Total Knee Arthroplasty Designs Research Articles

Influence of Total Knee Arthroplasty on Patellar Kinematics and Patellofemoral Pressure

BackgroundPatellofemoral complications are one of the main problems after total knee arthroplasty (TKA). The design of the TKA component may affect the patellar biomechanics, which may be associated with this postoperative complication. The purpose of this study was to assess the influence of TKA and prosthesis designs on the patellar kinematics and patellofemoral pressure. MethodsUsing fresh-frozen cadavers, we measured the patellofemoral pressure, patella offset, and patella tilt in the following 4 conditions: normal knee (patella replacement only), cruciate-retaining TKA, condylar-stabilizing TKA, and posterior-stabilized TKA. ResultsThe patellofemoral pressure increased significantly after the cruciate-retaining TKA and condylar-stabilizing TKA compared with the normal knee. The patella offset in the normal knee decreased with increasing knee flexion angles, while the patella offset in the TKA knees did not change significantly through the full range of motion. The amount of lateral patella tilt in the normal knee was significantly larger than the TKA knees in the full range of motion. ConclusionAlthough the femoral components are designed to reproduce an anatomical patellar tracking, the physiological patellar kinematics were not observed. Relatively high patellofemoral pressure and kinematic change after TKA may be associated with postoperative complications such as the anterior knee pain.

No differences between fixed- and mobile-bearing total knee arthroplasty.

For years, numerous studies have been performed to determine whether mobile-bearing total knee arthroplasty (MB-TKA) or fixed-bearing total knee arthroplasty (FB-TKA) is the preferential design in total knee arthroplasty. Reviews and meta-analyses on this subject have focused on a relatively small number of randomised controlled trials, possibly missing important results of smaller studies. The goal of this review was to provide a comprehensive overview of all literature comparing MB-TKA and FB-TKA in the treatment of osteoarthritis of the knee. An extensive literature search was performed in the PubMed database. All studies that compared MB-TKA with FB-TKA and looked at one of four theorised advantages (insert wear, signs of loosening, survival rate of the prosthesis and clinical outcome) were included. The initial search yielded 258 articles, of which 127 were included after the first screening. The included studies consisted of 9 meta-analyses, 3 systematic reviews, 48 RCT's, 44 comparative studies, 10 reviews and 13 studies that examined patients who received bilateral TKA (one MB-TKA and one FB-TKA). Combining the results of all studies showed that almost all studies found no difference between MB-TKA and FB-TKA. Even when examining all different types of studies on MB-TKA and FB-TKA, the results of this review showed no difference in insert wear, risk of loosening, survivorship or clinical outcome. In daily practice, the choice between MB-TKA and FB-TKA should be based on the experience and judgment of the surgeon, since no clear differences are observed in the scientific literature. III.

Clinical and Biomechanical Evaluations of Staged Bilateral Total Knee Arthroplasty Patients with Two Different Implant Designs.

Background:Various implants of total knee arthroplasty (TKA) are used in clinical practice and each presents specific design characteristics. No implant managed this day to reproduce perfectly the biomechanics of the natural knee during gait.Objectives:We therefore asked whether (1) differences in tridimensional (3D) kinematic data during gait could be observed in two different designs of TKA on the same patients, (2) if those gait kinematic data are comparable with those of asymptomatic knees and (3) if difference in clinical subjective scores can be observed between the two TKA designs on the same patient.Methods:We performed knee kinematic analysis on 15 patients (30 TKAs) with two different TKA implant designs (Nexgen, Zimmer and Triathlon, Stryker) on each knee and on 25 asymptomatic subjects (35 knees). Clinical evaluation included range of motion, weight bearing radiographs, questionnaire of joint perception, KOOS, WOMAC and SF-12.Results:Comparison between TKAs and asymptomatic knees revealed that asymptomatic knees had significantly less knee flexion at initial contact (p < 0.04) and more flexion for most of the swing phase (p between 0.004 and 0.04). Asymptomatic knees also had less varus at loading response, during stance phase and during most of the swing phase (p between 0.001 - 0.05). Transverse plane analysis showed a tendency for asymptomatic knees to be more in internal rotation during stance phase (p 0.02 - 0.04). Comparing both TKA designs, NexgenTM implant had significantly more flexion at the end of swing phase (p = 0.04) compared to knees with the TriathlonTM implant. In frontal plane, from initial contact to maximum mid stance angle and between the mean mid stance angle and initial contact NexgenTM TKA had significantly more adduction (varus, p =0.02 – 0.03). Clinical scores of both TKAs did not have significant difference.Conclusions:TKA with the tested implants did not reproduce natural knee kinematics during gait. In our cohort of patients, TKA implant design translated in limited kinematics differences during gait and on clinical results.

Does knee awareness differ between different knee arthroplasty prostheses? A matched, case-control, cross-sectional study.

BackgroundLow knee awareness after Total Knee Arthroplasty (TKA) has become the ultimate goal in trying to achieve a natural feeling knee that meet patient expectations. To accommodate this manufacturers of TKAs have developed new prosthetic designs that potentially could give patients a more natural feeling knee during activities.The purpose af this study was to compare the Forgotten Joint Score (FJS) and Oxford Knee Score (OKS) of patients treated with a previous generation standard Cruciate Retaining (CR) TKA to the scores obtained by patients treated with a newer generation CR TKA or a mobile bearing CR TKA.MethodsWe identified all patients receiving a new generation CR TKA or mobile bearing TKA at our institution between 2010 and 2012. These were matched to a population of patients receiving a standard CR TKA regarding age, gender, year of surgery, Kellgren-Lawrence (KL) grade and pre- and postoperative knee alignment. Patients were asked to complete the FJS and OKS questionnaires. Of the 316 patients completing the survey 64 standard CR TKAs to 35 new generation CR TKAs and 121 standard CR TKAs to 68 mobile bearing TKAs were matched. The FJS and OKS scores of the three TKA designs were compared.ResultsWhen comparing the new generation CR TKAs to the standard CR TKAs we found statistically significant higher OKS and FJS scores (6 (p = 0.04) and 16 (p = 0.03) points respectively) for the new generation CR TKAs. When comparing the mobile bearing TKAs to the standard CR TKAs we found a statistically significant higher OKS score (3 points, p = 0.04), and a higher but non-significant FJS score (4 points, p = 0.48) for the mobile bearing TKAs.ConclusionsPatients receiving the new generation CR TKA obtained higher FJS and OKS scores when compared to patients receiving a standard CR TKA, indicating that the use of this newer prosthetic design facilitate less knee awareness and better function after TKA.

Clinical outcome is not affected by total knee arthroplasty alignment.

This study aims to analyse the influence on total knee arthroplasty (TKA) clinical outcomes of biomechanical intra-operative computer-assisted surgery-measured parameters, together with radiographic and demographical data. Between 2007 and 2009, 227 computer-assisted surgery (CAS) primary TKAs were performed in 219 consecutive patients. Information about gender, age and body mass index (BMI) was collected for each patient. Before knee replacement, all patients underwent a complete radiographic examination and passive flexion-extension range of motion was recorded. All TKAs were implanted using an image-free knee navigation system. Patients included in the study were evaluated at 3, 6 and 12months of follow-up and then yearly. At each follow-up, subjects were asked to answer the validated Italian version of the Knee Injury and Osteoarthritis Outcome Score. One hundred and eighty patients (187 knees) had data available for analysis. Complications were reported in 13 patients (7.0%). Intra-operative CAS-measured parameters, together with age, BMI, gender, pre- and post-operative radiographic alignment, did not influence TKA clinical results at a mean 2years of follow-up. On the other hand, higher post-operative flexion arc of movement was suggestive of better clinical outcomes. TKA clinical outcome is influenced by post-operative knee flexion, other than neutral mechanical limb alignment. Therefore, it is recommended to prefer TKA designs that allow high flexion and to encourage early physical rehabilitation. IV.

Alignment of the lower extremity mechanical axis by computer-aided design and application in total knee arthroplasty.

The success of total knee arthroplasty (TKA) depends on many factors. The position of a prosthesis is vitally important. The purpose of the present study was to evaluate the value of a computer-aided establishing lower extremity mechanical axis in TKA using digital technology. A total of 36 cases of patients with TKA were randomly divided into the computer-aided design of navigation template group (NT) and conventional intramedullary positioning group (CIP). Three-dimensional (3D) CT scanning images of the hip, knee, and ankle were obtained in NT group. X-ray images and CT scans were transferred into the 3D reconstruction software. A 3D bone model of the hip, knee, ankle, as well as the modified loading, was reconstructed and saved in a stereolithographic format. In the 3D reconstruction model, the mechanical axis of the lower limb was determined, and the navigational templates produced an accurate model using a rapid prototyping technique. The THA in CIP group was performed according to a routine operation. CT scans were performed postoperatively to evaluate the accuracy of the two TKA methods. The averaged operative time of the NT group procedures was [Formula: see text]min shorter than those of the conventional procedures ([Formula: see text] min). The coronal femoral angle, coronal tibial angle, posterior tibial slope were [Formula: see text], [Formula: see text], [Formula: see text] in NT group and [Formula: see text], [Formula: see text], [Formula: see text] in CIP group, respectively. Statistically significant group differences were found. The navigation template produced through mechanical axis of lower extremity may provide a relative accurate and simple method for TKA.

Contact stress analysis of the anterior tibial post in bi-cruciate stabilized and mobile-bearing posterior stabilized total knee arthroplasty designs

In posterior-stabilized (PS) total knee arthroplasty (TKA), unexpected wear and fracture of the tibial post due to anterior post impingement have been reported. The purpose of this study was to determine the contact stress on the anterior aspect of the tibial post in four contemporary TKA designs. We evaluated one bi-cruciate stabilized design (Journey II) and three mobile-bearing PS designs (Vanguard RP, PFC Sigma RP, and NexGen LPS Mobile). The contact conditions at the anterior aspect of the tibial post were determined upon application of a posterior force of 100N to individual implants. Each measurement was sequentially performed five times, and the data were compared within and across designs using analysis of variance and a post-hoc test. The contact stress of the Journey II and Vanguard RP was less than the compressive yield stress for polyethylene (10MPa) at all tested flexion angles and degrees of rotation. The PFC Sigma RP did not show anterior tibial post impingement under any experimental conditions. The NexGen LPS Mobile demonstrated bilateral edge loading at the anterior tibial post and exceeded 10MPa of contact stress in some test conditions. Thus, the differences among implants in terms of the dimensions of the femoral anterior cam or intercondylar notch and the anterior aspect of the tibial post in the axial and sagittal planes led to significant differences in contact conditions. The present study helps the surgeon to be more aware that various contact conditions of the anterior aspect of the tibial post can occur in individual TKA designs.

Femorotibial kinematics and load patterns after total knee arthroplasty: An in vitro comparison of posterior-stabilized versus medial-stabilized design

BackgroundFemorotibial kinematics and contact patterns vary greatly with different total knee arthroplasty (TKA) designs. Therefore, guided motion knee systems were developed to restore natural knee kinematics and make them more predictable. The medial stabilized TKA design is supposed to replicate physiological kinematics more than the posterior-stabilized TKA system. We conducted this study to compare a newly developed medial stabilized design with a conventional posterior-stabilized design in terms of femorotibial kinematics and contact patterns in vitro. MethodsTwelve fresh-frozen knee specimens were tested in a weight-bearing knee rig after implantation of a posterior stabilized and medial-stabilized total knee arthroplasty under a loaded squat from 20° to 120° of flexion. Femorotibial joint contact pressures in the medial and lateral compartments were measured by pressure sensitive films and knee kinematics were recorded by an ultrasonic 3-dimensional motion analysis system. FindingsThe medial stabilized design showed a reduction of medial femorotibial translation compared to posterior-stabilized design (mean 3.5mm compared to 15.7mm, P<0.01). In the lateral compartment, both designs showed a posterior translation of the femur with flexion, but less in the medial stabilized design (mean 14.7mm compared to 19.0mm, P<0.01). In the medial femorotibial compartment of medial stabilized design, we observed an enlarged contact area and lower peak pressure, in contrast in the lateral compartment there was a reduced contact area and an increased peak pressure. InterpretationWhile posterior-stabilized design enforces a medio-lateral posterior translation, the medial stabilized arthroplasty system enables a combination of a lateral translation with a medial pivot, which restores the physiological knee kinematics better.

What Is the Frequency of Noise Generation in Modern Knee Arthroplasty and Is It Associated With Residual Symptoms?

Prior investigations have recognized the presence of patient-perceived noise generation after total knee arthroplasty (TKA). However, questions remain regarding its overall frequency after both TKA and unicompartmental knee arthroplasty (UKA) as well as with respect to its association with demographic and prosthesis-related factors and its association with patient-reported outcomes. The purposes of this study were (1) to determine the frequency with which patients report noise coming from the knee after TKA or UKA; (2) to identify patient and prosthesis-related factors associated with noise generation; and (3) to ascertain whether noise coming from the knee is associated with residual symptoms after knee arthroplasty. A five-center survey study was designed to identify patient-perceived noise and to quantify the degree of residual symptoms and functional deficits in patients after TKA or UKA. Data were collected by an independent, third-party survey center, which administered questions about residual symptoms, function, and pre- and postoperative activity levels. Patients meeting prespecified inclusion criteria were specifically questioned regarding perceived noises from their knee within the last 30 days; those who reported hearing noises sometimes, often, or extremely often were categorized as positive. We retrospectively identified 2671 patients who underwent TKA and 744 patients who underwent UKA and who met inclusion criteria; the final survey population included 1580 patients who underwent TKA and 476 patients who underwent UKA (68% response rate). TKA implant types included cruciate-retaining (59%), posterior-stabilized (16%), rotating-platform (13%), gender-specific (7%), and high-flex (5%). Differences in baseline demographic variables were accounted for using multiple logistic regression statistical analyses. Chi square analyses were used to compare the frequency of residual symptoms in those patients with and without noise generation. Overall, 27% (557 of 2056; 95% confidence interval [CI], 25-29) of all patients undergoing knee arthroplasty reported hearing grinding, popping, or clicking from their operative knee in the last 30 days. Men (odds ratio [OR], 1.3; 95% CI, 1.0-1.6; p = 0.02) and younger patients (χ2 [df = 7] = 67.3; p < 0.001) were more likely to report noise generation. After controlling for potential confounding variables, noise generation was more common after TKA (29%) than UKA (21%; OR, 1.5; 95% CI, 1.2-2.0; p < 0.001). Among TKA designs, the likelihood of noise generation was greater in posterior-stabilized (41%; OR, 2.5; 95% CI, 1.8-3.7; p < 0.001), rotating-platform (45%; OR, 2.8; 95% CI, 1.9-4.2; p < 0.001), and gender-specific (36%; OR, 2.0; 95% CI, 1.2-3.2; p = 0.007) designs than in cruciate-retaining (23%) knees. Patient-perceived noise generation was associated with residual symptoms, including difficulty getting in and out of a chair (38% versus 25%, p < 0.001), limp (39% versus 25%, p < 0.001), swelling (42% versus 24%, p < 0.001), and stiffness (40% versus 23%, p < 0.001) compared with those who did not report noise generation after TKA. Patients frequently perceive noises coming from the knee after arthroplasty, more so in TKA than UKA. Patients reporting noises from the knee were more likely to report functional limitations and the presence of a limp, swelling, and stiffness. Surgeons should inform patients preoperatively of this possibility, because unmet patient expectations are known to negatively impact patient satisfaction after surgery. Subsequent investigations should focus on determining if there is a causal relationship between noise generation and residual symptoms after knee arthroplasty. Level III, therapeutic study.

Morphometric analysis of the distal femur in total knee arthroplasty and native knees.

Analysis of the morphology of the distal femur, and by extension of the femoral components in total knee arthroplasty (TKA), has largely been related to the aspect ratio, which represents the width of the femur. Little is known about variations in trapezoidicity (i.e. whether the femur is more rectangular or more trapezoidal). This study aimed to quantify additional morphological characteristics of the distal femur and identify anatomical features associated with higher risks of over- or under-sizing of components in TKA. We analysed the shape of 114 arthritic knees at the time of primary TKA using the pre-operative CT scans. The aspect ratio and trapezoidicity ratio were quantified, and the post-operative prosthetic overhang was calculated. We compared the morphological characteristics with those of 12 TKA models. There was significant variation in both the aspect ratio and trapezoidicity ratio between individuals. Femoral trapezoidicity was mostly due to an inward curve of the medial cortex. Overhang was correlated with the aspect ratio (with a greater chance of overhang in narrow femurs), trapezoidicity ratio (with a greater chance in trapezoidal femurs), and the tibio-femoral angle (with a greater chance in valgus knees). This study shows that rectangular/trapezoidal variability of the distal femur cannot be ignored. Most of the femoral components which were tested appeared to be excessively rectangular when compared with the bony contours of the distal femur. These findings suggest that the design of TKA should be more concerned with matching the trapezoidal/rectangular shape of the native femur. The distal femur is considerably more trapezoidal than most femoral components, and therefore, care must be taken to avoid anterior prosthetic overhang in TKA

Analysis of failed premium versus standard total knee arthroplasty designs

Analysis of failed premium versus standard total knee arthroplasty designs

Evolution of trochlear compartment geometry in total knee arthroplasty.

The study aimed to compare trochlear profiles in recent total knee arthroplasty (TKA) models and to determine whether they feature improvements compared to their predecessors. The hypothesis was that recent TKA models have more anatomic trochlear compartments and would display no signs of trochlear dysplasia. The authors analyzed the geometry of the 6 following TKA models using engineering software: PFC and Attune (DePuy), NexGen and Persona (Zimmer), Noetos and KneeTec (Tornier). The mediolateral trochlear profiles were plotted at various flexion angles (0°, 15°, 30° and 45°) to deduce the sulcus angle. Analysis of sulcus angles reveals general convergence of recent designs towards anatomic values. At 0° of flexion, sulcus angles of recent implant models were between 156.0-157.4°, while those of previous generation models between 154.5-165.5°. At 30° of flexion, sulcus angles of recent models also lie within 145.7-148.6°, but those of previous models are between 149.5-152.0°. All three manufacturers deepened their trochlear profile at 30° of flexion in recent models compared to earlier designs. Sulcus angles converge towards anatomic values but still exceed radiologic signs of dysplasia by 2-5°. Recent TKA designs have more anatomic trochlear geometries than earlier TKA models by the same manufacturers, but trochlear compartments still exceed radiologic signs of trochlear dysplasia by 2° to 5°. The hypothesis that recent TKA models display no signs of trochlear dysplasia is therefore refuted. Surgeons should be aware of design limitations to optimize choice of implant and extensor mechanisms alignment. IV geometric implant analysis.

Modern Total Knee Arthroplasty Designs: Are we Improving Outcomes?

Although the volume of total knee Arthroplasties (TKAs) performed around the world continues to increase, recent studies on patient satisfaction as the primary outcome measure have shown that up to 30% of the patients remain unsatisfied. Especially in younger individuals, TKAs are associated with higher rates of revision and with decreased patient satisfaction. Because of these reports, several manufacturers have implemented specific design modifications and have increased the modularity of their systems. However, little is known of the safety and functionality of these newer designs. This editorial note highlights recent advances in TKA implant designs, focusing on the reported outcomes of high-flex and extremely modular new primary TKA designs.

Posterior Tibial Polyethylene Fracture in Cruciate-Retaining Total Knee Arthroplasty

Introduction One of the common prostheses for primary total knee arthroplasty (TKA) is a cruciate-retaining (CR) design. The tibial polyethylene inserts commonly used in TKA are made of ultra-high molecular weight polyethylene (UHMWPE). The CR TKA design retains the posterior cruciate ligament (PCL), which is believed to provide increased stability, promote femoral roll back, improve proprioception, and enhance stair-climbing ability. Delamination, adhesive wear, and abrasive wear of the polyethylene component are common mechanisms of failure, but fracture of the component at the posterior side in a CR TKA is rare. The cause of this type of failure is often multifactorial. This case report presents a case of posteromedial polyethylene fracture in a CR TKA.

Meta-Analysis of Outcomes of a Single-Radius Versus Multi-Radius Femoral Design in Total Knee Arthroplasty

BackgroundAlthough the single-radius (SR) femoral design is known to have theoretical advantages in many aspects, studies of clinical outcomes that compare the SR with the multiple-radius (MR) femoral design are controversial. We performed a meta-analysis to address the hypothesis that a SR femoral design in primary total knee arthroplasty improves patient outcomes. MethodsThe meta-analysis identified 15 articles reporting the clinical outcomes of 2212 knee replacements using the SR (n = 948) compared with the multiradius (MR; n = 1361) femoral design. Comparing SR with MR, we examined the Knee Society Score for the knee (KSS-knee), KSS-function, knee flexion, range of motion, complications, isometric peak torque of knee, and survival rate. ResultsThe range of motion of SR knees was lower than that of MR knees. No differences were found in the analyses of KSS-knee, KSS-function, knee flexion, complications, isometric peak torque of the knee, and survival rate. ConclusionOur meta-analysis does not provide clinical support for the previously reported theoretical advantages of the SR implant design.

Outcomes of a Newer-Generation Cementless Total Knee Arthroplasty Design.

Newer-generation cementless total knee arthroplasties (TKAs) aim to improve durability, function, and longevity. In a large series of cementless TKAs at a mean 4-year follow-up, the authors evaluated (1) survivorship, (2) range of motion, (3) patient-reported outcomes, and (4) complications. Mean age was 66 years (range, 34-88 years) and mean body mass index was 32.5 kg/m(2) (range, 20-54 kg/m(2)). Aseptic and septic implant survivorships were 99.6% and 99.5%, respectively. Mean extension, flexion, and Knee Society scores improved significantly. There were 3 septic failures. Aseptic failures included 3 aseptic loosenings, 1 polyethylene revision, and 1 revision to a cemented patella. This study showed excellent clinical and patient-reported outcomes of cementless TKA.

Relationship between Tibial Baseplate Design and Rotational Alignment Landmarks in Primary Total Knee Arthroplasty.

This study evaluated the influence of modern tibial baseplate designs when using the anterior tibial cortex as a primary rotational landmark for the tibial baseplate in TKA. Eighty patients undergoing TKA were randomized in two groups. Group 1 included 25 females and 15 males receiving a posterior-stabilized (PS) symmetric tibial baseplate while Group 2 included 24 females and 16 males receiving a PS anatomical tibial component. Identical surgical technique, including the use of the surgical transepicondylar femoral axis (sTEA) and the anterior tibial cortex (“Curve-on-Curve”) as rotational alignment landmarks, was used. All patients underwent CT evaluation performed with the knee in full extension. Three observers independently measured the rotational alignment of the tibial component in relation to the sTEA. The rotational alignment of the symmetric baseplate showed an average external rotation of 1.3° (minimum 5°, maximum −1°): 91% of the knees showed 0 ± 3° with respect to the surgical sTEA, being internally rotated in 20%. The rotational alignment of the anatomical baseplate showed an average external rotation of 4.1° (minimum 0.4°, maximum 8.9°): only 47.5% of the knees showed 0 ± 3°, being externally rotated in 100%. The difference between the two groups was statistically significant. This study confirms the reliability of the “Curve-on-Curve” technique as an adequate rotational alignment anatomical landmark in TKA: the use of an asymmetric tibial baseplate might lead to external rotation of the tibial component when this technique is intraoperatively chosen.

Can prosthesis design of total knee arthroplasty affect balance?

In this study, we aimed to investigate whether posterior cruciate ligament (PCL) retaining or substituting in total knee arthroplasty affect the balance. Between March 2010 and April 2014, a total of 41 patients who underwent total knee arthroplasty in our clinic were included in the study. A PCL-substitution prosthesis was used in 21 patients (group 1) and a PCL-retaining prosthesis was used in 20 patients (group 2). Balance and fall risk were evaluated using a balance assessment device. The patients were examined by the Berg Functional Balance Scale. The mean follow-up was 25.6±9.7 months. There was no statistically significant difference in static or dynamic overall stability, mediolateral stability or fall risk between the two types of prostheses. A significant difference in the dynamic anteroposterior stability index scores was observed between the groups. Our study results show that PCL-substitution prosthesis affects the balance positively in total knee arthroplasty. Therefore, PCL-substitution prosthesis design should be considered for patients who have risk factors for balance disorder, in particular.

Lower prosthesis-specific 10-year revision rate with crosslinked than with non-crosslinked polyethylene in primary total knee arthroplasty

Background and purpose — While highly crosslinked polyethylene has shown reduced in vivo wear and lower rates of revision for total hip arthroplasty, there have been few long-term studies on its use in total knee arthroplasty (TKA). We compared the rate of revision of non-crosslinked polyethylene to that of crosslinked polyethylene in patients who underwent TKA for osteoarthritis.Patients and methods — We examined data from the Australian Orthopaedic Association National Joint Replacement Registry on 302,214 primary TKA procedures with non-crosslinked polyethylene and 83,890 procedures with crosslinked polyethylene, all of which were performed for osteoarthritis. The survivorship of the different polyethylenes was estimated using the Kaplan-Meier method and was compared using proportional hazard models.Results — The 10-year cumulative revision rate for non-crosslinked polyethylene was 5.8% (95% CI: 5.7–6.0) and for crosslinked polyethylene it was 3.5% (95% CI: 3.2–3.8) (> 6.5-year HR = 2.2 (1.5–3.1); p < 0.001). There was no effect of surgical volume or method of prosthesis fixation on outcome. There were 4 different TKA designs that had a minimum of 2,500 procedures in at least 1 of the polyethylene groups and a follow-up of ≥ 5 years. 2 of these, the NexGen and the Natural Knee II, had a lower rate of revision for crosslinked polyethylene. The Scorpio NRG/Series 7000 and the Triathlon Knee did not show a lower rate of revision for crosslinked polyethylene.Interpretation — There is a lower rate of revision for crosslinked polyethylene in TKA, and this appears to be prosthesis-specific and when it occurs is most evident in patients < 65 years of age. The difference in revision rates was mainly due to revisions because of lysis and loosening.

Does Tourniquet Use in TKA Affect Recovery of Lower Extremity Strength and Function? A Randomized Trial.

Tourniquet use during total knee arthroplasty (TKA) improves visibility and reduces intraoperative blood loss. However, tourniquet use may also have a negative impact on early recovery of muscle strength and lower extremity function after TKA. The purpose of this study was (1) to determine whether tourniquet use affects recovery of quadriceps strength (primary outcome) during the first 3 postoperative months; and (2) to examine the effects of tourniquet application on secondary outcomes: voluntary quadriceps activation, hamstring strength, unilateral limb balance as well as the effect on operative time and blood loss. Twenty-eight patients (mean age 62 ± 6 years; 16 men) undergoing same-day bilateral TKA (56 lower extremities) were enrolled in a prospective, randomized study. Subjects were randomized to receive a tourniquet-assisted knee arthroplasty on one lower extremity while the contralateral limb underwent knee arthroplasty without extended tourniquet use. In the former group, the tourniquet was inflated just before the incision was made and released after cementation; in the latter group, a tourniquet was not used (10 of 28 [36%]) or inflated only during component cementation (18 of 28 [64%]). The choice of no tourniquet or use just during cementation was based on surgeon choice, because some surgeons felt a tourniquet during cementation was necessary to achieve a dry surgical field to maximize cement fixation. A median parapatellar approach and the identical posterior-stabilized TKA design were used by all four fellowship-trained knee surgeons involved. Isometric quadriceps strength, hamstring strength, voluntary quadriceps activation, and unilateral balance were assessed preoperatively, 3 weeks, and 3 months after bilateral knee arthroplasty. Other factors, including pain, range of motion, and lower extremity girth, were assessed for descriptive purposes at each of these time points as well as on the second postoperative day. Quadriceps strength was slightly lower in the tourniquet group compared with the no-tourniquet group (group difference = 11.27 Nm [95% confidence interval {CI}, 2.33-20.20]; p = 0.01), and these differences persisted at 3 months after surgery (group difference = 9.48 Nm [95% CI, 0.43-18.54]; p = 0.03). Hamstring strength did not differ between groups at any time point nor did measures of quadriceps voluntary activation or measures of unilateral balance ability. There was less estimated intraoperative blood loss in the tourniquet group (84 ± 26 mL) than in the no-tourniquet group (156 ± 63 mL) (group difference = -74 mL [95% CI, -100 to -49]; p < 0.001). However, there was no difference in total blood loss between the groups (group difference = -136 mL [95% CI, -318 to 45]; p = 0.13). Patients who underwent TKA using a tourniquet had diminished quadriceps strength during the first 3 months after TKA, the clinical significance of which is unclear. Future studies may be warranted to examine the effects of tourniquet use on long-term strength and functional outcomes. Level I, therapeutic study.