BACKGROUND: Total hip replacement is frequently used for osteoarthritis, rheumatoid arthritis, avascular necrosis of femoral head, et al. Although the operation is effective, some complications such as dislocation are serious and arouse more attention. OBJECTIVE: To review the research status of dislocation after total hip arthroplasty. RETRIEVAL STRATEGY: A computer-based online search of PubMed was undertaken for the English articles published between January 1997 and November 2007 with"hip replacement, dislocation". 496 related articles were collected from the above-mentioned database, including 445 original articles, and 57 review articles. Only articles ①about the influential factors for dislocation of hip joint; ②about the prevention and treatment of dislocation; ③highly correlated with the objective; and ④ published in recently or in authoritative journals were selected. Repetitive studies and Meta analyses were excluded. LITERATURE EVALUATION: Thirty-five articles were included, of which 9 were review articles and the others were clinical or empirical studies. DATA SYNTHESIS: ①Posterolateral approach in total hip arthroplasty increases the dislocation rate compared to anterior lateral approach and direct lateral approach. But when posterior articular capsule and extortor are sutured using absorbable thread before wound suture in total hip arthroplasty by posterolateral approach, the dislocation rate is increased and similar to anterior lateral approach and direct lateral approach. ②Large ball head of prosthesis can decrease the incidence of dislocation. In addition, the incidence of dislocation in prosthesis with skirted is less than prosthesis with no skirt. Elevated-rim acetabular liner can decrease but small offset distance can increase incidence of dislocation. ③Close reduction can cure early dislocation. If the dislocation is caused by infection, it is necessary to clear the wound, even take out the prosthesis for revision. Prosthesis location should be adjusted and hip joint with unbalance soft tissue should be treated by another surgery. ④If patients with recurrent dislocation, weak abductor, obvious soft tissue unbalance or other reason, it is better to use constrained prosthesis. CONCLUSION: Dislocation after total hip arthroplasty is caused by lots of complicated factors. With the acquaintance of factors and development of surgery techniques, the dislocation rate is significantly reduced than before. Complicated dislocation caused by soft tissue unbalance is the focus of future research.

[Objective]To investigate the indications,complications and mid-term results of total knee arthroplasties using rotating hinge knee prosthesis. [Methods]Thirty total knee arthroplasties using rotating hinge prosthesis were performed in twenty-eight patients from July 1998 to July 2008.Seven patients were male and twenty-one patients were female.The average age was 62 years(42-75 years).The diagnosis included osteoarthritis in 8 patients,rheumatoid arthritis in 2 patients,traumatic arthritis in 3 patients,Paget's disease patient,serious genu valgum in 7 patients and 10 failure TKAs.All patients were followed up for 12 to 120 months.The patients were evaluated according to knee score system and the complications were observed.[Results]The pain was relieved and function was improved in all knees.The average knee pain score increased from 19.5 to 77.9,and knee function score from 22.5 to 50.5.Range of motion of knees increased from 58.4?to 72.8?.No revision was needed in all patients,The complications included anterior knee pain(8 cases),extension lag(5 cases),prosthesis broken(1 case) and patella tendon rupture(1 case).[Conclusion]The mid-term results of total knee arthroplasty using rotating hinge knee for severe knee deformity are satisfactory.Complications should be prevented carefully.

Objective To investigate the relative motion between the femoral component and the tibial insert through the technology of fluoroscopy and digital model.Methods Sixteen female patients (16 knees) with knee osteoarthritis were performed TKA (GENESIS Ⅱ) from July 2007 to June 2008.The mean age was 66.4 years (range from 56 to 76 years).All patients were followed up 48 months to 60 months,with the mean of 56±3 months.The postoperative clinical function was evaluated by Knee Society Score (KSS).To match the digital model to the imaging data of fluoroscopy using 2D-3D automatic registration technology and reconstruct motion of the knee after TKA.The movement of contact position between femoral medial and lateral condyle and tibial insert and tibial internal rotation during flexion were measured.The contact time and range between femoral cam and tibial post were analyzed.Results The cases were statistically improved in KSS postoperatively,knee score was 93±5 and function score 88±13.The range of movement for femoral medial condyle was 8.5±2.5 mm,and the lateral condyle was 9.5±4.8 mm,the range of tibial internal rotation was 2.5°±8.4°.The contact of cam and post was observed after 30°-40° flexion of the knee,and the range was 8.0±1.8 mm.The greater tilting angle of the tibial plateau was,the later contact between cam and post happened.Conclusion The kinematics of tibiofemoral joint after TKA is different from the kinematics of normal knee.With knee flexion within 10°-30°,femoral medial condyle moves forward.When flexion is greater than 40°,medial and lateral condyle begins rollback.The time of contact of cam and post is relative to tibial prosthesis slope.

Objective To observe the efficacy of total ankle replacement in treatment of osteoarthritis of ankle joint.Methods Between October 1999 and October 2006,42 patients with ankle osteoarthritis were admitted in Beijing Jishuitan Hospital.All the patients met surgical indications and were performed total ankle replacement with S.T.A.R.system ( Scandinavian Total Ankle Replacement) (Waldemar Link,Hamburg,Germany).The pain in patients,motion and function of joint were evaluated pre- and post-operatively according to Kofoed scoring system,and the efficacy was evaluated with the Mayo'evaluation criteria of total ankle replacement.Results According to Kofoed scoring system,the postoperative situation was obviously superior to the preoperative in pain,motion and function of joint(P ＜ 0.05 ),and the excellent and good rate was 90.32％.While,the excellent and good rate was 87.5％with the Mayo' evaluation criteria of total ankle replacement.Conclusion Total ankle replacement,which can relieve pain,restore ankle function and improve ankle activity,provides another effective method for the patients who need ankle arthrodesis.