In vivo kinematics for fixed and mobile-bearing posterior stabilized knee prostheses

This is the first in vivo kinematic study to compare mobile-bearing with fixed-bearing prostheses in patients who had total knee arthroplasties. Femorotibial contact positions for 40 patients implanted with either a fixed-bearing or mobile-bearing prosthesis were analyzed using videofluoroscopy. Femorotibial contact paths were determined using a computer automated model-fitting technique. Nineteen of 20 patients in each group experienced posterior femoral rollback of their lateral condyles, with a mean of 3.6 and 3.7 mm for fixed-bearing and mobile-bearing prostheses respectively. Eighteen patients who had mobile-bearing prostheses and 17 patients with fixed-bearing knee prostheses experienced a normal pattern of axial rotation of 7.3 degrees and 4.1 degrees respectively. Eleven of 20 (55%) patients who had mobile-bearing prostheses implanted and eight of 20 (40%) patients who had fixed-bearing prostheses implanted did not experience femoral condylar lift-off. The remaining knees had condylar lift-off less than 2.4 mm for fixed-bearing prostheses and 1.7 mm for mobile-bearing prostheses, respectively. Patients who had mobile-bearing prostheses implanted experienced greater axial rotation and less condylar lift-off than patients who had fixed-bearing prostheses implanted. Both cruciate ligaments are sacrificed for the mobile and fixed-bearing total knee replacements. The results from the current study showed that, in both groups, the majority of patients experienced kinematics similar to those of a normal knee. However, the extent of lateral femoral condyle posterior rollback and the extent of axial rotation were less.     

固定平台与旋转平台全膝关节置换术的疗效对比

[目的]评价膝关节置换固定平台假体(fixed bearing,FB)和旋转平台假体(rotating platforms,RP)的疗效。[方法]64例患者随机接受FB或RP假体的全膝关节置换手术。临床和放射学随访至少2年。HSS评分评定膝关节功能及I-S指数进行髌骨评分;SF-12评分表评估生理及心理状况。术后3、6个月,1、2年复查X线片及上述各项评估。[结果]FB组患者与RP组患者各个随访时间点HSS评分比较,差异均无统计学意义(P>0.05)。两组患者末次随访时年龄、性别、体重指数(BMI)、疼痛评价、膝关节屈曲活动度、HSS总分、I-S指数及SF-12生理、心理状况比较,均无显著性意义(P>0.05)。对术前I-S指数和术后出现局部膝前痛(HSS疼痛评分<15)的比较,发现高位髌骨患者中术后膝前痛的发生率较低位及正常髌骨患者的发生率均升高。[结论]RP假体至少在安全性和有效性上等同于FB假体。使用两种假体均能获得满意的手术效果。     

Tibiofemoral conformity and kinematics of rotating-bearing knee prostheses

Increasing tibiofemoral articular conformity theoretically increases articular contact area and reduces contact stresses in total knee arthroplasty. Fixed-bearing knee designs possess relatively low tibiofemoral conformity, in part to allow tibiofemoral rotation without generating excessive stresses at the articulation or the implant-bone interface. This study analyzed knee kinematics of mobile-bearing designs in a closed chain dynamic knee extension model in posterior cruciate-retaining design with high- and low tibiofemoral conformity and posterior cruciate-substituting designs with and without rotational constraint. Overall, for all conditions, the mobile-bearing insert rotated with the femur in the presence of tibiofemoral axial rotation. In addition, the correlation of bearing rotation with femoral rotation was stronger for the high-conformity and rotationally-constrained designs than for the low-conformity designs and strongest for the posterior cruciate-retaining high-conformity condition. Changes in conformity or rotational constraint did not appear to affect femoral roll back, tibiofemoral axial rotation, or varus-valgus angulation. The results suggest that mobile-bearing inserts rotate with the femur and increasing conformity or rotational constraint in mobile-bearing design knee prostheses does not affect knee kinematics adversely, at least under closed chain knee extension conditions in vitro.     

Comparison of micromotion in mobile bearing and posterior stabilized total knee prostheses

Background On theoretical grounds mobile bearing total knees should reduce the micromotion of the tibial component relative to the bone.

Patients and methods We used radiostereometric analysis to measure the three-dimensional micromotion in 42 tibial components during 2 years of follow-up. The patients had been randomized as to whether they would receive a mobile bearing (MB) or posterior stabilized (PS) design. We expected that the MB knee would facilitate dissipation of forces from the prosthesis-bone interface by the motion of the bearing and by load sharing with the soft tissues, leading to less micromotion. In the PS designs, limited free rotation caused by the campost articulation might cause additional stress at the bone-prosthesis interface.

Results We found no significant differences between the MB and PS group at the 2-year follow-up evaluation with respect to Knee Society scores and radiographic results. The PS group had a higher variability in subsidence and anterior-posterior tilting of the component than the MB group.

Interpretation The low variability of the data in the MB knee prosthesis group suggests that this design is more predictable and forgiving with respect to micromotion of the tibial component.     

Mid-term results of rotating hinge knee prostheses

Between December 2002 and December 2007, we retrospectively assessed the mid term results of the Nexgen rotating hinge prosthesis in the hands of a single surgeon in difficult primary and complex revision situations. Forty four patients (46 knees) were included in the study: they were followed for an average of 62 months. Knee Society knee score improved from a preoperative mean value of 47 to a mean value of 81 at follow-up (p < 0.05) whereas the mean function score improved from 17 (0-40) to 67.5 (0-90) at follow-up (p < 001). Mean flexion range improved from 65 degrees to 96 degrees at follow-up (p < 0.05). In conclusion, rotating hinge knees gave satisfactory results in difficult revision situations associated with major bone loss, instability or periprosthetic fracture. They also provided satisfactory results in selected cases of advanced primary osteoarthritis.     

全膝关节表面置换患者应用固定平台和移动平台术后中期临床疗效Meta分析

[目的]通过Meta分析评价两种假体(固定平台和移动平台)在TKA患者术后3年以上临床疗效的差异。[方法]文献检索Pubmed、Ovid、Cochrane Library、Science Direct、Springer Link数据库,严格按照纳入和排除标准筛选文献,收集TKA患者应用移动平台和固定平台的高质量的随机对照研究,提取相关数据,采用Review Manager 5.0进行数据分析。[结果]共纳入9篇随机对照研究,Meta分析结果显示:移动平台与固定平台在膝关节评分(KSS)上差异无统计学意义,RR=0.19,95%CI(1.01,1.38),P=0.74,移动平台与固定平台术后膝关节活动度(ROM)差异无统计学意义,RR=1.11,95%CI(1.0,3.21),P=0.30;两者术后并发症的发生率差异无统计学的意义,RR=1.03,95%CI(0.63,1.68),P=0.92;两种假体在膝关节置换术后3年以上患者的满意率差异无统计学意义,RR=0.80,95%CI(0.34,1.91),P=0.62。[结论]对于TKA术后3年以上的患者,移动平台相对于固定平台没有明显的优势。     

旋转铰链型膝关节置换术后中期临床随访报告

[目的]探讨旋转铰链型人工膝关节临床应用的适应证,评价中期的临床疗效,分析术后并发症的原因。[方法]回顾性研究1999～2007年间应用旋转铰链型膝关节假体进行的初次膝关节置换病例,共计34例42膝,平均随访时间6.4年(2.3～10.4年)。这些患者膝关节术前均合并有较为严重的膝内翻、膝外翻或屈曲挛缩畸形,存在不同程度的膝关节不稳定或骨缺损。术后采用HSS评分及膝关节活动度评价临床效果。[结果] 1例术后发生人工关节周围迟发性感染;1例因外伤导致股骨假体近端的股骨干骨折;行切开复位内固定后发生假体周围感染;3例术后复查X线提示有髌骨倾斜或半脱位。所有患者膝关节疼痛均得到明显缓解,行走及上下楼能力均得到明显改善。HSS评分从术前的40.5分增加到术后的89.0分。[结论]旋转铰链型膝关节除适用于人工关节翻修术,还可应用于合并有重度膝关节畸形,存在大量骨缺损或膝关节不稳定的关节炎患者的初次置换。严格选择适应证,准确的手术操作,应用该假体可以获得满意的中期临床疗效。但如果术后出现合并症,处理将比较困难。     

In vivo kinematics of a low contact stress rotating platform total knee arthroplasty system under weight bearing and non-weight bearing condition

Background

The patterns and magnitudes of axial femorotibial rotation are variable due to the prosthesis design, ligamentous balancing, and surgical procedures. We aimed to investigate the effects of the weight bearing (WB) condition on the kinematics of mobile-bearing total knee arthroplasty (TKA).

Methods

We examined 12 patients (19 knees) implanted with a low contact stress (LCS) mobile-bearing TKA system using a two-dimensional to three-dimensional registration technique. The in vivo kinematics of dynamic deep knee flexion under WB and non-WB (NWB) conditions were compared. We evaluated the knee range of motion, femoral axial rotation relative to the tibial component, anteroposterior translation, and kinematic pathway of the femorotibial contact point for both the medial and lateral sides.

Results

Under the WB condition, the mean range of motion was 117.8° ± 16.7°. Under the NWB condition, the mean range of motion was 111.0° ± 4.4°. The mean range of axial rotation from full extension to maximum flexion was 3.0° ± 1.5° under the WB condition and 2.2° ± 1.0° under the NWB condition. With regard to the anteroposterior translation, the LCS mobile-bearing TKA system showed the same kinematic patterns under both conditions, except for axial rotation at 0°, 10°, and 110°. From hyperextension to maximum flexion, the kinematic pattern reflected a central pivot under both conditions.

Conclusions

In conclusion, this study demonstrated that, in an LCS mobile-bearing TKA system, knee kinematics showed the same patterns under NWB and WB conditions, except for axial rotation at the early phase. Further understanding of knee kinematics could provide us with useful information for future design concepts of TKA implants.     

全膝关节置换中固定平台假体和活动平台假体相比较的Meta分析

[目的]应用Meta分析的方法,评价全膝关节置换术(total knee arthroplasty,TKA)中应用固定平台型假体(fixed bearing total knee arthroplasty,FB)和活动平台型假体(mobile bearing total knee arthroplasty,MB)的疗效差异,为临床选择适当类型假体进行TKA术提供依据。[方法]计算机检索Pubmed、EMBASE、Ovid和Cochrane图书馆关于TKA术中应用FB和MB的随机或半随机对照试验,按照文中所述纳入标准收集后进行比较,利用RevMan5.0软件进行异质性分析及Meta分析,绘制森林图。[结果]本文检索了1979～2009年间发表的1 718篇关于TKA术中应用FB和MB的文献,经过筛选和评价,最后收集到已发表的14篇(共1 305例患者)随机或半随机的对照试验,符合本次Meta分析所纳入的试验标准。结果发现两组在KSS评分、关节活动度、患者满意率、放射学指标和假体相关并发症上差异无统计学意义(95%显著区间有重叠)。[结论]相对MB的先进设计理念,现有临床研究结果尚不支持在TKA术中应用MB疗效显著优于FB。     

旋转平台与固定平台全膝关节置换术的对比研究及髌骨置换与否对疗效的影响

目的评估旋转平台和固定平台假体全膝关节置换(TKA)两型假体间的疗效有无差异及髌骨置换与否对疗效的影响。方法选取同一医师施行的78侧初次TKA进行回顾。术前诊断包括骨关节炎、类风湿性关节炎等。施行固定平台TKA手术的患者共30侧,14侧置换髌骨;施行旋转平台TKA手术的共48侧,36侧置换髌骨。术前和术后随访行膝HSS评分、测量关节伸直角度和屈曲角度,以比较两型假体TKA疗效;比较髌骨置换组与未置换组TKA疗效;在髌骨置换组与未置换组中,分别比较固定平台TKA和旋转平台TKA的疗效。结果成功随访76侧,平均25.2个月。旋转平台组术后HSS评分、伸直角度与固定平台组间的差异无统计学意义,前者术后的屈曲角度(112.0±11.5)°优于固定平台组间的差异有统计学意义(t=3.270,P0.01)。髌骨未置换组术后HSS评分、伸直角度与髌骨置换组(102.5±15.1)°组间差异有统计学意义(t=2.469,P0.05;t=3.747,P0.01),术后屈曲角度与后者间的差别无统计学意义。髌骨未置换组中,旋转平台TKA与固定平台TKA的术后HSS评分、屈曲角度无差异,伸直角度差别无临床意义。髌骨置换组中,旋转平台TKA术后HSS评分、伸直角度与固定平台TKA间的差异无统计学意义,前者术后的屈曲角度(112.9±13.0)°与后者术后的屈曲角度(96.7±18.4)°比较差异有统计学意义(t=2.838,P0.05)。结论旋转平台假体与固定平台假体TKA术后总体疗效相似,旋转平台假体能够更好地改善关节屈曲角度;置换髌骨并不能更好地改善膝关节功能。     

旋转平台与后稳定固定平台膝关节假体分析

目的比较分析旋转平台、后稳定固定平台膝关节假体对初次单侧膝关节置换患者术后患肢功能恢复的影响。 方法回顾性分析初次行单侧膝关节置换术的350例膝关节病患者临床资料。纳入病例均经临床、X线片或CT确诊。其中选择旋转平台膝关节假体180例设为A组,选择后稳定固定平台膝关节假体170例设为B组,比较两组手术前后美国特种外科医院膝关节评分(HSS)、美国膝关节协会评分(KSS)、膝关节屈曲度(ROM)及静态稳定性指标,记录两组并发症情况。其中HSS、KSS、ROM、静态稳定性指标等计量资料行t检验,并发症等计数资料行χ²检验。 结果两组术后6个月HSS评分、KSS评分、ROM、横轴向躯体重心(GCP)偏移位置均较术前显著上升,GCP漂移轨迹均显著减少,差异有统计学意义(A组手术前后t ＝－105.415、－107.890、－23.829、56.647、78.339;B组手术前后t ＝－103.736、－136.420、－22.141、－26.077、69.119,均为P<0.05);A组术后6个月GCP漂移轨迹显著小于B组(t ＝7.082,P<0.05);两组并发症发生率比较差异无统计学意义(χ² ＝2.361,P>0.05)。 结论旋转平台与后稳定固定平台假体均能明显促初次单侧膝关节置换患者术后患肢功能恢复,并发症类似,但前者相对静态稳定性更好。     

Surface roughness of the proximal and distal bearing surface of mobile bearing total knee prostheses

Proximal and distal articulations surface roughness measurements were done on 8 mobile bearing knee designs immediately after removal from sterile packaging. Roughness parameters Ra and Rp based on ISO 97, representing mean deviation from the smooth surface line and mean peak to smooth surface line, were recorded using a contact surface profilometer at 10 random sites in the anteroposterior and mediolateral direction on the femoral and tibial metal components and the proximal and distal surface of the ultra-high molecular weight polyethylene (PE) inserts. No differences were found for surface roughness values for the metal components. Surface roughness values were greater for the distal PE bearing surfaces compared with the proximal PE bearing surfaces for each design tested. The roughness values for the PE inserts showed a directional dependence. Complex kinematics of mobile bearing knees coupled with this rougher distal interface could influence the rate of generation of wear particles and total volume of particles produced especially in the early postoperative period.     

旋转平台与固定平台假体全膝人工关节置换术的早期疗效比较

目的比较全膝人工关节置换术应用强生旋转平台与固定平台两种假体术后早期临床疗效。 方法回顾性收集2017年1月至2018年01月济宁医学院附属医院收治的79例86侧膝关节骨性关节炎患者进行回顾性研究,其中43例46膝应用强生旋转平台,其中男性18例（18膝,39.13%）,女性25例（28膝,60.87%）;左侧25膝（54.35%）,右膝21膝（45.65%）,年龄为55~77岁,平均（68±8）岁。36例（40膝）应用强生固定平台,其中男性16例（17膝,42.50%）,女性20例（23膝,57.50%）;左侧22膝（55.00%）,右膝18膝（45.00%）。年龄为54~80岁,平均（67±8）岁。所有患者均由同一位医师行固定平台假体或旋转平台假体初次TKA术。分别于手术前后评估膝关节HSS评分、膝关节活动度。 结果固定平台组或旋转平台组患者的术前活动度与末次随访活动度相比,差异均具有统计学意义（t=26.801,t=21.470,P<0.05）;固定平台组或旋转平台组患者的术前HSS评分与末次随访HSS评分相比,差异均具有统计学意义（t=35.180,t=35.053,P<0.05）。固定平台组与旋转平台组患者比较,术前及末次随访活动度差异均无统计学意义（均P>0.05）,固定平台组与旋转平台组患者比较,术前及末次随访HSS评分差异均无统计学意义（均P>0.05）。 结论旋转平台假体与固定平台假体TKA术后早期临床总体疗效相似。两种假体均能明显改善膝关节活动度及膝关节功能。无论使用哪种假体,短期随访时间内都不会影响到效果。     

Comparison of tibial rotation in fixed and mobile bearing total knee arthroplasty using computer navigation

Tibial rotation is an important aspect of knee function and can be altered after total knee arthroplasty (TKA). These alterations include decreased internal rotation with knee flexion as compared to the normal state and paradoxical external rotation with flexion. Mobile bearing total knee prostheses may allow greater unconstrained tibial rotation. I compared tibial rotation after fixed bearing or mobile bearing total knee arthroplasty in 82 patients who underwent TKA with the tibia cut first technique to ascertain any differences. Using intraoperative imageless computer navigation, measurements included the determination of tibial rotation from extension to 90° flexion before and after prosthetic implantation with non-weight-bearing range of motion. I found that tibial rotation was significantly reduced after fixed bearing total knee replacement as compared to mobile bearing. In addition, the tibial position compared to the distal femur in extension was more external in fixed bearings compared to mobile bearings. Placing the fixed tibial tray with increased internal rotation could explain this difference.

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Résumé  La rotation du tibia est un élément important sur le plan fonctionnel. Elle peut être altérée après une prothèse totale du genou. Ces altérations de la rotation portent sur une diminution de la rotation interne et paradoxalement une augmentation de la rotation externe en flexion. Une prothèse totale du genou à plateau mobile permet une libération plus importante de la rotation tibiale. Nous avons comparé cette rotation à partir de prothèses à la plateau fixe et à plateau mobile sur une série de 82 patients ayant bénéficie de cette arthroplastie avec une coupe première du tibia. Nous avons utilisé pour cela un système de navigation per opératoire. Nous avons trouvé à l’issue de cette étude que les rotations tibiales étaient significativement réduites après prothèse totale à plateau fixe versus prothèses à plateau mobile. Par ailleurs, la position du tibia en extension est en rotation externe par rapport au fémur distal. Cette rotation est plus importante dans les prothèses à plateau fixe que dans les prothèses à plateau mobile. Le positionnement du plateau tibial en rotation interne lors de l’intervention peut expliquer cette différence.

     

A comparative analysis between fixed bearing total knee arthroplasty (PFC Sigma) and rotating platform total knee arthroplasty (PFC-RP) with minimum 3-year follow-up

Background

Since the introduction of mobile bearing total knee designs nearly 30?years back, many studies have been done to evaluate its long-term result. Comparison with fixed bearing designs has been done in the past, but the studies were confounded by variables such as disease, surgeon, bone quality, pain tolerance, etc. We attempt to eliminate these variables in this study.

Methods

A total of 50 patients who had bilateral arthritis of the knee with similar deformity and pre-operative range of motion on both sides agreed to have one knee replaced with mobile bearing total knee design (PFC-RP) and the other with a fixed bearing design (PFC Sigma) were prospectively evaluated. Comparative analysis of both the designs was done at a mean follow-up of 40?months, minimizing patient, surgeon and observer related bias. Clinical and radiographic outcome, survival and complication rates were compared.

Results

At a mean follow-up of 40?months (range 36–47?months), no benefit of mobile bearing (PFC-RP) over fixed bearing design (PFC Sigma) could be demonstrated with respect to Knee Society scores, pain scores, range of flexion, subject preference or patello-femoral complication rates. Radiographs showed no difference in prosthetic alignment. No patient required a revision surgery till last follow-up.

Conclusions

Our study demonstrated no advantage of the mobile-bearing arthroplasty over fixed bearing arthroplasty with regard to clinical results at short-term follow-up. However, longer follow-up is necessary to confirm whether these results are sustained.     

Analysis of the kinematics of total knee prostheses with a medial pivot design

Analysis of the kinematics of the FINE Total Knee System (Nakashima Medical, Okayama, Japan) revealed that the medial condyle is fixed and the lateral condyle shows lateral posterior movement and tibial internal rotation. Analysis of the kinematics of the ADVANCE Total Knee System (Wright Medical Technology, Arlington, Tenn) revealed that the medial condyle is fixed and the lateral condyle shows anterior movement in the early stage, changing thereafter to posterior movement. With regard to rotation, initial external rotation subsequently changes to internal rotation. Analysis of the kinematics of the ADVANTIM Total Knee System (Wright Medical Technology) revealed that the bicondyle shows posterior movement, subsequently changing to anterior and posterior movements. Thus, unlike the FINE or ADVANCE Total Knee Systems, the ADVANTIM Total Knee System shows internal rotation.     

全膝关节置换术中旋转平台假体与固定平台假体短期随访对比(英文)

[目的]观察对照全膝关节置换术中旋转平台假体与固定平台假体的早期效果。[方法]从2011年8月~2012年12月收集了120位患者的样本,包括162例在此期间进行了膝关节置换术的膝关节。膝关节假体(旋转平台与固定平台)是通过随机抽样选出的。对所有患者在手术前与手术后1、6、12个月进行评估,全部使用标准评分方法 (美国膝关节协会评分,功能评分,活动度)。[结果]A组66位患者共85膝使用的是旋转平台假体,平均年龄为(63.13±7.18)岁。B组54位患者共77膝使用的是固定平台假体。平均年龄为(61.35±6.75)岁。平均随访时间为(8.25±6.22)个月。全膝关节置换术固定平台假体与旋转平台假体的平均膝关节协会评分在1年之后分别为(84.5±13.8)分和(82.2±15.7)分,平均膝关节功能评分在1年之后分别为(70.3±20.5)分和(71.4±19.3)分,全膝置换的固定平台假体与旋转平台假体平均活动度在一年之后分别为(103.2±13.5)°和(104.3±13.7)°。两组的术后效果并无差异(P0.05)。[结论]在旋转平台假体与固定平台假体设计中,当前研究表示没有明显的临床性、功能性和影像学上的差异。研究表明,控制其他可变因素,不论使用旋转平台假体或者固定平台假体设计,都不会在短期随访时间内影响到效果。     

Investigation on wear of knee prostheses under fixed kinematic conditions

Abstract:  Although polyethylene components have been used in the human joint for over 30 years, wear simulation studies are fundamental to assess wear resistance of total joint replacements. This assessment will help to obtain quality control and acquire further knowledge of the tribological processes that involve joint prostheses. As a result, the risk of implant failure of innovative prostheses will be reduced. The aim of the present study was to investigate the influence on wear of the polyethylene tibial inserts against metallic femoral components using a knee simulator following a standardized kinematics protocol (ISO/CD 14243-3.2). Four intact "small" size specimens of the tibial MP 913 were tested in a four-station knee wear simulator for two million cycles. The volumetric weight loss for the ultra-high-molecular-weight-polyethylene (UHMWPE) tibial inserts was 44 ± 2, 45 ± 3, and 47 ± 3 mg for the specimens #1–3, respectively. This study demonstrated a good repeatability among the stations of the knee simulator obtaining weight loss values congruent with those found by other authors using similar test conditions.     

Dislocation of rotating hinge total knee prostheses. A biomechanical analysis

BACKGROUND: Symptomatic instability and implant dislocation are occasionally encountered in patients with a rotating hinge total knee prosthesis. A biomechanical study of rotating hinge total knee implants was performed to determine the association between the design (length and taper) of the central rotational stem and the stability of the implant. METHODS: The stem lengths and tapers of knee implants made by seven manufacturers were measured. The tilting laxity of each design was tested by measuring the degree of tilting of the central rotational stem within the tibial housing that occurred with increasing amounts of distraction. The maximum amount of distraction that was possible before the stem dislocated was determined for each design. RESULTS: Implant designs with a short and/or markedly tapered central rotational stem had the greatest tilting, laxity, and instability of that stem. The Howmedica, Techmedica, Intermedics/Sulzer Medica, and Wright Medical Technology/ Dow Corning Wright designs required > or = 39 mm of distraction before they dislocated. The Biomet knee implant required 33 or 44 mm of distraction to dislocate, depending on the thickness of the polyethylene tray that was utilized. The S-ROM knee required only 26 mm of distraction before dislocation occurred. CONCLUSIONS: The measurements confirmed that the shorter the stem and the greater its taper, the greater the instability and laxity at any given amount of joint distraction.