In vivo kinematic analysis of cruciate-retaining total knee arthroplasty during weight-bearing and non-weight-bearing deep knee bending

The purpose of the present study was to evaluate the in vivo kinematics of the posterior cruciate ligament-retaining total knee arthroplasty during weight-bearing and non-weight-bearing deep knee bending and compare these 2 different conditions. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibia tray by 2-dimensional/3-dimensional registration. In the weight-bearing state, the femoral component showed central pivot and bicondylar posterior rollback pattern. During non-weight-bearing, the movement anteriorly occurred on both the medial and lateral side during early flexion, whereas bicondylar femoral component rollback occurred after that. During non-weight-bearing, both the medial and lateral condyle significantly moved anteriorly compared with the weight-bearing state during early flexion. However, bicondylar femoral rollback occurred under both these conditions.     

In vivo comparison of knee kinematics for subjects having either a posterior stabilized or cruciate retaining high-flexion total knee arthroplasty

The objective of this study was to determine the in vivo kinematics for subjects having either a fixed posterior stabilized (PS) or cruciate retaining (CR) high-flexion total knee arthroplasty (TKA). Three-dimensional kinematics from full extension to maximum flexion were determined for 30 subjects (15 PS, 15 CR) using fluoroscopy. On average, the PS subjects demonstrated 112 degrees of weight-bearing (WB) flexion, -6.4 mm of posterior femoral rollback, and 2.9 degrees of axial rotation. The CR subjects averaged 117 degrees of WB flexion, -4.9 mm of posterior femoral rollback, and 4.8 degrees of axial rotation. Posterior femoral rollback of the lateral condyle occurred for all PS TKAs and in 93% of the CR TKAs. Only 2 subjects in each group experienced greater than 1.0 mm of condylar lift-off. Subjects in both TKA groups demonstrated excellent WB ranges of motion and kinematic patterns similar to the normal knee, but less in magnitude.     

The effect of weight-bearing condition on kinematics of a high-flexion, posterior-stabilized knee prosthesis

The objective of this study was to investigate the effects of weight-bearing (WB) condition on the kinematics of total knee arthroplasty. We investigated 17 patients (20 knees) implanted with a high-flexion posterior-stabilized total knee arthroplasty using 2- to 3-dimensional registration techniques. In vivo kinematics of dynamic deep knee flexion under WB and non-WB (NWB) conditions were compared. Six degree-of-freedom kinematics and articular contacts including post-cam contact were evaluated. At midflexion, femorotibial contact points were located significantly more anteriorly under NWB than WB conditions. As a result, post-cam engagement occurred significantly earlier under NWB than WB conditions. With NWB conditions, early engagement of the femoral cam engages at the top part of tibial post, which puts it at risk of jumping the tibial post particularly if there is instability in midflexion.     

Rotational kinematics of a modern fixed-bearing posterior stabilized total knee arthroplasty

The purpose of this study was to evaluate the rotational kinematics of a fixed-bearing posteriorly stabilized total knee design in moderate and deep flexion. Three-dimensional kinematics analyses were conducted on 20 knees in 4 weight-bearing positions using 3-dimensional shape-matching techniques. Average maximum skeletal flexion was 138 degrees . Internal tibial rotation was demonstrated in 19 of 20 knees. The average internal tibial rotation in midflexed lunge was 5.5 degrees (-3.8 degrees to 14.1 degrees ) and in maximum flexion kneeling was 4.0 degrees (-3.1 degrees to 10.6 degrees ). Separation of articular surfaces was not identified. In this study, patients with this device demonstrated patterns of rotation similar to those previously reported for both the normal knee and rotating platform designs.     

Kinematic comparison between mobile-bearing and fixed-bearing inserts in NexGen legacy posterior stabilized flex total knee arthroplasty

Femoral component rollback and tibial rotation were evaluated using lateral radiographs taken during passive knee flexion under fluoroscopy in NexGen Legacy Posterior Stabilized Flex (Zimmer, Warsaw, Ind) total knee arthroplasties (TKAs; 30 with mobile insert and 26 with fixed insert). Measured maximal flexion angle demonstrated no significant differences. Femoral component rollback was observed predominantly in TKAs with fixed insert in more than 45 degrees flexion and correlated with maximal flexion angle in each group. Tibial internal rotation was more significant in TKAs with mobile insert in maximal flexion. However, tibial internal rotation from 90 degrees to maximal flexion, which demonstrated correlation with maximal flexion angle in each group, did not show significant difference. The kinematic differences between 2 inserts seemed to have little relevance to the maximal flexion angle.     

NexGen LPS Flex全膝关节置换的近期疗效观察

目的探讨高屈曲型NexGen LPS—Flex人工全膝关节置换的近期疗效。方法41例（47膝）行高屈曲型NexGen LPS-Flex人工膝假体置换。术前、术后测量膝关节活动度,并根据HSS膝关节评分系统进行评估。结果获随访32例（38膝）,时间12～42（28．03±8．86）个月。活动度从术前平均67．45°±10．50°改善到术后平均125．68°±10．14°。各种并发症的发生率低。术前HSS评分平均为44．7分±11分,术后HSS评分平均为90．3分±12分;根据HSS评分系统评定疗效：优14例,良16例,中2例,优良率达93．75％。结论高屈曲型NexGen LPS—Flex全膝关节置换的近期临床效果满意,长期效果还需进一步观察。     

Range of motion of standard and high-flexion cruciate retaining total knee prostheses

Recently, use of high-flexion design was introduced in cruciate-retaining (CR) total knee prostheses. The purpose of this study was to prospectively compare the ranges of motion (ROMs) of 89 knees with standard and 87 knees with high-flexion CR total knee prostheses. Differences in age, gender, diagnosis, preoperative ROM of the knee, and Knee Society Score between the 2 groups were not statistically significant. At 12-month follow-up, average ROM was 112.0 degrees +/- 12.6 degrees for standard, and 115.3 degrees +/- 13.4 degrees for high-flexion CR prosthesis (P = .101). To our knowledge, this is the first report on the ROM with the high-flexion CR total knee prosthesis. Using the technique of anterior referencing for femoral component sizing and using a fixed 7 degrees slope for the tibial component, we found no significant differences between groups with regard to ROM, clinical, or radiographic parameters.     

In vivo knee kinematics during stair and deep flexion activities in patients with bicruciate substituting total knee arthroplasty

Orthopedic surgeons and their patients continue to seek better functional outcomes after total knee arthroplasty. The bicruciate substituting (BCS) total knee arthroplasty design has been introduced to achieve more natural knee mechanics. The purpose of this study was to characterize kinematics in knees with BCS arthroplasty during deep flexion and stair activities using fluoroscopy and model-image registration. In 20 patients with 25 BCS knees, we observed average implant flexion of 128° during kneeling and consistent posterior condylar translations with knee flexion. Tibial rotations were qualitatively similar to those observed in the arthritic natural knee. Knee kinematics with BCS arthroplasty were qualitatively more similar to arthritic natural knees than knees with either posterior cruciate-retaining or posterior-stabilized arthroplasty.     

Kinematics of the stiff total knee arthroplasty

The kinematics of 10 total knee replacements with poor flexion (<90°) were compared with 11 replacements with good flexion (>110°) at a mean of 3 years from surgery using optical calibration with implant shape-matching techniques from radiographs taken in standing, early-lunge, and late-lunge positions. There were no significant differences between groups in anteroposterior translation of the medial and lateral femoral condyles or tibial rotation during standing and early lunge. Groups differed in amount of posterior translation of the femoral condyles during late lunge because of the poor-flexion group's inability to achieve the same amount of flexion as the good-flexion group. Poor flexion after total knee arthroplasty, we conclude, is not associated with abnormal kinematics in the setting of well-aligned, well-fixed implants.     

固定平台后稳定型假体全膝关节置换术后的运动学研究

 目的 探讨固定平台后稳定型假体全膝关节置换(total knee arthroplasty,TKA)术后膝关节在负重屈膝下蹲时的运动学特征。方法 选取10名健康志愿者和10例固定平台后稳定型假体TKA术后患者。制作骨骼及膝关节假体三维模型,在持续X线透视下完成负重下蹲动作,膝关节屈曲度每增加15°截取一幅图像。通过荧光透视分析技术完成三维模型与二维图像的匹配,再现股骨与胫骨在屈膝过程中的空间位置,通过连续的图像分析比较正常与固定平台后稳定型假体TKA术后膝关节在负重下蹲时股骨内、外髁前后移动及胫骨内外旋转幅度。结果 负重下蹲时,正常膝关节平均屈曲136°,股骨内、外髁分别后移(7.3±1.2) mm和(19.3±3.1) mm,胫骨平均内旋23.8°±3.4°;TKA术后膝关节平均屈曲125°,股骨内、外髁分别后移(1.4±1.6) mm和(6.4±1.7) mm,胫骨平均内旋8.5°±3.4°。结论 固定平台后稳定型假体TKA术后膝关节运动与正常膝关节相似,均表现出股骨内、外髁后移及胫骨内旋运动,但幅度小于正常膝关节,且在屈膝过程中存在股骨矛盾性前移及胫骨外旋现象。     

后稳定型全膝关节假体置换术后疗效分析

目的　分析后稳定型全膝关节假体置换术的处理方式、手术经验及疗效。方法　对 14例15膝行关节置换 ,使用Apollo后稳定型假体 ,单膝关节置换 13例 ,双膝同期置换 1例。原发疾病为类风湿性关节炎 3例 4膝 ,骨关节炎 11例 11膝。术后随访时间平均 11个月。结果　 15个膝关节术前伸曲活动度平均 75°,全膝关节置换术后 2个月关节活动度恢复至平均 10 0°。 14例患者均可自如行走、上下楼梯 ,膝关节稳定性好。 1膝术后脂肪液化致表层伤口裂开 ,清创后愈合 ,余膝术后伤口均愈合良好。结论　后稳定型假体植入的全膝关节置换手术方式简单、疗效肯定、术后并发症少。     

In Vivo Comparison of Knee Kinematics Before and After High-Flexion Posterior Cruciate-Retaining Total Knee Arthroplasty

The objectives of this study were to compare preoperative and postoperative knee kinematics for subjects implanted with flexion-enhanced posterior cruciate-retaining total knee arthroplasty during deep flexion and to examine flexion performance of the prosthesis design. Three-dimensional kinematics was analyzed by fluoroscopic examinations of subjects using a single-plane model-image registration technique. Preoperatively, knee kinematics demonstrated small posterior femoral translation and limited axial rotation. These motions differed significantly from patterns previously reported for normal knees. Postoperatively, flexion performance was maintained, averaging 130°, and kinematic patterns were similar to preoperative patterns. Although total knee arthroplasty can reduce pain and maintain functional performance, it appears that the characteristics of varus arthritic knee mechanics persist after arthroplasty.     

Fluoroscopic analysis of knee arthroplasty kinematics during deep flexion kneeling

Achieving deep knee flexion >145 degrees is a goal of many patients receiving knee arthroplasty in Asia and the Middle East, yet it is unknown whether knees with implants move similar to the natural knee in these postures. We studied 18 of 36 consecutively operated knees that were able to flex >145 degrees using fluoroscopic analysis during kneeling to maximum flexion. An average of 9 degrees tibial internal rotation was observed in deep flexion. Posterior condylar translations were observed from 80 degrees to 120 degrees flexion, and the condyles translated forward in flexion beyond 120 degrees. Separation of the condyles from the tibial surface was observed in 9 knees at flexion >130 degrees. Very deep flexion can be achieved and is well accommodated using contemporary posterior-stabilized knee arthroplasty, but the kinematics differ from the intact natural knee.     

Long-term survival analysis of the posterior cruciate condylar total knee arthroplasty: A 10-year evaluation

Long-term survivorship analysis was applied to 394 cruciate condylar type total knee arthroplasties. Clinical and radiographic parameters were evaluated. Failure was defined in three separate survival curves as revision, radiographic loosening, and a pain rating of 20 or less on the HSS knee score scale. Survival at 10 years, using only revision or recommended revision as the criterion for failure, was 94.7%. With the addition of the other two criteria, survival fell to 81% at 10 years. The posterior cruciate condylar knee survival is comparable to that of the total condylar knee when using comparable definitions of failure.     

In vivo determination of total knee arthroplasty kinematics: a multicenter analysis of an asymmetrical posterior cruciate retaining total knee arthroplasty

The objective of this study was to determine if consistent posterior femoral rollback of an asymmetrical posterior cruciate retaining (PCR) total knee arthroplasty was mostly influenced by the implant design, surgical technique, or presence of a well-functioning posterior cruciate ligament (PCL). Three-dimensional femorotibial kinematics was determined for 80 subjects implanted by 3 surgeons, and each subject was evaluated under fluoroscopic surveillance during a deep knee bend. All subjects in this present study having an intact PCL had a well-functioning PCR knee and experienced normal kinematic patterns, although less in magnitude than the normal knee. In addition, a surprising finding was that, on average, subjects without a PCL still achieved posterior femoral rollback from full extension to maximum knee flexion. The findings in this study revealed that implant design did contribute to the normal kinematics demonstrated by subjects having this asymmetrical PCR total knee arthroplasty.     

Comparison of a new mobile-bearing total knee prosthesis with a fixed-bearing prosthesis: a matched pair analysis

Background

New prosthesis designs should provide either superior function or durability. Before long time follow up studies are started it should at least prove its effectiveness in clinical outcomes. Therefore we have studied the early clinical results of a new mobile bearing total knee prosthesis (e.motion; Aesculap^®) in comparison with our established fixed-bearing device (PFC; DePuy^®) in a matched-pair analysis.

Patients and methods

About 30 consecutive patients received the new mobile bearing device and were matched with patients who received the PFC prosthesis according to age, gender, weight, axis and preoperative AKS-score. Outcomes were measured using the scores that are routinely documented in our arthroplasty register namely the American Knee Society Score (AKSS), the Oxford Knee Score (OKS), Functional Questionnaire of Hannover for Osteoarthritis (FFbH-OA), range of motion (ROM) and knee pain before and 2 years after the operation.

Results

No statistical differences could be found neither preoperative nor postoperative. Nevertheless the mobile bearing device had a slightly better ROM and function score.

Conclusion

This new device proved to be at least as effective in early clinical outcome as the established fixed bearing prosthesis. It has to be awaited whether it is advantageous in the long run.

     

Knee Kinematics in Anterior Cruciate Ligament-Substituting Arthroplasty With or Without the Posterior Cruciate Ligament

Few studies have compared functional kinematics in knees using identical prostheses with or without the posterior cruciate ligament (PCL). This study contrasted in vivo knee kinematics with an anterior cruciate ligament-substituting arthroplasty with and without PCL retention. We hypothesized that knees without PCLs would exhibit less femoral posterior translation, and consequently less maximum knee flexion. Fifty-six knees were studied using dynamic radiography at least one year post-surgery, with twenty-seven knees retaining the PCL and twenty-nine knees having the PCL sacrificed. Consistent with our hypothesis, PCL-sacrificing knees showed more anterior femoral condylar positions. Contrary to our hypothesis, PCL-sacrificing knees demonstrated greater knee flexion during kneeling (122° versus 115°). Contracted PCLs in severely deformed knees likely were the cause of limited flexion in some retaining knees.     

Comparison of In Vivo Patellofemoral Kinematics for Subjects Having High-Flexion Total Knee Arthroplasty Implant With Patients Having Normal Knees

This study compares the in vivo patellar kinematics of high-flexion posterior cruciate ligament-retaining and posterior-stabilized total knee arthroplasty (TKA) implants with that of the healthy knee. Twenty-seven subjects performing weight-bearing deep knee bends were analyzed under fluoroscopic surveillance from full extension to maximum flexion. The patellofemoral contact positions and patellar flexion were similar for both TKAs. At low flexion, the patellofemoral contact was significantly more distal on the healthy patella than on the TKA patella, but in deeper flexion, there was no difference among the 3 groups. The tibiopatellar angle was similar for all 3 groups, except at deep flexion where the healthy patella rotated significantly more than the implanted ones. Patellofemoral separation was observed in some TKA knees, whereas it was absent in the healthy knees.     

In vivo contact pressures in total knee arthroplasty

This study compared the in vivo femoropolyethylene contact pressures generated in fixed-bearing total knee arthroplasty (TKAs) with those in mobile-bearing TKAs. In vivo kinematics obtained from a 2-dimensional to 3-dimensional registration technique and soft tissue locations derived from computed tomographic scans were entered into a 3-dimensional inverse dynamics mathematical model to determine the in vivo bearing contact forces. The contact areas were obtained from the assembly of computer-aided design models of the components. The contact pressure was defined as the ratio of the contact forces to the contact areas. The results indicate that the in vivo contact pressures in each TKA are greater for the medial condyle than for the lateral condyle. The ability of the mobile-bearing TKA to rotate maintains higher femoropolyethylene contact, resulting in lesser contact pressures, as compared with the fixed-bearing TKA.     

Fixed versus rotating platform total knee arthroplasty: a prospective, randomized, single-blind study

The purpose of this randomized, single-blind clinical trial was to compare a rotating platform (RP) total knee arthroplasty to a fixed-bearing (FB) total knee arthroplasty. Ninety-five knees in 69 patients were implanted by 2 surgeons. There were no significant differences in the preoperative demographics. At a minimum of 2-year follow-up, clinical outcomes and complication rates were similar, with the exception that the RP group had significantly better stair-climbing scores (P = .04). Postoperative range of motion was equally good in both groups (FB knees, 1°-125°; RP knees, 1-126°). There were no bearing dislocations in the RP group. In conclusion, this RP design performs at least as well as the FB version, and the RP patients reported better stair-climbing ability. Enthusiasm for this finding should be tempered by the relatively small sample size.