan,No.20231958。
文摘BACKGROUND The incidence of lumbar tuberculosis is high worldwide,and effective treatment is a continuing problem.AIM To study the safety and efficacy of the multitrack and multianchor point screw technique combined with the contralateral Wiltse approach for lesion debridement to treat lumbar tuberculosis.METHODS The C-reactive protein(CRP)level,erythrocyte sedimentation rate(ESR),visual analogue scale(VAS)score,oswestry disability index(ODI)and American Spinal Injury Association(ASIA)grade were recorded and analysed pre-and postoperatively.RESULTS The CRP level and ESR returned to normal,and the VAS score and ODI were decreased at 3 mo postoperatively,with significant differences compared with the preoperative values(P<0.01).Neurological dysfunction was relieved,and the ASIA grade increased,with no adverse events.CONCLUSION The multitrack,multianchor point screw fixation technique combined with the contralateral Wiltse approach for debridement is an effective and safe method for the treatment of lumbar tuberculosis.
文摘In the light of screw addition, the distribution of instantaneous axes along the common perpendicular of the two screws is determined and all possible sorts of axodes are derived cinematically with the pitch of the relative motion screw in the gear pair as the basis and the transmission ratio i as an independent variable.
