BACKGROUND Percutaneous vertebroplasty(PVP)is an effective method for the treatment of neurologically intact Kümmell’s disease,but bone cement leakage during surgery is a problem that deserves attention.AIM To r...BACKGROUND Percutaneous vertebroplasty(PVP)is an effective method for the treatment of neurologically intact Kümmell’s disease,but bone cement leakage during surgery is a problem that deserves attention.AIM To reduce bone cement leakage and evaluate the effect of the sequential infusion of bone cement during PVP for the treatment of stage I or II Kümmell’s disease.METHODS Patients with Kümmell’s disease treated in our hospital from September 2015 to September 2018 were retrospectively analyzed.Patients meeting the inclusion and exclusion criteria were divided into two groups:Traditional single infusion and sequential infusion(SI).The visual analog scale(VAS)and Oswestry disability index(ODI)were evaluated and compared,and duration of operation,bone cement content and complications were recorded.RESULTS Forty-five patients were included in this study;there were 24 in the traditional single infusion group and 21 in the SI group.The VAS and ODI were significantly different for both groups when compared pre-and postoperatively,whereas the differences between 1 wk postoperatively and at the final follow-up were not statistically.When the VAS and ODI of the two groups were compared,there were no significant differences at any time point.The leakage rate of bone cement was significantly lower in the SI group(14.3%,3 of 21)than that in the traditional single infusion group(41.7%,10 of 24).CONCLUSION SI in unipedicular PVP is a safe and effective procedure for neurologically intact Kümmell’s disease,and this technique could decrease the incidence of bone cement leakage.展开更多
Runt-related transcription factor 1(Runx1)plays a key role in cartilage formation,but its function in articular cartilage formation is unclear.We generated non-inducible and inducible Runx1-deficient mice(Runx1^(f/f)C...Runt-related transcription factor 1(Runx1)plays a key role in cartilage formation,but its function in articular cartilage formation is unclear.We generated non-inducible and inducible Runx1-deficient mice(Runx1^(f/f)Col2α1-Cre and Runx1^(f/f)Col2α1-CreER mice)and found that chondrocyte-specific Runx1-deficient mice developed a spontaneous osteoarthritis(OA)-like phenotype and showed exacerbated articular cartilage destruction under OA,characterized by articular cartilage degradation and cartilage ossification,with decreased Col2α1 expression and increased Mmp13 and Adamts5 expression.RNA-sequencing analysis of hip articular cartilage from the Runx1^(f/f)Col2α1-Cre mice compared to that from wild-type mice and subsequent validation analyses demonstrated that Runx1 is a central regulator in multiple signaling pathways,converging signals of the Hippo/Yap,TGFβ/Smad,and Wnt/β-catenin pathways into a complex network to regulate the expression of downstream genes,thereby controlling a series of osteoarthritic pathological processes.RNA-sequencing analysis of mutant knee joints showed that Runx1’s role in signaling pathways in articular cartilage is different from that in whole knee joints,indicating that Runx1 regulation is tissue-specific.Histopathologic analysis confirmed that Runx1 deficiency decreased the levels of YAP and p-Smad2/3 and increased the levels of activeβ-catenin.Overexpression of Runx1 dramatically increased YAP expression in chondrocytes.Adeno-associated virus-mediated Runx1 overexpression in the knee joints of osteoarthritic mice showed the protective effect of Runx1 on articular cartilage damaged in OA.Our results notably showed that Runx1 is a central regulator of articular cartilage homeostasis by orchestrating the YAP,TGFβ,and Wnt signaling pathways in the formation of articular cartilage and OA,and targeting Runx1 and its downstream genes may facilitate the design of novel therapeutic approaches for OA.展开更多
Objective: To assess the effects of axial vibrations on gene expression and lumbar intervertebral disc degeneration in vivo. Methods: A modified bipedal rat model was established using a brachial plexus rhizotomy appr...Objective: To assess the effects of axial vibrations on gene expression and lumbar intervertebral disc degeneration in vivo. Methods: A modified bipedal rat model was established using a brachial plexus rhizotomy approach to imitate human upright posture. The experimental animals were randomly divided into three groups: control, vertical vibration, and whole-body vibration. Gene expression in degeneration of the intervertebral discs was assessed by reverse transcription-quantitative polymerase chain reaction. Results: The expression of aggrecan, Col1α1, Col2α1, and decorin were shown to be up-regulated in 14-week-old rats in the vertical vibration and whole-body vibration groups, whereas biglycan and versican expression was down-regulated in 14-week-old rats of the two experimental groups. Furthermore, biglycan and versican expression levels were shown to be lower in the whole-body vibration group than in the vertical vibration group(P<0.05). Conclusions: This in-vivo study demonstrated that vibrations can influence the expression of anabolic genes. Furthermore, whole-body vibrations seem to have a greater effect in this regard than vertical vibrations. A new method is expected to relieve the low back pain of the patients through our research.展开更多
BACKGROUND Fractures of the axis are commonly seen in spinal injuries. Upper cervical fractures are usually managed conservatively. However, the complications due to long-term external immobilization cannot be ignored...BACKGROUND Fractures of the axis are commonly seen in spinal injuries. Upper cervical fractures are usually managed conservatively. However, the complications due to long-term external immobilization cannot be ignored. The traditional open surgery has the disadvantages of too much blood loss and soft tissue injury. The aim of our paper is to introduce a minimally invasive surgical treatment for multiple axis fractures.CASE SUMMARY We report a 40-year-old Chinese male who had severe neck pain and difficult neck movement after falling from 3 meters. X-ray and computed tomography(CT) scan revealed an axis injury consisting of an odontoid Type Ⅲ fracture associated with a Hangman fracture categorized as a Levine-Edwards Type Ⅰ fracture. The patient underwent anterior odontoid screw fixation and posterior percutaneous screw fixation using intraoperative O-arm navigation. Neck pain was markedly improved after surgery. X-rays and CT scan reconstructions of 3-mo follow-up showed good stability and fusion. The range of cervical motion was well preserved.CONCLUSION Anterior odontoid screw fixation and posterior direct C2 percutaneous pedicle screw fixation with the aid of O-arm navigation and neurophysiological monitoring can be an interesting alternative option for complicated multiple axis fractures.展开更多
Inadequate strength at the bone/cement interface is one of the main drawbacks of poly(methylmethacrylate)(PMMA) bone cement in the current orthopedic surgeries. In the present work, a partially degradable PMMA/Mg comp...Inadequate strength at the bone/cement interface is one of the main drawbacks of poly(methylmethacrylate)(PMMA) bone cement in the current orthopedic surgeries. In the present work, a partially degradable PMMA/Mg composite bone cement (PMC) was developed for enhancing the bone/cement interfacial strength, which is proposed to be accomplished by increasing the osteo-conductivity of PMMA and enhancing the mechanical interlocking between bone tissue and the porous PMMA surface formed by the degradation of Mg on the surface of the cement. PMCs were prepared with various concentrations of Mg particles with different sizes and alloy compositions. The effects of Mg particle size, composition and content on the injectability, mechanical and degradation properties, and biocompatibility of PMCs were evaluated. The results show that these parameters affected the properties of the PMCs simultaneously. The good injectability and compressive strengths of PMMA were preserved, while the compatibility to osteoblasts was enhanced when adding Mg particles in a proper manner. The PMCs degraded at the surface with time and formed porous surface structures in the physiological environment, while maintaining the original compressive strengths. This preliminary study shows that the PMC is promising for minimally invasive orthopedic surgery;however, it still requires to be optimized and evaluated in the future.展开更多
BACKGROUND Vascular injury is a rare complication of femoral shaft fractures,and rupture of the deep femoral artery is more difficult to diagnose because of its anatomical location and symptoms.Despite its low inciden...BACKGROUND Vascular injury is a rare complication of femoral shaft fractures,and rupture of the deep femoral artery is more difficult to diagnose because of its anatomical location and symptoms.Despite its low incidence,deep femoral artery rupture can lead to life-threatening outcomes,such as compartment syndrome,making early identification and diagnosis critical.CASE SUMMARY A 45-year-old male patient was admitted to our hospital due to right lower limb trauma in a car accident,with complaints of severe pain and swelling on his right thigh.X-ray demonstrated a right femoral shaft fracture.During preparation for emergency surgery,his blood pressure and blood oxygen saturation dropped,and sensorimotor function was lost.Computed tomography angiography was performed immediately to confirm the diagnosis of rupture of the deep femoral artery and compartment syndrome,so fasciotomy and vacuum-assisted closure were performed.Rhabdomyolysis took place after the operation and the patient was treated with appropriate electrolyte correction and diuretic therapy.Twenty days after the fasciotomy,treatment with the Hoffman Type II External Fixation System was planned,but it was unable to be immobilized internally based on a new esophageal cancer diagnosis.We kept the external fixation for 1 year,and 3 years of follow-up showed improvement of the patient’s overall conditions and muscle strength.CONCLUSION For patients with thigh swelling,pain,anemia,and unstable vital signs,anterior femoral artery injury should be highly suspected.Once diagnosed,surgical treatment should be performed immediately and complications of artery rupture must be suspected and addressed in time.展开更多
BACKGROUND Posterior atlantoaxial dislocation(PAD)is a rare type of upper cervical spine disease.We sought to describe a unreported case of old PAD with os odontoideum(OO)and atlas hypoplasia(AH)and our unique treatme...BACKGROUND Posterior atlantoaxial dislocation(PAD)is a rare type of upper cervical spine disease.We sought to describe a unreported case of old PAD with os odontoideum(OO)and atlas hypoplasia(AH)and our unique treatment approach consisting of C1 single door laminoplasty with C1-3 posterior fixation and fusion.CASE SUMMARY A 70-year-old male patient who suffered from progressive aggravating numbness and limb weakness for 4 years without trauma,was diagnosed with old PAD with OO and AH.The patient underwent closed reduction and C1 single door laminoplasty with C1-3 posterior fixation and fusion instead of C1 laminectomy with occipitocervical fusion.During the 3-year follow-up,he was able to walk by himself instead of using a wheelchair and with a±25°range of head rotation as well as a±10°range of flexion-extension.Three-year follow-up images showed satisfactory reduction and fusion.CONCLUSION C1 single door laminoplasty with cervical fusion in PAD combined with spinal cord compression could be a suitable and effective surgical option.Compared with laminectomy and occipitocervical fusion,it retains more cervical range of motion,has a smaller incision and provides an adequate bone grafting space for atlantoaxial fusion.展开更多
BACKGROUND Anaplastic large cell lymphoma (ALCL) is a type of non-Hodgkin’s lymphoma (NHL). ALCL is rare as a bone lesion and in pregnancy. CASE SUMMARY We present the first case of anaplastic lymphoma kinase (ALK)+ ...BACKGROUND Anaplastic large cell lymphoma (ALCL) is a type of non-Hodgkin’s lymphoma (NHL). ALCL is rare as a bone lesion and in pregnancy. CASE SUMMARY We present the first case of anaplastic lymphoma kinase (ALK)+ ALCL of the thoracic spine during pregnancy. A 25-year-old pregnant woman was presented to us at 24 wk’ gestation with severe back pain and weakness in the left lower limb. Imaging examination showed lesions at T10 and T11. She underwent posterior pedicle screw fixation and vertebroplasty. Pathological examination showed ALK+ ALCL. The patient chose to have therapeutic abortion after surgery and received chemotherapy in the hematology department. She now remains disease free with no neurological deficit after 30 mo’ follow-up. CONCLUSION ALK+ ALCL with the thoracic spine involvement is uncommon, especially in pregnancy. Many symptoms can be misunderstood during pregnancy;therefore, when a pregnant patient has persistent back pain or lower limb neurological symptoms, imaging examinations should be performed.展开更多
Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduc...Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduction of various degrees of displacement in Pauwels I femoral neck fractures by a finite element analysis.Methods:Five reduction models of Pauwels type I femoral neck fracture were established using the Mimics 17.0(Materialize,Leuven,Belgia)and Hypermesh 12.0(Altair Engineering,Troy,MI,USA).According to the degree of fracture displacement,there were three models of positive support,an anatomic reduction model,and a negative 2mm reduction model.Finite element analysis was conducted using the ABAQUS 6.9 software(Simulia,Suresnes,France).The von Mises stress distribution and the stress peak of internal fixation in different models,the displacement between fracture blocks,and the principal strain of the femoral neck cancellous bone model were recorded under the axial stress of 2100 N.Results:The peak von Mises stress on screw of each model was located at the thread of the screw tip.The peak von Mises stress was the lowest at the tip of the anatomic reduction model screw(261.2 MPa).In the positive 4mm model,the von Mises stress peak was the highest(916.1 MPa).The anatomic reduction model showed the minimum displacement(0.388 mm)between fracture blocks.The maximum displacement was noted in the positive 4mm model(0.838 mm).The displacement in the positive 3mm model(0.721 mm)was smaller than that in the negative 2mm model(0.786 mm).Among the five models,the strain area of the femoral neck cancellous bone was mainly concentrated around the screw hole,and the area around the screw hole could be easily cut.Conclusions:Compared with negative buttress for femoral neck fracture,positive buttress can provide better biomechanical stability.In Pauwel type I fracture of femoral neck,the range of positive buttress should be controlled below 3mm as far as possible.展开更多
文摘BACKGROUND Percutaneous vertebroplasty(PVP)is an effective method for the treatment of neurologically intact Kümmell’s disease,but bone cement leakage during surgery is a problem that deserves attention.AIM To reduce bone cement leakage and evaluate the effect of the sequential infusion of bone cement during PVP for the treatment of stage I or II Kümmell’s disease.METHODS Patients with Kümmell’s disease treated in our hospital from September 2015 to September 2018 were retrospectively analyzed.Patients meeting the inclusion and exclusion criteria were divided into two groups:Traditional single infusion and sequential infusion(SI).The visual analog scale(VAS)and Oswestry disability index(ODI)were evaluated and compared,and duration of operation,bone cement content and complications were recorded.RESULTS Forty-five patients were included in this study;there were 24 in the traditional single infusion group and 21 in the SI group.The VAS and ODI were significantly different for both groups when compared pre-and postoperatively,whereas the differences between 1 wk postoperatively and at the final follow-up were not statistically.When the VAS and ODI of the two groups were compared,there were no significant differences at any time point.The leakage rate of bone cement was significantly lower in the SI group(14.3%,3 of 21)than that in the traditional single infusion group(41.7%,10 of 24).CONCLUSION SI in unipedicular PVP is a safe and effective procedure for neurologically intact Kümmell’s disease,and this technique could decrease the incidence of bone cement leakage.
基金supported by the National Institutes of Health[AR-070135 and AG-056438 to W.C.,and AR-075735 and AR-074954 to Y.P.L].Y.Z.(201706290105)and T.Z.(201406920028)were sponsored by the China Scholarship Council.
文摘Runt-related transcription factor 1(Runx1)plays a key role in cartilage formation,but its function in articular cartilage formation is unclear.We generated non-inducible and inducible Runx1-deficient mice(Runx1^(f/f)Col2α1-Cre and Runx1^(f/f)Col2α1-CreER mice)and found that chondrocyte-specific Runx1-deficient mice developed a spontaneous osteoarthritis(OA)-like phenotype and showed exacerbated articular cartilage destruction under OA,characterized by articular cartilage degradation and cartilage ossification,with decreased Col2α1 expression and increased Mmp13 and Adamts5 expression.RNA-sequencing analysis of hip articular cartilage from the Runx1^(f/f)Col2α1-Cre mice compared to that from wild-type mice and subsequent validation analyses demonstrated that Runx1 is a central regulator in multiple signaling pathways,converging signals of the Hippo/Yap,TGFβ/Smad,and Wnt/β-catenin pathways into a complex network to regulate the expression of downstream genes,thereby controlling a series of osteoarthritic pathological processes.RNA-sequencing analysis of mutant knee joints showed that Runx1’s role in signaling pathways in articular cartilage is different from that in whole knee joints,indicating that Runx1 regulation is tissue-specific.Histopathologic analysis confirmed that Runx1 deficiency decreased the levels of YAP and p-Smad2/3 and increased the levels of activeβ-catenin.Overexpression of Runx1 dramatically increased YAP expression in chondrocytes.Adeno-associated virus-mediated Runx1 overexpression in the knee joints of osteoarthritic mice showed the protective effect of Runx1 on articular cartilage damaged in OA.Our results notably showed that Runx1 is a central regulator of articular cartilage homeostasis by orchestrating the YAP,TGFβ,and Wnt signaling pathways in the formation of articular cartilage and OA,and targeting Runx1 and its downstream genes may facilitate the design of novel therapeutic approaches for OA.
基金supported by the National Natural Science Foundation of China(Grant No.81401768,81301646)the Natural Science Foundation of Jiangsu Province(Grant No.BK20140289)+1 种基金the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20123201120018)China Postdoctoral Science Foundation on the 53rd general program(Grant No.2013M531404)
文摘Objective: To assess the effects of axial vibrations on gene expression and lumbar intervertebral disc degeneration in vivo. Methods: A modified bipedal rat model was established using a brachial plexus rhizotomy approach to imitate human upright posture. The experimental animals were randomly divided into three groups: control, vertical vibration, and whole-body vibration. Gene expression in degeneration of the intervertebral discs was assessed by reverse transcription-quantitative polymerase chain reaction. Results: The expression of aggrecan, Col1α1, Col2α1, and decorin were shown to be up-regulated in 14-week-old rats in the vertical vibration and whole-body vibration groups, whereas biglycan and versican expression was down-regulated in 14-week-old rats of the two experimental groups. Furthermore, biglycan and versican expression levels were shown to be lower in the whole-body vibration group than in the vertical vibration group(P<0.05). Conclusions: This in-vivo study demonstrated that vibrations can influence the expression of anabolic genes. Furthermore, whole-body vibrations seem to have a greater effect in this regard than vertical vibrations. A new method is expected to relieve the low back pain of the patients through our research.
文摘BACKGROUND Fractures of the axis are commonly seen in spinal injuries. Upper cervical fractures are usually managed conservatively. However, the complications due to long-term external immobilization cannot be ignored. The traditional open surgery has the disadvantages of too much blood loss and soft tissue injury. The aim of our paper is to introduce a minimally invasive surgical treatment for multiple axis fractures.CASE SUMMARY We report a 40-year-old Chinese male who had severe neck pain and difficult neck movement after falling from 3 meters. X-ray and computed tomography(CT) scan revealed an axis injury consisting of an odontoid Type Ⅲ fracture associated with a Hangman fracture categorized as a Levine-Edwards Type Ⅰ fracture. The patient underwent anterior odontoid screw fixation and posterior percutaneous screw fixation using intraoperative O-arm navigation. Neck pain was markedly improved after surgery. X-rays and CT scan reconstructions of 3-mo follow-up showed good stability and fusion. The range of cervical motion was well preserved.CONCLUSION Anterior odontoid screw fixation and posterior direct C2 percutaneous pedicle screw fixation with the aid of O-arm navigation and neurophysiological monitoring can be an interesting alternative option for complicated multiple axis fractures.
基金supported by the National Natural Science Foundation of China (Nos. 81501858, 81622032, 51501109 and 51672184)the Principal Project of Natural Science Research of Jiangsu Higher Education Institutions (No. 17KJA180011)+1 种基金Jiangsu Innovation and Entrepreneurship Programthe Priority Academic Program Development of Jiangsu High Education Institutions (PAPD)
文摘Inadequate strength at the bone/cement interface is one of the main drawbacks of poly(methylmethacrylate)(PMMA) bone cement in the current orthopedic surgeries. In the present work, a partially degradable PMMA/Mg composite bone cement (PMC) was developed for enhancing the bone/cement interfacial strength, which is proposed to be accomplished by increasing the osteo-conductivity of PMMA and enhancing the mechanical interlocking between bone tissue and the porous PMMA surface formed by the degradation of Mg on the surface of the cement. PMCs were prepared with various concentrations of Mg particles with different sizes and alloy compositions. The effects of Mg particle size, composition and content on the injectability, mechanical and degradation properties, and biocompatibility of PMCs were evaluated. The results show that these parameters affected the properties of the PMCs simultaneously. The good injectability and compressive strengths of PMMA were preserved, while the compatibility to osteoblasts was enhanced when adding Mg particles in a proper manner. The PMCs degraded at the surface with time and formed porous surface structures in the physiological environment, while maintaining the original compressive strengths. This preliminary study shows that the PMC is promising for minimally invasive orthopedic surgery;however, it still requires to be optimized and evaluated in the future.
文摘BACKGROUND Vascular injury is a rare complication of femoral shaft fractures,and rupture of the deep femoral artery is more difficult to diagnose because of its anatomical location and symptoms.Despite its low incidence,deep femoral artery rupture can lead to life-threatening outcomes,such as compartment syndrome,making early identification and diagnosis critical.CASE SUMMARY A 45-year-old male patient was admitted to our hospital due to right lower limb trauma in a car accident,with complaints of severe pain and swelling on his right thigh.X-ray demonstrated a right femoral shaft fracture.During preparation for emergency surgery,his blood pressure and blood oxygen saturation dropped,and sensorimotor function was lost.Computed tomography angiography was performed immediately to confirm the diagnosis of rupture of the deep femoral artery and compartment syndrome,so fasciotomy and vacuum-assisted closure were performed.Rhabdomyolysis took place after the operation and the patient was treated with appropriate electrolyte correction and diuretic therapy.Twenty days after the fasciotomy,treatment with the Hoffman Type II External Fixation System was planned,but it was unable to be immobilized internally based on a new esophageal cancer diagnosis.We kept the external fixation for 1 year,and 3 years of follow-up showed improvement of the patient’s overall conditions and muscle strength.CONCLUSION For patients with thigh swelling,pain,anemia,and unstable vital signs,anterior femoral artery injury should be highly suspected.Once diagnosed,surgical treatment should be performed immediately and complications of artery rupture must be suspected and addressed in time.
文摘BACKGROUND Posterior atlantoaxial dislocation(PAD)is a rare type of upper cervical spine disease.We sought to describe a unreported case of old PAD with os odontoideum(OO)and atlas hypoplasia(AH)and our unique treatment approach consisting of C1 single door laminoplasty with C1-3 posterior fixation and fusion.CASE SUMMARY A 70-year-old male patient who suffered from progressive aggravating numbness and limb weakness for 4 years without trauma,was diagnosed with old PAD with OO and AH.The patient underwent closed reduction and C1 single door laminoplasty with C1-3 posterior fixation and fusion instead of C1 laminectomy with occipitocervical fusion.During the 3-year follow-up,he was able to walk by himself instead of using a wheelchair and with a±25°range of head rotation as well as a±10°range of flexion-extension.Three-year follow-up images showed satisfactory reduction and fusion.CONCLUSION C1 single door laminoplasty with cervical fusion in PAD combined with spinal cord compression could be a suitable and effective surgical option.Compared with laminectomy and occipitocervical fusion,it retains more cervical range of motion,has a smaller incision and provides an adequate bone grafting space for atlantoaxial fusion.
文摘BACKGROUND Anaplastic large cell lymphoma (ALCL) is a type of non-Hodgkin’s lymphoma (NHL). ALCL is rare as a bone lesion and in pregnancy. CASE SUMMARY We present the first case of anaplastic lymphoma kinase (ALK)+ ALCL of the thoracic spine during pregnancy. A 25-year-old pregnant woman was presented to us at 24 wk’ gestation with severe back pain and weakness in the left lower limb. Imaging examination showed lesions at T10 and T11. She underwent posterior pedicle screw fixation and vertebroplasty. Pathological examination showed ALK+ ALCL. The patient chose to have therapeutic abortion after surgery and received chemotherapy in the hematology department. She now remains disease free with no neurological deficit after 30 mo’ follow-up. CONCLUSION ALK+ ALCL with the thoracic spine involvement is uncommon, especially in pregnancy. Many symptoms can be misunderstood during pregnancy;therefore, when a pregnant patient has persistent back pain or lower limb neurological symptoms, imaging examinations should be performed.
基金This study was partially supported by a grant from the Zhejiang Medical Science Foundation of China(No.2019KY682).
文摘Background:Refractory femoral neck fractures cannot be anatomically reduced by closed traction reduction which may affect fracture healing.We evaluated the biomechanical effects of positive,negative,and anatomic reduction of various degrees of displacement in Pauwels I femoral neck fractures by a finite element analysis.Methods:Five reduction models of Pauwels type I femoral neck fracture were established using the Mimics 17.0(Materialize,Leuven,Belgia)and Hypermesh 12.0(Altair Engineering,Troy,MI,USA).According to the degree of fracture displacement,there were three models of positive support,an anatomic reduction model,and a negative 2mm reduction model.Finite element analysis was conducted using the ABAQUS 6.9 software(Simulia,Suresnes,France).The von Mises stress distribution and the stress peak of internal fixation in different models,the displacement between fracture blocks,and the principal strain of the femoral neck cancellous bone model were recorded under the axial stress of 2100 N.Results:The peak von Mises stress on screw of each model was located at the thread of the screw tip.The peak von Mises stress was the lowest at the tip of the anatomic reduction model screw(261.2 MPa).In the positive 4mm model,the von Mises stress peak was the highest(916.1 MPa).The anatomic reduction model showed the minimum displacement(0.388 mm)between fracture blocks.The maximum displacement was noted in the positive 4mm model(0.838 mm).The displacement in the positive 3mm model(0.721 mm)was smaller than that in the negative 2mm model(0.786 mm).Among the five models,the strain area of the femoral neck cancellous bone was mainly concentrated around the screw hole,and the area around the screw hole could be easily cut.Conclusions:Compared with negative buttress for femoral neck fracture,positive buttress can provide better biomechanical stability.In Pauwel type I fracture of femoral neck,the range of positive buttress should be controlled below 3mm as far as possible.
