Skip to main content
NCBI home page
Wiley Open Access Collection logoLink to Wiley Open Access Collection
. 2026 Aug 23;44(9):e70266. doi: 10.1002/jor.70266

Comparative Wear Behavior of Titanium Nitride‐Coated Titanium and Cobalt Chromium Femoral Components in Cementless Total Knee Arthroplasty

Harold I Salmons 1, Kailey Fitzgerald 2, Sally LiArno 2, Behzad Farshid 2, Geoffrey H Westrich 1,✉
PMCID: PMC13499976  PMID: 42633553

ABSTRACT

Femoral component surface roughness is a critical determinant of polyethylene wear in total knee arthroplasty (TKA). Titanium nitride (TiN) ceramic surface coatings have been developed to improve wear resistance and address concerns related to metal hypersensitivity; however, comprehensive wear data remain limited. This knee simulator study evaluated the performance of TiN‐coated titanium alloy (6 wt% aluminum, 4 wt% vanadium, balance titanium, Ti‐6Al‐4V) substrate femoral components compared with cobalt chromium (CoCr) femoral components. Mode I wear testing was conducted for 5.0 million cycles (mc) using highly crosslinked polyethylene tibial inserts, with wear rates and polyethylene debris morphology quantified. Mode III third‐body abrasive wear testing was performed on TiN‐coated femoral components using embedded 500 µm TiN‐coated particles for 3.0 mc. Surface roughness was measured using White Light Interferometry (arithmetic mean height, Sa), and surface integrity was assessed using scanning electron microscopy. Following 5.0 mc of Mode I wear, volumetric wear rates were equivalent between TiN‐coated and CoCr femoral components (1.03 vs 1.04 mm3/million cycles; p = 0.001), with no notable differences in polyethylene particle size (p = 0.114) or morphology. During third‐body testing, surface scratching of the TiN coating was observed without evidence of gross surface failure. As anticipated, the mean Sa of TiN‐coated femoral components increased through 3.0 mc of Mode III third‐body testing, while remaining lower than literature‐reported retrieved CoCr values (p = 0.001). In conclusion, TiN‐coated femoral components demonstrated comparable in vitro adhesive wear performance to CoCr and provided improved resistance to abrasive conditions, where long‐term resistance to abrasion is expected to govern reduced wear.

Keywords: third‐body wear, titanium nitride‐coated, total knee replacements, wear testing

1. Introduction

Total knee arthroplasty (TKA) has revolutionized the care for patients with end‐stage osteoarthritis of the knee. Despite excellent long‐term clinical outcomes, wear‐induced osteolysis, especially under abrasive conditions with cobalt chromium (CoCr) components, remains an important cause of implant failure, motivating ongoing efforts to develop alternative implant designs and bearing materials that minimize wear risk [1, 2, 3].

Surface roughness of the femoral component has been identified as a significant contributor to polyethylene tibial insert wear [4, 5, 6]. Prior retrieval investigations comparing alternative bearing materials, such as oxidized zirconium, to traditional CoCr femoral components have demonstrated reduced surface roughness and improved wear performance in these alternative materials [5, 6, 7]. Additional studies have shown that surface roughness of CoCr femoral components increases over time, likely due to a combination of Mode I wear and Mode III third‐body wear [8, 9]. Consequently, bearing surfaces with enhanced resistance to surface roughening remain an important focus of implant development.

Up to 14% of patients presenting for TKA report hypersensitivity to metals such as nickel [10, 11]. Although the clinical significance of metal hypersensitivity in TKA remains unclear, some surgeons elect to minimize the use of nickel or cobalt chromium‐containing alloys when possible [11]. In response, ceramic surface treatments, including oxidized zirconium and titanium nitride (TiN), were developed, with prior reviews summarizing their potential advantages in wear resistance and biocompatibility [5, 6, 12, 13]. Registry data with approximately 10 years of follow‐up and reported clinical outcomes for coated femoral component technologies have not consistently demonstrated improved clinical outcomes relative to conventional CoCr femoral components [14, 15, 16, 17, 18, 19, 20]. Nevertheless, the potential to reduce wear while addressing concerns regarding metallurgical hypersensitivity remains compelling [2].

Despite its biological inertness, high surface hardness, and proposed favorable wear characteristics, data regarding the wear performance, resistance to third‐body abrasion, and high‐resolution surface characterization of TiN‐coated femoral components remain limited [2, 21]. Retrieval analyses have identified third‐body abrasion and localized surface damage as clinically relevant failure modes, underscoring the importance of investigating coating performance under abrasive conditions [18, 19, 22, 23]. Therefore, the purpose of this study was to rigorously evaluate a newly introduced TiN‐coated titanium alloy (6 wt% aluminum, 4 wt% vanadium, balance titanium, Ti‐6Al‐4V) substrate femoral component under high‐stress, simulated Mode I and Mode III wear conditions [24]. We hypothesized that TiN‐coated components would demonstrate similar wear under Mode I wear conditions with superior resistance to surface roughening under Mode III third‐body wear conditions when compared to CoCr retrievals in literature.

2. Materials and Methods

In order to assess the wear performance of TiN‐coated Ti‐6Al‐4V femoral components (Triathlon Gold, Stryker, Mahwah, NJ), testing was conducted to simulate two distinct wear mechanisms: Mode I wear and Mode III third‐body wear as described by McKellop [24]. Mode I testing was performed to determine the wear rate generated primarily by adhesive interactions from articulation between the femoral component and the highly cross‐linked polyethylene insert. Adhesive wear occurs during sliding due to the micro‐welding at asperities between the two surfaces [25]. Abrasive wear, experienced during Mode III wear, occurs due to ploughing or cutting from contact with a harder particle or surface [25]. Mode III testing evaluated the TiN coating's resistance to damage caused by third‐body particles introduced into the region of contact. Testing for both methodologies are described below.

2.1. Mode I Wear Testing

Three TiN‐coated Ti‐6Al‐4V substrate femoral components (Triathlon Gold, Stryker, Mahwah, NJ) and three CoCr femoral components (Triathlon, Stryker, Mahwah, NJ), all of equivalent surface geometry, were utilized for this study. All femoral components were size 1 and articulated on a corresponding size 1, 9 mm thick highly crosslinked tibial insert (Triathlon X3, Stryker, Mahwah, NJ) seated in a size 1 titanium baseplate (Triathlon Tritanium, Stryker, Mahwah, NJ). Because the coating was the primary focus of this study and fatigue wear is considered most critical for coating evaluations, size 1 femoral components, the smallest femoral component in this system, were selected as the worst‐case evaluation [26]. The size 1 femoral components result in the lowest contact area and in turn, produce the highest contact stress, which is the main driver of fatigue wear and known to exacerbate surface damage during adhesive and abrasive wear mechanisms [27, 28, 29]. Two additional tibial inserts served as static soak controls to correct for net weight gain due to fluid absorption per ISO 14243‐2 [30] and ASTM F2025 [31].

Prior to testing, both the tibial inserts used as test specimens and those used as soak controls underwent pre‐soaking for 21 days in deionized (DI) water at 37° C to minimize the effects of initial fluid absorption. All components were cleaned and weighed using a balance with a resolution of 0.01 mg and a repeatability of 0.02 mg prior to the initial test setup.

A six‐station knee joint simulator (MTS, Eden Prairie, MN) was utilized and all components tested in accordance with ISO 14243‐3 [32]. Prior to testing, the femoral and tibial components were aligned in a CAD‐defined reference position and centered within the simulator to establish the initial anterior‐posterior (AP) and medio‐lateral (ML) alignment of the articulation. Varus/valgus freedom is applied by means of a pivot located in the tibial assembly. The femur was cemented with bone cement to the flexion arm fixture, which provided flexion as well as AP translation of the femur with respect to the tibia. The tibial insert was placed in the tibial baseplate, which was cemented into the tibial specimen chamber and centered under the femoral component. The axial load and internal‐external (IE) rotation were provided through the tibial specimen chamber via an axial/torsional actuator. The tibial specimen chambers were filled with Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) to ensure the specimens were fully submerged and lubricated during testing. The Alpha Calf Fraction serum was diluted to 50% using DI water to obtain a physiologically relevant protein level (20 g/L) [33] and combined with Gentamicin (5 mL/L) and Amphotericin B (10 mL/L) to retard serum decomposition. The resulting serum solution was filtered (0.2 µm) prior to use. The test setup is shown below in Figure 1. Testing was conducted for 5.0 mc with the test stopping every 0.5 mc to clean and weigh the tibial inserts, as well as visually inspect all wear scars.

Figure 1.

Figure 1

Open in a new tab

Schematic diagram of the test setup with the knee joint simulator (MTS, Eden Prairie, MN) based on ISO 14243‐3 [32], shown in the CAD‐defined reference position used for alignment. Machine components have been labeled for clarity.

At the completion of testing, the mass data from the tibial inserts was utilized to determine gravimetric weight loss and to convert the gravimetric weight loss to volume loss and volumetric wear rate for each sample in accordance with ISO 14243‐2 [30] and ASTM F2025 [31]. The mean ± standard deviation volumetric wear rate was determined for each group and reported to the first uncertain digit. A two‐sample equivalence test, with a confidence level of 95%, a power level of 80%, and equivalence margin of 2.00 mm3/mc, was performed to determine if the mean volumetric wear rate was equivalent between groups. The equivalence margin was determined by taking the difference between the highest observed mean from a historical, unpublished CoCr wear data set generated under the same testing conditions and the mean expected value for this test. This difference yielded a margin of 4.00 mm3/mc. To produce a more conservative test, the value was halved and a margin of 2.00 mm3/mc was utilized.

Lastly, serum from the final interval of testing (4.5 mc–5.0 mc) was sent to an outside vendor (Lucideon M + P, Greenville, SC) for testing to characterize the polyethylene debris particles. Serum from each simulator station was stirred, poured into a sterile container, refrigerated, and shipped overnight. In accordance with ISO 17853: 2011 [34] the serum was combined with hydrochloric acid and digested for 60 min at 50°C. Following digestion, the solution was combined with methanol and filtered onto a gold sputter‐coated 0.1 µm polycarbonate filter. The dried filter was imaged using a field‐emission scanning electron microscope (FE‐SEM) at a nominal magnification of 600X to obtain an adequate field of view, with measurements verified at 1600X and representative particle images captured at 2000X. Particles were isolated and characterized using methods described in ASTM F1877‐16 [35]. Measurements were provided for the following parameters in accordance with ASTM F1877‐16: aspect ratio, perimeter, form factor, roundness, equivalent circle diameter (ECD), and feret diameter (or length; representative of the particle size) [35]. A two‐sample Mann–Whitney U test was conducted at a 95% confidence level (α = 0.05) to determine whether the median feret diameters, as a representative of particle size, of the two populations were significantly different.

2.2. Mode III Third‐Body Wear Testing

To further stress the TiN coating, the three TiN‐coated Ti‐6Al‐4V femoral components underwent additional testing under abrasive third‐body conditions. One 500 µm TiN‐coated Ti‐6Al‐4V substrate particle was embedded in the center of the articulating region on each condyle of three new polyethylene inserts to simulate third‐body wear mechanisms as seen in Figure 2. Upon review of the literature, it was determined that particles do not typically embed directly in the insert and are more commonly found in surrounding soft tissue where they would not contribute to third‐body wear [36, 37, 38]. However, to stress the TiN coating, two TiN‐coated particles (one per condyle) were selected using the conservative assumption that all particles typically found in the joint and surrounding tissue embed in the polyethylene insert [37, 38]. To further increase the potential for coating damage, larger particles (500 µm) were used, in contrast to the much smaller metal and ceramic particles (< 50 µm) typically reported in retrieval studies [37, 38].

Figure 2.

Figure 2

Open in a new tab

Representative image of the inserts used to simulate third‐body conditions. The yellow arrows specify the location of the embedded 500 µm TiN‐coated Ti‐6Al‐4V particles.

Prior to testing, White Light Interferometry (WLI) (Zygo NewView 9000, Ametek, Middlefield, CT) was obtained on all femoral components to obtain the arithmetic mean height of the surface (surface roughness, Sa). Surface characterization was performed using a 10× objective lens and a 150 µm scan length, applying a 4th‐order polynomial surface removal to isolate texture from the overall part geometry. Each femoral component was secured with stable fixtures to obtain 18 measurement points: 9 points on the medial condyle and 9 points on the lateral condyle, all equally spaced from the posterior flange to the extension. The mean surface roughness for each component was calculated as the mean of the Sa values obtained from these 18 measurements. Scanning electron microscopy (SEM) (Quanta 650 Field Emission Microscope, Thermo Fisher Scientific, Waltham MA) was also performed on the femoral components to complement the WLI measurements described above and to provide a more detailed characterization of the TiN coating. SEM at high magnifications was focused on regions exhibiting notable surface features (such as scratches or material transfer) identified either by initial visual inspection or during the early stages of SEM setup while using finer magnifications and high rastering speeds.

Testing under third‐body conditions was conducted for 3.0 mc with the knee joint simulator (MTS, Eden Prairie, MN) in accordance with ISO 14243‐3 [32] as described for the Mode I wear test above. The test was stopped every 0.5 mc to hand clean and inspect the inserts, as well as obtain WLI data on the femoral components following the methods described for the Mode I wear test. During inspection, if the third‐body particle was deemed dislodged, a new particle was embedded on the polyethylene insert.

At the completion of testing, WLI and SEM data was obtained for all femoral components. The SEM data was qualitatively assessed for the failure mode of interest (adhesion failure) in accordance with ASTM C1624‐22 [39]. In addition, the mean ± standard deviation for the WLI data was determined. A literature search was conducted to identify studies that quantified the mean surface roughness of retrieved CoCr femoral components. The initial search yielded several studies reporting surface roughness measurements for explanted components; however, only a subset described implants that exhibited clear evidence of abrasive wear or extensive surface damage consistent with third‑body abrasion. Because the third‑body wear simulator protocol used in this study imposes more aggressive abrasive conditions than those typically encountered in vivo, the search was narrowed to studies whose reported damage patterns were sufficiently severe to provide meaningful comparison. Three studies were selected which included implants from different manufacturers with a range of implantation durations and revision indications. Due to the limited availability of retrieval data reporting areal roughness (Sa), studies reporting profile roughness (Ra) were included to provide a benchmark of surface damage severity. While Ra and Sa are not directly interchangeable, both describe surface height variation and are considered here for comparison within the same material system. Together, these studies provided sufficient variability to generate an estimate of the change in surface roughness over time in vivo for retrieved CoCr components subjected to abrasive conditions. Table 1 presents the mean surface roughness values for pristine and retrieved components reported by Muratoglu, Heyse, and Levesque, along with the corresponding measurement methods and standard deviations where available [1, 6, 40]. These values were subsequently averaged to determine a representative mean surface roughness for retrieved CoCr femoral components exposed to third‐body conditions in vivo [1, 6, 40]. The surface roughness data from the TiN‐coated Ti‐6Al‐4V femurs after third‐body testing was compared with mean surface roughness value determined from the literature for retrieved CoCr femoral components [1, 6, 40]. A one‐sample t‐test was used to determine whether the mean surface roughness for the TiN‐coated Ti‐6Al‐4V femurs in this study was significantly different than the mean surface roughness for retrieved CoCr femoral components.

Table 1.

Surface roughness values for non‐implanted and retrieved components from each of the three studies used to derive the means shown in Figure 9. Note that the values for Muratoglu et al. were reported individually for each condyle and averaged. Values for both cemented and cementless components were reported from Levesque et al. Measurement technique and roughness parameter (Ra or Sa) are specified for each study, with standard deviations included where available.

Reference Roughness for non‐implanted CoCr components (nm) Roughness for retrieved CoCr components (nm) Methods
Muratoglu [1] 80 146 ± 43 Surface profilometry, Ra
Heyse [6] 40 ± 10 210 ± 210 Optical interferometry, Sa
Levesque, cemented [40] 10 200 ± 100 Optical interferometry, Ra
Levesque, uncemented [40] 10 500 ± 300 Optical interferometry, Ra
Open in a new tab

3. Results

3.1. Mode I Wear Testing

Following 5.0 mc of Mode I wear testing, the worn tibial inserts for the two groups showed typical wear polishing or burnishing, deformation, striations, and scratches with no visual differences between groups. Machining marks remained visible in regions of non‐contact. No surface or sub‐surface cracks, pits or delamination were observed on any of the samples (Figure 3). The corresponding wear rate of the tibial inserts from the CoCr and TiN‐coated Ti‐6Al‐4V groups were found to be equivalent with a p‐value of 0.001 (Figure 4). Table 2 shows the volumetric wear rates for each individual CoCr and TiN‐coated Ti‐6Al‐4V sample, along with the mean and standard deviation for each group.

Figure 3.

Figure 3

Open in a new tab

Typical worn insert samples for CoCr (Left) and TiN‐coated Ti‐6Al‐4V (Right) groups following 5.0 mc of Mode I wear testing. The bottom images show the wear scars outlined for clarity. Burnishing is seen on the articular surface.

Figure 4.

Figure 4

Open in a new tab

Mean volumetric wear rate for the CoCr and TiN‐coated Ti‐6Al‐4V groups through 5.0 mc of Mode I wear testing. Wear rates for the two groups were found to be equivalent with a p‐value of 0.001.

Table 2.

Volumetric wear rates for each individual CoCr and TiN‐coated Ti‐6Al‐4V samples through 5.0 mc of Mode I wear testing along with the mean and standard deviation for each group.

Volumetric wear rate (mm3/mc)
CoCr TiN‐coated
0.88 0.93
1.11 0.60
1.12 1.55
Mean 1.04 Mean 1.03
STDV 0.14 STDV 0.48
Open in a new tab

Typical femoral components after 5.0 mc of Mode I wear testing from the CoCr and TiN‐coated Ti‐6Al‐4V groups are shown in Figure 5. Surface scratches were observed for all femoral components.

Figure 5.

Figure 5

Open in a new tab

The top image shows typical femoral components for the CoCr (left) and TiN‐coated Ti‐6Al‐4V (right) groups after 5.0 mc of adhesive wear testing. Surface scratches can be seen along the articulating path for all femoral components. The bottom image shows representative white light interferometry (WLI) images of the scratches shown in the top image, acquired using a Zygo NewView 9000 (Ametek, Middlefield, CT).

Figure 6 shows the mean particle morphology and size parameters measured in the polyethylene debris particle characterization conducted using serum from the final interval of testing (4.5 mc–5.0 mc). 679 particles from the CoCr group (station 1 = 269 particles, station 3 = 186 particles and station 5 = 224 particles) and 1024 particles from the TiN coated group (Station 2 = 421 particles, Station 4 = 242 particles, Station 6 = 361 particles) were analyzed in accordance with ISO 17853: 2011 [34]. As can be seen in Figure 6, all particles fell in similar ranges for each parameter studied. Furthermore, the feret diameter for the TiN‐coated Ti‐6Al‐4V group was found to not be significantly different (p = 0.114) than the CoCr group, suggesting that the osteolytic response for both groups will be similar.

Figure 6.

Figure 6

Open in a new tab

Mean particle morphology and size measurements per population group. 679 particles from the CoCr group (station 1 = 269 particles, station 3 = 186 particles and station 5 = 224 particles) and 1024 particles from the TiN coated group (Station 2 = 421 particles, Station 4 = 242 particles, Station 6 = 361 particles) were analyzed in accordance with ISO 17853: 2011 [34].

3.2. Third‐Body Abrasive Wear Testing

Scratches were observed for each of the TiN‐coated Ti‐6Al‐4V femoral components following third‐body testing as seen in Figure 7. The TiN‐coated Ti‐6Al‐4V femurs showed no signs of cracking, delamination, gross spallation, or substrate exposure as supported by the SEM data (Figure 8). As expected, the roughness of the TiN‐coated Ti‐6Al‐4V femoral components increased throughout the course of third‐body testing due to the introduction of scratches to the coating (Figure 7). That said, the mean Sa for the TiN‐coated Ti‐6Al‐4V femoral components after 3.0 mc of third‐body testing (Figure 9) was lower than roughness values observed on retrieved CoCr femurs in literature (Figure 9). A one‐sample t‐test confirmed that the mean surface roughness reported for CoCr femurs (264 nm) [1, 6, 40] was significantly different than the mean surface roughness for the TiN‐coated femurs in this study (85 nm) with a p value of 0.001.

Figure 7.

Figure 7

Open in a new tab

The left image shows a representative image of the scratches observed on a TiN‐coated Ti‐6Al‐4V femoral component following 3.0 mc of third‐body testing (8.0 mc of total testing). Arrows indicate the direction and location of scratches. The right image shows a representative white light interferometry (WLI) image of a scratch acquired using a Zygo NewView 9000 (Ametek, Middlefield, CT).

Figure 8.

Figure 8

Open in a new tab

Representative SEM micrographs of the surface of a TiN‐coated Ti‐6Al‐4V femoral component following 3.0 mc of third‐body testing (8.0 mc total testing). The left image was acquired in backscattered‐electron (BSE) mode, and the right image in secondary‐electron topography (Topo) mode. Black arrows indicate shallow surface scratches, and red arrows indicate limited third‐body material transfer.

Figure 9.

Figure 9

Open in a new tab

Mean surface roughness (Sa) of TiN‐coated Ti‐6Al‐4V femurs before and after 3.0 mc of third‐body testing (8.0 mc of total testing) compared with mean values for nonimplanted and retrieved CoCr femurs found in the literature [1, 6, 40].

4. Discussion

The present investigation evaluated the Mode I and Mode III third‐body wear characteristics of a new TiN‐coated Ti‐6Al‐4v substrate femoral component compared with traditional CoCr femoral components in TKA. The principal findings of this study included equivalent polyethylene wear rates between TiN‐coated and CoCr femoral components under Mode I conditions, similar polyethylene debris size and morphology between groups, increased roughening under third‐body abrasive conditions in TiN‐coated femoral components, without evidence of catastrophic coating damage, and significantly lower final surface roughness of TiN‐coated femoral components compared with literature‐reported CoCr values [1, 6, 40].

Wear‐related failure mechanisms in TKA remain incompletely resolved. Although the introduction of highly crosslinked polyethylene (HXLPE) tibial inserts has substantially reduced wear, femoral component surface roughness continues to play an important role in contributing to Mode I wear between the implant and the tibial polyethylene insert [41, 42, 43]. While CoCr has historically been the femoral material of choice, ceramic‐based surface treatments were developed to leverage increased material hardness and reduced surface roughness to further mitigate wear‐related failure [5, 9, 43]. In the present study, Mode I wear rates for TiN‐coated and CoCr femoral components were 1.03 and 1.04 mm3/million cycles, respectively. These values, along with visual assessment of the polyethylene inserts (Figure 3), indicate only mild wear for both study groups. These values were consistent with or lower than previously reported wear rates for contemporary TKA reported in the literature, with Okazaki et al. recommending a wear rate of 3.0 mm3/mc for the development of new knee joints with highly crosslinked polyethylene and Essner et al. and Schmidig et al. reporting wear rates of 7.3 ± 0.7 mm3/mc, 1.3 ± 0.4, respectively [44, 45, 46]. The Mode I wear rates in this study support the durable performance of both materials. Additionally, the polyethylene debris particles collected during the final testing interval (4.5–5.0 million cycles) showed no notable difference in size and morphology between the CoCr and TiN‐coated femoral components (Figure 6). Furthermore, the mean diameter for the polyethylene debris particles did not differ significantly between groups (p = 0.114), with particle sizes ranging from 0.1 to 10 µm—consistent with ranges reported for conventional TKA systems [47, 48]. These findings suggest that TiN‐coated femoral components do not increase the risk of wear‐induced osteolysis relative to traditional CoCr femoral components.

Although the TiN‐coated and CoCr femoral components exhibited similar initial surface roughness, long‐term resistance to abrasion is expected to govern reduced wear for TiN‐coated femoral components [49, 50]. Therefore, testing under Mode III conditions was critical to confirm this resistance and evaluate the coating integrity. Retention of bone, cement, metallic or ceramic debris within the joint is not uncommon and may contribute to clinically relevant Mode III third‐body abrasive wear [43]. This study therefore rigorously evaluated third‐body wear effects on TiN‐coated femoral components. As anticipated, scratching of the TiN coating was observed following third‐body testing; however, no evidence of severe damage—including cracking, delamination, gross spallation, or substrate exposure—was identified through visual, WLI, and SEM analysis. As anticipated, the mean Sa of the TiN‐coated femoral components increased over the course of 3.0 mc of third‐body testing with embedded 500 µm TiN‐coated particles (85 nm) while remaining significantly lower than reported roughness values for retrieved CoCr components (264 nm; p = 0.001) [1, 6, 40]. Notably, clinical retrieval data reported by Basgul et al. further support the durability of the TiN coating, demonstrating that no revisions were attributed to coating failure and that coating coverage remained intact without evidence of gross spallation across three total knee and five total hip retrievals. Mean implantation durations were 4.25 years for knee retrievals (range, 1.75–5.25 years) and 17.5 years for hip retrievals (range, 0.25–26 years), respectively [51]. These findings are consistent with the present results, which demonstrate maintained surface integrity under third‐body wear conditions, further reinforcing the robustness of TiN‐coated femoral components.

Collectively, these findings indicated favorable resistance to surface degradation of TiN‐coated femoral components under third‐body wear conditions.

This knee simulation study has several clinically relevant implications. In addition to demonstrating superior resistance to surface roughening under third‐body wear conditions in vitro in comparison to the retrieved CoCr femoral components in the literature, TiN‐coated femoral components may provide an option to patients with metal sensitivity concerns [2]. Dissatisfaction rates following TKA remain between 10% and 15% [52, 53, 54]. While the role of metal hypersensitivity in suboptimal outcomes is not well defined, minimizing the potential for implant‐related adverse reactions and maintaining durable wear performance are clinically appealing [2, 10, 11]. Existing data on this technology is compelling, with midterm clinical evidence and registry data supporting equivalent clinical outcomes between TiN‐coated versus uncoated TKAs [2, 14, 15, 16, 17, 18, 19, 20].

This study has several limitations. As a simulation‐based investigation, the sample size was necessarily limited; however, a rigorous testing protocol incorporating 5.0 mc of Mode I wear testing and 3.0 mc of abrasive wear testing was employed to assess implant performance under demanding conditions. Although limited sample size and low magnitudes contribute to variability in the measured wear rates, standard deviations observed during the Mode I testing in this study are consistent with what is typically reported in simulator‐based wear studies [44, 45, 46]. While the embedding procedure prevented polyethylene wear rate determination during abrasive testing, this evaluation demonstrated the TiN coating's improved resistance to abrasion, which is expected to result in long term improvements in wear [49, 50]. Additionally, third‐body roughness data for CoCr femoral components were based on values reported in the literature. While this represents a limitation, the TiN‐coated femoral components in the present study were subjected to more aggressive conditions than those expected in vivo, such that comparison to reported surface roughness values of explanted CoCr components represents a conservative benchmark. Inclusion of data from multiple manufacturers enhances the generalizability of these comparisons. Finally, as this was an in vitro biomechanical analysis, future in vivo investigations are required to more definitively assess long‐term clinical performance.

In conclusion, this study demonstrated equivalent Mode I wear rates, similar polyethylene debris characteristics, and improved resistance to third‐body abrasive surface roughening in a TiN‐coated Ti‐6Al‐4V femoral component compared with conventional CoCr alternatives. These findings support TiN‐coated femoral components as an alternative bearing surface in TKA with advantages in resisting abrasion and potentially mitigating wear. Further clinical studies are warranted to confirm these findings in vivo.

Author Contributions

All authors (H.I.S., K.F., S.L., B.F., G.H.W.) significantly contributed to the conduction of the present investigation, including data collection, manuscript preparation, revisions, and finalization. All authors have read and approved the final submitted manuscript.

Acknowledgments

The authors would like to thank Stryker Corporation (Mahwah, NJ, USA) for its financial and logistical support. Dr. Westrich's disclosures include the receipt of IP royalties, paid consultant, paid presenter or speaker and research support from Stryker. Ms. Fitzgerald and Dr. Farshid are paid employees of Stryker. Dr. LiArno is a paid employee of Stryker and holds stock or stock options. Dr. Salmons has no disclosures.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

References

  • 1. Muratoglu O. K., Burroughs B. R., Bragdon C. R., Christensen S., Lozynsky A., and Harris W. H., “Knee Simulator Wear of Polyethylene Tibias Articulating against Explanted Rough Femoral Components,” Clinical Orthopaedics & Related Research 428 (2004): 108–113, 10.1097/01.blo.0000143801.41885.8b. [DOI] [PubMed] [Google Scholar]
  • 2. Deroche E., Batailler C., Shatrov J., Gunst S., Servien E., and Lustig S., “No Clinical Difference at Mid‐Term Follow‐Up between Tin‐Coated Versus Uncoated Cemented Mobile‐Bearing Total Knee Arthroplasty: A Matched Cohort Study,” SICOT‐J 9 (2023): 5, 10.1051/sicotj/2023001. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 3. Asher D. P., Wright J. L., Hall D. J., et al., “Is Wear Still a Concern in Total Knee Arthroplasty With Contemporary Conventional and Highly Crosslinked Polyethylene Tibial Inserts in the Mid‐ to Long‐Term?,” Arthroplasty Today 30 (2024): 101550, 10.1016/j.artd.2024.101550. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 4. Kennard E., Scholes S. C., Sidaginamale R., et al., “A Comparative Surface Topographical Analysis of Explanted Total Knee Replacement Prostheses: Oxidised Zirconium vs Cobalt Chromium Femoral Components,” Medical Engineering & Physics 50 (2017): 59–64, 10.1016/j.medengphy.2017.10.003. [DOI] [PubMed] [Google Scholar]
  • 5. Brandt J. M., Guenther L., O'Brien S., Vecherya A., Turgeon T. R., and Bohm E. R., “Performance Assessment of Femoral Knee Components Made From Cobalt‐Chromium Alloy and Oxidized Zirconium,” Knee 20, no. 6 (2013): 388–396, 10.1016/j.knee.2013.01.004. [DOI] [PubMed] [Google Scholar]
  • 6. Heyse T. J., Elpers M. E., Nawabi D. H., Wright T. M., and Haas S. B., “Oxidized Zirconium Versus Cobalt‐Chromium in TKA: Profilometry of Retrieved Femoral Components,” Clinical Orthopaedics & Related Research 472, no. 1 (2014): 277–283, 10.1007/s11999-013-3078-4. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 7. Fabry C., Zietz C., Baumann A., Ehall R., and Bader R., “High Wear Resistance of Femoral Components Coated With Titanium Nitride: A Retrieval Analysis,” Knee Surgery, Sports Traumatology, Arthroscopy 26, no. 9 (2018): 2630–2639, 10.1007/s00167-017-4578-7. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 8. Arnholt C. M., MacDonald D. W., Klein G. R., et al., “What Is the Incidence of Cobalt‐Chromium Damage Modes on the Bearing Surface of Contemporary Femoral Component Designs for Total Knee Arthroplasty?,” Journal of Arthroplasty 33, no. 10 (2018): 3313–3319, 10.1016/j.arth.2018.05.020. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9. Roy M. E., Whiteside L. A., Ly K. K., and Gauvain M. J., “Cobalt‐Chromium Femoral Components Developed Scratches and Released Metal Debris in Simulated Wear Whereas Ceramic Femoral Components Did Not,” supplement, Bone & Joint Journal 103–B, no. 6 Supple A (2021): 94–101, 10.1302/0301-620X.103B6.BJJ-2020-2429.R1. [DOI] [PubMed] [Google Scholar]
  • 10. Desai M. M., Shah K. A., Mohapatra A., and Patel D. C., “Prevalence of Metal Hypersensitivity in Total Knee Replacement,” Journal of Orthopaedics 16, no. 6 (2019): 468–472, 10.1016/j.jor.2019.05.005. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 11. Bloemke A. and Clarke H., “Prevalence of Self‐Reported Metal Allergy in Patients Undergoing Primary Total Knee Arthroplasty,” Journal of Knee Surgery 28, no. 3 (2015): 243–246, 10.1055/s-0034-1381959. [DOI] [PubMed] [Google Scholar]
  • 12. Skjöldebrand C., Tipper J. L., Hatto P., Bryant M., Hall R. M., and Persson C., “Current Status and Future Potential of Wear‐Resistant Coatings and Articulating Surfaces for Hip and Knee Implants,” Materials Today Bio 15 (2022): 100270, 10.1016/j.mtbio.2022.100270. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 13. van Hove R. P., Sierevelt I. N., van Royen B. J., and Nolte P. A., “Titanium‐Nitride Coating of Orthopaedic Implants: A Review of the Literature,” BioMed Research International 2015 (2015): 485975, 10.1155/2015/485975. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 14. Glover A. W., Santini A. J. A., Davidson J. S., and Pope J. A., “Mid‐ to Long‐Term Survivorship of Oxidised Zirconium Total Knee Replacements Performed in Patients Under 50years of Age,” Knee 25, no. 4 (2018): 617–622, 10.1016/j.knee.2018.03.014. [DOI] [PubMed] [Google Scholar]
  • 15. Endoprothesenregister Deutschland (EPRD) ., EPRD Annual Report 2025 [Internet] (Berlin, Germany: Endoprothesenregister Deutschland (EPRD), 2026), https://www.eprd.de/en/. [Google Scholar]
  • 16. Fennelly J. T., Papalexandris S., Pope J., Yorke J., Davidson J. S., and Santini A. J., “Fifteen‐Year Survival Analysis of an Oxidised Zirconium Total Knee Arthroplasty,” Knee 45 (2023): 128–136, 10.1016/j.knee.2023.10.012. [DOI] [PubMed] [Google Scholar]
  • 17. Thienpont E., “Titanium Niobium Nitride Knee Implants Are Not Inferior to Chrome Cobalt Components for Primary Total Knee Arthroplasty at Medium‐Term Follow‐Up,” Archives of Orthopaedic and Trauma Surgery 143, no. 8 (2023): 5269–5275, 10.1007/s00402-022-04754-1. [DOI] [PubMed] [Google Scholar]
  • 18. D'Ambrosi R., Nuara A., Mariani I., Di Feo F., Ursino N., and Hirschmann M., “Titanium Niobium Nitride Mobile‐Bearing Unicompartmental Knee Arthroplasty Results in Good to Excellent Clinical and Radiographic Outcomes in Metal Allergy Patients With Medial Knee Osteoarthritis,” Journal of Arthroplasty 36, no. 1 (2021): 140–147.e2, 10.1016/j.arth.2020.07.028. [DOI] [PubMed] [Google Scholar]
  • 19. Łapaj Ł. and Rozwalka J., “Retrieval Analysis of TiN (Titanium nitride) Coated Knee Replacements: Coating Wear and Degradation In Vivo,” Journal of Biomedical Materials Research, Part B: Applied Biomaterials 108, no. 4 (2020): 1251–1261, 10.1002/jbm.b.34473. [DOI] [PubMed] [Google Scholar]
  • 20. Ahmed I., Salmon L. J., Waller A., Watanabe H., Roe J. P., and Pinczewski L. A., “Total Knee Arthroplasty With an Oxidised Zirconium Femoral Component: Ten‐Year Survivorship Analysis,” Bone & Joint Journal 98–B, no. 1 (2016): 58–64, 10.1302/0301-620X.98B1.36314. [DOI] [PubMed] [Google Scholar]
  • 21. Breugem S. J. M., Linnartz J., Sierevelt I., Bruijn J. D., and Driessen M. J. M., “Evaluation of 1031 Primary Titanium Nitride Coated Mobile Bearing Total Knee Arthroplasties in an Orthopedic Clinic,” World Journal of Orthopedics 8, no. 12 (2017): 922–928, 10.5312/wjo.v8.i12.922. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 22. Herbster M., Döring J., Nohava J., Lohmann C. H., Halle T., and Bertrand J., “Retrieval Study of Commercially Available Knee Implant Coatings TiN, TiNbn and ZrN on TiAl6V4 and CoCr28Mo6,” Journal of the Mechanical Behavior of Biomedical Materials 112 (2020): 104034, 10.1016/j.jmbbm.2020.104034. [DOI] [PubMed] [Google Scholar]
  • 23. Bormann T., Kraenzler S., Jaeger S., et al., “Stability of Ceramic Coatings on Retrieved Knee Prostheses,” Journal of the Mechanical Behavior of Biomedical Materials 144 (2023): 105997, 10.1016/j.jmbbm.2023.105997. [DOI] [PubMed] [Google Scholar]
  • 24. McKellop H. A., “The Lexicon of Polyethylene Wear in Artificial Joints,” Biomaterials 28, no. 34 (2007): 5049–5057, 10.1016/j.biomaterials.2007.07.040. [DOI] [PubMed] [Google Scholar]
  • 25. Powell S. N., Nadeem‐Tariq A., Kazemeini S., et al., “Tribological Failure in Modern Total Hip Arthroplasty: A Narrative Review of Third‐Body Wear, Oxidative Degradation, and Cross‐Linked Polyethylene Longevity,” Cureus 18, no. 2 (2026): e104167, 10.7759/cureus.104167. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26. Bull S. J. and Berasetegui E. G., “An Overview of the Potential of Quantitative Coating Adhesion Measurement by Scratch Testing,” Tribology International 39, no. 2 (2006): 99–114, 10.1016/j.triboint.2005.04.013. [DOI] [Google Scholar]
  • 27. Ries M. D., “Wear in Conventional and Highly Cross‐Linked Polyethylene,” in Total Knee Arthroplasty: A Guide to Get Better Performance [Internet], eds. Bellemans J., Ries M. D., and Victor J. M. K. (Springer, 2005), 361–364, 10.1007/3-540-27658-0_57. [DOI] [Google Scholar]
  • 28. Affatato S., Spinelli M., Zavalloni M., Mazzega‐Fabbro C., and Viceconti M., “Tribology and Total Hip Joint Replacement: Current Concepts in Mechanical Simulation,” Medical Engineering & Physics 30, no. 10 (2008): 1305–1317, 10.1016/j.medengphy.2008.07.006. [DOI] [PubMed] [Google Scholar]
  • 29. Varshney M. K., “Tribology and Bearing Surfaces for Hip (Including Ceramics),” in Essential Orthopedics (Jaypee Brothers Medical Publishers, 2016). [Google Scholar]
  • 30. ISO 14243‐2 ‐ Implants for Surgery ‐ Wear of Total Knee‐Joint Prostheses Part 2: Methods of Measurement (International Organization for Standardization (ISO), 2016). [Google Scholar]
  • 31. ASTM F2025‐06 ., Standard Practice for Gravimetric Measurement of Polymeric Components for Wear Assessment (ASTM International, 2025). 2025. [Google Scholar]
  • 32. ISO 14243‐3 + A1 ‐ Implants for Surgery — Wear of Total Knee‐Joint Prostheses Part 3: Loading and Displacement Parameters for Wear‐Testing Machines With Displacement Control and Corresponding Environmental Conditions for Test (International Organization for Standardization (ISO), 2016). [Google Scholar]
  • 33. Wang A., Essner A., and Schmidig G., “The Effects of Lubricant Composition on In Vitro Wear Testing of Polymeric Acetabular Components,” Journal of Biomedical Materials Research, Part B: Applied Biomaterials 68, no. 1 (2004): 45–52, 10.1002/jbm.b.10077. [DOI] [PubMed] [Google Scholar]
  • 34. ISO 17853 ‐ Wear of Implant Materials ‐ Polymer and Metal Wear Particles ‐ Isolation and Characterization (International Organization for Standardization (ISO), 2011). [Google Scholar]
  • 35. ASTM F1877‐24: Standard Practice for Characterization of Particles (ASTM International, 2024). [Google Scholar]
  • 36. Ho J., Mahajan J., Taylor M., Byers A., Arauz P., and Kwon Y. M., “Metallosis in Cemented Titanium Alloy Total Knee Arthroplasty Without Apparent Metal‐On‐Metal Articulation,” Knee 25, no. 4 (2018): 728–731, 10.1016/j.knee.2018.04.013. [DOI] [PubMed] [Google Scholar]
  • 37. La Budde J. K., Orosz J. F., Bonfiglio T. A., and Pellegrini V. D., “Particulate Titanium and Cobalt‐Chrome Metallic Debris in Failed Total Knee Arthroplasty. A Quantitative Histologic Analysis,” Journal of Arthroplasty 9, no. 3 (1994): 291–304, 10.1016/0883-5403(94)90084-1. [DOI] [PubMed] [Google Scholar]
  • 38. Stratton‐Powell A. A., Williams S., Tipper J. L., Redmond A. C., and Brockett C. L., “Mixed Material Wear Particle Isolation From Periprosthetic Tissue Surrounding Total Joint Replacements,” Journal of Biomedical Materials Research, Part B: Applied Biomaterials 110, no. 10 (2022): 2276–2289, 10.1002/jbm.b.35076. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 39. ASTM C1624‐22: Test Method for Adhesion Strength and Mechanical Failure Modes of Ceramic Coatings by Quantitative Single Point Scratch Testing (ASTM International, 2022). [Google Scholar]
  • 40. Levesque M., Livingston B. J., and Spector M., “Scratches on Condyles in Normal Functioning Total Knee Arthroplasty.” 44th Annual Meeting (Louisiana, 1998). [Google Scholar]
  • 41. Que L., Topoleski L. D. T., and Parks N. L., “Surface Roughness of Retrieved CoCrMo Alloy Femoral Components From PCA Artificial Total Knee Joints,” Journal of Biomedical Materials Research 53, no. 1 (2000): 111–118, 10.1002/(sici)1097-4636(2000)53:1<111::aid-jbm15>3.0.co;2-y. [DOI] [PubMed] [Google Scholar]
  • 42. Salmons H. I., Larson D. R., Ortiguera C. J., et al., “Multicenter Randomized Clinical Trial of Highly Cross‐Linked Polyethylene Versus Conventional Polyethylene in 518 Primary TKAs at 10 Years,” Journal of Bone and Joint Surgery 107, no. 2 (2025): 121–126, 10.2106/JBJS.24.00445. [DOI] [PubMed] [Google Scholar]
  • 43. Gascoyne T. C., Teeter M. G., Guenther L. E., Burnell C. D., Bohm E. R., and Naudie D. R., “In Vivo Wear Performance of Cobalt‐Chromium Versus Oxidized Zirconium Femoral Total Knee Replacements,” Journal of Arthroplasty 31, no. 1 (2016): 137–141, 10.1016/j.arth.2015.07.045. [DOI] [PubMed] [Google Scholar]
  • 44. Okazaki Y., Hosoba M., Miura S., and Mochizuki T., “Effects of Knee Simulator Control Method and Radiation Dose on UHMWPE Wear Rate, and Relationship between Wear Rate and Clinical Revision Rate in National Joint Registry,” Journal of the Mechanical Behavior of Biomedical Materials 90 (2019): 182–190, 10.1016/j.jmbbm.2018.09.034. [DOI] [PubMed] [Google Scholar]
  • 45. Essner A., Herrera L., Yau S. S., Wang A., Dumbleton J., and Manley M., “Sequentially Crosslinked and Annealed UHMWPE CRUHMWPE CR Knee Wear,” in 51st Annual Meeting of the Orthopaedic Research Society.
  • 46. Schmidig G., Essner A., and Wang A., “Knee Simulator Wear of Cross‐Linked UHMWPE.” 46th Annual Meeting (Orthopaedic Research Society, 2000). [Google Scholar]
  • 47. Green T., “Polyethylene Particles of a ‘Critical Size’ Are Necessary for the Induction of Cytokines by Macrophages In Vitro,” Biomaterials 19, no. 24 (1998): 2297–2302, 10.1016/s0142-9612(98)00140-9. [DOI] [PubMed] [Google Scholar]
  • 48. Matthews J. B., Green T. R., H. Stone M., Mike Wroblewski B., Fisher J., and Ingham E., “Comparison of the Response of Primary Human Peripheral Blood Mononuclear Phagocytes From Different Donors to Challenge With Model Polyethylene Particles of Known Size and Dose,” Biomaterials 21, no. 20 (2000): 2033–2044, 10.1016/s0142-9612(00)00089-2. [DOI] [PubMed] [Google Scholar]
  • 49. Saikko V., Calonius O., and Keränen J., “Effect of Counterface Roughness on the Wear of Conventional and Crosslinked Ultrahigh Molecular Weight Polyethylene Studied With a Multi‐Directional Motion Pin‐On‐Disk Device,” Journal of Biomedical Materials Research 57, no. 4 (2001): 506–512, 10.1002/1097-4636(20011215)57:4<506::aid-jbm1196>3.0.co;2-h. [DOI] [PubMed] [Google Scholar]
  • 50. Dowson D., Taheri S., and Wallbridge N. C., “The Role of Counterface Imperfections in the Wear of Polyethylene,” Wear 119, no. 3 (1987): 277–293, 10.1016/0043-1648(87)90036-6. [DOI] [Google Scholar]
  • 51. Basgul C., MacDonald D. W., Klein G. R., Piuzzi N. S., and Kurtz S. M., “Retrieval Analysis of Titanium Nitride Coatings for Orthopaedic Implants,” Journal of Arthroplasty 39, no. 9S1 (2024): S272–S279, 10.1016/j.arth.2024.07.001. [DOI] [PubMed] [Google Scholar]
  • 52. Noble P. C., Conditt M. A., Cook K. F., and Mathis K. B., “The John Insall Award: Patient Expectations Affect Satisfaction With Total Knee Arthroplasty,” Clinical Orthopaedics and Related Research 452 (2006): 35–43, 10.1097/01.blo.0000238825.63648.1e. [DOI] [PubMed] [Google Scholar]
  • 53. Singh M., Harary J., Schilling P. L., and Moschetti W. E., “Patient Satisfaction Is Nearly 90% after Total Knee Arthroplasty; We Are Better Than We Were,” Journal of Arthroplasty 40, no. 6 (2025): 1521–1525.e1, 10.1016/j.arth.2024.11.038. [DOI] [PubMed] [Google Scholar]
  • 54. DeFrance M. J. and Scuderi G. R., “Are 20% of Patients Actually Dissatisfied Following Total Knee Arthroplasty? A Systematic Review of the Literature,” Journal of Arthroplasty 38, no. 3 (2023): 594–599, 10.1016/j.arth.2022.10.011. [DOI] [PubMed] [Google Scholar]

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Articles from Journal of Orthopaedic Research are provided here courtesy of Wiley

RESOURCES