Metal-backed Tibial Components Research Articles

Biomechanical comparison of all-polyethylene total knee replacement and its metal-backed equivalent on periprosthetic tibia using the finite element method

BackgroundTotal knee arthroplasty (TKA) with all-polyethylene tibial (APT) components has shown comparable survivorship and clinical outcomes to that with metal-backed tibial (MBT). Although MBT is more frequently implanted, APT equivalents are considered a low-cost variant for elderly patients. A biomechanical analysis was assumed to be suitable to compare the response of the periprosthetic tibia after implantation of TKA NexGen APT and MBT equivalent.MethodsA standardised load model was used representing the highest load achieved during level walking. The geometry and material models were created using computed tomography data. In the analysis, a material model was created that represents a patient with osteopenia.ResultsThe equivalent strain distribution in the models of cancellous bone with an APT component showed values above 1000 με in the area below the medial tibial section, with MBT component were primarily localised in the stem tip area. For APT variants, the microstrain values in more than 80% of the volume were in the range from 300 to 1500 με, MBT only in less than 64% of the volume.ConclusionThe effect of APT implantation on the periprosthetic tibia was shown as equal or even superior to that of MBT despite maximum strain values occurring in different locations. On the basis of the strain distribution, the state of the bone tissue was analysed to determine whether bone tissue remodelling or remodelling would occur. Following clinical validation, outcomes could eventually modify the implant selection criteria and lead to more frequent implantation of APT components.

Implant Preference and Clinical Outcomes of Patients with Staged Bilateral Total Knee Arthroplasty: All-Polyethylene and Contralateral Metal-Backed Tibial Components

Numerous studies have compared metal-backed components (MBTs) and all-polyethylene tibial components (APTs), but none of them specifically analysed the clinical results and the overall patient preference in patients who had undergone a staged bilateral knee replacement. The purpose of this study is to compare clinical results, perceived range of motion, and overall implant preference among patients who had undergone staged bilateral knee replacement with an APT and contralateral knee replacement with MBTs. A dataset of 62 patients from a single centre who underwent staged bilateral TKA between 2009 and 2022 was selected and retrospectively analysed. Tibial component removal was performed in three knees overall, all of which had MBTs. The mean measured Knee Score (KS) of knees with APTs was 78.37 and that of contralateral knees with MBTs was 77.4. The mean measured Function (FS) of knees with APTs was 78.22, and that of contralateral knees with MBs was 76.29. The mean flexion angle of knees with APTs was 103.8 and that for knees with MBTs was 101.04 degrees. A total of 54.8% of the patients preferred the knee that received APTs over contralateral MBTs. In our cohort, TKA with an APT in one knee and an MBT in the contralateral knee recorded similar clinical results and perceived ranges of motion. Patients in general preferred the knee that received an APT over contralateral knee with an MBT.

Unicompartmental knee arthroplasties: does the type of tibial component selected influence implant survival?

Few information has been published on the survival of unicompartmental knee arthroplasty (UKA) and fixed-bearing tibial components. The aim of this study is to analyze if UKA survival varies according to UKA model used and to analyze the possible risk factors for UKA revision. A retrospective study analyzing 301 UKAs (ACCURIS, all-polyethylene tibial component, 152; Triathlon PKR, metal-backed tibial component, 149) was performed. Demographic parameters as well as implant survival and cause of prosthetic revision were analyzed. The Kaplan-Meier survival analysis, the log-rank test and the Cox multiple regression were used for the analysis. Average follow-up was 8.1 ± 3.08-years. Average age was 68.1 ± 8.6-years; 70.4% of subjects were women. The ACCURIS UKA group had a UKA revision rate higher compared to the Triathlon PKR group (16/152, 10.6% vs 5/149, 3.4%, respectively; p < 0.001). The main cause of prosthetic revision was aseptic loosening (5/21, 23.8%). All aseptic loosening cases and tibial component collapse were reported with the ACCURIS UKA group. Overall UKA survival was 98.01% (95% CI 95.62-99.1) at 1-year, 94.27% (95% CI 90.95-96.4) at 5-years and 92.38% (95% CI 88.48-94.99) at 10-years' follow-up. There were no differences in the Kaplan-Meier survival curves regarding operated side or affected tibiofemoral compartment (log-rank test = 0.614 and 0.763, respectively). However, Kaplan-Meier survival curve according to UKA model used was different (log-rank test = 0.033). The metal-backed component appeared to be a protector factor for UKA revision when adjusted for age, sex, operated side, and affected tibiofemoral compartment (Hazard Ratio 0.32, p = 0.031). Fixed-bearing UKAs showed excellent mid- and long-term survival rates. Aseptic loosening is the main cause of implant failure. PKR group (metal-backed component) seem to be a protector factor to UKA revision when it was compared with ACCURIS UKA group (all-polyethylene tibial component).

All-polyethylene versus metal-backed tibial components in total knee arthroplasty: a meta-analysis of randomized controlled trials

ObjectivesThe design of tibial trays for total knee arthroplasty (TKA) has been a topic of research for several decades. Although all-polyethylene trays were developed to address issues such as osteolysis and to enhance the longevity of the prosthesis, as well as knee range of motion, metal-backed designs have remained the most commonly used type of prosthesis. This meta-analysis aimed to compare the clinical, radiological, and survival outcomes of both designs.MethodsFive databases were searched from inception until October 1, 2020, for randomized controlled trials (RCTs) that compared the outcomes of all-polyethylene and metal-backed tibial components in TKA. The outcomes of interest included range of motion, knee society score, stairs climbing scores, radiostereographic analysis, survivorship and complication. This review was conducted in line with PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Risk of bias was assessed using the Newcastle–Ottawa tool.ResultsA total of 14 RCTs with 1367 TKA were included with a mean age of – years and – years for all-polyethylene and metal-backed tibial components groups, respectively. All-polyethylene group demonstrated statistically significant differences in five-year survivorship (OR 0.27; 95% CI 0.10–0.75; p value 0.01) and stairs climbing score (OR − 2.07; 95% CI − 3.27–0.87; p value 0.0007) when compared to the metal-backed group. The metal-backed design was significantly more radiographically stable in anterior–posterior, varus–valgus, and internal–external rotations at the 2-year follow-up compared to all-polyethylene tibias (OR − 0.09; 95% CI − 0.16 to − 0.02; p value 0.02) as per the pooled radiostereographic analysis. However, ten-year survivorship (OR 0.92; 95% CI 0.53–1.60; p value 0.78), range of motion (OR − 0.57; 95% CI − 2.00–0.85, p value 0.43), knee society scores (OR 1.38; 95% CI − 0.47–3.23, p value 0.14), and complications (OR 0.83; 95% CI 0.5–1.39, p value 0.48) were comparable between both groups.ConclusionsWhile this meta-analysis suggests that all-polyethylene tibial components in total knee arthroplasty may offer advantages over metal-backed components in terms of five-year survivorship, and stairs climbing score, this finding should be considered in the context of potential confounding factors. Nonetheless, based on the results, the all-polyethylene implant should be considered a viable choice for primary knee replacement.Level of evidenceI.

Clinical outcomes of cemented distal femur replacements with all-polyethylene tibial components for oncologic indications.

Endoprosthetic distal femoral replacement (DFR) is a well-established salvage procedure following resection of malignant tumors within the distal femur. Use of an all-polyethylene tibial (APT) component is cost-effective and avoids failure due to locking-mechanism issues and backside wear, but limits modularity and the option for late liner exchange. Due to a paucity of literature we sought to answer three questions: (1) What are the most common modes of implant failure for patients undergoing cemented DFR with APT for oncologic indications? (2) What is the survivorship, rate of all-cause reoperation, and rate of revision for aseptic loosening of these implants? And (3) Is there a difference in implant survivorship or patient demographics between cemented DFRs with APT performed as a primary reconstruction vs those performed as a revision procedure? To assess outcomes of cemented DFRs with APT components used for oncologic indications. After Institutional Review Board approval, a retrospective review of consecutive patients who underwent DFR between December 2000 to September 2020 was performed using a single-institutional database. Inclusion criteria consisted of all patients who underwent DFR with a GMRS® (Global Modular Replacement System, Stryker, Kalamazoo, MI, United States) cemented distal femoral endoprosthesis and APT component for an oncologic indication. Patients undergoing DFR for non-oncologic indications and patients with metal-backed tibial components were excluded. Implant failure was recorded using Henderson's classification and survivorship was reported using a competing risks analysis. 55 DFRs (55 patients) with an average age of 50.9 ± 20.7 years and average body mass index of 29.7 ± 8.3 kg/m2 were followed for 38.8 ± 54.9 mo (range 0.2-208.4). Of these, 60.0% were female and 52.7% were white. The majority of DFRs with APT in this cohort were indicated for oncologic diagnoses of osteogenic sarcoma (n = 22, 40.0%), giant cell tumor (n = 9, 16.4%), and metastatic carcinoma (n = 8, 14.6%). DFR with APT implantation was performed as a primary procedure in 29 patients (52.7%) and a revision procedure in 26 patients (47.3%). Overall, twenty patients (36.4%) experienced a postoperative complication requiring reoperation. The primary modes of implant failure included Henderson Type 1 (soft tissue failure, n = 6, 10.9%), Type 2 (aseptic loosening, n = 5, 9.1%), and Type 4 (infection, n = 6, 10.9%). There were no significant differences in patient demographics or rates of postoperative complications between the primary procedure and revision procedure subgroups. In total, 12 patients (21.8%) required a revision while 20 patients (36.4%) required a reoperation, resulting in three-year cumulative incidences of 24.0% (95%CI 9.9%-41.4%) and 47.2% (95%CI 27.5%-64.5%), respectively. This study demonstrates modest short-term survivorship following cemented DFR with APT components for oncologic indications. Soft tissue failure and endoprosthetic infection were the most common postoperative complications in our cohort.

Nonsteroidal Anti-Inflammatory Drugs and Oral Corticosteroids Mitigated the Risk of Arthrofibrosis After Total Knee Arthroplasty

BackgroundThe role of medications to prevent arthrofibrosis following total knee arthroplasty (TKA) remains unclear. We investigated the effect of common oral medications with reported antifibrotic properties on preventing arthrofibrosis and manipulation under anesthesia (MUA) following primary TKA. MethodsUsing our total joint registry, 9,771 patients (12,735 knees) who underwent TKA with cemented, posterior-stabilized, and metal-backed tibial components from 2000 to 2016 were identified. Arthrofibrosis, defined as range of motion (ROM) ≤90° for ≥12 weeks postoperatively or as ROM ≤90° requiring MUA, was diagnosed in 454 knees (4%) and matched 1:2 to controls. Mean age was 62 years (range, 19 to 87) and 57% were women. The majority of operative diagnoses were osteoarthritis. Perioperative use of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase inhibitors (statins), angiotensin converting enzyme inhibitors (ACE inhibitors), angiotensin II receptor blockers (ARBs), oral corticosteroids, antihistamines, and nonsteroidal anti-inflammatory drugs (NSAIDs) were manually confirmed. Medication effect in preventing arthrofibrosis and MUA was assessed using adjusted multivariable analyses. Mean follow-up was 8 years (range, 2 to 20). ResultsReduced risk of arthrofibrosis was associated with perioperative NSAID use (odds ratio (OR) 0.67, P = .045). A similar trend was observed with perioperative corticosteroids (OR 0.52, P = .098). Corticosteroids were associated with reduced risk of MUA (OR 0.26, P = .036), and NSAIDs trended towards reducing MUA (OR 0.69, P = .11). ConclusionThis investigation determined that perioperative NSAID use was associated with reduced risk of arthrofibrosis and trended towards reduced risk of subsequent MUA. Similarly, oral corticosteroids were associated with reduced risk of MUA and trended towards reduced risk of arthrofibrosis.

All-polyethylene tibia components have the same functional outcomes and survival, and are more cost-effective than metal-backed components in patients 70 years and older undergoing total knee arthroplasty

The tibial component of total knee arthroplasty can either be an all-polyethylene (AP) implant or a metal-backed (MB) implant. This study aims to compare the five-year functional outcomes of AP tibial components to MB components in patients aged over 70 years. Secondary aims are to compare quality of life, implant survivorship, and cost-effectiveness. A group of 130 patients who had received an AP tibial component were matched for demographic factors of age, BMI, American Society of Anesthesiologists (ASA) grade, sex, and preoperative Knee Society Score (KSS) to create a comparison group of 130 patients who received a MB tibial component. Functional outcome was assessed prospectively by KSS, quality of life by 12-Item Short-Form Health Survey questionnaire (SF-12), and range of motion (ROM), and implant survivorships were compared. The SF six-dimension (6D) was used to calculate the incremental cost effectiveness ratio (ICER) for AP compared to MB tibial components using quality-adjusted life year methodology. The AP group had a mean KSS-Knee of 83.4 (standard deviation (SD) 19.2) and the MB group a mean of 84.9 (SD 18.2; p = 0.631), while mean KSS-Function was 75.4 (SD 15.3) and 73.2 (SD 16.2 p = 0.472), respectively. The mental (44.3 vs 45.1; p = 0.464) and physical (44.8 vs 44.9; p = 0.893) dimensions of the SF-12 and ROM (97.9° vs 99.7°; p = 0.444) were not different between the groups. Implant survivorship at five years were 99.2% and 97.7% (p = 0.321). The AP group had a greater SF-6D gain of 0.145 compared to the MB group, with an associated cost saving of £406, which resulted in a negative ICER of -£406/0.145 = -£2,800. Therefore, the AP tibial component was dominant, being a more effective and less expensive intervention. There were no differences in functional outcomes or survivorship at five years between AP and MB tibial components in patients aged 70 years and older, however the AP component was shown to be more cost-effective. In the UK, only 1.4% of all total knee arthroplasties use an AP component; even a modest increase in usage nationally could lead to significant financial savings.Cite this article: Bone Jt Open2022;3(12):969-976.

Biomechanical analysis of all-polyethylene total knee arthroplasty on periprosthetic tibia using the finite element method

Background and objectiveTotal knee arthroplasty (TKA) with modern all-polyethylene tibial (APT) components has shown high long-term survival rates and comparable results to those with metal-backed tibial components. Nevertheless, APT components are primarily recommended for older and low-demand patients. There are no evidence-based biomechanical guidelines for orthopaedic surgeons to determine the appropriate lower age limit for implantation of APT components. A biomechanical analysis was assumed to be suitable to evaluate the clinical results in patients under 70 years. The scope of this study was to determine biomechanically the appropriate lower age limit for implantation of APT components. MethodsTo generate data of the highest possible quality, the geometry of the computational models was created based on computed tomography (CT) images of a representative patient. The cortical bone tissue model distinguishes the change in mechanical properties described in three parts from the tibial cut. The cancellous bone material model has a heterogeneous distribution of mechanical properties. The values used to determine the material properties of the tissues were obtained from measurements of a CT dataset comprising 45 patients. ResultsComputational modeling showed that in the majority of the periprosthetic volume, the von Mises strain equivalent ranges from 200 to 2700 με; these strain values induce bone modeling and remodeling. The highest measured deformation value was 2910 με. There was no significant difference in the induced mechanical response between bone models of the 60-year and 70-year age groups, and there was <3% difference from the 65-year age group. ConclusionsConsidering in silico limitations, we suggest that APT components could be conveniently used on a bone with mechanical properties of the examined age categories. Under defined loading conditions, implantation of TKA with APT components is expected to induce modeling and remodeling of the periprosthetic tibia. Following clinical validation, the results of our study could modify the indication criteria of the procedure, and lead to more frequent implantation of all-polyethylene TKA in younger patients.

Modular Metal-Backed Tibial Components Provide Minimal Mid-Term Survivorship Benefits Despite Increased Cost and Frequency of Use: A Retrospective Review of the American Joint Replacement Registry Database

BackgroundPrevious studies have demonstrated equivalent survivorship of modular metal-backed tibial (MBT) and all-polyethylene tibial (APT) components. The purpose of this study is to compare the utilization and outcomes of APT and MBT components in a large US database. MethodsThe American Joint Replacement Registry was queried to identify all patients undergoing primary total knee arthroplasty (TKA) during the study period from 2012 to 2019. These patients were divided into cohorts based on tibial component (APT or MBT). Cohort demographics including gender, hospital size, hospital teaching status, region, age, and Charlson Comorbidity Index were reported with descriptive statistics. Overall reoperation rates and revisions for infection, aseptic loosening, periprosthetic fracture, manipulation under anesthesia, and revision for other reasons were identified using International Classification of Diseases, Ninth Revision and Current Procedural Terminology codes and compared across APT and MBT cohorts. Kaplan-Meir survival analysis was performed based on reason for reoperation for APT and MBT. ResultsDuring the study period, 703,007 TKAs were reported with 97.8% utilizing MBT and 2.2% utilizing APT components. Despite the introduction of alternative payment models during the study period, the utilization of APT decreased from 5.8% in 2012 to 1.7% in 2019. The survival of APT and MBT TKAs were similar across the study period: 98.1% vs 98.6% at 8 years. The rate of reoperation for all-causes was higher for APT compared to MBT (1.36% vs 1.00%; odds ratio 1.52). ConclusionDespite their paucity of use and lower cost APT remained within a 0.4% margin of survivorship when compared to MBT implants for up to 8 years. Level of EvidenceLevel III, retrospective.

All-polyethylene unicompartmental knee arthroplasty is associated with increased risks of poorer knee society knee score and lower satisfaction in obese patients.

Although metal-backed tibial component (MB) is biomechanically superior to all-polyethylene (AP) implants in fixed-bearing unicompartmental knee arthroplasty (UKA), recent studies have shown comparable functional outcomes between the two. However, no study has examined this comparison in obese patients (BMI ≥ 30kg/m2). We investigated whether functional outcomes between the two implants differ among obese patients, and whether the extent of obesity influences these outcomes. Four hundred twenty-two UKA implants from 347 obese patients were reviewed retrospectively. Patients were assessed using the Knee Society Knee Score (KSKS) and Function Score (KSFS), the original Oxford Knee Score (OKS), and SF-36 Physical Component Summary (PCS) and Mental Component Summary (MCS). Minimal clinically important difference (MCID) attainment was recorded. Patients' fulfillment of expectations and satisfaction with the surgery outcome was also graded. Patients were further divided into lower obesity (BMI 30-34.9kg/m2) and higher obesity (BMI ≥ 35kg/m2) to examine effect modification. There were no differences in functional outcomes and quality-of-life scores, MCID attainment of functional scores, as well as satisfaction and expectation fulfillment between AP and MB. Among higher obesity patients, AP was associated with a poorer KSKS (p = 0.031) and lower proportion of satisfaction fulfillment (p = 0.041) 2years postoperatively compared to MB. We found no differences in functional and quality-of-life outcomes between fixed-bearing AP and MB tibial components among obese patients who underwent UKA. However, among higher obesity patients (BMI ≥ 35kg/m2), patients with AP tibial component were associated with lower KSKS score and a lower proportion of attaining satisfaction fulfillment 2years postoperatively.

Unicompartmental knee arthroplasty: all-poly versus metal-backed tibial component-a long-term follow-up study.

While considered a satisfactory solution, unicompartmental knee arthroplasty (UKA) still raises concerns in regard to its durability. These concerns particularly focus on the tibial component. This study aims to compare two different cemented tibial components belonging to the same UKA design: all polyethylene (AP) versus metal backed (MB), at a long-term follow-up. We retrospectively reviewed 143 successive patients, 83 of which underwent surgery with AP tibial component UKA (37 males, 46 females), and 67 with MB ones (17 males, 50 females). All implants had the same prosthetic design (Accuris UKA, Smith e Nephew) with identical femoral oxinium component but different tibial component, AP or MB. The KSS and KOOS were assessed at a mean of 11.5-year follow-up and compared to pre-operative, post-operative, and oneyear evaluation. Statistical analysis was performed with SPSS for Mac (version 17.0). To assess potential statistically significant differences, t test was used and significance was set at P< 0.05. Final KSS at a mean of 11.5-year follow-up was 94.27 for the AP group and 96.12 for the MB ones. The final KOOS was 87 for AP components and 89.67 for the MB group. These results demonstrated, in all cases, statistically significant better results for MB tibial components compared to AP regarding KSS (P= 0.048), KOOS (P= 0.000), and pain (P= 0.014) at the 11.5-year follow-up. Survivorship for AP tibial component implants was 97.6%, while it was 89.5% for MB ones. While the survivorship rate has been found to be greater for AP implants compared to MB tibial components, this study reveals statistically better functional results according to KSS and KOOS, and pain, at a long-term follow-up for MB implants.

What Is the Critical Tibial Resection Depth During Unicompartmental Knee Arthroplasty? A Biomechanical Study of Fracture Risk

BackgroundFracture after medial unicompartmental knee arthroplasty (UKA) is a rare complication. Biomechanical studies evaluating association between depth of resection and maximum load to failure are lacking. The purpose of this study is to establish the relationship between depth of resection of the medial tibial plateau and mean maximum load to failure. MethodsMedial tibial resections were performed from 2 to 10 mm in 25 standardized fourth-generation Sawbones composite tibias (Sawbones, Vashon Island, Washington). A metal-backed tibial component with a 9-mm polyethylene bearing was used (Stryker PKR). Tibias were mounted on a biomechanical testing apparatus (MTESTQuattro) and axially loaded cyclically 10 times per cycle and incrementally increased until failure occurred. ResultsLoad to failure was recorded in 25 proximal tibia model samples after medial UKA using sequential resections from 2 to 10 mm. Analysis of variance testing identified significant differences in mean maximum load to failure between groups (P = .0003). Analysis of regression models revealed a statistically significant fit of a quadratic model (R2 = 0.59, P = .0001). The inflection point of this quadratic curve was identified at 5.82 mm, indicating that the maximum load to failure across experimental models in this study began to decline beyond a resection depth of 5.82 mm. ConclusionIn this biomechanical model, medial tibial resections beyond 5.82 mm produced a significantly lower mean load to failure using a quadratic curve model. Resections from 2 to 6 mm showed no significant differences in mean load to failure. Identification of the tibial resection depth at which the mean load to failure significantly decreases is clinically relevant as this depth may increase the risk of periprosthetic fracture after a medial UKA.

Cement-In-Cement All-Polyethylene Tibial Revision: A Report of 3 Cases.

Debonding of the tibial component of total knee arthroplasty is a known complication that is typically treated with revision surgery, most commonly revision to a metal-backed tibial component with or without stems. Here, we present 3 cases of tibial component debonding revised to all-polyethylene tibial components with a cement-in-cement technique. In instances of tibial component debonding, if specific criteria are met, revising to an all-polyethylene tibia with retention of the primary cement mantle is an alternative to revision surgery with cement extraction and implantation of a modular metal-backed tibia.

Cementing technique for primary knee arthroplasty: a scoping review

Background and purpose — The optimal cementing technique for primary total knee arthroplasty (TKA) remains unclear. We therefore performed a scoping review based on available studies regarding cementation technique in primary TKA and unicondylar knee arthroplasty (UKA).Patients and methods — A search in 3 databases identified 1,554 studies. The inclusion criteria were literature that studied cementing technique in primary TKA or UKA. This included cement application methods, full or surface cementing, applying cement to the bone and/or prosthesis, stabilization of the implant during curing phase, bone irrigation technique, drilling holes in the bone, use of suction, and the timing of cementation. 57 studies met the inclusion criteria.Results — The evidence was unanimously in favor of pulsatile lavage irrigation, drying the bone, and drilling holes into the tibia during a TKA. All studies concerning suction recommended it during TKA cementation. 7 out of 11 studies favored the use of a cement gun and no studies showed that finger packing was statistically significantly better than using a cement gun. There is evidence that full cementation should be used if metal-backed tibial components are used. Applying the cement to both implant and bone seems to give better cement penetration.Interpretation — There are still many knowledge gaps regarding cementing technique in primary TKA. There seems to be sufficient evidence to recommend pulsatile lavage irrigation of the bone, drilling multiple holes, and drying the bone before cementing and implant insertion, and applying cement to both implant and on the bone.

Marker-based versus model-based radiostereometric analysis of total knee arthroplasty migration: a reanalysis with comparable mean outcomes despite distinct types of measurement error

Background and purpose — Pooling data of studies evaluating total knee arthroplasty migration using radiostereometric analysis (RSA) may be compromised when the RSA method used would influence estimated differences between groups. We therefore reanalyzed a marker-based RSA study with model-based RSA to assess possible limitations of each RSA method, including insert micromotions in modular TKA and their effect on estimated group differences.Patients and methods — All patients had received a cemented Triathlon implant (Stryker, Mahwah, NJ, USA) with either an all-polyethylene (n = 29) or a metal-backed (n = 28) tibial component. The latter group was reanalyzed with model-based RSA. Precision of each RSA method was calculated using double examinations. Bland–Altman plots were constructed to determine the limits of agreement between the 2 RSA methods. Polyethylene insert micromotion was quantified by measuring migration with respect to the metal tray. Finally, analyses of the original study were repeated with the model-based RSA results.Results — Systematic differences were found in translations between marker-based and model-based RSA as a result of different reference origins being used for migration calculations. Micromotions of the polyethylene insert within the metal tray were negligibly small. Mean migration results were comparable between marker-based and model-based RSA when using the same reference origin, even though conclusions on individual patients may differ between RSA methods due to various types of measurement error (e.g., marker occlusion and model-fit inaccuracies).Interpretation — At least for the studied TKA design, pooling mean migration data of different RSA methods appears justified. For translations, however, adjustments should be made to correct for differences in reference origin. Migration patterns of individual patients may differ as a result of distinct types of measurement error.

Metal-Backed Tibial Components Do Not Reduce Risk of Early Aseptic Loosening in Unicompartmental Knee Arthroplasty: A Systematic Review and Meta-Analysis.

Long-term results of unicompartmental knee arthroplasty (UKA) have shown a slightly higher revision rate than total knee arthroplasty (TKA), and implant fixation geometry seems to affect prosthetic survivorship. Whether metal-backed tibial component leads to superior performance over the all-polyethylene design is unclear, and a lack of evidence exists in literature. Our purpose was to demonstrate which implant design of UKA (all-polyethylene or metal-backed tibial component) is clinically superior regarding revision rates and clinical functioning, and investigate the role of potential factors that could affect the revision rate. A systematic review was conducted for clinical studies comparing all-polyethylene and metal-backed tibial components used in primary UKAs in terms of revision rates and clinical scores. Meta-regression techniques were used to explore factors modifying the observed effect. All causes of revision were extracted and analyzed, to find statistically significant differences between the two groups. Our research strategy generated a systematic review of nine studies comprising 1,101 UKAs in 1,088 patients with 87 revisions for any reason. Meta-analysis showed a higher, but not statistically significant, risk of aseptic revision in the all-polyethylene group. Studies with a smaller sample size and higher percentage of female patients were correlated to a higher relative risk of revision in favor of all-polyethylene UKAs. Differently, patients' age and duration of follow-up did not influence the risk ratio. The main cause for revision was aseptic loosening in both implants' component, with no statistically differences in the two groups examined. Our results do not show a superiority of the metal-backed tibial component in UKAs in terms of survivorship, although extreme care must be given for patients with high risk of early failure, such as female patients. However, surgical experience, in combination with careful patient selection, remains paramount and may lead to better long-term outcomes in patients requiring UKA. This is a Level III, therapeutic study.

All-polyethylene tibial components in young patients have stable fixation; a comparison RSA study

BackgroundAll-polyethylene (AP) tibial components in patients aged greater than 60 years have stable tibial migration patterns and favorable survival rates when compared to identical Metal-backed (MB) designs. Tibial component migration in younger patients has not been reported. The aim of this study was to examine the migration characteristics of patients aged less than 60 years compared to a previous cohort of AP and MB tibial components of identical design in older patients. MethodsA prospective consecutive study examined tibial component migration in 21 patients aged less than 60 years undergoing a cemented total knee arthroplasty with an AP tibial component by radiostereometric analysis (RSA) to 24 months. Results were compared to the authors' previous series of 21 patients aged greater than 60 years that were randomized to either an AP or MB tibial component. ResultsBoth age groups of patients implanted with an AP component had stable migration patterns with no patient having greater than 0.2° rotation or 0.2 mm maximum total point motion. Five of 11 MB tibial components displayed continued migration between one and two years. Subsidence was similar in all groups, whilst maximum total point motion was greater for the MB cohort (0.34 mm, 0.33 mm, 0.61 mm; AP <60, AP >60, MB). ConclusionsYoung patients implanted with an AP tibial component had stable tibial migration patterns comparable to older patients with the same AP implant. Regardless of age, AP tibial components were at least as stable as MB tibial components. Level of evidenceLevel II, Prospective comparative study.

A longitudinal analysis of functional outcome between all-polyethylene and metal-backed tibial components in total knee arthroplasty

A longitudinal analysis of functional outcome between all-polyethylene and metal-backed tibial components in total knee arthroplasty

Migration of all-polyethylene compared with metal-backed tibial components in cemented total knee arthroplasty

Background and purpose — With a rapidly increasing population in need of total knee arthroplasty (TKA), there is renewed interest in cost-saving all-polyethylene designs. Differences between metal-backed and all-polyethylene designs in initial component migration assessed by radiostereometric analysis (RSA), a proven predictor for late aseptic loosening, have been scantily reported. The purpose of this study was to compare implant migration and clinical outcomes of all-polyethylene tibial components versus metal-backed trays of similar geometrical shape.Patients and methods — In this randomized controlled trial, 59 patients received a cemented Triathlon condylar-stabilizing implant (Stryker, Mahwah, NJ, USA) with either an all-polyethylene (n = 29) or a metal-backed tibial component (n = 30). RSA measurements and clinical scores (the Knee Society Score, Forgotten Joint Score, and Knee Osteoarthritis and Injury Outcome Score) were evaluated at baseline and postoperatively at 3, 12, and 24 months. A linear mixed-effects model was used to analyze the repeated measurements.Results — A statistically significant difference in mean migration after 2 years was found in favor of the all-polyethylene group, with a mean maximum total point motion of 0.61 mm (95% CI 0.49–0.74) versus 0.81 mm (95% CI 0.68–0.96) for the cemented group (p = 0.03). However, this difference was smaller and not statistically significant after post hoc adjustment for surgeon effect. Both groups showed comparable improvements on all clinical outcome scores over time.Interpretation — The Triathlon all-polyethylene tibial component showed less migration, suggesting a lower risk of late loosening as compared with its metal-backed counterpart. However, the found surgeon effect warrants further investigation.

Obituary: A Remembrance of Nas S. Eftekhar (1935-2016).

Obituary: A Remembrance of Nas S. Eftekhar (1935-2016).