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Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – Influence of keel length, cementation area and tibial stem
Accepted Manuscript Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem Thomas M. Grupp, Khaled J. Saleh, Melanie Holderied, Andreas M. Pfaff, Christoph Schilling, Christian Schroeder, William M. Mihalko PII: DOI: Reference:
S0021-9290(17)30244-0 http://dx.doi.org/10.1016/j.jbiomech.2017.04.031 BM 8213
To appear in:
Journal of Biomechanics
Accepted Date:
30 April 2017
Please cite this article as: T.M. Grupp, K.J. Saleh, M. Holderied, A.M. Pfaff, C. Schilling, C. Schroeder, W.M. Mihalko, Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem, Journal of Biomechanics (2017), doi: http://dx.doi.org/10.1016/ j.jbiomech.2017.04.031
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
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Thomas M. Grupp , Khaled J. Saleh , Melanie Holderied , Andreas M. Pfaff , Christoph Schilling , 2 4 Christian Schroeder , William M. Mihalko 1
Aesculap AG Research & Development,Tuttlingen, Germany Ludwig Maximilians University Munich, Department of Orthopaedic Surgery, Physical Medicine & Rehabilitation, Campus Grosshadern, Munich, Germany 3 Division of Orthopaedics Southern Illinois University School of Medicine Springfield, IL, USA 4 Campbell Clinic Department of Orthopaedic Surgery & Biomedical Engineering, University of Tennessee, TN, USA 2
Corresponding author Prof. Dr. med. habil. Dr.-Ing. Thomas M. Grupp Research and Development AESCULAP AG Research & Development Am Aesculap-Platz D-78532 Tuttlingen, Germany Tel.: +49/7461/95-2667 Fax: +49/7461/95-382667 e-mail: [email protected]
Manuscript : 3988 words Abstract: 285 words Tables: 1 Figures: 9
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
Abstract The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau (VEGA® System Aesculap Tuttlingen, Germany) under dynamic compression-shear loading conditions in human tibiae. We performed the cemented tibial plateau implantations on 24 fresh-frozen human tibiae of a mean donor age of 70.7 years (range 47 – 97) The tibiae were divided into four groups of matched pairs based on comparable trabecular bone mineral density. To assess the primary stability under dynamic compression shear conditions, a 3D migration analysis of the tibial component relative to the bone based on displacements and deformations and an evaluation of the cement layer including penetration was performed by CT-based 3D segmentation. Within the tested implant fixation principles the mean load to failure of a 28 mm keel and a 12 mm stem (40 mm) was 4700 ± 1149 N and of a 28 mm keel length was 4560 ± 1429 N (p = 0.996), whereas the mean load to failure was 4920 ± 691 N in full cementation (p = 0.986) and 5580 ± 502 N with additional stem (p = 0.537), with no significant differences regarding the dynamic primary stability under dynamic compressionshear test conditions. From our observations, we conclude that there is no significant difference between a 40 mm and a 28 mm tibial keel & stem length and also between a surface and a full cementation in the effect on the primary stability of a posterior stabilised tibial plateau, in terms of failure load, migration characteristics and cement layer thickness including the penetration into the trabecular bone.
Keywords total knee arthroplasty, tibial keel & stem length, surface vs full cementation, primary stability, dynamic compression shear loading
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Introduction Total knee arthroplasty (TKA) can be considered as international standard of care for the treatment of degenerative osteoarthritis, rheumatoid arthritis and certain knee joint fractures based on survey in 18 countries, with a rising demand over the past two decades (Kurtz et al., 2011). Overall TKA revision rates for all reasons are comparably low with 5 to 10 % over a period of 10 to 15 years (Knutson et al., 1994; Furnes et al., 2007; Lygre et al., 2011; Graves et al., 2012; Sundberg et al., 2014). Sadoghi et al. (2013) performed a complication-based analysis of TKA revisions in a 30 years period entered in the joint registries of Sweden, Norway, Finland, Denmark, Australia and New Zealand and found the most common causes are aseptic loosening in 29.8 %, septic loosening in 14.8 %, pain in 9.5 % and wear in 8.2 % of the cases. Based on a multi-centre study evaluating 844 TKA revisions from 2010 to 2011 Lombardi et al. (2014) found a substantial number of 35 % of TKA failures occurring early within two years of primary surgery. Aseptic loosening was the predominant failure mode, whereas polyethylene wear was not a major cause of failure until more than 15 years service in vivo.
Apart of the patella in the fixation of knee implant components aseptic loosening of the tibial components remains a major concern (Schlegel et al., 2011; Cawley et al., 2013; Schlegel et al., 2015). During a 10-year period (2003 to 2012), 3,572 first time TKA revisions were reported in the Swedish knee arthroplasty register by Sundberg et al. (2014) with a total implant removal of 11.3 % and an exchange of either the tibia in 7.1 % or the femur in 0.9 % of the cases. For 17,782 cemented primary TKA’s evaluated within the Norwegian arthroplasty register during the years 1994 to 2009, Gothesen et al. (2013) extracted for aseptic loosening femur 49 cases and for tibia 136 cases, a ratio of 2.8. This emphasizes the need for stable primary and secondary fixation of tibial trays, which is dependent on multiple factors like implant design, bone interface preparation, surgical technique and cementation (Schlegel et al., 2015).
Several studies had been undertaken to examine the influence of implant design, bone fixation principle, surface structure and cementing technique on the primary stability of uni- or bicompartmental tibial implants in vitro and in vivo. To evaluate the primary stability of tibial plateaus, in vitro, in silico and ex vivo approaches had been undergone: cement penetration depth analysis in the proximal tibia (Maistrelli et al., 1995; Clarius et al., 2012), finite element analysis (FEA) to assess resulting bone stresses and strains (Completo et al., 2008; Kelly 2012; Cawley et al., 2012), static tension (Schlegel et al., 2011; Gebert de Uhlenbrock et al., 2012) or compression loading (Clarius et al., 2010; Completo et al., 2012; Jaeger et al., 2014) until interface failure. However, these test conditions do not reflect the in vivo physiologic loading 3
Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
modes, where the tibial plateau is predominantly subjected to combined compression and shear forces in a cyclic profile (Zhao et al., 2007; Kutzner et al., 2010; Bergmann et al., 2010; Grupp et al. 2013).
The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae.
Materials and Methods ®
We performed a cemented posterior stabilised tibial plateau implantation (VEGA
System Aesculap
Tuttlingen, Germany) on 24 fresh-frozen human tibiae of a mean donor age of 70.7 years (range 47 – 97) with the proximal third of the tibia. To determine bone mineral density (BMD) CT-scans (Sensation 64 Somatom, Siemens AG, Germany) were made of all tibiae prior to the implantation. The bone mineral density was quantitatively determined by measuring the Hounsfield units (HU) beyond the tibial plateau until a depth of 15 mm within the region of trabecular bone. We divided the tibiae into four groups of matched pairs; “TibiaSC40” (28 mm keel & 12 mm stem (40 mm), surface cementation), “TibiaSC28” (28 mm keel, surface cementation), “TibiaFC40” (28 mm keel & 12 mm stem (40 mm), full cementation) and “TibiaSC120S” (28 mm keel, surface cementation, 92 mm cementless stem) (Table 1, Figure 1). The bone preparation and implantation of the tibial component and the gliding surface was done at the dissected tibiae as described in the surgical technique of the VEGA® System (Aesculap Tuttlingen, Germany) for all groups. Pulsed lavage was used (500 ml, 2 minutes purging time) to clean the trabecular bone of the metaphyseal resected knee joint before cementation. A high viscosity bone cement (Palacos® R 20g powder/10 ml monomer, Heraeus Medical Wehrheim, Germany) was mixed with bowl and spatula for cement fixation of the tibia implants. The complete packet of bone cement was applied in equal parts on both the inferior surface of the tibial component and the resected tibial bone using a double-layer technique (surface cementation for the groups “TibiaSC28”, “TibiaSC40” and “TibiaSC120S” & full cementation for the group “TibiaFC40”). The tibial tray was inserted in the tibial bone and impacted onto the tibia using an impactor. For pressurisation of the bone cement during polymerisation the tibial component was axially compressed until the cement was cured. Bone cement was applied on the surface of the tibial component using the double-layer technique To analyze the cement layer, CT-scans were done before biomechanical testing (Figure 2) The CT-data was transferred to segmentation software (Amira 5.6, FEI, USA) and the prosthesis with cement layer was three-dimensionally reconstructed. CAD-Files of the prosthesis, in each size provided by the manufacturer, were used to determine the cement layer by subtracting the geometry of 4
Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
the prosthesis from the CT reconstruction (Geomagic, 3DS, USA). Finally, mean cement layer thickness was calculated by deviding the volume of the cement layer by the area under the tibial tray. After implantation the human tibiae were imbedded with polyurethane casting resin in a bole, 70 mm distally from the medial tibial component surface. This may imply that there is in the group “TibiaSC120S” some interaction between the supporting pot and the long 120 mm stem, as the resin would stiffen the tibia. In awareness of this potential interaction, an embedding level of 70 mm was decided to allow for a clinical representative tibio-femoral load range and avoid periprosthetic fractures of the donor tibiae. The tibiae were fixed on the test machine (DynaMess Stolberg, Germany) in a 20° flexed position (Figure 3) to simulate peak joint loading at 20° of flexion during stair climbing (Kutzner et al. 2010, Bergmann et al. 2014). The tibiofemoral contact force was applied in a peak sinusoidal waveform with a frequency of 0.65 Hz via the femoral component acting on the gliding surface with a ratio of 60% medial and 40% lateral. The contact point of the femoral component and the gliding surface was set at the vertical axis and a posterior offset, which was determined to (sin 20° x 37 mm) – 1.8 mm, respecting the femur component radius and resulting in a shift of the femoro-tibial contact points to the posterior portion of the curved gliding surface (T2 = 26.3 mm measured from the dorsal outer rim). This anatomical load application resulted in a main deformation of the proximal tibiae in distal and posterior direction (Figure 4). The donor of the tibiae had different body weights (range 41 – 100 kg), but even the tibio-femoral load is substantially influenced by individual anatomical, muscular and ligamentous situations. Accordingly, during the dynamic testing an initial tibio-femoral load of 1800 N was applied for 1000 cycles to cover the lower physiologic range followed by a stepwise load increase (Locati steps of 300 N, 1000 cycles) until failure or termination of the test at the highly demanding final load level of 6000 N (1.5-times HIGH100 for stair climbing) (Bergmann et al., 2014), to account for the unknown individual loading situation. The criterion of failure was set to a maximal movement increase in the joint articulation of 2 mm at a single load level, to detect a failed implant fixation macroscopically and avoid a severe periprosthetic fracture of the donor tibiae to enable a proper view on implant migration. To assess the primary stability at the implant-bone interface, the photo-optical measurement system ®
PONTOS 5M (GOM Braunschweig, Germany) with an accuracy of 5 µm in x and z direction and 10 µm in y direction was used. For this process standard-sticker points were placed on the implant and bone along the line of implant-bone interface and related to a defined global coordinate system. The coordinate system was defined with the origin of the tibial component and lateral of the setup (Figure 3). The positive x-axis pointed in the anterior direction, the y-axis in the medial or lateral direction depending on the legs’ side and the z-axis in the proximal direction of the tibial component. For the data analysis the data were standardized to an right
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knee. Therefore the direction of the y-axis, the rotation around x and z of the left knees were changed in this way that the y-axis pointed always to medial, the rotation around x in valgus direction and the rotation around ®
z as an internal rotation. With the picture series of PONTOS 5M and based on the detection of the points and definition of the components through the recognition of pixels and ellipsoidal forms, information about 3D coordinates, 3D displacements and deformation can be provided. A reference picture was taken at a preloading of 50 N. During the test each 100 cycles a picture series of a loading cycle was taken with a frequency of 15 Hz. The points were grouped to components “implant” and “bone”, where the XYZdisplacement of each component as well as the relative XYZ-displacement of the implant and bone were analyzed with GOM Inspect Professional V8. A repeated–measures analysis of variance (ANOVA) was performed to test for significant differences in the following parameters: bone mineral density, failure load, cement layer thickness and relative motion of each motion component between implant and bone. Prior to analysis, the normal distribution of the data (normal pp plots; p < 0.05) and the homogeneity of variance (Levene-test) were verified, that allowed for the use of ANOVA. Differences of the parameters between the four groups “TibiaSC40”, “TibiaSC28”, “TibiaFC40” and “TibiaSC120S” were evaluated with a Tukeys Honest Significant Difference-Test for unequal N as post hoc analysis. Additionally the correlation between failure load and BMD using the Spearman’s rank correlation coefficient rs was determined. Finally statistical analyses using Statistica 10 (StatSoft Europe GmbH, Hamburg, Germany) with a significance level of p < 0.05 was carried out.
Results To obtain matched pairs concerning primary stability testing in the TibiaSC40 group, the BMD was 218.6 ± 40.6 Hounsfield units (HU) and 219.1 ± 46.1 HU in the TibiaSC28 group (p = 0.999), whereas the BMD was 251.1 ± 40.9 HU in the TibiaFC40 and 246.8 ± 46.9 HU in the TibiaSC120S group (p = 0.998) demonstrating a similarity between the autologous tibiae groups. The relative BMD in Hounsfield units allows for comparisons between the groups – a convertion to an HA equivalent density based on a phantom was not intended. Using the TibiaSC40 group as a reference in homologous cross-comparisons an acceptable comparability was given to the TibiaFC40 (p = 0.646) and to the TibiaSC120S (p = 0.736) specimens. In BMD no statistical difference is given between the homologous cross-comparisons due to the genuine large variance and based on a cohort of n=6 donors per group the statistical power is very low (p = 0.23). The complete cement layer including the penetration into the trabecular bone showed a comparable thickness of the TibiaSC40 to the TibiaSC28 group (p = 0.895), while a slightly thinner cement layer has
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been achieved without statistical significance for the TibiaFC40 (p = 0.857) and the TibiaSC120S group (p = 0.724) (Figure 5). Under dynamic compression-shear test conditions, the mean load to failure in the TibiaSC40 group was 4700 ± 1149 N and 4560 ± 1429 N in the TibiaSC28 group (p = 0.996), whereas the mean load to failure was 4920 ± 691 N in the TibiaFC40 group (p = 0.986) and 5580 ± 502 N in the TibiaSC120S (p = 0.537) group, with no significant differences regarding the dynamic primary stability within the tested implant fixation principles (Figure 6 & 7). The failure mode was in all specimen subsidence of the tibial implant into the resected proximal tibiae. Between the final load level at failure and the BMD, no correlation was found in the TibiaSC40 (rs = 0.579; p = 0.228), in the TibiaSC28 (rs = 0.864; p = 0.059), in the TibiaFC40 (rs = 0.357; p = 0.556) and in the TibiaSC120S (rs = 0.558; p = 0.328) groups. The migration of the tibial implant relative to the bone (average vector of movement) was illustrated in a direct left-to-right comparison for the autologous pairs of human tibiae for the keel length TibiaSC40 versus TibiaSC28 (Figure 8). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the autologous groups yielded, no significant influence of the keel length on the relative translations in x, y and z direction (p > 0.92), and the relative rotations around x, y and z axes (p > 0.43). Migration of the tibial implant relative to the bone was also examined in a homologous comparison of BMD matched pairs of human tibiae for the surface cementation TibiaSC40 versus a full cementation TibiaFC40 (Figure 9). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the homologous groups yielded, no significant influence of a full cementation on the relative translations in x, y and z direction (p > 0.54), and the relative rotations around x, y and z axes (p > 0.77). Migration of the tibial implant relative to the bone was analysed in a homologous comparison of BMD matched pairs of human tibiae for the surface cementation TibiaSC40 versus a surface cementation with cementless stem TibiaSC120S (Figure 10). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the homologous groups yielded, no significant influence of an additional stem on the relative translations in x, y and z direction (p > 0.6), and the relative rotations around x, y and z axes (p > 0.71).
Discussion The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae.
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A major limitation of our in vitro test setup is given by the fact that it does not contain the patella-femoral joint. Due to that the resulting loads from the patella contact force on the femoral component and the contribution of the patella tendon force on the tibia are not integrated in the chosen load application, reflecting femoro-tibial peak load during stair climbing in an anatomical position (Bergmann et al. 2014). During stair climbing Bergmann et al. 2014 have shown in their in vivo knee load measurements (HIGH100) peak axial force values of about 4000 N at 20° flexion, acting distally in the direction of the tibia stem and a related transverse shear force of around 300 N acting in posterior direction. However, to enable the test with an uniaxial actuator it was decided to preserve the anatomical position of 20° femoro-tibial flexion and due to the shift of the femoro-tibial contact points to the posterior portion of the curved gliding surface the load application resulted in a main deformation of the proximal tibiae in distal and posterior direction – enabling for a clinically occurring posterior-distal migration of the tibial component into the bone (Figure 4). A second limitation of our study may arise by the fact that only the evaluation of the influence of the keel length (TibiaSC40 vs TibiaSC28) was based on autologous pairs of human tibiae, whereas the other two comparisons of a full cementation (TibiaSC40 vs TibiaFC40) of an additional stem (TibiaSC40 vs TibiaSC120S) were based on homologous pairs matched on the basis of bone mineral density. Due to a genuine large variance in donor bone mineral densities, the mean BMD’s and standard deviations are comparable in all three groups. However, unless the mean BMD of TibiaSC40 is 219.1 HU and of TibiaFC40 is 251.1 HU, the failure load for the surface cementation only is comparable to the fully cemented keel.
Different methods have been introduced to evaluate the influence of implant design aspects and cementation techniques on the primary stability of tibial plateaus (Maistrelli et al., 1995; Jaeger et al., 2014). Using computer tomography, Schlegel et al. 2011 measured the bone mineral density and bone cement penetration to study the influence of pulsed lavage on the cement fixation of bicompartmental tibial trays in six pairs of human tibiae. They used the extraction force as a parameter of the fixation strength at the implant-bone interface. In a post mortem examination of 22 bicompartmental tibial plateaus from 17 patients retrieved after 5.3 years (range 0 to 11 years) in situ, Gebert de Uhlenbrock et al. (2012) analysed the influence of the time in situ on fixation strength. In a static tension test, they found a trend that pull-out forces decrease with the time in situ, whereas they increase with depth of cement penetration. Gebert de Uhlenbrock et al. (2012) and Schlegel et al. (2011) mentioned as a limitation of their studies that axial tension as a measure of the implant-bone interface mechanical capacity could be easily performed, but it
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does not simulate physiological conditions where mainly dynamic compression combined with bending and shear is acting on the tibial tray (Kutzner et al., 2010; Bergmann et al., 2010; Grupp et al., 2013). Scott and Biant (2012) analysed the role of the design of the tibial components and stems in TKA in a review and found that tibial implants with a short central stem varying typically between 35 and 50 mm in length have favourable clinical survivorship indicating for a reduced clinically relevant stress shielding. Tibia designs with a central stem and fins like PFC Sigma, Genesis 2 and Columbus have shown promising overall fiveyear rates in the National Joint Registry for England and Wales (Scott and Biant, 2012). In contrast to that Foran et al. (2011) as Arsoy et al. (2013) reported for a precoated low-profile tibial component out of tivanium Ti6Al4V alloy higher failure rates with insufficient bonding at the implant-cement interface. For a short-keeled cemented tibial component out of a group of 80 consecutive TKA patients Ries et al. (2013) revealed a revision rate of 6.3 % after 1-year follow-up with failure at the implant-cement interface in 4 of the 5 revised cases. In the current study we found for the dynamic failure load between TibiaSC28 (4560 N) and TibiaSC40 (4700 N) no substantial difference (p = 0.9963) as well as for the xyz-displacements of the tibial tray relative to the bone, indicating that a keel length of 28 mm is able to create a sufficient primary stability of the tibial plateau and in addition to that the observed failure mode was migration into the metaphyseal head of the human tibiae and not debonding between implant and cement (Foran et al., 2011; Arsoy et al., 2013; Ries et al., 2013). A comparison between surface and full cementing technique of tibial trays has been reported in clinical follow-up studies (Saari et al., 2009). Based on a cohort of 232 primary TKA patients using either surface or full cementation of a mobile tibial tray with keel Galasso et al. (2013) reported cumulative survival rates at 8 years with an average follow-up of 5.6 years of 97.1 % for revision for any reason and of 99.3 % for mechanical reasons with no difference in clinical outcomes according to the tibial component cementation technique. They concluded that cementing the tibial keel has no advantage for primary TKA patients. In a longterm matched-pair analysis by Schlegel et al. (2015) comparing surface or full cementation of the tibial component in a total of 67 patients with a clinical follow-up of 10.3 years for SC and 12 years for FC, the survivorship at 10 years was 100 % for SC and 93.3 % for FC considering aseptic loosening as endpoint. They found no statistical difference between SC and FC in the longterm survivorship and questioned the advantage of FC, because their findings do not support the concern that SC results in inferior fixation even in patients with rheumatoid arthritis (56 % of patients in SC and 48 % in FC group). These results were also supported by Rossi et al. (2010), where no early loosening was observed for SC in a cohort of 70 TKA’s with a follow-up of 3.6 years. Kelly (2012) developed a combined experimental and computational method to
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examine the effect of surface and full cementation of the tibial component on the surrounding stress state in the periprosthetic trabecular bone with a remodeling algorithm for bone formation and resorption post implantationem. This FEA modeling allows to predict the peri-prosthetic strain experienced by bone after implantation and using this method Cawley et al. (2012) found statistically significant differences between SC and FC with lower stresses and strain recorded in cortical and trabecular bone directly under a fully cemented tibial baseplate, whereas high stress concentrations were computed for FC in the distal area due to bonding of the stem tip to the surrounding bone. Bone remodeling simulations predicted greater bone resorption for full cementation of the tibial tray Cawley et al. (2013), suggesting that FC would result in increased bone loss at the proximal tibia, whereas overall the SC model displayed the closest trabecular stress distribution to the intact bone Kelly (2012). Comparing surface versus full cementation within our study we measured no significant difference for the dynamic failure load between TibiaSC40 (4700 N) and TibiaFC40 (4920 N) (p = 0.986) as well as for the xyz-translational and -rotational implant displacements relative to the bone. Considering reduced stress-shielding and bone resorption as described by Cawley et al. (2012), our findings favour the surface cementation technique. Evaluating the primary stability behaviour of a surface cemented tibia with stem we found that the addition of a stem creates less variancy in all rotatory degrees of freedom, whereas the dynamic failure load was not substantially increased (p = 0.537) for TibiaSC120S (5580 N) compared to TibiaSC40 (4700 N). Analysing the single specimen characteristics the importance of sufficient cortical coverage and distal sliding fit conditions of the cementless stems has been experienced to obtain a high primary stability. In addition to that it should be considered that full tibial coverage combined with stiff cemented or press-fit stems leads to a bypassing of load of the proximal trabecular tibial bone and may result in stress shielding and metaphyseal tibial bone resorption (Scott and Biant, 2012).
From our observations, we conclude that there is no significant difference between a 40 mm (TibiaSC40) and a 28 mm tibial keel length (TibiaSC28) in the effect on the primary stability of surface cemented tibial plateaus, in terms of failure load, migration characteristics and cement layer thickness including the penetration into the trabecular bone. Moreover, the current findings lead us to suggest that there is no substantial benefit of a full cementation (TibiaFC40) versus a surface cementation (TibiaSC40) on the primary stability of a posterior stabilised tibial plateau, in terms of failure load, migration characteristics and cement layer thickness under dynamic compression-shear loading conditions in human tibiae.
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Acknowledgements The authors would like to thank Heidi Odemer for her assistance during the implantation of the tibial plateaus into the human cadaver knees and Elvira Stolinski for the graphical illustration of the different tested tibial plateau and stem configurations
Conflict of Interest Four of the authors (TMG,MH,AP,CSchi) are employees of Aesculap Tuttlingen a manufacturer of orthopaedic implants. Two of the authors (KJS,WMM) are advising surgeons in Aesculap R&D projects. One of the authors (CSchr) is getting research funding in correlation with Aesculap R&D projects.
Tables and Figures Table 1: Human tibiae donor characteristics, bone mineral density, implanted tibial tray version and component size Figure 1: Tibial implant configurations for TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S Figure 2: CT-based 3D segmentation of the cement layer to examine the cement layer depth – exemplary in surface cementation TibiaSC40-1 (left) and full cementation technique TibiaFC40-2 (right) Figure 3: Tibial tray implanted in a human tibia in a test-setup with a dynamic compression-shear testing in a 20° flexed position to simulate peak joint load during walking and stair climbing (Kutzner et al., 2010; Bergmann et al., 2014) with vertical femoral load application in a ratio of 60% medial and 40% lateral and 3D motion analysis system (left) with a point cluster on the bone and the implants and the loading setup (right) Figure 4: Deformation of the bone in anterior-posterior (x-axis) and tibia axis (z-axis) at a load level of 3000N in this representative example TibiaSC28-5 Figure 5: Average thickness of the cement layer for TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S analysed by a CT-based 3D segmentation – Box-Wisker plot for statistical analysis of the groups Figure 6: Primary stability testing of the TKA tibial components under dynamic compression-shear loading conditions in human tibiae to compare the TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S implantation principles – BMD, load level and cycles at failure for each specimen Figure 7: Final load level at failure due to migration into the bone in a comparison between TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S implantations – Box-Wisker plot for statistical analysis of the groups Figure 8: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in an autologous comparison for the TibiaSC40 versus the TibiaSC28 implantation groups at each load level
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Figure 9: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in a homologous comparison for the TibiaSC40 versus the TibiaFC40 implantation groups at each load level Figure 10: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in a homologous comparison for the TibiaSC40 versus the TibiaSC120S implantation groups at each load level
References Arsoy D, Pagnano MW, Lewallen DG, Hanssen AD, Sierra RJ: Aseptic tibial debonding as a cause of early failure in a modern total knee arthroplasty design. Clin Orthop Relat Res Vol. 471, pp. 94-101, 2013. Bergmann G, Heinlein B, Bender A, Graichen F, Rohlmann A, Halder A, et al.: Medio-lateral load distribution in the knee joint during walking. Abstract 17th Congress of the European Society of Biomechanics, July 4 – 8 Edinburgh UK, 2010. Bergmann G, Bender A, Graichen F, Dymke J, Rohlmann A, Trepczynski A, Heller MO, Kutzner I: Standardized Loads Acting in Knee Implants. PLoS ONE Vol. 9 No.1, 2014 e86035. doi:10.1371/journal.pone.0086035 Cawley DT, Kelly N, Simpkin A, Shannon FJ, McGarry JP: Full and surface tibial cementation in total knee arthroplasty – a biomechanical investigation of stress distribution and remodeling in the tibia. Clinical Biomechanics Vol. 27, pp. 390-397, 2012. Cawley DT, Kelly N, McGarry JP, Shannon FJ: Cementing techniques for the tibial component in primary total knee replacement. J Bone and Joint Surg Vol. 95B No. 3, pp. 295-300, 2013. Clarius M, Haas D, Aldinger PR, Jaeger S, Jakubowitz E, Seeger JB: Periprosthetic tibial fractures in unicompartmental knee arthroplasty as a function of extended sagittal saw cuts: An experimental study. The Knee Vol. 17, pp. 57-60, 2010. Clarius M, Seeger JB, Jaeger S, Mohr G, Bitsch RG: The importance of pulsed lavage on interface temperature and ligament tension force in cemented unicompartmental knee arthroplasty. Clinical Biomechanics Vol. 27, pp. 372-376, 2012. Completo A, Simoes JA, Fonseca F, Oliveira M: The influence of different tibial stem designs in load sharing and stability at the cement-bone interface in revision TKA. The Knee Vol. 15, pp. 227-232, 2008. Completo A, Fonseca F, Simoes JA, Ramos A, Relvas C: A new press-fit stem concept to reduce the risk of end-of-stem pain at revision TKA – A pre-clinical study. The Knee Vol. 19, pp. 537-542, 2012. Foran JR, Whited BW, Sporer SM: Early aseptic loosening with a precoated low-profile tibial component a case series. J Arthroplasty Vol. 26, pp. 1445-1450, 2011. Furnes O, Espehaug B, Lie SA, Vollset SE, Engesaeter LB, Havelin L: Failure mechanism after unicompartmental and tricompartmental primary knee replacement with cement. J Bone and Joint Surg Vol. 89A No. 3, pp. 519-525, 2007. Galasso O, Jenny JY, Saragaglia D, Miehlke RK: Full versus surface tibial baseplate cementation in total knee arthroplasty. Orthopedics Vol. 36 No. 2, pp. e151-e158, 2013. Gebert de Uhlenbrock A, Püschel V, Püschel K, Morlock MM, Bishop NE: Influence of time in-situ and implant type on fixation strength of cemented tibial trays – A post mortem retrieval analysis. Clinical Biomechanics Vol. 27 No. 9, pp. 929-935, 2012. Gothesen O, Espehaug B, Havelin L, Petursson G, Lygre S, Ellison P, Hallan G, Furnes O: Survival rates and causes of revision in cemented primary total knee replacement – Norwegian Arthroplasty Register 19942009. Bone Joint J Vol. 95B, pp. 636-42, 2013. Graves S, Tomkins A, Davidson D, et al.: Australian Orthopaedic Association National Hip and Knee Arthroplasty Registry – Annual Report, pp. 116-123, 2012. Grupp TM, Pietschmann MF, Holderied M, Scheele C, Schröder C, Jansson V, Müller PE: Primary stability of unicompartmental knee arthroplasty under dynamic compression-shear loading in human tibiae. Clinical Biomechanics Vol. 28, pp. 1006-1013, 2013.
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Jaeger S, Rieger JS, Bruckner T, Kretzer JP, Clarius M, Bitsch RG: The protective effect of pulsed lavage against implant subsidence and micromotion for cemented tibial unicompartmental knee components – an experimental cadaver study. J Arthroplasty Vol. 29 No. 4, pp. 727-732, 2014. Kelly N: An experimental and computational investigation of the inelastic behaviour of trabecular bone. The National University of Ireland, Galway. Doctoral Thesis, pp. 93-101, 2012. Knutson K, Lewold S, Robertsson O, Lidgren L: The Swedish knee arthroplasty register. A nation-wide study of 30,003 knees 1976-1992. Acta Orthop Scand. Vol. 65, pp. 375-386, 1994. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, Gómez-Barrena E, de Fátima de Pina M, Manno V, Torre M, Walter WL, de Steiger R, Geesink RGT, Peltola M, Röder C: International survey of primary and revision total knee replacement. Int Orthopaedics (SICOT) Vol. 35 No. 2, pp. 1783-89, 2011. Kutzner I, Heinlein B, Graichen F, Bender A, Rohlmann A, Halder A, et al.: Loading of the knee joint during activities of daily living measured in vivo in five subjects. J Biomechanics Vol. 43, pp. 2164-2173, 2010. Lombardi Jr AV, Berend KR, Adams JB: The revision knee arthroplasty – Why knee replacements fail in 2013 patient, surgeon or implant? J Bone and Joint Surg Vol. 96B No. 11, pp. 101-104, 2014. Lygre SHL, Espehaug B, Havelin LI, Vollset SE, Furnes O: Failure of total knee arthroplasty with or without patella resurfacing – A study from the Norwegian Arthroplasty Register with 0 -15 years follow-up. Acta Orthopaedica Vol. 82 No. 2, pp. 282-292, 2011. Maistrelli GL, Antonelli L, Fornasier V, Mahomed N: Cement penetration with pulsed lavage versus syringe irrigation in total knee arthroplasty. Clin. Orthop. Rel. Res. No. 312, pp. 261-265, 1995. Ries C, Heinichen M, Dietrich F, Jakubowitz E, Sobau C, Heisel C: Short-keeled cemented tibial components show an increased risk for aseptic loosening. Clin Orthop Relat Res Vol. 471, pp. 1008-1013, 2013. Rossi R, Bruzzone M, Bonasia DE, Ferro A, Castoldi F: No early tibial tray loosening after surface cementing technique in mobile bearing TKA. Knee Surg Sports Traumatol Arthroscopy Vol. 10, pp. 1360-1365, 2010. Sadoghi P, Liebensteiner M, Agreiter M, Leithner A, Böhler N, Labek G: Revision surgery after total joint arthroplasty: a complication-based analysis using worldwide arthroplasty registers. J Arthroplasty Vol. 28 No. 8, pp. 1329-1332, 2013. Saari T, Li MG, Wood D, Nivbrant B: Comparison of cementing techniques of the tibial component in total knee replacement. International Orthopaedics (SICOT) Vol. 33 No. 5, pp. 1239-1242, 2009. Schlegel UJ, Siewe J, Delank KS, Eysel P, Püschel K, Morlock MM, et al.: Pulsed lavage improves fixation strength of cemented tibial components. International Orthopaedics (SICOT) Vol. 35, pp. 1165-1169, 2011. Schlegel UJ, Bruckner T, Schneider M, Parsch D, Geiger F, Breusch SJ: Surface or full cementation of the tibial component in total knee arthroplasty: a matched-pair analysis of mid- to long-term results. Arch Orthop Trauma Surg Vol. 135 No. 5, pp. 703-708, 2015. Scott CEH, Biant LC: The role of the design of tibial components and stems in knee replacement – Instructional review. J Bone and Joint Surg Vol. 94B No. 8, pp. 1009-15, 2012. Sundberg M, Lidgren L, W-Dahl A, Robertsson O: Swedish knee arthroplasty register – Annual Report Lund University, Lund Sweden, 2014. Zhao D, Banks SA, D'Lima DD, Colwell CW, Fregly BJ: In vivo medial and lateral tibial loads during dynamic and high flexion activities. J Orthopaedic Research Vol. 25 No. 5, pp. 593-602, 2007.
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
1,2
3
1
1
1
Thomas M. Grupp , Khaled J. Saleh , Melanie Holderied , Andreas M. Pfaff , Christoph Schilling , 2 4 Christian Schroeder , William M. Mihalko 1
Aesculap AG Research & Development,Tuttlingen, Germany Ludwig Maximilians University Munich, Department of Orthopaedic Surgery, Physical Medicine & Rehabilitation, Campus Grosshadern, Munich, Germany 3 Division of Orthopaedics Southern Illinois University School of Medicine Springfield, IL, USA 4 Campbell Clinic Department of Orthopaedic Surgery & Biomedical Engineering, University of Tennessee, TN, USA 2
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Tables and Figures Table 1: Human tibiae donor characteristics, bone mineral density, implanted tibial tray version and component size Specimen
Sex
Age
Leg
BMD [HU]
height & weight
tibial tray size
TibiaSC40-1 TibiaSC28-1
female female
51 51
166 ± 37 172 ± 46
165 cm 64 kg
T3 T3
TibiaSC40-2 TibiaSC28-2
female female
87 87
right left left right
185 ± 54 186 ± 65
157 cm 59 kg
T2 T2
TibiaSC40-3 TibiaSC28-3
male male
67 67
left right
222 ± 51 229 ± 24
180 cm 100 kg
T4 T4
TibiaSC40-4 TibiaSC28-4
female female
47 47
right left
238 ± 84 228 ± 90
160 cm 59 kg
T3 T3
TibiaSC40-5 TibiaSC28-5
male male
68 68
right left
285 ± 37 285 ± 58
165 cm 59 kg
T4 T4
TibiaSC40-6 TibiaSC28-6
female female
97 97
right left
208 ± 83 145 ± 82
150 cm 41 kg
T2 T2
TibiaSC120S-1 TibiaFC40-1
male male
64 64
right left
216 ± 47 232 ± 132
175 cm 77 kg
T3, S92d14 T3
TibiaSC120S-2 TibiaFC40-2
male male
73 73
left right
202 ± 42 222 ± 63
173 cm 95 kg
T2, S92d12 T2
TibiaSC120S-3 TibiaFC40-3
female female
62 62
left right
241 ± 65 211 ± 48
163 cm 86 kg
TibiaSC120S-4 TibiaFC40-4
male male
76 76
left right
323 ± 52 288 ± 56
185 cm 45 kg
TibiaSC120S-5 TibiaFC40-5
female female
84 84
left right
252 ± 56 302 ± 47
160 cm 52 kg
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T2, S92d12 T2 T5, S92d14 T5 T2, S92d12 T2
S0021-9290(17)30244-0 http://dx.doi.org/10.1016/j.jbiomech.2017.04.031 BM 8213
To appear in:
Journal of Biomechanics
Accepted Date:
30 April 2017
Please cite this article as: T.M. Grupp, K.J. Saleh, M. Holderied, A.M. Pfaff, C. Schilling, C. Schroeder, W.M. Mihalko, Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem, Journal of Biomechanics (2017), doi: http://dx.doi.org/10.1016/ j.jbiomech.2017.04.031
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
1,2
3
1
1
1
Thomas M. Grupp , Khaled J. Saleh , Melanie Holderied , Andreas M. Pfaff , Christoph Schilling , 2 4 Christian Schroeder , William M. Mihalko 1
Aesculap AG Research & Development,Tuttlingen, Germany Ludwig Maximilians University Munich, Department of Orthopaedic Surgery, Physical Medicine & Rehabilitation, Campus Grosshadern, Munich, Germany 3 Division of Orthopaedics Southern Illinois University School of Medicine Springfield, IL, USA 4 Campbell Clinic Department of Orthopaedic Surgery & Biomedical Engineering, University of Tennessee, TN, USA 2
Corresponding author Prof. Dr. med. habil. Dr.-Ing. Thomas M. Grupp Research and Development AESCULAP AG Research & Development Am Aesculap-Platz D-78532 Tuttlingen, Germany Tel.: +49/7461/95-2667 Fax: +49/7461/95-382667 e-mail: [email protected]
Manuscript : 3988 words Abstract: 285 words Tables: 1 Figures: 9
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
Abstract The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau (VEGA® System Aesculap Tuttlingen, Germany) under dynamic compression-shear loading conditions in human tibiae. We performed the cemented tibial plateau implantations on 24 fresh-frozen human tibiae of a mean donor age of 70.7 years (range 47 – 97) The tibiae were divided into four groups of matched pairs based on comparable trabecular bone mineral density. To assess the primary stability under dynamic compression shear conditions, a 3D migration analysis of the tibial component relative to the bone based on displacements and deformations and an evaluation of the cement layer including penetration was performed by CT-based 3D segmentation. Within the tested implant fixation principles the mean load to failure of a 28 mm keel and a 12 mm stem (40 mm) was 4700 ± 1149 N and of a 28 mm keel length was 4560 ± 1429 N (p = 0.996), whereas the mean load to failure was 4920 ± 691 N in full cementation (p = 0.986) and 5580 ± 502 N with additional stem (p = 0.537), with no significant differences regarding the dynamic primary stability under dynamic compressionshear test conditions. From our observations, we conclude that there is no significant difference between a 40 mm and a 28 mm tibial keel & stem length and also between a surface and a full cementation in the effect on the primary stability of a posterior stabilised tibial plateau, in terms of failure load, migration characteristics and cement layer thickness including the penetration into the trabecular bone.
Keywords total knee arthroplasty, tibial keel & stem length, surface vs full cementation, primary stability, dynamic compression shear loading
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Introduction Total knee arthroplasty (TKA) can be considered as international standard of care for the treatment of degenerative osteoarthritis, rheumatoid arthritis and certain knee joint fractures based on survey in 18 countries, with a rising demand over the past two decades (Kurtz et al., 2011). Overall TKA revision rates for all reasons are comparably low with 5 to 10 % over a period of 10 to 15 years (Knutson et al., 1994; Furnes et al., 2007; Lygre et al., 2011; Graves et al., 2012; Sundberg et al., 2014). Sadoghi et al. (2013) performed a complication-based analysis of TKA revisions in a 30 years period entered in the joint registries of Sweden, Norway, Finland, Denmark, Australia and New Zealand and found the most common causes are aseptic loosening in 29.8 %, septic loosening in 14.8 %, pain in 9.5 % and wear in 8.2 % of the cases. Based on a multi-centre study evaluating 844 TKA revisions from 2010 to 2011 Lombardi et al. (2014) found a substantial number of 35 % of TKA failures occurring early within two years of primary surgery. Aseptic loosening was the predominant failure mode, whereas polyethylene wear was not a major cause of failure until more than 15 years service in vivo.
Apart of the patella in the fixation of knee implant components aseptic loosening of the tibial components remains a major concern (Schlegel et al., 2011; Cawley et al., 2013; Schlegel et al., 2015). During a 10-year period (2003 to 2012), 3,572 first time TKA revisions were reported in the Swedish knee arthroplasty register by Sundberg et al. (2014) with a total implant removal of 11.3 % and an exchange of either the tibia in 7.1 % or the femur in 0.9 % of the cases. For 17,782 cemented primary TKA’s evaluated within the Norwegian arthroplasty register during the years 1994 to 2009, Gothesen et al. (2013) extracted for aseptic loosening femur 49 cases and for tibia 136 cases, a ratio of 2.8. This emphasizes the need for stable primary and secondary fixation of tibial trays, which is dependent on multiple factors like implant design, bone interface preparation, surgical technique and cementation (Schlegel et al., 2015).
Several studies had been undertaken to examine the influence of implant design, bone fixation principle, surface structure and cementing technique on the primary stability of uni- or bicompartmental tibial implants in vitro and in vivo. To evaluate the primary stability of tibial plateaus, in vitro, in silico and ex vivo approaches had been undergone: cement penetration depth analysis in the proximal tibia (Maistrelli et al., 1995; Clarius et al., 2012), finite element analysis (FEA) to assess resulting bone stresses and strains (Completo et al., 2008; Kelly 2012; Cawley et al., 2012), static tension (Schlegel et al., 2011; Gebert de Uhlenbrock et al., 2012) or compression loading (Clarius et al., 2010; Completo et al., 2012; Jaeger et al., 2014) until interface failure. However, these test conditions do not reflect the in vivo physiologic loading 3
Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
modes, where the tibial plateau is predominantly subjected to combined compression and shear forces in a cyclic profile (Zhao et al., 2007; Kutzner et al., 2010; Bergmann et al., 2010; Grupp et al. 2013).
The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae.
Materials and Methods ®
We performed a cemented posterior stabilised tibial plateau implantation (VEGA
System Aesculap
Tuttlingen, Germany) on 24 fresh-frozen human tibiae of a mean donor age of 70.7 years (range 47 – 97) with the proximal third of the tibia. To determine bone mineral density (BMD) CT-scans (Sensation 64 Somatom, Siemens AG, Germany) were made of all tibiae prior to the implantation. The bone mineral density was quantitatively determined by measuring the Hounsfield units (HU) beyond the tibial plateau until a depth of 15 mm within the region of trabecular bone. We divided the tibiae into four groups of matched pairs; “TibiaSC40” (28 mm keel & 12 mm stem (40 mm), surface cementation), “TibiaSC28” (28 mm keel, surface cementation), “TibiaFC40” (28 mm keel & 12 mm stem (40 mm), full cementation) and “TibiaSC120S” (28 mm keel, surface cementation, 92 mm cementless stem) (Table 1, Figure 1). The bone preparation and implantation of the tibial component and the gliding surface was done at the dissected tibiae as described in the surgical technique of the VEGA® System (Aesculap Tuttlingen, Germany) for all groups. Pulsed lavage was used (500 ml, 2 minutes purging time) to clean the trabecular bone of the metaphyseal resected knee joint before cementation. A high viscosity bone cement (Palacos® R 20g powder/10 ml monomer, Heraeus Medical Wehrheim, Germany) was mixed with bowl and spatula for cement fixation of the tibia implants. The complete packet of bone cement was applied in equal parts on both the inferior surface of the tibial component and the resected tibial bone using a double-layer technique (surface cementation for the groups “TibiaSC28”, “TibiaSC40” and “TibiaSC120S” & full cementation for the group “TibiaFC40”). The tibial tray was inserted in the tibial bone and impacted onto the tibia using an impactor. For pressurisation of the bone cement during polymerisation the tibial component was axially compressed until the cement was cured. Bone cement was applied on the surface of the tibial component using the double-layer technique To analyze the cement layer, CT-scans were done before biomechanical testing (Figure 2) The CT-data was transferred to segmentation software (Amira 5.6, FEI, USA) and the prosthesis with cement layer was three-dimensionally reconstructed. CAD-Files of the prosthesis, in each size provided by the manufacturer, were used to determine the cement layer by subtracting the geometry of 4
Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
the prosthesis from the CT reconstruction (Geomagic, 3DS, USA). Finally, mean cement layer thickness was calculated by deviding the volume of the cement layer by the area under the tibial tray. After implantation the human tibiae were imbedded with polyurethane casting resin in a bole, 70 mm distally from the medial tibial component surface. This may imply that there is in the group “TibiaSC120S” some interaction between the supporting pot and the long 120 mm stem, as the resin would stiffen the tibia. In awareness of this potential interaction, an embedding level of 70 mm was decided to allow for a clinical representative tibio-femoral load range and avoid periprosthetic fractures of the donor tibiae. The tibiae were fixed on the test machine (DynaMess Stolberg, Germany) in a 20° flexed position (Figure 3) to simulate peak joint loading at 20° of flexion during stair climbing (Kutzner et al. 2010, Bergmann et al. 2014). The tibiofemoral contact force was applied in a peak sinusoidal waveform with a frequency of 0.65 Hz via the femoral component acting on the gliding surface with a ratio of 60% medial and 40% lateral. The contact point of the femoral component and the gliding surface was set at the vertical axis and a posterior offset, which was determined to (sin 20° x 37 mm) – 1.8 mm, respecting the femur component radius and resulting in a shift of the femoro-tibial contact points to the posterior portion of the curved gliding surface (T2 = 26.3 mm measured from the dorsal outer rim). This anatomical load application resulted in a main deformation of the proximal tibiae in distal and posterior direction (Figure 4). The donor of the tibiae had different body weights (range 41 – 100 kg), but even the tibio-femoral load is substantially influenced by individual anatomical, muscular and ligamentous situations. Accordingly, during the dynamic testing an initial tibio-femoral load of 1800 N was applied for 1000 cycles to cover the lower physiologic range followed by a stepwise load increase (Locati steps of 300 N, 1000 cycles) until failure or termination of the test at the highly demanding final load level of 6000 N (1.5-times HIGH100 for stair climbing) (Bergmann et al., 2014), to account for the unknown individual loading situation. The criterion of failure was set to a maximal movement increase in the joint articulation of 2 mm at a single load level, to detect a failed implant fixation macroscopically and avoid a severe periprosthetic fracture of the donor tibiae to enable a proper view on implant migration. To assess the primary stability at the implant-bone interface, the photo-optical measurement system ®
PONTOS 5M (GOM Braunschweig, Germany) with an accuracy of 5 µm in x and z direction and 10 µm in y direction was used. For this process standard-sticker points were placed on the implant and bone along the line of implant-bone interface and related to a defined global coordinate system. The coordinate system was defined with the origin of the tibial component and lateral of the setup (Figure 3). The positive x-axis pointed in the anterior direction, the y-axis in the medial or lateral direction depending on the legs’ side and the z-axis in the proximal direction of the tibial component. For the data analysis the data were standardized to an right
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
knee. Therefore the direction of the y-axis, the rotation around x and z of the left knees were changed in this way that the y-axis pointed always to medial, the rotation around x in valgus direction and the rotation around ®
z as an internal rotation. With the picture series of PONTOS 5M and based on the detection of the points and definition of the components through the recognition of pixels and ellipsoidal forms, information about 3D coordinates, 3D displacements and deformation can be provided. A reference picture was taken at a preloading of 50 N. During the test each 100 cycles a picture series of a loading cycle was taken with a frequency of 15 Hz. The points were grouped to components “implant” and “bone”, where the XYZdisplacement of each component as well as the relative XYZ-displacement of the implant and bone were analyzed with GOM Inspect Professional V8. A repeated–measures analysis of variance (ANOVA) was performed to test for significant differences in the following parameters: bone mineral density, failure load, cement layer thickness and relative motion of each motion component between implant and bone. Prior to analysis, the normal distribution of the data (normal pp plots; p < 0.05) and the homogeneity of variance (Levene-test) were verified, that allowed for the use of ANOVA. Differences of the parameters between the four groups “TibiaSC40”, “TibiaSC28”, “TibiaFC40” and “TibiaSC120S” were evaluated with a Tukeys Honest Significant Difference-Test for unequal N as post hoc analysis. Additionally the correlation between failure load and BMD using the Spearman’s rank correlation coefficient rs was determined. Finally statistical analyses using Statistica 10 (StatSoft Europe GmbH, Hamburg, Germany) with a significance level of p < 0.05 was carried out.
Results To obtain matched pairs concerning primary stability testing in the TibiaSC40 group, the BMD was 218.6 ± 40.6 Hounsfield units (HU) and 219.1 ± 46.1 HU in the TibiaSC28 group (p = 0.999), whereas the BMD was 251.1 ± 40.9 HU in the TibiaFC40 and 246.8 ± 46.9 HU in the TibiaSC120S group (p = 0.998) demonstrating a similarity between the autologous tibiae groups. The relative BMD in Hounsfield units allows for comparisons between the groups – a convertion to an HA equivalent density based on a phantom was not intended. Using the TibiaSC40 group as a reference in homologous cross-comparisons an acceptable comparability was given to the TibiaFC40 (p = 0.646) and to the TibiaSC120S (p = 0.736) specimens. In BMD no statistical difference is given between the homologous cross-comparisons due to the genuine large variance and based on a cohort of n=6 donors per group the statistical power is very low (p = 0.23). The complete cement layer including the penetration into the trabecular bone showed a comparable thickness of the TibiaSC40 to the TibiaSC28 group (p = 0.895), while a slightly thinner cement layer has
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been achieved without statistical significance for the TibiaFC40 (p = 0.857) and the TibiaSC120S group (p = 0.724) (Figure 5). Under dynamic compression-shear test conditions, the mean load to failure in the TibiaSC40 group was 4700 ± 1149 N and 4560 ± 1429 N in the TibiaSC28 group (p = 0.996), whereas the mean load to failure was 4920 ± 691 N in the TibiaFC40 group (p = 0.986) and 5580 ± 502 N in the TibiaSC120S (p = 0.537) group, with no significant differences regarding the dynamic primary stability within the tested implant fixation principles (Figure 6 & 7). The failure mode was in all specimen subsidence of the tibial implant into the resected proximal tibiae. Between the final load level at failure and the BMD, no correlation was found in the TibiaSC40 (rs = 0.579; p = 0.228), in the TibiaSC28 (rs = 0.864; p = 0.059), in the TibiaFC40 (rs = 0.357; p = 0.556) and in the TibiaSC120S (rs = 0.558; p = 0.328) groups. The migration of the tibial implant relative to the bone (average vector of movement) was illustrated in a direct left-to-right comparison for the autologous pairs of human tibiae for the keel length TibiaSC40 versus TibiaSC28 (Figure 8). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the autologous groups yielded, no significant influence of the keel length on the relative translations in x, y and z direction (p > 0.92), and the relative rotations around x, y and z axes (p > 0.43). Migration of the tibial implant relative to the bone was also examined in a homologous comparison of BMD matched pairs of human tibiae for the surface cementation TibiaSC40 versus a full cementation TibiaFC40 (Figure 9). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the homologous groups yielded, no significant influence of a full cementation on the relative translations in x, y and z direction (p > 0.54), and the relative rotations around x, y and z axes (p > 0.77). Migration of the tibial implant relative to the bone was analysed in a homologous comparison of BMD matched pairs of human tibiae for the surface cementation TibiaSC40 versus a surface cementation with cementless stem TibiaSC120S (Figure 10). At a load level of 3000 N (load level 5) and likewise at a load of 4500 N (load level 10), comparison of primary stability in the homologous groups yielded, no significant influence of an additional stem on the relative translations in x, y and z direction (p > 0.6), and the relative rotations around x, y and z axes (p > 0.71).
Discussion The objective of our study was to evaluate the impact of the tibial keel & stem length in surface cementation, of a full cemented keel and of an additional tibial stem on the primary stability of a posterior stabilised tibial plateau under dynamic compression-shear loading conditions in human tibiae.
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
A major limitation of our in vitro test setup is given by the fact that it does not contain the patella-femoral joint. Due to that the resulting loads from the patella contact force on the femoral component and the contribution of the patella tendon force on the tibia are not integrated in the chosen load application, reflecting femoro-tibial peak load during stair climbing in an anatomical position (Bergmann et al. 2014). During stair climbing Bergmann et al. 2014 have shown in their in vivo knee load measurements (HIGH100) peak axial force values of about 4000 N at 20° flexion, acting distally in the direction of the tibia stem and a related transverse shear force of around 300 N acting in posterior direction. However, to enable the test with an uniaxial actuator it was decided to preserve the anatomical position of 20° femoro-tibial flexion and due to the shift of the femoro-tibial contact points to the posterior portion of the curved gliding surface the load application resulted in a main deformation of the proximal tibiae in distal and posterior direction – enabling for a clinically occurring posterior-distal migration of the tibial component into the bone (Figure 4). A second limitation of our study may arise by the fact that only the evaluation of the influence of the keel length (TibiaSC40 vs TibiaSC28) was based on autologous pairs of human tibiae, whereas the other two comparisons of a full cementation (TibiaSC40 vs TibiaFC40) of an additional stem (TibiaSC40 vs TibiaSC120S) were based on homologous pairs matched on the basis of bone mineral density. Due to a genuine large variance in donor bone mineral densities, the mean BMD’s and standard deviations are comparable in all three groups. However, unless the mean BMD of TibiaSC40 is 219.1 HU and of TibiaFC40 is 251.1 HU, the failure load for the surface cementation only is comparable to the fully cemented keel.
Different methods have been introduced to evaluate the influence of implant design aspects and cementation techniques on the primary stability of tibial plateaus (Maistrelli et al., 1995; Jaeger et al., 2014). Using computer tomography, Schlegel et al. 2011 measured the bone mineral density and bone cement penetration to study the influence of pulsed lavage on the cement fixation of bicompartmental tibial trays in six pairs of human tibiae. They used the extraction force as a parameter of the fixation strength at the implant-bone interface. In a post mortem examination of 22 bicompartmental tibial plateaus from 17 patients retrieved after 5.3 years (range 0 to 11 years) in situ, Gebert de Uhlenbrock et al. (2012) analysed the influence of the time in situ on fixation strength. In a static tension test, they found a trend that pull-out forces decrease with the time in situ, whereas they increase with depth of cement penetration. Gebert de Uhlenbrock et al. (2012) and Schlegel et al. (2011) mentioned as a limitation of their studies that axial tension as a measure of the implant-bone interface mechanical capacity could be easily performed, but it
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
does not simulate physiological conditions where mainly dynamic compression combined with bending and shear is acting on the tibial tray (Kutzner et al., 2010; Bergmann et al., 2010; Grupp et al., 2013). Scott and Biant (2012) analysed the role of the design of the tibial components and stems in TKA in a review and found that tibial implants with a short central stem varying typically between 35 and 50 mm in length have favourable clinical survivorship indicating for a reduced clinically relevant stress shielding. Tibia designs with a central stem and fins like PFC Sigma, Genesis 2 and Columbus have shown promising overall fiveyear rates in the National Joint Registry for England and Wales (Scott and Biant, 2012). In contrast to that Foran et al. (2011) as Arsoy et al. (2013) reported for a precoated low-profile tibial component out of tivanium Ti6Al4V alloy higher failure rates with insufficient bonding at the implant-cement interface. For a short-keeled cemented tibial component out of a group of 80 consecutive TKA patients Ries et al. (2013) revealed a revision rate of 6.3 % after 1-year follow-up with failure at the implant-cement interface in 4 of the 5 revised cases. In the current study we found for the dynamic failure load between TibiaSC28 (4560 N) and TibiaSC40 (4700 N) no substantial difference (p = 0.9963) as well as for the xyz-displacements of the tibial tray relative to the bone, indicating that a keel length of 28 mm is able to create a sufficient primary stability of the tibial plateau and in addition to that the observed failure mode was migration into the metaphyseal head of the human tibiae and not debonding between implant and cement (Foran et al., 2011; Arsoy et al., 2013; Ries et al., 2013). A comparison between surface and full cementing technique of tibial trays has been reported in clinical follow-up studies (Saari et al., 2009). Based on a cohort of 232 primary TKA patients using either surface or full cementation of a mobile tibial tray with keel Galasso et al. (2013) reported cumulative survival rates at 8 years with an average follow-up of 5.6 years of 97.1 % for revision for any reason and of 99.3 % for mechanical reasons with no difference in clinical outcomes according to the tibial component cementation technique. They concluded that cementing the tibial keel has no advantage for primary TKA patients. In a longterm matched-pair analysis by Schlegel et al. (2015) comparing surface or full cementation of the tibial component in a total of 67 patients with a clinical follow-up of 10.3 years for SC and 12 years for FC, the survivorship at 10 years was 100 % for SC and 93.3 % for FC considering aseptic loosening as endpoint. They found no statistical difference between SC and FC in the longterm survivorship and questioned the advantage of FC, because their findings do not support the concern that SC results in inferior fixation even in patients with rheumatoid arthritis (56 % of patients in SC and 48 % in FC group). These results were also supported by Rossi et al. (2010), where no early loosening was observed for SC in a cohort of 70 TKA’s with a follow-up of 3.6 years. Kelly (2012) developed a combined experimental and computational method to
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
examine the effect of surface and full cementation of the tibial component on the surrounding stress state in the periprosthetic trabecular bone with a remodeling algorithm for bone formation and resorption post implantationem. This FEA modeling allows to predict the peri-prosthetic strain experienced by bone after implantation and using this method Cawley et al. (2012) found statistically significant differences between SC and FC with lower stresses and strain recorded in cortical and trabecular bone directly under a fully cemented tibial baseplate, whereas high stress concentrations were computed for FC in the distal area due to bonding of the stem tip to the surrounding bone. Bone remodeling simulations predicted greater bone resorption for full cementation of the tibial tray Cawley et al. (2013), suggesting that FC would result in increased bone loss at the proximal tibia, whereas overall the SC model displayed the closest trabecular stress distribution to the intact bone Kelly (2012). Comparing surface versus full cementation within our study we measured no significant difference for the dynamic failure load between TibiaSC40 (4700 N) and TibiaFC40 (4920 N) (p = 0.986) as well as for the xyz-translational and -rotational implant displacements relative to the bone. Considering reduced stress-shielding and bone resorption as described by Cawley et al. (2012), our findings favour the surface cementation technique. Evaluating the primary stability behaviour of a surface cemented tibia with stem we found that the addition of a stem creates less variancy in all rotatory degrees of freedom, whereas the dynamic failure load was not substantially increased (p = 0.537) for TibiaSC120S (5580 N) compared to TibiaSC40 (4700 N). Analysing the single specimen characteristics the importance of sufficient cortical coverage and distal sliding fit conditions of the cementless stems has been experienced to obtain a high primary stability. In addition to that it should be considered that full tibial coverage combined with stiff cemented or press-fit stems leads to a bypassing of load of the proximal trabecular tibial bone and may result in stress shielding and metaphyseal tibial bone resorption (Scott and Biant, 2012).
From our observations, we conclude that there is no significant difference between a 40 mm (TibiaSC40) and a 28 mm tibial keel length (TibiaSC28) in the effect on the primary stability of surface cemented tibial plateaus, in terms of failure load, migration characteristics and cement layer thickness including the penetration into the trabecular bone. Moreover, the current findings lead us to suggest that there is no substantial benefit of a full cementation (TibiaFC40) versus a surface cementation (TibiaSC40) on the primary stability of a posterior stabilised tibial plateau, in terms of failure load, migration characteristics and cement layer thickness under dynamic compression-shear loading conditions in human tibiae.
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Acknowledgements The authors would like to thank Heidi Odemer for her assistance during the implantation of the tibial plateaus into the human cadaver knees and Elvira Stolinski for the graphical illustration of the different tested tibial plateau and stem configurations
Conflict of Interest Four of the authors (TMG,MH,AP,CSchi) are employees of Aesculap Tuttlingen a manufacturer of orthopaedic implants. Two of the authors (KJS,WMM) are advising surgeons in Aesculap R&D projects. One of the authors (CSchr) is getting research funding in correlation with Aesculap R&D projects.
Tables and Figures Table 1: Human tibiae donor characteristics, bone mineral density, implanted tibial tray version and component size Figure 1: Tibial implant configurations for TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S Figure 2: CT-based 3D segmentation of the cement layer to examine the cement layer depth – exemplary in surface cementation TibiaSC40-1 (left) and full cementation technique TibiaFC40-2 (right) Figure 3: Tibial tray implanted in a human tibia in a test-setup with a dynamic compression-shear testing in a 20° flexed position to simulate peak joint load during walking and stair climbing (Kutzner et al., 2010; Bergmann et al., 2014) with vertical femoral load application in a ratio of 60% medial and 40% lateral and 3D motion analysis system (left) with a point cluster on the bone and the implants and the loading setup (right) Figure 4: Deformation of the bone in anterior-posterior (x-axis) and tibia axis (z-axis) at a load level of 3000N in this representative example TibiaSC28-5 Figure 5: Average thickness of the cement layer for TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S analysed by a CT-based 3D segmentation – Box-Wisker plot for statistical analysis of the groups Figure 6: Primary stability testing of the TKA tibial components under dynamic compression-shear loading conditions in human tibiae to compare the TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S implantation principles – BMD, load level and cycles at failure for each specimen Figure 7: Final load level at failure due to migration into the bone in a comparison between TibiaSC40, TibiaSC28, TibiaFC40 and TibiaSC120S implantations – Box-Wisker plot for statistical analysis of the groups Figure 8: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in an autologous comparison for the TibiaSC40 versus the TibiaSC28 implantation groups at each load level
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Figure 9: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in a homologous comparison for the TibiaSC40 versus the TibiaFC40 implantation groups at each load level Figure 10: Average vector of x,y,z movement (translation & rotation) of the tibial component relative to the bone in a homologous comparison for the TibiaSC40 versus the TibiaSC120S implantation groups at each load level
References Arsoy D, Pagnano MW, Lewallen DG, Hanssen AD, Sierra RJ: Aseptic tibial debonding as a cause of early failure in a modern total knee arthroplasty design. Clin Orthop Relat Res Vol. 471, pp. 94-101, 2013. Bergmann G, Heinlein B, Bender A, Graichen F, Rohlmann A, Halder A, et al.: Medio-lateral load distribution in the knee joint during walking. Abstract 17th Congress of the European Society of Biomechanics, July 4 – 8 Edinburgh UK, 2010. Bergmann G, Bender A, Graichen F, Dymke J, Rohlmann A, Trepczynski A, Heller MO, Kutzner I: Standardized Loads Acting in Knee Implants. PLoS ONE Vol. 9 No.1, 2014 e86035. doi:10.1371/journal.pone.0086035 Cawley DT, Kelly N, Simpkin A, Shannon FJ, McGarry JP: Full and surface tibial cementation in total knee arthroplasty – a biomechanical investigation of stress distribution and remodeling in the tibia. Clinical Biomechanics Vol. 27, pp. 390-397, 2012. Cawley DT, Kelly N, McGarry JP, Shannon FJ: Cementing techniques for the tibial component in primary total knee replacement. J Bone and Joint Surg Vol. 95B No. 3, pp. 295-300, 2013. Clarius M, Haas D, Aldinger PR, Jaeger S, Jakubowitz E, Seeger JB: Periprosthetic tibial fractures in unicompartmental knee arthroplasty as a function of extended sagittal saw cuts: An experimental study. The Knee Vol. 17, pp. 57-60, 2010. Clarius M, Seeger JB, Jaeger S, Mohr G, Bitsch RG: The importance of pulsed lavage on interface temperature and ligament tension force in cemented unicompartmental knee arthroplasty. Clinical Biomechanics Vol. 27, pp. 372-376, 2012. Completo A, Simoes JA, Fonseca F, Oliveira M: The influence of different tibial stem designs in load sharing and stability at the cement-bone interface in revision TKA. The Knee Vol. 15, pp. 227-232, 2008. Completo A, Fonseca F, Simoes JA, Ramos A, Relvas C: A new press-fit stem concept to reduce the risk of end-of-stem pain at revision TKA – A pre-clinical study. The Knee Vol. 19, pp. 537-542, 2012. Foran JR, Whited BW, Sporer SM: Early aseptic loosening with a precoated low-profile tibial component a case series. J Arthroplasty Vol. 26, pp. 1445-1450, 2011. Furnes O, Espehaug B, Lie SA, Vollset SE, Engesaeter LB, Havelin L: Failure mechanism after unicompartmental and tricompartmental primary knee replacement with cement. J Bone and Joint Surg Vol. 89A No. 3, pp. 519-525, 2007. Galasso O, Jenny JY, Saragaglia D, Miehlke RK: Full versus surface tibial baseplate cementation in total knee arthroplasty. Orthopedics Vol. 36 No. 2, pp. e151-e158, 2013. Gebert de Uhlenbrock A, Püschel V, Püschel K, Morlock MM, Bishop NE: Influence of time in-situ and implant type on fixation strength of cemented tibial trays – A post mortem retrieval analysis. Clinical Biomechanics Vol. 27 No. 9, pp. 929-935, 2012. Gothesen O, Espehaug B, Havelin L, Petursson G, Lygre S, Ellison P, Hallan G, Furnes O: Survival rates and causes of revision in cemented primary total knee replacement – Norwegian Arthroplasty Register 19942009. Bone Joint J Vol. 95B, pp. 636-42, 2013. Graves S, Tomkins A, Davidson D, et al.: Australian Orthopaedic Association National Hip and Knee Arthroplasty Registry – Annual Report, pp. 116-123, 2012. Grupp TM, Pietschmann MF, Holderied M, Scheele C, Schröder C, Jansson V, Müller PE: Primary stability of unicompartmental knee arthroplasty under dynamic compression-shear loading in human tibiae. Clinical Biomechanics Vol. 28, pp. 1006-1013, 2013.
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Jaeger S, Rieger JS, Bruckner T, Kretzer JP, Clarius M, Bitsch RG: The protective effect of pulsed lavage against implant subsidence and micromotion for cemented tibial unicompartmental knee components – an experimental cadaver study. J Arthroplasty Vol. 29 No. 4, pp. 727-732, 2014. Kelly N: An experimental and computational investigation of the inelastic behaviour of trabecular bone. The National University of Ireland, Galway. Doctoral Thesis, pp. 93-101, 2012. Knutson K, Lewold S, Robertsson O, Lidgren L: The Swedish knee arthroplasty register. A nation-wide study of 30,003 knees 1976-1992. Acta Orthop Scand. Vol. 65, pp. 375-386, 1994. Kurtz SM, Ong KL, Lau E, Widmer M, Maravic M, Gómez-Barrena E, de Fátima de Pina M, Manno V, Torre M, Walter WL, de Steiger R, Geesink RGT, Peltola M, Röder C: International survey of primary and revision total knee replacement. Int Orthopaedics (SICOT) Vol. 35 No. 2, pp. 1783-89, 2011. Kutzner I, Heinlein B, Graichen F, Bender A, Rohlmann A, Halder A, et al.: Loading of the knee joint during activities of daily living measured in vivo in five subjects. J Biomechanics Vol. 43, pp. 2164-2173, 2010. Lombardi Jr AV, Berend KR, Adams JB: The revision knee arthroplasty – Why knee replacements fail in 2013 patient, surgeon or implant? J Bone and Joint Surg Vol. 96B No. 11, pp. 101-104, 2014. Lygre SHL, Espehaug B, Havelin LI, Vollset SE, Furnes O: Failure of total knee arthroplasty with or without patella resurfacing – A study from the Norwegian Arthroplasty Register with 0 -15 years follow-up. Acta Orthopaedica Vol. 82 No. 2, pp. 282-292, 2011. Maistrelli GL, Antonelli L, Fornasier V, Mahomed N: Cement penetration with pulsed lavage versus syringe irrigation in total knee arthroplasty. Clin. Orthop. Rel. Res. No. 312, pp. 261-265, 1995. Ries C, Heinichen M, Dietrich F, Jakubowitz E, Sobau C, Heisel C: Short-keeled cemented tibial components show an increased risk for aseptic loosening. Clin Orthop Relat Res Vol. 471, pp. 1008-1013, 2013. Rossi R, Bruzzone M, Bonasia DE, Ferro A, Castoldi F: No early tibial tray loosening after surface cementing technique in mobile bearing TKA. Knee Surg Sports Traumatol Arthroscopy Vol. 10, pp. 1360-1365, 2010. Sadoghi P, Liebensteiner M, Agreiter M, Leithner A, Böhler N, Labek G: Revision surgery after total joint arthroplasty: a complication-based analysis using worldwide arthroplasty registers. J Arthroplasty Vol. 28 No. 8, pp. 1329-1332, 2013. Saari T, Li MG, Wood D, Nivbrant B: Comparison of cementing techniques of the tibial component in total knee replacement. International Orthopaedics (SICOT) Vol. 33 No. 5, pp. 1239-1242, 2009. Schlegel UJ, Siewe J, Delank KS, Eysel P, Püschel K, Morlock MM, et al.: Pulsed lavage improves fixation strength of cemented tibial components. International Orthopaedics (SICOT) Vol. 35, pp. 1165-1169, 2011. Schlegel UJ, Bruckner T, Schneider M, Parsch D, Geiger F, Breusch SJ: Surface or full cementation of the tibial component in total knee arthroplasty: a matched-pair analysis of mid- to long-term results. Arch Orthop Trauma Surg Vol. 135 No. 5, pp. 703-708, 2015. Scott CEH, Biant LC: The role of the design of tibial components and stems in knee replacement – Instructional review. J Bone and Joint Surg Vol. 94B No. 8, pp. 1009-15, 2012. Sundberg M, Lidgren L, W-Dahl A, Robertsson O: Swedish knee arthroplasty register – Annual Report Lund University, Lund Sweden, 2014. Zhao D, Banks SA, D'Lima DD, Colwell CW, Fregly BJ: In vivo medial and lateral tibial loads during dynamic and high flexion activities. J Orthopaedic Research Vol. 25 No. 5, pp. 593-602, 2007.
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Primary stability of tibial plateaus under dynamic compression-shear loading in human tibiae – influence of keel length, cementation area and tibial stem
1,2
3
1
1
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Thomas M. Grupp , Khaled J. Saleh , Melanie Holderied , Andreas M. Pfaff , Christoph Schilling , 2 4 Christian Schroeder , William M. Mihalko 1
Aesculap AG Research & Development,Tuttlingen, Germany Ludwig Maximilians University Munich, Department of Orthopaedic Surgery, Physical Medicine & Rehabilitation, Campus Grosshadern, Munich, Germany 3 Division of Orthopaedics Southern Illinois University School of Medicine Springfield, IL, USA 4 Campbell Clinic Department of Orthopaedic Surgery & Biomedical Engineering, University of Tennessee, TN, USA 2
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Primary stability of tibial plateaus in human tibiae_Rev.1 – J Biomechanics 2017
Tables and Figures Table 1: Human tibiae donor characteristics, bone mineral density, implanted tibial tray version and component size Specimen
Sex
Age
Leg
BMD [HU]
height & weight
tibial tray size
TibiaSC40-1 TibiaSC28-1
female female
51 51
166 ± 37 172 ± 46
165 cm 64 kg
T3 T3
TibiaSC40-2 TibiaSC28-2
female female
87 87
right left left right
185 ± 54 186 ± 65
157 cm 59 kg
T2 T2
TibiaSC40-3 TibiaSC28-3
male male
67 67
left right
222 ± 51 229 ± 24
180 cm 100 kg
T4 T4
TibiaSC40-4 TibiaSC28-4
female female
47 47
right left
238 ± 84 228 ± 90
160 cm 59 kg
T3 T3
TibiaSC40-5 TibiaSC28-5
male male
68 68
right left
285 ± 37 285 ± 58
165 cm 59 kg
T4 T4
TibiaSC40-6 TibiaSC28-6
female female
97 97
right left
208 ± 83 145 ± 82
150 cm 41 kg
T2 T2
TibiaSC120S-1 TibiaFC40-1
male male
64 64
right left
216 ± 47 232 ± 132
175 cm 77 kg
T3, S92d14 T3
TibiaSC120S-2 TibiaFC40-2
male male
73 73
left right
202 ± 42 222 ± 63
173 cm 95 kg
T2, S92d12 T2
TibiaSC120S-3 TibiaFC40-3
female female
62 62
left right
241 ± 65 211 ± 48
163 cm 86 kg
TibiaSC120S-4 TibiaFC40-4
male male
76 76
left right
323 ± 52 288 ± 56
185 cm 45 kg
TibiaSC120S-5 TibiaFC40-5
female female
84 84
left right
252 ± 56 302 ± 47
160 cm 52 kg
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T2, S92d12 T2 T5, S92d14 T5 T2, S92d12 T2