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.     

Comparison of fixed-bearing and mobile-bearing total knee arthroplasties.

The purpose of the current study was to directly compare the results of fixed-bearing and mobile-bearing total knee arthroplasties in the same patient who had bilateral simultaneous total knee replacements. A fixed-bearing total knee prosthesis (AMK) was implanted in one knee and a mobile-bearing total knee prosthesis (LCS) was implanted in the other knee in 116 patients. The average age of the patients was 65 years (range, 33-70 years). The average followup was 7.4 years (range, 6-8 years). Clinical and radiographic followup was done using Knee Society and Hospital for Special Surgery knee rating systems at 6 weeks, 3 months, 6 months, 1 year after surgery, and yearly thereafter. Total knee score, pain score, mean functional score, and range of motion were comparable in both groups. Two knee replacements (2%) in one patient with AMK prostheses were revised because of complete wear of tibial bearing polyethylene. One knee replacement (1%) in one patient with an LCS prosthesis was revised because of dislocation of the medial tibial bearing polyethylene and one knee replacement (1%) in one patient with an LCS prosthesis was revised because of complete wear of the medial tibial bearing polyethylene. No knee had aseptic loosening or osteolysis in either group. After a minimum followup of 6 years, the results of fixed- and mobile-bearing total knee prostheses in the current series are favorable. However, there is no evidence to prove the superiority of the mobile-bearing total knee design.     

In vivo kinematics of mobile-bearing knee arthroplasty in deep knee bending motion.

The current study aimed to analyze kinematics during deep knee bending motion by subjects with fully congruent mobile-bearing total knee arthroplasties allowing axial rotation and anteroposterior (AP) gliding. Twelve subjects were implanted with Dual Bearing Knee prostheses (DBK, slot type: Finsbury Orthopaedics, Surrey, UK). These implants include a mobile-bearing insert that is fully congruent with the femoral component throughout flexion and allows axial rotation and limited AP translation. Sequential fluoroscopic images were taken in the sagittal plane during loaded knee bending motion. In vivo kinematics were analyzed using a two- to three-dimensional registration technique, which uses computer-assisted design models to reproduce the spatial position of femoral and tibial components from single-view fluoroscopic images. The average femoral component demonstrated 13.4 degrees external axial rotation for 0-120 degrees flexion. On average, the medial condyle moved anteriorly 6.2 mm for 0-100 degrees flexion, then posteriorly 4.0 mm for 100-120 degrees flexion. On average, the lateral condyle moved anteriorly 1.0 mm for 0-40 degrees flexion, then posteriorly 8.7 mm for 40-120 degrees flexion. The typical subject exhibited a lateral pivot pattern from extension to 60 degrees flexion and a central pivot pattern from 60 degrees to 100 degrees flexion, patterns that are not usually observed in normal knees. Subsequently from 100 degrees to 120 degrees flexion, a rollback pattern was reproduced in which bilateral condyles moved backward.     

Dynamic activity dependence of in vivo normal knee kinematics

Dynamic knee kinematics were analyzed for normal knees in three activities, including two different types of maximum knee flexion. Continuous X‐ray images of kneel, squat, and stair climb motions were taken using a large flat panel detector. CT‐derived bone models were used for model registration‐based 3D kinematic measurement. Three‐dimensional joint kinematics and contact locations were determined using three methods: bone‐fixed coordinate systems, interrogation of CT‐based bone model surfaces, and interrogation of MR‐based articular cartilage model surfaces. The femur exhibited gradual external rotation throughout the flexion range. Tibiofemoral contact exhibited external rotation, with contact locations translating posterior while maintaining 15° to 20° external rotation from 20° to 80° of flexion. From 80° to maximum flexion, contact locations showed a medial pivot pattern. Kinematics based on bone‐fixed coordinate systems differed from kinematics based on interrogation of CT and MR surfaces. Knee kinematics varied significantly by activity, especially in deep flexion. No posterior subluxation occurred for either femoral condyle in maximum knee flexion. Normal knees accommodate a range of motions during various activities while maintaining geometric joint congruency. © Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:428–434, 2008     

Prevalence of osteolysis after simultaneous bilateral fixed- and mobile-bearing total knee arthroplasties in young patients

This study aimed to evaluate the clinical and radiographic results and to document the prevalence of osteolysis associated with fixed-bearing (anatomic modular knee) and mobile-bearing (low contact stress) total knee arthroplasties (TKAs) in 61 patients younger than 55 years who had bilateral simultaneous primary TKAs. Forty-five patients were female and 16 patients were male. The mean age of the patients was 48.3 years (range, 34-55 years). The mean postoperative Knee Society knee and functional score were similar in both groups (91 and 90 points and 85 and 86 points, respectively). Three knees (5%) in each group were revised for wear of the tibial bearing, and 1 knee (2%) in the mobile-bearing TKA was revised for dislocation of the meniscal bearing. Osteolysis was identified in both radiographs and computed tomography scans in 6 knees (10%) in the anatomic-modular-knee group and 4 knees (7%) in the low-contact-stress group.     

Comparison between the kinematics of fixed and rotating bearing knee prostheses

Rotating platform mobile bearing knee implants allow for increased tibiofemoral articular conformity without restricting axial rotation. In the current study, the effect of rotating platform knee replacement with and without posterior cruciate ligament substitution on knee kinematics was investigated. Five knees were implanted sequentially implanted with standard (fixed) bearings and then with rotating platform prostheses, each in posterior cruciate retaining and substituting designs. Three-dimensional kinematics for all knees were measured in an Oxford Knee Rig, which simulates dynamic quadriceps-driven closed kinetic chain knee extension under load. Rotating bearings did not significantly change knee kinematics when compared with fixed bearings. In this in vitro model, the cruciate retaining designs stayed more anterior, and had greater net femoral roll back and tibiofemoral valgus angulation with flexion than cruciate substituting designs.     

Highly cross-linked ultrahigh molecular weight polyethylene with improved fatigue resistance for total joint arthroplasty: recipient of the 2006 Hap Paul Award

Eliminating postirradiation melting and stabilizing the residual free radicals of radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) with vitamin E resulted in improved fatigue crack propagation resistance without compromising wear resistance. We designed a cantilever postbending test to determine the bending fatigue resistance of alpha-tocopherol-doped, irradiated UHMWPE (alpha-TPE) in comparison to conventional UHMWPE. The bending fatigue behavior of alpha-TPE was comparable to conventional UHMWPE. Upon accelerated aging, the fatigue resistance of alpha-TPE was substantially better than that of conventional UHMWPE. alpha-TPE has shown improved wear and oxidation resistance, migration stability of vitamin E, and improved mechanical properties. The use of this material may be beneficial in total knee arthroplasty where its improved fatigue properties may be an advantage under high stresses.     

固定平台与旋转平台假体用于外翻膝的早期疗效观察

目的:比较外翻膝人工全膝关节置换术应用旋转平台和固定平台两型假体的早期临床疗效。方法:选取2011年1月至2013年12月吉林大学第一医院骨关节外科由同一医师进行初次人工膝关节置换的17例(23膝)进行回顾性随访研究,其中男2例,女15例;年龄48～75岁,平均61.5岁。术前诊断为骨性关节炎14例(19膝),类风湿性关节炎3例(4膝),所有膝关节有外翻畸形。其中9例(12膝)使用固定平台型假体(PFC Sigma),8例(11膝)使用旋转平台型假体(PFC Sigma RP).术前和术后随访行KSS、HSS、WOMAC评分,测量关节活动度、胫股角等指标,进行统计学分析。结果:所有患者获随访,时间6～36个月,平均25个月。两组患者膝外翻畸形均得到矫正,术后末次随访的KSS、HSS、WOMAC评分及膝关节活动度、胫股角较术前明显改善(P<0.01).其中固定平台组和旋转平台组在术后KSS、HSS、WOMAC评分以及胫骨角、膝关节活范围改善度方面比较,差异无统计学意义(P>0.05);而术后末次随访膝关活动范围固定平台组(101.8±8.8)°与旋转平台组(108.4±7.2)°差异有统计学意义(P<0.05).旋转平台组没有发现垫片脱位,两组术后均无感染、腓总神经麻痹、脱位、膝关节不稳等并发症发生,X线检查未见假体骨溶解及松动发生。结论:外翻膝人工全膝关节置换术使用旋转平台和固定平台型假体均能获得满意的早期临床效果,两者的近期临床疗效比较无明显差异。     

Reasons for revision are associated with rerevised total knee arthroplasties: an analysis of 8,978 index revisions in the Dutch Arthroplasty Register

Background and purpose — From previous studies, we know that clinical outcomes of revision total knee arthroplasty (rTKA) differ among reasons for revision. Whether the prevalence of repeat rTKAs is different depending on the reason for index rTKA is unclear. Therefore, we (1) compared the repeat revision rates between the different reasons for index rTKA, and (2) evaluated whether the reason for repeat rTKA was the same as the reason for the index revision.Patients and methods — Patients (n = 8,978) who underwent an index rTKA between 2010 and 2018 as registered in the Dutch Arthroplasty Register were included. Reasons for revision, as reported by the surgeon, were categorized as: infection, loosening, malposition, instability, stiffness, patellar problems, and other. Competing risk analyses were performed to determine the cumulative repeat revision rates after an index rTKA for each reason for revision.Results — Overall, the cumulative repeat revision rate was 19% within 8 years after index rTKA. Patients revised for infection had the highest cumulative repeat revision rate (28%, 95% CI 25–32) within 8 years after index rTKA. The recurrence of the reason was more common than other reasons after index rTKA for infection (18%), instability (8%), stiffness (7%), and loosening (5%).Interpretation — Poorest outcomes were found for rTKA for infection: over 1 out of 4 infection rTKAs required another surgical intervention, mostly due to infection. Recurrence of other reasons for revision (instability, stiffness, and loosening) was also considerable. Our findings also emphasize the importance of a clear diagnosis before doing rTKA to avert second revision surgeries.

The number of revision total knee arthroplasties (rTKA) has increased over the past years, and projections predict further increases in the coming decades (Kurtz et al. 2007, Patel et al. 2015, LROI 2019). The outcome of these rTKAs is in general inferior compared with the outcome of the primary total knee arthroplasty (Greidanus et al. 2011, Baker et al. 2012, Nichols and Vose 2016). Evidence suggests that one of the determinants for outcome of rTKA is the indication for the revision. To illustrate, several studies have shown a poor prognosis when the rTKA is performed for infection or stiffness compared with revisions for aseptic loosening (Sheng et al. 2006, Pun and Ries 2008, Baker et al. 2012, Van Kempen et al. 2013, Leta et al. 2015). Poor results were reported in terms of complication rates, patient satisfaction, and survival of the prosthesis. However, the majority of these studies based their findings on small samples, and single-center cohorts.A repeat revision indicates that either the initial problem was not resolved despite the index revision, or that another problem occurred. Several reasons for a failed index rTKA can be: inaccurate diagnosis, the decision to choose operative versus nonoperative treatment, surgical failure, the occurrence of complications, or insufficient rehabilitation protocols. Insight into whether the reason for index rTKA is related to the same reason for the repeat rTKA might provide a base for improvement of treatment choices in these revision surgeries.Therefore, we (1) compared the repeat revision rates among the different reasons for index rTKA, and (2) evaluated how often the reason for repeat rTKA was the same as the reason for the index revision.     

A meta-analysis of the fixed-bearing and mobile-bearing prostheses in total knee arthroplasty

Introduction  

We asked whether the mobile-bearing knee prostheses could offer clinical and radiographic advantages over the fixed-bearing knee prostheses.     

Linear and volumetric wear of tibial inserts in posterior cruciate-retaining knee arthroplasties.

Linear and volumetric wear was measured in 33 tibial polyethylene inserts from three different cruciate-retaining knee systems retrieved at the time of revision surgery. Wear patterns also were evaluated and classified. Eccentric and asymmetric wear patterns were seen in 78% of inserts with flat articulating geometry versus 12% in inserts with curved anteroposterior geometry. The mean linear wear rate was .35 mm/year (range, .05-1.68 mm/year) and the mean volumetric wear rate was 794 mm3/year (range, 24-4088 mm3/year). Linear and volumetric wear rates showed a negative correlation with the length of implantation. Linear wear rates also showed a negative correlation with patient weight.     

Determining the necessity for routine pathologic examinations in uncomplicated total hip and total knee arthroplasties

Total hip and total knee arthroplasties (n = 951) were retrospectively reviewed to determine the cost-effectiveness of routine pathologic examination of surgical specimens in primary total hip and total knee replacements. Discrepancies between the postoperative diagnosis and the final pathologic diagnoses were recorded. Of the 951 cases reviewed, 27 (2.8%) noted conflicting postoperative and pathologic diagnosis. In all cases, the discrepancy was between a postoperative diagnosis of osteoarthritis and pathologic diagnosis of avascular necrosis. No new cases of neoplasia or inflammatory arthropathy were noted based on the pathologic interpretation. Sixteen of these discrepancies (5.1%) and were noted in total hip arthroplasties, and 11 (1.7%) were noted in total knee arthroplasties. In no case was postoperative medical or surgical treatment altered. Based on this review, strong consideration should be given to the elimination of routine pathologic evaluation of surgical specimens during primary joint arthroplasty, leaving this pathologic evaluation optional, at the discretion of the orthopaedic surgeon, rather than mandatory.     

Mechanical Circulatory Support device database of the International Society for Heart and Lung Transplantation: first annual report--2003.

Over the last 2 decades, mechanical circulatory support devices have been developed with the goal of supporting patients with advanced heart failure as a bridge to cardiac transplantation, a bridge to recovery, and an alternative to transplantation (also called chronic or destination therapy). The current generation of devices provides a differentiated spectrum of circulatory support. The major limitations of mechanical circulatory support devices are infection, coagulopathies and device dysfunction. The Scientific Council on Mechanical Circulatory Support of the International Society for Heart and Lung Transplantation has established an international database to generate critical data to advance knowledge about the effectiveness of mechanical circulatory support device therapy for one of the most difficult and costly contemporary medical problems, the malignant syndrome of advanced heart failure.