Objective In order to probe the possible biomechanical mechanism of lumbar vertebral injuries, we studied the nonlinear stress distribution on lumbar vertebrae at 1500N axial compression force and 15Nm bending moments during hambar flexion, extension, lateral bending and axial torsion using an available nonlinear finite element (FE) model of functional spine unit. Methods Three-dimensional nonlinear FE model was created based on CT data of L3-L4 motion segment. The segment mechanical responses to different loadings were evaluated by the range of disc bulging, the stress level of fibrousrings, facet loadings and equivalent stress distribution of posterior structure. Results Compression and flexion induced disc bulging in anterior region, whereas extension and lateral bending induced disc bulging posteriorly and posterolaterally. Axial torsion caused not only higher unilateral facet stress but also the concentrated stress on posteroleteral fibrousrings stress. The loadings in extension and axial compression were lower than in torsion but higher than in lateral bending and anterior flexion. Higher equivalent stress was found when compression and extension loadings were applied to the pedicle of vertebral arch and interarticularis. Conclusion Intervertebral disc beared higher compressive than tensile. The posterolateral regions of lumbar vertebrae were prone to be deformity and at higher risk of fibrousring failure. Stress failure could be occured when facets were overloaded with axial torsion,extension and extension force due to the importance of facets during lumbar movement.

Objective To explore relationship between anterior knee pain after total knee arthroplasty and patella resurfacing and prosthesis design,and to evaluate which femoral prosthesis is more friendly with patella:Genesis Ⅱ or PFC knee prostheses.Methods Data of 145 patients (145 knees) who had undergone primary total knee arthroplasty for treating osteoarthritis were retrospectively analyzed.Posterior-cruciate-substituting total knee prostheses were used in all patients.Among 74 patients who had undergone patella resurfacing,Genesis Ⅱ knee prosthesis was used in 32 patients and PFC knee prosthesis in 42 patients.Among 71 patients who had not undergone patella resurfacing,Genesis Ⅱ knee prosthesis was used in 38 patients and PFC knee prosthesis in 33 patients.The Hospital for Special Surgery(HSS) score,patella score,patellar function score,range of motion of knee,anterior knee pain scale,and patient satisfaction were used to evaluate clinical outcomes.At the same time,the imaging results were evaluated by X-rays.Results 144 patients were successfully followed up for 21 to 43 months (average,33 months).There was no significant difference in incidence of anterior knee pain between the group with patella resurfacing and the group without patella resurfacing,while a significant difference was found between patients receiving Genesis Ⅱ knee prosthesis and those receiving PFC knee prosthesis.Four patients who had undergone total knee arthroplasty using PFC prosthesis underwent reoperation.There were no significant differences in postoperative HSS score,range of motion of knee and patient satisfaction between the Genesis Ⅱ group and the PFC group,while there were significant differences in patella score and patellar function score between them.Conclusion Postoperative anterior knee pain was related to the prosthesis design,rather than to the patella resurfacing.Genesis Ⅱ knee prosthesis was more friendly with patella than PFC knee prosthesis.

Objective To investigate the effects of the jumbo cup in acetabular revision for patients with massive acetabular bone deficiency.Methods We retrospectively studies 48 patients (49 hips) who underwent jumbo cup revisions between 2006 and 2015 (19 men and 29 women;average age:62± 12 years).The acetabular bone defects were classified according to Paprosky classification (Paprosky Ⅱ 27 hips,Paprosky ⅢA 18 hips,Paprosky ⅢB 4 hips).Radiological assessments were conduced to evaluate the acetabular prosthesis loosening,dislocation and infection.The reasons for revisions were mechanical loosening in 41 cases,and infections in another 8 cases with cement spacer putted by last surgery.Results The operation duration and blood loss was 110 min (85-160 min) and 315 ml (270-455 ml) respectively.After an average follow-up of 6.8 years (1-11 years),Harris hip score was increased from 47.6±7.1 preoperatively to 82.4± 6.2 postoperatively.Osseointegration occurred in the acetabular components at 6 months postoperatively.Radiograph analysis showed satisfied position of acetabular cup without complications such as damages of vessels or nerves.The successful rate of jumbo cup revisions was 89.8％±4.4％.However,two in Paprosky ⅢA failures for periprosthetic infection occurred and two in Paprosky ⅢA,one in Paprosky ⅢA and the other in Paprosky ⅢB for acetabular component loosening.One patient in Paprosky ⅢB had weight-bearing pain and relieve slightly after conservative treatment.The radiologic study showed that there was no relationship between failure rate and acetabular abduction angle (r=0.06,P=0.53),rotation center migration in vertical direction (r=0.11,P=0.14) and horizontal direction (r=0.04,P=0.89).Conclusion The mid-term results show that using jumbo cup in revising acetabular failure with massive bone deficiency are optimal,which can be achieved by simplified operation procedures,reduction in the need of bone graft and promotion in acetabulum osseointegration.However,higher failure rate may occur in Paprosky ⅢB patients.

Objective To explore the effect and factors of patellofemoral arthroplasty (PFA) for isolated patellofemoral osteoarthritis.Methods Data of 18 patients (3 males,15 females) with isolated patellofemoral osteoarthritis underwent PFA from March 2006 to December 2014 were retrospectively analyzed.There were 3 males and 15 females with a mean age of 54 years (range,46-74 years).It was strict to grasp the surgical indications according to the clinical symptoms,signs and imaging data preoperatively.11 patients were operated with AVON patellofemoral prosthesis (Stryker Inc.) and the other 7 patients were operated with the Gender Solutions patellofemoral prosthesis (Zimmer Inc.).Active and passive functional rehabilitation exercise was encouraged at the early stage after operation.Visual analogue scale (VAS) was 5.33±0.99 (range,4-7) and hospital for special surgery knee score (HSS) was 53.28±5.71 (range,44-63) before operation.Results The mean duration of follow-up was 63.98 months (range,6-104 months).VAS after operation for 1 and 3 months were 1.17±0.79 (range,0-3) and 0.72±0.67 (range,0-2),and the pain was almost relieved after 9 months.HSS after operation for 1,3,9 months were 70.06±6.33 (range,61-80),86.06±5.12 (range,77-95) and 91.39±4.83 (range,82-97).HSS score of the latest follow-up was 92.06±4.05 (range,84-97),which was improved obviously from the preoperative ones.The excellent and good rate was 100％ (excellent 15 cases,good 3 cases).The satisfactory rate was 94.4％ (17/18).Only one case got slightly knee pain when walking up and down the stairs after 2 years,and the pain was relieved after being administered with NSAIDs and rest.No incision infection,rupture,prosthesis supported bone fracture,prosthesis loosening and other complication was occurred during the follow-up period in the other patients.Conclusion The clinical outcomes of PFA are strictly related to surgical indications,implant design and appropriate surgical technique.Therefore,based on the appropriate PFA implants,strict surgical indications,appropriate patients,excellent operation skills and actively functional rehabilitation exercise,PFA could treat the isolated patellofemoral osteoarthritis effectively.

Objective To investigate the outcomes of the treatments for the patients with Vancouver type B 1 periprosthetic femur fractures.Methods Seventeen patients with periprosthetic femoral fractures (5 males and 12 females;average age,70.4 years,range from 37 to 86 years) who underwent revision arthroplasty or open reduction and internal fixation between December 2006 and June 2016 were retrospectively reviewed.Periprosthetic femoral fractures occurred at the mean time of 65.1 months after arthroplasty.Twelve patients underwent open reduction and internal fixation and five cases underwent total hip or stem revision with Solution from Depuy,Wagner from Zimmer,Echelon from Smith & Nephew or Secur-Fit Max from Stryker due to primary bone loss,acetabular component wear or long-time prosthesis use respectively.Data were collected at 1,3,6 and 12 months and then each year postoperatively.All patients were followed up,and the results of X-ray,postoperative Harris hip score,stability of prosthesis and complications were also evaluated.Results A total of 5 patients underwent revision arthroplasty,and 12 patients underwent open reduction and internal fixation.The mean follow-up duration was 56 months (range from 7 to 120 months).Total blood loss in the open reduction and internal fixation group and in revision group was 385± 129 ml and 531± 113 ml respectively.The operation duration in the open reduction and internal fixation group was 72±36 min while it was 126±48 min in the revision group.The postoperative Harris hip score in the open reduction and internal fixation group was significantly increased compared with preoperative Harris hip score (68.8±18.4 vs.46.2±9.6),as well as in the revision group (75.0±8.9 vs.57.4±13.0).For the incidence of complications,in the open reduction and internal fixation group,one patient suffer with delayed fracture union,one patient complained about persistent pain and one suffered a secondary fracture,while in the revision group one suffered from blood loss and one with long-term pain.Conclusion Open reduction and internal fixation is an optimal intervention for Vancouver B 1 fracture,and revision arthroplasty can be considered as a safe alternative in patients with primary bone loss,implant of short survival time,severe liner wear or long-term prosthesis use.

Objective To investigate the risk factors related to the survival time of anti-protrusion cage in acetabular revision.Methods Data of 40 patients who had received acetabular revision using antiprotrusion cages between January 2002 and June 2010 were retrospectively analyzed.There were 16 males and 24 females,aged from 22 to 77 years (average,60.3 years).All patients were followed up for 12 to 82 months (average,39.2 months).According to the AAOS classification,there were 29 cases of type C and 11 cases of type D； while according to the Paprosky classification,there were 29 cases of type ⅢA and 11 cases of type Ⅲ B.The multiple regression analysis was utilized to investigate the relationships between different factors and anti-protrusion cage failure.The corresponding factors included gender,age,bone loss classification,superior or lateral migration of acetabular center of rotation,abduction angle,fixation manners (simple flange fixation or flange fixation plus transacetabular screw fixation),bone grafting techniques and cup type.Results At final follow-up,the average Harris score was 74.5±15.4.Two patients received rerevision due to prosthetic loosening.Obvious radiological loosening of prosthesis combined with pain was found in 2 cases.The statistical analysis indicated that superior migration of acetabular center of rotation,abduction angle and fixation manners were correlated with cup failure,especially when the superior migration was more than 8.5 mm or the abduction angle was larger than 53.5°.Flange fixation plus transacetabular screw fixation could reduce risk of cup failure.Conclusion There is a higher cup failure risk in acetabular revision using an anti-protrusion cage for patients with serious bone defect.However,implanting cup at the level of the true acetabulum as far as possible,decreasing abduction angle properly and using flange fixation plus transacetabular screw fixation can reduce cup failure risk.

Objective To investigate the changes in plasma very long chain fatty acids (VLCFAs),and to explore its relationship with obesity-related index in obese children.Methods One hundred and sixty-six obese children aged 7 to 12 years old were investigated and 148 health children matched with age and sex were selected as control group.Their height,weight,and waist circumference (WC) were measured.The percentage of body fat (PBF) was tested by dual-energy X-ray absorptiometry.Fasting blood triglycerides (TG),total cholesterol (TC),high density lipoprotein-cholesterol (HDL-C),low density lipoprotein-cholesterol (LDL-C) levels,fasting plasma glucose,and fasting insulin (FINS) were determined.The body mass index (BMI),BMI-Z score,waist to height ratio (WHtR),and homeostasis model assessment for insulin resistance (HOMA-IR) were calculated.The plasma VLCFAs were analyzed by gas chromatography-mass spectrometry.Results (1) Compared with normal control children,body weight,BMI,BMI-Z score,WC,WHtR,PBF,TG,TC,LDL-C,FINS,and HOMA-IR in obese children were increased (all P ＜ 0.05),and the level of HDL-C was decreased (P ＜ 0.05).(2) The plasma levels of docosamonoenoic acid (C22 ∶ 1 n-9) and arachidonic acid (C20 ∶ 4n-6) were decreased while the levels of arachicacid (C20 ∶ 0) and eicosapentaenoic acid (C20 ∶ 5n-3) increased in obese children compared to non-obese children.(3) The linear correlation analysis showed that PBF was positively correlated with C20 ∶ 0 and C20 ∶ 5n-3,and negatively correlated with C20 ∶ 4n-6.WHtR was negatively correlated with C22 ∶ 1 n-9 and positively correlated with C20 ∶ 0 (4) The multiple stepwise regression analysis showed that C20 ∶ 0 was the main factor for PBF,and C22 ∶ 1 n-9 and C20 ∶ 0 were the main factors for WHtR.Conclusion The metabolic abnormality of plasma very long chain fatty acids exists in obese children.The changes in C20 ∶ 0,C22 ∶ 1 n-9,and C20 ∶ 5n-3 may be associated with obesity in children.

ObjectiveTo investigate the size effect of hydroxyapatite nanoparticles on proliferation and apoptosis of osteoblast-like cells.MethodsCetyltrimethylammnonium bromide (CTAB) was used to regulate the size of nano hydroxyapatite (nHAP) particles.All obtained particles were characterized by transmission electron microscopy (TEM),X-ray diffraction,dynamic light scattering and chemical analysis.HAP films were obtained by slowly coating cover glasses with 1％ HAP particle suspension.MG-63 cells on three different films(20HAP,40HAP and 80HAP) were cocultured for up to 5 days.Cell proliferation assay was obtained by methyl thiazolyl tetrazolium (MTT).Cell apoptosis was detected by flow cytometric detection.Cell ultrastructure morphology was observed by TEM observation.ResultsnHAP with diameter of 20 nm,40 nm and 80 nm were synthesized and and analyzed.The MG-63 cells were cultured on three different fihns.The optical density value of cells on 20HAP was 1.22±0.13 after 5 days incubation,and there was no different compared to the control group(F=6.843,P=0.124).Cell number and viability were significantly higher on 20HAP compared to large nHAP after 5 days incubation.The percentage of apoptotic cells increased with increasiug nHAP particle size.TEM images showed 20HAP was found in cytoplasm and cell morphology had no changes.ConclusionBoth cell proliferation and cell apoptosis are related to the size of the nHAP particles.20HAP was the most effective on promoting cell growth and inhibiting cell apoptosis.

Objective To investigate the distribution characteristics of protein tyrosine phosphatase 1B (PTP1B) gene IVS6+G82A and Pro303Pro polymorphisms in Chinese children and determine the effect of PTP1B gene IVS6+G82A and Pro303Pro polymorphisms on the pathogenesis of childhood obesity. Methods A total of 147 Chinese obese and 118 healthy children were randomly selected and enrolled to identify IVS6+G82A and Pro303Pro genotypes by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) assay. Waist circumference (WC), waist to hip ratio (WHR), percentage of body fat (%BF),systolic blood pressure (SBP), diastolic blood pressure (DBP), fasting plasma glucose (FPG), serum triglycerides (TG), total cholesterol (TC), high density lipoprotein cholesterol (HDL-C), low density lipoprotein cholesterol (LDL-C), plasma fasting insulin (FINS), homeostasis model assessment for insulin resistance (HOMA-IR), and plasma leptin were examined. Results The allele frequencies of IVS6+G82A and Pro303Pro were 59.5% and 19.4% in obese children, and 53.4% and 11.0% in healthy children, respectively. There were significant differences in allele frequencies of Pro303Pro polymorphism between the obese and the control group. Pro303Pro polymorphism was associated with body mass index, WC, TG, and LDL C in the obese subjects. There was not di fference in the genotype distributions or allele frequencies of IVS6+G82A polymorphism between the obese and the control group. Further analysis showed no association between the genotypes of IVS6+G82A and clinical characteristics in the obese subjects. The linkage disequilibrium analysis for IVS6+G82A and Pro303Pro (D′: 0.441, r2: 0.027) was weak.Conclusion PTP1B gene Pro303Pro polymorphism might be associated with the pathogenesis of obesity in children and could affect the lipid metabolism in Chinese obese children.

Objective To compare the clinical results of percutaneous compression plating (PCCP)and Trigen short reconstruction intramedullary nail for intertrochanteric hip fractures. Methods During 2005 and 2008, the patients suffered with AO/OTA Al and A2 intertrochanteric hip fractures were divided into two groups; 36 fractures were treated with PCCP and 48 fractures with Trigen short reconstruction nail.During an average of (16.3±3.2) months follow-up, clinical evaluation involved visual analogue scale(VAS)score for pain in the 1st week, the 1st month, the 3rd month, the 6th month and the 12th month, and a Harris hip score one year post operation. Radiographs were examined for fracture healing-time, displacement scale of the neck screws and fracture impaction scale. All the complication in both groups was recorded. Results There were no difference in blood loss and operation time in both groups. The postoperative pain was significantly lower in the PCCP group in the initial three months after the surgery. Larger scale of fracture impaction and screw telescoping were seen in PCCP group. Also shorter healing time, higher Harris score results were achieved in PCCP group than those of Trigen short reconstruction nail group. Four peri-implant fractures occurred in Trigen short reconstruction nail group, which included one in the greater trochanter and three in the femoral shaft, but only one case need revision for bone displacement. In PCCP group, it was found that the superior neck screw was slightly displaced for tendency to cut-out in one patient. Conclusion Both PCCP and Trigen short reconstruction intramedullary nail can be successfully used to treat Al and A2 intertrochanteric hip fractures with minimal invasive technique. And the PCCP showed more rapid pain relief and bone healing, easily bony reduction and fewer complications.