Investigation into the analysis method for assessing contact stress in joint prosthesis

Contact stress is the important cause of wear and failure of knee joint prostheses implanted in the human body during movement.The calculation of contact stress on joint prostheses is often inaccurate due to the deviation of joint position during activity.This paper proposes a correction method for contact stress based on finite element results.Firstly,the contact stress and contact radius between femoral and tibial prostheses of knee joint were calculated and analyzed by Hertz contact theory.Then,individualized finite element models based on the individualized geometry of the joint prosthesis and individualized loading were constructed,and the finite element contact stress was analyzed.The finite element results were calibrated utilizing the Hertz contact theory.Additionally,this study investigated the impact of three gait patterns(normal gait,medial thrust gait,and bouncing gait)on the contact stress experienced by the tibial insert.The research methods and results can provide ideas for theoretical analysis and finite element simulation of prosthetic joint contact,as well as offer theoretical support and analysis methods for evaluating the lifespan of prosthetic joints.

Diagnostic value of serum Interleukin-6 combined with synovial IL-6 and C-reactive protein for prosthesis joint infection in patients after joint arthroplasty

Objective:To explore the diagnostic value of serum Interleukin-6(IL-6)combined with synovial IL-6 and C-reactive protein for prosthesis joint infection(PJI)in patients after joint arthroplasty.Methods:A total of 253 patients undergoing revision surgery after the first total hip and total knee arthroplasty in the Second Affiliated Hospital of Hainan Medical College from January 2018 to April 2020 were recruited as the study object.The patients were divided into the PJI group(n=85)and non-PJI group(n=168)according to whether there was PJI,and the baseline characteristics and the laboratory indexe were collected and compared between the two groups.the factors associated with PJI in patients after joint arthroplasty were analyzed by multivariate logistic regression model.And the diagnostic value of each marker for PJI in patients after joint arthroplasty was evaluated by Receiver Operating Characteristic(ROC)curve.Results:The incidence of PJI in this study was 33.6%.Compared with the non-PJI group,the patients in the PJI group had more diabetes mellitus and shorter prosthesis duration(P<0.05).The levels of serum C-reactive protein(CRP),serum interleukin-6(IL-6),synovial IL-6,synovial CRP,synovial leukocyte,synovial neutrophil and ESR in the PJI group were higher than those in non-PJI group,and the level of synovial lymphocyte was lower,with statistically significant differences(P<0.05).Multivariate logistic regression analysis showed that diabetes mellitus(OR=1.706,95%CI:1.02~2.376,P=0.037),prosthesis duration(OR=0.781,95%CI:0.690~0.884,P<0.001),serum IL-6(OR=1.008,95%CI:1.004~1.012,P=0.046),synovial IL-6(OR=1.004,95%CI:1.002~1.006,P=0.011)and synovial CRP(OR=1.481,95%CI:1.010~2.170,P=0.044)were independently related to PJI in patients after joint arthroplasty.ROC curve analysis showed that the area under ROC curve(AUC)of serum IL-6 combined with synovial IL-6 and CRP for diagnose PJI in patients after joint arthroplasty was significantly greater than each marker(0.941 vs 0.760,Z=6.333,P<0.001;0.941 vs 0.743,Z=7.189,P<0.001;0.941 vs 0.785,Z=4.999,P=0.006).Conclusion:Serum IL-6,synovial IL-6 and CRP were independently related to PJI in patients after joint arthroplasty.They all had some diagnostic value,and serum IL-6 combined with synovial IL-6 and CRP had higher capability to diagnose PJI in patients after joint arthroplasty than each marker alone.

Study on Biotribological Behavior of the Combined Joint of CoCrMo and UHMWPE/BHA Composite in a Hip Joint Simulator

UHMWPE composites reinforced with Bovine Bone Hydroxyapatite(BHA)in different contents were prepared by heat pressing formation method.A hip joint wear simulator was used to investigate the biotribological behavior of UHMWPE/BHA composite acetabular cups against CoCrMo alloy femoral heads in bovine synovia lubrication at 37±1 ℃.It was found that the addition of BHA powder to UHMWPE can improve the hardness and creep modulus of UHMWPE/BHA composites,and decrease their wear rates under bovine synovia lubrication.When the content of BHA filler particles was up to 30 wt%, UHMWPE/BHA composites demonstrated the well design performances of the surface and biotribological properties.Fatigue, ploughing and slight adhesive wear were the main wear mechanisms for UHMWPE and its composites.In addition,the sizes of wear particles became larger with an increase in BHA powder addition.These results suggest that BHA filler is a desirable component to increase the wear resistance of UHMWPE/BHA composites for biomedical applications.

Quantitative anatomic study of atlanto-odontoid joint and design of an artificial atlanto-odontoid joint for the orthopedic clinic

Objective： To observe and measure morphological parameters of the Chinese atlanto-odontoid joint anatomically in order to provide an anatomic data for designing artificial atlanto-odontoid joint used for substituting the destroyed atlanto-odontoid joint in the orthopedic clinic. Methods： The relative anatomic parameters of 32 sets of fresh Chinese adults ＇atlanto-odontoid joint specimens were measured with a digital caliper and a goulometer, including the width of anterior arch of atlas （ AW）, the thickness of atlas at the junction of anterior arch and lateral mass （ AD）, the thickness and height of anterior tubercle of atlas （ AT and AH ）, the middle height, length and width of the lateral mass （MHL, L and LW ）, the height, transverse and anteroposterior distance of odontoid process （DH, DW and DD）, the retroversion angle of odontoid process （ β° ）, the facial angle of odontoid process （ θ° ） and so on. The data were statistically analyzed in order to ascertain the morphological parameter ranges of artificial atlanto-odontoid joint. An artificial atlanto-odontoid joint was designed according to these data. The operations of anlanto-odontoid joint arthroplasty were conducted in 3 cases of adult cadaver specimens. Resnits： The width of AW was （ 20.45 ± 1.5 3 ） nun, AD （3.91 ±1.32） nun, AT and AH （9.43± 1.93） nun and （ 10.23± 1.32 ） mm, respectively, MHL and LW （ 13.68 ± 1.38 ） mm and （ 12.98 ±1.52 ） mm, respectively, DH （15.25±2.11）mm, DW and DD （9.69±1.38）mm and （ 11.26 ± 1.02 ） ram, respectively, β° （ 12.23 ± 4.27 ） degree, θ° （ 65.48 ±2.17 ） degree. The prosthesis was composed of atlas part, axis part and accessories. Neither the vertebral artery nor the medulla oblongata was injured. Conclusions： The design of artificial atlantoodontoid joint is feasible according to these parameters. The artificial joint can not only rebuild the stability of atlanto-axial joint, but also reserve the rotation function between atlas and axis. Every part of the joint has their own parameter ranges in purpose to firm fixation, convenient operation and good motion without further injury. The prosthesis can be used for patients suffering from compression of medulla oblongata and resection of dens when it is required.

氨甲环酸在人工关节外科领域的应用

关节外科手术失血量一般较大,初次人工全膝关节置换术(total knee arthroplasty,TKA)后的失血量可达到1000~1790 ml[1],初次人工全髋关节置换术(total hip arthroplasty,THA)失血量更大,平均可达到1944ml[2],脊柱外科手术亦有大量出血的风险。随着外科手术技术的提高,例如小切口全髋关节置换术(minimal incision THA,MIS-THA)等骨科微创手术,以及自体血回输、术后引流血回输、急性等溶性血液稀释。

Proximal humeral fractures treated with arthroplasty

Objective: To explore arthroplasty in treating 3- and 4-part fractures of the proximal humerus. Methods: A total of 132 patients with proximal humeral fractures were treated in our hospital from July 1997 to February 2003. According to Neer’s classification, the fractures of 45 patients (14 males and 31 females, aged 31-78 years, 56.1 years± 7.8 years on an average) belonged to 3- or 4-part fractures (10 patients with 4-part fracture and 35 with 3-part comminuted fracture) and they were treated with shoulder joint arthroplasty. Unipolar prosthesis replacement of the head of humerus was made in 28 cases, while bipolar prosthesis replacement in 2 cases and total shoulder joint replacement in 15 cases. Results: During the follow-up period (range: 12-72 months, mean: 37.3 months± 4.1 months), among the 45 patients who suffered from fractures of the proximal humerus and underwent arthroplasty surgery, 44 patients ( 97.8%) had no postoperative pain and were satisfied with the active range of motion and with the whole treatment results. And radiography showed that the prostheses were at their good position. One patient had postoperative pain because he had so narrow medullary cavity that the humeral prosthesis could not be put deeply enough and the prosthesis head was a little higher over the anatomic level. He did not have good postoperative active range of motion, either. Then he received a review surgery and got satisfied results. Temporary shoulder stiffness was observed in one patient. Manual release of these adhesions improved the shoulder function. No evidence of nonunion of the fracture segments around the humeral prosthesis stem was found. Conclusions: Shoulder arthroplasty is a dependable method to restore the comfort and function of the should joints of the patients with 3- or 4-part fractures of the proximal humerus.

Management of post-traumatic elbow instability after failed radial head excision： A case report

Radial head excision has always been a safe commonly used surgical procedure with a satisfactory clinical outcome for isolated comminuted radial head fractures. However, diagnosis of elbow instability is still very challenging and often underestimated in routine orthopaedic evaluation. We present the case of a 21-years old female treated with excision after radial head fracture, resulting in elbow instability. The patient underwent revision surgery after four weeks. We believe that ligament reconstruction without radial head substitution is a safe alternative choice for Mason 1II radial head fractures accompanied by complex ligament lesions.