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The impact of a laser-induced microgroove (LIM) architecture on mechanical responses of two cemented implant systems was evaluated. One system consisted of two aluminum alloy rods bonded end-to-end by polymethylmethacrylate cement. The second system consisted of a custom-made, aluminum tibial tray (TT) cemented in an artificial canine tibia. Control specimens for each system were polished smooth at the cement interface. For LIM samples in the rod system, microgrooves were engraved (100 µm depth, 200 µm width, 500 µm spacing) on the apposing surface of one of the two rods. For TT system testing, LIM engraving (100 µm spacing) was confined to the underside and keel of the tray. Morphological analysis of processed implant surfaces revealed success in laser microgrooving procedures. For cemented rods tested under static tension, load to failure was greater for LIM samples (279.0 ± 14.9 N vs. 126.5 ± 4.5 N). Neither non-grooved nor grooved TT samples failed under cyclic compression testing (100,000 cycles at 1 Hz). Compared with control specimens, LIM TT constructs exhibited higher load to failure under static compression and higher strain at the bone interface under cyclic compression. Laser-induced microgrooving has the potential to improve the performance of cemented orthopedic implants.

Aseptic loosening at the implant–cement interface is a well-documented cause of failure in joint arthroplasty. Traditionally, the strength of the implant–cement interface is determined using uni-axial normal and shear loading tests. However, during functional loading, the implant fixation sites are loaded under more complex stress conditions. For this purpose, the strength of the implant–cement interface under mixed-mode tensile and shear loading conditions was determined in this study using interface specimens with varying interface roughness. For the lowest roughness value analyzed (Ra=0.89μm), the interface strength was 0.40–1.95MPa at loading angles varying between pure tension and shear, whereas this was 4.90–9.90MPa for the highest roughness value (Ra=2.76μm). The interface strength during pure shear (1.95–9.90MPa) was substantially higher than during pure tension (0.58–6.67MPa). Polynomial regression was used to fit a second-order interpolation function through the experimental interface strength data (R2=0.85; p<0.001), relating the interface strength (S [MPa]) to the interface loading angle (α [degrees]) and interface roughness (Ra [μm]): S(α,Ra)=0.891Ra2+0.001α2−0.189Ra−0.064α−0.060. Finally, an interface failure criterion was derived from the interface strength measurements, describing the risk of failure at the implant–cement interface when subjected to a certain tensile and shear stress using only the interface strength in pure tensile and shear direction. The findings presented in this paper can be used in numerical models to simulate loosening at the implant–cement interface.

Purpose The Attune ® total knee arthroplasty system was introduced in 2013 to address lingering issues of patient dissatisfaction. However, recent literature reports concerns of early tibial tray debonding. The aim of this study was to compare the incidence of radiolucent lines, survivorship and patient reported outcome-measures between the Attune ® system and the well-established Triathlon ® system. Methods This retrospective database review was conducted at a single institution in Cork, Ireland. All primary Attune ® ( N  = 445) and Triathlon ® ( N  = 285) systems implanted between 2015 and 2016 were reviewed. Radiolucent lines were assessed for those with a minimum two-year radiological follow-up (Attune ®  = 338; Triathlon ®  = 231). X-rays were taken post op, at 6 months, 2 years and 5 years. Radiolucent lines were documented using the Modern Knee Society Radiographic System. Five-year survival was assessed using Kaplan–Meier analysis with the Log Rank method to determine statistical significance. The Oxford Knee Score and EQ-5D-5L, were collected pre-op, at 6 months, 2 years and 5 years post-operatively and compared using the Kruskal–Wallis Test. Results The Attune ® had a higher proportion of radiolucent lines at the tibial tray [87.1% (54/62) vs 61.4% (27/44); p  = 0.001] and at the implant–cement interface [62.9% (39/62) vs 43.2% (19/44); p  = 0.02]. Conversely, the Triathlon ® had a higher proportion AT the femur [38.6% (17/44) vs 12.9% (8/62); p  = 0.001] and at the cement–bone interface [56.8% (25/44) vs 37.1% (23/62); p  = 0.02]. The overall frequency of radiolucent lines was similar in both the Attune ® and Triathlon ® groups [17.8%, (60/338) vs 17.7%, (41/231); p  = 0.49]. There was no difference in revision-free survival analysis at 5 years (Attune ® 97.8% vs Triathlon ® 95.8%; p  = 0.129). The Attune ® performed better at 5 years in the Oxford Knee Score [Attune ®  = 42.6 (SD 5.2) vs Triathlon ®  = 41 (SD 6.4); p  = 0.001] and in the EQ-5D [Attune ®  = 0.773 (SD 0.187) vs Triathlon ®  = 0.729 (SD 0.218); p  = 0.013]. There was no difference at 5 years in the EQ-VAS [Attune ®  = 80.4 (SD 13.7) vs Triathlon ®  = 78.5 (SD 15.3); p  = 0.25]. Conclusion The Attune ® system exhibited a higher incidence of  radiolucent lines at the tibial tray. However, this did not lead to decreased survivorship at medium term follow-up compared to the Triathlon ® . Furthermore, improvements in patient reported outcomes modestly favoured the Attune ® system. Level of evidence III.

This study investigated the fixation of a cemented PEEK femoral TKA component. PEEK and CoCr implants were subjected to a walking gait cycle for 10 million cycles (MC), 100,000 cycles or 0 cycles (unloaded control). A method was developed to assess the fixation at the cement–implant interface, which exposed the implants to a fluorescent penetrant dye solution. The lateral condyles of the implants were then sectioned and viewed under fluorescence to investigate bonding at the cement–implant interface and cracking of the cement mantle. When tested for 100,000 cycles, debonding of the cement–implant interface occurred in both PEEK (61%) and CoCr (13%) implants. When the duration of testing was extended (10 MC), the percentage debonding was further increased for both materials to 88% and 61% for PEEK and CoCr, respectively. The unloaded PEEK specimens were 79% debonded, which suggests that, when PEEK femoral components are cemented, complete bonding may never occur. Analysis of cracks in the cement mantle showed an absence of full-thickness cracks in the unloaded control group. For the 100,000-cycle samples, on average, 1.3 and 0.7 cracks were observed for PEEK and CoCr specimens, respectively. After 10 MC, these increased to 24 for PEEK and 19 for CoCr. This was a preliminary study with a limited number of samples investigated, but shows that, after 10 MC under a walking gait, substantial debonding was visible for both PEEK and CoCr implants at the cement–implant interface and no significant difference in the number of cement cracks was found between the two materials.

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.

The failure of polymethyl methacrylate (PMMA) orthopedic cement is considered the most important problem in total hip arthroplasty and eventual prosthesis loosening. Fiber or particulate reinforcement has been used to improve the mechanical properties of bone cement. However, reinforced cements have also been limited by adhesion between the PMMA and implant. This study investigated the effect of bioceramic particle reinforcement (alumina; Al 2 O 3 ) with different volumes (0, 5, 10, 15 and 20 vol%) on both the mechanical behavior of bone cements and implant–cement interface resistance. Mechanical fixation at the implant–cement interface was evaluated in vitro under shear mode loading conditions. Based on the mechanical tests of the implant–cement interface, a finite element model of the interface sample was developed to analyze the interfacial behavior of the implant–cement adhesion. The results show that the highest elastic modulus, tensile strength, compressive strength, and Vickers hardness (5.01 GPa, 41.33 MPa, 100.26 MPa and 10.36, respectively) were obtained using the PMMA sample with 20 vol% alumina particles, which represent increases of 82.8%, 78.68%, 42.37% and 282%, respectively, compared with those of pure PMMA. Against all expectations, beyond 10 vol% alumina, the interface strength dropped. The results also show that there is a good correlation between the numerical and experimental analysis methods.

The purpose of this study was to investigate the effects of the undersurface roughness of total knee prosthesis on clinical outcomes. We compared the clinical and radiological outcomes and prosthesis survivals in patients who underwent total knee arthroplasty using prosthesis with identical designs but different surface roughness (average surface roughnesses (Ra), 5.0 μm vs. 11.6 μm). The results showed that the knee prostheses with a more roughened undersurface (Ra = 11.6 μm) produced significantly better functional results and enhanced prosthesis survival. The difference in surface roughness was associated with incidence of osteolysis and loosening at the tibial baseplate, but not at the femoral component. Overall, our results provided significant evidence that the use of roughened undersurface of tibial baseplate would be a way to prevent aseptic loosening.