Tibial Baseplate Research Articles

Soft-tissue landmarks for tibial baseplate rotational alignment in total knee arthroplasty: A cadaveric study.

The tip of the tibial tubercle (TTT) is used to assess tibial baseplate rotation in total knee arthroplasty (TKA); however, it can be difficult to palpate and visualize intraoperatively. Several more easily accessible soft-tissue structures have been proposed as intraoperative assessments, including the patellar tendon's medial border (MBPT) and the junction of the medial third of the patellar tendon (mt-PT). No studies have described the relationship between the TTT and these proposed landmarks. The aims of the study were to (1) determine the relationship of the soft-tissue landmarks to the TTT and (2) identify any sex differences in these measures. Measurements of the position of these soft-tissue landmarks relative to the TTT were made on 56 cadaveric knees (28 female) by two observers at the level of the standard tibial cut (10 mm distal to the lateral tibial plateau). The results obtained were compared by sex and side. On average, 50.7% (SD 6.79, range 33.1%-63.1%) of the patellar tendon footprint was medial to the TTT. There were no significant differences between the sexes or left and right lower limbs. However, there was large variability in the position of all the soft-tissue landmarks relative to the TTT. The results indicate that, on average, the patellar tendon footprint is evenly spread around the TTT. However, there is a large variability in the anatomical relationship between the soft-tissue landmarks and the TTT. Caution is advised if relying on these structures intraoperatively.

Cementless Total Knee Arthroplasty Using a Highly Porous Tibial Baseplate in Morbidly Obese Patients: Minimum 5-Year Follow-Up.

Morbidly obese patients undergoing cemented primary total knee arthroplasty (TKA) can pose a challenging problem with implant survivorship due to greater stress at the cement-bone interface. With the advent of additive manufacturing (three-dimensional printing), highly porous implants are now readily available. The purpose of this study was to review the results of primary TKA in the morbidly obese (body mass index [BMI] ≥ 40) patient using a highly porous cementless tibial baseplate. This is a retrospective study of 167 TKAs in patients with morbid obesity undergoing primary cementless TKA with a minimum 5-year follow-up. A total of 6 patients died and 14 were lost to follow-up, leaving 147 TKAs in 136 patients with a mean follow-up of 66 months (range 60-79 months). The average age was 59 years (range 36-84 years) and average BMI was 45 kg/m2 (range 39.5-63.9). Clinical results, patient-reported outcome measures, radiographs, and complications were reviewed. There were 9 failures requiring revision, including 3 for aseptic tibial loosening (2.0%), 2 for deep infection (1.4%), 2 for patellar resurfacing (1.4%), 1 for patella instability (0.7%), and 1 for extensor mechanism rupture (0.7%). Knee Society Score (KSS) improved from 48 to 90 at 2- and 5-year follow-up. KSS function score improved from 49 to 68 and 79 at 2- and 5-year follow-up, respectively. Survivorship with aseptic loosening as the endpoint was 98.0% at 5 years. Cementless TKA using a highly porous tibial baseplate in morbidly obese patients demonstrated excellent clinical results with 98% survivorship at 5 years and appears to offer durable long-term biologic fixation as an alternative to mechanical cement fixation in this challenging group of patients.

The Impact of Component Design and Fixation on Stress Shielding After Modern Total Knee Arthroplasty.

Total knee arthroplasty (TKA) tibial baseplate thickness, metallurgy, and implant fixation with cement may influence stress shielding. The purpose of the present study is to compare bone mineral density of 2 cemented and press-fit TKA designs with differing tibial baseplate thicknesses and metallurgy over a 2-year period to assess for changes in stress shielding. One-hundred one TKAs were performed in this Institutional Review Board-approved, prospective study. There were 4 cohorts: DePuy Attune cemented and press-fit, and Stryker Triathlon cemented and press-fit. The Attune tibial baseplate was thicker; both cemented tibial and femoral components were cobalt-chromium. The DePuy Attune press-fit had a cobalt-chromium sintered bead porous coating while the Stryker Triathlon was 3-dimensional printed highly porous titanium alloy. All patients had quantitative dual-energy X-ray absorptiometry scans performed at baseline (4-6 weeks postoperatively) and at 1 and 2 years postoperatively. Stress shielding was evaluated by comparing percent change in bone mineral density in 11 radiographic zones over 2 years. Over a 2-year period, there were no differences in stress shielding on the tibial side in either cemented or press-fit between Stryker Triathlon and DePuy Attune; however, there were differences on the femoral side. The press-fit tibial components of the Stryker Triathlon and DePuy Attune had either similar or less stress shielding over a 2-year period compared to their cemented counterparts. This study comparing 2 TKA implants with differing tibial tray thickness did not find significant differences in tibial stress shielding between designs. There was a difference in stress shielding on the femoral side between designs, suggesting that longer term follow-up is warranted.

Early Outcomes of a Universal Femoral Component with an Ultracongruent Insert.

A primary total knee arthroplasty (TKA) system was introduced with a modern universal femoral design with a wide range of size and constraint options to accommodate a variety of patient anatomy, while incorporating streamlined instrumentation for maximum operating room efficiency and economy. The purpose of this study is to review the early clinical outcomes and survivorship at minimum two-year follow up with this knee system. From September 2015 to December 2019, 797 patients (1004 knees) underwent primary total knee arthroplasty (TKA) at our center with the TJO Klassic® Complete Primary Knee System (Total Joint Orthopedics Inc., Salt Lake City, Utah) with ultracongruent bearings and were available for study with minimum two-year follow up. All office and hospital records were reviewed for patient demographics, preoperative and postoperative clinical assessments, including range of motion, Knee Society Scores (KSS), University of California at Los Angeles (UCLA) activity scales, complications, and reoperations. Mean follow up was 3.1 years (range, 2-6; standard deviation [SD] ±1.0). There were 471 female patients (59%) and 326 male patients (41%). Mean age at surgery was 69.3 years and mean body mass index was 32.9kg/m2. An all-polyethylene tibial component was used in 305 knees (30.4%) while a modular titanium tibial baseplate with polyethylene insert was used in 699 (69.6%). The patella was left unresurfaced in 381 knees (37.9%). KS scores, including pain component, clinical, and functional, as well as UCLA scores, all improved significantly (p<0.001). Two patients (3 knees) underwent revision. One patient required two-staged revision for treatment of infection in both knees, and one patient required patellar revision for aseptic loosening. Kaplan-Meier survival at 6.2 years was 98.4% (95% CI: ±0.97%) to endpoint of revision of any part for any cause and 99.6% (95% CI: ±0.36%) to endpoint of aseptic revision. At early minimum two-year follow up, this modern universal complete knee system used with ultracongruent bearings demonstrates excellent clinical outcomes and survival.

Posterior rim loading of a low-conforming tibial insert in unrestricted kinematic alignment is caused by rotational alignment of an asymmetric baseplate designed for mechanical alignment.

Because different targets are used for internal-external rotation, an asymmetric baseplate designed for mechanical alignment may lead to under-coverage and concomitant posterior rim loading in the lateral compartment following unrestricted kinematic alignment (KA) TKA. Recognizing that such loading can lead to premature wear and/or subsidence, our aim was to determine the cause(s) so that occurrence could be remedied. Our hypothesis was that baseplate design features such as asymmetric shape when aligned in KA would consistently contribute to posterior rim loading in the lateral compartment. Based on analysis of fluoroscopic images of 50 patients performing dynamic, weight bearing deep knee bend and step up and of postoperative CT images, five possible causes were investigated. Causes included internal rotation of the baseplate when positioned in KA; posterior position of the lateral femoral condyle at extension; internal tibial rotation with flexion; internal rotational deviation of the baseplate from the KA rotation target; and posterior slope. The incidence of posterior rim loading was 18% (9 of 50 patients). When positioned in KA, the asymmetric baseplate left 15% versus 10% of the AP depth of the lateral compartment uncovered posteriorly for posterior rim loading and non-posterior rim loading groups, respectively (p = 0.009). The lateral femoral condyle at extension was more posterior by 4mm for the posterior rim loading group (p = 0.003). Posterior rim loading in the lateral compartment was caused in part by the asymmetric design of the tibial baseplate designed for mechanical alignment which was internally rotated when positioned in KA thus under-covering a substantial percentage of the posterior lateral tibia. This highlights the need for new, asymmetric baseplates designed to maximize coverage when used in KA. III.

Total Knee Replacement with an Uncemented Porous Tantalum Tibia Component: A Failure Analysis.

Porous tantalum has been extensively used in orthopaedic surgery, including uncemented total knee arthroplasty (TKA). Favourable results were reported with earlier monobloc tibial components and the design evolved to modular implants. We aimed to analyse possible causes for extensive medial tibia bone loss, resulting in modular porous tantalum tibia baseplate fracture after primary TKA. Retrieved tissue samples were scanned with 3 MeV focused proton beam for Proton-Induced X-ray Emission (micro-PIXE) elemental analysis. Fractographic and microstructural analysis were performed by stereomicroscopy. A full 3D finite-element model was made for numerical analysis of stress–strain conditions of the tibial baseplate. Histological examination of tissue underneath the broken part of the tibial baseplate revealed dark-stained metal debris, which was confirmed by micro-PIXE to consist of tantalum and titanium. Fractographic analysis and tensile testing showed that the failure of the tibial baseplate fulfilled the criteria of a typical fatigue fracture. Microstructural analysis of the contact surface revealed signs of bone ingrowth in 22.5% of the surface only and was even less pronounced in the medial half of the tibial baseplate. Further studies are needed to confirm the responsibility of metal debris for an increased bone absorption leading to catastrophic tibial tray failure.

Can the tibial length predict the size of tibial component of total knee arthroplasty?

Total knee arthroplasty (TKA) is performed worldwide. TKA is performed to relief pain, correct deformities and improve mobility in patients with debilitating diseases of their knee joints. Templating is done as pre-operative planning for TKA. Certain parameters, such as shoe size, had been studied as predictor (s) for implant size. This study aimed to determine if the tibial length (TL) can also be as a predictor of a tibial component of TKA. TL and tibial plateau width (TPW) measurements were done on dry adult tibiae. Proximal tibiae were traced on tracing paper, to obtain anterior-posterior and lateral tracings. Length of tracings confirmed with measurement on dry bones. A TKA template, converted to 100% scale was used to estimate the tibial baseplate by two orthopaedic surgeons. A total of 51 matured, non-sexed, non-paired tibiae were studied. There was a statistically significant positive relationship between the TL and the TPW (P = 0.0001). Furthermore, a statistically significant positive relationship was also observed between the TL and the tibial implant baseplate (P = 0.0001). The study showed that a particular range of tibia length will accommodate certain sizes of the tibial implant baseplate. The tibia length can be used as a predictor of the size of tibial baseplate of TKA.

Incidence of Radiolucent Lines after Cemented Total Knee Arthroplasty.

Cemented Total Knee Arthroplasty (TKA) provides excellent long-term survival rates and functional results, however, radiolucent lines (RLLs) often appear during early post-operative follow-up and their incidence and clinical significance are unknown. The primary aim was to establish the incidence, location, frequency, and time taken for RLLs to appear within the first year after a primary cemented TKA with an anatomic tibial baseplate (Smith and Nephew, LEGION Total Knee System). This was a retrospective analysis of 135 primary cemented TKA in 131 patients over three years. We compared demographics, serial radiographs, and early clinical and functional outcomes. There were 65 TKAs (48%) in 62 patients who had RLLs within the first year post-operatively. Most were females (58.8%). Mean age was 68.3 ± 7.9 years. There were 88 RLLs, with the most and second commonest location at the medial tibial baseplate (38%) and anterior femoral flange (23%). 89% were in the bone-cement interface. The largest average length of RLLs were at the anterior flange of the femoral component (1.98 ± 1.33 mm). The average time to development was 6.5 ± 4.1 months. None of these patients had infections nor required revision. Patients with RLLs did not do worse in functional and clinical scoring at 1-year. There was a 48% incidence of physiological RLLs after cemented TKA, with the highest occurrence at the medial tibial baseplate at 38%. These radiolucent lines did not affect early post-operative clinical and functional outcomes of patients.

Inching Closer to the End of the Debate Between Fixed Versus Mobile-Bearing Total Ankle Arthroplasty: Commentary on an article by M. Assal, MD, et al.: "Three-Year Rates of Reoperation and Revision Following Mobile Versus Fixed-Bearing Total Ankle Arthroplasty. A Cohort of 302 Patients Treated with 2 Implants of Similar Design".

Commentary The study by Assal et al. presents an interesting perspective on fixed versus mobile-bearing prostheses in total ankle arthroplasty (TAA) because the study utilizes similarly designed prostheses from the same manufacturer, with all surgical procedures performed by 1 of 2 surgeons. The Salto (integra) prosthesis was designed by French surgeons in 1997, showing good initial results with short- and mid-term follow-up studies1,2. This prosthesis has a 3-component design with a mobile-bearing spacer. The Salto Talaris (integra) was introduced to the U.S. market in 2006 and to the European market in 2012. There were minor design changes between the Salto and the Salto Talaris, mainly to accommodate a fixed bearing on the tibial component of the latter prosthesis in order to allow 510(k) approval by the Food and Drug Administration in the U.S. Over the years, there have been multiple studies discussing the short- and mid-term outcomes of either the Salto or the Salto Talaris, with prostheses showing acceptable if not excellent results3-5. The debate regarding fixed versus mobile-bearing prostheses has been ongoing for many years. The concept of a mobile-bearing prosthesis was introduced with the theoretical advantage of having better-conforming articular surfaces and lower contact stress, with the dissipation of stress over a more consistent area of the joint. Another theoretical advantage was the self-correction and positioning of the polyethylene spacer, reducing wear and stress on the spacer itself. However, the majority of studies have not confirmed these theoretical advantages and in fact have suggested that the use of a mobile-bearing prosthesis leads to a higher rate of complications in the first year postoperatively6. In a 2014 study retrospectively comparing the use of fixed versus mobile-bearing prostheses with a minimum follow-up of 2 years, Gaudot et al. reported that mobile-bearing prostheses had higher rates of radiolucent lines (40%) and cyst formation (24%) compared with fixed-bearing prostheses (12% and 3%, respectively)7. One strength of the study by Assal et al. was that it included 2 relatively large cohorts, with 131 fixed-bearing TAAs and 171 mobile-bearing TAAs. The mobile-bearing procedures were performed in the earlier half of the study period. As a result, 1 theoretical concern was regarding the surgical experience of the surgeons over time; however, the surgeons had been performing mobile-bearing TAAs since 2000, with the study period beginning in 2004, so they were adequately experienced with the procedure by the outset of the study. The authors also reported that the complication rate in the mobile-bearing group was stable throughout the study period and did not decrease with time. The most important conclusion of this study was that the rate of revision was 3 times higher among mobile-bearing compared with fixed-bearing prostheses. Most concerning was that most of the reported failures of mobile-bearing TAAs were because of cyst formation and gutter impingement due to heterotopic bone formation, with these prostheses showing higher rates of heterotopic bone formation in the medial and lateral gutters. There were several questions that went unanswered in the study by Assal et al and that should be addressed in future studies. What caused the increased rate of lysis, cysts, hypertrophic bone, and failure among mobile-bearing TAAs? One possible explanation is the smaller spacer utilized in the mobile-bearing implant, which increases the load per square inch of the polyethylene insert, contributing to greater wear. Was there a higher rate of backside wear between the polyethylene insert and the tibial baseplate among mobile-bearing TAAs? This effect could cause an excess of problematic polyethylene debris. Was there potential for edge-loading between the polyethylene spacer and the tibial component if the overall alignment was not reasonably accurate? Along with these questions, the greatest shortcoming of the study was that it was not a prospective, randomized trial, but instead was essentially a comparison of the results of 2 longitudinal studies. However, 1 strength was that the study utilized 2 prostheses with similar designs from the same manufacturer, which will be of substantial value if the trial can continue to longer-term follow-ups. The debate regarding fixed versus mobile-bearing prostheses will continue, but the study by Assal et al. provided an interesting window into the potential shortcomings of mobile-bearing TAAs. I congratulate the authors on an excellent paper.

Adjusting Insert Thickness and Tibial Slope Do Not Correct Internal Tibial Rotation Loss Caused by PCL Resection: In Vitro Study of a Medial Constraint TKA Implanted with Unrestricted Calipered Kinematic Alignment.

Most medial stabilized (MS) total knee arthroplasty (TKA) implants recommend excision of the posterior cruciate ligament (PCL), which eliminates the ligament's tension effect on the tibia that drives tibial rotation and compromises passive internal tibial rotation in flexion. Whether increasing the insert thickness and reducing the posterior tibial slope corrects the loss of rotation without extension loss and undesirable anterior lift-off of the insert is unknown. In 10 fresh-frozen cadaveric knees, an MS design with a medial ball-in-socket (i.e., spherical joint) and lateral flat insert was implanted with unrestricted calipered kinematic alignment (KA) and PCL retention. Trial inserts with goniometric markings measured the internal-external orientation relative to the femoral component's medial condyle at maximum extension and 90 degrees of flexion. After PCL excision, these measurements were repeated with the same insert, a 1 mm thicker insert, and a 2- and 4-mm shim under the posterior tibial baseplate to reduce the tibial slope. Internal tibial rotation from maximum extension and 90 degrees of flexion was 15 degrees with PCL retention and 7 degrees with PCL excision (p < 0.000). With a 1 mm thicker insert, internal rotation was 8 degrees (p < 0.000), and four TKAs lost extension. With a 2 mm shim, internal rotation was 9 degrees (p = 0.001) and two TKAs lost extension. With a 4 mm shim, internal rotation was 10 degrees (p = 0.002) and five TKAs lost extension and three had anterior lift-off. The methods of inserting a 1 mm thicker insert and reducing the posterior slope did not correct the loss of internal tibial rotation after PCL excision and caused extension loss and anterior lift-off in several knees. PCL retention should be considered when using unrestricted calipered KA and implanting a medial ball-in-socket and lateral flat insert TKA design, so the progression of internal tibial rotation and coupled reduction in Q-angle throughout flexion matches the native knee, optimizing the retinacular ligaments' tension and patellofemoral tracking.

Previously Unrecognized Source of Error in the Change in Maximum Total Point Motion to Determine Continuous Migration of Unstable Tibial Baseplates.

In radiostereometric analysis (RSA), continuous migration denoted as ΔMTPM is the difference between maximum total point motion (MTPM) at 2 years relative to time zero and MTPM at 1 year relative to time zero. Continuous migration has been used to diagnose tibial baseplates as stable versus unstable when compared to a specified stability limit (i.e., value of ΔMTPM). If the same point experiences MTPM at 2 years and at 1 year (usually the case for marker-based RSA), then an implicit assumption is that the migration path between 2 years and 1 year is the same as the path between 1 year and time zero. This article uses vector analysis to demonstrate a source of error in ΔMTPM not previously recognized and estimates the magnitude of error based on the interplay of independent variables which affect the error. The two independent variables which affect the error are the angle between the two migration vectors (i.e., MTPM between time zero and 2 years and MTPM between time zero and 1 year) and the difference in magnitude of the two vectors. The relative error increased in an absolute sense as the angle between the vectors increased and decreased for larger differences in the magnitudes of the two vectors. For magnitude ratios ranging from 1.25 to 2, relative errors ranged from -21% to -3% at 10 deg and from -78% to -42% at 60 deg, respectively. Knowledge of these errors highlights a limitation in the use of ΔMTPM not previously recognized.

Does the anatomic design of total knee prosthesis allow for a better component fit than its nonanatomic predecessor? A matched cohort Study.

BackgroundTotal knee arthroplasty (TKA) is considered the most efficient treatment of end-stage osteoarthritis. There is an ongoing debate about proper implant designs and articulation types. One of the considered causes of unsatisfactory outcome and patients’ dissatisfaction is femoral or tibial component overhanging, which can lead to chronic knee pain and restricted motion. The aim of this study is to compare radiological outcomes of TKA using an anatomic PERSONA Posterior-Stabilized (PS) knee design with its nonanatomic predecessor, the NexGen LPS.MethodsA group of 39 patients who received the PERSONA PS system and 33 patients who received the NexGen LPS was included. PERSONA patients were matched to NexGen patients using a 0.1 propensity score threshold with priority given to exact matches. Anteroposterior, lateral, and long-leg radiographs were taken preoperatively and at 6 weeks postoperatively to perform radiological and statistical analysis.ResultsThe PERSONA subgroup had statistically higher posterior condylar offset. There is no statistically significant difference in posterior condylar offset ratio. There were less cases of femoral notching, femoral overhang, and placing tibial baseplate in the medial overhang in the PERSONA PS subgroup than in the NexGen subgroup (each statistically significant). Occurrence of tibial underhang was not statistically significant.ConclusionRadiological assessment in short-term follow-up showed excellent results for PERSONA knee design with better fit to native femur and tibia. In comparison to its predecessor, it also spares more bone tissue. As the aforementioned parameters are risk factors of lesser clinical outcomes, the PERSONA design gives high hopes for improvement of TKA satisfaction rate.

Computational tibial bone remodeling over a population after total knee arthroplasty: A comparative study.

Periprosthetic bone loss is an important factor in tibial implant failure mechanisms in total knee arthroplasty (TKA). The purpose of this study was to validate computational postoperative bone response using longitudinal clinical DEXA densities. Computational remodeling outcome over a population was obtained by incorporating the strain‐adaptive remodeling theory in finite element (FE) simulations of 26 different tibiae. Physiological loading conditions were applied, and bone mineral density (BMD) in three different regions of interest (ROIs) was considered over a postoperative time of 15 years. BMD outcome was compared directly to previously reported clinical BMD data of a comparable TKA cohort. Similar trends between computational and clinical bone remodeling over time were observed in the two proximal ROIs, with most rapid bone loss taking place in the initial months after TKA and BMD starting to level in the following years. The extent of absolute proximal BMD change was underestimated in the FE population compared with the clinical subject group, which might be the result of significantly higher initial clinical baseline BMD values. Large differences in remodeling response were found in the distal ROI, in which resorption was measured clinically, but a large BMD increase was predicted by the FE models. Multiple computational limitations, related to the FE mesh, loading conditions, and strain‐adaptive algorithm, likely contributed to the extensive local bone formation. Further research incorporating subject‐specific comparisons using follow‐up CT scans and more extensive physiological knee loading is recommended to optimize bone remodeling more distal to the tibial baseplate.

Range of Motion Comparison Following Total Knee Arthroplasty with and without Patella Resurfacing

Background: Despite significant evaluation, no consensus has been reach for best clinical practice for resurfacing the patella during total knee arthroplasty. Further complicating the ability to reach a conclusion is the inclusion of several different implant types used in previous research.&#x0D; Questions/Purpose: The purpose of this study was to compare post-TKA outcomes between two cruciate retaining implants with or without patella resurfacing.&#x0D; Methods: This retrospective review included 289 patients (380 knees) with a minimum six-month follow-up. All patients received a CR implant, with either a symmetric or an asymmetric tibial baseplate. Post-TKA knee flexion was categorized as &lt;120° and ≥120° and knee extension classified as 0° or &gt;0° and required knee manipulations were noted. Descriptive, nonparametric statistics were performed and a multivariate logistic regression was performed to determine risk of poor range of motion and manipulations.&#x0D; Results: Age was significantly lower in the resurfaced group (p=0.001) and the resurfaced group had longer tourniquet time (p=0.003). The symmetric-resurfaced group had ≥120° of flexion and full extension in 72% and 98.7% of patients, respectively. Compared to symmetric-resurfaced, all other groups had a significantly greater risk of not reaching 120° of knee flexion (p&lt;0.05). There were no significant differences in the risk of requiring a MUA between groups (p&gt;0.06).&#x0D; Conclusions: The effect of resurfacing the patella on post-TKA outcomes may be influenced by tibial implant design. Compared to all other combinations, a symmetric tibial baseplate and resurfaced patella resulted in the highest percentage of patients reaching ≥120°, with a low incidence of manipulations.

Tibial baseplate position and posterior cruciate ligament status impact patient-reported outcomes in conforming dual-pivot bearing total knee arthroplasty.

BackgroundIn an effort to optimize clinical outcomes and enhance stability, ultracongruent bearings have been increasingly used in primary total knee arthroplasty (TKA). The importance of the posterior cruciate ligament (PCL) and optimal sagittal tibial baseplate position in ultracongruent bearing TKA remains unknown. This study sought to determine whether these modifiable, surgical-technique-dependent variables meaningfully impact patient-reported outcome measures.MethodsA total of 759 primary TKAs of the same dual-pivot design performed using a consistent surgical technique between January 2016 and April 2019 were retrospectively reviewed. PCL status was recorded, and anteroposterior (AP) tibial baseplate position and posterior tibial slope were measured by two independent blinded raters. Patient-reported outcomes related to pain, function, satisfaction, and activity level were analyzed in relationship to PCL status, posterior tibial slope, and AP tibial baseplate position, in addition to other pertinent covariates.ResultsMedian age and body mass index of the cohort were 68.3 years and 33.4 kg/m2, respectively, with 73% being female. In multivariate analysis, partial or full release of the PCL was predictive of a knee “always” feeling normal (odds ratio 1.42, P = .041). Furthermore, tibial baseplate position closer to the middle of the tibia was associated with greater improvements in pain with level walking, pain while climbing stairs, and Knee Injury and Osteoarthritis Outcome Score for Joint Replacement total scores (P ≤ .079).ConclusionIn congruent dual-pivot bearing TKA, partially or fully releasing the PCL and AP tibial baseplate position closer to the middle of the tibia may provide greater improvement in pain and function scores at minimum 1-year follow-up.

Loosening of tibia baseplates after total knee arthroplasty: Evaluation of pull-out strength of tibia baseplate-cement Interface

BackgroundAseptic loosening is reported as the leading cause of revision total knee arthroplasty on the Australian National Joint Replacement Registry. Loosening of cemented tibial baseplates has been correlated with type of cement used, cementing technique, and cement contamination with biological material. The aim of this study was to evaluate the effect of cementing application and techniques including surface contamination and cement viscosity on fixation strength of tibia baseplates/cement interface. MethodsMechanical assessment of the fixation strength of tibia baseplates/cement interface was tested using a pull-out test on a material testing system. Different tibial baseplate design, cementing techniques, cement viscosity and contamination of the implant/cement interface with bone marrow were assessed to determine if they influenced force required to disrupt the cement/implant interface (pull-out strength). FindingsThe model with contamination of the cement prosthesis interface demonstrated a lower pull-out strength (p < 0.001). The model with the keel and baseplate cemented showed a higher pull-out strength compared to cementing the baseplate alone (p < 0.001). The use of low-viscosity cement resulted in a significantly higher failure force (p = 0.002) compared to high-viscosity cement when cementing the baseplate alone. InterpretationsBiomechanical testing demonstrated improved fixation with cementing the tibial keel and keeping surfaces free from contamination during the cementation process.

No significant difference in early clinical outcomes of custom versus off-the-shelf total knee arthroplasty: a systematic review and meta-analysis.

The purpose of this systematic review and meta-analysis was to collect, synthesise and critically appraise findings of clinical studies that report outcomes of custom total knee arthroplasty (TKA). The hypothesis was that, compared to off-the-shelf (OTS) TKA, custom TKA would yield better surgical, clinical and radiographic outcomes. This systematic review and meta-analysis was performed in accordance with the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). On 8 February 2021, two authors independently searched and screened articles using MEDLINE®, Embase® and the Cochrane Library without restriction on date of publication. Findings from eligible articles were narratively synthesised and tabulated, and when ≥ 3 comparative studies reported the same outcome, results were pooled and summarised in forest plots. Quality assessments of the studies were done according to the guidelines of the Joanna Briggs Institute (JBI) Checklists. A total of 15 articles were eligible for data extraction, of which 9 were case-control studies reporting on 929 custom versus 998 OTS TKA, 5 were case series reporting on results of 587 custom TKA, and 1 was a cross-sectional study reporting on results of 44 custom versus 132 OTS TKA. Five studies that compared early revision rates found the overall effect in favour of OTS TKA(odds ratio (OR), 0.4; p = n.s.) but the result did not reach statistical significance. Four studies found no statistically significant difference inKSS knee (standardised mean difference (SMD), -0.10; p = n.s.) and function (SMD, 0.03; p = n.s.), and five studies found no statistically significant difference in range of motion (SMD, 0.02; p = n.s.). One study that compared bone-implant fit between custom and three OTS tibial components found no overhang but revealed under-coverage of up to 18% in knees with custom tibial baseplates. Custom TKA demonstrated no significant benefits compared to OTS TKA in terms of pooled clinical outcomes, but had considerably higher early revision rates. The findings of the present systematic review and meta-analysis suggest the need for studies with better comparable groups and standardisation of reporting outcomes amongst studies, that could increase the quality of evidence and enable pooling of results in future meta-analyses. Level IV.

Significant differences in rates of aseptic loosening between two variations of a popular total knee arthroplasty design

PurposeThe NexGen Legacy Posterior Stabilised (LPS) prosthesis (Zimmer Biomet, Warsaw, IN, USA) has augmentable and non-augmentable tibial baseplate options. We have noted an anecdotal increase in the number of cases requiring early revision for aseptic loosening since adopting the non-augmentable option. The purpose of this study was to ascertain our rates of aseptic tibial loosening for the two implant types within five years of implantation and to investigate the causes for any difference observed.MethodsA database search was performed for all patients who underwent primary total knee arthroplasty (TKA) using the NexGen LPS between 2009 and 2015. Kaplan–Meier curves were plotted to assess for differences in revision rates between cohorts. We collected and compared data on gender, age, body mass index, component alignment and cement mantle quality as these were factors thought to affect the likelihood of aseptic loosening.ResultsTwo thousand one hundred seventy-two TKAs were included with five year follow-up. There were 759 augmentable knees of which 14 were revised and 1413 non-augmentable knees of which 48 were revised. The overall revision rate at five years was 1.84% in the augmentable cohort and 3.4% in the non-augmentable cohort. The revision rate for aseptic loosening was 0.26% in the augmentable group and 1.42% in the non-augmentable group (p = 0.0241).ConclusionsWe have identified increased rates of aseptic loosening in non-augmentable components. This highlights the effect that minor implant changes can have on outcomes. We recommend that clinicians remain alert to implant changes and publish their own results when important trends are observed.

Failure due to metallosis after cruciate retaining total knee replacement

Background: Rupture of PCL on cruciate retaining TKA can cause abnormal accelerated wear of polyethylene component which may result in metal/metal articulation and development of massive infiltration of metal debris in the periprosthetic soft tissue (metallosis). Patient and methods: Eight cases (Five females, 3 males, mean age 64.6 years) with failed primary cruciate retaining knee arthroplasty were retrospectively studied. Revisions were performed after a mean of 59.8 months due to pain and instability. All the patients had variable degrees of clinically relevant posterior knee instability. Infection was excluded in all cases through microbiological examination and synovial fluid analysis. Results: Abnormal direct metal-on-metal articulation between the femoral component and the tibial base plate with advanced polyethylene wear were found intraoperatively in all cases in addition to extensive tissues black staining, advanced osteolysis and pseudotumor formation. All cases were managed by single stage revision surgery with implant removal, profound synovectomy and revision using a more constrained modular revision knee system. Conclusion: Metallosis after total knee arthroplasty is a rare situation that should be suspected in total knee arthroplasty cases with radiologically evident advanced polyethylene wear especially in cruciate retaining knee systems. It could lead to significant osteolysis making revision surgery technically challenging.

Propagation of registration error into maximum total point motion to analyze tibial baseplate stability at six months using marker-based and model-based RSA

Maximum total point motion (MTPM) of a tibial baseplate at 6 months is used to predict long-term aseptic loosening after total knee arthroplasty. However, the propagation of registration error into MTPM for stable baseplates (i.e. baseplates with MTPM < 0.5 mm) manifested as bias (i.e. systematic error) and precision (i.e. random error) has not been quantified and compared to the 6-month stability limit for marker-based and model-based RSA, which have different magnitudes of registration error. To determine the bias and precision in MTPM for stable baseplates, registration errors in six degrees of freedom reported in the literature for marker-based and model-based RSA were applied to an example baseplate using computer simulations. Results revealed that the bias in MTPM for stable baseplates with model-based RSA is three to four times that of marker-based RSA, and that the precision in MTPM for stable baseplates with model-based RSA is double that of marker-based RSA. This assessment of bias and precision in MTPM for stable baseplates led to a method for adjusting the 6-month stability limit for model-based RSA where half the width of the 95% confidence interval on the mean MTPM and the bias in MTPM for marker-based RSA were subtracted from 0.5 mm to compute true MTPM. The bias in MTPM and half the width of the 95% confidence interval on the mean MTPM for model-based RSA were then added to the true MTPM to obtain the adjusted stability limit for model-based RSA which ranged from 0.57 mm to 0.64 mm.