| Part 1 Two dimensional and three dimensional registration techniques for the reconstruction of total knee replacement kinematicsObjective: Recently,radiographic images have been used in computerassisted surgery,and to more accurately evaluate motion in replaced human joints.The process involved three stages.Firstly,fluoroscopic images were digitized and processed to delineate the prosthesis,so that the sets of femoral and tibial images at their respective positions were obtained in the virtual single fluoroscopic imaging system.Secondly,the 3dimensional computerassisted design(CAD)models of the knee prosthesis were imported into the software.Thirdly,the borders of the CAD were manipulated to completely match the corresponding sets of femoral and tibial images on the lateral radiograph.Then,the relative 3D position orientations of the femoral and tibial prostheses that represented the in vivo positions of the prostheses were reproduced.There is a dispute about the accuracy of the two-and threedimensional image matching technology.In this study,the accuracy of the technique of with high precision 3D laser scanner in the measurement of the kinematics of the knee joint was studied by 3D laser scanner.Methods: The surgery was performed by the same senior surgeon using a posterior cruciate ligament-retaining total knee prothesis.There was 5 degree in slope in the tibial tray.The prosthesises were of the same design and same manufacturer and the polyethylene tray had not an inbuilt slope.It was the same surgeon who performed all the surgeries and he used the same technique each time.The posterior cruciate ligament was preserved while anterior cruciate ligament was resected.A proximal tibial osteotomy was performed with 5° of posterior movement along the sagittal plane on the cutting jig.The artificial knee joint knee prosthesis model slowly and continuously complete flexion of the knee from 0 degrees to 90 degrees in a single plane X-ray machine.The process involved three stages.Firstly,fluoroscopic images were digitized and processed to delineate the prosthesis,so that the sets of femoral and tibial images at their respective positions were obtained in the virtual single fluoroscopic imaging system.Secondly,the 3D CAD models of the knee prosthesis were imported into the software.Thirdly,the borders of the CAD were manipulated to completely match the corresponding sets of femoral and tibial images on the lateral radiograph.Then,the relative 3D position orientations of the femoral and tibial prostheses that represented the in vivo positions of the prostheses were reproduced.The flexion angle was defined as the angle between the anterior lange of the femoral component and the tibial tray on the lateral radiograph image,while the medial and lateral femorotibial articular contact points were defined as the nearest points between the femoral and tibial prostheses,which were the lowest points on the femoral condyle of the CAD models.The plane of the tibial tray was used as a reference plane,and the projection was moved in that plane to contact the femur.The contact region was visualized where proximity within the 0.2-mm threshold was regarded as the virtual contact region.Subsequently,the centre point of the contact region was specified as the contact point.In the tibial tray plane coordinate system,the origin was defined as the centre of the tibial tray surface,the x-axis was defined as the line connecting the medial to the lateral edges of the tibial tray surface,and the y-axis was defined as the line that bisected and was perpendicular to the x-axis.The anterior and posterior contact points of the x-axis were designated as positive and negative on the y-axis,respectively.The 3D laser scanner was used to measure the three-dimensional coordinates of the lowest point of the femur relative to the tibia in the three-dimensional space position.The error of the measurement position relative to the real position is compared,and the accuracy of the two dimensional and three-dimensional image matching technique in the kinematic measurement of the knee joint replacement is obtained.Results: The root mean square errors of the relative position of the femoral component in the tibial component coordinate system were 2.0°,0.6° and 0.5 degrees,perpendicular to the horizontal plane,coronal and displacement error is 0.4 mm,0.5 mm,1.5 mm.The rotation error is 3.5°,0.8°,0.6°,the maximum movement error is 0.6 mm,0.8 mm,2 mm.There was no significant difference between the two methods(P>0.05).Summary: The knee arthroplasty kinematic can be accurately measured with two dimensional and three dimensional registration techniques.The technique was shown to improve the design of prosthesis and the operation level of clinicians,so as to improve the quality of life of patients after surgery.Part 2 Effect of tibial slope changes on femorotibial contact kinematics after cruciate-retaining total knee arthroplastyObjective: The knee kinematic patterns have changed after total knee arthroplasty(TKA).The medial femorotibial articular contact point kept motionless or moved posteriorly for the normal knee.The medial femoral condyle appeares paradoxical anterior displacement after posterior cruciate ligament-retaining total knee arthroplasty(CR TKA).A 2-dimensional/3-dimensional registration was used to evaluate the effect of the changes of posterior tibial slope on the femorotibial articular contact kinematics in vivo kinematics for subjects implanted with posterior cruciate ligament-retaining total knee arthroplasty during weight-bearing,midflexion.Methods: 18 knees in 9 patients who underwent CR TKA of the same sizes for medial OA at 2 years after TKA were analyzed.Knees were classified into two groups according to the change in TS obtained by subtracting the post-operative value from the preoperative value: group 1,≧3°(n=10)and group 2,<3°(n=8).Before the operation,all patients had medial osteoarthritis(Kellgren-Lawrence grade III)with varus deformity and integral anterior cruciate ligaments.Patients with post-traumatic arthritis,rheumatoid arthritis,and/or valgus knees were excluded.In group 1,all patients were females with a mean age of 61.1 years(range,57-68 years)at operation and average postoperative time of 24.3 months(range,24-25 months)in the present study.The max knee flexion was 84°(range,60-90°).In group 2 all patients were females with a mean age of 61.3 years(range,57-68 years)at operation and average postoperative time of 24.2 months(range,24-25 months)in the present study.The max knee flexion was 83°(range,60-90°).There were no statistical differences between the two groups(n.s.).After the operation,all patients had more than 90 points based on the Knee Society Score,without any measurable ligament laxity and notable complications.The max knee flexion in group 1 and 2 was 125°(range,115-130°)and 123°(range,115-130°),respectively.Each subject was instructed to perform a weight-bearing leg bend from full extension to 90° flexion under weight bearing conditions,which was monitored by a single fluoroscopic imaging system.The process of flexion was accomplished sequentially with the assistance of handrails.Fluoroscopic images were digitized and processed to delineate the prothesis from surrounding tissues.The set of femoral and tibial images at their respective positions were placed in the virtual single fluoroscopic imaging system.The three dimensional(3D)computer-assisted design(CAD)models of the knee prothesis were imported into the software,thus,manipulating the borders of CAD and the corresponding prothesis on the lateral X-ray image to complete match.The relative 3D position and orientations of femoral and tibial prothesis which represented the in vivo positions of the prothesis was reproduced.Results: Femorotibial articular contact kinematics in Group 1 : At full extension(0°),the mean medial femorotibial articular contact point was-0.1±1.5mm(range,-3.1 to 1.9 mm).The medial femorotibial articular contact point moved continuously posteriorly during the process of knee flexion.At last(90°),the mean medial femorotibial articular contact point was-4.1±3.4mm(range,-11.4 to-0.7mm).Thus,the average moving distance was 4.0mm.At full extension(0°),the mean lateral femorotibial articular contact point was-1.1±1.1mm(range,-3.1 to 0.5 mm).In addition,the lateral femorotibial articular contact point moved continuously posteriorly during the process of knee flexion.At last(90°),the mean medial femorotibial articular contact point was-11.1±1.5mm(range,-12.9 to-8.1mm).Therefore,the mean moving distance was 10.0mm.From 0° to 90°,the mean lateral translation of femorotibial articular contact point was significantly greater than medial translation(P<0.001).Femorotibial articular contact kinematics of Group 2: At full extension(0°),the mean medial femorotibial articular contact point was 0.2±2.0mm(range,-2.8 to 2.7 mm).The medial femorotibial articular contact point showed paradoxical anterior translation from 50° to 90° of knee flexion.The mean medial femorotibial articular contact point moved to the most posterior location and reached-2.7±2.0mm(range,-5.6 to 0.1 mm)at 40° of knee flexion.Thus,the mean moving distance was 2.9mm.the medial femorotibial articular contact point moved anteriorly from 50° to 90°,reaching-0.5±1.8mm(range,-3.1 to 2.2 mm)at 90° of knee flexion.Accordingly,the mean moving distance was 2.2mm.At full extension(0°),the mean lateral femorotibial articular contact point was-2.8±1.7mm(range,-6.0 to-0.1 mm).Additionally,the lateral femorotibial articular contact point moved continuously posteriorly during the process of knee flexion.At last(90°),the mean lateral femorotibial articular contact point was-8.7±2.3mm(range,-11.5 to-4.9mm).The mean moving distance,therefore,was 5.9mm.From 0° to 90°,the mean lateral femorotibial articular contact point translation was significantly greater than medial translation(P<0.001).Summary: Increased reduction in tibial slope after TKA compared to pre-operative slope was shown to reduce paradoxical MFC movement.Part 3 Effect of tibial slope changes on knee function after cruciate-retaining total knee arthroplastyObjective: The outcome after total knee arthroplasty is affected by many factors.The present study was undertaken to evaluate the effect of posterior tibial slope changes on the outcome after cruciate-retaining total knee arthroplasty for subjects undergoing posterior cruciate ligament-retaining total knee arthroplasty.Methods: 20 knees in 10 patients who underwent posterior cruciate ligament-retaining total knee arthroplasty of the same sizes for medial OA at 1 years after TKA were analyzed.All 20 knees had varus deformity,which could flex over 90° before operation.All subjects were females with a mean age of 63.5 years(range,57-68 years)at surgery and average postoperative time of of 12.4 months(range,12-13 months)in the present study.All subjects had more than 90 points on the Knee Society Score and an accurate alignment,without notable complications after operation.Each subject was instructed to perform a weight-bearing leg bend from full extension to 90° flexion under weight bearing conditions,which was monitored by a single fluoroscopic imaging system.The process of flexion was accomplished sequentially with the assistance of handrails.Fluoroscopic images were digitized and processed to delineate the prothesis from surrounding tissues.The set of femoral and tibial images at their respective positions were placed in the virtual single fluoroscopic imaging system.The three dimensional(3D)computer-assisted design(CAD)models of the knee prothesis were imported into the software,thus,manipulating the borders of CAD and the corresponding prothesis on the lateral X-ray image to complete match.The relative 3D position and orientations of femoral and tibial prothesis which represented the in vivo positions of the prothesis was reproduced.Pain was measured by Visual analog scale,as knee function measured by questionnaires of Western Ontario and Mc Master Universities Osteoarthritis Index and Knee Society Score score.Results: In group 1,the medial femorotibial articular contact point moved continuously posteriorly from 0° to 90° of knee flexion(P<0.05).In contrast,in group 2,the medial femorotibial articular contact point moved posteriorly from 0° to 20°(P<0.05.).From 20° to 50°,the point remained almost motionless(P>0.05).,The point moved anteriorly from 50° to 90°(P<0.05).At last(90°),the mean medial femorotibial articular contact point in group 1 was significantly more anterior,as compared with group 2(P=0.007).The lateral femorotibial articular contact point of both two groups moved posteriorly with different extent.More significant posterior movement of the average lateral femorotibial articular contact point was observed in group 1 than in group 2 during the whole bending process(P<0.001).Comparison of TKA between two groups in the postoperative analysis showed that there was a significant difference between groups in pain and functional KSS and WOMAC score(P<0.05)Summary: A proper understanding decrease in posterior tibial slope for subjects receiving posterior cruciate ligament-retaining total knee arthroplasty resulted in improved postoperative outcome by preventing the appeaance of paradoxical MFC movement.Part 4 The relationship between clinical results and changes of posterior tibial slope in total knee arthroplastyObjective: The purpose of this study is to investigate the relationship between clinical results and changes of posterior tibial slope in posterior cruciate ligament-retaining total knee arthroplasty..Methods: 180 knees in 150 patients who underwent posterior cruciate ligament-retaining total knee arthroplasty from September 2012 to September 2013 were analyze.Knees were classified into five groups according to the change in TS obtained by subtracting the post-operative value from the preoperative value:: group 1,>5°;group 2,3°to 5°;group 3,0°to 3°;group 4,-3° to 0°;and group 5,<-3°.The relationship between clinical results and changes of posterior tibial slope,such as pain was measured by Visual analog scale,as knee function measured by questionnaires of Western Ontario and McMaster Universities Osteoarthritis Index、Knee Society Score score and complications were analyzed.Results: There was statistically significant between groups;There were no complications.Summary: There was important relationship between changes of posterior tibial slope and the knee function after cruciate-retaining total knee arthroplasty.Great changes could interfere with the recovery of knee function.There were no complications.Conclusion:The knee arthroplasty kinematic can be accurately measured with two dimensional and three dimensional registration techniques.The technique was shown to improve the design of prosthesis and the operation level of clinicians,so as to improve the quality of life of patients after surgery.Increased reduction in tibial slope after TKA compared to pre-operative slope was shown to reduce paradoxical MFC movement.A proper understanding decrease in posterior tibial slope for subjects receiving posterior cruciate ligament-retaining total knee arthroplasty resulted in improved postoperative outcome by preventing the appeaance of paradoxical MFC movement.There was important relationship between changes of posterior tibial slope and the knee function after cruciate-retaining total knee arthroplasty.Great changes could interfere with the recovery of knee function.There were no complications. |
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