Knee Arthroplasty Implants Research Articles

The Effects of Cyclic Loading and Motion on the Implant-Cement Interface and Cement Mantle of PEEK and Cobalt-Chromium Femoral Total Knee Arthroplasty Implants: A Preliminary Study.

This study investigated the fixation of a cemented PEEK femoral TKA component. PEEK and CoCr implants were subjected to a walking gait cycle for 10 million cycles (MC), 100,000 cycles or 0 cycles (unloaded control). A method was developed to assess the fixation at the cement–implant interface, which exposed the implants to a fluorescent penetrant dye solution. The lateral condyles of the implants were then sectioned and viewed under fluorescence to investigate bonding at the cement–implant interface and cracking of the cement mantle. When tested for 100,000 cycles, debonding of the cement–implant interface occurred in both PEEK (61%) and CoCr (13%) implants. When the duration of testing was extended (10 MC), the percentage debonding was further increased for both materials to 88% and 61% for PEEK and CoCr, respectively. The unloaded PEEK specimens were 79% debonded, which suggests that, when PEEK femoral components are cemented, complete bonding may never occur. Analysis of cracks in the cement mantle showed an absence of full-thickness cracks in the unloaded control group. For the 100,000-cycle samples, on average, 1.3 and 0.7 cracks were observed for PEEK and CoCr specimens, respectively. After 10 MC, these increased to 24 for PEEK and 19 for CoCr. This was a preliminary study with a limited number of samples investigated, but shows that, after 10 MC under a walking gait, substantial debonding was visible for both PEEK and CoCr implants at the cement–implant interface and no significant difference in the number of cement cracks was found between the two materials.

Knee Kinetics Of Patients With Different Types Of Total Knee Arthroplasty Implants During Downhill Walking

Ramping walking is a common daily activity that is often incorporated in rehabilitation for total knee arthroplasty (TKA) patients. However, no studies have investigated knee biomechanics of patients with total knee arthroplasty (TKA), and comparisons between posterior stabilized (PS), cruciate retaining (CR) and bi-cruciate stabilized (BCS) TKA implants during ramp walking. PURPOSE: To examine the differences in knee biomechanics between patients with the three different types of TKA implants and healthy controls during downhill walking on a 10° ramp. METHODS: Five BCS, 10 CR, 10 PS TKA patients and 10 healthy controls performed five downhill walking trials at their self-selected pace, on a 10° instrumented ramp mounted through rigid contact surface structures mounted onto two force platforms (AMTI). Three-dimensional kinematic data (240 Hz, Vicon) were collected in conjunction with ground reaction force data (1200 Hz). A 2 × 4 (limb × group) mixed design ANOVA was used to examine selected knee joint kinematic and kinetic variables. RESULTS: In downhill walking, a significant limb effect was found in peak loading-response (p=0.005) and push-off knee extension moment (KEM, p=0.015). Peak loading-response KEMs were smaller (p=0.006) in replaced limbs (0.94 Nm/kg) than non-replaced limbs (0.97 Nm/kg). Similar findings were seen in peak push-off (p=0.015) KEMs. Peak loading-response knee abduction moment (KAbM) were mostly similar between the replaced limbs of three TKA groups and healthy controls in downhill walking. Peak loading-response KAbMs were smaller in non-replaced limbs of BCS (-0.34 Nm/kg, p=0.018) and PS (-0.37 Nm/kg, p=0.001) patients compared to that in their non-replaced limbs (BCS: -0.53 Nm/kg & PS: -0.49 Nm/kg). CONCLUSION: The results from this study showed that during downhill walking, peak KEMs were lower in replaced limbs than non-replaced limbs for all TKR patients, suggesting a deficit in knee extensor strength regardless of TKA designs. Post-surgery rehabilitation should focus on eccentric strength training of quadriceps for their replaced knees to reduce the asymmetry in knee movement and loading. BCS and PS patients may need additional attention in strengthening of quadriceps and hamstrings of the replaced limbs.

Functional Flexion Instability After Rotating-Platform Total Knee Arthroplasty.

We sought to define "at risk" loading conditions associated with rotating-platform total knee arthroplasty (TKA-RP) implants that predispose to insert subluxation and spinout and to quantify tolerances for flexion-extension gap asymmetry and laxity in order to prevent these adverse events. Biomechanical testing was performed on 6 fresh-frozen cadaveric limbs with a TKA-RP implant with use of a gap-balancing technique, followed by sequential femoral component revision with variable-thickness polyethylene inserts to systematically represent 5 flexion-extension mismatch and asymmetry conditions. Each configuration was subjected to mechanical loading at 0°, 30°, and 60°. Rotational displacement of the insert on the tibial baseplate, lateral compartment separation, and insert concavity depth were measured with use of a digital caliper. Yield torque, a surrogate for ease of insert rotation and escape of the femoral component, was calculated with use of custom MATLAB code. Design-intended insert rotation decreased with increasing knee flexion angles in each loading configuration. Likewise, yield torque increased with increasing joint flexion and decreased with increasing joint laxity in all testing configurations. Insert instability and femoral condyle displacement were reproduced in positions of increasing knee flexion and asymmetrical flexion gap laxity. The depth of lateral polyethylene insert concavity determined femoral condylar capture and defined a narrow tolerance of <2 mm in the smallest implant sizes for flexion gap asymmetry leading to rotational insert instability. Decreased femoral-tibial articular surface conformity with increasing knee flexion and asymmetrical flexion gap laxity enable paradoxical motion of the femoral component on the upper insert surface rather than the undersurface, as designed. Mobile-bearing TKA-RP is a technically demanding procedure requiring a snug symmetrical flexion gap. As little as 2 mm of asymmetrical lateral flexion laxity can result in decreased conformity, condyle liftoff, and insert subluxation. Flexion beyond 30° decreases bearing surface contact area and predisposes to reduced insert rotation and mechanical malfunction.

High incidence of radiolucent lines at the implant–cement interface of a new total knee replacement

Recently introduced total knee arthroplasty (TKA) implants have been linked with the early development of periprosthetic radiolucency (PPRL). The aim of this study was to carry out a retrospective clinical and radiographical analysis of a consecutive series of a new TKA, and to assess the incidence and distribution of PPRL. A retrospective review of all new TKA implants performed by a single surgeon at a single hospital between March 2013 and October 2017 was performed. The minimum follow-up period was 3 months, with ongoing patient review at 6, 12 and 36 months. Sequential post-operative radiographs were performed to determine the presence of PPRL. A total of 122 TKAs were identified in 112 patients over the 4.5-year study period. The average follow-up time was 21 months (range 3-51 months). PPRL was noted in 29 TKAs (23.8%). When comparing the PPRL group to those without PPRL, there was a difference in body mass index, with body mass index associated with an increased likelihood of PPRL (P = 0.003). There was no difference in constraint of implant (P = 0.818), cement type (P = 0.340), patella resurfacing (P = 0.286), age (P = 0.984) gender (P = 0.376) or initial mechanical axis deviation (P = 0.054) between groups. PPRL were most commonly seen in tibial anterior-posterior (AP) zone 1 and zone 2 (96.6%), followed by femoral lateral zone 5 (58.6%), tibia lateral zone 1 (55.2%) and tibial lateral zone 2 (53.2%). No patients have required revision surgery. A high incidence of early PPRL is seen in patients undergoing primary TKA using a new implant system, mainly involving the tibial component. Ongoing clinical and radiological assessment for patients seems warranted based on these findings.

Hydroxyapatite-coated implants provide better fixation in total knee arthroplasty. A meta-analysis of randomized controlled trials.

BackgroundThe potential advantages of hydroxyapatite (HA)-coated cementless total knee arthroplasty (TKA) implants are bone stock preservation and biological fixation. Studies comparing the outcomes of HA-coated cementless, non HA-coated cementless (uncemented) and cemented TKA implants reported contradictory data. Our aim was to provide a comparison of the effects of HA coating of tibial stem on the stability and functionality of TKA implants.MethodsA systematic literature search was performed using MEDLINE, Scopus, EMBASE and the CENTRAL databases up to May 31st, 2019. The primary outcome was Maximum Total Point Motion (MTPM) of the tibial stem. This parameter is determined by radiosterometric analysis and refers to the migration pattern of the prosthesis stems. The clinical outcomes of the implanted joints were evaluated by the Knee Society Knee Score (KSS) and the Knee Society Function Score (KFS). Weighted mean difference (WMD) with 95% confidence interval (CI) were calculated with the random-effects model.ResultsAltogether, 11 randomized controlled trials (RCTs) with 902 patients for primary TKA implants were included. There was a statistically significant difference in the MTPM values with the use of HA-coated and uncoated uncemented implants (WMD = +0.28, CI: +0.01 to +0.56, P<0.001). However, HA-coated stems showed significantly higher migration when compared with the cemented prostheses (WMD = -0.29, CI: -0.41 to -0.16, P<0.001). The KSS values of HA-coated implants were significantly higher than those for the uncemented implants; moreover, KSS and KFS outcome scores were statistically not different between the HA-coated and cemented prosthesis cases.ConclusionHA-coating yields better stability than other, uncemented prostheses. More importantly, the HA-coating is not outperformed by cemented prosthesis in providing good functional outcome.

Clinical validation and accuracy testing of a radiographic decision aid for unicondylar knee arthroplasty patient selection in midterm follow-up.

The purpose of this study was to examine the predictive value concerning clinical outcome and implant survival, as well as the accuracy of individual tests of a recently published radiographic decision aid for unicondylar knee arthroplasty indication findings. In the retrospective part of the study, 98 consecutive patients who had undergone unicondylar knee arthroplasty (Phase 3 Oxford medial UKA) were included, using revision questionnaires, as well as the Forgotten Joint Score-12 (FJS-12) and Knee Osteoarthritis Outcome Score (KOOS) and analysed for suitability of the radiographic decision aid. Inappropriate and appropriate indications were then compared concerning the clinical outcome and implant survival. The prospective part of the study assessed the accuracy of the decision aid's radiographic tests (varus and valgus stress views, true lateral view and skyline view), and included 90 patients. Definition as appropriate for UKA procedure included medial bone-on-bone situation in varus stress views, full-thickness lateral cartilage and functional medial collateral ligament in valgus stress views, functional anterior cruciate ligament (ACL) in true lateral views and absence of lateral facet osteoarthritis with bone loss in skyline views. Pre-operative radiographic assessment with respect to the decision aid was then compared with intraoperative articular conditions. The clinical outcome was analysed using non-parametric tests (Mann-Whitney U), and revision rates were compared using the Fisher's exact test. Accuracy assessment included calculations of the sensitivity, specificity, negative predictive value and positive predictive value. A p value < 0.05 was considered statistically significant. Appropriate unicondylar knee arthroplasty with respect to the decision aid showed a significantly lower revision rate compared to inappropriate unicondylar knee arthroplasty (7.3% vs. 50.0%, p < 0.0001), as well as higher clinical outcome scores (FJS-12: 53.13 vs. 31.25, p = 0.041 and KOOS-QDL: 68.75 vs. 50.0, p = 0.036). The overall sensitivity (70.1%) and specificity (76.2%) for the radiographic decision aid was comparably low, which was essentially based on false negative cases (22.7%) regarding medial bone-to-bone conditions. The radiographic decision aid is a helpful tool to predict clinical outcome and implant survival of mobile-bearing unicondylar knee arthroplasty. Strict use of the radiographic decision aid may lead to increased exclusion of appropriate patients with unicondylar knee arthroplasty implantation.

Osteo-Compatibility of 3D Titanium Porous Coating Applied by Direct Energy Deposition (DED) for a Cementless Total Knee Arthroplasty Implant: in Vitro and in Vivo Study.

Direct energy deposition (DED) technology has gained increasing attention as a new implant surface technology that replicates the porous structure of natural bones facilitating osteoblast colonization and bone ingrowth. However, concerns have arisen over osteolysis or chronic inflammation that could be caused by Cobalt-chrome (CoCr) alloy and Titanium (Ti) nanoparticles produced during the fabrication process. Here, we evaluated whether a DED Ti-coated on CoCr alloy could improve osteoblast colonization and osseointegration in vitro and in vivo without causing any significant side effects. Three types of implant CoCr surfaces (smooth, sand-blasted and DED Ti-coated) were tested and compared. Three cell proliferation markers and six inflammatory cytokine markers were measured using SaOS2 osteoblast cells. Subsequently, X-ray and bone histomorphometric analyses were performed after implantation into rabbit femur. There were no differences between the DED group and positive control in cytokine assays. However, in the 5-bromo-2′-deoxyuridine (BrdU) assay the DED group exhibited even higher values than the positive control. For bone histomorphometry, DED was significantly superior within the 1000 µm bone area. The results suggest that DED Ti-coated metal printing does not affect the osteoblast viability or impair osseointegration in vitro and in vivo. Thus, this technology is biocompatible for coating the surfaces of cementless total knee arthroplasty (TKA) implants.

No clinical benefit from gender-specific total knee replacement implants: a systematic review

Introduction: Total knee arthroplasty (TKA) remains the treatment of choice for severe osteoarthritis of the knee and nearly 60% of patients undergoing TKA are women. Females present three notable anatomic differences. Thus, gender-specific (GS) components were introduced to accommodate the females’ anatomic differences. No systematic review has been published since 2014. The aim of this study was to perform a recent systematic review of the literature to determine whether there is any clinical benefit of gender-specific implants compared to conventional unisex implants in total knee arthroplasty (TKA). Methods: This study included prospective randomized controlled trials (PRCTs) comparing clinical and radiological outcomes, and complications in TKA with gender-specific implants and conventional implants. All studies had a minimum follow-up of two years. Results: Three PRCTs published between 2010 and 2012 were included. These studies showed a low risk of bias and were of very high quality. We did not find superior clinical outcomes for gender-specific prostheses compared to conventional prostheses. However, gender-specific TKA reduced the number of patients with femoral component overhang compared to conventional TKA. Conclusion: In our systematic review, despite a lower overhang rate, gender-specific implants in female TKA showed no clinical benefit over standard unisex implants. Good clinical results with significant improvement were observed with both designs. There is a notable absence of new studies on this subject in recent years, and further research needs to be performed using various gender-specific implant designs to further define the role of gender-specific implants. Level of evidence: Systematic review, Level IV

Removal of Well-Fixed Tibial Cone in Revision Total Knee Arthroplasty-A Uniquely Challenging Yet Necessary Scenario.

The number of revision total knee arthroplasties (TKA) performed in the United States continues to increase. While advancements in implant design and surgical technique have led to improved outcomes compared with historical data, these cases remain technically demanding with high rates of aseptic failure and worse patient reported outcome scores compared with primary total knee arthroplasty. One particular problem commonly encountered in revision knee arthroplasty is bone loss, particularly in the epiphyseal region, which negatively impacts the structural integrity of the implants. Various modular metaphyseal sleeves and cones in conjunction with stemmed implants have been designed to enhance metaphyseal fixation, corroborated by multiple studies demonstrating excellent midterm results involving cones, and sleeves. Commercially available revision systems that incorporate metaphyseal cones are currently widely utilized in revision TKA. For tibial defects, both symmetric and asymmetric cone options are available. Excellent midterm results have been reported with use of this device in the setting of severe proximal tibial bone loss in revision TKA surgery. With the enhanced fixation provided by various sleeve and cone augments, implant removal in the setting of recurrent infection or implant failure can be extremely challenging. Consequently, in this work, we sought to describe an algorithmic approach for removing a tibial cone in conjunction with the overlying tibial baseplate. A review of the literature has also been conducted for complex surgical techniques regarding removal of well-fixed implants in revision total knee arthroplasty.

A Retrospective Study Comparing a Patient-specific Design Total Knee Arthroplasty With an Off-the-Shelf Design: Unexpected Catastrophic Failure Seen in the Early Patient-specific Design.

Background:Patient-specific design (PSD) total knee arthroplasty implants are marketed to restore neutral mechanical-axis alignment (MAA) and provide better anatomic fit compared with standard off-the-shelf (OTS) total knee arthroplasty designs. The purpose was to compare the Knee Society scores, radiographic outcomes, and complications of PSD and OTS implants.Methods:Retrospective study analyzing PSD and OTS by a single surgeon. Implant design change in PSD occurred during the period of data collection leading to PSD-1 and PSD-2 subgroups. Radiographic data including MAA, femorotibial angle, coronal-tibial angle, tibial slope and patella-sulcus angle, and complications were analyzed. Minimum follow-up was 2 years or until revision, and patients completed Knee Society scores preoperatively and postoperatively at 3, 6, 12, 24 weeks, and final follow-up.Results:There were 136 patients (154 knees), average age (62.76 +/− 8.4 years), and follow-up (3.1 +/− 1.5 years). The groups included PSD-1 (77 knees), PSD-2 (36 knees), and OTS (41 knees). The PSD-2 group had better Knee Society function scores compared with PSD-1 and OTS at all timepoints except final follow-up. PSD-2 had significantly shorter hospital stay (P = 0.000012) and less hemoglobin drop (P = 0.032) compared with PSD-1 and OTS. No differences were observed in MAA (P = 0.349) or final range of motion (P = 0.629) between the 3 groups. PSD-2 had more normal femorotibial angle, coronal-tibial angle, and tibial slope compared with PSD-1 and OTS. Failures requiring revision were 23% (18/77) PSD-1, 0% PSD-2, and 3% (1/35) OTS. Most common modes of failure were tibial subsidence (56%) and polyethylene locking mechanism failure (22%) in PSD-1.Conclusion:Catastrophic failure was seen in the PSD-1 group with tibial subsidence and polyethylene locking mechanism failure. PSD-2 had better early Knee Society function scores, shorter hospital stay, lower hemoglobin drop, radiographic alignment, and no failures compared with PSD-1 and OTS.

Primary Total Knee Arthroplasty Implants as Functional Prosthetic Spacers for Definitive Management of Periprosthetic Joint Infection: A Multicenter Study

BackgroundThere are limited data on the utility of a standard primary total knee arthroplasty (TKA) femoral component with an all polyethylene tibia as a functional prosthetic spacer in place of a conventional all cement spacer for the management of periprosthetic joint infection (PJI). The aim of this multicenter study was to retrospectively review (1) ultimate treatment success; (2) reimplantation rates; (3) reoperation rates; and (4) change in knee range of motion in patients managed with functional prosthetic spacers following TKA PJI. MethodsA retrospective review was performed for patients at 2 tertiary care centers who underwent a functional prosthetic spacer implantation as part of a functional single-stage (n = 57) or all cement spacer conventional two-stage (n = 137) revision arthroplasty protocol over a 5-year period. Outcomes including reinfection, reimplantation, and reoperation rates, success rate as defined by the Delphi criteria, and final range of motion were compared between the 2 cohorts at a minimum of 2-year follow-up. ResultsThere was no significant difference in reinfection (14.0 vs 24.1%), reoperation (19.3 vs 27.7%), or success rates (78.9 vs 70.8%; P > .05 for all) between the one-stage and two-stage revision TKA cohorts. Mean final total arc of motion was also similar between the 2 groups (105.8 vs 101.8 degrees, respectively). ConclusionFunctional prosthetic spacers offer the advantage of a single procedure with decreased overall hospitalization and improved cost-effectiveness with analogous success rates (78.9%) compared with two-stage exchange (70.8%) at mid-term follow-up. Although long-term data are required to determine its longevity and efficacy, the outcomes in this study are encouraging. Level of Evidence3.

Evaluating quality of hospital care using time-to-event endpoints based on patient follow-up data

Revisions of hip and knee arthroplasty implants and cardiac pacemakers pose a large medical and economic burden for society. Consequently, the identification of health care providers with potential for quality improvements regarding the reduction of revision rates is a central aim of quality assurance in any healthcare system. Even though the time span between initial and possible subsequent operations is a classical time-to-event endpoint, hospital-specific quality indicators are in practice often measured as revisions within a fixed follow-up period and subsequently analyzed by traditional methods like proportions or logistic regression. Methods from survival analysis, in contrast, allow the inclusion of all observations, i.e. also those with early censoring or events, and make thus more efficient and more timely use of the available data than traditional methods. This may be obvious to a statistician but in an applied context with historic traditions, the introduction of more complicated methods needs a clear presentation of their added value. We demonstrate how standard survival methods like the Kaplan–Meier estimator and a multiplicative hazards model outperform traditional methods with regard to the identification of performance outliers. Following that, we use the proposed methods to analyze 640,000 hip and knee replacement operations with about 13,000 revisions between 2015 and 2016 in more than 1200 German hospitals in the annual evaluation of quality of care. Based on the results, performance outliers are identified which are to be further investigated qualitatively with regard to their provided quality of care and possible necessary measures for improvement. Survival analysis is a sound statistical framework for analyzing data in the context of quality assurance and survival methods outperform the statistical methods that are traditionally used in this area.

A Force Line Trajectory Measuring System and Algorithms for Unicondylar Knee Replacement Surgery.

The force line trajectory of the distal femoral prosthesis relative to the prosthesis gasket is an important factor in judging the appropriate position of implants in the Unicondylar Knee Arthroplasty (UKA) surgery, which is critical to the success of the UKA surgery. In this paper, we propose an UKA force line trajectory measurement system, which includes the pressure sensors array, the controlling circuits, the transceivers, and the receiving recorder. Data from twenty sensors are obtained by a multi-channel analog switch. The data is transmitted wirelessly and the force line trajectory is calculated and displayed on the screen in real-time. Radio frequency transmitter chip and the amplifier work only when the wireless data transmission to save power. The algorithm for force line trajectory fitting is proposed, with which we first get the pressure distribution and the maximum pressure point, and then we use maximum pressure points as the contacting points and fit the force line trajectory of the maximum pressure points by the improved least squares fitting algorithm. From the simulation and experimental results, we can find that the low power system meets the requirement of real-time display force line trajectory. The calculation amount of our algorithm is significantly reduced compared to the finite element analysis method. Compared with the iterative solution method, the calculation time of the thirty maximum pressure points and the force line trajectory fitting is reduced from 1.3ms to 0.018ms. Moreover, the proposed algorithm is easier to be realized in hardware in the future, which will increase data processing speed, transfer less data, and further reduce the system power.

Accuracy of a New Robotically Assisted Technique for Total Knee Arthroplasty: A Cadaveric Study

BackgroundAlthough the utility of robotic surgery has already been proven in cadaveric studies, it is our hypothesis that this newly designed robotically assisted system will achieve a high level of accuracy for bone resection. Therefore, we aimed to analyze in a cadaveric study the accuracy to achieve targeted angles and resection thickness. MethodsFor this study, 15 frozen cadaveric specimens (30 knees) were used. In this study, Zimmer Biomet (Warsaw, IN) knees, navigation system, and robot (ROSA Knee System; Zimmer Biomet) were used. Eight trained, board-certified orthopedic surgeons performed robotically assisted total knee arthroplasty implantation using the same robotic protocol with 3 different implant designs. The target angles obtained from the intraoperative planning were then compared to the angles of the bone cuts performed using the robotic system and measured with the computer-assisted system considered to be the gold standard. For each bone cut the resection thickness was measured 3 times by 2 different observers and compared to the values for the planned resections. ResultsAll angle mean differences were below 1° and standard deviations below 1°. For all 6 angles, the mean differences between the target angle and the measured values were not significantly different from 0 except for the femoral flexion angle which had a mean difference of 0.95°. The mean hip-knee-ankle axis difference was −0.03° ± 0.87°. All resection mean differences were below 0.7 mm and standard deviations below 1.1mm. ConclusionDespite the fact that this study was funded by Zimmer Biomet and only used Zimmer Biomet implants, robot, and navigation tools, the results of our in vitro study demonstrated that surgeons using this new surgical robot in total knee arthroplasty can perform highly accurate bone cuts to achieve the planned angles and resection thickness as measured using conventional navigation.

Primary constrained and hinged total knee arthroplasty: 2- and 5-year revision risk compared with unconstrained total knee arthroplasty: a report on 401 cases from the Norwegian Arthroplasty Register 1994–2017

Background and purpose — The number of primary, highly constrained knee arthroplasty implants has increased with a theoretically increased risk of early failure. Therefore we analyzed the risk of all revision following total knee arthroplasty (TKA) in patients receiving a hinged or condylar constrained knee (CCK) compared with a conventional unconstrained TKA.Patients and methods — The analyses included 401 primary highly constrained or hinged implants from 1994 to 2017. Kaplan–Meier survival curves were used to evaluate time to first revision with a maximum follow-up of 20 years. Cox regression was used to calculate hazard ratio (HR) comparing condylar constrained knee (CCK), hinged, and unconstrained TKA.Results — Kaplan–Meier estimated prosthesis survival after 2 years was 94.8% (95% CI 91.4–98.2) and 93.5% after 5 years for the primary CCK and 91.0% (CI 86.6–95.4) after 2 years and 85.5% after 5 years for the primary hinged TKA. Adjusted for sex, age groups, diagnosis, time period, previous surgery, and surgery time HR was 1.4 (CI 0.8–2.3) for the CCK and 2.4 (CI 1.6–3.7) for the hinged implants. The most common cause of revision in hinged implants was infection: 14 of 22 revisions. When excluding infection as revision cause, there were no differences in survival between the implant types. Estimated survival excluding infection revisions at 5 years was 96% for unconstrained, CCK, and hinged primary TKA implants.Interpretation — Primary rotating hinge total knee arthroplasty had a higher risk of revision compared with conventional TKA after 2 and 5 years’ follow-up. Infection was the most common cause of revision. When excluding infection revisions from the survival analysis, hinged and CCK implants had similar performance to unconstrained TKA.

General, regional and combination anesthesia in knee arthroplasty: A multicenter cohort-study of 15326 cases analyzing patient satisfaction and perioperative pain management

Aims and Objectives: In recent years, a steadily increasing number of total knee arthroplasty implants have been reported. After having ameliorated operation techniques and material, pain management and anesthetic methods have come into focus. Various anesthesia procedures for the surgical procedure itself as well as pain management programs have been developed. One of the main goals is to reduce postoperative pain and enable better and faster mobilization in the postoperative period. The present study aims to compare the use of general and regional anesthesia and their combination in terms of perioperative pain management and patient satisfaction. Materials and Methods: In the present cohort study, 15.326 patients were examined in 46 orthopedic departments after knee replacement surgery from 2009-2015. The parameters were analyzed on the first postoperative day as part of the project “QUIPS - Quality Improvement in Postoperative Pain Management”, an initiative to compare the outcome parameters in participating hospitals. Primary outcome values were pain levels (activity, minimum and maximum pain, and pain management satisfaction) on a NRS scale. Pain medication necessity was analyzed using the WHO pain ladder classification. Parameters were compared between the types of anesthesia used: general, regional and combination anesthesia. Results: Pain scores and pain management satisfaction were significantly better in the groups of either spinal or peripheral anesthesia combined with general anesthesia (p0.001, respectively). Patients who received the combination of general and spinal anesthesia were associated with the lowest need for opioids (p0.001). Conclusion: The use of a combined general and spinal anesthesia as well as using a combination of general and peripheral anesthesia in knee arthroplasty was associated with a highly significant advantage to other anesthetic techniques regarding perioperative pain management in daily clinical practice, but maybe below clinical relevance. Furthermore they were associated with positive tendency considering side effects and subjective well-being parameters.

No Detectable Polyethylene Wear 15 Years After Implantation of a Mobile–Bearing Total Knee Arthroplasty With Electron Beam–Irradiated Polyethylene

BackgroundThe present study was designed to evaluate the risk of significant polyethylene (PE) wear 10 years or more after implantation of a total knee arthroplasty (TKA) using electron beam–irradiated highly cross-linked PE component. MethodsAll patients operated between 2001 and 2004 for implantation of this particular TKA in the two participating centers were eligible for this study. All patients were contacted after the 10-year follow-up for repeat clinical examination and radiological evaluation. The occurrence of a revision prior to the final evaluation and its reason were recorded. The thickness of the PE piece was measured on plain X-rays. ResultsFive hundred seventy-eight TKAs were implanted during the study time-frame. One hundred sixteen patients deceased prior to the 10-year follow-up (20%). An additional 121 patients were lost to follow-up prior to the 10-year follow-up (21%). Complete follow-up at 10 years or more (including death or revision) was obtained for 448 cases (78%). Ten prosthetic revisions were performed for mechanical reasons during the follow-up time (2%). One single revision was performed because PE wear after 13 years. No significant PE wear was detected at the final radiographic evaluation for nonrevised cases. The 10-year survival rate for mechanical revision only was 98.0% and decreased to 96.2% at 15 years. ConclusionThe use of electron beam–irradiated PE was associated with an extremely low incidence of wear. This technology may be considered as safe regarding PE behavior for TKA after more than 10 years. Further improvement of PE manufacturing may be not required.

Cementless 3D Printed Highly Porous Titanium-Coated Baseplate Total Knee Arthroplasty: Survivorship and Outcomes at 2-Year Minimum Follow-Up.

Newer generation cementless total knee arthroplasty (TKA) implants continue to develop with demonstrated clinical success in multiple recent reports. The purpose of this study was to investigate (1) survivorship, (2) complications, and (3) clinical outcomes of a newer generation cementless and highly porous titanium-coated base plate manufactured using three-dimensional (3D) printing technology. We reviewed a single-surgeon, longitudinally maintained database of patients who underwent primary TKA using cementless, highly porous titanium-coated base plate implants from July 1, 2013 to December 31, 2016. A total of 523 patients were identified. Of this cohort, 496 patients had a minimum of 2-year follow-up and were included in our final analysis. Among these patients, 72 had bilateral TKA yielding a total of 568 TKAs. There were 133 men and 363 women who had a mean body mass index of 33 kg/m2 (range, 20-61 kg/m2). The mean age was 66 years (range, 33-88 years). Average follow-up was 36 months (range, 24-48 months). Indications for TKA included osteoarthritis in 432 patients (87%), rheumatoid arthritis in 40 patients (8%), and knee osteonecrosis in 24 (5%) patients. Implant survivorship was defined as any revision leading to explantation of the base plate for any reason. Kaplan-Meier analysis was performed to determine all-cause implant survivorship at final follow-up for every patient. Complications were assessed using the Knee Society standardized list of TKA complications. Clinical outcomes were determined using the Knee Society pain and function scores. Range-of-motion values were also collected. There were a total of four failures, all were due to aseptic loosening with a survivorship rate of 99% at mean follow-up of 3 years (95% confidence interval = 0.984-0.999). In addition, there were a total of 12 surgical and 10 medical complications. Surgical complications did not affect the base plate or result in any additional implant revisions. A total of nine patients had thromboembolic disease complications; all received medical treatment and recovered adequately. Radiological evaluation did not show any signs of loosening or failures in other patients at final follow-up. Knee Society Scores for pain and function improved from 55 and 56 points preoperatively to 92 and 84 points at 2 years postoperatively. Our results are in concordance with the excellent clinical outcomes and survivorship demonstrated for the newer generation cementless TKA implants. In our experience, 3D printed titanium base plates demonstrated clinical success and excellent survivorship at minimum follow-up of 2 years.

A high level of satisfaction after bicompartmental individualized knee arthroplasty with patient-specific implants and instruments

PurposeCustomized Individually Made (CIM) Bicompartmental Knee Arthroplasty (BKA) implants and three-dimensional printed customized instruments are available to fit to each patient’s unique anatomy, medial or lateral with patellofemoral. This study aimed to evaluate the clinical outcomes after CIM-BKA.MethodsFifty-five patients [59 knees; average age, 51 years; standard deviation (SD), 6.8; range 37–65 years] who underwent CIM-BKA were evaluated over an average of 3.8-year follow-up (SD 1.6; range 1–6 years). Forty-one knees underwent BKA combined medial and patellofemoral replacement (BKA-MP) and 18 knees underwent BKA combined lateral with patellofemoral replacement (BKA-LP). Survival rates, the modified Cincinnati Knee Rating Scale, WOMAC, VAS, SF-36, a satisfaction survey, and radiographic evaluation were used to evaluate outcomes.ResultsOverall, survival rates were 98% and 92% at 2 and 5 years, respectively. Of 56 knees (95%) that did not fail, all patient-reported functional scores significantly improved post-operatively (P < 0.01), regardless of the previous surgeries, with a high level of satisfaction (51/56 knees, 91%). Radiographically, all the femoral components fit perfectly and 56 knees (95%) of the tibial components fit with less than 2 mm of undercoverage or overhang. Three knees (5%) required the conversion to TKA and 17 knees (29%) required subsequent surgical procedures, of which multiply operated knees had higher rate than virgin knee [14/40 (35%) vs. 3/16 (19%)].ConclusionCIM-BKA allowed precise fit of the components and provided a significant improvement post-operatively with a high level of satisfaction over short- to mid-term follow-up. This novel CIM-BKA is resurfacing, and does not require 10-mm faceted cuts, being only 3-mm-thick, which preserves bone stock for the future. It may be a promising option for relatively young active patients with bicompartmental osteoarthritis with a longer term follow-up being necessary.Level of evidenceIV.

Computed tomography evaluation of total knee arthroplasty implants position after two different surgical methods of implantation.

The objectives of this study were to determine the reliability of a novel method of measuring the rotational alignment of an anatomical tibial tray, the difference in the rotational alignment of the femoral and tibial component according to pure measured resection or blended technique with tensor, and, finally, the difference in terms of clinical results according to the two different methods. We performed a total of 60 consecutive TKAs: 30 according to pure measured resection and 30 according to blended technique with tensor (FuZion®). Clinical scores and CT scan were done at sixmonths to measure patient's outcome and prosthetic components rotation. The method of measurement of tibial tray had high agreement between different radiological observers. Mean external rotation alignment of the femur was 2.7° in standard group and 0.5° in the FuZion® group. For all clinical indices, we observed a large and significant improvement at follow-up, better in blended technique group, but without a clear superiority, and no statistically significant difference was evident between the two groups. At follow-up, HSS was to 89.7 in the FuZion® group and 89.0 in the standard group, KSS (clinical) was 92.6 in and 91.3 respectively, and KSS (Functional) was 91.0 in the FuZion® group and 87.6 in the standard group. Our CT measurement method is reliable and reproducible. All patients operated with this personalized knee system design obtained excellent results; the customization of femoral rotation with a blended technique is, probably, the key to optimize the outcomes and achieve the state of forgotten knee.