Implant Interface Debonding After Total Knee Arthroplasty: A New Cause for Concern?

Passive Biotelemetric Detection of Tibial Debonding in Wireless Battery-Free Smart Knee Implants

Aseptic loosening is the dominant failure mechanism in contemporary knee replacement surgery, but diagnostic techniques are poorly sensitive to the early stages of loosening and poorly specific in delineating aseptic cases from infections. Smart implants have been proposed as a solution, but incorporating components for sensing, powering, processing, and communication increases device cost, size, and risk; hence, minimising onboard instrumentation is desirable. In this study, two wireless, battery-free smart implants were developed that used passive biotelemetry to measure fixation at the implant-cement interface of the tibial components. The sensing system comprised of a piezoelectric transducer and coil, with the transducer affixed to the superior surface of the tibial trays of both partial (PKR) and total knee replacement (TKR) systems. Fixation was measured via pulse-echo responses elicited via a three-coil inductive link. The instrumented systems could detect loss of fixation when the implants were partially debonded (+7.1% PKA, +32.6% TKA, both p < 0.001) and fully debonded in situ (+6.3% PKA, +32.5% TKA, both p < 0.001). Measurements were robust to variations in positioning of the external reader, soft tissue, and the femoral component. With low cost and small form factor, the smart implant concept could be adopted for clinical use, particularly for generating an understanding of uncertain aseptic loosening mechanisms.

Association Between Surface Modifications for Biologic Fixation and Aseptic Loosening of Uncemented Total Knee Arthroplasties

BACKGROUND

Various surface modifications are used in uncemented total knee arthroplasties (TKAs) to enhance bony ingrowth and longevity of implants. This study aimed to identify which surface modifications are used, whether they are associated with different revision rates for aseptic loosening, and which are underperforming compared to cemented implants.

METHODS

Data on all cemented and uncemented TKAs used between 2007 and 2021 were obtained from the Dutch Arthroplasty Register. Uncemented TKAs were divided into groups based on their surface modifications. Revision rates for aseptic loosening and major revisions were compared between groups. Kaplan-Meier, Competing-Risk, Log-rank tests, and Cox regression analyses were used. In total, 235,500 cemented and 10,749 uncemented primary TKAs were included. The different uncemented TKA groups included the following: 1,140 porous-hydroxyapatite (HA); 8,450 Porous-uncoated; 702 Grit-blasted-uncoated; and 172 Grit-blasted-Titanium-nitride (TiN) implants.

RESULTS

The 10-year revision rates for aseptic loosening and major revision of the cemented TKAs were 1.3 and 3.1%, and for uncemented TKAs 0.2 and 2.3% (porous-HA), 1.3 and 2.9% (porous-uncoated), 2.8 and 4.0% (grit-blasted-uncoated), and 7.9% and 17.4% (grit-blasted-TiN), respectively. Both type of revision rates varied significantly between the uncemented groups (log-rank tests, P < .001, P < .001). All grit-blasted implants had a significantly higher risk of aseptic loosening (P < .01), and porous-uncoated implants had a significantly lower risk of aseptic loosening than cemented implants (P = .03) after 10 years.

CONCLUSION

There were 4 main uncemented surface modifications identified, with different revision rates for aseptic loosening. Implants with porous-HA and porous-uncoated had the best revision rates, at least equal to cemented TKAs. Grit-blasted implants with and without TiN underperformed, possibly due to the interaction of other factors.

Continued Stabilization of a Cementless 3D-Printed Total Knee Arthroplasty: Five-Year Results of a Randomized Controlled Trial Using Radiostereometric Analysis

BACKGROUND

Three-dimensional (3D) printing of highly porous orthopaedic implants aims to promote better osseointegration, thus preventing aseptic loosening. However, short-term radiostereometric analysis (RSA) after total knee arthroplasty (TKA) has shown higher initial migration of cementless 3D-printed tibial components compared with their cemented counterparts. Therefore, critical evaluation of longer-term tibial component migration is needed. We investigated migration of a cementless 3D-printed and a cemented tibial component with otherwise similar TKA design during 5 years of follow-up, particularly the progression in migration beyond 2 years postoperatively.

METHODS

Seventy-two patients were randomized to a cementless 3D-printed Triathlon Tritanium (Stryker) cruciate-retaining (CR) TKA or a cemented Triathlon CR (Stryker) TKA implant. Implant migration was evaluated with RSA at baseline and postoperatively at 3 months and at 1, 2, and 5 years. The maximum total point motion (MTPM) of the tibial component was compared between the groups at 5 years, and progression in migration was assessed between 2 and 5 years. Individual implants were classified as continuously migrating if the MTPM was ≥0.1 mm/year beyond 2 years postoperatively. Clinical scores were evaluated, and a linear mixed-effects model was used to analyze repeated measurements.

RESULTS

At 5 years, the mean MTPM was 0.66 mm (95% confidence interval [CI], 0.56 to 0.78 mm) for the cementless group and 0.53 mm (95% CI, 0.43 to 0.64 mm) for the cemented group (p = 0.09). Between 2 and 5 years, there was no progression in mean MTPM for the cementless group (0.02 mm; 95% CI, -0.06 to 0.10 mm) versus 0.07 mm (95% CI, 0.00 to 0.14) for the cemented group. One implant was continuously migrating in the cementless group, and 4 were continuously migrating in the cemented group. The clinical scores were comparable between the groups across the entire time of follow-up.

CONCLUSIONS

No significant difference in mean migration was found at 5 years between the cementless and cemented TKA implants. Progression of tibial component migration was present beyond 2 years for the cemented implant, whereas the cementless implant remained stable after initial early migration.

LEVEL OF EVIDENCE

Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.

Consequences of using poly-ether-ether-ketone versus traditional implant on tibial cement penetration and short-term clinical outcomes during total knee arthroplasty: a randomized controlled trial

BACKGROUND

The use of poly-ether-ether-ketone (PEEK) prosthesis during total knee arthroplasty (TKA) is a relatively new concept. Several studies have suggested that the thickness of cement penetration during TKA may affect the stability of the implants. The present study aimed to compare the cement penetration and clinical performance between PEEK and traditional cobalt chromium molybdenum (CoCrMo) prosthesis during TKA.

METHODS

This study was a randomized controlled trial with level I of evidence. A total of 48 patients were randomly assigned to either the PEEK group (n = 24) or the CoCrMo group (n = 24). Mean bone cement penetration under the tibial baseplate was assessed radiographically in four zones in the anteroposterior view and two zones in the lateral view, in accordance with the Knee Society Scoring System. Furthermore, parameters such as the Knee Society Score (KSS), visual analogue scale (VAS) scores, complications and survivorship at 1 year postoperatively were also compared.

RESULTS

According to the results of this study, the mean bone cement penetration exhibited no significant difference between PEEK and CoCrMo groups (2.49 ± 0.61 mm vs. 2.53 ± 0.68 mm, p = 0.85). Additionally, there were no remarkable differences in the KSS clinical score, functional score, and VAS score between the two groups. Moreover, complications and survivorship were also statistically compared between the groups and presented no significant differences.

CONCLUSIONS

Based on the current findings, it can be concluded that PEEK implant present similar bone cement penetration, short-term clinical outcomes, and survivorship with traditional CoCrMo implant in TKA without added complications. Trial registration Chinese Clinical Trial Registry (ChiCTR2100047563).

Tibial Baseplate-Cement Interface Debonding in the ATTUNE Total Knee Arthroplasty System

Background

Acrylic bone cement is the most common method of fixation for primary total knee arthroplasty (TKA). Several studies have described good short-term outcomes; however, there have been reports of early failures due to tibial baseplate debonding at the implant-cement interface of The ATTUNE Knee System (DePuy Synthes, West Chester, PA). We examined the causes and rates of revision in patients who underwent TKA with this system to identify factors associated with this mode of early failure.

Methods

A retrospective review of electronic health records between 2013 and 2018 identified all patients undergoing TKA with the ATTUNE Knee System with a minimum 2-year follow-up. Cause of revision, patient, implant, instrumentation, cement, and surgeon variables were collected. A descriptive analysis was used to identify characteristics of surgeon (fellowship-trained, surgical volume), implant (baseplate, bearing), and cement (brand, viscosity) that were associated with aseptic loosening.

Results

A total of 668 patients representing 742 knees were identified. Eighteen (2.4%) required a revision surgery. Aseptic loosening was the leading cause of revision surgery (n = 10, 55.6%). All failures due to aseptic loosening involved debonding of the tibial implant-cement interface. A multivariate analysis identified low-volume surgeons (9.0%, P < .0001) and 1 specific brand of high-viscosity cement (14.3%, P < .0001) as risk factors for aseptic loosening.

Conclusions

This study represents the largest nonregistry review of the original ATTUNE Knee System. Surgeon case volume and cement viscosity were factors associated with an increased rate of early failure due to tibial baseplate implant-cement interface debonding.

Outcomes are Better With a Medial-Stabilized vs a Posterior-Stabilized Total Knee Implanted With Kinematic Alignment

BACKGROUND

There is no consensus whether a posterior-stabilized (PS) total knee device is superior to a more congruent, cruciate-substituting, medial-stabilized device (MS). This study compared the clinical outcomes of these devices. The primary hypothesis was that the clinical outcomes would be better in the MS group implanted with kinematic alignment.

METHODS

This prospective, randomized, single-center Level 1 study compared the outcomes of 99 patients who received a PS device and 101 patients who received an MS device implanted with kinematic alignment. Institutional Review Board approval and informed consent were obtained. Clinical and radiographic assessments were performed preoperatively, 6 weeks, 6 months, and annually.

RESULTS

All subjects reached the minimum follow-up of 2 years. There were no statistically significant differences in demographic characteristics, preoperative scores, or alignment (preoperative or postoperative). Tourniquet time was 7.24% longer for the PS group (40.28 min vs 37.56 min, P < .0086). There were significant differences between groups for the 1-year and 2-year Knee Society scores, Forgotten Joint Score, and ROM; in every case favoring the MS group. The FJS was 68.3 in the MS group at 2 years and 58.3 in the PS group (P = .02). The maximum flexion at 2 years was 132° in the MS group and 124° in the PS group (P < .0001).

CONCLUSION

The clinical outcomes of the MS group at 1 and 2 years were better. At the minimum 2-year follow-up, the results demonstrate the superiority of the medial-stabilized device in terms of multiple clinical outcomes.

LEVEL OF EVIDENCE

I.

Chitranjan S. Ranawat Award: Motion During Total Knee Cementing Significantly Decreases Tibial Implant Fixation Strength

BACKGROUND

Aseptic tibial loosening following primary total knee arthroplasty persists despite technique and device-related advancements. The mechanisms for this mode of failure are not well understood. We hypothesized that knee movement while the cement was curing dispersed lipids at the implant-cement interface and would result in decreased tibial fixation strength.

METHODS

A cadaveric study was performed utilizing 32 torso-to-toe specimens (64 knees). Four contemporary total knee arthroplasty designs were evaluated. Each implant design was randomly assigned to a cadaveric specimen pair with side-to-side randomization. Specimen densitometry was recorded. Each tibial implant was cemented using a standard technique. On one side, the tibial component was held without motion following impaction until complete cement polymerization. The contralateral knee tibial implant was taken through gentle range of motion and stability assessment 7 minutes after cement mixing. Axial tibial pull-out strength and interface failure examination was performed on each specimen.

RESULTS

The average pull-out strength for the no motion cohort (5,462 N) exceeded the motion cohort (4,473 N) (P = .001). The mean pull-out strength between implant designs in the no motion cohort varied significantly (implant A: 7,230 N, B: 5,806 N, C: 5,325 N, D 3,486 N; P = .007). Similarly, the motion cohort inter-implant variance was significant (P ≤ .001). Intra-implant pull-out strength was significantly higher in implant A than D. The average pull-out strength was significantly lower in specimens that failed at the implant-cement interface vs bone failures (4,089 ± 2,158 N vs 5,960 ± 2,010 N, P < .0025).

CONCLUSION

Knee motion during cement polymerization is associated with significant decreases in tibial implant fixational strength. Reduction in implant pull-out strength was identified with each implant design with motion and varied between designs. Across all tested designs, we recommend limiting motion while cementing the tibial implant to improve fixation strength.

Comparative retrieval analysis of a novel anatomic tibial tray backside: alterations in tibial component design and surface coating can increase cement adhesions and surface roughness

BACKGROUND

With the Persona® knee system a novel anatomic total knee design was developed, which has no pre-coating, whereas the predecessor knee system is pre-coated with polymethylmethacrylate (PMMA). Joint registry data have shown no decrease in risk of aseptic revision of PMMA pre-coated tibial components compared with non-pre-coated implants. The aim of this retrieval study was to compare the amount of cement adhesions, geometry and surface features between the two knee designs and to correlate them with the underlying reason for revision surgery.

METHODS

Retrieval analysis was performed of 15 NexGen® and 8 Persona® fixed-bearing knee implants from the same manufacturer retrieved from two knee revision centres. A photogrammetric method was used to grade the amount of cement attached to the tibial tray backside. The geometry and dimensions of the tibial trays, tray projections and peripheral lips were measured using digital callipers and compared between the two different designs. To measure the surface roughness on the backside of the tibial tray, a contact profilometer was used. To investigate differences between the two designs statistical analyses (t-test) were performed.

RESULTS

All Persona® trays showed evidence of cement adhesion with a % area of 75.4%; half of the NexGen® trays had cement adhesions, with a mean value of 20%. There was a significant difference in the percentage of area covered by cement between the two designs (p < 0.001). Results from the contact profilometer revealed that Persona® and NexGen® tray backsides showed a similar lateral (1.36 μm and 1.10 μm) and medial (1.39 μm and 1.12 μm) mean surface roughness with significant differentiation (p < 0.05) of the lateral and medial roughness values between the two designs. Persona® stems showed a significantly higher mean surface roughness (1.26) compared to NexGen® stems (0.89; p < 0.05).

CONCLUSION

The novel anatomic knee system showed significantly more cements adhesions and a higher surface roughness which was most likely attributed to the most obvious design and coating alteration of the tibial tray. This study provides first retrieval findings of a novel TKA design recently introduced to the market.

Do Metaphyseal Cones and Stems Provide Any Biomechanical Advantage for Moderate Contained Tibial Defects in Revision TKA? A Finite-Element Analysis Based on a Cadaver Model

BACKGROUND

Satisfactory management of bone defects is important to achieve an adequate reconstruction in revision TKA. Metaphyseal cones to address such defects in the proximal tibia are increasingly being used; however, the biomechanical superiority of cones over traditional techniques like fully cementing the implant into the defect has not yet been demonstrated. Moreover, although long stems are often used to bypass the defects, the biomechanical efficacy of long stems compared with short, cemented stems when combined with metaphyseal cones remains unclear.

QUESTIONS/PURPOSES

We developed and validated finite-element models of nine cadaveric specimens to determine: (1) whether using cones for addressing moderate metaphyseal tibial defects in revision TKA reduces the risk of implant-cement debonding compared with cementing the implant alone, and (2) when using metaphyseal cones, whether long, uncemented stems (or diaphyseal-engaging stems) reduce the risk of implant-cement debonding and the cone-bone micromotions compared with short, cemented stems.

METHODS

We divided nine cadaveric specimens (six male, three female, aged 57 to 73 years, BMI 24 to 47 kg/m2) with standardized tibial metaphyseal defects into three study groups: no cone with short (50-mm) cemented stem, in which the defect was filled with cement; cone with short (50-mm) cemented stem, in which a metaphyseal cone was implanted before cementing the implant; and cone with long, diaphyseal-engaging stem, which received a metaphyseal cone and the largest 150-mm stem that could fit the diaphyseal canal. The specimens were implanted and mechanically tested. Then, we developed and validated finite-element models to investigate the interaction between the implant and the bone during the demanding activity of stair ascent. We quantified the risk of implant debonding from the cement mantle by comparing the axial and shear stress at the cement-implant interface against an experimentally derived interface failure index criterion that has been previously used to quantify the risk of cement debonding. We considered the risk of debonding to be minimal when the failure index was below 10% of the strength of the interface (or failure index < 0.1). We also quantified the micromotion between the cone and the bone, as a guide to the likelihood of fixation by bone ingrowth. To this end, we assumed bone ingrowth for micromotion values below the most restrictive reported threshold for bone ingrowth, 20 µm.

RESULTS

When using a short, 50-mm cemented stem and cement alone to fill the defect, 77% to 86% of the cement-implant interface had minimal risk of debonding (failure index < 0.1). When using a short, 50-mm cemented stem with a cone, 87% to 93% of the cement-implant interface had minimal debonding risk. When combining a cone with a long (150-mm) uncemented stem, 92% to 94% of the cement-implant interface had minimal debonding risk. The differences in cone-bone micromotion between short, cemented stems and long, uncemented stems were minimal and, for both configurations, most cones had micromotions below the most restrictive 20-µm threshold for ingrowth. However, the maximum micromotion between the cone and the bone was in general smaller when using a long, uncemented stem (13-23 µm) than when using a short, cemented stem (11-31 µm).

CONCLUSION

Although the risk of debonding was low in all cases, metaphyseal cones help reduce the biomechanical burden on the implant-cement interface of short-stemmed implants in high-demand activities such as stair ascent. When using cones in revision TKA, long, diaphyseal-engaging stems did not provide a clear biomechanical advantage over short stems. Future studies should explore additional loading conditions, quantify the interspecimen variability, consider more critical defects, and evaluate the behavior of the reconstructive techniques under repetitive loads.

CLINICAL RELEVANCE

Cones and stems are routinely used to address tibial defects in revision TKA. Despite our finding that metaphyseal cones may help reduce the risk of implant-cement debonding and allow using shorter stems with comparable biomechanical behavior to longer stems, either cones or cement alone can provide comparable results in contained metaphyseal defects. However, longer term clinical studies are needed to compare these techniques over time.

Tibial tray debonding from the cement mantle is associated with deformation of the backside of polyethylene tibial inserts

AIMS

The aim of this study was to investigate whether wear and backside deformation of polyethylene (PE) tibial inserts may influence the cement cover of tibial trays of explanted total knee arthroplasties (TKAs).

METHODS

At our retrieval centre, we measured changes in the wear and deformation of PE inserts using coordinate measuring machines and light microscopy. The amount of cement cover on the backside of tibial trays was quantified as a percentage of the total surface. The study involved data from the explanted fixed-bearing components of four widely used contemporary designs of TKA (Attune, NexGen, Press Fit Condylar (PFC), and Triathlon), revised for any indication, and we compared them with components that used previous generations of PE. Regression modelling was used to identify variables related to the amount of cement cover on the retrieved trays.

RESULTS

A total of 114 explanted fixed-bearing TKAs were examined. This included 76 used with contemporary PE inserts which were compared with 15 used with older generation PEs. The Attune and NexGen (central locking) trays were found to have significantly less cement cover than Triathlon and PFC trays (peripheral locking group) (p = 0.001). The median planicity values of the PE inserts used with central locking trays were significantly greater than of those with peripheral locking inserts (205 vs 85 microns; p < 0.001). Attune and NexGen inserts had a characteristic pattern of backside deformation, with the outer edges of the PE deviating inferiorly, leaving the PE margins as the primary areas of articulation.

CONCLUSION

Explanted TKAs with central locking mechanisms were significantly more likely to debond from the cement mantle. The PE inserts of these designs showed characteristic patterns of deformation, which appeared to relate to the manufacturing process and may be exacerbated in vivo. This pattern of deformation was associated with PE wear occurring at the outer edges of the articulation, potentially increasing the frictional torque generated at this interface. Cite this article: Bone Joint J 2021;103-B(12):1791-1801.