| 1. The kinematic analysis of the posterior-stabilized, fixed-bearing and mobile-bearing posterior cruciate-retaining total knee arthroplasty Objective To explore whether anteroposterior femorotibial translation influenced maximum knee flexion in patients with total knee arthroplasty. Methods Patients with posterior-stabilized, fixed-bearing and mobile-bearing posterior cruciate-retaining total knee arthroplasty were selected 25 respectively. The criteria for inclusion were a preoperative diagnosis of end-stage osteoarthritis of the knee which had been operated more than one year before our study and had a good or excellent postoperative result and a final range of flexion of at least 90 °. Patients were 63~77 years, averaged 68 years, and were composed of 32 knees of male and 43 knees of female. The mean preoperative range of motion is: 77.8 °±15.1 °(the group of posterior-stabilized), 80.1°±12.9°(the group of fixed-bearing) and 76.4 °±12.7 °(the group of mobile-bearing). The ranges of anteroposterior femorotibial translations and maximum knee flexions were measured on lateral photograms. Analysis of variance was used to do mean comparisons between the posterior-stabilized, fixed-bearing and mobile-bearing posterior cruciate-retaining total knee arthroplasties. Linear regression was used to determine whether there was a significant relationship between anteroposterior femorotibial translation and maximum knee flexion. Results There was no statistical difference between preoperative ranges of motion of the three groups. The mean maximum flexions of the knees with posterior-stabilized, fixed-bearing and mobile-bearing posterior cruciate-retaining total knee arthroplasties were 118.0°±7.1°, 108.7°±7.9°and 100.2°±8.3°respectively. Analysis of variance showed there was a difference between them (F =32.86, P=0.0001). The mean anteroposterior femorotibial translations of the knees with posterior-stabilized, fixed-bearing and mobile-bearing total knee arthroplasties were (6.3±2.5)mm, (-1.2±4.6)mm, and (–4.7 ±3.7)mm respectively (femoral posterior translation was positive, anterior was negative). Analysis of variance showed there was a difference between them (F =57.71, P=0.0001). There was a statistically significant linear relationship between maximum knee flexion and anteroposterior femorotibial translation. The regression equation suggested that an additional 1.41°flexion would be obtain for each additional millimeter of posterior femoral translation. Conclusion The anteroposterior femorotibial translations were different between the knees with posterior stabilized, fixed-bearing and mobile-bearing total knee arthroplasties, and their maximum knee flexions were also different. One millimeter of anterior translation will make the maximum knee flexion decrease 1.41o. 2. Comparison of the clinical results of fixed-bearing and mobile-bearing total knee arthroplasty Objective: The purpose of this prospective randomized study was to compare the postoperative recovery and early clinical results of 2 groups of patients undergoing total knee arthroplaty (TKA): one group received a fixed-bearing posterior-stabilized prosthesis (scorpio) and the other group received a mobile-bearing prosthesis (Gemini MKⅡ). Methods: From January 2001 to December 2002, patients withosteoarthritis needed to treat with TKA were assigned at random to receive fixed-bearing TKA or mobile-bearing TKA. The fixed-bearing group was composed of 55 knees (53 patients), including 18 male and 35 female. For patients in the fixed-bearing group, the average age was 68.5 years, the average body mass index (BMI) was 25.5, the average varus deformity was 5.5°, the average flexion contracture was 8.5°and the average maximum knee flexion was 82.2°. The mobile-bearing group was composed of 53 knees (49 patients), including 15 male and 34 female. For the patients in the mobile-bearing group, the average age was 69 years, the average BMI was 26.5, the average varus deformity was 6.5°, the average flexion contracture was 8.4°and the average maximum knee flexion was 80.2°. The clinical and radiographic follow-up was performed at 1, 3, 6 and 12 months after the operation and yearly thereafter. At each follow-up recorded the total knee score, pain score, patient function score, patellar score and the range of motion of the knee. And anteroposterior and lateral radiographes were taken to evaluate the position of the prosthesis and the radiolucent lines around the prosthesis. Statistical evaluation was performed using Student's t test or chi-square test. Statistical significance was considered for P values less than 0.05. Results: There was no significant difference between the two groups for age, BMI, varus deformity, maximum knee flexion and flexion contracture preoperatively (P>0.05). The patients of 2 groups were followed up averaged 20 months (12~36 months). In the fixed-bearing group, the total knee score was 31.5 ±16.2 preoperatively, 90.4±9.7 postoperatively; pain score was 1.3±3.2 preoperatively, 4.7±6.2 postoperatively; patient function score was 37±10.5 preoperatively, 74±10.7 postoperatively; Patellar score was 13 ±4.3 preoperatively, 27.5 ±4.3 postoperatively. In the mobile-bearing group, the total knee score was 32.8 ±17.8kinematics of total knee arthroplasty preoperatively, 88.7±10.5 postoperatively; pain score was 0.9±3.0 preoperatively, 46.5±6.9 postoperatively; patient function score was 38±11.4 preoperatively, 75±15.4 postoperatively; patellar score was 14±5.9 preoperatively, 28±4.0 postoperatively. For all of these was no significant difference between the 2 groups (P>0.05). The postoperative maximum flexion of the fixed-bearing group and the mobile-bearing group was 108°±9.3°and 99.5°±10.1°respectively. There was significant difference between the 2 groups for the postoperative maximum flexion (P<0.05). In the fixed-bearing group, the femoral valgus angle was 95.5°±2.0°, the tibial angle was 90°±1.3°, the femoral component flexion angle was 4.3°±1.2°, the tibial slope angle was 6.8°±2.4°, and the patellar height (Install-Salvati ratio) was 0.94±0.16 preoperatively, 0.93±0.16 postoperatively. In the mobile-bearing group, the femoral valgus angle was 95.2°±2.1°, the tibial angle was 90.1°±1.5°, the femoral component flexion angle was 4.5°±1.2°, the tibial slope angle was 6.5°±2.5°and the patellar height (Install-Salvati ratio) was 0.95±0.18 preoperatively, 0.94±0.17 postoperatively. There was no significant difference of between the 2 groups for these data (P>0.05). The rate of the radiolucent line in fixed-bearing group and mobile-bearing group was no statistical difference (18.2% vs. 20.7%, P>0.05). Conclusion: The short-term results of the fixed-bearing posterior stabilized prosthesis (Scorpio) and the mobile-bearing prosthesis (Gemini MKⅡ) TKA were successful. There was no significance difference between the two groups for the total knee score, function score, pain score, patellar score and radiographic results. The postoperative maximum flexion in fixed-bearing group was higher than that in mobile-bearing group. 3. Effect of increased posterior tibial slope or partial posterior cruciate ligament release on kneeObjective: To compare the effects of increased posterior tibial slope or partial posterior cruciate ligament (PCL) release on knee kinematics of total knee arthroplasty (TKA). Methods: Six fresh human cadaver knees with no osteoarthritis and no deformity were used. Anteroposterior laxity, rotational laxity, varus and valgus laxity and maximum flexion angle were evaluated in 6 normal knees at flexion 0 o ,30 o ,60 o ,90 o and 120 o . Then PCL-retaining TKA was done on the knees. The same tests were performed on the knees after TKA with the same manner as in the normal knees. Then the femoral prosthesis was shifted 5mm posteriorly to simulate the tightly implanted knee. The same tests were performed on the tightly implanted knees. After that, the posterior tibial slope was increased 4oon the tightly implanted knees and the same tests were performed. Then the joint position of the tibia was restored to the original joint line by 4o-metal wedge. The PCL was partially released from the tibial attachment. The same tests were made as in the normal knees. Statistical analysis of the results was made using student's t test. Results: Anteroposterior laxity, rotational laxity and varus and valgus laxity of the tightly implanted knees At flexion 30°,60°,90°and 120°were significantly less than those of the normal TKA knees (P<0.05). Compared with the tightly implanted knees, anteroposterior laxity, rotational laxity and varus and valgus laxity at flexion 30°,60°,90°and 120°significantly improved after increased 4°posterior tibial slope (P<0.05); in the partial PCL released group, anteroposterior laxity at flexion 30°,60°,90°and 120°was significantly improved (P<0.05), varus and valgus laxity was significantly improved only at flexion 90°(P<0.05), and rotational laxity was significantly improved at flexion 30°,60°and 90°(P<0.05).
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