Tibial Baseplate Research Articles

Maximum Total Point Motion of Five Points Versus All Points in Assessing Tibial Baseplate Stability.

Maximum total point motion (MTPM), the point on a baseplate that migrates the most, has been used to assess the risk of tibial baseplate loosening using radiostereometric analysis (RSA). Two methods for determining MTPM for model-based RSA are to use either five points distributed around the perimeter of the baseplate or to use all points on the three-dimensional model. The objectives were to quantify the mean difference in MTPM using five points versus all points, compute the percent error relative to the 6-month stability limit for groups of patients, and determine the dependency of differences in MTPM on baseplate size and shape. A dataset of 10,000 migration values was generated using the mean and standard deviation of migration in six-degrees-of-freedom at 6 months from an RSA study. The dataset was used to simulate the migration of three-dimensional models (two baseplate shapes and two baseplate sizes) and calculate the difference in MTPM using five virtual points versus all points and the percent error (i.e., the difference in MTPM/stability limit) relative to the 6-month stability limit. The difference in the MTPM was about 0.02 mm, or 4% relative to the 6-month stability limit, which is not clinically important. Furthermore, results were not affected by baseplate shape or size. Researchers can decide whether to use five points or all points when computing MTPM for model-based RSA. The authors recommend using five points to maintain consistency with marker-based RSA.

Effect of varus alignment on the bone-implant interaction of a cementless tibial baseplate during gait.

Component alignment in total knee arthroplasty is a determining factor for implant longevity. Mechanical alignment, which provides balanced load transfer, is the most common alignment strategy. However, a retrospective review found that varus alignment, which could lead to unbalanced loading, can happen in up to 18% of tibial baseplates. This may be particularly burdensome for cementless tibial baseplates, which require low bone-implant micromotion and avoidance of bone overload to obtain bone ingrowth. Our aim was to assess the effect of varus alignment on the bone-implant interaction of cementless baseplates. We virtually implanted 11 patients with knee OA with a modern cementless tibial baseplate in mechanical alignment and in 2° of tibial varus alignment. We performed finite element simulations throughout gait, with loading conditions derived from literature. Throughout the stance phase, varus alignment had greater micromotion and percentage of bone volume at risk of failure than mechanical alignment. At mid-stance, when the most critical conditions occurred, the average increase in peak micromotion and amount of bone at risk of failure due to varus alignment were 79% and 59%, respectively. Varus alignment also resulted in the decrease of the surface area with micromotion compatible with bone ingrowth. However, for both alignments, this surface area was larger than the average area of ingrowth reported for well-fixed implants retrieved post-mortem. Our findings suggest that small varus deviations from mechanical alignment can adversely impact the biomechanics of the bone-implant interaction for cementless tibial baseplates during gait; however, the clinical implications of such changes remain unclear.

Early outcomes of a modern cemented total knee arthroplasty : is tibial loosening a concern?

Recent total knee arthroplasty (TKA) designs have featured more anatomical morphologies and shorter tibial keels. However, several reports have raised concerns about the impact of these modifications on implant longevity. The aim of this study was to report the early performance of a modern, cemented TKA design. All patients who received a primary, cemented TKA between 2012 and 2017 with a minimum two-year follow-up were included. The implant investigated features an asymmetrical tibial baseplate and shortened keel. Patient demographic details, Knee Society Scores (KSS), component alignment, and the presence of radiolucent lines at final follow-up were recorded. Kaplan-Meier analyses were performed to estimate survivorship. A total of 720 of 754 primary TKAs (95.5%) were included with a mean follow-up of 3.9 years (SD 1.3); 562 (78.1%) were cruciate-retaining and 158 (21.9%) were posterior-stabilized. A total of 11 (1.5%) required reoperation for periprosthetic joint infection and seven (1.0%) for aseptic tibial loosening (five cruciate-retaining, two posterior-stabilized). Loosening occurred at a mean of 3.3 years (0.9 to 6.5). There were no cases of loosening in the 33 patients who received a 14 mm × 30 mm tibial stem extension. All-cause survivorship was 96.6% at three years (95% confidence interval (CI) 95.3% to 98.0%) and 96.2% at five years (95% CI 94.8% to 97.7%). Survivorship with revision for aseptic loosening was 99.6% at three years (95% CI 99.1% to 100.0%) and 99.1% at five years (95% CI 98.4% to 99.9%). Tibial components were in significantly more varus in those with aseptic loosening (mean 3.4° (SD 3.7°) vs 1.3° (SD 2.0°); p = 0.015). There were no other differences in demographic, radiological, or surgical characteristics between revised and non-revised TKAs for aseptic loosening (p = 0.293 to 1.00). Mean KSS improved significantly from 57.3 (SD 9.5) preoperatively to 92.6 (SD 8.9) at the final follow-up (p < 0.001). This is the largest series to date of this design of implant. At short-term follow-up, the rate of aseptic tibial loosening is not overly concerning. Further observation is required to determine if there will be an abnormal rate of loosening at mid- to long-term follow-up. Cite this article: Bone Joint J2021;103-B(6 Supple A):51-58.

Considerable inter-individual variability of tibial geometric ratios renders bone-implant mismatch unavoidable using off-the-shelf total knee arthroplasty: a systematic review and meta-analysis.

The purpose of this systematic review and meta-analysis was to investigate the variability in tibial geometric ratios among knees of different sexes and races to determine whether commercially-available tibial baseplates accommodate the morphologic diversity. The hypothesis was that anthropometric studies report considerable variability of tibial geometric ratios among sexes and races. This systematic review and meta-analysis was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) criteria. Two authors independently conducted an electronic search using MEDLINE® and Embase® on 28 January 2021 for clinical studies reporting on tibial geometric ratios. Tibial geometric ratios, as reported by the clinical studies, were represented by plotting their means and two standard deviations for comparison to two symmetric and two asymmetric commercially-available tibial baseplates. A total of 27 articles that reported on a combined total of 20,944 knees were eligible for data extraction. Variation in tibial aspect ratios was equal among sexes. The greatest variation in aspect ratio was observed among East Asians, followed by Caucasians, African-Americans, Indian and Middle Easterns. The variation in tibial asymmetry ratio was larger among men compared to women. The greatest variation in asymmetry ratio was observed among African-Americans, followed by Caucasians, East Asians, Indian and Middle Easterns. Bone-implant mismatch of > 3mm overhang or > 4mm under-coverage with four commercially-available tibial baseplates occurred in large proportions of knees due to variations in aspect ratio (in 17-100% of knees) and asymmetry ratio (in 7-100% of knees). Anthropometric studies reported considerable inter-individual variability of tibial geometric ratios, which exceeded effects of sexual dimorphism and racial diversity. Bone-implant mismatch may be unavoidable in a large proportion of knees, when considering that a surgeon generally only uses one or a few TKA brands. These findings support the drive towards patient-specific implants to potentially achieve accurate bone-implant fit by implant customisation. IV.

Cementless Highly Porous Titanium Tibial Base Plate in Total Knee Arthroplasty – Midterm Outcomes.

Introduction &amp; Aims&#x0D; TKA in more active and young patients has prompted the interest in more durable and biological methods of Osteo-integration with cementless components. With the emergence of improved biomaterials like porous titanium and the success, search for a cementless TKA with long-term durability and survivorship may have ended. This is a retrospective study of 492 consecutive TKAs using Cementless tibial fixation, reporting on the early 4 years clinical and radiological outcomes.&#x0D; Method&#x0D; We studied 492 TKAs performed consecutively by a single surgeon between 1stJan. 2010 and 31stDec. 2015 using a cementless, fixed bearing tibial tray (porous–Regenerex, Vanguard, Zimmer-Biomet) and a cementless femoral component (Vanguard) with no exclusion criteria. Clinical and radiological follow-up was done on these patients and in addition a comprehensive joint registry review was performed on the whole cohort (Level II evidence).&#x0D; Results&#x0D; The average Knee Society Score at final follow-up was 89.33, average pre-op being 42.06. Average post-op WOMAC score was 43.45 and average pre-op was 77.78. On radiological examination, no patients had osteolysis around tibial base plate. In our series 9 patients were revised, out of which only 4 patients had the tibial tray and femoral component revised and 5 patients had patella resurfacing or liner exchange. Overall survivorship of the cementless tibial component is excellent with a survivorship of 99.4% at 5.9 years based on a comprehensive AOANJRR data.&#x0D; Conclusions&#x0D; Cementless tibial fixation using a porous titanium construct can provide stable bone ingrowth fixation on the tibial side with excellent and predictable early 4 to 5 year clinical and radiological outcomes.

Comparing the effect of tourniquet and tranexamic acid on the tibial cement mantle thickness in total knee arthroplasty.

This study aims to determine the efficacy of both tranexamic acid (TXA) and tourniquet on the tibial cement mantlethickness in total knee arthroplasty (TKA). We retrospectively reviewed the recorded data of patients with primary end-stage knee osteoarthritis who underwent TKA procedure during 2014-2016 at a single institution to evaluate the tibial cement mantle. Patients were categorized in two groups based on the use of tourniquet (groups 1 and 2). In addition, these groups were categorized into two different subgroups based on the use of TXA in groups 1 and 2 (group 1-A, B and group 2-A, B). Four zones at the tibial baseplate on the anteroposterior view and two zones on the lateral view were measured at the 4-6-week postoperative visit. A total of 28 patients (30 knees) were operated using tourniquet and TXA (group 1-A), 29 (30 knees) using tourniquet without TXA (group 1-B), 24 (28 knees) using TXA without tourniquet (group 2-A), and 38 (42 knees) without using TXA and tourniquet (group 2-B). Although a significant difference was found in the cumulative cement mantle penetration on postoperative X-rays between groups 1 and 2, no significant differences were found between groups A and B in both groups. This study reports that tourniquet use in TKA increased cement mantle penetration of the tibial component in primary TKA. The main strength of this study was that the TXA use alone exhibited no significant effect on the cement thickness.

Computer-assisted surgery and patient-specific instrumentation improve the accuracy of tibial baseplate rotation in total knee arthroplasty compared to conventional instrumentation: a systematic review and meta-analysis.

To determine whether patient-specific instrumentation (PSI), computer-assisted surgery (CAS) or robot-assisted surgery (RAS) enable more accurate rotational alignment of the tibial baseplate in primary total knee arthroplasty (TKA) compared to conventional instrumentation, in terms of deviation from the planned target and the proportion of outliers from the target zone. The authors independently conducted three structured electronic literature searches using the PubMed, Embase®, and Cochrane Central Register of Controlled Trials databases from 2007 to 2020. Studies were included if they compared rotational alignment of the tibial baseplate during TKA using conventional instrumentation versus PSI, CAS, and/or RAS, and reported deviation from preoperatively planned rotational alignment of the tibial baseplate in terms of absolute angles and/or number of outliers. Methodological quality of eligible studies was assessed by two researchers according to the Downs and Black Quality Checklist for Health Care Intervention Studies. Fifteen studies, that reported on 2925 knees, were eligible for this systematic review, of which 6 studies used PSI, and 9 used CAS. No studies were found for RAS. Of the studies that reported on angular deviation from preoperatively planned rotational alignment, most found smaller deviations using PSI (0.5° to 1.4°) compared to conventional instrumentation (1.0° to 1.6°). All studies that reported on proportions of outliers from a target zone (± 3°), found lower rates of outliers using PSI (0 to 22%) compared to conventional instrumentation (5 to 96%). Most studies reported smaller angular deviation from preoperatively planned rotational alignment using CAS (0.1° to 6.9°) compared to conventional instrumentation (1.1° to 7.8°). Of the studies that reported on proportions of outliers from a target zone (± 3°), most found fewer outliers using CAS (10 to 61%) compared to conventional instrumentation (17 to 78%). This systematic review and meta-analysis revealed that both CAS and PSI can improve the accuracy of rotational alignment of the tibial baseplate by decreasing angular deviation from the preoperatively planned target and reducing the proportion of outliers from the target zone. The clinical relevance is that PSI and CAS can improve alignment, though the thresholds necessary to grant better outcomes and survival remain unclear. IV.

Where Is the “Weak Link” of Fixation in Contemporary Cemented Total Knee Replacements?

BackgroundAseptic tibial loosening is a frequent cause of long-term failure following primary cemented total knee replacement. Failure of the tibial implant can occur at the implant-cement interface or at the cement-bone interface. Currently, it is unknown at which interface failure occurs in cases of aseptic tibial loosening. The following study was designed to determine which interface represents the “weak link” for tibial implant fixation. MethodsWe performed a retrospective analysis of 149 patients who were revised secondary to aseptic tibial loosening at our institution from 2005 to 2017. Operative reports and radiographs were reviewed on each patient to determine the location and pattern of fixation failure. ResultsImplant failure was more prevalent at the implant-cement than cement-bone interface, 140/149 (94.0%) vs 9/149 (6.0%). Additionally, we noted 2 distinct patterns of failure in patients that loosened at the implant-cement interface. Ninety of 140 (64.3%) patients developed varus collapse pattern of failure. Forty-nine of 140 (35.0%) patients developed failure between the implant-cement interface without angulation. All 149 patients had heterotopic bone formation anterior to the tibial baseplate, which was consistent regardless of which interface failed. ConclusionThe most frequent interface failure identified in our study was at the implant-cement interface, 140/149 (94.0%). This finding has substantial clinical ramifications. Because failure was predominantly at the implant-cement interface there may be design opportunities for increasing implant fixation to cement. Implants with improved undersurface tibial tray features may be necessary to mitigate the risk of failure at this interface, especially in overly active patients or those with elevated body mass indices.

Effects of tourniquet use on clinical outcomes and cement penetration in TKA when tranexamic acid administrated: a randomized controlled trial

BackgroundThe role of a tourniquet is still controversial for patients undergoing total knee arthroplasty (TKA). Our current study was performed to determine whether the nonuse of the tourniquet combine with tranexamic acid (TXA) application in TKA patients with end-stage osteoarthritis would accelerate the perioperative recovery rate and provide enough cement mantle thickness for implant fixation.MethodsIn this prospective, randomized controlled trial, 150 end-stage knee osteoarthritis patients receiving TKA were divided into three groups: group A (tourniquet group), group B (non-tourniquet group), and group C (tourniquet in cementation group). All enrolled patients received 3 g of intravenous TXA and 1 g topical TXA. The primary outcomes included blood loss variables and transfusion values. The secondary outcomes included VAS pain score, inflammatory factors level, range of motion, HSS score, postoperative hospital stay, and complication. Furthermore, by using a digital linear tomosynthesis technique, tibial baseplate bone cement mantle thickness was measured in four zones based on the knee society scoring system.ResultsNo significant difference was found among the three groups with regards to total blood loss, transfusion, and complication. However, patients in group B showed lower inflammatory factors levels, shorter length of hospital stay, better range of motion, and lower postoperative pain. No significant difference was found among the three groups in four zones in terms of bone cement mantle thickness.ConclusionsFor end-stage knee osteoarthritis patients, the absence of tourniquet did not appear to affect blood loss and cement penetration in TKA patients. Furthermore, less inflammation reaction and better knee function can be achieved without a tourniquet. We recommend no longer use a tourniquet in primary TKA for patients with end-stage osteoarthritis when TXA is administrated.Trial registrationChiCTR-INR-16009026.Level of evidenceTherapeutic Level I.

Propagation of registration errors into the change in maximum total point motion for determining stability of tibial baseplates

The change in maximum total point motion (ΔMTPM) is used to predict long-term risk of tibial baseplate loosening, however, effects of registration error on ΔMTPM have not been quantified for marker-based and model-based radiostereometric analysis (RSA). Registration errors for marker-based and model-based RSA were applied to a stable tibial baseplate in MATLAB simulations to determine the bias and precision in ΔMTPM and the proportions of baseplates which fell above the continuous migration stability limit. No bias error occurred, however, the precision of ΔMTPM was twice as large for model-based RSA than marker-based RSA, resulting in about 25% of stable baseplates falling above the continuous migration stability limit for model-based RSA. Reseachers should be aware of these limitations when applying this stability limit to assess tibial baseplate stability using model-based RSA.

The prevalence of posterolateral tibial baseplate overhang: An anatomical CT study

IntroductionTotal Knee Arthroplasty (TKA) is used in patients with osteoarthritis who have failed conservative management to reduce pain, improve functional outcomes and ultimately quality of life. However, less than optimal patient satisfaction has led to continued improvements in design and technology of TKA. One factor that can limit patient satisfaction is postero-lateral overhang of the tibial baseplate. The purpose of our study is to utilize pre-operative CT scans to assess the prevalence of posterolateral tibial overhang with the use of a symmetric tibial baseplate component in a popular knee system with robotic assistance. MethodsNinety-eight (98) consecutive patients who underwent robotic-assisted total knee arthroplasty (TKA) were included in this study. Using both the most medial aspect of the tibial tubercle and the medial ⅓ of the tibial tubercle as reference points, we quantified the extent of posterolateral overhang when determining the rotation of the tibial component. ResultsUsing the most medial aspect of the tibial tubercle as a reference point for rotation of the tibial baseplate, 63% of the instances of reviewed CT scans (369/588) had posterolateral overhang. Furthermore, 81% (406/588) had posterolateral overhang when using the medial ⅓ aspect of the tibial tubercle as the reference for rotation of the tibial baseplate. The average posterolateral tibial baseplate overhang was 1.5 mm (range 0–8 mm) when using the most medial aspect of the tibial tubercle and 2.4 mm (range 0–8 mm) when using the medial ⅓ tibial tubercle as the centering point for the tibial baseplate. DiscussionTibial baseplate overhang could lead to potential pain from irritation of soft tissues. To our knowledge, this is the first study that was able to valencquantify the amount of tibial baseplate overhang using pre-operative CT scans. Rotational alignment of the tibial baseplate needs to be balanced to ensure minimal lateral overhang while achieving sufficient external rotation of the tibial component. An asymmetric tibial component may provide a compromise in certain situations. Level of evidenceDiagnostic level IV case series.

Modular Tibial Stem Use and Risk of Revision for Aseptic Loosening in Cemented Primary Total Knee Arthroplasty

BackgroundModular tibial stem extensions in total knee arthroplasty (TKA) are designed to reduce the risk of aseptic loosening of the tibial base plate. However, these implants add significant cost and an evaluation of their effectiveness in reducing this risk of loosening has not been studied in a large cohort. We sought to evaluate modular tibial stem utilization in primary TKA. MethodsWe conducted a cohort study using our integrated healthcare system’s Total Joint Replacement Registry. Patients who underwent cemented primary TKA were identified (2009-2019). Propensity scores were used to 1:1 match patients without to those with a stem extension. Cox proportional-hazards regression was used to evaluate the risk for revision due to aseptic loosening. ResultsTen thousand four hundred seventy six TKA with a modular tibial stem were matched to 10,476 TKA without a tibial stem. Stem utilization associated with a lower risk of revision for loosening across all postoperative follow-up (hazard ratio = 0.38, 95% confidence interval = 0.17-0.85). ConclusionIn a matched cohort study, we observed presence of a stem extension was associated with a lower risk of revision for aseptic loosening. Further study to identify specific risk factors for aseptic loosening and confirm the findings presented here are warranted. Level of EvidenceLevel III.

Reorienting the tibial baseplate improves the registration accuracy of model-based radiostereometric analysis

Accuracy of model-based radiostereometric analysis (MBRSA) in calculating tibial baseplate migration depends on baseplate shape and orientation relative to the imaging planes. The primary objectives were to introduce a new method for determining the optimal baseplate orientation to minimize bias error during MBRSA and to demonstrate the clinical usefulness of the method using a knee positioning guide to repeatably orient the baseplate. A tibia phantom was rotated to achieve 24 different orientations with three pairs of radiographs acquired at each orientation. Radiographs were processed in MBRSA software and the mean maximum total point motion (MTPM), an indicator of bias error during model registration, was plotted as a function of the rotation angles to determine the optimal orientation and a range of acceptable orientations. The bias error decreased 85% between the reference orientation and the optimal orientation. An acceptable range of orientations was defined by a decrease in bias error more than 50%. Future researchers can use this method to determine the optimal orientation and a range of acceptable orientations for their specific baseplate to minimize bias error. Clinical usefulness was demonstrated by repeatedly imaging a knee model placed in a knee positioning guide (simulated clinical positioning) and demonstrating that the mean orientation ± one standard deviation fell within the acceptable range of orientations. Thus, use of a knee positioning guide was an effective tool for repeatable patient positioning and should be considered for future RSA studies to maintain consistent positioning during a longitudinal study.

Are asymmetric tibial baseplates superior in primary total knee arthroplasty? A systematic review of clinical studies

Background: Despite the asymmetric nature of the native tibial condyles, traditional primary total knee arthroplasty (TKA) has overwhelmingly employed the use of symmetric tibial baseplates. However, designs exist utilizing an asymmetric tibial baseplate that mimics normal tibial anatomy. The purpose of this review was to assess the functional and radiographic outcomes of asymmetric tibial base plates. Methods: Embase, MEDLINE, and Web of Science were searched for relevant literature from database inception until September 2019, and after screening by two reviewers, studies investigating the use of asymmetric tibial baseplates in primary TKA were included. Demographic data as well as data on revision rates, functional and radiographic outcomes, and complications were recorded. A risk of bias assessment was performed for all studies. Results: Overall, 24 studies were identified with a total of 4776 patients (4937 knees). Seventeen studies (1895 knees) reported a pooled revision rate of 2.4% (45/1845) at a mean follow-up of 72.9 mo. TKA with an asymmetric baseplate resulted in improvement of range of motion and functional outcome scores postoperatively, as well as radiographic evidence of good tibial component positioning and bone coverage. Lastly, the overall pooled complication rate of reporting studies was 12.7%. Conclusions: The use of an asymmetric tibial baseplate in primary TKA is a safe and effective option, with the potential for improved component alignment and tibial coverage. However, more evidence is needed to determine if there are significant differences in failure rates and postoperative functional outcomes before justifying the implementation of a new and potentially more costly technology. Level of Evidence: Level IV.

Effect of material selection on tibial post stresses in posterior-stabilized knee prosthesis.

AimsThe material and design of knee components can have a considerable effect on the contact characteristics of the tibial post. This study aimed to analyze the stress distribution on the tibial post when using different grades of polyethylene for the tibial inserts. In addition, the contact properties of fixed-bearing and mobile-bearing inserts were evaluated.MethodsThree different grades of polyethylene were compared in this study; conventional ultra high molecular weight polyethylene (UHMWPE), highly cross-linked polyethylene (HXLPE), and vitamin E-stabilized polyethylene (VEPE). In addition, tibial baseplates with a fixed-bearing and a mobile-bearing insert were evaluated to understand differences in the contact properties. The inserts were implanted in neutral alignment and with a 10° internal malrotation. The contact stress, von Mises stress, and equivalent plastic strain (PEEQ) on the tibial posts were extracted for comparison.ResultsThe stress and strain on the tibial post for the three polyethylenes greatly increased when the insert was placed in malrotation, showing a 38% to 56% increase in von Mises stress and a 335% to 434% increase in PEEQ. The VEPE insert had the lowest PEEQ among the three materials. The mobile-bearing design exhibited a lower increase in stress and strain around the tibial posts than the fixed-bearing design.ConclusionUsing VEPE for the tibial component potentially eliminates the risk of material permanent deformation. The mobile-bearing insert can help to avoid a dramatic increase in plastic strain around the tibial post in cases of malrotation. The mobility allows the pressure to be distributed on the tibial post and demonstrated lower stresses with all three polyethylenes simulated.Cite this article: Bone Joint Res 2020;9(11):768–777.

Low-Degree Tibial Slope Angle Prevents Component Overhang by Enlarging the Lateral Plateau Surface Area in Total Knee Arthroplasty.

This study aimed to investigate whether overhang or underhang around the tibial component that occurs during the placement of tibial baseplates was affected by different slope angles of the tibial plateau and determine the changes in the lateral and medial plateau diameters while changing the slope angle in total knee arthroplasty. Three-dimensional tibia models were reconstructed using the computed tomography scans of 120 tibial dry bones. Tibial plateau slope cuts were performed with 9, 7, 5, 3, and 0 degrees of slope angles 2-mm below the subchondral bone in the deepest point of the medial plateau. Total, lateral, and medial tibial plateau areas and overhang/underhang rates were measured at each cut level. Digital implantations of the asymmetric and symmetric tibial baseplates were made on the tibial plateau with each slope angles. Following the implantations, the slope angle that prevents overhang or underhang at the bone border and the slope angle that has more surface area was identified. A significant increase was noted in the total tibial surface area, lateral plateau surface area, and lateral anteroposterior distance, whereas the slope cut angles were changed from 9 to 0 degrees in both gender groups. It was found that the amount of posteromedial underhang and posterolateral overhang increased in both the asymmetric and symmetric tibial baseplates when the slope angle was changed from 0 to 9 degrees. Although the mediolateral diameter did not change after the proximal tibia cuts at different slope angles, the surface area and anteroposterior diameter of the lateral plateau could change, leading to increased lateral plateau area. Although prosthesis designs are highly compatible with the tibial surface area, it should be noted that the component overhangs, especially beyond the posterolateral edge, it can be prevented by changing the slope cut angle in males and females.

Application of 3D Printing in Hip and Knee Arthroplasty: A Narrative Review.

Ideal surgical positioning and placement of implants during arthroplasty are crucial for long-term survival and optimal functional outcomes. Inadequate bone stock or defects, and anatomical variations can influence the outcomes. Three-dimensional printing (3DP) is an evolving technology that could provide patient-specific instrumentation and implants for arthroplasty, taking into account anatomical variations and defects. However, its application in this field is still not adequately studied and described. The present review was conceptualised to assess the practicality, the pros and cons and the current status of usage of 3DP in the field of hip and knee arthroplasties and joint reconstruction surgeries. A PubMed database search was conducted and a total number of 135 hits were obtained, out of which only 30 articles were relevant. These 30 studies were assessed to obtain the qualitative evidence of the applicability and the current status of 3D printing in arthroplasty. Currently, 3DP is used for preoperative planning with 3D models, to assess bone defects and anatomy, to determine the appropriate cuts and to develop patient-specific instrumentation and implants (cages, liners, tibial base plates, femoral stem). Its models can be used for teaching and training young surgeons, as well as patient education regarding the surgical complexities. The outcomes of using customised instrumentations and implants have been promising and 3D printing can evolve into routine practice in the years to come. 3D printing in arthroplasty is an evolving field with promising results; however, current evidence is insufficient to determine significant advantages that can be termed cost effective and readily available.

Various Types of Medial Tibial Bone Resorption after Total Knee Arthroplasty Using a Thick Cobalt Chromium Tibial Baseplate.

Recent literature has implicated a thick cobalt chromium baseplate as a potential source of stress shielding and medial tibial bone resorption after total knee arthroplasty (TKA) in a Western population. The purpose was to calculate the incidence of various types and severity of medial tibial bone resorption utilizing a novel classification system after TKA with a thick cobalt chromium baseplate in Asian patients. Five hundred TKAs using Attune prostheses with mean follow-up of 3.4 years were evaluated, using the prospective radiographic data. The mean age was 71.3 years. The preoperative mechanical axis was varus, 11.2 degrees. The type and severity of medial tibial bone resorption were categorized as type U (resorption under the tibial baseplate up to 50% [U1] or beyond 50% [U2] of medial tibial tray width), C (resorption around the penetrated cement under the baseplate), and M (resorption on the medial tibial cortex without extension to the baseplate). Bone resorption of medial proximal tibia was observed in 96 knees (19.2%). Types U1 and U2 were seen in 46 and 28 knees, respectively. Type C was observed in 12 knees and type M in 10 knees. The type U resorption group had significantly more preoperative varus deformity (varus 12.9 vs. 10.9 degrees, p = 0.017). Medial tibial bone resorption after TKAs using a thick cobalt chromium baseplate is not uncommon and has various locations, types, and severities. The medial tibial bone resorption might be related to various causes, including stress shielding, thermal necrosis from cement in the bony hole, and bony devascularization. The type-U resorption has to be closely observed in patients with preoperative severe varus deformity. This is a Level IV study.

Correlation of tibial component size and rotation with outcomes after total knee arthroplasty

Tibial component design and positioning contribute more to patient satisfaction than previously realized. A surgeon needs to decide on the size and rotation, bearing in mind that coverage should be as high as possible, whilst malrotation and overhang should be avoided. No study investigates the impact of each of these components on clinical outcomes in a single cohort. This is a retrospective analysis of 1-year postoperative outcomes measured with the Knee Injury and Osteoarthritis Outcome (KOOS) Score, as well as a previously validated rotational CT protocol. Coverage, rotation from Insall's axis, and overhang of an asymmetric tibial baseplate were measured, and positive and negative correlations to clinical outcomes were calculated. A total of 499 knees were analyzed. Patient average age was 68.4years. Rotation within 7° internal and 5° external from Insall's axis was a "safe zone". Mean coverage was 76%. A total of 429 knees (94%) had a coverage of at least 70% and 102 knees (22%) greater than 80%. Overhang was detected in 23% of the cohort. Increased coverage was correlated to increased KOOS score and overhang correlated with a decreased KOOS score (p = 0.008). This study demonstrates the individual role of three aspects of tibial component implantation properties in postoperative pain and short-term functional outcomes. Upsizing to the point of overhang with rotational tolerance of 7° internal and 3° external to Insall's axis demonstrates best patient reported outcomes. Overhang decreases the clinical outcome by the same margin as loss of 16% of coverage.

A Biomechanical Comparison of the Effect of Baseplate Design and Bone Marrow Fat Infiltration on Tibial Baseplate Pullout Strength

BackgroundEarly clinical results of a new total knee arthroplasty (TKA) implant design show promise for improved outcomes and patellofemoral function scores. However, reports of early tibial component-cement interface debonding requiring revision have been published. This study investigated the biomechanical properties of three different tibial baseplates to understand potential causes of failure. MethodsPFC Sigma (control), Attune (1st generation) and Attune S+ (2nd generation) tibial baseplates were implanted into 4th generation sawbone tibia models using a standardized technique. Three of each baseplate were cemented with and without additional bovine bone marrow fat. All models were tested to failure with measured axial distraction force. Implant type, presence or absence of bovine marrow and load to failure were all recorded and compared. Two-way ANOVA followed by post-hoc pairwise comparisons were used to determine statistical significance, which was set to P < .05. ResultsThe 2nd generation tibial baseplates required significantly more force to failure. The presence of bovine marrow significantly reduced the pullout force of the implant designs overall. No significant difference was detected between the 1st generation and control baseplates. Failure mode for each model was also noted to be different irrespective of the presence or absence of bone marrow fat. ConclusionThe 2nd generation baseplates required significantly more force to failure compared with older designs. The presence of bone marrow during cementation of a tibial base plate significantly decreased axial pullout strength of a tibial baseplate in this laboratory model. All 1st generation baseplates exhibited debonding at the cement-implant interface.